JP2011110464A - Powder coating apparatus and powder coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a uniform coating film that is not uneven on the circumferential surface of a coated article. <P>SOLUTION: Coating is applied to the article 90 to be coated per fluidized bed dip coating by passing through a preheating apparatus 20 corresponding to a preheating process P1, a flow coating apparatus 30 corresponding to a fluidized bed dip coating process P2, and an ex post facto heater 40 corresponding to an ex post facto heating process P3. The preheating apparatus 20 includes an induction heating coil 21 as an induction heating means, a high frequency oscillator 22 that allows a high frequency current to flow in the induction heating coil 21, and a rotating mechanism 23 that axially rotates the article 90 to be coated around a shaft body 92. The flow coating apparatus 30 includes a fluidizing tank 31 and a blower 32 that fluidizes a powder coating material 50 inside the fluidizing tank 31. The ex post facto apparatus 40 is configured the same as the preheating apparatus 20 and performs the ex post facto heating process to the article 90 to be coated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a powder coating apparatus and a powder coating method for attaching a powdery paint (powder paint) to a workpiece made of a magnetic material having a cylindrical outer peripheral surface by a fluid immersion method.

  Conventionally, a powder coating apparatus to which a fluidized dipping method as described in Patent Document 1 is applied is known. This powder coating apparatus is loaded with a cylindrical object to be coated (an armature that constitutes a rotating part of an electric motor in Cited Document 1) in a fluidized tank in which fine powder paint (powder paint) is flowed. Then, the powder coating is adhered to the surface of the object to be coated, and thereby a coating film is formed on the surface of the object to be coated.

  Such a powder coating apparatus heat-treats an object to be coated and heats the object to be heated to a high temperature, and also heats and degreases a portion for evaporating the adhering oil, and the heated object to be coated with a powder coating. The electrostatic adhesion part that attaches the powder paint to the surface by loading it into the fluidized tank where the fluid is flowing, and the paint layer laminated on the surface of the object to be coated are heat treated to stabilize the paint application state And a curing part.

  In the heating and degreasing unit and the curing unit, the object to be coated is passed through the magnetic flux formed by the high voltage applied to the coil from the high-frequency oscillator (high voltage generator in the cited document 1). A so-called induction heating method is employed in which heat treatment is performed by Joule heat generated by eddy current.

  By adopting the fluidized immersion method using this induction heating method, the powder by the fluidized immersion method can be used at a lower apparatus cost and processing cost than when hot air obtained by a heating means such as a hot air furnace is used for the heat treatment. Body painting can be realized.

JP-A-9-38529

  By the way, in the powder coating apparatus described in Patent Document 1, the object to be coated is entirely exposed to the magnetic flux during conveyance. For this reason, the amount of magnetic flux to be exposed varies depending on the part, the object to be coated is difficult to be heated uniformly, and the surface temperature of the object to be coated may be uneven. If the surface temperature of the object to be coated is not uniform, the amount of powder paint adhering to the surface of the object to be coated and the state of welding at the electrostatic adhesion part will be uneven, resulting in a uniform surface to the object to be coated. And it has the problem that it is difficult to form a coating film with a beautiful finish.

  The present invention has been made in order to solve the conventional problems, and on the premise of adopting an induction heating method, the outer peripheral surface of an object to be coated having a cylindrical outer peripheral surface is uniformly induction heated. Therefore, an object of the present invention is to provide a powder coating apparatus and a powder coating method capable of forming a uniform coating film without unevenness on the outer peripheral surface of an object to be coated.

  A powder coating apparatus according to one aspect of the present invention includes a rotating mechanism that rotates a magnetic material-coated object having a cylindrical outer peripheral surface around its axis, and one of the outer peripheral surfaces of the object to be coated. It is possible to apply a magnetic flux to the part over the entire length in the axial direction, and an induction heating means for subjecting the object to be coated being rotated by the rotating mechanism to an induction heating process, and a powder coating is in a fluid state And a fluidized tank into which the article to be coated heated by the induction heating means is inserted (Claim 1).

  According to this configuration, the object to be coated is induction-heated by the induction heating means in a predetermined range in the circumferential direction of the outer peripheral surface. In addition to this, the object to be coated is rotated around its axis, and as a result, the outer peripheral surface is uniformly induction-heated over the entire circumference. When the object to be coated that has been subjected to induction heating is inserted into the fluidized tank, the flowing powder coating adheres to the peripheral surface of the object to be melted, and thereby the peripheral surface of the object to be coated. Is a state in which the coating film obtained by melting the powder coating is laminated and is in a painted state. Here, since the peripheral surface of the object to be coated is uniformly heated, the amount of the powder coating applied to the outer peripheral surface of the object to be heated becomes uniform. As a result, the outer peripheral surface of the object to be coated has a thickness dimension. A uniform coating film is formed.

  In the above-described configuration, the induction heating means is wound around the magnetic core, the magnetic core facing the outer peripheral surface of the object to be coated, and arranged in parallel with the axial direction of the object to be coated. An induction heating coil including a winding is desirable.

  According to this configuration, a magnetic path is formed between the magnetic core and a portion having a predetermined width in the circumferential direction on the outer peripheral surface of the object to be coated (portion facing the magnetic core), and an induction heating coil is generated. A magnetic flux path is provided. Accordingly, the outer peripheral surface of the object to be coated can be uniformly induction-heated in the axial direction by Joule heat accompanying the passage of magnetic flux, and further, the entire outer peripheral surface can be heated by rotating the object to be coated. Become.

  A powder coating method according to another aspect of the present invention includes a step of rotating an object made of a magnetic material having a cylindrical outer peripheral surface around its axis, and an outer periphery of the object to be coated in a rotating state. A step of inductively heating the object to be coated by causing a magnetic flux to act on a part of the surface over the entire length in the axial direction, and a fluidized tank in which a powder coating material flows through the induction-heated object to be coated And a step of adhering the powder coating material to the peripheral surface by immersing in the inside (Claim 3).

  According to this method, the object to be coated is rotated around its axis while the predetermined range in the circumferential direction of the outer circumferential surface is induction-heated. As a result, the outer circumferential surface is uniformly induction-heated over the entire circumference. It becomes like this. By inserting the object to be coated, which has been uniformly heated in this way, into the fluidized tank, the powder coating can be uniformly adhered to the outer peripheral surface of the object to be heated.

  In the above method, a process of rotating the processed object to which the powder coating material has been attached is rotated about its axis, and a center of the outer periphery of the processed object in a rotating state is rotated. It is desirable to further include the step of inductively heating the processed object to be processed by applying a magnetic flux over the entire length in the direction (Claim 4).

  According to this method, the induction heating process is performed again after the fluidized immersion process, and the so-called curing process is performed, so that the uniform thickness dimension of the coating film is achieved.

  According to the powder coating apparatus or the powder coating method of the present invention, an object made of a magnetic material having a cylindrical outer peripheral surface can be heated uniformly, and a uniform thickness coating film is formed on the outer peripheral surface of the object to be coated. Can be made. Therefore, for example, when the object to be coated is painted for the purpose of ensuring an electrically insulated state, for example, it is possible to effectively prevent the occurrence of inconvenience that causes a difference in insulation capacity depending on the location. In addition, when the purpose of the coating is to prevent rust, it is possible to effectively prevent the occurrence of inconvenience such as partial rusting.

It is explanatory drawing which shows one Embodiment of the powder coating apparatus and powder coating method which concern on this invention.

  FIG. 1 is an explanatory view showing an embodiment of a powder coating apparatus and a powder coating method according to the present invention. In FIG. 1, the size of the powder coating material 50 in the fluid coating device 30 is exaggerated. Moreover, in FIG. 1, the coating film laminated | stacked on the surface of the to-be-coated object 90 is shown by the point sketch.

  As shown in the upper part of FIG. 1, in the powder coating method according to this embodiment, a preheating process P1 in which an object 90 is subjected to an induction heating process in advance, and a heating process is performed in the preheating process P1. A coating process is performed in the fluid immersion process P2 in which a coating film is formed by a fluid immersion method in a fluid tank 31 in which the powder coating material 50 is filled in a fluidized state with respect to the coated object 90, and the fluid immersion process P2. The outer peripheral surface of the object to be coated 90 is subjected to powder coating by sequentially performing a post-heating process P3 for performing subsequent induction heating treatment for curing on the object 90 to be coated.

  In order to execute the above steps P1 to P3, the powder coating apparatus 10 is employed in the present embodiment. The powder coating apparatus 10 includes a preheating device 20, a fluid dipping device 30, and a post heating device 40. The pre-heating device 20, the fluid immersion device 30, and the post-heating device 40, which are the components of the powder coating apparatus 10, will be sequentially described in the description of each process.

  The object 90 is an article made of a magnetic material having a cylindrical outer peripheral surface. As such an article, a cylindrical body or a cylindrical body can be exemplified. The object 90 includes an object body 91 having a cylindrical outer peripheral surface, and a shaft body 92 penetrating at the center position of the object body 91. A coating process by a fluid dipping method is performed mainly on the outer peripheral surface of the object body 91 in the object 90.

  In the preheating step P1, the preheating device 20 is used. The preheating device 20 includes an induction heating coil (induction heating means) 21 whose winding core direction extends parallel to the shaft body 92 of the object 90 to be coated, and a high frequency oscillator 22 for causing a high frequency current to flow through the induction heating coil 21. And a rotating mechanism 23 that rotates the object 90 around the shaft body 92.

  The induction heating coil 21 is opposed to the outer peripheral surface of the object main body 91 in close proximity and is disposed in parallel with the shaft 92 of the object to be coated, and is wound around the magnetic core 211. Windings 212. The length of the magnetic core 211 is substantially equal to the axial length of the article main body 91. The winding 212 is wound over substantially the entire length of such a magnetic core 211. In the figure, an example in which one winding 212 is wound is shown, but a plurality of windings 212 may be divided into the magnetic core 211 and wound.

  The high frequency oscillator 22 has a predetermined high frequency oscillation circuit, converts AC power received from a commercial power source into a high frequency by the high frequency oscillation circuit, and supplies it to the induction heating coil 21. The induction heating coil 21 generates a magnetic flux along the longitudinal direction of the magnetic core 211 when given a high frequency current from the high frequency oscillator 22.

  The rotation mechanism 23 includes a drive motor 231 and a gear mechanism 232 interposed between the drive shaft of the drive motor 231 and the shaft body 92 (these are schematically shown in FIG. 1). . The drive rotation of the drive motor 231 is transmitted to the shaft body 92 after being decelerated to a predetermined speed by the gear mechanism 232. By the drive of the drive motor 231, the object 90 is rotated around the axis of the shaft body 92.

  According to the preheating device 20 having such a configuration, the magnetic core 211 of the induction heating coil 21 is disposed close to the outer peripheral surface of the article main body 91 and parallel to the shaft body 92. For this reason, a magnetic path comes to be formed between the magnetic core 211 and the surface layer portion 911 of the article main body 91 facing the magnetic core 211. The surface layer portion 911 has a certain range of width in the circumferential direction (generally, the width facing the magnetic core 211) on the outer peripheral surface of the article main body 91, and has a length extending over the entire length in the axial direction. It is.

  When a high frequency current from the high frequency oscillator 22 is passed through the induction heating coil 21, a magnetic flux is generated. This magnetic flux passes through a magnetic path formed by the magnetic core 211 and the surface layer portion 911. That is, the magnetic flux exits one end portion of the magnetic core 211 and enters one end portion of the surface layer portion 911, exits the other end portion of the surface layer portion 911, and returns to the other end portion of the magnetic core 211. In the surface layer portion 911, the magnetic flux passes through the region of the surface layer portion 911 with a predetermined magnetic penetration depth.

  As a result, the surface layer portion 911 of the article main body 91 is inductively heated by Joule heat due to eddy currents generated by the passage of the magnetic flux. Here, since the magnetic flux acts on the surface layer portion 911 over the entire length in the axial direction, the surface layer portion 911 has the same heating condition in the axial direction and is heated to the same temperature. Accordingly, if the object body 91 is rotated around the shaft body 92 at a constant speed in this state, the surface layer portion 911 is sequentially shifted in the circumferential direction of the object body 91. The outer peripheral surface of the main body 91 can be uniformly induction-heated.

  For this reason, in the preheating process P <b> 1, a high frequency current is caused to flow from the high frequency oscillator 22 to the induction heating coil 21 while the object body 91 is rotated around the shaft body 92 at a constant speed by the rotation mechanism 23. As a result, the outer peripheral surface of the article main body 91 is heated to the same temperature as a whole because the region corresponding to the surface layer portion 911 is continuously heated under the same conditions. The outer peripheral surface of the article main body 91 is heated to a temperature slightly higher than the melting point of the powder coating material 50 to be applied.

  Next, in the fluid immersion process P2, the fluid immersion apparatus 30 is used. The object to be coated 90 in which the outer peripheral surface of the object main body 91 is heated to a predetermined temperature in the preheating step P1 is inserted into the fluidized immersion device 30, where the object to be coated 90 is coated by the fluidized immersion method. Is done. The fluid dipping device 30 has a powder tank 50 loaded in advance and a fluid tank 31 into which an object 90 is inserted, and air is blown into the fluid tank 31 to float the powder paint 50 in the fluid tank 31. And an air blower 32 that forms an air flow for the purpose.

  The fluid tank 31 is provided with an air intake port 311 that is opened at the lower part of the side wall thereof, and the upper surface of the fluid tank 31 is entirely open. A filter 312 that covers the entire vicinity of the bottom surface in the fluid tank 31 is attached to a position above the air inlet 311 in the fluid tank 31. The filter 312 is formed of a sponge-like synthetic resin material. A space above the filter 312 in the fluid tank 31 is a fluid immersion chamber 33 in which the object to be coated 90 is subjected to a coating treatment by a fluid immersion method.

  By driving the blower 32, air is blown from the air intake port 311 to the lower part of the fluidized tank 31. This air is evenly diffused through the filter 312 and is uniformly supplied to the fluid immersion chamber 33. Therefore, in the fluid immersion chamber 33, the powder coating material 50 rises up and flows in a uniform state, and an environment suitable for fluid immersion treatment for the article 90 to be coated is obtained.

  The powder coating 50 is a fine powder coating that does not contain a volatile dispersion medium such as an organic solvent or water, and is formed by mixing a synthetic resin, a coloring pigment, a filler, an additive, and the like. As the powder coating material 50, those having a melting point of 250 ° C. to 400 ° C. and a particle size of about 80 to 150 μm can be suitably used. For example, various types such as polyvinyl chloride resin, polyethylene resin, nylon resin, etc. A synthetic resin material can be used.

  A predetermined amount of the powder coating material 50 is loaded in the fluid immersion chamber 33 of the fluid tank 31 in advance. Subsequently, the blower 32 is driven, and air is blown into the fluidized tank 31 through the air intake port 311. The blown air is introduced into the fluid immersion chamber 33 with the foreign matter removed through the filter 312, whereby the powder coating material 50 in the fluid immersion chamber 33 rises and flows in the fluid immersion chamber 33. become. In this state, the object to be coated 90 heated to a predetermined temperature in the preheating step P1 is immersed in the fluid immersion chamber 33.

  The flowing powder coating material 50 contacts and melt adheres to the surface of the object 90 heated to a temperature higher than its melting point, whereby a coating film is formed on the surface of the object 90 to be coated. Since the temperature of the peripheral surface of the object main body 91 is uniform, the coating film has a uniform thickness in the peripheral surface of the object main body 91 and the vicinity thereof. In the vicinity thereof, there is no coating unevenness, and the paint is beautifully applied.

  When the coating process by the fluid immersion method in the fluid immersion process P2 is completed, the article 90 to be coated is taken out from the fluid immersion apparatus 30 and supplied to the next post heating process P3. In the post-heating process P3, the object 90 to be coated is subjected to a post-heating process (curing process) on the molten coating film of the powder coating 50 laminated on the peripheral surface of the object body 91 in the previous fluid immersion process P2. It is a process of heating again.

  In the post-heating step P3, the post-heating device 40 configured similarly to the pre-heating device 20 is used (the pre-heating device 20 may be used again). The post-heating device 40 includes an induction heating coil 41 whose core direction extends parallel to the shaft body 92 of the workpiece 90, a high-frequency oscillator 42 for causing a high-frequency current to flow through the induction heating coil 41, and the workpiece 90. And a rotation mechanism 43 that rotates around the body 92. The induction heating coil 41 includes a magnetic core 411 disposed in parallel with the shaft body 92 and a winding 412 wound around the magnetic core 412. The rotation mechanism 43 includes a drive motor 231 and a gear mechanism 232 interposed between the drive shaft of the drive motor 231 and the shaft body 92. Since these components are the same as those of the induction heating coil 21, the high frequency oscillator 22, and the rotation mechanism 23 in the preheating device 20, the description thereof is omitted here.

  When the post-heating process P3 is performed, a high-frequency current is induced from the high-frequency oscillator 42 in a state in which the object body 91 is rotated around the shaft body 92 via the gear mechanism 432 and the shaft body 92 by driving the drive motor 431. Flowed through the heating coil 41. As a result, the induction heating coil 41 generates a magnetic flux, and this magnetic flux exits from one end face of the magnetic core 411 and passes through the surface layer portion 911 of the outer peripheral surface of the rotating object body 91 in the axial direction. It penetrates at the magnetic penetration depth and returns to the other end face of the magnetic core 411.

  Therefore, the surface layer portion 911 of the article main body 91 is heated by the Joule heat generated by the eddy current generated by the high-frequency magnetic flux. By this heating, the outer peripheral surface of the article main body 91 is uniformly heated, and the mechanism is the same as that in the preliminary heating device 20 described above. By such uniform heating, the curing treatment of the coating layer of the powder coating 50 formed on the outer peripheral surface of the article main body 91 is satisfactorily performed. When the post-heating treatment is completed, the article 90 is taken out from the post-heating device 40 and shipped as a product after a predetermined product inspection or temporarily stored in a warehouse.

  As described above in detail, the powder coating method according to the present embodiment has an outer peripheral surface of the object to be coated 90 while rotating the object 90 having a cylindrical outer peripheral surface around the axis center. A preheating step P1 in which a magnetic flux is applied to the surface layer portion 911 over the entire length in the axial direction to subject the peripheral surface to induction heating treatment, and the coating object 90 heat-treated in the preheating step P1 is powdered. A fluid immersion process P2 in which the powder coating 50 is attached to the peripheral surface of the object 90 by being immersed in the fluid tank 31 in which the paint 50 is flowing, and the powder coating 50 is applied to the peripheral surface in the fluid immersion process P2. The outer peripheral surface of the object to be coated 90 is coated by sequentially performing a post-heating process (thermal curing process) by subjecting the welded object 90 to induction heating treatment again, followed by a post-heating process P3. It is.

  According to this powder coating method (powder coating apparatus 10), since the surface layer portion 911 of the object 90 is sequentially induction-heated, the outer peripheral surface of the object 90 can be uniformly heated over the entire circumference. it can. Since the object 90 subjected to such uniform heating is inserted into the fluid tank 31, the flowing powder coating 50 adheres to the peripheral surface of the object 90 and melts. A coating film obtained by melting the powder coating material 50 can be laminated on the peripheral surface of the object 90.

  Therefore, if the object 90 is cylindrical or cylindrical, a coating film can be uniformly formed on the outer peripheral surface thereof. For example, a building material having a columnar or cylindrical shape ( (For example, pillars and beam materials), cylindrical steel pipes for water absorption, or various industrial parts that are columnar or cylindrical (for example, coating for insulation treatment of armatures that constitute rotating parts of electric motors) It can be suitably applied to.

  As mentioned above, although it demonstrated per embodiment of this invention, this invention is not limited to this, For example, the following deformation | transformation embodiment can be taken.

  (1) In said embodiment, the induction heating coils 21 and 41 and the to-be-coated object 90 arrange | positioned facing this induction heating coil 21 showed all the examples placed vertically. Instead of this, the induction heating coils 21 and 41 and the workpiece 90 may be arranged in the horizontal direction.

  (2) In the above embodiment, the upper surface of the fluid tank 31 is opened. Instead of this, a lid for closing the upper surface opening of the fluid tank 31 is provided, and an air vent is provided at an appropriate position of the lid. An opening may be provided, and air may be discharged from the opening through a predetermined filter. According to this modified embodiment, scattering of the powder coating material 50 flowing in the fluid tank 31 can be prevented.

  (3) In the above-described embodiment, only one induction heating coil 21 is employed. However, a plurality of induction heating coils 21 may be arranged around the workpiece 90.

  (4) In the above embodiment, the post-heating device 40 different from the pre-heating device 20 is employed in the post-heating step P3. However, the configuration of the pre-heating device 20 and the post-heating device 40 is exactly the same. Therefore, the preheating device 20 may be used for the post-heating process in the post-heating step P3 without providing the post-heating device 40. By doing so, it is possible to contribute to a reduction in equipment costs by the amount that the post-heating device 40 need not be provided.

  (5) In the above-described embodiment, the object 90 is subjected to the induction heating treatment as the final finish in the post-heating step P3 following the fluid immersion step P2, but in the fluid immersion step P2. When sufficiently adequate coating is performed, the post heating process P3 may be omitted.

P1 Preheating process P2 Fluid immersion process P3 Post heating process 1 Citation 10 Powder coating apparatus 20 Preheating apparatus 21 Induction heating coil 211 Magnetic core 212 Winding 22 High frequency oscillator 23 Rotating mechanism 231 Drive motor 232 Gear mechanism 30 Fluid coating apparatus DESCRIPTION OF SYMBOLS 31 Flow tank 311 Air intake port 312 Filter 32 Blower 33 Flow immersion chamber 40 Post-heating apparatus 41 Induction heating coil 411 Magnetic core 412 Winding 42 High frequency oscillator 43 Rotating mechanism 431 Drive motor 432 Gear mechanism 50 Powder coating material 90 Object 91 Body 911 Surface layer 92 Shaft body

Claims (4)

A rotating mechanism for rotating a workpiece made of a magnetic material having a cylindrical outer peripheral surface around its axis;
Induction heating, in which magnetic flux can be applied to a part of the outer peripheral surface of the object to be coated over the entire length in the axial direction, and the object to be coated being rotated by the rotating mechanism is subjected to induction heating treatment. Means,
A fluidized tank filled with a powder coating material and into which the object to be coated heated by the induction heating means is inserted;
A powder coating apparatus comprising:   The induction heating means includes: a magnetic core disposed opposite to the outer peripheral surface of the object to be coated and parallel to the axial direction of the object to be coated; and a winding wound around the magnetic core. The powder coating apparatus according to claim 1, wherein the powder coating apparatus includes an induction heating coil. A step of rotating a workpiece made of a magnetic material having a cylindrical outer peripheral surface around its axis;
A step of causing magnetic flux to act on a part of the outer peripheral surface of the object to be rotated in a rotating state over the entire length in the axial direction thereof, and induction heating the object to be coated;
A step of immersing the induction-heated object to be coated in a fluidized tank in which the powder coating is flowing and attaching the powder coating to the peripheral surface;
A powder coating method comprising: Rotating the treated object to which the powder coating material is attached around its axis;
A step of inducing a magnetic flux to act on a part of the outer peripheral surface of the treated object in a rotating state over the entire length in the axial direction thereof, and induction heating the treated object;
The powder coating method according to claim 3, further comprising:

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