JP4193953B2 - Electrostatic coating method for metal cylinders - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of electrostatic coating on a substantially cylindrical metal cylinder formed by laminating metal plates, and in particular, a rotor core or stator core used in rotating electrical equipment such as motors and generators. The present invention relates to an electrostatic coating method suitable for insulating coating.
[0002]
[Prior art]
Rotor cores or stator cores used in rotating electrical equipment such as motors and generators are formed by laminating a plurality of magnetic metal pieces made of silicon steel plates, etc. A coil insertion slot is formed. In the case of a stator core, a coil insertion slot is formed inside.
[0003]
FIG. 5 shows an example of the rotor core. The rotor core 10 is configured by laminating a plurality of magnetic metal pieces 15. The rotor core 10 has a shaft hole 13 at the center, and slots 11 along the axial direction are formed at predetermined intervals in the circumferential direction on the outer periphery. Between the slots 11, external teeth 12 for winding the coil are formed. In addition, 14 in the figure has shown the corner | angular part of the inner periphery of an end surface.
[0004]
Electrodeposition coating and electrostatic coating are known as methods for coating a metal cylinder formed by laminating metal plates such as the rotor core. However, electrodeposition coating has a problem that the equipment is large and the maintenance of the machine is difficult, and the production cost is generally increased.
[0005]
On the other hand, the electrostatic coating uses an electrostatic coating apparatus having a fluid tank having an upper surface opened and a perforated plate disposed on the lower surface, an electrode attached to the perforated plate, and a pressure equalizing chamber surrounding the lower space of the fluid tank. The resin powder is supplied to the fluid tank, the pressure air is introduced into the pressure equalizing chamber and ejected through the perforated plate, the resin powder in the fluid tank is fluidized, and positive or negative static electricity is applied to the electrode. The resin powder is charged to support the object to be coated with the opposite static electricity to the electrode above the fluid tank, and the resin powder adheres to the surface of the object to be coated. By doing so, the adhered resin powder is fused to form a coating film.
[0006]
[Problems to be solved by the invention]
However, when the entire surface is coated by electrostatic coating on a metal cylinder formed by laminating metal plates such as a rotor core, heating is performed when forming a coating film by fusing the resin powder. The air between the laminated metal plates expands, and air escape traces (holes) are generated on the surface of the coating film. When such holes are present, there is a problem that insulation withstand voltage and rust prevention cannot be ensured.
[0007]
In order to solve this problem, the present inventor disclosed in Japanese Patent Application No. 10-152720 (an unpublished application at the time of filing of the present application) an inner periphery of a metal cylindrical body made of a laminated iron core during electrostatic coating. Alternatively, the electrode shaft is brought into contact with the outer periphery along the axial direction, leaving the portion where the electrode shaft is in contact as an unpainted portion, and by painting it as an escape route for the expanded air between the laminates when heated. A coating method is proposed in which the generation of holes on the film surface is prevented, and then a room temperature curable resin coating is applied to the unpainted portion.
[0008]
However, it has been found that the above-described coating method also has the following problems. That is, when the unpainted portion of the inner periphery of the shaft hole is painted using a normal air spray gun, the coating film thickness becomes extremely thin, so that complete rust prevention is difficult.
[0009]
On the other hand, when trying to increase the coating film thickness for complete rust prevention, the viscosity of the coating material used is quite low, so that the coating material 33 is dripped as shown in FIG. there were. In particular, there is a problem that the paint 33 is not sufficiently adhered to a portion located at the inner peripheral corner portion 14 of the upper end surface of the iron core 10 and rust is generated in that portion. In the figure, 34 is a coating film formed by electrostatic coating.
[0010]
Conversely, if the viscosity of the paint is increased, the coating film thickness can be increased and the sagging of the paint can be prevented, but there is a problem that uneven coating tends to occur. In particular, as shown in FIG. 7, in the case of an object having a complicated shape having a groove 52 or the like on the inner periphery 54 of a cylindrical body 51 made of a laminated metal plate, the inside of the groove 52 is filled with a paint 53 and uniform. It was difficult to form a coating film with a sufficient thickness.
[0011]
Accordingly, an object of the present invention is an electrostatic coating method for a substantially cylindrical metal cylinder formed by laminating metal plates, such as a rotor core and a stator core, and includes a pin on a coating film. An object of the present invention is to provide a method capable of uniformly painting the inner periphery without generating holes or the like.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the electrostatic coating method of the present invention is supported on the inner periphery of a metal cylinder in the electrostatic coating method on a substantially cylindrical metal cylinder formed by laminating metal plates. A rod is inserted and abutted along the axial direction to support the metal cylinder, and the metal cylinder is disposed above the fluidized resin powder tank, and the metal cylinder is rotated in this state. A first coating step of electrostatically adhering the resin powder to the surface of the metal cylinder, and then heat-sealing the adhering resin powder to form a coating film; A liquid resin composition of room temperature curing type is applied to an unpainted portion in contact with a peripheral support rod, and a gas is blown onto the inner periphery of the metal cylinder, so that the inner periphery of the metal cylinder is applied. The applied liquid resin composition is uniformly extended, and then the liquid resin composition is hardened. By, characterized in that it comprises a second coating step of forming a coating film.
[0013]
According to the present invention, when electrostatically coating the metal cylinder in the first coating process, the resin powder does not adhere to the portion of the metal cylinder that is in contact with the support rod on the inner periphery. For this reason, when the coated resin powder is heat-fused to form a coating film, the unpainted portion serves as an air escape path between the laminated plates expanded by heating, preventing the occurrence of holes on the surface of the coated film. Can do.
[0014]
Next, as a second coating step, a room temperature curable liquid resin composition is applied to an unpainted portion of the inner periphery of the metal cylindrical body, and the liquid resin composition is uniformly extended by blowing gas, and then cured. By forming the coating film, a coating film having a predetermined thickness can be obtained without sagging or uneven coating.
[0015]
In the present invention, in the second coating step, with a pair of jigs having openings adapted to the inner periphery of the metal cylinder, the metal cylinder is supported with both end faces of the metal cylinder sandwiched therebetween, It is preferable to apply the liquid resin composition to the inner periphery of the metal cylinder and to spray the gas to the inner periphery of the metal cylinder while rotating the metal cylinder together with the jig.
[0016]
This prevents excessive paint from adhering to the end face of the metal cylinder, secures the film thickness of the inner peripheral corner of the upper end face of the metal cylinder for the upper jig, and the metal cylinder for the lower jig. The effect of eliminating the liquid pool in the lower inner circumference of the body is brought about.
[0017]
In the second coating step, an ultraviolet curable resin composition is used as the liquid resin composition, and the ultraviolet curable resin composition is applied to an unpainted portion on the inner periphery of the metal cylindrical body. After the gas spraying, it is desirable to cure the ultraviolet curable resin composition by irradiating the inner circumference of the metal cylinder with ultraviolet rays.
[0018]
Accordingly, the resin composition applied to the inner periphery of the metal cylindrical body can be cured by irradiating ultraviolet rays, so that heating is not required for curing the resin, and the resin composition can be cured instantaneously and uniformly. it can.
[0019]
Furthermore, it is preferable that the metal cylindrical body is a stator core or a rotor core used in a rotating electrical apparatus. Since these iron cores are made of a laminate of metal plates and require more complete insulation and rust prevention, the merit of applying the method of the present invention is particularly great.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
1-3 show one embodiment of the electrostatic coating method of the present invention, FIG. 1 is a front sectional view of an electrostatic coating apparatus used in the method, and FIG. 2 is a schematic diagram showing a second coating step of the method. Explanatory drawing and FIG. 3 are principal part expanded sectional views which show the state which apply | coated the resin composition in the 2nd coating process.
[0021]
As shown in FIG. 1, the electrostatic powder coating apparatus includes a frame 22 having an upper surface opened, a porous plate 24 covering the lower surface, and a casing 25 disposed on the lower surface of the porous plate 24. The fluid flow tank 23 into which the resin powder P is supplied and filled is formed by the frame body 22 and the porous plate 24, and the pressure equalizing chamber 26 is formed by the porous plate 24 and the housing 25. An air supply hole 27 for introducing the pressurized air AR is provided at a side portion of the pressure equalizing chamber 26. A plurality of electrodes 28 are attached to the porous plate 24, whereby positive or negative static electricity is applied to the resin powder P.
[0022]
A metal cylinder 16 formed by laminating metal plates such as a rotor core, which is an object to be coated, has an electrode shaft / support bar 21 inserted into the inner periphery of the shaft hole, and the axial direction is horizontal above the fluid tank 23. It is supported and arranged toward. Note that one end surface of the metal cylinder 16 is engaged with the step portion 21 a of the electrode shaft / support bar 21, and the other end surface is pressed by the cap 29, and is fixed to the electrode shaft / support bar 21. . The electrode shaft / support bar 21 is applied with a voltage opposite to that of the electrode 28 of the perforated plate 24 and is rotated by a driving source (not shown).
[0023]
Therefore, the first coating process using the electrostatic coating apparatus will be described. First, the pressure air AR is introduced into the pressure equalizing chamber 26 from the air supply hole 27 and is ejected through the perforated plate 24, whereby the fluid inside the fluid tank 23. The resin powder P is fluidized. Further, the electrode shaft / support bar 21 is rotated to gently rotate the metal cylinder 16.
[0024]
When a predetermined voltage is applied between the electrode shaft / support bar 21 and the electrode 28 in this state, the resin powder P is positively or negatively charged and floats by the electrode 28, and is passed through the electrode shaft / support bar 21. It adheres electrostatically to the metal cylinder 16 to which the opposite voltage is applied.
[0025]
In this case, the resin powder P that rises from the fluid tank 23 and flows upward includes (1) one that adheres to the outer periphery and slot of the metal cylinder 16 and (2) one that adheres to the end face of the metal cylinder 16. However, since the electrode shaft / support bar 21 is in contact with the inner periphery of the shaft hole of the metal cylindrical body 16, the resin powder does not adhere.
[0026]
In the above, a scraping body of resin powder is provided in the vicinity of the outer periphery of the metal cylindrical body 16, and the excess resin powder P adhering to the outer periphery of the metal cylindrical body 16 is scraped off. The resin powder P having an appropriate thickness may be always attached to the outer periphery of the 16. Further, as the resin powder P, for example, known powder coating powders such as polyester and epoxy are used.
[0027]
In this way, after the resin powder P is adhered to a portion other than the inner periphery of the shaft hole of the metal cylinder 16, the metal cylinder 16 is removed from the electrode shaft / support bar 21, or the metal cylinder 16 is supported as an electrode shaft. While being supported by the rod 21, it is put into a high-frequency heating furnace or a hot air drying furnace and heated to fuse the resin powder P to form a coating film.
[0028]
Since the metal cylinder 16 is formed by laminating metal plates, the air between the laminate plates expands during the heating and tends to flow out as bubbles, but as described above, the metal cylinder 16 Is supported by the electrode shaft / support bar 21 inserted in the shaft hole, and the resin powder P is not attached to the inner periphery of the shaft hole in contact with the electrode shaft / support bar 21, This expanded air can prevent the electrode shaft / support bar 21 from coming into contact with the inner peripheral portion where the resin powder P has not adhered and pinholes or the like in the coating film.
[0029]
Next, the second coating step will be described. As shown in FIG. 2 (a), both end surfaces of the metal cylindrical body 16 in which the coating film 34 is formed on the portion other than the inner periphery of the shaft hole in the first coating step. Is sandwiched and supported by a pair of jigs 32a and 32b having an opening adapted to the inner periphery of the metal cylinder 16, and the metal cylinder 16 is rotated while rotating the metal cylinder 16 together with the jig. The paint supply nozzle 31 is inserted into the shaft hole, and a room temperature curable liquid resin composition, in this embodiment, an ultraviolet curable liquid resin composition 33 is applied to the inner periphery thereof. The metal cylinder 16 may be fixed and the paint supply nozzle 31 may be rotated.
[0030]
Then, as shown in FIG. 2 (b), a gas such as air or nitrogen is blown from the gas supply nozzle 35 to the inner periphery of the metal cylindrical body 16 to uniformly extend the ultraviolet curable liquid resin composition 33. .
[0031]
At this time, as shown in FIG. 3, the liquid resin composition is placed on the end surface of the metal cylindrical body 16 by being sandwiched and supported by a pair of jigs 32 a and 32 b having an opening adapted to the inner periphery of the metal cylindrical body 16. It is possible to prevent 33 from adhering excessively. Further, the upper jig 32a secures the film thickness of the inner peripheral corner portion 44 on the upper end surface of the metal cylindrical body 16, and the lower jig 32b has an effect of eliminating the liquid pool in the lower inner circumference of the metal cylindrical body 16. Brought about.
[0032]
Further, by blowing gas from the gas supply nozzle 35 to the inner periphery of the metal cylindrical body 16, as shown in FIG. 4, even when a groove 42 or the like is formed in the inner periphery 43 of the metal cylindrical body 16, The resin composition 33 can be applied with a uniform thickness. Furthermore, the coating film thickness on the inner periphery of the shaft hole can be controlled by changing the gas spray pressure.
[0033]
In this way, after the ultraviolet curable liquid resin composition 33 is applied to the inner periphery of the metal cylindrical body 16, the metal cylindrical body 16 is supported by the support tool 37 as shown in FIG. While rotating the metal cylindrical body 16, the ultraviolet irradiation device 36 irradiates the inner peripheral surface of the metal cylindrical body 16 with ultraviolet UV. Thereby, the liquid resin composition 33 applied to the inner periphery of the metal cylindrical body 16 is cured, and a coating film 33a having a uniform film thickness is formed.
[0034]
The room temperature curable liquid resin composition is not limited to the ultraviolet curable resin composition as described above, and a solvent type resin composition that is cured by drying at room temperature can also be used.
[0035]
【The invention's effect】
As described above, according to the electrostatic coating method of the present invention, when electrostatic coating is performed in the first coating process, the resin powder does not adhere to the portion where the support rod on the inner periphery of the metal cylindrical body abuts. For this reason, when the coated resin powder is heat-fused to form a coating film, the unpainted portion serves as an air escape path between the laminated plates expanded by heating, thereby preventing the generation of holes on the surface of the coated film. it can.
[0036]
In addition, since the room temperature curing type liquid resin composition is applied to the unpainted portion of the inner periphery of the metal cylindrical body in the second coating step, the gas is blown to uniformly extend the liquid resin composition. It is possible to form a coating having a uniform thickness without sagging or uneven coating.
[0037]
Therefore, it is possible to form a coating film with excellent insulation and rust prevention, and electrostatic coating can be applied to parts that require dielectric strength after winding, such as rotor cores and stator cores. It was.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing an example of an electrostatic coating apparatus used in a first coating process of an electrostatic coating method of the present invention.
FIG. 2 is a schematic explanatory view showing an example of a second coating process of the electrostatic coating method of the present invention.
FIG. 3 is an enlarged cross-sectional view of a main part showing a state where a resin composition is applied in the second coating step of the electrostatic coating method of the present invention.
FIG. 4 is a plan view showing an example when a cylindrical body having a groove on the inner periphery is coated in the second coating step of the electrostatic coating method of the present invention.
FIG. 5 is a perspective view showing a rotor core as an example of a metal cylinder formed by stacking metal plates.
FIG. 6 is a cross-sectional view showing a state in which a room temperature curable liquid resin is applied to the inner periphery of a metal cylinder by a conventional method.
FIG. 7 is a cross-sectional view showing a state in which a room temperature curable liquid resin is applied to the inner periphery of a metal cylinder having grooves on the inner periphery by a conventional method.
[Explanation of symbols]
16 Metal cylindrical body 21 Ground electrode shaft / support rod 22 Frame body 23 Fluid tank 24 Perforated plate 25 Housing 26 Pressure equalizing chamber 27 Air supply hole 28 Electrode 31 Paint supply nozzle 32a Upper jig 32b Lower jig 33 UV curable liquid Resin composition 34 Coating film 35 formed by electrostatic coating Gas supply nozzle 36 Ultraviolet irradiation device P Resin powder

Claims (4)

In the method of electrostatic coating on a metal cylinder having a substantially cylindrical shape formed by laminating metal plates,
Supporting the metal cylinder by inserting a support rod into the inner circumference of the metal cylinder and bringing it into contact along the axial direction, and placing the metal cylinder above the resin powder flow tank, In this state, the resin powder is electrostatically attached to the surface of the metal cylinder while rotating the metal cylinder, and then the attached resin powder is heat-fused to form a coating film. Process,
By applying a room-temperature curable liquid resin composition to the unpainted portion of the inner periphery of the metal cylinder that is in contact with the support rod, and blowing a gas on the inner periphery of the metal cylinder, A second coating step of uniformly extending the liquid resin composition adhering to the inner periphery of the metal cylinder and then curing the liquid resin composition to form a coating film. Electrostatic coating method. In the second coating step, a pair of jigs having an opening that fits the inner periphery of the metal cylinder body supports the metal cylinder body with both end faces of the metal cylinder body sandwiched between the jig and the jig. The electrostatic coating method for a metal cylinder according to claim 1, wherein the liquid resin composition is applied to the inner periphery of the metal cylinder and gas is sprayed to the inner periphery of the metal cylinder while rotating the metal cylinder. . In the second coating step, an ultraviolet curable resin composition is used as the liquid resin composition, the ultraviolet curable resin composition is applied to an unpainted portion on the inner periphery of the metal cylindrical body, and the gas is sprayed. 3. The method of electrostatic coating of a metal cylinder according to claim 1 or 2, wherein the ultraviolet curable resin composition is cured by irradiating an inner periphery of the metal cylinder with ultraviolet rays after performing the step. The electrostatic coating method for a metal cylinder according to any one of claims 1 to 3, wherein the metal cylinder is a stator core or a rotor core used in a rotating electrical apparatus.

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