JP2005066598A - Manufacturing method of painted product and painted product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a coating film having a uniform thickness even on a rugged part such as a tooth part of a coated product (gears, etc.) even if it is a thick film.
SOLUTION: In step I, a tooth layer 2 of gears or spline shafts 1 is subjected to electrostatic powder coating to form a primary powder layer 3a. In step II, the powder layer of the tooth tip portion 2a is formed. After scraping and removing by suction, in step III, electrostatic powder coating is applied over the entire surface to form the secondary powder layer 3b, and in step IV, the coating film 5 is formed by induction heating. With such a method, a coated product (coated gears or the like) in which the coating film 5 having a uniform thickness is formed on the uneven portion can be obtained. In electrostatic powder coating, for example, a powder coating based on a thermoplastic resin such as nylon resin can be used. The thickness of the coating film may be about 150 to 200 μm. Ratio of the amount of deposition of the primary powder layer (g / m ²⁾ and the adhesion amount of the secondary powder layer (g / m ²⁾ for, when the total adhesion amount of the powder layer was 100, the former / the latter = It is about 20/80 to 80/20.
[Selection] Figure 1

Description

  The present invention relates to a method for forming a coating film with a uniform thickness on a metal article to be coated having an uneven surface, particularly gears and spline shafts, a method for producing a coated article, and a coating apparatus.

  Resin coatings are formed on metal spline shafts and metal gears for transmitting power in order to impart wear resistance, cushioning properties, soundproofing or silencing properties. When this resin film is formed by the fluidized immersion method, the heat capacity of the article to be coated (gears, etc.) is large, resulting in an increase in the thickness of the coating film. It cannot be formed. Therefore, for example, after coating to a film thickness of 300 μm or more (particularly about 500 to 600 μm) by the fluidized dipping method, a coating film having a film thickness of about 200 ± 20 μm is formed by machining. However, in this method, since it is necessary to machine each of the crests and troughs of each tooth of the gears, not only the production efficiency is reduced but also the cost is increased.

  On the other hand, gears and spline shafts are electrostatically powder coated to form a powder layer and heated to form a coating film. However, in this method, as the gears and spline shafts increase in size, it takes time to raise the material temperature in the heating furnace, and in the heating furnace, the temperature rises from the surface of the powder layer. It is difficult to form a coating film having a large thickness because the coating film is dropped or pinholes are generated.

  In order to solve the problem caused by the heating furnace, a coating film is also formed by combining electrostatic powder coating and high-frequency induction heating. For example, Japanese Patent Laid-Open No. 10-296182 discloses a resin powder layer (thermosetting resin powder such as epoxy resin) formed on a continuous metal body such as a metal wire, a metal tube, or a metal rod by electrostatic powder coating. Layer), the inner layer of the powder layer is fused by induction heating, a semi-fused resin layer is formed on the surface layer, and further heated to form a completely fused resin coating film. ing. In Japanese Patent No. 2725168, a steel stranded wire obtained by twisting a plurality of side wires around a core wire is temporarily released into individual wires, and resin powder is attached to the core wire and each side wire. A method for producing an anticorrosion-coated steel stranded wire that is heated in the process of retwisting to form an incompletely cured coating layer between the outer periphery and the core wire and the side wire, and the stranded steel stranded wire is heated and completely cured. It is disclosed.

  Further, Japanese Patent Publication No. 56-34153 discloses a powder coating while rotating an article to be coated having an uneven surface in an electrostatic fluidized immersion bath in which a powder coating of 100 to 250 mesh is fluidized and charged. The paint is adhered to the article to be coated, the powder paint on the unnecessary portion of the convex portion is removed by the suction means with the brush while rotating the article to be coated, and the article to be coated is heated by induction heating of about 100 to 200 KHz. A method of forming an insulating coating that heats to melt / adhere the powder coating is disclosed. In this method, electrostatic fluid immersion using a powder paint (epoxy resin paint) of 100 to 250 mesh is used in order to ensure electrical insulation in concave portions such as a rotor of a motor and to avoid formation of a coating film on the convex portions. In addition to forming a powder layer having a large film thickness by the method, a thick film is formed in the concave portion by removing the powder layer of the convex portion that does not require a coating film.

However, the electrostatic powder coating method and electrostatic fluid immersion method use charged powder particles, which inevitably increases the film thickness at the crest (top) of the tooth, and the charged particle electrical Due to the repulsion, the film thickness at the valleys and side walls is reduced. In particular, if the convex powder layer is removed by the suction means with the brush while rotating the article to be coated, the convex powder layer may fall into the concave portion. Therefore, even if induction heating is used, a product to be coated (such as gears and spline shaft teeth) cannot be coated with a uniform coating film.
JP-A-10-296182 Japanese Patent Publication No.56-34153

  Accordingly, an object of the present invention is to provide a manufacturing method and a coating apparatus for a coated product (gears, etc.) in which uneven portions such as tooth portions are coated with a coating film having a uniform thickness even if it is a thick film. is there.

  Another object of the present invention is to provide a method for manufacturing a coated product (such as gears) and a coating apparatus that have high sound deadening and wear resistance and a uniform film thickness distribution.

  Still another object of the present invention is to provide a method capable of forming a coating film having a uniform thickness even on a rugged portion such as a tooth portion, even if it is a thick film, even if the film thickness is large. Furthermore, by providing the dimensions of the article to be coated in advance, there is provided a method for producing a coated article that allows the dimensions of the coated article to be a predetermined dimension even if the thickness of the coating film is different in uneven portions such as teeth. There is to do.

  As a result of intensive studies to achieve the above-mentioned problems, the inventors of the present invention, as described above, in the electrostatic powder coating of gears, the thickness of the coating on the tooth tip portion is larger than that on the tooth valley portion and the side wall. By taking advantage of the increase in size, electrostatic powder coating is applied to the entire surface of the article to be coated (especially gears and spline shafts), and then the powder layer of the convex part (tooth tip part) is removed. It has been found that when an electrostatic powder coating is applied to the entire surface, a powder layer having a uniform thickness can be formed, and a coating film having a uniform thickness can be formed by heating from the inside of the powder layer by induction heating, thereby completing the present invention.

  That is, in the method for manufacturing a coated product according to the present invention, an undercoat is formed on the surface of a part to be coated that has an uneven portion for transmitting power, and powder is electrostatically applied to the part to be coated on which the undercoat is formed. After the adhesion, the part to be coated is induction-heated to melt the powder and adhere a coating film substantially free of bubbles to the part to be coated.

  Further, in one embodiment, an electrostatic powder coating is applied to an article to be coated (such as gears) having a concavo-convex portion to form a primary powder layer, and a powder layer of a convex portion (such as a tooth tip portion) is predetermined. After removing with the thickness of, electrostatic powder coating is applied over the entire surface to form a secondary powder layer, and a coating film is formed by heating by induction heating. By such a method, a coated product (coated gears, etc.) in which a coating film having a uniform thickness is formed on the uneven portion of the coated product can be obtained. Therefore, the method of the present embodiment is also useful as a method of forming a coating film having a uniform thickness on the unevenness (particularly the tooth portion) of the article to be coated (gears, etc.).

  Examples of the article to be coated having the uneven surface include various gears and spline shafts. In the electrostatic powder coating, a powder coating material having an average particle diameter of 10 to 70 μm (for example, a thermoplastic resin-based powder coating material such as nylon resin) can be used. As a means for removing the powder layer of the convex part (tooth tip part), a scraper means for scraping the powder layer can be used, and this scraper means may be movable in the axial direction of the article to be coated. In order to prevent the powder scraped off by this scraper means from dropping off and adhering to the bottom and side walls (dent valleys and side walls) of the recess, the scraper means normally sucks the scraped powder. A suction means for removing is provided.

The thickness of the coating film formed by electromagnetic induction heating can be selected according to the type of article to be coated, and in the coating of gears and spline shafts, a coating film of about 150 to 200 μm may be formed. As described above, the amount of powder coating adhered to the convex portion is larger than that of the concave portion and the concave portion side wall. Therefore, in order to form a coating film having a uniform thickness, when the total adhesion amount (g / m ² ) of the powder layer is 100, the adhesion amount (g / m ² ) of the primary powder layer and the secondary adhesion amount The ratio with the adhesion amount (g / m ² ) of the powder layer is usually about the former / the latter = 20/80 to 80/20.

  The coating apparatus of the present embodiment performs electrostatic powder coating on an object to be coated (gears, etc.) having an uneven surface, and forms a primary powder layer on the entire surface of the object to be coated (gears, etc.). Coating means, scraper means for removing the powder layer of the convex parts (such as gear tip parts) of the article to be coated, and powder of the convex parts (tooth tip part etc.) by this scraper means A coating means for forming a secondary powder layer on the entire surface of the article to be coated (gears, etc.) by electrostatic powder coating on the article to be coated (gears, etc.) from which the layer has been removed, and a primary And an induction heating means for heating the powder layer and the secondary powder layer. In powder coating, when the article to be coated is gears, the gears and spline shafts can be primary and secondary coated while rotating along the central axis.

  Also, in one embodiment of the method for producing a coated product, after the powder is electrostatically attached to a part to be coated having an uneven portion, the powder is melted by induction heating the part to be coated. A coating film is adhered to the article to be coated.

  In this embodiment, since the powder is melted by inductively heating the part to be coated in a state where the powder is electrostatically attached to the part to be coated having the concavo-convex portion, the powder layer is formed on the inner side. It will be heated by the parts to be painted. For this reason, it becomes easy for air bubbles to escape from the powder melted on the inside to the outside, and the bubbles can be prevented from being mixed into the coating film.

  Further, in the method for manufacturing a coated product according to an embodiment, the thickness of the powder adhered to the product to be coated is large and small so that the size of the coated product becomes a desired outer diameter according to the thickness. In addition, the dimensions of the part to be painted are set in advance.

  In this embodiment, the dimension of the part to be coated is set in advance according to the thickness of the powder adhered to the article to be coated so that the dimension of the coated article has a desired outer diameter. Therefore, secondary finishing (for example, broaching) is unnecessary, and the processing cost can be reduced.

  Moreover, in the manufacturing method of the coated article of one Embodiment, the film thickness of the said coating film was 100 micrometers thru | or 250 micrometers.

  In this embodiment, the coating film has a thickness of 100 μm to 250 μm. As a result, the operating sound (sounding sound) of the coated product can be reduced to a predetermined value or less, and the amount of wear can be reduced. When the film thickness is less than 100 μm, the operating sound (sounding sound) exceeds a predetermined value. On the other hand, even if the film thickness exceeds 250 μm, the operating noise does not decrease so much and the wear amount increases.

  Further, the coated product of one embodiment has a predetermined outer diameter dimension, a coating film having a predetermined film thickness is attached to a part to be coated, and substantially no bubbles are present in the coating film. It is said. In this embodiment, the coating film having a predetermined film thickness attached to the part to be coated includes the case where it is partially formed on the surface of the part to be coated and the case where it is formed on the entire surface.

  In this embodiment, since a coating film having a predetermined film thickness is attached to the painted part and there are substantially no bubbles in the coating film, the coating quality is improved.

  In one embodiment, the coating film is obtained by melting powder.

  In this embodiment, the coating film is substantially free of bubbles, and the coating film is obtained by melting powder, so that the coating film is thin and has excellent durability.

  Moreover, in the coated product of one Embodiment, the thickness of the said coating film has a size, and the dimension of the said to-be-coated part is set according to the thickness.

  In this embodiment, since the dimension of the part to be coated is set according to the thickness of the coating film, a secondary finishing process (for example, broaching process) is unnecessary, and the processing cost is reduced. it can.

  In one embodiment, the coating film has a thickness of 100 μm to 250 μm.

  In this embodiment, since the film thickness of the coating film is 100 μm to 250 μm, the operating sound (sounding sound) due to the coated product can be reduced to a predetermined value or less, and the wear amount can be reduced. When the film thickness is less than 100 μm, the operating sound (sounding sound) exceeds a predetermined value. On the other hand, even if the film thickness exceeds 250 μm, the operating noise does not decrease so much and the wear amount increases.

  In this invention, since the powder is melted by electromagnetic induction heating of the part to be coated in a state in which the powder is electrostatically attached to the part to be coated having the concavo-convex part, It will be heated by the parts to be painted. For this reason, it becomes easy for air bubbles to escape from the powder melted on the inside to the outside, and the bubbles can be prevented from being mixed into the coating film.

  Also, in the method for manufacturing a coated product according to one embodiment, after forming the primary powder layer, the convex powder layer is removed, the secondary powder layer is formed, and the coating film is formed by induction heating. Even if it is a thick film, the concavo-convex part can be covered with a coating film having a uniform thickness. In addition, when a nylon-based resin-based powder coating is used, it is possible to obtain a coated product (such as gears) that has high sound deadening and wear resistance and a uniform film thickness distribution at the uneven portions.

  Further, in the method for manufacturing a coated product according to one embodiment, the size of the part to be coated is small or large in thickness of the powder adhered to the coated product so that the size of the coated product has a desired outer diameter. Therefore, a secondary finishing process (for example, broaching process) is unnecessary, and the processing cost can be reduced.

  Moreover, in the manufacturing method of the coated article of one Embodiment, the film thickness of the said coating film was 100 micrometers thru | or 250 micrometers. As a result, the operating sound (sounding sound) of the coated product can be reduced to a predetermined value or less, and the amount of wear can be reduced. When the film thickness is less than 100 μm, the operating sound (sounding sound) exceeds a predetermined value. On the other hand, even if the film thickness exceeds 250 μm, the operating noise does not decrease so much and the wear amount increases.

  In addition, the coated product of one embodiment has a coating film with a predetermined film thickness attached to a painted part, and the coating quality is improved because there is substantially no air bubbles in the coating film.

  In the coated product of one embodiment, since the coating film is obtained by melting powder, the coating film is thin and has excellent durability.

  In addition, in the coated product of one embodiment, the thickness of the coating film is large and small, and the dimension of the part to be coated is set according to the thickness. Machining) is unnecessary, and machining costs can be reduced.

  Moreover, in the coated product of one embodiment, since the film thickness of the coating film is 100 μm to 250 μm, the operating sound (sounding sound) by this coated product can be reduced to a predetermined value or less, and the amount of wear is reduced. be able to. When the film thickness is less than 100 μm, the operating sound (sounding sound) exceeds a predetermined value. On the other hand, even if the film thickness exceeds 250 μm, the operating noise does not decrease so much and the wear amount increases.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a process diagram showing an example of a process of painting teeth of a spline shaft, FIG. 2 is a schematic perspective view showing a scraped state by a scraper means, and FIG. 3 is a schematic side view showing a spline shaft.

  In the present specification, “gears” and “spline shafts” may be simply referred to as “gears”.

[Formation process of primary powder layer]
In the step (I) of forming the primary powder layer, electrostatic powder coating is performed to form the primary powder layer on the surface of the article to be coated. In this example, first, the spline shaft 1 is pre-processed and primer-treated, and electrostatic powder coating is performed using an electrostatic spray gun as a coating means while rotating the spline shaft 1 with the axis of the spline shaft 1 as a central axis. The primary powder layer made of a powder coating of nylon resin base on the entire surface of the tooth part (or key groove part) 2 of the spline shaft 1, that is, the tooth tip part 2a, the side part 2b and the bottom part 2c of the tooth part 2. 3a is formed.

  In addition, surface treatment such as blasting (shot blasting, etc.) as well as surface treatment such as degreasing, pickling, electrolytic treatment, anodizing, chemical conversion, etc. are included as pretreatment of metal coated products. It is. Primer treatment is performed by a conventional method, for example, an epoxy resin, a phenol resin, a polyvinyl acetal resin, an organic primer containing a resin or an oligomer such as rubber, an inorganic primer containing a metal component such as magnesium, manganese, or silicon, or a mixed primer thereof. It can be performed by applying to the article to be coated. Furthermore, if necessary, the non-coating part of the article to be coated may be masked and used for electrostatic powder coating.

  As the powder coating, powder particles based on various thermoplastic resins or thermosetting resins that can be used as electrostatic powder coatings can be used. Examples of the thermoplastic resin include olefin resins (ethylene or polypropylene olefin homo- or copolymers, ethylene-vinyl acetate copolymers, ethylene- (meth) acrylic acid or salts thereof (ionomers, etc.)). Copolymer, propylene-ethylene copolymer, propylene-based copolymer such as propylene-butene copolymer), acrylic resin, vinyl chloride resin, nylon resin, polyester resin and the like. Examples of the thermosetting resin include an epoxy resin, a thermosetting polyester resin, and a thermosetting acrylic resin. In thermosetting polyester resins and thermosetting acrylic resins, a thermosetting system may be formed in combination with a crosslinking agent or a curing agent [amino resin (such as melamine resin)].

  Preferred resins are thermoplastic resins (polyethylene resin, nylon resin, etc.), particularly nylon resins, which have high wear resistance, impact resistance and durability, and high adhesion to metals. Examples of nylon resins include 6-nylon, 66-nylon, 46-nylon, 610-nylon, 616-nylon, 11-nylon, 12-nylon and 13-nylon homopolymerized nylon, 6 / 12-nylon. And copolymer nylon such as 66/12 nylon. Preferred nylon-based resins include homo- or copolymer nylons containing at least one nylon component selected from 11-nylon and 12-nylon.

  The average particle diameter of the powder coating is usually smaller than the powder coating used in the fluid immersion method and the electrostatic fluid immersion method. For example, the average particle size is 5 to 100 μm (for example, 10 to 70 μm, particularly 10 to 50 μm). ) You can choose from a range of degrees.

  In such powder coating, due to electrostatic repulsion of the charged powder particles, the amount of powder adhering to the tooth tip portion 2a of the tooth portion 2 is larger than that of the side portion 2b and the bottom portion 2c of the tooth portion 2. Therefore, even if the primary powder layer 3a is heated by induction heating, a coating film having a uniform thickness cannot be formed. In particular, when the film thickness of the coating is increased, the amount of powder attached to the side portion 2b and the bottom portion 2c of the tooth portion 2 is larger than the amount of powder attached to the tooth tip portion 2a of the tooth portion 2. The film thickness uniformity is greatly reduced.

[Scraping process]
Therefore, in the present invention, in the scraping step (II), the primary powder layer 3a adhering to the tooth tip portion 2a of the tooth portion 2 is scraped by the scraper means (scraping means) 4 and the powder is transferred to the tooth portion. In order to prevent falling off and adhering to the side and bottom of the powder, the powder is sucked and removed while scraping. In this example, the scraper means 4 is curved in a semicircular arc shape corresponding to the degree of curvature of the tooth tip portion (outer peripheral surface) of the spline shaft 1, and has a doctor portion for scraping the powder layer 3a at the tip. The flaky base 4a provided, the slit 4b formed in the base 4a at a predetermined distance from the tip of the doctor part, and the suction part 4c for sucking the powder guided by the slit part from the rear part It consists of and.

  Further, the scraper means 4 is relatively movable in the axial direction of the spline shaft in order to efficiently remove the powder layers 3a of the plurality of tooth tip portions 2a.

  It is also conceivable to scrape off the powder layer using a brush. However, when a brush is used, the powder layer adhering to the tooth tip part falls off at the trough part of the tooth part, and the powder layer at the trough part is scraped off, so that the surface of the tooth part is uniform over the entire surface. Cannot be covered with a thick coating.

[Secondary powder layer forming process]
In the secondary powder layer forming step (III), after removing the powder layer 3a of the tooth tip portion 2a with a predetermined thickness, the spline shaft 1 as the article to be coated is used by using an electrostatic spray gun as a coating means. Is rotated along the central axis, and electrostatic powder coating is performed to form a secondary powder layer 3 b on the entire surface of the tooth portion 2 of the spline shaft 1. That is, the secondary powder layer 3b is mainly formed on the tooth tip part 2a of the tooth part 2 by secondary coating, and the primary powder layer 3a and the secondary powder layer 3b are formed on the valley part 2c and the side part 2b of the tooth part 2. Since the laminated powder layer composed of the next powder layer 3b is formed, the surface of the tooth portion 2 can be covered with a powder layer having a uniform thickness throughout.

  More specifically, if the same kind of powder coating is used, the thickness of the coating film usually corresponds to the amount of powder adhered and the thickness of the powder layer. Therefore, the amount of powder attached to the tooth tip portion of the tooth portion by primary coating is X1, and the amount of powder attached to the valley portion and side wall portion of the tooth portion is X2 (X1> X2, ΔX = X1-X2), When the amount of powder adhering to the tooth tip portion of the tooth portion by secondary coating is Y1, and the amount of powder adhering to the valley portion and side wall portion of the tooth portion is Y2 (Y1> Y2, ΔY = Y1-Y2), Since the primary powder layer of the tooth tip is scraped off, if the primary powder layer and the secondary powder layer are formed so as to satisfy the relational expression Y1 = X2 + Y2, a coating film having a uniform thickness can be obtained. It can be formed on the uneven surface of the tooth portion.

  The amount of powder adhering to the crests, troughs, and sidewalls of the irregularities varies depending on the shape of the irregularities (sharpness of the crests, depth of the troughs, spacing and pitch of the crests and troughs, etc.). To do. Therefore, by measuring the relationship between the adhesion amounts X and Y and the thickness of the coating film by experiment in advance, a coating film having a uniform thickness can be formed on the uneven surface according to the shape and type of the article to be coated.

The adhesion amount (g / m ² ) of the primary powder layer and the secondary powder layer is usually the total adhesion amount (g / m ² ) of the powder layer, depending on the shape and size of the uneven portion of the article to be coated. Is 100, the ratio of the primary powder layer adhesion amount (g / m ² ) and the secondary powder layer adhesion amount (g / m ² ) is the former / the latter = 20/80 to 80/20. (Preferably 25/75 to 75/25, more preferably 30/70 to 70/30).

  In addition, since the adhesion amount of the powder corresponds to the thickness of the powder layer and the thickness of the coating film, the relationship of the adhesion amount is not only the relationship between the thickness of the primary powder layer and the thickness of the secondary powder layer. The relationship between the thickness of the primary coating film by the primary powder layer and the thickness of the secondary coating film by the secondary powder layer is also supported.

  The adhesion amount of the powder layer can be easily controlled by the spray amount (discharge amount) and spray time of the powder coating material. For example, depending on the thickness of the final coating film, in the primary powder layer forming step, the powder coating is sprayed from the spray gun for about 5 to 60 seconds (for example, 10 to 40 seconds) and electrostatically coated to perform primary coating. The powder layer is formed, and in the secondary powder layer forming step, the powder coating is sprayed from the spray gun for about 5 to 180 seconds (for example, 10 to 120 seconds) and electrostatically coated to form the secondary powder layer. Can be formed.

[Induction heating process]
In the induction heating step (IV), the teeth of the spline shaft 1 are heated by electromagnetic induction heating by induction heating means (induction heating furnace, etc.), cooled by cooling, etc., and if necessary, masking of the non-coating part is removed. A thick coating film 5 of a nylon resin base is formed on the portion 2 with a uniform thickness. The coating film 5 is composed of a primary coating film 5a corresponding to the primary powder layer 3a and a secondary coating film 5b corresponding to the secondary powder layer 3b. In the spline shaft 1 thus obtained, by mounting the tooth portion 2 in the boss so as to be movable in the axial direction, it is possible to prevent generation of noise due to the meshing between the tooth portion 2 and the boss, and wear resistance and Corrosion resistance can be improved, and power can be transmitted reliably while silenced.

  By using the induction heating, the primary powder layer 3a and the secondary powder layer 3b are melted by heating from the inside of the powder layer, and the coating film 5 having a uniform thickness is formed on the tooth surface for a short time. It can be formed efficiently inside. That is, the powder coating based on nylon resin not only has a higher melting point or softening point than a resin such as an epoxy resin, but also has a high dielectric constant and a low electrical insulation and charge amount. Therefore, when the thickness of the powder layer is increased, the adhesive force due to static electricity is greatly reduced. And when such a powder layer is heated by a heating furnace, the surface of the powder layer melts, but the inside is in a powder state, so excessive heating is required and a coating film with a uniform thickness cannot be formed. .

  On the other hand, if induction heating is used, it can be heated and melted from the inside of the powder layer, and even if the thickness of the powder layer is large, a coating film having a uniform thickness can be formed efficiently. When applied to spline shafts and gears, for example, even if the thickness of the coating film is large, a coating film having a uniform thickness can be formed on the surface of the tooth portion by electrostatic powder coating. In particular, the thickness (average value) of the coating on the tooth tip, bottom and sides of gears and spline shafts is about 100 to 300 μm (especially 150 to 200 μm), and the coating on the tooth tip and the bottom In addition, coated gears and spline shafts having an average thickness difference of 0 to 40 μm (preferably 0 to 30 μm, particularly 0 to 20 μm) can be easily obtained.

  When a resin-based powder coating with a high electrical insulation and charge amount and a low melting point or softening point is used, a thick powder layer can be formed. The inside may melt and flow out, and it may be difficult to form a thick coating film. Even in such a case, a thick coating film can be formed according to the characteristics of the powder coating material by adjusting the heating conditions by induction heating means (induction heating furnace or the like).

  The induction heating can be performed using a conventional high-frequency induction heating apparatus, and the induction heating frequency is, for example, about 0.5 to 200 kHz (for example, 0.5 to 100 kHz, preferably 1 to 80 kHz, more preferably 5 to 70 kHz, especially 10 to 50 kHz).

  In the process of forming the primary powder layer and / or the secondary powder layer, in the article to be coated (gears, etc.) having a central axis, the coating is performed while rotating around the axis as the central axis in order to increase the coating efficiency. Although it is advantageous to coat the coated product with electrostatic powder, it is not always necessary to perform electrostatic coating while rotating. For example, in the case of a plate-shaped article having a recess or a groove, electrostatic coating may be performed while moving in the vertical direction or the horizontal direction along the longitudinal direction. Moreover, what is necessary is just to form a powder layer over the whole surface of the uneven | corrugated | grooved part of a to-be-coated article for a primary powder layer and / or a secondary powder layer. In the primary coating and the secondary coating, the same powder paint may be used, or different powder paints may be used.

  In the scraping process (or selective removal process) for removing the powder on the convex portion, various removing means, for example, a scraper, can be used depending on the type and shape of the article to be coated. The powder layer may be scraped off in a direction intersecting or orthogonal to the extending direction of the portion (such as the portion), but it is efficient to scrape along the convex portion (such as the tooth portion). The doctor part of the scraper can be formed of, for example, paper, plastic, rubber, metal, etc., and in order to prevent the adhesion of charged particles, it is formed of a non-chargeable substrate (or conductive substrate). It is advantageous.

  For example, if the scraper scrapes while moving the powder layer formed on the convex part of the cylindrical rod (article to be coated) having a groove extending in the axial direction in the axial direction, it conforms to the curvature of the outer periphery of the article to be coated. Can be used as a scraper with a curved hollow cylindrical doctor part, a scraper with a curved doctor part such as a semicircular arc shape or a 1/4 arc shape, and a prismatic rod with a groove in the axial direction. ), The scraper having an L-shaped or plate-like doctor portion can be used. Furthermore, when scraping off the powder layer formed on the convex part of the plate-like body having grooves, a scraper having a flat doctor part may be used.

  In the scraping step, it is not necessary to completely remove the convex powder layer, it may be removed at a predetermined thickness, and as long as the film thickness is not greatly affected, it is removed to some extent. Also good.

  In order to prevent the powder layer of the convex part from falling into the concave part in the removing step, it is preferable to remove the scraped powder by a suction means. This suction means usually includes a motor and a fan for sucking the powder scraped from the slit, and a filter for restricting the passage of the sucked powder.

  The primary powder layer forming process, the scraping process, the secondary powder layer forming process, and the induction heating process may be performed separately, but in order to increase productivity, they are performed in a continuous process and automated. Is advantageous. For example, (1) After forming the primary powder layer, the article to be coated is transferred, the powder layer of the convex part is scraped off in the scraping process, and transferred to the secondary powder layer forming process to electrostatically coat Then, a secondary powder layer may be formed, transferred to an induction heating process, and a coating film may be formed by induction heating. (2) After forming a primary powder layer on a product to be coated by electrostatic coating, The powder layer of the convex part is scraped off at that place without being transferred, and a secondary powder layer is formed by electrostatic coating, and then transferred to an induction heating process to form a coating film by induction heating. May be. In the case of the latter (2), it is possible to reduce the transfer process of the article to be coated, and to form a coating film by electrostatic painting without significant change or modification of the painting line.

  In the induction heating step, heating may be performed at a temperature corresponding to the type of the powder coating material. When the powder coating material is a powder coating material having a thermosetting resin as a pace, if necessary, by induction heating or induction heating. The coating film may be cross-linked or cured by a subsequent heating step. Further, the article to be coated may be heated in advance and electrostatic powder coating may be performed.

  In this embodiment, the primary powder layer 3a and the secondary powder layer 3b are formed on the tooth portion 2 over the primary and secondary times, but when the step between the tooth root and the tip portion is large. The film thickness can be made uniform by executing the powder forming process three times and adjusting the film thickness in each process. Furthermore, the film thickness can be set to a desired value according to each part of the tooth. For example, the film thickness can be set thin at the tip of the tooth, and the film thickness can be set thick at the valley bottom.

  INDUSTRIAL APPLICABILITY The present invention is effective as a method for forming a coating film having a uniform thickness (particularly a thick coating film) on an uneven surface of a metal article to be coated by electrostatic powder coating. The kind of the article to be coated having the concavo-convex portion is not particularly limited as long as it has the concavo-convex portion, and may have various shapes such as a plate shape, a rod shape, a cylindrical shape, a disc shape, and an umbrella shape. INDUSTRIAL APPLICABILITY The present invention is suitable for coating a product to be coated having irregularities regularly, particularly gears.

  The thickness of the coating film at the concavo-convex portion can be selected according to the type of article to be coated, and is, for example, about 100 to 200 μm, preferably about 150 to 200 μm. Moreover, the variation in the thickness of the coating film in the concavo-convex portion is usually about ± 20 μm (particularly ± 15 μm).

  For gears, a wide range of gears that can be engaged with each other to transmit power, such as gears (spur gears, internal gears, helical gears, helical gears, racks and pinions, straight bevel gears, screw gears, discrepancy, etc. Spline shafts include a spline shaft (grooved shaft), a serration shaft whose spline teeth have a chevron cross section, and the like. In spline shafts, a coating film may be formed at least on the teeth. The tooth profile of the gears and spline shaft teeth is not particularly limited, and may be an involute tooth cycloid tooth profile. The cross-sectional shape of the tooth tip portion (tooth peak portion) may be an acute protrusion shape or an acute curved shape, but is usually an axis in which grooves extending in the axial direction are formed at intervals in the circumferential direction. It may have a shape having a curved top with a curvature along the tip circle, such as an attached shaft. Moreover, in spline shafts, the number of grooves is not particularly limited, and may be, for example, generally about 4 to 50 (for example, 10 to 20).

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
While rotating the spline shaft, 12-nylon-based powder coating (average particle size) on the spline shaft teeth (key groove portion, tooth root diameter 46 mmφ, length 80 mm, key groove number 20) using an electrostatic spray gun The powder was coated with electrostatic powder for 20 seconds to form a primary powder layer. While the sheet curved according to the curvature of the tooth portion was moved upward along the axis of the spline shaft, the primary powder layer of the tooth tip portion was scraped off and removed while sucking. Next, using the electrostatic spray gun and powder coating, the electrostatic powder coating is applied to the spline shaft teeth for 20 seconds to form a secondary powder layer, which is then heated in an induction heating furnace (frequency 27 kHz). A coating film was formed. The tooth part of the obtained spline shaft was cut in a direction orthogonal to the central axis, and measured at each of three measurement sites of the tooth tip part, the left and right side parts, and the bottom part, and the film thickness was evaluated as an average value. . The film thickness was measured at four locations on the cut piece shifted by 90 ° in the circumferential direction.

Comparative Example 1
While rotating the spline shaft, 12-nylon-based powder coating (average) on the spline shaft teeth (key groove portion, tooth root diameter 46 mmφ, length 80 mm, number of key grooves 20) using an electrostatic spray gun After electrostatic powder coating of a particle size of 32 μm) for 40 seconds, the coating film was formed by heating in a dielectric heating furnace (frequency 27 kHz). Then, the film thickness was measured in the same manner as in Example 1.

  The results are shown in Table 1.

Table 1

  As can be seen from Table 1, compared to the comparative example, in the example, a coating film having a uniform thickness can be formed on the tooth tip part, the bottom part, and the side part.

[Second Embodiment]
Next, a second embodiment of the method for manufacturing a coated product according to the present invention will be described with reference to FIGS. 5A, 5B, and 5C in order.

  First, as shown in FIG. 5A, a tip 53 shown by a broken line of a tooth portion 54 of a spline shaft 51 as a part to be coated is cut by a predetermined dimension. The cut dimensions are such that the powder adhesion thickness in the subsequent electrostatic adhesion process can be corrected for the thickening of the tip portion 53 compared to the valley portion 59 and the tooth side surface 57 other than the tip portion 53. Set. For example, this cut dimension is such that the tooth height is reduced by 20% of the coating thickness, but depending on the tooth shape, the tooth height is reduced by 10% to 60% of the coating thickness. It is set in the range of the dimensions to be allowed.

  Next, an undercoat 52 is formed on the entire surface of the spline shaft 51. This undercoat material consists of an organic primer or an inorganic primer. Examples of the organic primer include epoxy, phenol, polyvinyl acetal resin, rubber, and the like, and may include an oligomer. The inorganic primer includes one containing magnesium, manganese, silicon, or the like. The undercoat 52 serves to facilitate the adhesion of the powder 55 made of resin to the spline shaft 51 as a part to be coated made of metal.

  Next, as shown in FIG. 5B, a powder 55 made of a resin material is adhered onto the undercoat 52 by electrostatic coating. At this time, the powder 55 adheres to the tip portion 53 of the tooth portion 54 thicker than the other portions by a predetermined dimension.

As the resin material constituting the powder 55, a thermoplastic resin material or a thermosetting resin material can be employed. More specifically, examples of the thermoplastic resin material include nylon materials, olefin materials, fluorine materials, and others (PBT (polybutylene terephthalate), PET (polyethylene terephthalate), PPS (polyphenylene sulfide), etc.). . Examples of the nylon material include homopolymer materials such as aromatic polyamides represented by PA6, PA66, PA46, PA11, PA12, and PPA (polyphthalamide), PA (polyamide) resin, and solid lubricant (PE ( polyethylene), PTFE (polytetrafluoroethylene), etc. MoS _2), or, filler (calcium carbonate, either one or both of talc) can be employed is added to the materials. As the olefin-based material, PE (including HDPE (high density polyethylene), UHDPE (ultra high density polyethylene), etc.), PP (polypropylene), and the like can be used. Further, as the fluorine-based material, PTFE (polytetrafluoroethylene), PFA (p-fluorophenylalanine), FEP (fluorinated ethylene propylene), ETFE (ethylene tetrafluoroethylene), or the like can be employed. In addition, as the thermosetting resin material, it is possible to employ a curing resin such as epoxy or phenol, or a thermosetting polyester or acrylic resin using a crosslinking agent or a curing agent.

  Next, the spline shaft 51 is heated by electromagnetic induction to melt the powder 55 and attach the coating film 56 to the spline shaft 51 as shown in FIG. In this embodiment, the thickness of the coating film 56 is set in the range of 100 μm to 150 μm. According to such a film thickness setting of the coating film 56, as shown in the characteristic diagram of FIG. 6, the operating sound (sounding sound) can be reduced by 20% or more compared to the case where the coating film thickness is zero. It was. In FIG. 6, the relative value which set the operating sound in the case of no coating as 100 is shown. Further, according to the film thickness setting of the coating film 56, as shown in the characteristic diagram of FIG. 7, the amount of wear can be reduced by 46% at the maximum as compared with the case where the coating film thickness is 300 μm. As can be seen from the characteristic diagrams of FIGS. 6 and 7, if the coating film thickness is set in the range of 100 to 250 μm, the effect of reducing the operating noise and the effect of suppressing the wear amount can be obtained.

  In addition, according to this embodiment, the powder 55 is melted by induction heating the spline shaft 51 in a state where the powder 55 is electrostatically attached to the spline shaft 51 as a part to be coated having uneven portions. Let For this reason, since the layer of the powder 55 is heated by the spline shaft 51 on the inner side, it is easy for the bubbles to escape from the powder 55 melted on the inner side to the outside, and the bubbles are mixed into the coating film 56. The quality of the coating film 56 can be improved.

  That is, as schematically illustrated in FIG. 4 (A), in the case of induction heating, the powder 23 is electrodeposited on the part to be coated 21 to which the undercoat 22 has been applied, and then the part 21 to be coated is applied. By induction heating, the inner powder 23 in the vicinity of the undercoat 22 starts to melt first. As a result, air bubbles between the powders 23 are easily emitted to the outside, and as shown in FIG. 4B, a coating film 25 substantially free of air bubbles can be formed. This effect can be obtained even when electrostatic powder coating is performed after the article to be coated is heated in advance.

  On the other hand, in the case of oven heating, as shown in FIG. 4C, heating is performed from the outside of the powder 103 attached to the surface of the undercoat 102 of the part to be coated 101. 103 begins to melt from the outermost side. For this reason, as shown in FIG. 4D, the bubbles 106 between the powders 103 are easily confined in the coating film 105.

  Further, in this embodiment, the tip 53 of the tooth portion 54 of the spline shaft 51 before painting is cut by a predetermined dimension so that the dimension of the spline shaft 51 after painting becomes a desired outer diameter. The next finishing process (for example, broaching process) becomes unnecessary, and the processing cost can be reduced.

  In the above embodiment, the spline shaft 51 used for the drive shaft is employed as the part to be coated. However, the spline shaft 51 may be female or male. The part to be coated may be an intermediate shaft used for a handle joint. Furthermore, the part to be coated may be a hypoid gear as a power transmission (deceleration mechanism) part or a pinion gear as a pressure generation (gear pump) part. Further, as a material of the part to be coated, a steel material or a non-ferrous material (such as an aluminum alloy or a magnesium alloy) can be adopted.

  Moreover, in the said embodiment, the coating film of the predetermined film thickness adhering to to-be-coated part may be partially formed in the surface of to-be-coated part, and may be formed in the whole surface.

FIG. 1 is a process diagram showing an example of a coating process for teeth of a spline shaft. FIG. 2 is a schematic perspective view showing a scraped state by the scraper means. FIG. 3 is a schematic side view showing the spline shaft. 4 (A) and 4 (B) are schematic views showing a state where the powder is melted in the case of electromagnetic induction heating, and FIGS. 4 (C) and 4 (D) are those in which the powder is melted in the case of oven heating. It is a schematic diagram which shows the state to do. FIG. 5 (A) is a cross-sectional view showing a step of cutting the tip of the tooth portion as a pretreatment in the second embodiment of the present invention, and FIG. FIG. 5C is a cross-sectional view showing a state in which the powder is melted by electromagnetic induction heating of the sprunt shaft in the second embodiment. In the said 2nd Embodiment, it is a characteristic view which shows the relationship between the film thickness of a coating film, and an operating sound. In the said 2nd Embodiment, it is a characteristic view which shows the relationship between the film thickness of a coating film, and the amount of wear.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Spline shaft, 2 ... Tooth part, 2a ... Tooth tip part, 2b ... Side part,
2c ... bottom, 3a ... primary powder layer, 3b ... secondary powder layer,
4 ... scraper means, 5 ... coating film, 5a ... primary coating film,
5b ... secondary coating film,
21 ... parts to be coated, 23 ... powder, 51 ... spline shaft,
52,22 ... undercoat, 53 ... tip, 54 ... tooth, 55 ... powder,
56 ... Tanibe, 57 ... Side.

Claims (10)

  An undercoat is formed on the surface of the part to be coated having an uneven portion for transmitting power, and the powder is electrostatically attached to the part to be coated on which the undercoat is formed, and then the part to be coated is induction-heated. A method for producing a coated product, comprising: melting the powder and attaching a coating film substantially free of air bubbles to the part to be coated. In the manufacturing method of the coated goods of Claim 1,
The thickness of the powder to be applied to the part to be coated is large or small, and the dimension of the part to be coated is set in advance so that the dimension of the coated product becomes a desired dimension according to the thickness. A method for producing a coated product characterized by In the manufacturing method of the coated goods of Claim 1 or 2,
The difference between the desired dimension of the convex part of the uneven part of the coated product and the dimension of the convex part of the concave part of the coated part is the desired dimension of the concave part of the concave part of the coated part and the uneven part of the coated part. The difference between the size of the concave portion of the coated portion and the difference between the desired size of the side wall of the concavo-convex portion of the coated product and the size of the side wall of the concavo-convex portion of the part to be coated. Method. In the manufacturing method of the coated goods as described in any one of Claims 1 thru | or 3,
A method for producing a coated product, wherein the coating film has a thickness of 100 μm to 250 μm. In the manufacturing method of the coated goods as described in any one of Claims 1 thru | or 4,
A method for producing a coated product, wherein the resin constituting the powder is a powder of a nylon material.   A coating film having a predetermined thickness and a coating film having a predetermined film thickness is attached to a part to be coated having a concavo-convex part for transmitting power, and there is substantially no air bubble in the coating film. Painted. In the coated product according to claim 6,
The coated film is formed by melting powder. In the coated article according to claim 6 or 7,
A coated product characterized in that the thickness of the coating film is large and the dimension of the part to be coated is set according to the thickness. In the coated product according to claim 6, 7 or 8,
A coated product, wherein the coating film has a thickness of 100 μm to 250 μm. In the coated article according to claim 7, 8 or 9,
A coated product, wherein the resin constituting the powder is a powder of a nylon material.

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