JP5316926B2 - How to paint vehicle wheels - Google Patents

Description

  The present invention relates to a method for painting a vehicle wheel for painting both surfaces of a design surface, for example, to prevent the occurrence of rust at the edge portion on the back side of the disk surface of the vehicle wheel of a four-wheel vehicle. It is related with the coating method which can make it not give an unevenness | corrugation to the coating-film surface in the front side of.

  In a light alloy wheel manufactured by casting, which is an automobile (for example, passenger car) part, a multi-layer coating is applied to the surface of the wheel base in order to provide a high-quality appearance. For example, in general, a powder polyester coated with a thickness of about 50 to 100 μm in order to hide the irregularities of the casting surface, a primer layer made of acrylic, epoxy, urethane resin, etc., a polyester for producing an appearance color There are three-layer coatings composed of a color base layer mainly composed of an acrylic resin, and a clear layer for producing color of the color base layer and improving weather resistance, corrosion resistance and the like. In addition, in order to further enhance the high quality, there are some that have a metallic silver coating (plating coating) reminiscent of a polished surface of metal.

The same coating is performed on a steel plate material or the like. However, when these coatings are performed with a vehicle wheel by casting, it is necessary to consider a rust prevention measure for the edge portion formed by processing the wheel base. In particular, since the spoke part formed on the design surface has a vertical wall on the side, when the back side of the design surface is processed by lathe processing, the boundary between the cutting surface and this vertical wall has an acute angle or an angle close to an acute angle. Have. Since the resin used as the paint is baked at a temperature of about 200 to 300 ° C. after the coating film is formed, the resin shrinks to the center side of the painted surface at the time of baking, so the resin is pulled on both sides of the ridge at the edge portion. The film thickness of the coating film becomes thinner. As a result, the corrosion resistance at the edge portion is lowered and yarn rust is likely to occur, and when the yarn rust is generated and spreads around, the appearance is deteriorated.

  In order to prevent the occurrence of thread rust at the edge portion, for example, in Patent Document 1, after cutting the back side of the disk portion, the boundary between the inner peripheral surface of the decorative hole made of the casting surface and the back surface of the disk portion made of the cutting surface It is disclosed that the edge is chamfered and then the edge is brushed with a rotating brush and then painted. Patent Document 2 describes that a multi-layered coating film is formed on an edge portion to improve corrosion resistance.

JP 2007-106285 A JP-A-10-157401

In both Patent Document 1 and Patent Document 2, a drawing in which the coating is thickly applied at the edge portion is described, but a specific coating method of the paint is not described. In order to increase the film thickness at the edge part on the back side of the spoke part, it is necessary to apply at least the paint from the back side of the design surface. However, when the coating material is applied from the back side of the design surface, the appearance is easily deteriorated as compared with the case where the coating material is applied only from the front side of the design surface, and the yield is reduced.
The present invention provides a vehicle wheel coating method that solves this problem of yield reduction and can sufficiently take measures against yarn rust at the edge part on the back side of the spoke part.

In order to achieve the above object, a vehicle wheel coating method according to a first aspect of the present invention is such that a primer paint is applied on the front side and the back side of the design surface, and a color base paint is sprayed on the primer layer from the back side of the design surface. After that, the color base paint is sprayed from the front side of the design surface, and the color base paint is baked.
The vehicle wheel coating method according to the second aspect of the present invention is a vehicle wheel coating method in which a primer paint is applied on the front side and the back side of the design surface, and a color base paint is applied on the primer layer. The clear paint is sprayed on the color base coating from the back side of the design surface, and then the clear paint is sprayed from the front side of the design surface to burn the clear paint.
According to a third aspect of the present invention, there is provided a method for painting a vehicle wheel, wherein a primer paint is applied to the front side and the back side of the design surface, and a color base paint is sprayed on the primer layer from the back side of the design surface. The paint is sprayed from the front side of the design surface, the color base paint is baked, the clear paint is sprayed on the color base paint from the back side of the design surface, and then the clear paint is sprayed from the front side of the design surface. It is characterized by baking paint.

The color base paint or clear paint sprayed from the back side accumulates around the edge of the window portion of the design surface from the entire back side of the design surface. Part of the sprayed paint passes through the window part, and a part of the paint adheres to the side surface of the spoke part to form a number of convex parts such as goosebumps. Then, the paint sprayed from the front side is deposited on this convex part. Therefore, a smooth surface is obtained on the front side of the design surface, and a good appearance is obtained.
On the other hand, when the color base paint or clear paint is sprayed from the front side, the solvent resin paint sprayed from the back side adheres to the smoothly deposited paint layer and the convex part is generated on the surface. . For this reason, this convex part remains in the appearance after baking the paint, and appearance defects tend to occur.

  In any product in which the paint is applied on both sides of the design surface, it is preferable to spray the paint from the front side after spraying the paint from the back side. However, since this convex portion is unlikely to occur in powder coating by electrostatic coating, it is preferable to use the coating method of the present invention when a solvent resin coating is used for a color base coating or a clear coating.

If a powder resin paint is used for the primer layer, the film thickness can be increased and not only coating can be easily performed, but also the unevenness of the casting surface can be made inconspicuous.

In the case where the back side of the design surface of the cast vehicle wheel is cut, the processed surface and the side surface of the spoke part are likely to have an acute angle. Even if the paint is sprayed only from the front side, the resin wraps around to the backside to some extent, but if the ridge between the processed surface and the side surface of the design surface is too acute, the resin shrinks when baking the paint The resin thickness at the ridges becomes thin, the rust prevention property is lowered, and this causes thread rust. Therefore, many vehicle wheels in which the back side of the design surface is machined apply the paint also from the back side. Therefore, it is preferable to apply the coating method of the present invention.

  According to the present invention, in order to increase the rust prevention at the ridge line portion between the spoke portion and the processed surface on the back side of the design surface by spraying the paint on the vehicle wheel, Since it sprays from the front side after spraying from the back side, there is no scattering of the resin sprayed from the back side on the front side of the design surface, and a flat and good appearance surface can be obtained.

  The surface of the base (light alloy material) of the light alloy wheel is pretreated before providing the primer layer. In general, the pretreatment is performed by degreasing and pickling, followed by a chemical conversion treatment. In general, chromate treatment using chromium chromate or chromium phosphate is applied as a chemical conversion treatment solution, but from the viewpoint of environmental protection, a non-chromium chemical treatment solution using Ti acid or Zr acid is used. The

  The primer paint can be a polyester, acrylic, epoxy, or urethane resin. Use of an epoxy powder coating material (mainly composed of glycidyl ether type (for example, bisphenol A type), glycidyl ester type, glycidyl amine type, and cyclic oxirane type epoxy resin) having good adhesion to metal due to orientation of hydroxyl groups preferable. The epoxy-based powder coating is particularly composed of a glycidyl group / carboxyl group-crosslinked epoxy resin having an acid-terminated polyester resin as a curing agent from the viewpoint of cost and adhesion to the substrate, and has a high solid content concentration (40 to 40). 60 mass%) epoxy / polyester powder coating is preferred. By baking the epoxy polyester / hybrid powder coating material at a temperature of 150 to 180 ° C. for 10 to 30 minutes, a smooth and strong polymer cross-linked coating film is formed. As described above, the primer layer is formed to a thickness of about 40 to 200 μm when it is necessary to hide the unevenness of the cast surface of the light alloy wheel. An electrostatic coating apparatus is generally used for the coating apparatus.

As a colored solvent resin paint (color base) paint, there are, for example, those made of acrylic, polyester, epoxy resin, etc. and containing a solvent. When an epoxy-polyester hybrid powder coating is used for the primer layer, it is preferable to use a thermosetting acrylic resin-based colored coating. A thermosetting paint obtained by dissolving or dispersing an acrylic resin, a curing agent, a pigment or the like in an organic solvent is preferable. In order to protect the environment, a high solid type having a small proportion of the organic solvent is preferable. The light alloy wheel is sprayed with air spray or electrostatic coating. Film thickness 10~40μm are common. Known pigments such as organic pigments, inorganic pigments and metallic powders are used for the color base paint. In addition, additives such as a rust preventive pigment, a curing catalyst, an ultraviolet absorber, an ultraviolet stabilizer, an antioxidant, a surface conditioner, and a crack inhibitor can be blended.

  The clear coating applied on the colored solvent resin coating may be transparent, but it can be formed using a solvent-based clear coating in which a polymer or oligomer is dissolved in an organic solvent. As the clear paint, it is preferable to use an acrylic paint excellent in transparency, gloss, weather resistance and the like, for example, an acrylic solvent paint having a solid content concentration of about 40 to 50% by mass. For the acrylic paint, a thermosetting acrylic resin obtained by solution polymerization of an acrylic monomer and a functional monomer such as an epoxy group, a carboxyl group, or a hydroxyl group is used. In particular, a curable acrylic resin using melamine as a crosslinking agent is used, and it is preferable to use an acrylic solvent paint having a resin solid content concentration of about 40 to 50% by mass. The clear layer is formed on the surface of the colored solvent resin paint (color base) layer and then baked at a temperature of 130 to 180 ° C., for example, to a thickness of 10 to 40 μm.

Example 1
Details of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a diagram schematically showing a cross section of the coating of the present invention. In FIG. 1, 30 is a wheel base (cross section of the spoke part) formed by casting a metal such as Al, Mg, Fe or an alloy thereof, and a primer layer 11 made of powder resin on the surface thereof, a solvent resin paint. A multilayer coating film composed of the color base layer 12 is formed. A clear layer is formed on the color base layer 12. Usually, before forming this coating film, the surface of the substrate 30 is pretreated in order to improve the corrosion resistance. In the case where the substrate 30 is an aluminum alloy such as a casting, chemical conversion treatment represented by alkali degreasing and chromate treatment is performed. The chemical conversion film is formed to have an adhesion amount of 3 mg / m ² or more (preferably 5 to 20 mg / m ² ). The substrate 30 after the chemical conversion treatment is washed with water and dried.

A base body (integrated aluminum wheel by low pressure casting) made of an Al—Si—Mg alloy (equivalent to JIS AC4CH material) was subjected to alkali degreasing and chromate treatment, then washed with pure water, dried and pretreated.
Epoxy / polyester / hybrid powder paint (manufactured by Nippon Paint Co., Ltd.) is sprayed from both sides of the light alloy wheel design surface, laminated to a thickness of about 100 μm by electrostatic coating, at a temperature of 150 to 180 ° C., Bake for 30-60 minutes.
Then, a colored solvent resin coating (acrylic high solid thermosetting resin (acrylic melamine resin coating manufactured by Nippon Paint Kogyo Co., Ltd.)) is formed on the primer layer from the back side of the design surface so that the film thickness becomes 30 μm. Sprayed with a spray gun, then the direction of the wheel base was changed, and the same type of colored solvent resin paint was sprayed from the front side of the design surface so as to have a film thickness of 30 μm. Bake for ~ 30 minutes to form a color base layer.
On this color base layer, an acrylic high solid transparent thermosetting resin (solvent-based clear, manufactured by Nippon Paint Co., Ltd.) is sprayed from the design surface side with a spray gun so that the film thickness becomes 30 μm. Bake at 130-160 ° C. to form a clear layer.

  The wheel base body 30 in FIG. 1 is a cross section of the spoke portion, and the lower side in the figure is the processed surface 20 on the back side of the design surface. FIG. 2 shows the steps of the coating method of the present invention. The surface 21 is a chamfered portion of the ridge portion of the window of the design surface, and is a portion chamfered to remove a burr generated when the back surface 20 of the design surface is turned. A predetermined angle is formed between the chamfered surface 21 and the surface 20 on the back side of the design surface, and between the chamfered surface 21 and the spoke portion side surface 22. Since the primer layer shrinks toward the center of the surface when baked, the resin is pulled on both sides, and the primer layer at the ridge is thinned. Further, in order to increase the thickness of the coating film, a color base paint is applied from both sides of the design surface to form the color base layer 12. In the figure, the color base layer 12 is described by separating the layer 12b sprayed from the back side and the layer 12a sprayed from the front side. In addition, a layer 12c scattered to the front side of the design surface when the color base paint is sprayed from the back side is described. First, the color base paint sprayed from the back side of the design surface is deposited on the back side of the design surface, but the scattered paint wraps around the front side of the design surface to form a partially convex layer 12c. Although a large convex shape is schematically shown in the figure, a convex portion having a diameter of about 1 mm is actually formed in a cocoon skin shape. However, after that, the same paint is sprayed from the front side, so that the convex layer 12c is entirely covered, and the color base layer 12a on the front side of the design surface becomes a smooth surface.

FIG. 3 differs from Example 1 in the painting process, in which the color base paint is sprayed from the front side of the design surface from the front side and then sprayed again from the back side of the design surface. Unlike the cross section of the coating film in FIG. 1, the resin 12 scattered when the color base paint is sprayed from the back side adheres to the front side of the design surface to form a convex layer 12c. Actually, since the resin scatters in a mist form, a large number of convex layers 12c are formed, and the appearance is likely to be poor. A clear layer (not shown) is formed on the color base layer 12, but it is difficult to erase the convex layer 12c in appearance.
If the paint sprayed from the back side of the design surface is not exposed to the front side, the amount of paint discharged is reduced and painting takes time to prevent appearance defects, but only the painting process sprayed from the back side has a long cycle time. Therefore, the entire cycle time is lengthened.

(Example 2)
The clear paint is sprayed from the back side of the design surface onto the color base paint in the same manner as the color base paint of Example 1, and then sprayed from the front side of the design surface to deposit the paint, and the clear paint is baked and the primer layer A vehicle wheel with a three-layer coating of a color base layer and a clear layer was manufactured. The surface of the clear layer is a smooth surface and has a finish with no problem in appearance.
Both the color base layer and the clear layer can be easily sprayed from the back side of the design surface, and then sprayed from the front side of the design surface to deposit a paint, thereby easily obtaining a wheel with excellent appearance.

  On the other hand, the surface of the clear layer (spoke part and vertical wall part on the rim side) is cocoon-skinned when it is fired by spraying clear paint from the back side after spraying from the front side of the design surface. When applied, the shape is easily visible. Clear paints also have high viscosity because they contain additives, and as a result, they are not as rough as color base paints, and rough skin defects are likely to occur.

It is a figure which shows typically the coating-film cross section by the coating process of this invention. It is a flowchart which shows the coating process of this invention. It is a figure which shows typically the coating-film cross section by the comparative coating process.

Explanation of symbols

11: Primer layer, 12: Color base layer, 20: Processed surface on the back side of the design surface, 21: Chamfered surface of the spoke window portion, 22: Front side of the design surface (side surface of the spoke portion), 30: Light alloy wheel base body

Claims (4)

A vehicle wheel having a design surface including a window portion and a spoke portion forming the window portion, wherein the spoke portion has an edge portion, and the edge portion faces a side surface facing the window portion and the design surface. In contrast, a method for painting a vehicle wheel, which is formed from a back side surface and has an acute angle between the side surface and the back side surface, wherein primer paint is applied to the front side and back side of the design surface, Spray the color base paint from the back side of the design surface to the back side surface and the edge portion, and then spray the color base paint from the front side of the design surface to the side surface and the edge portion , A method for painting a vehicle wheel, wherein the color base paint is baked. A vehicle wheel having a design surface including a window portion and a spoke portion forming the window portion, wherein the spoke portion has an edge portion, and the edge portion faces a side surface facing the window portion and the design surface. In contrast, a method for painting a vehicle wheel, which is formed from a back side surface and has an acute angle between the side surface and the back side surface, wherein primer paint is applied to the front side and back side of the design surface, A color base paint is applied to the surface, and a clear paint is sprayed on the color base paint from the back side of the design surface to the back side surface and the edge portion, and then the clear paint is sprayed from the front side of the design surface. A method for painting a vehicle wheel, characterized in that the side surface and the edge portion are painted and the clear paint is baked. A vehicle wheel having a design surface including a window portion and a spoke portion forming the window portion, wherein the spoke portion has an edge portion, and the edge portion faces a side surface facing the window portion and the design surface. In contrast, a method for painting a vehicle wheel, which is formed from a back side surface and has an acute angle between the side surface and the back side surface, wherein primer paint is applied to the front side and back side of the design surface, Spray the color base paint from the back side of the design surface to the back side surface and the edge portion, and then spray the color base paint from the front side of the design surface to the side surface and the edge portion , the color base paint was baked, was coated on the surface and the edge portion of the back side from the back side spraying with the design surface clear coating over the color base paint, then the clear Paint only spray from the front side of the design surface was painted with the side surface and the edge portion, the method for coating a vehicle wheel, characterized in that baking the clear coating. The vehicle wheel has been cast molding, the vehicle according to any one of claims 1 to 3 wherein the back surface forming the edge portion is characterized in that to be machined How to paint the wheel.

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