JP7633501B2 - Manufacturing method for automobile spoilers - Google Patents

Description

The present invention relates to a method for manufacturing automobile spoilers.

An automobile spoiler is a part attached to the exterior of a vehicle to reduce lift. An example of an automobile spoiler is a real roof spoiler that is attached to the rear end of the top surface of the body.

Patent Document 1 discloses a method for manufacturing an automobile spoiler by sanding a hollow resin molded body obtained by blow molding and then painting the sanded area.

Japanese Patent Application Publication No. 6-48328

Incidentally, in some cases, recesses may form along the parting line of resin molded products, and if painting is performed without completely removing the recesses during sanding, streaks may form along the parting line after painting. On the other hand, if you try to completely remove the recesses during sanding, the amount of work required for sanding increases significantly.

The present invention was made in consideration of these circumstances, and provides a method for manufacturing a spoiler that can prevent streaks from forming along the parting line after painting while preventing a significant increase in the labor required for sanding.

According to the present invention, there is provided a method for manufacturing a spoiler for an automobile, comprising a molding step, a sanding step, and a painting step, in which in the molding step, a hollow resin molded body is formed so that a convex streak is formed along a parting line, in the sanding step, the convex streak is removed by sanding an area including the convex streak, and in the painting step, painting is performed on at least a part of the sanded area.

In the method of the present invention, convex ridges are formed along the parting line when forming the resin molded body, and painting is performed after the convex ridges are removed in a sanding process. In the sanding process, removing the convex ridges requires less work than removing the concave ridges, so there is no significant increase in the work required for sanding. In addition, since there are no concave ridges at the parting line after the convex ridges are removed, the formation of streaks along the parting line after painting is suppressed.

2 is a cross-sectional view showing a molding machine 20 for forming a resin molded body 2. FIG. 2 is a cross-sectional view showing a state after the molds 23 and 24 of the molding machine 20 in FIG. 1 have been closed. 3A and 3B are enlarged views of areas A and B in FIG. 1, and FIG. 3C is an enlarged view of area C in FIG. 2 is a cross-sectional view showing a resin molding 2, taken along a cross section perpendicular to the longitudinal direction of a protrusion 1. FIG. 5A is an enlarged view of region A in FIG. 4, FIG. 5B is a view after the protrusion 1 has been removed from the state of FIG. 5A, and FIG. 5C shows the state after the coating film 3 has been formed from the state of FIG. 5B.

The following describes the embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. In addition, each feature can be an invention independently.

The manufacturing method for a spoiler according to one embodiment of the present invention includes a molding process, a sanding process, and a painting process. Each process is explained below.

1. Molding Step In the molding step, as shown in FIGS. 1 to 5A, a hollow resin molded body 2 is formed so that a protrusion 1 is formed along a parting line PL.

The method for forming the resin molded body 2 is described in detail below.

Figure 1 shows a molding machine 20 for forming a resin molded body 2. The molding machine 20 is configured to mold a parison 22 extruded from a head 21 using a pair of openable and closable molds 23, 24 to form the resin molded body 2.

In one example, the parison 22 can be formed by extruding the molten resin obtained by melt-kneading the raw resin downward from a slit provided in the head 21. The raw resin is, for example, a thermoplastic resin such as polyolefin or polyester, and examples of polyolefin include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene-based elastomers, and mixtures thereof. The parison 22 is preferably cylindrical or composed of a pair of resin sheets. In either case, a hollow resin molded body 2 can be formed.

The molds 23 and 24 have cavity surfaces 23a and 24a and pinch-off portions 23b and 24b surrounding them. When the molds 23 and 24 are closed, the cavity surfaces 23a and 24a combine to form a cavity 25 that corresponds to the outer shape of the spoiler.

The parison 22 is introduced between the open molds 23, 24. The parison 22 is introduced between the open molds 23, 24. Then, as shown in FIG. 2, the molds 23, 24 are closed, and air is blown into the parison enclosed in the cavity 25, thereby molding the parison 22 into a shape that conforms to the inner surface of the cavity 25, thereby obtaining a resin molded body 2 with flash 2c.

This molding may be blow molding, in which air is blown into the parison enclosed within the cavity, or vacuum molding, in which the molds 23 and 24 apply a vacuum to the parison 22 to shape it to the cavity surfaces 23a and 24a, or a combination of both.

The parison 22 is compressed by the pinch-off portions 23b and 24b to be thinned. In conventional dies, the outer wall 2a of the resin molded body 2 is pushed toward the hollow portion 2b of the resin molded body 2 by the resin extruded from the pinch-off portions 23b and 24b, which may form a concave line along the parting line PL. On the other hand, in this embodiment, the pinch-off portions 23b and 24b have chamfered shapes 23b1 and 24b1 (shown in FIGS. 3A and 3B) on the edge on the cavity 25 side, so that the force pushing the outer wall 2a toward the hollow portion 2b is weakened. In addition, since the convex streak 1 is formed at the position corresponding to the pinch-off portions 23b and 24b, even if the outer wall 2a is pushed into the hollow portion 2b, the height of the convex streak 1 is simply reduced, and no concave streak is formed. Therefore, by using the dies 23 and 24 having the configuration of this embodiment, the formation of a concave streak along the parting line PL is suppressed.

Pinch-off portions 23b and 24b preferably have the same shape. The following explanation will be given using pinch-off portion 23b as an example, but the explanation also applies to pinch-off portion 24b.

The chamfered shape 23b1 may be a C-chamfer or an R-chamfer. As shown in FIG. 3A, the chamfered shape 23b1 has a height (length along the tip surface 23b2 of the pinch-off portion 23b) H1 of, for example, 0.1 to 2 mm, preferably 0.3 to 0.7 mm. Specifically, the height H1 may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, or 2.0 mm, or may be within a range between any two of the values exemplified here. The chamfered shape 23b1 has a width (length along a plane perpendicular to the tip surface 23b2) W1 of, for example, 0.1 to 2 mm, preferably 0.3 to 0.7 mm. Specifically, the width W1 may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, or 2.0 mm, and may be within a range between any two of the numerical values exemplified here. If the height H1 or width W1 is too small, a recessed streak is likely to be formed along the parting line PL. On the other hand, if the height H1 or width W1 is too large, the effort required to remove the protruding streak 1 in the sanding process increases accordingly.

Next, the molds 23 and 24 are opened, the resin molded body 2 with the burr 2c is removed, and the burr 2c is removed to obtain a hollow resin molded body 2 with a convex streak 1 formed along the parting line PL, as shown in Figures 4 and 5A.

As shown in FIG. 5A, the convex streak 1 preferably has a tapered shape in a cross section perpendicular to the longitudinal direction of the convex streak 1, and is preferably triangular. The explanation of the height H2 of the convex streak 1 is the same as the explanation of the height H1. The width W2 of the convex streak 1 is twice the width W1. Therefore, the width W2 is, for example, 0.2 to 4 mm, and preferably 0.6 to 1.4 mm. Specifically, the width W1 may be, for example, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 3.0, or 4.0 mm, and may be within a range between any two of the numerical values exemplified here. If the height H2 or width W2 is too small, a concave streak along the parting line PL is easily formed. On the other hand, if the height H2 or width W2 is too large, the effort required to remove the convex streak 1 in the sanding process increases accordingly.

2. Sanding Step In the sanding step, the region including the protrusion 1 is sanded to remove the protrusion 1 as shown in FIG. 5B.

The resin molded body 2 obtained in the molding process has minute irregularities on its surface due to die lines, melt fracture, and other factors, and the height from the deepest valley to the highest peak of this minute irregularity (hereinafter referred to as the "maximum height") is about 0.1 to 1 mm. Therefore, when manufacturing automobile spoilers by resin molding, which particularly require good appearance such as surface smoothness and gloss, the surface is smoothed by sanding. Sanding can be performed by rubbing the surface with sandpaper.

The maximum height of the minute irregularities after sanding is preferably 25 μm or less. By making the maximum height 25 μm or less, the surface of the resin molded body 2 can be made sufficiently smooth. The lower limit of this maximum height is not particularly limited, but is, for example, 4 μm. In addition to the fact that a maximum height of 4 μm is sufficient smoothness, it is not technically easy to make the maximum height less than 4 μm. Specifically, this maximum height is, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 μm, and may be within a range between any two of the values exemplified here. In addition, the maximum height in this invention is a numerical value of the surface roughness represented by the roughness symbol Rt, and conforms to JIS-B0601. The above maximum height is expressed as the average value obtained by randomly obtaining cross-sectional curves at several points (usually five points) from the surface of the measured object. In this case, it is necessary to extract only a reference length (usually 5 mm) from a portion that does not have exceptionally high peaks or deep valleys.

Sanding may be performed on the entire surface of the resin molded body 2, or on a portion of the surface of the resin molded body 2 that includes the ridges 1.

5C, in the painting step, painting is performed on at least a part of the area sanded in the sanding step to form a coating film 3. The area to be painted may be the same as the area to be sanded, or may be narrower or wider than the area to be sanded. It is preferable to sand and paint the entire surface of the resin molded body 2.

The sanded area is now smooth and can be painted to give you a great looking spoiler.

The thickness of the coating film 3 is, for example, 1 to 200 μm, and preferably 10 to 100 μm. Specific examples of this thickness include 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200 μm, and may be within a range between any two of the numerical values exemplified here.

The coating film 3 may be a single layer or multiple layers. In one example, the coating film 3 includes a primer coating film formed on the resin molded body 2 and a topcoat coating film formed on the primer coating film. The primer coating film and the topcoat coating film each have a thickness of, for example, 1 to 100 μm, and preferably 5 to 50 μm. Specifically, the thickness may be, for example, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 μm, and may be within a range between any two of the numerical values exemplified here. The primer coating film and the topcoat coating film may each be formed using, for example, an acrylic urethane paint.

Sanding may be performed after the primer coating is formed. In one example, the resin molded body 2 obtained in the molding process is subjected to a first sanding to remove the protruding ridges 1, after which a primer coating is formed, followed by a second sanding, and then a topcoat coating. In this case, the second sanding makes the surface of the resin molded body 2 even smoother, thereby further improving the appearance of the spoiler.

1: Convex strip 2: Resin molded body 2a: Outer wall 2b: Hollow portion 2c: Flash 3: Coating film 20: Molding machine 21: Head 22: Parison 23: Mold 23a: Cavity surface 23b: Pinch-off portion 23b1: Chamfered shape 23b2: Tip surface 24: Mold 24a: Cavity surface 24b: Pinch-off portion 24b1: Chamfered shape 25: Cavity PL: Parting line

Claims (1)

A method for manufacturing an automobile spoiler, comprising a molding step, a sanding step, and a painting step,
In the molding step, a hollow resin molded body is formed so that a protrusion is formed along a parting line,
In the molding step, the resin molded body is formed using a pair of molds, each of which includes a cavity surface that forms a cavity and a pinch-off portion that surrounds the cavity surface;
The pinch-off portion has a chamfered shape on an edge on the cavity side,
The convex strip is formed at a position where the chamfered shape of the pinch-off portion is provided ,
the convex rib has a triangular shape in a cross section of the convex rib perpendicular to a direction along the parting line along which the convex rib is formed ,
The height of the chamfered shape is 0.1 mm or more and 2 mm or less,
The width of the chamfered shape is 0.1 mm or more and 2 mm or less,
In the sanding step, the region including the protrusion is sanded to remove the protrusion,
In the painting step, painting is performed on at least a part of the sanded area,
The coating step includes a step of forming a primer coating film on the resin molded body, and a step of forming a topcoat coating film on the primer coating film,
The sanding step includes a step of performing a first sanding on the resin molded body obtained in the molding step, and a step of performing a second sanding after the step of forming the primer coating film and before the step of forming the topcoat coating film.