JP2697533B2 - Manufacturing method of hollow molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a hollow molded article having a partially hollow portion, and more particularly to a method for forming a hollow molded article having a substantially uniform wall thickness.

[0002]

2. Description of the Related Art For example, as shown in FIG. 11, a radiator grill 9 for an automobile has recently been made of resin. As shown in the figure, the radiator grill 9 includes a frame 90 and a grid portion 91 disposed inside the frame 90.
And Meanwhile, in the radiator grill, as shown in FIGS. 11 and 12, for example, the lower frame 92 is formed in a hollow shape along the longitudinal direction, and the hollow portion 95 is formed.
It is conceivable to form

The purpose of forming the hollow portion 95 is, for example, to reduce the weight of the radiator grill 9 and to reduce the amount of resin used to save resources.
The hollow portion 95 of the radiator grill is manufactured by a hollow molding method in which a resin is injected into a cavity of a molding die, and then a pressurized gas is injected into the softened resin.

FIGS. 14 and 15 show a molding process of a hollow portion. The resin 7 is injected from a gate 85 into a hollow portion forming portion 81 in a cavity of a molding die 8 (FIG. 1).
4) Then, pressurized gas is injected from the gate 85 into the resin 7 which is still in a softened state. As a result, FIG.
A hollow portion 95 is formed as shown in FIG.

[0005]

The hollow portion 95
Is formed at the center of the lower frame 92 as shown in FIG. However, in the hollow portion 95, as shown in FIG. 13, the wall thickness of the upper portion 951 may be small, and the wall thickness of the lower portion 952 and the side portion 953 may be large. That is, the wall thickness of the hollow portion becomes uneven.

In some cases, the upper portion 951 may be formed as a very thin skin. As described above, when the wall thickness is reduced, a problem in strength occurs. Therefore, it is necessary to prevent uneven thickness in the hollow portion.

[0007] Such a problem occurs not only in a radiator grill provided with a hollow portion but also in a hollow molded body such as a louver cowl top. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a method of manufacturing a hollow molded body capable of preventing wall thickness deviation in a hollow portion and forming a wall thickness of the hollow portion substantially uniformly. .

[0008]

According to the present invention, in manufacturing a hollow molded article having a partially hollow portion, a hollow portion in a cavity is partially provided along a longitudinal direction thereof, and the hollow portion is formed of a resin. And using a molding die disposed upstream of the pressurized gas, injecting a resin into the molding die and injecting a pressurized gas into the resin. is there.

What is most remarkable in the present invention is that a weir is provided along the longitudinal direction and partially on the upstream side of the resin and the pressurized gas in the hollow forming portion of the mold. And performing hollow molding using this mold. The seki is disposed on the upstream side of the flow of the resin and the pressurized gas along the longitudinal direction of the hollow portion forming portion. It is preferable that the length M is 8% to 60% of the length L (see FIG. 1) of the hollow portion. If it is less than 8%, it is difficult to prevent uneven thickness, while 60%
If it exceeds, the problem that the hollow portion becomes solid may occur.

Further, it is preferable that the width Y of the cut is 25 to 75% of the width W (FIG. 1) of the hollow portion forming portion. 25
If it is less than 75%, it is difficult to prevent uneven thickness, while if it exceeds 75%, the gap between the rubber and the hollow portion is too small to prevent the resin from flowing. Further, it is preferable that the height K of the seki is 40% or less of the height H (FIG. 1) of the hollow portion forming portion. If it exceeds 40%, the height of the hollow portion is reduced, and the strength of the hollow body formed at that portion may be reduced.

The seki is disposed between the hollow portion forming portion and the resin inflow passage so that the resin does not flow directly into the hollow portion forming portion but the resin bypasses and flows into the hollow portion forming portion. (See FIG. 2). Examples of the resin include polypropylene (PP) resin, acrylonitrile-butadiene-styrene (ABS) resin, polycarbonate (P)
C) Resin, acrylonitrile-ethylene-propylene-
Rubber styrene (AES) resin and the like.

The pressurized gas includes air, nitrogen gas and the like. The present invention can be applied to the manufacture of a hollow molded body such as one having only the lower portion or only the upper portion of the radiator grill shown in the embodiment, and having the entire outer periphery and the lower and upper portions hollow.

[0013]

Operation and Effect In the present invention, the above recess is provided in the hollow portion forming portion. Therefore, as shown in FIG. 2 to be described later, the resin 7 in the softened state injected from the gate toward the hollow portion forming portion has its flow front end 72 first abutting on the cut 2 and its flow velocity is reduced. Next, it flows into the hollow portion through the gap 11 between the hollow and the hollow portion.

In the hollow portion where the flow front end portion 72 flows, the cross section in the direction perpendicular to the longitudinal direction becomes smaller than that of the hollow portion on the downstream side due to the presence of the cut. I have. Therefore, the resin flows downstream along the longitudinal direction while uniformly contacting the wall surface around the hollow portion forming portion. Then, the resin in contact with the wall surface of the hollow portion is gradually cooled and solidified to increase its thickness.

[0015] Further, even on the downstream side where no cut is provided, the uniform flow in the longitudinal direction on the upstream side is maintained as it is, so that the resin uniformly contacts the wall surface around the hollow portion forming portion and solidifies upon cooling. Will be done. Therefore, when the pressurized gas is injected into the resin, since the resin is already uniformly cooled and solidified on the wall surface of the hollow portion, a hollow portion is formed at the center of the hollow portion. To go. Therefore, a hollow portion having a substantially uniform wall thickness without uneven thickness can be formed.

In contrast, in the conventional example, as shown in FIG. 14, the flow front end portion 72 of the resin 7 flows directly into the hollow portion forming portion 81. Therefore, the lower surface and the side surface of the downflow portion are rapidly cooled and solidified, and the wall thickness increases.

Therefore, even if a pressurized gas is injected into the resin, since the remaining resin in the softened state is small, as shown in FIG. It gives rise to As described above, according to the present invention, it is possible to provide a method of manufacturing a hollow molded body that can prevent wall thickness deviation and can form a wall thickness of a hollow portion substantially uniformly.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a hollow molded article according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 7 to 10, the hollow molded body of the present embodiment has a lower frame 3.
5 is a radiator grill in which a hollow portion 36 is provided.

In this embodiment, when manufacturing the radiator grill 3 (FIG. 7) having the hollow portion 36 in the lower frame 35, FIG.
As shown in FIG. 2, a molding die 10 having a stick 2 is used. The mold 10 has a hollow portion 12 in the cavity 1 along the longitudinal direction of the cavity forming portion 12 in the cavity 1, and the hollow portion 2 is disposed upstream of the resin 7 and the pressurized gas. is there.

The hollow portion is formed by injecting the resin 7 into the cavity 1 of the mold and injecting a pressurized gas into the resin 7 in a softened state. Also,
As shown in FIGS. 1 and 2, the width Y of the cut 2 is about 60% of the width W of the hollow portion 12, the length M of the cut 2 is about 30% of the length L of the hollow portion 12, 2, the maximum part height K is about 30% of the maximum part height H of the hollow part forming part 12.
It is.

The cut 2 has a curved upper surface 24 facing the curved ceiling portion 14 of the hollow portion forming portion 11. Then, as shown in FIGS. 1, 2, 5, and 6, a gap portion 11 is formed between the hollow portion forming portion 12 and the cut 2. Also, as shown in FIGS. 1, 5 and 6, on the downstream side of the sword 2, a hollow portion forming portion 12 without the sword 2 is provided.
Are formed.

The inflow path 13 to the hollow portion forming portion 12
(FIG. 1) shows that the gate 16
Is connected. The inflow path 13 is a part that forms the front part 34 (FIG. 7) of the radiator grill 3.

Next, in manufacturing the radiator grill 3, the resin 16 in a softened state is supplied from the gate 16.
Inject This resin 7, as shown in FIG.
It flows into the hollow part 12 below the wall 2 through the gap 11 between the hollow part 12 and the hollow part 12. At this time, as shown in FIG. 2, the flow front end portion 72 of the resin 7 first comes into contact with the block 2, the flow velocity thereof is reduced, and the gap 11 is formed.
, And flows into the hollow portion forming portion 12.

On the upstream side, the hollow portion 12 is smaller in cross section than the downstream hollow portion 12 due to the presence of the cut 2. Therefore, the resin 7 flows to the downstream side along the longitudinal direction while uniformly contacting the wall surface around the hollow portion forming portion. Then, the resin 7 in contact with the wall surface is cooled and solidified.

In the downstream hollow portion 12 where the cut 2 is not provided, since the uniform flow in the longitudinal direction on the upstream side is maintained as it is, the resin 7 is applied to the wall surface of the hollow portion 12. It contacts uniformly, cools and solidifies. Therefore, when the pressurized gas is injected into the resin 7, the resin is already uniformly cooled and solidified on the wall surface of the hollow portion, so that the hollow portion is formed at the center of the hollow portion. Is done.

Next, the lower frame 35 of the radiator grill 3 manufactured as described above will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 3 shows the lower frame 3 formed by the hollow portion forming portion 12 where the cut 2 is provided.
5 and FIG. 4 show a lower frame 35 formed by the downstream hollow portion forming portion 12 having no cut 2.

In each of the lower frames 35, a hollow portion 36 is formed near the center, and it can be seen that the peripheral wall has a substantially uniform wall thickness. The lower frame 35 shown in FIG. 3 has a recess 351 formed by the recess 2 (see FIG. 7).

Next, FIGS. 7 to 10 show the radiator grill 3 obtained according to this embodiment. The radiator grill 3 has a side frame 31, an upper frame 32, and a lower frame 35, and has a lattice portion 33 between them. The radiator grille 3 has a design front part 34 at the center thereof.

Then, as shown in FIG.
The lower frame 35 below the radiator grill has a recess 351 formed by the recess 2 on the back side of the radiator grill. As shown in FIG. 10, the gate 16 for injecting and injecting the resin and the pressurized gas is provided in the front surface portion 34, that is, the cavity corresponding to the lower central portion of the radiator grill.

FIGS. 8 and 9 show cross sections near the center portion and side portions of the radiator grill 3 (cross sections taken along arrows in FIG. 7). In FIG. 8, a lower recess 35 is provided in the lower frame 35.
1 can be seen, but there is no recess in FIG. Further, the lower frame 35 has substantially the same wall thickness in any part.

As described above, according to this embodiment, it is possible to manufacture a radiator grill having a hollow portion having a substantially uniform wall thickness without uneven thickness. In addition, since the resin flows while uniformly contacting the mold wall surface, there is no appearance defect such as a flow scratch.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram of a hollow portion forming portion and a sex of a mold cavity in an embodiment.

FIG. 2 is a cross-sectional view of a hollow portion forming part at the time of resin injection in the embodiment.

FIG. 3 is a cross-sectional view of a hollow portion and a lower frame of a portion provided with a cut in the embodiment.

FIG. 4 is a cross-sectional view of a hollow frame forming portion and a lower frame in a portion where there is no cut in the embodiment.

FIG. 5 is a sectional view taken along line AA of FIG. 2;

FIG. 6 is a sectional view taken along line BB of FIG. 2;

FIG. 7 is a perspective view of the radiator grill of the embodiment.

FIG. 8 is a sectional view taken along line CC of FIG. 7;

FIG. 9 is a cross-sectional view taken along line DD in FIG. 7;

FIG. 10 is a partially cutaway perspective view of the radiator grille according to the embodiment, in the vicinity of the recess.

FIG. 11 is an explanatory view of a conventional radiator grill.

FIG. 12 is a sectional view of a lower frame of a conventional radiator grill.

FIG. 13 is a cross-sectional view showing a problem of a lower frame of a conventional radiator grill.

FIG. 14 is an explanatory view of resin injection into a hollow portion forming portion in a conventional molding die.

FIG. 15 is an explanatory view at the time of forming a hollow portion in a conventional mold.

[Explanation of symbols]

 1. . . Cavity, 10. . . Mold, 11. . . 11. a gap; . . Hollow portion forming part, 2. . . Seki, 3. . . Radiator grill, 34. . . Front part, 35. . . Lower frame, 36. . . Hollow part, 7. . . Resin, 72. . . Flow tip,

Claims (3)

(57) [Claims] When manufacturing a hollow molded body having a partially hollow portion, a hollow portion in a cavity has a part in a longitudinal direction thereof, and the part is formed of resin and pressurized gas. A method for producing a hollow molded body, comprising injecting a resin into the molding die and injecting a pressurized gas into the resin using a molding die disposed on an upstream side. 2. The method for manufacturing a hollow molded article according to claim 1, wherein the seki is provided at a length of 8% to 60% of the length of the hollow portion forming portion. 3. The method according to claim 1, wherein the seki has a width of 25% to 75% of the width of the hollow portion forming portion.