JP3194336B2 - Method for producing rod-shaped hollow molded article and molded article - 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 producing a rod-shaped hollow molded article having an axial hollow portion therein, and a rod-shaped hollow molded article produced by the production method.

[0002]

2. Description of the Related Art In recent years, in order to save resources and reduce weight,
Various hollow molded articles are manufactured. As a molding method, a short shot molding method is used (for example, JP-A-56-56832). This hollow molding method is a method in which 50% to 90% of the volume of a synthetic resin is previously injected into a cavity, and then a fluid such as a gas is injected into the synthetic resin to form a hollow molded article. In addition,
The synthetic resin is injected in a state of being softened by heating, and is still in a softened state even when the fluid is injected. After the fluid injection, the mold is cooled and the synthetic resin is cured.

As such a hollow molded product, as shown in FIG. 10, for example, there is a grill guard 9 mounted on the front of a radiator grill of an automobile 900. The grill guard 9
Is a rod-shaped main body 90 having bent portions 91, 91 on the left and right sides.
And mounting portions 92, 92 at both ends. And
As shown in FIG. 11, the grill guard 9 includes a synthetic resin portion 98 forming an outer shell and a hollow portion 99.

[0004]

However, the conventional molding method has the following problems. That is, in the hollow molding method, as described above, the synthetic resin is injected partway into the cavity, and then the synthetic resin is further sent forward by the fluid to hollow the inside. As shown in FIGS. 11 and 12, in the case of a large molded product such as the grill guard 9, when gas is injected from the inner peripheral side surface of the grill guard 9 as shown in FIGS. In some cases, a thin portion 93 is formed at 910, or when a gas is injected from the outer peripheral side surface, the hollow portion 99 is biased outward to form a thin portion. This is thought to be due to the fact that as the molded product becomes larger, the amount of resin having relatively high fluidity increases, and the gas injection position has a slight influence.

[0005] The thin portion 93 is easily broken and has low strength, which causes a product defect. The thin portion 9
In the case of No. 3, the whitening phenomenon may occur because the synthetic resin, once cooled, rapidly expands and flows when the fluid is injected during molding. This whitening phenomenon deteriorates the appearance of the bent portion 91 of the grill guard 9 and does not look good.

In the case of forming a rod-shaped hollow molded product like the grill guard 9, as shown in FIG.
A molding die 8 having a cavity composed of a mounting portion forming portion 811 for forming the mounting portion 92 and a main body forming portion 812 for forming the rod-shaped main body 90 is used. First, the synthetic resin 980 in the softened state is formed by the mounting portion forming portion 811.
Is injected as described above, and then a fluid 990 for forming the axial hollow portion 99 is injected from the mounting portion forming portion 811.

However, when the fluid 990 is injected, as shown in FIG. 12, the fluid passage may already be eccentric in the mounting portion forming portion 811. In such a case, also in the main body forming portion 812, FIG.
As shown in the figure, the shaft-shaped hollow portion 99 is eccentric. Therefore, in the obtained grill guard 9, the axial hollow portion 99 in the rod-shaped main body 90 is eccentric, and the rod-shaped main body 90 is deformed or the rigidity is reduced. FIG. 13 shows a case where the shaft-shaped hollow portion 99 is formed at the center without being eccentric in the cross section of the rod-shaped main body 90 (A), and is eccentric (B,
The aspect of C) is shown.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a method of manufacturing a rod-shaped hollow molded article having no eccentricity of a shaft-shaped hollow portion and no deformation, and a rod-shaped hollow molded article.

[0009]

According to the present invention, a rod-shaped hollow molded article having a rod-shaped main body having a shaft-shaped hollow portion therein and a mounting portion integrally provided at an end of the rod-shaped main body is formed by using a molding die. In the method of molding with a synthetic resin, the molding die has a cavity including a main body molding part for molding a rod-shaped main body of the rod-shaped hollow molded article and an attachment part molding part for molding the attachment part. The mounting portion forming portion has a fluid injection groove extending along the axial direction and substantially at the center portion to the main body forming portion and opening at the center portion of the main body forming portion. A synthetic resin in a softened state is injected through the mounting portion forming portion in the direction of the main body forming portion, and then a fluid for forming the axial hollow portion is injected into the synthetic resin through the fluid injection groove. Features In the production method of the rod-shaped hollow molded article.

In the present invention, the most important point is that a groove for fluid injection extending to the main body forming portion is provided in the mounting portion forming portion of the forming die, and a softened synthetic resin is formed in the cavity at the time of molding. And then injecting a fluid for forming an axial hollow portion into the synthetic resin through the fluid injecting groove. The rod-shaped main body integrally has, at one end or both ends, a mounting portion for mounting the rod-shaped hollow molded product to a counterpart material. The rod-shaped main body has an axial hollow portion along the axis thereof.

Further, according to the present invention, when the rod-shaped main body has a bent portion and the shaft-shaped hollow portion is formed in the bent portion, the shaft-shaped hollow portion in the bent portion is not eccentric. It is. The mounting portion forming portion of the forming die has a fluid injection groove extending along the axial direction and extending to the main body forming portion at a central portion. The groove for fluid injection is provided to guide the fluid to the main body forming portion.

The groove for injecting the fluid is formed by a groove which is recessed from the mounting part forming part. The depth of the groove for fluid injection (M in FIG. 2) is 0.2 to 1.0 times the width (width in the depth direction of the groove for fluid injection, W in FIG. 2) in the mounting portion forming portion. It is preferable that If the ratio is less than 0.2 times, the effect of the present invention is low. On the other hand, if the ratio exceeds 1.0 times, the injection position of the fluid may vary and the hollow portion may be eccentric. In addition, more preferably, it is 0.3 to 0.6 times. Further, the grooves for fluid injection can be provided on both sides of the mounting portion forming portion (FIG. 7).

Further, the mounting portion may be one having an H-shape composed of a web and flanges provided on both sides thereof (FIG. 5) or one not having such a flange (FIG. 8). When a flange is provided, the strength of the mounting portion is improved, but on the other hand, the fluid injected during molding tends to flow toward the flange. Therefore, when the mounting portion having the flange is formed, the effect of the present invention is particularly large.

[0014] The rod-shaped hollow molded article obtained by the above-mentioned manufacturing method is a rod-shaped hollow molded article having a rod-shaped main body having a shaft-shaped hollow portion therein and a mounting portion integrally provided at an end of the rod-shaped main body. In the article, the mounting portion has a thickened portion along the axis of the mounting portion, and a hollow communication hole communicating with the shaft-shaped hollow portion of the rod-shaped main body inside the thickened portion. There is a rod-shaped hollow molded article characterized by the above.

In the rod-shaped hollow molded product, the thickened portion is a portion formed by the fluid injection groove of the mounting portion forming portion of the rod-shaped main body. According to this rod-shaped hollow molded product, since the mounting portion has the above-mentioned thickened portion, the mounting portion is not deformed and has high rigidity. In the rod-shaped hollow molded product, the thickness of the thickened portion is 0.2 to 0.2 mm of the thickness of the mounting portion.
It is preferably set to 1.0 times. If it is less than 0.2 times, the rigidity is not sufficiently improved. On the other hand, even if it exceeds 1.0 times, the effect corresponding thereto is small and the weight increases.

As the synthetic resin, for example, polypropylene (PP), acrylic butadiene styrene (AB)
S), various thermoplastic resins such as polyphenylene oxide (PPO) and soft vinyl chloride (PVC). Also,
The fluid, for example, inert gas (Ar, He, etc.), gases of non-oxidizing gas (N _2, etc.), or water, a liquid such as oil is used. In addition, there are a mode in which the fluid is injected after the injection of the synthetic resin, and a mode in which the synthetic resin and the fluid are simultaneously injected after a small amount of the synthetic resin is mixed.

The rod-shaped hollow molded articles to which the present invention can be applied include grill guards for automobiles, assist grips, roof carriers and handrails for houses and the like as described above.

[0018]

In the manufacturing method according to the present invention, the above-mentioned groove for fluid injection is formed in the mounting portion forming portion in the cavity of the forming die. In molding the rod-shaped hollow molded product, first, a synthetic resin that has been heated and is in a softened state is injected from the mounting portion forming portion, and then the fluid is injected from the mounting portion forming portion. At this time, the fluid is injected through the fluid injection groove.

The fluid that has entered the groove for injecting fluid advances in the groove for injecting fluid and enters the synthetic resin in the molded body. Then, an axial hollow portion is formed inside the rod-shaped main body while extruding the synthetic resin in the main body forming section forward. The shaft-shaped hollow portion is formed substantially at the center of the rod-shaped main body without eccentricity. The reason why the axial hollow portion is not eccentric is considered as follows.

That is, when the mounting portion and the rod-shaped main body having the shaft-shaped hollow portion are integrally formed, if the mounting portion forming portion does not have the above-described fluid injection groove, the fluid is injected into the mounting portion forming portion. The fluid proceeds through the synthetic resin filled in the mounting portion forming portion to a portion where the fluid can easily travel. Such a portion where the fluid easily advances is a portion where the synthetic resin has not yet sufficiently solidified and is in a softened state in the mounting portion forming portion.

However, the synthetic resin in the heated and softened state filled in the mounting portion molding portion does not always cool down from the outer periphery to the inside due to the temperature distribution of the molding die. For this reason, as described above, the fluid irregularly advances to the uncured portion where the fluid easily advances. Therefore,
When the fluid enters the main body forming portion, it may not enter the center portion of the main body forming portion but enter eccentrically near the peripheral portion. In such a case, the shaft-shaped hollow portion of the rod-shaped hollow molded product is eccentric.

On the other hand, in the present invention, a groove for fluid injection is provided along the axial direction at the central portion of the mounting portion forming portion, and the softened state in the groove for fluid injection is provided. Since the synthetic resin is far from the cavity wall,
Finally, it will cure. Therefore, as described above, the fluid injected into the synthetic resin in the mounting portion forming portion advances regularly in the softened synthetic resin substantially at the center of the fluid injection groove. Since the groove for fluid injection is opened at the central portion of the main body forming portion, the fluid advances in the central portion of the main body forming portion. Therefore, the shaft-shaped hollow portion in the rod-shaped main body is formed substantially at the center without eccentricity.

Further, since the shaft-shaped hollow portion is formed without eccentricity in the central portion of the rod-shaped main body, a rod-shaped hollow molded product free from deformation can be manufactured. Further, according to the rod-shaped hollow molded product of the present invention, a shaft-shaped hollow portion is formed in the center of the rod-shaped main body, and a thickened portion is provided in the mounting portion. can get.

As described above, according to the present invention, it is possible to provide a method for producing a rod-shaped hollow molded article having no eccentricity of a shaft-shaped hollow portion and no deformation, and a rod-shaped hollow molded article.

[0025]

【Example】

Example 1 A rod-shaped hollow molded product according to an example of the present invention and a method of manufacturing the same will be described with reference to FIGS. The rod-shaped hollow molded product to be obtained in this example is a grill guard attached to the front of an automobile (see a conventional example). As shown in FIGS. 5 and 6, the rod-shaped hollow molded product 4 has a rod-shaped main body 41 having a shaft-shaped hollow portion 49 therein, and mounting portions 42 provided integrally at both ends of the rod-shaped main body 41. Mounting part 4
2, a hollow communication hole 491 communicating with the shaft-shaped hollow portion 49 of the rod-shaped main body 41 is provided on the inside of the thickened portion 43 along the axis of the mounting portion. Have.

The rod-shaped main body 41 has a U-shape and comprises the shaft-shaped hollow portion 49 and a synthetic resin portion 48 forming an outer shell. In addition, a bent portion 411 is provided. The mounting part 42
Comprises a web 421 and flanges 422 on both sides thereof.

Next, a method for producing the rod-shaped hollow molded article 4 with a synthetic resin using a molding die will be described with reference to FIGS.
This will be described with reference to FIG. First, the molding die 1 includes a main body forming part 22 for forming a U-shaped rod-shaped main body 41 in the rod-shaped hollow molded product 4 and a mounting part forming part 21 for forming the mounting part 42. It has a cavity 2.

The mounting portion forming portion 21 is provided with a fluid injection groove 23 (FIG. 2) extending along the axial direction and extending to the main body forming portion at the center portion and opened at the center portion of the main body forming portion 22. ). In FIG. 2, the depth M of the groove 23 for fluid injection is about 0.1 mm of the width W of the mounting portion forming portion 21.
5 times.

Next, in molding, as shown in FIGS. 3 and 4, first, a synthetic resin 28 in a heated and softened state is injected from the gate 11 toward the main body forming section 22 through the mounting section forming section 21. The synthetic resin 28 is injected in an amount necessary for forming the outer shell of the rod-shaped hollow molded article. Next, from the gate 11, the mounting part forming part 21, the main body forming part 22
Nitrogen gas 29 as a fluid is injected into the synthetic resin 28 inside.

It is important that the nitrogen gas 29
Means to inject through the fluid injection groove 23 in the mounting part forming part 21. That is, as shown in FIG.
Inject into the wide part between 1.

At this time, since the synthetic resin in the vicinity of the fluid injection groove 23 is located far from the cavity wall surface of the molding die 1, its curing is slowest. Therefore, the nitrogen gas 29 injected into the fluid injection groove 23 advances forward through the resin 28 in the fluid injection groove 23 that has not been cured yet. The groove 23 for fluid injection is opened at the center of the main body forming portion 22, that is, at the center of the cross section in a direction perpendicular to the axial direction.

Therefore, the nitrogen gas 29 that has advanced through the groove 23 for fluid injection enters the central portion of the main body forming portion 22, that is, the central portion of the rod-shaped main body, and proceeds along the central portion of the main body forming portion 22. And, since the cross section of the main body forming part in the direction perpendicular to the axial direction is larger than that of the mounting part forming part,
The air that has entered the central portion of the main body molding portion travels through the central portion of the resin 28 in the main body molding portion (FIGS. 3 and 4).

Accordingly, in the rod-shaped hollow molded product obtained by the manufacturing method of this embodiment, as shown in FIGS. 5 and 6, a shaft-shaped hollow portion is formed at the center of the rod-shaped main body 41 without being eccentric. Also, in the bent portion 411 of the rod-shaped main body 41, the thickness of the incourse is almost the same as the other portions, and the incourse does not become thin unlike the conventional example. Therefore, the rod-shaped hollow molded product has no deformation and high rigidity. As described above, according to the present embodiment, the shaft-shaped hollow portion can be formed almost in the center without eccentricity, and a rod-shaped hollow molded product having no rigidity and high rigidity can be obtained.

Example 2 As shown in FIG. 7, this example shows a rod-shaped hollow molded product 4 of Example 1.
, The thickened portions 431, 43
This is an example in which No. 2 is formed. The enlarged portions 431 and 432 are
In the mounting part forming part 21 of the forming die in the first embodiment,
It can be formed by providing fluid injection grooves 23 on both sides (upper and lower sides in FIG. 2). Others are the same as the first embodiment.

According to this embodiment, since the groove 23 for injecting fluid is provided on both sides of the mounting portion forming portion 21, the synthetic resin in the groove 23 for injecting fluid slowly cures during molding. Therefore, the axial hollow portion 49 of the rod-shaped main body can be formed while slowly injecting the fluid. Therefore, the eccentricity of the shaft-shaped hollow portion 49 can be further prevented. Other effects similar to those of the first embodiment can be obtained.

Embodiment 3 In this embodiment, as shown in FIG. 8, an example in which the shape of the mounting portion 42 is plate-shaped in the rod-shaped hollow molded product 4 similar to that of Embodiment 1 is shown. That is, the mounting portion 42 does not have a flange unlike the mounting portion of the first embodiment. Others are the same as the first embodiment. In this embodiment, the same effect as in the first embodiment can be obtained.

Embodiment 4 In this embodiment, as shown in FIG. 9, a mounting seat 44 is provided on a flange 422 of the mounting portion 42 of the first embodiment. The mounting seat 44 is used when the rod-shaped hollow molded product 4 is mounted on a mating member, and is used to insert a T-bolt.
It has a bolt insertion hole 441. In this embodiment, the same effect as in the first embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a molding die according to a first embodiment.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is an explanatory view at the time of forming a rod-shaped hollow molded product in Example 1.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a partial perspective view of a rod-shaped hollow molded product obtained in Example 1.

FIG. 6 is a partial cross-sectional side view of a rod-shaped hollow molded product obtained in Example 1.

FIG. 7 is a perspective view of a mounting portion of a rod-shaped hollow molded product according to a second embodiment.

FIG. 8 is a perspective view of a mounting portion of a rod-shaped hollow molded product according to a third embodiment.

FIG. 9 is a perspective view of a mounting portion of a rod-shaped hollow molded product according to a fourth embodiment.

FIG. 10 is an explanatory view of a grill guard as a rod-shaped hollow molded product in a conventional example.

FIG. 11 is a partial cross-sectional side view of a grill guard in a conventional example.

FIG. 12 is an explanatory view at the time of forming a grill guard in a conventional example.

FIG. 13 is a sectional view showing a problem of a grill guard in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold, 2 ... Cavity, 21 ... Mounting part forming part, 22 ... Body forming part, 23 ... Fluid injection groove, 28 ... Synthetic resin, 29 ... · Air, 4 ··· rod-shaped hollow molded product, 41 · · · bar-shaped main body, 42 · · · mounting part, 43, 431, 432 · · · expanded part, 49. . . Shaft-shaped hollow,

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/37 B29C 49/00-49/06 B29D 23/00-23/24 B29L 23:00

Claims (6)

(57) [Claims] 1. A rod-shaped main body having an axial hollow portion therein,
In a method of molding a rod-shaped hollow molded product having an attachment portion integrally provided at an end portion of the rod-shaped main body with a synthetic resin using a molding die, the molding die comprises a rod-shaped main body in the rod-shaped hollow molded product. It has a cavity consisting of a main body forming part for molding and a mounting part forming part for forming the mounting part. The mounting part forming part extends along the axial direction and substantially in the center to the main body forming part. It has a groove for fluid injection which is extended and opened at the center of the main body molding part. In molding, first, a synthetic resin in a softened state in the direction of the main body molding part is injected through the mounting part molding part,
Then, a fluid for forming the shaft-shaped hollow portion is injected into the synthetic resin through the fluid injection groove. 2. The method according to claim 1, wherein the rod-shaped main body has a bent portion. 3. The groove according to claim 1, wherein the depth of the groove for injecting fluid is 0.2 to less than 0.2 of the width of the molded part of the mounting part.
A method for producing a rod-shaped hollow molded product, wherein the ratio is 1.0 times. 4. The method of manufacturing a rod-shaped hollow molded product according to claim 1, wherein said mounting portion has an H shape comprising a web and flanges provided on both sides thereof. 5. A rod-shaped main body having an axial hollow portion therein,
A rod-shaped hollow molded article having an attachment portion integrally provided at an end of the rod-shaped main body, wherein the attachment portion has a thickened portion along an axis of the attached portion, and the inside of the thickened portion is Wherein the hollow rod-shaped body has a hollow communication hole communicating with the shaft-shaped hollow portion of the rod-shaped main body. 6. The rod-shaped hollow molded article according to claim 5, wherein the rod-shaped main body has a bent portion.