JP2012245699A - Injection molding mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding mold capable of preventing the occurrence of sagging in the surface and an edge part of a rising part side in molding a foamed molded article having the rising part rising toward the back surface in at least one part of the circumferential edge and capable of obtaining the high quality formed molded article having excellent surface shape.SOLUTION: The injection molding mold 10 for molding the foamed molded article having the rising part rising toward the back surface in at least the part of the circumferential edge is provided with a pressing member 22 pressing from the tip side at least outside surface side of a part corresponding to the rising part in the foamed resin X injected and filled into the cavity 16 except the inside surface side.

Description

  The present invention relates to an injection mold.

  For example, foam molded products are used as automotive interior materials having excellent sound absorption and light weight. An injection mold is used for manufacturing such a foam molded product. As an injection mold, for example, there are a movable mold and a fixed mold that form a cavity, and after filling the foamed resin into the cavity formed by clamping them, the movable mold is used. There is known an injection mold in which molding is performed by causing the foamed resin to foam by reducing the pressure inside the cavity by slightly moving away from the stationary mold (core back).

On the other hand, there are various foam molded products, for example, a foam molded product having a flat plate-like base portion and a rising portion rising toward the back surface at at least a part of the periphery of the base portion. However, when a foam molded product having such a shape is manufactured with an injection mold, the following problems occur.
FIG. 9 shows an injection mold 110 having a movable mold 112 and a fixed mold 114, and a cavity 116 is formed by clamping them. The cavity 116 includes a base portion forming portion 116a that forms a flat plate-like base portion of the foam molded product and a rising portion forming portion 116b that forms a rising portion of the foam molded product. In the production of a foam molded product using the injection mold 110, as shown in FIG. 10, when the foamed resin Y injected and filled in the cavity 116 is foamed by the core back, the cavity forming surface of the movable mold 112 is formed. When the skin layer in the vicinity of the corner 112c formed by the upper surface 112a and the side surface 112b is pulled, the edge corresponding to the corner 112c in the obtained foamed molded product is sag, and the merchantability is impaired. Sometimes.

As a method for suppressing the sagging of the edge portion of the above-described foam molded product, for example, a method using an injection mold 210 illustrated in FIG. 11 is disclosed (Patent Document 1). The injection mold 210 has a movable mold 212 and a fixed mold 214 that form a cavity 216. The cavity 216 includes a base forming section 216a that forms the base of a foam molded article, and the foam molded article. It comprises a rising portion forming portion 216b that forms a rising portion. Further, a step is provided in a portion 214 a corresponding to the rising portion of the foam molded product on the cavity forming surface of the fixed side die 214.
In the production of the foam molded product using the injection mold 210, the thickness of the rising portion of the foam molded product is set to be thick due to the step, so that the foamed resin Y is foamed at the rising portion forming portion 216b of the cavity 216. As the amount increases, the foaming pressure increases. Therefore, at the time of foam molding, the foamed resin Y is filled in the vicinity of the corner portion 212c formed by the upper surface 212a and the side surface 212b of the cavity forming surface of the movable mold 212, and the corresponding edge portion of the obtained foam molded product is sag. An effect of suppressing the occurrence is obtained. However, even if the thickness of the rising portion is increased, if the skin layer is thick, the contraction force by the skin layer is also increased, so it is difficult to stably and sufficiently fill the foamed resin Y in the vicinity of the corner portion 212c. It is difficult to sufficiently obtain the effect of suppressing the sagging of the edge portion.

A method using the injection mold 310 illustrated in FIG. 12 is also known (for example, Patent Document 2). The injection mold 310 includes a movable mold 312 and a fixed mold 314 that form a cavity 316. The cavity 316 includes a base forming section 316a that forms a base of a foam molded article, and the foam molded article. It comprises a rising portion forming portion 316b that forms a rising portion. The fixed mold 314 is provided with a pressing member 318 that presses the foamed resin Y present in the rising portion forming portion 316b of the cavity 316, that is, the entire portion corresponding to the rising portion of the foam molded product.
In the production of a foam molded product using the injection mold 310, the foamed resin Y of the rising portion forming portion 316b of the cavity 316 is pressed by the pressing member 318 during the core back foaming, whereby the movable side mold 312 is pressed. The foamed resin Y is filled in the vicinity of the corner portion 312c formed by the upper surface 312a and the side surface 312b of the cavity forming surface, and the occurrence of sagging at the corresponding edge portion in the obtained foamed molded product is suppressed. However, in the manufacture of the foam molded product using the injection mold 310, the foamed resin Y in the vicinity 316c of the rising portion forming portion 316b in the base forming portion 316a of the cavity 316 is lifted by the pressing by the pressing member 318. Depending on the influence, not only the back surface of the base portion of the obtained foam molded article but also the surface may be distorted, and the quality may be deteriorated.

Further, as an injection mold for pressing the entire portion corresponding to the rising portion of the foam molded product, as shown in FIG. 13, a base forming portion 416a that forms the base of the foam molded product, and the rising of the foam molded product. A movable side mold 412 that forms a cavity 416 and a fixed side mold 414 that form a rising part forming part 416b that forms a part, and a base forming part together with the foamed resin Y that exists in the rising part forming part 416b of the cavity 416 An injection mold 410 provided with a pressing member 418 that presses a portion on the part forming portion 416b side in the foamed resin Y existing in 416a is conceivable.
When the injection mold 410 is used, as in the case of using the injection mold 310, the occurrence of sagging at the edge of the rising portion of the foam molded product is suppressed, but the surface of the base of the foam molded product is distorted. May occur and the quality may deteriorate.

JP 2009-262499 A JP2011-788

  The present invention is an injection mold for molding a foam-molded product having a rising portion that rises toward the back surface at least at a part of the periphery, and is formed by the surface of the foam-molded product and the outer surface on the rising portion side. It is an object of the present invention to provide an injection mold that can suppress the occurrence of sagging at the edge portion and that can produce a high-quality foamed molded article having a good surface shape.

The injection mold of the present invention is an injection mold for molding a foam molded product having a rising portion that rises toward the back surface at least at a part of the periphery,
A pressing member is provided that presses at least the outer surface side from the distal end side except for the inner surface side of the portion corresponding to the rising portion in the foamed resin injected and filled into the cavity.

  An injection mold according to the present invention is an injection mold for molding a foam molded product having a rising portion that rises toward the back surface on at least a part of the periphery, and is formed on the surface of the foam molded product and the rising portion side. It is possible to suppress the occurrence of sagging at the edge portion formed on the outer side surface and to manufacture a high-quality foam molded product having a good surface shape.

It is the perspective view which showed an example of the foaming molded product. It is sectional drawing which showed an example of the injection mold of this invention. It is sectional drawing to which the press member vicinity of the injection mold of FIG. 2 was expanded. It is sectional drawing which showed a mode that a foaming molded product was manufactured with the injection mold of FIG. It is sectional drawing which showed a mode that a foaming molded product was manufactured with the injection mold of FIG. It is the perspective view which showed the other example of the foaming molded product. It is sectional drawing which showed the other example of the injection mold of this invention. It is sectional drawing which showed the other example of the injection mold of this invention. It is sectional drawing which showed an example of the conventional injection mold. It is sectional drawing which showed a mode that a foaming molded product was manufactured with the injection mold of FIG. It is sectional drawing which showed the other example of the conventional injection mold. It is sectional drawing which showed the other example of the conventional injection mold. It is sectional drawing which showed an example of the injection mold.

The injection mold of the present invention is an injection mold that molds a foam molded product having a rising portion that rises toward the back surface on at least a part of the periphery. Hereinafter, as an example of an injection mold of the present invention, an injection mold for manufacturing the foamed molded article 1 illustrated in FIG. 1 by core back foaming by a counter pressure method will be described.
As shown in FIG. 1, the foam molded article 1 has a flat plate-like base portion 2 and rising portions 3 that rise toward the back surface 1 b at both ends of the base portion 2.

  As shown in FIGS. 2 and 3, the injection mold 10 of the present embodiment (hereinafter referred to as “mold 10”) has a movable mold 12 and a fixed mold 14, and is movable. A cavity 16 is formed by the side mold 12 and the fixed side mold 14.

The movable mold 12 has a recess 12a that forms a cavity 16 on the fixed mold 14 side. The movable mold 12 can be moved forward and backward toward the fixed mold 14.
The shape of the cavity 16 can be adjusted by adjusting the shape of the concave portion 12a of the movable mold 12 and the shape of the fixed mold 14 on the movable mold 12 side. The shape of the cavity 16 in this example is a shape corresponding to the shape of the foam molded product 1. That is, the cavity 16 has a base forming part 16 a that forms the base 2 of the foam molded product 1 and a rising part forming part 16 b that forms the rising part 3 of the foam molded product 1.

  On the cavity forming surface of the concave portion 12a of the movable side mold 12, a textured unevenness may be formed, or the unevenness may not be formed. Moreover, when forming the said unevenness | corrugation, you may form in both the upper surface 12b and the side surface 12c of a cavity formation surface, and you may form only in either the upper surface 12b or the side surface 12c.

An O for tightly sealing the cavity 16 formed by the movable mold 12 and the fixed mold 14 on the PL surface 18 with the fixed mold 14 positioned on the outer periphery of the concave portion 12a of the movable mold 12. A ring 20 is provided.
A gas flow path (not shown) for injecting and exhausting counter pressure gas (hereinafter referred to as “CP gas”) is formed inside the O-ring 20 of the PL surface 18 in the stationary mold 14.

Further, a portion corresponding to the rising portion 3 of the foamed molded article 1 to be formed in the foamed resin injected and filled in the cavity 16 is formed in the portion of the rising portion forming portion 16b in the fixed mold 14 of the mold 10. A pressing member 22 that presses at least the outer surface side from the distal end side except for the inner surface side is provided.
As illustrated in FIG. 3, the pressing member 22 includes a shaft portion 24 and a head portion 26 that is larger than the shaft portion 24. The pressing member 22 is inserted through the fixed mold 14 toward the movable mold 12 side. Further, the inner edge 26 a of the mold 10 in the head portion 26 includes a side surface 14 a of the rising portion forming portion 16 b on the cavity forming surface of the fixed mold 14 and a rising portion on the cavity forming surface of the movable mold 12. The upper surface 26b of the head portion 26 is located between the side surfaces 12c of the forming portion 16b, and coincides with the lower surface 14b of the rising portion forming portion 16b on the cavity forming surface of the stationary mold 14. That is, by projecting the pressing member 22 from the main body portion of the fixed-side mold 14, a part of the pressing member 22 on the cavity 16 side of the head portion 26 is formed on the rising portion forming portion 16 b of the cavity 16 as shown in FIG. 5. The side surface 12c side of the cavity forming surface of the movable mold 12 in the filled foam resin X can be partially pressed.

  In the production of the foam molded product 1 using the mold 10, the pressing member 22 protrudes from the fixed mold 14 when the movable mold 12 is core-backed. Then, as shown in FIG. 5, the foamed resin X present in the rising portion forming portion 16 b, that is, the portion corresponding to the rising portion 3 of the foamed molded product 1 in the foamed resin X present in the cavity 16, The foaming is performed in a state where at least the outer surface side is pressed from the tip side.

  As described above, in the conventional injection mold 210, even if the thickness of the rising portion is increased, if the skin layer is thick, the sagging of the edge portion is suppressed due to the influence of the increased shrinkage force by the skin layer. It is difficult to obtain a sufficient effect. On the other hand, the mold 10 of the present invention is movable by pressing at least the outer surface side of the foamed resin X existing in the rising portion forming portion 16b with the pressing member 22 without increasing the thickness of the rising portion. Foam molding can be performed in a state where a sufficient foamed resin is stably filled in the vicinity of the corner 12d formed by the upper surface 12b and the side surface 12c of the cavity forming surface of the side mold 12. Therefore, it can suppress that sagging arises in the edge part 4 by the side of the standing part 3 in the surface of the foaming molded article 1 shown in FIG.

  In addition, in the injection molds 310 and 410, as described above, the surface of the base portion of the obtained foam molded product may be distorted due to the pressing by the pressing members 318 and 418, and the quality may be deteriorated. On the other hand, in the mold 10 of the present invention, as shown in FIG. 5, the inner surface side of the foamed resin X of the rising portion forming portion 16 b is not pressed, so that the inner surface of the tip portion of the rising portion 3 of the foamed molded article 1 to be obtained. Although slight distortion occurs on the side, there is little adverse effect because it is on the back surface 1b side. In addition, since the distance from the tip portion of the rising portion 3 to the surface 1a is longer than the distance from the back surface 1b of the base portion 2 to the surface 1a, the influence of the distortion at the tip portion of the rising portion 3 hardly affects the surface 1a. A foam molded article 1 having a good shape on the surface 1a is obtained.

  Further, in the injection mold 410, the ratio of the foamed resin Y foaming in the rising portion forming portion 416b of the cavity 416 during foaming of the core back decreases, and the ratio of the skin layer around the rising portion in the obtained foamed molded product is reduced. Therefore, it is difficult to obtain effects such as weight reduction and rigidity improvement. On the other hand, in the mold 10 of the present invention, since the foamed resin X existing in the rising portion forming portion 16b is partially pressed, the foam molded product 1 having the base 2 which is foamed on the entire surface and improved in rigidity is obtained. .

The outer surface pressed by the pressing member 22 in the foamed resin X existing in the rising portion forming portion 16b with respect to the width D of the foamed resin X existing in the rising portion forming portion 16b (width of the rising portion forming portion 16b, FIG. 4). The ratio of the side width d ₁ (FIG. 4) is preferably 20 to 80%, and more preferably 40 to 60%. If the said ratio is more than a lower limit, it will become easy to suppress that the edge part 4 of the foaming molding 1 obtained is sagging. Moreover, if the said ratio is below an upper limit, it will become easy to suppress that distortion arises on the surface of the foaming molding 1 obtained.

The inner surface side of the foamed resin X present in the rising portion forming portion 16 b is not pressed by the pressing member 22. The width d of the unpressed portion of the foamed resin X present in the rising portion forming portion 16b with respect to the width D of the foamed resin X existing in the rising portion forming portion 16b (width of the rising portion forming portion 16b, FIG. 4) ₂ (FIG. 4) is preferably 20 to 80%, more preferably 40 to 60%. If the said ratio is more than a lower limit, it will become easy to suppress that distortion arises on the surface of the foaming molded article 1 obtained. Moreover, if the said ratio is below an upper limit, it will become easy to suppress that the edge part 4 of the foaming molding 1 obtained is sagging.

In this example, the direction in which the foamed resin is pressed by the pressing member 22 is the direction along the axial direction of the rising portion forming portion 16 b, that is, the direction along the axial direction of the rising portion 3 in the obtained foamed molded product 1. The pressing of the foamed resin by the pressing member 22 is not necessarily in the direction along the axial direction, and may be in a direction inclined with respect to the axial direction as long as the effect of the present invention is not impaired. .
The mechanism for projecting the pressing member 22 from the stationary mold 14 is not particularly limited, and examples thereof include a mechanism that uses hydraulic pressure, a spring, or the like.

  Further, the fixed side mold 14 is provided with a resin injection channel (not shown) for injecting a foamed resin into the cavity 16, and the resin injection channel is provided from a known injection molding machine equipped with an injection nozzle. The foamed resin can be injected and filled through.

Hereinafter, a method for manufacturing the foam molded article 1 using the mold 10 will be described. The method for manufacturing a foam molded article according to the present embodiment includes the following gas injection process, resin filling process, exhaust process, foaming process, and protruding process.
Gas injection step: CP gas is injected into the cavity 16.
Resin filling step: Foamed resin X is injected and filled into the cavity 16 into which CP gas has been injected.
Foaming step: The CP gas in the cavity 16 is exhausted, the movable mold 12 is core-backed, and the outer surface side of the portion corresponding to the rising portion 3 of the foamed molded product 1 in the foamed resin X is the tip side. The foamed resin X is foamed while being pressed by the pressing member 22.

Gas injection process:
First, as shown in FIGS. 2 and 3, the movable mold 12 is advanced toward the fixed mold 14 to clamp the movable mold 12 and the fixed mold 14, and the cavity is formed through the gas flow path. CP gas is injected into 16 and the pressure in the cavity 16 is adjusted to a predetermined pressure.
Examples of the CP gas include nitrogen gas and carbon dioxide gas.

  The pressure in the cavity 16 is preferably 100 KPa to 1000 KPa, and more preferably 300 KPa to 600 KPa. If the pressure in the cavity 16 is equal to or higher than the lower limit value, it is easy to suppress the formation of silver streaks on the surface of the obtained foamed molded product. If the pressure in the cavity 16 is equal to or lower than the upper limit value, it is easy to suppress the occurrence of avatar due to the residual CP gas in the cavity 16.

Resin filling process:
Next, as shown in FIG. 4, the foamed resin X is injected and filled into the cavity 16 into which the CP gas has been injected through the resin injection flow path. The injection-filled foamed resin X is filled in the cavity 16 in a state where foaming is suppressed because the inside of the cavity 16 is controlled to a high pressure.
Examples of the foamed resin X include polypropylene resin, polyethylene resin, and ABS resin.

Foaming process:
The CP gas in the cavity 16 injected and filled with the foamed resin X is exhausted through the gas flow path, and the movable mold 12 is retracted from the fixed mold 14 while maintaining the sealing property of the cavity 16 as shown in FIG. (Core back), the pressure in the cavity 16 is lowered, and the foaming reaction of the foamed resin X proceeds. At this time, in accordance with the retraction of the movable mold 12, the pressing member 22 protrudes from the fixed mold 14 and the foamed resin X present in the rising portion forming portion 16b, that is, the foamed resin X in the cavity 16 The foaming is performed in a state where the portion corresponding to the rising portion 3 of the foam molded product 1 is pressed by the pressing member 22 at least the outer surface side from the distal end side except the inner surface side.
After foam molding, the mold 10 is opened and the molded foam molded product 1 is taken out.

  As described above, by using the mold 10, it is possible to suppress the occurrence of sagging in the edge portion 4 formed by the surface 1a and the outer surface 3a of the rising portion 3, and the occurrence of distortion in the surface 1a. A high-quality foam molded article 1 in which sufficient foaming is performed in 3 is obtained.

  The injection mold of the present invention is not limited to the mold 10. For example, a core back foaming mold that does not use the counter pressure method may be used. The movable mold 10 and the fixed mold 12 are given as examples, and 10 may be a fixed mold and 12 may be a movable mold.

Moreover, the injection mold 10A illustrated in FIG. 7 (hereinafter referred to as “mold 10A”) for producing the foam molded product 1A illustrated in FIG. 6 may be used. In the foam molded product 1 </ b> A and the mold 10 </ b> A, the same portions as those of the foam molded product 1 and the mold 10 are denoted by the same reference numerals and description thereof is omitted.
The foam molded product 1 </ b> A is the same as the foam molded product 1 except that a flange portion 5 extending outward is formed at the tip portion of the rising portion 3. The mold 10A has a movable mold 12A having a concave portion 12e shaped to match the shape of the foam molded product 1A to be formed, and can form a cavity 16A having a shape complementary to the shape of the foam molded product 1A. , The same as the mold 10. Also in the production of the foam molded product 1A using the mold 10A, the pressing by the pressing member 22 causes the edge portion 4 formed by the surface 1a and the outer surface 3a of the rising portion 3 to sag, and the surface is distorted. This can be suppressed, and a high-quality foam molded article 1A in which sufficient foaming is performed at the rising portion 3 is obtained.

8 may be the injection mold 10B illustrated in FIG. 8 (hereinafter referred to as “mold 10B”). The same parts as those of the mold 10 in the mold 10B are denoted by the same reference numerals and description thereof is omitted.
The mold 10B is a mold for molding a foam molded product in which the outer surface side of the rising portion rises higher than the inner surface side. In the mold 10B, the height of the outer portion is high at the portion of the cavity 16B where the rising portion is molded, and the foamed resin filled in the outer portion is pressed in accordance with the retreat of the movable mold 12. The member 22 is pressed. Even in the production of a foam molded product using the mold 10B, it is possible to suppress the occurrence of sagging at the edge portion on the rising portion side in the obtained foam molded product.

DESCRIPTION OF SYMBOLS 1, 1A Foam molded product 2 Base part 3 Standing part 4 Edge part 5 Flange part 10, 10A, 10B Injection mold 12, 12, A, 12B Movable side mold 14 Fixed side mold 16, 16A, 16B Cavity 18 PL surface 20 O-ring 22 Press member 24 Shaft 26 Head

Claims (1)

An injection mold for molding a foamed molded article having a rising portion that rises toward the back surface at least at a part of the periphery,
An injection mold provided with a pressing member that presses at least the outer surface side from the tip side, excluding the inner surface side, of a portion corresponding to the rising portion in the foamed resin injected and filled into the cavity.

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