JPH0596566A - Manufacture of resin-molded product - Google Patents

Abstract

PURPOSE:To provide a method for manufacture of a hollow resin-molded product containing a core material wherein a resin layer and the core material are solidly united. CONSTITUTION:In a method wherein after inserting preliminarily molded core material 2 into a molding metal mold, the metal mold is closed and a resin molded product is molded integrally with the insert by injecting resin, a core is arranged so as to abut against or approach the core material 2 in the metal mold. After introducing the first resin 5 by an amount less than one volume of a metal mold cavity, fluid of a lower viscosity than the resin is forced into from a resin introducing nozzle or a fluid injection opening made in the molding metal mold, and a hollow part, is made inside the resin molded material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a resin molded product such as a steering wheel for steering a vehicle, a rear spoiler, a vehicle body protection molding, etc., in which a core material and a resin are integrally molded.

[0002]

2. Description of the Related Art Conventionally, insert molding which is integrally formed with a core material is manufactured by integrally molding a resin core by injection molding or injection reaction molding on a steel core material which is formed in advance by welding or the like. ing.

By the way, as a resin generally used for these molded products, for example, polypropylene or modified polyphenylene oxide resin is used, and when combined with a steel core material, the molded products become heavy. Easy,
For example, even if a pipe-shaped core material is used, the overall weight is large, which is an obstacle to weight reduction of the vehicle body. In recent years, light alloys are being adopted for core materials, but due to the high material price, it is difficult to use them extensively, especially for long rear spoilers equal to the entire width of the vehicle and protection malls that widely cover the sides of the body. In that case, the core material becomes large,
It is difficult to manufacture a core material with an expensive material. Therefore, if foam molding of the resin is performed, a light weight effect of several% can be expected,
On the other hand, since the foaming extends over the entire cross section, the strength of the grip portion of the steering wheel is reduced, and there is a risk that the bonding strength with the core cannot be maintained. Since bubbles are exposed on the surface, in the rear spoiler and protection molding where the surface appearance is highly demanded, the requirement cannot be satisfied by foam molding. Therefore, there is also a method of suppressing the surface foaming by using, for example, a counter pressure method, but since the weight reduction due to foaming can be obtained by only about 2 to 3% in this method, the advantage of sacrificing the bonding strength between the resin and the core material is obtained. Almost never.
A method of forming inside cells as a continuous space inside the resin molded body without forming dispersed bubbles like a foam, for example,
It is disclosed in Japanese Examined Patent Publication No. 61-53208. However, if an attempt is made to manufacture a resin molding containing a core material by this method,
A space is formed on the outer periphery of the core material, and the core material is in a free state. That is, in the steering wheel, when the operator grips the steering wheel to operate it, the inner core material and the outer skin of the grip portion are not connected to each other, so that the strength cannot be obtained, and in an extreme case, it may be difficult to operate. Whether it ’s a rear spoiler or a protection mall,
The core material and resin part are separated, and the desired product strength cannot be obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to improve the prior art to solve the above problems and to provide a lightweight resin molded product having a space portion capable of maintaining the bonding strength between the core material and the resin portion. It is to provide goods.

[0005]

DISCLOSURE OF THE INVENTION As a result of earnest studies, the inventor of the present invention has arranged a core so as to abut or come close to a core material inserted in a mold. After the introduction, a fluid having a viscosity lower than that of the resin is press-fitted, and more desirably, the core is removed to make a second space in the void of the molded product.
The present inventors have found that the above problems can be solved by introducing the above resin, and have reached the present invention.

That is, the present invention is a method of inserting a preformed core material into a molding die, closing the die and injecting a resin to form a resin molded product integrally with the insert. The core is arranged so as to come into contact with or come close to the core material, and after the first resin is introduced in an amount smaller than the mold cavity volume, the resin is introduced from the resin introduction nozzle or the fluid injection port provided in the molding die. Also press-fit a low viscosity fluid,
A method for producing a resin molded product, characterized in that a hollow portion is formed inside the resin molded body, and as another more preferable embodiment, after molding the first resin, the core is removed and It is a method of manufacturing a resin molded product in which the resin of No. 2 is injected.

The resin molded product of the present invention relates to a hollow resin product having a core material, and the core material and the resin are not in a free state but are firmly integrated with each other.

The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a grip portion of a steering wheel mold cavity. In FIG. 1, the core material 2 is inserted into the cavity 1, and the resin 5 is filled in the cavity in which the core 3 is placed in contact with (or close to) the core material in an amount smaller than the cavity capacity. Then, the core material integrated hollow steering wheel grip portion formed by injecting a fluid from a resin introducing nozzle or a fluid injecting port arranged separately in a mold is schematically shown. Figure 1
As can be seen from the above, this grip has a hollow portion 4 having a volume corresponding to the shortage of the resin filled in the cavity with respect to the cavity volume due to the injected fluid. The periphery of the core material 2 is not communicated by being blocked by the solidified resin layer on the periphery thereof.

Incidentally, FIG. 3 is a sectional view of a grip portion formed by a conventional hollow molding method using gas injection. In this case, the core material and the resin layer are separated from each other by the hollow portion, and are only slightly integrated with the spoke portion (not shown).

This is due to the operation described below. That is, when the resin is injected, the resin is first cooled and solidified on the surfaces of the cavity 1, the core material 2, and the core 3 at a relatively low temperature to form a skin layer on the inner and outer surfaces of the grip. And
The solidification of the resin proceeds relatively slowly at a place away from these surfaces. Then, when the inside of the skin layer is still fluid, a fluid having a viscosity lower than that of the resin, for example, an inert gas such as nitrogen, carbon dioxide, argon, or air is injected, and as described above. In addition, a hollow portion, which has a capacity corresponding to the shortage of the filled resin and is blocked by the continuous resin layer around the core, is formed inside the grip.

Thus, the hollow resin product in which the core material of the present invention is integrated has a hollow portion, but the hollow portion does not separate the core material and the resin, and can be firmly integrated. ..

A more preferred embodiment of the present invention is shown in FIG. FIG. 2 illustrates a case in which the core 3 and the resin are further injected into the voids in FIG. 1 to further strengthen the bond between the core material and the resin.

In the present invention, the core provided in the cavity may be a fixed die integrated with a die or a slide piece that can move back and forth in the cavity.

In the present invention, the first resin and the second resin may be the same or different, as long as they can be used in a resin molded product containing a core material.
There is no limitation on the type of resin.

[0016]

【Example】

Example 1 A method for manufacturing a steering wheel is shown in FIGS. A gas introduction mechanism 9 was provided in the nozzle of the injection molding machine.
A slide piece 7 is installed on the molding die (FIG. 4). It will be described according to the molding process.

In the forward movement of the slide piece, the core material 2 is inserted into the mold and the first resin shot (polypropylene, abbreviated as PP hereinafter) is injected (FIG. 5). Although the core material in the figure has a solid circular cross section, it may have a U-shape, a square shape, or a polygonal shape, and a core material having a hollow inside can be used. The first shot is an amount that fills about 75% of the inner volume of the mold cavity. Simultaneously with the completion of the first shot resin injection, the gas introduction mechanism of the nozzle is opened to blow the gas into the mold (FIG. 6). The gas is air, nitrogen,
It is an inert gas such as carbon dioxide or argon. The gas pressure is tens to hundreds of tens of kilograms per square centimeter. When the gas pressure is maintained and the resin 5 is cooled and solidified, the resin contracts from the inner surface of the hollow portion toward the surface of the product. This is in the opposite direction to the shrinkage in the usual thermoplastic injection molding. After the completion of the cooling and solidification of the resin in the first shot, the slide piece is retracted and the runner for the second shot is opened. And the second shot of resin (P
P) 6 is injected (FIG. 7). Through such a process, the core material and the partially hollow grip are more firmly and integrally formed by the resin connecting portion having the width of the slide piece.

Example 2 A method for manufacturing a steering wheel is shown in FIGS. A gas introduction mechanism 9 is provided in the nozzle of the first injection cylinder of the double-headed injection molding machine. This molding machine is constructed such that a two-sided molding die is attached to a rotary table, and the movable die is rotated to be exchangeable with each other (FIG. 8). The two mobile types have the same shape. It will be described according to the molding process.

The cavity of the fixed mold 10a is provided with the above-mentioned protrusion 3 which serves as the core, and the core material 2 is inserted so as to be in contact therewith, and the resin first shot (P
P) 5 is injected (FIG. 8). The first shot is an amount that fills about 75% of the inner volume of the first mold. Simultaneously with the completion of the first shot resin injection, the gas introduction mechanism of the nozzle is opened to blow the gas into the mold (FIG. 9). Example 1 for gas
It is an inert gas of the same type and pressure as. By holding this gas pressure, the resin is cooled and solidified. After the completion of the cooling and solidification of the resin for the first shot, the mold is opened, and the movable mold 12 is rotated together with the first shot molded product on the mold mounting table (see FIG.
0), it is closed in combination with the fixed mold 10b, and the second shot resin (PP) is injected from the second injection cylinder. The fixed mold 10b is not provided with a projection shape (see FIG.
1). Through such a process, the core material and the partially hollow grip are further firmly and integrally formed by the resin connecting portion having a width corresponding to the protrusion shape. Note that FIG. 12 is a partially enlarged explanatory view of the cavity in a state where gas is injected after injecting the first resin.

Embodiment 3 An embodiment of the rear spoiler will be described with reference to FIGS. 13 and 14 are cross-sectional views in the width direction of the rear spoiler molded product. The upper surface of the spoiler mounted on the vehicle is referred to as an A surface, and the lower surface is referred to as a B surface. The first molding die has a built-in gas introduction mechanism and molds the A side.
A core material that is a combination of a plate material and a hollow bar material is inserted into the first molding die. The mold is provided with a protrusion shape that is in contact with the core material or is close to the core material with a minute gap.
The resin and the gas are sequentially injected in the same manner as in the first embodiment to perform molding. The resin is ABS (acrylonitrile-butadiene-styrene) resin or modified polyphenylene oxide / polyamide hybrid resin (common name: mPPO / PA alloy), P
P etc. The one integrally molded by the first molding die is a molded product having a hollow portion with the concave groove 13 on the B surface side (FIG. 13). This molded product is once taken out from the first (A-side) molding die, the runner is cut off, the opening of the gas introduction portion is closed with a resin lid, and then inserted into the second (B-side) molding die. Like the first molding die, the second molding die also incorporates a gas introduction mechanism. The resin has a cavity capacity of 75
%, The same gas as in the other examples is introduced to obtain a hollow resin molded product (FIG. 14). In order to secure the bonding strength between the A side and the B side and eliminate the difference in the adhesion strength with the coating film and the solvent permeation at the resin-paint interface in the subsequent coating process, it is preferable to use the same or the same type of resin. Although safe, different resins can be used as long as these problems can be solved.

[0021]

As described above, according to the molding method of the present invention, the core material and the resin layer can be made hollow so as to secure the connecting portion having a certain width or more. It is possible to provide a lightweight resin molded product that can secure the bonding strength with the core material and that is closely bonded to the core material.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a grip portion of a steering wheel mold cavity.

FIG. 2 is an explanatory view of the same cross section when resin is further injected into the core portion in FIG.

FIG. 3 is an explanatory view of the same section in the case of molding by a conventional hollow molding method by gas injection.

FIG. 4 is an explanatory diagram of the first embodiment and shows a state in which a slide piece as a core is in contact with a core material in a cavity.

FIG. 5 is an explanatory diagram of the first embodiment and shows a state where the first resin is injected into the cavity.

FIG. 6 is an explanatory diagram of the first embodiment, showing a state where gas is injected into the cavity.

FIG. 7 is an explanatory diagram of the first embodiment, showing a state where the slide piece is retracted from the inside of the cavity and the second resin is injected into the void.

FIG. 8 is an explanatory diagram of the second embodiment and shows a state in which the first resin is injected into the cavity for the steering wheel.

FIG. 9 is an explanatory diagram of the second embodiment and shows a state where gas is injected into the cavity.

FIG. 10 is an explanatory diagram of the second embodiment and shows a state in which the mold is opened and the movable mold is rotated after gas injection.

FIG. 11 is an explanatory diagram of the second embodiment and shows a state in which the second resin is injected into a space in the grip portion of the steering wheel.

FIG. 12 is an explanatory view of the second embodiment and is a partially enlarged explanatory view of a cavity in a state where gas is injected after injecting a first resin.

FIG. 13 is an explanatory view of a third embodiment, showing a rear spoiler (first
The figure which shows the width direction cross section of a stage (A surface) molded product.

FIG. 14 is an explanatory view of the third embodiment, showing a cross section in the width direction of a rear spoiler whose both surfaces are molded.

[Explanation of symbols]

 1 Mold Cavity 2 Core Material 3 Core 4 Hollow Part 5 First Resin 6 Second Resin

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Claims (2)

[Claims] 1. A method of molding a resin molded product integrally with the insert by inserting a preformed core material into a molding die, closing the mold and injecting a resin, wherein the core material is formed on the mold. Place the core so that it comes into contact with or close to it, and after introducing the first resin in an amount smaller than the mold cavity volume, it has a lower viscosity than the resin injection nozzle or the fluid injection port provided in the molding die. A method for producing a resin molded product, characterized in that a fluid is press-fitted to form a hollow portion inside the resin molded product. 2. The resin molded product according to claim 1, wherein after the hollow portion is formed, the second resin is introduced into the void created by removing the core. Manufacturing method.