JPH05116176A - Manufacture of resin molded product - Google Patents

Abstract

PURPOSE:To provide the manufacturing process of a resin molded product which is light-weight and has a hollow core material with superb adhesive strength demonstrated on the adhesion between the core material and a resin layer. CONSTITUTION:First, a core material 1 having a closed space formed internally is previously introduced into a molding die, then the die is closed and a molten resin 2 is injected into the die to form the core material and the resin in one piece. In this process, at least, two orifices 3 communicating with the internal space are provided in the core material, and the core material is injected in such a manner that it is enveloped with the molten resin. Farther, a liquid which does not become mixed with the resin and is of lower viscosity than the resin is injected into the core material through at least, one of the orifices provided on the core material. Thus the liquid is charged into the interior of the core material under pressure.

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 resin molded product containing a core material having an internal space, such as a steering wheel for steering and an air port part.

[0002]

2. Description of the Related Art Conventionally, a steering wheel has been manufactured by integrally molding a resin core on a steel core material previously formed by welding or the like by injection molding or the like.

By the way, as a conventional resin for a steering wheel, polypropylene or vinyl chloride resin, for example, is used. However, even if a solid steering wheel is apt to be heavy, for example, a pipe-shaped core material is used, There was a problem in that the operation inertial force was large and the weight of the vehicle body was reduced. In recent years, light alloys have been adopted for core materials, but their widespread use is difficult due to the high material price. If foam molding of the resin is performed there, a light weight effect of several% can be expected, but on the other hand, since foaming extends over the grip and spoke cross section, there is a risk that the bonding strength between the outer peripheral resin of the steering wheel and the core cannot be maintained. .. Further, bubbles are exposed on the surface, which is not preferable in terms of product appearance. Therefore, there is also a method of suppressing surface foaming by using, for example, a counter pressure method, but this method reduces the weight by foaming by 2-3%.
There is little benefit in sacrificing the bond strength between the resin and the core, since only a small degree is obtained. Further, it is not possible to partially induce foaming, and performing foaming molding and non-foaming molding in separate steps complicates the manufacturing process, and it is possible to maintain a reasonably inexpensive lightweight and required strength. You can't get steering.

[0006] For example, Japanese Patent Publication No. 61-53208 discloses a method in which internal bubbles are formed as a continuous space inside a resin molded body without forming bubbles like a foamed body. Indeed, if the hollows are formed by this method, the dispersed microbubbles formed by the conventional foam molding can be concentratedly formed, which is advantageous in partially providing strength. However, if a resin molded product containing a core material such as a steering wheel is manufactured by this method, a space is formed around the core material, and the core material is in a free state, so that sufficient product strength is obtained. I can't.

Further, a lightweight hollow pipe material is usually a tube having a smooth outer surface. This makes it difficult to obtain the bonding strength with the resin to be cast. In the prior art, a pipe with irregularities is used by profile extrusion. However, such a deformed pipe core has an extremely strong anti-rotation effect in the radial direction, but has no stopping effect in the circumferential direction of the steering. Therefore, for example, in the steering in which the core material is overmolded with soft vinyl chloride, if a force is applied in the rotational direction to operate the steering wheel, the resin and the core material may be displaced.

[0006]

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 resin molded product which is lightweight and has excellent bonding strength between the hollow core material and the resin layer. It is to provide a manufacturing method.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventor has set a core material having at least two openings in a cavity and injecting resin, and then from at least one of the openings. The inventors have found that the above problems can be solved by injecting a fluid, and completed the present invention. That is, the present invention relates to a method of molding a core material having a closed space inside into a molding die in advance, then closing the die and injecting a molten resin to integrally mold the core material and the resin. , The core material is provided with at least two openings communicating with the internal space thereof, and the core material is injected so as to be cast with molten resin, and then the core material is not mixed with the resin through the at least one opening. A method for producing a resin molded article, comprising injecting a fluid having a viscosity lower than that of the resin to pressurize and fill the inside of the core material with the fluid.

The resin molded product of the present invention relates to a resin product having a hollow core material, in which the core material and the resin layer are firmly integrated.

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

FIG. 1 is a sectional view schematically explaining the principle of the present invention. The thermoplastic resin in a molten state is injected into the cavity in which the hollow core material 1 is set by injecting a slightly larger amount of the resin 2 than the capacity obtained by subtracting the core material capacity from the cavity capacity (hereinafter referred to as the effective capacity). A part of the resin is introduced into the inner space of the core material through the opening (through hole) 3 of the hollow core material which has been opened in advance while filling the inside (FIG. 1A).

At this time, when a fluid having a viscosity lower than that of the molten resin is injected from another core material opening, the resin once entering the inner space of the core material is pushed back by the fluid pressure applied to the inside of the core material, and again. It flows out of the core material through the through hole (Fig. 1B). As a result, it is possible to prevent a so-called “sink” due to volume contraction due to cooling of the resin, which is usually found in the thick portion of the resin molded product. This is because the resin pushed back can compensate the volume decrease of the resin due to cooling. Since the injected resin amount is slightly larger than the effective capacity, a part of the resin that has penetrated into the core material remains inside the openings and the core material, and the resin layer forms an anchor-shaped connecting arm inside the core material. As a result, the core material and the resin layer are firmly bonded (FIG. 1C). Also, even when the amount of injected resin is less than the effective capacity, part of the resin penetrates into the opening as above,
It is pushed back by the fluid pressure to form the hollow portion 4 near the opening (FIG. 1D). At this time, if there are openings for supplying the fluid and two or more openings other than the openings, as shown in FIG. 2, which is a longitudinal cross-sectional explanatory view of the molded product containing the hollow core material of the present invention, It is possible to form a molded body having a solid space between the openings and having a hollow only in the vicinity of the openings. Also in these cases, the resin layer 5 connected to the resin layer on the outer surface of the core material is formed near the inner surface of the core material opening. Therefore, even when the injection resin amount is smaller than the effective capacity, the core material and the resin layer around the core material can be firmly bonded by the anchor effect in the core material opening.

This is due to the operation described below. That is, when the resin is injected, the resin is first cooled and solidified on the cavity surface and the core material surface at a relatively low temperature to form a skin layer. Then, the solidification of the resin progresses relatively slowly at the location away from these surfaces. Then, when the inside of the skin layer still retains fluidity, a fluid having a viscosity lower than that of the molten resin, for example, an inert gas such as nitrogen, carbon dioxide gas, argon, or air is injected into the core material. Then, as described above, the resin that has entered the inside of the core material from the opening is pushed back to form a hollow portion near the opening. However, a part of the resin that has entered the inside of the core material through the opening is in contact with the inner surface of the core to be cooled and solidified to form a skin layer, so that a hollow part may be formed near the opening. A resin skin layer continuous with the resin layer surrounding the core is formed on the inner surface near the core opening. When the opening is considerably narrow, as shown in Example 1 below, even if the resin injection amount is smaller than the effective capacity of the cavity, a resin anchor is not formed in the opening without forming a hollow portion near the opening. Form.

[0013]

【Example】

Example 1 A method for manufacturing a steering wheel will be described with reference to FIG.

As shown in FIG. 3, a hollow core member was provided with an opening 7 for supplying a fluid in the vicinity of the mounting boss 6 of the steering wheel, and this was set in a mold. Note that FIG.
FIG. 5 is a cross-sectional explanatory view showing the relationship between the fluid supply nozzle 8 and the core material 1 in the mold in the direction of the steering wheel hollow core material shown in the plan view of FIG. 4 as viewed from the upper side surface of FIG. 4. In FIG. 3, 9 is a sealing material. Further, FIG. 5 is a partially enlarged view of the grip portion 11 in a section indicated by an arrow in FIG.

The hollow core material has eight openings of 1.5 mm in diameter in the grip portion 11 and the spoke portion 10.
In the above, an opening having a diameter of 2.5 mm was provided at four places.

Next, resin (polyvinyl chloride, hereinafter PV
2 is injected (abbreviated as C) (FIG. 6). Although the core material in the drawing has a hollow circular cross section, it may have a U-shape, a square shape, or a polygonal shape. The shot amount is an amount that fills about 90% of the inner volume (effective volume) of the mold. The resin was injected in the gate layout as shown in FIG. 6 so that the weld was not formed in the opening. Note that FIG. 6 is an explanatory view of a state in which the resin 2 is injected into the mold cavity in which the core material 1 is set. Figure 6
Middle 12 represents a runner. At the same time when the injection of the resin is completed, the gas introduction mechanism of the mold is opened to blow the gas into the core material. The gas is an inert gas such as air, nitrogen, argon, carbon dioxide, etc., and the pressure of the gas is several tens to hundreds of kilograms per square centimeter. When the resin is cooled and solidified while maintaining this gas pressure, the resin internal pressure decreases as the volume contraction of the grip portion and the spoke portion occurs due to the resin contraction. Since the pressure is maintained inside the core material by the gas, the pressure inside the core material is higher than that inside the resin layer. Therefore, the backflow of the resin occurs toward the grip portion and the spoke portion. As the resin cools and hardens, the effective flow diameter of the openings decreases. As shown in FIG. 8 which is an enlarged cross-sectional explanatory view of the grip portion, a small amount of resin intrudes from the opening of the core material of the grip portion which originally has a small diameter, but flows backward from the opening substantially narrowed by cooling and solidification. Since the amount of resin is small, the resin in the grip portion does not sink in the opening portion and forms a good anchor. On the other hand, since a large opening was provided in the spoke portion, the amount of resin that first penetrated was large, but since the thermal capacity was large by that amount, the opening is not substantially narrowed by cooling and solidification. That is, since the path of the resin that flows back by pressing the gas is wide and a relatively long period of time is secured, a considerable amount of the invaded resin returns to the resin portion and plays a role of a gas supply port for the resin. A hollow portion is formed near the opening (FIG. 7). At the same time, since the resin skin layer is formed on the inner surface near the opening, the anchor effect is also exhibited. Through such a process, the core material is firmly bonded to the grip by the anchor, and the spoke portion has a local hollow portion formed in the resin portion to integrally form a steering wheel which is safe, lightweight and has a predetermined bonding strength. It

Embodiment 2 An embodiment of a stand-off type rear spoiler will be described. FIG. 9 is a partial sectional perspective view of the rear spoiler. As shown in FIG. 9, the core material is a parallel pipe in the wing portion 13, and the small diameter openings are arranged so as to face each other. The leg portion 14 has a single tube shape and is provided with an opening having a large diameter. The opening of the leg single tube is airtightly connected to the gas introduction nozzle of the mold. It will be described according to the molding process.

FIG. 10 is a cross sectional view of the rear spoiler wing shown in FIG. 9 in the cavity in the width direction.
As shown in FIG. 10A, a core material is inserted in a mold, and a resin (modified polyphenylene oxide, hereinafter referred to as mPP) is used.
Eject (O). Resin is about 90 of the effective mold volume
It is an amount satisfying about%. Simultaneously with resin injection, the gas introduction mechanism of the nozzle is opened to blow the gas into the leg single tube of the core material in the mold (FIG. 10B). The gas is an inert gas of the same type and pressure as in Example 1. By holding this gas pressure, the resin is cooled and solidified. At this time, a small amount of gas is discharged toward the resin from the opening of the wing portion. A gas is blown between the two parallel tubes from the facing openings of the parallel tubes, so that a hollow portion is formed between the tubes. On the other hand, a large amount of gas is discharged from the pipe of the leg portion into the resin due to the larger opening than in the wing portion. Therefore, a large hollow portion is formed in the leg portion. Through such a process, the wing can form a thin and wide hollow portion and a solid rib portion, and the leg portion can form a large hollow portion.

..

As described above, according to the present invention, a hollow core material having an opening is insert-molded, and the inside of the core material is pressurized with a fluid through the opening, whereby a resin anchor or a hollow resin portion is formed. Can be selectively formed, and a lightweight molded resin product containing a hollow core material can be manufactured.
Further, the bonding strength between the resin layer and the core material can be obtained without the core material having a particularly irregular cross section.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a resin molded product containing a hollow core material, which schematically illustrates the principle of the present invention.

FIG. 2 is an explanatory view of a state where a resin hollow portion is formed in the hollow core material opening portion according to the present invention.

FIG. 3 is an explanatory view of the first embodiment and is a cross-sectional explanatory view showing a relationship between a fluid supply nozzle and a core material in a mold.

FIG. 4 is an explanatory view of the first embodiment and is a plan view of a hollow core material for a steering wheel.

5 is an explanatory view of the first embodiment and is a partially enlarged view of an arrow section of the grip portion in FIG. 4. FIG.

FIG. 6 is an explanatory view of the first embodiment and is an explanatory view showing a state where resin is injected into a cavity in which a hollow core material is set.

FIG. 7 is an explanatory diagram of the first embodiment and illustrates a state in which a fluid is injected into the core material after the resin is injected to form a hollow resin portion near the spoke opening.

FIG. 8 is an explanatory diagram of the first embodiment and is an explanatory diagram illustrating a state in which a resin anchor is formed in a narrow opening portion of the grip portion.

FIG. 9 is an explanatory view of the second embodiment and is a partial cross-sectional perspective view of the rear spoiler.

FIG. 10 is an explanatory view of the second embodiment and is a cross-sectional explanatory view in the width direction of the rear spoiler wing showing a state A in which a resin is injected into the cavity and a state B in which a fluid is injected into the cavity.

Claims (1)

[Claims] 1. A method of integrally molding a core material and a resin by inserting a core material having a closed space inside into a molding die in advance and then closing the die to inject a molten resin. At least two openings communicating with the inner space of the core material are provided, and after injection of the core material by casting with molten resin, the core material is not mixed with the resin through at least one opening provided in the core material, A method for producing a resin molded article, which comprises injecting a fluid having a viscosity lower than that of the resin to fill the inside of a core material with the fluid under pressure.