JPH05200792A - Injection-molding method for tubular body and mold structure for injection molding - Google Patents

Abstract

PURPOSE:To enhance the accuracy of a tubular body-molded shape by connecting detachably a core material to both end parts of an intermediate core material extractable from the opening of a curved through-hole for making it a core material, and providing a soluble part therearound so as to be a core. CONSTITUTION:On both end parts of an intermediate core material extractable 13 from the opening part 2b of the curved through hole 2 of a tubular molded article 1, an upper side core material 12 and a lower side core material 14 are fixed in a screwed relationship. By the core materials 12, 14, 13, a core material is formed. The core material 11 is set within a mold, and soluble resin is injected and then cured into the cavity for forming a core 22. The core 22 is put into the mold in order to form an article 1. After that, the screwed relation of the upside and downside core materials 12,14 is released, and the soluble resin residing therearound is melted and removed therefrom, and then the intermediate core material 13 is taken out and removed from the opening part 26. Accordingly, the core materials 12,14,13 with large rigidity can be used and, thus, deformation due to injection pressure is prevented with the result that the configurational accuracy of the article 1 can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a tubular body and an injection molding die structure which are particularly suitable for molding a curved tubular body.

[0002]

2. Description of the Related Art For example, an oil filler pipe for an automobile is often formed in a curved curved tube as shown in FIGS. 5 (a) and 5 (b), and a tubular body 51 having such a shape is formed by resin molding. In the case of doing, for example, the dividing line D indicated by the two-dot chain line
It is produced by forming two parts having a middle part divided along the, and then welding them together. That is, the straight pipe portions 51a and 51b on both end sides can be formed in a tubular shape by using cores that can be pulled out through the respective openings, but the curved portion 5 in the middle can be formed.
Even if the core 1c is formed by arranging the core therein, it is impossible to remove the core of this portion after that. Therefore, it is necessary to divide the core 1c as described above.

However, in the above-described divided structure, the strength is locally reduced along the line D welded to each other, and internal burrs are generated, so that sufficient quality is secured. It causes a problem that it is difficult to do. Therefore, for example, in Japanese Unexamined Patent Publication (Kokai) No. 2-263610, when molding a tubular body as described above, a curved core is made of a fusible material such as a low melting point metal, and resin molding is performed using this core. After carrying out, the molding method of melting and removing the core is disclosed. According to this method, it is possible to manufacture a tubular body that is more uniform over the whole, without using the above-described divided structure.

[0004]

However, when the method disclosed in the above publication is adopted and a tubular body is to be formed by injection molding, the core formed of a low melting point material is usually Since the rigidity is not so large, it is easy to deform in the molding die due to the injection pressure when injecting the product resin into the molding die. Causes a problem that is not obtained. In addition, in the above, it is necessary to produce the core using an amount of the soluble material that fills the entire through hole of the tubular body for each molding of the individual product, and as a result, the disposable soluble material is used. Since a large amount is required, there is a problem that the manufacturing cost becomes high.

[0005]

In order to solve the above-mentioned problems, an injection molding method for a tubular body according to claim 1 of the present invention comprises:
In an injection molding method of a tubular body having a curved through hole, at both ends of the intermediate core material having a shape that can be pulled out through the opening of the through hole, a direction from each of these ends toward each opening of the through hole. To form a core core by releasably connecting the rod-shaped end side core material extending to the outer periphery of the core core material, the outer shape of the outer shape along the peripheral surface of the through hole by the fusible material. A fusible part is provided to form a core,
Next, this core is fixed in an injection-molding die and injection-molded, and then the end side core material is removed, the fusible portion is dissolved and removed, and the intermediate core is removed from the molded product taken out from the die. The feature is that the material is taken out.

According to a second aspect of the present invention, there is provided an injection molding die structure of a tubular body having a curved through hole, in which the core material is sequentially connected in a shape along the through hole, and the core. The protruding region of the core material on each end side protruding from the fusible portion is fitted to the tubular body molding cavity in which the core made of the fusible portion provided on the outer periphery of the material is arranged. It is characterized in that a core fixing recess is formed.

[0007]

According to the injection molding method for a tubular body according to claim 1, the outer peripheral side of the core is made of a fusible material,
Since the core core material that can be formed of a metal material or the like having high rigidity is provided inside the core, it is possible to form the core having high rigidity as a whole so as not to be deformed by the injection pressure. As a result, it is possible to suppress a variation in wall thickness and the like, and form a tubular body with high shape accuracy. further,
Since the amount of the fusible material can be reduced by an amount corresponding to the volume occupied by the core core as described above, the manufacturing cost can be further reduced.

Further, according to the injection molding die structure of the present invention, the projecting region of each end side core member projecting from the fusible portion fixes the core in the injection molding die. It is configured as a skirting part. In this case, since the core material having high rigidity is directly fixed by the injection molding die, for example, the fusible portion is further extended to the skirting board portion of the product end and fixed in the injection molding die, Therefore, as compared with a configuration in which a fixing force is applied to the core material of the core through the fusible portion having low rigidity, a more firmly fixed state can be achieved.

Therefore, the immobile state of the core during injection molding can be obtained more stably, so that a tubular body having a higher shape accuracy can be molded. Also, since the soluble material is limited to the area corresponding to only the through hole of the resin product and not provided in the skirting board part, the amount of the soluble material becomes smaller,
As a result, the manufacturing cost can be reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

First, an example of the shape of a tubular body molded article formed by applying the present invention will be described with reference to FIG. 2 (b). The tubular product 1 shown in the figure has an outer shape curved in different directions on the upper side and the lower side, and
A through hole 2 that is curved along the outer shape is formed inside. The tubular product 1 is molded by injection molding a synthetic resin such as nylon containing glass fiber (hereinafter referred to as a product resin). The space between the flange portions 3 and 4 provided on the upper and lower end portions is formed with a substantially uniform thickness throughout.

The tubular product 1 having the above-mentioned shape is used for assembling the core material of the core, manufacturing of the core containing the core material, injection molding of the product resin,
It is molded through each step of removing the core.

Assembly of Core Core First, a core for filling the through hole 2 of the tubular product 1 is manufactured. The core is a core core 11 shown in FIG. 3 (a).
A fusible portion 27 described later is provided on the outer periphery of the. As shown in FIG. 1A, the core core 11 is made of, for example, a metallic material such as steel, and has a rod-shaped upper core (end core) 12, intermediate core 13, and lower core. (End side core material) 1
It is assembled by connecting 4 to each other.

The intermediate core member 13 is formed to have a length that can be located along an intermediate region near the inflection point between the upper side and the lower side in the through hole 2 of the tubular product 1 shown by the chain double-dashed line in the figure. ing. Further, at the position where this intermediate region is provided, the through hole 2
Both ends of the intermediate core material 13 can be linearly exposed from the outside through the openings 2a and 2b at the upper and lower ends, and the intermediate core material 13 can be moved along the curved through-hole 2 from the above-mentioned arrangement position and at least one of It is formed with a thickness and an outer shape that can be extracted through an opening, for example, the lower end opening 2b. Further, the intermediate core member 13 is formed with female screws 13a and 13b at both ends thereof in the axial direction toward the openings 2a and 2b of the through hole 2, respectively. The intermediate core material 13 is formed in a hollow shape by further providing inside both end communicating holes 13c for communicating the bottoms of the female screws 13a and 13b with each other.

On the other hand, the upper side core member 12 is a substantially cylindrical rod body which can be inserted through the upper side in the through hole 2 of the tubular product 1, and has a male screw portion 12a provided at the lower end thereof.
The upper side core member 12 is assembled to the intermediate core member 13 by screwing the upper core member 12 onto one of the female screws 13a of the intermediate core member 13. The upper core material 12 is inserted into the intermediate core material 13 from the screwing position to the upper end opening 2 of the through hole 2 of the tubular product 1.
An upper skirting portion 12b protruding beyond a and further upward
Is formed to have a length. This upper skirting part 12
On the upper end side of b, a flat surface portion 12c that is gripped by a screw fastening tool such as a spanner is provided. Also, through hole 2
Of the outer peripheral surface 12 from the upper end opening 2a to the external thread 12a
d has a taper angle of, for example, about 1 degree and is formed in a taper shape in which the diameter becomes smaller toward the lower side.

The lower side core member 14 is formed substantially upside down with the upper side core member 12 upside down. That is,
A male screw portion 14a screwed into the other female screw 13b of the intermediate core 13 is provided at the upper end portion, and the tubular body product 1 is provided at the lower end side.
The through hole 2 is formed to have a length having a lower skirting portion 14b projecting below the lower opening 2b. Also,
A flat surface portion 14c is provided on the lower skirting portion 14b, and an outer peripheral surface 14d from the lower end opening portion 2b of the through hole 2 to the male screw portion 14a is formed in a taper shape having a smaller diameter toward the upper side.

These upper core material 12 and lower core material 1
The core core material 11 is assembled by screwing 4 on both sides of the intermediate core material 13.

Manufacture of Core with Core Material Next, as shown in FIG. 3 (b), the core core material 11 is set in a core forming mold 21 and the core core material 11 is attached to the outer periphery thereof. The core 22 containing the core material is manufactured by injection molding a resin for forming a core, which will be described later. In the lower mold 23 of the core forming mold 21, a core forming cavity 25 having the same shape as the through hole 2 of the tubular product 1 is provided between the lower mold 23 and the upper mold 24 shown by a two-dot chain line in FIG. Is provided. Further, at both ends of the core forming cavity 25, the upper side core member 1 is provided.
2 and each skirting part 12b.1 in the lower side core material 14
Core material fixing recesses 26, 26 into which 4b is fitted are further formed so as to be continuous with the core forming cavity 25.

With the core core material 11 set in the core forming mold 21, the water-soluble resin is injected into the core forming cavity 25. As the water-soluble resin, for example, Belland polymer manufactured by Belland Co., USA is used. It is dissolved by immersion in water after curing, and its dissolution rate increases with water temperature.

By filling the above water-soluble resin in the space around the core core 11 in the core forming cavity 25 and curing it, as shown in FIG. 3 (c), the core core material is obtained. A core 22 in which a soluble portion 27 made of a water-soluble resin is integrally provided around 11 is manufactured. That is,
In this core 22, the outer shape of the fusible portion 27 is the tubular body product 1.
The shape of the through hole 2 is the same, and as shown in FIG. 1B, from the upper and lower end surfaces of the fusible portion 27, the skirting portions 12b and 14b of the core core material 11 are It has a protruding shape.

Injection Molding of Product Resin Next, the core 22 manufactured as described above is shown in FIG.
As shown in, set in the product injection mold 31 and
The tubular body product 1 is molded by injection molding the above-mentioned product resin. Lower mold 32 for product injection molding 31
Between the upper mold 33 shown by the chain double-dashed line in FIG.
A product forming cavity (tubular body forming cavity) 34 having the same shape as the outer shape of the tubular body product 1 is provided. Further, at both ends of the product forming cavity 34,
Core fixing recesses 35, 35 into which the respective skirting parts 12b, 14b are fitted are further formed in series with the product forming cavity 34.

The core 22 is set in the product injection molding die 31 having the above structure, and the product resin is injected into the product forming cavity 34. As a result, the product resin is filled in the space around the core 22 and cured, so that
The tubular body product 1 as shown in (c) is molded.

Removal of Core The tubular product 1 integrated with the core 22 is taken out from the product injection molding die 31 by injection molding of the product resin as described above, as shown in FIG. 1 (c). It From the tubular product 1 with the core 22, first, each skirting portion 12b of the upper core member 12 and the lower core member 14 protruding vertically is formed.
The upper side core material 12 and the lower side core material 14 are extracted by gripping 14b and rotating in a direction opposite to the screw fastening direction in the screwing portion with the intermediate core material 13 on each tip side. At this time, the upper and lower core members 12, 14
Is formed in a taper shape with a smaller diameter toward the tip side,
If a slight rotational displacement is initially obtained, thereafter, the operation of loosening the screw and the withdrawal after the screw is removed can be performed extremely easily.

In this way, the upper and lower core members 12, 14
The inside of the tubular product 1 after the removal of the
As shown in (a), the soluble portion 27 made of a water-soluble resin and the intermediate core material 13 in the soluble portion 27 remain. Then, in the fusible portion 27 and the intermediate core material 13, the extraction traces of the upper and lower core materials 12, 14 communicate with each other through the both-end communication holes 13c of the intermediate core material 13, so that the upper end side A hole is formed penetrating from the bottom to the lower end side along substantially the center line.

Next, a process of flowing hot water through the through hole as described above is performed. As a result, the soluble portion 27 made of the water-soluble resin gradually dissolves in the hot water, and as a result,
The fusible portion 27 is removed from the tubular body product 1. And
In this way, the fusible portion 27 is removed from the inside, and the intermediate core material 1
When 3 becomes movable, it moves in the through hole 2 toward the lower opening 2b by its own weight, and finally falls outside through the lower opening 2b. As a result,
As shown in (b), the fusible portion 27 and the intermediate core material 1 are
3 is also removed, and a tubular body product 1 having a through hole 2 of a predetermined shape inside is obtained.

As described above, in the above embodiment, when the tubular body product 1 having the curved through hole 2 is injection molded, the core 22 conforming to the overall shape of the through hole 2 is formed.
Is composed of the fusible portion 27 and the metallic core material 11 that reinforces the fusible portion 27 from the inside. Therefore, at the time of injection molding of the product resin, the core 22 that receives the injection pressure in the product forming cavity 34 is not deformed, whereby the tubular body product 1 with high shape accuracy can be molded.

Further, as described above, the core core material 11 that can be repeatedly used is provided on the center side of the core 22, so that the water-soluble resin that becomes disposable each time the individual tubular product 1 is molded. Since it is possible to use less than the amount corresponding to the volume of the entire through hole 2, the manufacturing cost can be made cheaper.

In the above embodiment, when the soluble portion 27 made of the water-soluble resin is removed from the tubular product 1, the traces of the upper and lower core members 12 and 14 and the intermediate core member 13 are removed. Since the hot water can be made to flow through the both end communication holes 13c, the water-soluble resin is melted into the hot water rather than simply immersed in the hot water and waiting for elution. As a result, it can be manufactured in a shorter time.

In the above embodiment, an example in which a screw fastening structure is adopted as a connecting structure for easily attaching / detaching the upper side / lower side core members 12/14 to the intermediate core member 13 has been described. It is possible to adopt and employ other structures such as a connection structure by combining. Although the soluble portion 27 is made of a water-soluble resin in the above, it is also possible to use another material such as a low melting point metal.

[0030]

As described above, the injection molding method for a tubular body according to the first aspect of the present invention is characterized in that both ends of the intermediate core material having a shape that can be pulled out through the opening of the through hole of the tubular body are provided. A rod-shaped end portion side core member extending in a direction from each end portion toward each opening of the through hole is detachably connected to form a core member, and at the outer periphery of the core member, A fusible portion having an outer shape along the peripheral surface of the through hole is provided by a molten material to form a core, and then the core is fixed in an injection molding die for injection molding. From the molded product taken out, the end side core material is extracted, the fusible portion is dissolved and removed, and the intermediate core material is taken out.

Thus, since the core core material which can be formed of a metal material having a high rigidity is provided inside the core, the core material having a high rigidity as a whole is formed so as not to be deformed by the injection pressure. Can form a child. As a result, it is possible to suppress a variation in wall thickness and the like and form a tubular body with high shape accuracy. Furthermore, since the amount of the soluble material can be reduced by the volume occupied by the core core material as described above, the production cost can be further reduced.

Further, in the injection molding die structure according to claim 2 of the present invention, a core material sequentially connected in a shape along the through hole of the tubular body, and a fusible portion provided on the outer periphery of the core material. A core-fixing concave portion is formed so as to be connected to a tubular-body-forming cavity in which the core made of is disposed, and to which the protruding region of the core member on each end side protruding from the fusible portion is fitted. Is.

As a result, the core material having a high rigidity is directly fixed by the injection molding die, so that the core can be fixed more firmly. Therefore, the immobile state of the core at the time of injection molding can be obtained more stably, so that a tubular body with higher shape accuracy can be molded. Further, since the soluble material can be provided corresponding to only the through-hole portion of the resin product without being provided in the skirting board portion of the core, the amount of the soluble material is further reduced. The production cost can be made cheaper.

[Brief description of drawings]

FIG. 1 shows a core and a molded body sequentially manufactured by applying the present invention, in which FIG. 1 (a) shows an upper core material and a lower core material connected to an intermediate core material. A cross-sectional view of the assembled core material, the same figure (b) is a cross-sectional view of the core made by providing a fusible portion around the core material, and the same figure (c) uses the core. FIG. 3 is a cross-sectional view of the tubular body product taken out after injection molding by injection molding.

FIG. 2 is a view showing a tubular body product accompanying the removal of the core after the injection molding, and FIG. 2 (a) is a tubular body product in which the upper side core material and the lower side core material are extracted. A cross-sectional view and FIG. 6B are cross-sectional views of the tubular body product after the fusible portion is dissolved and removed and the intermediate core material is taken out.

3A and 3B show the molding process of the core, wherein FIG. 3A is a perspective view of the core material, and FIG. 3B is a state in which the core is set in the core forming mold. FIG. 3C is a perspective view showing a state after injection molding of the fusible material into the core forming mold.

4A and 4B show an injection molding process of the tubular product, wherein FIG. 4A is a perspective view showing a state where a core is set in a product injection molding die, and FIG. 4B is the product. FIG. 3C is a perspective view showing a state after injection molding of the product resin into the injection molding die, and FIG. 6C is a perspective view of the tubular product taken out from the product injection molding die after the injection molding.

5A and 5B show a tubular body manufactured by a conventional split forming method, wherein FIG. 5A is a side view and FIG. 5B is a front view.

[Explanation of symbols]

1 Tubular Product 2 Through Holes 2a and 2b Opening 11 Core Core Material 12 Upper Side Core Material (End Side Core Material) 13 Intermediate Core Material 14 Lower Side Core Material (End Side Core Material) 22 Core 27 Yes Molten part 31 Product injection molding mold 34 Product forming cavity (tubular body molding cavity) 35 Core fixing recess

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Claims (2)

[Claims] 1. A method of injection molding a tubular body having a curved through hole, wherein both ends of an intermediate core material having a shape capable of being pulled out through an opening of the through hole are provided to the through hole. A rod-shaped end side core member extending in the direction toward the opening is detachably connected to each other to form a core member, and a peripheral surface of the through hole is formed by a fusible material on the outer periphery of the core member. To form a core by providing a fusible portion having an outer shape along with, and then fixing the core in an injection molding die to perform injection molding,
Then, an injection molding method for a tubular body, characterized in that the end side core material is extracted, the fusible portion is dissolved and removed, and the intermediate core material is extracted from the molded product taken out from the mold. 2. A structure for injection molding of a tubular body having a curved through hole, comprising a core material sequentially connected in a shape along the through hole and a fusible portion provided on the outer periphery of the core material. A core-fixing recess for fitting the projecting region of the core material on each end side projecting from the fusible part in a continuous manner to the tubular body molding cavity in which the core is formed. Characteristic injection mold structure.