JPH0754601Y2 - Hollow molded duct with protrusion - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded duct such as an air duct for intake and exhaust of an internal combustion engine, and more particularly to a hollow molded duct having a protrusion such as a fixing bracket.

2. Description of the Related Art In recent years, plastic blow molding technology has often been adopted in intake and exhaust ducts for automobiles. That is, a cylindrical body or a tubular body such as an intake / exhaust system duct is molded by blow molding in which a fluid (air, water) is blown into a thermoplastic parison that has been softened by heating and is freely expanded by fluid pressure.

FIG. 3 is a cross-sectional view of a structural example in which the bracket 2 is welded and joined to a predetermined position of the duct body 1, and a bolt (not shown) is screwed into the female screw portion 3 formed on the bracket 2 to fix the duct body 1 An example of an intake / exhaust duct fixed to an appropriate position of a vehicle body is shown.

That is, the bracket 2, which is a protrusion, is preliminarily molded as a unit. The bracket 2 is set in the blow molding die of the duct body 1, and the bracket 2 is welded and integrated during the blow molding by the parison. In the case of such a molding method, the bracket 2 influences and deforms toward the duct body 1 side (reference numeral 1a in the figure).
Occurs, and the deformed portion 1a becomes a resistance of the fluid.

In order to prevent the deformation of the duct body 1, the duct body 1 is once subjected to blow molding by blow molding. The obtained duct body 1 is set in an injection mold. The so-called injection that molds the bracket 2 with this injection mold.
Blow molding methods are known.

Problems to be Solved by the Invention By the way, when the air duct as shown in FIG. 3 is blow-molded by the injection blow molding method, the following problems occur.

Generally, a molded product obtained by blow molding has lower dimensional accuracy than an injection molded product. This also applies to the air duct shown in FIG. That is, when the blow-molded duct body 1 is set in the injection-molding die in a separate process, some gap is formed between the die and the outer surface of the duct body 1. Therefore, when the molten resin is injected to injection-mold the bracket 2, the molten resin will run out of the gap and leak out of the mold. Since the molten resin leaks out, the injection pressure cannot be made sufficient at the time of injection.

As a result, the joint strength between the duct body 1 and the bracket 2 after release may be insufficient, and peeling of the welded joint may occur. Further, the protrusion of the molten resin not only deteriorates the appearance but also deteriorates the product function. In addition, the protrusion of the molten resin during molding is costly if the blow molding precision of the duct body 1 and the machining precision of the injection mold are further increased in order to avoid this, so that the protrusion to some extent is unavoidable. is there.

The purpose of the present invention is injection blow molding in which a protrusion such as a bracket is injection-molded on the duct body of the hollow molded product, and if there is a situation where the extrusion of the molten resin cannot be avoided, improve this aesthetically. The purpose of the present invention is to provide a hollow molded duct with protrusions, which has been developed for the purpose.

The hollow molded duct with protrusions according to the present invention has a duct main body having an annular convex portion at a predetermined position on the outer surface thereof, and an annular convex portion having an outer ring portion solidified along the annular convex portion. And a protrusion provided inside the portion.

Function By the blow molding, the annular convex portion is formed at a predetermined position on the outer surface of the duct body. During pouring into the injection-molding die, the molten resin protrudes from the gap between the die and the annular protrusion along the annular protrusion. At this time, the molten resin protruding by cooling by the cooling water pipe of the injection molding die is cured. The hardening of the protruding molten resin closes the gap between the injection molding die and the annular convex portion. The required injection pressure can be secured thereafter by closing the gap.

After the mold is released from the mold, the solidified resin swells along the annular convex portion on the duct body side and is formed in an outer ring shape around the protrusion.

Embodiment An embodiment of the hollow molded duct with protrusion according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a structure in which a duct body 10 is blow-molded and a bracket 20 as a protrusion is injection-molded at a predetermined position of the duct body. At a predetermined position of the duct body 10 where the bracket 20 is welded by injection molding, a ring-shaped annular convex portion 11 is formed so as to bulge from the outer surface as shown in the figure.

As shown in FIG. 2, a mold for injection-molding the bracket 20.
30 has a cooling water pipe 31 built in around the lower part,
When molding is started, cooling water is allowed to pass through the cooling water pipe 31. The injection molding die 30 has a size substantially corresponding to the annular convex portion 11 of the duct body 10.

Next, in the molding mode, as a pre-process, the duct body 10 is hollow-molded by blow molding. Molded duct body 10
The injection molding die 30 is positioned so as to be supported by the annular convex portion 11 in conformity with the annular convex portion 11. At this time, there is some clearance C between the curved surface of the outer surface of the duct body 10 formed by blow molding and the lower end surface of the injection molding die 30 due to dimensional accuracy.

In the set injection molding die 30, cooling water is passed through the cooling water pipe 31. When the molten resin is supplied from the pouring port 32, the molten resin at the initial stage of pouring the molten resin from the clearance C to the mold.
30 Attempt to leak outside. In the clearance C, since the cooling atmosphere is formed by the cooling water pipe 31, the leaked molten resin 23 at the initial stage of pouring is cooled and hardened. The clearance C is closed by cooling and solidifying the molten resin 23. By this closing, the molten metal can be poured into the injection molding die 30 thereafter at a required injection pressure.

As shown in FIG. 1, after the mold release, the annular protrusion 11 of the duct body 10
The bracket 20 is injection molded inside the
The resin 23, which surrounds the annular projection 11 and surrounds the annular projection 11, is well-appeared and solidified.

In addition, the injection-molded bracket 20 is provided with a female screw portion 21 to which a bolt is screwed at the time of fixing, and a flange-shaped welding seat 22 which is welded to the duct body 10 side.

Effects of the Invention As described above, the hollow molded duct with protrusions according to the present invention is such that when the protrusions such as brackets are injection-molded on the duct body hollow-molded by blow molding, the initial molten resin is injected during pouring. Although it protrudes from the lower gap of the molding die,
The protruding resin is cooled and hardened in the cooling atmosphere of the cooling water pipe to seal the gap. As a result, the required injection pressure in the injection molding die is obtained, and the projection is welded to the duct body with sufficient joint strength.

Moreover, since the protruding resin has a well-formed shape around the protrusions, it is possible to improve the aesthetic appearance by overcoming the conventional problems.

[Brief description of drawings]

1 and 2 show a perspective view and a sectional view of an injection molding mode of a hollow molding duct with protrusions according to the present invention. FIG. 3 shows a sectional view of a conventional example. 10 …… duct body, 11 …… annular convex portion, 20 …… protrusion bracket, 23 …… extruded resin, 30 …… injection mold, 31 …… cooling water pipe.

Claims (1)

[Scope of utility model registration request] 1. A projection comprising a duct main body having an annular convex portion at a predetermined position on the outer surface, and a protrusion provided inside the annular convex portion having an outer ring portion solidified along the annular convex portion. Hollow molded duct with.