JPH02258316A - Production of double-wall noise insulator - Google Patents

Abstract

PURPOSE:To easily produce a double-wall noise insulator by blow-molding a flat hollow body made of synthetic resin material and introducing raw liquid of expandable resin into the hollow body and discharging the air in the hollow body and the generated gas through a discharge hole and also foaming and solidifying the raw liquid of resin. CONSTITUTION:A parison 1 made of synthetic resin is hung between the molds 2, 3 and the lower end thereof is closed. The parison is formed into a hollow body 4 by blowing air thereinto. Then both an introduction hole 5 and a discharge hole 6 are bored to the hollow body 4. The raw liquid 8 of expandable urethane is introduced from the vessels 7b, 7c having an introduction pipe 7a. This raw liquid 8 of urethane is foamed in the inside of the hollow body 4. The gas generated by foaming is discharged together with the air eliminated by the raw liquid 8 of urethane through the discharge hole 6. A porous sound absorbing material 9 is formed by solidifying the raw liquid of urethane. This raw liquid 8 of urethane is fluidized in the inside of the hollow body 4 and closely stuck to the inside wall 10 and the inner surface of the outside wall of the hollow body 4 by selecting the characteristics of the raw liquid 8 of urethane and properly deciding the rates of foaming and solidification and the expansion ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a double-wall sound insulating body incorporating a sound absorbing material.

(Prior Art) For example, an automobile engine is provided with a side cover for sound insulation. For the purpose of reducing weight, side covers are made of synthetic resin instead of iron plates. Such a sound insulator is integrally molded by blow molding in order to simplify the manufacturing method and reduce weight. It has a double-walled structure with an inner wall and an outer wall whose peripheral edges are integrally connected, and a cavity is formed inside. Depending on the shape of the part to which it is attached, it has a three-dimensionally uneven plate shape or bowl shape.

(Problem to be solved by the invention) Although the above-mentioned sound insulation body is easy to manufacture and lightweight, the inside of the double wall is a hollow space, so the noise is transmitted to one wall. It easily passes through the cavity and into the other wall, and the damping effect is insufficient and the sound insulation effect is low. In order to improve the sound insulation effect, it is possible to make the walls sufficiently thick or to sandwich sound absorbing material inside the double walls.

However, a material thick enough for sound insulation requires a large amount of material, is difficult to use with simple blow molding force, increases costs, and does not have the benefit of weight reduction. Products with a structure in which a sound-absorbing material, such as a porous foam made of synthetic resin, is sandwiched inside are complicated to manufacture.
Product quality also becomes unstable. In other words, in the structure described above, the inner and outer double wall parts are first molded separately using synthetic resin material by injection molding, and then assembled by sandwiching the molded sound absorbing material between them. must be welded. In this manufacturing method, the manufacturing process is complicated, including an assembly process and a welding process. Moreover, since the shape is three-dimensional and has many irregularities, it is difficult to mold the sound absorbing material to match the shape of the cavity. To avoid this, for example, if you try to assemble a plate-shaped elastic foam as a sound absorbing material and weld it together to make the sound absorbing material conform to the shape of the cavity, the sound absorbing material will be unreasonably deformed. This can cause cracks, or uneven force is applied to the welded area due to elastic repulsion, resulting in poor welding, or variations in product shape. Furthermore, the sound absorbing material and the inner surfaces of the inner and outer walls do not come into close contact with each other, and the sound insulation effect is not sufficiently improved.

(Means for solving the problem) A flat hollow body made of a synthetic resin material is molded by blow molding, an injection hole and a discharge hole are bored in the hollow body, and a foamable resin stock solution is injected through the injection hole. This is a manufacturing method in which the air inside the hollow body and the gas generated during foaming are released from the discharge hole, and the resin stock solution is foamed and solidified.

(Function) In this manufacturing method, the hollow body is formed in one step of blow molding. When the foamable resin stock solution is injected and foamed, the hollow body is expanded and expanded within the cavity without applying excessive force to the hollow body to form a shape that conforms to the shape of the cavity. Since the gas generated at this time and the air inside the cavity are released from the discharge hole, the stock solution spreads throughout the cavity and expands, coming into close contact with the inner surface of the inner wall and the outer wall.

(Example) An example is shown in the drawings. In FIG. 1, a parison l of synthetic filler is suspended between the molds 2.3, the lower end is closed and air is blown into the hollow body 4 (FIG. 2). This is a normal blow molding method. Next, the injection hole 5.8 is injected into the hollow body 4 shown in FIG. 2 through the injection hole 5. The urethane stock solution 8 is foamed inside the hollow body 4, and the urethane stock solution 8 is
When the gas generated by foaming is discharged from the discharge hole 6 together with the air removed by the porous sound absorbing material 9 (FIG. 3) and solidified, a porous sound absorbing material 9 (FIG. 3) is formed.

The characteristics of the urethane stock solution 8 are selected to appropriately determine the foaming solidification rate and foaming rate. The urethane stock solution 8 flows and spreads inside the hollow body 4, and as shown in FIG. It comes into close contact with the inner surface of the outer wall 11. This example is for engine side covers, but it can also be applied to manufacturing air cleaner casings and covers.

(Effects of the Invention) By the manufacturing method of the present invention, it is possible to extremely easily manufacture a double-walled sound insulating body whose inside is filled with a porous foamed resin serving as a sound absorbing material and which is in close contact with the inner surface of a hollow body. It is also a manufacturing method that can stabilize the quality of the product.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the first step of the present invention, FIG. 2 is a diagram showing the second step, and FIG. 3 is a diagram showing a cross section of the side cover. 4...Hollow body 5...Injection hole 6...
...Discharge hole 8...Urethane stock solution 9...
...Porous sound absorbing material 10...Inner wall 11.
・・・・・・Outer wall

Claims (1)

[Claims] A hollow body made of a synthetic resin material and having an inner wall and an outer wall is integrally molded by blow molding, an injection hole and a discharge hole are bored in the hollow body, and the foamable resin stock solution is poured into the injection hole. A method for manufacturing a double-walled sound insulator, in which the resin stock solution is foamed and solidified by injecting air from the discharge hole and releasing air and gas generated during foaming from the discharge hole.