JP2001030265A - Manufacture of module cover for air bag device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent cleavage characteristics and to obtain a required strength without cleaving vainly when not required, by forming at least a part of a mold out of an air permeable material in the case of supplying a resin into the mold to manufacture a module cover with a groove-like tear line. SOLUTION: A groove-like tear line for cleaving a module cover covering an air bag of a vehicle when the bag is developed is provided on the cover. To mold such a module cover by using a mold 11 disposed on a front surface side of the cover and a mold 12 having a protruding strip 13 disposed on a rear surface side of the cover to form a tear line on a mold surface, as the mold 11, a mold formed of an air permeable material is used. Thus, when a resin is cast in a cavity, gas in the cavity is displaced into pores of the material, the resin is smoothly fed in a tear line molding portion and entirely filled in the mold.

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 module cover for an airbag apparatus, and more particularly to an improvement in a method for manufacturing a module cover having a groove-shaped tear line by supplying resin into a mold.

[0002]

2. Description of the Related Art As is well known, an airbag device has an airbag which is rapidly deployed in an emergency such as a vehicle collision. As shown in FIG. 3, in normal times, the airbag 2 is folded and covered with the module cover 1. The airbag 2 is held together with an inflator 4 on a mounting plate 3 called, for example, a retainer, and the module cover 1 is also fixed to the mounting plate 3 with rivets 5, screws, bolts and the like.

The module cover 1 is provided with a groove-shaped cleavage start line for tearing the cover when the airbag 2 is deployed, that is, a tear line 1A. The tear line 1A is a portion having a lower strength than the surrounding portion, and has a thin portion having a predetermined shape (generally, a thickness of 0.5 to 1.0).
mm), and the module cover 1 is torn along the tear line 1A when the airbag 2 is deployed. In order to reinforce the module cover 1, a reinforcing member 6 such as cloth or mesh may be inserted.

Conventionally, urethane foam integral skin foam or thermoplastic is generally used as a material for the module cover of such an airbag.
These resin materials are injected into a mold having a predetermined shape to be molded.

[0005]

In the conventional method of manufacturing a module cover of an airbag device, a mold is used as a mold in order to form a thin portion of a groove-shaped tear line, as shown in FIG.
As shown in (1), molds 7 and 8 having ridges 7a for forming tear lines are used. Since the space between the ridges 7a of the mold 7 and the inner surface of the mold 8 is small, air or gas G generated from the resin material 9 accumulates, the flow of the resin material 9 is hindered, and molding is performed. This was the cause of the failure.

[0006] In order to prevent such defects, the injection pressure of the resin material is sometimes increased, but when the resin material is injected at a high pressure, residual stress is likely to be generated in the product. Also,
In some cases, the resin is oriented near the tear line to increase the strength, and the tear line may not be easily broken.

[0007] The tear line of the module cover is required to have a required strength such that the module cover is quickly torn when the airbag is deployed and is not easily torn by an external force in a normal state. There is a need for a method of manufacturing a module cover of an airbag device having such a thin and required tear line with a high yield without causing molding defects or the like.

The present invention has been made in view of the above circumstances, and an airbag apparatus capable of efficiently manufacturing a module cover having a tear line having excellent characteristics as a starting line for cleavage of a module cover at a high yield. It is an object of the present invention to provide a method of manufacturing a module cover.

[0009]

A method of manufacturing a module cover according to the present invention is a method of manufacturing a module cover having a groove-shaped tear line by supplying a resin into a mold, wherein at least a part of the mold is provided. Is made of a breathable material.

The permeable material has a porosity of 10 to 10.
A porous material of about 50% by volume is preferred. As this material, for example, a sintered metal, a ceramic, or the like can be used.

In the method of the present invention, since at least a part of the mold is made of a gas permeable material, gas present in the cavity is expelled into the pores of the gas permeable material. For this reason, the resin flows smoothly in the tear line molding section without obstructing the flow, and is filled in the entire mold.

[0012] The tear line of the module cover manufactured by the method of the present invention can be quickly cleaved when the airbag is deployed, and the resin is sufficiently supplied without generating voids, pinholes, flow marks, and the like. The tear line has the required strength and does not break when unnecessary. Further, even if the resin injection pressure is lower than in the past, gas does not accumulate in the cavity, and molding failure of the module cover is prevented. Further, the occurrence of residual stress in the product is also prevented.

As described above, according to the present invention, a module cover having excellent strength and cleavage characteristics can be efficiently manufactured at a high yield without forming defects.

[0014]

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

FIG. 1 is a sectional view showing a method for manufacturing a module cover according to an embodiment of the present invention.

In the illustrated method, a first mold (cavity mold) 11 arranged on the front side of the module cover and a second mold (cavity mold) arranged on the back side of the module cover. In performing molding using the (core mold) 12, a first mold 11 made of a breathable material is used. The second mold 12 is provided with a tear line forming ridge 13 on the mold surface.

In molding the module cover, the molds 11 and 12 are closed, and a resin is injected into the cavity from an injection port (gate) 15. Since the first mold 11 is made of a gas-permeable material, the gas that tends to accumulate in the vicinity of the ridge 13 is expelled into the pores of the gas-permeable material.
Gas does not accumulate around 3. Therefore, the resin flows very smoothly also in the vicinity of the ridge 13, and spreads sufficiently throughout the cavity. When injecting the resin, if necessary,
A module cover reinforcing member such as cloth or mesh may be arranged in the mold in advance.

The injected resin is sufficiently filled in the mold, and after the resin is cured, it is released from the mold. As a result, a tear line which is thin, has no defect, has a high resin filling rate, and has a required strength is formed. At the time of filling the resin, a tear line which is thin and has the required strength is formed even if the filling pressure is lower than in the past. According to such a low pressure filling method, no or almost no residual stress is generated in the module cover molded product. Further, it is also prevented that the resin is oriented near the tear line and the tear line becomes excessively high in strength and is not easily broken.

The example shown in FIG. 1 is an example of the present invention, and the present invention is not limited to the illustrated method. For example, only the first mold near the tear line may be made of a breathable material. The second mold may be made of a breathable material, or only the vicinity of the tear line of the second mold may be made of a breathable material. Further, both the first and second molds may be made of a breathable material.

When the first mold or the second mold is substantially made of a gas-permeable material, not only the vicinity of the ridge 13 but also other parts in the cavity (particularly, the most downstream side of the resin flow). However, accumulation of gas is prevented, and a module cover having no defects can be molded by low-pressure filling.

[0021]

As described in detail above, according to the method for manufacturing a module cover of the present invention, the cleavage characteristics are excellent, and
It is possible to efficiently manufacture a module cover having a tear line having a required strength that is not easily split when unnecessary, without causing molding defects, at a high yield.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a method for manufacturing a module cover of an airbag device of the present invention.

FIG. 2 is a sectional view showing a conventional example.

FIG. 3 is a sectional view of the airbag device.

[Explanation of symbols]

 Reference Signs List 1 module cover 1A tear line 2 airbag 7a, 13 convex line for forming tear line 11 first mold 12 second mold 15 gate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D054 AA02 AA13 BB02 BB23 BB30 DD09 FF17 4F202 AG28 AH25 AJ09 CA11 CB01 CK11 CP02

Claims (2)

[Claims] 1. A method for manufacturing a module cover having a concave groove-shaped tear line by supplying a resin into a mold.
A method for manufacturing a module cover of an airbag device, wherein at least a part of the mold is made of a breathable material. 2. The plurality of molds according to claim 1, wherein the molds include a first mold arranged on the front side of the module cover and a second mold arranged on the back side of the module cover. A method of manufacturing a module cover of an airbag device, wherein at least one of the molds is made of a breathable material.