JPH02171362A - Air bag storage cover - Google Patents

Abstract

PURPOSE:To obtain an air bag storage cover pleasant at the time of a part of a body being hit and excellent in configuration holding performance and durability as well as preventable positively from the scattering of a core layer at the time of the cover being split open by forming a facing layer of thermoplastic polymer specific hardness and a core layer of thermoplastic resin of specific bending elasticity and applying fragile configuration for split opening to the core layer. CONSTITUTION:An air bag storage cover 1 is formed of a facing layer 1A made of thermoplastic polymer of 20-90 in the JIS-A hardness of JIS-K6301 and a core layer 1B made of thermoplastic resin of more than 1,000kg/cm<2> in the bending elastic modulus of JIS-K7203 as well as of higher hardness than the thermoplastic polymer of the facing layer 1A. Fragile configuration 1C such as to be split open easily at the action starting time of the air bag, for instance, notch-formed thin configuration, scored slit configuration, or the like is applied to the core layer 1B. As a molding process method for manufacturing the air bag storage cover, injection molding method is considered to be one of the best from the viewpoint of design and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cover for accommodating an air bag that is inflated and deployed by sensing the impact, deformation, etc. at the time of a vehicle collision.

[Prior art] This type of cover has air bag operation (inflation).
Occasionally, the cover that houses it is shattered, and the fragments fly off and hit the passengers' faces or eyes, potentially causing injury. (Net, etc.) was generally inserted. (JP-A-62-234764, JP-A-5
0-127336, Utility Model 52-80928, Utility Model 5
0-43454, Utility Model Application Publication No. 51-25342, etc.).

Covers with such net-like inserts are usually manufactured by making the entire cover out of a relatively low-strength material such as polyurethane foam, and inserting a reinforcing net into the entire cover. It is common to provide a line in which the reinforcing material net is not inserted so that the reinforcing material net can be easily expanded and the cover easily destroyed when inflated.

On the other hand, Japanese Utility Model Application Publication No. 52-76042 discloses a skin layer made of hard urethane foam to give a smooth surface finish, and a core layer made of low-density (high-magnification foamed) urethane foam to make the entire cover soft. An air bag storage cover has been proposed which is composed of two layers and has a slit (a line for smooth expansion when the air bag is inflated) extending from the core layer to a part of the skin.

[Problems to be Solved by the Invention] Among the above-mentioned conventional air bag storage covers, the air bag storage cover with a net-like insert inserts a net-like reinforcing material, which requires a large number of manufacturing steps and is complicated. , Also, even if urethane foam molding (RIM)
Even with the use of the same method, it is difficult to manufacture with high precision, and there are problems in that the yield is low and the cost is high.

Furthermore, the cover disclosed in Japanese Utility Model Application Publication No. 52-76042 has a surface made of hard urethane foam (ASTM-D2240
, Shore hardness is 30 to 40), so if a part of your body hits it while driving a vehicle, you will not feel the softness and will feel uncomfortable. Furthermore, urethane-based materials have low impact strength and do not have reinforcing inserts, so airbag E'r1
Another drawback was that debris could sometimes fly off.

The present invention solves the above-mentioned problems of conventional airbag storage covers.The skin layer gives a soft feel, the core layer maintains a shape that can withstand external pressure, and is easily destroyed when the airbag is inflated. This is a cover for airbag storage that has a quality that prevents fragments from scattering even when the airbag is covered.It is manufactured using a simple molding method such as injection molding, with a high yield and high precision without producing defective products. Another object of the present invention is to provide an air bag storage cover that can be supplied with high productivity and good economic efficiency.

[Means for Solving the Problems] The air bag storage cover of the present invention conforms to JIS-63.
A skin layer made of a thermoplastic polymer with a JIS-A hardness of 01 from 20 to 90, and a flexural modulus of JIS-7203 of 1000 kg/crd or more and a hardness higher than that of the thermoplastic polymer of the skin layer. and a core layer made of a thermoplastic resin, and the core layer is characterized in that a portion is attached to the core layer to easily rupture when the airbag operation starts.

That is, in order to achieve the above object, the present inventors have made extensive studies and found that a thermoplastic polymer with a specific hardness is used as the skin layer, a thermoplastic resin with a specific bending elasticity is used as the core layer, and
The inventors have discovered that the above object can be achieved by providing the core layer with a brittle shape for cleavage, and have completed the present invention.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a schematic partial sectional front view showing a state in which an air bag storage cover according to an embodiment of the present invention is attached to an air bag, and FIG. 2 is a rear view of the air bag storage cover. .

In the figure, 1 is an air bag storage cover, 2 is an air bag, 3 is an inflator, 4 is a ring retainer, 5 is a pace retainer, 6 is a plate, and 7 is a rivet.

As shown in the figure, the air bag storage cover 1 of the present invention includes:
The skin layer IA is made of a thermoplastic polymer with a JIS-A hardness of 20 to 90 according to JIS-6301, and the skin layer IA has a flexural modulus of 1000 kg/cm' or more and the thermoplastic The core layer IB is made of a thermoplastic resin with a hardness higher than that of a polymer, and the core layer IB includes an IC with a fragile shape, such as a notch-like thin shape or a perforated shape, to easily rupture when the airbag starts operating. It has a slit shape, etc.

In the present invention, JIS-
Examples of thermoplastic polymers having a JIS-A hardness of 20 to 90 according to 6301 include olefins, styrenes, polyesters, and polyurethanes in the above hardness range;
Thermoplastic elastomers such as vinyl chloride and polyamide, and polyolefin soft materials within the above hardness range;
For example, ethylene-vinyl ester copolymer (EVA)
, ethylene-α-olefin (especially α-olefin having about 3 to 12 carbon atoms) copolymer, ethylene-unsaturated carboxylic acid or its conductor, copolymer, and soft vinyl chloride resin (PVC). Can be done. These can be used alone at 1 fffi or in a blend of 2 f1 or more, and can also be used in combination with other components as long as the hardness is within the above range.

Among the above-mentioned thermoplastic polymers, preferred are olefin elastomers, styrene elastomers, vinyl chloride elastomers, and
Soft PvC can be mentioned. Among these, olefin elastomers and styrene elastomers are particularly preferred since they exhibit a stable soft feel in the range of low to high temperatures.

In the present invention, among these thermoplastic polymers,
Those with a JIS-A hardness of 20 to 90 are selected, but those with hardness below the above range are highly flexible but have poor moldability (e.g. injection moldability) and mechanical strength and are easily damaged. There is a drawback. Further, those having a hardness exceeding the above range have no problem in molding processability, but have the disadvantage that they have a poor soft feel and are not practical. The hardness selection within the range of 20 to 90 varies depending on the thickness of the skin layer, but
It is desirable that the hardness is preferably in the range of 30 to 70, more preferably in the range of 40 to 65.

The thickness of the skin layer IA usually varies depending on the part of the cover 1 and is not uniform over the entire area, but in the present invention, the thickness of the skin layer IA is preferably 80% or more of the surface area of the skin layer IA. % or more preferably has a thickness of 0.5 mm or more. Although there is no particular upper limit to the wall thickness, it is appropriate to set it to about 10 m or less in view of design, economy, soft feel, airbag operating performance, molding process, etc.

Further, the skin layer IA may be foamed to a depth of about 3.0 times or less for the purpose of improving the soft feel and weight reduction.

In the present invention, used as a constituent material of the core layer IB,
As the thermoplastic resin having a bending modulus of 1000 kg/cm2 or more and a hardness higher than that of the thermoplastic polymer of the skin layer IA, homopolymers or copolymers of α-olefins such as ethylene and propylene (olefin polymers) are used. )
and polyamide, polyester resin, polycarbonate, ABS resin, high impact polystyrene (HI-PS)
, AS resin, etc. These resins may be used alone depending on the desired performance, or 2f! You may use a blend of the above.
Furthermore, as long as the elastic modulus and hardness are within the above ranges, fillers such as various elastomers, glass fibers, talc, calcium carbonate, silica, mica, etc., colorants, stabilizers, etc. can be filled using commonly used methods. It may be something that has been done.

Among these thermoplastic resins, preferred are high-density polyethylene (HD-PE), polypropylene, propylene-ethylene block or random copolymer, A
I apologize for mentioning BS resin. In particular, when using an olefin elastomer or a styrene elastomer for the skin layer IA, propylene polymers (especially propylene-ethylene block Particularly preferred are copolymers) and high-density polyethylene.

The bending modulus of such thermoplastic resin is 1000 kg/
If the hardness is less than c♂ or if the hardness is lower than the thermoplastic elastomer of the skin layer IA, sufficient shape retention will not be achieved and the material will be easily deformed by external pressure, making it unsuitable for use as an air bag storage cover. The bending elastic modulus is 1500 kg/cr from the viewpoint of the soft feel, movement characteristics, and shape retention of the entire cover.
rl'' to 30,000 kg/crn'.

The wall pressure of the core layer IB is not particularly limited, but is generally 1 to 1.
It is said to be approximately 3mm thick.

In the present invention, the core layer IB made of such a thermoplastic resin is given a brittle shape so that the core layer IB easily ruptures when the airbag operation starts.

This fragile shape may be a perforated slit shape, a thin notched shape, or various other shapes. Further, there are no particular restrictions on the formation location, formation range, etc., and are appropriately determined depending on the shape, strength, stress during airbag operation, etc. of the core layer IB.

Next, a method of manufacturing the air bag storage cover of the present invention will be described.

Examples of molding methods for manufacturing the airbag storage cover of the present invention include general molding methods used for thermoplastic resins, but injection molding is particularly preferred from the point of view of design, etc. can.

The injection molding method is the so-called insert injection method in which a core layer is molded in advance, the molded product is mounted in a mold leaving a space for the skin layer, and a skin material made of thermoplastic polymer is injection molded into the skin layer. Alternatively, the core layer is molded, then the cavity mold is separated, and without taking out the core molded product from the mold, a new cavity mold having a skin layer space is continuously covered and the skin material is injection molded. A two-color molding (double injection) method can be cited as an effective molding method.

At this time, it is necessary to give the core layer IB the aforementioned brittle shape so that the airbag can easily rupture when the airbag starts operating. As mentioned above, the fragile shape includes a notch-like thin shape and a perforated slit shape, but this shape is difficult to use when molding a core molded product. Alternatively, after the core molded product is molded, it may be processed to give such a shape, and then the skin layer may be laminated.

The airbag cover of the present invention may have the skin layer IA coated if necessary in order to improve the luxury of the vehicle interior, color matching with other interior parts, feel, etc. Coating the skin layer IA is also preferable from the viewpoint of scratch resistance.

[Function] In the air bag storage cover of the present invention, since the relatively hard core layer is covered with the soft skin layer,
Even if your body hits the cover, it is soft and you will not feel uncomfortable, and the core layer is hard, so even if some external force is applied, the cover will not be deformed, damaged, or damaged. There is no.

Furthermore, in the cover of the present invention, when the airbag inside the cover expands during a vehicle collision, etc., the cover ruptures along the fragile shape for cover rupture, which is provided in advance in the core layer. When the cover is torn apart, the hard core layer is tightly covered with the soft skin layer, so that the cover rupture fragments are not scattered.

[Examples] Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Examples 1 to 51, Comparative Examples 1 to 3 Using an in-line screw two-color injection molding machine with a mold clamping pressure of 350 tons, a perforated slit for cleavage (approximately 0.7 cm long) was formed using the core material shown in Table 1. A core layer (thickness: 1.0 to 3.0 mm) containing 29 fibers (29 pieces) is molded, and then a skin layer is formed with the skin material shown in Table 1 on top of it to a predetermined thickness. The air bag module cover 1 shown in FIG. 1 was obtained by injection molding.

In addition, in Example 4, a foamed skin layer was molded. In foam molding, 5 parts of a carbon dioxide blowing agent masterbatch (Fine Blow 52ON manufactured by Mitsubishi Yuka Co., Ltd.) was triblended to the skin material in two-color molding, and molding was performed.

Furthermore, in Example 5, the skin layer was painted.

For painting, after injection molding the cover, wipe the skin layer with isopropyl alcohol, then apply primer (MEX) manufactured by Itaben Kagaku Co., Ltd.
5440 and methyl ethyl ketone (1:1) to 7-10 μm
After spraying and drying at room temperature for 10 minutes, apply urethane top coat (MEX-6047: Curing agent F) manufactured by Itaben Kagaku Co., Ltd.
-3: Thinner 58u = 100: 10: 50)
This was carried out by spray coating 20 to 25 μm, drying at room temperature for 10 minutes, and baking at 80° C. for 30 to 45 minutes.

The obtained product was evaluated by the method described below, and the results were evaluated in the first
Shown in the table.

The materials used in Table 1 are as follows.

[Core material] PP-1; Brobylene-ethylene block cobolimer resin (Mitsubishi Yukas BC-8) MFR (230°C, 2.16 kg) = 1.8 g 710 minutes flexural modulus = 11000 kg/c Go JIS- A hardness = 100 PP-2: Blend of propylene-ethylene block copolymer resin and ethylene-propylene rubber (Mitsubishi Yuka Group BC47 Nippon Synthetic Rubber EPO7p = 60/40 (%)) BO2: MFR (230°C, 2 .16kg) -6,5g
710 minute flexural modulus - 11600 kg/c GoEPO7p: ML (too °C) = 70 Propylene content = 27% Blend: Flexural modulus - 4000 kg/cr
dJIS-A hardness = 99 E V A: Ethylene-vinyl acetate copolymer (Mitsubishi Yukas V601S) MFR (190°C, 2.16 kg) Rin 15 g/10 minutes Flexural modulus - 400 kg/c nfJ I S-
A hardness! 82 ABS: ABS resin (JSRAB manufactured by Japan Synthetic Rubber Co., Ltd.
SIO) Flexural modulus -18000kg/crr? JIS-A hardness = 100 [Skin material] TPO-1 Nioolefin thermoplastic elastomer (Thermolan J I S- manufactured by Mitsubishi Yuka) Hardness = 93 TPO-27 Olefin thermoplastic elastomer (Thermolan J I S- manufactured by Mitsubishi Yuka A hardness = 65 TPS-1: Styrenic thermoplastic elastomer (Mitsubishi Yuka Lavalon 5J J I S-A hardness = 45 TPS-2: Styrene thermoplastic elastomer (Mitsubishi Yuka T-320) JIS-A hardness = 15 [Evaluation method] ■ Soft feel As shown in Figure 1, a module cover assembled with airbag 2, airbag storage cover 1, retainer (mounting hardware) 4.5 and inflator 3, or cover 1 alone. The sample was left at -20℃ to 80℃ until it reached the ambient temperature, and then the cover was evaluated by the touch of the hands of 10 people. If 10 out of 10 felt it felt soft, it was rated 0. , If 8 out of 10 people answered, it was marked △, and if it was less than that, it was marked ×.

■ Shape retention As shown in Figure 1, the module cover assembled with the airbag 2, airbag storage cover 1, retainer (mounting hardware) 4.5, and inflator 3, or the cover 1 alone, is heated to 80℃ to 110℃. ℃ for a long time (<too.

hr) Leave it alone or heat cycle from -40℃ to 100℃ for 1
Leave it for 0 cycles, observe the state of deformation during or after the test, and if there is almost no deformation, it is considered suitable as an air bag storage cover (0), and if there is significant deformation, it is not suitable as an air bag storage cover (× ).

■ -20℃ Deployment Test Attach the module assembled in ■ and ■ to the steering wheel and leave it for a period of time to reach the ambient temperature of 20℃, and conduct the deployment test within 1 minute. At that time, the module cover cracks and scatters. Cases where the airbag did not operate normally, such as the cover cracking into sharp shapes and tearing the bag, were judged as unsuitable (x), and cases where normal operation was performed were judged as suitable (0).

■Productivity 20 products were manufactured in succession, and the external dimensions and weight of the molded products were checked.If all of the products passed, it was marked 0, if it was 90% or more, it was marked Δ, and if it was less than that, it was marked ×.

Comparative Example 4 For a comparative example, an air bag storage cover consisting of two layers, a skin layer of high-density urethane foam and a low-density urethane core layer, was manufactured and evaluated.

Molding is performed by insert molding, in which the core layer is molded in advance at a low foaming density using the rim urethane molding method and cured (hardened), then attached to a mold to form the skin layer, and then the skin layer is molded using the same method. It was done by law. Freon gas was used as the foaming material for forming the skin layer. This method required two curing steps and had poor productivity.

Regarding the obtained air bag storage cover, Example 1
The evaluation was carried out in the same manner as above, and the results are shown in Table 1.

Comparative Example 5 For further comparison, an air bag storage cover provided with a reinforcing net was manufactured and evaluated.

In this net-containing rim urethane molding, when molding two layers in the same manner as in Comparative Example 4, polyester fibers were knitted into a net shape, which was melted and cut into a shape along the cleavage of the cover, and metal fittings (hooks) were attached. Attach this to the rim mold,
The rim was molded with urethane. At this time, chlorofluorocarbon gas was used as a foaming material, and after demolding, it was cured at 100° C. for 30 minutes. With this method, it was difficult to create a safe skin layer by inserting the net, and the molding cycle was slow.

Regarding the obtained air bag storage cover, Example 1
The evaluation was carried out in the same manner as above, and the results are shown in Table 1.

As is clear from Table 1, the airbag storage covers of the present invention shown in Examples 1 to 5 had very good softness, shape retention, -20t deployment test, and productivity. there were.

[Effects of the Invention] As detailed above, the air bag storage cover of the present invention has a soft surface layer, so even if a part of the body hits it, it remains soft and provides a high sense of comfort. Since it is relatively hard, it has excellent shape retention and high durability. Then, when the airbag is activated, the cover quickly ruptures due to the fragile shape for rupturing the cover. Furthermore, the soft skin layer reliably prevents the core layer from scattering when the cover is torn.

Therefore, the air bag storage cover of the present invention can be easily and precisely manufactured using a streamlined molding method such as the two-color molding method, with almost no defective products, and with a high yield and reliably and efficiently. It is possible to significantly reduce the cost of the product.

[Brief explanation of the drawing]

FIG. 1 is a schematic partial sectional front view showing a state in which an air bag storage cover according to an embodiment of the present invention is attached to an air bag, and FIG. 2 is a rear view of the air bag storage cover according to an embodiment of the present invention. be. 1...Airbag storage cover IA...Skin layer, IB...Core layer, 2...
・Air bag, 3... Inflator -4,5-
・・Retainer Agent Patent Attorney Tsuyoshi Shigeno

Claims (1)

[Claims] (1) JIS-A hardness of JIS-K6301 is 20 to 9
0 thermoplastic polymer, and JIS-K7
It consists of a core layer made of a thermoplastic resin having a bending elastic modulus of 203 of 1000 kg/cm^2 or more and a harder hardness than the thermoplastic polymer of the skin layer, and the core layer has a core layer that is easily formed when the airbag starts operating. An air bag storage cover characterized by having a part for opening.