Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-09-14
2003-11-11
Mullis, Jeffrey (Department: 1711)
Land vehicles
Wheeled
Attachment
C280S728300, C525S088000, C525S240000
Reexamination Certificate
active
06644684
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an air bag cover for vehicles, and more particularly, to a cover for accommodating an air bag which is mounted in high-speed vehicles such as automobiles for protecting drivers and passenger(s) from collision accidents by inflation and deployment of the air bag in response to impact or deformation detected thereupon.
Air bag systems are adapted for protecting drivers and passengers) in vehicles from collision accidents, and include a sensor for detecting impact caused upon the collision and an air bag device.
The air bag device comprises an air bag, an air bag actuator, and a cover for accommodating these members, and is mounted in steering wheel, instrument panel, in front of an assistant seat, front pillar, side pillar, rear pillar, side of seat or the like.
When the vehicle receives,a large impact due to collision or the like, the air bag accommodated in an air bag casing is inflated, forces the cover to open from inside, and is deployed out into a vehicle compartment.
As the air bag covers used for air bag devices having such a structure, there are known those produced from foamed urethane with a metal core member, or those produced from foamed urethane with a hard plastic core member made of a polymer alloy composed of modified polyphenylene oxide axed 6-nylon as well as an inserted reinforcing member made of 6-nylon net or the like for the purpose of weight reduction.
However, in the case where the polymer alloy of modified polyphenylene oxide and 6-nylon is used as the core member, although the weight reduction is achieved, there is a tendency that the air bag is deteriorated in deployment property when used under a low temperature condition. Further, since the air bag cover of such a type has the net-like reinforcing member inserted therein, a number of complicated steps are required for the production thereof.
In order to solve these problems, in Japanese Patent Application Laid-Open (KOKAI) Nos. 1-202550 (1989), 2-171362 (1990), 2-220946 (1990) and 3-189252 (1991), there have been proposed two-color injection-molded air bag covers composed of a surface layer made of a soft thermoplastic elastomer and a core layer made of a hard thermoplastic elastomer having a good shape retention property, which are produced at a high yield by simplifying the above conventional production process of the air bag covers made of foamed urethane. Also, in Japanese Patent Application Laid-Open (KOKAI) Nos. 2,171364(1990), 4-151348(1992), 4-314648(1992) and 5-38996(1,993), there have been proposed single-layer injection-molded air bag covers which are produced at a reduced cost as compared to the above two-color injection-molded air bag cover.
According to these proposed methods, it is possible to produce air bag covers using ordinary injection-molding machines, and shorten a molding cycle thereof.
However, since latest models of air bag devices for protecting a passenger(s) of vehicles tend to be mounted in openings on an instrument panel located in front of assistant seat, front or side pillar, etc., air bag covers thereof have been required to have a less difference in rigidity and appearance from adjacent members.
The above two-color injection-molded air bag covers ox single-layer injection-molded air bag covers are provided with thin-wall portions (tear lines) to facilitate opening thereof upon deployment of the air bag, resulting in a less rigidity as well as unsatisfactory heat-deformation resistance.
In general, the above-described air bag is mounted within a steering wheel, and called a “tear-open” type air bag. More specifically, the air bag of this type is capable of inflating upon its operation so as to tear-open a cover portion thereof along tear seams or lines formed thereon, thereby allowing the air bag to be deployed into an occupant compartment of a vehicle. The air bag must be surely operated with a high safety. Therefore, it is necessary that the air bag cover is readily tear-opened along the tear seams or lines thereof. To achieve this requirement, the air bag cover is required to have a flexural modulus of not more than 500 MPa and a tensile strength of not more than 20 MPa.
On the other hand, in addition to the above-described tear-open type air bag cover mounted within a steering wheel, there is also known such an air bag which is accommodated within a pillar of the vehicle, and inflated along a side window upon its operation so as to cover the window in a curtain-like manner, thereby protecting occupants against impact force applied from a lateral direction of the vehicle. The air bag of this type is called a “non-tear-open” type or a “hinge” type, and have such a structure that when the air bag is inflated upon its operation, an air bag cover thereof is displaced or slightly deformed to form a clearance between the air bag cover and the pillar through which the air bag can be deployed into the occupant compartment. Thus, since the hinge-type air bag cover is not tear-opened, fitting portions of the air bag cover to which a load is applied during the operation, are required to have an appropriate strength. Therefore, the values of physical properties required for the hinge-type air bag cover are considerably different from those for the tear-open type air bag cover mounted on steering wheel of the vehicle. Also, the hinge-type air bag cover is free from flying fragmentation thereof upon the operation and, therefore, has advantages such as a less damage to occupants due to such fragmentations.
In addition, the hinge-type air bag cover fitted to the pillar will be frequently touched by a driver. Therefore, the air bag cover is required to have an appropriate strength without unstable feeling so as not to cause cave-in or depression upon touching.
In order to satisfy the above conflicting requirements at the same time, the hinge-type air bag cover is required to exhibit a flexural modulus of 550 to 800 MPa and a ratio of tensile break strength to flexural modulus of 0.03 to 0.07.
In Japanese Patent Application Laid-Open (KOKAI) No. 11-236483 (1999), there has been proposed the air bag cover (hinge-type) including a cover body, a fitting member securing the cover body to a stationary portion of vehicle, and a hinge member disposed near the fitting member. These members are arranged so as to be aligned with each other in the same plane. The air bag cover exhibits a good rigidity. However, since the air bag cover of such a type is molded from low-flowability resins in order to increase the strength of the hinge member, the molding of those having a complicated or elongated shape should be carried out at a high temperature, resulting in prolonged molding cycle and, therefore, deteriorated productivity. Further, the air bag cover tends to suffer from defects such as flow marks or the like, resulting in poor appearance.
As a result of the present inventors' earnest studies for solving the above problems, it has been found that when a thermoplastic elastomer composition containing specific components in specific amounts is used for the production of an air bag cover for vehicles, the obtained air bag cover can exhibit not only excellent rigidity and heat-deformation resistance without insertion of reinforcing members made of 6-nylon net or the like, but also high hinge strength and high fitting strength, and in addition, it has been found that the air bag cover can be fitted to or engaged with instrument panel or vehicle body directly or via other members such as metal inserts, is excellent in moldability and appearance, and can be operated with a high safety since it is free from breakage and flying-out into pieces upon deployment of the air bag. The present invention has been attained on the basis of the findings.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an air bag cover for vehicles in the form of a single-layer injection-molded product which exhibits not only excellent rigidity and heat-deformation resistance, but also has a high safety since it can be opened without br
Itou Motoko
Tsuji Tatsumi
Alexander John B.
Conlin David G.
Edwards & Angell LLP
Mitsubishi Chemical Corporation
Mullis Jeffrey
LandOfFree
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