1. The Field of the Invention
The present invention relates to airbag inflation systems in motor vehicles. More specifically, the invention relates to a panel retainer for securing a bolster panel to an airbag.
2. Technical Background
Inflatable airbags are well accepted for use in motor vehicles and have been credited with preventing numerous deaths and accidents. Some statistics estimate that frontal airbags reduce the fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belt and airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Airbag use presents clear benefits and vehicle owners are frequently willing to pay the added expense for airbags.
A modern airbag apparatus may include an electronic control unit (ECU) and one or more airbag modules. The ECU is usually installed in the middle of an automobile, between the passenger and engine compartment. If the vehicle has a driver airbag only, the ECU may be mounted in the steering wheel. The ECU includes a sensor which continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes an algorithm to determine if the vehicle is in an accident situation.
When the processor determines that there is an accident situation, the ECU transmits an electrical current to an initiator in the airbag module. The initiator triggers operation of the inflator or gas generator which, in some embodiments, uses a combination of compressed gas and solid fuel. The inflator inflates a textile airbag to impact a passenger and prevent injury to the passenger. In some airbag apparatuses, the airbag may be fully inflated within 50 thousandths of a second and deflated within two tenths of a second.
An airbag cover, also called a trim cover panel, covers a compartment containing the airbag module and may reside on a steering wheel, dashboard, vehicle door, vehicle wall, or beneath the dash board. The airbag cover is typically made of a rigid plastic and may be forced opened by the pressure from the deploying airbag. In deploying the airbag, it is preferable to retain the airbag cover to prevent the airbag cover from flying loose in the passenger compartment. If the airbag cover freely moves into the passenger compartment, it may injure a passenger.
Airbag apparatuses have been primarily designed for deployment in front of the torso of an occupant between the upper torso of an occupant and the windshield or instrument panel. Conventional airbags, such as driver""s or passenger airbags (hereinafter referenced as the xe2x80x9cprimary airbagxe2x80x9d), protect the occupant""s upper torso and head from colliding with a windshield or instrument panel. During a front end collision, if the occupant is restrained by a seat belt, the occupant""s upper torso bends at the waist and hits the primary airbag. However, depending on the design of the vehicle seat and force of the collision, there is a tendency for an occupant to slide forward along the seat and slip below the primary airbag, falling to the feet and leg compartment of the vehicle. The tendency is pronounced when the occupant is not properly restrained by a seat belt. Sliding of the occupant below the primary airbag is referred to as xe2x80x9csubmariningxe2x80x9d. When the occupant submarines, the primary airbag is less effective in protecting the occupant. Submarining is but one example of instances where extra support is needed to protect occupants or goods in an accident situation.
Submarining is more prevalent in vehicles which have large leg room compartments. Vehicles which have restricted leg room, such as sports cars, have a lower submarining tendency. In vehicles like sports cars, the distance between the legs and knees of the occupant and the instrument panel is shorter than the distance in vehicles like sport utility vehicles or trucks. In an accident in a sports car, the knees of the occupant often strike the instrument panel. The instrument panel prevents submarining. Generally, the material of the sports car instrument panel deforms to some degree to help protect the legs and knees of the occupant.
In order to prevent submarining in vehicles with large leg room compartments, a knee airbag system has been developed. The goal of the knee airbag system is, during an accident, to position a piece of rigid material similar to the material of the instrument panel in a sports car close to the occupant""s knees and legs creating leg and knee support, which prevents submarining. The knee airbag system allows a vehicle manufacturer to design vehicles with more leg room and still have safety comparable to that of vehicles with less leg room. To accomplish the goal, the knee airbag system is typically positioned in the lower portion of the instrument panel.
The knee airbag system includes an inflator, a housing, an airbag, and a trim cover panel. The housing is a conventional enclosure for securing the knee airbag components to the vehicle. The housing stores the knee airbag system components while the airbag is deflated and not needed. The inflator, once triggered, uses compressed gas, solid fuel, or their combination to produce rapidly expanding gas to inflate the airbag. As with conventional airbag systems, an airbag is a large textile bag which the gas inflates like a balloon. The knee airbag system may also include a fixed panel, called a load distribution panel or knee bolster panel. This bolster panel is important in providing sufficient support such that submarining is prevented.
In a system using a knee bolster airbag, a primary airbag provides a cushioning effect which protects the occupant""s face and head. In such a system, the knee airbag serves to restrain the legs and knees. However, without additional rigid support, the cushioning effect of the knee airbag allows the knees and legs to move a sufficient distance that submarining may still occur.
When an inflated knee airbag without rigid support contacts the legs, the flexible material of the airbag wraps around each leg. The surface area of the inflated knee airbag supporting the legs is reduced to the area where each leg contacts the knee airbag. If the force of the forward moving legs is distributed across the entire surface of the airbag, however, then the entire volume of gas in the airbag will compress resulting in more support of the legs. For this reason, a rigid support surface or xe2x80x9cload distribution panelxe2x80x9d is generally used in connection with a knee airbag. When such a load distribution panel is used the compressed volume of gas within the airbag creates a greatly increased opposing force pushing against the forward moving legs.
The load distribution panel is generally made of foam and hard plastic surrounding a metal substrate. The shape of the inflated airbag determines how to secure the load distribution panel. Since, the inflated knee airbag occupies a generally rectangular volume of the vehicle leg compartment, the load distribution panel is preferably rectangular. Optimal distribution of the impact force, through the volume of the inflated knee airbag, is accomplished preferably by securing each comer of the rectangular load distribution panel to the knee airbag.
Generally, the load distribution panel is secured to the front of the airbag to distribute the force of impact through the majority of the volume of gas in the inflated airbag. Securement of a load distribution panel and an airbag is a challenge because of the strong impact forces involved, the flexibility of the airbag, and the rigidity of the load distribution panel. Apparatus for securing the knee bolster panel to the knee airbag exist. For example, a load distribution panel may have threaded studs which pass through holes in the knee airbag. The studs then pass through holes in a retaining plate. The studs are secured to the retaining plate by nuts screwed onto the studs.
Another securement technique uses textile tethers installed completely inside the airbag. The tethers comprise sewn loops on each end. Each end of the tether is secured by a rivet or screw attached to a ring, similar to a key ring. The loop of the tether is connected to the ring in the same way keys are attached to key rings. One rivet attaches to the inflator or housing. The other rivet passes through a hole in the airbag to the outside and attaches to a load distribution panel.
A third securement technique uses rods and channels. The airbag is provided with rods which are secured using conventional means which include sewing, glueing, welding, and the like. The rods are secured so the majority of the rod is exposed and runs the length of the airbag. The load distribution panel comprises C-shaped channels which correspond in size and length to the rods on the airbag. The rods and channels are made of nylon, metal, of other engineering polymer. The load distribution panel is attached by snapping the C-shaped channels to the exposed portion of the rods.
These designs all have significant limitations because airbag modules are generally assembled prior to installation in the vehicle. Securing the airbag using a retaining plate and studs requires careful positioning of the studs through the retaining plate. Additionally, the attachment and tightening of the nuts onto the studs is challenging because attachment occurs inside the airbag by way of a hole intended to allow insertion of the inflator. Similarly the tether technique attaches the tethers at points internal to the airbag. Such precision requires extra skill and time in assembling the module. The rod and channel technique is external to the airbag, yet has several parts. Attaching some of the parts may require special tools such as a press, welder, or rivet gun. When a system has several parts, particularly ones requiring extra time and skill to attach, the probability of defective parts or defective installation rises. If too high, these probabilities prevent the manufacturer from using an assembly line.
Accordingly, it would be an advancement in the art to provide a load distribution panel retention apparatus which is easier to fabricate. A further advancement in the art would be to provide a load distribution panel retention apparatus which allows for quick and simple attachment of the load distribution panel to the airbag. It would be another advancement in the art to provide a load distribution panel retention apparatus that saves time and money. The present invention solves these problems in a novel and useful way.
The apparatus and method of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available load distribution panel retention apparatuses. Thus, the present invention provides a load distribution panel retention apparatus which provides easy attachment of a knee bolster panel and saves both time and money.
As mentioned above, in order for knee bolster airbag systems to operate effectively it is necessary to provide rigidity to the airbag. This is required in order to distribute the load over the entire volume of gas inside the inflated airbag. This load distribution function is provided herein by a load distribution panel. As further discussed above, it has been a problem in the art to adequately attach a load distribution panel to an airbag. The present invention provides an improved mechanism of attachment.
In one embodiment of the present invention, the load distribution panel retention apparatus comprises a planar piece of material, (hereinafter sometimes referred to as a xe2x80x9cPanel Retainerxe2x80x9d). The material is typically a nylon or polyester weave and may be in the shape of a square or rectangle. The panel retainer is configured to receive a load distribution panel. The panel retainer provides uniform securement of a load distribution panel to a knee airbag. The panel retainer is secured to the airbag along at least two of it""s opposing edges. Techniques for securement of the edges include, but are not limited to, glueing, velcro, sewing, welding, snapping, and the like. The panel retainer may be in the form of a sleeve or pocket. As a pocket, the panel retainer is secured along three edges to the airbag. As a sleeve, the panel retainer is rectangular in shape, rather than square.
The panel retainer may be configured to receive load distribution panels of various shapes and forms. For example, the load distribution panel could be in the shape of a rod, a plate, or a panel. The shape and form of the load distribution panel dictates the distance between the secured edges of the panel retainer. Alternatively, the panel retainer may be configured to receive a securing member of a load distribution panel, which securing member may be in the form of an arm, tab or flange.
In further embodiments, the invention may include one or more pieces of material in the form of straps. The straps are secured at each end to the airbag by way of conventional securement techniques described above. The straps are configured to receive and secure a load distribution panel. These straps may be oriented in parallel or criss-cross each other.
The present invention may also include one or more holes in the panel retainer to allow passage of decorative trim cover fasteners. The fasteners pass through the holes to secure the load distribution panel to a decorative trim cover panel. The size and position of the holes corresponds to the size and position of the fasteners.
The present invention further provides a method of knee airbag module assembly. In the method of the present invention, an airbag is provided. The airbag includes a planar panel retainer capable of receiving a load distribution panel. Also provided is a load distribution panel, a trim cover panel, and trim cover panel fasteners. The method includes placing the load distribution panel between the panel retainer and the airbag. The load distribution panel comprises one or more fasteners disposed therein. In other embodiments, the one or more fasteners are disposed in the trim cover panel. The fasteners are of the kind conventional in the art. i.e. tree clips, snaps, rivets, or the like. The fasteners are fit through holes in the panel retainer. Finally, the trim cover panel is attached to the load distribution panel by way of the fasteners.
These and other features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.