Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-03-08
2003-04-29
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Attachment
C280S743200, C280S739000, C280S729000
Reexamination Certificate
active
06554316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to airbag inflation systems in motor vehicles. More specifically, the invention relates to an airbag venting system for directing inflation gases through an airbag.
2. Technical Background
Inflatable airbags are well accepted for use in motor vehicles and have been credited with preventing numerous deaths and injuries. 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 compartments. 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 open 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 “primary airbag”), protect the occupant's upper torso and head from colliding with a windshield or instrument panel.
Airbag apparatuses are generally designed under the assumption that the occupant is riding in the vehicle in a forward facing seated position with both feet on the vehicle floor. When an occupant is not in this position the occupant or occupant's body part is said to be ‘out of position.’ As an occupant occasionally is ‘out of position’, airbag apparatus designs which are effective regardless of the occupant's position are advantageous.
In an accident situation involving a primary airbag, there are three phases which follow each other between the beginning of the accident and the end. In the inflation phase, the goal is to fully inflate the primary airbag to occupy a majority of space between an instrument panel and an occupant before the occupant moves significantly forward in the vehicle compartment. In this phase, the primary airbag fully inflates in response to a signal from the ECU within about 50 thousandths of a second.
Next, there is the impact phase in which the goal is to impact the occupant's body in such a manner as to reduce injuries to the occupant. Generally, a flat, soft surface best accomplishes the goal of this phase. The primary airbag and the occupant's upper torso collide. The primary airbag and occupant's upper torso then react to each other in response to the collision.
Finally, the last phase is the deflation phase. The goal in this phase is to bring the occupant's upper torso to a resting state without allowing the upper torso to collide with other rigid structures in the vehicle. The goal is accomplished by releasing the gas which inflated the primary airbag at a rate which is slower than the speed at which the occupant's body is moving forward.
Airbag apparatuses seek to meet the goals of all three phases. Meeting the goals of the inflation and deflation phases is the most challenging. Airbag apparatus designs must function within tight parameters of physics in order to protect a vehicle occupant involved in an accident. 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. Airbag apparatuses are generally small compact units which are capable of presenting the inflated primary airbag in front of a vehicle occupant before the occupant's upper torso moves significantly forward. Because of the short time interval between the start and end of an accident situation, the primary airbag must be inflated very rapidly. The high inflation rate causes the front surface of a conventional primary airbag to travel to within inches of an ‘in position’ occupant's upper torso at a rate around 200 miles per hour.
Most airbags provide a release for the gas within the airbag. This release is called venting. By venting the gas in the primary airbag, the impact forces of the occupant's torso are absorbed.
The venting of gas from the primary airbag should fall within certain timing parameters. First, the venting should not occur too early in the accident sequence. Second, the venting rate should not be too slow.
If venting occurs too early, such as during the inflation phase, then the primary airbag may be under inflated at the time of impact with the occupant. An under inflated bag provides less restraint and increases the likelihood of impact between the occupant and the interior of the vehicle. If a primary airbag vents gas too slowly, then the airbag may be too rigid to effectively protect the occupant.
When an occupant collides with the primary airbag, the occupant's body compresses the gas within the airbag. If there is no release of gas, then the compression stops and the textile bag presents a rigid structure resisting the forward movement of the occupant's body. But, if the airbag has structure to provide the desired rate of venting then the impact force of the occupant is transferred to gas inside the airbag. The gas reacts by pushing against other gas within the airbag. This forces gas out the vent structure at the desired rate. The force of impact is transferred to the gas within the airbag and then to the air outside the airbag. The desired rate of venting is reached by forming holes in the airbag. These holes may be half circle cuts in the bag, tear seams, multiple holes, or other like release mechanisms placed in the bag to ensure that the desired venting rate is reached and held constant during the deflation phase.
A constant venting rate results in fewer injuries to the occupant. A constant venting rate also allows the airbag to slow the occupant's body at a constant rate. The restraining force which the airbag is placing on the occupant is constant. The occupant's body is better able to withstand restraining forces when they are applied constantly over time.
Airbag apparatuses are installed in various different vehicles which convey occupants of varying shapes and sizes. One occupant may fit the optimal ‘in position’ requirements while another may not. Therefore, airbag designs which meet the goals of the three phases must accommodate for the variety among vehicle and occupants. Multi-chamber airbag apparatuses have been developed to accommodate th
DePottey Timothy A.
Schneider David W.
Shellabarger Brian T.
Soderstrom Pontus
Autoliv ASP Inc.
Brown Sally J.
Erickson James D.
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