Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-08-08
2004-05-11
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Attachment
C180S274000, C180S282000, C701S045000
Reexamination Certificate
active
06733036
ABSTRACT:
FIELD OF THE INVENTION
This invention is in the general field of wiring systems applied to vehicles and particularly to motor vehicles such as automobiles. It specifically addresses the use of a common wire bus or data bus for a plurality of sensors and actuators in a motor vehicle and particularly for safety systems including crash, occupant and other sensors, airbag modules and associated electronics.
BACKGROUND OF THE INVENTION
It is not uncommon for an automotive vehicle today to have many motors, other actuators, lights etc., controlled by one hundred or more switches and fifty or more relays and connected together by almost five hundred meters of wire, and close to one thousand pin connections grouped in various numbers into connectors. It is not surprising therefore that the electrical system in a vehicle is by far the most unreliable system of the vehicle and the probable cause of most warranty repairs.
Unfortunately, the automobile industry is taking a piecemeal approach to solving this problem when a revolutionary approach is called for. Indeed, the current trend in the automotive industry is to group several devices of the vehicle's electrical system together which are located geometrically or physically in the same area of the vehicle and connect them to a zone module which is then connected by communication and power buses to the remainder of the vehicle's electrical system. The resulting hybrid systems still contain substantially the same number and assortment of connectors with only about a 20% reduction in the amount of wire in the vehicle.
Most airbag modules in use today are large, heavy, expensive, and inefficient. As a result, airbags are now primarily only used for protecting the passenger and driver in a frontal impact, although at least three automobile manufacturers currently offer a small airbag providing limited protection in side impacts and some are now offering head protection airbags. The main advantage of airbags over other energy absorbing structures is that they utilize the space between the occupant and vehicle interior surfaces to absorb the kinetic energy of the occupant during a crash, cushioning the impending impact of the occupant with the vehicle interior surfaces. Airbags have been so successful in frontal impacts that it is only a matter of time before they are effectively used for side impact protection in all vehicles, protection for rear seat occupants and in place of current knee bolsters. Substantial improvements, however, must be made in airbags before they assume many of these additional tasks.
A good place to start describing the problems with current airbags is with a calculation of the amount of energy used in a typical airbag inflator and how much energy is required to inflate an airbag. By one analysis, the chemical propellant in a typical driver's side inflator contains approximately 50,000 foot pounds (68,000 joules) of energy. A calculation made to determine the energy required to inflate a driver's side airbag yields an estimate of about 500 foot pounds (680 joules). A comparison of these numbers shows that approximately 99% of the energy in a chemical propellant is lost, that is, generated but not needed for inflation of the airbag. One reason for this is that there is a mismatch between the output of a burning propellant and the inflation requirements of an airbag. In engineering this is known as an impedance mismatch. Stated simply, propellants naturally produce gases having high temperatures and high pressures and low gas flow rates. Airbags, on the other hand, need gases with low temperatures and low pressures and high gas flow rates.
In view of this impedance mismatch, inflators are, in theory at least, many times larger then they would have to be if the energy of the propellant contained within the inflator were efficiently utilized. Some attempts to partially solve this problem have resulted in a so-called “hybrid” inflator where a stored pressurized gas is heated by a propellant to inflate the airbag. Such systems are considerably more energy efficient, however, they also require a container of high pressure gas and means for monitoring the pressure in that container. Other systems have attempted to use aspiration techniques, but because of the geometry constraints of current car inflator designs and mounting locations, and for other reasons, currently used aspiration systems are only able to draw significantly less than 30% of the gas needed to inflate an airbag from the passenger compartment. Theoretical studies have shown that as much as 90% or more of the gas could be obtained in this manner.
Furthermore, since inflators are large and inefficient, severe restrictions have been placed on the type of propellants that can be used since the combustion products of the propellant must be breathable by automobile occupants. It is of little value to save an occupant from death in an automobile accident only to suffocate him from an excessive amount of carbon dioxide in the air within the passenger compartment after the accident. If inflators operated more efficiently, then alternate, more efficient but slightly toxic propellants could be used. Also, most current inflators are made from propellants, namely sodium azide, which are not totally consumed. Only about 40% of the mass of sodium azide propellants currently being used, for example, enters the airbag as gas. This residual mass is very hot and requires the inflator to be mounted away from combustible materials further adding to the mass and size of the airbag system and restricts the materials that can be used for the inflator.
It is a persistent problem in the art that many people are being seriously injured or even killed today by the airbag itself. This generally happens when an occupant is out-of-position and against an airbag module when the airbag deploys. In order to open the module cover, sometimes called the deployment door, substantial pressure must first build up in the airbag before enough force is generated to burst open the cover. This pressure is even greater if the occupant is in a position that prevents the door from opening. As a result, work is underway to substantially reduce the amount of energy required to open the deployment doors and devices have been developed which pop off the deployment door or else cut the deployment door material using pyrotechnics, for example.
One reason that this is such a significant problem is that the airbag module itself is quite large and, in particular, the airbags are made out of thick, heavy material and packaged in a poor, folded geometry. The airbag, for example, which protects the passenger is housed in a module which is typically about one third as long as the deployed airbag. All of this heavy airbag material must be rolled and folded inside this comparatively small module, thus requiring substantial energy to unfold during deployment. This situation could be substantially improved if the airbag module were to have an alternate geometry and if the airbag material were substantially lighter and thinner and, therefore, less massive and folded mainly parallel to the inflator. Even the time to deploy the airbag is substantially affected by the mass of the airbag material and the need to unfold an airbag with a complicated folding pattern. Parallel folding, as used herein, means that the airbag material is folded with the fold lines substantially parallel to the axis of the inflator without being folded over lengthwise as is now done with conventional airbag folding patterns.
Devices are now being offered on vehicles that will monitor the position of the occupant and prevent the airbag from deploying if the occupant is dangerously close to the module where he or she can be seriously injured by the deployment. Some systems will also prevent deployment if the seat in connection with which the airbag operates is unoccupied. An alternate approach is to move the deployment doors to a location away from normal occupant positions. One such location is the ceiling of the vehicle. One problem
Breed David S.
Du Vall Wilbur E.
Johnson Wendell C.
Automotive Technologies International Inc.
Dickson Paul N.
Roffe Brian
Rosenberg Laura B.
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