Land vehicles – Wheeled – Attachment
Reexamination Certificate
2000-04-28
2001-08-28
Rice, Kenneth R. (Department: 2617)
Land vehicles
Wheeled
Attachment
Reexamination Certificate
active
06279949
ABSTRACT:
TECHNICAL FIELD
The invention relates to a device for the rapid inflating of a folded gas bag for an occupant impact protection device in motor vehicles.
BACKGROUND OF THE INVENTION
Such protective devices have become known under the name “airbag” and in the meantime are installed as standard in modern motor vehicles. Airbag modules accommodated in the steering wheel of a motor vehicle are usual and are the most widespread, which in the case of an accident are triggered by an acceleration sensor, the folded gas bag being inflated explosion-like and forming between the driver and the steering wheel a cushion by which injuries are prevented, but at least reduced. Also, corresponding airbag modules have been provided as standard in the meantime for the passenger. Further airbag modules which are matched to particular accident situations, for example to a side impact, are likewise offered as additional equipment or even already as standard.
In all airbag modules, the gas bag can only develop an optimum protective effect when it is inflated promptly in a taut manner. In the case of front airbags, promptly means for example within 20 to 30 milliseconds. To achieve this, pyrotechnic charges are generally used, which can make available the necessary gas volume as a product of chemical conversions in the manner of an explosion.
As a gas bag which is inflated in a taut manner would act like an elastically deformable spring element and would throw back the occupant who is plunging into it, in all airbag systems care must be taken that the filling gases can also flow out from the gas bag again, because only thus can a substantially plastic collision behavior be achieved with optimum decrease of kinetic energy when a vehicle occupant plunges in. For this, either the material of the gas bag casing is designed so as to be gas-permeable in a defined manner, or else with a gas bag casing which is substantially impermeable to gas, separate outflow openings are provided. In both cases, it can not be avoided that already on filling the gas bag a greater or lesser proportion of the filling gases flows off and the maximum possible filling can not be achieved with a given propellant charge. If one nevertheless wishes to achieve a particular filling level, the propellant charge must be designed to be larger so that the quantity of filling gast to be regarded as loss, which flows off until the occupant plunges, can be compensated.
From this, the problem results of improving the device initially mentioned to the effect that on the one hand a gas bag, which is filled in a taut manner, can be made available and that on the other hand no losses of filling gases occur and the filling volume which is aimed for is achieved with the smallest possible quantity of propellant.
BRIEF SUMMARY OF THE INVENTION
The invention provides an inflation device in which the problem mentioned above is solved. This is achieved in a device for rapid inflation of a folded gas bag for an occupant impact protection device in motor vehicles which comprises a housing, a pyrotechnic propellant within the housing for generating filling gases, and an ignition device. The housing is equipped with a passage serving as an outflow duct for the filling gases from the gas bag, a cross-section of the passage being adapted to be exposed at least in part after an activation of the device.
With the passage, initially closed and then exposed in whole or in part, in the housing to receive the pyrotechnic propellant, it is possible to coordinate the start of the outflow of the filling gases from the gas bag chronologically with the plunging of the occupant into the gas bag. In combination with a gas bag casing which is impermeable to gas, thereby a premature outflow of gas can be avoided, so that no gas losses occur and no excess propellant is required.
According to an advantageous further development of the basic idea, provision is made that the passage is closed by a rupture membrane with a defined strength. Thereby, the chronological coordination of the start of outflow which is aimed for with the plunging of the occupant can be realized in a simple manner in that the strength of the rupture membrane is coordinated with the sudden rise in pressure occurring on plunging. The outflow is therefore triggered immediately by the plunging in. Between reaching the maximum gas bag filling and the plunging of the occupant, the gas bag which is filled in a taut state is. held as it were “in store” and the outflow of the filling gases for achieving the plastic impact- or collision behavior only begins when the compliance of the gas bag is required.
According to another advantageous further development of the basic idea, provision is made that the passage is closed by an actuator and that the passage, after an activation of the device, can be opened by the actuator at least in part as a function of at least one measured value. This somewhat more complicated version not only permits the chronological coordination of the start of outflow and the plunging process but also the establishing of the outflow cross-section and hence an influence on the energy absorption behavior of the gas bag as a function of at least one measured value. This can for example be the body weight of the occupant concerned, which can be easily determined by means of a suitable measurement transducer in the vehicle seat and can be passed on to the electronic control device for the gas bag. As is known, a heavy person requires a harder gas bag than a light person, because on plunging in, a higher kinetic energy has to be taken up. The hardness of the gas bag is determined primarily by the gas outflow rate. With a small outflow rate, a hard gas bag can be realized which is necessary for the optimum protection for heavy people. Vice versa, a soft gas bag can be realized with a high outflow rate, which then offers an optimum accident protection to light people.
Of course, other measured occupant specific, vehicle specific and crash specific values, such as for example amount and direction of the vehicle deceleration caused by an accident can also be taken into account for establishing the size of the outflow cross-section.
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Rice Kenneth R.
Tarolli, Sundheim, Covel Tummino & Szabo L.L.P.
TRW Automotive Safety Systems GmbH & Co. KG
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