Hybrid gas generator

Details Hybrid gas generator Hybrid gas generator

1999-09-01

2001-09-18

Tudor, Harold J. (Department: 3641)

Ammunition and explosives

Jacketed or cartridge gas generator

C280S737000, C280S741000

Reexamination Certificate

active

06289820

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a hybrid gas generator which contains an ignitable, gas-generating solid charge and a storage chamber containing a gas.
A hybrid gas generator for air bags is known from EP 0 616 578 B1, which contains an ignitable solid charge in a combustion chamber and a pressurized gas in a storage chamber. Upon the initiation of the gas generator, an ignition element ignites the solid charge. A hollow piston is driven by the combustion gases which are generated, with the hollow piston pushing through a closure element which closes the storage chamber, and with the pressurized gas contained in the storage chamber being able to flow out to the outlet. Moreover, the combustion gases generated by the solid charge flow into the storage chamber, where they mix with the compressed gas. When the closure element is destroyed, first of all cold compressed gas flows to the outlet. This prevents the hot combustion gases from arriving in the air bag first. Subsequently, a mixture of cold gas and combustion gas flows into the air bag.
Moreover, a hybrid gas generator is known from EP 0 669 231 A2, where a mixing chamber is arranged between a combustion chamber containing the solid charge and a storage chamber containing a compressed gas. The combustion chamber and the storage chamber are sealed by sealing discs which are destroyed by the combustion gases of the solid charge. In this respect, the combustion gas and the cold gas penetrate from opposite directions into the mixing chamber, with the flowing-out being impeded as a result. Moreover, the hot combustion gas loaded with harmful substances flows out initially because the sealing disc of the combustion chamber is the first one to be destroyed.
The known hybrid gas generators have a pressure buildup behaviour determined by their construction, with the maximum pressure and the pressure increase gradient being specified. In the process, the air bag connected to the gas generator is inflated very quickly and in one go. In the process, the passengers can be injured by the air bag if they are “out of position”.
SUMMARY OF THE INVENTION
The object of the invention is to create a hybrid gas generator which makes it possible to control the course of the pressure build-up with time in order to effect greater safety for the passengers.
With the gas generator in accordance with the invention, two solid charges are provided in different combustion chambers, with the second solid charge being ignitable in a time-delayed manner in relation to the first solid charge. In this way, the gas generation takes place with two different pressure increase gradients, with preferably first of all a relatively flat pressure increase and then a steeper pressure increase being realized. The instant of the steeper pressure increase can be determined very accurately by the ignition delay. The two solid charges can also be of different sizes or can provide different quantities of gas. The percentage pressure distribution of the entire charge to the two individual charges makes a purposeful influencing of the pressure characteristic possible. Within the scope of the invention, it is even possible to provide, in addition to the two solid charges, at least one further solid charge.
The hybrid gas generator in accordance with the invention makes the realization of different types of pressure build-up characteristics possible, indeed not only by means of the purposeful distribution of the charges and the control of the ignition procedures, but also by means of other structural modifications, for example the dimensioning of the cross section of the outflow openings.
According to a preferred development of the invention, the first solid charge and the closure element are arranged at opposite ends of the storage chamber, and the pushing element extends through the storage chamber. In this respect, the length of the pushing element can be varied in order to realize different pressure build-up characteristics. A further parameter is the dwell time of the combustion gases in the storage chamber before the closure element is opened. In this way, the heat transmission between the combustion gas and the storage gas can be influenced, this affecting the maximum pressure and the pressure increase gradient.
Further advantages and features of the invention are evident from the following description of various exemplifying embodiments.


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