Gas generator, in particular for a vehicle occupant restraint system, and method of activating a vehicle occupant restraint system

• US 20080169630A1
• Filed: 01/16/2008
• Published: 07/17/2008
• Est. Priority Date: 01/16/2007
• Status: Active Grant

• Current Assignee: TRW Airbag Systems GmbH (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: TRW Airbag Systems GmbH (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Herget, Christian, Last, Detlef
• Granted Patent: US 7,828,324 B2
• Time in Patent Office: Days
• US Class Current: 280/741
• CPC Class Codes: B60R 21/272 with means for increasing the pressure of the gas just before or during liberation, e.g. hybrid inflators
• CPC Class Codes: B60R 21/274 characterised by means to rupture or open the fluid source

Abstract

A gas generator, in particular for a vehicle occupant restraint system, has a pyrotechnical propellant (16), a combustion chamber (12) filled with the pyrotechnical propellant (16), an igniter (14) associated with the combustion chamber (12), a pressure chamber (18), filled with compressed gas, which is adjacent to the combustion chamber (12) and has a first opening (22) remote from the combustion chamber (12) closed by a first diaphragm (26), the diaphragm (26) being destroyed upon activation of the igniter (14), and a second pressure chamber (28) which is filled with compressed gas and has a second opening (34) closed by a second diaphragm (36). The second diaphragm (36) is likewise destroyed upon activation of the igniter (14), and the openings (22, 34) and the gas volumes of the pressure chambers (18, 28) are adapted so that compressed gas flows out from the second pressure chamber (28) for a longer period than compressed gas from the first pressure chamber (18) to increase a gas supply time of the gas generator (10). Further, a method of activating a vehicle occupant restraint system is described.

Claims

1. A gas generator, in particular for a vehicle occupant restraint system, comprising

a pyrotechnical propellant (16),

a combustion chamber (12) filled with said pyrotechnical propellant (16),

an igniter (14) associated with said combustion chamber (12),

a pressure chamber (18), filled with compressed gas, which is adjacent to said combustion chamber (12) and has a first opening (22) remote from said combustion chamber (12) closed by a first diaphragm (26), said diaphragm (26) being destroyed upon activation of said igniter (14), and

a second pressure chamber (28) which is filled with compressed gas and has a second opening (34) closed by a second diaphragm (36),

said second diaphragm (36) being likewise destroyed upon activation of said igniter (14), and said openings (22, 34) and the gas volumes of said pressure chambers (18, 28) being adapted so that compressed gas flows out from said second pressure chamber (28) for a longer period than compressed gas from said first pressure chamber (18) to increase a gas supply time of said gas generator (10).

2. The gas generator according to claim 1, wherein a shock wave is generated by activation of said igniter (14) and destruction of said first diaphragm (26), said second diaphragm (36) being destroyed by said shock wave.

3. The gas generator according to claim 1, wherein said combustion chamber (12), said first pressure chamber (18) and said second pressure chamber (28) are arranged one behind the other in an axial direction (A).

4. The gas generator according to claim 1, wherein a third diaphragm (46) is provided, said first pressure chamber (18) being separated from said combustion chamber (12) by said third diaphragm (46).

5. The gas generator according to claim 1, wherein said pressure chambers (18, 28) comprise discharge ends (21, 31), immediately facing each other, said first and second diaphragms (26, 36) being provided on said discharge ends (21, 31).

6. The gas generator according to claim 5, wherein the following applies to a minimum distance a between said discharge ends (21, 31) of said pressure chambers (18, 28):

$a=\frac{d_1}{4}·<br><br>\sqrt{\frac{M_2}{M_1}}+\frac{d_2}{4}·<br><br>\sqrt{\frac{M_1}{M_2}},$

where d₁ and d₂ are diameters of said first and second openings (22, 34), respectively, and M₁ and M₂ are molar masses of said compressed gas in said first and second pressure chambers (18, 28), respectively.

7. The gas generator according to claim 1, wherein a diffusor section (38) having a plurality of discharge ports (40) is provided, which is arranged between said first and second pressure chambers (18, 28).

8. The gas generator according to claim 7, wherein said diffusor section (38) is arranged on a side of said first pressure chamber (18) facing away from said combustion chamber (12).

9. The gas generator according to claim 1, wherein said second pressure chamber (28) has a throttle (50) arranged in an immediate vicinity of said second diaphragm (36).

10. The gas generator according to claim 1, wherein said first pressure chamber (18) has a smaller volume than said second pressure chamber (28).

11. The gas generator according to claim 1, wherein said first and second pressure chambers (18, 28) are filled with different compressed gases.

12. The gas generator according to claim 11, wherein a compressed gas in said first pressure chamber (18) has a lower viscosity than a compressed gas in said second pressure chamber (28).13. The gas generator according to claim 1, wherein an opening (34) covered by said second diaphragm (36) is smaller in cross-section than an opening covered by said first diaphragm (26).

13. The gas generator according to claim 1, wherein said second diaphragm (36) is larger than said first diaphragm (26).

14. A method of activating a vehicle occupant restraint system, comprising the following steps:

providing a gas generator (10) which includes a combustion chamber (12) having an associated igniter (14),

providing a first compressed gas container close to said combustion chamber (12),

providing a second compressed gas container remote from said combustion chamber (12),

generating a shock wave by activating said igniter (14) and by destroying a diaphragm (46) closing said first compressed gas container and facing said igniter (14),

opening a further diaphragm (26) of said first compressed gas container by said shock wave,

opening a diaphragm (36) of said second compressed gas container by said shock wave, and

outflow of compressed gas from both said first and said second compressed gas containers, with compressed gas flowing out from said second compressed gas container for a longer period than from said first compressed gas container to increase a gas supply time of said gas generator (10).