Hybrid inflator and vehicle safety system comprising said hybrid inflator as well as method of forming a shock wave

• US 10,173,633 B2
• Filed: 12/05/2016
• Issued: 01/08/2019
• Est. Priority Date: 12/10/2015
• 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: Last, Detlef, Seidl, Lorenz, Ruckdeschel, Rolf
• Primary Examiner(s): Freedman, Laura
• Application Number:
  US15/368,778
• Publication Number:
  US 20170166162A1
• Time in Patent Office: 764 Days
• CPC Class Codes: B60R 2021/2642 comprising a plurality of combustion chambers or sub-chambers
• CPC Class Codes: B60R 21/264 using instantaneous generation of gas, e.g. pyrotechnic B60R21/268 takes precedence
• 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
• CPC Class Codes: B60R 22/1954 characterised by fluid actuators, e.g. pyrotechnic gas generators actuating a cable B60R22/1952

Abstract

The invention relates to a hybrid inflator (10) includes at least one combustion chamber (15) in which propellant charge is arranged and which has a discharge end (20), the propellant charge being formed of at least one propellant element (26), at least one igniting unit (12) by which the propellant charge can be ignited. The hybrid inflator (10) also includes at least one bursting element (14, 14′, 14″) which in the inactivated state of the hybrid inflator (10) delimits the combustion chamber (15) against a gas supply chamber (16) at the discharge end (20). The bursting element (14, 14′, 14″) and a restraint element (18, 18′, 18″) maintain the propellant charge in its position and/or the bursting element (14, 14′, 14″) and the propellant charge delimit a shock gas volume (SGV), wherein in the activated state of the hybrid inflator (10) the shock gas volume (SGV) acts on the bursting element (14, 14′, 14″) like a gas pressure spring.

Claims

1. A hybrid inflator (10) comprising:

an outer housing (11) having a first axial end and a second axial end;

an igniting unit (12) by which a propellant charge, which is formed of at least one propellant element (26), can be ignited, the igniting unit (12) being formed on the first axial end of the outer housing (11); and

a bursting element (14, 14′

, 14″

) being attached to the outer housing (11), the bursting element (14, 14′

, 14″

), in an inactivated state of the hybrid inflator (10), dividing the outer housing (11) into a combustion chamber (15) having the propellant charge arranged therein and a gas supply chamber (16) being filled with a gas, the bursting element (14) having an opening area (36);

wherein

the combustion chamber (15) extends in a direction of a longitudinal inflator axis (L) from the first axial end of the outer housing (11) to the opening area (36) of the bursting element (14, 14′

, 14″

), the extension of the combustion chamber (15) defining a total empty volume of the combustion chamber (BKV); and

the bursting element (14, 14′

, 14″

) and at least one of the propellant charge and a restraint element (18, 18′

, 18″

), which maintains the propellant charge in its position, delimit a shock gas volume (SGV) which, in the inactivated state of the hybrid inflator (10), is formed spatially ahead of the bursting element (18, 18′

, 18″

) and, in an activated state of the hybrid inflator (10), acts on the bursting element (14, 14′

, 14″

) to open the opening area (36), an area in which the shock gas volume (SGV) is formed being substantially free from any propellant charge, a ratio of the shock gas volume (SGV) to the total empty volume of the combustion chamber (BKV) being at least 0.35.

2. The hybrid inflator (10) according to claim 1, wherein between the opening area (36) and the igniting unit (12) the propellant charge is arranged so that the shock gas volume (SGV) is configured free from propellant charge and has an axial length, which is parallel to the longitudinal inflator axis (L), that ranges from 9 mm to at least 40 mm.

3. The hybrid inflator (10) according to claim 1, wherein the ratio of the shock gas volume (SGV) to the total empty volume of the combustion chamber (BKV) is at least 0.45.

4. The hybrid inflator (10) according to claim 1, wherein the restraint element (18, 18′

, 18″

) is a combustion chamber screen (18′

) having a peripheral wall (35) arranged in the combustion chamber (15) and a universal ball joint-shaped portion (34) connected to an igniting unit facing end of the peripheral wall (35), the peripheral wall (35) having one of a hollow-cylindrical portion, a hollow truncated portion, and a hollow truncated pyramid portion.

5. The hybrid inflator according to claim 4, wherein the peripheral wall (35) has a longitudinal extension (L1) and the universal ball joint-shaped portion (34) has a longitudinal extension (L2), the longitudinal extension (L1) of the peripheral wall (35) being 1.2-2.5 times longer than the longitudinal extension (L2) of the universal ball joint-shaped portion (34).

6. The hybrid inflator according to claim 4, wherein the bursting element (14, 14′

, 14″

) is a bursting disk (14″

) that is attached to the outer housing (11) in a pressure-tight manner so that gas from the gas supply chamber (16) is unable to pass into the combustion chamber (15) through the bursting disk (14″

) and that the propellant charge in the combustion chamber (15) is under atmospheric pressure, the bursting disk (14″

) and the combustion chamber screen (18′

) delimiting the shock gas volume (SGV).

7. The hybrid inflator (10) according to claim 1, wherein the restraint element (18, 18′

, 18″

) is a spring (18″

) that has a first end (25) arranged in the bursting element (14, 14′

, 14″

), the spring (18″

) projecting from the bursting element (14, 14′

, 14″

) and toward the igniting unit (12) so that a second end of the spring (18″

) is spaced from the bursting element (14, 14′

, 14″

), an interior of the spring (18″

) forming a passage that delimits the shock gas volume (SGV) together with the bursting element (14, 14′

, 14″

).

8. The hybrid inflator (10) according to claim 1, wherein the at least one propellant element (26) is in the form of a plurality of propellant rings (26), each of the propellant rings (26) having a central through passage, the propellant rings (26) being arranged in parallel in the combustion chamber (15) so that an alignment of the central through passages forms a passage (27) that together with the bursting element (14, 14′

, 14″

) delimits the shock gas volume (SGV).

9. The hybrid inflator (10) according to claim 8, wherein the propellant rings (26) are designed and arranged so that for an entirety of plural propellant rings (26) a rib-shaped structure, viewed in an axial cross-section, having U-shaped or V-shaped clearances (37) is formed, a thickness of the propellant rings (26) being reduced from an outer periphery thereof toward a center thereof so that the propellant rings (26) can be ignited by the igniting unit (12) so that hot igniting gases and/or igniting particles can be supplied to the clearances (37).

10. The hybrid inflator (10) according to claim 8, wherein between the igniting unit (12) and a first propellant ring (28) of the propellant rings (26) in a gas flow direction (G) of the combustion chamber (15), an annular filling material (29) is arranged, and between the bursting element (14, 14′

, 14″

) and a last propellant ring (30) of the propellant rings (26) in the gas flow direction (G) of the combustion chamber (15), an annular spacer (31) is arranged, the annular spacer (31) having a passage (32) that together with the bursting element (14, 14′

, 14″

) and the passage (27) formed through the plurality of propellant rings (26) delimits the shock gas volume (SGV).

11. The hybrid inflator (10) according to claim 1, wherein a ratio of the shock gas volume (SGV) to an area (n*(rGVK)²) defined by a radius (rGVK) of an inner diameter of the gas supply chamber (16) is larger than 1 cm.

12. A vehicle safety system comprising a hybrid inflator (10) according to claim 1, an airbag unit and/or a crash sensor.

13. A method of forming a shock wave inside a hybrid inflator (10) according to claim 1, the method comprising the following steps of:

activating the igniting unit (12),

opening the opening area (36) of the bursting element (14, 14′

, 14″

) by pressing the shock gas volume (SGV) formed ahead of the bursting element (14, 14′

, 14″

) against the bursting element (14, 14′

, 14″

), and

generating a shock wave in the gas supply chamber (16) downstream of the bursting element (14, 14′

, 14″

).

14. The method according to claim 13, wherein at least one of the following further steps of:

guiding gas generated in the combustion chamber (15) in the direction of the bursting element (14, 14′

, 14″

),

guiding the shock gas volume (SGV) into the gas supply chamber (16),

igniting the propellant charge present in the combustion chamber (15), while the gas is guided in the direction of the bursting element (14, 14′

, 14″

),

supplying hot igniting gases and/or igniting particles to clearances (37) formed between propellant rings (26).

15. The hybrid inflator according to claim 1, wherein the outer housing (11) has a constriction (17) formed between the combustion chamber (15) and the gas supply chamber (16), the bursting element (14, 14′

, 14″

), which is in the form of a bursting sleeve (14′

), being inserted in the constriction (17), the busting sleeve (14′

) having a flat lid (23) with the opening area (36), a cylindrical peripheral wall (21) that is at least partially adjacent to an inner surface of the constriction (17), and a fastening portion (24) that is positioned in the combustion chamber (15) and abuts an inner wall of the outer housing (11), at least a portion of the peripheral wall (21) protruding in the direction of the longitudinal inflator axis (L) from the constricting (17) into the gas supply chamber (16) so that the flat lid (23) is positioned in the gas supply chamber (16).

16. The hybrid inflator (10) according to claim 15, wherein the restraint element (18, 18′

, 18″

) is a combustion chamber screen (18′

) having a peripheral wall (35) arranged in the combustion chamber (15) and a universal ball joint-shaped portion (34) connected to an igniting unit facing end of the peripheral wall (35), a gas supply chamber facing end of the peripheral wall (35) being connected to an igniting unit facing end of the bursting sleeve (14′

) so that the combustion chamber screen (18′

) projects in the direction of the longitudinal inflator axis (L) from the igniting unit facing end of the bursting sleeve (14′

) toward the igniting unit (12), the bursting sleeve (14′

) and the combustion chamber screen (18′

) delimiting the shock gas volume (SGV).

17. The hybrid inflator (10) according to claim 1, wherein the bursting element (14, 14′

) allows a fluid communication between the gas supply chamber (16) and the combustion chamber (15) so that gas from the gas supply chamber (16) is capable of flowing into the combustion chamber (15).

18. The hybrid inflator (10) according to claim 1, wherein when the igniting unit (12) is activated, the propellant charge is ignited and burnt to increase gas pressure in the combustion chamber (15), the gas pressure formed by the burnt propellant charge presses on the shock gas volume (SGV) to cause the shock gas volume (SGV) to act on the bursting element (14, 14′

, 14″

) to abruptly open the opening area (36), the abrupt opening of the opening area (36) generates a shock wave which enters and moves through the gas supply chamber (16) in the direction of the longitudinal inflator axis (L).

19. The hybrid inflator (10) according to claim 1, wherein the gas supply chamber (16) extends in the direction of the longitudinal inflator axis (L) from the combustion chamber (15) to the second axial end of the outer housing (11).

20. The hybrid inflator (10) according to claim 1, wherein the combustion chamber (15) is connected to the igniting unit (12) in the outer housing (11), and wherein the total empty volume of the combustion chamber (BKV) is a volume of the combustion chamber that extends from the first axial end of the outer housing (11) to the opening area (36) of the bursting element (14, 14′

, 14″

) without the igniting unit (12), any propellant charge, and any combustion chamber fittings.