The present invention relates generally to pyrotechnic gas generators for inflatable restraint devices, and more particularly to such a gas generating system having a low pressure, low temperature liquefied gas hybrid inflator.
Inflatable restraint systems or “airbag” systems have become a standard feature in many new vehicles. These systems have made significant contributions to automobile safety, however, as with the addition of any standard feature, they increase the cost, manufacturing complexity and weight of most vehicles. Technological advances addressing these concerns are therefore welcomed by the industry. In particular, the quality of the gaseous effluent from the gas generators has led to the investigation of the use of non-cryogenic gases, such as di-nitrogen monoxide (nitrous oxide or NO2) and carbon dioxide. In turn, the use of these gases sometimes implicates the issues of low temperature performance and low gas pressure output. Accordingly, improving the output by heating and pressurizing the gas or gas source while maintaining a low gas exit flow area for sustained gas release would be an improvement in the art, thereby increasing the utility of these non-cryogenic gases.
In accordance with the foregoing and other objects of the invention, a low pressure, low temperature liquefied gas hybrid inflator for an occupant restraint system is provided. The inflator includes a pyrotechnic section and a cold gas section that are separated by a burst shim rupturable upon activation of the pyrotechnic charge within the inflator. A perforated flexible member or compensation device is fixed about the interface of the cold gas and pyrotechnic sections to modulate the flow of gases into and out of each section, primarily the cold gas section. As the pyrotechnic section is activated, the hot gases pour through the orifice created by the burst shim and into the cold gas/stored gas portion of the gas generator to heat the cold stored two-phase “gases” (e.g. gas and liquid). A flexible member or compensation device is biased from a concave to a convex orientation, relative to the orifice, thereby permitting a relatively greater amount of hot gases into the cold gas section immediately after actuation of the pyrotechnic section.
The hot gases are controllably introduced into the cold gas section to increase the pressure and heat within the cold gas section of the inflator. As the pressure differential is reversed between the pyrotechnic and cold gas sections over time, the flexible member again resumes a concave orientation about the orifice, and the now-hot gases within the cold gas section are then shunted back through an orifice on the flexible member and into the pyrotechnic section. The gases then routed through gas exit burst shims and associated gas exit orifices within the pyrotechnic section, and then out of the hybrid inflator.
In sum, an inflator of the present invention contains: a housing, a cold gas chamber within the housing for storage of a stored gas supply, a pyrotechnic chamber within the housing, a pyrotechnic charge within the pyrotechnic chamber, a wall adjoining the cold gas and the pyrotechnic chambers, a gas orifice defined in the wall for passage of gas between the chambers, and a perforated flexible member contained within the cold gas chamber, wherein the flexible member is fixed about the orifice for modulation or controlled variation of gas flow through the orifice.
An inflator 10 of the present invention includes a perforated housing 12 containing gas exit orifices 14. A first chamber 16 within the housing 12 contains a stored gas supply, such as a compressed two-phase liquid/gas supply. A second chamber 18 contains a known pyrotechnic gas generant or charge 20 for producing gases upon actuation of the inflator 10. The gas generant charge 20 may be formed for example as exemplified in U.S. Pat. No. 5,035,757, herein incorporated by reference in its entirety. A wall 22 adjoins both the first and second chambers 16, 18 and is formed there between. A first orifice 24 is formed or defined in the wall 22 for passage of gases between the chambers as described herein.
In accordance with the present invention, a flexible disc or membrane 28 such as a Bellville washer or a bimetallic disc is fixed in close proximity to a first burst shim 26 and associated first orifice 24. The disc 28 may be spot-welded or otherwise fixed to the wall 22 thereby permitting hot gas flow there through upon pyrotechnic actuation without attenuating the flexible nature of the flexible member/disc 28. It should be appreciated that the flexible member, flexible disc, or flexible compensation device 28 maintains a concave seal and orientation above and relative to the burst shim 26 and orifice 24 prior to pyrotechnic actuation. Upon pyrotechnic actuation, the burst shim 26 ruptures thereby permitting hot gases to enter the first chamber 16 from the second chamber 18, and by virtue of the flexibility of the compensation device or Bellville washer 28, the outer periphery of the compensation device 28 is biased to present a convex orientation of the flexible disc/Bellville washer 28. This permits rapid heating of the stored gas by the hot gases pouring past the raised periphery 30 of the compensation device/flexible disc 28.
As the pressure differential existing between the pyrotechnic section 18 and the stored gas section 16 equalizes over time by virtue of hot gases passing into the stored gas section 16, and as the pressure presented by the hot gases entering into the stored liquid/gas chamber 16 is reduced, the resilient spring properties of the Bellville washer/flexible disc/compensation device again presents a concave orientation to the burst shim orifice thereby sealing the gas passage previously provided about the periphery 30 of the compensation device 28. At this point, a control orifice 32 provided in the Bellville washer/flexible disc/compensation device now provides a controlled flow of a mixture of hot pyrotechnic gas and stored gas from the stored gas section 16 through the control orifice 32, then through the first orifice 24, back into the pyrotechnic section 18, and out associated gas exit orifices 14 provided in the perforated housing 12. It should be appreciated that gas exit burst shims 34 provided adjacent the gas exit orifices 14 in a known manner are now rupturable based on the increased amount of gas pressure resulting from the additive pressure of the stored and pyrotechnic combined gases. It should further be appreciated that the first burst shim 26 initially covering the first orifice 24 providing fluid communication between the pyrotechnic and stored gas chambers 16, 18 of the inflator 10 is designed to rupture at a lower pressure than that of the burst shims 34 of the gas exit orifices 14 thereby ensuring sequential operation and mixing of gases as described above, prior to the gas exiting through the gas exit orifices 14 of the inflator 10.
It should be appreciated that the inflator 10 is structured in a known manner as will be appreciated by those of ordinary skill. For example, U.S. Pat. No. 7,131,663, US2006/0255577, US2006/0201572, and US2006/0249938, herein incorporated by reference, exemplify, but do not limit proposed construction of various constituents of the present inflator 10 as known in the art. Nevertheless, the present improvement involving the utilization of the compensation device 28 lies in the ability to introduce hot gases to the stored gas supply, such as a two-phase gas supply, in a controlled manner, thereby controllably increasing the pressure within the hybrid inflator 10. Furthermore, the improvement further lies in the ability to control the gas exit due to attenuating the gas pressure through the compensation device 28 as it exits the inflator 10 through the pyrotechnic section 18. The operation of the present hybrid inflator is illustrated in
As shown in
As shown in
As shown in
Referring now to
Referring again to
Safety belt assembly 150 may also include (or be in communication with) a crash event sensor 158 (for example, an inertia sensor or an accelerometer) including a known crash sensor algorithm that signals actuation of belt pretensioner 156 via, for example, activation of a pyrotechnic igniter (not shown) incorporated into the pretensioner. U.S. Pat. Nos. 6,505,790 and 6,419,177, previously incorporated herein by reference, provide illustrative examples of pretensioners actuated in such a manner.
It should be appreciated that safety belt assembly 150, airbag system 200, and more broadly, vehicle occupant protection system 180 exemplify but do not limit gas generating systems contemplated in accordance with the present invention.
It should further be understood that the preceding is merely a detailed description of various embodiments of this invention and that numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the scope of the invention. The preceding description, therefore, is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined only by the appended claims and their equivalents.
The present application claims the benefit of U.S. Provisional Application Ser. No. 60/878,035 having a filing date of Dec. 29, 2006.
Number | Name | Date | Kind |
---|---|---|---|
4751940 | Bergsma et al. | Jun 1988 | A |
5002050 | McGinnis | Mar 1991 | A |
5067449 | Bonde | Nov 1991 | A |
5738371 | Blackshire et al. | Apr 1998 | A |
5820160 | Johnson et al. | Oct 1998 | A |
5820162 | Fink | Oct 1998 | A |
5882036 | Moore et al. | Mar 1999 | A |
6012737 | Van Wynsberghe et al. | Jan 2000 | A |
6145876 | Hamilton | Nov 2000 | A |
6170868 | Butt et al. | Jan 2001 | B1 |
7131663 | Campbell et al. | Nov 2006 | B1 |
20030111831 | Horton et al. | Jun 2003 | A1 |
20050062272 | Smith et al. | Mar 2005 | A1 |
20060201572 | Matsuda et al. | Sep 2006 | A1 |
20060255577 | Nakayasu et al. | Nov 2006 | A1 |
20070085309 | Kelley et al. | Apr 2007 | A1 |
Number | Date | Country | |
---|---|---|---|
20080156223 A1 | Jul 2008 | US |
Number | Date | Country | |
---|---|---|---|
60878035 | Dec 2006 | US |