Metal Stamping Toroidal Hybrid Gas Generator
A hybrid inflator comprises a housing formed of welded-together metal stamping defining
a toroidal gas chamber surrounding a center tie and storing pressurized gas therein. The center tie has a generally cylindrical sidewall and an outlet wall at an upper end thereof defines a rupturably sealed outlet orifice.
An inverted stamped metal cup is matingly received in the center tie. The lip of the cup is welded to the lower end of the center tie, and the cup sidewall is circumferentially grooved for separating a sliding piston portion under pressure.
A squib support wall and squib closes the lower end of the center tie and inverted cup to define a combustion chamber containing a pyrotechnic gas generant which, upon ignition, causes the inverted cup to separate at the groove and drive the sliding piston upwardly to an open position uncovering inlet openings from the combustion chamber to the gas storage chamber. Hot gasses from the combustion chamber flow into the gas storage chamber and the outlet orifice rupturably opens permitting stored gas and combustion products to exit the inflator. The sliding piston and center tie are tapered to control movement of the piston by friction and deformation, together with lanced limit stop tabs. The cup has a convex bottom, deformation portions and may carry a lance to open the orifice. A baffle provides a surface on which incomplete products of combustion are collected and captures debris. A deformable outlet diffuser provides compact packaging.
Hybrid inflators for vehicle occupant restraint systems utilize a combination of stored inert gas and the products of combustion of pyrotechnic material to deploy an airbag. The inert gas is stored in a chamber at a relatively high pressure on the order of 2,000 to 4,000 pounds per square inch. The pressure chamber is adjacent to a combustion chamber that contains an initiator and a pyrotechnic material for producing hot combustion gasses which are delivered to the stored inert gas. The mixture of the hot combustion gasses and stored inert gasses are delivered through an outlet to inflate the airbag of the occupant restraint system.
Hybrid inflators are particularly useful in that no Azide is required in the inflation system, and that complex filters are not required to cool and clean the gasses.
The housings of hybrid inflators are generally fabricated of machined and/or forged metal parts and numerous configurations are provided in the art for delivering the hot combustion gasses of the pyrotechnic material to the gas storage chamber, and for opening an outlet passage of the housing for inflating the airbag.
Because the inflators in the foregoing patents, and particularly the ones which are toroidal in configuration, comprise machined and/or forged parts, they are accordingly complex in the number of parts and assembly, and high in cost. Given the widespread use of inflators, there is a corresponding need to reduce the complexity and cost thereof, as well as the size and weight without sacrificing efficient operation and reliability.
In accomplishing these and other objects of the invention herein, there is provided a hybrid inflator having a generally toroidal housing formed of welded-together metal stamped parts, the housing defining a stored gas chamber surrounding a center tie, and the gas chamber storing a pressurized inert gas. The center tie has a generally cylindrical sidewall and an outlet wall at the upper end thereof, the outlet wall defining a rupturably sealed outlet orifice. An igniter assembly including a pyrotechnic gas generant and squib initiator are mounted in the center tie with appropriate passages for delivering hot gasses to the stored gas and a mix of hot and stored gas to the airbag. According to one aspect of the invention, the igniter assembly includes an inverted stamped metal cup having a generally cylindrical sidewall matingly received in the generally cylindrical sidewall of the center tie. The metal cup has an end wall extending across the center tie to define, together with an upper portion of the center tie sidewall and the outlet wall, an outlet cavity adjacent the outlet orifice. The inverted cup also has a lip adjacent its open end secured to the lower end of the center tie, and the sidewall of the inverted cup adjacent the lip has a circumferential groove to provide for separation of the cup from the lip. A squib support wall closes the lower end of the center tie and inverted cup to define a combustion chamber cavity within the inverted cup. The pyrotechnic gas generant material is provided within the combustion chamber and the squib support wall mounts a squib for igniting it.
Upon ignition of the pyrotechnic gas generant material, the expanding combustion products including hot gasses cause the inverted cup to separate at the circumferential groove and drive the separated inverted cup upwardly in the center tie to an open position. The center tie defines at least one inlet opening from the combustion chamber to the gas chamber, and this inlet opening is positioned to be exposed for a flow of combustion products into the stored gas chamber when the inverted cup is driven to its open position. The combustion products including hot gas flow into the gas chamber to heat and thereby increase the pressure of the stored gas therein. The center tie also defines at least one outlet opening from the gas chamber to the outlet cavity, which opening remains unblocked by the inverted cup in its open position and thereby provide a flow path to the outlet orifice. The sealed outlet orifice rupturably opens after ignition of the pyrotechnic gas generant material, permitting stored gas and hot combustion gasses to exit the inflator through the outlet opening in the center tie wall, the outlet cavity and the outlet orifice.
According to one aspect of the invention, the outlet orifice is sealed by a diaphragm which ruptures upon increased pressure within the housing. According to another aspect of the invention, the rupturably sealed outlet orifice is opened by a lance extending from the inverted cup and driven through the orifice by the upward sliding motion of the inverted cup.
According to further aspects of the invention, the generally cylindrical center tie wall and the inverted cup have surfaces which taper inwardly in the direction of cup movement, wherein friction and deformation of the inverted cup occur as it slides upwardly limit the speed and extent of its upward travel. Additionally, the center tie wall in the outlet cavity above the inverted cup has inwardly lanced tabs which provide a mechanical limit stop for the inverted cup.
Another particular aspect of the invention is in providing a diffuser over the outlet orifice, and advantageously the diffuser is formed of a metal stamping part fitted snugly against the outlet orifice and deformable away from the outlet orifice by the inflation gasses exiting the inflator housing. The deformable diffuser provides a more compact inflator prior to operation, and also absorbs some of the energy from the initial surge of gas to provide a controlled initial inflation of the airbag.
by: Lucy
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