Adjustable performance hybrid inflator

Abstract: A hybrid inflator (170) includes a pressure bottle (174) containing compressed gas, combustible propellant (186) for augmenting the stored gas and defining an outlet for delivering inflation gas from the inflator (170) to a primary airbag cushion (14). The hybrid inflator (170) further includes a vent opening (110) defined as a second outlet from the pressure bottle (174) for releasing stored compressed gas therefrom and a rupturable diaphragm (120) positioned to prevent flow from the vent opening (110). A controller (20) provides a signal for operating a squib (238) for opening the primary outlet means and igniting the combustible propellant (186), and another signal for operating a squib (134) rupturing the diaphragm (120) covering the vent opening (110). The vent opening may be opened first to vent gas from the pressure bottle (174) in advance of opening the primary outlet (230), may be opened with or after the primary outlet, or not at all. The vented gas is variously used for a soft onset of inflation of the primary airbag cushion (14), for inflation of a supplemental airbag cushion including a knee bolster, or the gas is dispersed.

Description: FIELD OF THE INVENTION The invention herein relates to a hybrid inflator for a vehicle occupant restraint system, and more particularly to a hybrid inflator with performance adjustable by provision of a secondary gas outlet. The invention further relates to a hybrid inflator wherein a portion of the inflator flow is optionally delivered to a supplemental airbag cushion. BACKGROUND OF THE INVENTION Modern cars are equipped with air cushion restraint systems which deploy to protect occupants in the event of a vehicle crash. A driver's side restraint system includes an airbag which deploys from the steering wheel hub, and the passenger's side restraint system includes a larger airbag which deploys from the dashboard of the vehicle. Both the driver's side and passenger's side airbag cushion restraint systems often include hybrid inflators for providing inflation gasses to the airbag. The hybrid inflators include a compressed gas and a combustible material which provides heat and additional inflation gas augmenting the volume and pressure of the stored compressed gas. The performance of the airbag occupant restraint systems, and particularly the larger size passenger's side airbag, is preferably optimized as a function of variables associated with each particular crash. These variables include the severity of the crash and also include the size and position of the passenger as well as temperature conditions that may affect the performance of the inflator. For instance, the least aggressive deployment of the airbag is appropriate for a low speed crash with an out-of-position, small occupant, wherein the most aggressive deployment of the airbag may be appropriate for a head on high-speed crash with an adult passenger. The inflation of the bag is, of course, in large part controlled by the operation of the inflator. Previous efforts at adjusting the performance of a hybrid inflator have centered about operating the hybrid inflator in stages through its primary gas delivery outlet. For instance, in some instances a variable time delay between release of the compressed gas and ignition of the combustible material for augmenting the pressurized gas has been provided. In other instances, the combustible material has been provided in multiple or staged combustible units, with means for controlling the number of stages operated in a particular crash. An airbag restraint system has also been provided with a diffuser which vents a portion of the gas away from the airbag, after the gas has been released through the vent outlet. Modern vehicles are increasingly being equipped with supplemental airbag systems, such as knee bolsters and side impact airbags. Discreet inflators are usually provided for each of these systems. These supplemental restraint systems are generally inflated before the large passenger side airbag, in that the distance between the occupant's knees and the knee bolster or the distance between the occupant's shoulders and the side of the vehicle are small, necessitating a fast response. It would be advantageous if a single inflator could be adapted to provide inflation for the primary airbag cushion and to one or more supplemental airbag cushions as well. The German patent application DE 40 41 0491 A 1 (corresponding to the preamble of claim 1) teaches an inflator with two valves. The first valve is used for transfering gas to an airbag for expanding this airbag. The second valve, however, is used for venting the inflator. The valve for venting is designed such that one can control between a closed and an open state. SUMMARY OF THE INVENTION Accordingly, it is a principal object of the invention herein to improve a hybrid inflator with adjustable performance with regard to a reduction of overall cost and complexity. It is also an object of the invention herein to adapt an inflator for inflating a primary airbag and a supplemental airbag. In accomplishing these objects of the invention herein, there is provided a hybrid inflator comprising the features of claim 1. The performance of the inflator in providing inflator gas to the primary airbag is adjusted by venting compressed gas from pressure bottle. According to the invention, the vent opening permits gas to disperse, directs gas to the primary airbag prior to primary operation of the inflator, or is connected to a supplemental airbag cushion. The supplemental airbag is a knee bolster or side impact airbag. According to further embodiments of the invention herein, a vehicle occupant restraint system includes a crash sensor and means for producing first and second control signals as a function of crash parameters. A pressure bottle stores compressed gas and combustible means are mounted to the pressure bottle, upon ignition thereof in response to one of the control signals, ignites to augment inflation gas provided to the primary airbag cushion. The pressure bottle defines a primary outlet opening for delivering inflation gas to a primary airbag cushion and means for opening the primary outlet and igniting the combustible material in response to the first control signal. The pressure bottle further defines a vent outlet covered by a rupturable diaphragm to maintain the compressed gas within the pressure bottle, and means for rupturing the diaphragm in response to the other control signal. According to other embodiments of the invention, the vent opening is sealed by a burst disk which is opened by a squib. Additionally, the vent opening is defined by an outlet plate offset from the burst disk, and the vent opening is positioned transverse to and spaced from the flow of gas and products of combustion in the pressure bottle. According to still further embodiments of the invention, the vent outlet opening defined by the pressure bottle is vented from the airbag restraint system, is supplied to the primary airbag before opening of the primary outlet, or is connected to a supplemental airbag. The supplemental airbag is a knee bolster or side impact airbag. For a fuller understanding of the invention, its operating advantages and the specific objects attained by its use, reference is made to the accompanying drawings and descriptive matter in which the preferred embodiments are illustrated. DRAWINGS FIG. 1 is a longitudinal sectional view of an inflator according to the invention herein, included in a schematically illustrated airbag restraint system; and FIG. 2 is an enlarged fragmentary schematic view of another airbag restraint system according to the invention herein. The same reference numerals refer to the same elements throughout the various drawings. DESCRIPTION OF PREFERRED EMBODIMENTS With reference to FIG. 1 , an airbag restraint system 10 according to the invention herein includes an adjustable performance hybrid inflator 170 mounted in a reaction canister 12 for inflating a primary airbag 14. The adjustable performance hybrid inflator 170 is characterized by a vent assembly 110 which provides the feature of adjustable performance. A controller 20 operates the adjustable performance hybrid inflator 170, including the vent assembly 110, based upon input from one or more senscrs 22, 24, 26 and 28. The hybrid inflator 170 generally includes a pressure bottle 174 which contains compressed gas. The compressed gas is preferably argon and is maintained at a pressure ranging from 2,100 psi to 3,900 psi, in part depending upon the ambient temperature. The stored gas is retained within the pressure bottle 174 by a closure disk 222. More particularly, the closure disk 222 is positioned within a disk housing 214 which is attached to the discharge end 176 of the pressure bottle 174. A plurality of disk housing outlets 218 are defined through the disk housing 214 to allow the gas within the pressure bottle 174 to communicate with the interior of the disk housing 214 and thus exert a force on the closure disk 222 prior to operation of the inflator 170. The hybrid inflator 170 further comprises a gas generator 178 having a propellant 186 contained therein. The gas generator 178 is connected to the disk housing 214 and extends into the elongated pressure bottle 174. The gas generator 178 further includes an ignition assembly 190 positioned adjacent to the disk housing 214, and a propellant chamber 182 which contains the propellant 186 adjacent the ignition assembly 190. The ignition assembly 190 includes an activation plate 194 and a charge holder 200 in which an ignition charge 206 is contained. Primers 202 are positioned between impact members 198 extending from the top surface 196 of the activation plate 194 and the charge holder 200. A perforated retainer 242 is provided between the ignition assembly 190 and the gas generant 186. A propellant strainer 246 is positioned at the other end of the propellant chamber 182, and an outlet 210 is defined in the end of the propellant chamber. The inflator 170 further comprises a diffuser cap 226 which mounts a squib 238 and a projectile 234 in a sleeve 250 expending from the squib 238 toward the burst disk 222 end activation plate 194. The sleeve 250 is crimped at 254 and the projectile 234 is notched at 258 , to retain the projectile prior to firing the squib 238. The diffuser cap 226 defines a plurality of outlet openings 230 comprising the primary outlet of the inflator 170. Inflation gas exiting the outlets 230 is directed by the reaction canister 12 to inflate the primary airbag 14, as is well known in the art. When the squib 238 is fired, the projectile 234 is propelled through the burst disk 222, permitting a flow of compressed gas from the inflator 170. The projectile 234 strikes the top surface 196 of activation plate 194, operating primers 222 and the ignition charge 206 to ignite the propellant 186. The gasses generated by the combustion of the propellant 186 flow through the gas generator outlet 210 toward the end of the pressure bottle 174 and augment the inflation gas delivered from the pressure bottle. The inflator 170 is characterized by a vent assembly 110 which provides for adjustable performance of the inflator. The vent assembly 110 comprises a tubular sleeve 112 extending through opening 172 in the pressure bottle 174. Flange 114 extends outwardly from one end of sleeve 112, the flange 114 being shaped to conform to the interior of the pressure bottle 174 surrounding an opening 172 defined therein extending through the opening 172. The flange 114 mounts a rupturable diaphragm 120 extending across the sleeve 112 to seal the pressure bottle 174. The periphery of the diaphragm 120 is sealingly secured to the flange 114 and sleeve 112 is sealingly secured in opening 172 . A vent plate 130 is also secured to the flange 114 and extends across the end of the sleeve 112. The vent plate 130 defines a vent opening 132 sized to control release of gas from the pressure bottle 174 upon rupture of the diaphragm 120. The vent opening 132 is position spaced from and transverse to the output of gas generator 178, to minimize venting hot particles of combustion. A filter may be placed over the vent opening for that purpose, as well. The vent assembly 110 further includes a squib 134 mounted in an end wall 116 of the sleeve 112. The squib 134 has explosive material contained within a cover 136 positioned closely adjacent the diaphragm 120 for rupturing the diaphragm. The end wall 116 includes a plurality of openings 118 for exhausting gas released from the pressure bottle 174 through the vent opening 132. In the embodiment shown, the released gas is dispersed outside the reaction canister 12; however, it is also contemplated that the gas may be received in the reaction canister 12 for providing an early, soft onset of airbag deployment when squib 134 operates first. The squib 238 and the squib 134 are operated by electrical control signals delivered over lines 140 and 142, respectively, from the controller 20. The controller 20 operates the squibs 238 and 134 to adjust the performance of the hybrid inflator 170. To that end, the controller 20 is provided with a plurality of input signals reflecting parameters existing at the time of operation of the inflator. These input signals include a signal from crash sensor 22 indicating a crash condition. Occupant sensors 24 provide information concerning the occupant of the vehicle, to be protected by the airbag restraint system 10 , including such information as whether an occupant is present, and may also include the weight and position of the occupant, the latter information derived from plurality of sensors in the seats and seat belt assemblies. A temperature sensor 26 monitors the ambient temperature, which is related to the actual pressure of the gas in the pressure bottle 174. The control sensors 28 detect a variety of other useful parameters, such as the speed of the vehicle, the severity of the crash as measured by deceleration of the vehicle, the direction of the crash, and any other desired information. The controller 20 is programmed to operate the adjustable performance inflator 170 in the optimal manner, based on the input signals and its programming. For instance, if the ambient temperature is high, whereby the pressure of the gas in pressure bottle 174 is correspondingly high, squib 134 may be operated to vent excess pressure from the pressure bottle 174. Similarly, if the crash is at low speed, if the occupants are of light weight or if other parameters so indicate, the controller can operate the squib 134 to vent gas from the pressure bottle 174 rather than through the primary outlet into the airbag 14. It will be appreciated that the mass of gas in bottle 174 at the time the propellant 186 is burned has an effect on the performance of the propellant, providing additional opportunity for control of performance of the inflator. The controller can operate squib 134 in advance of, simultaneously with, or after operation of squib 238, as desired for the particular parameters of the crash. In some instances, the vent may not be opened at all. With reference to FIG. 2, another airbag restraint system 150 according to the invention is shown in a schematic, fragmentary view. The airbag restraint system 150 is similar to the airbag restraint system 10 described above, i.e., it includes an adjustable performance hybrid inflator 170 mounted in a reaction can 12 for inflating a primary airbag. The inflator 170 is characterized by the vent assembly (means for rupturing the diaphragm) 110 in pressure bottle 174, and a controller operates the squib 134 of the vent assembly 110 to deliver inflation gasses through the vent opening 132 via a signal provided on line 142. The controller, of course, also operates the other squib of the hybrid inflator 170, for delivering inflation gas to the primary airbag. The airbag restraint system 150 is further characterized in that the gas exiting the inflator 170 through the vent assembly 110 is delivered via conduit 154 to inflate a supplemental airbag 160. The supplemental airbag 160 may be a knee bolster, a side impact airbag, or the like. The controller operates the squibs to optimize performance of the inflator in deploying both the primary and supplemental airbags, the parameters depending on the particular installation, the particular type of supplemental airbag, and the various parameters associated with a particular crash condition. It will be appreciated that the inflator 170 is provided with sufficient capacity to inflate the primary and supplemental airbags, and that the overall cost and complexity of inflating more than one airbag is reduced through the use of a single inflator. Accordingly, preferred embodiments of airbag restraint systems and an adjustable performance hybrid inflator have been described which admirably achieve the objects of the invention herein. With reference to the description of the preferred embodiments, those skilled in the art will appreciate that it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described. Rather it is intended that the scope of the invention be determined by the appended claims thereof.

Claims: A hybrid inflator (170) of the type having a pressure bottle (174) containing compressed gas, combustible means (186) for augmenting the stored gas and outlet means (230) for delivering inflation gas from the inflator (170) to a primary airbag cushion (14), the inflator (170) comprising a vent opening (132) defined as a second outlet from the pressure bottle (174) for releasing stored compressed gas therefrom, characterised in that a rupturable diaphragm (120) is positioned to seal said vent opening (132) and prevent premature flow through said vent opening (132), and a means (110) for rupturing said diaphragm (120) is provided in order to deliver stored gas from pressure bottle (174) through the vent opening (132) in response to a control signal, whereby said means (110) for rupturing the diaphragm (120) exhibits a squib (134), said squib (134) having explosive material contained within a cover (136) positioned closely adjacent the diaphragm (120) for rupturing the diaphragm (120). An improved hybrid inflator as defined in Claim I wherein the pressure bottle (174) is elongated and the vent opening (132) is formed in the sidewall of the pressure bottle (174). A hybrid inflator (170) as defined in Claim 2 and further comprising a gas generator (178) incorporating the combustible means (186) for augmenting the stored gas, the gas generator (178) being contained within the pressure bottle (174) and having an outlet (210) directing the products of combustion toward the end of the pressure bottle. A hybrid inflator as defined in Claim I wherein the squib (134) is outside the pressure bottle (174). A hybrid inflator (170) as defined in Claim 1 and further comprising a vent plate (130) extending across the rupturable diaphragm (120), the vent plate (130) defining the vent opening (132), the vent plate (130) extending across a larger pressure bottle opening defined in the pressure bottle (174) sealed by the rupturable diaphragm (120). A hybrid inflator (170) as defined in Claim 5 wherein the rupturable diaphragm (120) and vent plate (130) are mounted to a sleeve (112) extending through the pressure bottle opening and the pressure bottle opening is defined in the sidewall of the pressure bottle. A hybrid inflator (170) as defined in Claim 6 wherein the sleeve (112) has a radially extending flange (114) received by the pressure bottle (174) surrounding the opening defined therethrough. A hybrid inflator (170) as defined in Claim 1 and further comprising a conduit (154) deployed to receive gas from the vent opening (132) and conduct gas received from the vent opening away from the pressure bottle (174).

Inventors: FAYE IAN C, HARRIS BRADLEY D, FAYE, IAN C., HARRIS, BRADLEY D.
Applicants: BOSCH GMBH ROBERT, MORTON INT INC, MORTON INTERNATIONAL, INC., ROBERT BOSCH GMBH
Application year: 1997
Main classification: B60R21
IPC codes: B60R21