Abstract:
An airbag module comprises an airbag inflatable through an opening in the airbag. An airbag inflator provides an inflation gas into the opening in the airbag. A flap has a first position permitting gas to flow to the opening in the airbag and a second position deflecting inflation gas away fro the opening in the airbag. A propellant discharges into a discharge space moving the flap between the first position to the second position. A hood at least partially covers the discharge space.

Description:
This patent application is a continuation-in-part of U.S. Nonprovisional patent application Ser. No. 10/359,256 filed on Feb. 6, 2003 and claims priority therefrom. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an airbag module and actuator for selectively diverting inflation gases away from the interior of an airbag. 
     Airbag modules comprise an airbag and an airbag inflator. When triggered by a crash detection system, the airbag inflator rapidly provides gas to inflate the airbag. The inflated airbag then serves as a cushion against injury for a vehicle occupant. 
     The location of the vehicle occupant with respect to the airbag may affect the effectiveness of the airbag as a cushion. If the vehicle occupant is too close to the airbag, full inflation of the airbag may result in less than optimal cushioning of any impact. Accordingly, it is desirable to inflate the airbag to less than full capacity when the vehicle occupant is too close to the airbag. 
     Systems exist that detect the location of the vehicle occupant. When these systems sense that the vehicle occupant is too close to the airbag, they inflate the airbag to less than full capacity. A dual-stage inflator serves to inflate the airbag in this way. The inflator&#39;s first stage partially inflates the airbag, while the second stage, if triggered, fills the airbag to a maximum level. 
     However, a dual-stage inflator is generally more expensive than a single-stage inflator. It would be desirable to be able to provide a virtually infinite variety of inflation levels. As an alternative to a dual-stage inflator, the present invention provides an airbag module that vents inflation gas away from the airbag when the airbag has reached an appropriate inflation level. 
     The airbag module of the present invention has a flap that moves from an open position that permits inflation gas to inflate the airbag to a closed position in which the inflation gas is deflected away from the opening in the airbag. In this way, the airbag module permits a greater variety of inflation levels for the airbag without adding significant cost to the manufacture of the airbag module. An actuator moves the flap from an open position to a closed position when signaled by a control unit that the airbag has reached an appropriate inflation level. 
     The actuator comprises a propellant that is ignited when the actuator is signaled to do so. Upon ignition the propellant generates a gas that rapidly expands to generate a force that moves the flap from the open position to the closed position. However, when ignited the propellant may emit a flash of light and discharge residual particles into the passenger compartment. While this light and these particles are by no means dangerous, during a vehicle crash they may alarm a vehicle occupant. 
     A need therefore exists for an airbag module and actuator that suppresses these undesirable effects. 
     SUMMARY OF THE INVENTION 
     Like existing airbag modules, the airbag module of the present invention comprises an airbag inflatable through an opening in the airbag. An inflator generates an inflation gas that passes through the opening in the airbag during deployment. Unlike known systems, the invention uses a flap that opens and closes the opening in the airbag. Typically, the flap is held in the open position to permit inflation gas to pass through the airbag during airbag deployment. When the airbag has reached an appropriate inflation level, a propellant discharges and moves the flap between the open position to the closed position. To prevent both light and residual particles from escaping into the passenger compartment, a hood covers the space where the propellant discharges. 
     The hood may comprise a hollow body that surrounds the discharge space. The propellant may be located in hollow body. By surrounding the area of propellant discharge, the hollow body shields the passenger compartment from light and particles generated by the propellant. 
     In addition, a piston may slide within the hollow body to increase the force of the propellant and even collide with the flap to close the opening in the airbag. The piston may have two positions: an actuated position following discharge and an unactuated position prior to discharge. In the unactuated position, the piston protrudes very little, if at all, out of the hollow body. On the other hand, in the actuated position, the piston extends from this position to actually contact the flap and thereby impart the momentum of the piston, and the pressure of the expanding gas to move the flap from the open position to the closed position. 
     The hollow body may have two pieces, an upper housing and a lower housing, and may further have a retaining lip to keep the piston from launching out of the hollow body completely. Pressure build-up within the hollow body may be significant in comparison to the scale of the piston and hollow body. Accordingly, a hole may vent inflation gas out of the hollow body to relieve this pressure build-up. The hole may be located on the piston. 
     The propellant may have a housing as well. The housing may be fitted with electrical contacts that ignite the propellant when signaled. To ignite the propellant, current is passed through these contacts from a controller. 
     The airbag actuator may accordingly have a propellant stored in a propellant housing. The actuator has a hollow body that receives the propellant and propellant housing in one end and receives a piston in the other end. Light and particles from the propellant reaction are then largely contained within the hollow body between the propellant housing and the piston. A hole in the piston reduces pressure build-up within the hollow body without allowing significant amounts of light and particles to escape during the reaction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
     FIG. 1 illustrates airbag module with airbag, inflator, flap and actuator with the flap in an open position. 
     FIG. 2 illustrates airbag module of FIG. 1 with the flap in a closed position. 
     FIG. 3 is a close up of the airbag module of FIGS. 1 and 2, highlighting actuator with piston in contact with the flap. 
     FIG. 4 is a cross-sectional view of actuator in unactuated position, showing propellant housing, piston, and hollow body. 
     FIG. 5 illustrates the actuator of FIG. 4 in actuated position. 
     FIG. 6 is a perspective view of propellant housing of FIGS. 4 and 5. 
     FIG. 7 is a perspective view of piston of FIGS. 4 and 5. 
     FIG. 8 is a perspective view of lower housing of hollow body of FIGS. 4 and 5. 
     FIG. 9 is a perspective view of upper housing of hollow body of FIGS. 4 and 5. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows an airbag module  10  according to the present invention. The airbag module comprises an airbag  14  with an opening in the airbag  18  and an airbag inflator  20 . The airbag inflator  20  and the airbag  14  are attached to an airbag housing  13 . A crash sensor  17  communicates with a control unit  16 , which instructs the airbag inflator  20  to generate inflation gas  25  and deploy the airbag  14  if the crash sensor  17  relays crash detection data that indicates a crash of a predetermined severity. During airbag deployment, the airbag inflator  20  inflates the airbag  14  with inflation gas  25  produced by a chemical or other physical reaction. The airbag inflator  20  has ports  21  that supply inflation gas  25  into the airbag  14  through the opening in the airbag  18 . As the airbag  14  inflates, a vehicle occupant position sensor  19  determines the position of a vehicle occupant, such as a passenger, relative to the airbag  14  and communicates this signal to the control unit  16 . If the airbag  14  is under-inflated based on the position of the vehicle occupant, a flap  22  remains in first position  26  (open position), permitting inflation gas  25  to continue to flow through the opening in the airbag  18  into the airbag  14 . 
     When the appropriate inflation level for the airbag  14  is reached based on the position of the vehicle occupant, the control unit  16  instructs an actuator  23  to ignite a propellant  34 . The propellant  34  ignites and rapidly transforms into an expanding gas that causes the flap  22  to move in the direction of second position  30  to thereby cover the opening in the airbag  18  and deflect further inflation gas  25  away from airbag  14 . 
     FIG. 3 illustrates how the actuator  23  causes the flap  22  to move toward a second position  30 . Specifically, when the airbag  14  has reached an appropriate inflation level, the control unit  16  instructs the actuator  23  to propel a piston  58  in a direction indicted by an arrow A towards the flap  22 . The piston  58  collides with the flap  22  imparting momentum to the flap  22  forcing it to bend at a groove  200  so that the bottom portion  202  of the flap can swing in the direction indicated by an arrow B towards a second position  30 . Inflation gas  25  from the ports  21  of the inflator  20  may assist the flap  22  in moving toward the second position  30  as momentum of the flap  22  in the direction indicated by the arrow B carries the flap  22  into the path of the inflation gas  25 . 
     FIG. 4 is a cross-sectional view of actuator  23  relative to flap  22  with actuator  23  unactuated. Here, the propellant  34  is contained within a propellant housing  86  that is a hollow cylinder storing the propellant  34 . FIG. 6 is a perspective view of the propellant housing  86 . As shown in FIG. 4, the propellant housing  86  is itself supported within a hollow cylinder of a hollow body  42 , which has a hollow body interior  46  that is a cylindrical cavity. The hollow body  42  has a first opening  51  and second opening  53  therein. The first opening  51  receives the propellant housing  86  as well as the upper housing  102  while the second opening  53  receives the piston  58 . 
     The actuator  23  employs the hollow body  42  to shield a vehicle occupant from light and particles released by the propellant  34  during actuation of the actuator  23  while still permitting the actuator  23  to move the flap  22  toward the second position  30 . The hollow body  42  may comprise an upper housing  102  and a lower housing  106 , although the hollow body  42  may be of a single piece design. The propellant housing  86  may be supported within the upper housing  102  by an interference fit. FIG. 4 also shows the piston  58 , also a hollow cylinder, resting on top of the propellant housing  86  and disposed within the lower housing  106  of the hollow body  42 . 
     The propellant housing  86  has a first electrical contact  90  and a second electrical contact  94 . The electrical contacts  90 ,  94  are in electrical conductive communication with the propellant  34  or an ignition charge (not shown) in proximity to the propellant  34 . To actuate the actuator  23 , the control unit  16  sends an electrical signal through a wiring harness  27  to the electrical contacts  90 ,  94 , which ignites the propellant  34  or the ignition charge. 
     As shown in FIG. 5, when current is passed through the first and second electrical contacts  90 ,  94  the propellant  34  within propellant housing  86  Ignites, generating gas, light and residual particles within a discharge space  38  of the hollow body interior  46 . The propellant housing  86  peels open in this process. Because this reaction occurs within the hollow body interior  46  of the hollow body  42 , the hollow body  42  prevents light and particles from escaping in any significant amount into a passenger compartment of a vehicle. 
     At the same time, without releasing this light and these particles, the actuator  23  can transfer pressure from the gas of propellant  34  to the flap  22 . Specifically, a piston  58  is free to slide within the hollow body  42  along the direction indicated by an arrow A. As pressure builds from the expansion of the gas generated by the propellant  34 , the piston  58  moves along the direction indicated by the arrow A into the flap  22 , imparting momentum to the flap  22  towards a second position  30 . 
     To relieve pressure build-up within the hollow body interior  46 , the piston  58  may also be provided with a vent  82 , here a hole. The vent  82  is sufficiently small, however, so that insignificant amounts of light and particles from the hollow body  42  exit through the vent. Because of the position of the vent  82  on the piston  58 , the flap  22  may further hide light and redirect particles escaping from the vent  82 . 
     In addition to preventing particles and light from escaping into the passenger compartment, the actuator  23  has a feature that retains the piston  58  to the hollow body  42 . As shown in FIG. 5, the hollow body  42  has a lip  74  that protrudes circumferentially around the hollow body interior  46  of the hollow body  42  around a second opening  53 . The lip  74  provides a stop for a catch  78  of the piston  58  to prevent the piston  58  from ejecting entirely out of the hollow body  42  during actuation. When the actuator  23  is in an actuated position  66 , the catch  78  is in contact with the lip  74 . The piston  58  and the hollow body  42  are cylindrical. Accordingly, the piston  58  has a first piston diameter D 2  and a second piston diameter D 3 . The second opening  53  has a hollow body diameter D 1 . The first piston diameter D 2  is greater than the hollow body diameter D 1  thereby preventing the piston  58  from extending beyond the catch  78 . The second piston diameter D 3  may pass through the second opening  53  because the second piston diameter D 3  is less than the hollow body diameter D 1 . Thus, during actuation, a portion of the piston  58  is retained within the hollow body  42  while another portion extends through a second opening  53  into contact with the flap  22 . 
     As shown in FIG. 7, the piston  58  has a vent  82 , in this example a hole. The piston  58  is generally cylindrical and has a cavity  59  to receive a portion of the propellant housing  86 . As shown in FIG. 5, the lip  78  extends circumferentially around a cavity  59  forming a skirt that retains the piston  58  to the hollow body  42  by contact with the lip  74 . 
     FIG. 8 is a perspective view of a lower housing  106  of the hollow body  42  while FIG. 9 is a perspective view of an upper housing  102  of the hollow body  42 . As shown in these figures and noted previously, the upper housing  102  and lower housing  106  comprise generally cylindrical shapes. The upper housing  102  has a first opening  51  and a second opening  53  therein. The first opening  51  has a threaded portion  101  that receives a threaded portion  103  of the upper housing  102 . A flange  112  attaches to the airbag housing  13  and thereby secures the actuator  23  to the airbag housing  13  upon ignition of the propellant  34 . In addition, the propellant housing  86  rests on a support surface  110  of the upper housing  102  to also prevent the propellant housing  86  from moving relative to the airbag housing  13 . In addition, the flange  112  is provided with a flat surface  114  that is in a specific location relative to the location of the electrical contacts  90 ,  94  to aid in the orienting of the actuator  23  to the wiring harness  27  connecting the control unit  16  to the actuator  23 . 
     The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.