Patent Publication Number: US-2002005631-A1

Title: Airbag module

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to an airbag module for a motor vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002] An airbag module generally comprises a housing which is closed by a door, an inflatable cushion, and an inflator. The door is defined by a tear (or weakened) line and a hinge or pivot axis. On detection of the need to inflate the cushion (by one or more sensors), the inflator is actuated to inflate the cushion. The act of inflating the cushion causes the weakened line defining the door to tear such the door pivots open to allow the cushion to fully inflate. In general, the tear line is substantially U-shaped and extends around a portion of the circumference of the door, with the remaining portion of the circumference defining a hinge or pivot axis for the door on opening. Any obstruction (such as an out-of-position vehicle occupant) which prevents the door from opening fully can affect the efficiency of the protection system.  
       SUMMARY OF THE INVENTION  
       [0003] It is an object of the present invention to overcome the above mentioned problem.  
       [0004] An airbag module in accordance with the present invention for a motor vehicle comprises a housing; a door having a pivot axis and a tear line, and normally closing the housing; an inflatable airbag cushion positioned in the housing; and an inflator for inflating the airbag cushion; wherein the pivot axis extends around at least a portion of the outer circumference of the door; wherein the door comprises at least three portions which are defined by the tear line; and wherein the tear line comprises at least three lines each of which extend radially outwards from substantially the centre of the door.  
       [0005] The present invention reduces the risk of the door encountering an obstruction on actuation of the airbag module. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0006] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
     [0007]FIG. 1 is a front view of an airbag module in accordance with the present invention with the door in the closed position;  
     [0008]FIG. 2 is a front view of the airbag module of FIG. 1 with the door in the open position; and  
     [0009]FIG. 3 is a front view of a second embodiment of airbag module in accordance with the present invention with the door in the open position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0010] Referring to FIGS. 1 and 2, the airbag module  10  comprises a housing  12  which is closed at one end by a door  14 ; an inflatable airbag cushion  16  which (prior to inflation) is located in the housing behind the door; and an inflator  18  for inflating the airbag cushion on actuation of the airbag module. In this arrangement, the airbag module  10  is for the protection of a driver seated in the driver&#39;s seat of a motor vehicle, and the door  14  is in the steering wheel  24  of the vehicle. The door  14  is normally attached to the airbag module  10 , and defined by, a weakened or tear line  20 , and a pivot or hinge axis  22 . On detection of a predetermined condition of the vehicle, the airbag module  10  is actuated whereby the weakened line  20  is torn and the door  14  opens by pivoting about the hinge axis  22  in a manner well known to those skilled in the art.  
     [0011] In accordance with the embodiment of FIGS. 1 and 2, the tear line  20  of the airbag module is substantially X-shaped, and the pivot or hinge axis  22  extends substantially around the outer circumference of the door  14 . In this embodiment, the door  14  has five portions  26 ,  30  which, in the closed position of the door (FIG. 1), are integrally joined, and which are defined by the tear line  20 . On actuation of the airbag module  10 , the tear line  20  is torn and the portions  26 ,  30  of the door  14  are separated from one another and pivot outwardly from their outer hinge axis  22 , such that the door opens (FIG. 2). With this arrangement, as the door  14  is defined by a number of portions  26 ,  30  each having a smaller surface area than the total surface area of the door, the risk of the portions hitting an obstruction on opening of the door is reduced. The tear line  20  is preferably split when the inflator  18  begins inflating the cushion  16 . As shown in FIGS. 1 and 2, the vehicle emblem  28  is preferably mounted on one of the portions  30  of the door  14 , which splits from the other portions  26  on actuation of the airbag module  10 . In this embodiment, the tear line comprises five lines  32  each of which extends radially outwards from substantially the centre of the door  14 .  
     [0012]FIG. 3 shows an alternative embodiment to the arrangement shown in FIGS. 1 and 2 in which like parts have been given the same reference numeral except with a prime (′). In FIG. 3, the airbag module  10 ′ includes a door  14 ′ which is defined by a weakened or tear line  20 ′ and a pivot or hinge axis  22 ′, in which the tear line is substantially H-shaped (with additional parallel lines extending perpendicularly from the central arm of the H), and the pivot axis extends around a portion of the outer circumference of the door. In this arrangement, the door  14 ′ has four portions which, in the closed position of the door, are integrally joined, and which are defined by the tear line  20 ′. On actuation of the airbag module  10 ′, the tear line  20 ′ is torn and the portions  26 ′,  30 ′ of the door  14 ′ are separated from one another and pivot outwardly from their outer hinge axis  22 ′, such that the door opens (FIG. 3). With this arrangement, as the door  14 ′ is defined by a number of portions  26 ′,  30 ′ having a smaller surface area than the total surface area of the door, the risk of the portions hitting an obstruction on opening of the door is reduced. The tear line  20 ′ is preferably split when the inflator  18 ′ begins inflating the cushion  16 ′. As shown in FIG. 3, the vehicle emblem  28 ′ is preferably mounted on one of the portions  30 ′ of the door  14 ′, which splits from the other portions  26 ′ on actuation of the airbag module  10 ′. In this embodiment, the tear line comprises four lines  32 ′ each of which extends radially outwards from substantially the centre of the door  14 ′, and two lines  34 ′ each of which extend around a portion of the outer circumference of the door.  
     [0013] In accordance with the present invention, the door of the airbag module is defined by at least three portions which are separated by a weakened or tear line, the tear line being defined by a number of lines extending radially outwards from the central area of the door, and preferably with at least two of the lines extending substantially diametrically across the door. Such an arrangement reduces the risk of the door encountering an obstruction on actuation of the airbag module and opening of the door.  
     [0014] In an alternative to the above described embodiments, the airbag module may be adapted for installation in the dashboard of the motor vehicle for a passenger seated in the front passenger seat of the vehicle. It will also be appreciated that other arrangements for the tear line, and the shape of the portions of the door, may be used.