Patent Publication Number: US-2005121883-A1

Title: Gas bag module

Description:
TECHNICAL FIELD  
      The invention relates to a gas bag module.  
     BACKGROUND OF THE INVENTION  
      It is known to use a gas conduit, also called gas lance, in order to direct gas for inflating the gas bag into the same upon an activation of the gas bag module. This concept has so far been implemented mainly in side gas bag modules arranged along a roof frame of a vehicle. The advantage of using a gas conduit resides in the fact that the gas generator does not have to be located directly in the gas bag module but may either be placed at another location in the vehicle or also in the immediate vicinity of the gas bag module, but at a location that is more favourable for the utilization of space. The gas conduit does not only have to be firmly and gas-tightly connected to the gas generator but also to any gas distribution elements. So far, this has been effected in most cases by welding, which however involves a lot of work and thus high costs.  
     BRIEF SUMMARY OF THE INVENTION  
      It is an object of the invention to provide an inexpensive gas bag module in which the gas used for inflating the gas bag is introduced into the gas bag via a gas conduit.  
      This is achieved in a gas bag module having a module housing including a mount for accommodating a gas bag arranged therein, a rear wall, and a gas bag exit side lying opposite to the rear wall. A gas generator is located outside the module housing, and a gas conduit which is connected by an inflow end to the gas generator, extends through the rear wall towards the gas bag exit side and has an outflow region at its free end. The gas generator is located completely outside the module housing, and the gas conduit has an outflow region at its free end only.  
      A simple fastening of a gas deflection member is created according to one embodiment in that the gas conduit is inserted at the inflow end through an opening in a gas guiding plate arranged in the gas bag and presses by a flange against an inner side of the gas guiding plate. This connection is very simple, because the gas conduit acts like a screw whose head is formed by the outflow region. The resulting form-fitting and non-positive fastening of the gas conduit can be carried out very cost-effectively as compared to the weld joint used in the prior art. The joint is formed in that the gas conduit carries a flange below the outflow region (e.g. an integrally molded flange or a washer) which preferably has a larger diameter than the outflow region. A further fastening of the gas conduit at the gas guiding plate is not absolutely necessary when the gas conduit is firmly fixed at the housing. The required gas-tightness is ensured as well, because the gas leaves the gas conduit through the outflow region above the flange and is guided via the latter directly onto the gas guiding plate.  
      The gas guiding plate is preferably designed at least in sections in the shape of a trough, the outflow region being located within the trough-shaped section. The walls of the trough-shaped section keep the hot gas away from the walls of the gas bag while the shape of the trough open upwardly ensures that the gas is able to escape into the gas bag over a large area. The gas conduit is inserted from the upper open side of the trough through the opening provided in the bottom of the trough.  
      The depth of the trough may decrease towards the ends of the gas guiding plate, the possibility existing to provide fastening means here for the gas guiding plate at the housing. Also by means of this fashioning the gas flow is guided in such a manner that the hot gas comes into contact with the walls of the gas bag as little as possible. Moreover, the gas guiding plate may at the same time be used for fastening the gas bag at the housing.  
      In order to achieve a maximum possible neutrality of thrust, the outflow region preferably comprises several radial outflow openings which are arranged in such a manner that the impulses of the partial gas flows flowing out of the individual outflow openings cancel each other out and there is a neutrality of thrust. One possibility to achieve this in a simple manner is to arrange the outflow openings at the upper end of the gas conduit radially and at the same angular distance. Four or five outflow openings may for example be provided.  
      Preferably, the gas generator is located on the underside of the mount, i.e. on the outside of the housing and not within the gas bag, which increases the flexibility of the fashioning of the gas bag module.  
      For a gas bag module designed to be as compact as possible the mount may have an elongated form and the gas guiding plate may be located offset in relation to an imaginary center line of the mount. By means of this arrangement the depth of the mount may be kept smaller on the side of the imaginary center line on which the gas guiding plate is arranged than on the other side of the imaginary center line. The gas generator may then be arranged below the shallower side of the mount.  
      For rapidly introducing a large amount of gas into the section of the gas bag which lies in a folded state on the deeper side of the mount, a portion of a side wall of the trough-shaped section facing towards the inside of the mount is preferably lowered.  
      Preferably, the gas conduit is firmly connected to the gas generator. The fastening is effected e.g. in that the gas conduit comprises an inflow region at the inflow end, and the gas generator is cylindrical and comprises a continuous opening perpendicular to a longitudinal axis and the gas conduit extends through the gas generator, the inflow region being located in the interior of the gas generator. The inflow end of the gas conduit at which the inflow region is formed may also be connected to the gas generator in a form-fitting manner or may for example be screwed to the latter. This fastening is preferably effected in that the inflow end extends through the gas generator and a nut and bolt connection is provided in this region by means of which an axial clamping force is exerted on the gas guiding plate and the gas generator. This means that the parts between the flange at the gas conduit and the nut and bolt connection are clamped and positioned with respect to each other, as in a screw-type connection. Not only the gas generator and the gas guiding plate but also the housing and the gas generator, if necessary, may be clamped in this manner.  
      The part of the gas conduit projecting into the outer housing preferably extends linearly and is spaced away both axially and radially from the gas bag folded into a package in order to form an empty space. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a schematic perspective view of a gas bag module in accordance with the invention, illustrated without a gas bag for reasons of clarity, in which the outflow region of the gas conduit is configured according to a first variant;  
       FIG. 2  shows the gas bag module of  FIG. 1 , the design of the outflow region of the gas conduit being varied with respect to  FIG. 1 ;  
       FIG. 3  shows a perspective view of a gas bag module in accordance with the invention seen from above at an angle;  
       FIG. 4  shows a perspective view of the gas bag module in accordance with the invention of  FIG. 3  from below at an angle;  
       FIG. 5  shows a sectional view of a gas bag module in accordance with the invention along the line V-V in  FIG. 2 ;  
       FIG. 6  shows a sectional view along the line VI-VI in  FIG. 2 ;  
       FIG. 7  shows a perspective view of a gas guiding plate connected to a gas conduit for use in a gas bag module in accordance with the invention;  
       FIG. 8  shows a schematic side view of the assembly unit of  FIG. 7 ;  
       FIG. 9  shows a perspective view of the gas conduit and the gas guiding plate according to  FIG. 7 ;  
       FIG. 10  shows a schematic side view of a gas bag module according to a further embodiment;  
       FIG. 11  shows a perspective view onto the gas bag module of  FIG. 10 ;  
       FIG. 12  shows a side view of the front face of the gas bag module of  FIG. 10 ; and  
       FIG. 13  shows a side view of the gas bag module according to  FIG. 10  with the gas bag in the inflated state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The module housing  10  (outer housing) of the gas bag module  12  shown in  FIG. 1  comprises a mount  14  which is defined by walls of the housing  10  and in which a folded gas bag  16  (schematically shown in  FIG. 6 ) is accommodated. A side wall  15  extends from a stepped rear wall  17  of the housing  10 , which is opposite to a gas bag exit side  19  (see  FIG. 6 ).  
      A gas guiding plate  18  is arranged in the mount  14  and within the gas bag  16 , namely offset from an imaginary center line M of the mount  14 . The gas guiding plate  18  comprises a trough-shaped inner section  20  (see e.g. FIGS.  7  to  9 ) whose side walls  22  oriented parallel to the walls of the mount  14  guide the gas intended for inflating the gas bag  16  on its way into the gas bag  16 . The trough-shaped section into which the gas bag  16  does not project forms a diffuser space for the gas streaming in.  
      The gas guiding plate  18  is flattened at both ends  24  and provided with fastening elements in the form of fastening bolts  26  by means of which it may be secured to the housing  10 . The rim of an inflation opening of the gas bag  16  may be clamped over a large surface area between the bottom of the housing  10  and the bottom of the trough-shaped section  20  of the gas guiding plate  18 . Additionally, the gas bag  16  may be provided with openings through which the fastening bolts  26  project in order to safely connect the gas bag to the housing  10 .  
      The bottom of the gas guiding plate  18  comprises an opening  28  which is located slightly offset from the center of the trough-shaped section  20  towards one of the ends  24  (see  FIG. 9 ).  
      A gas conduit  30  extends through this opening  28  and through an opening  29  in the rear wall  17  of the housing  10  (see e.g.  FIG. 6 ). Simultaneously, the gas conduit  30  extends substantially perpendicular to a flat bottom  31  of the trough-shaped section  20  (see e.g.  FIGS. 5 and 7 ) and is inserted, with its inflow end  33  ahead, through the gas guiding plate  18 .  
      The gas conduit  30  extending completely linearly comprises at its inflow end  33  two openings forming an inflow region  32 , while it comprises only at the opposite end an outflow region  34  having several radial outflow openings  36  located in the wall of the gas conduit  30  and distributed at equal angular distances. On account of this arrangement the outflow of the gas from the outflow region  34  is effected practically neutral in thrust, because the impulses of the individual gas flows cancel each other out. As shown in  FIG. 1 , five outflow openings  36  or, as shown in  FIG. 2 , four outflow openings  36  may for example be provided. Any number of outflow openings  36  other than the ones described herein are of course conceivable as well.  
      Directly below the outflow openings  36  the gas conduit carries an annular flange  38  which completely surrounds the gas conduit  30  circumferentially and has a larger diameter than the gas conduit  30  in the region of the outflow openings  36  and the opening  28 .  
      The gas conduit  30  is pushed through the opening  28  in the gas guiding plate  18  so far that the flange  38  rests on the gas guiding plate  18  and completely surrounds the opening  28 . In the example shown herein, the circumferential edge of the flange  38  extends on two opposite sides  40  in a straight line, whereby a locking against rotation of the gas conduit  30  with respect to the gas guiding plate  18  is formed in that the sides  40  of the flange  38  are in contact with the side walls  22  of the gas guiding plate  18  (see e.g. also  FIG. 6 ).  
      A gas generator  42  is arranged outside the housing  10  below the mount  14 . As for example apparent from  FIGS. 4 and 6 , the gas generator  42  is placed directly below the gas guiding plate, i.e. also offset from the imaginary center line M of the mount  14 .  
      The gas generator  42  has a cylindrical shape and a longitudinal axis G (see  FIG. 5 ). Perpendicular to this longitudinal axis G it comprises a through opening through which the gas conduit  30  projects. The inflow end  33  even sticks out somewhat of the gas generator  42 . The gas generator  42  comprises outflow openings (not shown) which are in fluid communication with the inflow region  32  of the gas conduit  30 , which is located within the through opening. In the example shown herein, two inflow openings lying opposite one another are provided in the inflow region  32 . The exact design of the inflow region is of course up to a person skilled in the art. The gas generator  42  extends with its longitudinal axis G parallel to the longitudinal extension of the elongated housing without protruding with respect to it in top view.  
      The gas conduit  30  is open on the front face at the inflow end  33 . The fastening of the gas conduit  30  at the gas generator  42  is effected via a closure cap  44  screwed into the open end of the gas conduit  30 . The closure cap  44  has a radially projecting border  45  (see  FIG. 6 ) pressing against a sleeve  47  which is placed onto the inflow end  33  on the outside and presses against the gas generator  42 . Thus, by means of the cap  44  the gas generator  42  is pressed against a downwardly protruding tubular extension  49  at the housing  10 . At the same time also the flange  38  is pressed downwards against the gas guiding plate  18  and the latter is pressed together with the gas bag  16  against the inner side of the gas guiding plate  18 . Thus, a clamping connection of all parts provided between the flange  38  and the nut and bolt connection at the inflow end  33  is achieved. Of course, further holding elements for fastening the gas generator  42  at the housing  10  may additionally be provided. The gas conduit  30  acts like a traction rod by means of which the gas generator  42  is pressed against the outside of the rear wall  17 .  
      On that side of the center line M below which the gas generator  42  is arranged, the mount  14  is designed to be shallower than on the other side of the center line M. The gas bag  16  completely fills up the mount  14 .  
      A section  37  of the side wall  22  of the gas guiding plate  18  facing towards the interior of the mount  14  is lowered, i.e. the height of the wall is reduced as compared to the remaining trough-shaped section  20 .  
      The lowered section  37  is located in the area of the outflow region  34  resulting in that a large amount of gas directly enters the section of the folded gas bag located in the deeper part of the mount  14 .  
      With the exception of the lowered section  37 , the outflow openings  36  are however located below an upper edge of the side walls  22  so that the gas flowing out reaches at first the gas guiding plate  18  before is enters the gas bag  16 .  
      The gas conduit  30  and the gas guiding plate  18  are preferably only fixed at each other via the clamping at the flange  38 . Since the gas conduit  30  is firmly connected to the gas generator  42  via the closure cap  44  and thus firmly to the housing  10  and the gas guiding plate  18  is fixed at the housing  10  via the fastening bolts  26 , a relative movement of the gas conduit  30  with respect to the gas guiding plate  18  is prevented. Since the flange  38  is located below the outflow region  34  so that no high pressure acts on the connection between the flange  38  and the gas guiding plate  18 , the gas tightness is also sufficient.  
      In assembling the gas bag module  12  the gas conduit is at first inserted into the gas guiding plate and the gas guiding plate placed in the gas bag  16 . Then the gas conduit is inserted through the opening  29  in the housing  10  and the inflow region is inserted through the through opening of the gas generator  42 , the sleeve  47  is slipped on and the closure cap  44  screwed in.  
      In  FIGS. 3 and 4  the mount  14  is closed by a protective cover  46  opening when the gas bag module  12  is activated.  
      In the embodiment according to FIGS.  10  to  13  the reference numbers already introduced are used again for parts having the same function. Their function is apparent from the foregoing description regarding the first exemplary embodiment.  
      Also in the embodiment according to FIGS.  10  to  13  the linear gas conduit  30  acts like a traction rod and presses the gas generator  42  against the outside of the rear wall  17 . As apparent in particular from  FIG. 11 , in this arrangement as well the module housing  10  is designed in top view in an elongated form. The gas generator  42  is oriented parallel to the longitudinal direction of the rear wall  17  and, as apparent from  FIG. 12 , does not protrude laterally relative to the rear wall  17  in top view so that the module is a compact unit.  
      In this embodiment there is no gas guiding plate  18 . The flange  38  presses from above against the rear wall  17 . Also in this embodiment the gas conduit  30  extends from the rear wall  17  linearly to the gas bag exit side  19  as well as rectangularly to the gas bag exit side and in the main exit direction of the gas bag. At its end provided in the module housing  10  two outflow openings  36  offset by 180° are provided in the corresponding outflow region  34  (see  FIG. 11 ), which point to the opposite front faces of the outer housing  10  and are thus aligned in longitudinal direction.  
      The gas conduit  30  extends into the middle of the package to which the gas bag  16  is folded. Around the gas conduit  30  the gas bag package is however spaced away from the latter both in axial and radial direction so that a gas distribution space  100  is formed. Since the outflow openings  36  are located at the upper end of the gas conduit  30  and the latter extends almost up to the gas bag exit side  19  so that only very few layers of the gas bag  16  remain above it, the gas generated by the gas generator  42  flows in the upper airbag package region into the latter. So the gas bag  16  is acted upon by the gas jet marked by arrows near the gas bag exit side  19 . Thus, a high friction of gas bag sections lying on top of each other is avoided. The gas bag  16  unfolds, as desired, from close to the gas bag exit side  19 , as apparent from  FIG. 13 . Due to the lateral inflow of gas on account of the outflow openings  36  lying opposite to each other by 180° a rapid deployment in width may take place, which is positive for restraining the occupant. The gas bag deployment starts with a partial volume and the remaining volume of the gas bag package folded in further down follows subsequently.  
      Incidentally, the gas bag  16  itself is clamped at the rear wall  17  by a simple fastening plate  102  (see  FIG. 13 ) and two insert screws  104 .  
      In all embodiments the gas conduit  30  has a circular cylindrical cross section.