Abstract:
A gas bag module for a vehicle occupant restraint device has a gas generator for inflating a gas bag, at least one discharge opening that is formed in a rigid component of the gas bag module and through which gas can be discharged that is produced by the gas generator and conveyed into the gas bag, and at least one valve flap, which in a closed position closes off the discharge opening and in an open position releases the discharge opening. The gas generator is arranged in an interior of the gas bag, and a wall section of the gas bag that covers the discharge opening is configured such that, when a pre-determined interior pressure is reached, it tears and releases the discharge opening.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a gas bag module for a vehicle occupant restraint device.  
       BACKGROUND OF THE INVENTION  
       [0002]     Usually, in a gas bag module, a gas bag is intended to be inflated as rapidly as possible with gas that is produced by a gas generator. However, in certain cases, it is desirable not to inflate the gas bag with the entire available volume of gas, or, more generally, to discharge gas, for this purpose discharge openings being provided in the gas bag module, the release of which makes it possible to limit the pressure in the gas bag.  
         [0003]     US 2004/0232677 A1 discloses a gas bag module in which several valve flaps, which can close off or release a plurality of discharge openings that are formed in a gas generator support, are connected by catch straps to a part of the gas bag wall that faces the vehicle occupant. When the gas bag module is activated, the valve flaps are in an open position, pointing towards the outside, or they are initially closed and are opened as a consequence of the increasing pressure in the gas bag interior. Therefore, the gas bag is not inflated with the entire available volume of gas. If the deploying gas bag comes into contact with the vehicle occupant before the gas bag has sufficiently deployed so that the catch straps are tightened, then the discharge openings remain open. In this way, the pressure of the deploying gas bag and therefore the force that is exerted upon the vehicle occupant are reduced. If the vehicle occupant is situated further from the gas bag module, then the gas bag deploys as described above, at first slowly, the discharge openings being open. However, as soon as the gas bag has deployed to the point that the catch straps are tightened, they pull the valve flaps towards the interior, as a result of which the discharge openings are closed off against the interior pressure of the gas bag. As a result, little or no gas is discharged through the discharge openings, and the entire volume of gas is used to inflate the gas bag.  
         [0004]     In the approach described, the gas generator must be arranged such that it initially injects into a housing of the gas bag module. An inflation opening of the gas bag is secured by a retaining ring in an edge area of the essentially pot-shaped housing such that the discharge openings are situated between the gas generator and the inflation opening of the gas bag.  
         [0005]     In contrast, the present invention provides a gas bag module in which, when the gas bag module is activated, the gas generator injects directly into the gas bag.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     This is achieved in a gas bag module for a vehicle occupant restraint device, having a gas generator for inflating a gas bag, at least one discharge opening that is formed in a rigid component of the gas bag module and through which gas can be discharged that is produced by the gas generator and conveyed into the gas bag, and at least one valve flap, which in a closed position closes off the discharge opening and in an open position releases the discharge opening. The gas generator is arranged in an interior of the gas bag, and a wall section of the gas bag that covers the discharge opening is configured such that, when a pre-determined interior pressure is reached, it tears and releases the discharge opening. The rigid component of the gas bag module in which the discharge opening is formed is intended to mean a rather or almost inflexible component such as a module housing or a gas generator support. Therefore, the principle that is known from US 2004/0232677 A1 can be realized in a so-called integrated gas bag module by the configuration according to the present invention. In the case of the present invention, the gas generator is almost completely enclosed by gas bag fabric, and only one or more igniters or attachment bolts of the gas generator pass to the outside through appropriate openings in the gas bag fabric. In this context, the gas generator injects directly into the gas bag, which advantageously influences the rapid deployment of the gas bag. As a result of the fact that the discharge opening in the installed condition is covered at least by the wall section of the gas bag, in the case of an approach featuring an initially open valve flap, foreign bodies such as dirt are effectively prevented from penetrating through the open flap into the gas bag.  
         [0007]     Preferably, at least one tensile strap is provided, whose first end is connected to a wall part of the gas bag which wall part in the inflated condition is close to an occupant, and whose second end interacts with the valve flap. The tensile strap advantageously is of a length such that it is tightened when the gas bag in being activated expands without hindrance. In this manner, a simple mechanism is provided that is not susceptible to malfunctioning.  
         [0008]     According to one preferred embodiment, when the tensile strap is tightened, the valve flap is placed in the closed position. This is precisely the case when the gas bag in being activated is able to expand without hindrance, i.e., for example, when it does not encounter at an early point in time a vehicle occupant who is situated closer to the gas bag module than usual.  
         [0009]     A retaining device can be provided that initially holds the valve flap in the open position. As a result, it is possible to achieve a softer gas bag even in an initial phase of the gas bag deployment, as a result of which the force exerted upon the vehicle occupant is reduced.  
         [0010]     The second end of the tensile strap is preferably connected to the retaining device. By a tightening of the tensile strap, the retaining device can be released. Therefore, if the gas bag expands without hindrance, thus resulting in a tightening of the tensile strap, then the valve flap that is no longer retained by the retaining device is brought into its closed position by the gas bag interior pressure. Thus the entire (remaining) volume of gas is used for deploying the gas bag and an optimal restraining effect is made available to the occupant.  
         [0011]     According to a first embodiment, the retaining device has a latching lever. The latter directly engages the opened valve flap and distinguishes itself by an especially simple configuration as well as a cost-effective manufacturing process.  
         [0012]     According to another embodiment, the retaining device has a destructible connecting part. In this context, the latter can possibly be a pre-damaged fabric or plastic part, which is connected to the valve flap or is molded integrally therewith. As a result of the tensile force of the tightened tensile strap, the connecting part rips or breaks and thus releases the valve flap, which thereupon moves into the closed position.  
         [0013]     The valve flap can in the open position protrude into an interior space of the gas bag module. The advantage in this configuration lies in the fact that the flap, after it is closed, remains in its closed position due to the gas bag interior pressure even when the tensile strap is slack in response to the vehicle occupant&#39;s plunging into the gas bag.  
         [0014]     Alternatively, the valve flap in the open position, seen from the gas bag module, protrudes outwards. Then it is possible that the closed flap is once again opened due to the gas bag interior pressure, with the tensile strap slackened (such as in response to the occupant&#39;s plunging into the gas bag), as a result of which a softer gas bag is presented to the occupant.  
         [0015]     The valve flap is preferably connected to the second end of the tensile strap. It is then closed by the tensile strap in opposition to the interior pressure.  
         [0016]     Advantageously, a mechanism is provided that holds the valve flap in the closed position after the tensile strap has been tightened. Therefore, in the event that the valve flap is opened outwards, the mechanism prevents a repeated opening of the flap (after closing).  
         [0017]     The mechanism can be a clamping mechanism, which acts upon the tensile strap. A clamping mechanism of this type is simply designed, cost-effective, but also effective.  
         [0018]     According to one configuration, the valve flap is a part of a valve component that is arranged in the interior of the gas bag and that has a frame that surrounds the valve flap. Alternatively, the valve flap can be part of a valve component that is mounted on an outside of the module housing. The valve component is simply inserted into the gas bag, or is attached to the module housing, and acts to secure the valve flap in the module.  
         [0019]     The valve flap is preferably an integral component part of the valve component, which can be made of plastic, e.g., in an injection molding method.  
         [0020]     The gas generator does not have to be directly connected to the valve component. However, the valve component can loosely contact the gas generator and can be secured to the module housing together with it by a common attachment means.  
         [0021]     According to one embodiment, the wall section of the gas bag that covers the discharge opening is pre-damaged in a controlled manner. When the gas bag interior pressure rises, the wall section tears and releases the discharge opening. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  depicts a sectional view of a gas bag module according to a first embodiment of the present invention, in the installed condition;  
         [0023]      FIG. 2  depicts a sectional view of the gas bag module from  FIG. 1  in an activated condition, having an open valve flap;  
         [0024]      FIG. 3  depicts a sectional view of the gas bag module from  FIG. 1  in the activated condition, having a closed valve flap;  
         [0025]      FIG. 4  depicts a detailed view of a gas bag module similar to that from  FIG. 1 ;  
         [0026]      FIG. 5  depicts a further detailed view of the gas bag module from  FIG. 4 ;  
         [0027]      FIG. 6  depicts a sectional view of a gas bag module according to a second embodiment of the present invention, in the installed condition;  
         [0028]      FIG. 7  depicts a sectional view of the gas bag module from  FIG. 6  in the activated condition, having a closed valve flap;  
         [0029]      FIG. 8  depicts a sectional view of a gas bag module according to a third embodiment of the present invention, in the installed condition;  
         [0030]      FIG. 9  depicts a sectional view of the gas bag module from  FIG. 8  in the activated condition, having an open valve flap;  
         [0031]      FIG. 10  depicts a perspective view of a gas bag module that is similar to that from  FIG. 8 , in the installed condition; and  
         [0032]      FIG. 11  depicts an exploded view of another alternative configuration of the gas bag module from  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]      FIG. 1  shows a gas bag module  10 , which is especially provided for use as a passenger-side gas bag module, but which is not limited thereto. Gas bag module  10  has a gas generator  12  and a gas bag  14 , which in the Figure is only sketched. In a rigid component of gas bag module  10  in the form of a housing  16 , a discharge opening  18  is provided that, in the installed condition of module  10  as shown in  FIG. 1 , is covered only by a wall section  20  of gas bag  14 . Wall section  20  prevents foreign bodies from penetrating into gas bag  14  through the otherwise open discharge opening  18 , and it has a predetermined breaking point in the form of a perforation  22  running roughly down the center over discharge opening  18 .  
         [0034]     Gas bag module  10  is a so-called integrated module, which means that gas generator  12  is arranged entirely within the interior of gas bag  14  and, when activated, injects directly into it. Only an igniter  24  of gas generator  12  passes through gas bag  14  and housing  16  to the outside and is attached by a nut  26  to housing  16 .  
         [0035]     Between gas generator  12  and gas bag  14 , a valve component  28  is inserted that includes a valve flap  30  and a frame  32  that surrounds valve flap  30 . Valve component  28  also has a flange  34  that rests against gas generator  12  and through which igniter  24  passes, and a retaining device in the form of a latching lever  36 , which is integrally formed with the rest of valve component  28 . Valve flap  30  is also integrally executed with the rest of valve component  28 . In the installed condition of gas bag module  10  as shown in  FIG. 1 , before a possible activation, valve flap  30  is in an open position, in which it protrudes into an interior space  38  of gas bag module  10 . Valve flap  30  is held in this open position by latching lever  36 , which it contacts with biasing.  
         [0036]     A first end of a tensile strap  40  is connected to a wall part  42  of gas bag  14 , which in the inflated condition of gas bag  14  is close to the vehicle occupant. A second end of tensile strap  40  is secured to latching lever  36 .  
         [0037]     If an accident is detected by an appropriate sensor device (not shown), gas generator  12  is ignited and produces a flow of gas, as a result of which the interior pressure in gas bag  14  rises. A cover (also not shown) of gas bag module  10  facing the passenger area opens, and gas bag  14  begins to deploy. Due to the increasing interior pressure within gas bag  14 , wall section  20  of gas bag  14  rips along perforation  22 , and gas can be discharged from gas bag module  10  through discharge opening  18  (see  FIG. 2 , arrow P 1 ).  
         [0038]     In the event that gas bag  14  can deploy without hindrance, for example, in not encountering a vehicle occupant at an early point in time, tensile strap  40  is pulled upwards in the direction of arrow P 2  in  FIG. 2  by wall part  42 , which is moving towards the vehicle occupant, and in this way the tensile strap is tightened.  
         [0039]     In the process, tensile strap  40  pulls latching lever  36  out of engagement with valve flap  30 , which as a result is unlatched and closes due to the interior pressure within gas bag  14 , i.e., the gas flow from gas generator  12  towards discharge opening  18  (see  FIG. 3 ). As a result, a further discharge of gas from gas bag  14  is prevented, and gas bag  14  offers the vehicle occupant an optimal restraining effect. However, if the deployment of gas bag  14  is hindered, for example, by a vehicle occupant who is situated closer than usual to gas bag module  10 , then tensile strap  40  remains slack, and latching lever  36  is not unlatched. Valve flap  30  therefore remains in the open position shown in  FIG. 2 , as a result of which a softer gas bag  14  is presented to the vehicle occupant.  
         [0040]      FIGS. 4 and 5  show detailed views of a gas bag module that is similar to that in FIGS.  1  to  3  in the non-activated condition. This gas bag module has two valve flaps  30 , which are held by a common latching lever  36 . For illustrative purposes, the Figures show no depiction of the gas bag ( FIG. 5 ) or the gas bag and the housing ( FIG. 4 ).  
         [0041]     A gas bag module  10  according to a second embodiment of the present invention is shown in  FIG. 6 , identical components bearing identical reference numerals, and only the differences with respect to the first embodiment being discussed below. Valve component  28  in accordance with  FIG. 6 , which is arranged in the interior of gas bag  14 , similarly has a retaining device, but instead of a latching lever a destructible connecting part  44  is provided that initially holds valve flap  30  in the open position. Connecting part  44  can be, for example, a pre-damaged fabric or plastic part. In order to ensure that connecting part  44  is reliably destroyed in the event of the tightening of tensile strap  40 , valve component  28  additionally has a deflection means  46  attached to it, through which tensile strap  40  is guided. The deflection means ensures that the force exerted by tensile strap  46  acts in the direction of connecting part  44 .  
         [0042]     Because the mode of functioning of gas bag module  10  according to the second embodiment corresponds to that of the first embodiment ( FIGS. 1 through 5 ) of the gas bag module, the mode of functioning will not be explained again.  FIG. 7  shows the gas bag module  10  from  FIG. 6  in the activated condition, after tensile strap  40  has tightened and valve flap  30  has closed.  
         [0043]      FIG. 8  shows a third embodiment of a gas bag module  10  according to the present invention, which essentially differs from those described above in the fact that valve flap  30  in the open position, seen from gas bag module  10 , is situated outside gas bag  14 . Therefore, no retaining device is provided on valve component  28 , but rather tensile strap  40  at its second end is directly connected to valve flap  30 .  
         [0044]     Furthermore, the gas bag module in accordance with  FIG. 8  is different in that valve component  28  is arranged on the outside of housing  16  and is connected by housing  16  to a frame  48  that is situated in the interior of gas bag  14 . Frame  48  also has a recess in the area of discharge opening  18 . In the installed condition shown in  FIG. 8 , before the activation of gas bag module  10 , valve flap  30  is closed. Wall section  20  of gas bag  14 , which is arranged in the area of discharge opening  18 , has a slot  50 , through which tensile strap  40  passes outside to valve flap  30 .  
         [0045]     In the third embodiment of gas bag module  10  as well, gas generator  12  in being activated is first ignited and produces a gas flow, as a result of which the interior pressure in gas bag  14  rises. Subsequently, the cover of module  10  opens, and gas bag  14  begins to deploy. As a result of the increasing interior pressure, wall section  20  in the area of slot  50  tears, and valve flap  30  is pressed open ( FIG. 9 ).  
         [0046]     In place of slot  50 , wall section  20  could also have a larger opening, even in the installed condition, through which the gas can flow.  
         [0047]     In the event that gas bag  14  can deploy without hindrance, tensile strap  40  is tightened, and valve flap  30  is pulled closed. Optionally, a clamping mechanism  52  can be provided on tensile strap  40  ( FIG. 11 ), by which valve flap  30 , once it is closed, is held in its closed position against the interior pressure of gas bag  14 .  
         [0048]     On the other hand, if the deployment of gas bag  14  is hindered, tensile strap  40  remains slack and as a result valve flap  30  remains open.  
         [0049]     Finally,  FIGS. 10 and 11  show alternative configurations of gas bag module  10 , which have a valve flap  30  that opens outwards and which have a plurality of discharge openings  18  in housing  16  that are selectively configured so as to be rectangular or round and that can be closed by a common valve flap  30 .