Abstract:
The invention relates to a hybrid inflator especially for a vehicle safety system, comprising an igniter ( 10 ), a combustion chamber ( 16 ) including a propellant charge ( 18 ) which is separated from the igniter ( 10 ) by a first bursting element ( 14 ) held by a bursting element holder ( 13 ), and comprising a compressed gas tank ( 20 ) filled with compressed gas and having at feast one discharge opening, the discharge opening being closed by a second bursting element ( 24 ) and the compressed gas tank ( 20 ) being fluid-communicated with the combustion chamber ( 16 ) so that the compressed gas surrounds the propellant charge ( 18 ). The invention excels by the fact that the bursting element holder ( 13 ) at least in portions delimits an ignition chamber ( 30 ) containing a booster charge ( 15 ), wherein a shock wave (SW) for opening the second bursting element ( 24 ) can be formed only when both the igniter ( 10 ) and the booster charge ( 15 ) have been ignited and, respectively, activated. The invention further deals with an airbag unit and a vehicle safety system comprising said hybrid inflator or said airbag unit. Moreover, the invention states a method of forming a shock wave within a hybrid inflator.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority from German Patent Application No. 10 2016 002 937.4, filed Mar. 11, 2016, the subject matter of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a hybrid inflator, especially for a vehicle safety system, according to the preamble of claim  1 . In addition, the invention relates to an airbag unit and a vehicle safety system comprising such hybrid inflator. The invention also relates to a method of forming a shock wave within a hybrid inflator. 
         [0003]    A hybrid inflator of the afore-mentioned type is known, for example, from U.S. Pat. No. 7,883,108 B2. The known hybrid inflator comprises a compressed gas tank including an igniter. The igniter is partially surrounded by a cap which, upon activation of the igniter, is opened on its end face in the direction of an axial longitudinal direction. A propellant charge in a combustion chamber is arranged axially downstream of the cap. Opposed to the igniter along the longitudinal axis, a bursting disk that closes an outlet opening for gas is provided. 
         [0004]    When the known hybrid inflator is triggered, the cap which is partially surrounding the igniter and which constitutes a first bursting element is ruptured or opened due to the increase in pressure in the igniter. In this way, a shock wave is formed which propagates centrally through a propellant charge disposed in the combustion chamber. The shock wave thus passes through the propellant charge and subsequently arrives at the bursting disk that acts as a second bursting element. The bursting disk yields to the shock wave and thus opens the outlet opening for gas. In this way, compressed gas as well as gas additionally generated by the propellant charge may exit the compressed gas tank and may fill an airbag, for example. 
         [0005]    One drawback of the known hybrid inflator is the overall size thereof. Especially the cross-sectional diameter of the known hybrid inflator is comparatively large as the combustion chamber projects tar into the compressed gas tank. It is another drawback that relatively high pressure is necessary to break the first bursting element, namely the cap. Therefore, a highly charged igniter containing a large amount of pyrotechnical charge is necessary which requires increased safety efforts during manufacture. Finally, the selection of material for the propellant charge is limited, as the pyrotechnical charge has to be ensured to reliably cause ignition of the propellant charge in the igniter. 
       SUMMARY OF THE INVENTION 
       [0006]    It is the object of the invention to state a hybrid inflator having a compact structure. Moreover, a hybrid inflator which is easy to adjust to different requirements of use is desirable. It is another object of the invention to state an airbag unit and a vehicle safety system comprising such hybrid inflator. Furthermore, the invention is intended to provide a method of forming a shock wave within a hybrid inflator. 
         [0007]    This object is achieved with respect to the hybrid inflator by the subject matter of the claims  1  or  2  or  3 , with respect to the airbag unit by the subject matter of claim  9 , with respect to the vehicle safety system by the subject matter of claim  10  and with respect to the method by the subject matter of claim  11 . 
         [0008]    Hence, the invention is based on the idea to provide a hybrid inflator especially for a vehicle safety system. The hybrid inflator includes an igniter, a combustion chamber containing propellant charge which is separated from the igniter by a first bursting element retained by a bursting element holder, and a compressed gas tank filled with compressed gas which includes at least one discharge opening, the discharge opening being closed by a second bursting element. The compressed gas tank is fluid-communicated with the combustion chamber so that the compressed gas surrounds the propellant charge. In accordance with the invention, the bursting element holder at least in portions delimits an ignition chamber containing a booster charge, wherein a shock wave for opening the second bursting element can only be formed when both the igniter and the booster charge are ignited and, respectively, activated, in particular, the booster charge may be provided as a component separate from the preferably prefabricated igniter. 
         [0009]    The concept of the invention substantially is to influence the triggering and, respectively, formation of the shock wave, especially to initiate the same at a predetermined position inside the hybrid inflator. In contrast to the state of the art according to U.S. Pat. No. 7,883,108 B2, the shock wave is not initiated by solely triggering the igniter. Rather, an additional booster charge is provided which has to be ignited so that a shock wave will actually form. Concretely speaking, the shock wave is provided to be formed only when the igniter and the booster charge are imperatively ignited. 
         [0010]    The shock wave is triggered after ignition of the igniter and of the booster charge. Since the shock wave will not form before the booster charge has been ignited, opening of the second bursting element is delayed. This delay may cause higher pressure to be built up inside the pressure tank, which may accelerate the filling of an airbag. At the same time, the overall size of the hybrid inflator may be reduced, as upon burn-off the booster charge provides additional gas volume. 
         [0011]    Alternatively or additionally to the delayed formation of a shock wave, in the afore-described hybrid inflator the first bursting element may be arranged so that the shock wave adapted to be triggered by the igniter and the booster charge can be initiated and, respectively, triggered in the axial longitudinal direction of the hybrid inflator between a first plane delimiting the propellant charge at its end facing the igniter and a second plane delimiting the propellant charge at its end facing away from the igniter. 
         [0012]    Accordingly, the axial longitudinal direction of the hybrid inflator is defined so that it extends from a first end of the hybrid inflator at which the igniter is located to a second opposite end at which a diffusor including discharge openings of the hybrid inflator is located. 
         [0013]    Moreover, as an alternative or in addition to the time-delayed formation of a shock wave, in the afore-described hybrid inflator the first bursting element may be arranged so that the shock wave to be triggered by the igniter and the booster charge can be initiated and, respectively, triggered in the axial longitudinal direction of the hybrid inflator only downstream of the propellant charge or starting from a second plane delimiting the propellant charge at its end facing away from the igniter. 
         [0014]    This aspect of the invention is backed by the idea to trigger the shock wave as late as at the longitudinally axial end of the propellant charge or behind or, respectively, downstream of the propellant charge. Thus, the shock wave is triggered locally behind the propellant charge. 
         [0015]    This aspect of the invention substantially differs from the state of the art according to U.S. Pat. No. 7,883,108 B2 by the fact that the shock wave is generated behind the propellant charge in so far as the shock wave no longer needs to propagate through a central opening of the propellant charge. This prevents the shock wave from being influenced by starting bum-off of the propellant change. 
         [0016]    in a preferred embodiment of the hybrid inflator according to the invention, the bursting element holder with the first bursting element and at least one end face of the igniter define a or, respectively, the ignition chamber in which the booster charge preferably being surrounded by atmospheric pressure is accommodated. Hence in a simple way a separate ignition chamber can be formed in which the booster charge may be arranged separately from the preferably prefabricated igniter. When the booster charge is surrounded by atmospheric pressure, merely a moisture-tight sealing of the booster charge and, respectively, of the ignition chamber against the environment of the hybrid inflator is necessary, whereas a gas-tight sealing is not required in this case. 
         [0017]    In a preferred embodiment of the hybrid inflator according to the invention, the combustion chamber includes a combustion chamber base delimiting the propellant charge along the longitudinal axis. Preferably, the combustion chamber base is adjacent to a or, respectively, the second plane which delimits the propellant charge at its end facing away from the igniter. Especially, the propellant charge may be formed of propellant pellets and/or propellant rings. This arrangement including the combustion chamber base offers the advantage that the combustion chamber base may be used for axially supporting the propellant charge. Even if the propellant charge itself is accommodated in a separate casing, for example a cage, the combustion chamber base has such supporting effect. 
         [0018]    In a further preferred configuration, the bursting element holder, especially the ignition chamber which is at least in portions delimited by the bursting membrane holder, extends substantially completely through the combustion chamber. In this way, the volume available inside the compressed gas tank is optimally exploited and it is simultaneously ensured that the shock wave being formed by bursting of the first bursting element is only triggered downstream of the propellant charge. At the same time, a comparatively large ignition chamber is provided which may be filled with the booster charge in variable density. Thus, the options of setting the performance of the hybrid inflator are increased. 
         [0019]    Further variants of the present invention may provide that a deflector having a central through hole is arranged in the axial longitudinal direction of the hybrid inflator starting from the igniter behind the combustion chamber. The deflector causes the ignition gas released by the booster charge to be deflected and in this way improves the burn-off of the propellant charge. The central through hole helps to achieve that the shock wave triggered may propagate unhindered up to the second bursting element. 
         [0020]    Concretely, a ring-shaped bulge may be provided to be formed in the deflector. The ring-shaped bulge may be designed so that ignition gas released by the booster charge can be deflected radially outwardly or along a longitudinal axis opposite to the axial longitudinal direction. This is advantageous especially when the propellant charge is arranged coaxially around the ignition chamber. The shock wave triggered behind the propellant charge may pass substantially unhindered through the central through hole of the deflector. The released ignition gas, in contrast, is deflected via the ring-shaped bulge to the outside and along the longitudinal axis opposite to the axial longitudinal direction so that the propellant charge in the combustion chamber burns off opposite to the axial longitudinal direction toward the igniter. This is of advantage even when a relatively large airbag has to be filled for the filling operation of which a quite long period of time is available. Then a comparatively slow bum-off of the propellant is advantageous to obtain filling of the airbag. 
         [0021]    The propellant charge may include propellant pellets and/or propellant rings. The use of propellant pellets offers the advantage that between the individual propellant pellets a comparatively large volume capable of being filled by compressed gas is retained. In contrast to this, when using propellant rings a larger volume and, respectively, a larger mass of propellant can be accommodated within the combustion chamber. 
         [0022]    Preferably the propellant pellets are arranged inside a ring-shaped cage. The case ensures that the propellant pellets remain at their predetermined positions. At the same time, openings in the case, on the one hand, cause the propellant pellets to be easily ignited and, on the other hand, cause the gas released by the propellant pellets to quickly escape from the combustion chamber. 
         [0023]    In a preferred configuration of the invention, the ignition chamber or the bursting element holder extends through a central through-hole of the cage and/or of the propellant rings. In this manner, the booster charge may be arranged substantially coaxially inside the propellant charge. This is beneficial to a compact design. 
         [0024]    The second bursting element preferably is arranged at a rear end of the compressed gas tank. Especially, in preferred embodiments the second bursting element is provided to close an opening disposed coaxially with respect to a longitudinal axis of the compressed gas tank and to be held by a further second bursting element holder which is tightly connected, especially welded, to the compressed gas tank. The coaxial arrangement of the second bursting element with respect to the longitudinal axis of the compressed gas tank guarantees that the shock wave triggered by the igniter and the booster charge arrives at the second bursting element substantially unhindered and thus the compressed gas tank will be opened and the compressed gas arranged therein will be released in an optimum way. 
         [0025]    One independent aspect of the invention relates to a gas bag unit, especially airbag unit, tor a vehicle safety system comprising an afore-described hybrid inflator. Furthermore, according to one independent aspect the invention relates to a vehicle safety system comprising such hybrid inflator or such airbag unit. 
         [0026]    Within the scope of the present invention, equally a method of forming a shock wave within a hybrid inflator is disclosed and claimed. The method may preferably be employed in a hybrid inflator which includes the afore-mentioned design features. The method according to the invention comprises the following steps of:
       a) activating an igniter; then   b) igniting a booster charge arranged downstream of the igniter in the axial longitudinal direction of the hybrid inflator and disposed in an ignition chamber; after that   c) opening a bursting element of the ignition chamber by at least partially burning off the booster charge so as to generate a shock wave; and after that   d) igniting a propellant charge inside a combustion chamber which is fluid-communicated with the opened ignition chamber.       
 
         [0031]    The afore-mentioned method steps preferably will be carried out in the shown order, with the entire process taking few milliseconds. It is a basic idea of the method according to the invention to generate the shock wave first by at least partly burning off the booster charge, with the booster charge having been ignited by the igniter before. Substantially the point in time of triggering the shock wave constitutes a peculiarity of the method according to the invention. Concretely, the shock wave preferably is generated only after the igniter and the booster charge have been ignited but before or simultaneously with the ignition of a propellant charge. 
         [0032]    In a preferred variant, it is concretely provided that the shock wave is generated or will form in the axial longitudinal direction of the hybrid inflator between a first plane delimiting the propellant charge at its end facing the igniter and a second plane delimiting the propellant charge at its end facing away from the igniter or only in the axial longitudinal direction downstream of a propellant charge arranged in the combustion chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    Hereinafter the invention shall be illustrated in detail by way of embodiments with reference to the enclosed schematic Figures, wherein: 
           [0034]      FIG. 1  shows a sectional view across a hybrid inflator according to the invention in accordance with a preferred embodiment, with the first bursting element being arranged between longitudinal ends of a propellant charge; 
           [0035]      FIG. 2  shows a sectional view across a hybrid inflator according to the invention in accordance with another embodiment, with the ignition chamber completely extending through the combustion chamber; 
           [0036]      FIG. 3  shows a sectional view across a hybrid inflator according to the invention in accordance with another preferred embodiment, with the first bursting element being arranged between longitudinal ends of the propellant charge which are formed by propellant rings; and 
           [0037]      FIG. 4  shows a sectional view across a hybrid inflator according to the invention in accordance with another preferred embodiment, with the propellant charge being formed by propellant rings through which the ignition chamber completely extends. 
       
    
    
     DESCRIPTION 
       [0038]    Each of the attached Figures illustrates a sectional view across a hybrid inflator according to the invention, wherein the embodiments according to  FIGS. 1 and 2  differ from the embodiments according to  FIGS. 3 and 4  by the type of the propellant charge  18 . 
         [0039]    In general, the hybrid inflator includes a compressed gas tank  20  which has a substantially tubular shape. The compressed gas tank  20  comprises a crimping  28  serving as a stop for a component delimiting a combustion chamber  16 , especially a combustion chamber base  19  or a deflector  25 . Proximally from the crimping  28  the combustion chamber  16  is disposed. Moreover, in said proximal portion of the compressed gas tank  20  an igniter  10  is positioned. The structure of the igniter  10  and of the compressed gas tank  20  will be described in the following. 
         [0040]    The igniter  10  is held in an igniter support  11  and includes two pins  12 . The pins  12  enable the igniter  10  to be electrically connected to a power source and, respectively, a controller so that the igniter  10  can be electrically triggered. Within the igniter  10  the two pins  12  are coupled to each other via a bridge wire (not shown) which immediately contacts a pyrotechnical charge stored inside the igniter  10 . The pyrotechnical charge is ignited by an electric current pulse causing the bridge wire to glow. The igniter support  11  in this case is a closure member of the hybrid inflator and, respectively, of the compressed gas tank  20  and closes a front end of the tubular compressed gas tank  20  in a gas-tight manner by means of a radially peripheral welding. 
         [0041]    As regards the igniter  10 , a second pyrotechnical igniter charge may be provided in addition to a first pyrotechnical igniter charge. Both of said pyrotechnical igniter charges are located within the igniter  10  which is known to be a separate pre-assembled component. 
         [0042]    in the axial longitudinal direction (A) of the hybrid inflator and, respectively, of the compressed gas tank  20  an ignition chamber  30  is connected to the igniter  10 . The ignition chamber  30  is delimited, on the one hand, by an end face of the igniter  10  and, on the other hand, by a bursting element holder  13  including a first bursting element  14 . inside the ignition chamber  30  a booster charge  15  is arranged. The booster charge  15  may be formed, for example, by granules having a grain size ranging preferably from 400 μm to 2000 μm or by preferably cylindrical pellets ranging in diameter e.g. from 15 mm to 10 mm and a corresponding height ranging e.g. from 0.75 mm to 5 mm. in addition, or as an alternative, also extrudate molds with or without axial through-passages are imaginable as booster charge  15 . In any case, the booster charge  15  comprises a propellant which may be gas-generating at least in part and/or may generate even hot particles in the case of its burn-off. 
         [0043]    The first bursting element  14  which is supported by the bursting element holder  13  is arranged coaxially with respect to the igniter  10 . The first bursting element  14  is welded into the bursting element holder  13  or is connected to the bursting element holder  13  by welding, respectively. 
         [0044]    The first bursting element  14  is preferably designed as a bursting disk. The first bursting element  14  is configured so that if ruptures under pressure and releases an opening so that ignition gas may escape from the ignition chamber  30 . For this purpose, the bursting disk may include appropriate predetermined breaking points in the form of notches or areas of weakened material, for example. 
         [0045]    The first bursting element  14  has the function, inter alia, to separate the ignition chamber  30  from the combustion chamber  16  and, respectively, the compressed gas tank  20  in a fluid-tight or gas-tight manner. In this way, different pressures may be prevailing in the ignition chamber  30  and in the compressed gas tank  20 , it is preferably provided that in the ignition chamber  30  atmospheric pressure is prevailing, whereas in the compressed gas tank  20  and in the combustion chamber  16  pressurized compressed gas is disposed. 
         [0046]    The ignition chamber  30  and, respectively, the bursting element bolder  13  extend into the combustion chamber  16 . The combustion chamber  16  is formed by a tubular portion of the compressed gas tank  20 . Within the combustion chamber  16  a cage  17  is arranged in the embodiments according to  FIGS. 1 and 2 . The cage  17  is substantially ring-shaped or tube-shaped and includes a central through-passage  31 . The ignition chamber  30  extends info the central through-passage  31   
         [0047]    Inside the cage  17  a propellant charge  18  is disposed, in the embodiments according to  FIGS. 1 and 2 , the propellant charge  18  is constituted by a plurality of propellant pellets  18   a.  The propellant pellets are arranged substantially at random inside the cage  17  so that a free volume forms between the propellant pellets  18   a.  Since the combustion chamber  16  is fluid-communicated in total with the compressed gas tank  20 , the free volume between the propellant pellets  18  may accommodate compressed gas disposed in the compressed gas tank  20 . in other words, the propellant pellets  18   a  are surrounded by the compressed gas being retained inside the compressed gas tank  20 . 
         [0048]    It applies to all embodiments illustrated in the drawings that the igniter  10 , the ignition chamber  30  and the bursting element bolder  13 , respectively, and the first bursting element  14  may be arranged substantially coaxially within the compressed gas tank  20 . A second bursting element  24  which is held at the distal end of the compressed gas tank  20  in a further second bursting element holder  23  may be disposed equally coaxially within the compressed gas tank. The second bursting element  24  preferably equally takes the shape of a bursting disk. The second bursting disk may be configured substantially analogously to the first bursting disk. 
         [0049]    The connection between the further second bursting element holder  23  and the compressed gas tank  20  is preferably established by welding. In particular, the further second bursting element holder  23  may be tightly connected to the compressed gas tank  20  by capacitor discharge welding. Proximally with respect to the second bursting element  24 , a filter  29  extends from the further second bursting element holder  23  info the interior of the compressed gas tank  20 . 
         [0050]    Moreover, a diffusor  22  is attached to the distal end of the compressed gas tank  20 , The diffusor  22  may be connected to the compressed gas tank  20  by crimping. The diffusor  22  substantially forms a bulged cap having lateral outlet openings for the compressed gas disposed in the compressed gas tank  20  as well as for the burn-off gas additionally generated by the propellant charge  18 . 
         [0051]    In order to prevent the propellant charge  18  from being inadvertently ignited in the combustion chamber  16  during welding of the further second bursting element holder  23  with the compressed gas tank  20  in the embodiments according to  FIGS. 1 and 3 , a weld-protection cover  21  is provided at the combustion chamber base  19  as spark protection. The weld-protection cover  21  is arranged on the combustion chamber base  19  and covers the through-passage  31 . This prevents sparks during welding of the further second bursting element holder  23  from getting in contact with the propellant charge  18 . 
         [0052]    The weld-protection cover  21  is not constituted by a conventional tamping glued onto the combustion chamber base  19 . Rather, the weld-protection cover  21  is provided to be flexible and/or permeable as regards gas permeability so as to allow for pressure compensation between the pressure tank  20  and the combustion chamber  16 . The weld-protection cover  21  itself may be flexible or may at least be flexibly supported. 
         [0053]    As is evident from the Figures, between the igniter  10  and the first bursting element  14  and, respectively, the first bursting disk the ignition chamber  30  containing the booster charge  15  is arranged. The booster charge  15  may be an ignition mixture of an ignition propellant, for example. A shock wave SW required for opening the second bursting element  24  is triggered by tearing or rupturing the first bursting element  24 . The first bursting element  14  is dimensioned or tailored to the igniter  10  and the booster charge  15  so that the first bursting element  14  ruptures only when both the igniter  10  and the booster charge  15  have been ignited and a corresponding pressure has been built up within the ignition chamber  30 . The shock wave SW may be triggered within the combustion chamber  16 . Especially, the shock wave SW may form between the longitudinal ends of the propellant charge  18 , as it is the case in the embodiments according to  FIGS. 1 and 3 , for example. The ignition chamber  30  extends to no more than approximately half of the propellant charge  18  into the through-passage  31 . In any case, the shock wave SW does not pass through the entire through-passage  31  but forms inside the through-passage  31 . The shock wave SW may form at approximately half the length of the through-passage  31 . 
         [0054]    In the embodiments according to  FIGS. 1 and 3 , the shock wave SW forms in the axial longitudinal direction A of the hybrid inflator between a first plane E 1  delimiting the propellant charge  18  at its end facing the igniter  10  and a second plane E 2  delimiting the propellant change  18  at its end facing away from the igniter  10 . 
         [0055]    In other words, the propellant charge  18  has a beginning viewed from the igniter  10  in the axial longitudinal direction A which is delimited by the first plane E 1  and it has an end which is delimited by the plane E 2 , with the two planes E 1  and E 2  being aligned perpendicularly to the axial longitudinal direction A. In accordance with  FIGS. 1 and 3 , between the beginning and the end of the propellant charge  18  the shock wave SW can be triggered or initiated, preferably only when both the igniter  10  and the booster charge  15  have been ignited before. 
         [0056]    The embodiments according to  FIGS. 2 and 4  differ mainly as to their structural design from the embodiments according to  FIGS. 1 and 3  in that the ignition chamber  30  and the bursting element holder  13 , respectively, completely extend through the through-passage  31  and a deflector  25  is arranged in the area of the crimping  28 . The deflector  25  may be a metal deflector, for example. Preferably the deflector  25  includes a ring-shaped bulge  26  and a through-hole  27 . The ring-shaped bulge  28  extends around the through-hole  27 . In other words, the through-hole  27  is arranged coaxially inside the ring-shaped bulge  26 . The bulge  26  is aligned so that the deflector  25  in total extends convexly in the axial longitudinal direction (A) of the hybrid inflator. The deflector  25  is arranged coaxially with respect to the longitudinal axis of the compressed gas tank  20 . 
         [0057]    In the embodiments according to  FIGS. 2 and 4 , the shock wave SW forms only downstream of the propellant charge  18  or starting from the afore-described second plane E 2  which delimits the propellant charge  18  at its end facing away from the igniter  10 . Concretely, the first bursting element  14  may be arranged in the plane E 2  which may also be understood to be a virtual delimitation for the propellant charge  18 . In other words, the propellant charge  18  and, respectively, the combustion chamber  16  end at said plane E 2  which is aligned perpendicularly to the axial longitudinal direction A of the compressed gas tank  20 . In this way, the shock wave is ensured to form as late as in or from said plane E 2  or in the axial longitudinal direction (A) downstream of said plane E 2 . Accordingly, the shock wave SW preferably will form only when both the igniter  10  and the booster charge  15  have been ignited before. 
         [0058]    The through-hole  27  is provided in order to allow the shock wave passing the deflector  25  unhindered. Preferably the through-hole  27  is dimensioned so that its diameter substantially corresponds to the diameter of the first bursting element  14 . The through-hole  27  in this respect is aligned to be coaxial and parallel to the first bursting disk  14 , After being formed at the end of the propellant charge  18 , the shock wave extends toward the deflector  25 . The shock wave SW passes the deflector  15  through the through-hole  27 . Subsequently the shook wave SW propagates through the compressed gas tank  20 . Then the shock wave SW impinges on the filter  29  and the second bursting element  24  disposed there behind. The increase in pressure caused by the shock wave SW in the area of the second bursting element  24  ensures that the second bursting element  24  ruptures and thus an outlet opening for the compressed gas is released in the compressed gas tank  20 . 
         [0059]    By its ring-shaped bulge  28 , the deflector  25  causes burn-off gas escaping from the ignition chamber  30  after opening of the first bursting element  14  to be deflected along the longitudinal axis and to be returned to the combustion chamber  16 . After deflection by the metal deflector  25  the burn-off gas thus flows through the combustion chamber  16  opposite to the axial longitudinal direction A and ignites the propellant charge  18 . In so far, the propellant charge  18  is arranged coaxially around the ignition chamber  30 . 
         [0060]    It is worth mentioning that the deflector  25  has the ring-shaped bulge  26  in the idle state already. Although additional deformation by the impact of pressure upon activation of the hybrid inflator is not excluded, such additional deformation is not necessary, however, to obtain the desired deflection of the ignition gas. 
         [0061]    The embodiments according to  FIGS. 3 and 4  differ from the embodiments according to  FIGS. 1 and 2  merely by the type of propellant charge. In the embodiments according to  FIGS. 1 and 2 , the propellant charge  18  is constituted by propellant pellets  18   a  which are arranged at random in a cage  17 . In the embodiments according to  FIGS. 3 and 4 , a cage  17  is dispensable as the propellant charge  18  is constituted by propellant rings  18   b.  The propellant rings  18   b  likewise form a through-passage  31  which is defined already by the shaping of the propellant rings  18   b.  The propellant rings  18   b  at least partially surround the ignition chamber  30  and the bursting element holder  13 , respectively. In other words, the bursting element holder  13  and, respectively, the ignition chamber  30  extend through the through-passage  31  which is delimited by an inner circumferential area of the propellant rings  18   b  being stacked along the longitudinal axis and, respectively, arranged adjacent to each other. 
         [0062]    In the embodiments according to  FIGS. 1 and 3 , the shock wave SW is formed inside the combustion chamber  16 , especially inside the through-passage  31 . In any case, in all embodiments the shock wave SW is formed only after, in addition to the igniter  10 , the booster charge  15  has been activated and ignited, respectively. Only the ignition of the booster charge  15  does cause sufficiently high increase in pressure inside the ignition chamber  30  so that the first bursting element  14  ruptures, in the embodiments according to  FIG. 2 and 4 , the shock wave is provided to be triggered only downstream of the propellant charge  18 , especially downstream of the through-passage  31 . 
       LIST OF REFERENCE NUMERALS 
       [0063]      10  igniter 
         [0064]      11  igniter carrier 
         [0065]      12  pin 
         [0066]      13  bursting element holder 
         [0067]      14  first bursting element 
         [0068]      15  booster charge 
         [0069]      16  combustion chamber 
         [0070]      17  cage 
         [0071]      18  propellant charge 
         [0072]      18   a  propellant pellet 
         [0073]      18   b  propellant ring 
         [0074]      19  combustion chamber base 
         [0075]      20  compressed gas tank 
         [0076]      21  weld-protection cover 
         [0077]      22  diffusor 
         [0078]      23  further second bursting element holder 
         [0079]      24  second bursting element 
         [0080]      25  deflector 
         [0081]      28  bulge 
         [0082]      27  through-hole 
         [0083]      28  crimping 
         [0084]      28  filter 
         [0085]      30  ignition chamber 
         [0086]      31  through-passage 
         [0087]    SW shock wave 
         [0088]    A axial longitudinal direction 
         [0089]    E 1  first plane 
         [0090]    E 2  second plane