Patent Publication Number: US-2023146277-A1

Title: Assembly comprising a diffuser and a gas generator, airbag module and method for installing an assembly

Description:
TECHNICAL FIELD 
     The invention relates to an assembly of an elongate inflator and a clamp-type diffusor enclosing an outflow area of the inflator. Further, the invention relates to an airbag module comprising such assembly and to methods for mounting such assembly. 
     BACKGROUND 
     In elongate inflators, also referred to as tubular inflators, the outflow area usually is formed by a plurality of outflow openings distributed over the circumference of an outer housing of the inflator. The outflow openings are frequently provided in a filter housing at an axial end of the inflator. Therefore, the gas flows out of the inflator in the radial direction. In order to keep the inflator thrust-neutral upon activation thereof, the outflow openings frequently are distributed evenly around the circumference. 
     In many airbag modules the inflator is arranged so that its outflow area is located inside the inflatable volume of the airbag. This design is found, for example, in curtain-type side airbags or else in side airbags which are installed in a seat back of a vehicle seat. 
     The airbag must be protected against the gas flow exiting the inflator. To this end, it is known, for example, to provide a specific fabric layer which surrounds the outflow area of the inflator in the circumferential direction and which both protects the airbag fabric and deflects the gas flow in the axial direction. An axially directed outflow offers the advantage that the gas can be better distributed within the airbag. 
     Moreover, it is known to provide a so-called gas lance which, as a main component, includes a tube section open at both ends and which is axially attached to an inflator to transfer the outflowing gas over a distance of several decimeters to an airbag disposed remote from the inflator. Although, in this way, a directed gas flow into the airbag can be generated, it is not possible, however, to dispose the outflow area of the inflator directly inside the airbag, thus inevitably causing the dimension of the airbag module to be increased. 
     SUMMARY 
     It is the object of the invention to provide an option for guiding the gas flowing out of the inflator into the airbag, while the construction dimension is small, the options of adaptation to different geometries are good and the manufacturing costs are low. 
     This object is achieved by an assembly comprising the features of claim  1 . The assembly consists of an elongate inflator having an outer housing with outflow openings distributed along the circumference which define an outflow area and an outflow direction, and of a clamp-type diffusor enclosing the outflow area, with the diffusor including a central receiving opening into which the outer housing of the inflator protrudes so that the diffusor circumferentially encloses an axial portion of the outer housing that comprises the outflow area. On the inner side of the diffusor delimiting the receiving opening, at least one bearing surface and at least one gas guiding surface are provided, the bearing surface bearing directly against the outer housing and the gas guiding surface being radially spaced apart from the outer housing while forming at least one collecting chamber into which gas flowing out of the outflow area is flowing. The collecting chamber opens into at least one outlet opening through which gas exits the diffusor in an outlet direction transversely to the outflow direction from the inflator. 
     The diffusor simultaneously deflects the gas flowing out of the inflator into one or more desired directions and protects the environment against direct contact with the outflowing gas. Since the diffusor directly surrounds the outflow area of the inflator, it can be manufactured to have small dimensions. 
     The diffusor can be easily configured so that substantially the whole gas flowing out of the inflator flows into one or more collecting chambers. 
     Preferably, the diffusor is a formed sheet ring. For example, it may be materialized as a punched and bent part. This manufacturing method permits to easily design the diffusor for different inflator and airbag geometries and to adapt it, for example, to an axial length of the outflow area of the inflator or a diameter of the inflator as well as to predefine the desired number, location, position and/or direction of the outlet openings. Alternatively, the diffusor can be made of a tube element, especially a steel tube. 
     In order to reduce the space required where possible, the diffusor should be designed to be so short in the axial direction that it projects at most insignificantly from the axial end of the inflator and thus the axial length of the assembly corresponds substantially to the axial length of the inflator. 
     The diffusor can extend, in the axial direction, completely over the outflow area of the inflator so that the whole outflowing gas initially flows into the diffusor. 
     In this application, the term of “axial length” or of “axial direction” is always used with reference to the longitudinal axis of the inflator. 
     The outlet direction from the diffusor extends preferably axially with respect to the longitudinal axis of the inflator, viz. in parallel to the longitudinal axis thereof. The gas flowing out of the outflow area of the inflator is deflected especially about 90° transversely to its outflow direction. 
     Of preference, at least two outlet openings which are oppositely directed are provided. In this case, the gas exits the diffusor in two directions being opposed but each facing along the axial direction. This enables the gas to be distributed more quickly inside the airbag and can keep the inflator substantially or even completely thrust-neutral. 
     The volume of the collecting chamber as well as the surface area of the outlet openings can be selected so that substantially no excessive excess pressure vis-à-vis the gas exiting the outflow area is formed in the diffusor. 
     The two outlet openings may be opposed along the axial direction. The surface area of the two outlet openings may be selected to be equal or different in size. In general, the selection of the number, the surface area and the position of the outlet openings is at the discretion of those skilled in the art. 
     Depending on the geometry of the airbag to be filled, also two oppositely directed outlet openings spaced apart from each other in the circumferential direction can be provided, for example. 
     The outlet openings can be easily materialized in the diffusor by the gas guiding surface being located, adjacent to the outlet openings, radially further outward than in the at least one associated collecting chamber remote from the outlet openings. In other words, the collecting chamber widens in the radial direction at the transition to the outlet opening so that, especially in a radial section, the outlet opening occupies a larger surface area than the collecting chamber and the gas can flow out of the diffusor without increased resistance. 
     In the area of the outlet openings, for example, both the gas guiding surface and the contact surface may be spaced radially apart from the outer periphery of the inflator so that an opening penetrating in the axial direction is formed through the entire diffusor and is open at both ends, wherein the two open ends define the outlet openings. 
     Generally, the collecting chamber(s) can be delimited via the bearing surface(s) in the axial direction and/or in the circumferential direction, with an appropriate selection of the extension of the bearing surfaces allowing for any geometry of one or more collecting chambers. Further guiding elements for the outflowing gas are not required. The bearing surfaces basically may be spaced completely apart from each other or else may merge into each other in portions. 
     In one possible embodiment, the diffusor is designed so that at least one collecting chamber is provided which does not continuously extend in the circumferential direction and which opens into at least one outlet opening at its two circumferential ends. The collecting chamber may extend, for example, over an angular portion of from about 200° to 350° and especially from 220° to 270°. 
     Two or more collecting chambers separated from each other in the circumferential direction may be provided, each opening into at least one outlet opening. It is also imaginable that one outlet opening is associated with plural collecting chambers. 
     In another possible embodiment, a collecting chamber is provided that opens into an outlet opening at an axial end. In this case, the gas need not first be guided along the circumferential direction but can be deflected directly in the axial direction by the gas guiding surface. 
     For example, the outlet opening may be formed, for example, by a radial gap between the outer housing and the inner side of the diffusor, which facilitates fabrication of the diffusor. The radial expansion of the diffusor can be delimited, in this configuration, to the radial distance of the gas guiding surface from the outer wall of the inflator. In particular, the outlet opening may be formed between the inner side of the gas guiding surface and the outer contour of the inflator by an axially opened slit. 
     The two afore-described embodiments can also be combined, of course, so that the diffusor includes both at least one collecting chamber opening into an outlet opening in the circumferential direction and at least one collecting chamber opening into an outlet opening in the axial direction. 
     The at least one bearing surface can be used to divide the gas flow exiting the inflator into at least two partial flows. The extension of the bearing surface can help easily define the number of the outflow openings of the inflator located beneath the gas guiding surface which in turn determine the proportion of the entire filling gas arriving at the respective partial flow and being guided via the respective gas guiding surface to one of the outlet openings. Preferably, the individual partial flows are guided into different collecting chambers and, from there, to different outlet openings. 
     In one possible embodiment, the bearing surface only extends in the circumferential direction around the outer housing. 
     In another possible embodiment, the bearing surface extends helically around the outer housing. 
     One form of the bearing surface which is especially simple to configure and by which partial gas flows with different gas quantities can be produced provides that, with a bearing surface peripheral around the entire circumference of the inflator, two first portions extending only in the circumferential direction and two second portions extending inclined to the circumferential direction and to the axial direction are provided, the second portions joining the first portions. Preferably, the bearing surface separates two collecting chambers separated in the axial direction and each having at least one separate outlet opening. The selection of the length and the inclination of the second portions extending inclined to the axial direction determines the number of the outflow openings which supply the respective partial gas flow with gas. 
     In another embodiment, plural outlet openings can be arranged to be circumferentially distributed. Preferably, the outlet openings are separated by separation webs which at least partially form the bearing surfaces of the diffusor delimiting the collecting chamber in the axial direction. Those outlet openings arranged to be circumferentially distributed which interrupt the bearing surface distributed over the circumference are arranged especially on the front side of the diffusor and thus, in the mounted state of the diffusor, toward a longitudinal end of the inflator. 
     The diffusor of the assembly may comprise at least one detent element for being attached and fastened to the inflator. Preferably, the diffusor in such embodiment comprises two or more detent elements. The detent element is configured to engage in a bead for fastening and fixing the diffusor on the inflator. By locking, the diffusor is fixed on the inflator via a positive connection. The detent elements help fasten the diffusor to the inflator in a simple manner. In addition, it is still possible to additionally fasten the diffusor to the inflator by pressing or welding. 
     In one embodiment, the detent element is disposed in connection to a bearing surface of the diffusor. Such diffusor having one or more detent elements may preferably be made from spring steel, especially an austempered spring steel. 
     Usually, the outflow area is provided at an axial end of the inflator so that also the diffusor is disposed at an axial end of the inflator. 
     In one embodiment of the assembly, the outflow area of the inflator may be divided into at least two zones which are separated from each other by a separation area of the outer housing without outflow openings. The zones including the outflow openings are preferably configured as axial zones each having circumferentially distributed outflow openings. 
     In a typical embodiment, in the assembly a bearing surface of the diffusor is positioned in the separation area between the zones. The bearing surface positioned in the separation area divides the gas exiting the two zones into two separate partial gas flows. Preferably, the diffusor accordingly has two collecting chambers which are arranged adjacent to the bearing surface positioned in the separation area, and one collecting chamber at a time collects the gas exiting one of the two zones. 
     The collecting chamber at the rear in the axial direction in such embodiment has an outlet opening, for example, that is formed by an open portion in a rearward facing sidewall of the diffusor. A partial gas flow can exit said outlet opening in an outlet direction facing away from the longitudinal end of the inflator. 
     The collecting chamber at the front in the axial direction in such embodiment has a circumferentially peripheral outlet opening in the form of a radial gap, for example. A partial gas flow can exit said outlet opening in the opposite direction vis-à-vis the partial gas flow exiting the rear collecting chamber. 
     The zones of the outflow area of the inflator may exhibit a symmetric spreading of the outflow openings. In this way, the assembly can be designed to be thrust-neutral with respect to the gas flowing out of the inflator so that 50% of the gas exit through the outlet opening of the collecting chamber at the front in the axial direction and 50% of the gas exit through the outlet opening of the collecting chamber at the rear in the axial direction. 
     Alternatively, the zones of the outflow area of the inflator may also have a non-symmetric distribution of the outflow openings, thus causing an uneven distribution of the gas flow. By such proportionally uneven distribution of the gas flow, a substantially even filling of differently large airbag chambers disposed at the front and rear sides can be achieved, for example. 
     A substantial advantage of such assembly resides in the fact that the diffusor can be designed as a standard component and the percentage of gas distribution can be easily adapted by adapting the number of the outflow openings associated with the respective zones in the outflow area of the inflator. 
     The above-mentioned object is also achieved by an airbag module comprising an airbag and an afore-described assembly in which the diffusor is completely arranged in an inflatable inner volume of the airbag. 
     In this case, it is not necessary to seal the bearing surfaces completely against the outer surface of the inflator, as possible leakage flows exit inside the airbag and thus cannot reach the environment. Therefore, complex seals can be dispensed with, which further reduces the manufacturing costs. 
     For mounting an afore-mentioned assembly, a method comprising the following steps is provided. A one-piece diffusor blank is fabricated of sheet metal in a punching and bending process, with all bearing surfaces and all gas guiding surfaces being pre-formed. The diffusor blank is bent about the outflow area of the inflator, wherein it adopts the final shape of the diffusor. Finally, the diffusor blank in portions is fixed to itself so as to circumferentially close the same, with its clamp shape being imparted to the diffusor. 
     Preferably, the diffusor blank is pre-tensioned in the last step and is then welded to itself. For this purpose, e.g., a laser welding process can be applied. 
     The fixation advantageously takes place at an area where the edge portions of the diffusor blank are superimposed. 
     As an alternative, for mounting an above-mentioned assembly, a method comprising the following steps can be provided. A one-piece diffusor is fabricated of a tube element or of a sheet metal, with all bearing surfaces and all gas guiding surfaces being pre-formed. The diffusor pre-fabricated in this way is slipped onto the outflow area of the inflator. For fastening the diffusor to the inflator, a bearing surface of the diffusor is plastically deformed in the area of a bead of the inflator so that the bearing surface engages at least partially or in portions along the periphery in the bead and a positive connection is established. The plastic deformation of the bearing surface in the area of the bead preferably can be produced by a pressing tool. 
     In another alternative method for mounting the assembly, the following steps can be provided. A one-piece diffusor is fabricated of a closed tube element or of a sheet metal, with all bearing surfaces, all gas guiding surfaces and all detent elements being pre-formed. The diffusor is slipped onto the outflow area of the inflator so that the detent elements engage at least in portions along the circumference in the bead and a positive locking is formed. When the diffusor is slipped on, the bearing surfaces with adjacent detent elements are bending radially outward. Upon reaching the beads of the inflator, the detent elements engage in the beads of the inflator so that the positive locking/latching of the diffusor on the inflator can be achieved. 
     Is not required to directly fasten the diffusor on the outer wall of the inflator by any means other than by clamping and/or pressing, and thus this is usually not intended but nevertheless possible. 
     This type of fabrication renders the use of a diffusor according to the invention independent of the outer contour of the inflator along the longitudinal axis thereof. 
     The material preferably used is a sheet steel or a steel tube. Especially in a diffusor comprising a detent element, additionally a spring steel, especially an austempered spring steel, can be used. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In the following, the invention will be illustrated in detail by way of plural embodiments and with reference to the attached drawings, wherein: 
         FIG.  1    shows a schematic perspective view of a longitudinal end of an inflator of an assembly according to the invention; 
         FIG.  2    shows a schematic perspective view of an assembly of an inflator and a diffusor according to the invention as set forth in a first embodiment; 
         FIG.  3    shows the diffusor from  FIG.  2    in a front view; 
         FIG.  4    shows an airbag module according to the invention including an assembly from  FIG.  2    in a longitudinal sectional view; 
         FIG.  5    shows a schematic perspective view of an assembly of an inflator and a diffusor according to the invention as set forth in a second embodiment; 
         FIG.  6    shows a schematic perspective view of the diffusor from  FIG.  5   ; 
         FIG.  7    shows a schematic perspective view of an assembly of an inflator and a diffusor according to the invention as set forth in a third embodiment; 
         FIG.  8    shows the diffusor from  FIG.  7    in a rear view; 
         FIG.  9    shows a schematic perspective view of a longitudinal end of an inflator of an assembly according to the invention; 
         FIG.  10    shows a schematic perspective view of an assembly of an inflator and a diffusor according to the invention as set forth in a fourth embodiment; 
         FIG.  11    shows a schematic longitudinal sectional view of the assembly from  FIG.  10   ; 
         FIGS.  12     a ) to  c ) show schematic views of different embodiments of a longitudinal end of an inflator of an assembly according to the invention; 
         FIGS.  13     a ) to  c ) show partly cut views of an assembly of an inflator with a diffusor according to the invention as set forth in a fifth embodiment; 
         FIG.  14    shows a schematic perspective view of the diffusor from  FIG.  13   ; 
         FIG.  15    shows a schematic perspective view of an assembly of an inflator and a diffusor according to the invention as set forth in a sixth embodiment; 
         FIG.  16    shows a schematic perspective view of an assembly of an inflator and a diffusor according to the invention as set forth in a seventh embodiment; 
         FIGS.  17     a ) and  b ) show enlarged partial views onto a front longitudinal end of the inflator with the diffusor according to  FIG.  16    in perspective a) rear and b) front views; 
         FIG.  18    shows the diffusor from  FIG.  16    in a perspective front view; 
         FIG.  19    shows a first schematic longitudinal section of the assembly from  FIG.  16   ; 
         FIG.  20    shows a second schematic longitudinal section of the assembly from  FIG.  16    during a mounting step of the diffusor; and 
         FIG.  21    shows the second schematic longitudinal section of the assembly from  FIG.  16    after completion of the mounting of the diffusor. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates an elongate inflator  10  that includes, at a longitudinal end  12  of its outer housing  14 , an outflow area  16  with a plurality of individual outflow openings  18  distributed over the circumference. The outflow openings  18  in this case are formed in a filter housing of the inflator  10  which is part of the outer housing  14  of the inflator  10 . 
     The outflow openings  18  are evenly distributed along the circumferential direction U in this case. At a cap sealing the longitudinal end  12  no outflow openings  18  are provided. When the inflator  10  is activated, the whole gas generated flows off through the outflow openings  18  of the outflow area  16  in an outflow direction R GG  extending in the radial direction r. 
     In the first embodiment of an assembly  20  illustrated in  FIG.  2   , the outflow area  16  of the inflator  10  is surrounded by a clamp-type diffusor  22  in the circumferential direction U. 
     The diffusor  22  includes a central receiving opening  24  (see  FIG.  3   ) into which and, in the shown case, also through which the outer housing  14  of the inflator  10  protrudes. In this embodiment, the longitudinal end  12  of the inflator  10 , more exactly speaking the cap thereof having no outflow openings, extends in the axial direction A (along the longitudinal axis of the inflator  10 ) a short distance beyond the diffusor  22 . This is also visible in  FIG.  4   . 
     Along the axial direction A, the diffusor  22  extends merely over a portion  26  that comprises the outflow area  16  and is only slightly wider than the outflow area  16  (see e.g.,  FIG.  4   ). 
     A gas guiding surface  30  extending over a large portion of the circumference of the outflow area  16 , here over about 225°, is formed on the inner side  28  of the receiving opening  24  of the diffusor  22 . 
     The gas guiding surface  30  is spaced apart from the outer housing  14  and the outflow openings  18  in the radial direction r so that gas exiting the outflow openings  18  flows into the clearance between the outer housing  14  of the inflator  10  and the gas guiding surface  30 , when the inflator  10  is activated. The space between the gas guiding surface  30  and the outer housing  14  thus forms a collecting chamber  32  for the gas flowing out of the inflator  10 . 
     The collecting chamber  32  is delimited, in the axial direction A, by two bearing surfaces  34  that bear directly against the outer housing  14  of the inflator  10 . In this example, both bearing surfaces  34  extend over the entire circumference of the inflator  10  so that the collecting chamber  32  is sealed in the axial direction A by the two bearing surfaces  34 . 
     The bearing surfaces  34  also provide for a connection of the diffusor  22  to the inflator  10 . Being under mechanical stress, they bear against the outer housing  14  of the inflator  10  and retain the diffusor  22  on the outer housing  14  via a clamping force. 
     The diffusor  22  has plural outlet openings  36  which are fluid-communicated with the collecting chamber  32  and out of which the gas flowing out of the inflator  10  exits the diffusor  22  and thus the assembly  20 . 
     The collecting chamber  32  at each of its two peripheral ends  47  opens into two outlet openings  36  opposed in the axial direction A. In the examples shown here, the surface of each of the outlet openings  36  is perpendicular to the axial direction A so that the gas exits the assembly  20  in an outlet direction RD along the axial direction A. 
     In this embodiment, a total of four outlet openings  36  are provided two of which are directed in opposite directions so that the gas flows out along the axial direction A in two opposite outlet directions R D . Opposite to the outflow direction R GG , the outflowing gas is deflected, in this example, about 90° from the radial direction r to the axial direction A. 
     In this example, the surface area of all outlet openings  36  is selected to be equal. Thus, the assembly  20  is thrust-neutral with respect to the gas flowing out of the inflator  10 . The surface area of the outlet openings  36  opposite in the axial direction A alternatively may also be selected to have a different size so that an uneven gas distribution is achieved (not shown). 
     The outlet openings  36  in this embodiment are formed by the gas guiding surface  30  in an outlet area  38  having a larger distance in the radial direction r from the outer housing  14  of the inflator  10  than in the area of the collecting chamber  32 . In the outlet area  38 , a sidewall  40  connecting the gas guiding surface  30  and the adjacent bearing surface  34  is interrupted so that the outlet opening  36  is formed. 
     In this embodiment, the outlet openings  36  are arranged symmetrically relative to each other in both opposite sidewalls  40 . 
     Here, two outlet areas  38  spatially separated from each other and each having two opposite outlet openings  36  are provided which are spaced along the circumferential direction by about 90° (see  FIGS.  2  and  3   ). 
     Optionally, between said two outlet areas  38  another small collecting chamber  32  is formed, but it is also possible that the gas guiding surface  30  there substantially bears against the outer housing  14  of the inflator  10  and covers some of the outflow openings  18 , where appropriate. 
     When the assembly  20  is installed in an airbag module, the inflator  10  is inserted into an airbag  42  so far that the longitudinal end  12  of the inflator  10  including the outflow area  16  and the diffusor  22  is completely located inside an inflatable inner volume  44  of the airbag  42 . This is indicated in  FIG.  4   . 
     Therefore, it is not necessary for the bearing surfaces  34  to seal the collecting chamber  32  gas-tightly to the outside, as the whole gas flowing out of the inflator  10  is released inside the airbag  42 . Therefore, small leakage flows can be accepted. 
     The diffusor  22  is manufactured by forming a sheet strip, for example made of sheet steel, into a diffusor blank in a punching and bending process (not shown). In this work step, all gas guiding surfaces  30  and bearing surfaces  34  are pre-formed. Said diffusor blank is bent, in another forming step, around the outflow area  16  of the inflator  10  in the circumferential direction U, wherein the bearing surfaces  34  come into bearing contact with the outer housing  14  of the inflator  10  and also the gas guiding surfaces  30  adopt their final positions so that the desired collecting chamber(s)  32  is/are formed between the gas guiding surfaces  30  and the outer housing  14 . 
     In an overlapping portion  46  (see  FIGS.  5  and  6   ), portions of the diffusor blank are superimposed in the radial direction r and are in contact with each other. In said overlapping portion  46 , the diffusor blank is fastened to itself, for example by a suitable welding process such as laser welding. The resulting weld  48  clamps the finished diffusor  22  to the inflator  10  under mechanical pretension. The diffusor blank is attached merely to itself by a material bond, but not to the inflator  10  by a material bond. 
     In addition, the diffusor  22  can be fastened to the inflator  10  by a suitable joining process such as crimping. For this purpose, the inflator  10  may include a bead  60  (see  FIG.  4   ). For connecting the diffusor  22  to the inflator  10 , the bearing surface  34  of the diffusor is plastically deformed in the region of the bead  60  so that at least portions of the bearing surface engage in the bead  60  along the circumference and a positive locking  62  is formed (see  FIG.  6   ). 
     Alternatively, the diffusor  22  may be completely pre-formed already before it is applied to the outflow area  16 . Such diffusor  22  can equally be manufactured of a sheet strip by a punching and bending process or of a tube element such as a steel tube. Preferably, such diffusor  22  is fastened onto the inflator  10 , as afore-described, by a suitable joining process such as through a pressing tool. 
       FIGS.  5  and  6    illustrate an assembly  20  according to a second embodiment. Since the individual elements only differ by their shape and position rather than by their function, the already introduced reference numerals shall be maintained. 
     In the second embodiment, the diffusor  22  is configured so that two collecting chambers  32  are formed which are spaced apart from each other along the circumferential direction U and each of which opens into a separate outlet area  38 . Each of the outlet areas has two outlet openings  36  which are arranged at opposed axial ends of the diffusor  22  and the surface of which is directed in opposite directions along the axial direction A. Along the axial direction A, the outlet area  38  is continuous and the collecting chamber  32  opens centrally into the outlet area  38 . In the circumferential direction U between the two collecting chambers  32  and between the two outlet areas  38 , the bearing surface  34  bears directly against the outer housing  14  of the inflator  10 . 
     The overlapping portion  46  in this example extends in the region of the two outlet areas  38  so that the sheet metal from which the diffusor  22  is made in this portion is double-layered and is fixed to each other at an appropriate position, here indicated by the weld  48 . 
     In this embodiment, too, the gas exiting the outflow area  16  of the inflator  10  in the radial direction r is initially deflected by the gas guiding surface  30  about 90° into the collecting chambers  20 , in the latter is guided to the outlet areas  38  where it is deflected about 90° again and is divided into two partial gas flows which, in the shown embodiment, exit the diffusor  22  substantially in equal intensity in opposite directions along the axial direction A. The gas volume in the individual partial gas flows is defined by the number of the outflow openings  18  in the region of the individual collecting chambers  32 . 
     The number, the arrangement, the shape and the size of the individual collecting chambers  32 , outlet areas  38  and outlet openings  36  are at the discretion of those skilled in the art, of course, and may be adapted for the respective inflator  10  and the respective application. In particular, the number, the arrangement, the shape and the size of the individual collecting chambers  32 , outlet areas  38  and outlet openings  36  may also be configured so that an uneven gas distribution is effectuated. 
       FIGS.  7  and  8    illustrate a third embodiment of an assembly  20 . In contrast to the just described embodiment, in the overlapping portion  46  the diffusor blank is not superimposed in the radial direction r, but two portions of the diffusor blank abut against each other along the circumferential direction U and are adjacent each other along the axial direction A and along the radial direction r. As afore-described, the diffusor blank in this portion is fixed to itself, shown here by a weld  48 . 
     It is another difference from the just described embodiment that a total of three collecting chambers  32   a,    32   b  are provided each of which opens into one single outlet opening  36   a,    36   b.    FIG.  7    shows the diffusor  22  in a front view from the longitudinal end  12  of the inflator  10 , whereas  FIG.  8    illustrates the diffusor  22  in a rear view. 
     Two first collecting chambers  32   a  are spaced apart from each other in the circumferential direction U and are shaped mirror-inverted with respect to a diameter of the inflator  10 . The gas guiding surface  30  in said two first collecting chambers  32   a  is shaped such that a respective rearward directed outlet opening  36   a  is formed. 
     The third collecting chamber  32   b  is located along the circumferential direction U between the two first described collecting chambers  32   a.  It has one single outlet opening  36   b  formed by a radial gap  50  between the diffusor  22  and the outer housing  14  of the inflator  10  and thus equally orientated with its surface area perpendicularly to the axial direction A so that gas flows out in an outlet direction R D  in parallel to the axial direction A, however directed forward and thus opposed to the gas exiting the outlet openings  36   a.    
     The outlet opening  36   b  is located at an axial end  51  of the second collecting chamber  32   b.    
     Just as in the other embodiments, the surfaces of the individual outlet openings  36   a,    36   b,  optionally  36 , as well as the size of the collecting chambers  32   a,    32   b , optionally  32 , are selected such that the assembly  20  is substantially thrust-neutral. 
     Alternatively, also in this case an uneven gas distribution is possible by adapting the surface areas of the individual outlet openings  36   a,    36   b  as well as the size of the collecting chambers  32   a,    32   b,  the size of the collecting chambers  32   a,    32   b  being adaptable especially by the location of the separation web  33  formed by the bearing surface  34 . Such proportionally uneven division of the gas flow can help obtain, for example, a substantially even filling of differently large airbag chambers disposed on the front and rear sides. 
     At the rear axial end of the diffusor  22 , a bearing surface  34  extends over the entire circumference of the inflator  10 . A bearing surface  34  at the front axial end of the diffusor  22  is interrupted in the area of the second collecting chamber  32   b.  This portion forms the radial gap  50 . 
     In general, here the longitudinal end  12  is considered to be the front end of the inflator  10 . Terms such as “front” and “rear” relate to this orientation. 
       FIGS.  10  and  11    show an assembly  20  according to a fourth embodiment. 
     This diffusor geometry, too, can be manufactured from a strip-shaped sheet or a tube element, such as by a punching and bending process. Alternatively, the diffusor can also be manufactured as a helically welded, seamlessly drawn or sheet-drawn component. 
     In this case, especially an inflator  10  as shown in  FIG.  9    can be used. The only difference from the inflator shown in  FIG.  1    resides in the fact that in the axial direction A the outflow area  16  is divided into two axial zones  52 ,  54  separated from each other by a separation area of the outer housing  14  formed as a strip and having no outflow openings  18 . Accordingly, especially for an uneven gas distribution, the zones  52  and  54  may be provided to exhibit a non-symmetric spreading of the outflow openings  18 . 
     The diffusor  22  of this embodiment has a central bearing surface  34   a  positioned in the separation area between the two zones  52 ,  54 . Thus, the central bearing surface  34   a  divides the gas exiting the two zones  52 ,  54  into two separate partial gas flows. 
     The diffusor has two collecting chambers that are arranged along the axial direction A adjacent to the bearing surface  34 . In line with the just described embodiment, the reference numerals  32   a,    32   b  are used for said collecting chambers. 
     Each of the collecting chambers  32   a,    32   b  collects the gas exiting one of the zones  52 ,  54 . 
     The rear collecting chamber  32   a  in this example includes one single outlet opening  36   a  which is formed by an open portion of a rearward facing sidewall  40  and from which a partial gas flow exits directed in an outlet direction R D  away from the longitudinal end  12  of the inflator  10 . 
     The front collecting chamber  32   b  in this example includes a circumferentially peripheral outlet opening  36   b  in the form of a radial gap  50  from which a partial gas flow exits in the opposite direction. This geometry is clearly visible in  FIG.  11   . 
     Each of the  FIGS.  12     a ) to  12   c ) illustrates the outer housing  14  of an inflator  10  in which in the axial direction A the outflow area  16  is divided into two axial zones  52 ,  54  separated from each other by a strip-shaped separation area  68  of the outer housing  14  without outflow openings  18 . 
     In each of the  FIGS.  12     a ) and  12   b ), an outer housing  14  of the inflator  10  is illustrated which is provided for an uneven gas distribution, wherein, for this purpose, the zones  52  and  54  show a non-symmetric spreading of the outflow openings  18 . In  FIG.  12     a ), the outflow openings  18  are distributed to the zones  52  and  54  such that about two thirds of the gas flow exit in the area of the zone  52  and about one third of the gas flow exits in the zone  54 . In  FIG.  12     b ), the outflow openings  18  are distributed to the zones  52  and  54  such that about one third of the gas flow exits in the area of the zone  52  and about two thirds of the gas flow exit in the zone  54 . 
     In  FIG.  12     c ), an outer housing  14  of the inflator  10  is illustrated which is provided for an even gas distribution, wherein, for this purpose, the zones  52  and  54  show a symmetric spreading of the outflow openings  18  so that about half of the gas flow exits in each of the zone  52  and the zone  54 . 
     a. As a matter of course, those skilled in the art can also produce other percentage ratios of the gas flow division by a spreading of the outflow openings  18  to the zones  52  and  54  adapted to the intended application of the assembly  20 . 
     Each of the  FIGS.  13     a ) to  13   c ) illustrates an assembly according to a fifth embodiment, wherein in the outer housing  14  of the inflator  10  of the assembly  20 , the outflow area  16  is divided in the axial direction A into two respective axial zones  52 ,  54  which are separated from each other by a strip-shaped separation area  68  of the outer housing  14  without outflow openings  18 . 
     Also, the diffusor  22  of this embodiment (see  FIG.  14   ) includes a central bearing surface  34   a  which is positioned in the separation area  68  between the two zones  52 ,  54 . The diffusor  22  has two collecting chambers  32   a  and  32   b  which are arranged along the axial direction A adjacent to the bearing surface  34   a.  Each of the collecting chambers  32   a,    32   b  collects the gas exiting one of the zones  52 ,  54 . Thus, the central bearing surface  34   a  divides the gas exiting the two zones  52 ,  54  into two separate partial gas flows. 
     In  FIG.  13     a ), the outflow openings  18  are distributed to the zones  52  and  54  in such a manner that, in the area of the zone  52 , about two thirds of the gas flow exit into the collecting chamber  32   b  and, in the zone  54 , about one third of the gas flow exits into the collecting chamber  32   a.  In  FIG.  13     b ), the outflow openings  18  are distributed to the zones  52  and  54  in such a manner that, in the area of the zone  52 , about one third of the gas flow exits into the collecting chamber  32   b  and, in the zone  54 , about two thirds of the gas flow exit into the collecting chamber  32   a.  In  FIG.  13     c ), the outflow openings  18  are spread symmetrically/evenly to the zones  52  and  54  so that about half of the gas flow exits in the zone  52  into the collecting chamber  32   b  and about half of the gas flow exits in the zone  54  into the collecting chamber  32   a.    
     The rear collecting chamber  32   a  in this example includes one single outlet opening  36   a  from which a partial gas flow exits in an outlet direction R D  directed away from the longitudinal end  12  of the inflator  10 . The front collecting chamber  32   a  in this example includes an outlet opening  36   b  in the form of a radial gap  50  from which a partial gas flow exits in the opposite direction. The gap  50  is interrupted, as is evident from  FIGS.  13     a ) to  13   c ), in the shown example in the circumferential direction by the bearing surface  34  at the longitudinal end  12 . 
     This diffusor geometry, too, can be manufactured from a strip-shaped sheet or a tube element, for example by a punching and bending process. Alternatively, also this diffusor may be manufactured as a helically welded, seamlessly drawn or sheet-drawn component. 
     It is the advantage of such assembly  20  according to the fifth embodiment that the diffusor  22  can be designed as a standard component: An adaptation of the percentage gas distribution that is especially dependent on the intended application of the assembly  20  can be caused by an adaptation of the outer housing  14  in a simple and inexpensive way. The adaptation of the outer housing  14  preferably takes place by an adaptation of the number of the outflow openings  18  associated with the respective zones  52  and  54  in the outflow area  16  of the outer housing  14  of the inflator  10 . 
       FIG.  15    illustrates a sixth embodiment of an assembly  20 . In contrast to the just described embodiment, the central bearing surface  34   a  is helical so that the axial width of the two collecting chambers  32   a,    32   b  varies along the circumferential direction U. 
     The helical shape of the central bearing surface  34  is obtained by said bearing surface  34   a  including two first portions  56  which extend only along the circumferential direction U and which are arranged offset against each other along the axial direction A, as well as two second portions  58  which extend inclined with respect to the axial direction A and the circumferential direction U and which interconnect the first portions  56 . This design helps define the size of the individual collecting chambers  32   a,    32   b  that determine the intensity of the individual partial gas flows. This geometry can be employed both with an inflator according to  FIG.  1    and with an inflator according to  FIG.  9   . 
     In this embodiment, too, the rear collecting chamber  32   a  has a rearward directed outlet opening  36   a,  whereas the front collecting chamber  32   b  includes a forward directed outlet opening  36   b  which is peripheral about the inflator  10  in the form of a radial gap at the front axial end  51  of the collecting chamber  32   b  in the circumferential direction U. 
       FIGS.  16  to  21    illustrate an assembly  20  according to a seventh embodiment.  FIG.  16    illustrates an inflator according to  FIG.  1    to the longitudinal end  12  of which a self-locking diffusor  22  is attached. Similar to the first embodiment, the longitudinal end  12  of the inflator  10 , more exactly speaking the cap thereof having no outflow openings, extends even in said sixth embodiment a short distance beyond the diffusor  22  in the axial direction A. This is clearly evident especially in  FIGS.  17 ,  19  and  21   . 
     The self-locking diffusor  22  is preferably made from spring steel. In the shown embodiment, the gas guiding surface  30  extends over the entire circumference. On the front side, the diffusor  22  has plural outlet openings  36   b  evenly spread over the circumference U here. The outlet openings  36   b  are separated by separation webs  33 ′ which moreover form the front bearing surfaces  34  (see  FIGS.  17   b    and  18 ). 
     On the rear side, in the shown embodiment, the diffusor  22  includes an outlet opening  36   a  that is formed by an opening in portions in the rear area of the gas guiding surface  30  (see  FIGS.  17   a    and  19 ). In the shown embodiment, an optional guiding element  64  is connected to the bearing surface  34  arranged in the area of the outlet opening  36   a.  Such guiding element  64  helps deflect the outlet direction RD of the gas into an outlet direction RD&#39; (see  FIG.  19   ). 
     The rear bearing surface  34  of the diffusor is divided, in the circumferential direction U, into plural portions by separating recesses  66 . In the embodiment according to  FIGS.  16  to  21   , the rear bearing surface  64  comprises four portions. Detent elements  62  that engage in the bead  60  of the inflator  10  in a mounted state of the diffusor  22  are connected to two of said portions of the bearing surface  34  which in this case are arranged adjacent to the portion of the bearing surface  34  in the area of the outlet opening  36   a.    
       FIGS.  20  and  21    illustrate a longitudinal section across the assembly  20  in an x-z plane at different times of the mounting of the diffusor  22  and the inflator  10 . 
       FIG.  20    illustrates the assembly  20 , while the diffusor  20  is slipped onto the inflator  22 . The bearing surfaces  34  including the detent elements  62  are bent outward in the radial direction r when the diffusor  22  is slipped on. Said bending-open of the detent elements  62  is enabled especially by separating recesses  66  in the area of the rear bearing surface  34 . 
       FIG.  21    illustrates the assembly  20  when the mounting is completed. Accordingly, it is clearly evident that the detent elements  62  are engaged in the bead  60  of the inflator  10  and the diffusor  22  is thus locked to the inflator  10  in a simple manner. For fixing the diffusor  22  to the inflator  10 , moreover the separation webs  33 ′ forming the front bearing surfaces  34  may be configured to be bent at least slightly outward equally in the radial direction r when the diffusor is mounted. Thus, the separation webs  33 ′ help generate, due to the inherent tension of the material in the mounted state, a pressing force directed to the central axis of the inflator  10  in the area of the front bearing surfaces  34 . As a matter of course, the diffusor  22  can be additionally fixed to the inflator  10 , apart from self-locking, by pressing or welding, for example. 
     All features of the individual embodiments can be combined with each other or exchanged for each other at the discretion of those skilled in the art, of course, with the desired application and the geometry of the inflator used having to be considered when selecting the shape of the diffusor.