Abstract:
A side airbag unit for a vehicle seat including a generally cylindrical gas generator unit having a longitudinal axis. The vehicle seat has a backrest with a front surface and a side surface. In order to achieve the result that the airbag requires little additional space and nevertheless is relatively easy to mount on the vehicle seat, the longitudinal axis extends generally parallel to the front surface and perpendicular to the side surface of the vehicle seat.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German patent application serial number 20 2004 009 002.3, filed Jun. 8, 2004 and PCT/EP2005/005975, filed Jun. 3, 2005. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to motor vehicle safety devices. More particularly, it relates to a vehicle seat including a side impact airbag unit. 
         [0004]    2. Description of Related Art 
         [0005]    Vehicle seats with side airbag units are known to protect vehicle occupants in case of a side collision. In these, the side airbag unit, mainly consisting of an airbag and a gas generator, is located in the area of the side surface of a backrest of the vehicle seat. The airbag inflates between the occupant and an inner structure of the vehicle in case of need. The gas generator is attached to the frame of the vehicle seat by means of a retaining element, whereby the longitudinal axis of the gas generator, which is generally of cylindrical form, extends substantially vertically and parallel to the side surface of the seat. Within this arrangement, the gas generator is basically completely surrounded by the airbag, which allows rapid filling of the airbag. Although this arrangement of the airbag is relatively simple, it has the disadvantage that additional space is needed outside the frame of the seat, which is often not available, particularly in the case of sports cars, roadsters and cabriolets. 
         [0006]    One known solution is to provide a vehicle seat in which a gas generator is accommodated inside a hollow tube of the frame of the seat. However, while such a solution is very space-saving, it is also very complicated. 
         [0007]    The object of the present invention is to improve a vehicle seat unit in such a way that the side airbag unit only needs a little additional space and nevertheless can be easily mounted on the vehicle seat. 
       SUMMARY OF THE INVENTION 
       [0008]    The solution according to the present invention is based on a different installation geometry of the gas generator. The longitudinal axis of a basically cylindrical gas generator basically runs horizontally and perpendicular to the side surface of the vehicle seat, so that the gas generator can extend wholly or partially into a backrest of the seat in a horizontal axial direction. This results in the desired saving of space. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Preferred embodiments of the invention are described below with reference to the drawings. The drawings are as follows: 
           [0010]      FIG. 1  is a side view of a backrest of a motor vehicle seat; 
           [0011]      FIG. 2  is a top view of a part of the backrest along section line A-A of  FIG. 1 ; 
           [0012]      FIG. 3  is a top view of a second embodiment of the backrest along section line A-A of  FIG. 1 ; 
           [0013]      FIG. 4  is a perspective view of a gas generator unit mounted on a mounting plate; 
           [0014]      FIG. 5  is a top view of a sleeve for the gas generator; and 
           [0015]      FIG. 6  is a longitudinal section through the sleeve of  FIG. 5 , showing the gas generator located inside the sleeve. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  shows a vertical section through a backrest  10  of a vehicle seat assembly. A cylindrical gas generator  30  is accommodated in backrest  10 , whose longitudinal axis extends horizontally and parallel to a front surface  12  of backrest  10 . Gas generator  30  is surrounded concentrically by sleeve  34 , whereby an annular gap  35  is present in a front area between gas generator  30  and sleeve  34 . In case of activation, gas streams from gas outlet openings of the gas generator through that annular gap into the airbag, as can clearly be seen from  FIG. 2 . 
         [0017]      FIG. 2  shows a section through the backrest of  FIG. 1  along section line A-A. As already mentioned, gas generator  30  and sleeve  34 , which surrounds said gas generator  30 , extends into the seat. A longitudinal axis L-L of gas generator  30  and sleeve  34  stands parallel to front surface  12  and basically perpendicular to a side surface  14  of backrest  10 . Sleeve  34  is attached, for example, by primping tightly with gas generator  30 , so that sleeve  34  also has the function of securing the gas generator  30  in addition to its function of guiding the gas. This means that sleeve  34  fulfils a double task. In this embodiment, sleeve  34  is attached to an angled mounting plate  36 , which in turn is attached to a frame  16  of the backrest.  FIG. 4  shows the angled mounting plate  36 , sleeve  34  and the rear end of gas generator  30 . For this purpose, sleeve  34  widens at its front end to a flange  34   a,  which lies in a plane which is perpendicular to the longitudinal axis of the gas generator. 
         [0018]    In front of gas generator  30 , airbag  40 , accommodated within an envelope  42 , is located in a hollow space  22  of a side bolster  18 . When the gas streams in, envelope  42  opens because of the expanding airbag  40 , for example, at a set break point (not shown). The airbag then exits from the seat and unfolds between the inner structure of the vehicle and the occupant. A cover  20  of the backrest also exhibits a set break point or a slit for this purpose. 
         [0019]    As can be seen in  FIG. 2 , gas outlet openings  32  are located on a circular ring on the jacket surface of the gas generator  30  running round the longitudinal axis L-L of the gas generator  30 . This circular ring lies in a vertical plane, which is perpendicular to the front surface and parallel to the side surface  14  of the backrest  10 . In case of activation, the gas streams from here into annular gap  35  formed between gas generator  30  and sleeve  34  and from there into the interior of airbag  40 . Therefore, the gas is redirected here from an initially radial flow direction into an axial flow direction. This is necessary, if the gas outlet openings  32  are located outside the interior of the airbag  40 , which allows the maximum space saving. In this embodiment, the gas outlet openings lie behind the front surface of mounting plate  36  in the area of frame  16 . The rear section of the gas generator  30  extends into an area of the backrest  10  inside frame  16 . 
         [0020]      FIG. 3  shows an alternate embodiment having a flat, pancake-type gas generator. This alternate gas generator  31  is also cylindrical and its longitudinal axis L-L extends parallel to front surface  12  and basically perpendicular to side surface  14 . Here, the geometry is chosen in such a way that gas outlet openings  33  lie inside an airbag  41 , so that a sleeve for gas diversion is not necessary. The maximum space-saving which can be achieved is therefore also somewhat less than in the first embodiment. Alternate gas generator  31  exhibits a flange  34   b,  which is attached together with mounting plate  36 . In the area of gas outlet openings  32 , a deflector annulus  37  is provided for the protection of the surrounding airbag fabric. 
         [0021]      FIGS. 5 and 6  show an alternative embodiment of the gas generator unit, consisting of sleeve  34  and gas generator  30 .  FIG. 6  is a longitudinal section through  FIG. 5 . 
         [0022]    The gas generator unit, consisting of sleeve and gas generator, is generally manufactured separately and stored until installation into the backrest  10 . The problematical aspect of the gas generator unit shown in  FIG. 2  is that it does not behave in a thrust neutral manner. If the gas generator ignites in case of a warehouse fire, gas enters the annular gap  35  and exits in an axial direction, resulting in corresponding acceleration. In the embodiment shown in  FIGS. 5 and 6 , this effect does not occur, or only in a much reduced form. 
         [0023]    Sleeve  34  consists, as also in the previous embodiments, of metal. In the area of annular gap  35 , it exhibits through-holes  35   a  which face the gas outlet opening  32 . These through-holes  35   a  are covered by a plastic ring  38 , forming a plastic element. The material and thickness of this plastic ring  38  are selected in such a way that it retains its stability for the period of operation of the gas generator. However, should a warehouse fire occur, plastic ring  38  melts and reveals the through-holes  35   a  , so that a large proportion of the gases coming from gas outlet openings  32  escapes through these symmetrically arranged through-holes  35   a.  This means that the gas generator unit basically behaves in a way which is thrust neutral. As an alternative to this it could be imagined that the entire sleeve  34  or at least the area of the annular gap of sleeve  34  could be manufactured of plastic, which loses its stability in case of fire. The embodiment shown here has, however, the advantage of greater overall mechanical stability. 
         [0024]    As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from spirit of this invention, as defined in the following claims.