Abstract:
A vehicle suspension system includes an airbag ( 10 ) arranged to act substantially horizontally so as to apply a substantially horizontal force to a horizontally movable force-transmitting member ( 12 ) and a parallelogram linkage ( 16, 17, 18, 19 ) that acts between the force-transmitting member ( 12 ) and a part ( 14 ) of the vehicle chassis ( 10 ).

Description:
FIELD OF THE INVENTION 
   This invention relates to vehicle suspension systems. 
   Vehicle suspension systems are known that include a vertically acting air bag. 
   However, the use of a vertically acting air bag imposes space and design restraints on the suspension system and it is accordingly an object of the present invention to provide a vehicle suspension system that includes the use of an air bag that acts substantially horizontally. 
   SUMMARY OF THE INVENTION 
   According to the present invention there is provided a vehicle suspension system for a vehicle having a chassis, the suspension system including:— 
   a) a horizontally movable force-transmitting member, 
   b) an airbag arranged to act substantially horizontally so as to apply a substantially horizontal force to the horizontally movable force-transmitting member, 
   c) a parallelogram linkage that acts between the force-transmitting member and a part of the vehicle chassis, 
   d) the parallelogram linkage including a rocker pivotally connected at its one end to said part of the vehicle chassis for pivotal movement relative thereto about a substantially horizontal pivot axis, and 
   e) a push rod connected at its one end to the rocker at a position intermediate the ends of the rocker. 
   The rocker is preferably pivotally connected at its other end to the force-transmitting member or to a component fixed to the force-transmitting member, and the push rod is preferably connected at its other end to a wheel hub support member suspended from the vehicle chassis by suspension links. 
   This arrangement provides for optimum vertical wheel displacement and variable ride height ability. 
   Two airbags may be mounted on the chassis so as to act transversely of the axis of the vehicle chassis, the airbags being disposed in a substantially back-to-back manner. This provides a balanced arrangement and avoids the application of torsional twisting loads to the chassis. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic side view of a vehicle suspension system in accordance with the present invention, 
       FIG. 2  is a front view of a first form of suspension system mounted on the chassis of a vehicle having a hub assembly drive system, 
       FIG. 3  is a plan view of the chassis, suspension system and drive system shown in  FIG. 2 , 
       FIG. 4  is a side view corresponding to  FIG. 2  but showing a wheel mounted on the hub assembly, 
       FIG. 5  is a plan view corresponding to  FIG. 3  but showing a wheel mounted on the hub assembly, 
       FIG. 6  is a plan view of a vehicle suspension system that includes two air bags arranged back-to-back, and 
       FIGS. 7 and 8  are perspective views of a front or rear axle suspension system that includes a longitudinally acting air bag. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As can be seen from the drawings, the suspension system includes an air bag  10  mounted on the vehicle chassis  11  and arranged to act horizontally so as to apply a resilient force to an air bag mounting plate  12  that carries a pivot mounting  13 . A part  14  of the chassis  11  carries a mounting  15  for a main pivot for one arm of a rocker  16 . The other arm of the rocker  16  is attached to pivot mounting  13 . The air bag  10  extends transversely to the centre line or axis of the vehicle chassis  11  and acts outwardly of the centre line of the chassis  11 . 
   The rocker  16  forms part of a parallelogram linkage system that also includes a first link  17 , a second link  18  and a third link  19 . One end of the first link  17  is connected to the mounting  15  and the other end of the first link  17  is connected to one end of the second link  18 . The other end of the second link  18  is connected to one end of the third link  19  and the other end of the third link  19  is connected, in turn, to the pivot mounting  13 . 
   The action of the parallelogram linkage system  16 ,  17 ,  18 ,  19  is such that, as the air bag mounting plate  12  moves horizontally, as indicated by the arrow  20  in  FIG. 1 , tilting movement of the air bag mounting plate  12  is prevented and the action of the air bag  10  is maintained horizontally. 
   The rocker  16  carries a pivot mounting  21  for a push rod  22  that is connected to a mounting  23  for a road wheel hub  24 , and the mounting  23  is supported by suspension links  25  connected to the chassis  10 . As shown in the drawings, a shock absorber  27  acts between the lower suspension link  25  and the chassis  11 . 
   The parallelogram linkage system  16 ,  17 ,  18 ,  19  connecting the chassis mounting  15  and the pivot mounting  13  carried by the air bag mounting plate  12  permits substantial, controlled vertical displacement of the road wheel hub  24  and the mounting  23  and provides for variable ride height. 
     FIGS. 4 and 5  show a wheel  26  mounted on the road wheel hub  24 . The wheel  26  has not been shown in  FIGS. 2 and 3  in order to enable details of the wheel hub  24  and the mounting  23  to be seen. 
   The drawings show the suspension system for a single wheel  26  of the vehicle and it will be appreciated that there will be another suspension system of mirror image form on the other side of the vehicle. This arrangement will then be repeated for each pair of wheels  26  of the vehicle. 
   Two airbags  10  will thus be mounted on the chassis  11  so as to act transversely of the axis of the vehicle chassis  11  and will be disposed in a substantially back-to-back manner. This provides a balanced arrangement and avoids the application of torsional twisting loads to the chassis  11 .