Abstract:
An air spring suspension for a rear axle of truck is stabilized using a trailing link constructed from a hollow, rectangular tube. The air spring is positioned between a portion of the trailing link extending beyond the rear axle and turning inwardly on the vehicle and the frame rails of the truck&#39;s chassis. An auxiliary spring is provided by a half leaf mounting beneath the trailing link. The suspension can provide cornering stabilization by providing a connecting link between the ends of the trailing links.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to vehicle suspension systems and more particularly to axle stabilizing systems.  
           [0003]    2. Description of the Problem  
           [0004]    Truck suspension systems provide isolation of passengers and cargo from road shock while keeping the vehicle stable and preserving operator control. These objectives are met using combinations of springs, motion damping devices and auxiliary axle positioning elements. Achieving acceptable levels of performance, while supporting the vehicle&#39;s weight over a wide range of vehicle load conditions, is preferably achieved with a mechanically simple, compact and light weight suspension system.  
           [0005]    The central element of any suspension system is the spring, and the four most popular, basic types of suspension systems used on trucks are categorized by the spring used, i.e.: leaf spring systems; equalizing beam systems; torsion bar systems; and air spring systems. Hybrid combinations of these are also used.  
           [0006]    Air spring based systems have recently gained in popularity and have been applied to both steering and non-steering axles as well as driven and undriven axles. In an air spring based system, air bellows are positioned with respect to an axle and a vehicle frame to support the frame from the axle. Air spring suspensions give excellent load and vibration isolation by eliminating the interleaf friction found in traditional multiple leaf spring designs and, in some systems, by allowing active control of the spring rate. In addition, an air spring usually has a lower deflection rate than a leaf spring exerting the same force, giving the system greater capacity for absorbing shocks for a given displacement between the axle and the frame. Air spring pressure can be adjusted to compensate for vehicle load changes by adding air to or exhausting air from the spring. This aspect of the springs also benefits other suspension design objects, since by adding or exhausting air the vehicle height need not vary with load or positioning of the load.  
           [0007]    A drawback of non-hybrid air spring suspension systems, especially when compared with leaf spring systems, is that they require more auxiliary stabilization to maintain the proper location and attitude of the axle with respect to the vehicle and to prevent excessive vehicle roll. Absent stabilization, air springs will extend to their maximum lengths or widths in the direction of least resistance and can cause an unevenly loaded vehicle to fall over to one side, while full leaf springs, because of twin points of connection to the vehicle frame both fore and aft of the axle, are partially self-stabilizing and provide better directed support.  
           [0008]    Auxiliary stabilization may be directed to controlling one or more specific types of undesired movement of a vehicle or axle. To some extent, the control of one type of movement may be more readily accomplished by trading off control of another type of movement. Some auxiliary stabilizing elements can even promote certain types of undesired vehicle body or axle movement while achieving control of some other movement. Among the problems to be controlled are vehicle roll occurring during cornering, suspension expansion adjacent a driven axle on acceleration (acceleration lift), and lateral deflection of the axle, particularly during turning. Some auxiliary stabilizing systems produce axle caster changes with vertical motion of an axle.  
           [0009]    Countering some or all of these problems is preferably obtained using auxiliary components which are not excessively complex, bulky or heavy, and which allow the full capacity of the air springs to be utilized. It would be further advantageous if the auxiliary elements provided a base for positioning an air spring.  
         SUMMARY OF THE INVENTION  
         [0010]    According to the invention there is provided a suspension for a vehicle from an axle, the vehicle having left and right side frame rails. The suspension comprises left and right side hangers depending from the left and right side frame rails forward of the axle. Left and right side trailing links depend from the left and right side hangers, respectively, with the trailing links being coupled to opposite ends of the axle and extending behind the axle where the left and right side trailing links have canted portions which are turned inward on one another in a plane to support an air spring. Left and right side couplings attach opposite ends of the axle to the left and right side trailing links. The left and right side trailing links are formed from hollow tubes with each trailing link having a filler insert within the hollow tube at the coupling between the trailing link and axle. Left and right side auxiliary leaf springs are located below the left and right side trailing links between the hangers and the axle to help support the load. The main load supporting air springs are located between the turned in portions of the trailing links and the left and right side frame rails. The turned in portion may be substantially formed by a sway bar positioned connecting the left and right side trailing links. 
       
    
    
       [0011]    Additional effects, features and advantages will be apparent in the written description that follows.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:  
         [0013]    [0013]FIG. 1 is a side elevation of a portion of a tandem axle truck chassis;  
         [0014]    [0014]FIG. 2 is a perspective view of the novel suspension;  
         [0015]    [0015]FIG. 3 is a perspective view of another embodiment of the suspension;  
         [0016]    [0016]FIGS. 4A and 4B are a top plan and side elevation of a possible configuration for a trailing member.  
         [0017]    [0017]FIGS. 5A, B and C are cross sectional views of a trailing member of the suspension taken along section lines  5 A,  5 B and  5 C in FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Referring now to the drawings and in particular to FIG. 1, a section of a truck chassis  10 , representing the sprung load of a vehicle, is illustrated. Chassis  10  has left and right side frame rails  12  and  14  running lengthwise down opposite sides of the vehicle. Frame rails  12  and  14  are supported from rear drive axles  16  and  18  by suspension systems  20  and  22 , the left side portions of which are visible in the drawing. The right side sections of the suspension are mirror images of the left side sections. The suspension systems can be substantially described with reference to one side of one of the suspension systems, here suspension  20 .  
         [0019]    The left side of suspension  20  has a primary load bearing element, here an air spring  22 . Air spring  22  rides on a turned in portion  32  of a trailing link assembly  24  located aft from axle  16 . Trailing link assembly  24  is suspended at its lead end from a hanger  26  which is attached to left side frame rail  12  ahead of axle  16 . Trailing link assembly  24  runs under axle  16  and extends behind the axle turning inwardly, that is toward the longitudinal center line of the vehicle to form turned in portion  32 . A shock absorber  30  is also coupled between the trailing link assembly  24  and left side frame rail  12  by suitable pivoting connectors. An auxiliary leaf spring  28  is located below trailing link assembly  24  running between hanger  26  and axle  16 . One end of leaf spring  28  is wrapped outside of trailing link assembly  24  on a bolt (not shown) framed in hanger  26 . Couplings between the axles and suspension assemblies have been deleted for ease of illustration. The hanger may be attached by other fasteners such as bolting or riveting.  
         [0020]    Referring now to FIG. 2, a perspective view of a suspension system  20  illustrates both left and right side components of the suspension, the left side components being viewed from the outside and the right side components being viewed from the inside. Left side and right side trailing link assemblies  24  and  124  are steel fabricated tubes typically having a rectangular cross sectional shape. Other cross sectional shapes are possible including elliptical and circular. The dimensions of the tube may or may not vary along the length of the tube. Trailing link assemblies  24  and  124  depend at one end from hangers  26  and  126 , respectively. Link  24  terminates at one end in a loop  58  which is wrapped around a bolt fixed in hanger  26  between sections  50  and  52 . Hanger sections  50  and  52  are stampings welded, formed, bolted, or riveted together to complete hanger  26 . A half leaf spring  28  is located directly under trailing link  24  between hanger  26  and coupling  34 . Leaf spring  28  wraps on loop  58  at one end and terminates under link  24  at its opposite end just outside of coupling  34  relative to the hanger  26 . The hanger assembly may be attached by other means such as bolting or riveting.  
         [0021]    Turned in sections  32  and  132  are an extension of the fabricated steel tube. Trailing link  24  and half leaf spring  28  are coupled to an axle using coupling  34 . Coupling  34  is constructed from two inverted U-bolts  36  and  38  set in a base  40 . Base  40  is positioned under leaf spring  28  and provides a support for the spring and trailing link  24 . The upper surface of trailing link  24  and U-bolts  36  and  38  are used to position conventional axle securing elements  42  and  43 . A shock absorber  30  is attached at a pivot  48  to base  40  and at a second pivot  46  in a frame  60  provided for attachment to a chassis frame rail.  
         [0022]    In FIG. 3 a fabricated sway bar  80  is fitted between open ends of the left and right side trailing links  24  and  124 . Sway bar  80  forms a substantial portion of the turned in portions of the trailing links  24  and  124 . Sway bar  80  has a substantially straight middle section and turns forward at the ends to mate with trailing links  24  and  124 .  
         [0023]    [0023]FIGS. 4A and 4B illustrate a possible external configuration for a representative trailing link member  200  having a rectangular cross sectional shape with constant dimensions. The trailing link or pivot bushing assembly  200  comprises a trailing link member  201  and a socket and bushing assembly  202  fitted into one end of trailing link member. Socket and bushing assembly  202  fits a conventional suspension hanger, being attached thereto by the ends of shaft  204 . Socket and bushing assembly  202  rotates on shaft  204 . There may be a rubber spacer  203  between the socket and bushing of the assembly  202 . The socket and bushing assembly  202 , also known as a pivot bushing, has a shaft  208  sized and shaped to fit snugly into a central passage  210  formed within trailing link member  201 . Shaft  208  is secured in position by a pair of nut and bolt fasteners  206 . Centrally positioned along beam  201  is an shock absorber attachment plate  212  which is mounted to the beam by a nut and bolt fastener  213 . A crush resistant core  220  is positioned within central passage  210  beginning at a point between nut and bolt assembly  213  and socket and bushing assembly  202  and terminating below bend  222  in canted section  214 . Trailing link member  212  has a parallel section  209  which runs parallel to a frame side rail and a canted section  214  aft of the axle. When the link member is mounted on a vehicle the canted section  214  turns inwardly toward the center line of the vehicle. Canted section  214  has a mounting hole  218  for attachment of an air spring. Trailing link member  201  is preferably a heat treated steel tube. The nut and bolt connector assemblies may be replaced by other fastening means such as rivets.  
         [0024]    FIGS.  5 A-C illustrate interior details of trailing link member  24 , and by extension sway bar  80  and trailing link  124 . Section  5 A is taken lengthwise along a portion of trailing link  24 . Sections  5 B and  5 C are taken across the link at locations spaced along the length of the link and together with Section  5 A illustrate the varying vertical spacing between upper wall  90  and lower wall  92 . A crush resistant filler  94  is placed in the hollow channel  64  to prevent coupling  34  from crushing the tube on installation. Filler  94  may be a solid block of nylon or steel or other material suitable for reinforcing the side walls  96  and  98  or may be another tube. The link is a rectangular tube which may be fabricated from flat roll stock rather than being forged. This substantially reduces the expenses of manufacture.  
         [0025]    The trailing links of the present invention provide axle stabilization for a rear driven axle with an air spring at minimal expense and complexity.  
         [0026]    While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.