Abstract:
A vehicle suspension system includes a mounting bracket adapted to be secured to a vehicle frame, a trailing arm member pivotably coupled to the first mounting bracket, an axle member adjustable between a first pinion angle and a second pinion angle, an axle mounting assembly securing the axle member to the trailing arm member and including an upwardly disposed, curved abutment surface, and a stop member adapted to be operably coupled to a vehicle frame, the stop member including a downwardly disposed, curved abutment surface adapted to abut the abutment surface of the axle mounting assembly, thereby limiting travel of the trailing arm with respect to the vehicle frame to a constant value when the axle member is at both the first pinion angle and the second pinion angle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a drive axle suspension system for heavy vehicles which has been optimized for reduced weight, reduced part count and increased durability. 
         [0003]    2. Technical Background 
         [0004]    Various suspension systems utilizing air springs have been developed for semi-tractor trailers and other heavy vehicles. These systems are typically designed to control the position of the chassis relative to an associated axle and to cushion any movement of the axle with respect to the chassis frame. Although these systems provide excellent chassis control over a wide range of loading conditions, conventional air spring systems typically do not offer acceptable resistance to vehicle roll, as is often experienced when the vehicle turns, nor do they offer acceptable resistance to lateral shifting of the vehicle. 
         [0005]    While specialized components have been added to air spring systems to reduce roll and lateral shift, many of these components add significant weight and cost and maintenance to the associated suspension system without greatly reducing the roll and lateral shift. Specifically, these designs typically incorporate single-piece trailing arms that require materials meeting torsional and sheer strength requirements, but that also may be tapped and threaded as required. Further, many of these components include complicated designs that are not only expensive to manufacture, but are also difficult to install or replace should damage to the component or related equipment occur. One particular assembly is adapted to stabilize the related suspension system by securing a torsional beam between a pair of trailing arms by bolts that extend through the torsional beam and into threaded apertures located in the ends of the beams. This particular assembly requires large securing bolts adapted to withstand significant torsional and sheering forces, and further requires the replacement or retapping of a trailing arm should the threads within the bolt receiving aperture become damaged or worn as well as maintenance burden. 
         [0006]    There is a need for a lightweight and inexpensive air spring suspension system that resists roll and lateral shift, will not significantly impact the ride-cushioning characteristics of such suspension system, provides a relative increase of structural integrity, and that can further be maintained and repaired quickly and cost-effectively. 
       SUMMARY OF THE INVENTION 
       [0007]    One aspect of the present invention is a vehicle suspension system that comprises a first mounting bracket adapted to be secured to a vehicle frame member, a first trailing arm member pivotably coupled to the first mounting bracket, a second mounting bracket adapted to be secured to a vehicle frame, a second trailing arm member pivotably coupled to the second mounting bracket, and an axle member extending between the first and second trailing arm members and adjustable between a first pinion angle and second pinion angle that is different than the first pinion angle. The vehicle suspension system further comprises a first axle mounting assembly securing the axle member to the first trailing arm member, and a second axle mounting assembly securing the axle member to the second trailing arm member, wherein at least one of the first axle mounting assembly and the second axle mounting assembly includes an upwardly-disposed, curved abutment surface. The vehicle suspension system still further includes a stop member adapted to be operably coupled to a vehicle frame, the stop member including a downwardly disposed, curved abutment surface adapted to abut the abutment surface of the axle mounting assembly, thereby limiting the travel of at least a select one of the first trailing arm member and the second trailing arm member with respect to a vehicle frame to a constant value when the axle member is at both the first pinion angle and the second pinion angle. 
         [0008]    Yet another aspect of the present invention is a vehicle suspension system that comprises a first mounting bracket adapted to be secured to a vehicle frame, a first trailing arm member pivotably coupled to the first mounting bracket, a second mounting bracket adapted to be secured to a vehicle frame, a second trailing arm member pivotably coupled to the second mounting bracket, and an axle extending between the first and second trailing arm members and adjustable between a first pinion angle and second pinion angle that is different than the first pinion angle. The vehicle suspension system further comprises an upwardly-disposed, curved first stop surface fixed for movement with the axle member, and a downwardly-disposed, curved second stop surface adapted to be fixed for movement with respect to a vehicle frame, and adapted to abut the first stop surface, thereby limiting travel at least a select one of the first trailing arm member and the second trailing arm member with respect to a vehicle frame to a constant value when the axle member is at both the first pinion angle and the second pinion angle. 
         [0009]    These and other advantages of the invention will be further understood and appreciated by those skilled in the art by reference to the following written specification, claims and appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a perspective view of a suspension system embodying the present invention; 
           [0011]      FIG. 2  is a side plan view of the suspension system; 
           [0012]      FIG. 3  is a top plan view of the suspension system; 
           [0013]      FIG. 4  is a perspective view of a lower control arm and a transverse beam assembly of the suspension; 
           [0014]      FIG. 5  is a perspective view of a v-rod, a v-rod bracket and a frame cross member; 
           [0015]      FIG. 5   a  is a cross-sectional view of the frame cross member taken along the line Va-Va,  FIG. 5 ; 
           [0016]      FIG. 5   b  is a cross-sectional view of the frame cross member taken along the line Vb-Vb,  FIG. 5 ; 
           [0017]      FIG. 6  is a perspective view of a bolt-on embodiment of an axle adapter bracket; 
           [0018]      FIG. 7  is a perspective view of a weld-on embodiment of the axle adapter bracket; 
           [0019]      FIG. 8  is a perspective view of a frame attachment bracket that includes an eccentric, non-weld alignment system; 
           [0020]      FIG. 9  is a perspective view of the v-rod bracket that includes a system of holes that are used to adjust a pinion angle of an axle; 
           [0021]      FIG. 10  is a perspective view of the v-rod bracket with a pinion plate; 
           [0022]      FIG. 11  is a perspective view of the frame cross member and includes a system of assembly holes that are used to adjust the pinion angle of the axle and a location of possible shims utilized therein; 
           [0023]      FIG. 12  is a detail perspective view of the frame cross member; 
           [0024]      FIG. 13  is a detail perspective view of a lower control arm assembly and a transverse beam joint; 
           [0025]      FIG. 14  is a cross-sectional view of a Z-shaped lower control arm, taken along the line XIV-XIV,  FIG. 4 ; 
           [0026]      FIG. 15  is a cross-sectional view of an I-shaped lower control arm, taken along the line XV-XV,  FIG. 4 ; 
           [0027]      FIG. 16  is an enlarged perspective view of an axle adapter assembly including a height control valve connection tab; 
           [0028]      FIG. 17  is an enlarged rear view of a rear end of the v-rod and includes a casting draft allowing increased roll compliance; 
           [0029]      FIG. 18  is an enlarged perspective view of an adjustable frame bracket clevis including a slotted adjustable connection; 
           [0030]      FIG. 19  is an enlarged bottom plan view of the frame bracket and lower control arm assembly and including the washers that may be moved to adjust for various frame widths; and 
           [0031]      FIG. 20  is an exploded perspective view of an alternative embodiment of the axle adapter that includes a through bolt bushing connection. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIGS. 1-3 . However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
         [0033]    A suspension system  10  ( FIGS. 1-3 ) is designed for heavy vehicle applications, which has a reduced weight and part count, and which is designed to be adapted to a full range of axle pinion angles. The suspension system  10  includes a pair of lower control arms  12  which are connected to a transverse beam  14 , a system of attachment brackets  16  that connect a drive axle  18  to the lower control arms  12 , an upper control arm or v-rod  20  that connects the axle  18  to a vehicle frame cross member  22 , a bracket  24  connecting the v-rod  20  to the axle  18 , a pair of mounting brackets  26  which attach the lower control arms  12  to a corresponding pair of vehicle frame members  28 , air springs  30  and shock absorbers  32 . The suspension system  10  creates a parallelogram geometry which minimizes the change in the axle pinion angle during articulation from full up to full down, as described below. 
         [0034]    In the illustrated example, each lower control arm  12  ( FIG. 4 ) comprises a cast beam with a round bushing receptacle  34  at a leading end  36  thereof, a second round bushing receptacle  38  positioned midway along length thereof, and an oval or ‘double D’ transverse beam receptacle  40  ( FIG. 13 ) at a trailing end  42  thereof. Each lower control arm  12  includes a necked section  44  near the leading end  36  and which provides additional torsional compliance for vehicle roll. The necked section  44  also provides additional clearance for other vehicle systems such as brake components (not shown). The lower control arm  12  also includes a through bolt bushing  46  located in the bushing receptacle  34  at the leading end  36 , and a bar-pin bushing  48  located in the bushing receptacle  38  positioned midway along the length thereof. 
         [0035]    The transverse beam  14  comprises a high strength steel tube characterized by an oval or ‘double D’ cross section having a pair of longitudinally extending flat surfaces  50  equally spaced about the circumference of the transverse beam  14  with radiused surfaces  52 . The oval cross section enhances the torque carrying capacity of the lower control arm assembly by converting torsional loads into compressive loads on the inside surface of the lower control arm transverse beam receptacle  40 . The oval or ‘double D’ cross section also maximizes the radii of the inside of the receptacle  40  on the lower control arm  12  thereby minimizing the stresses on the lower control arm  12  due to torsional loading. The flat area  50  located on the top surface of the transverse beam  14  provides an anti-rotation feature for mounting the air spring support  54 . The transverse beam  14  is relatively longer than that in previous suspension systems, thereby allowing greater torsional ‘wind-up’ and increasing axle articulation for a given stress state in the transverse beam  14 . It is noted that although the illustrated example includes a transverse beam having an oval-shaped cross-sectional configuration, other non-related shapes may also be utilized. 
         [0036]    In one embodiment, the connection between the lower control arm  12  and the transverse beam  14  is made in the manufacturing facility, is permanent, and does not require periodic service. The connection between the lower control arm  12  and the transverse beam  14  is characterized by the oval or ‘double D’ shape of the transverse beam  14  and the mating hole  40  in the lower control arm  12 . This connection can be made by a variety of methods, including welding, shrink fit, press fit, post assembly expansion of the tube, 
         [0037]    The permanent connection between the lower control arm  12  and the transverse beam  14  also provides a manner in which to capture the air spring support  54  to the transverse beam  14 . In one embodiment, the air spring support  54  includes a semi-round plate  56  which is welded to the upper surface  58  of the lower control arm  12  and a gusset  60  with a cut out  62  which matches the cross section of the transverse beam  14 . The gusset  60  and the semi-round plate  56  are welded together and slipped on to the transverse beam  14  at the time of assembly in the manufacturing facility. The semi-round plate  56  is then welded to the lower control arm  12 . In another embodiment, the separately welded air spring mount may be eliminated by integrating the air spring mount into the lower control arm casting. 
         [0038]    As best illustrated in  FIG. 14 , the lower control arm  12  may have a Z-shaped cross-sectional configuration in a forward portion and an I-shaped cross-sectional configuration in a rearward portion. This cross-sectional shape further optimizes size and weight of the beam for vehicle loads while retaining the ability to cast the bushing receptacles without complicated casting processes. 
         [0039]    As best illustrated in  FIGS. 6 and 16 , an axle adapter bracket  80  connects the lower control arm  12  to the axle  18  at the bushing receptacle  38  midway along the length of lower control arm  12 . A lower portion  82  of the axle adapter bracket  80  connects to the bar-pin bushings  48  via a pair of bolts  84 . An upper plate  86  of the axle adapter bracket  80  is clamped over the axle  18  and to the lower portion  82  via a plurality of bolts  88 . The lower portion  82  of the axle adapter includes a pair of mounting flanges  90  which form a clevis for connecting the lower end of the shock absorber  32 . The holes for mounting the shock absorber  32  may be drilled in several locations depending on the ride height and pinion angle of the suspension. An upper surface  92  of the upper plate  86  includes a pair of arched ribs  94  which maintain a consistent contact surface for the axle stop  96  ( FIG. 1 ) regardless of axle pinion angle. The axle stop  96  is a casting which provides a consistent maximum up travel position for the axle  18 . The axle stop  96  has a curved lower surface  97  which in conjunction with the arched ribs  94  of the axle adapter upper plate  96  creates a consistent travel limiter. The consistent axle stop allows the elimination of an internal bumper from the air spring, thereby reducing air spring component count, weight and overall cost. The shock absorber clevis also provides a mounting point for the suspension height control air valve mounting bracket  98 . 
         [0040]    In another embodiment, the lower portion  82  ( FIG. 7 ) of the axle adaptor bracket  80  may be welded directly to the axle  18  thus eliminating the upper axle adapter plate  86  and the associated plurality of bolts  88 . 
         [0041]    In yet another embodiment, the axle adapter lower portion  82  ( FIG. 20 ) is connected to a through bolt bushing  85  in the midway bushing receptacle  38  of the lower control arm  12  via a set of pucks  87  and slots  89  on the axle adapter casting  82  which significantly reduce the clearance required for a through bolt bushing at the axle. 
         [0042]    The upper control arm or ‘v-rod’  20  ( FIG. 5 ) comprises a generally triangular cast assembly with one bushing receptacle (not shown) in the trailing end  100  thereof, and two bushing receptacles  101  in the forward end  102  thereof. The forward ends  102  are each bolted via bar-pin bushings  104  directly to the vehicle cross member  22 . The trailing end  100  is bolted via a through bolt bushing  106  to the bracket  24  mounted to the top of the axle  18 . The v-rod  20  is integrated to minimize the component count as compared to a typical combination torque rod and track rod. Since the v-rod system is symmetric about the vehicle center line, it also provides a symmetric roll characteristic versus a traditional torque rod and track rod system. 
         [0043]    The bar-pin bushings  104  at the forward end  102  provide ease of installation to the vehicle cross member  22  via two bolts per bushing  104 , and an enhanced lateral stability due to the typical high bushing rate for radial bushing displacement. The bar-pin bushings  104  also provide a position to easily shim the suspension for small changes in axle pinion angle and alignment. As best illustrated in  FIG. 17 , the casting draft on the bushing receptacle is aligned to provide increased roll compliance. It is noted that the horizontal orientation of the through bolt bushing  106  at the trailing end  100  provides a low profile for enhanced axle travel. The through bolt also provides an interface for the v-rod bracket. The rear bushing  106  may also be provided as a vertical bar-pin bushing. Although the v-rod  20  is preferable cast, it may also be fabricated from stamped steel. Still further, the v-rod  20  may be assembled from two symmetric castings joined at the rear bushing thereby providing further roll compliance. 
         [0044]    The vehicle frame cross member  22  ( FIG. 5 ) comprises a steel material, and provides connection points for the forward end  102  of the v-rod  20  as well as strength and rigidity for the vehicle frame  28 . In the illustrated example, the vehicle frame cross member  22  ( FIG. 5   a ) is provided in a C-shaped cross-sectional configuration having a cut out section  110  in a lower flange  112  thereof to provide clearance for the vehicle drive line. The cut out  110  is reinforced by a C-shaped plate  115  ( FIG. 5   b ) welded in place. Alternatively, the frame cross member may be constructed from a single, integral piece. The cross member  22  also includes cut out areas at each end to provide space for various wiring harnesses and air lines, and sets of three holes (not shown) on each of the lower and upper flanges  112 ,  114  ( FIGS. 5A ,  11  and  12 ) thereof to provide a connection point for the cross member end pieces  124 . These sets of holes are arranged in a staggered pattern to error-proof assembly, thereby reducing the possibility of assembling the components in the wrong direction. The rear (vertical) face  116  of the center section  118  includes two attachment points for the v-rod  22 , each attachment point consisting of two bolt holes matching the bar-pin bushings  104  on the v-rod  22  and a roughly square cut out  126  to provide clearance for the end of the v-rod  22 . The rear face  116  of the center section  118  is canted at an angle from the vertical to provide a neutral angle for the bar-pin bushings  104 , thereby reducing the required bushing articulation and increasing bushing life. 
         [0045]    The cross member end pieces  124  ( FIG. 11 ) comprise bent plates with four holes  128  in a short flange  130  thereof, and nine holes  120  in a long flange  132  thereof. The holes  128  in the short flange  130  are arranged to align with the holes  134  in the suspension frame bracket  26 , thereby setting the fore/aft position of the cross member  22  relative to the suspension. The nine holes  120  in the long flanges  132  provide three possible positions to attach to the cross member center section  22 , the selection of assembly holes providing incremental adjustments of five degrees in the axle pinion angle. The sets of holes  120  in the long section  132  are staggered to match the holes in the cross member center section  22 . In an alternative embodiment, the sets of nine holes in the cross member end pieces are replaced by lateral slots to adjust the cross member assembly length for various vehicle applications. The length of the long flanges  132  is adjusted to provide cross member assemblies of varying length for various vehicle applications. Shims (not shown) may be added to the ends of the cross member  22  to adjust the overall length for various vehicle applications. Further, the center section of the cross member  22  may be varied in length for various vehicle applications. 
         [0046]    In still another alternative embodiment, the sets of nine holes in the cross member end pieces are replaced by longitudinal slots to adjust for various axle pinion angles. 
         [0047]    In the illustrated example, the suspension frame bracket  26  ( FIG. 8 ) comprises a single piece casting which provides a connection between the lower control arms  12  and the vehicle frame  28 . The relatively low profile of the top portion  140  provides clearance for other vehicle systems such as a fifth wheel. The lower end  142  forms a clevis which is clamped to the forward bushing  46  of the lower control arms  12  via a bolted connection. 
         [0048]    In one embodiment, the lower end  142  ( FIG. 18 ) of the frame bracket  26  includes a pair of round holes (not shown) for the clamped connection while the other has a pair of slots (not shown) which allow an adjustable connection. The bracket  26  with the slotted clevis also includes a round alignment puck  144  with an off center round hole (not shown) which mates to a recess  155  on the frame bracket  26 . Rotating the puck  144  causes the off center hole to travel forward or rearward providing a means of aligning the vehicle axle  18 . The puck  144  is rotated by inserting a standard socket wrench handle into a square hole  146  and applying a torque. The puck  144  is held in its final position by the clamp load imposed by the torque on the pivot bolt  147 . 
         [0049]    The frame brackets  28  ( FIG. 19 ) may be used with various vehicle frame widths and a fixed lower control arm assemblies of various widths. This is accomplished by placing a pair of washers  151  either one per side or both on either the inboard or outboard side. 
         [0050]    The v-rod  20  ( FIGS. 5 ,  9  and  10 ) is connected to the axle  18  via the v-rod axle bracket  24 . The bracket  24  comprises a cast part which is welded to the upper surface of the axle  18 , and provides a clevis  148  which is clamped onto the through bolt bushing  106  in the rear most end  100  of the v-rod  20  entrapping a pair of spacing washers  153  ( FIG. 17 ). The bracket  24  has a pair of slots  150  which allows the through bolt  152  to clamp at a variety of positions, a ridge  154  extend about a periphery of the bracket forming a square recess  155 , and a series of detents  156  along a top edge  158  of the ridge  154 . 
         [0051]    The clamp joint includes a pair of square pinion plates  160  each having one or more off center holes  162  for the through bolt bushing bolt  152  and are clamped into the square recess  155  on the bracket casting  24 . On the edges of the pinion plate  160  are notches  164 , the notches  164  being aligned in various positions with the detents  156  on the bracket casting  24  to create incremental, one degree, adjustments of the axle pinion angle. 
         [0052]    It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.