Abstract:
A distributed compliance air-ride axle/suspension system includes an integral structure preferably formed of a lightweight composite material, replacing traditional beams and an axle. The composite structure includes a plurality of plates of various sizes and shapes, with the size, shape and arrangement of the plates being determined by the load capacity model of a specific vehicle application. Traditional axle spindle ends are mounted on the integral plate structure, together with pivot bushings, air springs, and shock absorbers, to complete the air-ride axle/suspension system. The system in turn is pivotally mounted on frame brackets of a heavy-duty vehicle such as a semi-trailer or dump truck. Forces, loads and/or stresses imposed on the axle/suspension system during vehicle operation are distributed generally throughout the composite structure to achieve the desired structural roll compliance of the axle/suspension system for the particular application.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/504,591, filed Sep. 17, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to the art of axle/suspension systems for wheeled vehicles. More particularly, the invention is directed to the art of leading and trailing arm axle/suspension systems of heavy-duty vehicles, such as tractor-trailers or semi-trailers, which cushion the vehicle ride for occupants and cargo and stabilize the vehicle during operation.  
         [0004]     2. Background Art  
         [0005]     Heavy-duty vehicles, such as tractor-trailers or semi-trailers and dump trucks, typically include one or more suspension systems that connect the frame of the vehicle to the wheel-bearing axles of the vehicle. These suspension systems serve several purposes. Specifically, as a vehicle is traveling over-the-road, the wheels encounter various conditions which cause various forces, loads and/or stresses to be imposed on the axle and in turn the suspension assemblies which support the axle. These include impacts caused by vertical movement as well as roll or sway, which are associated at least in part with the suspension system. More particularly, while it is desirable for a suspension system to provide a cushioned, soft ride through means such as an air suspension, the system also must be designed to control the amount of sway imposed on the vehicle, and also stabilize the vehicle, such as by including a fairly rigid suspension structure. However, in order to prevent failure of the components of the system because of an overly rigid structure and to provide some tolerance for single-wheel impacts and the like, this rigidity must be offset or tempered by some degree of roll compliance in the suspension system.  
         [0006]     Prior art leading or trailing arm axle/suspension systems include air suspension systems, which typically include air springs for cushioning and shock absorbers for dampening. More particularly, the air springs and shock absorbers cushion the impact on the vehicle frame that is caused by vertical movement as the vehicle travels over-the-road and encounters changes in road height, such as pot holes, bumps, etc. The axle of the leading or trailing arm axle/suspension system acts as a very large anti-sway bar to help control rolling movements of the vehicle as it travels over-the-road, and rubber pivot bushings are utilized to connect the suspension beams to the vehicle frame and are softer in the vertical direction than in the fore-aft horizontal direction. Such TRI-FUNCTIONAL® bushings, as they are known in the art and which is a registered trademark of The Boler Company, the assignee of the present invention, exhibit compliance so that a certain degree of roll can be maintained, while the other components of the suspension assemblies remain relatively rigid and non-compliant.  
         [0007]     Another type of leading or trailing arm axle/suspension system is commonly referred to in the art as a “two pin axle connection” air suspension system. These axle/suspension systems include rigid trailing arm beam weldments that bolt onto axle seats via a pair of pins, which in turn are welded to the axle. To achieve roll compliance in the structure, the two pin axle connection systems utilize rubber bushings in the axle seats, as well as in the pivot joints that connect the trailing arms to the vehicle frame.  
         [0008]     Still another leading or trailing arm axle/suspension system is a spring beam-type air axle/suspension system, which includes trailing arms that are very stiff and thick leaf springs that are rigidly attached to the axle and are pivotally mounted to the vehicle frame. The leaf springs provide the roll compliance for the system.  
         [0009]     However, while all of the above-described axle/suspension systems of the prior art achieve their desired result of cushioning the vehicle ride and stabilizing the vehicle, they each involve multiple specialized components that increase manufacturing costs and contribute to increased weight of the vehicle, which in turn adversely affects the fuel efficiency of the vehicle. Moreover, the components typically used in such prior art systems include components which require frequent repair or replacement.  
         [0010]     The above-described problems of prior art axle/suspension systems are solved by the present invention through the use of an integrally formed composite structure which replaces traditional suspension beams and axles with a composite plate structure that exhibits roll compliance throughout the entire structure, rather than through just one or two discrete components such as the TRI-FUNCTIONAL® bushings, the axle seat bushings of the two-pin suspension system, and the monoleaf springs of the spring beam-type suspension systems.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     Objectives of the present invention include providing an axle/suspension system for wheeled vehicles, which exhibits roll compliance generally throughout its entire structure during operation of the vehicle to which it is attached.  
         [0012]     Another objective of the present invention is to provide such a distributed compliance axle/suspension system, which cushions the ride for occupants and cargo carried by the vehicle and stabilizes the vehicle during over-the-road operation.  
         [0013]     A further objective of the present invention is to provide such a distributed compliance axle/suspension system which is lighter in weight than prior art axle/suspension systems, can be economically manufactured by various processes and from various materials, and which is durable in use.  
         [0014]     Still another objective of the present invention is to provide such a distributed compliance axle/suspension system, which can be manufactured for use in various load capacity applications by adjusting the shapes and/or arrangements of the integral structure components.  
         [0015]     These objectives and advantages are obtained by the distributed compliance axle/suspension system of the present invention, the general nature of which may be stated as including an air-ride axle/suspension system for a wheeled vehicle, including a pair of pivot bushings for pivotally mounting the system to a frame of the vehicle, pairs of shock absorbers and air springs, and a pair of axle spindle ends for mounting wheels on the system, wherein the improvement comprises, an integral structure free of any discrete substantially roll compliant component, the pivot bushings, shock absorbers, air springs, and axle spindle ends being mounted on the integral structure, whereby roll forces encountered by the axle/suspension system during vehicle operation are distributed generally throughout the integral structure to enable the system to achieve roll compliance. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0016]     The preferred embodiment of the invention, illustrative of the best mode in which applicant has contemplated applying the principles, is set forth in the following description and is shown in the drawings, and is particularly and distinctly pointed out and set forth in the appended claims.  
         [0017]      FIG. 1  is a front perspective view of the beams and axle of a prior art trailing arm air-ride axle/suspension system;  
         [0018]      FIG. 2  is a schematic side elevational view of a prior art trailing arm air axle/suspension system of the type having a two pin axle connection and a bushing at the pivot attachment point of the beam to the vehicle frame, and further showing in phantom lines the far side beam to illustrate the compliance resulting from the bushings when roll forces are encountered during operation of the vehicle;  
         [0019]      FIG. 3  is a schematic side elevational view of a prior art leaf spring beam-type trailing arm air axle/suspension system, showing in phantom lines the far side beam to illustrate the type of compliant movement that may occur in the leaf springs when roll forces are imposed on the vehicle during its operation;  
         [0020]      FIG. 4  is a front perspective view of the distributed compliance air-ride axle/suspension system of the present invention;  
         [0021]      FIG. 5  is a view similar to  FIG. 4 , but showing only the composite plate structure which serves as the beams and axle of the system, and with the air springs, shock absorbers, bushings and axle spindle ends shown in  FIG. 4  removed;  
         [0022]      FIG. 6  is a top plan view of the structure shown in  FIG. 5 ;  
         [0023]      FIG. 7  is a side elevational view of the structure shown in  FIGS. 5 and 6 ;  
         [0024]      FIG. 8  is a front elevational view of the structure shown in  FIGS. 5 through 7 ;  
         [0025]      FIG. 9  is a bottom rear perspective view of the structure shown in  FIGS. 5 through 8 ;  
         [0026]      FIG. 10  is a view similar to  FIG. 4 , but showing the distributed compliance air-ride axle/suspension system pivotally mounted on vehicle frame hangers or brackets, and further showing brake equipment attached to the system;  
         [0027]      FIG. 11  is a rear perspective view of the assembly shown in  FIG. 10 ; and  
         [0028]      FIG. 12  is a bottom front perspective view of the assembly shown in  FIGS. 10 and 11 . 
     
    
       [0029]     Similar numerals refer to similar parts throughout the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     So that the present invention may be best understood, representative types of prior art axle/suspension systems now will be described. One type of prior art trailing arm air-ride axle/suspension system  10  is shown in  FIG. 1 , and generally includes two trailing arm beams  12  that are welded or otherwise rigidly affixed to an axle  14 . Axle  14  includes a center portion  16  and a pair of ends  18  each terminating in an axle spindle  17 . System  10  also typically includes air springs and shock absorbers (not shown). Normally, axle  14  acts as a very large anti-sway bar to help control rolling movements of the vehicle as it travels over-the-road. Rigid steel trailing arm beams  12  generally utilize rubber pivot bushings  19  that are softer in the vertical direction than the fore-aft horizontal direction, and are known in the art as TRI-FUNCTIONAL® bushings. Bushings  19  pivotally attach each suspension assembly to the vehicle frame via frame brackets or hangers (not shown). In system  10 , the compliance is designed into TRI-FUNCTIONAL® bushings  19 , so that a certain degree of roll can be maintained, while the other components of the system remain relatively rigid and non-compliant.  
         [0031]     Other types of trailing arm air-ride axle/suspension systems use different structures to achieve the above-described roll compliance. Referring to  FIG. 2 , a schematic of a different structure is shown, which is known in the art as a “two pin axle connection” suspension system  96 . Suspension system  96  typically includes rigid steel trailing arm beams  99  (the opposite side beam is shown in phantom lines to illustrate the roll-induced relative positions of the beams) that bolt onto respective axle seats  97  via a pair of pins  98 . Axle seats  97  in turn are welded to axle  100 . To achieve roll compliance in the structure, two pin axle connection suspension system  96  utilizes rubber bushings (hidden from view) in axle seat  97  about bolts  98 , as well as in a pivot joint  101  that connects each trailing arm  99  to the trailer frame brackets (not shown).  
         [0032]     Yet another type of prior art structure is a spring beam-type trailing arm air-ride axle/suspension system  105 , as shown schematically in  FIG. 3 . Suspension system  105  typically includes trailing arms  106  (the opposite side arm is shown in phantom lines to illustrate the roll-induced relative positions of the arms) that are very stiff and thick leaf springs, which are rigidly affixed to axle  107  such as by U-bolts  108 , and pivotally mounted to the vehicle frame at spring pivot end  109 . Leaf springs  106  provide the roll compliance for axle/suspension system  105 .  
         [0033]     All of the above-described axle/suspension systems of the prior art involve multiple specialized components that increase manufacturing cost. In addition, the components of such prior art axle/suspension systems generally contribute to increased weight of the system, which adversely affects the fuel efficiency of the vehicle to which they are attached. Furthermore, the discrete components used to achieve roll compliance are not always optimally effective or relatively long-lived. It is understood that the structures shown and described herein for prior art axle/suspension systems  10 ,  96  and  105  also have application in vehicles utilizing leading arm axle/suspension systems.  
         [0034]     As a result, a need has existed in the art to develop an axle/suspension system that overcomes the disadvantages of prior art systems and provides a light-weight, economical axle/suspension system having effective and long-lived structural components to achieve desired stability and roll compliance levels.  
         [0035]     Turning now to  FIGS. 4-12 , wherein the showings are for illustrating a preferred embodiment of the invention, and not for limiting the same,  FIG. 4  shows a distributed compliance axle/suspension system, indicated generally at  20 , which provides an impact-dampening connection between at least a portion of a frame of a vehicle (not shown) and the vehicle wheels supported by the system. Inventive axle/suspension system  20  maintains rigidity to enable the system to function with durability and stability, yet distributes roll compliance throughout its entire structure, rather than through just one or two components, such as bushings or leaf springs, as in prior art axle/suspension systems.  
         [0036]     Specifically, trailing arm air-ride axle/suspension system  20  of the present invention includes a composite structure  21 , axle spindles  84  and  86 , bushings  37  and  39 , shock absorbers  88  and  90 , and air springs  92  and  94 . System  20  replaces prior art axle/suspension systems, such as system  10  shown in  FIG. 1  (which, as noted, does not show the shock absorbers or air springs of the system).  
         [0037]     With particular reference to  FIGS. 5-9 , and in accordance with one of the important features of the present invention, composite structure  21  preferably is integrally formed and includes two generally parallel, transversely spaced trailing arms  22  and  24 , and a cross member  26  that extends between and connects the trailing arms and effectively functions as an axle. Trailing arms  22  and  24 , cross member  26  and other components of integral structure  21 , are made of plates of various shapes and sizes formed from a composite material, and bonded together as known in the art. For example, the plates may be formed of a composite material, for example, a glass fiber-reinforced thermosetting resin such as a fiberglass-reinforced thermoset polyester pultrusion, and the plates may be bonded using a known adhesive, or a process such as joining under heat and/or pressure.  
         [0038]     Each trailing arm  22 ,  24  includes a front end  28 ,  30  and a rear end  32 ,  34 , respectively. Disposed in front end  28 ,  30  of each trailing arm  22 ,  24  is a mounting tube  36 ,  38 , respectively, which defines an orifice  40 ,  42 , that facilitates pivotal connection of structure  21  to frame brackets or hangers  44 ,  46  (referring to  FIG. 10 ), as will be described in greater detail hereinbelow. Affixed to rear end  32 ,  34  of each trailing arm  22 ,  24  is a respective circular air spring mounting plate  48 ,  50 .  
         [0039]     Cross member  26  includes a vertical portion  52  and a front horizontal portion  54  that extends from vertical portion  52  to front end  28 ,  30  of each trailing arm  22 ,  24 , respectively, in a wing-like tapered fashion. Front horizontal portion  54  provides a structural connection with increased surface area between trailing arms  22 ,  24  and cross member  26 , which allows distribution of stress. A rear horizontal portion  56  extends from vertical portion  52  to rear end  32 ,  34  of each trailing arm  22 ,  24 , respectively, in a generally similar wing-like tapered manner, providing additional structural stability and distributed compliance for composite structure  21 . The combination of vertical portion  52  and front and rear horizontal portions  54 ,  56 , respectively, effectively replaces center portion  16  of axle  14  of prior art axle/suspension system  10  (referring back to  FIG. 1 ).  
         [0040]     Extending from an outboard surface of each trailing arm  22 ,  24  is a respective side member  58 ,  60 , each of which includes a respective vertical member  62 ,  64 . Each vertical member  62 ,  64  is aligned with cross member vertical portion  52 . Each side member  58 ,  60  also includes a front horizontal member  66 ,  68  and a rear horizontal member  70 ,  72 , respectively. Side members  58 ,  60  facilitate the mounting of respective opposing wheel flanges  74 ,  76  and enable attachment of axle spindle ends  84 ,  86  ( FIG. 4 ).  
         [0041]     Cross member  26  has a generally cross-sectional shape that resembles a cross. The size of the cross can be tuned or adjusted, such as by increasing or decreasing the size of vertical portion  52 , front horizontal portion  54  and/or rear horizontal portion  56 , to accommodate various deflection levels of vertical bending, fore-aft bending and torsional bending experienced by structure  21 , and in turn, axle/suspension system  20 . However, it is understood that the present invention contemplates cross-sectional shapes other than a cross, which also can be adjusted based on the particular application.  
         [0042]     Trailing arms  22 ,  24  and side members  58 ,  60  each also include a generally cross-shaped cross section. The size of these cross sections also can be adjusted in the same manner as described above for cross member  26 , to accommodate various deflection levels of vertical bending, side load bending and torsional bending. It is understood, as noted above, that the present invention contemplates adjustable cross-sectional shapes other than a cross.  
         [0043]     With additional reference to  FIGS. 10-12 , axle/suspension system  20  is shown in the environment in which it operates, including brake systems  78 ,  80  and frame hangers  44 ,  46 . It is understood that brake systems  78 ,  80  can be mounted in different locations/arrangements on axle/suspension system  20 , as is well-known in the art. Axle spindle ends  84 ,  86  bolt onto flanges  74 ,  76 , respectively, resulting in an assembly that simplifies field maintenance procedures and accommodates desired manufacturing assembly processes. Axle spindle ends  84 ,  86  may be sub-assemblies that are affixed onto axle/suspension system  20  by means known in the art, such as bolting, riveting, welding, etc. When axle spindle ends  84 ,  86  are mass-produced as fully-assembled components, they are added at the final assembly level. This easy installation allows axle spindle ends  84 ,  86  to be replaced in the field if bearing problems are encountered, in contrast to prior art axle spindles  17  such as shown in prior art axle/suspension system  10  ( FIG. 1 ), which are welded to axle ends  18 . However, it is understood that axle spindle ends  84 ,  86  could be non-removably bonded by any suitable means to composite structure  21  if desired without affecting the overall concept of the present invention.  
         [0044]     As mentioned above, axle/suspension system  20  includes integral structure  21 , which includes composite plates. Each plate may be made of the same composite material as the others, or a variety of composite materials may be used. Accordingly, any number of processes to form the plates, as known in the art, may be employed, such as pressing, molding, extruding, pultruding, pull winding, and filament winding. In addition, all or part of axle/suspension system  20 , including composite structure  21 , may be made out of aluminum or steel, as design and manufacturing requirements dictate.  
         [0045]     Various load capacity models of structure  21  can be made by changing the shape of the composite plates. Thus, it is important to note that various configurations of plates and sizes of plates are possible, as dictated by the deflection parameters of a particular application. Accordingly, the plates may take alternative arrangements and shapes, including rounded and cylindrical configurations.  
         [0046]     In this manner, deflections experienced by integrated axle/suspension system  20  are distributed throughout composite structure  21 , and thus system  20 , to achieve the roll compliance dictated by the particular application. By distributing the deflection throughout system  20 , the stresses resulting from the deflections also are distributed. This is in contrast to prior art axle/suspension systems, where such deflections are concentrated in TRI-FUNCTIONAL® bushings  19  (referring back to  FIG. 1 ), in monoleaf springs  106  (referring back to  FIG. 3 ), or in bushings of axle seat  97  (referring back to  FIG. 2 ).  
         [0047]     In addition, since trailing arms  22 ,  24  have a cross-section that is in the shape of a cross, rather than a generally rectangular box-like structure (as do trailing beams  12  of prior art axle/suspension system  10 ,  FIG. 1 ), shock absorbers  88 ,  90  can be mounted directly to trailing arms  22 ,  24 , respectively, rather than on an inboard-extending wing (see shock mounting wing  13  in  FIG. 1 ), thus avoiding additional unwanted material and weight. Moreover, air springs  92 ,  94  are mounted on plates  48 ,  50 , respectively, which are centered on trailing arms  22 ,  24 . Such centering provides a more efficient structure to support air springs  92 ,  94 . Many suspension systems of the prior art have air springs that are mounted in an offset position from the trailing arms, resulting in undesirable additional structures needed to mount the springs, and adding weight and cost to the system.  
         [0048]     The preferred embodiment of the integral composite plate structure  21  of the present invention results in a substantial weight savings, which creates greater fuel economy for the vehicle. The weight savings of system  20  leads to longer life of associated components. Because there is less unsprung mass, components such as shock absorbers  88 ,  90  and brake systems  78 ,  80  attached to the axle/suspension system last longer. The relatively light weight of axle/suspension system  20  also reduces the cost of an associated lift kit, as known in the art.  
         [0049]     Manufacturing time and cost also are reduced by the elimination of components associated with axle/suspension systems of the prior art. For example, a TRI-FUNCTIONAL® bushing  19  ( FIG. 1 ) is not needed because axle/suspension system  20  distributes deflection throughout its entire structure. Instead, a simple bonded journal or shot bushing  37 ,  39  ( FIG. 4 ) is mounted in its respective mounting tube  365   38 , and can be used for the pivot connection of trailing arms  22 ,  24 , to frame hangers  44 ,  46 . The pivot bushing costs less, weighs less and lasts longer than a TRI-FUNCTIONAL® bushing. Components attached to axle/suspension system  20 , such as hangers  44 ,  46 , also are simplified, as pivot bushing  37 ,  39  allows a smaller hanger size to be used, also resulting in less weight and cost.  
         [0050]     Because portions of axle/suspension system  20  are made from a composite material, and specifically integral structure  21 , paint is unnecessary for a major portion of system  20 , contributing to lower manufacturing costs. Composite structure  21  eliminates corrosion problems as well, resulting in a longer life of axle/suspension system  20 . Furthermore, the cost of the required manufacturing equipment and processes is greatly reduced. For example, it is possible that the current state-of-the-art friction welder used to weld spindles  17  on axle ends  18  ( FIG. 1 ) could be eliminated, in turn eliminating the entire process surrounding the friction welder. Manufacturing problems also are reduced, as the elimination of metal parts that have to be welded together eliminates warpage of the structure that is associated with welding.  
         [0051]     While the invention has been described in the context of trailing arm axle/suspension systems, the invention also applies to leading arm axle/suspension systems.  
         [0052]     The present invention has been described with reference to a specific embodiment. It shall be understood that this illustration is by way of example and not by way of limitation. Potential modifications and alterations may occur to others upon a reading and understanding of this disclosure, and it is understood that the invention includes all such modifications and alterations and equivalents thereof.  
         [0053]     Accordingly, the improved distributed compliance axle/suspension system for wheeled vehicles of the present invention is simplified, provides an effective, safe, inexpensive, and efficient system which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior art axle/suspension systems, and solves problems and obtains new results in the art.  
         [0054]     In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0055]     Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described.  
         [0056]     Having now described the features, discoveries and principles of the invention, the manner in which the improved distributed compliance axle/suspension system is constructed, arranged and used, the characteristics of the construction and arrangement, and the advantageous, new and useful results obtained; the new and useful structures, devices, elements, arrangements, parts and combinations, are set forth in the appended claims.