Patent Publication Number: US-2019168558-A1

Title: Double wishbone independent trailer suspension

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Patent Application No. 62/378,077, filed Aug. 22, 2016, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This patent application is directed to vehicle suspension and, more specifically, independent trailer suspension. 
     BACKGROUND 
     Traditional trailer suspension is based on one or more solid axles that connect the left and right hand wheels together. The axles are mounted on either a set of leaf springs or on a pair of trailing arms supported by pneumatic air springs, for example. A disadvantage of this arrangement is that it couples the movement of the left and right hand side wheels, which can cause tire wear and roll instability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the double wishbone independent trailer suspension introduced herein may be better understood by referring to the following Detailed Description in conjunction with the accompanying drawings, in which like reference numerals indicate identical or functionally similar elements: 
         FIG. 1  is a side view in elevation of a representative semi-trailer truck. 
         FIG. 2  is an isometric view of a double wishbone independent trailer suspension according to a representative embodiment. 
         FIG. 3  is an end view of the double wishbone independent trailer suspension introduced in  FIG. 2 . 
         FIG. 4  is a top plan view of the double wishbone independent trailer suspension shown in  FIGS. 2 and 3 . 
         FIG. 5  is a side view in elevation of the double wishbone independent trailer suspension shown in  FIGS. 2-4 . 
         FIG. 6  is a partial isometric view of the suspension sub-frame. 
         FIG. 7  is an isometric view of the spindle and wishbone arms as viewed from the spindle. 
         FIG. 8  is an isometric view of the spindle and wishbone arms as viewed from the wishbone arms. 
         FIG. 9  is an isometric view of the upper wishbone. 
         FIG. 10  is an isometric view of the lower wishbone. 
         FIG. 11  is an isometric view of the spindle. 
     
    
    
     The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed embodiments. Further, the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be expanded or reduced to help improve the understanding of the embodiments. Moreover, while the disclosed technology is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the embodiments described. On the contrary, the embodiments are intended to cover all modifications, equivalents, and alternatives falling within the scope of the embodiments as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Overview 
     A double wishbone independent trailer suspension is disclosed. In an embodiment, the double wishbone suspension includes a slider frame configured for attachment to a semi-trailer. The slider frame includes a longitudinal central beam and upper and lower clevis brackets located on opposite sides of the central beam. A pair of upper wishbones are attached to the upper clevis brackets and at least one air spring is positioned between the slider frame and each upper wishbone. A pair of lower wishbones are attached to the lower clevis brackets and a pair of spindles are each pivotably attached to a corresponding upper wishbone and a corresponding lower wishbone. 
     GENERAL DESCRIPTION 
     Various examples of the device and systems introduced above will now be described in further detail. The following description provides specific details for a thorough understanding and enabling description of these examples. One skilled in the relevant art will understand, however, that the techniques discussed herein may be practiced without many of these details. Likewise, one skilled in the relevant art will also understand that the technology can include many other features not described in detail herein. Additionally, some well-known structures or functions may not be shown or described in detail below so as to avoid unnecessarily obscuring the relevant description. 
     The terminology used below is to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of some specific examples of the embodiments. Indeed, some terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this section. 
     Traditional semi-trailer suspension is based on one or more solid axles that connect the left and right hand wheels together. The axles are mounted on either a set of leaf springs or on a pair of trailing arms supported by pneumatic air springs, in the case of an air ride system. A disadvantage of this arrangement is that it couples the movement of the left and right hand side wheels. Therefore, in an asymmetric loading condition such as a single wheel bump or lateral weight transfer under cornering, it is not possible for the single loaded wheel to move without having an effect on its opposite paired wheel. Due to the geometry of the solid axle based suspension, this movement when viewed from above the vehicle, will tend to create a rotation in the axle that introduces a steering input. This roll steer input typically pulls the trailer in the direction of the loaded wheel. Thus, in a situation where the trailer is cornering, the roll steer will act to pull the trailer deeper into the turn, potentially creating roll instability. 
     Coupling the wheels together also creates additional tire wear because any motion of one wheel will be transferred to its oppositely paired wheel which leads to increased tire scrubbing of the second wheel. Also, the solid axle suspension typically has a high unsprung mass which means the suspension will be less able to follow undulations in a road surface resulting in the additional possibility of wheel hop and other undesirable wheel movements that contribute to tire scrubbing and ultimately lower tire life. 
     In the case of traditional air ride suspensions, the solid axle is mounted on a pair of trailing arms that constrain the movement of the axle along the circumference of an arc. The axis of this arc is perpendicular to the longitudinal axis of the trailer. Under braking, this allows the wheel to hop reducing the vertical load on the wheel, in turn reducing the effectiveness of the braking force generated by the braking system and thus reducing the potential stopping distance of the vehicle. 
     The disclosed double wishbone suspension resolves these issues in at least two ways. First, it is an independent system that decouples the left and right side wheels. This means that the overall suspension has a lower unsprung weight for each wheel, thus allowing both wheels to better follow the variations in the road surface. By decoupling the left and right wheels there is also no interaction between them thus minimizing a potential source of tire wear. It also eliminates any roll steer effects as asymmetric deflection of suspension does not generate a steering input. Secondly, the hinge mechanism of this system is parallel to the longitudinal axis of the vehicle so under braking action, wheel movement does not reduce the braking force generated at the tire contact patch. 
       FIG. 1  is a schematic representation of a semi-trailer truck  10  including a tractor unit  12  connected to a semi-trailer  14 . Semi-trailer  14  includes a double wishbone independent trailer suspension  100  according to a representative embodiment. The double wishbone suspension  100  includes a slider frame  110  that is interchangeable with a conventional suspension system that connects to the two main frame rails of the trailer chassis (not shown). The double wishbone suspension  100  includes four spindles  112  each carrying two wheels  114 . In some embodiments, the slider frame  110  connects to the two main frame rails of the trailer chassis so that the entire suspension can be moved along the length of the chassis. This variation allows the driver to adjust the positioning of the trailer&#39;s wheels to compensate for variations in the type and load distribution of the cargo the trailer is carrying. In other embodiments, the slider frame  110  is integrally mounted (e.g., welded or bolted) to the trailer chassis. 
     With reference to  FIGS. 2-5 , the illustrated embodiment of the double wishbone suspension  100  includes four spindles  112  (wheels omitted for clarity) suspended from the sub-frame or slider frame  110 . Because all four spindles  112  are suspended from the slider frame  110  using the same double wishbone arrangement, a description of one is equally applicable to all four spindles  112 . Furthermore, although the embodiments disclosed herein are described with respect to a tandem axle (e.g., two pairs of opposed spindles), the disclosed technology can be applied to single axle suspensions (e.g., one pair of opposed spindles) or suspensions with more than two axles. 
     An upper control arm or wishbone  116  and a lower control arm or wishbone  118  extend from the slider frame  110  to the spindle  112 . As perhaps best shown in  FIG. 3 , a pair of air springs  120  are mounted on the slider frame  110  and connect to the upper wishbone  116  to support the trailer&#39;s weight. The dual air spring arrangement provides enhanced load capabilities in a relatively compact envelope for positioning in the slider frame  110 . A shock absorber  122  extends between the slider frame  110  and the lower wishbone  118  to help damp and control the movement of the double wishbone suspension. 
     As shown in  FIG. 6 , the slider frame  110  comprises a weldment including a central beam  124  extending along a frame axis A F . The frame axis A F  is substantially parallel to a longitudinal axis of the trailer&#39;s chassis. Multiple transvers beams  126  are connected to the central beam  124  with braces  127 . Various additional connecting members join the frame members together and provide mounting points for the suspension system components as shown in the figure. The slider frame  110  includes upper and lower clevis brackets  132  and  134 , respectively. The slider frame  110  also includes an air spring mount  128  with left and right angled air spring plates  130 . The slider frame  110  also includes upper shock mounts  136  adjacent the air spring mounts  128 . Although a particular frame structure is disclosed herein, other arrangements of beams and connecting members can be used without deviating from the scope of the disclosed technology. Furthermore, in some embodiments, the upper and lower clevis brackets  132 ,  134 , air spring mount  128 , and upper shock mount  136  can be attached (e.g., bolted or welded) directly to the trailer chassis rather than a separate sub-frame (e.g., slider frame). 
     With further reference to  FIGS. 7 and 8 , the upper wishbone  116  attaches to the upper clevis brackets  132  for rotation about an upper axis A U . Similarly, the lower wishbone  118  attaches to the lower clevis brackets  134  for rotation about a lower axis A L . The upper and lower axes A U , A L  are substantially parallel to each other as well as the frame axis A F . The wishbones can be fastened to their respective clevis brackets with suitable bolts, for example. The upper wishbone  116  includes an air spring mount  140  positioned at an angle corresponding to an associated air spring plate  130  of slider frame  110  ( FIG. 6 ). The angled air spring plate  130  and angled spring mount  140  compress the air spring  120  along its axis throughout a majority of the suspension travel. The air springs  120  can be attached to the mounting plates with suitable fasteners (not shown). As shown in  FIG. 8 , the shock absorber  122  is connected at a first end to the lower wishbone  118 . The second end of the shock absorber is connected to the upper shock mount  136  ( FIG. 6 ) of slider frame  110 . 
     The upper wishbone  116  comprises a weldment including a pair of arms  162  interconnected with a cross-brace  164  as shown in  FIG. 9 . Each arm  162  includes an inner rod end  144  threaded into the arm for connection to the upper clevis brackets  132  ( FIG. 6 ) of the slider frame  110 . The cross-brace  164  includes an outer rod end  142  for connection to the spindle  112  ( FIGS. 7 and 8 ). As shown in  FIG. 10 , the lower wishbone  118  comprises a weldment including a pair of arms  166  interconnected with a cross-brace  168 . Each arm  166  includes an inner rod end  146  for connection to the spindle  112  and an outer rod end  148  for connection to the lower clevis brackets  134  ( FIG. 6 ). A lower shock mount  150  is positioned on the cross-brace  168  for mounting the shock absorber  122  ( FIGS. 7 and 8 ). The rod ends ( 142 ,  144 ,  146 , and  148 ) of the upper and lower wishbones are connected to their respective clevis brackets and spindle with suitable bolts, for example. As used herein, the term wishbone generally refers to upper and lower control arms regardless of whether they resemble a wishbone or not. For example, the upper control arm  116  has a triangular shape resembling a wishbone. However, the lower control arm  118  resembles an H. Nevertheless, both are referred to herein as wishbones. 
     As can be appreciated with reference to  FIGS. 9 and 10 , the upper and lower wishbones  116 ,  118  directly connect to the spindle  112  at three points of contact (i.e., rod ends  142  and  148 ) to prevent rotation of the spindle relative to the slider frame  110 , thereby simplifying the suspension for use on a trailer which does not need steering capabilities. However, in some embodiments, the double wishbone suspension can be converted to a steerable configuration. In some embodiments, the double wishbone suspension can also be converted to a lift axle with the addition of suitable air actuators connected to at least one of the upper or lower wishbones. 
     It should be appreciated that the rod ends ( 142 ,  144 ,  146 , and  148 ) are threaded into their respective wishbones, thereby providing for wheel alignment adjustments, including for example camber and toe adjustment, also caster for steerable configurations. Although, the suspension pivots are shown and described as rod ends, other rotating or pivoting joint mechanisms can be used. As shown in  FIG. 11 , the spindle  112  comprises a weldment including an axle portion  152  attached to an upper spindle clevis  154  and two lower spindle devises  156  configured to receive the rod ends of the upper and lower wishbones ( 116 ,  118 ). 
     In some embodiments, the double wishbone independent trailer suspension can include pneumatic controls to adjust the ride height of the suspension, compensate for varying loads, and to further enhance roll stability. For example a suitable pneumatic system is described in co-pending U.S. Patent Application No. 62/378,081 (Attorney Docket No. 89143-8081.US00), filed Aug. 22, 2016, entitled PNEUMATIC ANTI-ROLL SYSTEM, the disclosure of which is incorporated herein by reference in its entirety. 
     In light of the foregoing, the double wishbone suspension provides the following improved features for a trailer suspension system: increased suspension mobility freedom by removing the solid axle constraint between the left and right wheel sets; shifts wheel hop vibration mode frequency away from low ground frequency excitation and removes the ground excitation of pendulum based trailing arm suspension; provides smoother ride quality caused by arbitrary left/right road profile excitation; removes roll steer and truck trailer lateral instability causing trailer rollover accidents; provides steerable trailer wheels for improved vehicle handling and stability in turns and improved tire wear with turning radius center of curvature; provides access to lower trailer design center of gravity height and improved vehicle stability; and provides for future suspension feedback control applications like electronic stability control. The disclosed double wishbone suspension also provides customer continuous improvement features with adjustment of upper and lower control arm geometry that affect: wheel toe and camber angles; trailer roll control associated with alternative left/right jounce/rebound; aftermarket suspension customization for customer specific ride and handling profiles and trailer response; and tuning of wheel hop and roll vibration modes. 
     Although a particular representative embodiment of the double wishbone suspension is described herein, it should not be interpreted as limiting and other embodiments and variations are possible. For example, the following features can be varied without deviating from the scope of the disclosed technology: total number of axles; location of each axle; track; overall width; ride height; ground clearance; jounce and rebound suspension travel either individually or both directions; load capacity; ride quality; handling characteristics; steerable axles; lift axles; steerable and lift axles combined; strength of individual components; weight of individual components; method of manufacture of individual components; and durability of individual components. 
     REMARKS 
     The above description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in some instances, well-known details are not described in order to avoid obscuring the description. Further, various modifications may be made without deviating from the scope of the embodiments. Accordingly, the embodiments are not limited except as by the appended claims. 
     Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not for other embodiments. 
     The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. It will be appreciated that the same thing can be said in more than one way. Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, and any special significance is not to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for some terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any term discussed herein, is illustrative only and is not intended to further limit the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions, will control.