Abstract:
A suspension arrangement for a vehicle including a leaf spring element having a substantially longitudinal configuration. Also included is a deflection limiting element coupled to said leaf spring element at an intermediate location thereof, wherein said deflection limiting element comprises a J-shaped spring element. Further included is a resilient element attached to said J-shaped spring element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims priority to U.S. patent application Ser. No. 12/990,612, filed Mar. 2, 2011, which claims the benefit of International Application Serial No. PCT/US2009/002782, filed May 4, 2009, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/126,426, filed May 2, 2008, each of which are incorporated herein by reference in their entireties. 
     FIELD OF THE INVENTION 
     This invention relates generally to suspension systems for vehicles, and more particularly, to a leaf suspension arrangement that employs a dual leaf suspension with a deflection limiting element disposed therebetween 
     BACKGROUND 
     Leaf spring systems have for many years been used for the suspension of wheeled vehicles. The central element of a leaf spring suspension system for a vehicle is termed a “semi-elliptical” spring configured as an arc-shaped length of spring steel having a substantially rectangular cross-section. At the center of the arc is provided an arrangement for coupling to the axle of the vehicle. At the ends are provided coupler holes for attaching the spring to the vehicle body. For heavy vehicles, leaf springs are stacked on one other to form layers of springs of different lengths. Leaf springs are still used in heavy commercial vehicles and railway carriages. In the case of very heavy vehicles, leaf springs provide the advantage of spreading the load over a larger region of the vehicle&#39;s chassis. A coil spring, on the other hand, will transfer the load to a single point. 
     The well-known Hotchkiss drive, the name of which derives from the French automobile firm of Hotchkiss, employs a solid axle that is coupled at its ends to the centers of respective semi-elliptical leaf springs. There are a number of problems with this form of drive arrangement. First, this drive system is characterized by high unsprung mass. Additionally, the use of a solid axle results in coupled left/right wheel motion. During heavy cornering and fast acceleration, this known system suffers from vertical deflection and wind-up. 
     One effort to address the problems associated with the Hotchkiss system employs a parallel leaf spring arrangement at each end of a solid axle. This known arrangement affords increased axle control, in the form of reduced power hop. Other advantages of this arrangement include roll under steer, auto load leveling and the gross vehicle weight, and no frame changes are required to convert from a Hotchkiss system. However, the parallel leaf spring arrangement employs a solid axle, and therefore does not provide the benefits of independent suspension. In addition, this arrangement is plagued with the disadvantage of high unsprung mass. 
     A de Dion tube vehicle suspension arrangement is a known form of semi-independent suspension and constitutes an improvement over the Hotchkiss drive. In this type of suspension, universal joints are employed at the wheel hubs and the differential, and additionally provided is a solid tubular beam that maintains the opposing wheels in parallel. The de Dion tube is not directly connected to the chassis and is not intended to flex. 
     The benefits of a de Dion suspension include a reduction in the unsprung weight compared to the Hotchkiss drive. This is achieved by coupling the differential to the chassis. In addition, there are no camber changes during suspension unloading. Since the camber of both wheels is set at zero degrees, the traction from wide tires is improved, and wheel hop under high power operations is reduced compared to an independent suspension. However, the de Dion tube adds unsprung weight. 
     SUMMARY OF THE INVENTION 
     According to one embodiment, a suspension arrangement for a vehicle includes a leaf spring element having a substantially longitudinal configuration. Also included is a deflection limiting element coupled to said leaf spring element at an intermediate location thereof, wherein said deflection limiting element comprises a J-shaped spring element. Further included is a resilient element attached to said J-shaped spring element. 
     According to another embodiment, a vehicle suspension arrangement for a vehicle of the type having a chassis rail and a longitudinal axle arranged substantially orthogonal to the chassis rail, the vehicle suspension arrangement including a primary leaf spring having a plan view longitudinal configuration, a first end for pivotally coupling to the chassis of the vehicle at a first pivot coupling, and a second end for coupling to the chassis of the vehicle at a second pivot coupling. Also included is a secondary leaf spring having a plan view longitudinal configuration, a first end for pivotally coupling to the chassis of the vehicle at a pivot coupling, and a second end for coupling to the longitudinal axle. Further included is a deflection limiting element disposed between the primary and secondary leaf springs for controlling a distance therebetween, the deflection limiting element disposed at an intermediate location relative to the first end and the second end of the secondary leaf spring. 
     According to yet another embodiment, a method of controlling a ride characteristic of a vehicle having a dual leaf suspension with first and second leaf elements is provided. The method includes limiting the distance between the first and second leaf elements with a J-shaped deflection limiting element disposed between the first and second leaf elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Comprehension of the invention is facilitated by reading the following detailed description, in conjunction with the annexed drawing, in which: 
         FIG. 1  is a perspective view of a suspension arrangement according to one embodiment of the invention; 
         FIG. 2  is a side plan simplified schematic illustration of a rotary joint suspension arrangement and a deflection limiting element in accordance with an aspect of the invention; 
         FIG. 3  is a simplified lateral plan representation of a half leaf spring with the deflection limiting element attached thereto; 
         FIG. 4  is a simplified schematic representation of a side view of the suspension arrangement constructed in accordance with another aspect of the invention; 
         FIG. 5  is a simplified schematic representation of a side view of the suspension arrangement in accordance with another aspect of the invention; and 
         FIGS. 6(   a ) and  6 ( b ) are simplified schematic representations that illustrate the stresses that result from leaf spring wind-up. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a perspective representation of a specific illustrative embodiment of the invention. As shown in this figure, a vehicle suspension system  100  has a chassis that is generally designated as chassis  110 . The chassis has a pair of substantially parallel chassis rails  112   a  and  112   b  that are coupled to one another by cross-braces  116  and  118 . 
     A differential drive arrangement  120  is fixedly coupled to the chassis and converts the rotatory motion of a drive shaft  122  to substantially orthogonal rotatory motion at half shafts  125   a  and  125   b . Each half shaft has an associated pair of universal joints (not specifically designated) that are arranged to be proximal and distal with respect to the differential drive arrangement. Thus, the half shafts, each of which has an associated longitudinal axis (not shown), accommodate transaxial motion, particularly by operation of the proximal universal joints. 
     Half shafts  125   a  and  125   b  are shown to be coupled at their distal ends to respective leaf springs  130   a  and  130   b . Referring to leaf spring  130   a , for example, the leaf spring is, in this specific illustrative embodiment of the invention, pivotally coupled at its forward end to a bracket  132   a . At its rearward end, leaf spring  130   a  is pivotally coupled to a link  134   a . As shown in this figure, there is additionally provided a half leaf spring  136   a  that is also, in this specific illustrative embodiment of the invention, coupled at its forward end to bracket  132   a . At its rearward end, half leaf spring  136   a  is coupled to the distal end of half shaft  125   a . Half leaf spring  136   a  is shown in this specific illustrative embodiment of the invention, to engage a fulcrum  133   a.    
     In this embodiment of the invention, there is attached to half leaf spring  136   a  a J-shaped spring element  160 . J-shaped spring element  160  is, in this specific illustrative embodiment of the invention, coupled to half leaf spring  136   a  by two fasteners (not specifically designated in this figure). J-shaped spring element  160 , additional elements of structure related thereto, such as an elastomeric fulcrum element (not shown in this figure) disposed between the J-shaped spring element and leaf spring  130   a , and its kinematic and other effects on the characteristics of half leaf spring  136   a  and leaf spring  130   a , will be described in greater detail below. A further J-shaped spring element is, in the practice of the invention, installed on half leaf spring  136   b . However, the further J-shaped spring element on half leaf spring  136   b  is not shown in this figure for sake of clarity of the figure. 
     There is additionally shown in this figure a transverse beam  140  that is coupled to cross-brace  116  by a damper  142  and to cross-brace  118  by a further damper  144 . Transverse beam  140  has installed thereon a pivoting member  150  to which are attached link elements  152  and  154 . The link elements are attached, via brackets (not specifically designated), to cross-brace  118 . 
     It is to be understood that the inventive J-shaped spring element  160  described herein is not limited in its application to the specific suspension arrangement represented in  FIG. 1 . Persons of skill in the art, in light of the teaching herein, will be able to generate additional embodiments of the J-shaped spring element as required to be accommodated within other vehicle suspension arrangements. Such additional embodiments may include, for example, a J-shaped spring element that more closely resemble an L-shaped spring element, as shown in the schematic representation of  FIG. 6(   b ); a C-shaped spring element (not shown); a pillar, or I-shaped spring element (not shown); a closed, or O-shaped spring element (not shown); a U-shaped spring element (not shown); or the like. However, for purposes of the description of the invention herein presented, the term “J-shaped spring element” shall be deemed to encompass all such alternative embodiments and equivalents thereof. 
       FIG. 2  is a side plan simplified schematic illustrations of a rotaryjoint suspension arrangement  200  and further having J-shaped spring element  160  constructed in accordance with the principles of the invention. Elements of structure that bear analogous correspondence to elements of structure that have previously been discussed are similarly designated in this figure. Referring to  FIG. 2 , it is seen that there is provided a leaf spring  130   a  that, in this specific illustrative embodiment of the invention, is pivotally coupled at its forward and rear ends, as previously described. There is additionally provided a half leaf spring  210  that is also, in this specific illustrative embodiment of the invention, pivotally coupled at a pivot mount  212  at its end distal to a further pivotal mounting  213  at a coupling member  214 . The coupling member is itself coupled to axle shaft  215 . 
       FIG. 2  further illustrates a pivot link mounting arrangement  220  wherein leaf spring  130   a  is securely clamped between clamping member  222  and  224 . Clamping member  224  is coupled to a pivot joint  226  that is itself engaged with coupling  214 . This arrangement permits a further degree of motion that reduce system internal loading on the pivot joint arrangement and leaf spring elements. 
     In accordance with the invention, there is provided J-shaped spring element  160  coupled to half leaf spring  210  by means of fasteners  162 . J-shaped spring element has a fulcrum element  164  formed, in this specific illustrative embodiment of the invention, of an elastomeric material. Fulcrum element  164 , as will be described below, communicates with leaf spring  130   a  to effect an advantageous change in the overall spring characteristic of the vehicle suspension. 
       FIG. 3  is a simplified lateral plan representation of the half leaf spring with the J-shaped spring element attached thereto. Elements of structure that have previously been discussed are similarly designated. As shown in this figure, J-shaped spring element  160  coupled to half leaf spring  210  by means of fasteners  162 . The J-shaped spring element has installed thereon a fulcrum element  164  formed, for example, of an elastomeric material. J-shaped spring element  160  has at each of its ends, terminations  168  that facilitate pivotal coupling of the J-shaped spring element to the chassis (not shown in this figure) and the axle (not shown in this figure) in a conventional manner. 
       FIG. 4  is a simplified schematic representation of a side view of a suspension system constructed in accordance with the principles of the invention with a 1st stage consisting of a coil spring. Elements of structure that have previously been discussed are similarly designated. Coil spring  455  provides vertical load support in combination with first stage leaf spring  457 . A lower leaf  460  of the 2nd stage is employed for additional control. In this specific illustrative embodiment of the invention, the center of axle  411  travels along a path that conforms to curved arrow  462 , as seen in the present side view. In accordance with the invention, J-shaped spring element  160  is shown to be coupled to lower leaf  460  by means of fasteners (not specifically designated in this figure). As previously noted, in other embodiments of the invention the J-shaped spring element is coupled to first stage leaf spring  457 , such other embodiments not being shown. 
       FIG. 5  is a simplified schematic representation of a side view of a suspension system constructed in accordance with the principles of the invention with a 1st stage consisting of an air-pressure responsive resilient element in the form of an air spring  455   a . Elements of structure that have previously been discussed are similarly designated. Air spring  455   a  provides vertical load support in combination with first stage leaf spring  457 . As described above in relation to  FIG. 4 , lower leaf  460  of the 2nd stage is employed for additional control. Center of axle  411  travels along a path that conforms to curved arrow  462 , as seen in the present side view. In accordance with the invention, J-shaped spring element  160  is shown to be coupled to lower leaf  460  by means of fasteners (not specifically designated in this figure). 
       FIGS. 6(   a ) and  6 ( b ) are simplified schematic representations that illustrate the stresses that result from leaf spring wind-up ( FIG. 6(   a )) without the J-shaped spring element, and the beneficial effect that is achieved when the J-shaped spring element is employed ( FIG. 6(   b )). The schematic representations of these figures represent computer models of the stresses applied in an embodiment of the invention installed on a Chrysler heavy duty truck (3500 series). As shown in  FIG. 6(   a ), there is not provided a J-shaped spring element, and the resulting wind-up of the primary leaf spring results in a stress applied that exceeds 1700 MPa. The rotational displacement resulting from this wind-up stress is on the order of 18.43[deg.], which translates into a stiffness parameter of approximately 34.5 Nm/degree. 
       FIG. 6(   b ) illustrates computer-modeled stresses that are applied to the leaf spring elements when the J-shaped spring element is employed (shaped substantially as an L-shaped spring element). As shown, the primary spring experiences a range of stresses from less than 700 MPa to approximately 660.85 MPa. Thus, the stress is reduced considerable by implementation of the J-shaped spring element. In addition, it is noted that the rotational displacement resulting from this wind-up stress is on the order of 4.40 [deg.], which translates into a stiffness parameter of approximately 152 Nm/degree. This equates to an increase in stiffness by a factor of 4.41, without significant increase in unsprung mass. 
     Although the invention has been described in terms of specific embodiments and applications, persons skilled in the art may, in light of this teaching, generate additional embodiments without exceeding the scope or departing from the spirit of the invention described herein. Accordingly, it is to be understood that the drawing and description in this disclosure are proffered to facilitate comprehension of the invention, and should not be construed to limit the scope thereof.