Patent Publication Number: US-2004046350-A1

Title: Method and apparatus for suspending a vehicular wheel assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] This is a Continuation-in-Part of U.S. patent application Ser. No. 10/152,083, filed on May 20, 2002, which claims the benefit of U.S. Provisional Application No. 60/292,355, filed May 21, 2001 and U.S. Provisional Application No. 60/499,305, filed Aug. 29, 2003, each of which are hereby incorporated by reference in their entireties. This application contains subject matter which is related to the subject matter of U.S. Pat. No. 6,173,978, issued Jan. 16, 2001, U.S. Pat. No. 6,550,797, issued Apr. 22, 2003 and U.S. patent application Ser. No. 10/385,404, filed on Mar. 10, 2003, each of which are hereby incorporated by reference in their entireties. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] This invention relates in general to vehicle suspensions systems, and deals more particularly with vehicle suspensions capable of controlling vehicle roll and pitch.  
       BACKGROUND OF THE INVENTION  
       [0003] The suspension of a vehicle determines the ride characteristics of the vehicle such as its roll and pitch. The term “roll” refers to rotational movement of the vehicle body about a longitudinal axis of the vehicle. Roll is typically encountered during cornering. The term “pitch” refers to rotational movement of the vehicle body about a widthwise axis of the vehicle. Pitch is typically encountered during acceleration (acceleration “squat”) and during braking (braking “dive”).  
       [0004] Vehicle suspension systems can be characterized as either active or passive. Many fundamental aspects of vehicle suspension systems are discussed in reference tomes such as ‘Race Car Vehicle Dynamics’, by William F. Milliken and Douglas L. Milliken (1995), herein incorporated by reference in its entirety.  
       [0005] “Active” suspension systems typically adjust suspension elements during use in response to sensed operating conditions. Active suspension systems are often relatively complex, prohibitively expensive, or both. Passive suspension systems, on the other hand, typically include anti-roll or stabilizer bars, or the like that cannot be adjusted during use. Passive suspension systems are typically relatively simple and affordable.  
       [0006] In passive suspension systems that utilize elements such as springs and anti-roll bars to reduce cornering roll, there is a trade-off between reduction in roll and the smoothness of the ride. Spring and shock rates that increase the smoothness of the ride often counteract the effect of conventional anti-roll devices. Moreover, such anti-roll devices do not compensate for variations in weight distribution of the vehicle that can also significantly affect rolling characteristics.  
       [0007] With the forgoing problems and concerns in mind, it is the general object of the present invention to provide a vehicular suspension system which overcomes the above-described drawbacks while providing favorable roll and pitch characteristics.  
       SUMMARY OF THE INVENTION  
       [0008] It is, therefore, an object to provide a vehicular suspension system that provides favorable roll and pitch characteristics.  
       [0009] According to the present invention, a suspension for a vehicle having a body is provided. The suspension includes a first wheel assembly suspension and a second wheel assembly suspension. The first wheel assembly suspension extends between a first wheel assembly and the body. The first wheel assembly suspension includes an instant center. The second wheel assembly suspension extends between a second wheel assembly and the body. The second wheel assembly suspension includes an instant center. The first wheel assembly and the second wheel assembly are aligned so that a vertical centerline of each wheel assembly lies within a vertical plane that extends therebetween. In one embodiment, the instant center of each wheel assembly suspension is located within the vertical plane, below a roll center located within the vertical plane.  
       [0010] According to a further aspect of the invention, a method for suspending a vehicle having a body is provided that includes the steps of: (1) providing a first wheel assembly suspension that extends between a first wheel assembly and the body, wherein the first wheel assembly suspension includes an instant center; (2) providing a second wheel assembly suspension that extends between a second wheel assembly and the body, wherein the second wheel assembly suspension includes an instant center; (3) aligning the first wheel assembly and the second wheel assembly so that a vertical centerline of each wheel assembly lies within a vertical plane that extends therebetween; and (4) positioning the first wheel assembly suspension and the second wheel assembly suspension so that the instant center of each wheel assembly suspension is located within the vertical plane, below a roll center located within the vertical plane.  
       [0011] An advantage of the present suspension is that it is possible to create a relatively high and stable roll center using the present suspension, and therefore a desirable stable vehicular suspension. The relatively high roll center can be maintained in approximately the same position during expected motion of the vehicle.  
       [0012] These and other objects, features, and advantages of the present invention will become apparent in light of the drawings and detailed description of the present invention provided below.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013]FIG. 1 is a diagrammatic front view of a vehicle showing the present suspensions.  
     [0014]FIG. 2 is a diagrammatic view of a support arm used within the present suspension.  
     [0015]FIG. 3 is a diagram showing relative plane positioning.  
     [0016]FIG. 4 is a diagram that illustrates the relationship of the support arm planes within a vertical transverse (or “widthwise”) extending plane passing through the vertical centerline of the wheels.  
     [0017]FIG. 5 is a diagram showing relative plane positioning.  
     [0018]FIG. 6 is a diagram that illustrates the relationship of the support arm planes within a longitudinally extending plane passing through the vertical centerline of the wheel.  
     [0019]FIG. 7 is a diagrammatic top view of a vehicle illustrating the orientation of the body mount lines of the present suspension relative to a longitudinally extending line.  
     [0020]FIG. 8 is a diagrammatic elevation view of the present suspension illustrating the position of the ball joint mounts relative to the wheel assembly.  
     [0021]FIG. 9 is a diagram that illustrates the relationship of the kingpin axis and the wheel assembly so that the positionability of the kingpin axis possible with the present suspension can be fully appreciated.  
     [0022]FIG. 10 is a diagrammatic view of an embodiment of the present suspension that includes a spring assembly.  
     [0023]FIG. 11 is a diagrammatic view of a spring assembly embodiment that can be used with the present invention suspension.  
     [0024]FIG. 12 is a diagrammatic view of a spring assembly embodiment that can be used with the present invention suspension.  
     [0025] FIGS.  13 - 15  are diagrams illustrating Ackermann steering geometry between the front wheels of a vehicle. FIG. 13 shows wheels having one-hundred percent Ackermann. FIG. 14 shows wheels having “neutral” Ackermann (also referred to as parallel orientation), and FIG. 15 shows wheels having reverse Ackermann.  
     [0026]FIG. 16 is a diagrammatic isometric view of a suspension system, according to another embodiment of the present invention.  
     [0027]FIG. 17 is a front schematic view of the suspension system illustrated in FIG. 16.  
     [0028]FIG. 18 is a diagrammatic isometric view of yet another embodiment of the suspension system.  
     [0029]FIG. 19 is a front schematic view of the roll center of the vehicle as the wheel assembly moves through its path. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0030] A vehicular suspension is described herein that can be used on a wide variety of different vehicular applications. The suspension is used with independently suspended wheel assemblies. The wheel assembly may be driven or non-driven. Consequently, the suspension can be used with rear wheel drive (RWD), front wheel drive (FWD), and all wheel drive (AWD) vehicles.  
     [0031] Referring to FIGS. 1 and 2, the present suspension  20 , 21  for a vehicular wheel assembly  22  includes a pair of support arms  24 , 26  extending between the body  28  of the vehicle and the wheel assembly  22 . The terms “vehicle body” or “body of the vehicle” as used herein are defined as including the frame and chassis components attached thereto; e.g. sheet metal components, frame rails, doors, fenders, panels, interior, drivetrain, etc. In some vehicular applications, a subframe is coupled with structural components integrated into the sheet metal components of the vehicle in place of a conventional full frame. Other vehicular applications utilize a “unibody” style chassis that does not have an independent frame or subframe. Rather, all structural components are directly integrated into the sheet metal components of the vehicle. The present invention contemplates and is useful with all of these different types of vehicle bodies, and is not therefore limited to use with any one of the above.  
     [0032] The elements of the wheel assembly  22  will vary depending on the nature of the car (e.g., RWD, FWD, AWD) and in most instances also depend on the position of wheel assembly  22  on the vehicle. The wheel assembly  22  elements can be generally described as including a spindle  30  and a wheel (may also be referred to as a tire)  32 . The spindle  30  includes an upper ball joint  34  and a lower ball joint  36 . Rear suspensions do not typically include conventional ball joints, but rather include pivotable mount; e.g., bushings, etc. To simplify the description herein, the term “ball joint” is used herein, unless otherwise specified, to refer to any type of pivotal connection for connecting the support arm  24 , 26  to the spindle  30 , including but not limited to, conventional ball joints, heim joints, bushings, etc. The wheel  32  is rotatably mounted on the spindle  30  in a manner known within the art.  
     [0033] Referring to FIG. 2, each support arm  24 , 26  includes a ball joint mount  38  (also referred to as a wheel assembly mount), a first body mount  40 , a first member  42 , a second body mount  44 , and a second member  46 . The first member  42  extends between the ball joint mount  38  and the first body mount  40 . The second member  46  extends between the ball joint mount  38  and the second body mount  44 . Some embodiments further include one or more lateral members  48  extending between the first and second members  42 , 46  to increase the rigidity of the support arm  24 , 26  and/or to provide an attachment point for additional suspension members (e.g., springs, shocks, etc.). The vehicle body  28  is pivotally attached to the support arm  24 , 26  at the first and second body mounts  40 , 44 . In some instances, one or both body mounts  40 , 44  include a pliable bushing that provides a limited amount of motion in addition to rotational motion around a pivot axis extending between the body mounts  40 , 44 . The ball joint mount  38  and the body mounts  40 , 44  in each support arm  24 , 26  define a plane. The first and second members  42 , 46  (and the lateral member(s)  48  if present) are not necessarily disposed in the plane of the support arm  24 , 26  of which they are a part, although they can be in some applications. The exact geometry of the first and second member  42 , 46  (and lateral member(s)  48 ) will vary to accommodate the application at hand.  
     [0034] Referring to FIGS. 1 and 3, the pair of support arms  24 , 26  extending between the body  28  of the vehicle and the wheel assembly  22  are arranged vis-à-vis the body  28  and the wheel assembly  22  such that one of the support arms  24  extends between the lower ball joint  36  and a pair of upper body mount connection points  50 , and the other support arm  26  extends between the upper ball joint  34  and a pair of lower body mount connection points  52 . The pair of upper body mount connection points  50  is disposed vertically above the pair of lower body mount connection points  52 , although not necessarily in the same vertically extending plane, when the vehicle wheels  32  are in contact with or proximate the ground. The members  42 , 46  of one of the support arms  24 , 26  are received between the members  42 , 46  of the other support arm  26 , 24 . Hence, the support arms  24 , 26  may be described as crossing one another in an “X” shaped arrangement, without normally touching one another.  
     [0035] The support arms  24 , 26  described above represent a preferred embodiment of the present invention, but do not represent all the possible embodiments of support arms  24 , 26 . In alternative embodiments, one or both of the support arms  24 , 26  can be replaced with independent links that extend along paths similar to those of the above-described support arms  24 , 26 ; e.g., a pair of independent links, each including a ball joint mount  38  on one end and a body mount  40 , 44  on the opposite end. Independent links can be used in place of one or both of the support arms  24 , 26 .  
     [0036]FIG. 4 shows a diagram representing a symmetrical suspension arrangement, including a pair of wheel assembly suspensions  20 , 21 , for a pair of wheel assemblies  22  each disposed on a side of the vehicle body  28  such as that shown in FIG. 1. The diagram is shown along a vertical plane  54  that passes through the vertical centerline  56  of both wheel assemblies  22 . FIG. 5 shows the plane  54  in a perspective view to better illustrate the position of the plane  54  relative to the wheel assemblies  22 . The lines  58 , 60  formed at the intersection of each support arm plane with the vertical plane  54  are shown in FIG. 4. Note that the support arm plane intersection lines  58 , 60  cross one another in each suspension  20 , 21  when viewed in this plane  54 . The intersection point  62 , 63  of the lines  58 , 60  is defined as the instant center (IC) for the front elevation view of that suspension  20 , 21 . FIG. 4 also shows a pair of lines  64 , 66  that intersect at the roll center  68  of the vehicle body  28 . One line  64  passes through the center of the tire ground contact patch  70  and the IC  62  on one side of the vehicle body  28 . The other line  66  passes through the center of the tire ground contact patch  71  and the IC  63  on the opposite side of the vehicle body  28 .  
     [0037] The vertical position of the roll center  68  relative to the center of gravity of the vehicle body  28  is significant because it affects the roll of the vehicle. The position of the roll center  68  can be adjusted by altering the relative positioning of the support arms  24 , 26  on either or both sides of the vehicle, and thereby alter the position of the IC  62 , 63  which is defined by the planes of the support arms  24 , 26 . An advantage provided by the present suspension is that it is possible to create a relatively high and stable roll center  68  using a pair of the present suspensions; i.e., a relatively high roll center than can be maintained in approximately the same position during expected motion of the vehicle.  
     [0038] It should also be noted that the roll center shown in FIG. 4 is intersected by the vertical centerline  72  of the vehicle body  28 . The roll center  68  intersects the centerline  72  because the suspensions on each side of the vehicle body  28  are symmetrical with one another. In some instances there is advantage to making the suspensions non-symmetrical and thereby cause the roll center  68  to be disposed on one side of the vehicle centerline  72 . In addition, under certain loading or body movement conditions, the roll center  68  may move to either side of the vehicle centerline  72 .  
     [0039] Referring to FIG. 6, the orientation of the support arm planes for a wheel suspension  20 , 21  also has important implications relative to other suspension parameters such as anti-dive, anti-squat, and anti-lift; i.e., suspension characteristics in the fore and aft direction of the vehicle (also referred to as “pitch”). FIG. 6 diagrammatically shows a side-view of a wheel assembly  22 . The view is shown along a longitudinal vertical plane  74 , 76  that passes through the centerline of the wheels  32  on one side of the vehicle body (see FIG. 3). In FIG. 6, the wheel  32  outline is shown in phantom to locate the other elements of the drawing. The lines  78 , 80  formed by the intersection of the support arm planes with the plane  74 , 76  passing through the centerline of the wheels  32  on that side of the vehicle body  28  illustrate an embodiment where the support arm planes are not parallel to a horizontal plane  82  (see FIG. 3). The lines  78 , 80  can be extended to a convergence point  84  that is the instant center of the suspension  20 , 21  in the side view.  
     [0040] A line  86  extending between the side view IC  84  and the center of the tire contact patch  70 , 71  on the ground forms an angle β with a horizontally extending line  88  that passes through the widthwise plane  54  extending through the centerline of the wheels  32 . The tangent of the angle β is directly related to the anti-dive, anti-lift, or anti-squat of the vehicle wheel assembly  22  being considered. Increasing or decreasing the magnitude of the angle β enables the adjustment of the anti-dive, anti-squat, or anti-lift to be suited to the application. The present suspension  20 , 21  facilitates the positioning of the convergence point  84  vertically and horizontally and thereby enables the use of a variety of advantageous β angle&#39;s for various vehicular applications. The convergence point  84  can also be positionally described in terms of a side view swing arm (svsa) height and length. The svsa height represents either: 1) the difference in vertical distance between the horizontal line  88  aligned with the wheel contact and the IC  84 ; or 2) the difference in vertical distance between the horizontal plane passing through the centerline of the wheel assembly and the IC. Which svsa height is appropriate depends on the position of the wheel assembly, whether it is driven, etc. The methodology to determine which is used is known and will therefore not be discussed further herein. The svsa length is the distance between the vertical centerline of the wheel assembly and the IC.  
     [0041] Referring to FIG. 7, the body mount line  90 , 92 , 94 , 96  of each support arm  24 , 26  can also be skewed from the longitudinally extending vertical axis  98  by an angle γ. The body mount line  90 , 92 , 94 , 96  is defined as a line that extends between the two body mounts  40 , 44  of the support arm  24 , 26 . FIG. 7 diagrammatically shows the wheel suspensions  20 , 21  of a vehicle in a horizontal plane to illustrate the angle γ extending between the body mount line  90 , 92 , 94 , 96  of each suspension  20 , 21  and a longitudinal line parallel to axis  98 . The suspensions  20 , 21  shown in FIG. 7 are all skewed by the angle δ. The exact amount of skew can vary to suit the application at hand and need not be similar between suspensions  20 , 21 ; e.g., front and rear wheel suspensions  20 , 21  having different skew angles, or between side to side suspensions  20 , 21  having different skew angles. The ability of the present suspension to be skewed from the longitudinal axis  98  of the vehicle makes it advantageously adaptable to a variety of vehicular applications.  
     [0042] Referring to FIG. 8, the crossed orientation of the support arms  24 , 26  within the present suspension facilitates positioning the ball joint mounts  34 , 36  relative to the wheel  32 . Historically, the spindle  30  of a wheel assembly  22  pivoted about a solid axle known as a “kingpin”. Later improvements replaced the kingpin with ball joints. The line  100  between the two pivot points  34 , 36  is still, however, referred to as the kingpin axis (or wheel assembly mount line). As can be seen in FIG. 8, the kingpin axis  100  passing through the ball joint mounts  34 , 36  of the support arms  24 , 26  forms an angle λ relative to the vertical centerline (disposed within plane  74 , 76  as diagrammatically shown in FIG. 3) of the wheel  32 .  
     [0043] In some instances, the kingpin axis  100  may be parallel to the vertical centerline  74 , 76  of the wheel  32  (zero degree angle—0°). In other instances, the angle between the kingpin axis  100  and the vertical centerline  74 , 76  is greater than zero and the kingpin axis  100  can therefore be described as extending toward (or away from) the vertical centerline  74 , 76 . The angle of the kingpin axis  100  relative to the vertical centerline  74 , 76 , and the position where the kingpin axis  100  intersects the vertical centerline  74 , 76 , are both significant because of the effects they have relative to the scrub radius of the wheel  32  and the length of the spindle  30 . The crossed orientation of the support arms  24 , 26  within the present suspension  20 , 21  enables the ball joint mount  38  from each support arm  24 , 26  to be positioned relatively close to the vertical centerline  74 , 76  of the wheel  32 .  
     [0044] Referring to FIG. 9, the crossed orientation of the support arms  24 , 26  within the present suspension  20 , 21  also provides favorable positionability of the ball joint mounts  38  vis-a-vis the caster angle and the trail of the kingpin axis  100 . The caster angle  102  refers to the angle of the kingpin axis  100  relative to the vertical centerline  56  of the wheel assembly  22  (or wheel  32 ) in the side-view of the wheel  32 . The trail  104  refers to the distance between the vertical centerline  56  of the wheel  32  and the point of intersection  106  between the kingpin axis  100  and the horizontal plane  106  containing the contact patch  70 , 71  of the wheel  32 .  
     [0045] Referring to FIGS.  10 - 12 , the present suspension  20 , 21  utilizes a spring assembly  108  that extends between, and is pivotally attached to, one of the support arms  24 , 26  (or spindle  30 ) and the vehicle body  28 . FIG. 10 shows the spring assembly  108  attached to the support arm  24  that is pivotally attached to the lower ball joint  36 , but in alternative embodiments the spring assembly  108  could be attached to the other support arm  26 . In one embodiment, the spring assembly  108  is a coil over shock that includes a load bearing spring and a shock absorber. A coil spring may also be mounted independently of a shock absorber. In addition, a torsion bar may be used with or in place of a coil spring. The spring assembly  108  is mounted so that the assembly is skewed at an angle φ of approximately fifteen degrees from vertical when the wheel  32  is a normal ride height. Skewing the spring assembly  108  in this manner with the geometry of the present suspension  20 , 21  creates a favorable wheel load rate characteristic. Specifically, the wheel load rate decreases as the wheel  32  travels upward, in the direction toward the vehicle body  28 . This occurs because the vertical component of the force transmitted through the spring assembly  108  decreases as the lower attachment point  110  of the spring assembly  108  rotates upward with the wheel  32 , while the spring assembly  108  pivots about its upper pivot point  112 . In some instances, more than one spring assembly is utilized, extending between the vehicle body  28  and one of the support arms  24 , 26  in a manner similar to that described above. The additional spring assemblies  108  may or may not include a shock absorber.  
     [0046] Referring to FIG. 11, in some embodiments, the spring assembly  108  includes a rebound spring  130  disposed within the shock absorber  120  that acts between the rod end  132  of the shock absorber piston  134  and the housing  136  of the shock. The rebound spring  130  is not attached to the piston  134  and therefore only acts in compression for a portion of the rod travel within the shock housing  136  beyond a predetermined engagement point  138 . In circumstances where wheel assembly  22  (and therefore suspension  20 , 21 ) travel causes the spring assembly  108  to extend beyond the engagement point  138  (i.e., below “normal ride height”), the rebound spring  130  compresses and thereby opposes the travel of the suspension  20 , 21  and attached wheel assembly  22 . In circumstances where the wheel assembly travel causes the spring assembly  108  to compress above the engagement point  138  (i.e., above normal ride height), the rebound spring  130  is not engaged and consequently has no effect on the travel of the suspension  20 , 21  and attached wheel assembly  22 .  
     [0047] Referring to FIG. 12, in another embodiment, the spring assembly  108  includes a center shaft  114 , a first spring  116 , and a second spring  118 . The spring assembly  108  further includes an additional motion damper  120 . The center shaft  114  is received within the first and second springs  116 , 118  and the motion damper  120  is attached to the center shaft  114 . Acceptable motion dampers  120  include, but are not limited to, a gas or liquid type shock absorber. The first spring  116  extends between a first end spring flange  122  and a center spring flange  124 . The first end spring flange  122  is either fixed to the center shaft  114  or is travel-limited by a first stop attached to the center shaft  114 . In either case, the first stop prevents the first end spring flange  122  from traveling further toward the adjacent end  126  of the spring assembly  108 . The second spring  118  extends between the center spring flange  124  and a second end spring flange  128 . A second stop attached to the outer body of the motion damper  120  (or other member similarly fixed) limits the travel of the center spring flange  124  and therefore the second spring  118  in the direction toward the first spring  116 . The spring assembly  108  shown in FIG. 11 shows the second spring  118  disposed around the periphery of the motion damper  120 .  
     [0048] In an uninstalled condition (or if the vehicle is lifted and the wheel assembly  22  is allowed to extend to its fully extended position), the first spring  116 , which acts on and between the first end spring flange  122  and the center spring flange  124 , is preferably only lightly loaded. The second spring  118 , which acts on and between the second end spring flange  128  and the center spring flange  124 , is preferably pre-loaded in compression by an amount appropriate for the application at hand. As the spring assembly  108  is loaded, only the first spring  116  will compress until the force provided by the first spring  116  equals or exceeds the initial pre-loaded force of the second spring  118 . When only the first spring  116  is compressing, the spring assembly  108  acts as thought the first spring  116  is the only spring present; i.e., a single spring system. When the force of the first spring  116  exceeds the initial pre-loaded force of the second spring  118 , the force of each spring  116 , 118  will equal and each spring will compress some amount. The exact amount either spring  116 , 118  will compress will depend on the spring rate of the particular spring. Under these conditions, the spring assembly  108  acts as though it is a twin spring system where the springs  116 , 118  are acting in series. As such, the center spring flange  124  can be described as floating between the first and second springs  116 , 118 . If, for example, the first and second springs  116 , 118  are identical four hundred pound springs, the spring assembly  108  will initially act as though it is a single four hundred pound spring system. When the force of the first spring  116  equals that of the second spring  118 , however, the spring assembly  108  will begin to act as a two spring in series system. As a result, the effective spring force of the first and second springs  116 , 118  acting in series will be equal to approximately one half of one of the springs acting independently; i.e., two hundred pounds.  
     [0049] The spring assembly  108  acts as a load path between vehicle body  28  and the suspension support arms  24 , 26 , and ultimately between the vehicle body  28  and the wheel  32  since the four wheels  32  support the entire weight of the vehicle. The spring assembly  108  can be mounted in a variety of positions, but is preferably mounted in such a manner that the centerline of the spring assembly  108  is skewed from a vertically extending line by an angle φ as described above. The attachment points of the spring assembly  108  and the relative positions of the body mounts  40 , 44  and ball joint mount  38  of the support arm  24 , 26  to which the spring assembly  108  is attached will define the arcuate path of travel possible for the wheel assembly  22 . The geometry of the present suspension support arms  24 , 26 , the orientation of the spring assembly  108  relative to the support arm  24 , 28  and the vertical plane, and the twin spring characteristics of the spring assembly  108  enable the spring assembly  108  to provide a diminishing load rate to the wheel assembly  22 , and therefore the wheel  32  to the ground, as the spring assembly  108  is compressed past an equilibrium point.  
     [0050] Referring to FIGS.  12 - 14 , it is known to use Ackermann to account for the difference in turning radius between the vehicle wheel  32  (shown diagrammatically) disposed along the inner radius track in a turn and the vehicle wheel  32  disposed along the outer radius track. It is also known that turning can produce lift on the vehicle body. The amount of Ackermann created by the front suspension when the steering wheel is turned can be used to counteract the lift produced on the vehicle  28  body during the turn. For example, increasing the Ackermann can produce anti-lift. The support arms  24 , 26  of the present wheel assembly suspension  20 , 21  facilitate the creation of Ackermann because of their positionability relative to the vehicle body  28 .  
     [0051] Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the invention. For example, FIG. 1 shows a diagrammatic front view of a vehicle having a pair of the present suspensions  20 , 21 . The support arms  24 , 26  of those suspensions are symmetrical and do not cross the centerline  72  of the vehicle. In alternative embodiments, the support arms  24 , 26  of one or both suspensions  20 , 21  may cross the centerline  72 , and potentially cross each other. Extending the support arms  24 , 26  can provide favorable camber characteristics for a wheel assembly  22 .  
     [0052] As discussed previously, an important aspect of the suspension geometry according to the present invention is to create a high roll center that exhibits minimal movement as the wheel moves through its travel. The orientation of the support, or control, arms of the suspension system define the roll center of the vehicle. The control arms control the majority of the camber change as the wheel moves up and down through its travel. It will be readily appreciated that various known spring and shock elements may be selectively attached to one or more of the control arms of the suspension system without departing from the broader aspects of the present invention.  
     [0053] Another important aspect of the present invention is understanding that the roll center is not defined by steering links. Steering links merely assist in controlling the majority of the toe change as the wheel moves up and down during its travel. The geometry of the suspension systems of the present invention may be applied equally well in conjunction with any steering system/links typically found on the front or rear of known vehicles.  
     [0054] While it is known in the art that high roll center suspensions exhibit reduced vehicle roll during cornering, the present invention also facilitates anti-dive, anti-lift, and anti-squat dynamics. The anti-dive dynamics of the suspension system of the present invention acts to reduce lowering of the front of the vehicle during braking, if applied to the front wheel assemblies of the vehicle. The anti-lift dynamics of the suspension system of the present invention acts to reduce rising of the rear of the vehicle during braking, if applied to the rear wheel assemblies of the vehicle. The anti-squat dynamics of the suspension system of the present invention act to reduce lowering of the rear of the vehicle during acceleration, if applied to the rear wheel assemblies of the vehicle.  
     [0055]FIG. 16 illustrates a diagrammatic isometric view of yet another embodiment of the suspension system  300  of the present invention. As shown in FIG. 1, a transverse, vertical plane  302  passes through a centerline of a wheel assembly  304 , passing through the center C of the wheel assembly  304 , and is substantially perpendicular to the longitudinal axis X of a vehicle body  306 , schematically represented in broken lines in FIG. 16. The wheel assembly  304  rotates via a bearing, or the like, disposed inside a known spindle/knuckle assembly  310 .  
     [0056] The spindle/knuckle assembly  310  is schematically shown in FIG. 16 and may take many different forms and configurations without departing from the broader aspects of the present invention. In typical applications, the spindle/knuckle assembly  310  may include an attachment point for an unillustrated steering link which is positioned farther forward than the control arm attachment points on the spindle/knuckle assembly  310 , in the case of ‘front-steer’ vehicles. In the case of ‘rear-steer’ vehicles, the steering link attachment point is positioned farther rearward than the control arm attachment points. The steering link attachment point on the spindle/knuckle assembly  310  is not shown, for clarity.  
     [0057] As shown in FIG. 16, the suspension system  300  includes an upper control arm  312  attached to the spindle/knuckle assembly  310  vertically above the center C of the wheel assembly  304 . In a preferred embodiment, the upper control arm  312  is a single, two degree of restriction member such as an “A-arm.” In this embodiment, the upper control arm  312  will have two vehicle attachment points  314  on the vehicle body  306  and one wheel assembly attachment point  316  on the spindle/knuckle assembly  304 . As understood in the art, a degree of restriction refers to how many degrees of freedom at the spindle/knuckle are controlled by the member/control arm. It will be readily appreciated that the vehicle attachment points  314 , and the wheel assembly attachment point  316 , are affixed for rotational movement.  
     [0058] In accordance with the present invention, the upper control arm  312  need not take the form of an A-frame, as shown in FIG. 16. Alternatively, the upper control arm  312  may be comprised of two separate control arms, each having a single degree of restriction. In this alternate embodiment, each of the two separate upper control arms will have one attachment point on the body  306  and one attachment point on the spindle/knuckle assembly  310  vertically above the center C of the wheel assembly  304 .  
     [0059] Moreover, the upper control arm  312  may also be comprised of a single control arm having a single degree of restriction. This single control arm has one attachment point on the body  306  and one attachment point on the spindle/knuckle assembly  304 , vertically above the center C of the wheel assembly  304 . This embodiment requires a longitudinally oriented, non-steering member having single degree of freedom and one attachment point on the body  306  and one attachment point on the spindle/knuckle assembly  304 , oriented vertically in-between the attachment point of the upper control arm  312  on the spindle/knuckle assembly  310  and the attachment point of a lower control arm  318  on the spindle/knuckle assembly  310 , as will be discussed below.  
     [0060] Still referring to FIG. 16, the suspension system  300  includes the lower control arm  318  attached to the spindle/knuckle  318  oriented vertically below the center C of the wheel assembly  304 . In a preferred embodiment, the lower control arm  318  is a single, two degree of restriction member such as an “A-arm.” In this embodiment, the lower control arm  318  will have two vehicle attachment points  320  on the body  306 , and one wheel assembly attachment point  322  on the spindle/knuckle assembly  304 . It will be readily appreciated that the vehicle attachment points  320 , and the wheel assembly attachment point  322 , are affixed for rotational movement.  
     [0061] In accordance with the present invention, the lower control arm  318  need not take the form of an A-frame, as shown in FIG. 16. Alternatively, the lower control arm  318  may be comprised of two separate control arms, each having a single degree of restriction. In this alternative embodiment, each of the two separate lower control arms will have one attachment point on the body  306  and one attachment point on the spindle/knuckle assembly  304 , oriented vertically below the center C of the wheel assembly  304 .  
     [0062] Moreover, the lower control arm  318  may also be comprised of a single control arm having a single degree of restriction. This single control arm has one attachment point on the body  306  and one attachment point on the spindle/knuckle assembly  304 , vertically above the center C of the wheel assembly  304 . This embodiment requires a longitudinally oriented, non-steering member having single degree of freedom and one attachment point on the body  306  and one attachment point on the spindle/knuckle assembly  304 , oriented vertically in-between the attachment point of the upper control arm  312  on the spindle/knuckle assembly  310  and the attachment point of the lower control arm  318  on the spindle/knuckle assembly  310 .  
     [0063] Referring to FIG. 17, a front view of the suspension system  300  of FIG. 16 is shown, including the wheel assembly  304  and a ground plane  324  in contact with the wheel assembly  304 . As shown in FIG. 17, an upper control arm line segment  326 , and a lower control arm line segment  328 , are defined. As is also shown in FIG. 17, the upper control arm line segment  326  is shorter than the lower control arm line segment  328 , in accordance with a preferred embodiment of the present invention.  
     [0064] The line segments,  326  and  328 , illustrated in FIG. 17 are formed by the intersection of the transverse plane  302  and the planes defined by the upper control arms  312  and the lower control arms  318 . In particular, the upper line segment  326  is formed by the intersection of the transverse plane  302  and the plane defined by the attachment points,  314  and  316 , of the A-arm upper control arm  312  shown in FIG. 16. Similarly, the lower line segment  328  is formed by the intersection of the transverse plane  302  and the plane defined by the attachment points,  320  and  322 , of the A-arm lower control arm  318 , also shown in FIG. 16.  
     [0065] In the alternative embodiment of the upper control arm  312  which includes two separate control arms, discussed previously, the upper line segment  326  is formed by the intersection of the transverse plane  302  and the plane defined by the attachment points  314  on the vehicle body  306  of each upper control arm and the midpoint  338  of the line segment connecting the upper attachment points of the each upper control arm to the spindle/kingpin assembly  304 , as shown in FIG. 18. Similarly, the lower line segment  328  is formed by the intersection of the transverse plane  302  and the plane defined by the attachment points  320  on the vehicle body  306  of each lower control arm and the midpoint  340  of the line segment connecting the lower attachment points of the each lower control arm to the spindle/kingpin assembly  304 , as is also shown in FIG. 18.  
     [0066] In yet another alternative embodiment of the suspension system of the present invention, where the upper control arm  312  is formed of a single control arm, the upper line segment  326  is formed by the intersection of the transverse plane  302  and the plane of the single upper control arm defined as being parallel to the longitudinal axis of the vehicle and passing through the line created by the endpoints of the substantially transverse single, upper control arm. Similarly, when the lower control arm  312  is formed of a single control arm, the lower line segment  328  is formed by the intersection of the transverse plane  302  and the plane of the single lower control arm defined as being parallel to the longitudinal axis of the vehicle and passing through the line created by the endpoints of the substantially transverse single lower control arm.  
     [0067] This embodiment requires a longitudinally oriented, non-steering member having single degree of freedom and one attachment point on the body  306  and one attachment point on the spindle/knuckle assembly  304 , oriented vertically in-between the attachment point of the upper control arm  312  on the spindle/knuckle assembly  310  and the attachment point of a lower control arm  318  on the spindle/knuckle assembly  310   
     [0068] Having now explained the formation of the line segments,  326  and  328 , the determination of the endpoints of these line segments will now be discussed. As shown in FIG. 17, the upper line segment  326  includes an upper first endpoint  330 . The upper first endpoint  330  of the upper control arm line segment  326  is defined by the upper control arm attachment point  316  on the spindle/kingpin assembly  304  as projected onto the transverse plane  302 , and as viewed from the front of the vehicle. Similarly, the first endpoint  332  of the lower control arm line segment  328  is defined by the lower control arm attachment point  322  on the spindle/kingpin assembly  304  as projected onto the transverse plane  302 , and as viewed from the front of the vehicle.  
     [0069] As shown in FIG. 17, an upper second endpoint  334  of the upper control arm line segment  326  is defined by the intersection of the transverse plane  302  and a line extending through the vehicle attachment points  314 , as shown in FIG. 16. This determination of the upper second endpoint  334  applies both where the upper control arms  312  are formed as an A-arm, or as two separate control arms. Alternatively, in the embodiment where the upper control arm  312  is formed of a single control arm, the upper second endpoint  334  is defined by the vehicle attachment point of the single upper control arm as projected onto the transverse plane  302 , and as viewed from the front of the vehicle.  
     [0070] Similarly, a lower second endpoint  336  of the lower control arm line segment  328  is defined by the intersection of the transverse plane  302  and a line extending through the vehicle attachment points  320 , as shown in FIG. 16. This determination of the upper second endpoint  334  applies both where the lower control arms  318  are formed as an A-arm, or as two separate control arms. Alternatively, in the embodiment where the lower control arm  318  is formed of a single control arm, the lower second endpoint  336  is defined by the vehicle attachment point of the single lower control arm as projected onto the transverse plane  302 , and as viewed from the front of the vehicle.  
     [0071] In accordance with another important aspect of the present invention, an extension  340  of the upper line segment  334  is oriented so as to intersect the lower line segment  328  at the instant center I of the suspension system  300 . That is, an important aspect of the present invention lies in the recognition that the upper line segment  326  and the lower line segment  328  need not actually cross one another in superposition, provided that the upper control arms  312  and the lower control arms  318  are arranged in a manner such that an extension of the line segments,  326  and  328 , intersect at the instant center I of the suspension system  300 .  
     [0072] Another important aspect of the present invention lies in ensuring that the roll center of the vehicle  306  lies above the ride-height instant center for each wheel assembly, and that the instant center of each wheel assembly be oriented on the same side of the longitudinal vehicle center line as is each wheel assembly.  
     [0073] Operation of the suspension system  300  will now be explained in conjunction with FIG. 19. As shown in FIG. 19, the wheel assembly  304  is shown in relation to the centerline L of the vehicle  306 , as viewed from the front of the vehicle  306 , and roll force center  342  of the vehicle body  306 . As the wheel assembly  304  moves upwards, the instant center ( 10 ) moves upwards. As the wheel/tire ( 2 ) moves downwards, the instant center I will move downwards. When the wheel assembly  304  is at normal driving position with respect to the vehicle body  306  such as when the vehicle  306  is driving straight on a smooth highway, a line through the center  344  of the ‘ride height’ tire-ground contact patch and the instant center I of the suspension system  300  intersects the centerline L of the vehicle  306  at the roll force center  342 . When the wheel assembly  304  is as far below the vehicle body  306  as the suspension system  300  will allow, a line through the center  346  of the ‘full rebound’ tire-ground contact patch and the instant center I of the suspension system  300  intersects the centerline L of the vehicle  306  at the roll force center  342 . Similarly, when the wheel assembly  304  is as far up towards the vehicle body  306  as the suspension system  300  will allow, a line through the center  348  of the ‘full jounce’ tire-ground contact patch and the instant center I of the suspension system  300  also intersects the centerline L of the vehicle  306  at the roll force center  342 .  
     [0074] As is known in the art, the roll center of a vehicle is determined by projecting a line from the center of the tire-ground contact patch through the front view of the instant center. It is therefore an important aspect of the present invention that, as shown in FIG. 19, the location of the roll force center  342  is kept substantially constant as the wheel assembly  304  moves through its path, from a full jounce, or bounce, position to a full rebound position. Moreover, by configuring upper and lower control arms,  312  and  318 , in the manner discussed in conjunction with FIGS.  16 - 18 , the present invention may ensure that a line drawn from the center of the tire-ground contact patch through the front view of the instant center I results in substantially the same roll center for the vehicle  306 , thus reducing vehicle roll while also creating anti-dive, anti-lift and anti-squat dynamics. It will be readily appreciated that the suspension system  300  may be adapted to the front wheel assemblies of a vehicle, to the rear wheel assemblies of a vehicles or to both. Moreover, the suspension systems discussed in connection with FIGS.  1 - 19  may also be applied to non-wheel vehicles, such as but not limited to track or tread vehicles, without departing from the broader aspects of the present invention.