Abstract:
A flexure joint suspension system for use in recreational vehicles such as ATVs. A recreational vehicle having an independent suspension consisting of a flexible material operatively coupling the vehicle chassis to a suspension arm thereby adapting the recreational vehicle for dirt track, rough terrain and general off-highway use, as Well as for running on smooth road surfaces. The flexure joint suspension system may be used in a recreational vehicle of the type used either for utility purposes, such as utility vehicles, or for sports or leisure activities, such as ATVs, snowmobiles, and motorcycles.

Description:
FIELD  
       [0001]     The invention relates to vehicle suspensions, and, more particularly, to flexure joint suspension systems on recreational vehicles such as all terrain vehicles (ATVs), snowmobiles, motorcycles, and utility vehicles.  
       BACKGROUND  
       [0002]     Recreational vehicles designed for off-road and all-terrain use, such as ATVs, snowmobiles, motorcycles, and utility vehicles, which feature propulsion systems, such as internal combustion engines, electric motors and hybrids, are known in the art. Open wheel or “Cart”-type vehicles have used a flexible suspension arm attachment which improves traction over irregular track surfaces. These vehicles employ suspension arm systems which are pivotally mounted to the chassis of the vehicle, allowing movement of the suspension arm system relative to the vehicle chassis.  
         [0003]     Current recreational vehicle suspensions, such as those used in ATVs, snowmobiles, motorcycles, and utility vehicles, use rotational-type pivot joints to couple the suspension arms to the chassis of the vehicle. Typically, these rotational-type pivot joints include a ball joint. Vehicle stability and handling may be achieved by providing a fully independent suspension to each of the vehicle&#39;s wheels. However, rotational-type pivot joints can be costly because of the number of parts involved. Because of the relative movement between these parts, the joints need to be lubricated to reduce friction, and may require periodic maintenance. Also, because of the environment in which many recreational vehicles are operated, rotational-type pivot joints are often exposed to conditions that make them susceptible to dirt, debris, and corrosion, which creates friction and limits the flexibility of the joint, and can cause premature wear.  
         [0004]     Recently, some racecars (such as Indy-style CART racecars) have used flexible members to mount suspension arms as part of their overall suspension system. These vehicles typically operate at very high speeds on relatively flat surfaces.  
         [0005]     It is desirable to provide a suspension coupling system for recreational vehicles, such as ATVs, snowmobiles, motorcycles, and utility vehicles, that provides the flexibility required for all terrain use, in a cost effective, easy to maintain manner.  
       BRIEF SUMMARY  
       [0006]     In an embodiment of the invention, a flexure joint suspension system couples a suspension arm to a chassis of a recreational vehicle, such as an ATV, snowmobile, motorcycle and/or utility vehicle, thereby improving traction and reducing maintenance requirements and costs associated therewith. The flexure joint suspension system may function to isolate the operator from ground irregularities. The flexure joint suspension system can be used to improve this isolation by acting like a damper between the suspension and the chassis.  
         [0007]     In a further embodiment of the invention, a flexure joint comprises a body of flexible material adapted to operatively couple a suspension arm to a chassis of a recreational vehicle. The flexure joint can be designed to be compliant such that the suspension geometry can be modified or adjusted. This change in the suspension geometry is called compliance. This compliance can be modified to adjust the ride and handling parameters of the recreational vehicle. Additionally, during an accident or other suspension damaging event, the flexure joint may be adapted to “tear away” from the chassis, potentially saving the chassis from more extensive damage.  
         [0008]     In another embodiment of the invention, a method of coupling a suspension arm to a chassis of a recreational vehicle using a flexure joint is disclosed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a perspective view of an ATV in which the embodiments of the invention may be incorporated.  
         [0010]      FIG. 2  is cross-sectional view of a flexure joint suspension system according to a preferred embodiment of the invention.  
         [0011]      FIG. 3  is a perspective view of the flexure joint according to a preferred embodiment of the invention incorporating a bolt-mounting configuration.  
         [0012]      FIG. 4  is a cross-sectional view of a flexure joint suspension system according to a preferred embodiment of the invention incorporating a welded configuration.  
         [0013]      FIG. 5  is a cross-sectional view of a flexure joint suspension system according to an embodiment of the invention incorporating a single flexure joint suspension arm in conjunction with an optional pivotally mounted suspension arm system. 
     
    
     DETAILED DESCRIPTION  
       [0014]     The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered identically. The drawings depict selected embodiments and are not intended to limit the scope of the invention. It will be understood that embodiments shown in the drawings and described below are merely for illustrative purposes, and are not intended to limit the scope of the invention as defined in the claims.  
         [0015]      FIG. 1  is a perspective view of an ATV  10 . The ATV  10  includes a chassis  12 , a left front wheel  14 , a right front wheel  16 , a left rear wheel  18 , and a right rear wheel (not visible in  FIG. 1 ). The ATV  10  also includes an engine  22  that is carried by the chassis  12 . The engine  22  is preferably coupled to at least some wheels of the ATV  10  via a drive train for propelling the ATV  10 . The engine  22  may be used to power each rear wheel, and in some cases, also each front wheel. Although the invention is herein described and illustrated in the corresponding drawing figures in the context of ATVs, it is to be understood that the invention is not so limited and applies equally in the context of other recreational vehicles, such as utility vehicles, motorcycles, and snowmobiles.  
         [0016]      FIG. 2  is cross-sectional view of a flexure joint suspension system  80  according to a preferred embodiment of the invention which may be used in the ATV  10  shown in  FIG. 1 . While the details of particular embodiments of the invention are described with reference to this particular suspension system  80 , it will be understood that variations in the structure and components of the suspension system  80  may be made without departing from the scope of the invention. The suspension system  80  shown in  FIG. 2  includes upper and lower suspension arms  30 ,  32  which may be pivotally mounted to the wheel mount assembly  20 , using a ball joint, for example. The upper and lower suspension arms  30 ,  32  are operatively coupled to the chassis  12  using flexure joints  40  mounted to the chassis by means of upper and lower chassis brackets  50 ,  52 , and mounted to the upper and lower suspension arms  30 ,  32  by means of upper and lower suspension arm brackets  60 ,  62 , respectively. The flexure joints  40  will be described in greater detail hereinafter with reference to  FIG. 3 .  
         [0017]     Fastening means, such as bolt fasteners  70 , may be employed for mounting the flexure joints  40  to the suspension arms  30 ,  32  and to the chassis  12 , as shown in  FIG. 2  using conventional bolt fasteners  70  positioned through apertures in the flexure joints  40  and through apertures in each of the chassis and suspension arm brackets  50 ,  52 ,  60 ,  62 . Other types of fastening means may be employed to accomplish this purpose without departing from the scope of the invention. For example, the flexure joint  40  may be welded to either the chassis brackets  50 ,  52  or the suspension arms  30 ,  32 , or both. A clamping mechanism may also be used to mount the flexure joint  40  to the chassis brackets  50 ,  52  and/or the suspension arms  30 ,  32 , potentially obviating the need for one or more apertures in the flexure joint  40 .  
         [0018]      FIG. 3  is a perspective view of a flexure joint  40  according to an embodiment of the invention incorporating apertures  42  to support a bolt-mounting configuration.  FIG. 3  illustrates an embodiment of the invention in which the thickness  44  and width  46  of the flexure joint  40  is varied over its length  48  to obtain the desired flexibility characteristics. The length  48  of the flexure joint  40  may range from about 0.125 inches to about 24 inches, and may more preferably range from about 3.5 inches to about 6 inches. In an embodiment, the thickness  44  of the flexure joint  40  may range from about 0.10 inches to about 2.5 inches, and may more preferably range from about 0.25 inches to about 0.5 inches, and the width  46  may range from about 0.10 inches to about 24 inches, and may more preferably range from about 2 inches to about 4 inches.  
         [0019]     The flexure joint  40 , in some embodiments, may be designed to break or “tear away,” for example during an accident or other potentially suspension-damaging event. This feature may prevent further damage to the vehicle chassis, in an accident for example, by allowing the flexure joint  40  to be the point of failure, rather than the chassis  12  or the suspension arms  30 ,  32 . The flexure joint  40  may also be easier and less costly to replace in such an event.  
         [0020]     The flexure joint  40  may be composed of any material possessing the desired flexibility characteristics, such as plastic, rubber, a metal such as steel, or a composite material such as fiberglass, carbon fiber, Kevlar, or other such suitable material. The flexure joint  40  may also be composed of a laminated structure comprising two or more layers of materials such as those listed above.  
         [0021]     The flexure joint  40  may alternately be defined by a material property, the modulus of elasticity. The modulus of elasticity (Young&#39;s modulus) is a fundamental material constant, and is an index of the flexibility (or stiffness) of the material. For many common structural materials, the strain is an essentially linear function of the stress over the range of stresses normally encountered.  
         [0022]     The modulus of elasticity, E, is given by the following equation:
 
 E =Δσ/Δε,
 
 where: 
        E =the modulus of elasticity (measured in units of force per unit area),     σ=stress (measured in units of force per unit area), and     ε=strain (a dimensionless ratio of length units, i.e., inches/inch).        
 
         [0026]     The material that makes up the flexure joint  40  and its dimensions and shape are designed to provide the flexure joint  40  with a modulus of elasticity ranging from about 0.7 MPa to about 200 GPa, and more preferably from about 120 GPa to about 180 GPa.  
         [0027]      FIG. 4  is a cross-sectional view of a flexure joint suspension system  82  according to an embodiment of the invention incorporating a metal flexure joint in a welded configuration, using conventional welding techniques. Each weld  72  performs the function of the bolt fasteners  70  in the suspension system  80  of  FIG. 2 .  
         [0028]      FIG. 5  is a cross-sectional view of a flexure joint suspension  84  system according to an embodiment of the invention incorporating a single flexure joint  40  coupled to suspension arm  30  and a rotational-type pivot joint  86  coupling a second suspension arm  32 . As would be understood by one having ordinary skill in the art, the single flexure joint  40  could be coupled to either the upper or lower suspension arm  30 ,  32  according to embodiments of the invention.  
         [0029]     Thus, embodiments of the FLEXURE PIVOTS FOR RECREATIONAL VEHICLE SUSPENSION are disclosed. One skilled in the art will appreciate that the invention can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the invention is limited only by the claims that follow.