Abstract:
An improved rear suspension assembly is provided for snowmobiles, which includes a link assembly operatively connecting the rear suspension arm to a front cushion absorber so that the pivot movement of the rear suspension arm actuates the front shock absorber assembly. In one embodiment of the present invention, a rocker arm is pivotally attached to the slide frame assembly and has a front end thereof pivotally attached to the front shock absorber assembly, and has a rear end pivotally attached through a link rod to the rear suspension arm. The present invention advantageously improves the dynamic response of the rear suspension during snowmobile acceleration, and therefore prevents the skis of the snowmobile from lifting off from the ground.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/488,437 filed Jul. 21, 2003, the contents of which are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to suspension assemblies for tracked vehicles, and more particularly to rear suspension assemblies for snowmobiles. 
   BACKGROUND OF THE INVENTION 
   The dynamic response of a rear suspension assembly of a tracked vehicle such as a snowmobile, to the multitude of loads imposed upon it during operation, has a significant affect on the overall performance and rider comfort of the vehicle. Three types of loads are regularly exerted upon a tracked vehicle. The impact loads imposed upon the rear suspension as the vehicle travels rough terrain and encounters bumps are of the most concern. There are also internal forces developed during rapid acceleration, which causes a weight transfer from the front of the vehicle to the rear. This tends to lift the skis off the ground and thus interferes with steering. Furthermore, there are centrifugal forces imposed on the vehicle when the vehicle makes turns at high speeds. The complex interaction of the forces which occur in the rear suspension assembly during vigorous operation have demanded optimal design of mechanisms for absorbing and attenuating the complex combination of loads imposed upon a modern high performance snowmobile. 
   The fundamental structure of the rear suspension of a tracked vehicle such as a snowmobile has remained essentially constant for many years. Conventionally, the rear suspension supports the endless track, which is tensioned to surround a pair of parallel slide rails, a plurality of idler wheels and at least one drive wheel or sprocket. A shock absorbing mechanism involving compressed springs, hydraulic dampers, etc., urges the slide frame assembly and the chassis (also known as a frame) of the snowmobile apart, against the weight supported above the suspension in a static condition. 
   One example of a conventional rear suspension of a snowmobile is described in U.S. Pat. No. 5,727,643, issued to Kawano et al. on Mar. 17, 1998. Kawano et al. discloses a suspension device for providing a resilient support for a snowmobile body, including a frame for supporting the snowmobile body. A slide rail is operatively connected to the frame for pressing a crawler belt against a snow surface. A swing arm includes a first end pivotally supported on the frame and a second end pivotally mounted on the slide rail. A shock absorber assembly includes a first end pivotally supported on a shaft adjacent to the first end of the swing arm, a second end of the shock absorber assembly being connected to the frame through a progressive link pivotally supported on the swing arm. 
   Another example of a conventional rear suspension of a snowmobile is disclosed in U.S. Pat. No. 5,904,216, issued to Furusawa on May 18, 1999. Furusawa discloses a rear suspension of a snowmobile including two angular suspension arm assemblies, which connect the slide frame assembly to the snowmobile chassis. These suspension arm assemblies are moveable independently of one another in order to permit the slide frame assembly to accommodate itself to static and dynamic forces arising during operation. A single cushion unit extends horizontally and is operatively connected at opposed ends thereof to the respective suspension arm assemblies in order to support and attenuate the loads. 
   Irregularities in the terrain traveled by the snowmobile produce displacements and deflections of the front suspension that supports the vehicle on the skis, and of the rear suspension. Depending upon their magnitude, frequency and strength, these deflections cause more or less discomfort to the operator and passenger of the snowmobile. It has been recognized that suspension displacements that produce angular acceleration of the snowmobile and its operator about a transverse horizontal axis, produce more discomfort than displacements that merely produce vertical acceleration of the vehicle and its operator. Therefore, coupled suspension systems have been developed, in which the pivotal movement of the two suspension arm assemblies are coupled and the slide rails are thereby generally kept parallel to the vehicle so that the operator and passenger of the snowmobile are less affected by the uneven terrain. 
   Although conventional rear suspension systems available provide a relatively comfortable ride to the passengers, it is desirable to further improve the rear suspension assemblies for tracked vehicles, particularly snowmobiles. 
   SUMMARY OF THE INVENTION 
   One object of the present invention is to provide a rear suspension assembly for a tracked vehicle, such as a snowmobile, which includes a shock absorber assembly operatively connected to the rear suspension arm and is adapted to be actuated not only by the movement of the front portions of slide rails relative to the chassis but also actuated by the pivot movement of the rear suspension arm relative to the chassis. 
   In accordance with one aspect of the present invention, a suspension assembly for mounting an endless track to a chassis of a tracked vehicle is provided. The suspension assembly comprises a slide frame assembly, a front suspension arm and a rear suspension arm. The front suspension arm is operatively attached at a lower end thereof to the slide frame assembly, and is pivotally attached at an upper end thereof to the chassis. The rear suspension arm is operatively attached at a lower end thereof to the slide frame assembly, and is pivotally attached at an upper end thereof to the chassis. A first shock absorber assembly is operatively attached at an upper end thereof to the chassis, and is operatively attached to both the slide frame assembly and the rear suspension arm through a link assembly such that the pivot movement of the rear suspension arm relative to the chassis actuates the first shock absorber assembly. 
   In accordance with another aspect of the present invention, there is provided a snowmobile suspension assembly which comprises a slide frame assembly on downwardly and rearwardly angled front and rear suspension arms that are pivotally supported in a chassis. The slide frame assembly is urged downwardly into contact with a ground-engaging portion of a snowmobile endless drive track. A rear shock absorber assembly is operatively attached to the suspension assembly for absorbing impact forces applied to the slide frame assembly. A front shock absorber assembly is operatively attached at a first end thereof to the front suspension arm, and is operatively attached at a second end thereof to the rear suspension arm. Thus, the pivotal movement of the first and second suspension arms relative to the chassis actuates the first shock absorber assembly. 
   In accordance with a further aspect of the present invention, there is provided a snowmobile which comprises a chassis including a tunnel at a rear portion thereof; a pair of skis operatively attached to the chassis at a front portion thereof for steering the snowmobile; an engine attached to the chassis; and an endless drive track disposed below the tunnel and operatively connected to the engine; and a rear suspension assembly for supporting and tensioning the endless drive track. The rear suspension assembly includes a pair of slide rails contacting a ground-engaging portion of the endless drive track. A front suspension arm is operatively attached at a lower end thereof to the slide rails, and is operatively attached at an upper end thereof to the tunnel. A rear suspension arm is operatively attached at a lower end thereof to the slide rails, and is operatively attached at an upper end thereof to the tunnel. There is provided a first shock absorber assembly operatively attached at an upper end thereof to the chassis, and operatively attached at the lower end to both the slide rails and the rear suspension arm through a link assembly. Thus, the pivotal movement of the rear suspension arm relative to the tunnel, actuates the first shock absorber assembly. 
   In one embodiment of the present invention a rocker arm is provided to operatively connect the first or front shock absorber assembly to the rear suspension arm. The rocker arm includes a front end, a rear end and a middle portion disposed therebetween. The rocker arm is preferably pivotally attached at its middle portion to the slide frame assembly, and the front end thereof is pivotally connected to the lower end of the first or front shock absorber assembly which in turn is operatively attached at the upper end thereof to the chassis. The rear end of the rocker arm is operatively connected to the upper end of the rear suspension arm, preferably through a link rod. 
   It is preferable to include a second or rear shock absorber assembly in the snowmobile suspension assembly. The lower ends of both the link rod and the second or rear shock absorber assembly are pivotally connected to the rear end of the rocker arm. A rear bracket which is affixed to the upper end of the rear suspension arm and is adapted to pivot together with the rear suspension arm relative to the chassis, is provided to pivotally connect, at different locations of the rear bracket, the upper ends of the respective link rod and the second or rear shock absorber assembly. Thus, the first or front shock absorber assembly is actuated not only by the movement of the front portion of the slide frame assembly relative to the chassis, but also actuated by the pivotal movement of the rear suspension arm relative to the chassis. 
   The suspension assembly of the present invention advantageously provides the first or front shock absorber assembly in an operation condition with a rising rate so that in most instances the first or front shock absorber assembly will be absorbing large impacts without having the compression stroke thereof bottom out. This is desirable, particularly for the front shock absorber assembly which extends across the limited space between the slide frame assembly and the tunnel, and thus usually has a limited stroke distance. 
   The suspension assembly of the present invention will further improve the dynamic feature thereof when the vehicle is in acceleration. It is known that during acceleration the tension in the track pulls the rear ends of the slide rails up towards the tunnel and pushes the front ends of the slide rails onto the ground, which transfers the weight of the vehicle to the rear thereof and tends to lift the skis off the ground. In the conventional snowmobile suspension assemblies the first or front shock absorber assembly pushes the front portions of the slide rails away from the tunnel during acceleration so that the undesirable condition is aggravated. With the suspension assembly of the present invention, testing has shown that the first or front shock absorber assembly is substantially unloaded during acceleration, which allows the front ends of the slide rails to move up towards the tunnel. Therefore, less weight is transferred to the rear of the vehicle and less weight is removed from the skis so that the skis are prevented from lifting off the ground during acceleration. 
   Other features and advantages of the present invention will be better understood with reference to the preferred embodiments described hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings, showing by way of illustration the preferred embodiments thereof, in which: 
       FIG. 1  is a schematic side view of a snowmobile incorporating one embodiment of the present invention; 
       FIG. 2  is a perspective view of a conventional rear suspension assembly of a snowmobile in which the front shock absorber assembly is operatively connected between the chassis and the slide frame assembly without linkage to the rear suspension arm; 
       FIG. 3  is a schematic side elevational view of a rear suspension of a snowmobile according to the embodiment of the present invention of  FIG. 1 ; 
       FIG. 4  is an enlarged portion of  FIG. 3 , showing a link assembly operatively connecting the front shock absorber assembly and the rear suspension arm; 
       FIG. 5  is a further enlarged portion of  FIG. 4 , showing the details of the rocker arm of the link assembly used in the embodiment of  FIG. 3 ; 
       FIG. 6  is a partial rear, side perspective view of the rear suspension assembly of  FIG. 3 , showing the left side of the suspension assembly that has been cut down the middle; 
       FIG. 7  is a top plan view of the rear suspension assembly of  FIG. 3 , with one of the top coil springs removed; 
       FIG. 8  is a partial side elevational view of a rear suspension assembly of a snowmobile according to another embodiment of the present invention; and 
       FIG. 9  is a schematic side elevational view of a rear suspension assembly of a snowmobile according to a further embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now in detail to the drawings, and primarily to  FIG. 1 , a snowmobile incorporating the present invention is identified generally by the reference numeral  100 . 
   The snowmobile  100  includes a forward end  102  and a rearward end  104 , which are defined consistently with the forward travel direction of the vehicle. The snowmobile  100  includes a chassis  106  which normally includes a rear tunnel  108 , an engine cradle portion  110  and a front suspension assembly portion  112 . An engine  114  which is schematically illustrated, is carried by the engine cradle portion  110  of the chassis  106 . A ski and steering assembly (not indicated) is provided, in which two skis  116  (only one is shown) are positioned at the forward end  102  of the snowmobile  100 , and are attached to the front suspension assembly portion  112  of the chassis  106  through a front suspension assembly  118 . The front suspension assembly  118  includes ski legs  120 , supporting arms  122  and ball joints (not shown) for operatively joining the respective ski legs  120 , supporting arms  122  and a steering column  124 . The steering column  124  at its upper end is attached to a steering device such as a handlebar  126  which is positioned forward of a rider and behind the engine  114  to rotate the ski legs  120  and thus the skis  116 , in order to steer the vehicle. 
   An endless drive track  128  is positioned at the rear end  104  of the snowmobile  100  and is disposed under tunnel  108 , being connected operatively to the engine  114  through a belt transmission system  130  which is schematically illustrated by broken lines. Thus, the endless drive track  128  is driven to run about a rear suspension assembly  132  for propulsion of the snowmobile  100 . The rear suspension assembly  132  is the subject matter of the present invention and will be described in detail with reference to the other figures of the drawings hereinafter. 
   At the front end  102  of the snowmobile  100 , there are provided fairings  134  that enclose the engine  114  and the belt transmission system  130 , thereby providing an external shell that not only protects the engine  114  and the belt transmission system  130 , but can also be decorated to make the snowmobile  100  more aesthetically pleasing. Typically, the fairings  134  include a hood (not indicated) and one or more side panels (not indicated) which are both openable to allow for access to the engine  114  and the belt transmission system  130  when this is required, for example for inspection or maintenance of the engine  114  and/or the belt transmission system  130 . A windshield  136  may be connected to the fairings  134  near the front end  102  of the snowmobile  100 , or may be attached directly to the handlebar  126 . The windshield  136  acts as a windscreen to lessen the force of the air on the rider while the snowmobile  100  is moving. 
   A seat  138  extends from the rear end  104  of the snowmobile  100  to the fairings  134 . A rear portion of the seat  138  may include a storage compartment, or may be used to accept a passenger seat (not indicated). Two foot rests  140  only (only one shown) are positioned on opposed sides of the snowmobile  100  below the seat  138  to accommodate the rider&#39;s feet. 
   Referring to  FIGS. 3–7 , the endless drive track  128  is engaged with and driven by a drive sprocket  142  which is journaled by the rear tunnel  108  and is driven by the engine  114  through the belt transmission system  130  of  FIG. 1 . The endless drive track  128  is suspended for movement relative to the chassis  106 , by the rear suspension assembly  132 . The rear suspension assembly  132  includes a slide frame assembly  144  which primarily includes a pair of spaced apart slide rails  146  that engage the back side of the ground-engaging portion of the endless drive track  128 . 
   The slide frame assembly  144  journals a plurality of backup rollers  148  (see  FIGS. 6 and 7 ) and a larger, idler roller  150 . In addition, further rollers  152  are carried by the rear tunnel  108 , in order to define the path over which the endless drive track  128  travels. 
   A pair of downwardly and rearwardly angled front suspension arms  154  are pivotally attached at the upper ends thereof to the rear tunnel  108  by means of a tube and shaft assembly (not indicated). The tube and shaft assembly includes a tube  156  rotatably supported by a shaft  158  which extends laterally with respect to the rear tunnel  108  and through the tube  156 , and is supported at the opposed ends thereof by the rear tunnel  108 . The upper ends of the front suspension arms  154  are both affixed, preferably by welding, to the tube  156  so that the two front suspension arms  154  are adapted to pivot about the shaft  158 . The lower ends of the front suspension arms  154  are pivotally attached to the respective slide rails  146  of the slide frame assembly  144  by means of a pivot pin assembly  160 . Thus, the movement of the front portions of the slide rails  146  relative to the rear tunnel  108  of the chassis  106  causes the front suspension arms  154  to rotate together with the tube  156  about the shaft  158 , relative to the rear tunnel  108 . 
   The front suspension arms  154  in this embodiment are made of tubular metal and the attachment thereof to the tube  156  are preferably reinforced by triangular plates  162  (See  FIG. 7 ) which are preferably welded to both the tube  156  and the front suspension arms  154 . 
   A rear suspension arm  164  which is preferably made of a hollow metal configuration having a substantially consistent rectangular cross section, is downwardly and rearwardly angled and is disposed behind the front suspension arms  154 . The rear suspension arm  164  is pivotally attached to the rear tunnel  108  of the chassis  106  by means of a tube and shaft assembly (not indicated). 
   The tube and shaft assembly includes a tube  166  rotatably supported by a shaft  168  which is substantially parallel to the shaft  158  and is mounted at the opposed ends thereof to the rear tunnel  108 . The upper end of the rear suspension arm  164  is affixed by for example, welding to the tube  166  so that the rear suspension arm  164  is adapted to pivot about the shaft  168 . 
   The lower end of the rear suspension arm  164  is pivotally connected to a pair of rear rocker arms  174  by means of a hollow cross bar  172 . The rear rocker arms  174  flank the rear suspension arm  164  and are in turn pivotally attached to a rear portion of the respective slide rails  146 . A pair of blocks  170  are attached to the opposed ends of the hollow cross bar  172 . Rear stoppers  176  are attached to the respective slide rails  146 , positioned rearward of the rear rocker arms  174  to limit the pivot movement of the rear rocker arms  174  in the clockwise direction. Each of the rear stoppers  176  is mounted to, for example, a bracket (not indicated) that is in turn mounted to slide frame assembly  144 . The rear stoppers  176  can alternatively be the integral extensions of the slider frame assembly  144  themselves. The blocks  170  are fastened to a shaft  178  which rotates within the hollow cross bar  172  and is fastened at its opposed ends to the rear rocker  174 . The blocks  170  are preferably made of elastomer, such as rubber, polyurethane resin, delrin, nylon or aluminum could also be used for the blocks. 
   In order to attenuate the impact loads generated when the blocks  170  collide with the rear stoppers  176 , the rear stoppers can be made of or coated with a resilient material such as rubber or a polymer. Such a resilient material used on the stoppers  176  also help to reduce wear of the blocks  170 . 
   In operation the rear suspension arm  164  is coupled to the front suspension arms  154  such that when the rear portions of the slide rails  146  are under impact forces and are pushed towards the rear tunnel  108  of the chassis  106 , the front portion of the slide rails  146  will also be pushed towards the rear tunnel  108  because the clockwise rotation of the rear rocker arms  174  about the cross bar  175  is limited by the rear stoppers  176 . A front shock absorber assembly  180  is disposed between the rear tunnel  108  and the slide frame assembly  144 , located at front portions of the slide rails  146 . The front shock absorber assembly  180  is a damping unit which usually includes a hydraulic damper and a coil spring for absorbing the impact energy when impact forces are applied to the opposite ends of the damping unit. The coil spring pushes the damping unit to extend so that the hydraulic damper is in the best position to absorb the impact energies. The shock absorber assembly  180  is well known in the art and will not be further described herein. 
   The front shock absorber assembly  180  is operatively attached at an upper end thereof to the rear tunnel  108  of the chassis, by means of a front bracket  182 . The front bracket  182  is affixed, preferably by welding, to the tube  156  and is thereby adapted to pivot about the shaft  158  together with the front suspension arms  154 , with respect to the rear tunnel  108 . The upper end of the front shock absorber assembly  180  is pivotally connected to the front bracket  182  such that the axial force will be applied to the upper end of the front shock absorber assembly  180  when the front suspension arms  154  pivot. However, it is not necessary to attach the front shock absorber assembly  180  to the front suspension arms  154  in order to practice the present invention. 
   The front shock absorber assembly  180  is operatively attached at a lower end thereof to the slide frame assembly  144  by means of a front rocker arm  184 . The front rocker arm  184  is a v-shaped bracket and is pivotally attached at its middle portion to the slide frame assembly  144  by means of a cross bar  186  which extends between, and is attached at its opposed ends to the two slide rails  146 . 
   The front rocker arm  184  further includes a front end which is pivotally connected to the lower end of the front shock absorber assembly  180 , and a rear end which is operatively attached to the rear suspension arm  164 , via a link rod  188  and a rear bracket  190 . The rear bracket  190  is affixed, preferably by welding to the tube  166  (more clearly shown in  FIG. 4 ) and is thereby adapted to pivot about the shaft  168  together with the rear suspension arm  164 , with respect to the rear tunnel  108  of the chassis  106 . The two link rods  188  are disposed in a parallel relationship, and are pivotally connected at their rear ends to the rear bracket  190  by means of a pin  192 , and are pivotally connected at their front ends to the rear end of the front rocker arm  184  by means  194  (more clearly shown in  FIG. 5 ). 
   Therefore, the front rocker arm  184 , the parallel link rods  188  and the rear bracket  190  form a link assembly through which the pivot movement of the rear suspension arm  164  about the shaft  168  and relative to the rear tunnel  108  of the chassis  106 , causes a pivot movement of the front rocker arm  184  about the cross bar  186  to actuate the front shock absorber assembly  180 , thereby applying an axial force to the lower end of the front shock absorber assembly  180 . 
   It should be noted that Distance A between the rear end of the front rocker arm  184  and the pivot attachment location where the cross bar  186  is located, at the middle portion thereof is preferably longer than Distance B between the front end of the rocker arm  184  and that pivotal attachment location at the middle portion of the rocker arm  184  (See  FIG.5 ). 
   Although not required in order to practice the present invention, it is preferable to further provide a rear shock absorber assembly  196  which is disposed between the parallel link rods  188  for packing reasons. The rear shock absorber assembly  196 , is pivotally connected at its upper end to the rear bracket  190  by means of a pin  198  (more clearly shown in  FIG. 4 ), and is pivotally connected at its lower end to the rear end of the front rocker arm  184  by the pin  194  which also pivotally connects the link rods  188  to the front rocker arms  184 . The rear shock absorber assembly  196 , similar to the front shock absorber assembly  180 , is well known in the art, and therefore will not be described in detail. 
   It should be noted that the upper end of the rear shock absorber assembly  196  is pivotally connected to the rear bracket  190  at a location different from the location where the rear end of the link rods  188  is pivotally connected to the rear bracket  190  such that forces applied to the respective rear shock absorber assembly  196  and the link rods  188  are substantially in opposite directions when the rear bracket  190  pivots. For example, the pins  192  and  198  are substantially, diametrically opposed about the shaft  168 . 
   Referring to  FIGS. 3 and 7 , a torsion coil spring  200  is provided in order to push the slide frame assembly  144  apart from the rear tunnel  108  of the chassis  106 , and to maintain the front and rear shock absorber assemblies  180 ,  196  substantially in extended condition when no substantial loads are applied thereon. The torsion coil spring  200  surrounds the tube  166  and is positioned at one end thereof. A first end  202  of the spring  200  is attached to the rear suspension arm  164 , and a second end  204  thereof is attached to the slide frame assembly  144 , under a preloaded condition so that a predetermined torsion of force is applied to the rear suspension arm  164 , tending to pivot the rear suspension arm  164  about the shaft  168  away from the rear tunnel  108  of the chassis  106 . 
   A second torsion coil spring (not shown) can be provided, surrounding the tube  166  and being positioned at the other end of the tube  166  in order to provide, in combination with the torsion coil spring  200 , a symmetrical configuration to the rear suspension assembly  132 . 
   A pair of flexible tension straps  206  are attached at their upper ends to the tube  156  which is supported by the shaft  158  to the rear tunnel  108  of the chassis  106 , and are attached at their lower ends to the slide frame assembly  144  by means of a cross bar  208  which extends between and is attached at their opposed ends to the front ends of the slide rails  146 . The flexible tension straps  206  prevent the slide frame assembly  144  from being pushed too far away from the rear tunnel  108  and thereby maintain the front and rear suspension arms  154 ,  164  in their respective predetermined angled positions while not intervening with the operation of the rear suspension assembly  132 . 
   In an alternative arrangement,(see  FIGS. 6 and 7 ) a pair of sleeve members  210  which are offset from the tube  156 , are affixed, preferably by welding to the opposed ends of the tube  156 . The shaft  158  of  FIG. 3  can rotatably extend through the pair of sleeve members  210 , rather than through the tube  156 , and are attached at their opposed ends to the rear tunnel  108  of the chassis  106 . In such an alternative arrangement, the rear suspension assembly  132  functions similarly as described above. In this case, the front bracket  182  and the tube  156  together pivot about the shaft received by the sleeve members  210  and thereby apply an axial force to the upper end of the front shock absorber assembly  180 . 
   Referring to  FIG. 8  and in accordance with another embodiment of the present invention, a portion of a rear suspension assembly  132 A is illustrated. In the rear suspension assembly  132 A, the front rocker arm  184  is attached at its middle portion to the front suspension arms  154 , rather than to the slide frame assembly  144  as shown in  FIG. 3 . In this embodiment, the cross bar  186  which pivotally connects the front rocker arm  184  extends between and is attached at their opposed ends to a lower portion of the respective front suspension arms  154 . Other components are arranged similarly to the rear suspension assembly  132  of  FIG. 3 , and will not be redundantly described. 
   Referring to  FIG. 9  and in accordance with a further embodiment of the present invention, a rear suspension assembly  132 B is similar to the rear suspension assembly  132  of  FIG. 3 . Similar components are indicated by similar numerals, and therefore will not be redundantly described. The difference between  FIG. 3  and  FIG. 9  is described as follows. 
   The front bracket  182  of  FIG. 3  is omitted in  FIG. 9 , and therefore the upper end of the front shock absorber assembly  180  is directly attached to the tube  156  and is adapted to pivot about the shaft  158 . 
   The pair of link rods  188  are pivotally attached at their rear ends to the rear suspension arm  146 , preferably to the upper portion thereof, by the pin  192 , rather than being pivotally attached to the rear bracket  190  as shown in  FIG. 3 . 
   The rear suspension assembly  132 B according to this embodiment of the present invention functions similarly to the rear suspension assembly  132  of  FIG. 3 . The various alternative arrangements or embodiments of the present invention illustrated in  FIGS. 8 and 9  are exemplary but not exhaustive, illustrating that the present invention can be implemented in various embodiments without departing from the principal of the present invention. 
   It should be further noted that the duplicated components in the embodiments as above described, such as the two front suspension arms, two link rods and the two torsion coil springs etc., are provided for the convenience of the assembly packaging. A snowmobile rear suspension assembly including only one of the each duplicated components will function similarly in an appropriately arranged configuration. 
   It should still further be noted that although the embodiments as above described illustrate a rear suspension assembly only having a rear to front coupling, the present invention is applicable to a rear suspension assembly that is not coupled, and is also applicable to a rear suspension assembly that is coupled both from rear to front and front to rear as disclosed in U.S. Pat. No. 6,206,124. 
   Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.