Abstract:
A wheel isolator coupling comprising a sprocket for engaging a drive member, the sprocket fixedly connected to a first adaptor, the sprocket rotationally engaged with a shaft through a first bearing, a wheel portion fixedly connected to a second adaptor, the wheel portion rotationally engaged with the shaft through a second bearing, the first adaptor having at least one receiving portion, at least one compressible member disposed within the receiving portion, the second adaptor having a radially extending member for engaging the compressible member within the receiving portion, and the sprocket imparting no axial force to the first bearing.

Description:
FIELD OF THE INVENTION 
     The invention relates to a wheel isolator coupling, and more particularly, to a wheel isolator coupling comprising a sprocket which imparts no axial force to a sprocket bearing. 
     BACKGROUND OF THE INVENTION 
     Isolators are used in motorcycle rear wheel drives in order to reduce the noise, vibration and harshness (NVH) that may otherwise be transmitted to the rider. 
     Prior art couplings transmit axial loads from the sprocket to wheel shaft bearings due to the means of containing the vibration isolating materials within the sprocket hub. Axial loads can cause premature failure of the wheel bearings. 
     Representative of the art is U.S. Pat. No. 5,240,087 (1993) which discloses a one-sided rear swing arm suspension system for a motorcycle having a chain-driven rear wheel, in which the tension of the drive chain may be adjusted without affecting the ride height of the motorcycle. The suspension system includes a rear swing arm that is pivotably attached to the body of the motorcycle, and which extends rearwardly around and alongside the rear wheel. The rear end of the swing arm includes elongate recesses which guide and receive an adjustment yoke. The rear wheel is journalled on a spindle that extends transversely from the adjustment yoke. The yoke is positionable longitudinally on the swing arm by means of an adjustment stud extending from the swing arm, and a corresponding adjustment nut entrapped in the neck of the yoke. A single adjustment clamp nut on the end of the spindle operates to secure the spindle to the yoke and to also secure the yoke to the swing arm at a selected position corresponding to a desired chain tension. 
     Reference is also made to copending U.S. patent application Ser. No. 11/726,091 filed Mar. 21, 2007, published as U.S. Patent Application Publication No. 2008/0234080 A1, directed to a wheel isolator. 
     What is needed is a wheel isolator coupling comprising a sprocket which imparts no axial force to a sprocket bearing. The present invention meets this need. 
     SUMMARY OF THE INVENTION 
     The primary aspect of the invention is to provide a wheel isolator coupling comprising a sprocket which imparts no axial force to a sprocket bearing. 
     Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings. 
     The invention comprises a wheel isolator coupling comprising a sprocket for engaging a drive member, the sprocket fixedly connected to a first adaptor, the sprocket rotationally engaged with a shaft through a first bearing, a wheel portion fixedly connected to a second adaptor, the wheel portion rotationally engaged with the shaft through a second bearing, the first adaptor having at least one receiving portion, at least one compressible member disposed within the receiving portion, the second adaptor having a radially extending member for engaging the compressible member within the receiving portion, and the sprocket imparting no axial force to the first bearing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention. 
         FIG. 1  is an exploded view of the isolator coupling. 
         FIG. 2  is a cross-sectional view of the isolator coupling. 
         FIG. 3  is an exploded view of an alternate embodiment. 
         FIG. 4  is a cross sectional view of the alternate embodiment in  FIG. 3 . 
         FIG. 5  is an exploded view of an alternate embodiment. 
         FIG. 6  is a cross sectional view of the alternate embodiment in  FIG. 5 . 
         FIG. 7  is an exploded view of an alternate embodiment. 
         FIG. 8  is a cross-sectional view of the embodiment in  FIG. 7 . 
         FIG. 9  is an exploded view of an alternate embodiment. 
         FIG. 10  is a cross sectional view of the embodiment in  FIG. 9 . 
         FIG. 11  is an exploded view of an alternate embodiment. 
         FIG. 12  is a cross sectional view of the embodiment in  FIG. 11 . 
         FIG. 13  is an exploded view of an alternate embodiment. 
         FIG. 14  is a cross sectional view of the embodiment in  FIG. 13 . 
         FIG. 15  is a detail is the sprocket adaptor. 
         FIG. 16  is a perspective view of the wheel adaptor cap. 
         FIG. 17  is a detail of  FIG. 1 . 
         FIG. 18  is a detail of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The inventive motorcycle wheel isolator coupling significantly reduces the noise, vibration and harshness (NVH) associated with prior art motorcycle rear wheel drive systems. The benefit of the isolator coupling manifests best during dynamic transient events, namely transmission speed shifting, the high speed downshifting, and the hard launch from a full stop. In these events, the impact shock load (torque) is absorbed by the soft rubber cushion. 
       FIG. 1  is an exploded view of the isolator coupling. Coupling  100  comprises the sprocket  10 . Sprocket  10  is connected to sprocket adaptor  20  using bolts  11 . Sprocket adaptor  20  comprises receiving portions  21 . The sprocket assembly ( 10 ,  11 ,  20 ) is not directly attached to the wheel  40 . 
     Wheel adaptor  30  is connected to wheel  40  by bolts  31 . Wheel  40  is typically a part of a motorcycle rear suspension which includes a swing arm (not shown). Wheel shaft  60  is typically connected to the swing arm. A drive member, namely, a toothed belt B engages toothed belt engaging surface  12  of sprocket  10 . Toothed belts are known in the art. Belt B transmits torque from an engine transmission sprocket (not shown) to the sprocket  10  which turns wheel  40  thereby driving the motorcycle forward. A tire (not shown) is mounted to wheel  40 . The tire contacts the ground. 
     Wheel adaptor  30  comprises planar radial members  32  which extend radially outward from the center of member  30 . Members  32  cooperatively engage into receiving portions  21  of sprocket adaptor  20 . 
     Disposed between members  32  and within receiving portions  21  are spaces into which are disposed elastic blocks  50 . 
     This arrangement contains any elastic block expansion in the axial direction between the wheel  40  and wheel adaptor  30 . During assembly when wheel adaptor  30  is bolted onto the wheel  40 , the force of axial expansion of the elastic blocks  50  is canceled out to each other, therefore results the zero axial force applied onto the sprocket bearing  70 . Axial force is parallel to the wheel shaft (axle)  60 . This is a significant improvement over conventional isolator coupling design. In particular, with this design a single deep grooved ball bearing  70  may be used instead of the double row ball bearing used commonly in the sprocket necessary to survive the high axial force associated with the prior art coupling. 
     Elastic blocks  50  are compressible to dissipate energy during operation. Elastic blocks  50  comprise any material known in the art suitable for the service. Elastic blocks  50  may comprise those disclosed in co-pending U.S. application Ser. No. 11/726,091 filed Mar. 21, 2007, published as U.S. Patent Application Publication No. 2008/0234080 A1, incorporated herein in its entirety by reference. 
     The isolator coupling is a self contained, standalone unit. It does not rely on the form of the mated parts (i.e. wheel or sprocket) as a part of the isolator assembly. Therefore, it is possible to use the inventive isolator coupling as a ‘standard’ isolator unit that may be used on different motorcycle platforms and applications. 
       FIG. 2  is a cross-sectional view of the isolator coupling. Wheel adaptor  30  is bolted to wheel  40 . Sprocket adaptor  20  is bolted to sprocket  10 . Blocks  50  are disposed between wheel adaptor  30  members  32  and sprocket adaptor  20 . The wheel is held in mechanical, torsional engagement with the sprocket solely by the blocks. There is no “hard” bolted connection between the sprocket and the wheel. 
     The wheel and sprocket are engaged with the wheel shaft  60  by bearings  70 ,  71 . A bearing raceway spacer  61  keeps the proper spacing between bearings  70 ,  71 . Nut  80  retains the wheel on the axle. 
     Bearing  70  is preferably a single groove ball bearing. Bearing  71  is a dual groove ball bearing. 
     Blocks  50  exert a vector force pair (F) along the axial direction. One force of the pair is applied to the wheel at the contact point “a”. The other force is applied at the wheel adaptor  30  at the contact point “b” in the opposite direction. 
     The overall net effect of the forces:
 
Σ F=F−F= 0
 
     The overall net effect of the moments:
 
Σ M=F*h−F*h= 0
 
     Therefore, there is neither axial force nor moment effect to the sprocket bearing  70  caused by the rubber block expansion in the axial direction. The axial direction is parallel to the wheel shaft  60 , which is also the axis of rotation. 
       FIG. 15  is a detail is the sprocket adaptor. Sprocket adaptor  20  comprises receiving portions  21 . Spokes  22  extend from outer ring  23  to inner ring  24 . Bolts  11  engage sprocket adaptor  20  through holes  25  in outer ring  23 . Wheel shaft  60  extends through inner ring  24 . Spokes  22  interlock the sprocket adaptor  20  with the wheel adaptor  30  so the adaptors cannot be pulled apart by operation of the isolator coupling. 
     Blocks  50  are disposed within receiving portions  21  between members  32  and spokes  22 . During operation torque is transmitted from members  32  through blocks  50  to spokes  22 . 
     In an alternate embodiment a wheel adaptor cap  33  on the wheel side is shown in  FIG. 3 .  FIG. 3  is an exploded view of an alternate embodiment. Instead of using a wheel side wall as working surface of the isolator as shown in  FIG. 1 , the wheel adaptor cap  33  is used. In this embodiment cap  33  is pressed onto the wheel adaptor  30  by an interference fit between the member  32  and the open slot  34 , see  FIG. 16 . However, it is possible to make the connection using other suitable mechanical means such as with a fastener (bolt) or welding. 
       FIG. 4  is a cross sectional view of the alternate embodiment in  FIG. 3 . 
       FIG. 16  is a perspective view of the wheel adaptor cap. Slots  34  are equally spaced about wheel cap  33 . Although each wheel cap is shown extending radially, any shape for slot  34  would be suitable. 
       FIG. 5  is an exploded view of an alternate embodiment. By mounting the sprocket adaptor  20  directly onto wheel  40  using bolts  31  instead of to sprocket  10 , the arrangement is substantially reversed from the sequence in  FIG. 1 . 
       FIG. 6  is a cross sectional view of the alternate embodiment in  FIG. 5 . In this embodiment wheel adapter  30  is fixedly connected to sprocket  10  using bolts  11 . Sprocket adaptor  20  is fixedly connected to wheel  40  using bolts  31 . Wheel adaptor  30  is axially held in engagement with sprocket adapter to spokes  22  (see  FIG. 15 ). 
       FIG. 7  is an exploded view of an alternate embodiment. This embodiment is the same as described in  FIG. 5  with the exception that in this embodiment wheel cap  33  is disposed between sprocket adaptor  20  and sprocket  10 . 
       FIG. 8  is a cross-sectional view of the embodiment in  FIG. 7 . Sprocket adaptor  20  is fixedly connected to wheel  40  using bolts  31 . 
       FIG. 9  is an exploded view of an alternate embodiment. This embodiment is the same as described in  FIG. 1  with the exception that holes  25  are disposed on inner ring  24  instead of on outer ring  23 . 
       FIG. 10  is a cross sectional view of the embodiment in  FIG. 9 . 
       FIG. 11  is an exploded view of an alternate embodiment. This embodiment is the same as described in  FIG. 5  with the exception that holes  25  are disposed on inner ring  24  instead of outer ring  23 . 
       FIG. 12  is a cross sectional view of the embodiment in  FIG. 11 . 
       FIG. 13  is an exploded view of an alternate embodiment. This embodiment is the same as described in  FIG. 11  with the exception that wheel cap  33  is disposed between sprocket adaptor  20  and sprocket  10 . 
       FIG. 14  is a cross sectional view of the embodiment in  FIG. 13 . 
       FIG. 17  is a detail of  FIG. 1 . This detail is as viewed from the sprocket perspective. Wheel adaptor  30  is shown engaged with sprocket adaptor  20 . Holes  25  receive bolts  11 . Holes  35  receive bolts  31 . 
       FIG. 18  is a detail of  FIG. 1 . This detail is the opposite side of the view in  FIG. 17  as viewed from the wheel perspective. Blocks  50  are contained within receiving portions  21  and are shown on either side of spokes  22 . Members  32  are disposed between each section of adjacent blocks  50 . Bolts  31  project through holes  35  to fasten wheel adaptor  30  to the wheel  40  (not shown). In so doing the sprocket adaptor  20  and blocks  50  are held between the wheel adaptor  30  and wheel  40 . 
     Driving torque is transmitted from a belt to the sprocket  10  and then to the sprocket adaptor  20  to spokes  22  and then to each block  50  and then to each member  32  and then to the wheel  40 . Downshift and engine braking torque is transmitted in the opposite direction. 
     The detail shown in  FIGS. 17 and 18  describe the isolator coupling as a stand alone unit. This means the isolator can be used on any wheel and sprocket combination, so long as the sprocket is fastened to the sprocket adaptor  20  and the wheel is fastened to the wheel adaptor  30 . 
     Although forms of the invention have been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.