Abstract:
An attachment stay is fixed to corresponding fork pipes, a shaft is inserted between through holes of respective attachment stays, one end of a cushion arm is rotatably supported on the shaft via a ball bearing and a needle bearing, and a lower end of a shock absorber is rotatably attached to a middle section of the cushion arm to provide a front suspension structure offering a high degree of freedom during assembly of the cushion arm.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a front suspension structure of a motorcycle, more particularly to a front suspension structure having a shock absorber and a front fork provided as separate components.  
           [0003]    2. Background Art  
           [0004]    Japanese Patent Laid-open No. Sho. 59-20784 discloses a motorcycle link-type front suspension structure of the related art having a shock absorber that is not assembled inside a front fork, but is instead arranged separately and independently from a front fork. The disclosed front suspension structure has a swing arm (axle support arm) provided so as to bridge between a lower end of a front fork and an axle, a lower end of a cushion arm linked to the middle of the swing arm, an upper end of the cushion arm linked to a lower end of the shock absorber, and an upper end of the shock absorber linked to a top bridge.  
           [0005]    With these types of front suspension structures, vibration of the swing arm during travel is conveyed to the shock absorber through the cushion arm, and a specified buffering action is exhibited. The lower end of the cushion arm is directly attached to the front fork in the above-described technique of the related art. Also, the upper end of the cushion arm is attached to the front fork via a tension rod.  
           [0006]    However, the front fork and the cushion arm are manufactured separately, and it is inevitable that a distance between left and right fork pipes will vary as each manufactured component will exhibit varying design values. Accordingly, the extent to which left and right fork pipes constituting the front fork are parallel, and the position of the top bridge and a bottom bridge etc. will be slightly different as the actual manufactured values for each manufactured component will vary from desired design parameters.  
           [0007]    The method of attaching the cushion arm of this type of conventional structure to a front fork involves fixing a bracket to the front fork and linking the cushion arm to this bracket at specified locations. Unfortunately, the distance and degree of parallelism between the fork pipes is slightly different for each manufactured component, thereby making it difficult to obtain lateral positional precision and parallel positional precision for the installation and positioning of the cushion arm.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention overcomes the shortcomings associated with the related art and achieves other advantages not realized by the related art.  
           [0009]    An object of the present invention is to improve the installation of cushion arms in front suspension structures by improving the lateral positioning precision and parallel precision of installed components.  
           [0010]    A further object of the present invention is to provide a front suspension structure that offers simple and reliable positional adjustment of front suspension components, including stays and cushion arms.  
           [0011]    A further object of the present invention is to reduce friction as a result of shock absorbing motion being conveyed between components of a front suspension structure.  
           [0012]    These and other objects are accomplished by a front suspension structure comprising a front fork having right and left fork pipes, a cushion arm attachment stay attached to each of the right and left fork pipes, a cushion arm for oscillating in response to a vertical motion transmitted from the front fork, a top bridge and a bottom bridge, and a shock absorber, wherein the front fork and the shock absorber are separate components with an upper end of the shock absorber linked to a top bridge side, and a lower end of the shock absorber linked to the cushion arm, the cushion arm swingably supported between the cushion arm attachment stays via a shaft.  
           [0013]    These and other objects are accomplished by a front suspension support structure connected to a steering system of a motorcycle, the front suspension structure comprising a top bridge attached to an upper end of the steering system, a bottom bridge attached to a lower end of the steering system, an upper part of a front fork supported by the top bridge and the bottom bridge, and a lower end of the front fork is connected to an arm holder, a first end of an axle support arm is swingably attached to an axle of a front wheel of the motorcycle, cushion arm attachment stays attached to the front fork, and a cushion arm, swingably supported between the cushion arm attachment stays and linking a lower end of a shock absorber via a shaft.  
           [0014]    In order to make it possible to positionally adjust the stays attached to each of the left and right fork pipes in an axial direction of the fork pipes and around the fork pipes, the attachment position and attachment direction of the stay relative to the cushion arm is adjusted, and the lateral positioning precision and parallel precision can be improved. According to a preferred embodiment of the present invention, positional adjustment can be accomplished through the simple adjustment of a few securing bolts.  
           [0015]    Furthermore, by using a divided structure for the cushion arm attachment stays, positional adjustment can be carried out easily.  
           [0016]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
         [0018]    [0018]FIG. 1 is a side elevation view of a front suspension structure according to an embodiment of the present invention;  
         [0019]    [0019]FIG. 2 is a perspective view of the front suspension structure according to an embodiment of the present invention;  
         [0020]    [0020]FIG. 3 is a cross sectional view of the front suspension structure according to an embodiment of the present invention taken along line A-A in FIG. 1; and  
         [0021]    [0021]FIG. 4 is a side elevation view of a front suspension structure according to a further embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a side elevation view of a front suspension structure according to an embodiment of the present invention. FIG. 2 is a perspective view of the front suspension structure according to an embodiment of the present invention. FIG. 3 is a cross sectional view of the front suspension structure according to an embodiment of the present invention taken along line A-A in FIG. 1. FIG. 4 is a side elevation view of a front suspension structure according to a further embodiment of the present invention.  
         [0023]    [0023]FIG. 1 is a side elevation view of a front suspension structure according to an embodiment of the present invention. As shown in FIG. 1, a steering system  2  is inserted into a headpipe  1  so as to be capable of rotation, with a top bridge  3  being attached to an upper end of the steering system  2  and a bottom bridge  4  being attached to a lower end of the steering system  2 . An upper part of a front fork  5  is supported by the top bridge  3  and bottom bridge  4 , and a lower end of the front fork  5  is inserted into an arm holder  6 .  
         [0024]    A first end of an axle support arm (pivot arm)  8  is swingably attached to an axle  7  of a front wheel of a motorcycle. The shape of this axle support arm  8  is substantially V-shaped when viewed from the side, and a second end of the axle support arm  8  rotatably hinges at a lower end of the arm holder  6 .  
         [0025]    An upper end of a shock absorber  10  is rotatably attached to the top bridge through an attachment stay  9 . Cushion arm attachment stays  11 ,  11  are fixed to left and right fork pipes  5   a ,  5   a  constituting the front fork  5  so as to overlap on the bottom bridge  4 .  
         [0026]    A slot  12  is formed in a part of each attachment stay for gripping the fork pipe  5   a , and the attachment stays  11  are secured to the fork pipes  5   a  by screwing in bolts  13  to a desired tightness. Further, it is possible to adjust the attachment position of the attachment stay  11  in the axial direction of the fork pipe  5   a  by loosening the bolts. Accordingly, the attachment direction in a peripheral direction of the fork pipes  5   a  can also be adjusted.  
         [0027]    A through hole  14  and a slot are formed in a projecting portion of each attachment stay  11 . A bolt shaft  15  is passed between the through holes  14 , and the shaft  15  is fixed between the attachment stays  11 ,  11  by tightening with bolts  16 .  
         [0028]    A first end of a cushion arm  18  is rotatably supported on the shaft  15  via a ball bearing  19  and a needle bearing  20 . A lower end of the shock absorber  10  is rotatably attached to a middle section of the cushion arm  18 .  
         [0029]    An upper end of a connecting member  21  is rotatably linked to an other end of the cushion am  18 . An upper end of a push rod  22  is rotatably linked to a lower end of the connecting member  21 , and a lower end of the push rod  22  is rotatably linked to a middle section of the axle support arm  8 .  
         [0030]    Accordingly, an upper arm  23  is rotatably suspended between the upper end of the push rod  22  and the front fork  5 , and a quadrilateral link is formed by the upper arm  23 , fork pipes  5   a , push rod  22  and the axle support arm  8 .  
         [0031]    Further, one end of an attachment stay  25  for a brake caliper  24  is attached to the front wheel axle  7 . A torque link  26  is suspended between an other end of the attachment stay  25  and the front fork  5 , and a fender  27  is attached to the attachment stay  25 .  
         [0032]    In the above-described structure, if the wheel is moved up and down due to unevenness on the road, the axle support arm  8  vibrates up and down. The energy from this vibration is conveyed to the cushion arm  18 , and the shock absorber  10  expands and contracts due to the vibration of the cushion arm  18  to exert a shock absorbing effect or dampening effect.  
         [0033]    [0033]FIG. 4 is a side elevation view of a front suspension structure according to a further embodiment of the present invention. As seen in FIG. 4, an attachment stay  11  is fixed to a lower side of the bottom bridge  4 . By fixing an attachment stay  11  to each fork pipe  5   a  with this type of arrangement, similar effects and advantages as described above can be achieved.  
         [0034]    In all of the embodiments, a cushion arm  18  is swingably supported by a shaft  17  through a ball bearing  19  and a needle bearing  20 . However, this is not a necessary limitation as long as a bearing is at least used to provide swingable support of the cushion arm  18 .  
         [0035]    According to the invention described hereinabove, a stay  9  is attached to each of the left and right fork pipes  5   a  constituting a front fork  5 , and a cushion arm  18  linking a lower end of a shock absorber  10  via a shaft  17  is swingably supported between these stays  19 . Accordingly, it is possible to improve lateral positioning precision and ensure a parallel arrangement between adjacent components by adjusting the attachment positions and attachment directions of the stays. In addition, friction resulting from typical vibration in conventional structural arrangements is drastically reduced through the present invention.  
         [0036]    Also, since it ispossible to alter the position of the stays in an axial direction of the front fork, it is easy to carry out alteration of the link ratio specifications as desired by an operator or technician.  
         [0037]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.