Patent Abstract:
An inexpensive damping force generating mechanism capable of generating both a compression side damping force and a tensile side damping force has a simple, lightweight structure. The damping force generating mechanism provides an inexpensive axle suspension capable of simplifying the suspension structure, reducing the weight, and effectively utilizing space. The damping force generating mechanism includes an elastic body which generates a damping force when being pressed. An internal pressure generating member is inserted in the elastic body and resists the pressing force.

Full Description:
BACKGROUND OF THE INVENTION  
         [1]    1. 1. Field of the Invention  
           [2]    2. The present invention relates to a damping force generating mechanism for generating a damping force by pressing an elastic body.  
           [3]    3. 2. Description of the Background Art  
           [4]    4. A damping force generating mechanism is used for various portions required for absorbing vibration, for example, used for a so-called bottom link type suspension of a motorcycle in which a front wheel is suspended from lower end portions of a front fork through links. A general example of such a bottom link type suspension is shown in FIG. 16 (see Japanese Patent Laid-open No. Sho 62-187608).  
           [5]    5. Referring to FIG. 16, there is shown a scooter type motorcycle  01 . A steering shaft  03  is turnably fitted in a head pipe  02 . A pair of right and left front forked portions  04  are integrally mounted on the lower end of the steering shaft  03 . A front wheel  06  is suspended from the lower ends of the front forked portions  04  through rocking arms  05  as link members.  
           [6]    6. With respect to the rocking arm  05 , the base end thereof is pivotably supported on the lower end portion of the front forked portion  04 , and the free end portion thereof rotatably supports the front wheel  06 . A suspension spring  07  is interposed between the upper portion of the front forked portion  04  and an approximately central portion of the rocking arm  05 .  
           [7]    7. A shock load applied to the front wheel from irregularities on the ground is damped by the suspension springs  07 . However, when a shock load is applied with an abrupt shock load, the suspension springs are largely rebounded after being contracted once.  
           [8]    8. In an example described in Japanese Patent Publication No. Sho 57-49432, as shown in FIG. 17, a front end of a link  012  is pivotably supported on the lower end portion of a front forked portion  011  containing a hydraulic damping mechanism. A front wheel  013  is rotatably supported on a central portion of the link  012 . A subcushion unit  14  is interposed between the rear end of the link  012  and the central portion of the front forked portion  011 .  
           [9]    9. The subcushion unit  014  includes a cylindrical main body  015  pivotably mounted on the front forked portion  011 . A piston  016  is slidably inserted in the cylindrical main body  015  and is connected to a leading end of a rod  017  pivotably mounted on the link  012 . A cushion rubber  018  utilized as a damping member is inserted in the cylindrical main body  015  in such a manner as to be mounted on the upper surface of the piston  016 . A stopper rubber  019  utilized as a stopper member is inserted in the cylindrical main body  015  in such a manner as to be mounted on the lower surface of the piston  016 .  
           [10]    10. The subcushion unit  014  thus generates a compression side damping force by the cushion rubber  018 , and also generates a tensile side damping force by the stopper rubber  019 . Consequently, the subcushion unit  014  can suppress both the bound and rebound of the front wheel  013 .  
           [11]    11. The above subcushion unit  014 , however, has a disadvantage. Since the piston  016  is slid in the cylindrical main body  015 , and the cushion rubber  018  and the stopper rubber  019  are separately provided on the upper and lower surfaces of the piston  016 , the mechanism is complicated in structure, being heavy and expensive.  
         SUMMARY OF THE INVENTION  
         [12]    12. In view of the foregoing, an object of the present invention is to provide an inexpensive damping, force generating mechanism capable of generating both a compression side damping force and a tensile side damping force with a simple, lightweight structure.  
           [13]    13. To achieve the above object, a damping force generating mechanism is provided including an elastic body which generates a damping force when being pressed, and an internal pressure generating member inserted in the elastic body which resists the pressing force.  
           [14]    14. With this configuration, the mechanism enables a large displacement due to bending deformation of the elastic body and thereby it enables absorption of a sufficient energy. The creep generated upon bending deformation of the elastic body can be reduced by repulsion of the internal pressure generating member inserted in the elastic body accompanied by compressed deformation of the internal pressure generating member. Accordingly, a damping force generating mechanism can be obtained which is capable of reducing the characteristic change due to permanent set. The restoring ability after release of a load is also excellent due to repulsion of the internal pressure generating member.  
           [15]    15. The internal pressure generating member may comprise a spring member. With this configuration, the creep of the elastic body is reduced by repulsion of the spring member accompanied by the compression thereof. Accordingly, it is possible to make the characteristic change due to permanent set smaller and to enhance the restoring ability.  
           [16]    16. The internal pressure generating member may comprise a partitioned chamber containing a compressive gas or liquid. With this configuration, the creep of the elastic member is reduced by repulsion of a compressive gas or liquid compressed and deformed together with the partitioned chamber. Accordingly, it is possible to make the characteristic change due to permanent set smaller and to enhance the restoring ability.  
           [17]    17. The internal pressure generating member may comprise an elastic organic material. The internal pressure generating member, which is made from the organic material, can be easily molded in a shape most suitable for the application. The organic material may have a hollow portion. With this configuration, when the organic material is compressed, a specific repulsive force can be obtained by the presence of the hollow portion. The organic material may be a polyester-urethane based material. With this configuration, it is possible to obtain a specific repulsive force by a large elasticity of a polyester-urethane based material.  
           [18]    18. To further achieve the object of the invention, a damping force generating mechanism is provided which includes an elastic body which generates a damping force when being pressed, and a restricting wall for suppressing expansion of the elastic body generated in the direction perpendicular to the pressing direction of the elastic body.  
           [19]    19. When the elastic body is pressed, the expansion of the elastic body in the direction perpendicular to the pressing direction is restricted by the restricting wall. As such, the force of the elastic body applied to the restricting wall becomes larger and the sliding resistance of the elastic body is increased. As a result, a desirable relationship of load to displacement can be easily obtained by the action of the sliding resistance of the elastic body in addition to the elastic characteristic of the elastic body.  
           [20]    20. The elastic body may be separated from the restricting wall with a gap therebetween at the beginning of pressing of the elastic body, and brought into contact with the restricting wall with progressive pressing of the elastic body.  
           [21]    21. At the beginning of the pressing, since the elastic body is not brought into contact with the restricting wall due to the gap therebetween, the load is gradually increased with an increase in displacement only by the elastic characteristic of the elastic body. However, as the elastic body is pressed to a state where the elastic body is in contact with the restricting wall, the load is rapidly increased with an increase in displacement by a combination of the sliding resistance of the elastic body and the elastic characteristics of the elastic body. As a result, a desirable relationship of the load to the displacement can be obtained.  
           [22]    22. The contact area of the elastic body with the restricting wall may be enlarged with further progress of pressing of the elastic body. With this configuration, after the pressed elastic body is brought into contact with the restricting wall, the contact area of the elastic body with the restricting wall is enlarged and thereby the sliding resistance of the elastic body is increased. As a result, a desirable smooth relationship of the increased load to the increased displacement can be obtained.  
           [23]    23. The elastic body may have a hollow portion opened to the restricting wall side, with an intermediate elastic body inserted in the hollow portion. Therefore, when the elastic body is pressed, the intermediate elastic body is compressed, being swelled out of the opening of the hollow portion, and is brought in press-contact with the restricting wall.  
           [24]    24. When the elastic body is pressed, sliding resistance is generated due to the contact of the elastic body with the restricting wall in addition to the elastic characteristics of the elastic body, and also the sliding resistance of the intermediate elastic body due to the pressing contact of the restricting wall with the intermediate elastic body compressed and swelled from the opening of the hollow portion. As a result, a desirable relationship of the load to the displacement of the elastic body can be easily obtained.  
           [25]    25. To further achieve the object of the invention, a damping force generating mechanism is provided which includes an elastic body which generates a damping force when being pressed, a hollow portion opened in the elastic body in the direction perpendicular to the pressing direction, an intermediate elastic body inserted in the hollow portion, and a restricting wall provided opposite to the opening of the hollow portion. Thus, when the elastic body is pressed, the intermediate elastic body is compressed, being swelled out of the opening of the hollow portion, and is brought into pressing contact with the restricting wall.  
           [26]    26. At the beginning of the pressing of the elastic body, elastic characteristics of the elastic body and the intermediate elastic body are generated. However, as the pressing of the elastic body proceeds, the intermediate elastic body is compressed, being swelled out of the hollow portion of the elastic body, and is brought into contact with the restricting wall. Thus, sliding resistance of the intermediate elastic body is generated. As a result, a desirable relationship of the load to the displacement of the elastic body can be easily obtained.  
           [27]    27. 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  
       [28]    28. 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:  
         [29]    29.FIG. 1 is a side view of a scooter-type motorcycle including a wheel suspension to which a damping force generating mechanism according to a first embodiment is applied, with parts partially omitted;  
         [30]    30.FIG. 2 is a side view of a front forked portion and the vicinity thereof;  
         [31]    31.FIG. 3 is a sectional view of essential portions of the front fork portion;  
         [32]    32.FIG. 4 is a sectional view taken on line IV-IV of FIG. 3;  
         [33]    33.FIG. 5 is an exploded view in perspective of a case, lid member and locking piece;  
         [34]    34.FIG. 6 is a sectional view of an elastic rubber body;  
         [35]    35.FIG. 7 is a view seen in the direction shown by arrow VII of FIG. 6;  
         [36]    36.FIG. 8 is a view seen in the direction shown by arrow VIII of FIG. 6;  
         [37]    37.FIG. 9 is a view seen in the direction shown by arrow IX of FIG. 6;  
         [38]    38.FIG. 10 is a graph showing an elastic characteristic of the elastic rubber body;  
         [39]    39.FIG. 11 is a sectional view of essential portions of a front forked portion according to a modification of the first embodiment;  
         [40]    40.FIG. 12 is a view seen from in the direction shown by arrow XII of FIG. 11, showing a locking portion of a lever with an elastic rubber body;  
         [41]    41.FIG. 13 is a view showing another example of the locking portion of the lever with the elastic rubber body shown in FIG. 12;  
         [42]    42.FIG. 14 is a sectional view of essential portions of a front forked portion according to another modification of the first embodiment;  
         [43]    43.FIG. 15 is a view seen from in the direction shown by arrow XV of FIG. 14, showing a locking portion of a lever with an elastic rubber body;  
         [44]    44.FIG. 16 is a view showing a motorcycle including a prior art front wheel suspension;  
         [45]    45.FIG. 17 is a sectional view showing another prior art front wheel suspension;  
         [46]    46.FIG. 18 is a side view of an elastic body containing a spring member according to a second embodiment;  
         [47]    47.FIG. 19 is a top view of the elastic body shown in FIG. 18;  
         [48]    48.FIG. 20 is a sectional view showing a damping force generating mechanism of a wheel suspension;  
         [49]    49.FIG. 21 is a sectional view showing the damping force generating mechanism of FIG. 20, which is in a state different from that in FIG. 20;  
         [50]    50.FIG. 22 is a graph showing an elastic characteristic of the damping force generating mechanism shown in FIG. 20;  
         [51]    51.FIG. 23 is a graph showing a change in creep amount with an elapsed time for the damping force generating mechanism shown in FIG. 20;  
         [52]    52.FIG. 24 is a sectional view of essential portions of a wheel suspension using a damping force generating mechanism according a modification of the second embodiment;  
         [53]    53.FIG. 25 is a sectional view of the essential portions of the damping force generating mechanism of FIG. 24, which is in a state different from that shown in FIG. 24;  
         [54]    54.FIG. 26 is a view showing a damping force generating mechanism of a wheel suspension according to a third embodiment;  
         [55]    55.FIG. 27 is a sectional view taken on line XXXVII-XXXVII of FIG. 26;  
         [56]    56.FIG. 28 is a sectional view showing the damping force generating mechanism of the wheel suspension of FIG. 26, which is in a state different from that in FIG. 26;  
         [57]    57.FIG. 29 is a sectional view taken on line XXIX-XXIX of FIG. 28;  
         [58]    58.FIG. 30 is a graph showing an elastic characteristic of the damping force generating mechanism shown in FIG. 26;  
         [59]    59.FIG. 31 is a sectional view of essential portions of a wheel suspension using a damping force generating mechanism according to a modification of the third embodiment;  
         [60]    60.FIG. 32 is a transverse sectional view taken on line XXXII-XXXII of FIG. 31;  
         [61]    61.FIG. 33 is a sectional view of the damping force generating mechanism of FIG. 31, which is in a state different from that in FIG. 31;  
         [62]    62.FIG. 34 is a sectional view of essential portions of a wheel suspension using a damping force generating mechanism according to another modification of the third embodiment; and  
         [63]    63.FIG. 35 is a sectional view of the damping force generating mechanism of FIG. 34, which is in a state different from that in FIG. 34.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [64]    64. A damping force generating mechanism according to a first embodiment is described with reference to FIGS.  1  to  10 . FIG. 1 is a side view of a scooter-type motorcycle  1  including a wheel suspension to which a damping force generating mechanism in the embodiment is applied, with parts partially omitted.  
         [65]    65. A low level floor  4  is formed between a front portion  2  and a rear portion  3  of the body. A down frame  6  extends downwardly from a head pipe  5  provided on the front portion  2  of the body, being curved rearwardly from the lower end portion, and is integrated with the floor  4 .  
         [66]    66. A steering shaft  7  is turnably fitted to the head pipe  5 . A pair of right and left front forked portions  8  are integrally mounted on the lower end of the steering shaft  7 , and they extend downwardly therefrom. A rocking arm  9  as a link member is pivotably supported at the lower end of each front forked portion  8  by means of a pivot arm bolt  11 . A front wheel  13  is rotatably supported by the free ends of the rocking arms  9  through a front axle  12 .  
         [67]    67. The front forked portion  8  is U-shaped in cross section with a front wall and both side walls. The right and left side walls at the lower end portion of the front forked portion  8  have bolt holes. A bush  14  provided in a base end pivot portion  9   a  of the rocking arm  9  is fitted between both side walls of the front forked portion  8  at a position corresponding to the bolt holes. The bush  14  is rotatably supported by a pivot arm bolt  11  passing through the bush  14  and the bolt holes of the side walls of the front forked portion  8 . Each side of the base end pivot portion  9   a  of the rocking arm  9  is formed in a cylindrical shape having an enlarged diameter. A plate-like lever  10  is integrated with the outer peripheral surface of the cylindrical side portion of the base end pivot portion  9   a  and extends therefrom in the radial direction.  
         [68]    68. In a state in which the rocking arm  9  extends rearwardly from the base end pivot portion  9   a , the lever  10  extends obliquely, upward at an angle of about 60 degrees relative to the rocking arm  9 . That is, it extends between the front forked portion  8  and the rocking arm  9 .  
         [69]    69. A fan-shaped case  15  is fixedly inserted in the front fork portion  8  at a position adjacent to the upper portion of the base end pivot portion  9   a  of the rocking arm  9 .  
         [70]    70. As shown in FIG. 5, the case  15  is formed into a box-like shape having a fan-shaped side wall  15   a , an outer peripheral wall  15   b , a front wall  15   c  and a rear wall  15   d . A slot  15   e  is formed in the side wall  15   a  along the front edge, and three circular holes  15   f  are formed in upper and lower ends of the front wall  15   c  and in the upper end of the rear wall  15   d  in such a manner as to pass therethrough in the right and left direction, that is, in the width direction.  
         [71]    71. As shown in FIG. 5, there is provided a plate-like lid member  16  opposed to the side wall  15   a  for blocking the opening of the case  15 . The lid member  16 , which is formed into the same fan-shape as that of the side wall  15   a , has a slot  16   e  corresponding to the slot  15   e , and three circular holes  16   f  corresponding to the circular holes  15   f.    
         [72]    72. A locking piece  17  is locked in the slots  15   e  and  16   e  opposed to each other. In a state in which the lid member  16  is fitted to the ease  15 , only the lower side of the case  15  is opened.  
         [73]    73. An elastic rubber body  20  is contained in the case  15  covered with the lid member  16 . The elastic rubber body  20  is formed into a shape shown in FIGS.  6  to  9 . That is, the elastic rubber body  20  has a fan-shaped cross section similar to but smaller than that of the inner space of the case  15 , and also has a large projection  20   a  projecting from the rear surface of the fan-shaped cross section. In addition, corners at upper and lower ends of the front side of the fan-shaped cross section are slightly cut off.  
         [74]    74. A circular hole  20   b  and a large-sized irregular rectangular hole  20   c  are formed fore and aft in the elastic rubber body  20  having the above contour in such a manner as to pass through the elastic rubber body  20  in the width direction. Slots  20   e  and  20   f  are also formed in the elastic rubber body  20 . The slot  20   e  (corresponding to the slot  15   e  of the above case  15 ) is disposed between the circular hole  20   b  and the front surface of the elastic rubber body  20  in such a manner as to extend in parallel to the front surface. The slot  20   f  passes through a base portion of the projection  20   a  in parallel to the rear surface of the elastic rubber body  20 .  
         [75]    75. The elastic rubber body  20  exhibits a hysteresis characteristic of compression and tensile actions, and it has both elastic and damper functions.  
         [76]    76. The elastic rubber body  20 , case  15 , and the like are assembled as follows. The lever  10  integrated with the rocking arm  9  is made to pass through the slot  20   f  formed in the base portion of the projection  20   a  of the elastic rubber body  20 , to be thus mounted in the elastic rubber body  20 . The case  15  covers the elastic rubber body  20  from the left side, and the lid member  16  closes the case  15  from the right side. Thus, the lever  10  is in a state being inserted in the case  15  through the lower opening of the case  15 .  
         [77]    77. The locking piece  17  is made to pass through the slot  15   e  of the case  15 , the slot  20   e  of the elastic rubber body  20 , and the slot  16   e  of the lid member  16 , and hence to be fitted in the slots  15   e ,  20   e  and  16   e . Then, a screw  25  is threaded into the circular hole  15   f  formed in the upper end portion of the rear wall  15   d  of the case  15  and in the circular hole  16   f  of the lid member  16  corresponding to the circular hole  15   f , to thus integrally fix the case  15  to the lid member  16 .  
         [78]    78. The case  15  covered with the lid member  20 , which is mounted to the lever  10  through the elastic rubber body  20 , is inserted into the recess on the back side of the front forked portion  8  to the extent that the front wall  15   c  of the case  15  is brought into contact with the bottom of the recess.  
         [79]    79. Each of the right and left side walls of the front fork portion  8  has circular holes at specific upper and lower positions along the bottom. The circular holes  15   f  and  16   f  of the case  15  and the lid member  16  are aligned with the above circular holes, and bolts  26  are made to pass through these circular holes and are attached to nuts. Accordingly, the case  15  and the lid member  16  are co-fastened to the front forked portion  8  with the bolts  26 , to be thus fixed thereto.  
         [80]    80. In the assembled state, the elastic rubber body  20  is disposed in the case  15  as shown in FIGS. 3 and 4. That is, with respect to the elastic rubber body  20 , the front end portion is positioned in a state being locked by the locking piece  17 , the rear portion is held by the lever  10  inserted in the slot  20   f , and the projection  20   a  projecting rearward is allowed to be brought in contact with the rear wall  15   d  of the case  15 .  
         [81]    81. In this way, the front wheel suspension in this embodiment has a very simple structure that the elastic rubber  20  is interposed between the front forked portion  8  and the lever  10  in a state in which the front portion thereof is locked by the locking piece  17  and the rear portion thereof is locked by the lever  10 .  
         [82]    82. When the front wheel  13  is applied with a shock generated by irregularities of the ground and the rocking arm  9  is rocked, the positional states of the rocking arm  9  and the lever  10  integrated with the rocking arm  9  are changed from states indicated by a solid line of FIG. 3 to states indicated by a two-dot chain line. As a result, the lever  10  compresses the elastic rubber body  20  in the forward direction, that is, on the front forked portion  8  side, and elastically deforms it, to thereby generates a compression side damping force.  
         [83]    83. In this case, the elastic rubber body  20  has a progressive elastic characteristic shown in FIG. 10 in which the increasing ratio of a load to a displacement is large in a large displacement region as compared with a small displacement region. Specifically, in a small displacement region that only the irregular rectangular hole  20   c  of the elastic rubber body  20  is deformed, a compressive stress is moderately generated to the displacement, but in a large displacement region that not only the irregular rectangular hole  20   c  but also the circular hole  20   b  are deformed, the compressive stress is rapidly increased with the displacement.  
         [84]    84. On the other hand, when the rocking arm  9  and the lever  10  are reversely rocked, the main body of the elastic rubber body  20  generates a tensile damping force, and simultaneously the projection  20   a  is pressed and compressed by the rear wall  15   d  of the case  15 , thus acting as a rebound stopper.  
         [85]    85. Accordingly, while the front wheel suspension in this embodiment has the simple structure in which the elastic rubber body  20  is interposed between the front fork portion  8  and the lever  10 , it exhibits a desirable damping effect due to the function of the elastic rubber body  20  generating both a compression side damping force and a tensile side damping force thereby effectively absorbing shock applied from the ground to the front wheel  13 .  
         [86]    86. In this way, the front wheel suspension in this embodiment does not require a pivot for supporting the elastic rubber body  20 , and has no sliding portion for a piston or the like, so that it can obtain a stable damping characteristic without the occurrence of any sliding friction, thereby enhancing the durability with a simple, lightweight, and inexpensive structure.  
         [87]    87. It is to be noted that it becomes possible to obtain various other elastic characteristics of the elastic rubber body  20  by changing the shapes of the circular hole  20   b  and the irregular rectangular hole  20   c  of the elastic rubber body  20 , and hence to easily provide an elastic body most suitable for each kind of vehicle.  
         [88]    88. Next, the structure of a front wheel suspension disposed at the lower end portion of a front forked portion  40  according to a modification of the first embodiment will be described with reference to FIGS. 11 and 12. This modification has the same basic structure as that of the first embodiment, except for slightly changed shapes of the parts. A base end pivot portion  41   a  of a rocking arm  41  is rockably supported, by means of a pivot arm bolt  42 , at the lower end of the front forked portion  40 . The rocking arm  41  has a plate-like lever  43  extending from the base end pivot arm portion  41   a  in the radial direction. A fan-shaped case  44  adjacent to the upper side of the base end pivot portion  41   a  of the rocking arm  41  is fixedly fitted in the front forked portion  40 .  
         [89]    89. An elastic rubber body  45 , which has throughholes  45   b  and  45   c  passing through the elastic rubber body  45  in the width direction, is fitted in the case  44 . A locking piece  46  passes through the front portion of the elastic rubber body  45  and locks it. A lever  43  is inserted in a slot  45   d  formed in the rear portion of the elastic rubber body  45 , and a projection  45   a  projecting rearwardly from the rear portion is allowed to be brought into contact with the rear wall of the case  44 .  
         [90]    90. The lever  43  has a swelled portion  43   b , a stepped portion  43   c , and a flange portion  43   d . As shown in FIG. 12, the swelled portion  43   b  is swelled right and left, that is, in the width direction on the base end side from a locking portion  43   a  to be locked with the elastic rubber body  45 , and the stepped portion  43   c  is formed at the boundary between the locking portion  43   a  and swelled portion  43   b . The flange portion  43   d  projects upward from the leading end of the lever  43 , as shown in FIG. 11.  
         [91]    91. The lever  43  passes through the slot  45   d  of the elastic rubber body  45 , and the elastic rubber body  45  is locked with the locking piece  43   a . At the same time, the elastic rubber body  45  is held between the stepped portion  43   c  and the flange portion  43   d  of the lever  43 . The sliding motion of the elastic rubber body  45  relative to the lever  43  is thus restricted by the stepped portion  43   c  and the flange portion  43   d  of the lever  43 . This allows the elastic rubber body  45  to effectively generate a damping force.  
         [92]    92.FIG. 13 shows another example of the lever. A lever  50  has a fitting portion  50   c  on the base end side of a locking portion  50   a  at the boundary between the locking portion  50   a  and a swelled portion  50   b , and also has on the leading end side a flange portion  50   d  projecting in the right and left direction. An elastic rubber body  51  is held between the fitting portion  50   c  and the flange portion  50   d  of the lever  50 , so that the sliding motion of the elastic rubber body  45  relative to the lever  43  is restricted.  
         [93]    93. Next, another modification of the first embodiment will be described with reference to FIGS. 14 and 15. The modification, which also concerns a front wheel suspension provided on the lower end portion of a front forked portion  60 , is substantially similar to the above modification shown in FIGS. 11 and 12 in terms of shapes of a rocking arm  61 , a lever  63 , a case  64 , and an elastic rubber body  65 , but is different therefrom in terms of the structure of restricting the sliding motion of the elastic rubber body  65  relative to the lever  63 .  
         [94]    94. A circular hole  63   b  is formed in a plate-like locking portion  63   a  of the lever  63 , and a circular hole  65   e  corresponding to the circular hole  63   b  is formed in the elastic rubber body  65 . The circular hole  65   e  is continuous to a slot  65   d  formed in a rear projection  65   a , and further to a recess formed in the opposed portion, to the slot  65   d , of the rear portion of the elastic rubber body  65 . A knock pin  66  is inserted in the circular hole  63   b  of the lever  63  and the circular hole  65   e  of the elastic rubber body  65 .  
         [95]    95. Accordingly, the sliding motion of the elastic rubber body  65  relative to the lever  63  is restricted by the knock pin  66 , so that the elastic rubber body  65  is allowed to effectively generate a damping force. The lever  63 , which has no flange portion at the leading end thereof, is easily inserted in the slot  65   d  of the elastic rubber body  65  upon assembly.  
         [96]    96. Although description has been made by example of the front wheel suspension for a motorcycle in the above first embodiment and modifications thereof, the present invention can be applied to a rear wheel suspension, and used as a damper mechanism for a power transmission of an engine and a damper mechanism for a cam chain tensioner.  
         [97]    97. Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.  18  to  23 . In the second embodiment also concerning a front suspension mechanism as in the first embodiment, parts corresponding to those in the first embodiment are indicated by the same reference characters.  
         [98]    98.FIGS. 18 and 19 shows the second embodiment, in which four holes having different shapes and passing through an elastic rubber body  120   i  in the width direction are formed in the elastic rubber body  120 . The four holes, an elliptic hole  120   b  (corresponding to the slot  15   e  of the case  15  in the previous embodiment), an irregularly elliptic hole  120   c , a developed fan-shaped hole  120   d , and a contracted fan-shaped hole  120   e  are arranged from the front side in this order. Further, a through-slot  120   f  is formed in the base portion of a projection  120   a  along the rear surface of the elastic rubber body  120 .  
         [99]    99. A metal spring member  121  as an internal pressure generating member is inserted in the developed fan-shaped hole  120   d . The spring member  121  is composed of radially extending plate springs arranged in a fan-shape corresponding to the internal space of the developed fan-shaped hole  120   d . The spring member  121  is made repulsive against a compression side pressing force while generating an internal pressure.  
         [100]    100. The elastic rubber body  120  is contained in a case  15  in a state shown in FIG. 20. That is, with respect to the elastic rubber body  120 , the front end portion is locked and positioned by a locking piece  17  passing through the front portion. A lever  10  is inserted in the slot  120   f , and a projection  120   a  projecting rearwardly is brought into contact with a rear wall  15   d  of the case  15 .  
         [101]    101. As described above, the front wheel suspension in this embodiment has a simple structure in which the elastic rubber body  120  containing the spring member  121  is interposed between a front forked portion  8  and the lever  10  in the state that the front portion of the elastic rubber body  120  is locked with the locking piece  17  and the rear portion of the elastic rubber body  120  is locked with the lever  10 .  
         [102]    102. When a front wheel  13  is applied with shock generated by irregularities of the ground or a load upon braking and thereby the rocking arm  9  is rocked, the rocking arm  9  and the lever  10  integrated with the rocking arm  9  are rocked from a state shown in FIG. 20 to a state shown in FIG. 21. The lever  10  thus presses the elastic rubber body  120  forward onto the front forked portion  8 , and it elastically deforms the elastic rubber body  120 . As a result, the spring member  121  inserted in the elastic rubber body  120  is compressed and is made repulsive while generating an internal pressure.  
         [103]    103. In this case, the elastic rubber body  120  has an elastic characteristic shown in FIG. 22, in which the displacement of the elastic rubber body  120  is increased from the initial state having an initial strain to a sufficiently large value by increasing the applied load, and then the displacement is decreased along the hysteresis curve by decreasing the load and finally it becomes zero when the load reaches zero. Accordingly, the elastic rubber body  120  can ensure a large displacement and obtain sufficient energy absorption, and further it improves the initial strain.  
         [104]    104. The result of an experiment of examining the generation amount of creep of the elastic rubber body  120  containing the spring member  121  is shown in FIG. 23. In FIG. 23, an example of using the prior art elastic body not containing the spring member is shown by a broken line, and the example using the elastic rubber body  120  containing the spring member  121  is shown by a solid line. As is apparent from this figure, the creep amount of the elastic rubber body  120  is significantly reduced as compared with the prior art elastic body.  
         [105]    105. The characteristic change of the elastic rubber body  120  due to fatigue is thus small. Further, the elastic rubber body  120  is excellent in restoring ability after release of a load. That is, while the prior art elastic body causes approximately 100% of the permanent strain, the elastic rubber body  120  only causes approximately 40% of the permanent strain.  
         [106]    106. A modification of the second embodiment will be described with reference to FIGS. 24 and 25. The modification is the same as the second embodiment, except for an elastic body  130  and an internal pressure generating member  131  inserted in the elastic body  130 . In this modification, parts corresponding to those in the second embodiment are indicated by the same characters.  
         [107]    107. The elastic body  130  is made from polyester elastomer and has an outer shape being substantially the same as that of the elastic body  120  in the second embodiment. Further, an elliptic hole  130   b , and an irregularly elliptic hole  130   c  formed in the elastic body  130 , and a slot  130   f  passing through the elastic body  130  along the base portion of a rear projection  130   a  are formed in the same shapes as those of the corresponding ones in the second embodiment. In this modification, however, the developed fan-shaped hole  120   d  and the contracted fan-shaped hole  120   e  are omitted, and instead, an irregular circular hole  130   d  is formed and an internal pressure generating member  131  is inserted in the irregular circular hole  130   d.    
         [108]    108. The internal pressure generating member  131  is made from polyester-urethane being softer and more elastic than the elastic body  130  and is formed in a cylindrical shape having a specific wall thickness. When the elastic body  130  is applied with a load and a rocking arm  9  is rocked, the rocking arm  9  and a lever  10  integrated with the rocking arm  9  are rocked from a state shown in FIG. 24 to a state shown in FIG. 25, so that the lever  10  presses the elastic body  130  forward to a front forked portion  8  and thereby it elastically deforms the elastic body  130 . In such a state, the internal pressure generating member  131  inserted in the elastic body  130  is compressed and is made repulsive while generating an internal pressure.  
         [109]    109. The elastic body  130  can ensure a large displacement and obtain a sufficient energy absorption, and it is significantly reduced in creep by the effect of the internal pressure generating member  131  and thereby it is small in characteristic change due to fatigue. Further, the elastic body  130  is excellent in restoring ability after release of a load.  
         [110]    110. In addition, the elastic body may be made from rubber in place of polyester-urethane. Also, with respect to the internal pressure generating member  131  made from polyester-urethane, the cylindrical hollow type may be replaced with a solid type. And, a different elastic substance may be inserted in the hollow portion of the elastic body.  
         [111]    111. The internal pressure generating member may be made from an organic material having a specific elasticity, in place of polyester-urethane. In this case, the organic material can be easily molded into a shape most effective to the application use of the elastic body.  
         [112]    112. Additionally, it may be considered to form an enclosed partition chamber containing a compressive gas or liquid in the elastic body. When the elastic body is pressed and deformed, the gas or liquid contained in the partition chamber is compressed to generate an internal pressure. Such an elastic body is allowed to be significantly reduced in creep and hence to be reduced in characteristic change, and also to enhance the restoring ability after release of a load.  
         [113]    113. A third embodiment of the present invention will be described with reference to FIGS.  26  to  30 . In the third embodiment also concerning a front wheel suspension as in the previous embodiments, parts corresponding to those in the previous embodiments are indicated by the same characters. FIG. 27 shows the third embodiment using an elastic body  220  made from polyester elastomer. The elastic body  220  is formed in a shape being substantially similar to but smaller than that of the inner space of the case  15 . The elastic body  220  has right and left side surfaces  220 R and  220 L which are substantially parallel to each other and are slightly curved in such a manner as to be gradually close to each other in the direction from the front side to the rear side, and it has a large projection  220   a  projecting from the rear portion thereof.  
         [114]    114. Three holes of different shapes are formed in the elastic rubber body  220  having such a contour. These holes, an elliptic hole  220   b  (corresponding to the elliptic hole  15   e  of the case  15  in the previous embodiment), an irregular elliptic hole  220   c , and an irregular elliptic hole  220   d  are arranged from the front side in this order. Further, a slot hole  220   e  is formed which passes through the base portion of the projection  220   a  along the rear surface of the elastic rubber body  220 .  
         [115]    115. As shown in FIG. 27, the right and left side surfaces  220 R and  220 L of the elastic body  220  contained in the case  15  are respectively brought into contact with a side wall  15   a  of the case  15  and a lid member  16  on the front side of the elastic body  220 , that is, on the side locked with a locking piece  17 , and they are gradually separated from the side wall  15   a  of the case  15  and the lid member  16  with the increased gap as nearing the rear side. In this way, the front wheel suspension in this embodiment has a simple structure in which the elastic body  220  is interposed between a front forked portion  8  and a lever  10  in such a manner that the front portion thereof is locked with the locking piece  17  and the rear portion thereof is locked with the lever  10 .  
         [116]    116. When a front wheel  13  is applied with a shock generated by irregularities on the ground or a load upon braking and thereby the rocking arm  9  is rocked, the rocking arm  9  and the lever  10  integrated with the rocking arm  9  are rocked as shown in FIGS. 28 and 29, so that the lever  10  presses the elastic body  220  forward to the front forked portion  8  and thereby it elastically deforms the elastic body  220 .  
         [117]    117. When being pressed, the elastic body  220  is expanded in the direction perpendicular to the pressing direction, that is, in the vertical direction and also in the right and left direction. The expansion of the elastic body  220  in the right and left direction causes the right and left side surfaces  220 R and  220 L to be swelled and to be respectively brought in contact with the side wall  15   a  of the case  15  and the lid member  16 . Consequently, the expansion of the elastic body  220  is suppressed by the above contact, and as the pressing of the elastic body  220  proceeds, the contact area thereof is increased, so that the sliding resistance of the elastic body  220  at the contact surface of the right and left side surfaces  220 R and  220 L with the side wall  15   a  of the case  15  and the lid member  16  is increased. Thus, as the displacement (stroke) of the elastic body  220  is increased, the sliding resistance as well as the elastic force of the elastic body  220  is progressively increased.  
         [118]    118. The stroke-load characteristic in this embodiment is shown by a solid line of FIG. 30. The stroke-load characteristic forms a hysteresis curve. At the beginning of the motion of the elastic body  220 , that is, when the stroke is small, the sliding resistance of the elastic body  220  is small and thereby the gradient of the curve of the load to the stroke is moderate. When the stroke becomes relatively large, the sliding resistance is added to the elastic force, and thereby the gradient of the curve is increased. When the stroke becomes very large, the gradient is further increased by the action of the progressively increased sliding resistance. In this way, the front wheel suspension in this embodiment exhibits the desirable damping effect.  
         [119]    119. The action of the sliding resistance can be easily adjusted by changing the shapes of the right and left side surfaces  220 R and  220 L of the elastic body  220 , to thereby easily obtain a specific stroke-load characteristic.  
         [120]    120. A modification of the third embodiment will be described with reference to FIGS.  31  to  33 . In the modification also concerning a front wheel suspension as in the third embodiment, parts corresponding to those in the third embodiment are indicated by the same characters. An elastic body  230  is formed into the same shape as that of the elastic body  220  in the third embodiment. However, in the elastic body  230 , an intermediate elastic body  235  is inserted in an irregular elliptic hole  230 C as one of hollow portions. The intermediate elastic body  235  is made from a material smaller in elastic modulus than the elastic body  230 , that is, deformable easier than the elastic body  230 .  
         [121]    121. In a state before the rocking arm  9  is rocked (see FIGS. 31 and 32), as shown in FIG. 32, the intermediate elastic body  235  is fitted in the irregular elliptic hole  230   c , that is, not swelled from the right and left openings of the irregular elliptic hole  230   c.    
         [122]    122. When the front wheel  13  is applied to shock generated by irregularities on the ground and the rocking arm  9  is rocked, the elastic body  230  is pressed and elastically deformed, so that the irregular elliptic hole  230   c  is also compressed in the pressing direction and it compresses the intermediate elastic body  235  contained in the hole  230   c . At this time, the intermediate elastic body  235  made from a soft material is easily deformed, being expanded in the direction perpendicular to the compression direction, and is swelled from the right and left openings of the irregular elliptic hole  230   c  to be brought in contact with the side wall  15   a  of the case  15  and the lid member  16 . The expansion of the intermediate elastic body  235  is thus suppressed by the above contact, and consequently the sliding resistance thereof at the contact surface is increased.  
         [123]    123. As described above, right and left side surfaces  230 R and  230 L of the elastic body  230  itself are brought in contact with the side wall  15   a  of the case  15  and the lid member  16  respectively, so that the sliding resistance of the elastic body  230  is increased. As a result, the elastic forces of the elastic body  230  and the intermediate elastic body  235  and the sliding resistance of the elastic body  230  are further added with the sliding resistance of the intermediate elastic body  235 . The stroke-load characteristic of the front wheel suspension having the above configuration is shown by a broken line of FIG. 30.  
         [124]    124. In the stroke-load characteristic of this modification, the gradient of the curve is rapidly raised in a early region with a small stroke, as compared with the characteristic of the third embodiment shown by the solid line. In this way, the front wheel suspension in this modification is allowed to change the stroke-load characteristic with a simple structure in which the intermediate elastic body  235  is inserted and hence to easily obtain a specific characteristic.  
         [125]    125. Another modification will be described with reference to FIGS. 34 and 35. This modification has the same basic structure as that of the previous modification shown in FIGS.  31  to  33 , except that the shape of an elastic body  240  is slightly different from that of the above-described elastic body  230 . In this modification, parts corresponding to those in the previous modification are indicated by the same characters.  
         [126]    126. The elastic body  240  having right and left side surfaces  240 R and  240 L parallel to each other is contained in the case  15  between the side wall  15   a  and the lid member  16  with gaps therebetween. As shown in FIG. 35, even when the elastic body  240  is pressed, the right and left side surfaces  240 R and  240 L are not brought in contact with the side wall  15   a  and the lid member  16  with gaps kept therebetween. Accordingly, upon pressing of the elastic body  240 , the expansion thereof is not restricted, differently from the elastic body  230  in the previous modification.  
         [127]    127. An intermediate elastic body  245  is inserted in an irregular elliptic hole  240   c  of the elastic body  240 , and as shown in FIG. 34, before the elastic body  240  is pressed, the intermediate elastic body  245  is contained in the irregular elliptic hole  240   c . However, as shown in FIG. 35, when the elastic body  240  is pressed, the intermediate elastic body  245  is compressed and expanded in the direction perpendicular to the compression direction, being swelled from the right and left openings of the irregular elliptic hole  240   c , and is brought in contact with the side wall  15   a  of the case  15  and the lid member  16 . The expansion of the intermediate elastic body  245  is thus suppressed by the above contact, and thereby the sliding resistance thereof at the contact surface is increased.  
         [128]    128. Accordingly, when the elastic body  240  is pressed, the elastic force of the elastic body  240  is added with the sliding resistance of the intermediate elastic body  245 , so that there can be obtained a stroke-load characteristic different from that in the previous modification.  
         [129]    129. 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.

Technology Classification (CPC): 5