Abstract:
A transmission apparatus of an all-terrain vehicle includes: a non-stage transmission disposed in a power transmission path from an engine to drive wheels; a forward and backward movement switching device capable of switching to a forward movement position, a neutral position, or a backward movement position, the forward and backward movement switching device being disposed in the power transmission path at a position near said engine; and a shift operation device for switching forward and backward movement disposed on a handle bar at a position adjacent to a handle grip, the shift operation device and the forward and backward movement switching device being interlocked with each other.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a transmission apparatus of an all-terrain vehicle having, in a power transmission path from an engine to drive wheels, a non-stage transmission, such as V belt non-stage transmission, and a forward and backward movement switching device capable of switching to a forward movement position, neutral position, or backward movement position. 
   2. Description of the Related Art 
   In this kind of all-terrain vehicle, a forward and backward movement switching device installed on the vehicle together with a non-stage transmission such as a V belt non-stage transmission is shifted to the forward movement position during regular running. The speed is automatically changed by the V belt non-stage transmission during running. If necessary, the vehicle is stopped once, the forward and backward movement switching device is shifted to the backward movement position, and the vehicle is restarted running. 
   As a shift operation device for operating the forward and backward movement switching device, conventionally, a lever type shift operation device is arranged in the neighborhood of a fuel tank which is positioned in front of a seat of the vehicle. The forward and backward movement switching device is shifted to the forward movement position or backward movement position by operating a shift lever of the lever type shift operation device, as described in Japanese patent laid-open publication No. 8-337131 and Japanese patent publication No. 3040971, etc. 
   In the forward and backward movement switching device described in the above-mentioned publications, the shift lever is arranged, for example, in a gate plate having an H-type or I-type guide slit and switches to the neutral position, forward movement position, or backward movement position by moving the shift lever along the guide slit. 
   In the vehicle that the shift operation device for switching forward and backward movement positions is arranged near the fuel tank which is far away from a grip of a handle, the rider must release his hand from the grip in order to grasp the shift lever and perform the shift operation viewing the gate plate. Therefore, the rider cannot operate the shift lever in the same riding posture as that during running so that the shift operation is made troublesome. Further, in the case that the shift lever is arranged near the fuel tank, the space around the legs of the rider is limited. 
   SUMMARY OF THE INVENTION 
   The present invention has been made to improve a shift operability of a forward and backward movement switching device of an all-terrain vehicle. More specifically, the objectives of the present invention are to provide a transmission apparatus of an all-terrain vehicle capable of enabling a rider to comfortably perform a shift operation while maintaining to grasp the grips by both hands and to easily discriminate the conditions of the shift operation. 
   According to the first aspect of the present invention, a transmission apparatus of the all-terrain vehicle comprises: a non-stage transmission disposed in a power transmission path from an engine to drive wheels; a forward and backward movement switching device capable of switching to a forward movement position, a neutral position, or a backward movement position, the forward and backward movement switching device being disposed in the power transmission path at a position near the engine; and a shift operation device for switching forward and backward movement disposed on a handle bar at a position adjacent to a handle grip, the shift operation device and the forward and backward movement switching device being interlocked with each other. 
   By use of such a constitution, the rider can perform the shift operation for switching forward and backward movement almost in the same riding posture as that during running without releasing a hand from the grip, thus the shift operability for switching forward and backward movement is improved. Further, since the shift operation device is disposed on the handle bar at a position adjacent to the handle grip, the space around the legs of the rider can be widely reserved. 
   Preferably, in the transmission apparatus of the all-terrain vehicle, the shift operation device is a rotary type and has a rotary member which is rotatable about an axis of the handle bar. 
   Preferably, the transmission apparatus of an all-terrain vehicle further comprises a stopper mechanism to prevent the forward and backward switching device from shifting from the neutral position to the backward movement position, the stopper mechanism being adapted to be released at a time of a brake operation of the vehicle. 
   According to the second aspect of the present invention, a transmission apparatus of the all-terrain vehicle comprises: a non-stage transmission disposed in a power transmission path from an engine to drive wheels; a forward and backward movement switching device capable of switching to a forward movement position, a neutral position, or a backward movement position, the forward and backward movement switching device being disposed in the power transmission path at a position near the engine; and a stopper mechanism to prevent a switching rotary part of the forward and backward switching device from moving from the neutral position to the backward movement position, the stopper mechanism being interlocked with a brake device, and the stopper mechanism being adapted to be released at a time of a brake operation. 
   By use of such a constitution, a brake operation is needed in order to perform a backward shift by the forward and backward movement switching device, and the shift operation to backward movement can be automatically recognized, and during the shift operation, the vehicle can be prevented from moving back and forth. 
   Preferably, the transmission apparatus of the all-terrain vehicle further comprises: a shift operation device for switching forward and backward movement disposed on a handle bar at a position adjacent to a handle grip, the shift operation device and the forward and backward movement switching device being interlocked with each other. 
   By use of such a constitution, the rider can perform the shift operation for switching forward and backward movement almost in the same riding posture as that during running without releasing a hand from the grip, thus the shift operability for switching forward and backward movement is improved, and moreover, since a brake operation is needed in order to perform a backward shift, the shift operation to backward movement can be automatically recognized and the vehicle can be prevented from moving back and forth during a shift operation. 
   Preferably, in the transmission apparatus of the all-terrain vehicle, the shift operation device is a rotary type and has a rotary member which is rotatable about an axis of the handle bar. 
   Preferably, in the transmission apparatus of the all-terrain vehicle, the stopper mechanism has a stopper member capable of entering and leaving a moving track between the neutral position and the backward movement position of the switching rotary part of the forward and backward movement switching device, the stopper member being configured to be kept in a state that the stopper member enters the moving track by elastic means to restrict a movement of the switching rotary part and leave the moving track by the brake operation. 
   By use of such a constitution, the structure of the stopper mechanism can be simplified, and when returning the switching device from the backward movement position to the neutral position, the brake operation is not required and the stopper mechanism is automatically returned to the operating state, thus the operability is improved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings, in which: 
       FIG. 1  is a plan view of an all-terrain vehicle to which the present invention is applied; 
       FIG. 2  is a left side view of the all-terrain vehicle shown in  FIG. 1 ; 
       FIG. 3  is a right side view of the body frame and an engine of the all-terrain vehicle shown in  FIG. 1 ; 
       FIG. 4  is an enlarged view of the section IV—IV shown in  FIG. 3 ; 
       FIG. 5  is a right side view showing the rear end of the crankcase and footbrake; 
       FIG. 6  is a plan view of  FIG. 5 ; 
       FIG. 7  is an enlarged plan view showing the adjust bolt of the stopper mechanism; 
       FIG. 8  is a front view of the shift operation device; 
       FIG. 9  is a left side view (view of the arrow IX shown in  FIG. 8 ) of the shift operation device; 
       FIG. 10  is a plan view of the shift operation device; 
       FIG. 11  is a sectional view of XI—XI shown in  FIG. 9 ; 
       FIG. 12  is a sectional exploded view of XI—XI shown in  FIG. 9 ; 
       FIG. 13  is a sectional view of XIII—XIII shown in  FIG. 8 ; and 
       FIG. 14  is a sectional view of XIV—XIV shown in  FIG. 8 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   [Outline of All-Terrain Vehicle] 
   In  FIG. 1 , for simplicity of explanation, “Left” and “Right” shown in the drawing indicate that the left direction and right direction viewed from a rider are the left direction and right direction of an all-terrain vehicle. 
   The all-terrain vehicle has a pair of front wheels  1  and a pair of rear wheels  2  and an engine  3  disposed between the wheels  1  and  2 . In the neighborhood of the rear of the engine  3 , a pair of bar-shaped steps  8  and  9  are provided and in the neighborhood of the step  9  on the right side, a footbrake  10  is installed in a rotatative state. 
   On the front side of the upper part of a vehicle body, a handle bar  12  is arranged, and behind the handle bar  12 , a seat  13  is arranged, and above the front wheels  1  and the rear wheels  2 , a front fender  15  and a rear fender  16  are respectively arranged. 
   On the right side of a crankcase  4  of the engine  3 , a V belt non-stage transmission  5  is provided and on the rear of the crankcase  4 , a gear type forward and backward movement switching device  6  is stored. Between a power output shaft  17  protruded from the rear end of the forward and backward movement switching device  6  and a final speed reducer  18  for driving the rear wheels, a drive shaft  19  is installed via universal couplings. 
   At the right end of the handle bar  12 , a right acceleration grip  21  is provided in a rotative state and a front wheel brake lever  22  is also provided, and at the left end of the handle bar  12 , a left grip  23  is fixed and a rear wheel brake lever  24  is provided. Furthermore, on the handle bar  12  neighboring the left grip  23 , a shift operation device  26  for switching forward and backward movement of the vehicle is provided, and the shift operation device  26  for switching forward and backward movement is interlocked with an outside shift lever  73  of the forward and backward movement switching device  6  by a pair of cable transfer devices  77  and  78  for transferring operational force. 
     FIG. 2  is a left side view of the all-terrain vehicle, wherein a V-type 2-cylinder engine  3  is loaded, and the engine  3  is stored and supported in a body frame  27 , and at the front end of the body frame  27 , a radiator  28  is arranged. 
   The handle bar  12  is fixed to the upper end of a steering shaft  11 , and the steering shaft  11  is supported by a shaft support case (head pipe)  29  installed on the front of the body frame  27  in a rotative state, and the lower end of the steering shaft  11  is interlocked with a front wheel steering device  30 . 
   The final speed reducer  18  for driving the rear wheels is supported by the body frame  27  so as to freely swing in the vertical direction via a swing arm  31  storing the drive shaft  19  and elastically supported by a rear suspension  33 . 
   [V Belt Non-Stage Transmission] 
     FIG. 3  is a right side view of the body frame  27  and the engine  3 , wherein the V belt non-stage transmission  5  is composed of a drive pulley  35  mounted on the crank shaft  7 , a driven pulley  37  mounted on a driven shaft  36 , and a V belt  38  wound between the pulleys  35  and  37  and in the same way as the well-known V belt non-stage transmission, due to changes in the number of rotations of the engine and the load from the rear wheel side, the effective pulley diameters of the respective pulleys  35  and  37  is automatically adjusted, thus automatic non-stage speed variation is realized. 
   [Forward and Backward Movement Switching Device] 
     FIG. 4  is an enlarged view of the section IV—IV shown in  FIG. 3 . Properly, it shows a state that the forward and backward movement switching device  6  is cut and developed by a plane passing an input shaft  40 , a backward movement idle shaft  41 , an intermediate output shaft  42 , and an output shaft  43  and in the drawing, the transverse direction (indicated in the drawing) of the vehicle and the transverse direction of the drawing are opposite to each other. The gear type forward and backward movement switching device  6 , as mentioned above, has the input shaft  40 , the backward movement idle shaft  41 , the intermediate output shaft  42 , and the output shaft  43  and the input shaft  40  is formed integrally with the driven shaft  36  of the V belt non-stage transmission  5  and supported by the left and right side walls of the crankcase  4  via a bearing  45 . At the left end of the input shaft  40 , a backward movement input gear  50  is arranged, and at the right end, a forward movement input gear  51  is arranged, and between the input gears  50  and  51 , a shift sleeve  52  is spline-fit in an axially movable state. 
   The backward movement input gear  50  has a dog pawl  50   a  on the end face (right end face) on the side of the shift sleeve  52 , is fit into the input shaft  40  in a rotative state via the needle bearing, and mates with a backward movement output gear  55  of the intermediate output shaft  42  via an idle gear  54  of the backward movement idle shaft  41 . The forward movement input gear  51  has a dog pawl  51   a  on the end face (left end face) on the side of the shift sleeve, is fit into the input shaft  40  in a rotative state via the needle bearing, and mates with a forward movement output gear  56  of the intermediate output shaft  42 . The intermediate output shaft  42  is interlocked with the output shaft  40  via a transmission gear  47  and an output gear  48 . The output gear  43  is interlocked with the power output shaft  17  ( FIGS. 1 and 3 ) via the bevel gear mechanism not shown in the drawing. Further,  FIG. 4  is a sectional development elevation of the forward and backward movement device  6  which is cut by a plane passing the shafts  40 ,  41 ,  42 , and  43 , so that the distance between the intermediate output shaft  42  and the input shaft  40  displayed on the drawing is longer the actual distance. Therefore, the forward movement input gear  51  and the forward movement output gear  56  displayed on the drawing are away from each other. However, actually, they mate with each other as mentioned above. 
   On both end faces of the shift sleeve  52  in the axial direction, a backward movement dog pawl  58  opposite to the dog pawl  50   a  of the backward movement input gear  50  in a matable state and a forward movement dog pawl  59  opposite to the dog pawl  51   a  of the forward movement input gear  51  in a matable state are formed, and in the middle of the shift sleeve  52  in the direction of the axis, an outer peripheral ring slit  60  is formed, and a shift fork  61  is engaged with the ring slit  60 . The shift fork  61  is fixed to a shift rod  62  supported by the crankcase  4  in a transversely movable state and can move in the transverse direction integrally with the shift rod  62 . 
   The shift fork  61  and the shift sleeve  52  shown in  FIG. 4  are in the state of the neutral position and the dog pawls  58  and  59  of the shift sleeve  52  are provided respectively at predetermined intervals in the direction of the axis from the dog pawls  50   a  and  51   a  of the input gears  50  and  51 . When the shift sleeve  52  is moved from the neutral position toward the backward movement input gear  50  (in the direction of the arrow B 3 ), the backward movement dog pawl  58  mates with the dog pawl  50   a  of the backward movement input gear  50  and enters the backward movement state. On the other hand, when the shift sleeve  52  is moved from the neutral position toward the forward movement input gear  51  (in the direction of the arrow A 3 ), the forward movement dog pawl  59  mates with the dog pawl  51   a  of the forward movement input gear  51  and enters the forward movement state. 
   At the left end of the shift rod  62 , a plurality of notches  65  for positioning the shift rod  62  at the forward movement position, neutral position, or backward movement position at predetermined intervals in the axial direction are formed and, a positioning ball  67  pressed by a spring  66  is joined to the notches  65 . The right end of the shift rod  62  is projected into a shift lever chamber  69  formed at the right rear end of the crankcase  4 , and a shift pin  64  having a projected top is provided on the projected part thereof. 
   In an upper wall case  70  of the shift lever chamber  69 , a shift lever shaft  71  is supported in a rotative state and at the lower end of the shift lever shaft  71 , an inner shift lever  72  extending forward and joining to the shift pin  64  is fixed. The upper end of the shift lever shaft  71  is projected upward from the shift lever chamber  69  and an outer shift lever  73  is fixed to it. 
     FIG. 6  is a plan view in which the outer shift lever  73  having a U-shaped section (vertically folded in two) is fixed to the shift lever shaft  71  via an L-shaped bracket  75 , extended from the shift lever shaft  71  like two wings, and at the ends of both wings, wire joint holes  76  are formed, respectively. To the joint holes  76 , inner wire end terminals  77   b  and  78   b  of the cable transfer devices  77  and  78  are respectively joined and the outer wire end terminals of the cable transfer devices  77  and  78  are supported by a rear cylinder head  14  of the engine  3  via a bracket  79 . 
   [Stopper Mechanism] 
   In  FIG. 6 , on the outer shift lever  73 , to prevent the outer shift lever  73  from rotation in the direction of the arrow B 2  from the neutral position N to the backward movement position R, a stopper mechanism composed of an adjust bolt  83  and a stopper pin  86  is arranged and the stopper mechanism is interlocked with the footbrake  10  via a cable device  90  and can be released by the stepping operation on the footbrake  10 . 
   A stopper piece  80  is integrally formed with the outer shift lever  73  so as to project almost perpendicularly (almost right backward) to the line connecting the joint holes  76 . A nut  82  is welded to a downward-facing folded part  80   a  of the stopper piece  80 . The stopper adjust bolt  83  is screwed into the nut  82  in a posture along the rotational direction of the outer shift lever  73 . The adjust bolt  83  is fixed by a locking nut  84  in a desired projection amount. 
   In  FIG. 6 , the outer shift lever  73  is positioned in the neutral position N, and the stopper pin  86  is arranged on the side of the backward movement position R (in the direction of the arrow B 2 ) at a predetermined interval K from an end face  83   a  of the adjust bolt  83  in the neutral position N. 
   The stopper pin  86  is arranged in the moving track of the adjust bolt  83  when the outer shift lever  73  rotates in the direction of the arrow B 2  from the neutral position N to the backward movement position R so as to freely enter or leave the moving track of the adjust bolt  83 . The stopper pin  86  is connected to an inner wire  90   a  of the cable device  90  for the stopper mechanism and supported in a pin case  88  in an axially movable state. The stopper pin  86  is projected into the moving track of the adjust bolt  83  by the spring  89  in the pin case  88  and leaves right backward from the moving track against the spring  89  in the pin case  88  by pulling the inner wire  90   a . The pin case  88  is fixed to the crankcase  4  via a bracket  87 . 
     FIG. 5  is a partial sectional right side view showing the relationship between the outer shift lever  73  and the footbrake  10 . The cable device  90  for the stopper mechanism is extended in the neighborhood of a brake shaft  92  and flexibly attached to a joint projection  91  fixed to the brake shaft  92  or the footbrake  10 . When the footbrake  10  is stepped on, the joint projection  91  rotating integrally with the footbrake  10  pulls the inner wire  90   a , thereby the stopper pin  86  is pulled so as to leave from the moving track of the adjust bolt  83 . 
     FIG. 7  is an enlarged plan view of the adjust bolt  83  of the stopper mechanism, and the end of the adjust bolt  83  is formed in a columnar shape with an enlarged diameter, and in the base end face (right end face) of the adjust bolt  83 , a joint slit  93  to which a minus screwdriver can be joined is formed. When the screwdriver is joined into the joint slit  93  and the projection amount of the adjust bolt  83  is adjusted, the gap K between the stopper pin  86  in the neutral position and the end face  83   a  of the adjust bolt  83  can be adjusted. The gap K, even if the end face  83   a  of the adjust bolt  83  makes contact with the stopper pin  86 , is adjusted so as to prevent the backward movement dog pawl  58  of the shift sleeve  52  in the neutral position N shown in  FIG. 4  from making contact with the dog pawl  50   a  of the backward movement input gear  50 . 
   [Shift Operation Device and Locking Mechanism] 
     FIGS. 8 to 14  are detailed drawings of the shift operation device  26  for switching forward and backward movement. In  FIG. 8  showing a front view, the shift operation device  26  for switching forward and backward movement, as mentioned above, is mounted on the handle bar  12  neighboring the left grip  23  so that a rider can perform the shift operation in a state that he grasps the left grip  23 . 
     FIG. 12  is a longitudinal sectional exploded view (an exploded view of the section XI—XI shown in  FIG. 9 ) of the shift operation device  26 , which is composed of a holder case  95  fixed to the handle bar  12  and a rotor assembly  96  supported by the holder case  95  in a rotative state around the axis of the handle bar  12 . 
   The holder case  95  is structured so as to be vertically divided into two and upper and lower halved members  95   a  and  95   b  are joined to each other. The rotor assembly  96  is composed of a cylindrical body  100  integrally having a right reel  97  and a left dial part  98 , a ring rubber cover  101  fit into the outer periphery of the dial part  98 , and a ring cap  103  fixed to the left end face of the dial part  98  by a bolt  102 . 
   A circular slit  105  for winding the inner wire is formed on the reel  97 , and on the dial part  98 , a locking mechanism composed of a locking pawl  108  and a coil spring  109  and a positioning mechanism composed of a positioning ball  110  and a coil spring  111  are provided. The locking pawl  108  is supported in the dial part  98  in a radially movable state, formed integrally with an unlocking knob  113 , and pressed outward in the radial direction by the coil spring  109  integrally with the unlocking knob  113 . 
   In  FIG. 11  which is a longitudinal sectional view of the shift operation device  26  after being assembled, the locking pawl  108  is projected rightward from the dial part  98  and engaged with one of three locking notches  115   a ,  115   b , and  115   c  ( FIG. 13 ) formed on the left end face of the holder case  95 , for example, the neutral position locking notch  115   b . The unlocking knob  113  is projected outward from the peripheral surface of the dial part  98  and a knob cover  101   a  of the rubber cover  101  is fit on the outward projected part. When the unlocking knob  113  is pressed inward in the radial direction against the coil spring  109 , the locking pawl  108  is moved inward in the radial direction so as to be unlocked from the locking notch  115   b.    
   The positioning ball  110  is stored in the dial part  98  in an axially movable state, pressed rightward by the coil spring  111 , and engaged with one of three positioning slits  116   a ,  116   b , and  116   c  ( FIG. 13 ) formed on the left end surface of the holder case  95 , for example, the neutral positioning slit  116   b.    
     FIG. 13  is a sectional view along the line XIII—XIII shown in  FIG. 8 . An inward-facing projection  118  is formed on the inner peripheral surface of the holder case  95 , and the projection  118  is engaged with a positioning hole  119  of the handle bar  12 , thereby fixes the holder case  95  so as to disable rotation. 
   The three locking notches  115   a ,  115   b , and  115   c  formed on the left end face of the holder case  95  are formed at intervals in the peripheral direction, and the notch  115   a  positioned on the front side is a forward movement position locking notch, and the notch  115   b  positioned halfway is a neutral position locking notch, and the notch  115   c  positioned on the rear side is a backward movement position locking notch. The respective locking notches  115   a ,  115   b , and  115   c  are open on the axis side, thus the locking pawl  108  can enter or leave from the axis side. 
   The positioning slits  116   a ,  116   b , and  116   c  are arranged at a phase difference of almost 180° from the locking notches  115   a ,  115   b , and  115   c , and the slit  116   c  positioned on the front side is a backward movement positioning slit, and the slit  116   b  positioned halfway is a neutral positioning slit, and the slit  116   a  positioned on the rear side is a forward movement positioning slit. 
   In  FIG. 10  showing a plan view, on the cover  101 , a plurality of non-slip projections  121  are formed at intervals in the peripheral direction and on the knob cover  101   a , a triangular mark  122  is provided. On the other hand, on the surface of the holder case  95 , symbols indicating the neutral position N, the forward movement position (drive position) D, and the backward movement position R are indicated and as a mutual relationship between the positions N, D, and R, the forward movement position D is disposed before the neutral position N in the peripheral direction, and the backward movement position R is disposed behind the neutral position N in the peripheral direction. 
   [Cable Transfer Devices for Transferring the Shift Operation Force] 
     FIG. 14  is a sectional view along the line XIV—XIV shown in  FIG. 8 . The first and second cable transfer devices  77  and  78  are inserted from underneath into the holder case  95 , and inner wires  77   a  and  78   a  thereof are respectively wound round the reel  97  from the rear side and front side, and end terminals  77   b  and  78   b  are joined into joint holes  125  and  126  of the reel  97 . When the reel  97  is rotated, as shown in  FIG. 14 , in the direction of the arrow A 1  from the neutral position N, the reel  97  pulls the inner wire  77   a  of the first cable transfer device  77  and loosens the inner wire  78   a  of the second cable transfer device  78 . On the other hand, when the reel  97  is rotated inversely in the direction of the arrow B 1 , the reel  97  pulls the inner wire  78   a  of the second cable transfer device  78  and loosens the inner wire  77   a  of the first cable transfer device  77 . 
   Further, on the lower side of the reel  97 , a notch  130  at a fixed angle is formed, and into the notch  130 , an inward-facing projection  131  formed on a lower holder case  95   b  is projected, thus the maximum rotation range of the reel  97  is controlled. 
   Both cable transfer devices  77  and  78  reach the neighborhood of the handle shaft  11  along the handle bar  12  shown in  FIG. 2 , extend downward in the neighborhood of the handle shaft  11 , and respectively extend backward along the left and right pipes of the body frame  27 , thus as shown in  FIG. 6 , the inner wires  77   a  and  78   a  are connected to both ends of the outer shift lever  73 . 
   [Operation and Function] 
   [Neutral State] 
   When the rotor assembly  96  is arranged in the neutral position N as shown in  FIGS. 8 to 10 , i.e., when the unlocking knob  113  and the mark  122  are fit to the neutral position N, as shown by a solid line in  FIG. 13 , the locking pawl  108  is joined to the neutral position locking notch  115   b , thus the rotor assembly  96  is locked at the neutral position N and can move toward neither the forward movement position D (in the direction of the arrow A 1 ) nor the backward movement position R (in the direction of the arrow B 1 ). Further, the positioning ball  110  is also joined to the neutral positioning slit  116   b  as shown by a solid line in  FIG. 13  and the rotor assembly  96  is prevented from play in the rotational direction. 
   In  FIG. 6 , the outer shift lever  73  is also arranged in the neutral position N, so that the adjust bolt  83  is opposite to the stopper pin  86  projected with a predetermined gap K, thereby, the outer shift lever  73  is prevented from moving toward the backward movement position R (in the direction of the arrow B 2 ). Namely, moving from the neutral position to the backward movement position is double locked by the stopper mechanism shown in  FIG. 6  and the locking mechanism of the shift operation device  26  shown in  FIG. 11 . 
   In  FIG. 4 , the shift sleeve  52  is arranged in the neutral position N and the left and right dog pawls  58  and  59  of the shift sleeve  52  are away from the dog pawls  50   a  and  50   b  of the input gears  50  and  51  for backward movement and forward movement. Therefore, the interval between the input shaft  40  and the input gears  50  and  51  is in a state that the transmitting of power is interrupted. 
   [Shift from the Neutral Position to the Forward Movement Position] 
   To shift from the neutral position to the forward movement position, the unlocking knob  113  shown in  FIG. 9  is pushed to unlock the locking pawl  108  shown in  FIG. 11  and the rotor assembly  96  is rotated toward the forward movement position D in the direction of the arrow A 1 . Namely, when the unlocking knob  113  shown in  FIG. 11  is pushed by finger, the locking pawl  108  is dislocated downward from the neutral position locking notch  115   b , and the rotor assembly  96  is rotated in the direction of the arrow A 1  shown in  FIG. 13  with the unlocking state kept, and at the point of time when the positioning ball  110  is joined into the forward movement positioning slit  116   a  on the rear side, the unlocking knob  113  ( FIG. 9 ) is released from the finger. Then, as shown by a hypothetical line in  FIG. 13 , the locking pawl  108  moving up to the forward movement position locking notch  115   a  is automatically fit into the forward movement position locking notch  115   a  by the coil spring  109 . By doing this, the rotor assembly  96  is locked in the forward movement position D so as to prevent from moving in directions of the arrows A 1  and AB 1 . Further, the positioning ball  110  is joined into the forward movement positioning slit  116   a  on the rear side, so that the rotor assembly  96  is prevented from play in the rotational direction. 
   In  FIG. 14 , in correspondence with the rotation of the rotor assembly  96  toward the forward movement position D, the inner wire  77   a  of the first cable transfer device  77  is pulled and the inner wire  78   a  of the second cable transfer device  78  is loosened. 
   In  FIG. 6 , when the inner wire  77   a  of the first cable transfer device  77  is pulled, the outer shift lever  73  is rotated in the direction of the arrow A 2  from the neutral position N to the forward movement position D. Integrally with the rotation of the outer shift lever  73  toward the arrow A 2 , the shift lever shaft  71  and the inner shift lever  72  shown in  FIG. 4  are also rotated, and the shift rod  62  is moved toward the forward movement position D (in the direction of the arrow A 3 ), and the forward movement dog pawl  59  of the shift sleeve  52  mates with the dog pawl  51   a  of the forward movement input gear  51 . 
   In such a forward movement state, the power transferred into the forward and backward movement switching device  6  from the engine  3  shown in  FIG. 1  via the V belt non-stage transmission  5  is transferred to the output shaft  43 , as shown in  FIG. 4 , via the input shaft  40 , the shift sleeve  52 , the dog pawls  59  and  51   a , the forward movement input gear  51 , the forward movement output gear  56 , the intermediate output shaft  42 , the transfer gear  47 , and the output gear  48  and transferred to the rear wheels  2 , as shown in  FIG. 1 , via the power output shaft  17 , the drive shaft  19 , and the final speed reducer  18  for the rear wheels. 
   [Shift from the Forward Movement Position to the Neutral Position] 
   To shift from the forward movement position to the neutral position, the unlocking knob  113  shown in  FIG. 9  is pushed to unlock the locking paw  118  and the rotor assembly  96  is rotated in the direction of the arrow B 1  from the forward movement position D to the neutral position N. 
   The basic operation is the same as that of the shift from the neutral position to the forward movement position, so that the explanation will be simplified. In  FIG. 13 , the locking pawl  108  returning to the neutral position N is automatically fit into the neutral position locking notch  115   b  by the coil spring  109  and locks the rotor assembly  96  in the neutral position N. Further, the positioning ball  110  is joined into the neutral positioning slit  116   b.    
   [Shift from the Neutral Position to the Backward Movement Position] 
   To shift from the neutral position to the backward movement position, both the stopper release operation by the footbrake  10  shown in  FIG. 1  and the unlocking operation by the unlocking knob  113  shown in  FIG. 11  are necessary. Namely, in  FIG. 5 , when the footbrake  10  is stepped on, the stopper pin  86  is pulled via the joint projection  91  and stopper mechanism cable device  90  and separated from the moving track of the adjust bolt  83  shown in  FIG. 6 , thereby, the stopper mechanism is released. In addition to the release operation, when the unlocking knob  113  of the shift operation device  26  shown in  FIG. 11  is pushed, the locking pawl  108  is dislocated and unlocked from the neutral position locking notch  115   b . In the state that the locking mechanism and stopper mechanism are released like this, the rotor assembly  96  is rotated in the direction of the arrow B 1  from the neutral position N to the backward movement position R shown in  FIG. 13 . 
   When the unlocking knob  113  is released from finger at the point of time when the positioning ball  110  is joined into the backward movement positioning slit  116   c  on the front side, the locking pawl  108  moving up to the backward movement position locking notch  115   c  is automatically fit into the backward movement position locking notch  115   c  by the coil spring  109 . By doing this, the rotor assembly  96  is locked in the backward movement position R so as to prevent it from moving in directions of the arrows A 1  and AB 1 . Further, the positioning ball  110  is joined into the backward movement positioning slit  116   c  on the front side, thereby the rotor assembly  96  is prevented from play in the rotational direction. 
   In  FIG. 14 , in correspondence with the rotation of the rotor assembly  96  toward the backward movement position D, the inner wire  78   a  of the second cable transfer device  78  is pulled and the inner wire  77   a  of the first cable transfer device  77  is loosened. 
   In  FIG. 6 , the stopper pin  86  is pulled in by the stepping operation of the footbrake  10 , so that the moving track of the adjust bolt  83  toward the backward movement position D is put into the open state, and the inner wire  78   a  of the second cable transfer device  78  is pulled in this state, thus the outer shift lever  73  is rotated in the direction of the arrow B 2  from the neutral position N to the backward movement position R. Integrally with the rotation of the outer shift lever  73  in the direction of the arrow B 2 , the shift lever shaft  71  and the inner shift lever  72  shown in  FIG. 4  are also rotated, and the shift rod  62  is moved in the direction of the arrow B 3  toward the backward movement position R, and the backward movement dog pawl  58  of the shift sleeve  52  mates with the dog pawl  50   a  of the backward movement input gear  50 . 
   When a vehicle is moved backward with the footbrake  10  in  FIG. 6  being returned to OFF after shifting to the backward movement position as mentioned above, the stopper pin  86  intends to return to the projection state from the pull-in state by the spring in the pin case  88 . However, the end face of the stopper pin  86  makes contact with the side of the adjust bolt  83  in the backward movement position R and the stopper pin  86  is kept in the pull-in state. Further, the strength of the spring set in the pin case  88  is weaker than that of the return spring of the footbrake  10  and even when the stopper pin  86  is stopped in the pull-in state as mentioned above, by the absorption operation due to bending of the cable device  90  and the strength of the footbrake return spring, the footbrake  10  is returned to its normal off state. 
   In the backward movement state, the power transferred into the forward and backward movement switching device  6  from the engine  3  shown in  FIG. 1  via the V belt non-stage transmission  5  is transferred to the output shaft  43 , as shown in  FIG. 4 , via the input shaft  40 , the shift sleeve  52 , the dog pawls  59  and  50   a , the backward movement input gear  50 , the backward movement idle gear  54 , the backward movement output gear  55 , the intermediate output shaft  42 , the transfer gear  47 , and the output gear  48  and transferred to the rear wheels  2 , as shown in  FIG. 1 , via the power output shaft  17 , the drive shaft  19 , and the final speed reducer  18  for the rear wheels. 
   [Shift from the Backward Movement Position to the Neutral Position] 
   To return to the neutral position from the backward movement position, the stopper release operation by the footbrake  10  shown in  FIG. 1  is not necessary and the shift operation can be performed only by the unlocking operation by the unlocking knob  113  shown in  FIG. 11 . Namely, when the unlocking knob  113  of the shift operation device  26  shown in  FIG. 9  is pushed, the locking pawl  108  in the backward movement position R shown in  FIG. 13  is dislocated from the backward movement position locking notch  115   c  toward the axis of the handle bar  12  and in this unlocked state, the rotor assembly  96  is rotated in the direction of the arrow A 1  from the backward movement position R to the neutral position N. 
   In correspondence with the aforementioned shift operation, the outer shift lever  73  shown in  FIG. 6  is pulled by the first cable transfer device  77 , thereby returned in the direction of the arrow A 2  from the backward movement position R to the neutral position N. At this time, the adjust bolt  83  is moved in the direction of the arrow A 2  by sliding on the end of the stopper pin  86  in the pull-in state, and at the point of time when the adjust pint  83  is dislocated from the end face of the stopper pin  86 , the stopper pin  86  is automatically projected by the spring in the pin case  88  and the mechanism is returned to the stopper operation state. 
   [Adjustment of the Stopper Mechanism] 
   In  FIG. 4 , to prevent the shift sleeve  52  in the neutral position N from making contact with the dog pawls  50   a  and  51   a  of the input gears  50  and  51  due to a manufacture error or play in the axial direction, the gap K between the adjust bolt  83  and the stopper pin  86  shown in  FIG. 7  is adjusted. Concretely, the gap K is adjusted so as to prevent the dog pawl  58  of the shift sleeve  52  shown in  FIG. 4  from making contact with the dog pawl  50   a  of the backward movement input gear  50  even when the adjust bolt  83  makes contact with the stopper pin  86 . 
   As shown in  FIG. 1 , the outer shift lever  73  is arranged at the right rear end of the crankcase  4 , and the tool joint slit  93  of the adjust bolt  86  shown in  FIG. 7  is directed right forward, thus a rider or an operator can simply loosen the locking nut  84  from the side of the vehicle and adjust the rotation of the adjust bolt  86 . 
   In this embodiment, the stopper mechanism is provided on the outer shift lever  73  arranged above the right rear end of the crankcase  4 , and the stopper mechanism is interlocked with the footbrake  10  arranged on the right step  9 , so that the cables placed from the footbrake  10  to the stopper mechanism may be short, and only external cables may be used, thereby, the mounting operation can be simplified. 
   In the above-mentioned embodiment, since the stopper mechanism, which is interlocked with the brake device, is provided in order to prevent the switching rotary part of the forward and backward movement switching device from moving to the backward movement position from the neutral position, a brake operation is needed in order to perform a backward shift by the forward and backward movement switching device. Therefore, the shift operation to backward movement can be automatically recognized, and during the shift operation, the vehicle can be prevented from moving back and forth. 
   In the above-mentioned embodiment, since the locking mechanism of the shift operation device and the stopper mechanism of the forward and backward movement switching device interlocked with the brake device are provided, to perform the shift operation from the neutral position to the backward movement position, the double locking mechanism must be released beforehand, thereby, the recognition of the shift operation to the backward movement can be made surer. 
   Some modifications can be applied to the above-mentioned embodiment as follows. 
   (1) The stopper mechanism composed of the stopper pin and adjust bolt may be interlocked with a brake device of a hand lever type. 
   (2) As the forward and backward movement switching device, a structure that forward movements of two steps, neutral and backward movements can be switched mutually may be used. Furthermore, the arrangement location of the forward and backward movement switching device is not limited to the rear part of the engine unit including the transmission, for example, it may be arranged on the side, front side, or in other places. 
   (3) As the switching rotary part of the forward and backward movement switching device in which the stopper mechanism interlocked with the brake device is provided, the inner shift lever  72  may be used in stead of the outer shift lever  73  shown in  FIG. 5 . 
   (4) Other than the V belt non-stage transmission, for example, a torque converter for an all-terrain vehicle may be used. 
   Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof.