Abstract:
A differential mechanism regulating device which is mechanically connected to two manipulators is miniaturized. When a first cable and a second cable are pulled, a collecting member moves its position. As a result of this movement, the collecting member tilts a portion of an arm by way of a rod. As a result, a differential lock is released. The operation of the first cable and the operation of the second cable can be merged by the collecting member, and it is sufficient to connect only a collecting transmission member to the arm. The connection between the arm and the collecting transmission member can be simplified thus realizing the miniaturization of the differential mechanism.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-210205, filed Oct. 7, 2013, and Japanese Patent Application No. 2014-166167, filed Aug. 18, 2014, the contents of which are incorporated herein by reference, in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to an improvement in a differential gear provided with a differential lock mechanism. 
     BACKGROUND OF THE INVENTION 
     A differential gear is a device for generating a difference in rotational speed between left and right wheels. There may be a case where it is necessary not to provide a difference in rotational speed between left and right wheels depending on a traveling state. In this case, a mechanism which regulates the differential gear (hereinafter referred to as a differential lock mechanism) is attached to the differential gear. Various proposals have been made with respect to such a differential gear provided with a differential lock mechanism (see JP-A-2011-117511 (FIG. 3), for example). 
     As shown in FIG. 3 of JP-A-2011-117511, a fork member is tilted by a lever member indicated by an imaginary line, and a lock pin is inserted into pin holes with the fork member. As a result, an output-side cam is integrally joined to a ring gear thus establishing a differential locked state. That is, by operating the lever member by a manipulator, it is possible to perform switching of a drive mode as represented by switching between lock (differential lock) and unlock (release of differential lock) in a differential gear. 
     Aside from a differential lock during traveling, there has been a demand for a differential gear which is brought into a locked state even during parking. In this case, it is necessary to provide a manipulator for changing over a drive mode and a manipulator for parking. 
     Accordingly, it is necessary to provide the structure where a cable is extended from the drive mode manipulator and the cable is mechanically connected to a differential lock mechanism. A cable is also extended from the manipulator for parking and the cable is mechanically connected to the differential lock mechanism. Since the structure has two connection portions, there is a tendency for the structure of a differential gear provided with a differential lock mechanism to become complicated and large. 
     However, amidst a demand for the miniaturization of a vehicle, there has been also a demand for miniaturization of a differential gear provided with a differential lock mechanism. 
     SUMMARY OF THE INVENTION 
     A differential gear provided with a differential lock mechanism which is mechanically connected to two manipulators is miniaturized according to the following description. 
     A first aspect is directed to a differential gear provided with a differential lock mechanism which includes: 
     a differential mechanism which transmits a drive force inputted from a power unit to left and right drive shafts, and generates the difference in rotational speed between left and right wheels connected to the left and right drive shafts; 
     a differential lock mechanism which is attached to the differential mechanism and brings the differential mechanism into a non-differential state; and 
     a switching means which is attached to the differential lock mechanism, and changes over a state of the differential lock mechanism between an operation state and a release state, wherein 
     a first manipulator to which one end of a first cable is connected, and which is capable of operating the switching means through the first cable, 
     a second manipulator which is in addition to the first manipulator, to which one end of a second cable is connected, and which is capable of operating the switching means through the second cable, 
     a collecting member which is provided between the first and second cables and the switching means, to which the other end of the first cable and the other end of the second cable are connected, and which transmits an operational force from the first manipulator and the second manipulator, and 
     a collecting transmission member which connects the collecting member and the switching means to each other and transmits an operational force of the collecting member to the switching means are provided. 
     A second aspect is characterized in that the switching means includes a spring which always biases the differential mechanism to a non-differential state side. 
     A third aspect is characterized in that an elongated hole is formed in the collecting member or the switching means, the elongated hole preventing the switching means from being operated while allowing the collecting member to move when only one of the first and second manipulators is operated. 
     A fourth aspect is characterized in that the first and second cables are connected to the collecting member by way of adjusters which adjust cable lengths of the first and second cables. 
     A fifth aspect is characterized in that the differential gear includes a cable stay which supports one ends of the first and second cables, and the differential gear includes a casing which houses the cable stay and the collecting member, and the casing is mounted on an upper surface of a gear casing which houses the differential mechanism. 
     A sixth aspect is characterized in that the first manipulator is a switching lever which changes over a drive mode, and the second manipulator is a switching lever being operated during parking of a vehicle. 
     A seventh aspect is characterized in that the differential mechanism includes a cylindrical shaft through which one of the left and right drive shafts penetrates and is collectively housed in the gear casing, a bearing which supports the cylindrical shaft and a rotary shaft which is rotated by the switching means are mounted on the gear casing, and the bearing is arranged in the vicinity of the rotary shaft and overlaps with the rotary shaft in a vehicle width direction. 
     An eighth aspect is characterized in that the differential gear includes a cable stay which supports one ends of the first and second cables, and the differential gear includes a casing which houses the cable stay and the collecting member, and the casing is connected to the differential mechanism by way of a third cable arranged between the casing and the differential mechanism. 
     A ninth aspect is characterized in that an inspection lid is mounted on a foot rest floor on which a passenger places his feet in an openable/closeable manner, and the casing is arranged in a region below the inspection lid. 
     A tenth aspect is characterized in that the switching means to which the third cable is connected and an exhaust pipe are arranged above the differential mechanism and between left and right vehicle body frames, the switching means is arranged on a left side or a right side of the exhaust pipe in the vehicle width direction, and a heat shield panel which shields heat emitted to the switching means from the exhaust pipe is arranged between the exhaust pipe and the switching means. 
     In the first aspect, the collecting member and the collecting transmission member are interposed between the first and second cables and the switching means. The operation of the first cable and the operation of the second cable can be merged by the collecting member, and it is sufficient to connect only the collecting transmission member to the switching means. The connection between the switching means and the collecting transmission member becomes extremely simple thus miniaturizing the connection between the switching means and the collecting transmission member. As a result, it is possible to miniaturize the differential gear provided with a differential lock mechanism which is mechanically connected to two manipulators. 
     In the second aspect, when a collected force generated by the collecting member is not transmitted to the switching means, the differential mechanism is held in a non-differential state (differential locked state). That is, the differential locked state is maintained even when the first or the second cable is slackened by stretching or the like. 
     In the third aspect, the elongated hole which prevents the switching means from being operated, while allowing the collecting member to move when only one of the first and second manipulators is operated, is formed in the collecting member or the switching means. That is, the differential gear is configured such that the differential lock is not released when only one of the first and second manipulators is operated. 
     In the fourth aspect, the posture adjustment and the position adjustment of the collecting member and the adjustment of cable lengths can be collectively performed and hence, maintainability of the differential gear can be enhanced. 
     In the fifth aspect, the cable stay and the collecting member are housed in the casing. Since no foreign substance such as soil or sand is deposited on the cable stay and the collecting member, the smooth movement of the cable and the smooth operation of the collecting member are maintained. Further, the casing is arranged on the upper surface of the gear casing and hence, scattered pebbles or the like minimally impinge on the casing. 
     In the sixth aspect, the first manipulator is a switching lever which changes over a drive mode, and the second manipulator is a switching lever operated during parking of a vehicle. Accordingly, provided that the differential lock is brought into a differential locked state by the switching lever operated during parking, the differential lock is not released even when the switching lever for changing over the drive mode is operated. 
     In the seventh aspect, in mounting the bearing which supports the cylindrical shaft and the rotary shaft which is rotated by the switching means on the gear casing, the rotary shaft is arranged in the vicinity of the bearing. Since the bearing and the rotary shaft are arranged close to each other, increase in size of the gear casing can be suppressed whereby the differential gear provided with a differential lock mechanism can be formed into a compact shape. 
     In the eighth aspect, by arranging the third cable between the casing and the differential mechanism, the casing can be arranged at a position away from the differential mechanism. The casing can be arranged at a relatively free position and hence, it is possible to enhance maintenability such as the adjustment of a play of the cable. 
     In the ninth aspect, the inspection lid is mounted on the foot rest floor on which a passenger places his feet in an openable/closeable manner, and the casing is arranged in a region below the inspection lid. That is, by making use of a space where a passenger places his feet which can ensure a wide space, the maintenance such as the adjustment of a play of the cable can be performed through an opening formed in such a space. 
     In the tenth aspect, the heat shield panel is arranged between the exhaust pipe and the switching means. Heat emitted to the switching means from the exhaust pipe can be shielded and hence, the switching means, which should be protected from dirt, can be covered by a dustproof cover made of a resin. That is, the third cable can be wired on an upper surface of the differential mechanism while preventing a thermal influence of the exhaust pipe. Due to the provision of the heat shield plate, the exhaust pipe and the switching means can be arranged close to each other and hence, accessories can be arranged on the vehicle in a compact manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages of the invention will become apparent in the following description taken in conjunction with the drawings, wherein: 
         FIG. 1  is a plan view (schematic view) showing a drive system of a vehicle; 
         FIG. 2  is a perspective view of first and second manipulators and a shift lever panel; 
         FIG. 3  is a perspective view of a shift lever mechanism; 
         FIG. 4  is a constitutional view of a part of a transmission; 
         FIG. 5  is an operational view of the second manipulator; 
         FIG. 6  is an operational view of the second manipulator; 
         FIG. 7  is a planar cross-sectional view of a differential gear provided with a differential lock mechanism; 
         FIG. 8  is a perspective view of a collecting member and a casing; 
         FIG. 9  is a plan view of the collecting member and a cable stay; 
         FIG. 10  is an explanatory view for explaining the manner of operation of the collecting member, where  FIG. 10(   a ) is a state in which a first cable is pulled,  FIG. 10(   b ) is a state in which a second cable is pulled, and  FIG. 10(   c ) is a state in which both a first cable and second cable are pulled; 
         FIG. 11  is a plan view (schematic view) showing a drive system of a vehicle according to a modification; 
         FIG. 12  is a plan view of the vehicle; 
         FIG. 13  is a plan view showing a differential gear provided with a rear differential lock mechanism and an area around the differential gear; 
         FIG. 14  is an enlarged view of a part (including an arm  97 ) in  FIG. 13 ; 
         FIG. 15  is an enlarged view of a part (including a collecting member  106 ) in  FIG. 13 ; and 
         FIG. 16  is a side view of a U-shaped frame shown in  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the invention is explained hereinafter by reference to attached drawings. 
     First and second manipulators are explained by reference to  FIG. 1  to  FIG. 6 , and a differential gear provided with a differential lock mechanism according to the invention is explained in detail by reference to  FIG. 7  and drawings which follow  FIG. 7 . 
     As shown in  FIG. 1 , a vehicle  10  includes: a power unit  11 ; a transmission  12  which transmits power of the power unit  11  with a speed change and is represented by a gear transmission; a front propeller shaft  13  and a rear propeller shaft  14  which extend frontward and rearward from the transmission  12  for transmission of power; a front differential gear  15  which distributes power transmitted through the front propeller shaft  13  to left and right sides; a differential gear  70  provided with a rear differential lock mechanism which distributes power transmitted through the rear propeller shaft  14  to left and right sides; front drive wheels  18 L,  18 R which constitute left and right wheels and are driven by the front differential gear  15  through drive shafts  17 L,  17 R (“L” being a suffix indicating a left side with reference to a driver, “R” being a suffix indicating a right side with reference to the driver, the same definition being also applied to the explanation made hereinafter); and rear drive wheels  21 L,  21 R which constitute left and right wheels and are driven by the differential gear  70  provided with a rear differential lock mechanism through drive shafts  19 L,  19 R. 
     The vehicle  10  may preferably be an all-terrain vehicle which can travel not only on a flat road surface but also on irregular ground such as wilderness. Accordingly, the front differential gear  15  includes: a front differential lock mechanism  22 ; and a two-wheel drive/four-wheel drive switching mechanism  23 . 
     The differential gear  70  provided with a rear differential lock mechanism includes a differential lock mechanism  90  which brings a differential mechanism ( FIG. 7 , symbol  74 ) into a non-differential state. 
     The vehicle  10  further includes a steering handle  25 , and a driver&#39;s seat  26  on which a driver is seated, and a first manipulator  27  and a second manipulator  41  are arranged on a right side of the driver&#39;s seat  26  in the vehicle width direction. 
     In case of a so-called left-hand drive vehicle, the first manipulator  27  and the second manipulator  41  are arranged on a left side of the driver. 
     In this embodiment, the first manipulator  27  is a switching lever which changes over a drive mode. The first manipulator  27  is connected to the front differential lock mechanism  22  through a first wire  31 , is connected to the two-wheel drive/four-wheel drive switching mechanism  23  through a second wire  32 , and is connected to a slide member  91  through a first cable  33 . 
     In this embodiment, the second manipulator  41  is a switching lever which changes over a traveling mode (including a parking mode), that is, a shift lever. The second manipulator  41  is connected to the transmission  12  through a third wire  34 , and is connected to the slide member  91  through a second cable  35 . Hereinafter, the second manipulator  41  is referred to as a shift lever  41 . 
     As shown in  FIG. 2 , a shift lever panel  37  is mounted on a vehicle body frame  36  (a bracket and a column mounted on the vehicle body frame also constituting parts of the vehicle body frame). An L-shaped hole  38  is formed in the shift lever panel  37 , and the shift lever  41  is inserted into the hole  38 . In this embodiment, the first manipulator  27  is inserted into a hole formed on a right side of the shift lever panel  37 . 
     One end of the first wire  31 , one end of the second wire  32  and one end of the first cable  33  are connected to the first manipulator  27 . By rotating or moving the first manipulator  27 , the first wire  31 , the second wire  32  and the first cable  33  are operated. 
     To be more specific, the first manipulator  27  is inserted into a U-shaped groove  39  formed in the shift lever panel  37 . Four positions  39 A to  39 D can be set in the groove  39 . By selectively moving the first manipulator  27  to one of these positions  39 A to  39 D, a drive mode and a differential mode shown in Table explained hereinafter are selected. 
     
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Position 
                 Drive mode 
                 Front differential 
                 Rear differential 
               
               
                   
               
             
             
               
                 39A 
                 four-wheel driving 
                 locked 
                 locked 
               
               
                 39B 
                 four-wheel driving 
                 free 
                 Locked 
               
               
                 39C 
                 two-wheel driving 
                 free 
                 Locked 
               
               
                 39D 
                 two-wheel driving 
                 free 
                 Free 
               
               
                   
               
             
          
         
       
     
     The first manipulator  27  which changes over a drive mode is arranged on a right side, and the second manipulator (shift lever  41 ) which changes over a traveling mode (including a parking mode) is arranged on a left side. That is, two manipulators  27 ,  41  for different purposes of use are operated without interference therebetween, and a differential lock operation is performed as a part of such an operation. 
     As shown in  FIG. 3 , a shift lever mechanism  40  is constituted of: the shift lever panel  37  which is mounted on the vehicle body frame  36 ; the shift lever  41  which is inserted into the L-shaped hole  38  formed in the shift lever panel  37 ; and various parts affiliated with the shift lever  41 . The L-shaped hole  38  and the various parts are explained in detail hereinafter. 
     The L-shaped hole  38  is constituted of: a guide groove  42  which extends in the longitudinal direction of the vehicle; and a parking gate  44  which extends in an elongated manner in the vehicle width direction toward a driver side from a corner  43  on a front end of the hole  38 . A low-speed forward gate  48 , a high-speed forward gate  47 , a neutral gate  46 , and a reverse gate  45  are formed in the guide groove  42 . A driver can set the shift lever  41  at any one of the following: the low-speed forward gate  48 , the high-speed forward gate  47 , the neutral gate  46 , the reverse gate  45 , and the parking gate  44 . This gate setting action is referred to as a shift operation. 
     A first rotary member  52 A is rotatably supported on the vehicle body frame  36  by a first support pin  51 . A U-shaped portion  52  and a first lever portion  53  are formed on the first rotary member  52 A. The U-shaped portion  52  of the first rotary member  52 A is mounted on the vehicle body frame  36  by the first support pin  51 , and one end of the third wire  34  is connected to the first lever portion  53  which extends rearward in the longitudinal direction of the vehicle from the U-shaped portion  52 . 
     A proximal portion  41 A of the shift lever  41  is mounted on the U-shaped portion  52  by way of a second support pin  54  which extends in the direction orthogonal to the first support pin  51 . A second lever  55  (second rotary member  55 A) extends in the vehicle width direction and toward a driver side from the proximal portion  41 A. A distal end  55   a  of the second lever  55  is bent rearward in the longitudinal direction of the vehicle, and one end of the second cable  35  is connected to the distal end  55   a  by way of a ball plunger  56 . 
     A first axis of rotation  58 , which also functions as a center axis of the first support pin  51 , passes an area in the vicinity of the center of a ball ( FIG. 5 , symbol  56   b ) in the ball plunger  56 . A second axis of rotation  59 , which also functions as a center axis of the second support pin  54 , is arranged orthogonal to and in the vicinity of the first axis of rotation  58 . 
     The more preferred structure is the structure adopted in this embodiment where the first axis of rotation  58 , which also functions as the center axis of the first support pin  51 , passes the center of the ball ( FIG. 5 , symbol  56   b ) in the ball plunger  56 , and the second axis of rotation  59 , which also functions as the center axis of the second support pin  54 , orthogonally intersects with the first axis of rotation  58 . 
     When the shift lever  41  is set at the guide groove  42 , the shift lever  41  rotates about the first axis of rotation  58 . As a result, the third wire  34  is pulled so that the transmission ( FIG. 1 , symbol  12 ) performs switching corresponding to a traveling mode. When the shift lever  41  arrives at the corner  43 , the shift lever  41  arrives at an entrance of the parking gate  44 . 
       FIG. 4  is a view showing a portion of the transmission. The transmission  12  includes a drive force transmission shut-off mechanism  12 A which regulates the rotation of the propeller shaft  14 . As the drive force transmission shut-off mechanism  12 A regulates the rotation of the propeller shaft  14 , the rotation of the drive shafts  19 L,  19 R is also regulated so that the rotation of the rear drive wheels  21 L,  21 R is also regulated. 
     The drive force transmission shut-off mechanism  12 A includes: a parking gear  61 ; a parking pole shaft  62  rotated by the third wire  34 ; a parking pole  63  rotated by the parking pole shaft  62 ; and a return spring  64  biasing the parking pole  63  to a non-parking side. In  FIG. 3 , when the shift lever  41  arrives at the entrance of the parking gate  44 , the parking pole  63  is rotated against the return spring  64  shown in  FIG. 4  so that a pawl  65  meshes with the parking gear  61 . 
     As a result of this operation, a first parking state is acquired. In the parking state, the rotation of the propeller shaft  14  connected to the transmission  12  is also regulated and hence, the propeller shaft  14  is brought into a locked state. 
     As shown in  FIG. 2 , a torsion spring  67  is mounted around the second support pin  54 , and the torsion spring  67  biases the shift lever  41  in the direction in which the shift lever  41  is separated from the corner  43 . That is, due to a biasing action of the torsion spring  67 , the shift lever  41  is pushed to a deep portion of any one of the following: the low-speed forward gate  48 , the high-speed forward gate  47 , the neutral gate  46 , the reverse gate  45 , and the parking gate  44  shown in  FIG. 3 . 
     Next, the manner of operation of the parking gate  44  is explained. 
       FIG. 5  shows a state where the shift lever  41  is at the corner ( FIG. 3 , symbol  43 ). The shift lever  41  is rotated about the second axis of rotation  59  toward a vehicle body center side from such a state. 
       FIG. 6  shows the shift lever  41  after being rotated. The second cable  35  is pushed downward so that a second parking state can be acquired. The second parking state is described in detail later. 
     In  FIG. 5 , by rotating the shift lever  41  in the direction passing through the paper which the drawing is on (in the longitudinal direction of the vehicle), one traveling mode is selected from a group of traveling modes consisting of a low-speed traveling mode, a high-speed traveling mode, a neutral mode, a reversing mode, and a first parking state. In performing such a mode selecting operation, the U-shaped portion  52  is merely rotated about the first axis of rotation  58  and hence, the ball  56   b  in the ball plunger  56  is always disposed on the first axis of rotation  58 . As a result, the second lever  55  is not rotated and hence, the second cable  35  is neither pushed nor pulled. 
     On the other hand, when the second lever  55  is rotated about the second axis of rotation  59  as shown in  FIG. 6 , the U-shaped portion  52  is held in a stopped state and hence, a traveling mode is not influenced by the rotation of the second lever  55 . 
     To summarize the movements of the respective members caused by the operation of the shift lever  41  for bringing the vehicle into a parking state, firstly, when the shift lever  41  is operated to the corner  43  along the guide groove  42 , the first rotary member  52 A is rotated so that the third wire  34  is pulled. As a result, the parking pole  63  of the drive force transmission shut-off mechanism  12 A is rotated and hence, the pawl  65  is engaged with the parking gear  61  whereby the transmission of power is shut off. 
     When the shift lever  41  is further operated toward the parking gate  44  side on a left side, the second lever  55  (second rotary member  55 A) is rotated so that the second cable  35  is pulled. Accordingly, an arm  97  is rotated, and a slide member  91  is operated due to the rotation of the arm  97  and hence, the differential lock mechanism  90  is brought into a locked state. 
     Accordingly, when the shift lever  41  is operated to an end portion  44 A of the parking gate  44 , it is possible to bring the drive force transmission shut-off mechanism  12 A into an ON state (shut-off state), and it is also possible to bring the differential lock mechanism  90  into a locked state. 
     As has been described heretofore, the transmission  12  and the differential lock mechanism  90  shown in  FIG. 1  can be operated by one shift lever  41 . The differential gear  70  provided with a rear differential lock mechanism on which the differential lock mechanism  90  is mounted is explained in detail hereinafter. 
     As shown in  FIG. 7 , the differential gear  70  provided with a rear differential lock mechanism includes: a pinion gear  71  mounted on an end portion of the rear propeller shaft  14 ; a ring gear  72  meshing with the pinion gear  71 ; a differential casing  73  rotated together with the ring gear  72  and forming a differential machine chamber therein; the differential mechanism  74  housed in the differential casing  73  and capable of making a difference in rotational speed between the left and right wheels; left and right output-side cams  75 L,  75 R constituting portions of the differential mechanism  74  and transmitting power transmitted to the ring gear  72  to the drive shafts  19 L,  19 R respectively; and a gear casing  76  housing the ring gear  72  and the differential casing  73  therein. 
     A washer (shim)  88  and a disc spring  89  are interposed between the ring gear  72  and the right output-side cam  75 R, and the right output-side cam  75 R is biased to a left output-side cam  75 L side. 
     Spline grooves  75 La are formed on the left output-side cam  75 L, and one end of the drive shaft  19 L is fitted into the spline groove  75 La. In the same manner, spline grooves  75 Ra are formed on the right output-side cam  75 R, and one end of the drive shaft  19 R is fitted into the spline grooves  75 Ra. 
     The gear casing  76  is constituted of: a first casing half body  77  rotatably supporting the pinion gear  71 ; and a second casing half body  79  connected to the first casing half body  77  using bolts  78 . The differential lock mechanism  90  is housed in the second casing half body  79 . 
     The differential casing  73  is rotatably mounted on the gear casing  76  by means of two bearings  85 L,  85 R. To be more specific, a portion of the differential casing  73  away from the ring gear  72  is formed into a cylindrical shaft  81 , and the cylindrical shaft  81  has a diameter thereof narrowed toward a distal end thereof thus forming a large-diameter portion  82  and a small-diameter portion  84 . The small-diameter portion  84  is supported on the gear casing  76  by way of the bearing  85 L. 
     The slide member  91 , which is one of the constitutional elements of the differential lock mechanism  90 , is fitted on the large-diameter portion  82  in an axially movable manner. 
     A rotary shaft  92  is rotatably mounted on the second casing half body  79  at a position in the vicinity of the bearing  85 L. An arm  97  which constitutes a switching means is mounted on one end of the rotary shaft  92 , a shift fork  93  is mounted on a middle portion of the rotary shaft  92 , and the shift fork  93  is fitted in the slide member  91 . 
     The rotary shaft  92  is biased in the clockwise direction in the drawing by a spring (preferably, torsion spring)  94  mounted on the second casing half body  79  and hence, the shift fork  93  slides the slide member  91  toward a differential casing  73  side. As a result, a pin  96  mounted on the slide member  91  is engaged with the left output-side cam  75 L and hence, the rotation of the left output-side cam  75 L is prevented by the pin  96  whereby the differential mechanism  74  is brought into a non-differential state, that is, a differential locked state. 
     In a state where an external force is not applied to the rotary shaft  92 , a differential locked state is always maintained due to an action of the torsion spring  94 . 
     When the arm  97  is tilted in the counterclockwise direction in the drawing by an external force, the rotary shaft  92  is rotated and hence, the shift fork  93  is tilted. Accordingly, the slide member  91  moves in the direction away from the differential casing  73  and hence, the pin  96  is removed from the left output-side cam  75 L. As a result, the left output-side cam  75 L becomes rotatable and hence, the differential mechanism  74  is brought into a differential state. 
     Hereinafter, the mechanism for tilting the arm  97  is explained in detail. 
     As shown in  FIG. 8 , one end of the rotary shaft  92  projects from the second casing half body  79 , and the arm  97  is mounted on the one projecting end. 
     A protective casing body  101  is fastened to the second casing half body  79  together with a cable stay  103  using bolts  102 ,  102 . The protective casing body  101  is covered with a lid  104 , and the lid  104  is fixed to the protective casing body  101  using bolts  105 . That is, the protective casing body  101 , the lid  104  and the bolt  105  form a protective casing  100 . 
     In  FIG. 9 , the cable stay  103  is a metal-made pressed product, and has a first wall  103   a  and a second wall  103   b . The first wall  103   a  guides the first cable  33  while supporting the first cable  33 . The second wall  103   b  guides the second cable  35  while supporting the second cable  35 . In the protective casing body  101 , a collecting member  106  is housed together with the cable stay  103 . 
     As shown in  FIG. 8 , the collecting member  106  is a pressed product, and is constituted of: an upper plate portion  107  having an I shape as viewed in a plan view; a lower plate portion  108  having an I shape as viewed in a plan view; and a bridge portion  109  which connects the upper plate portion  107  and the lower plate portion  108  to each other. 
     As shown in  FIG. 9 , in the collecting member  106 , an elongated hole  111  is formed in a center portion of the upper plate portion  107  and a center portion of the lower plate portion  108  respectively. First and second blocks  112 ,  113  are provided between the upper plate portion  107  and the lower plate portion  108  with the elongated holes  111  sandwiched between the first and second blocks  112 ,  113 , wherein the first block  112  is arranged on a right side of the elongated holes  111  and the second block  113  is arranged on a left side of the elongated holes  111 . 
     The first block  112  is a columnar piece having a hole through which the first cable  33  passes. A male threaded portion  33   a  is formed on one end of the first cable  33 , and a first adjuster  115  is threadedly engaged with the male threaded portion  33   a.    
     A distal end of the first adjuster  115  is arcuately notched and hence, the rotation of the first adjuster  115  can be stopped by bringing the distal end of the first adjuster  115  into contact with the first block  112 . By rotating the first adjuster  115  by 180° per unit, a length of the first cable  33  can be adjusted. 
     In the same manner, the second block  113  is a columnar piece having a hole through which the second cable  35  passes. A male threaded portion  35   a  is formed on one end of the second cable  35 , and a second adjuster  116  is threadedly engaged with the male threaded portion  35   a.    
     A distal end of the second adjuster  116  is arcuately notched and hence, the rotation of the second adjuster  116  can be stopped by bringing the distal end of the second adjuster  116  into contact with the second block  113 . By rotating the second adjuster  116  by 180° per unit, a length of the second cable  35  can be adjusted. 
     A third block  118  and a third adjuster  119  are mounted also on the arm  97 . 
     A slider pin  122  which extends from a slider  121  is movably mounted in the elongated hole  111  formed in the collecting member  106 . A rod  123  which forms a collecting transmission member is extended from the slider  121 , and the rod  123  passes through the third block  118 . In such a state, the third adjuster  119  is threadedly engaged with the rod  123 . In the drawing, the slider pin  122  is arranged at an end of the elongated hole  111  on a cable stay  103  side. 
     The position and the posture of the collecting member  106  with reference to the cable stay  103  can be adjusted by the first and second adjusters  115 ,  116 . Further, a length of the first cable  33  can be adjusted by the first adjuster  115 , and a length of the second cable  35  can be adjusted by the second adjuster  116 . 
     An angle of the arm  97  can be adjusted by the third adjuster  119 . 
     These plural adjustments can be collectively carried out around the protective casing body  101  thus enhancing the maintenance property of the differential gear. Since the protective casing body  101  is covered with the lid ( FIG. 8 , symbol  104 ), there exists no possibility that a foreign substance such as mud will get deposited on the cable stay  103  and the collecting member  106  and hence, the movement of the first and second cables  33 ,  35  becomes smooth and, at the same time, the collecting member  106  can be moved smoothly. 
     Next, the manner of operation of the collecting member  106  is explained. 
     When the first manipulator  27  is tilted to the posture shown in  FIG. 2 , the first cable  33  is slackened and when the second cable  35  is slackened, the collecting member  106  takes the configuration shown in  FIG. 9 . 
     In  FIG. 2 , when only the first manipulator  27  is tilted rightward in the drawing, the first cable  33  is pulled. The second cable  35  is kept in a slackened state. 
     When the first cable  33  is pulled, as shown in  FIG. 10(   a ), the collecting member  106  indicated by an imaginary line is rotated in the counterclockwise direction in the drawing using the second block  113  as the center of rotation, and takes the posture indicated by a solid line. Then, the elongated hole  111  moves such that the slider pin  122  moves to an end of the elongated hole  111  on an arm  97  side. Since the slider pin  122  merely moves within a range of the elongated hole  111 , the arm  97  is not yet tilted. 
     In  FIG. 2 , when only the second manipulator  41  is tilted rightward in the drawing, the second cable  35  is pulled. The first cable  33  is kept in a slackened state. 
     When the second cable  35  is pulled, as shown in  FIG. 10(   b ), the collecting member  106  indicated by an imaginary line is rotated in the clockwise direction in the drawing using the first block  112  as the center of rotation, and takes the posture indicated by a solid line. Then, the elongated hole  111  moves such that the slider pin  122  moves to an end of the elongated hole  111  on an arm  97  side. Since the slider pin  122  merely moves within a range of the elongated hole  111 , the arm  97  is not yet tilted. 
     Accordingly, even when the first cable  33  or the second cable  35  is pulled by only one of either the first manipulator ( FIG. 1 , symbol  27 ) or the second manipulator ( FIG. 1 , symbol  41 ), the arm  97  is not tilted. 
     On the other hand, in  FIG. 2 , when both the first manipulator  27  and the second manipulator  41  are tilted rightward in the drawing, the first cable  33  and the second cable  35  are pulled. 
     When the first cable  33  and the second cable  35  are pulled, as shown in  FIG. 10(   c ), the collecting member  106  indicated by an imaginary line moves to a position indicated by a solid line. Due to such a movement, the collecting member  106  tilts the arm  97  by way of the rod  123  from the position indicated by an imaginary line to the position indicated by a solid line. As a result, the pin  96  shown in  FIG. 7  is removed from the left output-side cam  75 L and hence, the differential mechanism  74  is brought into a differential state (differential lock released state). 
     In  FIG. 7 , the rotary shaft  92  is arranged in the vicinity of one bearing  85 L. To be more specific, at least one of a first tangent line  124  and a second tangent line  125  which orthogonally intersect with the drive shaft  19 L and are tangent to two side surfaces of the bearing  85 L intersects with the rotary shaft  92 . 
     As has been described above, although the rotary shaft  92  is mounted on the second casing half body  79 , the projection of the second casing half body  79  can be suppressed thus preventing increasing the size of the differential gear  70  provided with a rear differential lock mechanism and the differential lock mechanism  90 . 
     Further, in an attempt to directly connect the first and second cables  33 ,  35  to the arm  97  in  FIG. 9 , the arm  97  becomes increased in size, and a shape of the arm  97  becomes complicated. In this respect, by interposing the collecting member  106  between the cables and the arm, it is sufficient to merely connect the rod  123  to the arm  97  so that miniaturization and the simplification of the arm  97  can be realized. 
     In this embodiment, the elongated holes  111  are formed in the collecting member  106 . However, the elongated holes  111  may be formed in the arm  97 . Although the arm  97  becomes slightly increased in size in this case, miniaturization of the collecting member  106  can be realized. 
     Next, a modification of the differential gear provided with a differential lock mechanism is explained. 
     As shown in  FIG. 11 , an exhaust pipe  131  extending from the power unit  11  extends toward a rear side of the vehicle while passing above the differential gear  70  provided with a rear differential lock mechanism, and is connected to a muffler  132 . 
     The collecting member  106  is arranged away from the differential gear  70  provided with a rear differential lock mechanism which incorporates the differential mechanism ( FIG. 7 , symbol  74 ) therein, and is also arranged at a position sufficiently away from the exhaust pipe  131  which is a high-temperature member. Accordingly, a switching means  97  (hereinafter referred to as “arm  97 ”) and the collecting member  106  are connected to each other by way of a third cable  133 . The third cable  133  has a sufficient length and also has excellent flexibility. 
     Other constitutional elements of the differential gear  70  provided with a rear differential lock mechanism are merely indicated by symbols used in  FIG. 1 , and the detailed explanation of such constitutional elements is omitted. 
     As shown in  FIG. 12 , a vehicle  10  is an all-terrain vehicle which includes: front wheels  18 L,  18 R; rear drive wheels  21 L,  21 R; a front seat  134  on which three passengers can be seated; a rear seat  135  on which two passengers can be seated; a foot rest floor  136  arranged in front of the front seat  134 ; and a foot rest floor  137  arranged in front of the rear seat  135 . 
     An inspection lid  138  is mounted on the foot rest floor  137  in an openable/closeable manner. 
     As shown in  FIG. 13 , vehicle body frames  141 L,  141 R, the exhaust pipe  131 , the muffler  132 , and the differential gear  70  provided with a rear differential lock mechanism are arranged below the foot rest floor  137 . The arm  97  attached to the differential gear  70  provided with a rear differential lock mechanism is arranged between the vehicle body frame  141 L and the vehicle body frame  141 R. The arm  97  is arranged on a left side of the exhaust pipe  131  in the vehicle width direction, and a heat shield panel  143  is disposed between the arm  97  and the exhaust pipe  131 . 
     The structure of part of  FIG. 13  is explained by reference to  FIG. 14  to  FIG. 16 . 
     As shown in  FIG. 14 , to ensure the smooth operation of the arm  97  and a spring  145 , the arm  97  and the spring  145  are protected by a dustproof cover  139 . To show the inside of the dustproof cover  139 , a center portion of the dustproof cover  139  is described in a see-through manner. The dustproof cover  139  has a complicated shape and hence, it is preferable to form the dustproof cover  139  using a resin. However, the dustproof cover  139  made of a resin has a problem on heat resistance. 
     Accordingly, the heat shield panel  143  is disposed in a raised manner between the exhaust pipe  131  and the arm  97 . The heat shield panel  143  is mounted on a second casing half body  79  of the differential gear  70  provided with a rear differential lock mechanism using bolts  144 . Heat emitted from the high temperature exhaust pipe  131  is shielded by the heat shield panel  143 . Accordingly, it is possible to adopt the resin-made dustproof cover  139 . 
     As shown in  FIG. 15 , plates  146  extend outwardly from the vehicle body frame  141 L in the vehicle width direction, a proximal portion of the U-shaped frame  147  is inserted between two plates  146 ,  146 , and the U-shaped frame  147  is fixed to the plates  146 ,  146  using bolts  148 ,  148 . A region  149  surrounded by the U-shaped frame  147  and the vehicle body frame  141 L can be visually recognized from above by removing the inspection lid ( FIG. 12 , symbol:  138 ). 
     A casing  100  is arranged in the region  149 . By removing a lid (indicated by symbol  104  in  FIG. 3 ), the inside of a protective casing body  101  can be observed from above. In the inside of the protective casing body  101 A, a cable stay  103  which supports the first and second cables  33 ,  35  in a movable manner and a collecting member  106  which collects the first to third cables  33 ,  35 ,  133  together are arranged. Other constitutional elements have been explained by reference to  FIG. 9  and hence, these constitutional elements are indicated by the symbols used in  FIG. 9 , and the detailed explanation of such constitutional elements is omitted. 
     However, this modification includes a stopper member  151  not shown in  FIG. 9  as an additional constitutional element. The stopper member  151  is a frame body extending from the cable stay  103 , and restricts a position of a slider pin  122  on a pulling side. 
     The protective casing body  101  guides the collecting member  106  and, at the same time, plays a role of protecting the collecting member  106  from muddy water, scattered pebbles and dust. However, when the protective casing or the lid  104  which covers the protective casing body is made of a resin, it is necessary to take a countermeasure against heat. 
     As shown in  FIG. 13 , by adopting the third cable  133  having sufficient flexibility and a sufficient length, the casing  100  can be arranged at a position sufficiently away from the exhaust pipe  131  which is a high-temperature member. 
     As shown in  FIG. 16 , a U-shaped pipe  152  having a U-shape as viewed in a side view is brought into contact with the U-shaped frame  147  having a U-shape as viewed in a plan view from below, and the U-shaped pipe  152  is welded to the U-shaped frame  147 . A casing bracket  153  which is a pressed product formed by pressing a metal plate is welded to the U-shaped pipe  152 . A protective casing half body  101  shown in  FIG. 15  is placed on the casing bracket  153 , and is fixed to the casing bracket  153  using bolts  154 ,  154 . 
     Although the invention is preferably applicable to an all-terrain vehicle, there exist no problems in applying the invention to vehicles in general. 
     The invention is preferably applicable to an all-terrain vehicle. 
     Although a specific form of embodiment of the instant invention has been described above and illustrated in the accompanying drawings in order to be more clearly understood, the above description is made by way of example and not as a limitation to the scope of the instant invention. It is contemplated that various modifications apparent to one of ordinary skill in the art could be made without departing from the scope of the invention which is to be determined by the following claims.