Abstract:
A tractor, including: a link mechanism fixation-member which regulates rotation of the HST trunnion shaft by abutting the link mechanism; a link mechanism fixation-member operation lever which makes the link mechanism fixation-member about the link mechanism, or makes the link mechanism fixation-member move in a direction so as to get apart from the link mechanism; a brake pedal which is provided at the other side of the left-and-right sides of the step floor; and a link mechanism joining-cancellation mechanism which makes, in a case where the link mechanism fixation-member is abutting the link mechanism, the link mechanism fixation-member move in a direction so as to get apart from the link mechanism when stepping-on of the brake pedal is performed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a tractor which performs working inside a farm field, for example. 
         [0003]    2. Related Art of the Invention 
         [0004]    Known is a tractor comprising a frontward/rearward movement pedal which is provided at the right side of the step floor, and having an auto-cruise function (for example, refer to Japanese Patent Application Publication No. 2013-181553). 
         [0005]    Additionally, the frontward/rearward movement pedal is a seesaw-type pedal, for example, for switching the frontward movement and rearward movement of the vehicle. 
         [0006]    Moreover, the auto-cruise function is a function of maintaining the outputting of the HST (Hydro Static Transmission) regardless of the stepping-on operations of the frontward/rearward movement pedal, and suppressing the fluctuation of the vehicle traveling-speed. 
         [0007]    A worker can reduce fatigue utilizing an auto-cruise function like this. 
       SUMMARY OF THE INVENTION 
       [0008]    However, in the conventional tractor mentioned above, a controller controls the HST trunnion motor for changing the HST trunnion opening-degree. 
         [0009]    Additionally, the controller switches the execution and the cancellation of the auto-cruise function based on ON/OFF of the auto-cruise switch which is operated by the worker. 
         [0010]    Because of this, in the conventional tractor, it is necessary for the worker to expressly operate, even on the occasion of performing a pedal operation of the brake pedal for the purpose of emergency stopping or the like, the auto-cruise switch for canceling the auto-cruise function, and cancellation of the auto-cruise function has been bothersome. 
         [0011]    The present invention furnishes, in consideration of the conventional problem mentioned above, a tractor for which cancellation of the auto-cruise function is able to be performed with a simpler operation. 
         [0012]    The 1 st  aspect of the present invention is a tractor, comprising: 
         [0013]    an HST; 
         [0014]    a frontward/rearward movement pedal which is connected to an HST trunnion shaft of the HST, and is provided at one side of left-and-right sides of a step floor; 
         [0015]    a link mechanism which is provided at other side of the left-and-right sides of the step floor; 
         [0016]    a frontward/rearward movement pedal rotation-shaft which extends in a left-and-right direction below the step floor, with both end parts of the frontward/rearward movement pedal rotation-shaft being respectively connected to the frontward/rearward movement pedal and the link mechanism, and rotates in correspondence to swinging of the frontward/rearward movement pedal; 
         [0017]    a link mechanism fixation-member which regulates rotation of the HST trunnion shaft by abutting the link mechanism; 
         [0018]    a link mechanism fixation-member operation lever which makes the link mechanism fixation-member abut the link mechanism, or makes the link mechanism fixation-member move in a direction so as to get apart from the link mechanism; 
         [0019]    a brake pedal which is provided at the other side of the left-and-right sides of the step floor; and 
         [0020]    a link mechanism joining-cancellation mechanism which makes, in a case where the link mechanism fixation-member is abutting the link mechanism, the link mechanism fixation-member move in a direction so as to get apart from the link mechanism when stepping-on of the brake pedal is performed. 
         [0021]    By means of this, since when stepping-on of the brake pedal is performed, the link mechanism fixation-member is made to move in a direction so as to get apart from the link mechanism, cancellation of the auto-cruise function is able to be performed with a simpler operation. 
         [0022]    The 2 nd  aspect of the present invention is the tractor according to the 1 st  aspect of the present invention, wherein 
         [0023]    the link mechanism fixation-member, the link mechanism fixation-member operation lever, and the link mechanism joining-cancellation mechanism are provided at the other side of the left-and-right sides of the step floor. 
         [0024]    By means of this, since the link mechanism fixation-member, the link mechanism fixation-member operation lever, and the link mechanism joining-cancellation mechanism are provided at the other side of the left-and-right sides of the step floor, a compact machine-body layout is able to be realized. 
         [0025]    The 3 rd  aspect of the present invention is the tractor according to the 1 st  aspect of the present invention, wherein 
         [0026]    the link mechanism joining-cancellation mechanism comprises a link mechanism joining-cancellation plate which makes, by abutting the link mechanism fixation-member, the link mechanism fixation-member move in a direction so as to get apart from the link mechanism when stepping-on of the brake pedal is performed. 
         [0027]    By means of this, since a link mechanism joining-cancellation plate is comprised which makes, by abutting the link mechanism fixation-member, the link mechanism fixation-member move in a direction so as to get apart from the link mechanism, cancellation of the auto-cruise function is able to be performed with a more simplified configuration. 
         [0028]    The 4 th  aspect of the present invention is the tractor according to the 3 rd  aspect of the present invention, wherein 
         [0029]    the brake pedal comprises a left brake pedal which corresponds to a brake of a vehicle-wheel at a left side, and a right brake pedal which corresponds to a brake of a vehicle-wheel at a right side, and 
         [0030]    the link mechanism joining-cancellation plate comprises a first plate corresponding to the left brake pedal, and a second plate corresponding to the right brake pedal. 
         [0031]    By means of this, since a first plate corresponding to the left brake pedal, and a second plate corresponding to the right brake pedal are comprised, the auto-cruise function is able to be cancelled only by performing a pedal operation of at least one of the two brake pedals. 
         [0032]    The 5 th  aspect of the present invention is the tractor according to the 4 th  aspect of the present invention, wherein 
         [0033]    the link mechanism fixation-member comprises an abutted part which is abutted by the link mechanism joining-cancellation plate, and 
         [0034]    the abutted part comprises a first abutted part which is abutted by the first plate, and a second abutted part which is abutted by the second plate. 
         [0035]    By means of this, since a first abutted part which is abutted by the first plate, and a second abutted part which is abutted by the second plate are comprises, cancellation of the auto-cruise function is able to be more surely performed. 
         [0036]    The 6 th  aspect of the present invention is the tractor according to the 2 nd  aspect of the present invention, wherein 
         [0037]    the link mechanism joining-cancellation mechanism comprises a link mechanism joining-cancellation plate which makes, by abutting the link mechanism fixation-member, the link mechanism fixation-member move in a direction so as to get apart from the link mechanism when stepping-on of the brake pedal is performed. 
         [0038]    By means of this, since a link mechanism joining-cancellation plate is comprised which makes, by abutting the link mechanism fixation-member, the link mechanism fixation-member move in a direction so as to get apart from the link mechanism, cancellation of the auto-cruise function is able to be performed with a more simplified configuration. 
         [0039]    The 7 th  aspect of the present invention is the tractor according to the 6 th  aspect of the present invention, wherein 
         [0040]    the brake pedal comprises a left brake pedal which corresponds to a brake of a vehicle-wheel at a left side, and a right brake pedal which corresponds to a brake of a vehicle-wheel at a right side, and 
         [0041]    the link mechanism joining-cancellation plate comprises a first plate corresponding to the left brake pedal, and a second plate corresponding to the right brake pedal. 
         [0042]    By means of this, since a first plate corresponding to the left brake pedal, and a second plate corresponding to the right brake pedal are comprised, the auto-cruise function is able to be cancelled only by performing a pedal operation of at least one of the two brake pedals. 
         [0043]    The 8 th  aspect of the present invention is the tractor according to the 7 th  aspect of the present invention, wherein 
         [0044]    the link mechanism fixation-member comprises an abutted part which is abutted by the link mechanism joining-cancellation plate, and 
         [0045]    the abutted part comprises a first abutted part which is abutted by the first plate, and a second abutted part which is abutted by the second plate. 
         [0046]    By means of this, since a first abutted part which is abutted by the first plate, and a second abutted part which is abutted by the second plate are comprises, cancellation of the auto-cruise function is able to be more surely performed. 
         [0047]    By the present invention, a tractor for which cancellation of the auto-cruise function is able to be performed with a simpler operation can be furnished. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]      FIG. 1  is a left side view of the tractor of the embodiment in the present invention; 
           [0049]      FIG. 2  is a partial top view of the neighborhood of the step floor of the tractor of the embodiment in the present invention; 
           [0050]      FIG. 3  is a partial perspective view (No.  1 ) of the neighborhood of the operation column cover of the tractor of the embodiment in the present invention; 
           [0051]      FIG. 4  is a top view of the tractor of the embodiment in the present invention; 
           [0052]      FIG. 5  is a front view of the tractor of the embodiment in the present invention; 
           [0053]      FIG. 6  is a partial right side view of the neighborhood of the step floor of the tractor of the embodiment in the present invention; 
           [0054]      FIG. 7  is a partial rear view of the neighborhood of the step floor of the tractor of the embodiment in the present invention; 
           [0055]      FIG. 8  is a partial left side view (No.  1 ) of the neighborhood of the step floor of the tractor of the embodiment in the present invention; 
           [0056]      FIG. 9  is a partial front view of the neighborhood of the step floor of the tractor of the embodiment in the present invention; 
           [0057]      FIG. 10  is a partial left side view (No.  2 ) of the neighborhood of the step floor of the tractor of the embodiment in the present invention; and 
           [0058]      FIG. 11  is a partial perspective view (No.  2 ) of the neighborhood of the operation column cover of the tractor of the embodiment in the present invention. 
       
    
    
     DESCRIPTION OF SYMBOLS 
       [0000]    
       
           1  bonnet 
           2  engine 
           3 L,  3 R front wheel 
           4 L,  4 R rear wheel 
           10  HST case 
           11  HST 
           12  HST trunnion shaft 
           13  HST trunnion arm 
           20  transmission case 
           31  driving seat 
           32  steering handle 
           33  operation column cover 
           34  dash panel 
           35  hose cover 
           40  step floor 
           50 L,  50 R brake pedal 
           51  brake pedal connector 
           52 L,  52 R return spring 
           60  frontward/rearward movement pedal 
           61  pedal base part 
           62  pedal stepping-on part 
           70  connection shaft 
           80  frontward/rearward movement pedal rotation-shaft 
           90  neutrality posture adjustment-mechanism 
           91  hub 
           92  neutrality plate 
           93  adjustment knob-member 
           100  link mechanism 
           101  arm 
           102  rod 
           103  cruise plate 
           104  rotation arm-member 
           105  plate 
           106  rod 
           107  upper-end plate 
           110  link mechanism fixation-member 
           111  joining plate 
           112 L,  112 R link mechanism joining-cancellation bearing 
           113  plate 
           120  link mechanism fixation-member operation lever 
           121  return spring 
           130  link mechanism joining-cancellation mechanism 
           131 L,  131 R link mechanism joining-cancellation plate 
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0102]    In the following, referring to the drawings, descriptions are given in detail regarding embodiments in the present invention. 
         [0103]    In the beginning, referring to  FIGS. 1 to 5 , descriptions are specifically given regarding the configuration and action of the tractor of the present embodiment. 
         [0104]    Here,  FIG. 1  is a left side view of the tractor of the embodiment in the present invention,  FIG. 2  is a partial top view of the neighborhood of a step floor  40  of the tractor of the embodiment in the present invention,  FIG. 3  is a partial perspective view (No.  1 ) of the neighborhood of an operation column cover  33  of the tractor of the embodiment in the present invention,  FIG. 4  is a top view of the tractor of the embodiment in the present invention, and  FIG. 5  is a front view of the tractor of the embodiment in the present invention. 
         [0105]    Additionally, in  FIG. 2 , the step floor  40  and the like are not shown, so that descriptions in the following will become easier to understand. 
         [0106]    In the inner part of a bonnet  1  of the vehicle-body front part, an engine  2  (refer to  FIG. 2 ) is loaded. 
         [0107]    A transmission case  20  (refer to  FIG. 2 ) is provided at the lower side of the step floor  40 . 
         [0108]    An HST case  10  (refer to  FIG. 2 ) which houses an HST  11  (refer to  FIG. 2 ) is provided at the front side of the transmission case  20 . 
         [0109]    Rotary motive force of the engine  2  is transmitted via the HST  11  to a speed-changing device of the inner part of the transmission case  20 . And, the rotary motive force with speed-decreasing having been carried out at the said speed-changing device is transmitted to left and right front wheels  3 L and  3 R, and left and right rear wheels  4 L and  4 R. 
         [0110]    Behind the engine  2 , a steering handle  32  for carrying out steerage with the front wheels  3 L and  3 R is supplied. 
         [0111]    Behind the steering handle  32 , a driving seat  31  is provided. 
         [0112]    At the vehicle-body rear part, a working machine (not shown) such as a rotary tilling device or the like is installed utilizing a mechanism such as a 3-point link mechanism or the like. 
         [0113]    A hose cover  35  covers hoses which are joined to the steering handle  32 . 
         [0114]    On the step floor  40  at the left side of the operation column cover  33 , brake pedals  50 L and  50 R (refer to  FIG. 3 ) for performing braking with the rear wheels  4 L and  4 R in correspondence to a stepping-on operation of a worker are arranged. 
         [0115]    On the step floor  40  at the right side of the operation column cover  33 , a frontward/rearward movement pedal  60  for switching the frontward movement and rearward movement of the vehicle is arranged. 
         [0116]    As will be mentioned in detail later, modulation of the HST trunnion opening-degree of the HST  11  is performed in correspondence to a stepping-on operation of the seesaw-type frontward/rearward movement pedal  60 , and non-step speed-changing corresponding to frontward movement speed-increasing, neutrality and rearward movement speed-increasing is realized. 
         [0117]    Next, mainly referring to  FIGS. 2 and 6  to  9 , descriptions are more specifically given regarding the configuration and action of the tractor of the present embodiment. 
         [0118]    Here,  FIG. 6  is a partial right side view of the neighborhood of the step floor  40  of the tractor of the embodiment in the present invention,  FIG. 7  is a partial rear view of the neighborhood of the step floor  40  of the tractor of the embodiment in the present invention,  FIG. 8  is a partial left side view (No.  1 ) of the neighborhood of the step floor  40  of the tractor of the embodiment in the present invention, and  FIG. 9  is a partial front view of the neighborhood of the step floor  40  of the tractor of the embodiment in the present invention. 
         [0119]    Additionally, in  FIGS. 6 to 9 , not either the step floor  40 , or the engine  2 , the HST case  10 , the transmission case  20  and the like are shown, so that descriptions in the following will become easier to understand. 
         [0120]    For a start, mainly referring to  FIGS. 6 and 7 , descriptions are given regarding the HST  11 , and the frontward/rearward movement pedal  60  which is connected to an HST trunnion shaft  12  of the HST  11 . 
         [0121]    An HST trunnion arm  13  is connected to an end part  12   a  (refer to  FIG. 2 ) at the right side of the HST trunnion shaft  12 . 
         [0122]    The connection between the HST trunnion arm  13  and the end part  12   a  is fixedly performed. 
         [0123]    A connection shaft  70  in the front-and-rear direction connects the HST trunnion arm  13  and a pedal base part  61  of the frontward/rearward movement pedal  60 . 
         [0124]    Like this, the connection shaft  70  is a single shaft, and the connection configuration of the HST trunnion arm  13  and the pedal base part  61  of the frontward/rearward movement pedal  60  is extremely simplified. 
         [0125]    The connection between the connection shaft  70  and the HST trunnion arm  13  is rotatably performed utilizing a pin  70   a,  and the connection between the connection shaft  70  and the pedal base part  61  is rotatably performed utilizing a pin  70   b.    
         [0126]    The connection shaft  70  protrudes from the rear part of the HST case  10  to the rear, and passes the lateral of the transmission case  20  (refer to  FIG. 2 ). 
         [0127]    Like this, the connection configuration of the HST trunnion arm  13  and the pedal base part  61  of the frontward/rearward movement pedal  60  is realized with an extremely short distance. 
         [0128]    A frontward/rearward movement pedal rotation-shaft  80  rotates in correspondence to swinging of the frontward/rearward movement pedal  60 , and penetrates the transmission case  20  in the left-and-right direction (refer to  FIG. 2 ). 
         [0129]    Like this, the upper-part space of the inner part of the transmission case  20  is effectively utilized, and a compact machine-body layout is realized. 
         [0130]    The connection between an end part  80   a  at the right side of the frontward/rearward movement pedal rotation-shaft  80  and the pedal base part  61  is fixedly performed. 
         [0131]    A pedal stepping-on part  62  of the frontward/rearward movement pedal  60 , to which a stepping-on operation by the right foot of the worker is performed, is connected to the pedal base part  61 . The connection between the pedal base part  61  and the pedal stepping-on part  62  is fixedly performed utilizing bolts  60   a  and  60   b.    
         [0132]    Hereupon, in the pedal stepping-on part  62 , a round hole the bolt  60   a  penetrates and a long hole the bolt  60   b  penetrates are provided, and the attachment angle of the pedal stepping-on part  62  to the pedal base part  61  is adjustable. 
         [0133]    It is desirable that the posture of the HST trunnion plate (not shown) which is rotatable around the HST trunnion shaft  12  should, at the time when the posture of the pedal stepping-on part  62  is the horizontality posture, coincide with the neutrality posture for which the HST trunnion opening-degree is zero. 
         [0134]    Accordingly, the connection state of the configuration elements mentioned above is adjusted so that the horizontality posture of the pedal stepping-on part  62  is compatible with the neutrality posture of the HST trunnion plate, that is to say the neutrality posture of the HST trunnion shaft  12 . 
         [0135]    When a pedal operation of the frontward/rearward movement pedal  60  is performed in the frontward direction which is the direction indicated with an arrow B, the rotation of the HST trunnion shaft  12  is performed in the direction indicated with an arrow A, and frontward movement speed-increasing is performed. 
         [0136]    In contrast to the above-mentioned, when a pedal operation of the frontward/rearward movement pedal  60  is performed in the rearward direction which is the direction opposite to the direction indicated with the arrow B, the rotation of the HST trunnion shaft  12  is performed in the direction opposite to the direction indicated with the arrow A, and rearward movement speed-increasing is performed. 
         [0137]    Thus, non-step speed-changing corresponding to frontward movement speed-increasing, neutrality and rearward movement speed-increasing, which is in correspondence to a stepping-on operation of the seesaw-type frontward/rearward movement pedal  60 , is realized. 
         [0138]    Subsequently, mainly referring to  FIG. 8 , descriptions are given regarding a neutrality posture adjustment-mechanism  90  for adjusting the neutrality posture of the HST trunnion shaft  12 . 
         [0139]    The neutrality posture adjustment-mechanism  90  has a hub  91 , a neutrality plate  92  and an adjustment knob-member  93 . 
         [0140]    The connection between an end part  80   b  at the left side of the frontward/rearward movement pedal rotation-shaft  80  and the hub  91  is fixedly performed. 
         [0141]    The connection between the hub  91  and the neutrality plate  92  is rotatably performed utilizing a pin  90   a.    
         [0142]    The connection between the neutrality plate  92  and the adjustment knob-member  93  is fixedly performed. 
         [0143]    The adjustment knob-member  93  is rotatable with an adjustment fulcrum pin  90   b  as an eccentric fulcrum shaft. 
         [0144]    When an adjustment rotation operation of the adjustment knob-member  93  by the worker is performed in the direction indicated with an arrow D, the rotation of the frontward/rearward movement pedal rotation-shaft  80  is performed in the direction indicated with an arrow C, and the rotation of the HST trunnion shaft  12  is performed in the direction indicated with the arrow A (refer to  FIG. 6 ). 
         [0145]    An adjustment rotation operation like this is effective in a case where the neutrality posture of the HST trunnion shaft  12  has shifted to the rearward movement speed-increasing side. 
         [0146]    In contrast to the above-mentioned, when an adjustment rotation operation of the adjustment knob-member  93  by the worker is performed in the direction opposite to the direction indicated with the arrow D, the rotation of the frontward/rearward movement pedal rotation-shaft  80  is performed in the direction opposite to the direction indicated with the arrow C, and the rotation of the HST trunnion shaft  12  is performed in the direction opposite to the direction indicated with the arrow A (refer to  FIG. 6 ). 
         [0147]    An adjustment rotation operation like this is effective in a case where the neutrality posture of the HST trunnion shaft  12  has shifted to the frontward movement speed-increasing side. 
         [0148]    Since shifting of the neutrality posture of the HST trunnion shaft  12  is not frequently generated, the neutrality posture adjustment-mechanism  90  is usually used at the time of building in a factory, or at the time of assembling after dismantling in maintenance after shipping. 
         [0149]    It is desirable that, after an adjustment rotation operation of the adjustment knob-member  93  by the worker is completed, the attachment angle of the pedal stepping-on part  62  to the pedal base part  61  should be adjusted so that the horizontality posture of the pedal stepping-on part  62  is compatible with the neutrality posture of the HST trunnion shaft  12 . 
         [0150]    Subsequently, mainly referring to  FIGS. 8 and 9 , descriptions are given regarding a configuration for fixing the rotation angle of the frontward/rearward movement pedal rotation-shaft  80 , namely, the rotation angle of the HST trunnion shaft  12  and letting the vehicle traveling-speed constant. 
         [0151]    Of course, the positions where a joining plate  111  which is the joining part of a link mechanism fixation-member  110  abuts an upper-end plate  107  which is the upper-end part of a link mechanism  100  are, at a plurality of spots, correspondingly to the rotation angles of the HST trunnion shaft  12 , continuously or discretely provided. 
         [0152]    An arm  101  of the link mechanism  100  is connected to the end part  80   b  at the left side of the frontward/rearward movement pedal rotation-shaft  80 . 
         [0153]    More specific descriptions are given as follows. 
         [0154]    Namely, the link mechanism  100  has the arm  101 , a rod  102 , a cruise plate  103 , a rotation arm-member  104  (refer to  FIG. 2 ), a plate  105 , a rod  106  and the upper-end plate  107 . 
         [0155]    The connection between the end part  80   b  and the arm  101  is fixedly performed. 
         [0156]    The connection between the arm  101  and the rod  102  is rotatably performed utilizing a pin  100   a.    
         [0157]    The connection between the rod  102  and the cruise plate  103  is rotatably performed utilizing a pin  100   b.    
         [0158]    The connection between the cruise plate  103  and the rotation arm-member  104  is fixedly performed. 
         [0159]    The rotation arm-member  104  is rotatable with the adjustment fulcrum pin  90   b  as a fulcrum shaft. 
         [0160]    Additionally, the rotation arm-member  104  and the adjustment knob-member  93  independently rotate individually in correspondence to rotation of the frontward/rearward movement pedal rotation-shaft  80 , but the adjustment fulcrum pin  90   b  is a common fulcrum shaft of the rotation arm-member  104  and the adjustment knob-member  93 , and the number of components is curtailed. 
         [0161]    The connection between the rotation arm-member  104  and the plate  105  is fixedly performed. 
         [0162]    The connection between the plate  105  and the rod  106  is rotatably performed utilizing a pin  100   c.    
         [0163]    The connection between the rod  106  and the upper-end plate  107  is rotatably performed utilizing a pin  100   d.    
         [0164]    The upper-end plate  107  is rotatable with a fulcrum pin  100   e  as a fulcrum shaft. 
         [0165]    When a pedal operation of the frontward/rearward movement pedal  60  is performed in the frontward direction which is the direction indicated with the arrow B (refer to  FIG. 6 ), the rotation of the frontward/rearward movement pedal rotation-shaft  80  is performed in the direction indicated with the arrow C, the sliding of the rod  106  is performed in the upward direction which is the direction indicated with an arrow E, and the rotation of the upper-end plate  107  is performed in the downward direction which is the direction indicated with an arrow F. 
         [0166]    In contrast to the above-mentioned, when a pedal operation of the frontward/rearward movement pedal  60  is performed in the rearward direction which is the direction opposite to the direction indicated with the arrow B (refer to  FIG. 6 ), the rotation of the frontward/rearward movement pedal rotation-shaft  80  is performed in the direction opposite to the direction indicated with the arrow C, the sliding of the rod  106  is performed in the downward direction which is the direction opposite to the direction indicated with the arrow E, and the rotation of the upper-end plate  107  is performed in the upward direction which is the direction opposite to the direction indicated with the arrow F. 
         [0167]    The link mechanism fixation-member  110  has the joining plate  111  which selectively fixes the position of the upper-end plate  107  by selectively performing freely attachable and detachable link mechanism joining with the upper-end plate  107 . 
         [0168]    A link mechanism fixation-member operation lever  120  makes link mechanism joining be performed by making the joining plate  111  move in correspondence to an instruction of the worker. 
         [0169]    More specific descriptions are given as follows. 
         [0170]    Namely, the joining plate  111  has a toothed part  111   a  which performs link mechanism joining by meshing with a toothed part  107   a  of the upper-end plate  107 . 
         [0171]    A fulcrum hub  111   b,  to which the joining plate  111  is fixedly connected by welding or the like, is loosely fitted to a rotation-shaft  110   a  and is rotatable around the rotation-shaft  110   a.    
         [0172]    The connection between the fulcrum hub  111   b  and the link mechanism fixation-member operation lever  120  is fixedly performed. 
         [0173]    When a lever operation of the link mechanism fixation-member operation lever  120  is performed in the upward direction which is the direction indicated with an arrow G, the rotation of the joining plate  111  is performed in the downward direction which is the direction indicated with an arrow H, and the link mechanism joining is executed. 
         [0174]    In contrast to the above-mentioned, when at the time when link mechanism joining is being executed, a lever operation of the link mechanism fixation-member operation lever  120  is performed in the downward direction which is the direction opposite to the direction indicated with the arrow G, the rotation of the joining plate  111  is performed in the upward direction which is the direction opposite to the direction indicated with the arrow H, and the link mechanism joining is cancelled. 
         [0175]    It may be allowed that the connection state of the configuration elements mentioned above is adjusted so that link mechanism joining is executable only at the time when frontward movement is being performed in correspondence to a stepping-on operation of the frontward/rearward movement pedal  60 . 
         [0176]    Additionally, it is desirable that the link mechanism fixation-member operation lever  120  should be rearward below the rotation-shaft  110   a,  and that the joining plate  111  should be frontward above the rotation-shaft  110   a.    
         [0177]    This is because at the time when a lever operation of the link mechanism fixation-member operation lever  120  has been performed in the upward direction, the rotation of the joining plate  111  is performed in the downward direction, and a configuration such that the toothed part  111   a  of the joining plate  111  presses down the toothed part  107   a  of the upper-end plate  107  from above is easily realized. 
         [0178]    Moreover, it is desirable that the link mechanism fixation-member operation lever  120  should be provided, for example, in the neighborhood of the hose cover  35  which is at the machine-body left-and-right central part. 
         [0179]    This is because not only does an operation of the link mechanism fixation-member operation lever  120 , with the link mechanism fixation-member operation lever  120  being contiguous to the worker, become easy for the worker, but also, as will be mentioned later, a configuration such that link mechanism joining-cancellation bearings  112 L and  112 R (refer to  FIG. 11 ) are contiguous to link mechanism joining-cancellation plates  131 L and  131 R (refer to  FIG. 11 ) is easily realized. 
         [0180]    Like this, since the auto-cruise function for which the fluctuation of the vehicle traveling-speed is suppressed is executed or cancelled not with a pedal operation by the foot, but by a lever operation by the hand, generation of a situation complicated for the worker where it is necessary to use both feet at the same time, for example, is suppressed. 
         [0181]    Further regarding the configuration and action relating to the link mechanism fixation-member  110  and the link mechanism fixation-member operation lever  120 , descriptions are given later together with the configuration and action relating to a link mechanism joining-cancellation mechanism  130 . 
         [0182]    Next, mainly referring to  FIGS. 10 and 11 , descriptions are still more specifically given regarding the configuration and action of the tractor of the present embodiment. 
         [0183]    Here,  FIG. 10  is a partial left side view (No.  2 ) of the neighborhood of the step floor  40  of the tractor of the embodiment in the present invention, and  FIG. 11  is a partial perspective view (No.  2 ) of the neighborhood of the operation column cover  33  of the tractor of the embodiment in the present invention. 
         [0184]    Additionally, in  FIG. 11 , a dash panel  34  (refer to  FIG. 3 ) and the like are not shown, so that descriptions in the following will become easier to understand. 
         [0185]    Descriptions are given regarding the link mechanism joining-cancellation mechanism  130  which cancels, in a case where link mechanism joining is being performed, the link mechanism joining at the time when stepping-on of at least one of the brake pedals  50 L and  50 R (refer to  FIG. 11 ) has been performed. 
         [0186]    The link mechanism joining-cancellation mechanism  130  has the link mechanism joining-cancellation plates  131 L and  131 R (refer to  FIG. 11 ) as the first plate and the second plate, which move in correspondence to swinging of at least one of the brake pedals  50 L and  50 R and respectively abut the link mechanism joining-cancellation bearings  112 L and  112 R (refer to  FIG. 11 ) of the link mechanism fixation-member  110 . 
         [0187]    That is to say, the link mechanism joining-cancellation mechanism  130  has, correspondingly to the two brake pedals  50 L and  50 R, the link mechanism joining-cancellation plates  131 L and  131 R. 
         [0188]    And, the link mechanism fixation-member  110  has, correspondingly to the two brake pedals  50 L and  50 R, the link mechanism joining-cancellation bearings  112 L and  112 R as the first abutted part and the second abutted part, which are abutted by the link mechanism joining-cancellation plates  131 L and  131 R. 
         [0189]    More specific descriptions are given as follows. 
         [0190]    Namely, the link mechanism fixation-member  110  has the link mechanism joining-cancellation bearings  112 L and  112 R which are fixedly connected to the fulcrum hub  111   b.    
         [0191]    The attachment positions of the link mechanism joining-cancellation bearings  112 L and  112 R are, since the attachment of these are performed utilizing a plate  113 , and bolts  113   a  and  113   b,  adjustable. 
         [0192]    Fulcrum hubs  131 La and  131 Ra (refer to  FIG. 11 ), to which the link mechanism joining-cancellation plates  131 L and  131 R are respectively fixedly connected by welding or the like, are loosely fitted to a rotation-shaft  130   a  and are individually rotatable around the rotation-shaft  130   a.    
         [0193]    Additionally, it is desirable that the rotation-shaft  130   a  and the rotation-shaft  110   a  should be roughly parallel, and that the distance between the rotation-shaft  130   a  and the rotation-shaft  110   a  should be not too large. 
         [0194]    This is because the link mechanism joining-cancellation bearings  112 L and  112 R are contiguous to the link mechanism joining-cancellation plates  131 L and  131 R, and a configuration such that the lengths of the link mechanism joining-cancellation plates  131 L and  131 R become short is easily realized. 
         [0195]    The connections between the fulcrum hubs  131 La and  131 Ra and the brake pedals  50 L and  50 R are respectively fixedly performed. 
         [0196]    When a pedal operation of the brake pedal  50 L is performed in the frontward direction which is the direction indicated with an arrow I, the rotation of the fulcrum hub  131 La is performed in the direction indicated with an arrow J, and the rotation of the link mechanism joining-cancellation plate  131 L is performed in the downward direction which is the direction indicated with an arrow K. 
         [0197]    And, in a case where link mechanism joining is being performed, the link mechanism joining-cancellation plate  131 L abuts the link mechanism joining-cancellation bearing  112 L, the rotation of the joining plate  111  is performed in the upward direction which is the direction opposite to the direction indicated with the arrow H (refer to  FIG. 8 ), and the link mechanism joining is cancelled. 
         [0198]    In contrast to the above-mentioned, when a pedal operation of the brake pedal  50 R is performed in the frontward direction which is the direction indicated with the arrow I, the rotation of the fulcrum hub  131 Ra is performed in the direction indicated with the arrow J, and the rotation of the link mechanism joining-cancellation plate  131 R is performed in the downward direction which is the direction indicated with the arrow K. 
         [0199]    And, in a case where link mechanism joining is being performed, the link mechanism joining-cancellation plate  131 R abuts the link mechanism joining-cancellation bearing  112 R, the rotation of the joining plate  111  is performed in the upward direction which is the direction opposite to the direction indicated with the arrow H, and the link mechanism joining is cancelled. 
         [0200]    Of course, in a case where the brake pedals  50 L and  50 R are connected by a brake pedal connector  51  (refer to  FIG. 11 ), both of the brake pedals  50 L and  50 R swing at the time when stepping-on of at least one of the brake pedals  50 L and  50 R has been performed. 
         [0201]    Additionally, it is desirable that the brake pedals  50 L and  50 R should be rearward below the rotation-shaft  130   a,  and that the rotation-shaft  130   a  should be frontward above the rotation-shaft  110   a.    
         [0202]    This is because, for example, at the time when a pedal operation of the brake pedal  50 L has been performed in the frontward direction, the rotation of the link mechanism joining-cancellation plate  131 L is then performed in the downward direction, and a configuration such that abutting is performed so that the link mechanism joining-cancellation plate  131 L presses down the link mechanism joining-cancellation bearing  112 L from above is easily realized. 
         [0203]    If a configuration such that the link mechanism joining-cancellation bearing  112 L which has been abutted by the link mechanism joining-cancellation plate  131 L rotates is adopted, since the shock by the abutting is moderated, the link mechanism joining is smoothly cancelled, which is more desirable. 
         [0204]    Like this, at the time when the auto-cruise function is being executed, it is not necessary to use the right foot for a pedal operation of the frontward/rearward movement pedal  60  and, since the auto-cruise function can be cancelled only by using the left foot for a pedal operation of at least one of the brake pedals  50 L and  50 R, generation of a situation where it is necessary to use both feet at the same time is suppressed. 
         [0205]    Automatic cancellation of the auto-cruise function accompanying a pedal operation of at least one of the brake pedals  50 L and  50 R is not a prerequisite measure. 
         [0206]    However, it is more desirable from a viewpoint of safety and the like that, on the occasion of a pedal operation of the brake pedals  50 L and  50 R which is sometimes performed for the purpose of emergency stopping or the like, if the auto-cruise function is being executed, the very auto-cruise function being executed should be cancelled. 
         [0207]    In the present embodiment, on the occasion of a pedal operation of at least one of the brake pedals  50 L and  50 R, since automatic cancellation of the auto-cruise function is performed, it is not necessary for the worker to expressly perform a lever operation of the link mechanism fixation-member operation lever  120  for canceling the auto-cruise function. 
         [0208]    Of course, if the worker performs as necessary a lever operation of the link mechanism fixation-member operation lever  120  for executing link mechanism joining, the auto-cruise function is again executed. 
         [0209]    Additionally, since energization by a return spring  121  (refer to  FIG. 11 ) is being performed toward the link mechanism fixation-member operation lever  120 , when link mechanism joining is cancelled, the link mechanism fixation-member operation lever  120  returns to the initial position. 
         [0210]    Moreover, since energizations by return springs  52 L and  52 R (refer to  FIG. 11 ) are respectively being performed toward the brake pedals  50 L and  50 R, when a pedal operation becomes not performed, the brake pedals  50 L and  50 R return to the initial positions. 
         [0211]    Like this, with an extremely simplified configuration, the auto-cruise function can be cancelled only by performing a pedal operation of at least one of the two brake pedals  50 L and  50 R. 
         [0212]    Additionally, in the present embodiment, the frontward/rearward movement pedal  60  and the HST trunnion arm  13  are provided at the right side of the step floor  40 , and the link mechanism  100  and the brake pedals  50 L and  50 R are provided at the left side of the step floor  40 . 
         [0213]    However, regarding a configuration like this, it may be allowed that the left and the right are entirely exchanged. 
         [0214]    That is to say, it may be allowed that the frontward/rearward movement pedal  60  and the HST trunnion arm  13  are provided at the left side of the step floor  40 , and that the link mechanism  100  and the brake pedals  50 L and  50 R are provided at the right side of the step floor  40 . 
         [0215]    Moreover, the auto-cruise function of the present embodiment is also cancelled with, besides a stepping-on operation of the brake pedals  50 L and  50 R, a stepping-on operation of the frontward/rearward movement pedal  60  to the frontward movement side, namely, an operation to the speed-increasing side. Namely, during the auto-cruise, when the frontward/rearward movement pedal  60  is stepped on to the frontward movement side, the link mechanism acts, and the joining between the joining plate  111  and the upper-end plate  107  is cancelled. 
         [0216]    Additionally, for the present embodiment, during the auto-cruise, the auto-cruise function is not cancelled even when the frontward/rearward movement pedal is stepped on to the rearward movement side, while the auto-cruise function is cancelled with the link mechanism acting when the frontward/rearward movement pedal is stepped on to the frontward movement side, but detailed descriptions of the operativeness concerned are omitted. 
         [0217]    A tractor in the present invention is such that cancellation of the auto-cruise function is able to be performed with a simpler operation, and is useful for the purpose of utilizing for a tractor which performs working inside a farm field, for example.