Patent Publication Number: US-2023158884-A1

Title: Tractor

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to a tractor. 
     Description of Related Art 
     As shown in patent literature 1 and 2, for example, the tractor is equipped with an engine bonnet (bonnet) that forms an engine compartment, and in the engine compartment, an exhaust-gas cleaning device (exhaust-gas cleaning process device) is installed above the engine. 
     PRIOR ART LITERATURE 
     [Patent Literature 1] JP 2013-112284 A 
     [Patent Literature 2] JP 2015-143508 A 
     There is a demand for a tractor to be provided with a plurality of exhaust-gas cleaning devices for cleaning exhaust gas discharged from an engine. Examples of the plurality of exhaust-gas cleaning devices include an exhaust-gas cleaning device that cleans exhaust gas using a cleaning filter and an exhaust-gas cleaning device that cleans exhaust gas using a reducing agent. 
     When the conventional art is adopted and the first exhaust-gas cleaning device and the second exhaust-gas cleaning device are installed in the engine compartment, the first exhaust-gas cleaning device and the second exhaust-gas cleaning device are located above the engine, and thus, even when the size of one of the first exhaust-gas cleaning device and the second exhaust-gas cleaning device is smaller than the size of the other exhaust-gas cleaning device, the mounting height of the engine bonnet must be set to correspond to the larger exhaust-gas cleaning device. Therefore, the mounting height of the engine bonnet is increased. 
     SUMMARY 
     One or more embodiments of the present invention provide a tractor for which it is possible to provide a first exhaust-gas cleaning device and a second exhaust-gas cleaning device in an engine compartment while keeping the mounting height of the engine bonnet low, keeping the front-back length of the engine compartment short, and supporting the first exhaust-gas cleaning device and the second exhaust-gas cleaning device onto the vehicle body frame while in an appropriate connection state. 
     The tractor of one or more embodiments of the present invention is provided with: a vehicle body; an engine bonnet forming an engine compartment; an engine that is disposed in the engine compartment; a first exhaust-gas cleaning device and a second exhaust-gas cleaning device provided in the engine compartment for purifying exhaust gas discharged from the engine; and a support member (i.e., a supporting tool) supported by the vehicle body frame and supporting the first exhaust-gas cleaning device and the second exhaust-gas cleaning device is provided, the first exhaust-gas cleaning device being provided above the engine and having a long side substantially parallel to a vehicle-body lateral width direction (or a vehicle-body horizontal direction), and the second exhaust-gas cleaning being provided behind the engine and having a long side substantially parallel to the vehicle-body lateral width direction; wherein, the supporting member is provided with a support column extending upward from the vehicle body frame along the front portion of the second exhaust-gas cleaning device while supporting the front portion and a support arm extending forward from the upper portion of the support column along a lower portion of the first exhaust-gas cleaning device while supporting the lower portion. 
     According to this configuration, the first exhaust-gas cleaning device, which is the smaller of the first exhaust-gas cleaning device and the second exhaust-gas cleaning device, is installed above the engine, and the larger second exhaust-gas cleaning device is installed behind the engine, and the mounting height of the engine bonnet can be set based on the size of the small first exhaust-gas cleaning device. Furthermore, since the long sides of both the first and second exhaust-gas cleaning devices are substantially parallel to the vehicle-body lateral width direction, the first and second exhaust-gas cleaning devices can be accommodated compared to the case where the long sides are substantially parallel to the vehicle-body longitudinal direction, and it is possible to shorten the length of the space in a vehicle-body longitudinal direction (or a vehicle-body front-back direction) necessary for the installation of the first exhaust-gas cleaning device, while keeping the mounting height of the engine bonnet low and the longitudinal length of the engine compartment shorter, and a second exhaust-gas cleaning device can be provided in the engine compartment. 
     Because the positional relationship between the first exhaust-gas cleaning device and the second exhaust-gas cleaning device is supported by the vehicle body frame in a state where the positional relationship is set by the support member, the first exhaust-gas cleaning device and the second exhaust-gas cleaning device can be easily connected; for example, even in a connection structure that does not have a function enabling adjustment of the positional relationship between the first exhaust-gas cleaning device and the second exhaust-gas cleaning device, the first exhaust- gas cleaning device and the second exhaust-gas cleaning device can be connected in a positional relationship advantageous for connection. 
     In one or more embodiments of the present invention, the vehicle body frame is provided with a flywheel housing extending backward from the back portion of the engine and positioned below the second exhaust-gas cleaning device, and the support column extends upward from the flywheel housing toward the vehicle body. 
     According to this configuration, since the support column extends upward from the flywheel housing located below the second exhaust-gas cleaning device, the length of the support column can be shortened, and it is possible to firmly support the first exhaust-gas cleaning device and the second exhaust-gas cleaning device onto the vehicle body frame such that the first exhaust-gas cleaning device and the second exhaust-gas cleaning device do not readily swing. 
     The tractor of one or more embodiments of the present invention is provided with a position adjustment tool that can adjust a support position of the second exhaust-gas cleaning device on the support column in a vehicle-body vertical direction (or a vehicle-body up-down direction), the vehicle-body longitudinal direction, and the vehicle-body lateral width direction. 
     According to the present configuration, even when there is a positional shift between the first exhaust-gas cleaning device and the second exhaust-gas cleaning device in the vehicle-body vertical direction, the vehicle-body longitudinal direction, and the vehicle-body lateral width direction due to manufacturing errors in the support member, by for example, adjusting the positional shift via the position adjustment tool, for example, the first exhaust-gas cleaning device and the second exhaust-gas cleaning device can be connected even in a connection structure not provided with a function for correcting the positional shift, and thus the connection structure can be simplified in that a special positional shift adjustment portion is not required in a connection structure that connects the first exhaust-gas cleaning device and the second exhaust-gas cleaning device. 
     The tractor of one or more embodiments of the present invention is provided with a lower support portion that is supported below the support column and supports a lower portion of the second exhaust-gas cleaning device. 
     According to this configuration, the front portion of the second exhaust-gas cleaning device is supported by the support column, and the lower portion of the second exhaust-gas cleaning device is supported by the support column, and thus the second exhaust-gas cleaning device can be firmly supported by the support member. 
     The tractor of one or more embodiments of the present invention is provided with a second position adjustment tool that can adjust a support position of the second exhaust-gas cleaning device on the lower support portion in the vehicle-body vertical direction, the vehicle-body longitudinal direction, and the vehicle-body lateral width direction. 
     According to the present configuration, even when there is a positional shift between the first exhaust-gas cleaning device and the second exhaust-gas cleaning device in the vehicle-body vertical direction, the vehicle-body longitudinal direction, and the vehicle-body lateral width direction due to manufacturing errors in the support member, for example, by adjusting the positional shift via a second position adjustment tool, for example, the first exhaust-gas cleaning device and the second exhaust-gas cleaning device can be connected even in a connection structure not provided with a function for correcting the positional shift, and thus the connection structure can be simplified in that a special positional shift adjustment portion is not required in a connection structure that connects the first exhaust-gas cleaning device and the second exhaust-gas cleaning device. 
     In one or more embodiments of the present invention, the lower portion of the support column comprises a washer portion that is connected to the vehicle body frame to make the support column supported by the vehicle body frame, and the lower support portion constitutes a part of the washer portion. 
     According to this configuration, the washer portion serves as a connection member for supporting the lower support portion on the support column, and thus the structure of providing the lower support portion on the support post portion can be simplified without requiring a special connection member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a left side view illustrating an entirety of a tractor. 
         FIG.  2    is a left side view illustrating a first exhaust-gas cleaning device and a second exhaust-gas cleaning device. 
         FIG.  3    is a plan view illustrating the first exhaust-gas cleaning device and the second exhaust-gas cleaning device. 
         FIG.  4    is a back view illustrating a support member. 
         FIG.  5    is a perspective view of the support member in an exploded state. 
         FIG.  6    is a right side view illustrating left and right brake operation devices. 
         FIG.  7    is an explanatory diagram illustrating a summary of assembly of the brake pedal. 
         FIG.  8    is a back view illustrating a steering-post cover and a panel cover. 
         FIG.  9    is a back view of a panel cover provided with another example of one or more embodiments. 
         FIG.  10    is a perspective view of a steering-post cover provided with another example of one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention are described below based on the drawings. 
     Note that in the following description, in regards to a traveling vehicle body of a tractor, the direction of arrow F illustrated in  FIG.  1    is defined as “vehicle-body front”, the direction of arrow B is defined as “vehicle-body back”, the direction of arrow U is defined as “vehicle-body up”, the direction of arrow D is defined as “vehicle-body down”, the direction heading toward the surface of the page is defined as “vehicle-body left”, and the direction heading toward the reverse face of the page is defined as “vehicle-body right”. 
     [Overall Configuration of Tractor] 
     As illustrated in  FIG.  1   , the tractor is provided with a traveling vehicle body  3  supported by a pair of left and right front wheels  1 , which can be steered and driven, and a pair of left and right back wheels  2 , which can be driven. A vehicle body frame  4  of the traveling vehicle body  3  is constituted by an engine  5 , a flywheel housing  6  connected to a back portion of the engine  5 , a clutch housing  7  connected to a back portion of the flywheel housing  6 , a transmission case  7   a  connected to a back portion of the clutch housing  7 , and a front frame  8  connected to a lower portion of the engine  5 . A motor unit  9  provided with the engine  5  is formed in a front portion of the traveling vehicle body  3 . A driver&#39;s seat  10  and a driving unit  12 , which is provided with a steering wheel  11  whereby a steering operation of the front wheels  1  is performed, are formed in a back portion of the traveling vehicle body  3 . A linking mechanism  13 , which connects a work apparatus such as a rotary tilling apparatus (not illustrated) in a manner enabling a raising and lowering operation of the work apparatus, and a power takeoff shaft  14 , which takes power from the engine  5  and outputs this to the connected work apparatus, are provided in a back portion of the transmission case  7   a.  Reference numeral  20  illustrated in  FIG.  1    is a ROPS frame. 
     [Configuration of Motor Unit] 
     As illustrated in  FIGS.  1  and  2   , the motor unit  9  is provided with an engine compartment  15 . The engine compartment  15  is formed by an engine bonnet  16 , which covers the engine compartment  15  from above and the front; a partition member  17  that forms a partition between the engine compartment  15  and the driving unit  12 ; and the like. 
     As illustrated in  FIGS.  1  and  2   , the engine  5 , a radiator  18  that cools the engine  5 , and a first exhaust-gas cleaning device (DPF)  21  and second exhaust-gas cleaning device (SCR)  22  that perform cleaning processes of exhaust gas exhausted by the engine  5  are provided in the engine compartment  15 . 
     [Configuration of Radiator] 
     As illustrated in  FIG.  1   , the radiator  18  is provided in front of the engine  5 . A blowing action of a rotary fan  19  positioned between the radiator  18  and the engine  5  introduces cooling air from outside the engine compartment  15  to inside the engine compartment and supplies the cooling air to the radiator  18 . The cooling air is supplied to the radiator  18  in a state of the cooling air passing through the radiator  18  from front to back. In the radiator  18 , engine cooling water is cooled by heat exchange between the supplied cooling air and the engine cooling water. The engine  5  is cooled by the cooled engine cooling water being supplied to the engine  5 . 
     [Configurations of First Exhaust-Gas Cleaning Device and Second Exhaust-Gas Cleaning Device] 
     The engine  5  is a diesel engine. As illustrated in  FIGS.  2  and  3   , the first exhaust-gas cleaning device  21  is provided above the engine  5  in a state wherein a long side of the first exhaust-gas cleaning device is substantially parallel to a vehicle-body lateral width direction. A maximum length H in a vehicle-body vertical direction of the first exhaust-gas cleaning device  21  is set to be shorter than a maximum length W in a vehicle-body longitudinal direction of the first exhaust-gas cleaning device  21 . As illustrated in  FIGS.  2  and  3   , an exhaust-gas suctioning portion  21   a,  which is provided to a part on one end side, in a vehicle-body lateral width direction, of the first exhaust-gas cleaning device  21 , and an exhaust-gas exhausting portion  5   a,  which is provided to the engine  5 , are connected. An exhaust-gas discharging portion  21   b  is provided to a part on another end side, in the vehicle-body lateral width direction, of the first exhaust-gas cleaning device  21 . In one or more embodiments, the exhaust-gas suctioning portion  21   a  protrudes downward from a lower portion of the first exhaust-gas cleaning device  21  at an end portion on a vehicle-body left horizontal side of the first exhaust-gas cleaning device  21 , and the exhaust-gas discharging portion  21   b  protrudes backward from an end portion on a vehicle-body right horizontal side of the first exhaust-gas cleaning device  21 . 
     In the first exhaust-gas cleaning device  21 , the exhaust gas exhausted by the engine  5  from the exhaust-gas exhausting portion  5   a  is suctioned by the exhaust-gas suctioning portion  21   a  into the device, and diesel microparticles included in the suctioned exhaust gas are collected by a collection filter (not illustrated). This performs an exhaust-gas cleaning process of decreasing the diesel microparticles. The exhaust gas subjected to the cleaning process is discharged from the exhaust-gas discharging portion  21   b.    
     As illustrated in  FIGS.  2  and  3   , the second exhaust-gas cleaning device  22  is provided behind the engine  5  in a state wherein a long side of the second exhaust-gas cleaning device is substantially parallel to the vehicle-body lateral width direction. An exhaust-gas introduction portion  22   a,  which is provided to a part on one end side, in the vehicle-body lateral width direction, of the second exhaust-gas cleaning device  22 , and the exhaust-gas discharging portion  21   b  of the first exhaust-gas cleaning device  21  are connected by a connecting pipe  23 . An exhaust-gas discharging portion  22   b  is provided to a part on another end side, in the vehicle-body lateral width direction, of the second exhaust-gas cleaning device  22 . In one or more embodiments, the exhaust-gas introduction portion  22   a  is provided to an end portion on a vehicle-body left horizontal side of the second exhaust-gas cleaning device  22 , and the exhaust-gas discharging portion  22   b  is provided to an end portion on a vehicle-body right horizontal side of the second exhaust-gas cleaning device  22 . 
     In the second exhaust-gas cleaning device  22 , the exhaust gas discharged by the first exhaust-gas cleaning device  21  from the exhaust-gas discharging portion  21   b  is supplied by the connecting pipe  23  to the exhaust-gas introduction portion  22   a  and introduced by the exhaust-gas introduction portion  22   a  into the device, and the introduced exhaust gas is subjected to the cleaning process by a reducing agent. Specifically, aqueous urea as the reducing agent is injected into the introduced exhaust gas, hydrolyzing the exhaust gas. This performs an exhaust-gas cleaning process of decreasing nitrogen oxides included in the exhaust gas. The exhaust gas subjected to the cleaning process is exhausted from the exhaust-gas discharging portion  22   b  to a vehicle-body horizontal outer side. 
     As illustrated in  FIG.  3   , the first exhaust-gas cleaning device  21  is supported in an attachment disposition wherein the part on the other end side, in the vehicle-body lateral width direction, is swung and displaced toward a vehicle-body front side with respect to the part on the one end side, in the vehicle-body lateral width direction, in a state wherein the exhaust-gas suctioning portion  21   a  is a swinging shaft. That is, the first exhaust-gas cleaning device  21  is supported in a disposition wherein in a plan view, the longitudinal direction thereof is inclined relative to the vehicle-body lateral width direction. As illustrated in  FIG.  2   , the exhaust-gas introduction portion  22   a  of the second exhaust-gas cleaning device  22  extends diagonally backward and upward from the second exhaust-gas cleaning device  22 . A positional relationship between the exhaust-gas discharging portion  21   b  of the first exhaust-gas cleaning device  21  and the exhaust-gas introduction portion  22   a  of the second exhaust-gas cleaning device  22  can be made to be a positional relationship appropriate for adopting a connecting pipe  23  having no bellows or other adjustment means of adjusting the positional relationship between the exhaust-gas discharging portion  21   b  and the exhaust-gas introduction portion  22   a.  This can be done by bringing the first exhaust-gas cleaning device  21  and the second exhaust-gas cleaning device  22  in proximity to each other in the vehicle-body longitudinal direction and by directly connecting the exhaust-gas suctioning portion  21   a  of the first exhaust-gas cleaning device  21  to the exhaust-gas exhausting portion  5   a  of the engine  5 . 
     As illustrated in  FIGS.  2  and  3   , a back portion  21   c  of the first exhaust-gas cleaning device  21  is positioned on a vehicle-body back side of a back end portion of the engine  5 . In a plan view, the back portion  21   c  of the first exhaust-gas cleaning device  21  and the second exhaust-gas cleaning device  22  overlap. 
     As illustrated in  FIGS.  2  and  3   , the partition member  17  that forms the partition between the engine compartment  15  and the driving unit  12  is provided across a back location of the second exhaust-gas cleaning device  22  and a lower location of the second exhaust-gas cleaning device  22 . The partition member  17  is configured so a part  17   a —positioned in the lower location of the second exhaust-gas cleaning device  22 —of the partition member  17  is positioned further toward a vehicle-body front side than a part  17   b —positioned in the back location of the second exhaust-gas cleaning device  22 —of the partition member  17 . The part  17   a —positioned in the lower location of the second exhaust-gas cleaning device  22 —of the partition member  17  is provided with a portion in an inclined state that, in moving toward its lower end side, is positioned more to a vehicle-body front side. A footwell of the driving unit  12  can be extended below the second exhaust-gas cleaning device  22 . 
     As illustrated in  FIG.  6   , electrical wires  24  are provided across the engine compartment  15  and the driving unit  12 . In one or more embodiments, a plurality of electrical wires  24  is provided. However, it is also possible for only one to be provided. The electrical wires  24  enter from the engine compartment  15  into the footwell of the driving unit  12  by passing below a part positioned in a central portion in the vehicle-body lateral width direction of the partition member  17 . The electrical wires  24  transmit information relating to actuation of the engine  5  to gauges of the driving unit  12 . A portion of the electrical wires  24  that is positioned on a driving-unit side of the partition member  17  is wired in a state of conforming to the part  17   a —positioned in the lower location of the second exhaust-gas cleaning device  22 —of the partition member  17  in the footwell of the driving unit  12 . The electrical wires  24  pass through a conduit  25 . The conduit  25  is supported on the partition member  17  by a clamp  26 . 
     [Support Member of Exhaust-Gas Cleaning Devices] 
     As illustrated in  FIGS.  2 ,  3 , and  4   , the first exhaust-gas cleaning device  21  and the second exhaust-gas cleaning device  22  are supported on the vehicle body frame  4  via a support member (i.e., the supporting tool)  30 . The first exhaust-gas cleaning device  21  and the second exhaust-gas cleaning device  22  are supported by the vehicle body frame  4  in a state wherein the positional relationship between the exhaust-gas discharging portion  21   b  of the first exhaust-gas cleaning device  21  and the exhaust-gas introduction portion  22   a  of the second exhaust-gas cleaning device  22  is set by the support member  30 . 
     As illustrated in  FIGS.  2 ,  3 ,  4 , and  5   , the support member  30  is provided with a support column  31  that extends upward from the vehicle body frame  4  in a state of conforming to a front portion  22   c  of the second exhaust-gas cleaning device  22  and supports the front portion  22   c  of the second exhaust-gas cleaning device  22 , a support arm  32  that extends in a vehicle-body forward direction from an upper portion of the support column  31  in a state of conforming to a lower portion  21   d  of the first exhaust-gas cleaning device  21  and supports the lower portion  21   d  of the first exhaust-gas cleaning device  21 , and a lower support portion  33  that is provided to a lower portion of the support column  31  and supports a lower portion  22   d  of the second exhaust-gas cleaning device  22 . 
     As illustrated in  FIGS.  2 ,  4 , and  5   , the support column  31  has a washer portion  34  provided to the lower portion of the support column  31  and is supported on the vehicle body frame  4  by the washer portion  34  being connected to the vehicle body frame  4 . The connection of the washer portion  34  to the vehicle body frame  4  is performed by the flywheel housing  6  constituting the vehicle body frame  4 . The flywheel housing  6  is positioned below the second exhaust-gas cleaning device  22  and can keep a length of the support column  31  short. 
     As illustrated in  FIGS.  2 ,  4 , and  5   , the support column  31  is provided with left and right strut rods  31   a  lined up at an interval in the vehicle-body lateral width direction. A lower strut-portion reinforcing rod  31   b,  which connects lower portions of the strut rods  31   a,  and an upper strut-portion reinforcing rod  31   c,  which connects upper portions of the strut rods  31   a,  are provided across the left and right strut rods  31   a.  The left and right strut rods  31   a  are constituted by steel pipes. 
     As illustrated in  FIGS.  2 ,  4 , and  5   , a front support portion  31   d  supporting the second exhaust-gas cleaning device  22  is provided to each of the left and right strut rods  31   a.  The front portion  22   c  of the second exhaust-gas cleaning device  22  is supported by the support column  31  by front connecting portions  22   e —provided in two locations, left and right, in the front portion  22   c  of the second exhaust-gas cleaning device  22 —being connected to the front support portion  31   d.    
     As illustrated in  FIGS.  2 ,  4 , and  5   , washer plates  34   a  provided to respective lower portions of the left and right strut rods  31   a  are provided to the washer portion  34 . In the washer portion  34 , the left and right washer plates  34   a  being connected to the flywheel housing  6  by a plurality of connecting bolts provides a detachable connection to the flywheel housing  6 . 
     As illustrated in  FIGS.  2 ,  4 , and  5   , the lower support portion  33  is provided with lower support pieces  33   a  provided to the lower portions of the left and right strut rods  31   a.  The left and right lower support pieces  33   a  are provided to the strut rods  31   a  by being formed on the washer plates  34   a.  The lower support portion  33  is provided to the washer portion  34 . The lower portion  22   d  of the second exhaust-gas cleaning device  22  is supported by the lower support portion  33  by lower connecting portions  22   f —provided in two locations, left and right, in the lower portion  22   d  of the second exhaust-gas cleaning device  22 —being connected to the lower support pieces  33   a.    
     As illustrated in  FIGS.  2 ,  4 , and  5   , the support arm  32  is provided with arm bodies  32   a  that extend in the vehicle-body forward direction from respective upper portions of the left and right strut rods  31   a.  An arm reinforcing rod  32   b  connecting the left and right arm bodies  32   a  is provided across distal end portions of the left and right arm bodies  32   a.  Among the left and right arm bodies  32   a,  the left arm body  32   a  is configured to connect via a relay member  32   c  to a lower connecting portion  21   e  provided to the lower portion  21   d  of the first exhaust-gas cleaning device  21 . The right arm body  32   a  is configured to connect directly to the lower connecting portion  21   e  of the first exhaust-gas cleaning device  21 . 
     [Configuration of Position Adjustment of Exhaust-Gas Cleaning Devices] 
     As illustrated in  FIGS.  2 ,  4 , and  5   , the support member  30  is provided with a position adjustment tool  35  that can adjust a support position—in the vehicle-body vertical direction, the vehicle-body longitudinal direction, and the vehicle-body lateral width direction—of the second exhaust-gas cleaning device  22  on the support column  31  and with a second position adjustment tool  37  that can adjust a support position—in the vehicle-body vertical direction, the vehicle-body longitudinal direction, and the vehicle-body lateral width direction—of the second exhaust-gas cleaning device  22  on the lower support portion  33 . 
     When there is a position shift between the exhaust-gas discharging portion  21   b  of the first exhaust-gas cleaning device  21  and the exhaust-gas introduction portion  22   a  of the second exhaust-gas cleaning device  22 , so the positional relationship between the exhaust-gas discharging portion  21   b  and the exhaust-gas introduction portion  22   a  becomes appropriate and the exhaust-gas discharging portion  21   b  and the exhaust-gas introduction portion  22   a  can be appropriately connected by the connecting pipe  23  having no position adjustment function, the positional relationship between the exhaust-gas discharging portion  21   b  and the exhaust-gas introduction portion  22   a  can be adjusted by the position adjustment tool  35  and the second position adjustment tool  37 . 
     Specifically, as illustrated in  FIGS.  2 ,  4 , and  5   , the position adjustment tool  35  is provided with an adjustment member  36  positioned between the front connection portion  22   e  of the second exhaust-gas cleaning device  22  and the front support portion  31   d  of the support column  31 , a first connecting bolt  36   a  connecting the front connecting portion  22   e  and the adjustment member  36 , and a second connecting bolt  36   b  connecting the front support portion  31   d  and the adjustment member  36 . 
     As illustrated in  FIGS.  2 ,  4 , and  5   , the second position adjustment tool  37  is provided with a second adjustment member  38  positioned between the lower connecting portion  22   f  of the second exhaust-gas cleaning device  22  and the lower support piece  33   a  of the support column  31 , a third connecting bolt  38   a  connecting the lower connecting portion  22   f  and the second adjustment member  38 , and a fourth connecting bolt  38   b  connecting the lower support piece  33   a  and the second adjustment member  38 . 
     A hole diameter of a through hole (not illustrated) of the adjustment member  36  into which the first connecting bolt  36   a  is inserted is made greater than an outer diameter of the first connecting bolt  36   a  for a configuration enabling position shifting of the front connecting portion  22   e  relative to the adjustment member  36 . A through hole (not illustrated) of the position adjustment member  36  into which the second connecting bolt  36   b  is inserted is made greater than an outer diameter of the second connecting bolt  36   b  for a configuration enabling position shifting of the adjustment member  36  relative to the front support portion  31   d.    
     A hole diameter of a through hole (not illustrated) of the second adjustment member  38  into which the third bolt  38   a  is inserted is made greater than an outer diameter of the third connecting bolt  38   a  for a configuration enabling position shifting of the adjustment member  36  relative to the front support portion  31   d.  A hole diameter of a through hole (not illustrated) of the second adjustment member  38  into which the fourth connecting bolt  38   b  is inserted is made greater than an outer diameter of the fourth connecting bolt  38   b  for a configuration enabling position shifting of the adjustment member  36  relative to the front support portion  31   d.    
     In the position adjustment tool  35 , among the first connecting bolt  36   a,  the second connecting bolt  36   b,  the third connecting bolt  38   a,  and the fourth connecting bolt  38   b,  tightening of a connecting bolt corresponding to desired position adjustment is loosened. Performing an operation of moving the second exhaust-gas cleaning device  22  shifts the position of the second exhaust-gas cleaning device  22  relative to the support member  30 . This changes the support position—in the vehicle-body vertical direction, the vehicle-body longitudinal direction, and the vehicle-body lateral width direction—of the second exhaust-gas cleaning device  22  on the support column  31  in a manner corresponding to the operation that is performed of moving the second exhaust-gas cleaning device  22 . 
     In the second position adjustment tool  37 , among the first connecting bolt  36   a,  the second connecting bolt  36   b,  the third connecting bolt  38   a,  and the fourth connecting bolt  38   b,  tightening of a connecting bolt corresponding to desired position adjustment is loosened. Performing an operation of moving the second exhaust-gas cleaning device  22  shifts the position of the second exhaust-gas cleaning device  22  relative to the support member  30 . This changes the support position—in the vehicle-body vertical direction, the vehicle-body longitudinal direction, and the vehicle-body lateral width direction—of the second exhaust-gas cleaning device  22  on the lower support portion  33  in a manner corresponding to the operation that is performed of moving the second exhaust-gas cleaning device  22 . 
     [Configuration of Driving Unit]As illustrated in  FIG.  1   , the driving unit  12  is provided behind the engine compartment  15 . As illustrated in  FIGS.  1 ,  3 , and  8   , the driving unit  12  is provided with the driver&#39;s seat  10 , the steering wheel  11  whereby the steering operation of the front wheels  1  is performed, a left brake operation unit  40 L whereby brakes (not illustrated) for the left back wheel are operated, and a right brake operation unit  40 R whereby brakes (not illustrated) for the right back wheel are operated. 
     [Configurations of Left Brake Operation Unit and Right Brake Operation Unit] 
     As illustrated in  FIG.  8   , the left brake operation unit  40 L and the right brake operation unit  40 R are provided to the right and below the steering wheel  11 . As illustrated in  FIGS.  3 ,  6 , and  8   , the left brake operation unit  40 L and the right brake operation unit  40 R are each provided with a brake pedal  41 , a return spring  42  that subjects the brake pedal  41  to an operation of being returned to an initial position (“off”), and a master cylinder  43  connected to the brake pedal  41 . 
     As illustrated in  FIG.  6   , the brake pedal  41  is provided with a pedal arm  41   a  and with a footboard  41   b  provided at a lower end portion of the pedal arm  41   a.  A support shaft  44  is provided at an upper portion of the pedal arm  41   a.  The support shaft  44  is supported by a support portion  45  provided to the traveling vehicle body  3 . The brake pedal  41  is supported on the traveling vehicle body  3  in a state of being able to swing between the initial position (“off”) and a braking position (“on”) by using a shaft core P of the support shaft  44  as a swinging fulcrum. The brake pedal  41  is positioned to the initial position (“off”) by the pedal arm  41   a  abutting a stopper  47 . 
     As illustrated in  FIG.  6   , the partition member  17  forming the partition between the engine compartment  15  and the driving unit  12  is disposed further toward a vehicle-body front side than the brake pedal  41 . The return spring  42  is engaged to the pedal arm  41   a  and a spring support portion  17   d  provided to the partition member  17 . The return spring  42  biases the brake pedal  41  to swing to the initial position (“off”) by using the partition member  17  as a counterforce member. 
     As illustrated in  FIG.  6   , the partition member  17  is configured so the part  17   a,  which corresponds to the footboard  41   b,  of the partition member  17  is positioned further toward a vehicle-body front side than the part  17   b,  which corresponds to the support shaft  44 , of the partition member  17 . A front portion of the footwell of the driving unit  12  can be extended forward past the support shaft  44 . 
     As illustrated in  FIG.  6   , the master cylinder  43  is provided on a vehicle-body back side of the support shaft  44  of the brake pedal  41 . The master cylinder  43  is fixed in a detachable manner to the support portion  45 . A slidable operation shaft  43   a  of the master cylinder  43  and an operation arm  41   c  provided to the brake pedal  41  are interconnected. The operation arm  41   c  extends from the pedal arm  41   a  toward an opposite side of a side whereon the footboard  41   b  is positioned relative to the support shaft  44 . 
     In both the left brake operation unit  40 L and the right brake operation unit  40 R, when the brake pedal  41  is subjected to a stepping operation against the return spring  42  and enters the braking position (“on”), the operation shaft  43   a  of the master cylinder  43  is subjected to a sliding operation to a pushed-in side by the operation arm  41   c.  The master cylinder  43  supplies operational hydraulic pressure to the brakes (not illustrated), and the brakes perform an operation of switching to a braking state. When the stepping operation of the brake pedal  41  is released, the brake pedal  41  is subjected to an operation of returning to the initial position (“off”) by the return spring  42 , and the operation shaft  43   a  of the master cylinder  43  is subjected to a sliding operation to a pulled-out side by the operation arm  41   c . The imparting of the operational hydraulic pressure by the master cylinder  43  to the brakes is released, and the brakes perform an operation of switching to an initial state. 
     [Configuration of Return Spring] 
     As illustrated in  FIGS.  3  and  6   , the return spring  42  is constituted by a torsion coil spring and is provided with a coil portion  42   a , an arm  42   b  extending from one end side of the coil portion  42   a,  and an arm  42   c  extending from another end side of the coil portion  42   a.  The coil portion  42   a  is fitted onto the support shaft  44 , and the return spring  42  is supported by the support shaft  44 . The arm  42   b  on the one end side is engaged to the spring support portion  17   d  of the partition member  17 . The arm  42   c  on the other end side is engaged to the pedal arm  41   a.    
     As illustrated in  FIG.  6   , a bent end portion  42   d  engaged to the pedal arm  41   a  is provided to the arm  42   c  on the other end side. A through hole  46  whereto the bent end portion  42   d  is engaged is provided to the pedal arm  41   a . A shape of the through hole  46  is made to be a shape into which the bent end portion  42   d,  which moves along the shaft core P of the support shaft  44 , can be inserted. The return spring  42  and the brake pedal  41  can be assembled by the following assembly outline. 
     As illustrated in  FIG.  7   , the coil portion  42   a  fits the return spring  42  onto the support shaft  44 , and the arm  42   b  on the one end side is placed in a state of being engaged to the partition member  17 . The return spring  42  is in a free state. The stopper  47  is removed from the support portion  45 . The brake pedal  41  is attached to the support shaft  44  and swung up, and the brake pedal  41  is operated in a disposition opposing the support shaft, wherein the footboard  41   b  is positioned in a position higher than when the brake pedal  41  is positioned in the initial position (“off”). The brake pedal  41  in this attitude of opposing the support shaft is guided to the support shaft  44  and moved toward the return spring  42 . By moving the brake pedal  41 , the bent end portion  42   d  of the return spring  42  moves toward the pedal arm  41   a  in a direction along the shaft core p of the support shaft  44 , is inserted into the through hole  46  from an inner side of the pedal arm  41   a,  and moves to an outer side of the pedal arm  41   a.  Next, the brake pedal  41  is swung down. At this time, the operation arm  41   c  enters a slit  17   e  provided in the partition member  17 . The stopper  47  is attached to the support portion  45 , and the brake pedal  41  is moved to the initial position (“off”). This causes the brake pedal  41  to be stopped by the stopper  47 . As illustrated in  FIG.  6   , the bent end portion  42   d  engages to the pedal arm  41   a,  the return spring  42  is provided with an elastic restoring force, and the brake pedal  41  enters a state of being biased and swung to the initial position (“off”) by the return spring  42 . The slit  17   e  is closed off once assembly of the brake pedal  41  is finished. 
     [Configurations of Steering-Post Cover and Panel Cover] 
     The steering wheel  11  is supported in a state of being able to change positions in the vehicle-body longitudinal direction and the vehicle-body vertical direction. As illustrated in  FIG.  8   , a steering-post cover  50  is inserted into a through hole  52  of a panel cover  51  supported on the traveling vehicle body  3 . When the steering wheel  11  changes positions in the vehicle-body longitudinal direction, the steering-post cover  50  follows the steering wheel  11  and swings in the vehicle-body longitudinal direction relative to the panel cover  51 . A bellows-shaped expandable cover  53  is connected across a proximal-side lower portion of the steering-post cover  50  and a lower portion  51   a  of the panel cover  51 . The expandable cover  53  expands and contracts according to the swinging of the steering-post cover  50  but, regardless of the swinging of the steering-post cover  50 , places a gap between the steering-post cover  50  and the lower portion  51   a  of the panel cover  51  in a closed state. Between a part opposing a distal-side wall portion of the steering-post cover  50  of the panel cover  51  and the distal-side wall portion of the steering-post cover  50 , a gap that allows the steering-post cover  50  to swing is provided. However, above the gap and on the distal-side wall portion of the steering-post cover  50 , a bulging portion that bulges toward a cover outer side and makes the gap difficult to see from above is provided. In the panel cover  51 , a face portion  51   b  corresponding to a side portion of the steering-post cover  50  is raised to the proximal side. Even if the steering-post cover  50  swings, the face portion  51   b  makes it difficult to see the gap between the steering-post cover  50  and the panel cover  51  on a horizontal side of the steering-post cover  50 . 
     Other Embodiments 
     (1)  FIG.  9    is a back view of a panel cover  55  provided with another example of one or more embodiments.  FIG.  10    is a perspective view of a steering post cover  56  provided with another example of one or more embodiments. In the panel cover  55  provided with another example, below a through hole  57  into which the steering-post cover  56  is inserted, an opening  58  and a proximal wall  59  extending upward from a lower edge portion of the opening  58  are provided. In the steering-post cover  56 , on a proximal-side lower portion, a proximal extended portion  61  that extends lower than a lower end  60   a  of a horizontal wall portion  60  is provided, and on a distal-side lower portion, a distal extended portion  62  that extends lower than the lower end  60   a  of the horizontal wall portion  60  is provided. The proximal wall  59 , the proximal extended portion  61 , and the distal extended portion  62  serve as hiding walls that make it difficult to see into an area below the panel cover  55  via a gap arising between the steering-post cover  56  and the panel cover  55  on a proximal side and horizontal side of the steering-post cover  56 . 
     (2) In the embodiments described above, a configuration in which the support column  31  extends from the flywheel housing  6  is given, but the configuration is not limited thereto, and the support column  31  may extend from any portion of the vehicle body frame  4 . 
     (3) In the embodiments described above, an example in which the position adjustment tool  35  is provided is given, but the position adjustment tool  35  need not be provided. 
     (4) In the embodiments described above, an example in which the lower support portion  33  and the second position adjustment tool  37  is provided is given, but the lower support portion  33  need not be provided. Also, the lower support portion  33  may be provided, and the second position adjustment tool  37  need not be provided. 
     (5) In the embodiments described above, an example in which the lower support portion  33  is provided on the washer portion  34  is given, but the lower support portion  33  need not be provided on the washer portion  34  and may be provided directly on the support column  31 . 
     INDUSTRIAL APPLICABILITY 
     One or more embodiments of the present invention can be applied to a tractor provided with an engine bonnet forming an engine compartment. 
     Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.