JP2016080047A - Work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a connection structure of various operation tools and each corresponding transmission gear mechanism simple with less failure.SOLUTION: An auxiliary transmission fork shaft 682 and a creep fork shaft 672 are arranged in a transmission case in a parallel manner. At the auxiliary transmission fork shaft 682, an auxiliary transmission fork 683 is provided, and at the creep fork shaft 672, a creep fork 673 is provided. When moving one fork shaft 672 (682) in the longitudinal direction by an operation of one operation tool, the fork shafts 672, 682 are pivotally supported by their own forks 673, 683 respectively so that the other fork shaft 682 (672) guides the one fork 673 (683) on the operation shaft 672 (682) side in the longitudinal direction.SELECTED DRAWING: Figure 24

Description

  For example, the present invention relates to a work vehicle such as a farm work machine such as a tractor and a special work machine such as a crane truck.

  Conventionally, in work vehicles such as tractors and wheel loaders, an engine is mounted on the front part of the body frame, a transmission case is connected to the rear part of the body frame, and the traveling body is supported by the front and rear traveling units. The transmission case incorporates, for example, a traveling transmission gear mechanism, a differential gear mechanism, a PTO transmission gear mechanism, and the like. The power of the front engine is transmitted to the rear transmission case, and is transmitted from the differential gear mechanism in the transmission case to at least the left and right rear traveling units. Power is also transmitted from the PTO transmission gear mechanism in the transmission case to a working unit such as a rotary tiller (see, for example, Patent Document 1).

JP 2010-52734 A

  By the way, in this type of work vehicle, various operation tools arranged in the control unit and the corresponding transmission gear mechanisms are electrically linked or mechanically linked. In the structure in which the operation tool and the transmission gear mechanism are electrically interlocked and connected, electronic devices such as electric actuators are required. However, the electronic devices are easily affected by mud and the like, and a work vehicle is used for farm work or the like. In such a case, the electronic devices are likely to suffer from malfunction and failure due to the mud, and there is room for examination in terms of improving reliability. On the other hand, in the structure in which the operation tool and the transmission gear mechanism are mechanically interlocked and connected, there is less failure than the above-described electrical connection structure, but the structure is likely to be complicated and the component cost may increase.

  This invention makes it a technical subject to provide the working vehicle which examined and improved the above present condition.

  According to a first aspect of the present invention, there is provided a work vehicle including an engine mounted on a traveling machine body and a transmission case that shifts the power of the engine, and a hydraulic continuously variable gear that continuously changes the power of the engine in the transmission case. A transmission, a sub-transmission gear mechanism that shifts the transmission power via the hydraulic continuously variable transmission to a plurality of stages, a creep transmission gear mechanism that shifts the transmission power via the hydraulic continuously variable transmission to an ultra-low speed, and a sub-transmission A sub-transmission operating tool for shifting the sub-transmission gear mechanism via a fork shaft; and a creep transmission operating tool for shifting the creep transmission gear mechanism via a creep fork shaft; A creep fork shaft is arranged in parallel in the transmission case, the auxiliary transmission fork shaft is provided with an auxiliary transmission fork, and the creep fork shaft is provided on the creep fork shaft. A leap fork is provided, and when one fork shaft is moved in the longitudinal direction by operating one operating tool, the other fork shaft guides the fork on the one fork shaft side in the longitudinal direction. The fork shaft is pivotally supported on the mutual forks.

  According to a second aspect of the present invention, the work vehicle according to the first aspect further includes a shift check member that prohibits both the high speed side operation of the auxiliary transmission operation tool and the operation of entering the creep transmission operation tool. It is.

  According to a third aspect of the present invention, in the work vehicle according to the first or second aspect, the mission case is divided into three parts of a front case, an intermediate case, and a rear case, and the intermediate case and the rear case The front case is made of aluminum die cast, and the hydraulic continuously variable transmission, the auxiliary transmission gear mechanism, and the creep transmission gear mechanism are located in the front case. It is.

  According to the present invention, in a work vehicle including an engine mounted on a traveling machine body and a transmission case that changes the power of the engine, a hydraulic continuously variable transmission that continuously changes the power of the engine in the transmission case. A sub-transmission gear mechanism for shifting the transmission power via the hydraulic continuously variable transmission to a plurality of stages, a creep transmission gear mechanism for shifting the transmission power via the hydraulic continuously variable transmission to an ultra-low speed, and a sub-transmission fork shaft A sub-transmission operating tool for shifting the sub-transmission gear mechanism via a creep, and a creep transmission operating tool for shifting the creep transmission gear mechanism via a creep fork shaft, the sub-transmission fork shaft and the creep fork The auxiliary fork shaft is provided with an auxiliary transmission fork, and the creep fork shaft is provided with a shaft. When a leap fork is provided and one fork shaft is moved in the longitudinal direction by operation of one operating tool, the other fork shaft guides the fork on the one operating shaft side in the longitudinal direction. Since the fork shafts are pivotally supported by the mutual forks, the structure for supporting both the forks so that they can be operated can be simplified and configured compactly, and the auxiliary transmission gear mechanism and the auxiliary transmission operating tool are mechanically connected. The structure for interlocking connection and the structure for mechanically interlocking the creep transmission gear mechanism and the creep transmission operation tool can be arranged in a space-saving manner in the mission case, and the number of parts can be reduced to reduce the part cost. Can be suppressed.

  According to the second aspect of the present invention, since the shift check member for prohibiting both the high-speed side operation of the sub-shift operation tool and the operation of entering the creep shift operation tool is provided, the sub-transmission gear mechanism and the creep shift mechanism are provided. A combination of unnecessary shifts with the gear mechanism can be accurately excluded, and the possibility of damage such as gear tooth spilling can be avoided.

  According to the invention of claim 3, the transmission case is divided into three parts of a front case, an intermediate case and a rear case, and the intermediate case and the rear case are made of cast iron, while the front case Since the hydraulic continuously variable transmission, the auxiliary transmission gear mechanism, and the creep transmission gear mechanism are positioned in the front case, the hydraulic pressure is applied to the lighter front case side. By arranging the continuously variable transmission, the auxiliary transmission gear mechanism, and the creep transmission gear mechanism, the mission case can be well balanced.

It is a left view of a tractor. It is a right view of a tractor. It is a top view of a tractor. It is left side explanatory drawing of a traveling body. It is right side explanatory drawing of a traveling body. It is a top view of a traveling body. It is the perspective view which looked at the traveling body from the left rear. It is the perspective view which looked at the traveling body from the right rear. It is the expansion perspective view which looked at the traveling body from the left side. It is the expansion perspective view which looked at the traveling body from the right side. It is the perspective view which looked at the traveling body from the left front. It is the perspective view which looked at the traveling body from the right side. It is a skeleton figure of the power transmission system of a tractor. It is a hydraulic circuit diagram of a tractor. It is left side explanatory drawing which shows the internal structure of a mission case. It is plane explanatory drawing which shows the internal structure of a mission case. It is a perspective explanatory view showing the internal structure of a mission case. It is left side sectional drawing of a mission case front part. It is a left side sectional view of a mission case middle part. It is left side surface sectional drawing of a mission case rear part. It is back surface explanatory drawing of a mission case. It is the perspective view which looked at the structure around the control seat from the left front. It is left side explanatory drawing which shows the relationship between various levers and a mission case. It is a schematic perspective view which shows the switching action | operation structure of a driving subtransmission gear mechanism and a creep transmission gear mechanism. It is a schematic perspective view explaining a gear shift check member.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings for a farm tractor. As shown in FIGS. 1 to 8, the traveling machine body 2 of the tractor 1 is supported by a pair of left and right rear wheels 4 as well as a pair of left and right front wheels 3 as a traveling unit. The pair of left and right rear wheels 4 corresponds to the rear traveling unit. A diesel engine 5 (hereinafter simply referred to as an engine) is mounted on the front portion of the traveling machine body 2, and the tractor 1 is configured to travel forward and backward by driving the rear wheel 4 or the front wheel 3 with the engine 5. . The engine 5 is covered with a bonnet 6. A cabin 7 as a control unit is installed on the upper surface of the traveling machine body 2. Inside the cabin 7, a steering seat 8 and a steering handle 9 for steering the front wheel 3 are arranged. Steps 10 on which the operator gets on and off are provided on the left and right outer sides of the cabin 7. A fuel tank 11 for supplying fuel to the engine 5 is provided below the bottom of the cabin 7.

  The traveling machine body 2 includes an engine frame 14 having a front bumper 12 and a front axle case 13, and left and right machine body frames 15 detachably fixed to a rear portion of the engine frame 14. A front axle 16 is rotatably protruded outward from the left and right ends of the front axle case 13. The front wheels 3 are attached to the left and right ends of the front axle case 13 via the front axle 16. A transmission case 17 is connected to the rear part of the body frame 15 for appropriately changing the rotational power from the engine 5 and transmitting it to the front and rear four wheels 3, 3, 4, 4. A tank frame 18 having a rectangular frame plate shape in a bottom view projecting outward in the left and right directions is bolted to the lower surface sides of the left and right body frames 15 and the mission case 17. The fuel tank 11 of the embodiment is divided into left and right two parts. The left and right fuel tanks 11 are distributed and mounted on the upper surface side of the left and right projecting portions of the tank frame 18. Left and right rear axle cases 19 are mounted on the left and right outer surfaces of the mission case 17 so as to protrude outward. Left and right rear axle cases 20 are rotatably inserted in the left and right rear axle cases 19. The rear wheel 4 is attached to the mission case 17 via the rear axle 20. Upper portions of the left and right rear wheels 4 are covered with left and right rear fenders 21.

  A hydraulic lifting mechanism 22 that lifts and lowers a ground working machine (not shown) such as a rotary tiller is detachably attached to the rear part of the mission case 17. The ground work machine is connected to the rear portion of the transmission case 17 via a three-point link mechanism 111 including a pair of left and right lower links 23 and a top link 24. On the rear side surface of the mission case 17, a PTO shaft 25 for transmitting a PTO driving force to a working machine such as a rotary tiller is provided to project rearward.

  A flywheel 26 (see FIGS. 4 to 6, 10, and 11) is directly attached to an output shaft (piston rod) of the engine 5 that projects rearward from the rear side surface of the engine 5. A main shaft 27 projecting rearward from the flywheel 26 and a main transmission input shaft 28 projecting forward from the front side of the transmission case 17 are connected via a power transmission shaft 29 having universal shaft joints at both ends. 4 to 6). In the mission case 17, a hydraulic continuously variable transmission 500, a forward / reverse switching mechanism 501, a traveling transmission gear mechanism, a rear wheel differential gear mechanism 506, and the like are arranged. The rotational power of the engine 5 is transmitted to the main transmission input shaft 28 of the transmission case 17 via the main driving shaft 27 and the power transmission shaft 29, and is appropriately shifted by the hydraulic continuously variable transmission 500 and the traveling transmission gear mechanism. The power is transmitted to the left and right rear wheels 4 via the rear wheel differential gear mechanism 506.

  The front wheel output shaft 30 projecting forward from the front lower part of the transmission case 17 is transmitted to the front wheel projecting rearward from the front axle case 13 containing the front wheel differential gear mechanism 507 via the front wheel drive shaft 31. The shaft 508 is connected. Transmission power by the hydraulic continuously variable transmission 500 and the traveling transmission gear mechanism in the transmission case 17 is transmitted from the front wheel output shaft 30, the front wheel drive shaft 31, and the front wheel transmission shaft 508 to the front wheel differential gear in the front axle case 13. It is configured to be transmitted to the left and right front wheels 3 via a mechanism 507.

  Next, the internal structure of the cabin 7 will be described with reference to FIGS. 3, 7 and 8. A steering column 32 is disposed in front of the control seat 8 in the cabin 7. The steering column 32 is erected in a state of being embedded in the back side of the dashboard 33 disposed on the front side inside the cabin 7. A steering handle 9 having a substantially round shape in plan view is attached to the upper end side of the handle shaft that protrudes upward from the upper surface of the steering column 32.

  On the right side of the steering column 32, a pair of left and right brake pedals 35 for braking the traveling machine body 2 are disposed. On the left side of the steering column 32, a forward / reverse switching lever 36 (reverser lever) for switching the traveling direction of the traveling machine body 2 between forward and reverse and a power transmission clutch (not shown) are disconnected. A clutch pedal 37 is provided.

  An erroneous operation preventing body 38 (reverser guard) extending along the forward / reverse switching lever 36 is disposed on the left side of the steering column 32 and below the forward / reverse switching lever 36. By disposing an erroneous operation prevention body 38 as a contact preventer below the forward / reverse switching lever 36, the operator is prevented from inadvertently contacting the forward / reverse switching lever 36 when getting on and off the tractor 1. An operation display panel 39 incorporating a liquid crystal panel is provided on the upper rear side of the dashboard 33.

  An accelerator pedal 41 for controlling the rotational speed of the engine 5 or the vehicle speed is arranged on the right side of the steering column 32 on the floor plate 40 in front of the control seat 8 in the cabin 7. Note that substantially the entire top surface of the floor plate 40 is formed as a flat surface. Side columns 42 are arranged on both the left and right sides of the control seat 8. Between the control seat 8 and the left side column 42, the parking brake lever 43 for executing the operation of maintaining the left and right rear wheels 4 in a braking state and the traveling speed (vehicle speed) of the tractor 1 are forcibly greatly increased. An ultra-low speed lever 44 (creep lever) to be reduced, a sub-shift lever 45 for switching the output range of the traveling sub-transmission gear mechanism 503 in the transmission case 17, and a PTO for switching the driving speed of the PTO shaft 25. A shift lever 46 is arranged. A differential lock pedal 47 for turning on / off the differential drive of the left and right rear wheels 4 is disposed below the control seat 8. A sub-PTO lever 48 for performing an operation for driving the PTO shaft 25 in synchronization with the vehicle speed or an operation for driving it in the reverse direction is disposed on the left rear side of the control seat 8.

  Between the control seat 8 and the right side column 42, an armrest 49 for placing an arm or elbow of an operator seated on the control seat 8 is provided. The armrest 49 is configured separately from the control seat 8 and has a main transmission lever 50 that increases and decreases the traveling speed of the tractor 1 and a dial type that manually changes and adjusts the height position of a ground working machine such as a rotary tiller. Working part position dial 51 (elevating dial). In addition, the armrest 49 is configured to be able to be turned up and rotated in a plurality of stages with the rear end lower part as a fulcrum.

  In the right side column 42, in order from the front side, a throttle lever 52 that sets and holds the rotational speed of the engine 5, and a PTO clutch switch 53 that interrupts power transmission from the PTO shaft 25 to a work machine such as a rotary tiller A plurality of hydraulic operation levers 54 (SCV levers) for switching the hydraulic external take-off valve 430 (see FIG. 14) arranged on the upper surface side of the mission case 17 are arranged. Here, the hydraulic external take-off valve 430 is for controlling supply of hydraulic oil to hydraulic equipment of another work machine such as a front loader retrofitted to the tractor 1. In the embodiment, four hydraulic operation levers 54 are arranged in accordance with the number of hydraulic external take-out valves (four stations).

  Furthermore, as shown in FIGS. 9 to 12, left and right front support bases 96 that support the front side of the cabin 7 and left and right rear support bases 97 that support the rear part of the cabin 7 are provided. The front support 96 is bolted to the front and rear intermediate portions of the outer side surfaces of the left and right aircraft frames 15, and the front bottom of the cabin 7 is anti-vibrated on the upper surface of the front support 96 via the anti-vibration rubber body 98. The rear support base 97 is bolted to the middle portion of the left and right widths of the upper surfaces of the left and right rear axle cases 19 that are horizontally extended in the left-right direction, and the vibration-proof rubber body 99 is attached to the upper surface side of the rear support base 97. The rear bottom portion of the cabin 7 is supported by vibration isolation. Further, as shown in FIGS. 4 and 5, etc., the rear support base 97 is disposed on the upper surface side of the rear axle case 19, and the steady bracket 101 is disposed on the lower surface side of the rear axle case 19. The fastening bracket 101 is fastened with bolts, and both ends of the steady rod body 103 with turnbuckles that can be expanded and contracted are connected to the middle portion of the lower link 23 and the steady bracket 101 that extend in the front-rear direction. The horizontal vibration of 23 is prevented.

  Next, the diesel engine 5 and the engine room structure under the hood 6 will be described with reference to FIGS. The diesel engine 5 has a cylinder head mounted on a cylinder block having a built-in engine output shaft and piston, and is connected to an air cleaner 221 via a turbocharger 211 on the right side surface of the diesel engine 5 (cylinder head). And an EGR device 210 that recirculates a part of the exhaust gas from the exhaust manifold 204, and a part of the exhaust gas discharged to the exhaust manifold 204 is returned to the intake manifold 203. The maximum combustion temperature during high-load operation is lowered, and NOx (nitrogen oxide) emissions from the diesel engine 5 are reduced. On the other hand, the exhaust manifold 204 connected to the tail pipe 229 and the turbocharger 211 are arranged on the left side surface of the diesel engine 5 (cylinder head). That is, the intake manifold 203 and the exhaust manifold 204 are distributed and arranged on the left and right side surfaces along the engine output shaft in the engine 5. A cooling fan 206 is disposed on the front side of the diesel engine 5 (cylinder block).

  In addition, as shown in FIGS. 4 to 8 and the like, the diesel engine 5 includes a continuously regenerative exhaust gas purifying device 224 (DPF) disposed on the upper surface side of the diesel engine 5 (above the exhaust manifold 204). A tail pipe 229 is connected to the exhaust side of the purification device 224. The exhaust gas purifying device 224 removes particulate matter (PM) in the exhaust gas discharged from the engine 5 through the tail pipe 229 to the outside of the machine, and at the same time, carbon monoxide (CO) and carbonization in the exhaust gas. Hydrogen (HC) is configured to be reduced.

  Furthermore, as shown in FIGS. 1 to 3 and the like, the bonnet 6 has a front grill 231 at the front lower side, and covers the upper surface side and the front surface side of the engine room 200. Side engine covers 232 formed of a perforated plate are arranged on the lower left and right sides of the bonnet 6 to cover the left and right sides of the engine room 200. That is, the hood 6 and the engine cover 232 cover the front, upper, and left and right sides of the diesel engine 5.

  Further, as shown in FIGS. 4 to 8, a radiator 235 having a fan shroud 234 attached to the back side is erected on the engine frame 14 so as to be positioned on the front side of the engine 5. The fan shroud 234 surrounds the outer peripheral side of the cooling fan 206 and allows the radiator 235 and the cooling fan 206 to communicate with each other. An air cleaner 221 is disposed above the front surface of the radiator 235. In addition to the above intercooler, an oil cooler, a fuel cooler, and the like are installed on the front side of the radiator 235.

  On the other hand, as shown in FIGS. 9 to 12 and the like, the pair of left and right body frames 15 are connected by a support beam frame 236. The supporting beam frame 236 is bolted to the left and right airframe frames 15 and is installed on the front end portions (rear side of the engine 5) of the left and right airframe frames 15 via the engine legs having vibration-proof rubber. The rear part of the diesel engine 5 is connected to the upper surface of the support beam frame 236. 1, 2, 4, 5, 11, and 12, left and right front engine legs 238 having anti-vibration rubber are provided in the middle of the pair of left and right engine frames 14. The left and right side surfaces of the front part of the diesel engine 5 are connected. That is, the front side of the diesel engine 5 is supported on the engine frame 14 by vibration isolation, and the rear part of the diesel engine 5 is supported on the front end sides of the pair of left and right body frames 15 via the support beam frame 236.

  Next, with reference to FIGS. 4-12, the attachment structure of the mission case 17, the hydraulic lifting mechanism 22, and the three-point link mechanism 111 will be described. The transmission case 17 includes a front transmission case 112 having a main transmission input shaft 28 and the like, a rear transmission case 113 having a rear axle case 19 and the like, and a front side of the rear transmission case 113 on the rear side of the front transmission case 112. An intermediate case 114 to be connected is provided. The rear end portions of the left and right machine body frames 15 are connected to the left and right side surfaces of the intermediate case 114 via the left and right upper and lower machine body connecting shafts 115 and 116. That is, the rear end portions of the left and right airframe frames 15 are connected to the left and right side surfaces of the intermediate case 114 by the two upper airframe connecting shaft bodies 115 and the two lower airframe connecting shaft bodies 116. The transmission case 17 is integrally connected to form the rear part of the traveling machine body 2, and the front transmission case 112 or the power transmission shaft 29 is disposed between the left and right machine body frames 15, so that the front transmission case is provided. 112 and the like are protected. The left and right rear axle cases 19 are attached to the left and right sides of the rear transmission case 113 so as to protrude outward. In the embodiment, the intermediate case 114 and the rear transmission case 113 are made of cast iron, while the front transmission case 112 is made of aluminum die cast.

  According to the above configuration, since the transmission case 17 is divided into the three parts of the front transmission case 112, the intermediate case 114, and the rear case 113, parts such as shafts and gears are provided in each case 112-114. After being assembled in advance, the front transmission case 112, the intermediate case 114, and the rear transmission case 113 can be assembled. Therefore, the assembly of the mission case 17 can be performed accurately and efficiently.

  Also, left and right rear axle cases 19 are attached to the left and right sides of the rear transmission case 113, and an intermediate case 114 that connects the front transmission case 112 and the rear transmission case 113 is connected to the left and right body frames 15 constituting the traveling vehicle body 2. Therefore, for example, it is possible to remove the front transmission case 112 while the intermediate case 114 and the rear transmission case 113 are attached to the machine body frame 15 and perform operations such as shaft and gear exchange. Therefore, the frequency of dropping (removing) the entire mission case 17 from the tractor 1 can be remarkably lowered, and the workability during maintenance and repair can be improved.

  Further, while the intermediate case 114 and the rear transmission case 113 are made of cast iron, and the front transmission case 112 is made of aluminum die cast, the intermediate case 114 connected to the body frame 15 and the left and right rear axle cases 19 are made. The rear transmission case 113 to which the two are connected can be configured with high rigidity as a strength member constituting the traveling machine body 2. In addition, the front transmission case 112 that is not a strength member can be reduced in weight. Therefore, it is possible to reduce the weight of the transmission case 17 as a whole while sufficiently securing the rigidity of the traveling machine body 2.

  As shown in FIGS. 4 to 12, the hydraulic lifting mechanism 22 includes left and right hydraulic lift cylinders 117 that are controlled by operation of the working unit position dial 51 and the like, and the upper surface of the rear transmission case 113 of the transmission case 17. The left and right lift arms 120 are connected to the left and right lower links 23, and the left and right lift arms 120 are pivotally supported via a lift fulcrum shaft 119 on an openable and closable upper surface lid 118. Left and right lift rods 121 are provided. A part of the right lift rod 121 is formed by a horizontal cylinder 122 for hydraulic control, and the length of the right lift rod 121 is configured to be adjustable by the horizontal cylinder 122.

  7, 8, 10, etc., the top link hinge 123 is fixed to the back side of the top cover 118, and the top link 24 is connected to the top link hinge 123 via a hinge pin. When the ground work machine is supported by the top link 24 and the left and right lower links 23, the piston of the horizontal cylinder 122 is expanded and contracted to change the length of the right lift rod 121. The angle is configured to change.

  Next, the internal structure of the mission case 17 and the power transmission system of the tractor 1 will be described with reference to FIG. 13 and FIGS. The transmission case 17 includes a front transmission case 112 having a main transmission input shaft 28 and the like, a rear transmission case 113 having a rear axle case 19 and the like, and a front side of the rear transmission case 113 connected to the rear side of the front transmission case 112. An intermediate case 114 is provided. The mission case 17 is formed in a hollow box shape as a whole.

  A front lid member 491 is disposed on the front surface of the mission case 17, that is, on the front surface of the front transmission case 112. The front lid member 491 is detachably fastened to the front surface of the front transmission case 112 with a plurality of bolts. A rear cover member 492 is disposed on the rear surface of the transmission case 17, that is, on the rear surface of the rear transmission case 113. The rear lid member 492 is detachably fastened to the rear surface of the rear transmission case 113 with a plurality of bolts. An intermediate partition wall 493 that partitions the front transmission case 112 and the intermediate case 114 is integrally formed on the front side in the intermediate case 114. A rear partition wall 494 that partitions the inside of the rear transmission case 113 forward and backward is integrally formed in the middle part of the rear transmission case 113.

  Therefore, the inside of the mission case 17 is divided into three chambers, a front chamber 495, a rear chamber 496, and an intermediate chamber 497, by the middle and rear partition walls 493 and 494. A space between the front lid member 491 and the intermediate partition wall 493 in the transmission case 17 (inside the front transmission case 112) is a front chamber 495. A rear chamber 496 is formed between the rear lid member 492 and the rear partition wall 494 (inside the rear side of the rear transmission case 113). A space between the intermediate partition wall 493 and the rear partition wall 494 (inside the intermediate case 114 and the front side of the rear transmission case 113) is an intermediate chamber 497. The front chamber 495, the intermediate chamber 497, and the rear chamber 496 communicate with each other by cutting out part of the partition walls 493 and 494 so that the hydraulic oil (lubricating oil) in the chambers 495 to 497 can move to each other. doing.

  In the front chamber 495 (in the front transmission case 112) of the transmission case 17, a mechanical creep transmission gear mechanism 502 that shifts rotational power via the hydraulic continuously variable transmission 500 and a forward / reverse switching mechanism 501 described later. In addition, a traveling auxiliary transmission gear mechanism 503 and a two-wheel drive / four-wheel drive switching mechanism 504 for switching between the two-wheel drive and the four-wheel drive of the front and rear wheels 3, 4 are arranged. A forward / reverse switching mechanism 501 is provided in the intermediate chamber 497 of the mission case 17 (inside the intermediate case 114 and the front of the rear transmission case 113) to switch the rotational power from the hydraulic continuously variable transmission 500 in the forward or reverse direction. ing. In the rear chamber 496 of the transmission case 17 (inside the rear side of the rear transmission case 113), a PTO transmission mechanism 505 for appropriately changing the rotational power from the engine 5 and transmitting it to the PTO shaft 25, and a creep transmission gear mechanism 502 or A rear wheel differential gear mechanism 506 that transmits rotational power via the traveling auxiliary transmission gear mechanism 503 to the left and right rear wheels 4 is disposed. The creep transmission gear mechanism 502 and the traveling auxiliary transmission gear mechanism 503 correspond to a traveling transmission gear mechanism that multi-shifts the transmission output via the forward / reverse switching mechanism 501. A work case hydraulic pump 481 that is driven by the rotational power of the engine 5 and a pump case 480 that houses the traveling hydraulic pump 482 are attached to the front portion of the rear outer case 113.

  As shown in FIGS. 4 to 6, a flywheel 26 is directly connected to the output shaft of the engine 5 projecting rearward from the rear side surface of the engine 5. A main transmission input shaft 28 projecting forward from the front side (front cover member 491) of the transmission case 17 is connected to a main driving shaft 27 projecting rearward from the flywheel 26 via a power transmission shaft 29 having universal joints at both ends. It is connected. The rotational power of the engine 5 is transmitted to the main transmission input shaft 28 of the transmission case 17 (front transmission case 112) via the main driving shaft 27 and the power transmission shaft 29, and the hydraulic continuously variable transmission 500 and the creep transmission gear mechanism. After being appropriately shifted by 502 or the traveling auxiliary transmission gear mechanism 503, it is transmitted to the rear wheel differential gear mechanism 506 to drive the left and right rear wheels 4. Shift power via the creep transmission gear mechanism 502 or the traveling auxiliary transmission gear mechanism 503 is transmitted from the two-wheel drive and four-wheel drive switching mechanism 504 to the front axle via the front wheel output shaft 30, the front wheel drive shaft 31, and the front wheel transmission shaft 508. This is transmitted to the front wheel differential gear mechanism 507 in the case 13 to drive the left and right front wheels 3.

  The main transmission input shaft 28 protruding forward from the front lid member 491 extends in the front-rear direction from the front transmission case 112 to the intermediate case 114 (from the front chamber 495 to the intermediate chamber 497). A midway portion before and after the main transmission input shaft 28 is rotatably supported by the intermediate partition wall 493. The rear end side of the main transmission input shaft 28 is rotatably supported by an intermediate auxiliary plate 498 that is detachably fastened to the front surface side (intermediate chamber 497 side) of the rear partition wall 494. The intermediate auxiliary plate 498 and the rear partition wall 494 are arranged so that a gap in the front-rear direction is left between the two plates 498 and 494. From the front transmission case 112 to the intermediate case 114 (from the front chamber 495 to the intermediate chamber 497), an input transmission shaft 511 for transmitting power from the main transmission input shaft 28 is arranged in parallel with the main transmission input shaft 28. . In the front transmission case 112 (in the front chamber 495), a hydraulic continuously variable transmission 500 is disposed via an input transmission shaft 511. The front side of the hydraulic continuously variable transmission 500 is attached to the inner surface side of the front lid member 491 that detachably closes the front opening of the front transmission case 112. The rear end side of the input transmission shaft 511 is rotatably supported by the intermediate auxiliary plate 498 and the rear partition wall 494.

  The hydraulic continuously variable transmission 500 in the front chamber 495 is an inline type in which a main transmission output shaft 512 is concentrically disposed on an input transmission shaft 511. A cylindrical main transmission output shaft 512 is fitted in a portion of the input transmission shaft 511 in the intermediate chamber 497. The front end side of the main transmission output shaft 512 passes through the intermediate partition wall 493 and is rotatably supported on the intermediate partition wall 493. The rear end side of the main transmission output shaft 512 is rotatably supported by the intermediate auxiliary plate 498. Therefore, the rear end side that is the input side of the input transmission shaft 511 protrudes rearward from the rear end of the main transmission output shaft 512. A main transmission input gear 513 is fitted on the rear end side of the main transmission input shaft 28 (between the intermediate auxiliary plate 498 and the rear partition wall 494) so as not to be relatively rotatable. An input transmission gear 514 that always meshes with the main transmission input gear 513 is fixed to the rear end side of the input transmission shaft 511 (between the intermediate auxiliary plate 498 and the rear partition wall 494). Accordingly, the rotational power of the main transmission input shaft 28 is transmitted to the hydraulic continuously variable transmission 500 via the main transmission input gear 513, the input transmission gear 514, and the input transmission shaft 511. A main transmission high-speed gear 516, a main transmission reverse gear 517, and a main transmission low-speed gear 515 are fitted on the main transmission output shaft 512 so as not to rotate relative to each other for traveling output.

  The hydraulic continuously variable transmission 500 includes a variable displacement hydraulic pump unit 521 and a constant displacement hydraulic motor unit 522 that is operated by high-pressure hydraulic oil discharged from the hydraulic pump unit 521. The hydraulic pump unit 521 is provided with a pump swash plate 523 that can change the inclination angle with respect to the axis of the input transmission shaft 511 and adjust the amount of hydraulic oil supplied. A main transmission hydraulic cylinder 524 that changes and adjusts the inclination angle of the pump swash plate 523 with respect to the axis of the input transmission shaft 511 is linked to the pump swash plate 523. In the embodiment, the main transmission hydraulic cylinder 524 is assembled to the hydraulic continuously variable transmission 500 and unitized as one member. By changing the inclination angle of the pump swash plate 523 by driving the main transmission hydraulic cylinder 524, the amount of hydraulic oil supplied from the hydraulic pump unit 521 to the hydraulic motor unit 522 is changed and adjusted, and the main variable speed transmission 500 of the hydraulic continuously variable transmission 500 is changed. A speed change operation is performed.

  That is, when the main transmission hydraulic cylinder 524 is driven in proportion to the operation amount of the main transmission lever 50, the inclination angle of the pump swash plate 523 with respect to the axis of the input transmission shaft 511 is changed accordingly. The pump swash plate 523 of the embodiment adjusts the angle in a range between one (positive) maximum inclination angle and the other (negative) maximum inclination angle with a neutral angle of substantially zero inclination (before and after including zero) interposed therebetween. It is possible to set an angle that is inclined to one of the two times when the vehicle speed of the traveling machine body 2 is the lowest (in this case, an inclination angle that is negative and near the maximum).

  When the inclination angle of the pump swash plate 523 is substantially zero (neutral angle), the hydraulic motor unit 522 is not driven by the hydraulic pump unit 521, and the main transmission output shaft 512 rotates at substantially the same rotational speed as the input transmission shaft 511. To do. When the pump swash plate 523 is tilted in one direction (positive tilt angle) with respect to the axis of the input transmission shaft 511, the hydraulic pump unit 521 activates the hydraulic motor unit 522 at a higher speed than the input transmission shaft 511. The main transmission output shaft 512 rotates at a high rotational speed. For this reason, the rotational speed of the hydraulic motor unit 522 is added to the rotational speed of the input transmission shaft 511 and transmitted to the main transmission output shaft 512. As a result, the shift power (vehicle speed) from the main shift output shaft 512 is changed in proportion to the tilt angle (positive tilt angle) of the pump swash plate 523 within a range of rotation speed higher than the rotation speed of the input transmission shaft 511. Is done. When the pump swash plate 523 is positive and has an inclination angle near the maximum, the traveling machine body 2 reaches the maximum vehicle speed.

  When the pump swash plate 523 is tilted in the other direction (negative tilt angle) with respect to the axis of the input transmission shaft 511, the hydraulic pump unit 521 decelerates (reverses) the hydraulic motor unit 522, and the input transmission shaft The main transmission output shaft 512 rotates at a rotational speed lower than 511. For this reason, the rotational speed of the hydraulic motor unit 522 is subtracted from the rotational speed of the input transmission shaft 511 and transmitted to the main transmission output shaft 512. As a result, the speed change power from the main speed change output shaft 512 is changed in proportion to the inclination angle (negative inclination angle) of the pump swash plate 523 within the range of the rotation speed lower than the rotation speed of the input transmission shaft 511. When the pump swash plate 523 is negative and has an inclination angle near the maximum, the traveling machine body 2 has the minimum vehicle speed.

  A pump drive gear 484 is fitted on the pump drive shaft 483 that drives both the working machine and traveling hydraulic pumps 481 and 482 so as not to be relatively rotatable. The pump drive gear 484 connects the main transmission input gear 513 of the main transmission input shaft 28 via a flat gear mechanism 485 so that power can be transmitted. A lubricating oil pump 518 is provided between the intermediate auxiliary plate 498 and the rear partition wall 494 to supply hydraulic oil for lubrication to the hydraulic continuously variable transmission 500, the forward / reverse switching mechanism 501 and the like. The pump gear 520 fixed to the pump shaft 519 of the lubricating oil pump 518 is always meshed with the input transmission gear 514 of the input transmission shaft 511. Therefore, the working machine and traveling hydraulic pumps 481 and 482 and the lubricating oil pump 518 are driven by the rotational power of the engine 5.

  Next, a forward / backward switching structure executed via the forward / reverse switching mechanism 501 will be described. A planetary gear mechanism 526, which is a forward high-speed gear mechanism, and a low-speed gear pair 525, which is a forward low-speed gear mechanism, are disposed at a location in the intermediate chamber 497 of the main transmission input shaft 28 (on the rear side of the main transmission input shaft 28). doing. The planetary gear mechanism 526 includes a sun gear 531 that rotates integrally with an input-side transmission gear 529 that is rotatably supported on the main transmission input shaft 28, and a carrier 532 that rotatably supports a plurality of planetary gears 533 on the same radius. And a ring gear 534 having inner teeth on the inner peripheral surface. The sun gear 531 and the ring gear 534 are rotatably fitted on the main transmission input shaft 28. The carrier 532 is fitted to the main transmission input shaft 28 so as not to be relatively rotatable. The sun gear 531 meshes with each planetary gear 533 of the carrier 532 from the inside of the radius. Further, the inner teeth of the ring gear 534 mesh with the planetary gears 533 from the radially outer side. An output side transmission gear 530 that rotates integrally with the ring gear 534 is also rotatably supported on the main transmission input shaft 28. The input-side low-speed gear 527 and the output-side low-speed gear 528 constituting the low-speed gear pair 525 have an integral structure, and can rotate between the planetary gear mechanism 526 and the main transmission input gear 513 of the main transmission input shaft 28. It is pivotally supported.

  In the intermediate chamber 497 of the transmission case 17 (inside the intermediate case 114 and the front side of the rear transmission case 113), the main transmission input shaft 28, the input transmission shaft 511, the travel relay shaft 535 extending in parallel with the main transmission output shaft 512, and A travel transmission shaft 536 is disposed. The front end side of the travel relay shaft 535 is rotatably supported by the intermediate partition wall 493. A rear end side of the travel relay shaft 535 is rotatably supported on the intermediate auxiliary plate 498. The front end side of the traveling transmission shaft 536 is rotatably supported by the intermediate partition wall 493. The rear end side of the travel transmission shaft 536 is rotatably supported by the intermediate auxiliary plate 498.

  A forward / reverse switching mechanism 501 is provided on the travel relay shaft 535. That is, the traveling relay shaft 535 has a forward high-speed gear 540 coupled by a wet multi-plate forward high-speed hydraulic clutch 539, a reverse gear 542 coupled by a wet multi-plate reverse hydraulic clutch 541, and a wet multi-plate. A forward low-speed gear 538 connected by a forward low-speed hydraulic clutch 537 of the mold is fitted. A travel relay gear 543 is fitted between the forward high speed hydraulic clutch 539 and the reverse gear 542 in the travel relay shaft 535 so as not to be relatively rotatable. A travel transmission gear 544 that always meshes with the travel relay gear 543 is fitted to the travel transmission shaft 536 so as not to be relatively rotatable. The main transmission low speed gear 515 of the main transmission output shaft 512 is always meshed with the input low speed gear 527 of the low speed gear pair 525 on the main transmission input shaft 28 side, and the output low speed gear 528 is always meshed with the forward low speed gear 538. The main transmission high speed gear 516 of the main transmission output shaft 512 is always meshed with the input transmission gear 529 of the planetary gear mechanism 526 on the main transmission input shaft 28 side, and the output transmission gear 530 is always meshed with the forward high speed gear 540. A main transmission reverse gear 517 of the main transmission output shaft 512 is always meshed with the reverse gear 542.

  When the forward / reverse switching lever 36 is operated to the forward side, the forward low-speed hydraulic clutch 537 or the forward high-speed hydraulic clutch 539 is in a power connection state, and the forward low-speed gear 538 or forward high-speed gear 540 and the travel relay shaft 535 are connected to each other so as not to be relatively rotatable. Is done. As a result, forward low-speed or high-speed rotational power is transmitted from the main transmission output shaft 512 to the travel relay shaft 535 via the low-speed gear pair 525 or the planetary gear mechanism 526, and power is transmitted from the travel relay shaft 535 to the travel transmission shaft 536. Communicated. When the forward / reverse switching lever 36 is operated to the reverse side, the reverse hydraulic clutch 541 enters a power connection state, and the reverse gear 542 and the travel relay shaft 535 are coupled so as not to be relatively rotatable. As a result, the reverse rotational power is transmitted from the main transmission output shaft 512 to the travel relay shaft 535 via the low speed gear pair 525 or the planetary gear mechanism 526, and the power is transmitted from the travel relay shaft 535 to the travel transmission shaft 536.

  Note that which of the forward low-speed hydraulic clutch 537 and the forward high-speed hydraulic clutch 539 is in the power connection state by the forward operation of the forward / reverse switching lever 36 is determined according to the operation amount of the main transmission lever 50. When the forward / reverse switching lever 36 is in the neutral position, all the hydraulic clutches 537, 539, and 541 are in the power cut state, and the driving force from the main transmission output shaft 512 is substantially zero (the main clutch disengaged state). )become.

  Next, an ultra-low speed, low-speed and high-speed switching structure executed through the creep transmission gear mechanism 502 and the traveling auxiliary transmission gear mechanism 503, which are traveling transmission gear mechanisms, will be described. In the front chamber 495 of the transmission case (in the front transmission case 112), a mechanical creep transmission gear mechanism 502 and a traveling auxiliary transmission gear mechanism 503 for shifting rotational power via the forward / reverse switching mechanism 501 are arranged. Yes. In this case, a travel counter shaft 545 extending coaxially with the travel transmission shaft 536 is disposed in the front chamber 495 (in the front transmission case 112). A sub-transmission shaft 546 extending in parallel with the travel counter shaft 545 is disposed from the front transmission case 112 to the rear transmission case 113 (from the front chamber 495 through the intermediate chamber 497 to the rear chamber 496). The front end side of the travel counter shaft 545 is rotatably supported by the front lid member 491. The rear end side of the travel counter shaft 545 is rotatably supported by the intermediate partition wall 493. The front end side of the auxiliary transmission shaft 546 is rotatably supported by the front lid member 491. The middle part of the auxiliary transmission shaft 546 is rotatably supported by the intermediate partition wall 493. The rear end side of the auxiliary transmission shaft 546 is rotatably supported by the intermediate auxiliary plate 498 and the rear partition wall 494.

  A transmission gear 547 and a creep gear 548 are provided on the rear side of the travel counter shaft 545. The transmission gear 547 is rotatably fitted to the travel counter shaft 545 and is pivotally supported on the intermediate partition wall 493 while being connected to the travel transmission shaft 536 so as to rotate integrally therewith. The creep gear 548 is fitted on the travel counter shaft 545 so as not to be relatively rotatable. A creep shifter 549 is spline-fitted between the transmission gear 547 and the creep gear 548 of the travel counter shaft 545 so as not to be relatively rotatable and slidable in the axial direction. The creep shifter 549 slides by turning the ultra low speed lever 44 on and off, and the transmission gear 547 and the creep gear 548 are alternatively connected to the travel counter shaft 545. A reduction gear pair 550 is rotatably fitted in a portion of the auxiliary transmission shaft 546 in the front chamber 495 (front transmission case 112). The input side reduction gear 551 and the output side reduction gear 552 constituting the reduction gear pair 550 have an integral structure, and the transmission gear 547 of the travel counter shaft 545 always meshes with the input side reduction gear 551 of the auxiliary transmission shaft 546, The creep gear 548 is always meshed with the output side reduction gear 552.

  A low speed relay gear 553 and a high speed relay gear 554 are provided on the front side of the travel counter shaft 545. The low speed relay gear 553 is fixed to the travel counter shaft 545. The high-speed relay gear 554 is fitted on the travel counter shaft 545 so as not to be relatively rotatable. A low-speed gear 555 that meshes with the low-speed relay gear 553 and a high-speed gear 556 that meshes with the high-speed relay gear 554 are rotatably fitted on the auxiliary transmission shaft 546 on the front side of the reduction gear pair 550. A sub-transmission shifter 557 is spline-fitted between the low-speed gear 555 and the high-speed gear 556 in the sub-transmission shaft 546 so as not to be relatively rotatable and slidable in the axial direction. By operating the sub transmission lever 45, the sub transmission shifter 557 slides and the low speed gear 555 and the high speed gear 556 are alternatively connected to the sub transmission shaft 546.

  In the embodiment, when the super low speed lever 44 is turned on and the sub transmission lever 45 is operated to the low speed side, the creep gear 548 is connected to the travel counter shaft 545 so as not to be relatively rotatable, and the low speed gear 555 is connected to the sub transmission shaft 546. A relatively low speed travel driving force is output from the travel transmission shaft 536 to the front wheel 3 and the rear wheel 4 via the travel counter shaft 545 and the auxiliary transmission shaft 546. The ultra-low speed lever 44 and the auxiliary transmission lever 45 are interlocked and connected via a shift check member (details will be described later), and the high-speed side operation of the auxiliary transmission lever 45 and the entry operation of the ultra-low speed lever 45 are performed. It is configured to prohibit compatibility. That is, the sub-shift lever 45 cannot be operated to the high speed side when the ultra-low speed lever 44 is operated and the ultra-low speed lever 44 cannot be operated when the sub-speed lever 45 is operated to the high speed side. .

  When the super low speed lever 44 is turned off and the sub transmission lever 45 is operated to the low speed side, the transmission gear 547 is connected to the travel counter shaft 545 so as not to rotate relative to it, and the low speed gear 555 cannot be rotated relative to the sub transmission shaft 546. And a low-speed traveling driving force is output from the traveling transmission shaft 536 to the front wheels 3 and the rear wheels 4 via the traveling counter shaft 545 and the auxiliary transmission shaft 546. When the super low speed lever 44 is turned off and the sub transmission lever 45 is operated to the high speed side, the transmission gear 547 is connected to the travel counter shaft 545 so as not to rotate relative to it, and the high speed gear 556 cannot be rotated relative to the sub transmission shaft 546. And a high-speed travel driving force is output from the travel transmission shaft 536 to the front wheels 3 and the rear wheels 4 via the travel counter shaft 545 and the auxiliary transmission shaft 546.

  The rear end side of the auxiliary transmission shaft 546 passes through the rear partition wall 494 and extends into the rear chamber 496. A pinion 558 is provided at the rear end of the auxiliary transmission shaft 546. Further, in the rear chamber 496 (inside the rear side of the rear transmission case 113), a rear wheel differential gear mechanism 506 for transmitting the driving force to the left and right rear wheels 4 is disposed. The rear wheel differential gear mechanism 506 includes a ring gear 559 that meshes with the pinion 558 of the auxiliary transmission shaft 546, a differential gear case 560 provided in the ring gear 559, and a pair of differential output shafts 561 that extend in the left-right direction. Yes. A differential output shaft 561 is connected to the rear axle 20 via a final gear 562 and the like. The rear wheel 4 is attached to the front end side of the rear axle 20.

  Brake mechanisms 563 are arranged on the left and right differential output shafts 561, respectively. The brake mechanism 563 brakes the left and right rear wheels 4 by two systems, that is, operation of the brake pedal 35 and automatic control. That is, each brake mechanism 563 is configured such that when the brake pedal 35 is depressed, the corresponding differential output shaft 561 and thus the rear wheel 4 are braked. When the steering angle of the steering wheel 9 is equal to or greater than a predetermined angle, the brake cylinder 630 (see FIG. 14) is actuated by the switching operation of the autobrake solenoid valve 631 (see FIG. 14) with respect to the rear wheel 4 on the inside of the turn. The brake mechanism 563 for the rear wheel 4 is configured to automatically perform a braking operation (so-called autobrake). For this reason, the tractor 1 can easily execute a small turning turn such as a U-turn (direction change at a headland in a field).

  The rear wheel differential gear mechanism 506 is provided with a differential lock mechanism 585 that stops its own differential (the left and right differential output shafts 561 are always driven at a constant speed). When the differential lock pin constituting the differential lock mechanism 585 is engaged with the differential gear of the differential gear case 560 by depressing the differential lock pedal 47, the differential gear is fixed to the differential gear case 560, and the differential function of the differential gear is determined. Stops, and the left and right differential output shafts 561 are driven at a constant speed.

  Next, the switching structure between the two-wheel drive and the four-wheel drive of the front and rear wheels 3 and 4 executed through the two-wheel drive and four-wheel drive switching mechanism 504 will be described. A two-wheel drive / four-wheel drive switching mechanism 504 is disposed in the front chamber 495 (front transmission case 112) of the mission case. In this case, a front wheel input shaft 568 and a front wheel output shaft 30 extending in parallel with the travel counter shaft 545 and the auxiliary transmission shaft 546 are disposed in the front chamber 495 (in the front transmission case 112). A driven gear 569 fitted to the front wheel input shaft 568 so as not to rotate relative to the main drive gear 569 fitted so as not to rotate relative to the front end side of the auxiliary transmission shaft 546 is always meshed. A double-speed relay gear 571 and a four-wheel drive relay gear 572 are fitted to the front wheel input shaft 568 so as not to rotate relative to each other on both sides of the driven gear 570.

  A two-wheel drive / four-wheel drive switching mechanism 504 is provided on the front wheel output shaft 30. That is, the front wheel output shaft 30 is fitted with a double speed gear 574 connected by a wet multi-plate type double-speed hydraulic clutch 573 and a four-wheel drive gear 576 connected by a wet multi-plate type four-wheel hydraulic clutch 575. doing. The double speed relay gear 571 of the front wheel input shaft 568 is always meshed with the double speed gear 574 of the front wheel output shaft 30, and the four-wheel drive relay gear 572 is meshed with the four-wheel gear 576.

  When a drive changeover switch or a drive changeover lever (not shown) is operated to the four-wheel drive side, the four-wheel drive hydraulic clutch 575 enters a power connection state, and the front wheel output shaft 30 and the four-wheel drive gear 576 are connected so as not to be relatively rotatable. Then, as a result of the rotational power being transmitted from the auxiliary transmission shaft 546 to the front wheel output shaft 30 via the front wheel input shaft 568 and the four-wheel drive gear 576, the tractor 1 is a four-wheeled vehicle driven by the front wheel 3 together with the rear wheel 4. It becomes a driving state. When the steering handle 9 is operated to make a U-turn or the like and the steering angle becomes equal to or greater than a predetermined angle, the double speed hydraulic clutch 573 is in a power connection state, and the front wheel output shaft 30 and the double speed gear 574 are connected so as not to be relatively rotatable. Then, the rotational power is transmitted from the auxiliary transmission shaft 546 to the front wheel output shaft 30 via the front wheel input shaft 568 and the double speed gear 574, so that the rotational speed of the front wheel 3 by the rotational power via the four-wheel drive gear 576 is increased. The front wheel 3 is driven at a high speed about twice as high.

  Power is transmitted to the front wheels 3 through the front wheel transmission shaft 508 projecting rearward from the front axle case 13 and the front wheel output shaft 30 projecting forward from the lower front surface of the transmission case 17 (front lid member 491). The front wheel drive shaft 31 is connected. In the front axle case 13, a front wheel differential gear mechanism 507 that transmits a driving force to the left and right front wheels 3 is disposed. The front wheel differential gear mechanism 507 includes a ring gear 578 that meshes with a pinion 577 provided on the front end side of the front wheel transmission shaft 508, a differential gear case 579 provided on the ring gear 578, and a pair of differential output shafts 580 extending in the left-right direction. And. A differential output shaft 580 is connected to the front axle 16 via a final gear 581 or the like. The front wheel 3 is attached to the front end side of the front axle 16. A steering hydraulic cylinder 622 (see FIG. 14) for power steering is provided on the outer surface of the front axle case 13 to change the traveling direction of the front wheel 3 to the left and right by the steering operation of the steering handle 9.

  Next, the drive speed switching structure (three forward rotations and one reverse rotation) of the PTO shaft 25 executed via the PTO transmission mechanism 505 will be described. A PTO transmission mechanism 505 that transmits power from the engine 5 to the PTO shaft 25 is disposed in the rear chamber 496 of the transmission case 17 (inside the rear side of the rear transmission case 113). In this case, a PTO input shaft 591 extending coaxially with the main transmission input shaft 28 is connected to the rear end side of the main transmission input shaft 28 via a PTO hydraulic clutch 590 for power transmission interruption. The PTO input shaft 591 is disposed in the rear chamber 496. In this case, the front end side of the PTO input shaft 591 is rotatably supported on the rear partition wall 494. As shown in FIG. 20, upper and lower support wall portions 613 and 614 that partition the rear chamber 496 forward and backward are integrally formed in the rear chamber 496. A midway portion between the front and rear of the PTO input shaft 591 is rotatably supported on the upper support wall portion 613 in the rear chamber 496. The rear end side of the PTO input shaft 591 is rotatably supported on the inner surface side of the rear cover member 492.

  In the rear chamber 496, a PTO transmission shaft 592, a PTO counter shaft 593, and a PTO shaft 25 extending in parallel with the PTO input shaft 591 are disposed. The front end side of the PTO transmission shaft 592 is rotatably supported on the upper support wall 613, and the rear end side of the PTO transmission shaft 592 is rotatably supported on the inner surface side of the rear lid member 492. The front end side of the PTO counter shaft 593 is rotatably supported on the lower support wall portion 614, and the rear end side of the PTO counter shaft 593 is rotatably supported on the inner surface side of the rear lid member 492. The PTO shaft 25 protrudes rearward from the rear lid member 492. A front end side of the PTO shaft 25 is rotatably supported on the lower support wall portion 614.

  When the power connection operation of the PTO clutch switch 53 is performed, the PTO hydraulic clutch 590 is in a power connection state, and the main transmission input shaft 28 and the PTO input shaft 591 are coupled so as not to be relatively rotatable. As a result, rotational power is transmitted from the main transmission input shaft 28 toward the PTO input shaft 591.

  The PTO input shaft 591 is provided with a medium speed input gear 597, a low speed input gear 595, a high speed input gear 596, and a reverse shifter gear 598 in order from the front side. The medium-speed input gear 597, the low-speed input gear 595, and the high-speed input gear 596 are fitted on the PTO input shaft 591 so as not to be relatively rotatable. The reverse shifter gear 598 is spline-fitted to the PTO input shaft 591 so as not to rotate relative to the PTO input shaft 591 and to be slidable in the axial direction.

  On the other hand, the PTO transmission shaft 592 is rotatably fitted with a PTO medium speed gear 601 that meshes with the medium speed input gear 597, a PTO low speed gear 599 that meshes with the low speed input gear 595, and a PTO high speed gear 600 that meshes with the high speed input gear 596. doing. A pair of front and rear PTO transmission shifters 602 and 603 are spline-fitted to the PTO transmission shaft 592 so as not to be relatively rotatable and to be slidable in the axial direction. The first PTO shift shifter 602 is disposed between the PTO medium speed gear 601 and the PTO low speed gear 599. The second PTO speed shifter 603 is disposed on the rear end side with respect to the PTO high speed gear 600. The pair of front and rear PTO shift shifters 602 and 603 are configured to slide in the axial direction in conjunction with the operation of the PTO shift lever 46. A PTO transmission gear 604 is fixed between the PTO low-speed gear 599 and the PTO high-speed gear 600 in the PTO transmission shaft 592.

  The PTO counter shaft 593 has a PTO counter gear 605 that meshes with the PTO transmission gear 604, a PTO relay gear 606 that meshes with a PTO output gear 608 that is non-rotatably fitted to the PTO shaft 25, and a PTO reverse gear 607. It is impossible to fit. When the sub-PTO lever 48 is engaged with the PTO speed change lever 46 in a neutral state, the reverse shifter gear 598 slides and the reverse shifter gear 598 meshes with the PTO reverse gear 607 of the PTO counter shaft 593. ing.

  When the PTO speed change lever 46 is operated to shift, the pair of front and rear PTO speed shifters 602 and 603 slide along the PTO speed change shaft 592, and the PTO low speed gear 595, the PTO medium speed gear 597, and the PTO high speed gear 596 become the PTO speed change shaft. 592 is alternatively connected. As a result, the low-speed to high-speed PTO shift outputs are transmitted from the PTO shift shaft 592 to the PTO counter shaft 593 via the PTO transmission gear 604 and the PTO counter gear 605, and further, the PTO relay gear 607 and the PTO output gear 608 are transmitted. Is transmitted to the PTO shaft 25.

  When the sub PTO lever 48 is turned on and operated, the reverse shifter gear 598 is engaged with the PTO reverse gear 607, and the rotational power of the PTO input shaft 591 is transmitted to the PTO counter shaft 593 via the reverse shifter gear 598 and the PTO reverse gear 607. Then, the reverse PTO shift output is transmitted from the PTO counter shaft 593 to the PTO shaft 25 via the PTO relay gear 607 and the PTO output gear 608.

  As is clear from the above description, the PTO transmission mechanism 505 of the embodiment is located behind the upper and lower support wall portions 613 and 614 in the rear chamber 496. A rear wheel differential gear mechanism 506 is disposed in front of the upper and lower support wall portions 613 and 614 in the rear chamber 496. Thus, in the embodiment, in the rear chamber 496 of the mission case 17, the rear wheel differential gear mechanism 506 and the PTO transmission mechanism 505 (PTO transmission system) are selected and arranged in a simple and compact manner. The assembling workability and maintainability of the case 17 are improved.

  Further, as is apparent from the shaft support structure of each of the shafts 25, 591, 592, 593 such as the PTO shaft 25, the rear cover member 492 that detachably closes the rear opening of the transmission case 17 can be attached and detached to remove the rear cover member 492. The PTO speed change mechanism 505 is configured to be able to enter and leave the chamber 496 behind the upper and lower support walls 613 and 614. When the PTO transmission mechanism 505 is mounted on the rear side of the rear chamber 496 from the upper and lower support wall portions 613 and 614, the PTO transmission mechanism 505 is supported by the upper and lower support wall portions 613 and 614 and the rear lid member 492. ing. For this reason, if the rear cover member 492 is removed from the mission case 17, the PTO transmission mechanism 505 can be exposed. Therefore, the assembly workability and disassembly workability of the mission case 17 and the maintenance performance of the PTO transmission mechanism 505 can be further improved.

  In the embodiment, the PTO input shaft 591 and the PTO transmission shaft 592 are supported by the upper support wall portion 613 and the rear cover member 492, and the PTO counter shaft 593 and the PTO shaft 25 are supported by the lower support wall portion 614 and the rear cover member 492. Is supported. Then, the positional relationship between these shafts 25, 591 to 593 is set so as to be positioned at the top of the rectangle in the rear view (see FIG. 21), and the upper PTO input shaft 591 to the middle PTO speed change shaft 592 and the PTO counter shaft. The PTO output is transmitted to the lower PTO shaft 25 via 593. If comprised in this way, it will become possible to cancel each other's reaction force of each axis | shaft 25,591-593 accompanying increase in output of PTO. As a result, vibration transmission to the mission case 17 and the traveling machine body 2 can be reduced.

  In the rear transmission case 113, a longitudinal longitudinal vehicle speed tuning shaft 564 extending in parallel with the auxiliary transmission shaft 546 is disposed from the intermediate chamber 497 to the rear chamber 496. A vehicle speed tuning input gear 565 is fitted on the front end side of the vehicle speed tuning shaft 564 so as not to be relatively rotatable. The vehicle speed tuning input gear 565 is always meshed with a power branch gear 566 that is fitted in a position in the intermediate chamber 497 of the auxiliary transmission shaft 546 so as not to be relatively rotatable. A vehicle speed tuning output gear 610 that is rotatably fitted to the front side of the PTO output gear 608 in the PTO shaft 25 is always meshed with a vehicle speed tuning relay gear 609 fixed to the rear end portion of the vehicle speed tuning shaft 564. . A vehicle speed tuning shifter 611 is spline-fitted between the vehicle speed tuning output gear 610 and the PTO output gear 608 of the PTO shaft 25 so as not to be relatively rotatable and slidable in the axial direction. When the sub PTO lever 48 is turned on while the PTO speed change lever 46 is operated in a neutral state, the vehicle speed tuning shifter 611 slides and the vehicle speed tuning output gear 610 is connected to the PTO shaft 25. As a result, the vehicle speed tuning output from the auxiliary transmission shaft 546 via the vehicle speed tuning shaft 564 is transmitted to the PTO shaft 25.

  Here, in the embodiment, the function of the sub PTO lever 48 is made different depending on the drive specification of the PTO shaft 25. In other words, in the specification that allows the PTO shaft 25 to be driven in reverse, the reverse shifter gear 598 is slid by manual operation of the sub PTO lever 48 and the reverse PTO shift output is transmitted to the PTO shaft 25. In the specification for driving the PTO shaft 25 in synchronization with the vehicle speed, the vehicle speed synchronization shifter 611 is slid by manual operation of the sub-PTO lever 48, and the PTO shift output synchronized with the vehicle speed is transmitted to the PTO shaft 25.

  In any of the specifications, the PTO speed change lever 46 and the sub PTO lever 48 are interlocked and connected via a PTO check member (details will be described later). It is configured to prohibit compatibility with the lever 48 entering operation. In other words, the PTO speed change lever 46 cannot be shifted to any position other than neutral when the sub PTO lever 48 is engaged, and the sub PTO lever 48 cannot be engaged when the speed change operation is performed other than neutral. ing.

  Here, FIG. 23 shows an example of specifications for driving the PTO shaft 25 in synchronization with the vehicle speed. In this example, the PTO speed change lever 46 is interlocked and connected to a main PTO operation shaft 696 that protrudes outward from the left side rear portion of the rear speed change case 113 (mission case 17) via a main PTO link body 695. When the PTO shift lever 46 is shifted, the main PTO operation shaft 696 is rotated via the main PTO link body 695, and the pair of front and rear PTO shift shifters 602 and 603 are slid along the PTO transmission shaft 592. As a result, the PTO low-speed gear 595, the PTO medium-speed gear 597, and the PTO high-speed gear 596 are selectively connected to the PTO speed change shaft 592, and the low-speed to high-speed PTO speed change outputs (forward output) are supplied to the PTO shaft 25. Communicated.

  Further, the sub PTO lever 48 is interlocked and connected to a sub PTO operation shaft 698 protruding outward from the rear portion of the left side surface of the rear transmission case 113 (mission case 17) via a sub PTO link body 697. When the sub PTO lever 48 is turned on, the sub PTO operation shaft 698 rotates via the sub PTO link body 697 and the vehicle speed tuning shifter 611 is slid along the PTO shaft 25. As a result, the vehicle speed tuning output gear 610 is connected to the PTO shaft 25, and the vehicle speed tuning output from the auxiliary transmission shaft 546 via the vehicle speed tuning shaft 564 is transmitted to the PTO shaft 25.

  Next, the hydraulic circuit 620 structure of the tractor 1 will be described with reference to FIG. The hydraulic circuit 620 of the tractor 1 includes a working machine hydraulic pump 481 and a traveling hydraulic pump 482 that are driven by the rotational power of the engine 5. In the embodiment, the mission case 17 is used as a working oil tank, and the working oil in the mission case 17 is supplied to the working machine hydraulic pump 481 and the traveling hydraulic pump 482. The traveling hydraulic pump 482 is connected to the steering hydraulic cylinder 622 for power steering by the steering handle 9 via the control valve mechanism 621 for power steering, and the hydraulic pump 521 and the hydraulic motor 522 of the hydraulic continuously variable transmission 500. Is connected to a closed loop oil passage 623 connecting the two. While the engine 5 is being driven, the hydraulic oil from the traveling hydraulic pump 482 is always replenished to the closed loop oil passage 623.

  The traveling hydraulic pump 482 includes a main transmission hydraulic switching valve 624 for the main transmission hydraulic cylinder 524 of the hydraulic continuously variable transmission 500, a double speed hydraulic switching valve 625 for the double speed hydraulic clutch 573, and a four-wheel drive for the four-wheel hydraulic clutch 575. The hydraulic switching valve 626 is connected to a PTO clutch electromagnetic valve 627 for the PTO hydraulic clutch 590 and a switching valve 628 operated thereby.

  Further, the traveling hydraulic pump 482 includes left and right autobrake solenoid valves 631 as switching valves that actuate a pair of left and right autobrake brake cylinders 630, and a forward low speed clutch solenoid valve 632 that actuates a forward low speed hydraulic clutch 537. A forward high-speed clutch electromagnetic valve 633 for operating the forward high-speed hydraulic clutch 539, a reverse clutch electromagnetic valve 634 for operating the reverse hydraulic clutch 541, and master control for controlling the supply of hydraulic oil to the clutch electromagnetic valves 632 to 634 It is connected to the electromagnetic valve 635.

  The work machine hydraulic pump 481 is configured to provide a tread (distance between wheels) between a plurality of hydraulic external extraction valves 430 arranged on the upper surface of the hydraulic lifting mechanism 22 on the rear side of the upper surface of the mission case 17 and the left and right rear wheels 4. Left and right tread adjustment solenoid valves 646 that control the supply of hydraulic oil to the right and left tread adjustment hydraulic cylinders 645, and a tilt control solenoid valve 647 that controls the supply of hydraulic oil to the horizontal cylinder 122 provided on the right lift rod 121 , An ascending oil pressure switching valve 648 and a descending oil pressure switching valve 649 for controlling the supply of hydraulic oil to the hydraulic lift cylinder 117 in the hydraulic lifting mechanism 22, an ascending control electromagnetic valve 650 for switching the ascending oil pressure switching valve 648, and a descending oil pressure The switching valve 649 is connected to a lowering control electromagnetic valve 651 for operating.

  When the left and right tread adjusting electromagnetic valves 646 are switched and driven, the left and right tread adjusting hydraulic cylinders 645 extend and contract to move the left and right rear axle cases 19 in the left and right directions. As a result, the tread between the left and right rear wheels 4 becomes longer or shorter. When the tilt control electromagnetic valve 647 is switched and driven, the horizontal cylinder 122 expands and contracts, and the right lower link 23 moves up and down with the lower link pin on the front side as a fulcrum. As a result, the ground work machine tilts left and right with respect to the traveling machine body 2 via the left and right lower links 23, and the left and right tilt angles of the ground work machine change. When the raising hydraulic switching valve 648 is switched by the raising control electromagnetic valve 650 or the lowering hydraulic switching valve 649 is switched by the lowering control electromagnetic valve 651, the hydraulic lift cylinder 117 expands and contracts, and the lift arm 120 and both the left and right lowers are moved. Both links 23 move up and down. As a result, the ground work machine moves up and down, and the height position of the ground work machine changes.

  The hydraulic circuit 620 of the tractor 1 includes a lubricating oil pump 518 that is driven by the rotational power of the engine 5 in addition to the aforementioned working machine hydraulic pump 481 and traveling hydraulic pump 482. The lubricating oil pump 518 includes a PTO clutch hydraulic pressure switching valve 641 that supplies hydraulic oil (lubricating oil) to the lubricating portion of the PTO hydraulic clutch 590, and a lubricating portion of the input transmission shaft 511 that supports the hydraulic continuously variable transmission 500. The forward low-speed clutch hydraulic pressure switching valve 642 that supplies hydraulic oil (lubricating oil) to the lubricating portion of the forward low-speed hydraulic clutch 537, and the forward high-speed clutch hydraulic pressure that supplies hydraulic oil (lubricating oil) to the lubricating portion of the forward high-speed hydraulic clutch 539. The switching valve 643 is connected to a reverse clutch hydraulic pressure switching valve 644 that supplies hydraulic oil (lubricating oil) to the lubricating portion of the reverse hydraulic clutch 541. The hydraulic circuit 620 includes a relief valve, a flow rate adjustment valve, a check valve, an oil cooler, an oil filter, and the like.

  As is apparent from the above description and FIGS. 13 and 15 to 20, the engine 5 mounted on the traveling machine body 2, the transmission case 17 for shifting the power of the engine 5, and the left and right sides of the transmission case 17 And a rear traveling unit 4 provided via an axle case 19, and a differential mechanism 506 for transmitting transmission power via the mission case 17 to the left and right rear traveling units 4 is disposed in the mission case 17. In the working vehicle, a front chamber 495, an intermediate chamber 497, and a rear chamber 496 are formed in the mission case 17, and the rear chamber 496 includes support wall portions 613 and 614 that divide the rear chamber 496 in the front-rear direction. The differential mechanism 506 is disposed in front of the support wall portions 613 and 614 in the rear chamber 496, and the power of the engine 5 is changed to change the speed of the missile. Since the PTO speed change mechanism 505 for transmitting to the PTO shaft 25 protruding rearward from the rear case 17 is arranged behind the support wall portions 613 and 614 in the rear chamber 496, the rear of the transmission case 17 is In the chamber 496, the differential mechanism 506 and the PTO transmission mechanism 505 (PTO transmission system) can be selected and arranged in a simple and compact manner, and the assembly workability and maintenance performance of the mission case 17 can be improved.

  In addition, a rear lid member 492 that detachably closes the rear opening of the transmission case 17 is provided, and the rear lid member 492 is detachably attached to the rear chamber 496 behind the support wall portions 613 and 614. In the state where the PTO transmission mechanism 505 is configured to be able to enter and exit, and the PTO transmission mechanism 505 is mounted on the rear side of the rear chamber 496 with respect to the support wall portions 613 and 614, the support wall portions 613 and 614 Since the PTO transmission mechanism 505 is supported by the rear cover member 492, the PTO transmission mechanism 505 can be exposed by removing the rear cover member 492 from the transmission case 17. Therefore, the assembly workability and disassembly workability of the transmission case 17 and the maintenance performance of the PTO transmission mechanism 505 can be further improved.

  Further, the three shafts 591 to 593 and the PTO shaft 25 constituting the PTO speed change mechanism 505 are pivoted to the support wall portions 613 and 614 and the rear cover member 492 so as to be positioned at the vertex of the rectangle in the rear view. Therefore, the reaction forces of the shafts 25, 591 to 593 accompanying the increase in the PTO output can be offset. As a result, the life of the bearing structure for each of the shafts 25, 591 to 593 can be extended, and vibration transmission to the transmission case 17 and the traveling machine body 2 can be reduced.

  Next, a structure for switching and operating the traveling auxiliary transmission gear mechanism 503 and the creep transmission gear mechanism 502 will be described with reference to FIGS. 15, 17, and 22 to 25. As shown in detail in FIG. 22, between the control seat 8 and the left side column 42, a parking brake lever 43 for performing an operation of maintaining the left and right rear wheels 4 in a braking state, and a creep shift operation tool. Are an ultra-low speed lever 44 (creep lever), an auxiliary transmission lever 45 which is an auxiliary transmission operating tool, and a PTO transmission lever 46 which switches the driving speed of the PTO shaft 25. In the embodiment, the parking brake lever 43 is located closer to the control seat 8. The ultra-low speed lever 44, the auxiliary transmission lever 45, and the PTO transmission lever 46 are positioned near the left side column 42, and the ultra-low speed lever 44, the auxiliary transmission lever 45, and the PTO transmission lever 46 are arranged in this order from the front. The parking brake lever 43 is configured to be rotatable up and down, and the ultra-low speed lever 44, the auxiliary transmission lever 45, and the PTO transmission lever 46 are configured to be capable of rotating forward and backward.

  As shown in FIG. 23, the base end side of the ultra-low speed lever 44 is interlocked with a creep operation shaft 671 that protrudes outward from the front portion of the left side surface of the rear transmission case 113 (mission case 17) via a creep link body 670. It is connected. Similarly, the base end side of the sub-transmission lever 45 is interlocked and connected to a sub-transmission operation shaft 681 protruding outward from the left side front portion of the rear transmission case 113 (mission case 17) via the sub-transmission link body 680. doing.

  Near the left inner surface of the transmission case 17, a creep fork shaft extends from the front transmission case 112 to the front of the rear transmission case 113 (from the front chamber 495 to the intermediate chamber 497) and extends in parallel with the main transmission input shaft 28 and the like. 672 and an auxiliary transmission fork shaft 682 are arranged. The creep fork shaft 672 and the auxiliary transmission fork shaft 682 extend in parallel with each other while being close to each other. A creep fork 673 engaged with a creep shifter 549 on the travel counter shaft 545 is fixed to a midway portion of the creep fork shaft 672. An auxiliary transmission fork 683 engaged with an auxiliary transmission shifter 557 on the auxiliary transmission shaft 546 is fixed to the distal end side of the auxiliary transmission fork shaft 682. The distal end side of the creep fork shaft 672 passes through the auxiliary transmission fork 683 so as to be slidable back and forth. A midway portion of the auxiliary transmission fork shaft 682 passes through the creep fork 673 so as to be slidable back and forth. That is, the fork shafts 672 and 682 are pivotally supported by the forks 673 and 683 of each other.

  An engagement notch groove 674 is formed on the rear end side of the creep fork shaft 672. A creep switching arm 675 protruding upward is fixed to the inner end side of the creep operation shaft 671. The tip cam portion 676 of the creep switching arm 675 is slidably engaged with the engagement notch groove 674 of the creep fork shaft 672. Further, an engagement notch groove 684 is also formed on the rear end side of the auxiliary transmission fork shaft 682. A sub shift switching arm 685 protruding downward is fixed to the inner end side of the sub shift operation shaft 681. The tip cam portion 686 of the auxiliary transmission switching arm 685 is slidably engaged with the engagement notch groove 684 of the auxiliary transmission fork shaft 682.

  When the ultra-low speed lever 44 is tilted forward, the creep operation shaft 671 is rotated counterclockwise in FIG. 23 via the creep link body 670 and the creep switching arm 675 is tilted forward to move the creep fork shaft 672 forward. Move to. In this case, since the middle part of the auxiliary transmission fork shaft 682 penetrates the creep fork 673 so as to be slidable back and forth, the auxiliary transmission fork shaft 682 passes the creep fork 673 parallel to the travel counter shaft 545, the auxiliary transmission shaft 546, and the like. Guide forward. Then, the creep shifter 549 slides forward along the travel counter shaft 545, and the creep gear 548 and the travel counter shaft 545 are connected so as not to rotate relative to each other, so that the creep is entered.

  When the ultra-low speed lever 44 is tilted backward, the creep operation shaft 671 is rotated clockwise through the creep link body 670 to tilt the creep switching arm 675 backward, and the creep fork shaft 672 is moved backward. Move. In this case, the auxiliary transmission fork shaft 682 guides the creep fork 673 in the rearward direction parallel to the travel counter shaft 545, the auxiliary transmission shaft 546, and the like. Then, the creep shifter 549 slides rearward along the travel counter shaft 545, the transmission gear 547 and the travel counter shaft 545 are connected so as not to be relatively rotatable, and a creep cut state is established.

  When the auxiliary transmission lever 45 is tilted backward from the neutral position, the auxiliary transmission operation shaft 681 rotates clockwise through the auxiliary transmission link body 680 to tilt the auxiliary transmission switching arm 685 forward, thereby The shift fork shaft 682 is moved forward. In this case, the front end side of the creep fork shaft 672 penetrates the auxiliary transmission fork 683 so as to be slidable back and forth. To guide. Then, the auxiliary transmission shifter 557 slides forward along the auxiliary transmission shaft 546, the low speed gear 555 and the auxiliary transmission shaft 546 are connected so as not to be relatively rotatable, and the auxiliary transmission low speed state is set.

  When the auxiliary transmission lever 45 is tilted forward from the neutral position, the auxiliary transmission operation shaft 681 rotates counterclockwise in FIG. 23 via the auxiliary transmission link body 680, and the auxiliary transmission switching arm 685 is tilted backward, The auxiliary transmission fork shaft 682 is moved rearward. In this case, the creep fork shaft 672 guides the auxiliary transmission fork 683 in the rearward direction parallel to the travel counter shaft 545, the auxiliary transmission shaft 546, and the like. Then, the auxiliary transmission shifter 557 slides rearward along the auxiliary transmission shaft 546, the high speed gear 556 and the auxiliary transmission shaft 546 are connected so as not to be relatively rotatable, and the auxiliary transmission high speed state is obtained.

  As can be seen from the above description, the creep fork shaft 672 and the auxiliary speed change fork shaft 682 are configured such that when the one fork shaft 672 (682) is moved in the longitudinal direction by the operation of one operation tool 44 (45), The fork shaft 682 (672) is linked to the fork 673 (683) on the one fork shaft 672 (683) side in the longitudinal direction.

  The ultra-low speed lever 44 and the auxiliary transmission lever 45 are interlocked and connected via a shift check member 690 so as to prohibit both the high-speed side operation of the auxiliary transmission lever 45 and the entry operation of the ultra-low speed lever 45. It is configured. That is, the sub-shift lever 45 cannot be operated to the high speed side when the ultra-low speed lever 44 is operated and the ultra-low speed lever 44 cannot be operated when the sub-speed lever 45 is operated to the high speed side. .

  In this case, an upwardly opening stopper groove 691 is formed on the rear end side of the auxiliary transmission fork shaft 682, and a check pin 692 protruding into the stopper groove 691 is attached to the middle part of the creep switching arm 675. (See FIG. 25). The stopper groove 691 and the check pin 692 constitute a shift check member 690. In the embodiment, the front inner end surface 693 of the stopper groove 691 when the auxiliary transmission lever 45 is operated on the high speed side and the restraining pin 692 when the ultra low speed lever 45 is operated are overlapped with each other. When the ultra-low speed lever 44 is operated and the auxiliary transmission lever 45 is operated to the high speed side, the front inner end surface 693 of the stopper groove 691 and the check pin 692 are in contact with each other and set to interfere with each other.

  For this reason, even if the auxiliary transmission lever 45 is to be operated to the high speed side with the ultra low speed lever 44 being engaged, the front inner end surface 693 of the stopper groove 691 abuts against the check pin 692 and the auxiliary transmission fork shaft 683 is moved backward. Thus, the auxiliary transmission lever 45 cannot be operated on the high speed side. Further, even if the super-low speed lever 44 is operated with the auxiliary transmission lever 45 operated to the high speed side, the check pin 692 comes into contact with the front inner end surface 693 of the stopper groove 691, and the creep fork shaft 673 moves forward. It is impossible to enter and operate the ultra-low speed lever 44. The stopper groove 691 and the check pin 692 do not interfere with each other except when the super low speed lever 44 is operated and the auxiliary transmission lever 45 is operated to the high speed side.

  As apparent from the above description and FIGS. 15, 17, and 22 to 25, in a work vehicle including the engine 5 mounted on the traveling machine body 2 and the transmission case 17 that changes the power of the engine 5, In the transmission case 17, a hydraulic continuously variable transmission 500 that continuously changes the power of the engine 5, a sub-transmission gear mechanism 503 that changes the transmission power via the hydraulic continuously variable transmission 500 in a plurality of stages, A creep transmission gear mechanism 502 that shifts the transmission power via the hydraulic continuously variable transmission 500 to an ultra-low speed, a sub-transmission operating tool 45 that operates the sub-transmission gear mechanism 503 via the sub-transmission fork shaft 682, and a creep fork. A creep shift operation tool 44 for shifting the creep transmission gear mechanism 502 through a shaft 672, and the auxiliary transmission fork shaft 682 and the A leap fork shaft 672 is arranged in parallel in the transmission case 17, the auxiliary transmission fork shaft 682 is provided with an auxiliary transmission fork 683, the creep fork shaft 672 is provided with a creep fork 673, one operating tool. 44 (45), when one fork shaft 672 (682) is moved in the longitudinal direction, the other fork shaft 682 (672) moves the fork 673 (683) on the one operating shaft 672 (682) side to the aforementioned fork 673 (683). Since the mutual fork shafts 672 and 682 are pivotally supported by the mutual forks 673 and 683 so as to be guided in the longitudinal direction, the structure for supporting the both forks 673 and 683 so as to be operable is simplified and compact. The auxiliary transmission gear mechanism 503 and the auxiliary transmission operating tool 45 are mechanically interlocked and connected. In addition, the structure in which the creep transmission gear mechanism 502 and the creep transmission operation tool 44 are mechanically interlocked and connected can be arranged in a space-saving manner in the mission case 17, and the number of parts can be reduced to reduce the cost of parts. it can.

  Further, since the shift control member 690 that prohibits both the high speed side operation of the auxiliary transmission operation tool 45 and the operation of entering the creep transmission operation tool 44 is provided, the auxiliary transmission gear mechanism 503 and the creep transmission gear mechanism are provided. Unnecessary speed change combinations with 502 can be accurately excluded, and the possibility of damage such as gear tooth spilling can be avoided.

  Further, the transmission case 17 is divided into three parts, a front case 112, an intermediate case 114, and a rear case 113, and the intermediate case 114 and the rear case 113 are made of cast iron, while the front case 112 is made of aluminum die-cast, and the hydraulic continuously variable transmission 500, the auxiliary transmission gear mechanism 503, and the creep transmission gear mechanism 502 are positioned in the front case 112. By arranging the hydraulic continuously variable transmission 500, the auxiliary transmission gear mechanism 503, and the creep transmission gear mechanism 502 on the case 112 side, the transmission case 17 can be well balanced.

  In addition, the structure of each part in this invention is not limited to embodiment of illustration, A various change is possible in the range which does not deviate from the meaning of this invention.

2 traveling machine body 5 diesel engine 17 transmission case 25 PTO shaft 44 ultra-low speed lever 45 auxiliary transmission lever 112 front transmission case 113 rear transmission case 114 intermediate case 495 front chamber 496 rear chamber 497 intermediate chamber 500 hydraulic continuously variable transmission 502 creep transmission Gear mechanism 503 Sub-transmission gear mechanism 672 Creep fork shaft 672
673 Creep fork 682 Sub-transmission fork shaft 682
683 Sub-shift fork 690 Shift check member

Claims (3)

In a work vehicle comprising an engine mounted on a traveling machine body and a transmission case for shifting the power of the engine,
In the transmission case, a hydraulic continuously variable transmission that continuously changes the power of the engine, a sub-transmission gear mechanism that changes the transmission power via the hydraulic continuously variable transmission in multiple stages, and the hydraulic continuously variable transmission A creep transmission gear mechanism for shifting the transmission power via the machine to an ultra-low speed, a sub-transmission operating tool for shifting the sub-transmission gear mechanism via a sub-transmission fork shaft, and the creep transmission gear mechanism via a creep fork shaft A creep transmission operating tool for shifting the gear, the auxiliary transmission fork shaft and the creep fork shaft are arranged in parallel in the transmission case, the auxiliary transmission fork shaft is provided with an auxiliary transmission fork, and the creep The fork shaft has a creep fork,
When one fork shaft is moved in the longitudinal direction by operation of one operating tool, the other fork shafts are connected to each other so that the other fork shaft guides the fork on the one fork shaft side in the longitudinal direction. Which is pivotally supported on the fork,
Work vehicle. A shift check member that prohibits both high-speed operation of the sub-shift operation tool and entering operation of the creep shift operation tool;
The work vehicle according to claim 1. The mission case is divided into three parts, a front case, an intermediate case, and a rear case, and the intermediate case and the rear case are made of cast iron, while the front case is made of aluminum die cast,
The hydraulic continuously variable transmission, the auxiliary transmission gear mechanism, and the creep transmission gear mechanism are located in the front case;
The work vehicle according to claim 1 or 2.

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