JP6335727B2 - Work vehicle - Google Patents

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).

  In the work vehicle of Patent Document 1, an inline hydraulic continuously variable transmission is assembled in a mission case. The hydraulic continuously variable transmission includes a hydraulic pump unit that transmits power from an engine via an input shaft, and a hydraulic motor unit that transmits a shift output to a rear traveling unit or the like via an output shaft. The input shaft and the output shaft are concentric double shafts, and a cylinder block that rotates integrally with the input shaft is fitted on the input shaft. A hydraulic pump part is fitted on one side of the input shaft across the cylinder block, and a hydraulic motor part is fitted on the other side. In the work vehicle of Patent Document 1, a hydraulic continuously variable transmission is accommodated adjacent to the differential gear mechanism on the rear side in the transmission case.

JP 2010-52734 A

  By the way, from the viewpoint of improving assembly and maintenance, and reducing the number of parts, the transmission case has a traveling transmission system such as a hydraulic continuously variable transmission and a traveling transmission gear mechanism, a PTO transmission gear mechanism, and a PTO shaft. It is preferable to arrange a PTO transmission system such as the above together for each system. However, in the configuration of Patent Document 1, a traveling transmission gear mechanism, a PTO transmission gear mechanism, and the like are arranged on the front side in the transmission case, and a differential gear mechanism, a hydraulic continuously variable transmission, and a PTO shaft are arranged on the rear side of the transmission case. Etc., and there was no coherence for each transmission system, and there was still room for improvement in terms of assembly, maintenance, and the number of parts.

  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 an engine mounted on a traveling machine body, a hydraulic continuously variable transmission for shifting the power of the engine, a transmission case incorporating the hydraulic continuously variable transmission, and rear left and right sides of the transmission case. In a work vehicle including a rear traveling unit provided via an axle case, the transmission case is divided into three parts, a front case, an intermediate case, and a rear case, and extends from the front case to the intermediate case. An input shaft for transmitting the power of the engine and an input transmission shaft for transmitting power from the input shaft are arranged in parallel to each other, and the hydraulic stepless is provided in the front case via the input transmission shaft. output via the forward-reverse switching mechanism together to place the transmission arranged a running gear mechanism for multi-speed, wherein the in the intermediate case, forward the output of the hydrostatic transmission or It is that are arranged the forward-reverse switching mechanism rolling switching direction.

According to a second aspect of the present invention, in the work vehicle according to the first aspect, the intermediate case and the rear case are made of cast iron, while the front case is made of aluminum die cast , The rear end portions of the left and right aircraft frames are connected, and the aircraft frame and the transmission case are integrally connected .

  According to the first aspect of the present invention, the engine mounted on the traveling body, the hydraulic continuously variable transmission for shifting the power of the engine, the transmission case incorporating the hydraulic continuously variable transmission, and the left and right sides of the transmission case In a work vehicle including a rear traveling part provided via a rear axle case, the transmission case is divided into three parts, a front case, an intermediate case, and a rear case. After the parts such as gears and gears are assembled in advance, the front case, the intermediate case, and the rear case can be assembled. Therefore, the assembly of the mission case can be performed accurately and efficiently.

  Further, an input shaft that transmits the power of the engine and an input transmission shaft that transmits power from the input shaft are arranged in parallel to each other from the front case to the intermediate case, and in the front case, The hydraulic continuously variable transmission is disposed via the input transmission shaft, and a forward / reverse switching mechanism for switching the output of the hydraulic continuously variable transmission in the forward or reverse direction is disposed in the intermediate case. The travel transmission system can be accommodated together in the front case and the intermediate case (the front of the transmission case), and the assembly and maintenance of the transmission case can be improved.

  According to the invention of claim 2, the intermediate case and the rear case are made of cast iron, while the front case is made of aluminum die cast, and the output through the forward / reverse switching mechanism is provided in the front case. Since a traveling transmission gear mechanism that performs multi-stage shifting is further arranged, the forward / reverse switching mechanism is disposed on the heavy intermediate case side, and the hydraulic continuously variable transmission and the traveling transmission gear are disposed on the lighter front case side. The mechanism will be distributed. Therefore, the weight balance of the mission case can be improved.

It is a left view of a tractor. It is a top view of a tractor. It is a right view of a tractor. It is the perspective view which looked at the tractor from diagonally right back. It is left side explanatory drawing of a traveling body. It is left side explanatory drawing which shows the detailed structure of a traveling body. It is the perspective view which looked at the traveling body from diagonally left rear. It is right side explanatory drawing of a traveling body. It is right side explanatory drawing which shows the detailed structure of a traveling body. It is the perspective view which looked at the traveling machine body from diagonally right rear. It is a skeleton figure of the power transmission system of a tractor. It is a left view of a mission case. It is the perspective view which looked at the mission case from diagonally left front. It is explanatory drawing seen from the left side which shows the internal structure of a mission case. It is plane view 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 a left side sectional view of the front part of the mission case. It is a left side sectional view of the middle part of the mission case. It is sectional drawing of the left side view of the rear part of a mission case. It is a hydraulic circuit diagram of a tractor. It is a hydraulic circuit diagram of the lubrication system of a tractor.

  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 10, 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 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 is attached to an output shaft (piston rod) of the engine 5 protruding 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. FIG. 1, FIG. 7 and FIG. 10). 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. 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, there is a one-touch lift lever 34 for forcibly moving a working machine such as a rotary tiller to the highest position or the lowest position, and a pair of left and right brake pedals 35 for braking the traveling machine body 2. And are arranged. 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) for reducing the speed, a sub-shift lever 45 for switching the output range of the traveling sub-speed gear mechanism in the transmission case 17, and a PTO speed change for switching the driving speed of the PTO shaft 25. A 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 reverse PTO lever 48 that performs an operation of driving the PTO shaft 25 in the reverse direction is disposed on the left rear side of the control seat 8.

  Between the control seat 8, the control seat 8, and the left side column 42, an armrest 49 for placing the arm and elbow of the 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.

  The left side column 42 includes, in order from the front side, a throttle lever 52 that sets and maintains the rotational speed of the engine 5, and a PTO clutch switch 53 that performs intermittent operation of power transmission from the PTO shaft 25 to a working machine such as a rotary tiller. A plurality of hydraulic operation levers 54 (SCV levers) for switching the hydraulic external take-off valves (sub-control valves, not shown) arranged on the upper surface side of the mission case 17 are arranged. Here, the hydraulic external take-off valve is for controlling supply of hydraulic oil to hydraulic equipment of another work machine such as a front loader that is 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).

  Further, as shown in FIGS. 7 and 10, 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. 11, 15, etc., a rear support 97 is disposed on the upper surface side of the rear axle case 19 so that the end face of the cross section sandwiches the rear axle case 19 having a substantially rectangular tube shape. An anti-rest bracket 101 is arranged on the lower surface side, and the rear support base 97 and the anti-rest bracket 101 are fastened with bolts 102, and can be adjusted to extend and contract between the middle portion of the lower link 23 extending in the front-rear direction and the anti-rest bracket 101. Both ends of the steady stop rod body 103 with a turnbuckle are connected to prevent the lower link 23 from shaking in the left-right direction.

  Next, the diesel engine 5 and the engine room structure under the hood 6 will be described with reference to FIGS. 6, 9, 10 and the like. The diesel engine 5 has a cylinder head mounted on a cylinder block containing an engine output shaft and a 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). An intake manifold 203 and an EGR device 210 that recirculates a part of the exhaust gas from the exhaust manifold 204 are arranged, and a part of the exhaust gas discharged to the exhaust manifold 204 is returned to the intake manifold 203 to increase the amount of exhaust gas. The maximum combustion temperature during load operation is lowered, and the amount of NOx (nitrogen oxide) emissions from the diesel engine 5 is 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, in the engine 5, 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, and the cooling fan 206 is arranged on the front side of the diesel engine 5 (cylinder block).

  In addition, as shown in FIGS. 6, 9, 10, etc., the diesel engine 5 includes a continuously regenerative exhaust gas purification device 224 (DPF) disposed on the upper surface side of the diesel engine 5 (above the exhaust manifold 204). The tail pipe 229 is connected to the exhaust side of the exhaust gas 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.

  Further, as shown in FIGS. 1, 6, 9, 10, etc., the bonnet 6 has a front grille 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, 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. A rectangular frame-like frame 226 is provided on the front side of the radiator 235, and an air cleaner 221 is disposed above the front surface of the frame frame 226. In addition to the above intercooler, an oil cooler, a fuel cooler, and the like are installed in the frame frame 226.

  On the other hand, as shown in FIG. 10 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. Note that the left and right side surfaces of the front part of the diesel engine 5 are connected to the middle part of the pair of left and right engine frames 14 via left and right front engine legs 238 having anti-vibration rubber. 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.

  A bonnet shield plate (shielding plate) 244 is erected on the upper surface of the support beam frame 236 via a pair of left and right support frames. The back of the hood 6 is covered with a hood shield plate 244. The engine room 200 in which the diesel engine 5 is housed is formed in a space surrounded by the hood 6, the left and right side engine covers 232, the fan shroud 234, and the hood shield plate 244. In addition, the heat insulation layer is formed between the cabin 7 arrange | positioned behind the bonnet 6 and the bonnet shield board 244 by arrange | positioning the bonnet shield board 244 away from the cabin 7 front surface. Accordingly, the cabin 7 side can be prevented from being heated by exhaust heat from the engine room 200, so that the operator in the cabin 7 is comfortable without being affected by the exhaust heat of the diesel engine 5 or the exhaust gas purification device 224. Can be maneuvered.

  Further, a pair of left and right beam frames 248 are installed between the upper part of the fan shroud 234 and the upper part of the bonnet shield plate 244. The upper part of the fan shroud 234 and the upper part of the bonnet shield plate 244 are connected by a pair of beam frames 248, and these members are integrated to form a robust frame structure of the engine room 200 as a whole. The left and right edges of the heat shield plate 250 are fixed to the beam frame 248, and the exhaust gas purifying device 224 on the upper side of the diesel engine 5 is covered with the heat shield plate 250. By disposing the heat shield plate 250 on the exhaust gas purification device 224, it is possible to prevent the bonnet 6 from being heated by the exhaust heat of the exhaust gas purification device 224 and the diesel engine 5, and to prevent the hood 6 and the heat shield plate 250 from being heated. A space is formed in between so that the inside of the engine room 200 below the heat shield plate 250 is insulated from the outside air so that the exhaust gas purification device 224 can be operated in a high temperature environment.

  A bonnet support bracket 255 is provided on the upper front edge of the bonnet shield plate 244, the rear end of the bonnet 6 is rotatably supported, and the front part of the bonnet 6 is moved up and down with the hinge portion of the bonnet support bracket 255 as a fulcrum. It is configured as follows. In addition, expandable and contractible gas springs 256 are disposed on the left and right sides of the heat shield plate 250 below the bonnet 6. One end (rear end) of a pair of left and right gas springs 256 is pivotally attached to the rear end side of the pair of left and right beam frames 248, and the other end (front end) of the gas spring 256 is pivotally attached to the upper inner surface of the bonnet 6. . Therefore, by lifting the front part of the bonnet 6, the front part of the bonnet 6 is moved upward with the hinge part of the bonnet support bracket 255 as an axis fulcrum, and the upper surface side of the front part of the engine room 200 is opened. Maintenance work can be performed.

  Next, with reference to FIGS. 5 to 10, a mounting structure of the hydraulic lifting mechanism 22 and the 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 ends 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.

  The hydraulic lift mechanism 22 can be opened and closed provided on the upper side of the rear shift case 113 of the transmission case 17 and the left and right hydraulic lift cylinders 117 that are controlled by operation of the one-touch lift lever 34 or the working unit position dial 51. Left and right lift arms 120 that pivotally support the base end side of the upper lid 118 via a lift fulcrum shaft 119 and the left and right lift rods 121 that connect the left and right lift arms 120 to the left and right lower links 23. have. 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 and 10 and the like, a 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 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 cover member 492 is detachably fastened to the rear surface of the rear transmission case 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 and 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. After transmitting the rotational power from the engine 5 to the PTO shaft 25 by appropriately shifting and transmitting the rotational power via the creep transmission gear mechanism 502 or the traveling auxiliary transmission gear mechanism 503 to the left and right rear wheels 4. A wheel differential gear mechanism 506 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 pump case 480 accommodating a traveling hydraulic pump 481 driven by the rotational power of the engine 5 and a working machine hydraulic pump 482 is attached to the front portion of the left outer surface of the rear transmission case 113.

  As shown in FIGS. 1, 7, and 10, a flywheel 26 is directly connected to an output shaft of the engine 5 that projects 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.

  According to the above configuration, the main transmission input shaft 28 that transmits the power of the engine 5 and the input transmission shaft 511 that transmits power from the main transmission input shaft 28 are parallel to each other from the front transmission case 112 to the intermediate case 114. The hydraulic continuously variable transmission 500 is disposed in the front transmission case 112 via the input transmission shaft 511 (particularly, a front lid member 491 that removably closes the front opening of the front transmission case 112). For example, if only the front transmission case 112 is removed while the intermediate case 114 and the rear transmission case 113 are attached to the fuselage frame 15, the hydraulic continuously variable transmission 500 is attached to the inner surface side of the hydraulic continuously variable transmission 500. Can be exposed. The maintainability of the hydraulic continuously variable transmission 500 arranged in the mission case 17 can be improved.

  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.

  According to the above configuration, the main transmission input shaft 28 that transmits the power of the engine 5 and the input transmission shaft 511 that transmits power from the main transmission input shaft 28 are parallel to each other from the front transmission case 112 to the intermediate case 114. The hydraulic continuously variable transmission 500 is disposed in the front transmission case 112 via the input transmission shaft 511, and the output of the hydraulic continuously variable transmission 500 is forwardly or reversely rotated in the intermediate case 114. Since the forward / reverse switching mechanism 501 is arranged to switch to the front transmission case 112 and the intermediate case 114 (the front part of the transmission case 17), the traveling transmission system can be accommodated together, and the traveling transmission system and thus the assembly of the transmission case 17 can be assembled. And maintenance can be improved.

  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 check mechanism (not shown) so that the auxiliary transmission lever 45 cannot be operated to the high speed side when the ultra-low speed lever 44 is engaged. It is composed.

  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.

  In the embodiment, the hydraulic continuously variable transmission 500 is placed in the front transmission case 112 (the front chamber 495) so as to be higher than the creep transmission gear mechanism 502 and the traveling auxiliary transmission gear mechanism 503 as the traveling transmission gear mechanism. It is arranged. For this reason, the traveling transmission gear mechanism (the creep transmission gear mechanism 502 and the traveling auxiliary transmission gear mechanism 503) in which the stirring resistance of the hydraulic oil in the transmission case 17 is smaller than that of the hydraulic continuously variable transmission 500 is brought to a low position. The possibility that the hydraulic oil in the transmission case 17 is agitated by the hydraulic continuously variable transmission 500 can be reduced (the agitation resistance of the hydraulic oil caused by the hydraulic continuously variable transmission 500 can be reduced). Therefore, the transmission efficiency of the hydraulic continuously variable transmission 500 can be improved.

  Further, while the intermediate case 114 and the rear transmission case 113 are made of cast iron, the front transmission case 112 is made of aluminum die cast, and the output from the forward / reverse switching mechanism 501 is shifted in multiple stages in the front transmission case 112. Since the creep transmission gear mechanism 502 and the traveling auxiliary transmission gear mechanism 503 as the traveling transmission gear mechanism are further arranged, the forward / reverse switching mechanism 501 is provided on the heavy intermediate case 114 side, and the lightweight front transmission case 112 side is provided. Thus, the hydraulic continuously variable transmission 500, the creep transmission gear mechanism 502 as the traveling transmission gear mechanism, and the traveling auxiliary transmission gear mechanism 503 are distributed. Therefore, the weight balance of the mission case 17 can be improved.

  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. 20) is actuated by the switching operation of the autobrake solenoid valve 631 (see FIG. 20) 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.

  In the rear transmission case 113, a longitudinally-rearly-long parking brake shaft 564 extending in parallel with the auxiliary transmission shaft 546 is disposed from the intermediate chamber 497 to the rear chamber 496. A parking brake gear 565 is fitted on the front end side of the parking brake shaft 564 so as not to be relatively rotatable. The parking brake gear 565 always meshes with a lock 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 parking brake 567 such as a wet multi-plate disc is provided between the intermediate auxiliary plate 498 and the rear partition wall 494 in the parking brake shaft 564. When the parking brake 567 is braked by the braking operation of the parking brake lever 43, the parking brake shaft 564 and the parking brake gear 565 are locked so as not to rotate. As a result, the lock gear 566 and the auxiliary transmission shaft 546 are locked so as not to rotate, and the left and right rear wheels 4 are braked.

  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. 20) for power steering is provided on the outer surface of the front axle case 13 to change the traveling direction of the front wheels 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 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 PTO shaft 25 protrudes rearward from the rear lid member 492. When the power connection operation is performed on the PTO clutch switch 53, 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. By operating the reverse PTO lever 48 in reverse with the PTO shift lever 46 in a neutral operation, 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. doing.

  When the PTO shift lever 46 is shifted, the pair of front and rear PTO shift shifters 602 and 603 slide along the PTO shift shaft 592 and the PTO low speed gear 595, the PTO medium speed gear 597, and the PTO high speed gear 596 are moved to the PTO shift 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. The PTO speed change lever 46 and the reverse direction PTO lever 48 are interlocked and connected via a check mechanism (not shown), and the reverse speed PTO lever 48 cannot be operated to enter the reverse direction when the PTO speed change lever 46 is changed to a speed other than neutral. It is configured as follows.

  When the reverse rotation PTO lever 48 is operated for reverse rotation, the reverse shifter gear 598 is engaged with the PTO reverse rotation gear 607, and the rotational power of the PTO input shaft 591 is transmitted to the PTO counter shaft 593 via the reverse rotation shifter gear 598 and the PTO reverse rotation 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.

  Note that the 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 the vehicle speed tuning input gear 609 fixed to the rear end portion of the parking brake shaft 594. ing. 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. By entering and operating a PTO vehicle speed tuning lever (not shown), 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 synchronization output from the auxiliary transmission shaft 546 via the parking brake shaft 594 is transmitted to the PTO shaft 25.

  Next, the structure of the hydraulic circuit 620 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. A hydraulic switching valve 626, a PTO clutch electromagnetic valve 627 for the PTO hydraulic clutch 590, a switching valve 628 operated thereby, and a differential lock electromagnetic valve 629 for the differential lock cylinder 586 for operating the differential lock mechanism are connected.

  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. And a forward high speed clutch electromagnetic valve 633 that operates the forward high speed hydraulic clutch 539 and a reverse clutch electromagnetic valve 634 that operates the reverse hydraulic clutch 541. The work machine hydraulic pump 481 is connected to a control valve mechanism 635 that supplies hydraulic oil to the left and right hydraulic lift cylinders 117 in the hydraulic lifting mechanism 22. 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.

  Next, the structure of the hydraulic circuit 640 of the lubrication system in the tractor 1 will be described with reference to FIG. The hydraulic circuit 640 of the lubrication system in the tractor 1 includes a lubricating oil pump 518 that is driven by the rotational power of the engine 5. 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.

  As apparent from the above description and FIGS. 11 to 19, the engine 5 mounted on the traveling machine body 2, the hydraulic continuously variable transmission 500 for shifting the power of the engine 5, and the hydraulic continuously variable transmission 500 are incorporated. In the work vehicle 1 including the transmission case 17 and the rear traveling unit 4 provided on the left and right sides of the transmission case 17 via the rear axle case 19, the transmission case 17 is connected to the front case 112, the intermediate case 114, and the intermediate case 114. Since the rear case 113 is divided into three parts, the front case 112, the intermediate case 114 and the rear case 113 are assembled after parts such as shafts and gears are assembled in advance in the cases 112 to 114. Can be assembled. Therefore, the assembly of the mission case 17 can be performed accurately and efficiently.

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

  In the embodiment, 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. Therefore, the intermediate case 114 connected to the body frame 15, The rear case 113 to which the left and right rear axle cases 19 are connected can be configured with high rigidity as a strength member constituting the traveling machine body 2. In addition, the front 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.

  Further, an input shaft 28 that transmits power of the engine 5 and an input transmission shaft 511 that transmits power from the input shaft 28 are arranged in parallel to each other from the front case 112 to the intermediate case 114, and Since the hydraulic continuously variable transmission 500 is disposed in the part case 112 via the input transmission shaft 511, for example, the intermediate case 114 and the rear case 113 remain attached to the body frame 15 and the front case If only the part case 112 is removed, the hydraulic continuously variable transmission 500 can be exposed. The maintainability of the hydraulic continuously variable transmission 500 disposed in the mission case 17 can be improved.

  As apparent from the above description and FIGS. 11 to 19, the engine 5 mounted on the traveling machine body 2, the hydraulic continuously variable transmission 500 for shifting the power of the engine 5, and the hydraulic continuously variable transmission 500 are incorporated. In the work vehicle 1 including the transmission case 17 and the rear traveling unit 4 provided on the left and right sides of the transmission case 17 via the rear axle case 19, the transmission case 17 is connected to the front case 112, the intermediate case 114, and the intermediate case 114. The rear case 113 is divided into three parts. The input shaft 28 transmits power of the engine 5 from the front case 112 to the intermediate case 114, and the input transmission shaft 511 transmits power from the input shaft 28. Are arranged in parallel with each other, and the hydraulic continuously variable transmission 500 is arranged in the front case 112 via the input transmission shaft 511. In the intermediate case 114, a forward / reverse switching mechanism 501 for switching the output of the hydraulic continuously variable transmission 500 in the normal rotation direction or the reverse rotation direction is disposed. Therefore, the front case 112 and the intermediate case 114 ( The traveling transmission system can be accommodated together in the front of the transmission case 17, and the assembly and maintenance of the transmission case 17 can be improved.

  Further, while the intermediate case 114 and the rear case 113 are made of cast iron, the front case 112 is made of aluminum die-cast, and the output through the forward / reverse switching mechanism 500 is multistage in the front case 112. Since the traveling transmission gear mechanisms 502 and 503 for shifting are further arranged, the forward / reverse switching mechanism 501 is disposed on the heavy intermediate case 114 side, and the hydraulic continuously variable transmission is disposed on the lighter front case 112 side. 500 and the traveling transmission gear mechanisms 502 and 503 are distributed. Therefore, the weight balance of the mission case 17 can be improved.

  As apparent from the above description and FIGS. 11 to 19, the engine 5 mounted on the traveling machine body 2, the hydraulic continuously variable transmission 500 for shifting the power of the engine 5, and the hydraulic continuously variable transmission 500 are incorporated. In the work vehicle 1 including the transmission case 17 and the rear traveling unit 4 provided on the left and right sides of the transmission case 17 via the rear axle case 19, the transmission case 17 is connected to the front case 112, the intermediate case 114, and the intermediate case 114. The rear case 113 is divided into three parts. The input shaft 28 transmits power of the engine 5 from the front case 112 to the intermediate case 114, and the input transmission shaft 511 transmits power from the input shaft 28. Are arranged in parallel with each other, and the hydraulic continuously variable transmission 500 is arranged in the front case 112 via the input transmission shaft 511. Since 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 case 112, the front lid member 491 can be removed from the transmission case 17. Thus, the hydraulic continuously variable transmission 500 can be exposed. Therefore, the maintainability of the hydraulic continuously variable transmission 500 arranged in the mission case 17 can be improved.

  Further, in the front case 112, travel transmission gear mechanisms 502, 503 for shifting the output via the forward / reverse switching mechanism 501 in multiple stages are further arranged, and are positioned higher than the travel transmission gear mechanisms 502, 503. As described above, since the hydraulic continuously variable transmission 500 is disposed in the front case 112, the traveling transmission gear in which the agitation resistance of the hydraulic oil in the transmission case 17 is smaller than that of the hydraulic continuously variable transmission 500. Since the mechanisms 502 and 503 are in the low position, it is possible to reduce the possibility that the hydraulic oil in the transmission case 17 is agitated by the hydraulic continuously variable transmission 500 (the hydraulic oil agitation resistance by the hydraulic continuously variable transmission 500). Can be reduced). Therefore, the transmission efficiency of the hydraulic continuously variable transmission 500 can be improved.

  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 112 front transmission case 113 rear transmission case 114 intermediate case 491 front cover member 492 rear cover member 493 intermediate partition wall 494 rear partition wall 495 front chamber 496 rear chamber 497 intermediate chamber 498 intermediate auxiliary plate 500 Hydraulic continuously variable transmission 501 Forward / reverse switching mechanism 502 Creep transmission gear mechanism 503 Traveling auxiliary transmission gear mechanism

Claims (2)

An engine mounted on the traveling machine body, a hydraulic continuously variable transmission for shifting the power of the engine, a transmission case incorporating the hydraulic continuously variable transmission, and a rear axle case provided on both left and right sides of the transmission case In a work vehicle comprising a rear traveling unit,
The transmission case is divided into three parts, a front case, an intermediate case, and a rear case, and an input shaft through which the engine power is transmitted from the front case to the intermediate case, and power transmission from the input shaft Are arranged in parallel to each other, and the hydraulic continuously variable transmission is arranged in the front case via the input transmission shaft, and the output via the forward / reverse switching mechanism is subjected to multi-stage shifting. a traveling gear mechanism disposed, wherein the in the intermediate case, and arranging the forward-reverse switching mechanism for switching the output of said hydrostatic transmission in the forward or reverse direction,
Work vehicle. While the intermediate case and the rear case are made of cast iron, the front case is made of aluminum die cast, and the left and right machine body frame rear ends are connected to the left and right sides of the intermediate case, and the machine frame and the The mission cases are connected as a unit,
The work vehicle according to claim 1.

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