JP2016077203A - Work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work vehicle capable of easily simplifying assembly of a lifting valve body 652 to a transmission case 17 as well as maintenance work, and improving assembly easiness of the transmission case 17.SOLUTION: A work vehicle comprises a traveling machine body 2 on which an engine 5 is mounted, a link mechanism 111 for mounting a work machine to the traveling machine body 2, and a lifting mechanism 22 for moving the link mechanism 111 upward and downward. A part of the traveling machine body 2 is constituted by a transmission case 17. A part of the link mechanism 111 is constituted by left and right lower links 23. A part of the lifting mechanism 22 is constituted by lift cylinders 117. The work machine is mounted to the traveling machine body 2 through the left and right lower links 23 so as to be liftable. The work vehicle is configured to have a lifting valve body 652 for actuating the lift cylinders 117. The transmission case 17 comprises a front case 112, an intermediate case 114, and a rear case 113. The lifting valve body 652 is disposed in a top face lid body 118 placed on a top face of the rear case 113.SELECTED DRAWING: Figure 24

Description

  The present invention relates to a work vehicle such as a farm tractor that pulls a ground work machine such as a tillage work machine or a sowing work machine.

  Conventionally, a transmission case is disposed at the rear of a farm tractor as a work vehicle, and a link mechanism and a lifting mechanism such as a lift arm and a lift cylinder for moving the link mechanism up and down are attached via the transmission case. There is a technique in which a rotary tiller and the like are installed in a rear portion via an elevating mechanism so as to be movable up and down, and a ground work is executed (cultivating a field). (See Patent Document 1)

JP 2010-52734 A

  In the prior art, it is necessary to install hydraulic equipment that drives each part of the agricultural tractor, and since the transmission case is used as a hydraulic oil tank for the hydraulic equipment, the structure in which the hydraulic equipment is installed on the upper side of the transmission case is used. The installation structure of the hydraulic equipment is likely to be complicated. For example, the assembly and maintenance work of the lift valve to the transmission case cannot be easily simplified, and the assembly workability of the transmission case cannot be improved.

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

  The invention according to claim 1 includes a traveling machine body on which an engine is mounted, a link mechanism that mounts a work machine on the traveling machine body, and a lifting mechanism that moves the link mechanism up and down. A part of the traveling machine body is a transmission case. A part of the link mechanism is composed of left and right lower links, a part of the lifting mechanism is composed of a lift cylinder, and the work equipment is lifted and lowered to the traveling machine body via the left and right lower links. In a work vehicle that can be mounted, the structure includes a lift valve body that operates the lift cylinder, and the transmission case includes a front case, an intermediate case, and a rear case, and is provided on an upper surface of the rear case. The raising / lowering valve body is disposed on the upper cover body to be installed.

  According to a second aspect of the present invention, the work vehicle according to the first aspect includes a valve plate that is hydraulically connected to the lift cylinder via a hydraulic pipe, a hydraulic proportional valve as the lift valve body, and the top cover. The valve plate is placed on the front upper surface of the body, and the elevating valve body (the hydraulic proportional valve) is placed on the upper surface of the valve plate.

  According to a third aspect of the present invention, in the work vehicle according to the second aspect, the transmission case forms a front chamber by the front case, and forms an intermediate chamber in front of the intermediate case and the rear case, and the rear portion. A rear chamber is configured at the rear of the case, and the intermediate chamber and the rear chamber are partitioned through a partition plate provided in the rear case, and the upper surface side of the rear plate is defined as the upper surface side of the rear chamber. It is configured to be opened and covered with the upper surface lid.

  According to a fourth aspect of the present invention, in the work vehicle according to the third aspect, the left and right lift arms are connected to the left and right lift cylinders and the left and right lower links. And left and right lift arms.

  According to a fifth aspect of the present invention, in the work vehicle according to the second aspect, a part of the link mechanism is configured by a top link, and a top link hinge to which the top link is connected is a rear surface side of the upper surface lid. It is fixedly supported by.

  According to the first aspect of the present invention, the vehicle includes a traveling machine body on which an engine is mounted, a link mechanism that mounts a work machine on the traveling machine body, and a lifting mechanism that moves up and down the link mechanism. A transmission case is configured, a part of the link mechanism is configured with left and right lower links, a part of the lifting mechanism is configured with a lift cylinder, and a work machine is connected to the traveling machine body via left and right lower links. In a work vehicle that is mounted so as to be able to move up and down, the structure includes a lifting valve body that operates the lift cylinder, and the transmission case includes a front case, an intermediate case, and a rear case, and the rear case includes Since the elevating valve body is arranged on the upper surface cover body installed on the upper surface, hydraulic equipment parts relating to the elevating mechanism provided behind the transmission case are provided. Can unit configuration and arranged together on a surface the lid can be easily simplified assembly and maintenance operations such as lifting the valve body to the transmission case, it is possible to improve the assembly efficiency of the transmission case.

  According to the invention which concerns on Claim 2, While providing the valve plate hydraulically connected to the said lift cylinder via hydraulic piping, and the hydraulic proportional valve as said raising / lowering valve body, On the upper surface front part of the said upper surface cover body, the said Since the valve plate is placed and the lift valve body (the hydraulic proportional valve) is placed on the top surface of the valve plate, the lift valve is placed on the top cover body via the valve plate constituting a hydraulic circuit. While the body (the hydraulic proportional valve) is assembled, the valve plate can be attached to and detached from the upper surface lid, while the valve plate is assembled to the upper surface lid, The top cover can be attached and detached, and assembly and maintenance workability of the lift valve body (hydraulic proportional valve) can be simplified.

  According to the invention according to claim 3, the transmission case forms a front chamber by the front case, forms an intermediate chamber in front of the intermediate case and the rear case, and forms a rear chamber in the rear of the rear case. In addition, the intermediate chamber and the rear chamber are partitioned through a partition plate provided in the rear case, and the upper surface side of the upper surface of the rear chamber is opened by opening the upper surface side behind the partition plate. The valve plate can be attached to and detached from the upper surface of the upper cover body while simplifying the assembly and maintenance of the hydraulic proportional valve that switches the input and output of hydraulic oil to and from the lift valve body. Thus, it is possible to easily perform assembly or maintenance work for the gears in the rear chamber.

  According to the invention which concerns on Claim 4, It is a structure provided with the left-and-right lift arm which connects the said left-and-right lift cylinder and the left-and-right lower link, Comprising: Since it is arranged, an elevating mechanism (elevating valve body, lift arm) can be arranged on the upper surface side of the upper surface lid, and assembly and maintenance work of the elevating mechanism to the mission case can be simplified.

  According to the invention which concerns on Claim 5, while comprising a part of said link mechanism by a top link, the top link hinge with which the said top link is connected was fixedly supported by the rear surface side of the said upper surface cover body. Therefore, an elevating mechanism (elevating valve body, lift arm, top link) can be arranged on the upper surface side or rear surface side of the upper surface lid, and assembly and maintenance work of the link mechanism (lift arm, top link) to the transmission case Can be improved easily.

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 a left view of a mission case. It is a right view of a mission case. It is a top view of a mission case. It is the perspective view which looked at the rear part upper surface of the mission case from the left front. It is a left sectional view of a mission case. It is the perspective view which looked at the mission case from the left front. It is front sectional drawing of a mission case. It is the perspective view which looked at the rear part of the mission case from the left front. It is a disassembled perspective view of the rear part of a mission case. It is sectional explanatory drawing which decomposed | disassembled the mission case rear part.

  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 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 projecting a PTO driving force to a ground working machine such as a rotary tiller is provided to project rearward.

  A flywheel 26 (see FIGS. 4 to 6, 10, and 11) is connected to an output shaft (piston rod) of the engine 5 that protrudes 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). As shown in FIG. 13, a hydraulic continuously variable transmission 500, a forward / reverse switching mechanism 501, travel transmission gear mechanisms 502, 503, 504, a rear wheel differential gear mechanism 506, and the like are arranged inside the mission case 17. Yes. 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 shifted by the hydraulic continuously variable transmission 500 and the traveling transmission gear mechanism. 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 (two-wheel drive / four-wheel drive switching mechanism 504) in the mission 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 axle. It is configured to be transmitted to the left and right front wheels 3 via a front wheel differential gear mechanism 507 in the case 13.

  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 on the rear side of a 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.

  A pair of left and right brake pedals 35 for braking the traveling machine body 2 are disposed on the lower right side of the steering column 32. On the upper 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 is disposed. On the lower left side of the steering column 32, a clutch pedal 37 for disengaging the outputs of the hydraulic continuously variable transmission 500 (forward low speed hydraulic clutch 537, forward high speed hydraulic clutch 539, reverse hydraulic clutch 541) is disposed. . The master control solenoid valve 635 is turned on by stepping on the clutch pedal 37, and the forward output or the reverse output of the hydraulic continuously variable transmission 500 is cut off (see FIG. 14).

  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 causing the erroneous operation preventing body 38, which is a contact prevention tool, to protrude outward from 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. ing. 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. Left and right side columns 42 are arranged on both left and right sides of the control seat 8. Between the control seat 8 and the left side column 42, a parking brake lever 43 that maintains the left and right rear wheels 4 in a braking state, and an ultra-low speed that forcibly and significantly reduces the forward travel speed (vehicle speed) of the tractor 1 A lever 44 (creep operation lever), a sub-transmission lever 45 that switches the output range of the traveling sub-transmission gear mechanism 503 in the mission case 17, and a PTO transmission lever 46 that switches the driving speed of the PTO shaft 25 are arranged. . A differential lock pedal 47 for turning on and off the differential drive of the left and right rear wheels 4 is disposed below the control seat 8. A reverse PTO lever 48 for performing an operation of driving the PTO shaft 25 in the reverse direction is disposed on the left rear side of the control seat 8 (see FIG. 10).

  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 includes a main transmission lever 50 that increases / decreases the traveling speed of the tractor 1, a dial type work unit position dial 51 (elevating dial) that manually changes and adjusts the height position of a ground work machine such as a rotary tiller. It has. 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 a 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).

  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. That is, the diesel engine 5 and the cabin 7 are supported by the traveling machine body 2 (the engine frame 14, the machine frame 15, and the rear axle case 19, which are integrally connected) via the plurality of vibration-proof rubber bodies. . 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 support beam frame 236 is bolted to the left and right airframe frames 15 and is erected on the front end portions (rear side of the engine 5) of the left and right airframe frames 15, and the rear engine legs 237 having vibration-proof rubber bodies. The rear part of the diesel engine 5 is connected to the upper surface of the support beam frame 236 via As shown in FIGS. 1, 2, 4, 5, 11, and 12, left and right front engine legs 238 having anti-vibration rubber bodies 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 to each other. 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 high-rigid cast iron, while the front transmission case 112 is made of aluminum die cast that is lightweight and has good workability.

  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.

  The left and right rear axle cases 19 are attached to the left and right sides of the rear transmission case 113, and the middle of the high-rigidity structure connecting the front transmission case 112 and the rear transmission case 113 to the left and right body frames 15 constituting the traveling vehicle body 2. Since the case 114 is connected, for example, with the intermediate case 114 and the rear transmission case 113 attached to the body frame 15, only the front transmission case 112 is removed, and the hydraulic continuously variable transmission 500 and the like are installed. Maintenance or repair work such as replacement of the shaft and gear in the front transmission case 112 can be performed. Therefore, the frequency of the disassembling work for removing the entire mission case 17 from the tractor 1 can be remarkably reduced, and the workability at the time of 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.

  On the other hand, 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 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, 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 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 left outer surface of the rear transmission case 113.

  As shown in FIGS. 4 to 6, a flywheel 26 is connected to an output shaft (crankshaft) 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 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. It is transmitted to the front-wheel differential gear mechanism 507 in the case 13 so as 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 inside the front lid member 491 on which the front portion of the hydraulic continuously variable transmission 500 is supported, and the front lid member 491 and the hydraulic continuously variable transmission 500 are combined into one member. As a unit. 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 has a range between a maximum tilt angle of one (forward rotation) and a maximum tilt angle of the other (reverse rotation) with a neutral angle of the tilt angle of substantially zero (before and after including zero). When the vehicle speed of the traveling machine body 2 is the lowest, when the vehicle speed of the traveling machine body 2 is the medium speed, the swash plate inclination angle near the maximum reverse rotation is set to the stop state. The swash plate angle is set to an inclination angle near substantially zero, and is set to the swash plate inclination angle near the maximum of forward rotation when the vehicle speed of the traveling machine body 2 is the highest. Note that when the vehicle speed of the traveling machine body 2 is near the minimum (swash plate inclination angle near the maximum of reverse rotation), the starting force or the low-speed traveling force of the traveling machine body 2 can be easily secured.

  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 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.

  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 brakes the corresponding left or right or both differential output shafts 561 by depressing the left or right brake pedal 35, and the corresponding left or right rear wheel. 4 is configured to brake. 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 operation works). 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 the differential between the left and right rear wheels 4 (the left and right differential output shafts 561 are always driven at a constant speed). When the differential lock pin (not shown) constituting the differential lock mechanism 585 is engaged with the differential gear of the differential gear case 560 by the depression operation of the differential lock pedal 47, the differential gear is fixed to the differential gear case 560, and the differential gear The right and left differential output shafts 561 (left and right rear wheels 4) 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 to be relatively non-rotatable is always meshed with a main gear 569 fitted so as to be relatively non-rotatable on the front end side of the auxiliary transmission shaft 546. 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. Further, when the steering angle becomes equal to or greater than a predetermined angle by operating the steering handle 9 to make a U-turn or the like, the double speed hydraulic clutch 573 is automatically connected to the power, and the front wheel output shaft 30 and the double speed gear 574 are connected so as not to be relatively rotatable. Is done. 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 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 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. 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.

  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. 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 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 a master control electromagnetic valve 635 for controlling the supply of hydraulic oil to the clutch electromagnetic valves. And connected to.

  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 adjustment solenoid valves 646 are switched and driven with the left and right rear wheels 4 jacked up and floating from the ground, the left and right tread adjustment hydraulic cylinders 645 expand and contract to move the left and right rear axle cases 19 left and right. It is expanded and contracted in the direction (see FIGS. 6 and 14). 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 is switched by the raising control solenoid valve or the lowering hydraulic switching valve is switched by the lowering control solenoid valve, the hydraulic lift cylinder 117 expands and contracts, and both the lift arm 120 and the left and right lower links 23 are moved together. 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. A forward low speed clutch hydraulic pressure switching valve 642 that supplies hydraulic oil to the lubricating portion of the forward low speed hydraulic clutch 537, a forward high speed clutch hydraulic pressure switching valve 643 that supplies hydraulic oil to the lubricating portion of the forward high speed hydraulic clutch 539, and a reverse hydraulic clutch. It connects with the reverse clutch hydraulic pressure switching valve 644 which supplies hydraulic oil to the lubrication part of 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 apparent from the above description and FIGS. 1 and 13 to 24, the traveling machine body 2 on which the diesel engine 5 is mounted, the three-point link mechanism 111 on which the work machine is mounted on the traveling machine body 2, and the three-point link mechanism 111. A part of the traveling machine body 2 is constituted by the mission case 17, a part of the three-point link mechanism 111 is constituted by the left and right lower links 23, and a part of the elevator mechanism 22 is provided. In a work vehicle in which a rotary tiller work machine and the like are attached to the traveling machine body 2 via the left and right lower links 23 so as to be able to move up and down, the rising hydraulic pressure switching as a lifting valve body 652 for operating the lift cylinder 117 is performed. The transmission case 17 has a structure including a valve 648 and a descending hydraulic pressure switching valve 649. The transmission case 17 includes a front transmission case 112, an intermediate case 114, and a rear transmission. Together constituted by chromatography scan 113 are arranged a top lid 118 to lift the valve body 652 installed on the upper surface of the rear transmission case 113 (increasing the hydraulic selector valve 648 and the descending hydraulic switching valve 649).

  Accordingly, the hydraulic device parts related to the lifting mechanism 22 provided behind the mission case 17 can be arranged together on the upper cover 118 to constitute a unit, and the lifting valve body 652 (the rising hydraulic pressure changeover valve 648 and the upper hydraulic switch valve 648 disposed on the upper surface side of the mission case 17 can be configured. The assembly and maintenance work of the lowering hydraulic pressure changeover valve 649) can be easily simplified, and the ease of assembly of the transmission case 17 can be improved. Further, the elevating valve body 652 can be supported on the front portion of the upper surface lid 118, the lift arm 120 can be supported on the rear portion of the upper surface lid 118 via the lift fulcrum shaft 119, and the upper surface of the transmission case 17 (rear transmission case 113). The lifting mechanism 22 can be installed compactly on the side. In addition, the autobrake solenoid valve 631 is supported on the upper surface of the rear transmission case 113 in front of the upper cover 118, and the tilt control solenoid valve 647 is supported on the upper surface of the upper cover 118 behind the valve plate 655. On the upper surface of the upper cover 118, a hydraulic valve device related to the lifting mechanism 22 is disposed, and on the upper surface of the upper cover 118 close to the left and right brake mechanisms 563 on both sides of the rear transmission case 113, an autobrake solenoid valve 631 is provided. The hydraulic devices can be functionally installed by effectively utilizing the upper surface of the rear transmission case 113.

  As shown in FIGS. 14 to 24, a valve plate 655 that is hydraulically connected to the lift cylinder 117 via a hydraulic pipe, and hydraulic proportional valves (a lift control solenoid valve 650 and a drop control solenoid valve 651) as the lift valve body 652 are provided. In addition, a valve plate 655 is placed on the upper surface front portion of the top cover 118, and a lift valve body 652 (a lift control solenoid valve 650 and a drop control solenoid valve 651 as hydraulic proportional valves) is placed on the top surface of the valve plate 655. doing. Therefore, ascending / descending valve body 652 (rising oil pressure switching valve 648 and descending oil pressure switching valve 649, ascending control solenoid valve 650 and descending control solenoid valve 651) is attached to the upper surface lid body 118 via the valve plate 655 constituting the hydraulic circuit. In this state, the valve plate 655 can be attached to and detached from the upper surface lid 118, while the upper surface lid 118 can be attached to and detached from the upper surface of the transmission case 17 with the valve plate 655 assembled to the upper surface lid 118. Assembly and maintenance workability of the body 652 can be simplified.

  As shown in FIGS. 13 to 24, in the transmission case 17, the front transmission case 112 forms a front chamber 495, the intermediate case 114 and the rear transmission case 113 in front form an intermediate chamber 497, and the rear transmission case 113 rearward. The rear chamber 496 is configured, and the intermediate chamber 497 and the rear chamber 496 are partitioned through a rear partition wall 494 as a partition plate provided in the rear transmission case 113, and the rear partition wall is formed on the upper surface side of the rear chamber 496. The upper surface side behind 494 is opened and covered with the upper surface lid 118. Therefore, the assembly and maintenance of hydraulic valve devices (the rising hydraulic pressure switching valve 648 and the lowering hydraulic pressure switching valve 649, the raising control electromagnetic valve 650 and the lowering control electromagnetic valve 651) that switch the operation oil to and from the raising and lowering valve body 652 can be simplified. However, the valve plate 655 can be attached to and detached from the upper surface of the upper cover 118 to perform assembly or maintenance work for the gear (rear wheel differential gear mechanism 506) in the rear chamber 496.

  As shown in FIGS. 14 to 24, the left and right lift cylinders 117 and the left and right lower links 23 are connected to each other, and a lift fulcrum shaft as a lift fulcrum shaft is provided at the rear portion of the upper cover 118. The left and right lift arms 120 are pivotally supported at both left and right ends of the lift fulcrum shaft 119 so that the lift fulcrum shaft can be rotated. Left and right lift arms 120 are arranged via 119. Therefore, the elevating mechanism 22 (elevating valve body 652 and lift arm 120) can be disposed on the upper surface side of the upper surface lid 118, and assembly and maintenance work of the elevating mechanism 22 to the mission case 17 can be simplified.

  As shown in FIGS. 14 to 24, a part of the three-point link mechanism 111 is configured by the top link 24, and the top link hinge 656 is bolted to the rear surface of the upper cover 118. A top link hinge 656 to be coupled is fixedly supported on the rear surface side of the upper cover 118. Therefore, the elevating mechanism 22 (elevating valve body 652, lift arm 120, top link 24) can be disposed on the upper surface side or rear surface side of the upper surface lid 118, and the link mechanism 111 (lift arm 120, top link 24) to the transmission case 17 can be provided. ) Assembly and maintenance workability can be easily improved.

  As apparent from the above description and FIGS. 1 and 13 to 24, the traveling machine body 2 on which the diesel engine 5 is mounted, the three-point link mechanism 111 on which the work machine is mounted on the traveling machine body 2, and the three-point link mechanism 111. A part of the traveling machine body 2 is constituted by the mission case 17, a part of the three-point link mechanism 111 is constituted by the left and right lower links 23, and a part of the elevator mechanism 22 is provided. In a work vehicle in which a rotary tiller working machine (not shown) and the like is attached to the traveling machine body 2 via the left and right lower links 23 so as to be lifted and lowered, The transmission case 17 includes a front transmission case 112, an intermediate case 114, and a rear transmission case 113. While being the slope control solenoid valve 647 as a horizontal control valve to actuate the horizontal cylinder 122 is disposed on the upper surface lid 118 of the rear transmission case 113. Accordingly, the hydraulic device parts (tilt control electromagnetic valve 647) related to the lifting mechanism 22 provided behind the mission case 17 can be arranged together on the upper cover 118, and the unit can be configured. The assembly of the tilt control electromagnetic valve 647 to the mission case 17 is possible. In addition, maintenance work and the like can be easily simplified, and the ease of assembly of the mission case 17 can be improved.

  As apparent from FIGS. 13 to 24, the lift cylinder 117 is provided with a valve plate 655 that is hydraulically connected via a hydraulic pipe, and the valve plate 655 is placed on the upper front portion of the upper cover 118, and the upper surface of the valve plate 655 is placed. In addition, an elevating valve body 652 is mounted on the upper surface lid 118, and an inclination control electromagnetic valve 647 is disposed on the rear surface of the upper surface lid body 118. Accordingly, the valve plate 655 can be attached to and detached from the upper surface lid body 118 in a state where the elevation valve body 652 and the tilt control electromagnetic valve 647 are assembled to the upper surface lid body 118 via the valve plate constituting the hydraulic circuit. In a state where the valve plate 655 is assembled to the lid body 118, the upper surface lid body 118 can be attached to and detached from the upper surface of the mission case 17, and assembly and maintenance workability of the lift valve body 652 and the tilt control electromagnetic valve 647 can be simplified.

  As apparent from FIGS. 13 to 24, the structure includes left and right lift arms 120 that connect the left and right lift cylinders 117 and the left and right lower links 23. A lift fulcrum shaft 119 is provided, and the left and right lift arms 120 are arranged via the lift fulcrum shaft 119. The lift valve body 652 and the lift fulcrum shaft at the front of the upper surface of the upper cover 118 among the upper surfaces of the upper cover 118 are provided. An inclination control electromagnetic valve 647 is disposed on the upper surface between 119. Therefore, the tilt control electromagnetic valve 647 can be arranged on the upper surface side closer to the horizontal cylinder 122 among the upper surface side of the upper surface lid 118 while the assembly and maintenance of the lift valve body 652 can be simplified. It is possible to simplify the hydraulic piping work or the maintenance work of 122 and the tilt control electromagnetic valve 647.

  As apparent from the above description and FIGS. 1, 5, and 13 to 24, the traveling machine body 2 on which the diesel engine 5 is mounted, the transmission case 17 that changes the power of the diesel engine 5, and the traveling machine body 2 are attached and detached. In a work vehicle provided with a hydraulic external take-off valve 430 as a hydraulic external take-out mechanism that supplies hydraulic oil to a hydraulically-driven work machine (front loader work machine or the like) that can be mounted as possible, a three-point link mechanism 111 is attached to the transmission case 17 In this structure, a lift fulcrum shaft 119 is pivotally supported by a lift arm 120 which is a part of a lifting mechanism 22 for moving up and down. The transmission case 17 includes a front transmission case 112 and an intermediate case 114. And a rear transmission case 113, and a lift fulcrum shaft 119 is provided on the upper cover 118 of the rear transmission case 113. It is arranged hydraulic outcoupling valve 430 above the lift pivot shaft 119 providing portion top lid 118. Therefore, the hydraulic equipment parts (hydraulic external take-off valve 430) relating to the lifting mechanism 22 provided behind the mission case 17 can be arranged together on the upper cover 118, and a unit configuration can be formed. Assembling the hydraulic external take-out valve 430 to the mission case 17 In addition, maintenance work and the like can be easily simplified, and the ease of assembly of the mission case 17 can be improved.

  As is apparent from FIGS. 13 to 24, the elevating mechanism 22 operates the horizontal cylinder 122 that changes the left / right inclination angle of the tilling work machine (not shown) supported by the three-point link mechanism 111 and the horizontal cylinder 122. A tilt control electromagnetic valve 647 serving as a horizontal control valve is provided, and the hydraulic external take-out mechanism is provided with a hydraulic external take-out valve 430 that switches in and out of the hydraulic oil to and from the hydraulically driven working machine, A hydraulic external take-off valve 430 is placed on the upper surface 118 and behind the tilt control electromagnetic valve 647. Therefore, the upper cover 118 can be attached to and detached from the mission case 17 with the hydraulic external take-off valve 430 and the tilt control solenoid valve 647 assembled to the upper cover 118, and the hydraulic external take-out valve 430 and the tilt control solenoid valve 647 can be connected. Assembly and maintenance workability can be simplified. The hydraulic external take-off valve 430 can be arranged at the position where the hydraulic pipe is easily provided at the rearmost part of the upper surface of the transmission case 17 to improve the handling workability of the hydraulic external take-out valve 430.

  As apparent from FIGS. 5, 6, and 13 to 24, the tread adjustment hydraulic cylinder 645 that changes the widths of the left and right wheels 3 and 4 so as to face the ridge width of the field and the tread adjustment hydraulic cylinder 645 are controlled to operate. The tread adjusting electromagnetic valve 646 is arranged on the upper surface side of the hydraulic external take-off valve 430, and the rear surface side of the cabin 7 on which the operator gets on the rear fender 21 of the left and right rear wheels 4 is provided. Thus, the front side and the left and right side surfaces of the hydraulic external take-out valve 430 and the tread adjusting electromagnetic valve 646 are configured to be enclosed. That is, the hydraulic external take-off valve 430 is detachably mounted on the upper face side between the left and right lift arms 120 in the upper face side of the upper cover body, and the tread adjusting electromagnetic valve 646 is attached and detached on the upper face side of the hydraulic external take-out valve 430. It is placed as possible. Therefore, while the assembly and maintenance of the hydraulic external take-out valve 430 can be simplified, the hydraulic piping work or maintenance work of the hydraulic external take-out valve 430 and the tread adjusting electromagnetic valve 646 on the upper surface side of the upper cover 118 is performed. It can be simplified. In addition, the tread adjusting hydraulic cylinder 645 and the tread adjusting electromagnetic valve 646 can be easily assembled to the airframe structure without the tread adjusting hydraulic cylinder 645, and the tread adjusting hydraulic cylinder 645 can be provided with a small number of replacement parts. The airframe structure can be configured at low cost.

2 traveling machine body 5 diesel engine 17 mission case 22 hydraulic lifting mechanism 23 lower link 24 top link 111 three-point link mechanism 112 front transmission case 113 rear transmission case 114 intermediate case 117 hydraulic lift cylinder 118 upper surface cover 119 lift fulcrum shaft ( Lifting fulcrum shaft)
120 Lift arm 494 Rear partition wall (partition plate)
495 Front chamber 496 Rear chamber 497 Intermediate chamber 648 Ascending hydraulic pressure switching valve (elevating valve body)
649 Lowering hydraulic pressure switching valve (elevating valve body)
650 Ascent control solenoid valve (elevating valve body, hydraulic proportional valve)
651 Lowering control solenoid valve (elevating valve body, hydraulic proportional valve)
652 Lifting valve body 655 Valve plate 656 Top link hinge

Claims (5)

A traveling machine body on which an engine is mounted; a link mechanism that mounts a work machine on the traveling machine body; and a lifting mechanism that moves the link mechanism up and down. A part of the traveling machine body is configured by a transmission case, and the link mechanism In a work vehicle in which a part of the left and right lower links are configured, a part of the lifting mechanism is configured by a lift cylinder, and a work machine is mounted on the traveling machine body so as to be lifted and lowered via the left and right lower links.
A structure including a lift valve body for operating the lift cylinder, wherein the transmission case is composed of a front case, an intermediate case, and a rear case, and an upper surface cover body installed on an upper surface of the rear case. A work vehicle comprising the lift valve body.   The valve plate includes a valve plate that is hydraulically connected to the lift cylinder via a hydraulic pipe, and a hydraulic proportional valve that serves as the elevating valve body, and the valve plate is placed on an upper front portion of the upper cover body, The work vehicle according to claim 1, wherein the lift valve body (the hydraulic proportional valve) is placed on an upper surface.   The transmission case forms a front chamber with the front case, forms an intermediate chamber in front of the intermediate case and the rear case, forms a rear chamber behind the rear case, and is installed in the rear case. The intermediate chamber and the rear chamber are partitioned through a partition plate, and the upper surface side of the rear chamber among the upper surface side of the rear chamber is opened and covered with the upper surface cover. The work vehicle according to claim 2.   The left and right lift arms for connecting the left and right lift cylinders and the left and right lower links are provided, and the left and right lift arms are arranged on the upper surface lid via an elevating fulcrum shaft. The work vehicle as described in.   The work according to claim 2, wherein a part of the link mechanism is constituted by a top link, and a top link hinge to which the top link is coupled is fixedly supported on a rear surface side of the upper surface lid. vehicle.

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