JP4632424B2 - Work vehicle - Google Patents

Description

  The present invention relates to a work vehicle such as a tractor used for agricultural work or a wheel loader used for civil engineering work.

  Conventionally, in general, in the tractor or wheel loader described above, an engine is installed at the front of the aircraft, a mission case is installed at the rear of the aircraft, and the aircraft is supported by front and rear wheels. In this case, the engine is mounted on the front part of the body frame, and the transmission case is arranged on the rear part of the body frame (for example, Patent Document 1).

In the above-described tractor, wheel loader, or the like, when the left and right wheels are driven, the power of the engine mounted on the front portion of the airframe is transmitted to the left and right wheels via the traveling speed change mechanism and the differential gear mechanism. In this case, as disclosed in Patent Document 2, the traveling transmission mechanism is provided with a hydraulic continuously variable transmission. The hydraulic continuously variable transmission includes a cylinder block and first and first cylinder blocks. And a pump and a motor plunger housed in the two plunger holes, and first and second spool valves that selectively communicate the plunger hole with the first oil chamber or the second oil chamber. Then, communication between the first and second plunger holes and the first and second oil chambers is switched by the first and second spool valves, and the first and second hydraulic chambers passing through the first and second oil chambers are switched to the first and second hydraulic chambers. The second plunger hole was configured to be connected. An inline continuously variable transmission in which an input shaft for transmitting power from the engine and an output shaft for transmitting hydraulic shift output to the left and right wheels are arranged concentrically, and constitutes the continuously variable transmission The hydraulic pump unit and the hydraulic motor unit are arranged on both sides of the motor, and the input shaft and the output shaft are configured as a double shaft.
JP-A-11-334395 JP 2002-89655 A

  However, when the technique of Patent Document 2 is applied to the tractor of Patent Document 1, for example, in a transmission structure in which the mechanisms of the traveling sub-transmission gear, the differential gear, and the PTO transmission gear are installed in the transmission case, The continuously variable transmission is provided in the case. For example, in a structure in which a speed change actuator for controlling the output of the continuously variable transmission or a switching means for controlling the speed change actuator is attached to the outside of the transmission case, the connection between the speed change portion of the continuously variable transmission and the speed change actuator is easy. There was a problem that could not be done. On the other hand, in a structure in which the speed change actuator for controlling the output of the continuously variable transmission or the switching means for controlling the speed change actuator is mounted inside the transmission case, operations such as assembly and maintenance of the speed change actuator or the switching means are performed in the speed change gear. Or there was a problem limited by the differential gear.

  An object of the present invention is to provide a work vehicle that can easily connect a speed change portion and a speed change actuator of the continuously variable transmission and can easily perform operations such as assembly and maintenance of the speed change actuator or switching means.

In the invention according to claim 1 , an input shaft to which power from the engine is transmitted is disposed in the transmission case, and an output shaft is fitted to the input shaft so as to be relatively rotatable. A cylinder block that constitutes a continuously variable transmission, a hydraulic pump part on one side sandwiching the cylinder block, and a hydraulic motor part on the other side are fitted, and at least traveling driving force from the output shaft via the hydraulic motor part In a work vehicle configured to transmit power, a shift hydraulic cylinder for detachably installing a side wall member for bearing one end of the input shaft to the transmission case and controlling the shift of the hydraulic pump unit A shift oil pressure switching valve for operating the speed change hydraulic cylinder is disposed on the side wall member, a cylinder chamber in which a piston of the speed change hydraulic cylinder is provided, and a speed change spool of the speed change oil pressure change valve. A spool chamber to be provided is formed in the side wall member, and includes a proportional control valve for switching and controlling the shift hydraulic pressure switching valve, the proportional control valve is a proportional control valve housing fastened to the rear side wall member; The proportional control valve housing includes a proportional control spool installed in a slidable manner, wherein the piston and the proportional control spool are arranged to be slidable in the vertical direction, and on the lower side of the piston. The speed change spool is installed, and the speed change spool is slidably arranged in the left-right direction.

According to a second aspect of the present invention, the proportional control valve housing is provided with a proportional control solenoid and a manual switching lever for operating the proportional control spool.

The invention according to claim 1 is not limited to the transmission hydraulic cylinder , such as a transmission structure of a tractor, in which a traveling auxiliary transmission gear, a differential gear, a PTO transmission gear, and the like are installed inside the transmission case. The side wall member can be attached to and detached from the transmission case with the shift hydraulic pressure switching valve attached to the side wall member. Accordingly, the relative position between the transmission unit of the continuously variable transmission and the transmission hydraulic cylinder is determined by the connection between the side wall member and the transmission case, and the workability such as assembly and maintenance can be improved.

In the invention according to claim 1 , an input shaft to which power from the engine is transmitted is disposed in the transmission case, and an output shaft is fitted to the input shaft so as to be relatively rotatable. A cylinder block that constitutes a continuously variable transmission, a hydraulic pump part on one side sandwiching the cylinder block, and a hydraulic motor part on the other side are fitted, and at least traveling driving force from the output shaft via the hydraulic motor part In a work vehicle configured to transmit power, a shift hydraulic cylinder for detachably installing a side wall member for bearing one end of the input shaft to the transmission case and controlling the shift of the hydraulic pump unit A shift oil pressure switching valve for operating the speed change hydraulic cylinder is disposed on the side wall member, a cylinder chamber in which a piston of the speed change hydraulic cylinder is provided, and a speed change spool of the speed change oil pressure change valve. A spool chamber to be provided is formed in the side wall member, and includes a proportional control valve for switching and controlling the shift hydraulic pressure switching valve, and the proportional control valve is a proportional control valve housing fastened to the rear side wall member; The proportional control valve housing includes a proportional control spool installed in a slidable manner, wherein the piston and the proportional control spool are arranged to be slidable in the vertical direction, and on the lower side of the piston. Since the transmission spool is installed and the transmission spool is slidably arranged in the left-right direction, the piston, the transmission spool, and the proportional control spool can be compactly arranged on the rear side wall member.

In the invention according to claim 2 , since the proportional control valve housing is provided with a proportional control solenoid and a manual switching lever for operating the proportional control spool, for example, a shift lever or a shift pedal, etc. A remote operation structure for controlling the shift of the hydraulic pump unit via a proportional control solenoid and a manual operation structure for controlling the shift of the hydraulic pump unit via the manual switching lever are easily configured. In the case of maintenance work or emergency, the hydraulic pump unit can be controlled to shift through the manual switching lever.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, drawings when an embodiment of the present invention is applied to a farm tractor as a work vehicle will be described. 1 is a side view of the tractor, FIG. 2 is a rear perspective view thereof, FIG. 3 is an explanatory side view thereof, FIG. 4 is a perspective view of the tractor body, and FIG. 5 is a skeleton diagram of power transmission.

  As shown in FIGS. 1 to 4, the tractor 1 supports a traveling machine body 2 by a pair of left and right rear wheels 4 as well as a pair of left and right front wheels 3, and is rear-mounted by an engine 5 mounted on the front part of the traveling machine body 2. By driving the wheel 4 and the front wheel 3, the vehicle is configured to travel forward and backward. The engine 5 is covered with a bonnet 6. In addition, a cabin 7 is installed on the upper surface of the traveling machine body 2, and a steering seat 8 and a steering handle 9 that moves the front wheel 3 to the left and right by steering are installed in the cabin 7. The A step 10 on which the operator gets on and off is provided on the outside of the cabin 7, and a fuel tank 11 for supplying fuel to the engine 5 is provided on the inside of the step 10 and 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 16 that are detachably fixed to the rear portion of the engine frame 14 with bolts 15. A mission case 17 is connected to the rear portion of the body frame 16 for transmitting the rotation of the engine 5 to the rear wheels 4 and the front wheels 3 with appropriate speed change. In this case, the rear wheel 4 is rearwardly attached to the transmission case 17 so as to protrude outward from the outer surface of the transmission case 17 and to the outer end of the rear axle case 18. It is attached via a gear case 19 that is mounted so as to extend.

  A hydraulic working machine lifting mechanism 20 for lifting and lowering a working machine (not shown) such as a tiller is detachably attached to the upper surface of the rear portion of the mission case 17. The working machine such as a tiller is connected to the rear part of the mission case 17 via a lower link 21 and a top link 22. Further, a PTO shaft 23 for the working machine such as the tiller is provided on the rear side surface of the mission case 17 so as to protrude rearward.

  FIG. 30 shows a hydraulic circuit 200 of the tractor 1 of the present embodiment, and includes a working machine hydraulic pump 94 and a traveling hydraulic pump 95 that are operated by the rotational force of the engine 5, as will be described later. The traveling hydraulic pump 95 is connected to a hydraulic cylinder 93 for power steering by the round handle 9 via a control valve 202 for power steering, and a switching valve for operating a brake cylinder 68 for a pair of left and right auto brakes 65, respectively. Are connected to left and right autobrake solenoid valves 67a and 67b. Further, the traveling hydraulic pump 95 is provided for the PTO clutch hydraulic solenoid valve (proportional control valve) 104 for the PTO clutch 100 and the transmission parts of the transmission case 17, that is, the hydraulic continuously variable transmission 29 for main transmission described later. Proportional control valve 203 for switching main shift, shift hydraulic switching valve 204 operated thereby, shift shift electromagnetic valve 666 of traveling sub shift hydraulic cylinder 55, hydraulic clutch 40 for switching forward and reverse traveling, 42, a forward clutch electromagnetic valve 46, a reverse clutch electromagnetic valve 48, a four-wheel hydraulic solenoid valve 80 for a four-wheel hydraulic clutch 74 for simultaneously driving the front wheel 3 and the rear wheel 4, and a front wheel 3 is connected to a double speed hydraulic solenoid valve 82 for a double speed hydraulic clutch 76 for switching to double speed drive. The work machine hydraulic pump 94 is connected to a control electromagnetic valve 201 for supplying hydraulic oil to the single-acting hydraulic cylinder 205 in the work machine lifting mechanism 20. As shown in FIG. 15, the hydraulic circuit 200 includes a relief valve, a flow rate adjusting valve, a check valve, an oil cooler, an oil filter, and the like.

  5 to 7 show the mission case 17. The mission case 17 is partitioned inside and behind by a partition wall 31. A front side wall member 32 is detachably fixed to the front side of the mission case 17 with bolts. A rear side wall member 33 is detachably fixed to the rear side of the mission case 17 with bolts. The mission case 17 is formed in a box shape, and a front chamber 34 and a rear chamber 35 are formed inside the mission case 17. The front chamber 34 and the rear chamber 35 are in communication with each other so that the hydraulic oil (lubricating oil) inside these chambers moves relative to each other.

  As shown in FIG. 5, the front side wall member 32 is provided with a front wheel drive case 69 described later. In the front chamber 34, a travel auxiliary transmission gear mechanism 30 and a PTO transmission gear mechanism 96, which will be described later, are arranged. In the rear chamber 35, a hydraulic continuously variable transmission 29, which is a traveling main transmission mechanism described later, and a differential gear mechanism 58 are arranged.

  An engine output shaft 24 is provided on the rear side surface of the engine 5 so as to protrude rearward. A flywheel 25 is attached to the engine output shaft 24 so as to be directly connected. Between a main drive shaft 26 projecting rearward from the flywheel 25 and a main transmission input shaft 27 projecting forward from the front surface of the transmission case 17 via an extendable power transmission shaft 28 having a universal joint at both ends. Connect. The rotation of the engine 5 is transmitted to the main transmission input shaft 27 in the transmission case 17, and then appropriately shifted by the hydraulic continuously variable transmission 29 and the traveling auxiliary transmission gear mechanism 30, via the differential gear mechanism 58. Thus, the driving force is transmitted to the rear wheel 4. Further, the rotation of the engine 5 that has been appropriately shifted by the traveling auxiliary transmission gear mechanism 30 is transmitted to the front wheels 3 via the front wheel drive case 69 and the differential gear mechanism 86 of the front axle case 13. Become.

  Next, FIG. 8 and FIG. 9 show an inline hydraulic continuously variable transmission 29 in which a main transmission output shaft 36 is concentrically arranged on the main transmission input shaft 27. A hydraulic continuously variable transmission 29 is installed in the rear chamber 35 via a main transmission input shaft 27. The rear end side of the main transmission input shaft 27 extends to the rear side wall member 33. The rear end side of the main transmission input shaft 27 opposite to the input side (front end side) of the main transmission input shaft 27 is rotatably supported by the rear side wall member 33 by a ball bearing 504.

  A cylindrical main transmission output shaft 36 is fitted on the front side of the hydraulic continuously variable transmission 29, that is, on the input side of the main transmission input shaft 27. A main transmission output gear 37 for taking out the main transmission output from the hydraulic continuously variable transmission 29 is provided on the main transmission output shaft 36. The middle of the main transmission output shaft 36 is penetrated by the partition wall 31, and the front end and the rear end protrude into the front chamber 34 and the rear chamber 35, respectively. The middle of the main transmission output shaft 36 is rotatably supported on the partition wall 31 by two sets of ball bearings 502. A main transmission output gear 37 is provided at the front end portion of the main transmission output shaft 36. The input side of the main transmission input shaft 27 protrudes forward from the front end of the main transmission output shaft 36 such that the input side of the main transmission input shaft 27 projects forward from the front end of the main transmission output shaft 36 via the roller bearing 503. (See FIG. 9).

  As will be described below, the hydraulic continuously variable transmission 29 includes a variable displacement type shifting hydraulic pump unit 500 and a constant displacement type shifting hydraulic pressure that operates with high-pressure hydraulic fluid discharged from the hydraulic pump unit 500. A motor unit 501.

  A cylinder block 505 for the hydraulic pump unit 500 and the hydraulic motor unit 501 is fitted on the main transmission input shaft 27 substantially in the middle between the partition wall 31 and the rear side wall member 33. The main transmission input shaft 27 and the cylinder block 505 are connected by a spline 525. The hydraulic pump unit 500 is disposed on one side of the main transmission input shaft 27 opposite to the input side with the cylinder block 505 interposed therebetween. A hydraulic motor unit 501 is disposed on the other side of the cylinder block 505 that is the input side of the main transmission input shaft 27.

  The hydraulic pump unit 500 includes a first holder 510 that is fixed to the inner side surface of the transmission case 17 so as to face the side surface of the cylinder block 505, and a tilt angle that can be changed with respect to the axis of the main transmission input shaft 27. A pump swash plate 509 disposed in the holder 510, a shoe 508 slidably provided on the pump swash plate 509, a pump plunger 506 connected to the shoe 508 through a spherical universal joint, and the pump plunger 506 connected to the cylinder block 505 And a first plunger hole 507 arranged to be freely accessible. One end of the pump plunger 506 protrudes from the side surface of the cylinder block 505 toward the pump swash plate 509 (right side in FIG. 8). The hydraulic pump unit 500 includes a cylinder block 505, a pump plunger 506, a shoe 508, a pump swash plate 509, and a first holder 510.

  A sleeve 511 fitted to the main transmission input shaft 27, a roller bearing 512, and radial and thrust load roller bearings 513 are interposed between the main transmission input shaft 27 and the first holder 510. A nut 514 is provided behind the main transmission input shaft 27 to prevent the roller bearing 513 from coming out.

  The cylinder block 505 is provided with the same number of first spool valves 536 as the pump plungers 506. In addition, a first radial bearing 537 is disposed in the first holder 510. The first radial bearing 537 is provided in the first holder 510 so as to be inclined at a constant inclination angle with respect to the axis of the main transmission input shaft 27. In FIG. 8, the position rotated about 90 degrees with respect to the pump swash plate 509 (the front side of the drawing of FIG. 8) is separated from the side surface of the cylinder block 505 by about 180 degrees (the back side of the drawing of FIG. 8). The first radial bearing 537 is inclined and supported such that the first radial bearing 537 is close to the side surface of the cylinder block 505.

  On the other hand, the hydraulic motor unit 501 includes a second holder 519 arranged to face the side surface of the cylinder block 505, and a second holder 519 so as to maintain a constant inclination angle with respect to the axis of the main transmission input shaft 27. A motor swash plate 518 to be fixed, a shoe 517 slidably provided on the motor swash plate 518, a motor plunger 515 connected to the shoe 517 via a spherical universal joint, and the motor plunger 515 to be able to enter and exit the cylinder block 505 A second plunger hole 516 is provided. One end of the motor plunger 515 protrudes from the side surface of the cylinder block 505 in the direction of the motor swash plate 518 (left side in FIG. 8). The hydraulic motor unit 501 includes a cylinder block 505, a motor plunger 515, a shoe 517, a motor swash plate 518, and a second holder 519.

  A joint member 526 is fixed to the second holder 519 with a bolt 527. The output shaft 36 and the joint member 525 are connected by a spline 528.

  Between the main transmission input shaft 27 and the second holder 519, radial load roller bearings 520 and 521, a sleeve 522 fitted to the main transmission input shaft 27, a radial and thrust load roller bearing 523, Intervenes. A nut 524 is provided to prevent the roller bearing 523 from coming out of the main transmission input shaft 27.

  The cylinder block 505 is provided with the same number of second spool valves 540 as the motor plungers 515. In addition, a second radial bearing 541 is disposed in the second holder 519. The second radial bearing 541 is provided in the second holder 519 so as to be inclined at a constant inclination angle with respect to the axis of the main transmission input shaft 27. In FIG. 8, the cylinder block 505 is on the opposite side (back side in FIG. 8) about 180 degrees so that the position rotated about 90 degrees with respect to the motor swash plate 518 (front side in FIG. 8) is close to the side surface of the cylinder block 505. The second radial bearing 541 is configured to be tilted and supported so as to be separated from the side surface of the first radial bearing.

  The pump plungers 506 and the same number of motor plungers 515 as the pump plungers 506 are alternately arranged on the same circumference of the rotation center of the cylinder block 505.

  Further, a ring groove-shaped first oil chamber 530 and a ring groove-shaped second oil chamber 531 are formed in the shaft hole of the cylinder block 505 into which the main transmission input shaft 27 is inserted. The cylinder block 505 is formed with a first valve hole 532 and a second valve hole 533 that are arranged at substantially equal intervals on the same circumference of the rotation center. The first valve hole 532 and the second valve hole 533 communicate with the first oil chamber 530 and the second oil chamber 531, respectively. The first plunger hole 507 communicates with the first valve hole 532 via the first oil passage 534, and the second plunger hole 516 communicates with the second valve hole 533 via the second oil chamber 531.

  A first spool valve 536 is inserted into the first valve hole 532. The first spool valves 536 are arranged at substantially equal intervals on the same circumference of the rotation center of the cylinder block 505. The tip of the first spool valve 536 protrudes in the direction of the first holder 510 from the first valve hole 532 with the back pressure spring force, and the tip of the first spool valve 536 abuts the side surface of the outer ring 538 of the first radial bearing 537. Be touched. Then, the first spool valve 536 reciprocates once in one rotation of the cylinder block 505, and the first plunger hole 507 is connected to the first oil chamber 530 or the second oil via the first valve hole 532 and the first oil passage 534. The chamber 531 is configured to communicate with each other alternately.

  A second spool valve 540 is inserted into the second valve hole 533. The second spool valves 540 are arranged at substantially equal intervals on the same circumference of the rotation center of the cylinder block 505. The tip of the second spool valve 540 protrudes in the direction of the second holder 519 from the second valve hole 533 due to the back pressure spring force, and the tip of the second spool valve 540 contacts the side surface of the outer ring 542 of the second radial bearing 541. Be touched. Then, the second spool valve 540 reciprocates once by one rotation of the cylinder block 505, and the second plunger hole 516 passes through the second valve hole 533 and the second oil passage 535, and passes through the first oil chamber 530 or the second oil. The chamber 531 is configured to communicate with each other alternately.

  Further, a hydraulic oil supply oil passage 543 is formed in the central portion of the main transmission input shaft 27 in the axial direction. The supply oil passage 543 is opened at the rear end face of the main transmission input shaft 27 and communicates with the discharge port of the traveling hydraulic pump 95 described above. The first charge valve 544 replenishes the first oil chamber 530 with the hydraulic oil in the hydraulic oil supply oil passage 543, and the second charge valve 545 replenishes the second oil chamber 531 with the hydraulic oil in the hydraulic oil supply oil passage 543. And are provided.

  And with respect to the hydraulic closed circuit formed between the first and second plunger holes 507 and 516 and the first and second oil chambers 530 and 531, the first and second charge valves 544 and 545 are passed through, The hydraulic oil is supplied from the hydraulic oil supply oil passage 543. It should be noted that hydraulic oil is supplied from the hydraulic oil supply oil passage 543 to the rotating portions of the hydraulic pump unit 500 and the motor unit 501 as lubricating oil via check valves.

  Further, the pump swash plate 509 is disposed on the outer periphery of the small diameter portion of the first holder 510 via an inclination angle adjustment fulcrum 555 as described later (see FIG. 9). The pump swash plate 509 is provided such that its inclination angle is adjustable with respect to the axis of the main transmission input shaft 27. A main transmission hydraulic cylinder 556 for main transmission, which is a transmission actuator for changing the inclination angle of the pump swash plate 509 with respect to the axis of the main transmission input shaft 27, is provided (see FIG. 9). The main transmission hydraulic cylinder 556 is configured to change the inclination angle of the pump swash plate 509 so that the main transmission operation of the continuously variable transmission 29 is performed. The first holder 510 is coupled to the rear side wall member 33 that is a non-rotating portion of the transmission case 17 via the holder coupling member 690 so that the pump swash plate 509 does not rotate with respect to the main transmission input shaft 27. (See Figure 14).

  The main transmission operation of the inline hydraulic continuously variable transmission 29 will be described below. The hydraulic cylinder 556 is controlled by a main transmission lever or the like, and the inclination angle of the pump swash plate 509 is changed with respect to the axis line of the main transmission input shaft 27.

  First, even if the cylinder block 505 is rotated when the tilt angle of the pump swash plate 509 is kept substantially zero so that the pump swash plate 509 is substantially orthogonal to the axis of the main transmission input shaft 27, the first plunger hole The pump plunger 506 is supported in a substantially constant posture at 507 so that the pump plunger 506 does not move forward and backward, and the hydraulic oil in the first plunger hole 507 is not discharged from the first oil passage 534 toward the first valve hole 532 in the discharge stroke of the pump plunger 506. The hydraulic oil is not supplied from the first plunger hole 507 to the second plunger hole 516, and the motor plunger 515 does not advance. Further, since the hydraulic oil is not drawn into the first plunger hole 507 even during the suction stroke of the pump plunger 506, the hydraulic oil is not discharged from the second plunger hole 516 into the first plunger hole 507, and the motor plunger 515 does not retract.

  That is, when the tilt angle of the pump swash plate 509 is substantially zero, the transmission motor 501 is not driven by the transmission pump unit 500. Therefore, the motor swash plate 518 is fixed to the cylinder block 505 via the motor plunger 515, and the cylinder block 505 and the motor swash plate 518 rotate at the same rotational speed in the same direction. The main transmission output shaft 36 is rotated at substantially the same rotational speed, and the rotational speed of the main transmission input shaft 27 is transmitted to the main transmission output gear 37 without being changed.

  Next, when the pump swash plate 509 is tilted with respect to the axis of the main transmission input shaft 27, the rotation of the cylinder block 505 that rotates integrally with the main transmission input shaft 27 causes the outer ring 538 of the first radial bearing 537 to be The 1-spool valve 536 slides back and forth, and the first oil chamber 530 or the second oil chamber 531 communicates with the first plunger hole 507 alternately every half rotation of the cylinder block 505. Further, the second spool valve 540 slides back and forth at the outer ring 542 of the second radial bearing 541, and the first oil chamber 530 or the second oil chamber 531 alternates with the second plunger hole 516 every half rotation of the cylinder block 505. Communicated with A closed hydraulic circuit is formed between the first plunger hole 507 and the second plunger hole 516, and hydraulic oil is pumped from the first plunger hole 507 to the second plunger hole 516 in the discharge stroke of the pump plunger 506, The hydraulic fluid is returned from the second plunger hole 516 to the first plunger hole 507 during the suction stroke of the pump plunger 506, and the operation of the axial piston pump and the motor is performed.

  When the pump swash plate 509 is inclined in one direction (positive inclination angle) with respect to the axis line of the main transmission input shaft 27, the motor swash plate 518 is rotated in the same direction as the cylinder block 505, and the transmission motor 501 is rotated. The main transmission output shaft 36 is rotated at a higher rotational speed than the main transmission input shaft 27, and the rotational speed of the main transmission input shaft 27 is increased and transmitted to the main transmission output gear 37. . That is, the rotation speed of the transmission motor 501 driven by the transmission pump 500 is added to the rotation speed of the main transmission input shaft 27 and transmitted to the main transmission output gear 37. Therefore, the shift output (travel speed) from the main shift output gear 37 is proportional to the inclination (positive inclination angle) of the pump swash plate 509 within the range of the rotation speed higher than the rotation speed of the main transmission input shaft 27. As a result, the maximum traveling speed is reached at the maximum inclination (positive inclination angle) of the pump swash plate 509.

  Further, when the pump swash plate 509 is inclined in the other direction (negative inclination angle) with respect to the axis of the main transmission input shaft 27, the motor swash plate 518 is rotated in the direction opposite to the cylinder block 505, and the transmission motor The main transmission output shaft 36 is rotated at a lower rotational speed than the main transmission input shaft 27, and the rotational speed of the main transmission input shaft 27 is decelerated and transmitted to the main transmission output gear 37.

  That is, the rotation speed of the transmission motor 501 driven by the transmission pump 500 is subtracted from the rotation speed of the main transmission input shaft 27 and transmitted to the main transmission output gear 37. Therefore, the shift output (travel speed) from the main shift output gear 37 is proportional to the inclination (negative inclination angle) of the pump swash plate 509 within the range of the rotation speed lower than the rotation speed of the main transmission input shaft 27. As a result, the minimum traveling speed is reached at the maximum inclination (negative inclination angle) of the pump swash plate 509.

  Next, as shown in FIGS. 5 and 6, the front chamber 34 of the mission case 17 has a forward gear 41 and a reverse gear 43 for switching between forward and reverse, and a traveling auxiliary gear for switching between low speed and high speed. A transmission gear mechanism 30 is disposed.

  A description will be given of switching between forward and reverse movements through the forward gear 41 and the reverse gear 43. As shown in FIG. 6, a travel counter shaft 38 and a reverse rotation shaft 39 are disposed in the front chamber 34 where the main transmission output gear 37 is disposed. The travel counter shaft 38 is fitted with a forward gear 41 connected by a forward wet multi-plate hydraulic clutch 40 and a reverse gear 43 connected by a reverse wet multi-plate hydraulic clutch 42. Is done. The forward gear 41 is meshed with the main transmission output gear 37. The main transmission output gear 37 is engaged with a reverse gear 44 provided on the reverse shaft 39. The reverse gear 43 meshes with a reverse output gear 45 provided on the reverse shaft 39.

  Then, by a forward operation of the main transmission lever (not shown), the clutch cylinder 47 is operated by the forward hydraulic solenoid valve 46 and the forward hydraulic clutch 40 is continued, and the main transmission output gear 37 and the travel counter shaft 38 are advanced. It connects so that it may be connected with the gear 41 (refer FIG. 5, FIG. 6).

  On the other hand, by a reverse operation of the main speed change lever (not shown), the reverse hydraulic solenoid valve 48 operates the clutch cylinder 49 to continue the reverse hydraulic clutch 42, and the main speed change output gear 37 and the travel counter shaft 38 move backward. It connects so that it may be connected with the gear 43 (refer FIG. 5, FIG. 6).

  When the main transmission lever (not shown) is supported at the neutral position, both the forward and reverse wet multi-plate hydraulic clutches 40 and 42 are disconnected, and the front wheel 3 and the rear wheel 4 are both disconnected. The traveling drive force from the main transmission output gear 37 that is output to the engine is substantially zero (main clutch disengaged state).

  Next, switching between the low speed and the high speed performed through the traveling auxiliary transmission gear mechanism 30 will be described. As shown in FIGS. 5 and 6, a traveling auxiliary transmission gear mechanism 30 and an auxiliary transmission shaft 50 are disposed in the front chamber 34 of the transmission case 17. Between the travel counter shaft 38 and the auxiliary transmission shaft 50, low-speed gears 51 and 52 for auxiliary transmission and high-speed gears 53 and 54 for auxiliary transmission are provided. Further, a low speed clutch 56 and a high speed clutch 57 which are continued or disconnected by the auxiliary transmission hydraulic cylinder 55 are provided. The low speed clutch 56 or the high speed clutch 57 is continued in the auxiliary speed change hydraulic cylinder 55 by operating the auxiliary speed change lever (not shown) or detecting the rotational speed of the engine 5. The high-speed gear 54 is connected, and the driving force is output from the auxiliary transmission shaft 50 to the front wheels 3 and the rear wheels 4.

  The rear end of the auxiliary transmission shaft 50 extends through the partition wall 31 and extends into the rear chamber 35 of the transmission case 17 (see FIG. 5). A pinion 59 is provided at the rear end portion of the auxiliary transmission shaft 50. In addition, a differential gear mechanism 58 that transmits traveling driving force to the left and right rear wheels 4 is disposed in the rear chamber 35. The differential gear mechanism 58 includes a ring gear 60 that meshes with a pinion 59 at the rear end of the auxiliary transmission shaft 50, a differential gear case 61 provided in the ring gear 60, and left and right differential output shafts 62. The differential output shaft 62 is connected to the rear axle 64 by a final gear 63 or the like, and is configured to drive the rear wheel 4 provided on the rear axle 64.

  Further, a brake 65 is installed on the differential output shaft 62, and the brake 65 is configured to be braked by operating the left and right brake pedals 66. On the other hand, when the steering angle of the handle 9 is detected, the brake cylinder 68 is actuated by the autobrake solenoid valve 67, the brake 65 is automatically braked, and a turning travel such as a U-turn is performed. Yes.

  Next, as shown in FIGS. 5 and 6, switching between the two-wheel drive and the four-wheel drive of the front and rear wheels 3, 4 will be described.

  A front wheel drive case 69 is provided on the front side wall member 32 of the mission case 17. The front wheel drive case 69 is provided with a front wheel input shaft 72 and a front wheel output shaft 73. The front wheel input shaft 72 is connected to the auxiliary transmission shaft 50 by gears 70 and 71. The front wheel output shaft 73 is fitted with a four-wheel drive gear 75 connected by a four-wheel drive hydraulic clutch 74 and a double speed gear 77 connected by a double speed hydraulic clutch 76. The four-wheel drive gear 75 and the double speed gear 77 are connected to the front wheel input shaft 72 by gears 78 and 79, respectively.

  Then, by the four-wheel drive operation of the switching lever (not shown) of the two-wheel drive and the four-wheel drive, the clutch cylinder 81 is operated by the four-wheel hydraulic solenoid valve 80 and the four-wheel drive hydraulic clutch 74 is continued, and the front wheel input shaft 72 and the front wheel output shaft 73 are connected by a four-wheel drive gear 75, and the front wheel 3 is driven together with the rear wheel 4.

  Next, as shown in FIGS. 5 and 6, switching of the double speed drive of the front wheels 3 will be described.

  Upon detection of the U-turn (direction change at the headland in the field) operation of the steering handle 9, the clutch cylinder 83 is operated by the double speed hydraulic solenoid valve 82, and the double speed hydraulic clutch 76 is continued. And the front wheel output shaft 73 are connected by a double speed gear 77 so that the front wheel 3 is driven at a speed approximately twice as high as that when the front wheel 3 is driven by the four-wheel drive gear 75. Configure.

  As shown in FIG. 5, the front wheel 3 is powered between a front wheel input shaft 84 projecting rearward from the front axle case 13 and a front wheel output shaft 73 projecting forward from the front surface of the transmission case 17. Are connected via a front wheel drive shaft 85 that transmits In addition, a differential gear mechanism 86 that transmits traveling driving force to the left and right front wheels 3 is disposed inside the front axle case 13.

  The differential gear mechanism 86 includes a ring gear 88 that meshes with a pinion 87 at the front end of the front wheel input shaft 84, a differential gear case 89 provided in the ring gear 88, and left and right differential output shafts 90. A front axle 92 is connected to the differential output shaft 90 by a final gear 91 or the like, and a front wheel 3 provided on the front axle 92 is driven. Further, on the outer surface of the front axle case 13, a hydraulic cylinder 93 for power steering that changes the traveling direction of the front wheel to the right and left by the steering operation of the steering handle 9 is disposed.

  As shown in FIGS. 5 and 7, on the front side of the front side wall member 32 of the mission case 17, a working machine hydraulic pump 94 for supplying hydraulic fluid to the working machine lifting mechanism 20, a mission case And a traveling hydraulic pump 95 for supplying hydraulic oil to each of the 17 transmission parts and the hydraulic cylinder 93 for power steering. A transmission case 17 is used in combination as an oil tank so that hydraulic oil in the case 17 is supplied to the hydraulic pumps 94 and 95.

  Next, switching of the driving speed of the PTO shaft 23 (four forward rotations and one reverse rotation) will be described with reference to FIGS. The front chamber 34 of the transmission case 17 is provided with a PTO transmission gear mechanism 96 that transmits power from the engine 5 to the PTO shaft 23 and a pump drive shaft 97 that transmits power from the engine 5 to the hydraulic pumps 94 and 95 ( (See FIG. 7).

  As shown in FIG. 7, the PTO transmission gear mechanism 96 described in detail later includes a PTO counter shaft 98 and a PTO transmission output shaft 99. The PTO input gear 101 connected by the PTO hydraulic clutch 100 is fitted on the PTO counter shaft 98. An input side gear 102 provided on the main transmission input shaft 27 and an output side gear 103 of the pump drive shaft 97 are meshed with the PTO input gear 101, and the pump drive shaft 97 is connected to the main transmission input shaft 27.

  Then, by continuing the operation of the PTO clutch lever (not shown), the clutch cylinder 105 is operated by the PTO clutch hydraulic solenoid valve 104 (see FIG. 5), and the PTO hydraulic clutch 100 is continued. The PTO counter shaft 98 is connected to the PTO input gear 101.

  Further, a first speed gear 106, a second speed gear 107, a third speed gear 108, a fourth speed gear 109, and a reverse gear 110 are fitted on the PTO speed change output shaft 99 for PTO output (FIG. 5, see FIG.

  A shift shifter 111 is pivotally supported on the PTO shift output shaft 99 by a spline. The gears 106, 107, 108, 109, 110 are configured to be alternatively connected to the PTO shift output shaft 99 by a shift shifter 111. A shift arm 112 connected to a PTO shift lever (not shown) is engaged with the shift shifter 111. Then, a shift operation of the PTO shift lever (not shown) causes the shift shifter 111 to move linearly along the axis of the PTO shift output shaft 99 by the shift arm 112, and each gear 106, 107, 108, 109, Any one of 110 is selected and connected to the PTO shift output shaft 99 (see FIGS. 5 and 7). Therefore, the first, second, third, fourth, and reverse PTO shift outputs are transmitted from the PTO shift output shaft 99 to the PTO shaft 23 via the gears 113 and 114.

  In FIG. 6, a rotation detection gear 115 provided on the reverse rotation shaft 39 and a pickup 116 for detecting the rotation of the main transmission output gear 37 are installed facing each other, and the output rotation speed of the main transmission mechanism 29 is set by the pickup 116. Configure to detect. Further, a pickup 117 for detecting the rotation of the gear 78 of the front wheel input shaft 72 is installed, and the traveling speed (vehicle speed) is detected by the pickup 117 based on the rotation of the front wheel input shaft 72 and the auxiliary transmission shaft 50. Configure.

  As is apparent from the above description and FIG. 8 and the like, a transmission case 17 is provided that transmits power from the engine 5, and a hydraulic shift output is provided to the input shaft 27 that transmits power from the engine 5 and the left and right wheels 3 and 4. An inline-type continuously variable transmission 29 arranged on the same axis line as the output shaft 36 to be transmitted is disposed in the transmission case 17, and hydraulic pressure is applied to one side across the cylinder block 505 constituting the continuously variable transmission 29. In a working vehicle in which the hydraulic motor unit 501 is disposed on the other side of the pump unit 500 and the output shaft 36 is fitted on the input shaft 27 to form a dual shaft configuration, the input side of the input shaft 27 and the cylinder block The hydraulic motor 501 is disposed between the input shaft 27 and the output side of the output shaft 36 on the same side. Therefore, for example, even if the traveling auxiliary transmission gear, the differential gear, the PTO transmission gear, and the like are installed inside the transmission case 17 as in the transmission structure of the tractor 1, The installation space for the transmission 29 can be easily secured. An installation space such as a PTO transmission gear or a traveling auxiliary transmission gear is secured in the front portion of the transmission case 17 on the input side of the input shaft 27. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and the manufacturing cost can be reduced. Can be reduced.

  An output shaft 36 is rotatably supported by a bearing 502 inside the transmission case 17, and a front side of a swash plate 518 of a hydraulic motor unit 501 provided in the continuously variable transmission 29 and a rear side of the output shaft 36. Are connected by a spline 528 so as to be separable. Therefore, the operation of attaching or removing the continuously variable transmission 29 can be performed in a state where the hydraulic pump unit 500 and the hydraulic motor unit 501 are respectively disposed on both sides of the cylinder block 505 and supported by the input shaft 27. The output shaft 36 can be pivotally supported on the transmission case 17 by a bearing structure independent of the continuously variable transmission 29, and the transmission case 36 is continuously variable with respect to the transmission case 17 with the output shaft 36 pivotally supported on the transmission case 17. The machine 29 can be attached and detached, and the continuously variable transmission 29 can be easily attached or removed.

  Further, the continuously variable transmission 29 and a differential gear mechanism 58 for transmitting power to the left and right wheels 4 are provided in the transmission case 17. Therefore, the continuously variable transmission 29 can be arranged in a compact manner by using the excess space inside the transmission case 17 provided with the differential gear mechanism 58. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and the manufacturing cost Can be reduced.

  Further, the inside of the transmission case 17 is divided into front and rear, the transmission gear mechanisms 30 and 96 are arranged on the front side inside the transmission case 17, and the continuously variable transmission 29 and the differential gear mechanism are arranged on the rear side inside the transmission case 17. 58 is disposed. Therefore, the continuously variable transmission 29 can be installed in a compact manner by utilizing the rear space of the mission case 17 in which the differential gear mechanism 58 is provided. Moreover, the transmission gear mechanisms 30 and 96 such as the PTO transmission gear or the traveling auxiliary transmission gear arranged at the front part of the transmission case 17 and the continuously variable transmission 29 and the differential gear mechanism 58 arranged at the rear part of the transmission case 17 are used. For example, the inside of the box-shaped transmission case 17 can be used effectively, and the continuously variable transmission 29 can be arranged in a compact manner. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and the manufacturing cost can be reduced.

  10 is a cross-sectional view in plan view of the mission case 17, FIG. 11 is an enlarged view in cross-section in plan view of the rear portion of the mission case 17, and FIG.

  As shown in FIGS. 6, 8, 10 to 12, the continuously variable transmission 29 and the differential gear mechanism 58 are provided in the rear chamber 35 of the transmission case 17. The differential gear mechanism 58 includes a differential lock mechanism 560 that stops the differential operation (the right and left differential output shafts 62 are always driven at a constant speed). A differential lock mechanism 560 is disposed on one side of the differential gear case 61, and the ring gear 60 is fixed to the other side of the differential gear case 61 with bolts. The end of the differential gear case 61 on the same side as the ring gear 60 installation side is supported by the bearing holder 559 by a bearing. The bearing holder 559 is fixed to the transmission case 17 with bolts, and a large-diameter bearing having a large load resistance is used for the bearing holder 559.

  As shown in FIG. 11, a differential lock mechanism 560 is provided on one side and a ring gear 60 is provided on the other side with the differential gear case 61 interposed therebetween. The continuously variable transmission 29 is disposed on the same side as the side where the differential lock mechanism 560 is installed.

  The differential lock mechanism 560 includes a lock pin 561 that is detachably provided in the differential gear case 61, a slider 562 to which one end of the lock pin 561 is fixed, a lock arm 563 that the slider 562 engages, and a lock arm 563 that slides. And an operation shaft 564 that is movably supported. Normally, the lock pin 561 is supported so as to be separated from the differential gear 565 in the differential gear case 61 so that a differential output is transmitted from the differential gear case 61 to the left and right differential output shafts 62.

  On the other hand, when the lock pin 651 is engaged with the differential gear 565 by operating a differential lock lever (or pedal) (not shown), the differential gear 565 is fixed to the differential gear case 61, and the differential function of the differential gear 565 is changed. It stops so that the left and right differential output shafts 62 are driven at a constant speed.

  As shown in FIG. 12, a predetermined amount or more of hydraulic oil 566 is placed inside the mission case 17. The differential output shaft 62 is disposed at substantially the same height as the oil level (upper surface) of the hydraulic oil 566. The continuously variable transmission 29 is disposed at a position higher than the axis of the differential output shaft 62. Therefore, the continuously variable transmission 29 is disposed above the oil level of the hydraulic oil 566 inside the mission case 17.

  Next, assembly and removal of the continuously variable transmission 29 from the transmission case 17 will be described. When the continuously variable transmission 29 is incorporated into the transmission case 17, the continuously variable transmission 29 is attached to the main transmission input shaft 27, and the rear end of the main transmission input shaft 27 is supported by the rear side wall member 33 by the bearing 504. In this state, these are inserted into the transmission case 17 from behind, the main transmission input shaft 27 passes through the inner hole of the main transmission output shaft 36, and the joint member 525 is connected to the main transmission output shaft 36 by the spline 528. The continuously variable transmission 29 is assembled in the transmission case 17.

  On the other hand, when the continuously variable transmission 29 is removed from the main transmission input shaft 27, the continuously variable transmission 29 is attached to the main transmission input shaft 27, and the rear end of the main transmission input shaft 27 is attached to the rear side wall member 33 with a bearing 504. , The rear side wall member 33 is removed from the transmission case 17, and the joint member 525 connected to the main transmission output shaft 36 by the spline 528 is detached from the main transmission output shaft 36, and the partition wall 31 is connected to the main wall 31. With the speed change output shaft 36 pivotally supported by the bearing 502, the main speed change input shaft 27 and the continuously variable transmission 29 are removed together with the rear side wall member 33, and these are taken out behind the transmission case 17, Maintenance work for the continuously variable transmission 29 is performed.

  As is clear from the above description and FIG. 11, a main transmission input shaft 27 to which power from the engine 5 is transmitted is disposed in the mission case 17, and the main transmission output shaft 36 is relative to the input shaft 27. The input shaft 27 includes a cylinder block 505 constituting the continuously variable transmission 29, a hydraulic pump unit 500 on one side and a hydraulic motor unit 501 on the other side sandwiching the cylinder block 505. Work that is fitted and configured to transmit power from the output shaft 36 to the differential gear mechanism 58 via the hydraulic motor unit 501, and to transmit power from the differential gear mechanism 58 to at least the left and right wheels 3 and 4. In the vehicle, the continuously variable transmission 29 and the differential gear mechanism 58 are installed in the rear part of the mission case 17, the input side of the input shaft and the output side of the output shaft are arranged on the same side, and the mission Case 17 It was and from configured to be capable of the continuously variable transmission 29 to the rear. Therefore, for example, even when the traveling auxiliary transmission gear, the differential gear, the PTO transmission gear, and the like are installed inside the transmission case 17 as in the transmission structure of the tractor 1, the rear side of the transmission case 17 An installation space for the continuously variable transmission 29 can be easily secured. An operation of attaching and detaching the continuously variable transmission 29 can be performed in a state where the differential gear mechanism 58 is incorporated. An installation space such as a traveling auxiliary transmission gear or a PTO transmission gear is secured in the front portion of the transmission case 17 on the input side of the input shaft 27. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, assembled, and Workability such as disassembly is improved, and manufacturing costs can be reduced.

  Further, since the continuously variable transmission 29 is arranged on the same side as the side where the differential lock mechanism 560 for stopping the differential of the differential gear mechanism 58 is installed, the transmission case 17 provided with the differential gear mechanism 58 is provided. The continuously variable transmission 29 can be arranged in a compact manner by using an internal surplus space, and the installation of the differential gear mechanism 58 or the differential lock mechanism 560 is hardly restricted by the installation of the continuously variable transmission 29, For example, the transmission case or the like of the tractor 1 can be reduced in size or weight, and workability such as assembly and disassembly can be improved to reduce manufacturing costs.

  The output shaft 36 is rotatably supported inside the transmission case 17 by a bearing 502, and the swash plate 518 of the hydraulic motor unit 501 and the output shaft 36 are arranged in the axial direction of the input shaft 272. Since the spline 528 is connected so as to be separable, transmission gear mechanisms 30 and 96 such as a traveling auxiliary transmission gear or a PTO transmission gear arranged at the front of the transmission case 17 and a continuously variable transmission arranged at the rear of the transmission case 171. By using the transmission 29 and the differential gear mechanism 58, for example, the inside of the box-shaped transmission case 17 can be effectively used, and the continuously variable transmission 29 can be arranged in a compact manner. For example, the transmission case of the tractor 1 can be downsized or The weight can be reduced, the workability such as assembly and disassembly is improved, and the manufacturing cost can be reduced.

  As is clear from the above description and FIG. 12, the input shaft 27 to which power from the engine 5 is transmitted is disposed in the mission case 17, and the output shaft 36 can be rotated relative to the input shaft 27. A cylinder block 505 constituting the continuously variable transmission 29, a hydraulic pump unit 500 on one side, and a hydraulic motor unit 501 on the other side are fitted on the input shaft 27, Power is transmitted from the output shaft 36 to the differential gear mechanism 58 via the hydraulic motor unit 501, and power is transmitted from the differential output shaft 62 of the differential gear mechanism 58 to at least the left and right wheels 3 and 4. In the work vehicle, the input side of the input shaft 27 and the output side of the output shaft 336 are arranged on the same side, and the continuously variable transmission 29 and the differential gear mechanism 58 are installed in the rear part of the transmission case 17. And the differential output The high position the axis of the shaft 62 is arranged the continuously variable transmission 29. Therefore, for example, even if the traveling auxiliary transmission gear, the differential gear, the PTO transmission gear, and the like are installed inside the transmission case 17 as in the transmission structure of the tractor 1, The installation space for the transmission 29 can be easily secured. The continuously variable transmission 29 can be attached and detached while the differential gear mechanism 58 is incorporated in the rear part of the transmission case 17. An installation space such as a PTO transmission gear or a traveling auxiliary transmission gear is secured in the front portion of the transmission case 17 on the input side of the input shaft 27. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and can be assembled and Workability such as disassembly is improved, and manufacturing costs can be reduced.

  Further, since the continuously variable transmission 29 is disposed above the oil level of the hydraulic oil 566 inside the transmission case 17, the hydraulic oil 566 is hardly agitated by the rotation of the continuously variable transmission 29. There is no problem that the rotational load of the step transmission 29 increases due to the stirring of the hydraulic oil 566, and the power transmission loss of the continuously variable transmission 29 can be reduced. Further, there is no problem that the hydraulic oil 566 is stirred by the continuously variable transmission 29 and the oil temperature of the hydraulic oil 566 rises.

  Further, the ring gear 60 that is the input gear of the differential gear mechanism 58 is sandwiched, and the bearing holder 559 of the ring gear 60 is disposed on one side, and the continuously variable transmission 29 is disposed on the other side. The space necessary for installing the bearing holder 559 at the rear part of the transmission case 17 in which the machine 29 and the differential gear mechanism 58 are arranged can be secured without being limited to the continuously variable transmission 29. In addition, the continuously variable transmission 29 can be compactly arranged by using the surplus space on the side opposite to the bearing holder 559 across the ring gear 60 that is the input gear. For example, the inside of the rear portion of the box-shaped mission case 17 can be effectively utilized, the mission case 17 and the like can be reduced in size or weight, workability such as assembly and disassembly can be improved, and manufacturing costs can be reduced.

  Next, the structure of the main transmission hydraulic cylinder 556 for shifting the continuously variable transmission 29 will be described in detail with reference to FIGS. 9, 12, 14, and 23 to 29. A cylinder chamber 691 of the main transmission hydraulic cylinder 556 is formed in the rear side wall member 33. The piston 557 of the main transmission hydraulic cylinder 556 is inserted into the cylinder chamber 691 of the main transmission hydraulic cylinder 556. The piston 557 is disposed in the cylinder chamber 691 so as to be slidable in the vertical direction. A depression 692 is formed on the outer periphery of the middle of the piston 557. A square columnar base end pin 693 is engaged with the recess 692. A square columnar base end pin 693 is rotatably disposed on one end side of the main transmission arm 558. The middle of the main transmission arm 558 is rotatably supported on the holder connecting member 690 via the arm shaft 694. A square columnar tip pin 696 is slidably engaged with an arm groove 695 on the other end side of the main transmission arm 558. A quadrangular prism-shaped tip pin 696 is rotatably supported on a semicircular tilt angle adjustment fulcrum 555 of the pump swash plate 509. A rotation guide 697 for supporting the tilt angle adjustment fulcrum 555 is disposed in the first holder 510. The rotation guide 697 forms a semi-cylindrical surface concentric with the rotation center of the pump swash plate 509. The tilt angle of the pump swash plate 509 is changed by the guidance of the rotation guide 697.

  As shown in FIG. 12, a PTO shaft 23 is arranged in the center of the left and right width of the mission case 17 (one tractor body). A differential gear mechanism 58 is arranged on the right side of the PTO shaft 23 in the traveling direction. A continuously variable transmission 29 is arranged obliquely above the left side of the PTO shaft 23 in the traveling direction. A piston 557 is arranged on the left side of the continuously variable transmission 29 in the traveling direction. A main transmission hydraulic cylinder 556 is disposed at the corner of the rear side wall member 33 obliquely above the left side in the traveling direction. The main transmission hydraulic cylinder 556 and this switching mechanism are installed compactly above the left side of the rear side wall member 33.

  As shown in FIG. 23, the main transmission arm 558 and the arm shaft 694 are disposed at substantially the same height as the axis of the continuously variable transmission 29. As shown in FIG. 24, the main transmission arm 558 is disposed on the left side of the continuously variable transmission 29 in the traveling direction and substantially parallel to this axis. The piston 557 is installed substantially vertically in the rear side wall member 33 so as to slide in the vertical direction. The piston 557 can be installed only by forming the main transmission hydraulic cylinder 556 formation portion of the rear side wall member 33 slightly larger than the diameter of the piston 557. Pump swash plate 509 and first holder 510 are connected to main transmission input shaft 27 so that pump swash plate 509 does not rotate, and first holder 510 and holder connecting member 690 are connected. The piston 557 can be installed substantially horizontally in the rear side wall member 33 so as to slide in the left-right direction.

  As is clear from the above description and FIGS. 8 and 23, the input shaft 27 to which the power from the engine 5 is transmitted is disposed in the mission case 17, and the output shaft 36 is relative to the input shaft 27. The input shaft 27 is covered with a cylinder block 505 that constitutes the continuously variable transmission 29, a hydraulic pump unit 500 on one side, and a hydraulic motor unit 501 on the other side. In a work vehicle configured to be fitted and transmit a driving force from the output shaft 36 to at least the left and right wheels 3 and 4 via the hydraulic motor unit 501, the cylinder block is sandwiched between the hydraulic pump unit 500. The main transmission hydraulic pressure 505 is disposed on the side of the rear side wall member 33, which is a side wall member of the transmission case 17, and is a speed change actuator for controlling the speed of the hydraulic pump unit 500. Linda 556, was placed in the rear side wall member 33. Therefore, for example, even if a traveling auxiliary transmission gear, a differential gear, a PTO transmission gear, and the like are installed inside the transmission case 17 as in the transmission structure of the tractor 1, the rear side wall member 33 is not With the stage transmission 29 and the main transmission hydraulic cylinder 556 attached, the rear side wall member 33 can be attached to and detached from the transmission case 17, and the workability such as assembly and maintenance can be improved. An installation space for the continuously variable transmission 19 and the main transmission hydraulic cylinder 556 can be secured inside the rear side wall member 33. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and the manufacturing cost can be reduced.

  Further, a differential gear mechanism 58 for transmitting power to the left and right wheels 3 and 4 is provided in the transmission case 17 so that the input side of the input shaft 27 and the output side of the output shaft 36 are arranged on the same side. The continuously variable transmission 29 is disposed on the side of the differential gear mechanism 58, the main transmission hydraulic cylinder 556 is installed on the rear side wall member 33 of the transmission case 17, and the continuously variable transmission 29 and the The main transmission hydraulic cylinder 556 is configured to be removable to the rear of the mission case 17 together with the rear side wall member 33. Therefore, the continuously variable transmission 29 and the main transmission hydraulic cylinder 556 can be arranged in a compact manner by utilizing the excess space inside the transmission case 17 in which the differential gear mechanism 58 is provided. For example, the transmission case 17 of the tractor 1 can be downsized. Alternatively, the weight can be reduced and the manufacturing cost can be reduced.

  The output shaft 36 is rotatably supported inside the mission case 17 via a bearing 502. On the other hand, the hydraulic motor unit 501 includes a cylinder block 505, a motor plunger 515, a shoe 517, a motor swash plate 518, and a second holder 519. A joint member 526 is fixed to the second holder 519 with a bolt 527. Then, the output shaft 36 and the joint member 525 are connected by a spline 528, the output portion of the hydraulic motor portion 501 and the output shaft 36 are connected in a separable manner, and the input shaft 27 is movable in the axial direction. The output shaft 36 is fitted on the input side. Therefore, the output shaft 36 can be pivotally supported on the transmission case 17 by a bearing 502 structure independent of the continuously variable transmission 29, and the transmission case 36 is pivotally supported on the transmission case 17 in the transmission case. The continuously variable transmission 29 can be attached to and detached from the transmission 17, and the continuously variable transmission 29 can be easily attached or detached. With the gear mechanism 58, for example, the inside of the box-shaped transmission case 17 can be effectively used, and the continuously variable transmission 29 can be arranged in a compact manner. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and manufactured. Cost can be reduced.

  Next, referring to FIGS. 30 to 35, a transmission case 17 in which a proportional control valve 203 for main shift switching for controlling the main shift hydraulic cylinder 556 and a shift hydraulic switching valve 204 operated thereby is installed. The structure will be described in detail.

  The proportional control valve 203 is formed of a proportional control valve housing 700 that is fastened to the rear side wall member 33, and a proportional control spool 701 that is slidably provided in the proportional control valve housing 700 (see FIGS. 32 and 33). The proportional control valve housing 700 is installed on the left outer surface in the traveling direction of the rear side wall member 33. The proportional control spool 701 is configured to slide in the vertical direction, like the main transmission piston 557.

  The proportional control valve housing 700 is provided with a proportional control solenoid 705 and a manual switching lever 706 (see FIGS. 34 and 35). The proportional control solenoid 705 is energized when the operator operates a main shift lever or main shift pedal (not shown) so as to move the proportional control spool 701 in proportion to the operation amount of the main shift lever or the main shift pedal. To control. On the other hand, the manual switching lever 706 is configured such that an operator operates the manual switching lever 706 to switch the proportional control spool 701, for example, during maintenance work.

  The transmission hydraulic pressure switching valve 204 is formed of a transmission hydraulic pressure switching valve housing 703 installed in the spool chamber 702 of the rear side wall member 33 and a transmission spool 704 installed slidably in the transmission hydraulic pressure switching valve housing 703 (FIG. 33, FIG. 34). One end side of the spool chamber 702 is opened on the left outer surface in the advancing direction of the rear side wall member 33, and the other end side of the spool chamber 702 is extended rightward in the advancing direction. The transmission hydraulic pressure switching valve housing 703 is arranged below the main transmission hydraulic cylinder 556 so as to be able to enter / exit into the spool chamber 702 from the left outer side of the rear side wall member 33. The transmission spool 704 is configured to slide in the left-right direction toward the traveling direction.

  The main transmission operation of the inline hydraulic continuously variable transmission 29 will be described below. When the operator operates a main shift pedal or a main shift lever (not shown), the hydraulic electromagnetic proportional control valve 203 is switched, and proportional control that operates in proportion to the depression amount of the main shift pedal (or the operation amount of the main shift lever). With the hydraulic oil from the valve 203, the transmission hydraulic pressure switching valve 204 is operated to control the main transmission hydraulic cylinder 556. When the piston 557 is moved up or down, the main transmission arm 558 rotates around the arm shaft 694, the tilt angle adjustment fulcrum 555 and the rotation guide 697 rotate and guide the pump swash plate 509, and the main transmission input. The inclination angle of the pump swash plate 509 is changed with respect to the axis of the shaft 27, and the main transmission operation of the continuously variable transmission 29 is performed.

  As is clear from the above description and FIGS. 23, 30, and 33, the input shaft 27 to which the power from the engine 5 is transmitted is disposed in the mission case 17, and the output shaft 36 is connected to the input shaft 27. The input shaft 27 is fitted so as to be relatively rotatable, and the input shaft 27 includes a cylinder block 505 constituting the continuously variable transmission 29, a hydraulic pump unit 500 on one side, and a hydraulic motor unit 501 on the other side across the cylinder block 505. And a rear side wall for bearing one end side of the input shaft 27 in a work vehicle configured to transmit at least traveling driving force from the output shaft 36 via the hydraulic motor unit 501. A member 33 is detachably installed on the transmission case 17 and a main transmission hydraulic cylinder 556 which is a transmission actuator for controlling the transmission of the hydraulic pump unit 500, and the transmission actuator Since the shift hydraulic pressure switching valve 204, which is a switching means for actuating 56, is disposed on the rear side wall member 33, for example, as in the transmission structure of the tractor 1, the traveling auxiliary transmission gear and the differential gear Even if the PTO transmission gear or the like is installed inside the transmission case 17, the rear side wall member 33 is attached to the rear case member 17 in a state where the transmission actuator 556 and the switching means 204 are attached to the rear side wall member 33. It will be removable. Accordingly, the relative position between the transmission portion of the continuously variable transmission 29 and the transmission actuator 556 is determined by the connection between the rear side wall member 33 and the transmission case 17, and the workability such as assembly and maintenance can be improved. become.

  As is apparent from FIGS. 23, 33, etc., the speed change actuator is constituted by a speed change hydraulic cylinder 556, the change means is constituted by a speed change hydraulic pressure switching valve 204, and the speed change hydraulic cylinder 556 is used for main speed change. A cylinder chamber 691 in which the piston 557 is provided and a spool chamber 702 in which the speed change spool 704 of the speed change hydraulic pressure switching valve 204 is provided are formed in the rear side wall member 33. The means 204 can be disposed compactly on the rear side wall member 33. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and the manufacturing cost can be reduced.

  Further, as is clear from FIG. 23 and the like, a main transmission arm 558 for shifting the hydraulic pump unit 500 is disposed in the transmission case 17, and the input shaft 27 and the main transmission arm 558 are arranged at substantially the same height. The one end side of the main transmission arm 558 is connected to the main transmission piston 557 that is movable in the vertical direction, so that the installation space for the input shaft 27 and the rear side wall member 33 is used. Thus, the main transmission arm 558 and the main transmission piston 557 can be arranged in a compact manner. For example, the transmission case 17 of the tractor 1 can be reduced in size or weight, and the manufacturing cost can be reduced.

  Further, as is apparent from FIG. 33 and the like, a proportional control valve 203 for switching the shift hydraulic pressure switching valve 204 is provided. The proportional control valve 203 is fastened to the rear side wall member 33. And a proportional control spool 701 installed in the proportional control valve housing 700 so as to be slidable, the shift actuator 556 and the shift hydraulic pressure switching valve 204 are attached to the side wall member 33 in the state described above. The proportional control valve 203 can be attached to and detached from the side wall member 33. Therefore, workability such as assembly and maintenance of the proportional control valve 203 can be improved.

  Further, as is apparent from FIG. 33 and the like, the proportional control valve housing 700 is formed on the rear side wall member 33 so that the piston 557, the transmission spool 704, and the proportional control spool 701 are disposed close to each other. Since it is installed on the outer side surface, a hydraulic circuit for connecting the piston 557, the transmission spool 704, and the proportional control spool 701 can be formed compactly on the rear side wall member 33.

  As is apparent from FIG. 33 and the like, the piston 557 and the proportional control spool 701 are slidably arranged in the vertical direction, while the speed change spool 704 is installed below the piston 557, and the speed change is performed. Since the spool 704 is slidably disposed in the left-right direction, the piston 557, the speed change spool 704, and the proportional control spool 701 can be compactly disposed on the rear side wall member 33.

  As is apparent from FIG. 33 and the like, the proportional control valve housing 700 is provided with a proportional control solenoid 705 and a manual switching lever 706 for operating the proportional control spool 701. A remote control structure for controlling the shift of the hydraulic pump unit 500 via a proportional control solenoid 705 using a lever or a shift pedal, and for controlling the shift of the hydraulic pump unit 500 via the manual switching lever 706. The manual operation structure can be easily configured, and the hydraulic pump unit 500 can be shift-controlled via the manual switching lever 706 during maintenance work or emergency.

  Next, the PTO transmission gear mechanism 96 will be described in detail with reference to FIG. 5, FIG. 7, FIG. 16, and FIG.

  As shown in FIG. 16, the PTO counter shaft 98 is pivotally supported on the partition wall 31 and the front wall member 32 via ball bearings. The PTO counter shaft 98 is integrally formed with a first speed counter gear 600 that is always meshed with the first speed gear 106 for PTO output. The PTO counter shaft 98 has a second speed counter gear 601 that is always meshed with the second speed gear 107 for PTO output, a third speed counter gear 602 that is always meshed with the third speed gear 108 for PTO output, and a fourth speed for PTO output. A four-speed counter gear 603 that always meshes with the gear 109 is fitted. Counter gears 601, 602, and 603 are connected to the PTO counter shaft 98 by splines.

  The front end side of the PTO speed change output shaft 99 arranged in parallel with the PTO counter shaft 98 passes through the partition wall 31 and extends into the front chamber 34. The middle of the PTO speed change output shaft 99 is pivotally supported by the partition wall 31 via a ball bearing 604. On the front end side of the PTO speed change output shaft 99, there are a reverse gear 110, a first gear 106, a second gear 107, a third gear 108, and a fourth gear 109 from the front side (left side in FIG. 16) in order. Each is arranged (see FIG. 16).

  A reverse gear 110, a first speed gear 106, and a fourth speed gear 109 are pivotally supported on the PTO speed change output shaft 99 via ball bearings 605, 606, and 607, respectively. The second speed gear 107 is pivotally supported via a ball bearing 608 fitted on the rear boss portion of the first speed gear 106. The third speed gear 108 is pivotally supported via a ball bearing 609 fitted on the front boss portion of the fourth speed gear 109 (see FIG. 16).

  A plurality of engaging projections 610 are formed at appropriate intervals along the circumferential direction at the outer peripheral rear end of the rear boss of the first speed gear 106. The boss portion of the second speed gear 107 protrudes rearward from the boss portion of the first speed gear 106. A plurality of engagement protrusions 611 are formed at appropriate intervals along the circumferential direction at the rear end portion of the inner hole of the boss portion of the second speed gear 107. The boss portion of the third speed gear 108 protrudes forward from the boss portion of the fourth speed gear 109. A plurality of engaging projections 612 are formed at appropriate intervals along the circumferential direction at the front end of the inner hole of the boss portion of the third speed gear 108. A plurality of engagement protrusions 613 are formed at appropriate intervals along the circumferential direction at the outer peripheral front end of the front boss portion of the fourth speed gear 109 (see FIG. 16).

  As shown in FIG. 16, a PTO speed change operation shaft 614 is installed inside the mission case 17 so as to be substantially parallel to the PTO speed change output shaft 99. A reverse idle gear 620 is rotatably supported on the PTO speed change operation shaft 614 via a ball bearing 621. The reverse idle gear 620 is meshed with the reverse gear 110 and the first speed counter gear 600.

  The PTO shift shifter 111 includes a forward shifter 615 and a reverse shifter 616. The forward shifter 615 and the reverse shifter 616 are fitted on the PTO speed change output shaft 99 and are movably connected via a spline. PTO output first-speed and second-speed gears 106 and 107 and PTO output third-speed and fourth-speed gears 108 and 109 are arranged across the forward shifter 615 (see FIG. 16).

  A plurality of engaging claws 622 that engage with the engaging protrusions 610 of the first speed gear 106 are formed at appropriate intervals along the circumferential direction at the front end of the inner hole of the forward shifter 615. A plurality of engaging claws 623 that engage with the engaging protrusions 611 of the second speed gear 107 are formed at appropriate intervals along the circumferential direction at the outer peripheral front end of the forward rotation shifter 615. A plurality of engagement claws 624 that engage with the engagement protrusions 612 of the third speed gear 108 are formed at appropriate intervals along the circumferential direction at the outer peripheral rear end of the forward rotation shifter 615. A plurality of engaging claws 625 that engage with the engaging protrusions 613 of the fourth speed gear 109 are formed at appropriate intervals along the circumferential direction at the rear end of the inner hole of the forward shifter 615 (see FIG. 16). ).

  The reverse gear 110 projects this boss portion forward (left side in FIG. 16). A plurality of engaging protrusions 626 are formed at appropriate intervals along the circumferential direction at the front end portion of the inner hole of the boss portion of the reverse gear 110. A plurality of engagement claws 627 that engage with the engagement protrusions 626 of the reverse gear 110 are formed at appropriate intervals along the circumferential direction at the rear outer end of the reverse shifter 616 (see FIG. 16).

  The PTO transmission arm 112 includes a forward transmission arm 617 and a reverse transmission arm 618. The forward rotation transmission arm 617 and the reverse rotation transmission arm 618 are fixed by a single shaft 619 so as to be integrally movable back and forth. A forward rotation shifter 615 is connected to the forward rotation transmission arm 617. A reverse shifter 616 is connected to the reverse shift arm 618. (See FIG. 16).

  Next, the switching operation of the PTO transmission mechanism 96 will be described. FIGS. 16 and 17 show a state in which the reverse gear 110 and the reverse shifter 616 are connected via the engaging protrusion 626 and the engaging claw 627 so that the PTO speed change output shaft 99 is reversely rotated. When the reverse shifter 616 is moved forward from the position shown in FIG. 17 by an operation of a PTO shift lever (not shown), the reverse shifter 616 is separated from the reverse gear 110, and the reverse operation of the PTO shift output shaft 99 is stopped. At this time, the forward shifter 615 moves forward together with the reverse shifter 616.

  As shown in FIG. 17, when the forward rotation shifter 615 is moved forward by a predetermined distance C1 from the state where the reverse rotation shifter 616 is connected to the reverse rotation gear 110, the fourth speed gear 109 and the forward rotation shifter 615 are The PTO speed change output shaft 99 is connected to the engagement protrusion 613 and the engagement claw 625 and rotates at the fourth speed.

  When the forward rotation shifter 615 moves further forward by a predetermined distance C2 from the state in which the forward rotation shifter 615 is connected to the fourth speed gear 109, the third speed gear 108 and the forward rotation shifter 615 are engaged with the engagement protrusion 612 and the engagement gear 612. The PTO speed change output shaft 99 is connected at the third speed (see FIG. 17).

  When the forward rotation shifter 615 is moved further forward by a predetermined distance C3 from the state where the forward rotation shifter 615 is connected to the third speed gear 108, the second speed gear 10 and the forward rotation shifter 615 are engaged with the engaging protrusion 611 and the engagement gear 611. The PTO speed change output shaft 99 is connected at the second speed through the joint claw 623 (see FIG. 17).

  When the forward rotation shifter 615 moves further forward by a predetermined distance C4 from the state in which the forward rotation shifter 615 is connected to the second speed gear 107, the first speed gear 106 and the forward rotation shifter 615 are engaged with the engagement protrusion 610 and the engagement. The PTO speed change output shaft 99 is connected at the first speed by being connected via the joint 622 (see FIG. 17).

  Contrary to the above, when an operation of moving the forward rotation shifter 615 backward from the state where the PTO shift output shaft 99 is in the first speed is performed in the order of the first speed, the second speed, the third speed, the fourth speed, and the reverse rotation, The rotation of the PTO speed change output shaft 99 is switched.

  As is clear from the above description and FIGS. 16, 17, etc., the continuously variable transmission 29 that shifts the power transmitted from the engine 5 for traveling output to the transmission case 17 to which power is transmitted from the engine 5, and The auxiliary transmission gear mechanism 30, the differential gear mechanism 58 for transmitting the power output from the auxiliary transmission gear mechanism 30 to the left and right wheels 3 and 4, and the power transmitted from the engine 5 are shifted for PTO output. In a work vehicle equipped with a PTO transmission gear mechanism 96, the PTO transmission gear mechanism 96 is a plurality of forward rotation gears 106, 107, 108, 109 that are a plurality of forward rotation gears that output a plurality of forward rotation driving forces. A reverse gear 110 that outputs reverse driving force, and a PTO speed change output shaft 99 in which the first to fourth gears 106, 107, 108, 109 and the reverse gear 110 are arranged on the same axis. , And a PTO transmission shifter 111 for selecting the outputs of the first to fourth speed gear 106, 107, 108, and 109 and reverse gear 110 with linear switching operation along its axis. Therefore, in the case of shifting the 1st to 4th speed gears and the reverse gears as in the prior art, it is necessary to shift more than the width of each gear. The transmission gear mechanism 96 can be compactly arranged inside the mission case 17, and the installation space for the continuously variable transmission 29 can be easily secured inside the mission case 17. For example, even when the traveling auxiliary transmission gear mechanism 30, the differential gear mechanism 58, the PTO transmission gear mechanism 96, and the like are installed inside the transmission case 17 as in the transmission structure of the tractor 1, the transmission case 17 is The size and weight can be reduced, and the manufacturing cost of the mission case 17 and the like can be reduced.

  In particular, engagement claws 622, 623, 624, and 625 are alternately formed on the inner diameter portion and the outer diameter portion of one forward rotation shifter 615, and the boss portions of the first to fourth gears 106, 107, 108, and 109 are formed. Engagement protrusions 610, 611, 612, and 613 are alternately formed on the inner diameter part and the outer diameter part, and the engagement claws 622, 623, 624, and 625 become engagement protrusions 610 and 611 as the forward shifter 615 slides. , 612, 613 selectively mesh with each other. Accordingly, the sliding amount of the forward rotation shifter 615 is reduced compared with the conventional one in which the 1st to 4th gears slide, and the mounting width of the 1st to 4th gears 106, 107, 108, 109 (PTO speed change output). The mounting dimension in the axial direction of the shaft 99 can be made compact.

  The PTO shift shifter 111 includes a forward rotation shifter 615 that controls the output of the first to fourth gears 106, 107, 108, and 109 and a reverse shifter 616 that controls the output of the reverse gear 110. A reverse shifter 616 was connected to the diverter shifter 615. Therefore, for example, a plurality of the first to fourth speed gears 106, 107, 108, 109, the reverse gear 110, the forward rotation shifter 615, and the reverse rotation shifter 616 are fitted on the PTO speed change output shaft 99. In the structure, the forward shifter 615 and the reverse shifter 616 can be moved substantially simultaneously by a continuous PTO speed change operation, the PTO speed change gear mechanism 96 can be compactly installed in the transmission case 17, and the transmission case 17 can be made smaller or lighter. The manufacturing cost of the mission case 17 and the like can be reduced.

  The PTO transmission gear mechanism 96 is rotatable about the normal transmission gear shift arm 617 connected to the normal rotation shifter 615, the PTO transmission operation shaft 614 provided with the normal rotation transmission arm 617, and the PTO transmission operation shaft 614. And a reverse idle gear 620 that supports the shaft. Therefore, the forward transmission gear shift arm 617 and the reverse rotation idle gear 620 can be supported by using the PTO speed change operation shaft 614, and a dedicated shaft for supporting the reverse rotation idle gear 620 becomes unnecessary. The PTO transmission gear mechanism 96 can be compactly installed in the transmission case 17, the transmission case 17 can be reduced in size or weight, and the manufacturing cost of the transmission case 17 and the like can be reduced.

  Next, referring to FIGS. 5, 13, 14, 18, 19, and 20, the forward hydraulic solenoid valve 46, the reverse hydraulic solenoid valve 48, the autobrake solenoid valve 67, and the four-wheel drive hydraulic solenoid valve 80. The mounting structure of the double speed hydraulic solenoid valve 82 and the PTO clutch hydraulic solenoid valve 104 will be described in detail.

  As shown in FIGS. 18 to 20, a base member 650 is detachably fixed to the rear side surface of the front side wall member 32 via a bolt. The front surface of the base member 650 is connected to the rear surface of the front side wall member 32. The base member 650 is disposed at a position lower than the auxiliary transmission shaft 50, the differential output shaft 62, and the hydraulic oil 566. The electromagnetic valves 46, 48, 67, 80, 82, 104 are installed on the rear surface of the base member 650 so as to protrude rearward. A flat plate cover 651 covers the rear surface of each solenoid valve 46, 48, 67, 80, 82, 104. The flat cover 651 is detachably fixed to the base member 650 with bolts.

  As shown in FIGS. 13, 14, 18, and 19, the mission case 17 is provided with an oil filter 652 for filtering the working oil. An oil filter 652 is disposed behind the base member 650 with the electromagnetic valves 46, 48, 67, 80, 82, 104 interposed between the base member 650 and the base member 650. The oil filter 652 is detachably fixed to the filter lid 653. The filter lid 653 is formed integrally with the fastening member 654. A fastening member 654 is detachably fixed to the outer surface of the mission case 17 via a bolt 655. The oil supply pipe 656 of the working machine hydraulic pump 94 and the traveling hydraulic pump 95 is communicated with the filter lid 653 via the oil passage pipe 657.

  Next, assembly and removal of the electromagnetic valves 46, 48, 67, 80, 82, and 104 with respect to the mission case 17 will be described. When each solenoid valve 46, 48, 67, 80, 82, 104 is incorporated in the mission case 17, each solenoid valve 46, 48, 67, 80, 82, 104 is first attached to the base member 650. Thereafter, the base member 650 is fixed to the rear surface of the front side wall member 32. Next, the front side wall member 32 is fixed to the front surface portion of the transmission case 17, and the electromagnetic valves 46, 48, 67, 80, 82, 104 are installed in the transmission case 17.

  When the electromagnetic valves 46, 48, 67, 80, 82, 104 are installed in the transmission case 17, the electromagnetic valves 46, 48 are provided in the clutch cylinders 47, 49, 81, 83, 105 shown in FIG. , 80, 82, 104 are communicated via a perforated oil passage (not shown) formed in the front side wall member 32 and the base member 650. When the respective solenoid valves 46, 48, 80, 82, 104 are controlled by appropriate means, the respective clutch cylinders 47, 49, 81, 83, 105 are operated, and the respective clutches 40, 42, 74 shown in FIG. , 76, 100 are respectively switched.

  On the other hand, when removing each solenoid valve 46, 48, 80, 82, 104 provided in the mission case 17, the procedure is reversed. First, the front side wall member 32 is removed from the mission case 17. Then, the base member 650 is removed from the front side wall member 32, and the electromagnetic valves 46, 48, 80, 82, 104 are replaced or maintained.

  The oil filter 652 is replaced by first removing the oil passage pipe 657 from the fastening member 654 and the oil supply pipe 656, then removing the fastening member 654 from the transmission case 17, and taking out the oil filter 652 from the transmission case 17. The filter of the oil filter 652 is replaced. In addition, the oil filter 652 after the filter replacement is assembled into the mission case 17 again in the reverse procedure.

  As is apparent from the above description and FIGS. 18 and 20, a continuously variable transmission that shifts the power transmitted from the engine 5 for traveling output inside the transmission case 17 to which power is transmitted from the engine 5. 29, the auxiliary transmission gear mechanism 30, the differential gear mechanism 58 for transmitting the power output from the auxiliary transmission gear mechanism 30 to the left and right wheels 3 and 4, and the power transmitted from the engine 5 for PTO output. In a work vehicle provided with a plurality of electromagnetic valves 80, 82, and 104 for controlling the shift of the auxiliary transmission gear mechanism 30 or the PTO transmission gear mechanism 96, a transmission PTO transmission gear mechanism 96 is provided. The solenoid valves 80, 82, 104 are disposed on the base member 650 at a position lower than the oil level of the hydraulic oil 566 inside the mission case 17. Solenoid valve 80,82,104 has been placed. Therefore, the solenoid valves 80, 82, 104 are always maintained in an oil bath state, and plating for preventing the solenoid valves 80, 82, 104 from rusting is unnecessary. Manufacturing cost can be reduced. Further, compared to a structure in which the electromagnetic valves 80, 82, 104 are installed outside the mission case 17, a special member for protecting the electromagnetic valves 80, 82, 104 is not necessary.

  Since the front side wall member 32 is installed on the front side surface of the transmission case 17 and the base member 650 is disposed on the inner side of the front side wall member 32, the plurality of electromagnetic valves 80, 82, 104 are connected to the base member 650. The transmission case 17 can be installed in a compact manner. In addition, the electromagnetic valves 80, 82, 104 can be installed in a compact manner by effectively utilizing the front space of the mission case 17. Further, the front side wall member 32 and the base member 650 can be used for hydraulic connection between each switching control unit such as the traveling auxiliary transmission gear mechanism 30 or the PTO transmission gear mechanism 96 and the plurality of electromagnetic valves 80, 82, 104. It is possible to reduce the number of installed hydraulic pipes for constituting the hydraulic circuit of the electromagnetic valves 80, 82, 104.

  In addition, an oil filter 652 for filtering the hydraulic oil inside the transmission case 17 is provided inside, and the oil filter 652 is disposed so as to face the base member 650 with the electromagnetic valves 80, 82, 104 interposed therebetween. Compared to the structure in which the oil filter 652 and the solenoid valves 80, 82, 104 are spaced apart and disposed inside the mission case 17, the installation space for the oil filter 652 is secured inside the mission case 17. The installation space for the electromagnetic valves 80, 82, 104 and the base member 650 can be easily secured, and hydraulic components such as the oil filter 652 and the electromagnetic valves 80, 82, 104 can be compactly installed in the transmission case 17. .

  Next, with reference to FIG. 5, FIG. 6, FIG. 21, and FIG. 22, the transmission structure and the transmission control of the auxiliary transmission gear mechanism 30 will be described in detail.

  As shown in FIG. 21, the auxiliary transmission hydraulic cylinder 55 is configured in a double-action structure including a piston rod 661 on one side of the piston 660. The auxiliary transmission hydraulic cylinder 55 is formed with a first cylinder chamber 662 in which a piston rod 661 is provided and the other second cylinder chamber 663. An auxiliary transmission shifter 665 is connected to the tip of the piston rod 661 via a shift arm 664. The low speed clutch 56 or the high speed clutch 57 is continued by the auxiliary transmission shifter 665 and the auxiliary transmission shaft 50 is driven at a low speed or a high speed.

  The first cylinder chamber 662 is in direct communication with the discharge side of the traveling hydraulic pump 95. The second cylinder chamber 663 communicates with the discharge side of the traveling hydraulic pump 95 via a two-position three-port high-speed hydraulic switching valve 666. The high speed hydraulic switching valve 666 includes a high speed solenoid 667. When the high speed hydraulic switching valve 666 is switched by the high speed solenoid 667 and the second cylinder chamber 663 is communicated to the discharge side of the traveling hydraulic pump 95 via the high speed hydraulic switching valve 666, the pressure receiving pressure on both sides of the piston 660 is received. Due to this difference, the piston 660 moves in the direction in which the piston rod 661 protrudes, and the high speed clutch 57 is continued to drive the auxiliary transmission shaft 50 at high speed (see FIG. 21). In addition, the code | symbol 668 of FIG. 21 is a relief valve.

  As shown in FIG. 21, a travel controller 669 for controlling the high speed solenoid 667 is provided. The travel controller 669 is connected to a high-speed solenoid 667, a high-speed switch 670 and a low-speed switch 671 for sub-shifting, a power application key switch 672, and an electronic governor controller 673 that controls the rotation of the engine 5. Travel controller 669 is connected to battery 674 via key switch 672. The key switch 672 is connected to a starter 675 for starting the engine 5 (see FIG. 21).

  The electronic governor controller 673 is connected to a governor 676 that adjusts the fuel of the engine 5 and an engine rotation sensor 677 that detects the rotational speed of the engine 5. When the position of a fuel adjustment rack (not shown) provided in the governor 676 is adjusted by manual operation of the throttle lever 678 and the rotation speed of the engine 5 is set, the set rotation speed of the throttle lever 678 and the rotation speed of the engine 5 are set. So that the position of the fuel adjustment rack is automatically adjusted via an electromagnetic solenoid (not shown) for driving the fuel adjustment rack so that the rotation of the engine 5 does not change due to a load change or the like. (See FIG. 21).

  Next, the shift control of the auxiliary transmission gear mechanism 30 will be described as shown in FIG. When the key switch 672 is turned on (S1) and the starter 675 is operated to start the engine 5 (S2), the rotational speed of the engine 5 is input from the engine rotation sensor 677 to the travel controller 669 (S3). When a certain period of time (for example, the time necessary for the engine 5 to substantially match the engine speed set by the throttle lever 678) has elapsed (S4), high-speed operation of the auxiliary transmission gear mechanism 30 is permitted (S4). S5). When the high speed switch 670 is turned on (S6), the high speed solenoid 667 is excited, the high speed hydraulic switching valve 666 is switched, the piston rod 661 is advanced, the high speed clutch 57 is continued, and the auxiliary transmission gear is engaged. The mechanism 30 is switched to the high speed side (S7). On the other hand, when the high speed switch 670 is not turned on, or when the low speed switch 671 is turned on after the high speed switch 670 is turned on (S8), the high speed solenoid 667 is turned off and the high speed hydraulic switch is performed. The valve 666 is switched by the return spring, the piston rod 661 is retracted, the low speed clutch 56 is continued, and the auxiliary transmission gear mechanism 30 is switched to the low speed side (S9).

  As is apparent from the above description and FIGS. 21 and 22, the continuously variable transmission 29 and the auxiliary transmission gear mechanism 30 for traveling output are provided in the transmission case 17 to which power is transmitted from the engine 5. A differential gear mechanism 58 that transmits power to the wheels 3 and 4 is disposed, and a traveling hydraulic pump 95 that is a sub-transmission hydraulic pump driven by the engine 5 and the sub-transmission gear mechanism 30 are shifted. In a work vehicle including a sub-transmission hydraulic cylinder 55 to be controlled, the sub-transmission hydraulic cylinder 55 is arranged so that the sub-transmission gear mechanism 30 is switched to a low speed side when an operation for starting the engine 5 is performed. The sub-shift hydraulic cylinder 55 is configured to be capable of shifting to the high speed side when the speed change operation is performed on the low speed side and a predetermined time has elapsed after the engine 5 is started. Therefore, for example, as in the transmission structure of the tractor 1, the engine 5 can be started with the traveling clutch continued, or the traveling clutch is omitted and the engine 5 and the hydraulic continuously variable transmission 29 are directly connected. Even if it is a thing, the said engine 5 is started in the state which switched the said auxiliary transmission gear mechanism 30 to the low speed side, and the dashing operation | movement which the tractor 1 moves unexpectedly at high speed by the start of the engine 5 can be prevented.

  The auxiliary transmission hydraulic cylinder 55 has a double-acting structure including a piston rod 661 on one side of the piston 660, and the tip end side of the piston rod 661 is connected to the transmission switching portion of the auxiliary transmission gear mechanism 30. Therefore, the sub-transmission gear mechanism 30 is operated at a low speed when the engine 5 is started by utilizing the difference in hydraulic force between the first cylinder chamber 662 provided with the piston rod 661 and the other second cylinder chamber 663. The sub-transmission gear cylinder 30 can be simplified, the sub-transmission gear mechanism 30 can be simplified, and the sub-transmission gear mechanism can be simplified. 30 manufacturing costs can be reduced.

  In addition, the first cylinder chamber 662 on the side where the piston rod 661 is provided is in direct communication with the auxiliary transmission hydraulic pump 95, and the other second cylinder chamber 663 is connected to the auxiliary transmission via a high speed hydraulic switching valve 666. It was configured to communicate with the hydraulic pump 95. Therefore, the high-speed hydraulic switching valve 666 can be controlled so that the auxiliary transmission hydraulic cylinder 55 can be operated to the low speed side or the high speed side, and the auxiliary transmission gear mechanism 30 can be switched to the low speed side or the high speed side. The auxiliary transmission gear mechanism 30 and the like can be reduced in size or weight, and the manufacturing cost of the auxiliary transmission gear mechanism 30 can be reduced.

It is a side view of the tractor for farm work. It is a diagonally rear perspective view of a tractor. It is side surface explanatory drawing of a tractor. It is a perspective view of a tractor airframe. It is a skeleton diagram of power transmission. It is explanatory drawing of the travel transmission part of a mission case. It is explanatory drawing of the PTO transmission part of a mission case. It is explanatory drawing of the transmission without a transmission of a transmission case. It is a hydraulic circuit diagram of the continuously variable transmission of the transmission case. It is a plane view sectional explanatory view of a mission case. It is expansion explanatory drawing of FIG. It is rear view explanatory drawing of a mission case. It is plane view explanatory drawing which shows the inside of a mission case. It is side view explanatory drawing which shows the inside of a mission case. It is a perspective explanatory view showing the inside of a mission case. It is expansion explanatory drawing of the PTO transmission part of a mission case. It is expansion explanatory drawing of FIG. It is bottom explanatory drawing which shows the inside of a mission case. It is a bottom perspective view showing an oil filter and a solenoid valve. It is the bottom perspective view which removed the oil filter. It is traveling control explanatory drawing. It is a flowchart of traveling control. It is a side view which shows the speed change operation part of a continuously variable transmission. It is a top view which shows the speed change operation part of a continuously variable transmission. It is a front perspective view which shows the speed change operation part of a continuously variable transmission. It is a perspective view which shows a continuously variable transmission and a rear side wall member. It is a back perspective view which shows the speed change operation part of a continuously variable transmission. It is explanatory drawing of the main transmission arm. It is explanatory drawing of the main transmission arm. It is a hydraulic circuit diagram of the whole tractor of the present invention. It is front explanatory drawing which shows a speed-change actuator and a switching means. It is back surface explanatory drawing of a side wall member. It is back surface explanatory drawing which shows a speed-change actuator and a switching means. It is a perspective view of a side wall member. It is a perspective view which shows a speed-change actuator and a switching means.

5 Engine 17 Mission case 27 Input shaft 29 Continuously variable transmission 33 Rear side wall member (side wall member)
36 Output shaft 203 Proportional control valve 204 Shifting hydraulic pressure switching valve (switching means)
500 Hydraulic pump unit 501 Hydraulic motor unit 505 Cylinder block 556 Main transmission hydraulic cylinder (transmission actuator)
557 Piston 558 Main transmission arm 691 Cylinder chamber 700 Proportional control valve housing 701 Proportional control spool 702 Spool chamber 704 Shifting spool 705 Proportional control solenoid 706 Manual switching lever

Claims (2)

An input shaft for transmitting power from the engine is disposed in the transmission case, and an output shaft is rotatably fitted to the input shaft, and the input shaft is a cylinder constituting a continuously variable transmission. A block, a hydraulic pump part on one side sandwiching the block, and a hydraulic motor part on the other side are fitted, and at least traveling driving force is transmitted from the output shaft via the hydraulic motor part. In a work vehicle
The side wall member for bearing one end of said input shaft is installed detachably on the transmission case, wherein the shift hydraulic cylinder for shifting control of the hydraulic pump unit, shift hydraulic pressure for actuating said speed change hydraulic cylinder A switching valve is disposed on the side wall member;
A cylinder chamber in which a piston of the transmission hydraulic cylinder is installed and a spool chamber in which a transmission spool of the transmission hydraulic pressure switching valve is installed are formed in the side wall member,
A proportional control valve for switching and controlling the shift hydraulic pressure switching valve, wherein the proportional control valve is a proportional control valve housing that is fastened to the side wall member; and a proportional control that is slidably provided in the proportional control valve housing. A structure comprising a spool,
The piston and the proportional control spool are arranged to be slidable in the vertical direction, the speed change spool is installed below the piston, and the speed change spool is arranged to be slidable in the left-right direction. Work vehicle. The work vehicle according to claim 1 , wherein a proportional control solenoid and a manual switching lever for operating the proportional control spool are arranged in the proportional control valve housing .

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