JP5202710B2 - Work vehicle - Google Patents

Description

  The present invention relates to a work vehicle equipped with a hydraulic continuously variable transmission such as a tractor used for agricultural work or a wheel loader used for civil engineering work, and more particularly, starts (forwards or reverses) the work vehicle. The present invention relates to a configuration for controlling the output rotational speed from a hydraulic continuously variable transmission.

  In a recent work vehicle such as a tractor or wheel loader, for example, in Patent Document 1, in order to improve work efficiency, in Patent Document 1, the rotational power of an engine is divided into a hydrostatic continuously variable transmission (HST) and a gear type sub-shift (low speed, high speed). A throttle lever that sets and holds the output rotational speed of the engine, and a shift pedal that changes the output rotational speed of the hydrostatic continuously variable transmission. A configuration is disclosed in which when the shift pedal is depressed, the accelerator operating portion is pushed by the shift pedal, and the engine output speed set and held by the throttle lever can be increased.

  Further, in a work vehicle such as a tractor or a wheel loader, for example, in Japanese Patent Application Laid-Open No. 2004-228561, a forward clutch and a reverse clutch that are turned on and off by an operation of a forward / reverse switching lever, and an accelerator are disclosed in order to simplify the switching operation between forward and reverse. A hydraulic continuously variable transmission that changes the number of revolutions by depressing the pedal, and transmits the power from the engine to the traveling wheel via the forward / reverse clutch and the hydraulic continuously variable transmission to move the traveling wheel forward or A configuration that can be driven backward is disclosed.

  Further, in order to apply to a comparatively narrow work area in which the travel speed range (during forward) such as a work vehicle such as a tractor or a wheel loader is several km / h to several tens km / h, in Patent Document 2, the hydrostatic pressure is Instead of a continuously variable transmission, an input shaft that transmits power from the engine and an output shaft that transmits hydraulic shift output to the left and right wheels are concentrically arranged on both sides of the cylinder block constituting the continuously variable transmission. By adopting a so-called inline type continuously variable transmission in which a hydraulic pump part and a hydraulic motor part are arranged, and the input shaft and output shaft are configured as a double shaft, no hydraulic oil leakage occurs and power transmission efficiency It is disclosed that the fuel consumption of the engine can be reduced. As shown in Patent Document 3, it is also known to control the output rotation speed of a transmission based on a preset gear ratio pattern.

JP 2003-226165 A JP 2003-72430 A JP-A-1-237227

  By the way, the gear transmission has high power transmission efficiency, but there is a problem that the operability cannot be improved by the stepped shift. In addition, the hydraulic continuously variable transmission mechanism has excellent operability due to the continuously variable transmission that can start from zero, with the initial speed starting from zero, but there is a limit to the power transmission efficiency and there is a problem that the power loss at low speed increases. is there. Furthermore, although the belt-type continuously variable transmission mechanism using the V belt and the pulley can perform a highly efficient continuously variable transmission, there is a problem that the initial speed cannot start from zero.

  When the output of the hydraulic transmission mechanism and the gear transmission output are combined and output by the differential action of the planetary gear mechanism and the engine output is transmitted in a shift manner, high power transmission efficiency and a continuously variable transmission capable of zero start can be obtained. Here, when the speed is set so that the combined output from the planetary gear mechanism can move forward and backward (forward / reverse) with a stop (zero), the reverse shift side of the combined output is reduced and output backward, It is possible to increase the speed change region on the forward rotation side of the combined output for forward output and to make the hydraulic shift output highly efficient at a general work speed. However, for example, if the oil viscosity of the hydraulic transmission mechanism changes due to temperature (continuous operation or air temperature), the combined output stop (zero) position moves to the reverse side or forward side, and the shift operation position stops. There is a problem that a forward or backward output is generated when In this respect, there is a problem that electrical control for automatically adjusting the stop (zero) position of the composite output is necessary, and the structure is complicated and the manufacturing cost is increased.

  Therefore, the present invention seeks to provide a work vehicle that has been improved by examining these current conditions.

In order to achieve the above object, a first aspect of the present invention is a traveling machine body equipped with an engine, a hydraulic continuously variable transmission with a hydraulic pump and a hydraulic motor for shifting power from the engine, and power from the engine. A transmission output of the hydraulic continuously variable transmission that combines the output of the hydraulic motor and the output of the hydraulic motor as a one-way rotational force, and a one-way rotational force from the main transmission output shaft. A forward / reverse switching mechanism that switches to a forward rotation output or a reverse rotation output, a traveling clutch that transmits a shift output from the hydraulic continuously variable transmission to a traveling wheel of the traveling machine body, a brake that brakes the traveling wheel, an operation member for changing the transmission ratio of the hydrostatic continuously variable transmission, in a work vehicle and an actuator for adjusting the swash plate angle of the hydraulic pump, the operating member during running of the traveling machine body When operated in the standing position, the swash plate angle of the hydraulic pump becomes the maximum reverse rotation angle, and the output from the hydraulic motor is in the reverse rotation direction output control state and the reverse rotation speed from the engine and the reverse rotation from the hydraulic motor. When the number of revolutions coincides and the output number of revolutions of the main transmission output shaft becomes zero, and then the traveling speed of the traveling machine body becomes a predetermined speed or less, the traveling clutch is disengaged and the brake is operated. After that, the swash plate angle of the hydraulic pump is shifted to zero, and the rotational speed transmitted from the hydraulic motor to the main transmission output shaft is made zero .

According to the present invention, a traveling machine body equipped with an engine, a hydraulic continuously variable transmission with a hydraulic pump and a hydraulic motor for shifting power from the engine, power from the engine and output from the hydraulic motor, The main transmission output shaft to which the transmission output of the hydraulic continuously variable transmission combined with the transmission is transmitted as a one-way rotational force, and the one-way rotational force from the main transmission output shaft is switched to a normal rotation output or a reverse rotation output. A forward / reverse switching mechanism, a travel clutch that transmits a shift output from the hydraulic continuously variable transmission to a traveling wheel of the traveling machine body, a brake that brakes the traveling wheel, and a shift of the hydraulic continuously variable transmission an operation member for changing the ratio, the work vehicle and an actuator for adjusting the swash plate angle of the hydraulic pump, is operated to the neutral position the operating member during running of the traveling machine body, before When the swash plate angle of the hydraulic pump is the maximum reverse rotation angle, the output from the hydraulic motor is in the output control state in the reverse rotation direction, and the normal rotation speed from the engine matches the reverse rotation speed from the hydraulic motor. When the output rotational speed of the main transmission output shaft becomes zero and the traveling speed of the traveling machine body becomes a predetermined speed or less, the traveling clutch is disengaged and the brake is operated, and then the hydraulic pump The rotation speed transmitted from the hydraulic motor to the main transmission output shaft is made zero, so that the output torque at the time of zero start can be easily secured, and zero start or slow speed performance can be achieved. In addition to being able to improve, even in high-speed moving work with a large load, the output of high power transmission efficiency can be effectively used, and the work efficiency can be easily improved. In addition, there is an effect that it is possible to easily eliminate the problem that the main transmission output shaft rotates and the traveling machine body moves forward and backward when the hydraulic speed change operation is stopped (when the operation tool is neutral). .

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 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 a side 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 hydraulic circuit diagram in the whole tractor of the present invention. It is a top view which shows the cabin part of a tractor. It is a functional block diagram of the control means of this invention. It is a gear ratio diagram. It is a flowchart of start (brake) control. It is a flowchart of gear ratio adaptive control. It is a flowchart of forward / reverse switching control. It is a flowchart of stop control. It is a flowchart of clutch pedal control.

  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, FIG. 4 is a perspective view of the tractor body, FIG. 5 is a skeleton diagram of power transmission, and FIG. 18 is a speed ratio pattern diagram showing the relationship between the operation amount of the speed change lever and the speed ratio, FIG. 19 is a flowchart of start / brake control, FIG. 20 is a flowchart of speed ratio adaptive control, and FIG. 21 is a flowchart of stop control. FIG. 22 is a flowchart of forward / reverse switching control, and FIG. 23 is a flowchart of clutch pedal control.

  As shown in FIGS. 1 to 4, the tractor 1 as a work vehicle supports a traveling machine body 2 with a pair of left and right rear wheels 4 as well as a pair of left and right front wheels 3, and is mounted on a front portion of the traveling machine body 2. By driving the rear wheel 4 and the front wheel 3 at 5, the vehicle is configured to travel forward and backward. The engine 5 is covered with a bonnet 6. Further, a cabin 7 is installed on the upper surface of the traveling machine body 2. Inside the cabin 7, there is a steering seat 8 and a steering handle (round handle) 9 that moves the front wheel 3 left and right by steering. And are installed. A step 10 on which the operator gets on and off the cabin 7 is provided, and a fuel tank 11 for supplying fuel to the engine 5 is provided on the inner side of the cabin 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. A 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. 15 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. The proportional control valve 203, the switching valve 204 actuated thereby, the shift shift electromagnetic valve 666 of the traveling auxiliary shifting hydraulic cylinder 55, the forward hydraulic clutch 40 for switching forward and backward traveling, and the backward hydraulic clutch 42 The forward clutch solenoid valve 46, the reverse clutch solenoid valve 48, the four-wheel drive hydraulic solenoid valve 80 for the four-wheel drive hydraulic clutch 74 for simultaneously driving the front wheel 3 and the rear wheel 4, and the 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 and a rear side wall member 33 are detachably fixed to the front side and the rear side of the mission case 17 with bolts, respectively. 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. 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. Yes.

  Next, FIG. 8 shows an inline hydraulic continuously variable transmission 29 in which a main transmission output shaft 36 is concentrically disposed 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 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. 8).

  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 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 one holder 510, a shoe 508 slidably provided on the pump swash plate 509, a pump plunger 506 connected to the shoe 508 via a spherical universal joint, and the pump plunger 506 in a cylinder block 505 is provided with a first plunger hole 507 disposed so as to freely enter and exit. 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).

  A joint member 526 is fixed to the second holder 519 with a bolt 527. The output shaft 36 and the joint member 526 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. Further, the first charge valve 544 for supplying hydraulic oil in the hydraulic oil supply oil passage 543 to the first oil chamber 530 and the second charge valve 545 for supplying hydraulic oil in the hydraulic oil supply oil passage 543 to the second oil chamber 531. 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. 13). 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 operation, 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. 13). 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 FIG. 13).

  The main transmission operation of the inline hydraulic continuously variable transmission 29 will be described below. The changeover valve 204 is operated by hydraulic oil from a proportional control electromagnetic valve 203 that operates in proportion to a tilting operation amount of a shift operation lever 232 that is an operation tool described later, and the hydraulic cylinder 556 is controlled. The inclination angle of the pump swash plate 509 is changed with respect to the axis.

  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 inclination angle of the pump swash plate 509 is substantially zero (speed ratio 1), the hydraulic motor unit 501 is not driven by the hydraulic 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 506 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 tilted in one direction (positive tilt angle) with respect to the axis 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 hydraulic motor unit 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. It is done. That is, the rotational speed of the hydraulic motor unit 501 driven by the hydraulic pump unit 500 is added to the rotational 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 of the pump swash plate 509 (positive inclination angle, gear ratio 2).

  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 of the pump swash plate 509 (negative inclination angle, gear ratio 0). In the embodiment, when the negative inclination angle of the pump swash plate 509 is approximately 11 degrees, the gear ratio is zero. Although slightly different depending on the gear ratio pattern described later, the gear ratio is set to be maximum when the positive inclination angle is approximately 11 degrees.

  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, when the shift operation lever 232, which will be described later, is moved forward, the clutch cylinder 47 is operated by the forward clutch solenoid valve 46, the forward hydraulic clutch 40 is continued, and the main shift output gear 37 and the travel counter shaft 38 are moved forward. It connects so that it may be connected with the gear 41 (refer FIG. 5, FIG. 6).

  On the other hand, the reverse operation of the shift operation lever 232 causes the clutch cylinder 49 to be actuated by the reverse clutch solenoid valve 48 to continue the reverse hydraulic clutch 42, and the main transmission output gear 3 and the travel counter shaft 38 are connected to the reverse gear. It connects so that it may be connected by 43 (refer FIG. 5, FIG. 6).

  It should be noted that both the forward and reverse wet multi-plate hydraulic clutches 40 and 42 are disconnected when the shift operation lever 232 is in the neutral position where neither the forward-side tilting operation nor the reverse-side tilting operation is performed. The traveling drive force from the main transmission output gear 37 output to the front wheels 3 and the rear wheels 4 is configured to be substantially zero (main clutch disengaged state).

  Next, the switching between the low speed and the high speed performed via 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 transmission hydraulic cylinder 55 by manual operation of the auxiliary transmission high / low speed changeover switch 222 described later, or by detecting the rotational speed of the engine 5, and the auxiliary transmission shaft. The low speed gear 52 or the high speed gear 54 is connected to the motor 50 so that 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 (see FIG. 5).

  In addition, left and right brakes 65 are installed on the left and right differential output shafts 62, respectively, so that the left and right brakes 65 are braked by operation of a left and right brake pedal 230 described later. The left and right brake pedal 230 includes two pedals, and the left and right brake pedal 230 and the left and right brake 65 are mechanically connected to each other via a rod or a wire and a link mechanism (not shown). The left and right brake pedal 230 can be locked to the braking position via a parking lever (not shown), and the left and right brake 65 can be operated as a parking brake when the engine 5 is stopped. On the other hand, when the steering angle of the steering wheel 9 is detected, the left and right brake cylinders 68 are operated by the left and right autobrake solenoid valves 67a and 67b, respectively, and either one or both of the left and right brakes 65 (refer to FIG. ) Is automatically braked so that a turning run such as a U-turn is performed.

  Next, switching between the two-wheel drive and the four-wheel drive of the front and rear wheels 3 and 4 will be described. As shown in FIGS. 5 and 6, 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 a four-wheel drive operation of a four-wheel drive mode switch 246, which will be described later, for switching operation between the two-wheel drive and the four-wheel drive, the clutch cylinder 81 is operated by the four-wheel drive hydraulic solenoid valve 80 and the hydraulic clutch 74 for the four-wheel drive is continued. The front wheel input shaft 72 and the front wheel output shaft 73 are connected by a four-wheel drive gear 75 so that the front wheel 3 is driven together with the rear wheel 4.

  Next, switching of the double speed drive of the front wheel 3 will be described. As shown in FIGS. 5 and 6, detection of left and right steering sensors 218 and 219 to detect a U-turn (direction change at a headland in a farm) operation of the steering handle 9, and a double speed mode switch to be described later When 247 is entered (front wheel double speed operation), the clutch cylinder 83 is operated by the double speed hydraulic solenoid valve 82, the double speed hydraulic clutch 76 is continued, and the front wheel input shaft 72 and the front wheel output shaft 73 are connected to the double speed gear. The front wheel 3 is configured to be driven at a speed approximately twice as high as that when the front wheel 3 is driven by the four-wheel drive gear 75.

  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 work machine hydraulic pump 94 for supplying hydraulic fluid to the work machine lifting mechanism 20, and the mission case 17. And a traveling hydraulic pump 95 for supplying hydraulic oil to 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, the PTO clutch lever (not shown) or the PTO cutoff switch 223 (described later) is continuously operated to operate the clutch cylinder 105 by the PTO clutch hydraulic solenoid valve 104 (see FIG. 5), and the PTO hydraulic clutch 100 is continued. The main transmission input shaft 27 and the PTO counter shaft 98 are connected by a 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 an electromagnetic pickup type main transmission output portion rotation sensor 116 for detecting the rotation of the main transmission output gear 37 are installed to face each other, and the main transmission mechanism The output speed of 29 is detected by the main transmission output unit rotation sensor 116. Further, an electromagnetic pickup type vehicle speed sensor 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 determined based on the rotation of the front wheel input shaft 72 and the auxiliary transmission shaft 50. It is comprised so that it may be detected by.

  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 work 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 double shaft configuration, the input side of the input shaft 27 and the cylinder block 505 are arranged. The hydraulic motor 501 is disposed between the input side of 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, a continuously variable transmission is provided at the rear of the transmission case 17. The installation space for the machine 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.

  The differential gear mechanism 58 includes a differential lock mechanism (not shown) that stops the differential operation (the left and right differential output shafts 62 are always driven at a constant speed). When the lock pin provided in the differential gear case so as to freely enter and exit is engaged with the differential gear by operating a differential lock lever (or pedal) (not shown), the differential gear is fixed to the differential gear case. The differential function is stopped, and the left and right differential output shafts 62 are driven at a constant speed.

  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, 11, 13, and 14. 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 disposed in the cylinder chamber 691 of the main transmission hydraulic cylinder 556 so as to be slidable in the vertical direction. A square columnar base end pin 693 is engaged with a recess 692 formed in the outer periphery of the piston 557 in the middle. 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 FIGS. 11 and 12, the 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 (FIG. 10). 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 (FIG. 14). 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 direction of travel (FIG. 14).

  As shown in FIG. 13, 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. 14, 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.

  The speed change operation of the main speed change hydraulic cylinder 556 will be described. When the forward clutch solenoid valve 46 or the reverse clutch solenoid valve 48 (see FIGS. 5, 6, and 17) is switched by the forward side tilting operation or the reverse side tilting operation of the shift operation lever 232, the main transmission hydraulic cylinder 556 is moved. Operate. When the piston 557 moves 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 pump swash plate The configuration is such that the main transmission operation of the continuously variable transmission 29 is performed by changing the inclination angle of 509. 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.

  Next, referring to FIGS. 5, 10, 11, and 12, the forward clutch solenoid valve 46, the reverse clutch solenoid valve 48, the left and right autobrake solenoid valves 67a and 67b, the four-wheel drive hydraulic solenoid valve 80, and the double speed The mounting structure of the hydraulic solenoid valve 82 and the PTO clutch hydraulic solenoid valve 104 will be described in detail.

  As shown in FIGS. 10 to 12, a base member 650 is disposed on the rear side surface of the front side wall member 32 at a position lower than the auxiliary transmission shaft 50, the differential output shaft 62, and the hydraulic oil 566, and the bolt It is detachably fixed via. The electromagnetic valves 46, 48, 67 a, 67 b, 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 a, 67 b, 80, 82, 104. The flat cover 651 is detachably fixed to the base member 650 with bolts.

  As shown in FIGS. 10 and 11, the oil filter 652 for filtering the working oil has a mission behind the plate cover 651 with respect to each electromagnetic valve 46, 48, 67 a, 67 b, 80, 82, 104. Arranged in the case 17. 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.

  In each clutch cylinder 47, 49, 81, 83, 105 shown in FIG. 5, each solenoid valve 46, 48, 80, 82, 104 is a perforated oil passage formed in the front wall member 32 and the base member 650 ( (Not shown). 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.

  Next, the speed change structure of the auxiliary transmission gear mechanism 30 will be described in detail with reference to FIGS. As shown in FIG. 9, the auxiliary transmission hydraulic cylinder 55 is configured in a double-acting structure in which a piston rod 661 is provided 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 so that the auxiliary transmission shaft 50 is driven at low speed or 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 shift shift switching valve 666. The shift shift switching valve 666 includes a shift solenoid 667. When the shift shift switching valve 666 is switched by the shift solenoid 667 and the second cylinder chamber 663 is communicated to the discharge side of the traveling hydraulic pump 95 via the shift shift switching valve 666, the difference in pressure receiving pressure on both sides of the piston 660 Thus, 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. 9).

  Next, traveling control (shift control) of the work vehicle (traveling vehicle) of the present embodiment will be described. FIG. 17 is a functional block diagram of the travel control means. A travel controller 210 such as a microcomputer having a ROM storing a control program and a RAM storing various data is connected to a battery via a power application key switch 211. 254. The key switch 211 is connected to a starter 212 for starting the engine 5.

  The travel controller 210 is connected to an electronic governor controller 213 that controls the rotation of the engine 5. The electronic governor controller 213 is connected to a governor 214 that adjusts the fuel of the engine 5 and an engine rotation sensor 215 that detects the rotational speed of the engine 5. When a fuel adjustment rack (not shown) provided in the governor 214 detects the rotational position of the manually operated throttle lever 206 with the throttle potentiometer 217, and the rotational speed of the engine 5 is set based on the detected value The fuel adjustment rack is automatically operated via an electromagnetic solenoid (not shown) for driving the fuel adjustment rack so that the set rotation speed of the throttle lever 206 and the rotation speed of the engine 5 coincide with each other by a signal from the electronic governor controller 213. The position of the engine 5 is adjusted to prevent the rotation of the engine 5 from changing due to a load change or the like. In other words, the engine 5 is configured to maintain a substantially constant rotation speed regardless of the load change.

  Further, as shown in FIG. 17, the travel controller 210 includes various sensors and switches of the input system, that is, a left for detecting the amount of leftward rotation (left steering angle) of the round handle (steering handle) 9. A left steering sensor 218 as a steering switch, a right steering sensor 219 as a right steering switch for detecting the amount of rightward rotation (right steering angle) of the round handle 9, and forward movement for the operator to shift the traveling speed A shift potentiometer 220 as a potentiometer and a reverse potentiometer, a transmission ratio setting dial 221, a high-speed / low-speed switch 222 for switching the auxiliary transmission gear mechanism 30 between high speed and low speed, and the number of rotations of the main transmission output section are detected. For detecting the rotational speed (traveling speed) of the front and rear wheels 3, 4. A speed sensor 117, a PTO cut-off switch 223 for turning on and off the PTO clutch 100 to cut off the output to the PTO shaft 23, a brake pedal switch 231 for detecting when the brake pedal 230 is depressed, and a left and right brake electromagnetic An auto brake switch 245 that enables automatic control of the valves 67a and 67b, a four-wheel drive mode switch 246 that enables automatic control of the four-wheel hydraulic solenoid valve 80, and a double speed mode switch 247 that enables automatic control of the double speed hydraulic solenoid valve 82. A clutch switch 248 that detects when a clutch pedal 227 (to be described later) is depressed and turns off the forward clutch electromagnetic valve 46 and the reverse clutch electromagnetic valve 47 with the highest priority over other controls is connected. Note that the shift potentiometer 219 is a lever operation position sensor that converts and detects the forward side tilt amount or the reverse side tilt amount of the shift operation lever 232.

  As shown in FIG. 17, the travel controller 210 includes various output-type electromagnetic valves, that is, a forward clutch electromagnetic valve 46 and a reverse clutch electromagnetic valve 48 of the main transmission mechanism, and a high-speed clutch that switches the sub-shift between high speed and low speed. A solenoid valve 666; a proportional control solenoid valve 203 for operating the main transmission hydraulic cylinder 556 in proportion to the forward side reverse amount or the reverse side reverse amount of the speed change operation lever 232; left and right brake electromagnetic valves 67a and 67b; The solenoid valve 80, the double speed hydraulic solenoid valve 82, and the PTO clutch solenoid valve 104 are connected.

  In the present embodiment, a round handle (steering handle) 9 is arranged on the steering column 234 protruding from the floor plate 235 in front of the steering seat 8 in the driving section (cabin) 7 shown in FIG. A throttle lever 206 is disposed, and a clutch pedal 227 and a left and right brake pedal 230 are disposed in parallel below the steering column 234. On the other hand, on the left side of the steering column 234, a shift operation lever 232 is disposed so as to be able to rotate forward (in the advancing direction of the body) or backward. A vehicle speed setting dial 211 is disposed on the grip portion 232a of the shift operation lever 232, and the operator grips the grip portion 232a with the left hand and operates the vehicle speed setting dial 211 with the finger of the gripped hand.

  Further, the floor plate 235 on the right side of the steering column 234 has the engine 5 rotation speed set by the throttle lever 206 as the minimum rotation speed, and the engine 5 rotation speed is increased or decreased within a range of higher rotation speeds. An accelerator pedal 226 is provided for this purpose. On the right column of the control seat 8, an auxiliary transmission changeover switch 222, a PTO cutoff switch 223, and a work implement elevating lever 259 are arranged, and on the left column of the control seat 8, a PTO speed change lever 224 is arranged. Yes. A differential lock pedal 225 is disposed in front of the left column of the control seat 8.

  The shift operation lever 232 can be manually moved by the operator to the neutral position in the upright position, the forward shift position tilted forward (traveling direction), and the reverse shift position tilted backward, respectively. It is configured. On the other hand, a shift potentiometer 220 such as a linear potentiometer is provided as a lever rotation detection sensor for detecting the forward side tilt operation amount (tilt angle) or the reverse side tilt operation amount (tilt angle) of the shift operation lever 232. .

  In other words, the shift operation lever 232 is configured to be held at the neutral position or the operation position by the maintenance force of a friction brake mechanism (not shown), while the forward operation or reverse operation amount of the transmission operation lever 232 is predetermined. When the above is reached, spring means (not shown) that resists the tilting operation force of the speed change operation lever 232 is provided, and the operation resistance force suddenly falls in the middle of the forward side tilting operation or reverse side tilting operation of the speed change operation lever 232. It is configured to increase. As a result, when the shift operation lever 232 is tilted and operated exceeding the normal forward side tilt operation amount or the reverse side tilt operation amount, the resistance force (lever tilt operation force) resisting the tilt operation force of the shift operation lever 232 is stepped. It is configured so that the operator can easily feel that the acceleration is intended to be accelerated beyond a predetermined value.

  Next, constant speed ratio control (speed ratio adaptive control) will be described. Here, the gear ratio refers to the ratio of the rotational speed of the output shaft 36 of the hydraulic continuously variable transmission 29 to the engine 5 rotational speed. same as below.

  An input shaft 27 to which power from the engine 5 is transmitted is disposed in a mission case 17 mounted on the traveling machine body 2, and the input shaft 27, a hydraulic pump unit 500 for shifting, a hydraulic motor unit 501, an output shaft 36, In a work vehicle that includes a hydraulic continuously variable transmission 29 arranged on the same axis and configured to transmit at least traveling driving force from the output shaft 36 via the hydraulic motor unit 501, a preset target The actual (real) gear ratio may not match the gear ratio due to environmental changes and disturbances (mainly loads related to travel). Therefore, a control for causing the electronic governor controller 213 to feed back the actual (real) engine 5 rotation speed and the rotation speed of the output shaft 36 to be close to or coincide with the target speed ratio is a constant speed ratio control (speed ratio adaptive control). That's it. In other words, while controlling the rotational speed of the engine 5 so as to be maintained at a substantially constant value regardless of the fluctuation of the load, the actual (real) gear ratio is within a predetermined value% of the target gear ratio. The proportional solenoid valve 203 for controlling the gear ratio of the hydraulic continuously variable transmission 29 is controlled. Therefore, the speed ratio pattern of the speed ratio of the rotational speed of the output shaft 36 in the hydraulic continuously variable transmission 29 with respect to the rotational speed of the engine 5 is stored in a RAM (anytime readable / writable memory) as pattern storage means in the travel controller 210.

  This speed ratio pattern is a pattern in which the speed ratio increases in proportion to an increase in the operation amount of the speed change operation lever 232 (the forward side tilting operation amount or the reverse side tilting operation amount). The proportional function is a linear function. It may be a function of a quadratic curve. The pattern storage means stores a plurality of speed ratio patterns in a function table format or a map format (see a gear ratio diagram as shown in FIG. 18). According to the type of farm work and the field conditions (soil quality, paddy field, field land, etc.), in the embodiment of FIG. 18, 15 types of speed ratio patterns (speed ratio lines) are prepared and stored in advance in the pattern storage means. I am letting. When the operator selects the scale of the transmission ratio setting device (setting dial) 221, any one pattern can be set (instructed) from among a plurality of types of transmission ratio patterns. In other words, the gear ratio setting device (setting dial) 221 is for changing (adjusting setting) the rate of change of the gear ratio corresponding to the operation amount of the gear shift operation lever 232.

In the embodiment shown in FIG. 18, the amount of operation of the speed change lever 232 (shown as a percentage of the maximum tilting operation amount is shown on the horizontal axis, the rightward is for the forward side tilting operation, and the leftward is for the backward side tilting operation) , The vertical axis (see the left vertical axis) is the speed ratio of the rotational speed of the output shaft 36 in the hydraulic continuously variable transmission 29 to the rotational speed of the engine 5 [(the rotational speed of the output shaft 36 / the rotational speed of the engine 5) = 0-2] is taken to show the gear ratio pattern diagram. In FIG. 18, No.
1 to No. 15, the forward speed ratio pattern and the reverse speed ratio pattern are set to be the same (symmetrical). Further, FIG. 18 shows a diagram (indicated by a broken line) showing a change in lever tilting operation force with respect to the operation amount of the shift operation lever 232. That is, the lever vertical operation force (indicated by% of the maximum value) is taken on the right vertical axis.

  In the present embodiment, the shifting operation lever 232 has a tilting operation force at the midway portion (for example, about 70% of the total tilting operation amount) of the shifting operation lever 232. The spring means increases rapidly. That is, when the operation amount of the shifting operation lever 232 is from 0% to about 70%, the operation force of the shifting operation lever 232 is linearly proportional to the low gradient by resisting the biasing force of the friction brake mechanism. To increase. At the position where the shifting operation lever 232 tilting operation amount is about 70%, the resistance force by the spring means described above is added, so that the shifting operation lever 232 tilting operation force suddenly changes from about 20% of the maximum value to about 50%. Then, when the operation amount of the shifting operation lever 232 after that is about 70% to 100%, the operation force of the shifting operation lever 232 increases in a substantially linear proportion with a high gradient.

Each speed ratio pattern (speed ratio line) is also made different between a region where the amount of tilting operation of the speed change lever 232 is less than the position where it is about 70% and a region where it is larger. In the embodiment of FIG. 18, No. 1 to No. 11 lines (No. 1 in order from the lower line in FIG. 18).
In No. 11), the gradient of the transmission ratio line is low in the region where the tilting operation amount of the transmission operation lever 232 is less than the position of about 70%, and the gradient of the transmission ratio line is in the region exceeding the position of about 70%. It is set to be high. When adopting the gear ratio line, when the operator intends to accelerate, when the operator tilts and operates the shift operation lever 232 beyond the range of the normal operation amount of the shift operation lever 232 (within about 70%), This can be perceived by a rapid increase in the operating force of the shifting operation lever 232. Also, as will be described later, when the operator wants to increase the speed beyond the speed set by the gear ratio setting dial 221 in response to environmental changes, disturbances, etc., the operator needs to change the setting of the speed ratio setting dial 221. By simply depressing the shift operation lever 232 by a predetermined amount or more and avoiding this, the speed can be increased easily.

In the No. 12 line (the twelfth line from the lower line in FIG. 18), the speed change lever 232
The gear ratio line is set almost in a straight line until the tilting operation amount is 0% to 100%.

In the lines of No. 13 and No. 14 (No. 13 and No. 14 counted from the lower line in FIG. 18), the amount of the tilting operation amount of the speed change operation lever 232 exceeds the range of about 70%. The gradient of the transmission ratio line is set lower than the gradient in the region where the position is less than about 70%. The speed ratio line of No. 15 is a straight line that becomes the speed ratio 2 at a position where the amount of tilting operation of the speed change operation lever 232 is about 70% (immediately before the aforementioned spring means acts on the speed change operation lever 232).

  Next, the start / brake control of the traveling machine body will be described with reference to the flowchart shown in FIG. First, when starting the engine 5 (S1), it is determined whether or not the speed change lever 232 is in the neutral position (S2). When the speed change lever 232 is not in the neutral position (S2: no), the travel controller 210 corrects the applied voltage value of the proportional control solenoid valve 203 to shift the swash plate angle of the hydraulic pump unit 500 to -11 degrees. To shift to gear ratio 0 (S3). In this state, the output rotational speed from the hydraulic continuously variable transmission 29 becomes zero. That is, the main transmission input shaft 27 is rotating and the main transmission output shaft 36 is stopped.

  On the other hand, when the speed change lever 232 is in the neutral position (S2: yes), when the time T1 has elapsed (S4: yes), the speed change amount of the speed change lever 232 from the speed change potentiometer 220 (the forward side tilting operation amount or the reverse side). The operation amount) is read into the travel controller 210 (S5). Based on the read numerical value, it is determined whether or not the shift operation lever 232 is in the forward (reverse) operation position (S6). When the shift operation lever 232 is not in the forward (reverse) operation position (S6: no), a travel stop control (see FIG. 22) described later is executed (S7).

  On the other hand, when the operator moves the speed change lever 232 to the forward (reverse) operation position (S6: yes), the travel controller 210 corrects the applied voltage value of the proportional control electromagnetic valve 203, so that the hydraulic pump unit 500 The swash plate angle is shifted to -11 degrees and moved to the gear ratio 0 (S8). In this state, regardless of the output rotational speed of the engine 5, the main transmission output shaft 36 is stopped and the rotational speed of the main transmission output section is maintained at substantially zero.

  At the time of shifting to this gear ratio 0, the forward clutch solenoid valve 46 (reverse clutch solenoid valve 48) is operated to excite the forward or reverse clutch solenoid valves 46, 48, and the forward or reverse hydraulic clutches 40, 42 are activated. Is executed (S9).

  When the time T2 has elapsed since the clutch engagement operation (S10: yes), the left and right brakes that turn off the autobrake solenoid valve 67 for the brake cylinder 68 of the rear wheel 4 and release the braking of the rear wheel 4 by the left and right brakes 65. The release is executed (S11).

  Further, when T3 time has elapsed from the release of the left and right brakes (S12: yes), the forward (reverse) operation position of the speed change operation lever 232 is detected by the speed change potentiometer 220 and read into the travel controller 210, based on this read value. Then, the speed ratio adaptive control (described later) is performed in which the speed ratio of the hydraulic continuously variable transmission 29 is controlled to a speed ratio corresponding to the position of the speed change lever 232 by increasing or decreasing the rotational speed of the main speed change output shaft 36. 20) is executed (S13).

  As described above, when the speed change operation lever 232 is operated to the forward (reverse) operation position and travels forward while the speed ratio adaptive control is being executed, the speed change operation lever 232 in the forward (reverse) operation position. Is operated backward (forward) (S14: yes), forward / reverse switching control (see FIG. 21) described later is executed (S15).

  Next, the gear ratio adaptive control mode will be described with reference to the flowchart of the gear ratio control (FIG. 20). As described above, the proportional control solenoid valve 203 is operated in proportion to the shift operation amount (the forward side tilting operation amount or the reverse side tilting operation amount) of the shift operation lever 232, and the main transmission hydraulic cylinder 556 is driven by the hydraulic fluid from now on. The hydraulic oil discharge amount of the hydraulic pump unit 500 of the hydraulic continuously variable transmission 29 that is the main transmission mechanism is controlled by being driven. In this case, automatic control is performed in which the ultimate target value or the maintenance target of the gear ratio set by the setting dial 221 is adapted to the change in the environment, and more specifically, the shift operation amount of the shift operation lever 232 (forward side tilt operation) Or the reverse side tilting operation amount) is automatically monitored and automatically controlled so as to follow the target line of the speed ratio set by the speed ratio setting dial 221 in accordance with the change in the speed change operation amount. Thus, the rotational speed of the main transmission output shaft 36 can be changed and adjusted steplessly. Therefore, in the gear ratio adaptive control, when the operator selects and determines a desired gear ratio pattern according to the work type or the like with the speed ratio setting dial 221 (S16), the RAM of the travel controller 210 (memory that can be read and written as needed). The predetermined gear ratio pattern stored in is read out. Next, when the operator moves the shift operation lever 232 forward (reverse operation) in order to move the tractor 1 forward (reverse), the forward movement operation amount (reverse operation amount) from the shift potentiometer 220 is increased. Is read into the travel controller 210 (S17). Based on the read numerical value, the calculation unit of the travel controller 210 calculates a target speed ratio value corresponding to the forward side tilt operation amount (reverse side tilt operation amount) on the selected speed ratio pattern (S18). .

  On the other hand, the traveling controller 210 reads the engine speed from the engine rotation sensor 206 at every constant time interval (sampling time interval) during traveling, and detects the main transmission output section rotation speed by the main transmission output section rotation sensor 116. And read (S19). Whether the current gear ratio value is substantially equal to the target gear ratio value by calculating the current gear ratio value from the ratio between the engine speed (denominator) and the main gear shift output speed (numerator) at the sampling time (current) Is discriminated (S20).

  When the current gear ratio value is separated from the target gear ratio value by more than a predetermined percentage (S20: no), the travel controller 210 corrects the applied voltage value of the proportional control solenoid valve 203, so that the hydraulic pump unit 500 A main speed change operation is executed in which the swash plate angle is changed and adjusted, and the amount of hydraulic oil discharged to the hydraulic motor unit 501 is controlled to increase or decrease the rotational speed of the main speed change output shaft 36 (S21). If the current speed ratio value is substantially equal to the target speed ratio value (when the current speed ratio value is within ± predetermined% with respect to the target speed ratio value) (S20: yes), the rotational speed of the main speed change output shaft 36 is maintained. (S22).

  Thus, feedback control is performed so that the current gear ratio value approaches (or matches) the target gear ratio value. In these cases, for example, the output torque fluctuation of the engine 5 is insufficient due to disturbance such as an increase in driving load when the tractor enters a soil area containing a lot of water from a dry soil area. Of course, when the engine 5 rotational speed deviates from a predetermined value due to circumstances or environmental changes, the electronic governor controller 213 is operated to control the engine 5 rotational speed to be maintained at the predetermined value.

  If such gear ratio adaptive control is employed, the operator once sets the gear ratio pattern with the gear ratio setting dial 221 and then only operates the gear shift operation lever 232 to change the environment or work vehicle. When the actual gear ratio value deviates from the target gear ratio value due to fluctuations in the travel load of the vehicle, it can be automatically controlled so that it automatically approaches the target gear ratio value, and the operation operation of the work vehicle can be controlled continuously. It can be made extremely simple by approximating the driving operation in the attached car, and there is an effect that fatigue for a long time work can be reduced.

  Further, since the automatic control is executed by correcting the operation of the proportional control solenoid valve 203, there is an effect that the control can be performed finely and quickly. Further, since the electronic governor 214 for controlling the rotational speed of the engine 5 according to the load is provided, it is not necessary for the operator to manually adjust the engine throttle, and the rotational speed of the engine 5 and the hydraulic stepless speed change. The engine speed and the pump swash plate 509 angle can be controlled so that the output of the machine 29 can be kept highly efficient, and the traveling operation of the work vehicle can be changed to the traveling operation in an automobile with a continuously variable transmission mechanism. It can be approximated to make it extremely simple, and there is an effect that fatigue for a long time can be reduced. Instead of detecting the rotational speed of the main transmission unit, it is also possible to detect the vehicle speed (the rotational speed of the wheel) and calculate the gear ratio as an equivalent meaning.

  Next, the forward / reverse switching control of the traveling aircraft will be described with reference to the flowchart shown in FIG. When at least one of the left and right brakes 65 is in an inoperative state and at least one of the left and right rear wheels 4 is not braked, the traveling body is moving forward (or moving backward) in the gear ratio adaptive control of FIG. To be judged. When traveling work is being performed with the gear ratio adaptive control (S23), the reciprocating traveling control mode is set in which the traveling machine body moves backward (or moves backward) to moves backward (or moves forward). At this time, the engine speed from the engine speed sensor 215, the main speed output section speed from the main speed output section rotation sensor 116, and the vehicle speed from the vehicle speed sensor 117 are read (S24). When the traveling vehicle is traveling forward (or reverse) (S25: yes), it is determined whether or not the shift operation lever 232 opposite to the traveling direction is operated by being tilted backward (or forward) ( S25).

  When the shift operation lever 232 opposite to the traveling direction is operated to be moved backward (or forward) (S26: yes), the traveling controller 210 corrects the applied voltage value of the proportional control solenoid valve 203. Then, the swash plate angle of the hydraulic pump unit 500 is shifted to -11 degrees and moved to the gear ratio 0 (S27), and the output rotational speed from the hydraulic continuously variable transmission 29 is made zero. At this time, if the vehicle speed decelerates to a predetermined minute speed V1 (for example, about 0.1 km / hour) or less (S28: yes), the forward clutch electromagnetic valve 46 (reverse clutch electromagnetic valve 48) is turned OFF to move forward. The hydraulic clutch 40 (reverse hydraulic clutch 42) is disengaged (S29).

  When T4 time has elapsed from the clutch disengagement operation of the forward clutch 40 (reverse clutch 42) (S30), the reverse clutch electromagnetic valve 48 (forward clutch electromagnetic valve 46) is turned ON, and the reverse hydraulic clutch 42 (forward hydraulic clutch). 40) is turned on (S31).

  Thereafter, when T5 time elapses from the clutch engagement operation (forward hydraulic clutch 40) (S32), the gear ratio adaptive control shown in FIG. 20 is performed (S33). The traveling machine body is temporarily stopped from forward (reverse) travel at a speed calculated from the reverse operation amount of the shift operation lever 232 (forward operation amount) and the set value of the transmission ratio setting dial 221. After that, shift to reverse (forward) travel. By alternately performing the forward side tilting operation and the reverse side tilting operation of the shift operation lever 232, the traveling direction of the traveling machine body is alternately switched between forward traveling and backward traveling, and the traveling machine body can be smoothly reciprocated.

  As is clear from the above description and FIGS. 17 and 21, the shift potentiometer 220 that is a shift sensor that detects the operation amount (backward tilt operation amount) of the shift operation lever 232 by moving the shift operation lever 232 forward, A main transmission hydraulic cylinder 556 that is an actuator that adjusts the swash plate angle of the hydraulic pump 500 based on a detection value, a transmission output unit rotation sensor 116 that detects the rotation speed of the output shaft 36, and a control unit 210. . The control means 210 applies the brake 65 to the traveling wheels 3, 4, and moves the forward hydraulic clutch 40 and the reverse hydraulic clutch 42 in a state where the shift operation lever 232 is not tilted forward (backward tilt operation). It will be controlled to cut both.

  Further, when the shift drive output detected by the shift output unit rotation sensor 116 is equal to or lower than the forward / reverse switching speed V1, the forward hydraulic clutch 40 or the forward clutch 40 according to the forward side tilting operation (reverse side tilting operation) of the shift operation lever 232 Control is performed so that one of the reverse hydraulic clutches 42 is engaged. Therefore, it is possible to prevent reverse running during switching between forward and reverse. Each operation such as tractor 1 or wheel loader that requires frequent switching between forward and reverse, alternating between forward and reverse, and frequent stop and start operations can be made extremely simple, and long-time work can be reduced in fatigue. There is an effect.

  When confirming that either the forward hydraulic clutch 40 or the reverse hydraulic clutch 42 is engaged, the brake 65 of the traveling wheels 3 and 4 is controlled so as to be released. It is possible to prevent the reverse running and start the running vehicle smoothly. Since the forward and reverse hydraulic clutches 40 and 42 are disposed downstream of the output shaft 36 in the hydraulic continuously variable transmission 29, the conventional engine 5 and the hydraulic continuously variable transmission are provided. The main clutch disposed between the machine 29 and the like can be omitted, and the structure can be simplified. As the traveling wheels, a pair of left and right traveling crawlers (not shown) may be provided instead of the left and right front and rear wheels 3, 4, and a pair of left and right traveling crawlers may be provided instead of the left and right rear wheels 4.

  Furthermore, a gear ratio setting dial 221 that is a gear ratio setting device for setting a gear ratio pattern of the hydraulic continuously variable transmission 29 and a pattern storage unit 210 that stores a plurality of gear ratio patterns are provided. The output rotational speed of the hydraulic continuously variable transmission 29 is controlled in accordance with a gear ratio pattern preset by the gear ratio setting unit 221 in accordance with the forward side tilting operation amount (reverse side tilting operation amount). Thus, once the operator sets the gear ratio pattern of the gear ratio with the gear ratio setting unit 221, the operator only needs to operate the gear change lever 232 to change the environment, travel of the tractor 1 that is a work vehicle, or the work load. When the actual gear ratio value deviates from the target gear ratio value due to fluctuations, it can be automatically controlled so as to automatically approach the target gear ratio value, and the traveling operation of the work vehicle 1 is equipped with a continuously variable transmission mechanism. Is approximated to the running operation in a motor vehicle can be extremely easy, an effect that the prolonged activity fatigue can be reduced.

  In addition, when the shift operation lever 232 is moved forward (reverse), the vehicle speed is below a certain level when the shift operation lever 232 is moved backward (reverse), when the shift operation lever 232 is moved backward (reverse). Since control is performed so that the forward hydraulic clutch 40 is turned off and then the reverse hydraulic clutch 42 is turned on, for example, in a reciprocating operation, an ultra-low speed output (low efficiency) of the hydraulic continuously variable transmission 29 is achieved. The output range) is cut, and the hydraulic continuously variable transmission 29 can be switched from forward to reverse before it becomes a low-efficiency output. When the vehicle is switched from forward to reverse, it is possible to prevent the traveling acceleration performance and the like from being lowered, and the traveling machine power can be properly maintained.

  Next, the travel stop control of the traveling machine body will be described with reference to the flowchart shown in FIG. When at least one of the left and right brakes 65 is in an inoperative state and at least one of the left and right rear wheels 4 is not braked, a traveling operation such as the gear ratio adaptive control shown in FIG. It is judged that he is moving backward. During traveling work such as the gear ratio adaptive control (S34), it is determined whether or not the speed change lever 232 is in the neutral position (S35).

  When the operation of returning the shift operation lever 232 from the forward side (reverse side) tilting operation position to the neutral position is performed and the shift operation lever 232 is in the neutral position (S35: yes), the swash plate angle of the hydraulic pump unit 500 Is changed to approximately −11 degrees, for example, and moved to a gear ratio of zero. In this state, hydraulic oil from the hydraulic pump unit 500 is supplied to the hydraulic motor unit 501, and the relative rotation direction of the hydraulic motor unit 501 is opposite to that of the input shaft 27 (hydraulic pump unit 500). The main transmission output gear 37 connected to 500 is absolutely stopped, and the rotational speed of the main transmission output section becomes substantially zero regardless of the output rotational speed of the engine 5.

  When the shift operation lever 232 is returned from the forward side (reverse side) tilting operation position to the neutral position (S35: yes), the engine speed from the engine rotation sensor 215, the main shift from the main shift output unit rotation sensor 116, and so on. The output section rotational speed and the vehicle speed from the vehicle speed sensor 117 are read (S36).

  When the vehicle speed becomes equal to or less than a predetermined minute speed V1 (for example, about 0.1 km / hour) (S37: yes), the travel controller 210 considers that the operator intends to stop traveling, and the travel controller 210 46 and the reverse clutch solenoid valve 48 are both turned off to cut off the driving force to the traveling portion (S38).

  Further, an autobrake operation is performed in which the autobrake solenoid valve 67 for the brake cylinder 68 of the rear wheel 4 is turned on to apply braking (S39). As a result, the travel of the tractor 1 is stopped (S40). Therefore, when the engine 5 is started, the operator erroneously sets the speed ratio with the speed ratio setting dial 221 first, or the operation tool (speed change operation lever 232) first. Even if you defeat and operate, it is safe because it does not start.

  Then, it is determined whether or not a further T6 time has elapsed since the stop of the travel in step S40 (S41). If the T6 time has elapsed (S41: yes), the swash plate angle of the hydraulic pump unit 500 is set to approximately 0 degrees. The shift ratio is set to 1 (S42). In this state, hydraulic fluid from the hydraulic pump unit 500 is not supplied to the hydraulic motor unit 501, oil leakage due to wasteful circulation of hydraulic fluid in the hydraulic continuously variable transmission 29 is reduced, and wasteful fuel consumption of the engine 5 is reduced. There is an effect of disappearing. That is, after the time T6 has elapsed, the operator does not perform operations such as a gear ratio setting by the gear ratio setting dial 221 for work and a forward side tilting operation (backward side tilting operation) of the speed change operation lever 232 for starting traveling. Then, it is possible not to apply a load to the engine 5 and to avoid useless fuel consumption.

  Next, clutch pedal control will be described with reference to the flowchart shown in FIG. When at least one of the left and right brakes 65 is in an inoperative state and at least one of the left and right rear wheels 4 is not braked, a traveling operation such as the gear ratio adaptive control shown in FIG. It is judged that he is moving backward. During traveling work such as gear ratio adaptive control (S43), it is determined whether or not the clutch pedal 227 is depressed (S44).

  When a stepping operation for moving the clutch pedal 227 from the initial position to the depressed position is performed and the clutch pedal 227 is depressed (S44: yes), the travel controller 210 includes the forward clutch electromagnetic valve 46 and the reverse clutch electromagnetic. Forward / reverse clutch disengagement is executed in which both valves 48 are turned off to cut off the driving force to the traveling portion (S45). Next, the engine speed from the engine speed sensor 215, the main speed output section speed from the main speed output section rotation sensor 116, and the vehicle speed from the vehicle speed sensor 117 are read (S46).

  When the vehicle speed becomes equal to or less than a predetermined minute speed V1 (for example, about 0.1 km / hour) (S47: yes), it is considered that the operator intends to stop traveling, and the traveling controller 210 An auto brake 65 operation is performed in which the auto brake solenoid valve 67 for the brake cylinder 68 is turned on to apply the brake (S48). Thereby, traveling of the tractor 1 is stopped (S49).

  Then, it is determined whether or not T7 time has elapsed since the stop of travel in step S49 (S50). If T7 time has elapsed (S50: yes), the swash plate angle of the hydraulic pump unit 500 is set to approximately 0 degrees. The shift ratio is set to 1 (S51). In this state, since hydraulic oil from the hydraulic pump unit 500 is not supplied to the hydraulic motor unit 501, the load on the engine 5 for driving the hydraulic continuously variable transmission 29 is reduced, and when the clutch pedal 227 is depressed, There is an effect that troubles such as the engine 5 or the hydraulic continuously variable transmission 29 can be prevented or reduced.

  Note that if an abnormality occurs in the traveling work or the farm work machine during the rotation of the engine 5 due to, for example, a failure of the electric system, the operator simply depresses the clutch pedal 227 and the gear ratio adaptive control output of the traveling controller 210 is output. The forward clutch solenoid valve 46 and the reverse clutch solenoid valve 48 are turned off to forcibly and urgently cut off the power transmission to the traveling system, and the auto brake 65 is actuated so that the left and right rear The vehicle can be forcedly and urgently stopped by braking the wheels 4 to ensure safety.

  As is clear from the above description and FIGS. 17 and 19 to 22, etc., a hydraulic system that shifts the power from the engine 5 mounted on the traveling machine body 2 having traveling wheels such as the front wheels 3 and the rear wheels 4. A continuously variable transmission 29, a shift operation lever 232 that changes the gear ratio of the hydraulic continuously variable transmission 29, and a traveling that transmits a shift drive output from the hydraulic continuously variable transmission 29 to the traveling wheels 3 and 4. In a work vehicle comprising a forward hydraulic clutch 40 and a reverse hydraulic clutch 42 as clutches for driving, and a brake 65 for braking the traveling wheel 4, a shift for detecting an operation amount and an operation direction of the shift operation lever 232 A speed change sensor 220 such as a potentiometer, a speed change output part rotation sensor 116 for detecting the output speed of the hydraulic continuously variable transmission 29, and a control means 21 such as a travel controller. When the shift drive output detected by the shift output unit rotation sensor 116 is equal to or less than the forward / reverse switching speed, the forward hydraulic clutch 40 or the reverse hydraulic clutch 42 is controlled according to the operation direction of the shift operation lever 232. When the brake 65 of the traveling wheel 4 is confirmed to be released, control is performed to change the gear ratio of the hydraulic continuously variable transmission 29 according to the amount of operation of the speed change operation lever 232. Therefore, both the forward / reverse hydraulic clutches 40 and 42 and the shifting operation of the hydraulic continuously variable transmission 29 can be simplified by operating the shift operation lever 232. it can. For example, in each operation of the tractor 1 or the wheel loader that needs to frequently perform operations such as starting and stopping, or alternately repeating forward and reverse switching operations, the operator operates the speed change operation lever 232 to Operations such as acceleration and deceleration at the time of stopping can be made extremely simple, engine troubles can be easily prevented, and fatigue during long working hours can be reduced.

  As apparent from the above description and FIGS. 17 and 20, the control means 210 includes a speed ratio setting device 221 such as a speed ratio setting dial for setting the speed ratio pattern of the hydraulic continuously variable transmission 29, and a plurality of speed ratio setting devices 221. Pattern storage means for storing the gear ratio pattern, and the output of the hydraulic continuously variable transmission 29 according to the gear ratio pattern preset by the gear ratio setter 221 in accordance with the operation amount of the gear shift operation lever 232. Since the speed is controlled, the operator once sets the speed ratio pattern of the speed ratio with the speed ratio setting device 221, and then only operates the speed change lever 232 to change the environment or the work vehicle 1. When the actual gear ratio value deviates from the target gear ratio value due to fluctuations in travel load, it can be automatically controlled so that it automatically approaches the target gear ratio value. Operation extremely able to simplify, can reduce the fatigue of a long period of work.

  As is apparent from the above description and FIGS. 17, 20, 22, and the like, the control unit 210 applies the brake 65 to the traveling wheel 4 and the forward hydraulic clutch in a state where the speed change operation lever 232 is neutral. The tractor 1 or the wheel loader needs to frequently perform, for example, a start and stop operation, or an alternating forward and reverse switching operation, because the control is performed so that both the hydraulic drive clutch 40 and the reverse hydraulic clutch 42 are disconnected. Each work such as can be made extremely simple, and fatigue during a long work can be reduced.

  As is apparent from the above description and FIGS. 17, 20, 21, and the like, the control unit 210 reduces the vehicle speed to a certain value or less when the shift operation lever 232 is operated from the forward (reverse) side to the reverse (forward) side. The forward (reverse) hydraulic clutch 40 is controlled to be disengaged, and when the predetermined time has elapsed after the forward (reverse) clutch 40 is disengaged, the reverse (forward) hydraulic clutch 42 is controlled to be engaged. When a certain period of time has elapsed since the (forward) hydraulic clutch 42 is engaged, the output rotational speed of the hydraulic continuously variable transmission 29 is controlled along the gear ratio pattern. That is, the brake release of the rear wheel 4 as the traveling wheel is confirmed to be released in the state where the forward hydraulic clutch 40 (or the backward hydraulic clutch 42) as the traveling clutch is engaged and operated by the forward operation or the reverse operation of the speed change operation lever 232. When this is done, the output rotational speed of the hydraulic continuously variable transmission 29 is controlled based on a preset gear ratio pattern in accordance with the operation amount of the speed change lever 232. In reciprocating operation, etc., the ultra-low speed output (low efficiency output range) of the hydraulic continuously variable transmission 29 is cut, and the traveling direction is changed from forward to backward before the hydraulic continuously variable transmission 29 becomes low efficiency output. You can switch from reverse to forward. Therefore, when the traveling direction is switched from forward to reverse (backward to forward), it is possible to prevent the travel acceleration performance from being deteriorated and improve the traveling mobility. For example, in each operation such as a tractor or a wheel loader that requires frequent operations such as starting and stopping, or repeating forward and backward operations, the operator operates the speed change operation lever 232 to increase the speed at the time of starting or Deceleration when stopping can be easily controlled, engine troubles can be easily prevented, and the operator's fatigue in continuous work for a long time can be reduced.

  As is clear from the above description and FIGS. 17, 20, and 23, a clutch pedal 227 that cuts both the forward clutch 40 and the reverse clutch 42 is provided, and when the clutch pedal 227 is depressed, the forward and reverse When the vehicle speed falls below a certain level, the brake 65 is controlled to operate. When the brake 65 is operated and a certain time has elapsed, the hydraulic continuously variable transmission is controlled. The machine 29 is controlled so that this gear ratio becomes zero. That is, a clutch pedal 227 that cuts off the forward hydraulic clutch 40 and the reverse hydraulic clutch 42 is provided, and the brake 65 is controlled to be operated when the vehicle speed falls below a certain level by depressing the clutch pedal 227, Since the output speed of the hydraulic continuously variable transmission 29 is set to zero when a certain time has elapsed after the brake 65 is actuated, the operator simply performs a stepping operation on the clutch pedal 227. The vehicle 1 can be stopped. For example, it is possible to prevent an accident or the like caused by a trouble in automatic control of the control means 210, and the operator can quickly cope with the environment and operation results. Further, for example, it is possible to improve driving operability such as turning or reciprocating work in which forward and reverse switching operations are frequently performed.

  As is clear from the above description and FIGS. 16 and 17, the gear ratio setting device 221 is disposed in the grip portion 232 a of the speed change operation lever 232. The shift ratio setting device 221 can be operated with the finger of the hand holding the shift control lever 232 with the other hand and the operator holding the shift control lever 232 with the other hand. For example, a gear shift operation for switching the gear ratio setting unit 221 during a gear shift operation (stepless gear shift operation) for moving the gear shift operation lever 232 with the operator holding the handle 9 and the gear shift operation lever 232 with both hands (see FIG. The stepped shift operation for selecting the shift pattern shown in FIG. 18 can be simplified.

  As is clear from the above description, according to the embodiment, the traveling machine body 2 on which the engine 5 is mounted, the hydraulic pump 500 that shifts the power from the engine 5, and the hydraulic continuously variable transmission 29 with the hydraulic motor 501, A main transmission output shaft 36 to which a shift output of the hydraulic continuously variable transmission 29, which is a combination of power from the engine 5 and output from the hydraulic motor 501, is transmitted as rotational force in one direction, and the main shift In the work vehicle 1 provided with the forward / reverse switching mechanisms 41 and 43 that switch the rotational force in one direction from the output shaft 36 to the forward rotation output or the reverse rotation output, the output from the hydraulic motor 501 is the output control state in the reverse rotation direction. When the forward rotation speed from the engine 5 and the reverse rotation speed from the hydraulic motor 501 coincide with each other, the traveling speed of the traveling machine body 2 is configured to be zero. Therefore, the output torque at the time of zero start can be easily secured, and the zero start or slow speed performance can be improved. The effect that can be improved easily. Further, it is possible to easily eliminate the problem that the main transmission output shaft 36 rotates and moves the traveling machine body 2 forward and backward when the hydraulic speed change operation is stopped (when the operation lever 232 is neutral). There is an effect.

  Further, an operation tool 232 for changing the gear ratio of the hydraulic continuously variable transmission 29 and an actuator 556 for adjusting the swash plate angle of the hydraulic pump 500 are further provided, and the operation tool 232 is moved from the neutral position to the maximum. By operating to the forward operation position, the swash plate angle of the hydraulic pump 500 is changed from the maximum reverse rotation angle to the maximum normal rotation angle, and the moving speed of the traveling machine body 2 is changed from zero to the maximum speed. Therefore, there is an effect that the vehicle can move forward smoothly and easily by shifting operation.

1 Tractor (work vehicle)
2 traveling machine body 5 engine 29 hydraulic continuously variable transmission 40 forward hydraulic clutch (traveling clutch)
42 Reverse hydraulic clutch (travel clutch)
65 Brake 227 Clutch pedal 232 Shifting control lever

Claims (1)

A traveling body equipped with an engine, a hydraulic continuously variable transmission with a hydraulic pump and a hydraulic motor for shifting the power from the engine, and the hydraulic type that combines the power from the engine and the output from the hydraulic motor A main transmission output shaft to which the transmission output of the continuously variable transmission is transmitted as a unidirectional rotational force, and a forward / reverse switching mechanism for switching the unidirectional rotational force from the main transmission output shaft to a normal output or a reverse output; A travel clutch that transmits a shift output from the hydraulic continuously variable transmission to a traveling wheel of the traveling machine body, a brake that brakes the traveling wheel, and an operation tool that changes a gear ratio of the hydraulic continuously variable transmission. And a work vehicle comprising an actuator for adjusting a swash plate angle of the hydraulic pump ,
When the operating tool is operated to the neutral position during traveling of the traveling machine body, the swash plate angle of the hydraulic pump becomes the maximum reverse rotation angle, and the output from the hydraulic motor is in the output control state in the reverse rotation direction. When the rotational speed coincides with the reverse rotational speed from the hydraulic motor, the output rotational speed of the main transmission output shaft becomes zero, and then the traveling speed of the traveling machine body becomes a predetermined speed or less, the traveling speed The clutch is disengaged and the brake is operated, and then the swash plate angle of the hydraulic pump is shifted to zero, so that the rotational speed transmitted from the hydraulic motor to the main transmission output shaft is zero.
Work vehicle.

Images