JP4650930B2 - Control device for 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. More specifically, the traveling speed of the work vehicle is set to, for example, a low speed. The present invention relates to a control means for switching a sub-transmission mechanism for switching to multiple stages such as high speed.

  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.

In addition, in order to apply to a relatively narrow low-speed work area where the travel speed range (during forward) such as a work vehicle such as a tractor or wheel loader is several km / h to several tens km / h, In place of the hydrostatic continuously variable transmission, a cylinder block that constitutes a continuously variable transmission, in which 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 arranged concentrically. By adopting a so-called inline type continuously variable transmission in which a hydraulic pump part and a hydraulic motor part are arranged on both sides of the motor, and the input shaft and the output shaft are configured as a double shaft, no hydraulic oil leakage occurs. It is disclosed that the power transmission efficiency is good and the fuel consumption of the engine is small.
JP 2003-226165 A JP 2002-89655 A

  By the way, in a work vehicle such as a tractor, for example, a farm field or earthwork work such as field cultivation / plowing work, ground breaking / leveling work, paddy field cultivation, multi-laying, etc., needs to run at a very low speed. On the other hand, traveling on the road such as towing or transporting work equipment is required to travel at a relatively high speed. Therefore, the driving force of the engine is transmitted to the traveling wheels via the continuously variable transmission and the gear auxiliary transmission mechanism. However, in a conventional work vehicle such as a tractor, for example, a forward / reverse clutch, a sub-transmission mechanism, and the like are installed on the output side of the inline type continuously variable transmission of Patent Document 2, and a shift drive output from the continuously variable transmission is generated. There is no transmission to the traveling wheel via the forward / reverse clutch and the auxiliary transmission mechanism, and there is no effective transmission control for switching the auxiliary transmission mechanism.

  An object of the present invention is to provide a control device for a work vehicle that can easily prevent an engine trouble or the like while performing an operation of switching a sub-transmission mechanism by a simple operation such as an operation of a shift switch, for example. It is.

In order to achieve the above object, a control device for a work vehicle according to a first aspect of the present invention includes a hydraulic continuously variable transmission for shifting power from an engine mounted on a traveling machine body having traveling wheels, and the hydraulic type. From a shift pedal for changing the transmission ratio of the continuously variable transmission, a forward clutch and a reverse clutch for transmitting a shift drive output from the hydraulic continuously variable transmission to the traveling wheels, and from the hydraulic continuously variable transmission In a work vehicle in which the main transmission operation of the hydraulic continuously variable transmission operates in proportion to the amount of depression of the forward pedal or the reverse pedal as a shift pedal. The forward hydraulic clutch is continued by the depressing operation, and the main transmission output gear and the travel counter shaft are connected by the forward gear, while the reverse hydraulic clutch is engaged by the depressing operation of the reverse pedal. Is, a structure in which the main transmission output gear and traveling counter shaft is coupled at the reverse gear, a shift sensor for detecting the depression amount of the shift pedal, the rotational speed of the output shaft of the hydraulic CVT A shift output rotation sensor for detecting, a sub-shift switching means for switching the sub-transmission mechanism, and a control means, and by turning on the high-speed side of the sub-shift switching means, the engaged forward clutch or reverse clutch is disengaged, At the same time when the auxiliary transmission mechanism is switched to the high speed side, the speed change drive output from the hydraulic continuously variable transmission is decelerated , and when the rotational speeds of the input side and the output side of the forward clutch or the reverse clutch coincide, Either the forward clutch or the reverse clutch, which has been entered immediately before operating the shift switching means on the high speed side, is engaged again .

According to a second aspect of the present invention, in the work vehicle control device according to the first aspect, the traveling operation can be continued when the high-speed / low-speed selector switch is switched from the sub-speed to the high-speed side while the engine is rotating. In this state, the low speed clutch for the sub-transmission is disengaged and the high-speed clutch is continued. At the same time, the transmission ratio of the hydraulic continuously variable transmission is lowered so that the main transmission output section rotation speed matches the sub-transmission output section rotation speed. When the vehicle speed drops below the specified speed, the left and right brakes should be turned off. At approximately the same time as the on / off operation is performed, the high speed clutch is continued and the forward clutch or the reverse clutch that was just before switching the high speed / low speed changeover switch from the low speed side to the high speed side is again engaged. It is intended to be.

According to the first aspect of the present invention, the forward clutch entered immediately before operating the auxiliary transmission switching means on the high speed side when the rotational speeds of the input side and the output side of the forward clutch or the reverse clutch substantially coincide. Alternatively, since either one of the reverse clutches is controlled to be engaged again, for example, the traveling body is not stopped or the shift drive output of the hydraulic continuously variable transmission is made neutral (substantially zero rotation). Without changing the speed change output of the sub-transmission mechanism from low speed to high speed, making each operation of the tractor or wheel loader extremely simple, improving traveling mobility, and Fatigue can be reduced. In addition, there is an effect that the reverse running in the middle of the auxiliary transmission switching can be prevented. For example, since the forward / reverse clutch and the subtransmission mechanism are disposed downstream of the output shaft of the hydraulic continuously variable transmission, the conventional engine, the hydraulic continuously variable transmission, The main clutch disposed between the two can be omitted, and the structure can be simplified .

According to a second aspect of the present invention, when the high speed side operation of the sub shift switching means is confirmed, and the engaged forward clutch or reverse clutch is turned off, the sub shift switching means is operated at the high speed side. When the vehicle speed falls below a certain level before either the forward clutch or the reverse clutch that was entered immediately before is re-engaged, the sub-shift switching is performed so that the running wheel is braked. Even if both the forward clutch and the reverse clutch are disengaged by the high-speed side operation of the means, it is possible to prevent reverse running that moves in the direction opposite to the traveling direction before the disengaged forward clutch or reverse clutch is disengaged, For example, the traveling sub-shift can be shifted from a low speed to a high speed by preventing the traveling machine body from running backward when traveling uphill or downhill.

  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 of the tractor, 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. FIG. 19 is a speed ratio pattern diagram showing the relationship between the pedal depression amount and the speed ratio, FIG. 20 is a speed ratio adaptive control flowchart, FIG. 21 is a stop control flowchart, and FIG. 22 is a forward / reverse switching control flowchart. 23 is a flowchart of sub-shift high-speed switching 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 forward control clutch for operating the proportional control valve 203, the switching valve 204 operated thereby, the shift shift electromagnetic valve 666 of the hydraulic cylinder 55 for traveling auxiliary speed change, and the hydraulic clutches 40, 42 for switching forward and reverse traveling. To switch the 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 to double speed drive. The double speed hydraulic solenoid valve 82 for the double speed hydraulic clutch 76 is connected. 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. The first charge valve 544 replenishes the first oil chamber 530 with the hydraulic oil in the hydraulic oil supply oil passage 543, and the second charge valve 545 replenishes the second oil chamber 531 with the hydraulic oil in the hydraulic oil supply oil passage 543. And are provided.

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

  Further, the pump swash plate 509 is disposed on the outer periphery of the small diameter portion of the first holder 510 via an inclination angle adjustment fulcrum 555 as described later (see FIG. 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. A switching valve 204 is operated by hydraulic oil from a proportional control solenoid valve 203 that operates in proportion to the amount of depression of a forward pedal 232 or a reverse pedal 233, which will be described later, and the hydraulic cylinder 556 is controlled. The inclination angle of the pump swash plate 509 is changed with respect to the 27 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 tilt angle of the pump swash plate 509 is substantially zero (speed ratio 1), the transmission motor 501 is not driven by the transmission pump 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 5016 every half rotation of the cylinder block 505. Communicated with A closed hydraulic circuit is formed between the first plunger hole 507 and the second plunger hole 516, and hydraulic oil is pumped from the first plunger hole 507 to the second plunger hole 516 in the discharge stroke of the pump plunger 506, The hydraulic fluid is returned from the second plunger hole 516 to the first plunger hole 507 during the suction stroke of the pump plunger 506, and the operation of the axial piston pump and the motor is performed.

  When the pump swash plate 509 is inclined in one direction (positive inclination angle) with respect to the axis line of the main transmission input shaft 27, the motor swash plate 518 is rotated in the same direction as the cylinder block 505, and the transmission motor 501 is rotated. The main transmission output shaft 36 is rotated at a higher rotational speed than the main transmission input shaft 27, and the rotational speed of the main transmission input shaft 27 is increased and transmitted to the main transmission output gear 37. . That is, the rotation speed of the transmission motor 501 driven by the transmission pump 500 is added to the rotation speed of the main transmission input shaft 27 and transmitted to the main transmission output gear 37. Therefore, the shift output (travel speed) from the main shift output gear 37 is proportional to the inclination (positive inclination angle) of the pump swash plate 509 within the range of the rotation speed higher than the rotation speed of the main transmission input shaft 27. As a result, the maximum traveling speed is reached at the maximum inclination 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 forward pedal 232 described later is depressed, the clutch cylinder 47 is operated by the forward clutch solenoid valve 46 to continue the forward hydraulic clutch 40, and the main transmission output gear 37 and the travel counter shaft 38 are connected to the forward gear 41. (See FIGS. 5 and 6).

  On the other hand, when the reverse pedal 233, which will be described later, is depressed, the clutch cylinder 49 is operated by the reverse clutch solenoid valve 48 to continue the reverse hydraulic clutch 42, and the main transmission output gear 37 and the travel counter shaft 38 are connected to the reverse gear 43. (See FIGS. 5 and 6).

  In the neutral position where neither the forward pedal 232 nor the reverse pedal 233 is depressed, both the forward and reverse wet multi-plate hydraulic clutches 40 and 42 are both disconnected, and the front wheel 3 and the rear The travel driving force from the main transmission output gear 37 output to the 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 is composed of one pedal or two pedals, and the left and right brake pedal 230 and the left and right brake 65 are mechanically connected 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 handle 9 is detected, the left and right autobrake solenoid valves 67a and 67b actuate the brake cylinder 68, so that either the left or right brake 65 (see FIG. 5, but only one is shown). A braking operation is automatically performed, and a turning travel 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 the four-wheel drive operation of the switching lever (not shown) 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 four-wheel drive hydraulic clutch 74 is continued, and the front wheel input The shaft 72 and the front wheel output shaft 73 are connected by a four-wheel drive gear 75, and the front wheel 3 is driven together with the rear wheel 4.

  Next, switching of the double speed drive of the front wheel 3 will be described. As shown in FIGS. 5 and 6, the clutch cylinder 83 is actuated by the double-speed hydraulic solenoid valve 82 upon detection of a U-turn (direction change at the headland in the field) operation of the steering handle 9, and the double-speed hydraulic pressure is actuated. The clutch 76 is continued, the front wheel input shaft 72 and the front wheel output shaft 73 are connected by the double speed gear 77, and about twice as fast as the speed when the front wheel 3 is driven by the four-wheel drive gear 75. The front wheel 3 is configured to be driven at a high speed.

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

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

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

  In FIG. 6, a rotation detection gear 115 provided on the reverse rotation shaft 39 and 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 corresponding forward clutch solenoid valve 46 or reverse clutch solenoid valve 48 (see FIGS. 5, 6 and 18) is switched by a depression operation of a forward pedal 232 or a reverse pedal 233, which will be described later, the main transmission hydraulic cylinder 556 is operated. . 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. 18 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. (Not shown). 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. 18, the travel controller 210 includes various sensors and switches of the input system, that is, a steering potentiometer 218 that detects the amount of rotation (steering angle) of the round handle (steering handle) 9, and an operator A forward potentiometer 219 and a reverse potentiometer 220 as shift potentiometers for shifting the traveling speed, a gear 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, The main shift output unit rotation sensor 116 for detecting the rotation speed of the main shift output unit, the vehicle speed sensor 117 for detecting the rotation speed (traveling speed) of the front and rear wheels 3 and 4, and the PTO clutch 100 are turned on and off. When the PTO shut-off switch 223 for shutting off the output to the PTO shaft 23 and the brake pedal 230 are depressed And the brake pedal switch 231 for detecting the record is connected. The forward potentiometer 219 is a pedal depression position sensor that converts and detects the depression amount of the forward pedal 232 as a shift pedal, and the reverse potentiometer 220 is a pedal that converts and detects the depression amount of the reverse pedal 233 as a transmission pedal. It is a depression position sensor.

  As shown in FIG. 18, the travel controller 210 includes a forcible operation button 226 for forcibly turning off various output-type electromagnetic valves, that is, the forward clutch electromagnetic valve 46 and the reverse clutch electromagnetic valve 48 of the main transmission mechanism. A high-speed clutch solenoid valve 666 that switches the sub-shift between high speed and low speed, and a proportional control solenoid valve that operates the main transmission hydraulic cylinder 556 in proportion to the depression amount of a later-described shift pedal (forward pedal 232 and reverse pedal 233). 203 and left and right brake solenoid valves 67a and 67b 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 and a brake pedal 230 are arranged. Further, a forward pedal 232 and a reverse pedal 233 are arranged obliquely in parallel on the floor plate 235 on the right side of the steering column 234. A vehicle speed setting dial 211, a sub shift changeover switch 222, and a PTO cutoff switch 223 are disposed on the right column of the control seat 8, and a PTO shift lever 224 is disposed on the left column of the control seat 8. A differential lock pedal 225 is disposed in front of the left column of the control seat 8.

  The forward pedal 232 and the reverse pedal 233 are configured such that the stepping resistance increases rapidly in the middle of the stepping amount. That is, as shown in FIG. 17, like a normal pedal, the tread board (or pedal arm) 236 is mounted so as to be vertically rotatable with respect to the floor board 235 around the pivot shaft 237 at the base end thereof. . The tread plate 236 is supported via a sliding support shaft 238 and a link mechanism 239 in the middle of the lower surface thereof, and a return spring (first spring means) 241 mounted between the bracket 240 and the link mechanism 239 is attached. The pedal tread plate 236 is configured to return to the initial position by the force. On the other hand, when the pedal depressing amount (or stepping angle θ) of the tread plate 236 exceeds a predetermined value, the pedal tread plate (or pedal arm) 236 is brought into contact with and pressed. Second spring means 242 that resists pressure is erected on the floor plate 235. Accordingly, when the stepping plate 236 is depressed beyond the normal depression amount, the depression resistance force (pedal depression force) of the pedal 232 (233) increases stepwise, and the operator intends to accelerate more than a predetermined value. It is configured so that it can be easily felt.

  Further, a forward potentiometer 219 such as a linear potentiometer or a reverse potentiometer 220 is provided between the bracket 240 and the link mechanism 239 and the like as a stepping detection sensor for detecting the pedal depression amount (or depression angle) of the stepping plate 236. Yes.

  Next, constant speed ratio control will be described. Here, the constant speed ratio control means that an input shaft 27 to which power from the engine 5 is transmitted is arranged in a transmission case 17 mounted on the traveling machine body 2, and the input shaft 27 and a hydraulic pump unit 500 for shifting are arranged. And a hydraulic continuously variable transmission 29 in which the hydraulic motor unit 501 and the output shaft 36 are arranged on the same axis, and at least traveling driving force is transmitted from the output shaft 36 via the hydraulic motor unit 501. In this work vehicle, the engine 5 is controlled so as to keep the rotational speed of the engine 5 at a substantially constant value regardless of the fluctuation of the load. On the other hand, the speed ratio pattern of the speed ratio of the rotation speed of the output shaft 36 in the hydraulic continuously variable transmission 29 with respect to the speed of the engine 5 is stored in a RAM (a 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 depression amount of the speed change pedal (forward pedal 232 and reverse pedal 233), and the proportional function may be a linear function. It may be a function of a quadratic curve. The pattern storage means stores a plurality of gear ratio patterns in a function table format or a map format (see a gear ratio diagram as shown in FIG. 19). According to the type of farm work and field conditions (soil quality, paddy field, field land, etc.), in the embodiment shown in FIG. 19, 15 types of speed ratio patterns (speed ratio lines) are prepared and stored in the pattern storage means in advance. 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 and setting) the rate of change of the gear ratio corresponding to the amount of depression of the shift pedals (forward pedal 232, reverse pedal 233).

  In the embodiment shown in FIG. 19, the horizontal axis represents the pedal depression amount (indicated as a percentage of the maximum depression amount, the rightward direction is for the forward pedal, the leftward direction is for the reverse pedal), and 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 with respect 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]. A diagram of the pattern is shown. In FIG. 19, No. 1 to No. 15 are set in order from the lower line, and the forward speed ratio pattern and the reverse speed ratio pattern are set to be the same (symmetric). Further, FIG. 19 shows a diagram (indicated by a broken line) showing a change in the pedal effort with respect to the pedal depression amount. That is, the right vertical axis represents the pedal effort (indicated as a percentage of the maximum value).

  In the present embodiment, the pedaling force of the forward pedal 232 (or the reverse pedal 233) is suddenly increased by the second spring means 242 having the above-described configuration at the midway portion (for example, a position at about 70% of the total pedaling amount). It is supposed to be. That is, when the pedal depression amount is from 0% to about 70%, the pedal depression force increases linearly and proportionally with a low gradient by resisting the urging force of the first spring means 241. At a position where the pedal depression amount is about 70%, the resistance force by the second spring means 242 is added, so the pedal depression force suddenly changes from about 20% of the maximum value to about 50%, and the pedal depression amount thereafter is about 70%. From 100 to 100%, the pedal effort increases in a substantially linear proportion with a high gradient.

  Each speed ratio pattern (speed ratio line) is also different between a region where the pedal depression amount is less than about 70% and a region where the pedal depression amount is larger than that. In the embodiment of FIG. 19, in the No. 1 to No. 11 line (No. 1 to No. 11 in order from the lower line in FIG. 19), the pedal depression amount is less than the position of about 70%. The gradient of the gear ratio line is set to be low in the region, and the gradient of the gear ratio line is set to be high in the region exceeding the position of about 70%. When the gear ratio line is adopted, when the operator depresses the pedals 232 and 233 beyond the normal pedal depression amount range (within about 70%) with the intention of accelerating, the pedal depression force increases rapidly. I can feel it. 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 pedals 232 and 233 by a predetermined amount or more, the speed can be increased easily.

  In the No. 12 line (the twelfth line from the lower line in FIG. 19), the gear ratio line is set substantially in a straight line until the pedal depression amount is 0% to 100%.

  In the No. 13 and No. 14 lines (referred to as No. 13 and No. 14 from the lower line in FIG. 19), the gradient of the transmission ratio line in the region where the pedal depression amount exceeds about 70%. Is set lower than the gradient in an area less than about 70% of the position. The gear ratio line of No. 15 is a straight line that becomes the gear ratio 2 at a position where the pedal depression amount is about 70% (immediately before the pedal contacts the second spring means 242).

  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 electromagnetic valve 203 is operated in proportion to the amount of depression of the forward pedal 232 (or the reverse pedal 233), and the main transmission hydraulic cylinder 556 is driven by the hydraulic oil from now on, so that the hydraulic pressure that is the main transmission mechanism. The hydraulic oil discharge amount of the hydraulic pump unit 500 of the continuously variable transmission 29 is controlled. In this case, automatic control is performed in which the ultimate target value or the maintenance target of the speed ratio set with the setting dial 221 is adapted to changes in the environment, more specifically, the amount of depression of the speed change pedals 232 and 233 is self-monitored, The automatic control is performed 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 depression 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, the engine is started (S1), and then the operator selects and determines a desired gear ratio pattern according to the work type or the like with the gear ratio setting dial 221 (S2). A predetermined speed ratio pattern stored in the RAM (a readable / writable memory) of the controller 210 is read out. Next, when the operator depresses the forward pedal 232 (reverse pedal 233) to move the tractor 1 forward (reverse), the pedal depression amount is read into the travel controller 210 from the forward potentiometer 219 (reverse potentiometer 220) (S3). Based on the read numerical value, the calculation unit of the travel controller 210 calculates a target gear ratio value corresponding to the pedal depression amount on the selected gear ratio pattern (S4).

  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 (S5). 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 determined (S6).

  When the current gear ratio value is separated from the target gear ratio value by more than a predetermined percentage (S6: 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 shift operation is executed to change or adjust the swash plate angle and control the amount of hydraulic oil discharged to the hydraulic motor unit 501 to increase or decrease the rotational speed of the main shift output shaft 36 (S7). If the current gear ratio value is substantially equal to the target gear ratio value (if the current gear ratio value is within ± predetermined% with respect to the target gear ratio value) (S6: yes), the rotational speed of the main gear output shaft 36 is maintained. (S8).

  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 only needs to operate the forward pedal 232 or the reverse pedal 233, which is a gearshift pedal, after setting the gear ratio pattern of the gear ratio with the gear ratio setting dial 221. When the actual gear ratio value deviates from the target gear ratio value due to environmental changes or fluctuations in the work vehicle's running load, it can be automatically controlled so that it automatically approaches the target gear ratio value. The traveling operation can be made extremely simple by approximating the traveling operation in an automobile with a continuously variable transmission mechanism, and there is an effect that fatigue for a long time 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 travel stop control of the traveling machine body will be described with reference to the flowchart shown in FIG. When starting the tractor 1 of the present embodiment, first, the operator turns the key switch 211 to the ON position to turn on the travel controller 210 and the like to start up the electrical system. While depressing the brake pedal 230, the key switch (key SW) 211 is rotated to the operating position of the starter 212 (S11), and the engine 5 is started (S12). Next, when the key switch 211 is returned to the ON position (S13: yes), the swash plate angle of the hydraulic pump unit 500 is changed to, for example, approximately -11 degrees and moved to the gear ratio 0 (S14). 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.

  It is determined whether or not T1 time has elapsed from the time when the speed ratio is shifted to 0 (S15), and while the T1 time has not elapsed (S15: no), the travel controller 210 performs the forward clutch solenoid valve 46 and the reverse drive. Both clutch electromagnetic valves 48 are turned off to cut off the driving force to the traveling portion (S16). 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 the brake (S17). As a result, the travel of the tractor 1 is stopped (S18). Therefore, when the engine 5 is started, the operator erroneously sets the speed ratio with the speed ratio setting dial 221 first, or first sets the speed change pedal (the forward pedal 232 or the reverse speed). Even if the pedal 233) is depressed, it is safe because it does not start.

  Then, it is determined whether or not a further T2 time has elapsed since the stop of travel in step S18 (S19). If the T2 time has elapsed (S19: yes), the swash plate angle of the hydraulic pump unit 500 is set to approximately 0 degrees. The shift ratio is set to 1 (S20). 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. In other words, when the operator does not perform operations such as setting the gear ratio with the gear ratio setting dial 221 for work and stepping on the gear pedals 232 and 233 for starting running after the time T2 elapses, a load is applied to the engine 5. In this way, wasteful fuel consumption can be avoided.

  In step S15, if the time T1 has elapsed (S15: yes), the above-described traveling operation such as gear ratio adaptive control is executed (S21). It is determined whether or not the shift pedals 232 and 233 are depressed during the traveling operation (S22). When the shift pedals 232 and 233 are not depressed (S22: no), 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 Is read (S23), and if the vehicle speed falls below a predetermined minute speed V1 (for example, about 0.1 km / hour) (S24: yes), it is assumed that the operator intends to stop traveling and the above-described step S16 is performed. Migrate to As a result, the operator can safely stop without stepping on the brake pedal 230, and after the passage of time T2, there is no oil leakage due to wasteful circulation of hydraulic oil in the hydraulic continuously variable transmission mechanism, and fuel efficiency is improved. There is an effect that can be done.

  If the vehicle speed is greater than the predetermined minute speed V1 (S24: no), it is assumed that the operator intends to continue the traveling work, and the traveling work such as gear ratio adaptive control in step S21 is executed. To do.

  Note that, for example, when an abnormality occurs in the traveling work or the farm work machine during the rotation of the engine 5 due to an electrical system failure or the like, when the operator presses the forcible operation button 226 (see FIG. 18), the automatic brake is activated. At the same time, the forcible operation switch 227 is turned off, and the forward clutch electromagnetic valve 46 and the reverse clutch electromagnetic valve 48 are turned off regardless of the output of the traveling controller 210, so that the power transmission to the traveling system is forced and emergency. Can be blocked and safety can be achieved.

  Next, the forward / reverse switching control of the traveling machine body will be described with reference to the flowchart shown in FIG. First, the engine 5 is started (S31), and then the operator selects and determines a desired gear ratio pattern according to the work type or the like with the gear ratio setting dial 221 (S32). A predetermined gear ratio pattern stored in a memory (read / write memory as needed) is read out. At this time, it is determined whether the left and right rear brakes 65 are actuated to brake the left and right rear wheels 4 to stop the traveling machine body (S33).

  When the left and right brakes 65 are actuated to brake the left and right rear wheels 4 (S33: yes), the start control mode is set to advance (or reverse) from the state where the traveling machine body is stopped by the travel stop control of FIG. . When the operator depresses the forward pedal 232 (reverse pedal 233) to move the tractor 1 forward (reverse), the pedal depression amount is read from the forward potentiometer 219 (reverse potentiometer 220) into the travel controller 210 (S34). When the traveling machine body is stopped by the travel stop control of FIG. 21 and the swash plate angle of the hydraulic pump unit 500 is shifted to approximately 0 degrees and maintained at the gear ratio 1 (S35: yes), the hydraulic pump unit 500 The swash plate angle is shifted to approximately -11 degrees and moved to a gear ratio 0 (S36).

  When the swash plate angle of the hydraulic pump unit 500 is 0 (S37: yes), that is, when the main transmission output gear 37 is absolutely stopped, the forward clutch electromagnetic valve 46 (reverse clutch electromagnetic valve 48) is set. The forward clutch 40 (reverse clutch 42) is engaged (S38), the braking of the rear wheel 4 by the left and right brakes 65 is released (S39), and the gear ratio adaptive control of FIG. 20 described above is performed (S46). The vehicle travels forward (reverse) from a state where the traveling machine body is stopped at a speed calculated based on the amount of depression of the forward pedal 232 (or the reverse pedal 233) and the set value of the transmission ratio setting dial 221. The vehicle can start smoothly by depressing the forward pedal 232 (or the reverse pedal 233).

  On the other hand, when at least one of the left and right brakes 65 is in an inactive state and at least one of the left and right rear wheels 4 is not braked (S33: no), the traveling machine body moves forward (or reverse) by the gear ratio adaptive control of FIG. Thus, the reciprocating travel control mode in which the traveling machine body moves backward (or moves forward) from the state where the traveling body moves forward (or moves backward) is set. 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 (S40). When the traveling machine is traveling forward (or reverse) (S41: yes), it is determined whether or not the reverse pedal 233 (or forward pedal 232) is depressed on the opposite side to the traveling direction (S42).

If the reverse pedal 233 (or forward pedal 232) on the opposite side of the travel direction is depressed (S42: yes), the vehicle speed is set to a predetermined value by stopping the forward pedal 232 (or reverse pedal 233) in the travel direction. When decelerating to a minute speed V1 (for example, about 0.1 km / hour) or less (S43: yes), the forward clutch solenoid valve 46 (reverse clutch solenoid valve 48) is turned off and the forward clutch 40 (reverse clutch 42) is turned off. (S44). At substantially the same time, the reverse clutch solenoid valve 48 (forward clutch solenoid valve 46) is turned on, the reverse clutch 42 (forward clutch 40) is turned on (S45), and the gear ratio adaptive control shown in FIG. 20 is performed (S46). . At a speed calculated based on the amount of depression of the forward pedal 232 (or the reverse pedal 233) and the set value of the transmission ratio setting dial 221, the traveling machine body moves backward (reverse) and travels backward (forward) ) Shift to driving. By alternately depressing the forward pedal 232 and the reverse pedal 233, the traveling direction of the traveling machine body is alternately switched between the forward traveling and the backward traveling, and the traveling machine body can be smoothly reciprocated.

  As is clear from the above description and FIGS. 18 and 22, the transmission case 17 mounted on the tractor 1 traveling machine body including the traveling front and rear wheels 3 and 4, and the input shaft 27 to which the power from the engine 5 is transmitted. A hydraulic continuously variable transmission 29 including a hydraulic pump 500, a hydraulic motor 501, and an output shaft 36; a forward pedal 232 and a reverse pedal 233 which are shift pedals for changing the gear ratio of the hydraulic continuously variable transmission 29; A forward clutch 40 and a reverse clutch 42 for transmitting a shift drive output from the hydraulic continuously variable transmission 29 to the traveling wheels 3 and 4, and a brake 65 for braking the traveling wheels 3 and 4, The traveling wheels 3 and 4 are driven via forward or reverse clutches 40 and 42 to change the vehicle speed in accordance with the amount of depression of the shift pedals 232 and 233. In the work vehicle constructed as described above, the forward and reverse potentiometers 219 and 220, which are shift sensors for detecting the depression amounts of the shift pedals 232 and 233, and the inclination of the hydraulic pump 500 based on the detected values of the shift sensors 219 and 220, respectively. In a state where the main transmission hydraulic cylinder 556 which is an actuator for adjusting the plate angle, the transmission output rotation sensor 116 for detecting the rotation speed of the output shaft 36, and the shift pedals 232 and 233 are not depressed, the traveling wheels 3, 4 and a control means 210 for controlling to apply the brake 65 and to disengage both the forward clutch 40 and the reverse clutch 42. 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, control is performed so that either the forward clutch 40 or the reverse clutch 42 is engaged according to the depression of the shift pedals 232 and 233. To do. When it is confirmed that either the forward clutch 40 or the reverse clutch 42 is engaged, the brakes 65 of the traveling wheels 3 and 4 are released. Therefore, each operation of the tractor 1 or the wheel loader that needs to frequently perform forward and backward switching, traveling stop and start operations, which are alternately repeated, can be made extremely simple, and a long time operation can be fatigued. There is an effect that it can be reduced.

  Further, reverse running during switching between forward and reverse can be prevented. Since the forward and reverse 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 used. 29 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.

  The shift pedal 232 includes 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. , 233, the output rotational speed of the hydraulic continuously variable transmission 29 is controlled in accordance with a speed ratio pattern set in advance by the speed ratio setting unit 221, so that the operator temporarily After setting the gear ratio pattern of the gear ratio with the gear ratio setting unit 221, it is only necessary to operate the speed change pedals 232 and 233 due to environmental changes, travel of the tractor 1 that is a work vehicle, or fluctuations in the work load. When the transmission gear ratio value deviates from the target transmission gear ratio value, it can be automatically controlled so as to automatically approach the target transmission gear ratio value, and the traveling operation of the work vehicle 1 is automatically performed with a continuously variable transmission mechanism. Is approximated to the running operation can be extremely easy in an effect that the prolonged activity fatigue can be reduced.

  The shift pedal is composed of a forward pedal 232 and a reverse pedal 233. When the reverse pedal 233 is depressed during forward travel, the forward clutch 40 is disengaged when the vehicle speed becomes below a certain level, and the reverse travel is performed substantially simultaneously. Since the clutch 42 is controlled to be engaged, for example, in a reciprocating operation, the ultra-low speed output (low efficiency output region) of the hydraulic continuously variable transmission 29 is cut, and the hydraulic continuously variable transmission is cut. It is possible to switch from forward to reverse before 29 becomes 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.

  The shift pedal is composed of a forward pedal 232 and a reverse pedal 233. When the forward pedal 232 is depressed during reverse, the reverse clutch 42 is disengaged when the vehicle speed is below a certain level, and the vehicle moves forward at the same time. Since the clutch 40 is controlled so as to be engaged, for example, in a reciprocating operation, the ultra-low speed output (low efficiency output region) of the hydraulic continuously variable transmission 29 is cut, and the hydraulic continuously variable transmission is cut. Before 29 becomes low efficiency output, it is possible to switch from reverse to forward. When switching from reverse to forward, it is possible to prevent a decrease in travel acceleration performance and the like, and it is possible to maintain the travel machine power appropriately.

  Note that the forward pedal 232 and the reverse pedal 233 are formed by one pedal (or lever), and the stepping direction of the pedal is made different between forward and reverse, or the forward movement of one pedal (or lever) The reverse shift output (the same stepping direction) can be switched with a switch or the like, and the forward and reverse shifts can be operated with the same pedal (or lever). Further, the forward and reverse pedals 232 and 233 may be formed by forward and reverse levers, or a pedal and a lever may be used in combination.

  Next, the sub-shift high-speed switching control of the traveling machine body will be described with reference to the flowchart shown in FIG. First, when the engine 5 is rotating (S50: yes), when the high-speed / low-speed switch 222 is turned on and the sub-shift is switched from the low-speed side to the high-speed side (S51). : Yes), the main shift output unit rotation speed from the main shift output unit rotation sensor 116 and the vehicle speed from the vehicle speed sensor 117 are read (S53), the forward clutch 40 (reverse clutch 42) is disconnected (S54), and the vehicle speed is It is determined whether or not the speed is equal to or higher than a predetermined speed V1 (S55).

  Subsequently, when the vehicle speed is not equal to or less than a predetermined speed V1 (for example, about 0.1 km / hour) (S55: no), and the traveling operation can be continued (the vehicle speed is maintained at a predetermined speed V1 or higher), the high speed clutch The electromagnetic valve 666 is turned on (S56), the auxiliary transmission hydraulic cylinder 55 is operated to the high speed side, the auxiliary transmission low speed clutch 56 is disconnected, and the high speed clutch 57 is continued. At substantially the same time, the proportional control electromagnetic valve 203 is operated to shift the swash plate angle of the hydraulic pump unit 500 in the gear ratio reduction direction (S57). Then, the main transmission output portion rotation speed (the rotation speed of the main transmission output shaft 36) detected by the main transmission output portion rotation sensor 116 and the sub transmission output portion rotation speed (the rotation speed of the sub transmission shaft 50) detected by the vehicle speed sensor 117 It is determined whether or not the rotation number) matches (S58). When the rotational speed of the main transmission output shaft 36 and the rotational speed of the sub transmission shaft 50 substantially coincide with each other (S58: yes), the high speed / low speed changeover switch 222 is immediately before switching from the low speed side to the high speed side. The forward clutch 40 (reverse clutch 42) is engaged again (S59), and the gear ratio adaptive control shown in FIG. 20 is performed (S60). Thus, after the rotational speed of the main transmission output shaft 36 and the rotational speed of the auxiliary transmission shaft 50 are substantially matched, the forward clutch 40 (reverse clutch 42) is engaged again, so the forward clutch 40 (reverse clutch) When 42) is turned on again, it is possible to prevent the vehicle speed from rapidly changing due to the difference in the rotational speed between the main transmission output shaft 36 and the auxiliary transmission shaft 50.

  On the other hand, when it is determined whether or not the vehicle speed detected by the vehicle speed sensor 117 is equal to or higher than the predetermined speed V1 (S55), the vehicle speed is equal to or lower than the predetermined speed V1 (for example, about 0.1 km / hour). (S55: yes), the left and right brakes 65 are applied and actuated (S61) to prevent reverse running on an uphill or downhill. At substantially the same time, the high-speed clutch electromagnetic valve 666 is turned on and the high-speed clutch 57 is continued (S62). Next, the forward clutch 40 (reverse clutch 42), which was entered immediately before the high speed / low speed changeover switch 222 is switched from the low speed side to the high speed side, is turned on again (S63), and the left and right brake wheels 65 are turned off to operate the left and right rear wheels. 4 is released (S64), and the gear ratio adaptive control shown in FIG. 20 is performed (S60).

  As is clear from the above description and FIGS. 18 and 23, the transmission case 17 mounted on the tractor 1 having the front and rear wheels 3 and 4, the input shaft 27 to which the power from the engine 5 is transmitted, and the hydraulic pressure A hydraulic continuously variable transmission 29 comprising a pump 500, a hydraulic motor 501 and an output shaft 36; a forward pedal 232 and a reverse pedal 233 which are shift pedals for changing the transmission ratio of the hydraulic continuously variable transmission 29; A forward clutch 40 and a reverse clutch 42 that transmit the shift drive output from the hydraulic continuously variable transmission 29 to the traveling wheels 3 and 4, and the shift drive output from the hydraulic continuously variable transmission 29 are subjected to multiple shifts. An auxiliary transmission gear mechanism 30 and a brake 65 that brakes the traveling wheels 3 and 4 are provided, and the vehicle speed is changed in accordance with the depression amount of the transmission pedals 232 and 233. In the work vehicle constructed as described above, the forward and reverse potentiometers 219 and 220, which are shift sensors for detecting the depression amounts of the shift pedals 232 and 233, and the inclination of the hydraulic pump 500 based on the detected values of the shift sensors 219 and 220, respectively. A main transmission hydraulic cylinder 556 that is an actuator for adjusting the plate angle, a transmission output rotation sensor 116 that detects the rotation speed of the output shaft 36, and a sub transmission hydraulic cylinder that is a sub transmission switching means for switching the sub transmission mechanism 30. 55 and a travel controller 210 that is a control means, the control means 210 disconnects the engaged forward clutch 40 or the reverse clutch 42 when the high speed side operation of the auxiliary transmission switching means 55 is confirmed, The auxiliary transmission mechanism 30 is controlled to be switched to the high speed side, and the auxiliary transmission mechanism 30 is switched to the high speed side. At the same time, the shift drive output from the hydraulic continuously variable transmission 29 is controlled to decelerate, and when the rotational speeds of the forward clutch 40 or the reverse clutch 42 are substantially coincident with each other, Control is performed so that either the forward clutch 40 or the reverse clutch 42 that has been entered immediately before the auxiliary transmission switching means 55 is operated on the high speed side is engaged again. Therefore, for example, the shift output of the subtransmission mechanism 30 is switched from low speed to high speed without stopping the traveling machine body 1 or without making the shift drive output of the hydraulic continuously variable transmission 29 neutral (substantially zero rotation). Thus, each operation of the tractor 1 or the wheel loader can be made extremely simple, traveling mobility can be improved, and fatigue in a long-time operation can be reduced. In addition, there is an effect that the reverse running in the middle of the auxiliary transmission switching can be prevented. For example, the forward / reverse clutches 40 and 42 and the subtransmission mechanism 30 are disposed downstream of the output shaft 36 in the hydraulic continuously variable transmission 29. The main clutch and the like disposed between the hydraulic continuously variable transmission 29 can be omitted, and the structure can be simplified.

  Also, when the high speed side operation of the sub shift switching means 55 is confirmed and the forward clutch 40 or the reverse clutch 42 in the engaged state is turned off, the sub shift change means 55 is entered immediately before the high speed side operation is performed. When the vehicle speed falls below a certain level before either the forward clutch 40 or the reverse clutch 42 that has been turned on again, control is performed so that the brake 65 is applied to the traveling wheel 4. Even if both the forward clutch 40 and the reverse clutch 42 are disconnected by the high-speed operation at 55, the reverse travel moves in the direction opposite to the travel direction before the engaged forward clutch 40 or the reverse clutch 42 is disconnected. For example, the traveling sub-shift can be shifted from a low speed to a high speed by preventing the traveling machine body from running backward when traveling uphill or downhill.

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 side view which shows a forward (reverse) pedal part. It is a functional block diagram of the control means of this invention. It is a gear ratio diagram. It is a flowchart of gear ratio adaptive control. It is a flowchart of stop control. It is a flowchart of forward / reverse switching control. It is a flowchart of auxiliary transmission high-speed switching control.

DESCRIPTION OF SYMBOLS 1 Tractor 3 Front wheel 4 Rear wheel 5 Engine 17 Transmission case 27 Input shaft 29 Continuously variable transmission 30 Sub transmission gear mechanism 36 Output shaft 40 Forward clutch 42 Reverse clutch 55 Sub transmission hydraulic cylinder (sub transmission switching means)
65 Brake 116 Main transmission output part rotation sensor 210 Travel controller (control means)
219 Forward potentiometer (shift sensor)
220 Reverse potentiometer (shift sensor)
221 Gear ratio setting dial (speed ratio setting device)
232 Forward pedal (shift pedal)
233 Reverse pedal (shift pedal)
500 Hydraulic pump section 501 Hydraulic motor section 556 Main transmission hydraulic cylinder (transmission actuator)

Claims (2)

A hydraulic continuously variable transmission for shifting power from an engine mounted on a traveling machine body having traveling wheels, a transmission pedal for changing a transmission ratio of the hydraulic continuously variable transmission, and the hydraulic continuously variable transmission the speed drive output and the forward clutch and reverse clutch for transmitting the driving wheels from, a subtransmission mechanism which the speed change drive output from the hydrostatic continuously variable transmission for a multi-speed, the hydraulic CVT In a work vehicle in which the main shift operation operates in proportion to the amount of depression of the forward pedal or the reverse pedal as a shift pedal ,
The forward hydraulic clutch is continued by depressing the forward pedal, and the main transmission output gear and the travel counter shaft are connected by the forward gear, while the backward hydraulic clutch is continued by depressing the reverse pedal, The main transmission output gear and the travel counter shaft are connected by a reverse gear,
A shift sensor for detecting the depression amount of the shift pedal, a shift output rotation sensor for detecting the rotation speed of the output shaft of the hydraulic continuously variable transmission, a sub shift switching means for switching the sub shift mechanism, and a control means And
By high side operation of the subtransmission switching means off the forward clutch or reverse clutch state enters, when switching the subtransmission mechanism speed side simultaneously, while decelerating the speed change drive output from the hydrostatic continuously variable transmission When the rotational speed of the input side and the output side of the forward clutch or the reverse clutch coincides, either the forward clutch or the reverse clutch that was entered immediately before operating the auxiliary transmission switching means is re-entered. A control device for a work vehicle. When the high-speed / low-speed selector switch is switched from the low-speed side shift to the high-speed side while the engine is rotating, in the state where the running operation can be continued, the low-speed clutch for the secondary shift is disengaged and the high-speed clutch is continued almost simultaneously, When the gear ratio of the hydraulic continuously variable transmission is lowered and the main gear shift output section speed matches the sub gear shift output section speed, it is just before the high speed / low speed switch is switched from the low speed side to the high speed side. If the forward or reverse clutch is engaged again, and the vehicle speed falls below the specified speed, the left and right brakes are applied and the high speed clutch is continued almost simultaneously when the left and right brakes are applied. 2. The control device for a work vehicle according to claim 1, wherein the forward clutch or the reverse clutch that was entered immediately before switching to the high speed side is engaged again .

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