JP2007030624A - Control device of working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a working machine which can reduce fatigue of operator's long hour work and simply improve driving operationality of the working machine though the operation changing the speed ration of a continuously variable transmission is executed with a simple operation of a forward travel pedal or the like. <P>SOLUTION: The control device of the working machine is equipped with a hydraulic continuously variable transmission changing the speed of a power from an engine mounted on the traveling machine body, a forward travel pedal changing the speed ration of the hydraulic continuously variable transmission, a speed change sensor detecting a stepping amount of the forward travel pedal in the working vehicle composed so as to change the speed of the hydraulic continuously variable transmission based on the operation amount of the forward travel pedal, a speed set means selecting any one of a plurality of the speed ration pattern capable of multi-purposely changing the maximum output of the hydraulic continuously variable transmission, a control means controlling the output rotation number of the hydraulic continuously variable transmission, and a locking means maintaining the forward travel pedal to the stepping position operated by the operator. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 transmission ratio of the continuously variable transmission is changed. The present invention relates to a control device for switching the traveling speed of the working vehicle.

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 and high speed). And a throttle lever for setting and holding the output speed of the engine. In addition, an accelerator / shift pedal is provided for changing the engine speed and the output speed of the hydrostatic continuously variable transmission. When the shift pedal is depressed, the transmission ratio of the continuously variable transmission is changed, and the accelerator operation unit is pushed by the shift pedal to increase the engine output speed set and held by the throttle lever. A configuration that can be made is disclosed.
JP 2003-226165 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, for tilling work that requires continuous movement (substantially linear travel) at a substantially constant speed, in conventional work vehicles such as tractors, driving operations can be performed by using a semi-fixed shift lever and shift pedal together. Maintenance and the reduction of operator fatigue, a cumbersome operation using the shift lever and shift pedal separately was necessary. On the other hand, when the work vehicle is moved only by the operation of the shift pedal, the moving speed of the work vehicle can be changed by a simple operation compared to a structure in which the shift lever and the shift pedal are used separately. When the work vehicle is turned on the headland in the field, the work vehicle is temporarily decelerated and turned, so that there is a problem that the travel speed of the previous stroke cannot be easily reproduced in the next stroke. Further, in a work vehicle such as a tractor or a wheel loader, when carrying out earthwork work or the like by repeating forward and reverse alternately, it is necessary to install an operation tool for switching forward and reverse separately from the shift pedal.

  An object of the present invention is to perform an operation of changing the gear ratio of the continuously variable transmission by a simple operation such as an operation of a forward pedal, etc. It is an object of the present invention to provide a control device for a work vehicle that can easily improve the driving operability of the vehicle.

  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 that shifts power from an engine mounted on a traveling machine body, and the hydraulic continuously variable transmission. In a work vehicle configured to shift the hydraulic stepless transmission based on an operation amount of the forward pedal and a forward pedal that changes a transmission ratio, a shift sensor that detects an amount of depression of the forward pedal Speed setting means for selecting any one of a plurality of gear ratio patterns capable of changing the maximum output of the hydraulic continuously variable transmission in a multi-stage manner, and controlling the output rotational speed of the hydraulic continuously variable transmission And a lock means for maintaining the forward pedal in a depressed position operated by an operator.

  According to a second aspect of the present invention, in the control device for a work vehicle according to the first aspect, the lock operating tool that operates the locking means to maintain the forward pedal in the depressed position, and the forward pedal maintenance of the locking means. And a release operation tool for releasing the operation.

  According to a third aspect of the present invention, in the work vehicle control device according to the first aspect, the control means uses the speed ratio pattern set by the speed setting means when the forward pedal is at a maximum depression position. The output speed of the hydraulic continuously variable transmission is controlled in accordance with the speed ratio pattern set by the speed setting means in accordance with the amount of depression of the forward pedal.

  According to a fourth aspect of the present invention, in the work vehicle control device according to the third aspect, the speed setting means includes a plurality of speed ratio patterns obtained by changing the maximum output of the hydraulic continuously variable transmission in a multistage manner. It is configured to be switchable between a selected position and a neutral position where the output of the hydraulic continuously variable transmission is substantially zero.

  According to a fifth aspect of the present invention, in the control apparatus for a work vehicle according to the third or fourth aspect, an accelerator unit that changes a rotational speed of the engine and a clutch mechanism that connects the forward pedal to the accelerator unit. It is provided.

  According to a sixth aspect of the present invention, in the work vehicle control device according to any one of the first to fifth aspects, the reverse pedal for changing the gear ratio of the hydraulic continuously variable transmission, and the forward pedal and the reverse pedal operate simultaneously. It is provided with a check mechanism that prevents this.

  According to the first aspect of the present invention, a hydraulic continuously variable transmission that shifts power from an engine mounted on a traveling machine body, a forward pedal that changes a gear ratio of the hydraulic continuously variable transmission, and the forward In a work vehicle configured to shift the hydraulic continuously variable transmission based on an operation amount of a pedal, a shift sensor that detects a depression amount of the forward pedal, and a maximum of the hydraulic continuously variable transmission A speed setting means for selecting any one of a plurality of gear ratio patterns whose output can be changed in multiple stages; and a control means for controlling an output rotational speed of the hydraulic continuously variable transmission. Therefore, when the forward pedal is maintained in the depressed position by the locking means, the operator's foot is accidentally released from the forward pedal. It is, be able to continue working to maintain the moving speed suitable for work. Further, for example, an operator operates the forward pedal to a maximum step, changes the maximum shift drive output rotational speed of the hydraulic continuously variable transmission, and sets the speed at which the work vehicle continuously moves to a speed suitable for work conditions. Can be determined. Tilling work that reciprocates by changing direction at the headland in the field can be made extremely simple. In a tractor, a wheel loader, etc., the traveling mobility of the reciprocating work which repeats a change of direction can be improved, and fatigue in a long-time work can be reduced.

  According to a second aspect of the present invention, the lock means is operated to operate the lock means to maintain the forward pedal in the depressed position, and the release operation tool is to release the forward pedal maintenance operation of the lock means. Thus, for example, the forward pedal can be manually locked by an operator, and the forward pedal can be unlocked by the operator, and the operator can clearly recognize the forward pedal lock and release and operate it reliably. . An erroneous operation of locking or releasing the forward pedal can be easily prevented.

  According to a third aspect of the present invention, the control means stores the speed ratio pattern set by the speed setting means when the forward pedal is at the maximum depression position, and corresponds to the depression amount of the forward pedal. Then, the output rotational speed of the hydraulic continuously variable transmission is controlled along the speed ratio pattern set by the speed setting means, so that the operator depresses the forward pedal to the maximum stepping position and Only by operating the locking means, the shift output of the previous stroke of the hydraulic continuously variable transmission can be smoothly reproduced in the next stroke. For example, it is possible to very easily perform a tilling operation in which the direction is changed and reciprocated at a headland in a field.

  According to a fourth aspect of the present invention, the speed setting means includes a selection position of a plurality of transmission ratio patterns in which the maximum output of the hydraulic continuously variable transmission is changed in multiple stages, and the hydraulic continuously variable transmission. Is switched to the neutral position where the output of the motor is substantially zero, so that when the operator depresses the forward pedal and operates the locking means to lock it to the maximum stepping position or the like, the speed setting means Is operated by the operator, and the speed change output speed of the hydraulic continuously variable transmission can be changed in multiple stages. Operations similar to conventional shift levers such as stopping the work vehicle (shift neutral) and multi-speed switching of moving speed can be simplified. Further, even if the engine is operated, the speed setting means is switched to the neutral position and the operator leaves the control seat, so that even if the operator erroneously steps the forward pedal or the like, It is possible to prevent the continuously variable transmission from malfunctioning.

  According to a fifth aspect of the present invention, the accelerator means for changing the engine speed and the clutch mechanism for connecting the forward pedal to the accelerator means are provided. When the pedal is connected via the clutch mechanism, the shift output of the hydraulic continuously variable transmission and the rotational speed of the engine can be smoothly switched by simply stepping on the forward pedal. For example, in a travel region where the travel direction is greatly changed, both the shift output of the hydraulic continuously variable transmission and the engine speed are reduced by reducing the amount of depression of the forward pedal, and the work vehicle is moved. Speed can be easily reduced. On the other hand, in a traveling area where the vehicle travels substantially straight, only by increasing the depression amount of the forward pedal, both the shift output of the hydraulic continuously variable transmission and the engine speed are increased, and the moving speed of the work vehicle is increased. It can be increased easily. The mobility and turning operability of the work vehicle can be improved, and engine troubles can be easily prevented.

  According to a sixth aspect of the present invention, there is provided a reverse pedal that changes a gear ratio of the hydraulic continuously variable transmission, and a check mechanism that prevents the forward pedal and the reverse pedal from operating simultaneously. Therefore, for example, even if the operator depresses the forward pedal and the reverse pedal at the same time, the depressing operation can be blocked by the check mechanism, and malfunction of the shift sensor or the control means can be easily prevented. The mounting structure of the forward pedal and the reverse pedal or the installation structure of the shift sensor can be made compact and at low cost.

  DESCRIPTION OF EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings (FIGS. 1 to 24). FIG. 1 is a side view of a farm tractor, FIG. 2 is a perspective view of the tractor as viewed obliquely from the rear, FIG. 3 is a skeleton diagram of a power transmission system, FIG. 4 is a hydraulic circuit diagram of a hydraulic continuously variable transmission, and FIG. 6 is a plan view of the cabin, and FIG. 7 is a functional block diagram of the control means.

  As shown in FIGS. 1 and 2, a 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 with the engine 5, the vehicle 5 is configured to travel forward and backward. In this case, a pair of left and right traveling units is configured by a set of front and rear wheels 3 and 4 positioned on the left side in the traveling direction of the traveling machine body 2 and a set of front and rear wheels 3 and 4 positioned on the right side in the traveling direction.

  The engine 5 is covered with a bonnet 6. A cabin 7 is installed on the upper surface of the traveling machine body 2, and a steering seat 8 on which an operator is seated and a steering column 234 positioned in front of the steering seat 8 are mounted in the cabin 7. Yes. A steering handle 9 (round handle) as steering means is provided on the top of the steering column 234. When the operator seated on the control seat 8 rotates the control handle 9, the steering angle (steering angle) of the left and right front wheels 3 and 3 changes according to the operation amount (rotation amount). Yes. A pair of left and right steps 10 for an operator to get on and off are provided on the left and right outer portions of the cabin 7. Fuel for supplying fuel to the engine 5 on the inner side of the step 10 and below the bottom of the cabin 7 A tank 11 is provided.

  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 transmission case 17 is connected to the rear part of the machine body frame 16 for transmitting the output from the engine 5 to the rear wheel 4 (front wheel 3) by appropriately shifting the output. In this case, the rear wheel 4 is 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 the gear case 19 made.

  A hydraulic working unit lifting mechanism 20 for lifting and lowering a working unit (not shown) such as a tillage machine is detachably attached to the upper surface of the rear portion of the mission case 17. A working unit such as a field cultivator 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 driving the working unit is provided on the rear side surface of the mission case 17.

  FIG. 5 shows a hydraulic circuit 200 of the tractor 1 in this embodiment. The hydraulic circuit 200 of the tractor 1 includes a hydraulic pump 94 for the lifting mechanism 20 that is operated by the rotational force of the engine 5, and a traveling hydraulic pump 95. The traveling hydraulic pump 95 is connected to the power steering hydraulic cylinder 93 by the steering handle 9 via the power steering hydraulic mechanism 202, and operates the brake cylinder 68 for the brake 65 for the left and right rear wheels 4 respectively. It is connected to left and right brake solenoid valves 67a and 67b, which are switching valves.

  Further, the traveling hydraulic pump 95 includes a PTO clutch hydraulic solenoid valve (proportional control valve) 104 for the PTO clutch 100, a proportional control valve 203 for a main transmission hydraulic continuously variable transmission 29 described later, and a switching valve operated thereby. 204, a high-speed clutch electromagnetic valve 666 of the traveling sub-transmission hydraulic cylinder 55, a forward clutch electromagnetic valve 46 and a reverse clutch electromagnetic valve for operating the forward switching hydraulic clutch 40 and the reverse switching hydraulic clutch 42 of the traveling machine body 2. 48, a 4WD hydraulic solenoid valve 80 for the 4WD hydraulic clutch 74 for driving the front wheel 3 and the rear wheel 4 simultaneously, and a double speed hydraulic electromagnetic for the double speed hydraulic clutch 76 for switching the front wheel 3 to double speed drive. It is connected to the valve 82.

  The working unit hydraulic pump 94 is connected to a control electromagnetic valve 201 for supplying hydraulic oil to a single-acting hydraulic cylinder 205 in the working unit lifting mechanism 20. Charge oil is supplied from the working unit hydraulic pump 94 to the hydraulic continuously variable transmission 29. The hydraulic circuit 200 includes a relief valve, a flow rate adjustment valve, a check valve, an oil cooler, an oil filter, and the like.

  FIG. 3 shows the mission case 17. The interior of the mission case 17 is partitioned forward and backward 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. The mission case 17 is formed in a substantially square 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. 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 projects rearward from the rear side of the engine 5, and a flywheel 25 is directly connected to the engine output shaft 24. The main drive shaft 26 projecting backward from the flywheel 25 and the main transmission input shaft 27 projecting forward from the front surface of the transmission case 17 are connected via a power transmission shaft 28 having universal joints at both ends and extending and contracting. Has been. The rotational power of the engine 5 is transmitted to the main transmission input shaft 27, and then is appropriately shifted by the hydraulic continuously variable transmission 29 and the traveling auxiliary transmission gear mechanism 30, and the rear wheel 4 is connected via the differential gear mechanism 58. It is configured to transmit this driving force. 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.

  As shown in FIGS. 3 and 4, the inline hydraulic continuously variable transmission 29 provided in the rear chamber 35 includes a variable displacement type hydraulic pump unit 500 for shifting and a high pressure discharged from the hydraulic pump unit 500. And a constant displacement type shifting hydraulic motor unit 501 that operates with the hydraulic oil. A cylindrical main transmission output shaft 36 is concentrically fitted to the main transmission input shaft 27. The rear end side of the main transmission input shaft 27 is rotatably supported on the rear side wall member 33 by a bearing. 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 between the partition wall 31 and the rear side wall member 33. The hydraulic pump unit 500 is disposed at the rear of the cylinder block 505 opposite to the input side of the main transmission input shaft 27. The hydraulic motor unit 501 is disposed in front of the cylinder block 505 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 front end and the rear end of the main transmission output shaft 36 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 ball bearings. A main transmission output gear 37 is provided at the front end portion of the main transmission output shaft 36. The input side (front end side) of the main transmission input shaft 27 is rotatably supported in the shaft hole of the main transmission output shaft 36 via a roller bearing so as to protrude forward from the front end of the main transmission output shaft 36.

  As shown in FIG. 4, the hydraulic pump unit 500 includes a pump swash plate 509 whose inclination angle can be changed with respect to the axis of the main transmission input shaft 27, and a pump plunger 506 connected to the pump swash plate 509. . A first plunger hole 507 is formed in the cylinder block 505 for disposing the pump plunger 506 so as to freely enter and exit. The cylinder block 505 is provided with the same number of first spool valves 536 as the pump plungers 506. Further, a first radial bearing 538 for operating the first spool valve 536 is disposed so as to be inclined at a constant inclination angle with respect to the axis of the main transmission input shaft 27.

  On the other hand, the hydraulic motor unit 501 includes a motor swash plate 518 that maintains a constant inclination angle with respect to the axis of the main transmission input shaft 27, a motor plunger 515 that is connected to the motor swash plate 518, and a motor plunger 515 that is a cylinder block. A second plunger hole 516 is provided in the 505 so as to be freely accessible. The cylinder block 505 is provided with the same number of second spool valves 540 as the motor plungers 515. Further, a second radial bearing 542 for operating the second spool valve 540 is disposed at a constant inclination angle with respect to the axis of the main transmission input shaft 27. The pump plungers 506 and the same number of motor plungers 515 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 535, and the second plunger hole 516 communicates with the second valve hole 533 via the second oil passage 534.

  The first spool valves 536 inserted into the first valve holes 532 are arranged at substantially equal intervals on the same circumference of the rotation center of the cylinder block 505. The front end of the first spool valve 536 that protrudes from the first valve hole 532 with the back pressure spring force is brought into contact with the outer ring side surface of the first radial bearing 538. Then, the first spool valve 536 reciprocates once by 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 535. The chamber 531 is configured to communicate with each other alternately.

  Further, the second spool valves 540 inserted into the second valve holes 533 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 that protrudes from the second valve hole 533 with the back pressure spring force is brought into contact with the side surface of the outer ring of the second radial bearing 542. 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 534, and passes through the first oil chamber 530 or the second oil. The chamber 531 is configured to communicate with each other alternately. The first charge valve 544 for supplying hydraulic oil from the traveling hydraulic pump 95 to the first oil chamber 530, and the second charge valve for supplying hydraulic oil from the hydraulic oil supply oil passage 543 to the second oil chamber 531. 545.

  Further, the pump swash plate 509 is rotatably disposed on the attachment portion of the rear side wall member 33 via an inclination angle adjustment fulcrum 555. The pump swash plate 509 is configured 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 that is an actuator for main transmission operation that changes the inclination angle of the pump swash plate 509 with respect to the axis of the main transmission input shaft 27 is provided (see FIGS. 4 and 5). 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 main transmission operation of the inline hydraulic continuously variable transmission 29 will be described below. The changeover valve 204 is operated by hydraulic oil from a proportional control solenoid valve 203 that operates in proportion to the amount of depression of a forward pedal 232 or a reverse pedal 233 (details will be described later) as a gear ratio operation means (transmission pedal). The transmission hydraulic cylinder 556 (see FIG. 5) is controlled, and the inclination angle of the pump swash plate 509 provided in the hydraulic pump unit 500 is changed with respect to the axis line of the main transmission input shaft 27.

  When the tilt angle of the pump swash plate 509 is substantially zero, the hydraulic motor unit 501 is not driven by the hydraulic pump unit 500, so the cylinder block 505 fitted to the main transmission input shaft 27 and the hydraulic motor unit 501 are provided. The motor swash plate 518 rotated in the same direction at substantially the same rotational speed, the main transmission output shaft 36 is rotated at substantially the same rotational speed as the main transmission input shaft 27, and the rotational speed of the main transmission input shaft 27 is changed. Without being transmitted to the main transmission output gear 37.

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

  Further, when the pump swash plate 509 is inclined in the other direction (negative inclination angle) with respect to the axis line 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 hydraulic motor The part 501 is decelerated (reversed), 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 reduced and transmitted to the main transmission output gear 37. That is, the rotational speed of the hydraulic motor unit 501 is subtracted from the rotational speed of the main transmission input shaft 27 and transmitted to the main transmission output gear 37. Therefore, the shift output (traveling speed) from the main shift output gear 37 is proportional to the tilt angle (negative tilt angle) of the pump swash plate 509 within the range of the rotational speed lower than the rotational speed of the main transmission input shaft 27. Is changed to the lowest traveling speed (vehicle speed = 0) at the maximum inclination (negative inclination angle) of the pump swash plate 509. In the embodiment, when the negative inclination angle of the pump swash plate 509 is approximately 11 degrees, the gear ratio is zero (neutral = stopped state). Although slightly different depending on the gear ratio pattern described later, the gear ratio is set to be maximum (maximum speed) when the positive inclination angle is approximately 11 degrees.

  As shown in FIG. 3, in the front chamber 34 of the transmission case 17, the forward gear 41 and the reverse gear 43 for switching between the forward and backward travel of the traveling machine body 2 and the low speed and the high speed are switched. A traveling sub-transmission gear mechanism 30 is disposed. A configuration for switching between forward and reverse via the forward gear 41 and the reverse gear 43 will be described. A travel counter shaft 38 and a reverse 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. A reverse gear 43 is engaged with the main transmission output gear 37 via a reverse gear 44 provided on the reverse shaft 39. It should be noted that an electromagnetic pickup type main transmission output shaft rotation sensor 116 (see FIG. 7) for detecting the rotation of the main transmission output gear 37 is disposed opposite to the rotation detection gear 115 provided on the reverse rotation shaft 39. .

  Then, when the forward pedal 232 described later is depressed, the clutch cylinder 47 is operated by the forward clutch electromagnetic valve 46 and the hydraulic clutch 40 is continued, and the main transmission output gear 37 and the travel counter shaft 38 are connected by the forward gear 41. Connected. Further, when the reverse pedal 233 described later is depressed, the clutch cylinder 49 is operated by the reverse clutch solenoid valve 48 and the hydraulic clutch 42 is continued, and the main transmission output gear 37 and the travel counter shaft 38 are connected to the reverse rotation shaft 39. Are connected via a reverse gear 43 (see FIG. 3). In the neutral position where neither the forward pedal 232 nor the reverse pedal 233 is depressed, both the forward and reverse hydraulic clutches 40 and 42 are both disconnected and output to the front wheel 3 and the rear wheel 4. The travel drive force from the main transmission output gear 37 is substantially zero (main clutch disengaged state).

  Next, a configuration for switching between the low speed and the high speed via the traveling auxiliary transmission gear mechanism 30 will be described. As shown in FIG. 3, a traveling auxiliary transmission gear mechanism 30 and an auxiliary transmission shaft 50 are arranged in the front chamber 34 of the transmission case 17. The travel counter shaft 38 is provided with a low-speed gear 51 and a high-speed gear 53 for auxiliary transmission, while the auxiliary transmission shaft 50 is provided with a low-speed gear 52 that meshes with the low-speed gear 51 of the travel counter shaft 38 and a high-speed of the travel counter shaft 38. A high-speed gear 54 that meshes with the gear 53 is provided. Further, the auxiliary transmission shaft 50 includes a low speed clutch 56 and a high speed clutch 57 that can be connected and disconnected by an auxiliary transmission hydraulic cylinder 55. Then, the low speed clutch 56 or the high speed clutch 57 is continued by controlling the auxiliary transmission hydraulic cylinder 55 (details will be described later) by operating the auxiliary transmission changeover switch 222 as the auxiliary transmission operation means or detecting the rotational speed of the engine 5. The low speed gear 52 or the high speed gear 54 is connected to the auxiliary transmission shaft 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 portion of the auxiliary transmission shaft 50 extends through the partition wall 31 to the inside of the rear chamber 35 of the transmission case 17 (see FIG. 3). In the rear chamber 35, a differential gear mechanism 58 that transmits a driving force to the left and right rear wheels 4 is disposed. 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 a differential output shaft 62 that extends in the left-right direction. . The differential output shaft 62 is connected to the rear axle 64 by a final gear 63 or the like, and drives the rear wheel 4 of the rear axle 64 (see FIG. 5). Further, left and right brakes 65 are installed on the left and right differential output shafts 62, respectively, and the base end side of one brake pedal 230 on the rear side of the steering column 234 is rotatably connected to the brake pedal shaft 255 (FIG. 7). reference). The brake pedal 230 and the left and right brake 65 are mechanically connected via a pair of left and right brake rods 250, a link mechanism 251 and the like. A parking lever 252 and a hook 253 are provided to lock the brake pedal 230 in the braking position, and the left and right brake 65 can be operated as a parking brake (see FIG. 16). On the other hand, when the steering angle of the steering wheel 9 is detected, the brake cylinder 68 is operated by the left and right autobrake solenoid valves 67a and 67b, and the brake 65 inside the turning is automatically braked.

  Next, a description will be given of a switching structure between the two-wheel drive and the four-wheel drive of the front and rear wheels 3 and 4. As shown in FIG. 3, the front wheel drive case 69 provided on the front side wall member 32 of the mission case 17 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 through gears 70 and 71 so that power can be transmitted. The front wheel output shaft 73 is connected to the front wheel output shaft 73 via a four-wheel drive gear 75 connected to the front wheel output shaft 73 via a four-wheel drive hydraulic clutch 74 and a double speed hydraulic clutch 76. The double speed gear 77 is fitted. The four-wheel drive gear 75 meshes with the gear 78 of the front wheel input shaft 72, and the double speed gear 77 meshes with the gear 79 of the front wheel input shaft 72. Then, by operating a switching lever (not shown) between 2WD and 4WD to the 4WD side, the clutch cylinder 81 is operated by the 4WD hydraulic electromagnetic valve 80, and the 4WD hydraulic clutch 74 is continued. The front wheel input shaft 72 and the front wheel output shaft 73 are connected by a four-wheel drive gear 75 so that the front wheel 3 is driven together with the rear wheel 4 (see FIG. 3).

  Next, the switching configuration of the double speed drive of the front wheel 3 will be described. By detecting the U-turn (direction change at the headland in the field) of the steering handle 9, the clutch cylinder 83 is operated by the double-speed hydraulic solenoid valve 82 and the double-speed hydraulic clutch 76 is continued. The front wheel output shaft 73 is connected by a double speed gear 77 so that the front wheel 3 is driven at a speed approximately twice as high as the speed when the front wheel 3 is driven by the four-wheel drive gear 75. Configure (see FIG. 3). An electromagnetic pickup type vehicle speed sensor 117 (see FIG. 7) for detecting the rotation of the gear 78 is installed in the vicinity of the gear 78 of the front wheel input shaft 72.

  As shown in FIG. 3, power is transmitted to the front wheels 3 between a front wheel transmission 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. The front wheel drive shaft 85 is connected. 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 transmission shaft 84, a differential gear case 89 provided on 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.

  Next, a configuration for switching the drive speed of the PTO shaft 23 (four forward rotations and one reverse rotation) will be described. As shown in FIG. 3, the front chamber 34 of the mission case 17 has a PTO transmission gear mechanism 96 for transmitting power from the engine 5 to the PTO shaft 23, and power from the engine 5 to each hydraulic pump 94, A pump drive shaft 97 for transmission to 95 is provided. The PTO transmission gear mechanism 96 includes a PTO counter shaft 98 and a PTO transmission output shaft 99. A PTO input gear 101 is connected to the PTO counter shaft 98 via a PTO hydraulic clutch 100. The PTO input gear 101 is engaged with the input side gear 102 of the main transmission input shaft 27 and the output side gear 103 of the pump drive shaft 97, and the pump drive shaft 97 is connected to the main transmission input shaft 27. Then, by operating the PTO clutch lever (not shown), the clutch cylinder 105 is operated by the hydraulic solenoid valve 104 (see FIGS. 5 and 7) to continue the PTO hydraulic clutch 100, and the main transmission input shaft 27 and the PTO counter shaft 98 are connected by the PTO input gear 101.

  The PTO speed change output shaft 99 is fitted with 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. A speed change arm 112 connected to a PTO speed change lever 224 (see FIG. 6) is engaged with a speed change shifter 111 for selectively connecting the gears 106 to 110 to the PTO speed change output shaft 99. The PTO speed change lever 224 is operated to change the 1st to 4th speed and the reverse PTO speed change output from the PTO speed change output shaft 99 to the PTO shaft 23 via the gears 113 and 114. (See FIG. 3).

  Next, with reference to FIGS. 3 and 4, the speed change structure of the traveling auxiliary transmission gear mechanism 30 will be described in detail. As shown in FIG. 4, the auxiliary transmission hydraulic cylinder 55 is formed with a first cylinder chamber 662 in which a piston rod 661 on one side of the piston 660 is provided and a second cylinder chamber 663 on the other side. The low speed clutch 56 or the high speed clutch 57 is continued by the shift arm 664 at the tip of the piston 660, and the auxiliary transmission shaft 50 is driven at a low speed or a high speed. The first cylinder chamber 662 communicates directly 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 the high speed clutch electromagnetic valve 666. The high speed clutch solenoid valve 666 is switched by a speed change solenoid 667, and the high speed clutch 57 is continued to drive the auxiliary speed change shaft 50 at a high speed (see FIG. 3).

  Next, with reference to FIG. 17, the traveling control (shift control) of the work vehicle in the present embodiment will be described. A travel controller 210 as a control means is connected to a battery 254 via a power application key switch 211. The key switch 211 is connected to a starter 212 for starting the engine 5. An electronic governor controller 213 that controls the rotation of the engine 5 is connected to the travel controller 210. The electronic governor controller 213 is connected to an engine governor 214 that adjusts the fuel of the engine 5, an engine rotation sensor 215 that detects the rotational speed of the engine 5, a throttle potentiometer 217 that detects the operating position of the throttle lever 206, and the like. When the operator manually operates the throttle lever 206, the electronic governor controller 213 controls the engine governor 214 so that the throttle potentiometer 217 value matches the engine speed. Note that the engine speed is maintained at a speed corresponding to the position of the throttle lever 206 regardless of load fluctuations.

  The travel controller 210 also includes a forward clutch solenoid valve 46 for the forward hydraulic clutch 40, a reverse clutch solenoid valve 48 for the reverse hydraulic clutch 42, a high-speed clutch solenoid valve 666 for the travel auxiliary transmission hydraulic cylinder 55, and a forward pedal. 232 and a proportional control solenoid valve 203 for operating the main transmission hydraulic cylinder 556 in proportion to the depression amount of the reverse pedal 233, left and right brake pedal solenoid valves 67a and 67b, and a PTO clutch hydraulic solenoid valve for the PTO clutch 100 ( Proportional control valve) 104 and the like are connected.

  Further, the travel controller 210 includes a shift potentiometer that detects the operation amount (depression amount) of the left steering switch 218 and the right steering switch 119, the forward pedal 232, and the reverse pedal 233 that detect the rotation amount (steering angle) of the steering handle 9. 220, a transmission ratio setting device 221 that switches the transmission ratio pattern (see FIG. 18) of the continuously variable transmission 29 in multiple stages, an auxiliary transmission changeover switch 222 that switches the traveling auxiliary transmission gear mechanism 30 at high speed, and the output of the main transmission output shaft 36. A main transmission output shaft rotation sensor 116 that detects the number of rotations, a vehicle speed sensor 117 that detects the rotation speed (traveling speed) of the front and rear wheels 3 and 4, a brake pedal switch 231 that detects the depression of the brake pedal 230, and forward or neutral or Operable forward / reverse selector switch 223 and the like are connected to each reverse switching position.

  The steering handle 9 is disposed on the steering column 234 protruding from the floor plate 235 in front of the steering seat 8 in the cabin 7 shown in FIGS. 6 and 7. On the right side surface of the steering column 234, there are a throttle lever 206 for adjusting the rotational speed of the engine 5, an accelerator connecting lever 127 described later, and a pedal lock lever 128 for maintaining the forward pedal 232 and the reverse pedal 233 in a substantially constant posture. Is arranged. A brake pedal 230, a forward pedal 232, and a reverse pedal 233 are arranged in parallel below the right side of the steering column 234. On the left side of the control seat 8, a PTO speed change lever 224, a differential lock pedal 225 and the like are arranged. On the right side of the control seat 8, a work machine lifting lever 259 is arranged.

  As shown in FIG. 7, a dial installation base 121 is integrally formed on the front end side of the right armrest 8a made of synthetic resin on the right side of the control seat 8 by synthetic resin molding. The dial installation base 121 is provided with a vehicle speed setting dial 211, an auxiliary transmission changeover switch 222, and a forward / reverse changeover switch 223. An operator sitting on the control seat 8 puts his right hand on the right armrest 8a, and the operator operates the vehicle speed setting dial 211, the auxiliary transmission changeover switch 222 or the forward / reverse changeover switch 223 with the right hand.

  As shown in FIG. 17, a work implement attitude controller 122 is disposed inside the right armrest 8 a whose upper surface side is closed with an openable and closable upper surface lid 123. The working machine attitude controller 122 includes an inclination dial 124 for adjusting the horizontal inclination of a rotary tiller (not shown) and a tilling depth dial for adjusting the tilling depth of a tilling claw (not shown) of the rotary tiller. 125 is arranged. The operator sitting on the control seat 8 operates the tilt dial 124 or the tilling depth dial 125 with the right hand. The rotary tiller is connected via the lower link 21 and the top link 22. Further, the right armrest 8a and the left armrest 8b of the control seat 8 are provided so that the front end side can be lifted (shifted from a substantially horizontal posture to a substantially vertical posture) around the rotation support shaft 120 on the rear end side. . In addition, an accessory box 126 for an operator to put a water bottle or the like is disposed below the right armrest 8a.

  The attachment structure of the forward pedal 232 and the reverse pedal 233 will be described with reference to FIGS. The forward pedal 232 and the reverse pedal 233 are rotatably fitted to the brake pedal shaft 255 with the pivot support shaft portions 237a and 237b at the base ends of the pedal arms 232a and 233a. The stepping plates 236a and 236b of the forward pedal 232 and the reverse pedal 233 are mounted so as to be able to be depressed diagonally downward from an initial (neutral) position on the upper surface of the floor plate 235 with the pivot support shaft portions 237a and 237b as the center. A transmission link mechanism 275 is provided that transmits the pedal depression amounts of the forward pedal and the reverse pedal to the shift potentiometer 220 that is a shift sensor.

  As shown in FIGS. 8 to 13, the transmission link mechanism 275 includes a pair of check links 238 a and 238 b that respectively connect the forward pedal 232 and the reverse pedal 233 to a cam plate 258 described later, and the forward pedal 232 and the reverse pedal 233. A neutral position restoring means 241 for returning the pedal to a neutral position (position at which the shift output is substantially zero) and a stepping resistance change for increasing the pedal depression force when the pedal depression amount (depression angle θ) of the stepping plates 236a and 236b exceeds a predetermined value. Means 242. Note that a shift frame 266 for installing the neutral position restoring means 241 and the stepping resistance changing means 242 is disposed at the attachment portion of the steering column 234.

  As shown in FIG. 9 to FIG. 11, link arms 239a and 239b are respectively installed on the respective rotation support shaft portions 237a and 237b, and one end portion of each check link 238a and 238b is connected to each link via the link shaft 268a and 268b. Each of the arms 239a and 239b is rotatably connected. The other ends of the check links 238a and 238b are rotatably connected to an intermediate portion of a cam plate 258 described later via a support shaft 269. When the forward and reverse treads 236a and 236b are supported at the initial (neutral) position, the forward check link 238a and the link arm 239a, and the reverse check link 238b and the link arm 239b are The links 238a and 238b and the link arms 239a and 239b are disposed at positions that are substantially symmetrical with respect to a straight line connecting the brake pedal shaft 255 and the support shaft 269. The initial (neutral) position described above is a shift neutral position where the pedal depression amount is substantially zero (a shift neutral position where the shift output from the continuously variable transmission 29 is substantially zero).

  As a result, when the operator steps on one of the stepping plates 236a (236b) of the forward pedal 232 or the reverse pedal 233, the stepping plate 236a (236b) on the stepped-on side moves in the stepping direction (slanting forward and downward), The other tread plate 236b (236a) that has not been stepped on moves in a direction (backward obliquely upward) opposite to the stepping direction (front diagonally downward) of the stepped plate 236a (236b) on the stepped-on side. When the operator steps on the stepping plates 236a and 236b of both the forward and reverse pedals 232 and 233, the pedals 232 and 233 are connected to each other by connecting the check links 238a and 238b and the cam plate 258. Since it is restrained, both the treads 236a and 236b do not move in the stepping direction (front obliquely downward).

  As shown in FIGS. 9 to 11, the neutral position restoring means 241 is a T-shaped cam having a return spring 256 for returning the footboards 236a, 236b to the initial (neutral) position and a cam groove 257 at the tip. It consists of a plate 258 and a cam roller 265 that is movably provided in the cam groove 257. A base end portion of the cam plate 258 is rotatably connected to one end portion of the transmission frame 266 via the cam shaft 270. The camshaft 270 is disposed on the transmission frame 266. One end of the return spring 256 is locked to the cam shaft 270. The other end side of the return spring 256 is engaged with a roller shaft 267 for fitting the cam roller 265 rotatably. When the cam roller 265 is positioned at a substantially middle portion of the cam groove 257, the roller shaft 267, the support shaft 269, and the cam shaft 270 are arranged on the same straight line.

  As a result, the return spring 256 is most contracted, and the stepping plates 236a and 236b of the forward pedal 232 and the reverse pedal 233 are respectively held in the initial (neutral) positions. On the other hand, when the operator steps on one of the forward or reverse tread plates 236 a and 236 b, the cam plate 258 rotates in the forward or reverse direction against the return spring 256 force, and the cam roller 265 moves in the cam groove 257. The return spring 256 is extended from the substantially intermediate portion to one end side in proportion to the amount of movement of the cam roller 265. The force for extending the return spring 256 is the pedal depression force in the low speed operation range when the forward or reverse pedals 232 and 233 are depressed to move at low speed.

  As shown in FIGS. 11 and 12, the stepping resistance changing means 242 includes a stepping force increasing spring 260 for increasing the stepping force of the stepping plates 236a and 236b, a pressing force increasing spring 260, and a spring seat 261 and a pulling spring seat 262. A spring cylinder 263 disposed between them, a push-pull rod 264 that connects one end side to the push spring seat 261 and the pull spring seat 262, and a shaft that is rotatable to the other end side of the push-pull rod 264 via a roller shaft 267. The cam roller 265 is supported. A support arm 272 of the spring cylinder 263 is rotatably connected to the transmission frame 266 via the arm shaft 273. When the stepping plates 236a and 236b are stepped on and the cam roller 265 is moved to the end of the cam groove 257, the stepping plates 236a and 236b are further stepped on and the cam plate 258 is further rotated continuously in the same direction. The rod 264 moves in the pushing direction or the pulling direction, and the pushing spring seat 261 or the pulling spring seat 262 moves to compress the pedaling force increasing spring 260.

  The force (pedal depressing reaction force) that compresses the depressing force increasing spring 260 is the pedal depressing force in the high-speed operation area when moving forward at a high speed by depressing either one of the forward or reverse pedals 232 and 233. The depressing resistance force of the forward pedal 232 and the reverse pedal 233 increases abruptly in the middle of the depression. That is, when the stepping plates 236a and 236b are stepped over beyond the amount of stepping in the low-speed movement region (until the cam roller 265 moves to the end of the cam groove 257), the stepping reaction force (pedal stepping force) of the pedal 232 (233) is stepped on. The resistance is rapidly increased by the resistance changing means 242, and the operator can distinguish the high-speed operating range of the pedal 232 (233).

  As shown in FIGS. 9 to 11, a shift potentiometer 220 as a stepping detection sensor for detecting the stepping amount (or stepping angle) of each of the stepping plates 236 a and 236 b is provided between the bracket 240 and the sensor link 271. . The bracket 240 is integrally connected to the transmission frame 266. The sensor link 271 is integrally connected to the cam plate 258. The sensor arm 220a of the transmission potentiometer 220 is constantly pressed against the sensor link 271 by the spring force of a spring (not shown) built in the transmission potentiometer 220. The sensor arm 220a rotates in conjunction with the sensor link 271.

  With reference to FIGS. 8 to 11, an operation in which the operator depresses the forward pedal 232 or the reverse pedal 233 to move the tractor 1 forward or backward to move forward or backward will be described. First, an operation when the forward pedal 232 is stepped on will be described. When the operator steps on the forward tread plate 236a, the cam plate 258 is pushed down via the check link 238a and rotates counterclockwise in FIG. By the rotation of the cam plate 258, the cam roller 265 moves in the cam groove 257, and the return spring 256 is extended. On the other hand, the shift potentiometer 220 is operated via the sensor link 271 to detect the depression amount (or depression angle) of the forward pedal 232, and the shift drive output (forward speed) from the continuously variable transmission 29 is detected as the forward pedal 232. The speed increases in proportion to the amount of pedaling.

  In a state where the forward tread plate 236a is depressed and the cam roller 265 moves to the end of the cam groove 257, the operator further depresses the forward tread plate 236a to increase the speed change drive output (forward speed). When operated, the push / pull rod 264 is pulled down via the cam plate 258, the pedal effort increasing spring 260 is compressed via the tension spring seat 262, and the pedal effort of the forward pedal 232 is increased. The operator can depress the forward pedal 232 from the low speed operation area to the high speed operation area while the operator feels a sudden change in the pedaling force of the forward pedal 232.

  When the operator removes his / her foot from the forward pedal 232, the pulling spring seat 262 returns to the initial position by the stepping force increasing spring 260 force, and the cam plate 258 returns to the neutral (initial) position by the return spring 256 force, The forward pedal 232 is returned to the initial position. When the forward pedal 232 is depressed, the reverse pedal 233 moves in a direction opposite to the depression direction, while when the operator releases the foot from the forward pedal 232, the reverse pedal 233 also returns to the initial position.

  On the other hand, the operation when the reverse pedal 233 is stepped on will be described. When the operator steps on the reverse tread plate 236b, the cam plate 258 is pulled up via the check link 238b and rotates clockwise in FIG. By the rotation of the cam plate 258, the cam roller 265 moves in the cam groove 257 and extends the return spring 256, while the transmission potentiometer 220 is operated via the sensor link 271 to detect the amount of depression of the reverse pedal 233, The shift drive output (reverse speed) from the continuously variable transmission 29 is increased in proportion to the depression amount of the reverse pedal 233.

  In a state where the reverse stepping plate 236b is depressed and the cam roller 265 moves to the end of the cam groove 257, the operator further depresses the reverse stepping plate 236b so as to increase the speed change drive output (reverse speed). When operated, the push-pull rod 264 is pushed up via the cam plate 258, the pedal effort increasing spring 260 is compressed via the push spring seat 261, and the pedal effort of the reverse pedal 233 is increased. The operator can depress the reverse pedal 233 from the low speed operation range to the high speed operation range while the operator feels a sudden change in the pedaling force of the reverse pedal 233.

  When the operator lifts his / her foot away from the reverse pedal 233, the push spring seat 261 returns to the initial position by the stepping force increasing spring 260 force, and the cam plate 258 returns to the initial (neutral) position by the return spring 256 force, The reverse pedal 233 is returned to the initial position. Further, when the reverse pedal 233 is depressed, the forward pedal 232 moves in a direction opposite to the depressing direction, while when the operator releases his / her foot from the reverse pedal 233, the forward pedal 232 also returns to the initial position.

  The accelerator connecting lever 127 will be described with reference to FIGS. 8 to 10 and FIGS. 12 to 15.

  As shown in FIGS. 9, 10, and 13, a transmission frame 266 and a lever fulcrum frame 130 are integrally connected to the column frame 129 of the steering column 234. A lever fulcrum shaft 131 is integrally formed by extending the base end of the throttle lever 206 substantially horizontally in the left-right direction. The lever fulcrum shaft 131 is rotatably disposed on the lever fulcrum frame 130. The lever fulcrum shaft 131 is fitted with an accelerator bearing 134 with a one-way rotation clutch that can be rotated by one-way rotation of the lever fulcrum shaft 131 (the speed increasing operation direction of the lever 206). A throttle arm 133 is disposed on the accelerator bearing 134. The throttle arm 133 is connected to the engine governor 214 via the throttle link 132. A disc spring 135 for maintaining the throttle lever 206 in an arbitrary operation position is fitted on the lever fulcrum shaft 131. When the throttle lever 206 is rotated against the braking force of the disc spring 135 (in the front-rear direction), the throttle arm 133 is rotated in conjunction with the engine governor 214 to operate the engine 5 at the rotational speed. change. That is, when the throttle lever 206 is rotated in the imaginary line direction (counterclockwise) from the solid line position in FIG. 10, the throttle arm 133 is rotated so that the rotational speed of the engine 5 increases to, for example, the maximum output rotational speed. Then, the engine governor 214 is operated. When the throttle lever 206 is rotated from the imaginary line direction to the direction (clockwise) to return to the solid line position in FIG. 10, the throttle arm 133 returns to the return spring so that the rotational speed of the engine 5 decreases to, for example, the idling rotational speed. (Not shown) Moves backward with force.

  As shown in FIGS. 10 and 13, the accelerator interlocking mechanism 118 that connects the forward pedal 232 and the engine governor 214 includes an accelerator interlocking arm 136, a clutch arm 139, and an accelerator operating arm 142. The base end portion of the accelerator interlocking arm 136 is rotatably fitted on the lever fulcrum shaft 131. The accelerator interlocking arm 136 is integrally formed with a protrusion 137 that makes contact with the throttle arm 133. When the accelerator interlocking arm 136 rotates in the speed increasing direction (counterclockwise in FIG. 10), the protrusion 137 of the accelerator interlocking arm 136 pushes the throttle arm 133, and the throttle arm 133 is increased in the speed increasing direction (counterclockwise in FIG. 10). Rotate. On the other hand, when the accelerator interlocking arm 136 returns to the deceleration direction (the clockwise direction in FIG. 10) which is the initial position side, the protrusion 137 of the accelerator interlocking arm 136 moves away from the throttle arm 133, and the throttle arm 133 is decelerated in the deceleration direction. (Turn clockwise in FIG. 10) The throttle arm 133 is moved back by a spring force until the throttle arm 133 is rotated by the throttle lever 206.

  One end of a guide bar 138 is connected to the accelerator interlocking arm 136. A clutch arm 139 is fitted on the guide rod 138 so as to be slidable in the axial direction. The clutch arm 139 is integrally formed with an abutting body 139a for abutting against an accelerator operating arm 142 described later. The shift member 140 connected to the clutch arm 139 is fitted on the lever fulcrum shaft 131 so as to be slidable. A lever holder 141 is rotatably fitted on the lever fulcrum shaft 131. The accelerator connecting lever 127 is slidably inserted into the lever holder 141. The accelerator connecting lever 127 is disposed so as to be slidable in the axial direction of the lever fulcrum shaft 131 via the lever holder 141. The shift member 140 is connected to the accelerator connecting lever 127 via the shift arm 140a. On the other hand, an accelerator operation arm 142 for contacting the contact body 139a is disposed on the rotation support shaft portion 237a of the forward pedal 232. On the upper surface side of the accelerator operation arm 142, a plate-shaped malfunction prevention body 143 for preventing malfunction of the contact body 139a is disposed.

  Next, the operation of the accelerator connecting lever 127 and the operation of the accelerator interlocking mechanism 118 will be described. When the accelerator connecting lever 127 is at the solid line position in FIG. 13, the contact body 139 a of the clutch arm 139 is supported at a position deviating from the turning locus of the accelerator operation arm 142. In this case, even if the operator depresses the forward pedal 232 and rotates the accelerator operation arm 142 in the clockwise direction in FIG. 10, the accelerator operation arm 142 does not contact the contact body 139a of the clutch arm 139. 139 does not rotate. That is, even if the operator depresses the forward pedal 232, the rotational speed of the engine 5 is not changed by the operation of the forward pedal 232. When the operator operates the throttle lever 206, only the rotational speed of the engine 5 is changed.

  On the other hand, when the operator pulls the accelerator connecting lever 127 to move it from the solid line position to the virtual line position in FIG. Supported by When the operator depresses the forward pedal 232, the accelerator operation arm 142 comes into contact with the contact body 139a of the clutch arm 139. Therefore, the clutch arm 139 is rotated by the accelerator operation arm 142, and the throttle arm 133 is rotated to the acceleration side via the protrusion 137. That is, when the operator depresses the forward pedal 232, the rotational speed of the engine 5 is changed to the speed increasing side in proportion to the amount of depression of the forward pedal 232. When the operator removes his / her foot from the forward pedal 232 and returns it, the rotational speed of the engine 5 also returns to the rotational speed before the speed increase (the rotational speed set by the throttle lever 206). Further, even if the operator depresses the reverse pedal 233, the accelerator operation arm 142 rotates in a direction away from the clutch arm 139 (counterclockwise in FIG. 10), so that the rotational speed of the engine 5 is not changed.

  When the operator depresses the forward pedal 232 and the operator pulls the accelerator connecting lever 127, the contact body 139a of the clutch arm 139 contacts the malfunction preventing body 143, and the accelerator connecting lever 127 is shown by a solid line in FIG. It is prevented from moving from the position to the virtual line position. Therefore, the contact body 139a of the clutch arm 139 is supported at a position deviating from the turning locus of the accelerator operation arm 142.

  When the lever shaft 131 of the throttle lever 206 is formed to be extendable / contractable via the expansion / contraction joint member 150 and the expansion / contraction joint member 150 is disposed between the lever holder 141 and the shift arm 140a, the lever holder 141 and the shift arm 140a are arranged. Is connected with a rod (not shown) or the like to move the throttle lever 206 in the axial direction of the lever shaft 131 so that the contact body 139a of the clutch arm 139 can be brought into contact with or separated from the accelerator operation arm 142. . By using the throttle lever 206 also, the accelerator connecting lever 127 can be made unnecessary.

  The configuration of the pedal lock lever 128 will be described with reference to FIGS. 9 and 10 and FIGS. 12 to 16. As a constant speed moving mechanism 119 for maintaining the moving speed of the tractor 1 substantially constant, a lock arm 146 and a lock gear 147 are provided. A lever shaft 144 at the base end of the pedal lock lever 128 is pivotally supported on the column frame 129 via a bearing body 145. The base end portion of the lock arm 146 is connected to the lever shaft 144. An engaging claw 146 a is integrally fixed to the distal end portion of the lock arm 146. A fan-shaped lock gear 147 that engages and disengages the engagement claw 146a is integrally fixed to the rotation support shaft portion 237b of the reverse pedal 233. The brake pedal 230 is connected to the lock arm 146 through a release wire 148 and a link (see FIG. 16). The lock arm 146 is connected to a switching spring 149 that works over the fulcrum to maintain the pedal lock lever 128 in the locked position or the unlocked position (see FIG. 10).

  Next, the operation of the pedal lock lever 128 and the operation of the constant speed moving mechanism 119 will be described. The pedal lock lever 128 is maintained by the switching spring 149 at the position switched by the operator at either the phantom line position or the solid line position in FIGS. 9 and 10. When the pedal lock lever 128 is in the solid line position, the engagement claw 146a of the lock arm 146 is engaged with the lock gear 147, and the forward pedal 232 and the reverse pedal 233 are maintained at substantially constant positions. For example, the operator depresses the forward pedal 232 or the reverse pedal 233 to an arbitrary position, the pedal lock lever 128 at the phantom line position in FIG. In this case, the forward pedal 232 and the reverse pedal 233 are maintained at the operation positions, and the tractor 1 moves in the forward or reverse direction at a substantially constant speed even if the operator lifts his / her foot from the forward pedal 232 or the reverse pedal 233.

  Further, when the operator depresses the forward pedal 232 to the maximum depressed position, the pedal lock lever 128 at the phantom line position in FIG. 10 is operated to the solid line position, and the engagement claw 146a is engaged with the lock gear 147, the forward movement is performed. The pedal 232 is fixedly maintained at the maximum depressed position, the forward moving speed of the work vehicle is maintained at a substantially maximum speed, and the tractor 1 moves in the forward direction at the substantially maximum speed even when the operator lifts his / her foot from the forward pedal 232. . Thus, when the tractor 1 is moving forward at a substantially maximum speed, the speed ratio setting dial 211 can be operated by the operator to set the speed of neutral or multi-stage shift (see FIG. 18). That is, when the operator removes his / her foot from the forward pedal 232 (reverse pedal 233) and the operator simply operates the gear ratio setting dial 211, the main gear shift output of the hydraulic continuously variable transmission 29 is switched to a neutral state. The main shift output of the hydraulic continuously variable transmission 29 can be shifted in multiple stages.

  Further, when the pedal lock lever 128 is switched to the solid line position (FIG. 10), when the operator depresses the brake pedal 230, the lock arm 146 in the engaged position is moved to the non-engaged position side via the release wire 148. Be pulled. Therefore, the lock arm 146 moves from the solid line position (engagement position) in FIG. 10 to the phantom line position (non-engagement position) to release the engagement between the engagement claw 146a and the lock gear 147, and the forward pedal 232 and the reverse pedal. Keep 233 operational. When the operator takes his or her foot off the forward pedal 232 or the reverse pedal 233, when the operator depresses the brake pedal 230, the forward pedal 232 or the reverse pedal 233 returns to the initial (neutral) position. When the moving speed (vehicle speed) becomes below a certain level, both the forward hydraulic clutch 40 and the reverse hydraulic clutch 42 are automatically kept off and the left and right brakes 65 are automatically operated. The left and right rear wheels 4 are braked.

  Next, constant speed ratio control (speed ratio adaptive control) will be described. Here, the gear ratio means the ratio of the rotational speed of the output shaft 36 of the hydraulic continuously variable transmission 29 to the engine 5 rotational speed. same as below. In the tractor 1 equipped with the hydraulic continuously variable transmission 29, the control for feeding back the actual rotation speed of the output shaft 36 to the travel controller 210 to match the target speed ratio is referred to as speed ratio adaptive control. That is, the speed of the hydraulic continuously variable transmission 29 is controlled so that the actual speed ratio becomes the target speed ratio while the engine speed is controlled to be substantially constant regardless of the load variation. The proportional solenoid valve 203 for controlling the forward and reverse pedals 232 and 233 is controlled by a plurality of speed ratio patterns as the speed ratio of the hydraulic continuously variable transmission 29 with respect to the depression amount of the forward and reverse pedals 232 and 233. It is stored in a readable / writable memory as needed.

  This speed ratio pattern is a pattern in which the speed ratio increases in proportion to the amount of depression of the forward pedal 232 and the reverse pedal 233 as the speed pedal. In the embodiment of FIG. 18, there are 15 speed ratio patterns. (Transmission ratio lines No. 1 to No. 15) are prepared and stored in advance in the pattern storage means. When the operator selects the scale of the transmission ratio setting dial 221 (for example, N, 1, 2, 3,..., 14, 15), one pattern can be set from a plurality of transmission ratio patterns. In other words, the transmission ratio setting dial 221 is for changing (setting) the change ratio of the transmission ratio corresponding to the depression amount of the forward pedal 232 and the reverse pedal 233. When the scale of the setting dial 221 is N (shift neutral), the output of the hydraulic continuously variable transmission 29 is set to substantially zero (the gear ratio is 0) regardless of the depression amount of the forward pedal 232 and the reverse pedal 233. maintain.

  In the embodiment shown in FIG. 18, the abscissa represents the pedal depression amount (indicated as a percentage of the maximum depression amount, the rightward is for the forward pedal and the leftward is for the reverse pedal), and the vertical axis (see the left vertical axis). Shows a diagram of a gear ratio pattern by taking the gear ratio (0 to 2) of the rotational speed of the output shaft 36 with respect to the rotational speed of the engine 5. In FIG. 1-No. 15, the forward speed ratio pattern and the reverse speed ratio pattern are set to be the same (symmetrical). Furthermore, a diagram (indicated by a broken line) showing a change in pedal depression force with respect to the pedal depression amount is described. That is, the pedaling force (indicated by% of the maximum value) is taken on the right vertical axis.

  In this embodiment, the pedaling force of the forward pedal 232 (or the reverse pedal 233) is suddenly increased by the depression resistance changing means 242 in the middle of the depression amount (for example, a position at about 70% of the total depression amount). ing. 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 neutral position restoring means 241. At the position where the pedal depression amount is about 70%, the resistance force by the depression resistance changing 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. 1-No. In line No. 11 (referred to as No. 1 to No. 11 in order from the lower line in FIG. 18), the gradient of the gear ratio ratio is low in an area where the pedal depression amount is less than about 70%, and about 70%. In the region beyond the position, the gradient of the transmission ratio line is set to be high. When the operator intends to accelerate and depresses the pedals 232 and 233 beyond the normal pedal depression amount range (within about 70%), it can be felt by a sudden increase in pedal depression force. Further, the speed can be increased simply by the operator simply depressing the pedals 232 and 233 beyond the normal pedal depression range (about 70%).

  No. In the 12 line (the 12th line from the lower line in FIG. 18), the gear ratio line is set to be substantially straight until the pedal depression amount is 0% to 100%. No. 13 and no. In the No. 14 line (No. 13 and No. 14 counted from the lower line in FIG. 18), the gradient of the transmission ratio line in the region where the pedal depression amount exceeds about 70% is about 70%. It is set lower than the gradient in the area less than the position. No. A transmission gear ratio line of 15 is a straight line that becomes the transmission gear ratio 2 at a position where the pedal depression amount is about 70% (immediately before the depression resistance changing means 242 acts on the pedal).

  Next, the gear ratio adaptive control mode will be described with reference to the flowchart of the gear ratio control (FIG. 19). 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 to drive the hydraulic pump unit 500 of the hydraulic continuously variable transmission 29. The amount of pressure oil discharged is controlled. The control is automatic control for executing the gear ratio pattern (No. 1 to No. 15) set by the setting dial 221. More specifically, the amount of depression of the shift pedals 232 and 233 is self-monitored and the amount of depression is determined. Is automatically controlled so as to follow the target line of the gear ratio set by the gear ratio setting dial 221 in accordance with the change of the gear ratio. Thus, the rotational speed of the main transmission output shaft 36 can be changed and adjusted steplessly. In the gear ratio adaptive control in FIG. 9, the engine is started (S1), and the operator depresses the forward pedal 232 to the maximum depression position (S2: yes), and the gear ratio setting dial 221 is used according to the work type and the like. When the operator selects and determines a desired gear ratio pattern (No. 1 to No. 15) (S3), a predetermined gear ratio pattern (No. 1) stored in the RAM (memory that can be read and written at any time) of the travel controller 210 is selected. 1 to No. 15) are read (S4).

  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 from the shift potentiometer 220 to the travel controller 210 (S5). 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 (No. 1 to No. 15) (S6). . When the scale of the setting dial 221 is N (shift neutral), the output of the hydraulic continuously variable transmission 29 is maintained at substantially zero (the gear ratio is 0) regardless of the depression amount of the forward pedal 232 and the reverse pedal 233. The

  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 (S7). Whether the current gear ratio value is substantially equal to the target gear ratio value by calculating the current gear ratio value from the ratio between the engine speed (denominator) and the main gear shift output speed (numerator) at the sampling time (current) Is discriminated (S8). When the current gear ratio value is separated from the target gear ratio value by more than a predetermined percentage (S8: 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 rotation speed of the main shift output shaft 36 (S9).

  If the current speed ratio value is substantially equal to the target speed ratio value (when the current speed ratio value is within ± predetermined% with respect to the target speed ratio value) (S8: yes), the rotation speed of the main speed change output shaft 36 is maintained. (S10). Thus, feedback control is performed so that the current gear ratio value matches the target gear ratio value. It should be noted that when the output torque fluctuation of the engine 5 is insufficient due to disturbance such as an increase in traveling load, such as when the tractor enters a soil area containing a lot of water from a dry soil area, or when the environment changes Of course, when the engine 5 rotational speed deviates from the predetermined value, the electronic governor controller 213 is operated to control the engine 5 rotational speed to be maintained at the predetermined value.

  If such a gear ratio adaptive control is employed, the operator can change the environment by simply operating the forward pedal 232 or the reverse pedal 233 after setting the gear ratio pattern of the gear ratio once with the gear ratio setting dial 221. When the actual gear ratio value deviates from the target gear ratio value due to fluctuations in the travel load of the work vehicle or the work vehicle, automatic control can be performed so as to automatically approach the target gear ratio value. In addition, since the electronic governor 214 for controlling the rotational speed of the engine 5 with a load is provided, both the rotational speed of the engine 5 and the output of the hydraulic continuously variable transmission 29 are maintained with high efficiency. The engine speed and the pump swash plate 509 angle can be controlled. The traveling operation of the work vehicle can be simplified by approximating the traveling operation in an automobile with a continuously variable transmission mechanism. Fatigue can be reduced even during long-term work.

  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 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, regardless of the output speed of the engine 5, the rotation of the output shaft 36 becomes substantially zero and the main transmission output gear 37 stops.

  It is determined whether or not T1 time has elapsed from the time when the speed ratio is shifted to 0 (S15). 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, the automatic brake electromagnetic valve 67 for the brake cylinder 68 is turned on to execute braking of the rear wheel 4 (automatic brake operation) (S17). As a result, the travel of the tractor 1 is stopped (S18). Therefore, even if the operator depresses the shift pedal (the forward pedal 232 or the reverse pedal 233) and starts the engine 5, the engine 5 does not start.

  Then, it is determined whether or not a further T2 time has elapsed since the travel stop in step S18 (S19). When the T2 time has elapsed (S19: yes), the swash plate angle of the hydraulic pump unit 500 is shifted to approximately 0 degrees. To a gear ratio of 1 (S20). In this case, the hydraulic oil from the hydraulic pump unit 500 is not supplied to the hydraulic motor unit 501, and the hydraulic oil of the hydraulic continuously variable transmission 29 does not circulate. That is, when the operator does not depress the forward pedal 232 or the reverse pedal 233 (does not start traveling) during the time period T2, the load on the engine 5 can be reduced and unnecessary fuel consumption can be avoided.

  In step S15, if the time T1 has elapsed (S15: yes), traveling work such as the gear ratio adaptive control described above is executed (S21). During this traveling operation, it is determined whether or not the forward or reverse pedals 232 and 233 are depressed (S22). If the forward or reverse pedals 232 and 233 are not depressed (S22: no), the engine speed from the engine speed sensor 215, the main speed output speed from the main speed change output section 116, and the vehicle speed sensor 117 When the vehicle speed is read (S23), and 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 steps are performed. The process proceeds to S16. Thereby, the operator can stop without stepping on the brake pedal 230. On the other hand, when the vehicle speed is higher 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 the gear ratio adaptive control in step S21 is executed. To do.

  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), the forward pedal 232 is depressed, and the operator selects and determines a desired gear ratio pattern with the gear ratio setting dial 221 according to the work type and the like (S32). At this time, it is determined whether the left and right 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 into the travel controller 210 from the forward potentiometer 219 (reverse potentiometer 220) (S34). When the traveling machine body is stopped by the travel stop control of FIG. 20 and the gear ratio is 1 (S35: yes) in which the swash plate angle of the hydraulic pump unit 500 is shifted to approximately 0 degrees (S35: yes), the swash plate angle of the hydraulic pump unit 500 is set. The shift is made to approximately −11 degrees and the gear ratio is moved to 0 (S36).

  When the swash plate angle of the hydraulic pump unit 500 reaches 0 (S37: yes), that is, when the main transmission output gear 37 is absolutely stopped, the forward clutch solenoid valve 46 (reverse clutch solenoid valve 48) is operated. Then, 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. 19 described above is performed (S46). The tractor 1 moves forward (reverse) at a speed calculated from the depression amount of the forward pedal 232 (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 (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 body travels forward (or reverse) (S41: yes), it is determined whether or not the reverse pedal 233 (forward pedal 232) on the opposite side to the traveling direction is depressed (S42).

  When the reverse pedal 233 (forward pedal 232) on the opposite side to the traveling direction is depressed (S42: yes), the vehicle speed is reduced to the minute speed V1 (stopping the depression of the forward pedal 232 (reverse pedal 233) in the traveling direction. For example, when the speed is reduced to about 0.1 km / hour or less (S43: yes), the forward clutch electromagnetic valve 46 (reverse clutch electromagnetic 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. 19 is performed (S46). . At a speed calculated by the amount of depression of the forward pedal 232 (reverse pedal 233) and the setting value of the transmission ratio setting dial 221, the traveling machine body moves backward (reverse) and moves backward (forward) through a temporary stop state. Move to move. By alternately depressing the forward pedal 232 and the reverse pedal 233, the traveling movement direction of the traveling machine body is alternately switched between forward and backward movements, and the traveling machine body can be smoothly reciprocated.

  Next, the sub-speed changeover 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 sub-shift is switched from the low speed side to the high speed side by setting the high speed / low speed (sub shift) switch 222 to the sub shift high speed ON. (S51: yes), the main transmission output unit rotation speed from the main transmission 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), It is determined whether or not the vehicle speed is equal to or higher than the speed V1 (S55).

  Subsequently, when the vehicle speed is not equal to or lower than a predetermined speed V1 (for example, about 0.1 km / hour) (S55: no) but is equal to or higher than the speed V1 at which the operation can be continued, the high-speed clutch 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 solenoid valve 203 is operated to shift the swash plate angle of the hydraulic pump unit 500 in the gear ratio reduction direction (S57). Then, it is determined whether or not the rotational speed of the main transmission output shaft 36 detected by the main transmission output part rotation sensor 116 matches the rotational speed of the auxiliary transmission shaft 50 detected by the vehicle speed sensor 117 (S58). . When the rotational speed of the main transmission output shaft 36 and the rotational speed of the auxiliary transmission shaft 50 substantially coincide with each other (S58: yes), the forward clutch entered just before the changeover switch 222 is switched from the low speed side to the high speed side. 40 (reverse clutch 42) is engaged again (S59), and the gear ratio adaptive control shown in FIG. 19 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), when the vehicle speed is equal to or lower than the speed V1 (for example, about 0.1 km / hour) (S55: yes), The left and right brakes 65 are turned on and operated (S61) to prevent reverse running on the uphill or downhill. At substantially the same time, the high-speed clutch solenoid valve 666 is turned on to continue the high-speed clutch 57 (S62), and the forward clutch 40 (reverse clutch 42) that was just before the changeover switch 222 was switched from low speed to high speed is re-entered. (S63), the left and right brakes 65 are turned off to release the braking of the left and right rear wheels 4 (S64), and the gear ratio adaptive control shown in FIG. 19 is performed (S60). The traveling sub-shift can be shifted from a low speed to a high speed by preventing the tractor 1 from running backward on an uphill or downhill.

  Next, the sub shift low 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 and the high-speed clutch 57 of the sub-transmission gear mechanism 30 is engaged (S70: yes), when the high-speed / low-speed (sub-transmission) changeover switch 222 is OFF (S71: no). The vehicle travels at a sub-speed (S72). On the other hand, when the changeover switch 222 is turned on at a low speed and the sub-shift is switched from a high speed to a low speed (S71: yes), the swash plate angle of the hydraulic pump unit 500 is equal to or greater than a certain speed ratio (C1 = 0.7). (S73: yes), the proportional control solenoid valve 203 is controlled so as to be equal to or less than the constant speed ratio C1, and the main speed change output from the continuously variable transmission 29 is decelerated to the constant speed ratio C1 or less (S74). That is, if the swash plate angle of the hydraulic pump unit 500 is greater than or equal to the gear ratio C1 when the sub-shift is high, the maximum speed when the sub-shift is low (the swash plate angle of the hydraulic pump unit 500 is the gear ratio 2) is approximately. The swash plate angle of the hydraulic pump unit 500 is changed to a gear ratio C1 or less so as to be the same or less. In this way, the traveling speed when the sub-shift is high is reduced so that the sub-shift is less than the maximum speed when the sub-shift is low. Before the sub-shift is switched from the high speed to the low speed, the front and rear wheels 3 and 4 are driven below the maximum speed of the sub-speed to prevent a sudden increase in the output load of the continuously variable transmission 29. It should be noted that the traveling speed when the swash plate angle of the hydraulic pump section 500 with the high speed sub-shift is the gear ratio C1 and the traveling speed when the swash plate angle of the hydraulic pump section 500 with the maximum sub-speed and the low speed is the speed ratio 2. The speed is substantially the same.

  As described above, when the main transmission output from the continuously variable transmission 29 is decelerated to a constant gear ratio C1 or less (S74), the main transmission output unit rotation speed from the main transmission output unit rotation sensor 116 and the vehicle speed sensor 117 (S75), the forward clutch 40 (reverse clutch 42) is disengaged (S76), and it is determined whether or not the vehicle speed is equal to or higher than a predetermined speed V1 (for example, about 0.1 km / hour) (S77). ).

  If the vehicle speed is not lower than the speed V1 (S77: no) and the operation can be continued, the high-speed clutch solenoid valve 666 is turned off (S78), and the auxiliary transmission hydraulic cylinder 55 is operated to the lower speed side, The high speed clutch 57 is disconnected and the low speed clutch 56 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 increasing direction (S79). Then, it is determined whether or not the rotational speed of the main transmission output shaft 36 detected by the main transmission output part rotation sensor 116 matches the rotational speed of the auxiliary transmission shaft 50 detected by the vehicle speed sensor 117 (S80). . When the rotational speed of the main transmission output shaft 36 and the rotational speed of the sub-transmission shaft 50 are substantially coincident (S80: yes), the forward clutch 40 (reverse drive) that has entered immediately before the changeover switch 222 is switched from high speed to low speed. The clutch 42) is again engaged (S81), and the gear ratio adaptive control shown in FIG. 19 is performed (S82). 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 turned on again, and the forward clutch 40 (reverse clutch 42) is turned on again. This can prevent the vehicle speed from changing suddenly.

  On the other hand, when the vehicle speed is equal to or lower than the predetermined speed V1 (for example, about 0.1 km / hour) in step 77 described above (S77: yes), the left and right brakes 65 are turned on and operated (S83). Prevent retrograde. At substantially the same time, the high-speed clutch electromagnetic valve 666 is turned off and the low-speed clutch 56 is continued (S84). Next, the forward clutch 40 (reverse clutch 42), which was entered immediately before the high speed / low speed changeover switch 222 is switched from high speed to low speed, is again engaged (S85), the left and right brakes 65 are turned off, and the left and right rear wheels 4 are operated. The braking is released (S86), and the gear ratio adaptive control shown in FIG. 19 is performed (S82). For this reason, it is possible to reduce the shock from the sub-shift high-speed travel to the sub-speed low-speed travel without stopping the tractor 1 and without making the shift drive output of the hydraulic continuously variable transmission 29 neutral (substantially zero rotation). The workability of the tractor 1 or the wheel loader can be improved.

  Next, the forward / backward hand operation control will be described with reference to the flowchart shown in FIG. First, when the hand operation in which the forward / reverse selector switch 223 is operated to the neutral position is neutral (S87: yes), the above-described gear ratio adaptive control of FIG. 19 is performed (S88). On the other hand, when the forward pedal 232 is maintained at the maximum depressed position by the operation of the lock lever 128 and the forward / reverse selector switch 223 is switched to the forward position (S89: yes), the operator selects a desired gear ratio according to the type of work. The speed ratio setting dial 221 value with the selected / determined pattern is read (S90), and a predetermined speed ratio pattern (neutral N or No. 1 to No. 15 in FIG. 18) stored in the RAM of the travel controller 210 is read. Then, the forward clutch solenoid valve 46 is actuated, the forward clutch 40 is engaged (S91), and the gear ratio pattern selected by the operator with the gear ratio setting dial 221 (neutral N or No. 1 to No. 15 in FIG. 28). The forward control for operating the proportional control solenoid valve 203 is executed so as to maintain the maximum speed (S92).

  As a result, the output of the hydraulic continuously variable transmission 29 becomes zero in the gear ratio pattern (neutral N) and the tractor 1 stops, or the gear ratio pattern selected by the operator with the gear ratio setting dial 221 (see FIG. 18). No. 1 to No. 15) are maintained at the maximum speed, and the tractor 1 moves in the forward direction at a substantially constant speed. When the operator selects another speed ratio pattern different from the current speed ratio pattern with the speed ratio setting dial 221, the output of the hydraulic continuously variable transmission 29 is changed in multiple stages. When the forward / reverse selector switch 223 is operated to the neutral position and the hand operation returns to neutral (S93: yes), the auto brake solenoid valve 67 for the brake cylinder 68 is turned on to brake the rear wheel 4 (S94). ). Thereby, traveling of the tractor 1 is stopped.

  On the other hand, when the forward pedal 232 is maintained at the maximum depressed position by operating the lock lever 128 and the forward / reverse selector switch 223 is switched to the reverse position (S95: yes), the gear ratio setting dial 221 value is read (S96). A predetermined gear ratio pattern (neutral N or No. 1 to No. 15 in FIG. 18) stored in the travel controller 210 is read out. Then, the reverse clutch solenoid valve 48 is operated with the gear ratio pattern (No. 1 to No. 15 in FIG. 18), the reverse clutch 42 is turned on (S97), and the gear ratio selected by the operator with the gear ratio setting dial 221. Reverse control for operating the proportional control solenoid valve 203 is performed so as to maintain the maximum speed of the pattern (S98). As a result, the tractor 1 moves in the reverse direction at a substantially constant speed.

  In this way, when the forward / reverse selector switch 223 is switched to the forward or reverse position, the forward pedal 232 is first maintained at the maximum foot position by the lock lever 128, and the forward pedal 232 and the reverse pedal 233 are fixed at fixed positions. 19, the operator selects / determines the gear ratio pattern in FIG. 19 with the setting dial 221, switches the forward / reverse selector switch 223 to the forward or reverse position, and starts to move, and the moving speed of the tractor 1 is changed to the multi-speed shift of the setting dial 221. To switch the tractor 1. When the operator selects another speed ratio pattern different from the current speed ratio pattern with the speed ratio setting dial 221, the output of the hydraulic continuously variable transmission 29 is changed in multiple stages. When the forward / reverse selector switch 223 is operated to the neutral position (S99: yes), the autobrake solenoid valve 67 is turned on to brake the rear wheel 4 (S100). Thereby, traveling of the tractor 1 is stopped. Note that the tractor 1 stops when the neutral ratio N (transmission ratio pattern) is selected.

  Further, when the forward / reverse selector switch 223 is operated to the forward or reverse position, when the engine 5 is started and the vehicle speed is equal to or lower than a predetermined speed V1 (for example, about 0.1 km / hour), high / low speed ( The sub-shift) changeover switch 222 is turned on, the high-speed clutch solenoid valve 666 is turned on, the sub-shift hydraulic cylinder 55 is actuated to the high speed side, the sub-shift low-speed clutch 56 is turned off, and the high-speed clutch 57 is turned on. The sub-shift can be switched from the low speed side to the high speed side. Similarly, when the vehicle speed is equal to or lower than the predetermined speed V1, the changeover switch 222 is turned off, the high speed clutch solenoid valve 666 is turned off, the high speed clutch 57 for sub speed change is turned off, and the low speed clutch 56 is continued. The sub-shift is switched from high speed to low speed. When the forward / reverse selector switch 223 is operated to the forward or reverse position, the high-speed clutch solenoid valve 666 may be kept off and the continuation of the low-speed clutch 56 may be maintained regardless of the operation of the selector switch 222.

  As is apparent from the above description and FIGS. 10 and 13, the hydraulic continuously variable transmission 29 that shifts the power from the engine 5 mounted on the traveling machine body 2, and the gear ratio of the hydraulic continuously variable transmission 29 In a work vehicle configured to shift the hydraulic continuously variable transmission 29 based on an operation amount of the forward pedal 232 and the forward pedal 232, the amount of depression of the forward pedal 232 is detected. Select one of a transmission potentiometer 220 as a transmission sensor and a plurality of transmission ratio patterns (N, No. 1 to No. 15) capable of changing the maximum output of the hydraulic continuously variable transmission 29 in multiple stages. A speed ratio setting dial 221 serving as a speed setting means, and a travel controller 210 serving as a control means for controlling the output rotational speed of the hydraulic continuously variable transmission 29, the forward pedal 232 is provided with a constant speed moving mechanism 119 as a lock means for maintaining the stepped position operated by the operator, so that when the forward pedal 232 is maintained at the stepped position by the lock means 119, the operator's foot Even if the forward pedal 232 is accidentally separated from the forward pedal 232, the work can be continued while maintaining a moving speed suitable for the work content. Further, for example, an operator operates the forward pedal 232 to the maximum step, changes the maximum shift drive output rotation speed of the hydraulic continuously variable transmission 29, and sets the speed at which the tractor 1 as the work vehicle continuously moves. The speed can be determined according to the working conditions. Tilling work that reciprocates by changing direction at the headland in the field can be made extremely simple. In the tractor 1 or the wheel loader, it is possible to improve the traveling mobility of the reciprocating work that repeats the direction change, and to reduce fatigue in the long-time work.

  As is clear from the above description and FIGS. 10 and 13, the pedal lock lever 128 as a lock operating tool for operating the constant speed moving mechanism 119 to maintain the forward pedal 232 in the depressed position, and the constant speed movement. For example, an operator can lock the forward pedal 232 by hand and the forward pedal 232 can be operated by the operator. The release operation can be performed with the foot, and the operator can clearly recognize the lock and release of the forward pedal 232 and operate it reliably. An erroneous operation of locking or releasing the forward pedal 232 can be easily prevented. Further, the operator can step on the forward pedal 232 to the maximum stepping position, and the forward pedal 232 can be maintained at the stepped position by the constant speed moving mechanism 119. Therefore, the operator releases the maintenance of the constant speed moving mechanism 119. After the change of direction, the forward pedal 232 that has been stepped on to the maximum foot position is maintained by the constant speed moving mechanism 119, so that the shift output of the previous stroke of the hydraulic continuously variable transmission 29 can be smoothly performed in the next stroke. Can be reproduced. In the tractor 1 or the wheel loader, it is possible to improve the traveling mobility of the reciprocating work that repeats the direction change, and to reduce fatigue in the long-time work.

  As is clear from the above description and FIGS. 17 and 19, the travel controller 210 determines that the speed ratio pattern (N, No.) set by the speed ratio setting dial 221 when the forward pedal 232 is at the maximum depression position. .. No. 1 to No. 15) and according to the gear ratio pattern (N, No. 1 to No. 15) set by the gear ratio setting dial 221 in accordance with the depression amount of the forward pedal 232. Since the output rotational speed of the hydraulic continuously variable transmission 29 is controlled, the operator simply depresses the forward pedal 232 to the maximum stepping position and operates the constant speed moving mechanism 119. The shift output of the previous stroke of the step transmission 29 can be smoothly reproduced in the next stroke. For example, it is possible to very easily perform a tilling operation in which the direction is changed and reciprocated at a headland in a field.

  As apparent from the above description and FIGS. 17 and 19, the transmission ratio setting dial 221 has a plurality of transmission ratio patterns (N, No. 1) in which the maximum output of the hydraulic continuously variable transmission 29 is changed in multiple stages. 1 to No. 15) and a neutral position where the output of the hydraulic continuously variable transmission 29 is made substantially zero, the operator depresses the forward pedal 232. When the constant speed moving mechanism 119 is operated and locked at the maximum stepping position or the like, the gear ratio setting dial 221 is operated by the operator so that the speed change output speed of the hydraulic continuously variable transmission 29 is multistage. Can be changed. Operations similar to conventional shift levers, such as stopping the tractor 1 (shift neutral) and switching the moving speed in multiple stages, can be simplified. Even if the engine 5 is operated, even if the operator accidentally depresses the forward pedal 232 or the like by switching the transmission ratio setting dial 221 to the neutral position and leaving the operator seat 8, It is possible to prevent the hydraulic continuously variable transmission 29 from malfunctioning due to erroneous operation.

  As is clear from the above description and FIGS. 10 and 13, the throttle arm 133 as an accelerator means for changing the rotational speed of the engine 5 and the accelerator as a clutch mechanism for connecting the forward pedal 232 to the throttle arm 133. Since the interlock mechanism 118 is provided, when the throttle arm 133 and the forward pedal 232 are connected via the accelerator interlock mechanism 118, the hydraulic pedal can be operated only by stepping on the forward pedal 232. The shift output of the step transmission 29 and the rotation speed of the engine 5 can be switched smoothly. For example, in a travel area in which the travel direction is greatly changed, both the shift output of the hydraulic continuously variable transmission 29 and the rotational speed of the engine 5 are reduced by reducing the amount of depression of the forward pedal 232, and the tractor The moving speed of 1 can be easily decelerated. On the other hand, in a traveling area where the vehicle travels substantially straight, both the shift output of the hydraulic continuously variable transmission 29 and the rotational speed of the engine 5 are increased by simply increasing the amount of depression of the forward pedal 232, and the tractor 1 The movement speed can be increased easily. The mobility and turning operability of the tractor 1 can be improved, and engine troubles can be easily prevented.

  As is apparent from the above description and FIGS. 9 and 10, the reverse pedal 233 for changing the transmission ratio of the hydraulic continuously variable transmission 29, and the forward pedal 232 and the reverse pedal 233 are prevented from operating simultaneously. Since the transmission link mechanism 275 as a check mechanism is provided, for example, even if the operator depresses the forward pedal 232 and the reverse pedal 233 at the same time, the depressing operation can be prevented by the transmission link mechanism 275, and the transmission potentiometer It is possible to easily prevent 220 or the traveling controller 210 from malfunctioning. The mounting structure of the forward pedal 232 and the reverse pedal 233 or the installation structure of the transmission potentiometer 220 can be configured in a compact and low cost manner.

It is a side view of the tractor for farm work. It is a diagonally rear perspective view of a tractor. It is a skeleton diagram of power transmission. It is a hydraulic circuit diagram of the continuously variable transmission of the transmission case. 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 top view which shows a forward (reverse) pedal part. It is a side view which shows a forward (reverse) pedal part. It is a side view which shows the check mechanism part of a forward (backward) pedal. It is a side view which shows a constant speed moving mechanism part. It is a side view which shows a stepping resistance change means part. It is a top view which shows a neutral position restoring means part and stepping resistance changing means part. It is a top view which shows an accelerator interlocking mechanism part. It is a rear view which shows an accelerator interlocking mechanism part. It is a back surface enlarged view which shows an accelerator interlocking mechanism part. It is a side view which shows a brake 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. It is a flowchart of sub transmission low speed switching control. It is a flowchart of forward / backward hand operation control.

Explanation of symbols

2 traveling machine body 5 engine 29 continuously variable transmission 40 forward clutch 42 reverse clutch 116 main transmission output portion rotation sensor 118 accelerator interlock mechanism (clutch mechanism)
119 Constant speed moving mechanism (locking means)
127 Accelerator connecting lever (clutch operating tool)
128 Pedal lock lever (lock operation tool)
133 Throttle arm (accelerator means)
206 Throttle lever 210 Travel controller (control means)
220 Speed change potentiometer (speed change sensor)
221 Gear ratio setting dial (speed setting means)
230 Brake pedal (release operation tool)
232 Forward pedal 233 Reverse pedal 275 Transmission link mechanism (checking mechanism)

Claims (6)

A hydraulic continuously variable transmission that shifts power from an engine mounted on a traveling machine body, a forward pedal that changes a gear ratio of the hydraulic continuously variable transmission, and the hydraulic type based on an operation amount of the forward pedal In a work vehicle configured to shift the continuously variable transmission,
A speed change sensor for detecting the amount of depression of the forward pedal, speed setting means for selecting any one of a plurality of speed change ratio patterns capable of changing the maximum output of the hydraulic continuously variable transmission in multiple stages, and the hydraulic pressure Control means for controlling the output rotational speed of the continuously variable transmission,
A control device for a work vehicle, comprising: locking means for maintaining the forward pedal at a depressed position operated by an operator.   The lock operation tool for operating the lock means to maintain the forward pedal in the depressed position, and a release operation tool for releasing the forward pedal maintenance operation of the lock means. Control device for work vehicle. The control means stores the gear ratio pattern set by the speed setting means when the forward pedal is at the maximum depression position,
2. The output rotational speed of the hydraulic continuously variable transmission is controlled according to a speed ratio pattern set by the speed setting means in accordance with a depression amount of the forward pedal. Control device for work vehicle.   The speed setting means includes a selection position of a plurality of transmission ratio patterns obtained by changing the maximum output of the hydraulic continuously variable transmission in a multistage manner, and a neutral position where the output of the hydraulic continuously variable transmission is substantially zero. 4. The work vehicle control device according to claim 3, wherein the control device is switchable.   5. The work vehicle control device according to claim 3, further comprising: an accelerator unit that changes a rotational speed of the engine; and a clutch mechanism that connects the forward pedal to the accelerator unit. 6. The reverse pedal according to claim 1, further comprising: a reverse pedal for changing a gear ratio of the hydraulic continuously variable transmission; and a check mechanism for preventing the forward pedal and the reverse pedal from operating simultaneously. Control device for work vehicle.

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