JP6435680B2 - Work vehicle - Google Patents

Description

  The present invention relates to a work vehicle.

  A work vehicle such as an agricultural tractor that performs work on a farm field includes a transmission having a plurality of shift speeds, and travels while switching on the gear speed according to the speed when traveling on the road or when working on a farm field. For example, in the traveling speed change structure for a work vehicle described in Patent Document 1, when the transmission is shifted, the hydraulic clutch in the transmission state is depressurized to be in the disconnected state, and the hydraulic clutch corresponding to the shift command is increased to be in the transmission state. By doing so, the gear position is switched.

Japanese Patent No. 4971903

  However, since the work vehicle travels on the road or travels while performing work on the field, the driving force required for travel varies greatly depending on the travel state. For this reason, for example, when a large driving force is required, the operator requests the transmission to change the speed in a short time in order not to interrupt the driving force toward the wheels. On the other hand, when shifting is performed in a short time, a shift shock may occur due to a sudden change in the driving force transmitted to the wheel side during shifting, which may cause a deterioration in riding comfort. As described above, it has been very difficult to perform an appropriate shift according to the preference of the operator with respect to the traveling state.

  The present invention has been made in view of the above, and an object of the present invention is to provide a work vehicle capable of performing a shift according to the preference of the worker.

In order to solve the above-described problems and achieve the object, a plurality of work vehicles according to the present invention are provided corresponding to the shift stages of the transmission mechanism (65) having a plurality of shift stages, and the corresponding shift gears. Of the connection pressure when the hydraulic clutch (82, 93) for shifting and the hydraulic clutch (82, 93) are connected when the power is transmitted at the gear and released when the power at the corresponding gear is shut off. A pressure adjuster (55) that changes and adjusts the degree of pressure increase, and the connection pressure (151) of the hydraulic clutch (82, 93) corresponding to the shift stage on the shift source side when the shift stage is shifted. While the pressure is reduced, the connection pressure (152) of the hydraulic clutch (82, 93) corresponding to the shift stage on the shift destination side is increased, and the pressure adjuster (55) Corresponding to the stage Serial change adjust the degree of boost versus time of the connection pressure of the hydraulic clutch (82,93) (152), a traveling speed is a speed range during road work speed is the speed area when working in the field And a change range of the pressure increase with respect to time of the connection pressure (152) by the pressure adjuster (55) is more than the change range at the travel speed. The change range at the working speed can be changed to a higher range .

  Further, in the work vehicle, when the oil temperature of the hydraulic oil for operating the hydraulic clutch (82, 93) is equal to or lower than a preset temperature when switching the gear position for transmitting power, the pressure adjustment is performed. It is preferable that the adjustment by the tool (55) is restricted and the connection pressure (152) of the hydraulic clutch (82, 93) corresponding to the shift stage on the shift destination side is increased by a preset pressure increase.

  The work vehicle further includes a traction load detection means (58) for detecting a traction load during traveling, and when the traction load detected by the traction load detection means (58) is greater than or equal to a set value, the shift destination It is preferable that the degree of pressure increase of the connection pressure (152) of the hydraulic clutch (82, 93) corresponding to the shift stage on the side is corrected to a higher side.

  The work vehicle according to the present invention has an effect that gear shifting according to the preference of the worker can be performed.

FIG. 1 is a schematic diagram of a tractor according to an embodiment. FIG. 2 is an AA arrow view of FIG. 3 is a BB arrow view of FIG. FIG. 4 is a view taken along the line CC in FIG. FIG. 5 is a plan view of the cabin shown in FIG. FIG. 6 is a perspective view of the cabin shown in FIG. FIG. 7 is a cross-sectional view of the transmission provided in the tractor shown in FIG. FIG. 8 is a functional block diagram of each device related to the speed change in the speed change mechanism. FIG. 9 is an explanatory view of a change in clutch connection pressure during gear shifting. FIG. 10 is an explanatory diagram of changing the clutch connection pressure overlap. FIG. 11 is a front view of the switch box. FIG. 12 is a view taken along the line DD in FIG.

  Hereinafter, an embodiment of a work vehicle according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

Embodiment
FIG. 1 is a schematic diagram of a tractor according to an embodiment. FIG. 2 is an AA arrow view of FIG. 3 is a BB arrow view of FIG. FIG. 4 is a view taken along the line CC in FIG. In the following description, the front-rear direction, the left-right direction, and the up-down direction in the normal usage mode of the tractor 1 according to this embodiment will be described as the front-rear direction, the left-right direction, and the up-down direction in each part. A tractor 1 according to the present embodiment, which is a work vehicle that performs work on a farm field or the like, includes a front wheel 3 provided as a steering wheel and a rear wheel 4 provided as a drive wheel. Among these, the rear wheel 4 receives a rotational power generated by an engine (not shown) mounted in a hood 6 at the front of the airframe as a power source for the tractor 1 and a transmission 7 having a plurality of shift stages (FIG. 7). The rear wheel 4 generates a driving force by this rotational power. In addition, the transmission 7 can transmit the rotational power generated by the engine to the front wheels 3 as necessary. In this case, the front wheels 3 and the rear wheels 4 generate driving force. To do. That is, the transmission device 7 can be switched between two-wheel drive and four-wheel drive.

  Further, a fender 28 is provided at a position from the upper side of the rear wheel 4 to the front side so as to cover the rear wheel 4 and suppress scattering of the soil wound up by the rear wheel 4. Further, a connecting device 8 to which a working machine such as a rotary (not shown) can be mounted is disposed at the rear of the machine body of the tractor 1.

  Further, the tractor 1 includes a cabin 10 that enters when an operator steers the tractor 1. The cabin 10 has a roof 12 at the upper end, and further includes a plurality of pillars 15 that constitute the cabin 10 and are vertical pillars formed to extend in the vertical direction of the tractor 1. That is, the cabin 10 has a front pillar 16, a center pillar 17, and a rear pillar 18 as a plurality of pillars 15, and one of these pillars 15 is arranged on each side in the lateral direction of the body. It is installed.

  Among these, the front pillar 16 is formed downward from the vicinity of the front end of the roof 12 in the longitudinal direction of the machine body, and the rear pillar 18 is formed downward from the vicinity of the rear end of the roof 12. The center pillar 17 is disposed at a position between the front pillar 16 and the rear pillar 18 in the longitudinal direction of the machine body, and is formed downward from the roof 12. These pillars 15 are made of a metal material and are members that secure the strength of the cabin 10.

  Further, a window 22 made of transparent glass or the like is attached between the pillars 15. Accordingly, the cabin 10 can visually recognize the outside from the inside through the window 22 while forming a closed space inside. The cabin 10 has an opening / closing door 20 on the side surface, and the opening / closing door 20 is disposed between the front pillar 16 and the center pillar 17. The open / close door 20 is connected to the center pillar 17 by a hinge 21. Thus, the opening / closing door 20 is disposed so as to be rotatable around the center pillar 17 as an axis, and by this rotation, the front pillar 16 and the center pillar 17 can be opened and closed. A window 22 made of transparent glass or the like is also attached to the open / close door 20 so that the outside can be visually recognized from the inside through the window 22 even at the position where the open / close door 20 is disposed. Yes. Further, when the opening / closing door 20 is closed, the cabin 10 becomes a space in which the interior is substantially sealed.

  In addition, a side mirror 24 that is used when viewing the rear of the tractor 1 is attached to the front pillar 16 positioned in front of the opening / closing door 20. Further, a work lamp 26 that illuminates the front of the tractor 1 by emitting light is disposed at the front upper end of the window 22 disposed on the front side of the machine body. The work lamps 26 are disposed at two locations near the left and right ends near the upper end of the window 22.

  Further, a step 30 for raising and lowering the cabin 10 is disposed below the open / close door 20 on the outer surface of the cabin 10. That is, since the cabin 10 of the tractor 1 is located at a relatively high position away from the ground, the step 30 moves up and down with the foot when going into and out of the cabin 10 to enter the cabin 10. This makes it easy for workers to enter and exit. This step 30 has a column 31 extending downward from the vicinity of the lower end of the open / close door 20, and the column 31 has a plurality of feet that are used when an operator enters and exits the cabin 10. The parts 32 are connected side by side in the vertical direction of the machine body. The step 30 is configured by supporting the plurality of footrest portions 32 with the support columns 31 as described above, and the step 30 configured as described above is disposed on the left and right sides of the tractor 1.

  FIG. 5 is a plan view of the cabin shown in FIG. FIG. 6 is a perspective view of the cabin shown in FIG. In the cabin 10, there is disposed a cockpit seat 40 where an operator of the tractor 1 sits when operating the tractor 1, and the front wheel 3 which is a steering wheel is steered in front of the cockpit seat 40. A handle 41 is provided for operation. The handle 41 is disposed on the upper end side of the handle post 42 that instructs the handle 41 to be rotatable. The handle post 42 is provided with a forward / reverse switching lever 43 on the side for switching the traveling direction of the tractor 1 between forward and reverse.

  In addition, a clutch pedal 45, a brake pedal 46, and an accelerator pedal 47 are installed below the handle post 42, that is, in the vicinity of the worker's feet when the worker is sitting on the cockpit 40. Among these, the brake pedal 46 is provided with two brake pedals 46 for the left rear wheel 4 and right rear wheel 4, and these two brake pedals 46 can be connected. It has become. Therefore, when the two brake pedals 46 are operated independently, it is possible to generate a braking force independently for the left and right rear wheels 4, and the two brake pedals 46 are connected. When operated in a state, it is possible to generate a braking force for both the left and right rear wheels 4.

  Further, on the right side of the cockpit 40 in the cabin 10 in the left-right direction of the fuselage, an operation panel 50 provided with members for performing various driving operations of the tractor 1 is provided. For example, a throttle lever 51, a main shift increase / decrease switch 52, a sub shift lever 53, a sub control lever 54, a sensitivity adjustment dial 55, and a draft ratio adjustment dial 56 are disposed on the operation panel 50.

  Among these, the throttle lever 51 is mainly used when working in the field, and it is possible to adjust the engine speed similarly to the accelerator pedal 47, and further, by maintaining an arbitrary operation state, It is a lever that can maintain the engine speed at an arbitrary speed. The main shift increase / decrease switch 52 is a switch capable of switching the shift stage of the transmission 7 having a plurality of shift stages, and is a switch for switching to a high speed shift stage having a small reduction ratio. , And a switch for switching to a low speed side gear stage which is a gear stage having a large reduction ratio.

  The sub-shift lever 53 is an operation lever provided as a speed change operation tool for performing a speed change operation between a traveling speed that is a speed area when traveling on the road and a working speed that is a speed area when working on the field. Yes. The sub-shift lever 53 can be further switched between the medium speed side and the low speed side when the work speed is selected. Specifically, the sub-transmission lever 53 can switch the speed range during travel of the tractor 1 determined by the reduction ratio in the transmission 7 between high speed, medium speed, and low speed, and the high speed as the travel speed. Medium speed and low speed are assigned as work speeds. For this reason, the auxiliary speed change lever 53 can be switched to the traveling speed by switching to high speed, and can be switched to the working speed by switching to medium speed or low speed. Further, the auxiliary transmission lever 53 can be switched to neutral. When the auxiliary transmission lever 53 is switched to neutral, the power generated by the engine is not transmitted to the front wheels 3 and the rear wheels 4, and the tractor 1 The transmission 7 can be switched so as not to run.

  Further, the sub-con lever 54 is a lever that can adjust the hydraulic pressure supplied to the working machine connected to the connecting device 8, and can operate the working machine in an arbitrary operating state by adjusting the hydraulic pressure. Is possible. The sensitivity adjustment dial 55 is an adjusting means that can adjust a speed change state such as a speed when the speed change is performed by the transmission 7.

  The draft ratio adjustment dial 56 is a load adjusting means for adjusting a traction load when a traction work is performed by connecting a work machine to the connection device 8. Specifically, the tractor 1 is provided with a draft sensor 58 (see FIG. 8) that is a traction load detection means for detecting a traction load during traveling in the coupling device 8, and the coupling device 8 is a draft sensor 58. The position of the work implement in the vertical direction can be adjusted according to the detected traction load. For example, when the traction load detected by the draft sensor 58 is large, the load from the farm field received by the work implement is reduced by operating the connecting device 8 to move the position of the work implement upward. The load can be reduced.

  The draft ratio adjustment dial 56 is a member that adjusts the balance between the working position of the working machine capable of adjusting the position in the vertical direction in this way and the traction load. For example, when it is turned to the left side, the working machine The position that is the working position of the vehicle is prioritized, and the sensitivity to the traction load becomes dull. In this case, the working machine is less changed from the set position, and the movement in the vertical direction is reduced. Further, when the draft ratio adjustment dial 56 is turned to the right, priority is given to the load at the time of towing, and the sensitivity to the towing load becomes sharp. In this case, when the traction load detected by the draft sensor 58 increases, the work machine moves upward so that the traction load decreases, and when the traction load detected by the draft sensor 58 decreases, the work implement descends to the set work position. Therefore, the traction load should not be too large.

  FIG. 7 is a cross-sectional view of the transmission provided in the tractor shown in FIG. In the transmission 7, a transmission input shaft 60 that is an input shaft of the transmission 7 is connected via a main clutch 61. Further, the transmission 7 has a transmission mechanism 65 that shifts the power generated by the engine and outputs it to each part. The transmission input shaft 60 is an input shaft of the transmission mechanism 65. The transmission mechanism 65 includes a forward / reverse switching mechanism 70, a main transmission mechanism 80, a Hi-Lo transmission mechanism 90, and a sub transmission mechanism 100. The main transmission mechanism 80, the Hi-Lo transmission mechanism 90, and a sub transmission mechanism 100 The transmission mechanism 100 has a plurality of shift stages.

  Among these, the forward / reverse switching mechanism 70 can transmit the power input to the transmission input shaft 60 to the main transmission input shaft 81 that is the input shaft of the forward / reverse switching mechanism 70. In accordance with the operation of the forward / reverse switching lever 43, the rotation direction can be switched and transmitted.

  Specifically, the forward / reverse switching mechanism 70 includes a plurality of forward / reverse drive gears 72 disposed on the transmission input shaft 60, a plurality of forward / backward driven gears 73 disposed on the main transmission input shaft 81, There are two sets, one for forward and one for reverse. Among these, the forward / reverse drive gear 72 and the forward / reverse driven gear 73 are directly meshed with each other, whereas the backward / forward drive gear 72 and the forward / reverse driven gear 73 are connected via the counter gear 74. Are engaged.

  The forward / reverse driven gear 73 is rotatable integrally with the main transmission input shaft 81, while the forward / reverse drive gear 72 is disposed so as to be rotatable relative to the transmission input shaft 60. ing. Each forward / backward drive gear 72 and the transmission input shaft 60 that can rotate relative to each other can be switched between connection and release by a forward / reverse switching clutch 71. The forward / reverse switching clutch 71 is configured as a multi-plate friction clutch operated by hydraulic pressure, that is, a hydraulic clutch, and is provided corresponding to each of the forward / reverse drive gears 72 for forward movement and reverse movement. The forward / reverse switching clutch 71 is operated by hydraulic pressure generated by a hydraulic pump 146 (see FIG. 8) that generates hydraulic pressure by operating with power generated by the engine, and is switched between connection and release.

  When the forward / reverse drive gear 72 and the transmission input shaft 60 are connected to the forward / reverse switching clutch 71, the corresponding forward / reverse drive gear 72 and the transmission input shaft 60 are connected, and the forward / reverse switching clutch 71 is released. By doing so, the corresponding forward / reverse drive gear 72 and the transmission input shaft 60 are released. For this reason, when the forward / reverse switching clutch 71 corresponding to the forward / reverse drive gear 72 is connected, the power input to the transmission input shaft 60 is transferred from the forward / reverse drive gear 72 to the forward / reverse drive gear 72. The power transmitted to the meshing forward / reverse driven gear 73 is transmitted to the main transmission input shaft 81.

  Further, when the forward / reverse switching clutch 71 corresponding to the reverse drive gear 72 for reverse drive is connected, the power input to the transmission input shaft 60 is engaged in the forward / reverse drive gear 72 via the counter gear 74. The power transmitted to the driven gear 73 and transmitted to the forward / reverse driven gear 73 is transmitted to the main transmission input shaft 81. In this case, since the power is transmitted to the forward / reverse driven gear 73 via the counter gear 74, the rotation direction of the main transmission input shaft 81 rotated by the transmitted power is the forward / reverse drive gear 72 for forward movement. When the forward / reverse switching clutch 71 corresponding to is connected, the rotational direction of the main transmission input shaft 81 is opposite to the rotational direction.

  Further, the main transmission mechanism 80 can transmit the power transmitted to the main transmission input shaft 81 by the forward / reverse switching mechanism 70 to the Hi-Lo input shaft 91 that is the input shaft of the Hi-Lo transmission mechanism 90. In this case, the transmission ratio can be switched and transmitted in accordance with the operation of the main transmission increase / decrease switch 52.

  Specifically, the main transmission mechanism 80 includes a plurality of main transmission drive gears 83 disposed on the main transmission input shaft 81 and a plurality of main transmission drive gears 83 disposed on the Hi-Lo input shaft 91 and meshing with the main transmission drive gear 83. Main transmission driven gear 84. The main transmission drive gear 83 and the main transmission driven gear 84 are provided as four sets, with the main transmission drive gear 83 and the main transmission driven gear 84 meshing with each other. The gear 83 and the main transmission driven gear 84 have different gear ratios.

  The main transmission driven gear 84 is rotatable integrally with the Hi-Lo input shaft 91, while the main transmission driving gear 83 is disposed so as to be rotatable relative to the main transmission input shaft 81. Has been. The main transmission drive gear 83 and the main transmission input shaft 81 that can rotate relative to each other can be switched between connection and release by a main transmission clutch 82. The main transmission clutch 82 is configured as a multi-plate friction clutch that is operated by hydraulic pressure similarly to the forward / reverse switching clutch 71 and can be switched between connection and release, and corresponds to each of the four main transmission drive gears 83. Is provided.

  The main transmission drive gear 83 and the main transmission input shaft 81 are connected by the main transmission clutch 82, so that the corresponding main transmission driving gear 83 and the main transmission input shaft 81 are connected, and the main transmission clutch 82 is released. As a result, the corresponding main transmission drive gear 83 and the main transmission input shaft 81 are released. Therefore, when any one of the four main transmission clutches 82 is connected, the power input to the main transmission input shaft 81 is the main transmission drive gear corresponding to the connected main transmission clutch 82. The power transmitted from 83 to the main transmission driven gear 84 meshing with the main transmission drive gear 83 is transmitted to the Hi-Lo input shaft 91.

  That is, power is transmitted between the main transmission input shaft 81 and the Hi-Lo input shaft 91 by the main transmission driving gear 83 and the main transmission driven gear 84 corresponding to the connected main transmission clutch 82. Further, since the four sets of the main transmission drive gear 83 and the main transmission driven gear 84 have different transmission ratios, the main transmission clutch to be connected between the main transmission input shaft 81 and the Hi-Lo input shaft 91. By 82, power is transmitted at different gear ratios. In addition, a plurality of main transmission clutches 82 are provided corresponding to the shift stages of the main transmission mechanism 80 as described above, and are connected when power is transmitted at the corresponding shift stages, so that the power at the corresponding shift stages is transmitted. It is a hydraulic clutch for shifting that is released when disconnected.

  Further, the Hi-Lo transmission mechanism 90 can transmit the power transmitted to the Hi-Lo input shaft 91 by the main transmission mechanism 80 to the sub-transmission mechanism 100 side. According to the speed change state of the speed change mechanism 80, the gear ratio can be switched and transmitted. Specifically, the Hi-Lo transmission mechanism 90 includes two Hi-Lo drive gears 94 disposed on the Hi-Lo input shaft 91 and a Hi-Lo output shaft 92 that is an output shaft of the Hi-Lo transmission mechanism 90. And two Hi-Lo driven gears 95 disposed on the top and meshing with the Hi-Lo drive gear 94. That is, the Hi-Lo drive gear 94 and the Hi-Lo driven gear 95 are provided as two sets, with the Hi-Lo drive gear 94 and the Hi-Lo driven gear 95 meshing with each other. The Hi-Lo drive gear 94 and the Hi-Lo driven gear 95 have different gear ratios.

  The Hi-Lo drive gear 94 can rotate integrally with the Hi-Lo input shaft 91, while the Hi-Lo driven gear 95 can rotate relative to the Hi-Lo output shaft 92. It is arranged. Each Hi-Lo driven gear 95 and the Hi-Lo output shaft 92 that can rotate relative to each other can be switched between connection and release by a Hi-Lo switching clutch 93. The Hi-Lo switching clutch 93 is configured as a multi-plate friction clutch that is operated by hydraulic pressure similarly to the forward / reverse switching clutch 71 and the main transmission clutch 82 and can be switched between connection and release, and is driven by two Hi-Lo driven gears. Corresponding to each of the gears 95 is provided.

  The Hi-Lo driven gear 95 and the Hi-Lo output shaft 92 are connected to the corresponding Hi-Lo driven gear 95 and the Hi-Lo output shaft 92 when the Hi-Lo switching clutch 93 is connected. When the Lo switching clutch 93 is released, the corresponding Hi-Lo driven gear 95 and the Hi-Lo output shaft 92 are released. Therefore, when one of the two Hi-Lo switching clutches 93 is connected, the power input to the Hi-Lo input shaft 91 is connected to the connected Hi-Lo switching clutch 93. The power transmitted to the Hi-Lo driven gear 95 from the Hi-Lo drive gear 94 meshing with the Hi-Lo driven gear 95 corresponding to is transmitted to the Hi-Lo output shaft 92.

  That is, power is transmitted between the Hi-Lo input shaft 91 and the Hi-Lo output shaft 92 by the Hi-Lo driven gear 95 and the Hi-Lo drive gear 94 corresponding to the connected Hi-Lo switching clutch 93. The Further, since the two sets of Hi-Lo drive gear 94 and Hi-Lo driven gear 95 have different gear ratios, the Hi-Lo input shaft 91 and the Hi-Lo output shaft 92 are connected. The Hi-Lo switching clutch 93 transmits power at different speed ratios. Further, a plurality of Hi-Lo switching clutches 93 are provided corresponding to the shift stages of the Hi-Lo transmission mechanism 90 as described above, and are connected when power is transmitted at the corresponding shift stages, and the corresponding shift stages are provided. It is a hydraulic clutch for shifting that is released when the power is cut off.

  The auxiliary transmission mechanism 100 can transmit power from the Hi-Lo transmission mechanism 90 by an auxiliary transmission mechanism input member 101 provided on the Hi-Lo output shaft 92. The sub-transmission mechanism 100 outputs the power transmitted from the Hi-Lo transmission mechanism 90 by the sub-transmission output shaft 104 that is the output shaft of the sub-transmission mechanism 100 by switching the gear ratio according to the operation of the sub-transmission lever 53. It is possible to do.

  Specifically, the auxiliary transmission mechanism 100 includes two auxiliary transmission shifters 105 that are operated by operating the auxiliary transmission lever 53 and can switch the power transmission path from the auxiliary transmission mechanism input member 101 to the auxiliary transmission output shaft 104. ing. The auxiliary transmission mechanism input member 101 is provided at the end of the Hi-Lo output shaft 92 on the auxiliary transmission mechanism 100 side, and one of the two auxiliary transmission shifters 105 is an auxiliary transmission output shaft. 104 is arranged in the vicinity of the end portion on the Hi-Lo output shaft 92 side. The auxiliary transmission shifter 105 can be switched between connection and disconnection of the auxiliary transmission mechanism input member 101 and the auxiliary transmission output shaft 104, that is, the Hi-Lo output shaft 92 and the auxiliary transmission output shaft 104. It is possible to switch between direct connection and non-connection.

  Further, the auxiliary transmission mechanism input member 101 meshes with a first counter shaft gear 106 provided on the auxiliary transmission first counter shaft 102 of the auxiliary transmission mechanism 100. Further, the sub-transmission output shaft 104 is provided with a plurality of output shaft gears 108 that rotate relative to the sub-transmission output shaft 104, and the motive power transmitted to the sub-transmission first counter shaft 102 is partially The output shaft gear 108 can be transmitted. The auxiliary transmission shifter 105 capable of switching between direct connection and non-connection between the Hi-Lo output shaft 92 and the auxiliary transmission output shaft 104 can also connect the output shaft gear 108 and the auxiliary transmission output shaft 104. ing. In this case, the motive power from the Hi-Lo output shaft 92 is not directly transmitted from the Hi-Lo output shaft 92 to the sub-transmission output shaft 104, but via the sub-transmission first counter shaft 102. Is transmitted to.

  The subtransmission mechanism 100 has a subtransmission second countershaft 103 provided with a plurality of second countershaft gears 107, and the plurality of second countershaft gears 107 with respect to the subtransmission output shaft 104. The plurality of output shaft gears 108 that can rotate relative to each other mesh with each other. Of the two auxiliary transmission shifters 105, the other auxiliary transmission shifter 105 is connected to the output shaft gear 108 and the auxiliary transmission output shaft 104, of which the power is transmitted from the second countershaft gear 107, out of the plurality of output shaft gears 108. It is possible to switch between release and release. When the output shaft gear 108 and the auxiliary transmission output shaft 104 are connected by the auxiliary transmission shifter 105, the power from the Hi-Lo output shaft 92 is directly transferred from the Hi-Lo output shaft 92 to the auxiliary transmission output shaft 104. Instead of being transmitted, it is transmitted to the sub-transmission output shaft 104 via the sub-transmission first counter shaft 102 and the sub-transmission second counter shaft 103.

  The sub-transmission mechanism 100 switches the connection state between the sub-transmission output shaft 104 and the sub-transmission mechanism input member 101 and the output shaft gear 108 by the two sub transmission shifters 105 in this way, so that the Hi-Lo output shaft 92 is switched. To the auxiliary transmission output shaft 104 can be switched to one of three paths. Further, the auxiliary transmission shifter 105 is connected to the auxiliary transmission lever 53 by a cable, and operates according to the operation of the auxiliary transmission lever 53. Thus, the subtransmission mechanism 100 can output the power transmitted from the Hi-Lo output shaft 92 at a three-stage gear ratio according to the operation of the subtransmission lever 53.

  An auxiliary transmission output gear 109 that is an output portion of the auxiliary transmission mechanism 100 is provided at an end of the auxiliary transmission output shaft 104 opposite to the end portion on the Hi-Lo output shaft 92 side. Meshes with the differential gear for the rear wheel 4. As a result, the power transmitted to the auxiliary transmission output gear 109, that is, the power output after being shifted by the speed change mechanism 65 is transmitted to the rear wheel 4.

  The transmission 7 also has a PTO output mechanism 120 that transmits power generated by the engine to a PTO (Power take-off) shaft (not shown). This PTO output mechanism 120 can receive power from the transmission input shaft 60, and transmits power to the PTO shaft side, and a PTO clutch 121 that switches between transmission and interruption of power to the PTO shaft side. And a PTO transmission 122 that shifts at the same time.

  Further, the transmission 7 includes a front wheel side power transmission mechanism 130 that transmits power generated by the engine to the front wheel 3 side. The front wheel side power transmission mechanism 130 is a sub-shift first countershaft of the sub-transmission mechanism 100. It is possible to receive power from 102. The front wheel side power transmission mechanism 130 includes a front wheel acceleration switching mechanism 131 that switches the rotational speed when the power received from the auxiliary transmission mechanism 100 is transmitted to the front wheel 3 side.

  That is, the front wheel acceleration switching mechanism 131 is capable of switching whether to increase the speed when transmitting power to the front wheel 3 side, and switching to a state in which power is not transmitted to the front wheel 3 side. This makes it possible to switch between four-wheel drive and two-wheel drive. The front wheel side power transmission mechanism 130 can be output to the differential gear side for the front wheel 3, whereby the power output from the front wheel side power transmission mechanism 130 can be transmitted to the front wheel 3. .

  FIG. 8 is a functional block diagram of each device related to the speed change in the speed change mechanism. The tractor 1 according to the present embodiment can perform shift control and the like of the transmission 7 by electronic control. For this reason, the tractor 1 includes a controller 140 that controls each part. The controller 140 includes a processing unit having a CPU (Central Processing Unit) and the like, a storage unit such as a RAM (Random Access Memory), and an input / output unit, which are connected to each other and exchange signals with each other. It is possible. The storage unit stores a computer program for controlling the tractor 1. The controller 140 is connected to sensors and switches for acquiring information of each part and actuators such as solenoids that actually operate.

  For example, the controller 140 is connected to the forward / reverse switching lever 43, the main shift increase / decrease switch 52, the sensitivity adjustment dial 55, the draft ratio adjustment dial 56, the draft sensor 58, and the like. The controller 140 is connected to a hydraulic control device 145 that controls the hydraulic pressure generated by the hydraulic pump 146 and supplies the hydraulic pressure to each hydraulic device. For this reason, the hydraulic pressure control device 145 is connected to a hydraulic pump 146 that is a source of hydraulic pressure, a forward / reverse switching clutch 71 that operates by hydraulic pressure, a main transmission clutch 82, a Hi-Lo switching clutch 93, and the like.

  When the tractor 1 is controlled by the controller 140, for example, based on an input operation from the operator to the main shift increase / decrease switch 52 and the like, the processing unit reads the computer program into a memory incorporated in the processing unit. The operation of the tractor 1 is controlled by calculating and controlling actuators such as the hydraulic control device 145 according to the calculation result. At that time, the processing unit appropriately stores a numerical value in the middle of the calculation in the storage unit, and retrieves the stored numerical value and executes the calculation.

  The tractor 1 according to the present embodiment is configured as described above, and the operation thereof will be described below. When the tractor 1 travels, the main transmission increase / decrease switch 52 instructs the main transmission mechanism 80 and the Hi-Lo transmission mechanism 90 to shift, and the accelerator pedal 47 and the throttle lever 51 adjust the engine speed. Further, when the traveling direction is switched, the forward / reverse switching lever 43 is operated to switch between forward and reverse. Among these operations, those that detect the operation electrically are transmitted to the controller 140, and the controller 140 operates the actuators based on the transmitted information, thereby controlling the engine operation and shifting. The shift control of the device 7 is performed and the vehicle travels in an arbitrary traveling state.

  Further, the course is adjusted by operating the handle 41, and the deceleration is performed by operating the brake pedal 46. The brake pedal 46 is used not only during deceleration but also during a sudden turn. That is, when making a sharp turn, the brake pedal 46 corresponding to the inner rear wheel 4 in the turning direction is operated to generate a braking force only on the rear wheel 4 so that the front wheel 3 is steered. It is possible to make a small turn rather than turning.

  In addition, the tractor 1 can perform work on the farm field or travel on the road. However, an appropriate speed region is different between the farm field and the road. For this reason, when the tractor 1 is traveling, the auxiliary transmission lever 53 is operated in accordance with a traveling state such as a traveling place, thereby switching the auxiliary transmission mechanism 100 and switching the speed region. That is, by operating the sub-shift lever 53, the sub-shift is switched between the traveling speed and the working speed, thereby switching the speed region during traveling.

  For example, when traveling on the road, the auxiliary transmission lever 53 is moved to a high-speed selection position that is the traveling speed. In addition, since the work speed can be switched between medium speed and low speed, when working on the field, the medium speed selection position or the low speed selection position is selected according to the speed during the work. Then, the auxiliary transmission lever 53 is moved. When the auxiliary transmission lever 53 is operated, the state of the auxiliary transmission shifter 105 of the auxiliary transmission mechanism 100 is switched according to the operation position. Therefore, the auxiliary transmission mechanism 100 is switched by changing the state of the auxiliary transmission shifter 105. Can be switched between high speed, medium speed, and low speed. When the auxiliary transmission lever 53 is set to the neutral position, the auxiliary transmission shifter 105 moves to a position where the auxiliary transmission mechanism 100 does not transmit power. As a result, power is not transmitted from the speed change mechanism 65 of the transmission 7 to the front wheels 3 and the rear wheels 4, so the tractor 1 does not travel.

  The main transmission mechanism 80 and the Hi-Lo transmission mechanism 90 can be shifted regardless of the speed region switched by the sub-shift lever 53. This shift is performed by operating the main shift increase / decrease switch 52. To do. When the main transmission increase / decrease switch 52 is operated, the main transmission mechanism 80 and the Hi-Lo transmission mechanism 90 can be switched to any one of the eight shift stages. That is, the main speed change mechanism 80 has four speed stages with different speed ratios, and the Hi-Lo speed change mechanism 90 has two speed stages with different speed ratios. Eight shift stages having different gear ratios are realized.

  The main shift increase / decrease switch 52 has two switches, a switch for switching to a high speed side shift stage and a switch for switching to a low speed side shift stage. By operating these two switches, the main shift switch The gear stage of the mechanism 80 and the Hi-Lo transmission mechanism 90 are sequentially switched so that the gear ratio changes according to the operated switch.

  Specifically, among the eight shift speeds, the first to fourth speeds are such that the main speed change mechanism 80 is in the state where the speed change stage of the Hi-Lo speed change mechanism 90 is set to Lo, which is the speed change stage with the larger reduction ratio. These four shift stages correspond respectively in order from the side with the larger reduction ratio to the side with the smaller reduction ratio. Of the eight shift speeds, the fifth to eighth speeds are the four speeds of the main speed change mechanism 80 when the speed change speed of the Hi-Lo speed change mechanism 90 is set to Hi, which is the speed change speed with the smaller reduction gear ratio. The speed stages correspond respectively in order from the side with the larger reduction ratio to the side with the smaller reduction ratio. For this reason, when the gear position is switched from the fourth speed to the fifth speed, the gear position of the Hi-Lo transmission mechanism 90 is switched from Lo to Hi, and the gear position of the main transmission mechanism 80 is changed to the gear position with the smallest reduction ratio. To the gear position with the largest reduction ratio.

  As described above, when switching the gear position of the main transmission mechanism 80 or the Hi-Lo transmission mechanism 90, a control signal is transmitted from the controller 140 to the hydraulic control device 145, and the hydraulic pressure generated by the hydraulic pump 146 is changed to the controller 140. Is supplied to the main transmission clutch 82 and the Hi-Lo switching clutch 93 under the control of the control signal.

  Specifically, hydraulic pressure is supplied to the main transmission clutch 82 and the Hi-Lo switching clutch 93 corresponding to the selected gear position among the main transmission clutch 82 and the Hi-Lo switching clutch 93 that are respectively provided in plural. Connect these clutches. As a result, the desired main transmission drive gear 83 and the main transmission input shaft 81 are connected, or the Hi-Lo driven gear 95 and the Hi-Lo output shaft 92 are connected to transmit power at the desired shift stage. Enable.

  In addition, since the hydraulic pressure is not supplied to the main transmission clutch 82 and the Hi-Lo switching clutch 93 corresponding to the gears other than the gears, these clutches are released. As a result, the main transmission drive gear 83 and the main transmission input shaft 81 of these shift stages, the Hi-Lo driven gear 95, and the Hi-Lo output shaft 92 rotate relative to each other, and the transmission of power is not performed at this shift stage. No longer done.

  Similarly, when the forward / reverse switching lever 43 is switched and the traveling direction of the tractor 1 is switched, a control signal is transmitted from the controller 140 to the hydraulic control device 145 based on the state of the forward / reverse switching lever 43. As a result, the hydraulic control device 145 controls the hydraulic pressure generated by the hydraulic pump 146 based on the control signal from the controller 140 and supplies the hydraulic pressure to the forward / reverse switching clutch 71.

  Accordingly, the hydraulic pressure is supplied to the forward / reverse switching clutch 71 on the traveling direction side selected by the forward / reverse switching lever 43, and the forward / reverse switching clutch 71 is connected by this hydraulic pressure. Therefore, the forward / reverse switching mechanism 70 is connected to the forward / reverse drive gear 72 on the side to which the forward / reverse switching clutch 71 is connected and the transmission input shaft 60, and the power transmitted to the forward / reverse switching mechanism 70 is the forward direction. Alternatively, it is transmitted to the main transmission mechanism 80 side by rotation in the reverse direction.

  Switching of the power transmission path in the speed change mechanism 65 is performed as described above, but the tractor 1 according to the present embodiment can adjust the switching state by operating the sensitivity adjustment dial 55. ing. The sensitivity adjustment dial 55 is configured as a pressure adjuster that changes and adjusts the degree of increase in connection pressure when the main transmission clutch 82 and the Hi-Lo switching clutch 93 are connected, and changes and adjusts the degree of increase in connection pressure. Thus, it is possible to adjust the state of the shift operation at the time of shifting the gear position.

  In other words, the main transmission mechanism 80 and the Hi-Lo transmission mechanism 90 reduce the connection pressure of the main transmission clutch 82 and the Hi-Lo switching clutch 93 corresponding to the transmission-side shift stage, while shifting the shift stage. The main transmission clutch 82 and the Hi-Lo switching clutch 93 to be connected are switched by increasing the connection pressure of the main transmission clutch 82 and the Hi-Lo switching clutch 93 corresponding to the shift stage on the shift destination side. The sensitivity adjustment dial 55 thus connects the main transmission clutch 82 and the Hi-Lo switching clutch 93 corresponding to the shift stage on the shift destination side when switching the main transmission clutch 82 and the Hi-Lo switching clutch 93 to be connected. It is possible to change and adjust the degree of pressure increase.

  Specifically, the sensitivity adjustment dial 55 is provided so as to be rotatable within a predetermined range, and one end side of the rotation range is set as +, and the other end side is set as −. By adjusting the rotation position, the degree of increase in the connection pressure can be adjusted. The sensitivity adjustment dial 55 has + and-, when the sensitivity adjustment dial 55 is rotated clockwise, it is rotated to the + side, and when it is rotated counterclockwise, it is moved to the-side. It is provided so as to rotate, and the degree of increase in the connection pressure can be adjusted steplessly.

  FIG. 9 is an explanatory view of a change in clutch connection pressure during gear shifting. A description will be given of a change in clutch connection pressure at the time of gear shifting. When the gear position of the main transmission mechanism 80 is switched, the connection of the main gear clutch 82 corresponding to the gear gear of the gear shift source with the sensitivity adjustment dial 55 in the center. The shift source connection pressure 151 that is a pressure is reduced in a short time. On the other hand, the shift destination connection pressure 152 that is the connection pressure of the main transmission clutch 82 corresponding to the shift stage on the shift destination side is held at the specified pressure P1 for a specified time before the shift source connection pressure 151 starts to decrease, Thereafter, boosting is performed.

  The increase in the shift destination connection pressure 152 is more gradual than the decrease in the shift source connection pressure 151. Therefore, the shift destination connection pressure 152 increases after the shift source connection pressure 151 completes the decrease. The boosting is completed after the elapse of a predetermined time after the lowering of the transmission source connection pressure 151 is completed. When switching the shift speed, the main transmission clutch 82 corresponding to the shift speed of the shift destination is gently connected, so that transmission of power at the shift speed of the shift destination is also started gently.

  Further, when the sensitivity adjustment dial 55 is maximized to the − side, the shift destination connection pressure 152 is increased more gently than when the sensitivity adjustment dial 55 is in the center. In this case as well, the specified pressure P1 is held for a specified time before the transmission source connection pressure 151 starts to decrease, and then the pressure is increased. The magnitude of the specified pressure P1 and the specified time to be held at the specified pressure P1 are as follows. This is the same as when the sensitivity adjustment dial 55 is in the center. When the sensitivity adjustment dial 55 is maximized to the-side, the degree of pressure increase when the shift destination connection pressure 152 is increased after the lapse of the specified time held at the specified pressure P1 is centered on the sensitivity adjustment dial 55. It will be slower than the case.

  Further, in this case, when the sensitivity adjustment dial 55 is set to the center, the shift destination connection pressure 152 is rapidly increased after a time comparable to the time until the shift destination connection pressure 152 reaches the pressure for completing the connection. To a pressure that completes the connection. For this reason, even when the sensitivity adjustment dial 55 is maximized to the-side, the shift time itself is the same as when the sensitivity adjustment dial 55 is set to the center. The way to start becomes gradual.

  On the other hand, when the sensitivity adjustment dial 55 is maximized to the + side, the shift destination connection pressure 152 increases more rapidly than when the sensitivity adjustment dial 55 is set to the center. Also in this case, the magnitude and the prescribed time of the prescribed pressure P1 before the transmission source connection pressure 151 starts to decrease are the same as when the sensitivity adjustment dial 55 is set at the center. When the sensitivity adjustment dial 55 is maximized to the + side, the degree of pressure increase when the shift destination connection pressure 152 is increased after the lapse of the specified time held at the specified pressure P1 is centered on the sensitivity adjustment dial 55. It becomes larger than the case, and the pressure is increased rapidly.

  For this reason, the shift destination connection pressure 152 is a pressure that completes the connection in a short time compared to the case where the sensitivity adjustment dial 55 is set at the center. For this reason, when the sensitivity adjustment dial 55 is maximized to the + side, the main transmission clutch 82 corresponding to the shift destination shift stage is suddenly connected to transmit power at the shift destination shift stage. It starts abruptly in a short time.

  The shift destination connection pressure 152 at the time of the shift stage can be changed by the sensitivity adjustment dial 55 as described above. However, the shift destination connection pressure 152 is changed by the auxiliary transmission lever 53. The change range differs depending on whether the speed is switched to the traveling speed or the work side. That is, the change range of the pressure increase of the shift destination connection pressure 152 by the sensitivity adjustment dial 55 can be changed to a higher range in the change range at the working speed than in the change range at the traveling speed.

  Specifically, when the sub-shift lever 53 is switched to the traveling speed, the degree of increase in the shift destination connection pressure 152 with respect to time is the time when the sub-shift lever 53 is switched to the working speed. About 1/2 of the degree of pressure increase of the shift destination connection pressure 152. For this reason, when the sub transmission lever 53 is switched to the working speed, the speed change destination with respect to time by adjusting the sensitivity adjustment dial 55 is compared with the case where the sub transmission lever 53 is switched to the traveling speed. The change range of the degree of increase of the connection pressure 152 is increased.

  Further, when changing the gear position for transmitting power, if the temperature of the hydraulic oil for operating the main transmission clutch 82 is equal to or lower than a preset temperature, the adjustment by the sensitivity adjustment dial 55 is restricted, and the shift destination is connected. The pressure 152 is increased by a preset pressure increase. For example, when the oil temperature of the hydraulic oil that generates hydraulic pressure by the hydraulic pump 146 is 20 ° C. or lower, regardless of the operation of the sensitivity adjustment dial 55, the shift destination connection pressure 152 is increased in advance and stored in the storage unit of the controller 140. Is performed by the boosting stored in. The pressure increase set in advance in this way is set so that the shift destination connection pressure 152 becomes moderately higher than the pressure increase when the oil temperature of the hydraulic oil is higher than the set temperature.

  In this case, the temperature of the hydraulic oil is detected by a temperature sensor (not shown) provided on the hydraulic oil flow path. When the oil temperature detected by the temperature sensor is equal to or lower than the preset temperature, the controller 140 restricts the pressure increase of the gear shift destination connection pressure 152 with respect to the adjustment by the sensitivity adjustment dial 55, and the gear shift destination connection pressure 152. The hydraulic control device 145 is controlled so as to increase the pressure by a preset pressure increase.

  During the shift of the transmission 7, when the shift stage of the main transmission mechanism 80 is shifted, the degree of increase of the shift destination connection pressure 152, that is, the boost curve can be changed and adjusted by the sensitivity adjustment dial 55 as described above. When the sensitivity adjustment dial 55 is operated, the pressure increase curve of the shift destination connection pressure 152 is changed in the same manner even when the shift speed of the Hi-Lo transmission mechanism 90 is changed. In other words, the main transmission mechanism 80 and the Hi-Lo transmission mechanism 90 are switched to the first to eighth gears by combining them, and therefore, in the Hi-Lo transmission mechanism 90, The same control as that of the main transmission mechanism 80 is also performed when a shift is performed between the Lo-side gear.

  Further, since the shift between the fourth speed and the fifth speed is performed by both the main transmission mechanism 80 and the Hi-Lo transmission mechanism 90, the main transmission mechanism 80 is used when performing a shift between them. And the Hi-Lo speed change mechanism 90, the boost curve of the speed change destination connection pressure 152 is changed and adjusted by the sensitivity adjustment dial 55.

  Further, when working on the farm field, the tractor 1 pulls the work machine by connecting a work machine corresponding to the content of the work to the connecting device 8 and operates the work machine by the PTO output mechanism 120. Do. In this case, the traction load at the time of towing the work implement is detected by the draft sensor 58, and control according to the traction load, such as raising and lowering the work implement as necessary, is performed.

  Further, when shifting the gear position of the speed change mechanism 65 during work on the field while towing the work implement, if the traction load detected by the draft sensor 58 is greater than or equal to the set value, the shift destination connection pressure 152 The boosting curve is corrected to the higher boosting level. That is, when the traction load detected by the draft sensor 58 is greater than or equal to the set value, the pressure increase curve of the shift destination connection pressure 152 is rapidly increased at any adjustment position regardless of the adjustment position of the sensitivity adjustment dial 55. Correct to the side to be used. As a result, when the traction load at the time of towing the work implement is greater than or equal to the set value, transmission of power is started relatively early at the shift destination shift stage when the shift stage is shifted.

  The set value of the traction load in this case is set in advance as a traction load that needs to start transmission of power at the shift destination gear stage in advance, and is stored in the storage unit of the controller 140. The controller 140 compares the set value stored in the storage unit with the traction load detected by the draft sensor 58, and transmits a control signal corresponding to the comparison result to the hydraulic control device 145 to cause the hydraulic control device 145 to Control.

  Further, when the work implement is connected to the connecting device 8 in this way and the work is performed on the field, the balance between the work position of the work implement and the traction load is adjusted by operating the draft ratio adjustment dial 56. Work while. At that time, the controller 140 changes the pressure increase curve of the speed change destination connection pressure 152 at the time of the speed change of the speed change mechanism 65 according to the adjustment operation of the draft ratio adjustment dial 56.

  Specifically, when the draft ratio adjustment dial 56 is at a position where the working position of the work implement is important, that is, when the draft ratio adjustment dial 56 is turned to the leftmost position, The ratio adjustment dial 56 increases the degree of pressure increase of the shift destination connection pressure 152 at the time of shifting, so as to increase the connection pressure more rapidly than in other cases. In this way, the controller 140 controls the hydraulic control device 145 so that the transmission destination connection pressure 152 is rapidly increased and power transmission is started at an early stage at the transmission destination gear stage during the transmission.

  The tractor 1 according to the above embodiment can change and adjust the degree of increase of the shift destination connection pressure 152 in the main transmission clutch 82 and the Hi-Lo switching clutch 93 by the sensitivity adjustment dial 55. Thus, it is possible to adjust how the gear position is changed during the shift. When the travel load is small, such as on the road, the shift destination connection pressure 152 is gradually increased from a low pressure to change the speed smoothly. When the travel load is large, such as on the field, the shift destination connection pressure 152 is By rapidly boosting the pressure, the speed can be adjusted so that the power is cut off less. As a result, it is possible to perform a shift according to the operator's preference.

  Further, the change range of the pressure increase of the shift destination connection pressure 152 by the sensitivity adjustment dial 55 is the change range when the sub transmission lever 53 is set to the working speed than the change range when the sub transmission lever 53 is set to the traveling speed. However, since it can be changed up to a high range, it is possible to more reliably prevent the deceleration caused by the power interruption when working on the field. Further, at the traveling speed, a shift shock caused by the shift destination connection pressure 152 becoming too high can be prevented. As a result, regardless of whether the traveling speed or the working speed is selected, it is possible to perform a shift suitable for the traveling situation.

  Further, when switching the gear position, when the oil temperature of the hydraulic oil is equal to or lower than a preset temperature, the adjustment by the sensitivity adjustment dial 55 is restricted, and the shift destination connection pressure 152 is increased by a preset increase. Therefore, the shift control can be prevented from being performed inappropriately due to the low oil temperature. That is, when the oil temperature is low, the viscosity of the hydraulic oil increases. Therefore, when the main transmission clutch 82 and the Hi-Lo switching clutch 93 are operated by hydraulic pressure, the hydraulic pressure can be appropriately applied to these clutches. The clutch may not perform the desired operation. In this case, there is a possibility that a so-called double-engagement in which the shift destination clutch is connected before the shift source clutch is released may occur. For this reason, when the oil temperature of the hydraulic oil is lower than the set temperature, the adjustment by the sensitivity adjustment dial 55 is restricted, and the shift destination connection pressure 152 is gradually increased, for example, so that the shift source clutch is After being released, the shift destination clutch can be connected, and double biting can be suppressed. As a result, it is possible to suppress a shift problem that occurs due to the low oil temperature of the hydraulic oil.

  Further, the shift destination connection pressure 152 is held at the specified pressure P1 for a specified time before the shift source connection pressure 151 starts to decrease, and then is increased before the shift source connection pressure 151 is lowered. It can suppress that the connection pressure 152 becomes high. As a result, shifting can be performed with higher accuracy, and shifting can be performed without interrupting transmission of power while preventing double biting.

  Further, when the sensitivity adjustment dial 55 is adjusted to the left rotation side, the pressure increase of the gear shift destination connection pressure 152 becomes moderate, and is suitable for a low traveling load state. The pressure 152 is rapidly increased to be suitable for a high traveling load state, and can be gradually changed in a stepless manner during that time. As a result, the pressure increase curve of the shift destination connection pressure 152 can be made according to various work conditions, and the gear can be appropriately changed according to various work conditions.

  Further, when working on a farm field towing a work machine, if the traction load detected by the draft sensor 58 is greater than or equal to a set value, the pressure increase curve of the shift destination connection pressure 152 is corrected to a higher degree of pressure increase. Therefore, it is possible to prevent the power transmitted to the drive wheels from being interrupted at the time of shifting during traveling with a high traction load. In other words, when the traction load is large, the power transmitted to the drive wheel side by the transmission 7 is also large. Therefore, if this power transmission is interrupted, a shift shock may occur. For this reason, when the traction load is greater than or equal to the set value, the pressure increase curve of the shift destination connection pressure 152 is corrected to a higher side, and the power transmitted to the drive wheels is prevented from being interrupted, thereby reducing shock during shifting. it can. As a result, it is possible to ensure the riding comfort in a state where the traction load is large, and it is possible to suppress a decrease in speed due to the interruption of power transmission.

  Further, when the draft ratio adjustment dial 56 is in the position position, the shift destination connection pressure 152 is rapidly increased at the time of shifting the gear position. It can suppress that the power to transmit interrupts. In other words, when the draft ratio adjustment dial 56 is in the position position, the work implement is not moved up or down in accordance with the traction load, or even if the traction load is large, the work implement remains in the same position in order to reduce the degree of elevation. Work will continue. For this reason, even if the traction load is large, the work is continued as it is, and if the time required for the shift is long, a shock may occur at the time of the shift because the power is interrupted. Therefore, when the draft ratio adjustment dial 56 is in the position position, the power transmitted to the drive wheels can be prevented from being interrupted during the shift by rapidly increasing the shift destination connection pressure 152, and the shock during the shift can be suppressed. Can be reduced. As a result, it is possible to secure a ride comfort when performing work with priority on the position of the work implement, and it is possible to suppress a decrease in speed due to interruption of power transmission.

[Modification]
In the tractor 1 according to the embodiment, the shift destination connection pressure 152 is held at the specified pressure P1 for a specified time before the shift source connection pressure 151 starts to decrease during the shift of the shift speed, and then is increased. However, the speed change destination connection pressure 152 may be increased after the speed change source connection pressure 151 is reliably reduced. For example, when the shift source connection pressure 151 is set to a specified pressure P2 that indicates that the shift destination connection pressure 152 may be increased at the time of shifting, and the shift source connection pressure 151 becomes equal to or lower than the specified pressure P2, The shift destination connection pressure 152 held at the specified pressure P1 may be increased. At the time of gear shifting, the gear shift source connection pressure 151 and the gear shift destination connection pressure 152 are both high by increasing the gear shift destination connection pressure 152 after the gear shift source connection pressure 151 becomes equal to or lower than the specified pressure P2. It is possible to prevent the pressure from becoming low or the pressure from being lowered. Thereby, it is possible to prevent double-engagement of the gear stage during the shift, and it is possible to prevent the time during which no power is transmitted by the transmission mechanism 65 from being increased, and it is possible to realize a shift with little variation in the shift operation. As a result, the shift feeling can be stabilized.

  Further, in the tractor 1 according to the embodiment, when the traction load detected by the draft sensor 58 is equal to or higher than the set value, the boost curve of the shift destination connection pressure 152 is corrected to the higher side. The boosting curve may be automatically changed according to the value of the traction load detected by the draft sensor 58. That is, the boost curve of the shift destination connection pressure 152 is not corrected according to the magnitude of the traction load, but is corrected according to whether or not the traction load is greater than or equal to the set value. You may make it change suitably. For example, as the traction load detected by the draft sensor 58 increases, the degree of increase in the shift destination connection pressure 152 may be increased to increase the pressure rapidly. Thereby, it is possible to perform gear shifting at an appropriate timing according to the traction load, and to realize an optimum gear shifting feeling.

  Moreover, although the connection apparatus 8 can raise / lower the working machine to connect, you may change the pressure | voltage rise curve of the transmission destination connection pressure 152 according to raising / lowering of this working machine. For example, since the traction load is small when the work implement is raised, in such a case, the shift destination connection pressure 152 is gradually increased regardless of the state of the draft ratio adjustment dial 56. Also good. As a result, when the traction load is small, it is possible to suppress sudden engagement of the clutch at the shift destination gear stage, and it is possible to improve the feeling during shift more reliably.

  Further, in the tractor 1 according to the embodiment, when the sensitivity adjustment dial 55 is maximum on the + side, the shift destination connection pressure 152 has a boost curve that rapidly increases, but the sensitivity adjustment dial 55 is maximum on the + side. In this case, the connection may be equivalent to the ON / OFF valve at the total pressure command value. As a result, the shift destination connection pressure 152 can be increased in a shorter time, so that the power cut-off can be reduced and the shift shock can be more reliably reduced.

  Further, when correcting the shift destination connection pressure 152 in accordance with the operation of the sensitivity adjustment dial 55, in addition to the oil temperature of the hydraulic fluid, the traction load, the operation of the auxiliary transmission lever 53 and the draft ratio adjustment dial 56, etc. May be based on. For example, a sensor for detecting the inclination of the tractor 1 in the front-rear direction, that is, pitching, is provided, and the shift destination connection pressure 152 corresponding to the operation of the sensitivity adjustment dial 55 depending on whether the tractor 1 is climbing up or down. You may correct | amend. Since the traveling load differs depending on whether the tractor 1 travels uphill or downhill, the shift destination connection pressure 152 is corrected by this amount, so that the shift according to the preference of the operator can be performed more accurately. It can be carried out.

  In the tractor 1 according to the embodiment, the speed adjustment curve 55 of the shift destination connection pressure 152 is adjusted by operating the sensitivity adjustment dial 55 to realize the shift according to the operator's preference. The state may be realized by other than adjusting the pressure increase curve of the shift destination connection pressure 152. FIG. 10 is an explanatory diagram of changing the clutch connection pressure overlap. For example, as shown in FIG. 10, the shift destination connection pressure 152 decreases the overlap with the shift source connection pressure 151 as the sensitivity adjustment dial 55 is set to the − side, and the sensitivity adjustment dial 55 is set to the + side. Accordingly, the overlap with the transmission source connection pressure 151 may be increased.

  In other words, when the shift of the main transmission mechanism 80 is described, when the overlap of the shift destination connection pressure 152 with respect to the shift source connection pressure 151 is reduced, the main shift clutch 82 corresponding to the shift source shift stage is released. After the completion, the connection of the main transmission clutch 82 corresponding to the shift destination gear is started. As a result, the transmission destination gear stage begins to transmit power after power transmission is substantially not performed at the transmission source gear stage.

  On the other hand, when the overlap of the shift destination connection pressure 152 with respect to the shift source connection pressure 151 is increased, before the disengagement of the main transmission clutch 82 corresponding to the shift source shift stage is completed, the shift destination shift stage is completed. The connection of the main transmission clutch 82 corresponding to is started. As a result, the transmission speed of the shift destination starts little by little before the transmission of power at the transmission speed shift stage becomes completely impossible, and the transmission of power at the transmission speed of the transmission speed starts. The power transmission path is switched to the shift speed of the shift destination in a short time after the operation is stopped.

  As described above, when the overlap is changed, the time for switching the power transmission path changes. Therefore, when the desired shift state is realized by operating the sensitivity adjustment dial 55, the sensitivity adjustment dial 55 is changed. The overlap may be adjusted according to the operation.

  Specifically, when the sensitivity adjustment dial 55 is maximized to the-side, the shift destination connection pressure 152 has less overlap with the shift source connection pressure 151 than when the sensitivity adjustment dial 55 is in the center. To do. That is, the timing at which the shift destination connection pressure 152 is increased is delayed with respect to the decrease in the shift source connection pressure 151. As a result, after the transmission of power at the shift speed of the shift source is almost completed, transmission of power is started at the shift speed of the shift destination.

  On the other hand, when the sensitivity adjustment dial 55 is maximized to the + side, the shift destination connection pressure 152 has a larger overlap with the shift source connection pressure 151 than when the sensitivity adjustment dial 55 is in the center. . That is, the speed change destination connection pressure 152 is raised earlier than the speed change source connection pressure 151. As a result, before the transmission of power at the shift source gear stage is completed, transmission of power starts at the shift destination shift stage, and the power transmission path is switched to the shift destination shift stage in a short time.

  When changing the gear position, not only the main transmission mechanism 80 but also the Hi-Lo transmission mechanism 90 is changed so that the gear position is changed. Therefore, when the sensitivity adjustment dial 55 is operated, only the main transmission clutch 82 is operated. Not only that, the connection pressure overlap also changes in the Hi-Lo switching clutch 93.

  As described above, by operating the sensitivity adjustment dial 55 to change and adjust the overlap of the connection pressures in the main transmission clutch 82 and the Hi-Lo switching clutch 93, the gear position at the time of shifting between the road and the field is changed. Can be adjusted. As a result, when the driving load is small, such as on the road, the connection pressure overlap is increased and the gear is gently shifted to change smoothly.When the driving load is large, such as driving on the field, By changing the connection pressure in a short time while reducing the overlap of the connection pressure, it is possible to adjust the speed so as to reduce the interruption of power. As a result, it is possible to perform a shift according to the operator's preference.

  In addition, when it is possible to change the overlap of the clutch connection pressure at the time of shifting, the overlap is reduced to 0 regardless of the setting state of the sensitivity adjustment dial 55 when the auxiliary transmission lever 53 is switched to the traveling speed. It may be. That is, the shift destination connection pressure 152 may be increased after the shift source connection pressure 151 is completely reduced. As a result, it is possible to reduce a shift shock during traveling on the road with a small traveling load.

  Even when the overlap of the clutch connection pressure at the time of shifting can be changed, the overlap may be changed according to the oil temperature of the hydraulic oil. For example, when the oil temperature is lower than the set temperature, the sensitivity The overlap may be zero regardless of the state of the adjustment dial 55. Thereby, it is possible to suppress the occurrence of double engagement due to the fact that the clutch does not perform the desired operation due to the high viscosity of the hydraulic oil, and it occurs due to the low oil temperature of the hydraulic oil. It is possible to suppress the problem of shifting. In addition, in this way, when changing the overlap according to the oil temperature of the hydraulic oil, the overlap control is not switched according to the oil temperature of the hydraulic oil, instead of switching the control for the overlap above and below the set temperature. You may make it correct | amend the quantity of this in steps. As a result, it is possible to prevent the shift feeling from changing suddenly due to the oil temperature of the hydraulic oil changing across the set temperature.

  Even when the overlap of the clutch connection pressure at the time of shifting can be changed, the overlap may be changed according to the lifting and lowering of the work implement. For example, when the work implement is raised, the sensitivity Regardless of the state of the adjustment dial 55, the overlap may be reduced. Thereby, when the traction load is small, it is possible to suppress a shock caused by switching the gear position in a short time, and it is possible to improve the feeling at the time of shifting more reliably.

  Even when the overlap of the clutch connection pressure at the time of shifting can be changed, the overlap may be changed between when the draft ratio adjustment dial 56 is in the position position and when it is not, for example, When the draft ratio adjustment dial 56 is at the position, the overlap may be increased. As a result, when the draft ratio adjustment dial 56, which may increase the traction load, is in the position position, the time for changing the gear position is shortened and the power is hardly interrupted, so that the shock at the time of shifting can be reduced. Therefore, it is possible to secure a ride comfort when performing work with priority on the position of the work implement, and it is possible to suppress a decrease in speed due to interruption of power transmission.

  Even when the overlap of the clutch connection pressure at the time of shifting can be changed, the overlap may be changed according to the traction load. For example, the traction load detected by the draft sensor 58 is greater than or equal to a set value. In some cases, the overlap may be increased. Thereby, it can suppress that the power transmitted to a drive wheel at the time of a gear shift is interrupted, and can reduce the shock at the time of a gear shift. As a result, it is possible to ensure the riding comfort in a state where the traction load is large, and it is possible to suppress a decrease in speed due to the interruption of power transmission.

  Further, the clutch connection pressure at the time of shifting may be changed in accordance with the sensitivity adjustment dial 55 for both the boost curve and overlap of the shift destination connection pressure 152. By changing both the boost curve and the overlap, the method for adjusting the shift state increases, so the range of change can be increased, and the shift according to the preference of the operator can be performed more reliably. Can do.

  In the tractor 1 according to the embodiment, the sensitivity adjustment dial 55 is disposed on the operation panel 50 provided on the side of the cockpit 40. However, the sensitivity adjustment dial 55 is disposed in a place other than this. It may be. FIG. 11 is a front view of the switch box. FIG. 12 is a view taken along the line DD in FIG. For example, the sensitivity adjustment dial 55 may be disposed on the switch box 160. The switch box 160 includes a switch panel 161 on which various switches and dials are disposed, and includes a lid 162 that can be opened and closed. The switch box 160 can operate switches and dials on the switch panel 161 by opening the lid 162. When the lid 162 is closed, the lid 162 covers the switch panel 161. As a result, the switches and dials cannot be operated.

  The sensitivity adjustment dial 55 may be disposed on the switch panel 161 of the switch box 160 configured as described above. As described above, by disposing in the switch box 160 having the lid 162, it is possible to prevent the operator from touching the sensitivity adjustment dial 55 unexpectedly, and the transmission destination connection pressure 152 is changed unintentionally. It can be suppressed.

  Further, the sensitivity adjustment dial 55 may not be placed in the switch box 160 but may be disposed at a position where it is difficult to touch the operator while sitting on the cockpit 40, such as right rear of the cockpit 40. Thus, even if the sensitivity adjustment dial 55 is disposed at a position where it is difficult for the operator to touch, the operator can be prevented from touching the sensitivity adjustment dial 55 unexpectedly, and the shift destination connection pressure can be prevented unintentionally. It can suppress that 152 is changed.

  Further, in the tractor 1 according to the embodiment, the sub-transmission mechanism 100 is configured to perform a shift by operating the sub-transmission shifter 105, but similarly to the main transmission mechanism 80 and the Hi-Lo transmission mechanism 90. The auxiliary transmission mechanism 100 may also be configured to be able to change gears by a hydraulic clutch. In this case, the speed of the subtransmission mechanism 100 may be changed and adjusted by the sensitivity adjustment dial 55 for the degree of increase in the connection pressure of the hydraulic clutch and the overlap corresponding to the shift speed of the shift destination.

1 Tractor (work vehicle)
3 Front wheel 4 Rear wheel 7 Transmission device 8 Coupling device 10 Cabin 20 Open / close door 30 Step 40 Pilot seat 41 Handle 42 Handle post 43 Forward / reverse switching lever 50 Operation panel 51 Throttle lever 52 Main gear change switch 53 Sub gear lever )
55 Sensitivity adjustment dial (pressure adjuster)
56 Draft ratio adjustment dial 58 Draft sensor (traction load detection means)
DESCRIPTION OF SYMBOLS 60 Transmission input shaft 65 Transmission mechanism 70 Forward / reverse switching mechanism 71 Forward / reverse switching clutch 72 Forward / reverse drive gear 73 Forward / reverse driven gear 74 Counter gear 80 Main transmission mechanism 81 Main transmission input shaft 82 Main transmission clutch (hydraulic clutch)
83 Main transmission drive gear 84 Main transmission driven gear 90 Hi-Lo transmission mechanism 91 Hi-Lo input shaft 92 Hi-Lo output shaft 93 Hi-Lo switching clutch (hydraulic clutch)
94 Hi-Lo drive gear 95 Hi-Lo driven gear 100 Sub transmission mechanism 120 PTO output mechanism 130 Front wheel side power transmission mechanism 140 Controller 145 Hydraulic control device 146 Hydraulic pump 151 Transmission source connection pressure 152 Shift destination connection pressure 160 Switch box

Claims (3)

A plurality of speed change mechanisms having a plurality of speed stages are provided corresponding to the speed stages, and are connected when power is transmitted at the corresponding speed stages and released when power is cut off at the corresponding speed stages. Hydraulic clutch,
A pressure adjuster that changes and adjusts the degree of increase in the connection pressure when the hydraulic clutch is connected;
With
At the time of shifting at the shift speed, the connection pressure of the hydraulic clutch corresponding to the shift speed on the shift source side is decreased while the connection pressure of the hydraulic clutch corresponding to the shift speed on the shift destination side is increased. ,
The pressure adjuster changes and adjusts the degree of pressure increase with respect to time of the connection pressure of the hydraulic clutch corresponding to the shift stage on the shift destination side ,
A shift operation tool that performs a shift operation between a traveling speed that is a speed region when traveling on the road and a working speed that is a speed region when working on the field,
The change range of the pressure increase with respect to the time of the connection pressure by the pressure adjuster can be changed to a higher range in the change range at the working speed than the change range at the traveling speed. Work vehicle. When changing the gear position for transmitting power, if the oil temperature of the hydraulic oil that operates the hydraulic clutch is equal to or lower than a preset temperature, adjustment by the pressure adjuster is restricted, and 2. The work vehicle according to claim 1, wherein the connection pressure of the hydraulic clutch corresponding to a gear stage is increased by a preset pressure increase. A traction load detection means for detecting a traction load during traveling is provided,
2. The degree of increase in the connection pressure of the hydraulic clutch corresponding to the shift stage on the shift destination side is corrected to a higher side when the traction load detected by the traction load detection means is greater than or equal to a set value. Or the working vehicle of 2 .

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