JP5516129B2 - Work vehicle - Google Patents

Description

  The present invention relates to a work vehicle including a speed change transmission device capable of selecting multiple speed change positions.

  A work vehicle equipped with a gear transmission capable of selecting multiple gear positions can select the required vehicle speed by manual shifting by operating the speed-increasing switch and the deceleration switch for sequentially switching the gear-shifting position. It is possible to adjust a wide range of gear shifts, and like the work vehicle described in Patent Document 1, not only a gear shift by manual operation but also a gear shift by accelerator pedal operation are known.

  The accelerator shift system is configured by computer control that selects a shift position corresponding to an engine load from a predetermined start shift position that is a shift position suitable for starting on a road or the like, according to an accelerator pedal depression operation, and applies accelerator shift. When the vehicle is stopped, the accelerator gear change switch is turned on to start the aircraft without causing a sense of incongruity, and the accelerator pedal operation thereafter allows the speed to be adjusted according to the driving situation on the road.

Japanese Patent No. 3891171

  However, the accelerator shifting method requires that the accelerator shift switch be turned on while the vehicle is stopped. Therefore, there is a problem that the vehicle cannot be switched to the accelerator shifting unless the vehicle is stopped once during traveling.

  It is an object of the present invention to smoothly shift to an accelerator shift without incurring a sudden shift even when the accelerator shift control is performed to adjust the vehicle speed according to the depression operation of an accelerator pedal following a predetermined start. An object of the present invention is to provide a working vehicle capable of

The invention according to claim 1 corresponds to a transmission device that adjusts the traveling speed by a multi-stage shift position, a manual shift system that selects the shift position by a manual operation member, and depression of an accelerator pedal from a predetermined start shift position. In a work vehicle having an accelerator shift method for switching the speed increase to the selected shift position and a shift method switching member for switching these shift methods, the gear shift transmission at that time is switched to the accelerator shift method by the shift method switching member while the vehicle is running. The accelerator shift system is applied with the shift position of the device as the new start shift position, and a maximum speed restriction switch that can be switched from the full speed range shift mode to the maximum speed restriction mode by turning on the switch is provided. The speed changeable speed is limited by switching to the maximum speed restriction mode .

If the shift mode switching member is used to switch to the accelerator shift mode while the vehicle is running, the shift position at that time becomes a new start shift position, so that the shift to the accelerator shift can be made without a shift shock. Correspondingly, shift adjustment is possible. Further, the speed changeable speed is limited by switching to the highest speed restriction mode by turning on the highest speed restriction switch.

According to a second aspect of the present invention, in the configuration according to the first aspect, the maximum speed restriction switch is configured to operate in a maximum speed restriction mode when the speed change mode switching member is turned on and the auxiliary speed change lever is at a high speed. The high speed is set up to the regulated speed set in the memory, and the meter panel also displays a range up to the regulated speed of the main shift.

According to a third aspect of the present invention, in the configuration of the second aspect, the switching between the full speed range shift mode and the maximum speed restriction mode is configured such that the mode is switched by operating the maximum speed restriction switch only at the time of a stop. It is characterized by.

According to a fourth aspect of the present invention, in the configuration of the third aspect , the end of the accelerator shift by switching the sub-shift position of the sub-transmission device provided in the transmission or the operation of the shift system switching member, or the end thereof The new start shift position is returned to the initial start shift position when the shift position due to acceleration of the accelerator shift until the time reaches the initial start shift position.

  When the accelerator gear shift ends or when the shift position by the shift between them reaches the initial start shift position, the start vehicle shift position is returned to the original and the next normal start running is possible. In other words, in the case where the vehicle travels at a lower speed than the original start shift position, the changed start shift position is maintained.

When the work vehicle according to the first aspect of the present invention is switched to the accelerator transmission system by the transmission system switching member while the vehicle is traveling, the shift position at that time is newly set to the start transmission position. Thus, the shift can be adjusted in correspondence with the subsequent accelerator pedal operation. Therefore, it is possible to smoothly shift to the vehicle speed adjustment by the accelerator shifting method without requiring the conventional complicated operation of switching to the accelerator shifting after stopping and without causing a shift shock at the time of switching.
In addition, by limiting the speed that can be changed by turning the highest speed restriction switch on, even if the accelerator depressing becomes unstable due to running on uneven roads such as saddles with large shaking of the aircraft, the fast vehicle speed range Therefore, it is possible to travel safely with the accelerator shifting function turned on without requiring a cumbersome operation of the shifting method switching member for turning off the accelerator shifting each time.

The work vehicle of the invention according to claim 2 can regulate the maximum speed in addition to the effect of claim 1.

In addition to the effect of claim 2, the work vehicle of the invention according to claim 3 switches the maximum speed restriction mode to the maximum speed restriction mode during traveling at a vehicle speed exceeding the restriction speed of the maximum speed restriction mode. It is possible to avoid danger by suddenly slowing down.

In addition to the effect of claim 3 , the work vehicle of the invention according to claim 4 is based on the start shift position at the end of the accelerator shift or when the shift position by the shift between them reaches the initial start shift position. When the vehicle is returned to the vehicle, the next normal start is possible, and in other cases, i.e., when the vehicle is traveling at a lower speed than the original start shift position, the changed start shift position is maintained. Even if the vehicle stops temporarily, the same running state is reproduced, so it is possible to prevent a sudden start after stopping in a low speed region that is less than the normal starting vehicle speed, and to ensure stable accelerator-shifting running. .

Side view of tractor Tractor cabin interior perspective view Front view of the tractor switch box Front view of meter panel 24-speed shift pattern diagram Shift pattern diagram of 32-speed Transmission diagram of mission case with constant PTO shaft rotation including reverse rotation Transmission diagram of a mission case of the type that PTO shaft rotation corresponds to the vehicle speed Transmission diagram of the main part of the mission case with 3-speed sub-shift Control block diagram Block diagram of transmission system Perspective view of the main part of the console Perspective view of essential parts of the four-stage configuration (a) and the three-stage configuration (b) of the auxiliary transmission lever A sketch of the switch panel of the electrohydraulic operation box Shift control flow chart Flow chart for checking flag when stopping Flow chart of check flag reset at stop Flow chart of stop control Flow chart of maximum speed regulation control Flow chart of regulation speed change processing Display example of main shift in full speed range shift mode (a) and maximum speed restriction mode (b)

Hereinafter, description will be given based on the drawings.
FIG. 1 is an overall side view of a tractor shown as an example of a work vehicle according to the present invention. The power of a common rail type diesel engine 2 mounted in a bonnet 1 at the front of the body is used to transmit PTO shaft rotation constant mission case 3A (first stage). 1 transmission case) or a PTO shaft rotating vehicle speed compatible transmission case 3B (second transmission case), and the gear is appropriately shifted and transmitted to the front wheel shaft 4 and the rear wheel shaft 5, and both the front wheel 6 and the rear wheel 7 or the rear Only the wheel 7 is driven. An operator sitting in a seat 10 provided in a cabin 26 on the airframe travels while operating the steering handle 8 standing at the center to steer the front wheels 6. A work machine such as a rotary tiller is mounted on the hitch 9 protruding rearward of the machine body, and the work machine mounted on the hitch 9 is driven by the PTO shaft 11 protruding rearward from the transmission case 3A (3B). .

  As shown in FIGS. 2 and 3, a steering handle 8 is erected on the front side of the cockpit 10 inside the cabin 26, and a forward / reverse lever 169 is provided on the lower right side thereof. On the left side of the cockpit 10, a parking brake lever 170 and a first PTO transmission lever 171 and a second PTO transmission lever 172 for shifting the PTO shaft that outputs power to the work machine are arranged.

  The lower floor surface of the steering handle 8 is provided with a left brake pedal 216 and a right brake pedal 217 for braking the left and right front and rear wheels 6 and 7, respectively, and an entire brake pedal 218 for braking all the wheels at once. An accelerator pedal 173 that controls the rotation of the engine 2 is provided. This accelerator pedal 173 is used to adjust the traveling speed.

  Note that when the left brake pedal 216 and the right brake pedal 217 are depressed simultaneously, the brake is braked, and the gear stage of the main transmission is shifted to the low speed side to cause the engine brake to act. Further, when the left brake pedal 216 and the right brake pedal 217 are depressed more than a predetermined limit depression amount, the rotational speed of the engine 2 is decreased. At this time, if the left brake pedal 216 and the right brake pedal 217 are depressed and restored, the rotation of the engine 2 is restored, and the power transmission to the front and rear wheels 6 and 7 and the power transmission to the PTO output shaft are restored. After that, release the brake.

  A front panel 174 on which a meter panel 136 (FIG. 4) for displaying a traveling speed and a gear position and an operation panel (not shown) for displaying a use status of a work machine are disposed on the front side of the steering handle 8.

  When a throttle lever 175 is erected on the right side of the cockpit 10 and is tilted forward from the foremost idling position, the rotation of the engine 2 increases. The throttle lever 175 is also used when setting the engine speed during operation. 176 is a seesaw-type first engine rotation storage switch. When the switch is tilted upward, the first stored rotational speed is obtained. When the switch is tilted downward, the second stored rotational speed is obtained. When the finger is released, the position returns to the neutral position.

  177 is a seesaw-type second engine rotation memory switch. When the switch is tilted upward, the rotational speed increases. When the switch is tilted downward, the rotational speed decreases, and the rotational speed when the switch is released is stored. The rotation speed of the engine 2 is set by turning the first engine rotation storage switch 176 upward or downward, and tilting the second engine rotation storage switch 177 upward or downward to increase or decrease the rotational speed. When 176 and 177 are released, the rotation speed at that time is stored as the set rotation speed of the first engine rotation storage switch 176.

  Next to the throttle lever 175, an auxiliary transmission lever 178 is erected. The sub-shift lever 178 has three speeds of low speed, medium speed and high speed, or four speed positions of ultra low speed, low speed, medium speed and high speed. At each stage, a sub-transmission D (mechanical four-stage transmission clutch D) in a mission case 3A (3B), which will be described later, is shifted to a very low speed, a low speed, a medium speed, and a high speed, and the main transmission B, C (hydraulic pressure 4) The step shifting gear clutch device B and the high / low hydraulic pressure switching clutch C) can shift to eight steps.

  Although not shown, the auxiliary transmission lever 178 is provided with an accelerator transmission setting switch 160 for changing the accelerator transmission pattern to a low transmission area H1 and a high transmission area H2, and an auxiliary transmission lever operation position sensor 147. Yes. The accelerator shift setting switch 160 is also used as a synchronization clutch button 162 for switching the sub-shift position to ultra low speed, low speed, medium speed, and high speed, and at the road running position, the clutch button 162 is used to change the low speed range H1 and the high shift speed. You may enable it to change to the area H2.

  FIG. 5 shows the shift pattern of the sub-shift three-speed shift, and FIG. 6 shows the shift pattern of the sub-shift four-speed shift. When the sub-shift lever 178 is on the road, the main transmissions B and C (four-speed transmission clutch unit B and high-low hydraulic switching clutch C) are automatically shifted according to the degree of depression of the accelerator pedal 173. Two types of shift patterns are prepared: a low shift range H1 and a high shift range H2.

  The shift pattern of the low shift range H1 and the high shift range H2 is changed by the accelerator shift setting switch 160. Once the shift pattern is set, after the accelerator control is canceled or the engine is stopped, and the accelerator control is performed again, the previous setting is performed. A shift pattern is obtained.

  The main transmissions B and C are constituted by a four-speed shift of the transmission clutch device B having a hydraulic four-speed shift and a two-speed shift of the high / low hydraulic pressure switching clutch C, and the total number of shift stages is eight. The vehicle speed according to the shift speed is a total of 32 shift speeds in combination with the super-low speed, low speed, medium speed, and high speed sub-shift 4-speed shift of the sub-shift lever 178.

179 and 180 are sub-control levers for taking out external hydraulic pressure, and are used when hydraulic oil is supplied to a hydraulic cylinder or the like of the work machine. Reference numerals 181 and 182 denote mounting grooves for the spare hydraulic sub-control lever. 183 is a draft ratio adjustment die Ya Le, becomes position side when turning to the left, shallower lift variation is reduced tilling depth of the working machine to a load, and a draft side turning back to the right, The amount of change in the lifting / lowering of the work implement with respect to the load increases, increasing the tillage depth.

184 is adjusted die Ya Le raised, increasing the height of the three-point linkage and the work machine turning to the left is reduced.
When raise highest by the working machine or when striking the tractor body, if good operating efficiency for those work continues to not raise so high, is adjusted in this raised adjust die ya le 184. 185 is a tilt adjustment die ya le, turn to the left and the working machine is turned upward to the right, turn to the right and the working machine is right down to the reverse.

  186 is a 4WD changeover switch, which has a traveling loader, front wheel accelerated turning, and 2WD turn positions. The traveling loader is usually 2WD traveling, and automatically switches to 4WD when becoming muddy, steep hills, or uneven roads. Even if the switch is made, the brake is applied, or the vehicle is stopped during operation, the state becomes 4WD. 2WD is a rear-wheel two-wheel drive, and 4WD is a front-and-rear four-wheel drive. In the front wheel acceleration turning, when turning at 4WD, the speed of the front wheel is increased to enable quick turning. In the 2WD turn, the front wheel drive is cut off in the 4WD turn and the rear wheel is turned on one side of the brake, allowing quick and smooth turn in a hard field.

  Reference numeral 187 denotes a horizontal cylinder raising / lowering switch, which can move the horizontal cylinder of the three-point link of the work implement, and is used for attaching / detaching the work implement. Reference numeral 188 denotes a PTO switch. When the switch is pushed and turned to the right, the PTO clutch is engaged. 189 is a PTO automatic switch. When turned to the left, it becomes manual, and when the PTO clutch is engaged, the PTO shaft always rotates. When turned to the right, it automatically turns and stops rotating when the travel clutch is stepped on or the three-point link is raised. This PTO automatic switch 189 is mainly used during paddy field work.

Reference numeral 190 denotes a diff lock switch. When the diff lock switch is pressed once outward, the diff lock state is set. It cannot be pushed inward, but switches each time it is pushed outward.
Reference numeral 191 denotes a work implement raising / lowering lever, which is lowered on the front side and raised on the rear side. 192 is a working machine lifting switch, raised to the uppermost position set by the raising adjusting die Ya le 184 by pressing once the rear, is lowered to a position set by the working machine lifting lever 191 and pressed once front .
Reference numeral 193 denotes a travel shift increase switch, and 194 a travel shift decrease switch, which is a switch for setting the speed range of the low shift range H1 and the high shift range H2 by the accelerator pedal 173. Each time the travel shift increase switch 193 is pressed once, the start shift stage is shifted up, and every time the travel shift decrease switch 194 is pressed once, the start shift stage is shifted down. It should be noted that a switch for setting the maximum shift speeds of the low shift range H1 and the high shift range H2 may be provided to change the maximum shift speed. Reference numeral 196 denotes a switch box. When the lid is opened, various adjustment switches shown in FIG. 3 are arranged.

In the switch box 196 in FIG. 3, reference numeral 197 denotes a work machine ascent / descent monitor lamp which is lit and displayed when the work machine is raised and lowered. 198 in AT shift sensitivity die Ya Le, when the automatic transmission by pressing the AT shift work switch 202, a die Ya le to change the sensitivity to increasing decelerating the vehicle speed.

199 is a descending speed die Ya Le adjusting the descending speed of the working machine, since the working machine is lowered faster by turning to the right used when the lighter working machine, contrary to the turn to the left and the working machine is lowered slowly So use it for heavy working machines.
200 is a travel brake adjusting die Ya Le, to adjust the depth of the pivot brake which acts on the time input of the automatic brake ON OFF switch 208.

  The AT shift road switch 201 automatically shifts the main transmission devices B and C (four-speed transmission clutch device B and high / low hydraulic pressure switching clutch C) by the accelerator pedal 173 when the auxiliary transmission lever 178 is at a high speed position, and performs AT shift work. The switch 202 automatically shifts the main transmission with the accelerator pedal 173 during work travel, that is, when the sub-transmission lever 178 is not at the high speed position, and when turned on, the main transmission is switched to the previous time according to the transmission position of the sub-transmission lever 178. When the gear is automatically shifted to the longest used gear and turned off, the gear shifts to the main gear that is arbitrarily set according to the gear shift position of the sub-shift lever 178.

  203 is a connection sensitivity shift switch for the main shift, which changes the connection feeling when the main shift is shifted. When the switch is turned on, the monitor is turned on and a gentle shift is performed. When the switch is turned off, the monitor is turned off and suddenly connected. If the connection sensitivity shift switch 203 is turned off and a traction system such as a plow is operated, the shift connection time of the main transmission is shortened, and the operation can be performed lightly.

  Reference numeral 204 is a connection sensitivity PTO switch, which has a rotary, pasture 1 and pasture 2, and when it is set to rotary, the PTO connection becomes faster, and the rotary immediately turns with a rotational force that does not lose the resistance of the soil. When it is set to 2, the connection of PTO becomes loose and it is used with pasture work machines and snow blowers.

  205 is a horizontal sensitivity switch, and the operation sensitivity of the automatic horizontal control device of the work machine changes. When the switch is pressed, the movement of the automatic horizontal control becomes slow, and when the switch is pressed again, it returns to the original state.

  Reference numeral 206 denotes a backup on / off switch, and when it is turned on, the work machine automatically rises during reverse travel. Reference numeral 207 denotes an auto lift on / off switch. When the handle is turned on with the auto lift on / off, the work machine is automatically raised. 208 is an auto brake on / off switch. When the handle is turned on with the brake turned on, the brake is automatically applied only to the rear wheel inside the turn.

209 in the horizontal change-over switch, when the self-leveling automatically maintains a horizontal working machine in the horizontal sensor enables adjustment in inclination adjusting die ya le 185 when the manual, 3 with respect to the tractor body when the parallel When the point links are always kept parallel and inclined, the three point links are held at a constant inclination angle with respect to the ground.
Reference numeral 210 denotes a 3P changeover switch, which performs control changeover selection based on the lift cylinder mounting position to the three-point link.
211 is an auto accelerator switch, and when the work machine is raised in the on state, the engine speed is reduced to 1700 rpm.

(Meter panel)
A meter panel 136 shown in FIG. 4 is provided in the front panel 174 of the tractor operation unit described above. The meter panel 136 is composed of a liquid crystal panel, and displays a shift position 160A of the auxiliary transmission lever 178, a shift stage 160B of the main transmission, and a traveling speed 160C. Also, the remaining amount of the fuel tank and the temperature state of the engine coolant are displayed. Prior to these displays, for example, abnormal contents and emergency contents may be displayed.

FIG. 4A is a display example at a normal time other than on the road. All eight speeds 160B of the main transmission are displayed, indicating that the sub-transmission lever 178 is in the middle speed position, the main transmission is in the second speed, and the running speed is 2.9 km / h. .
FIG. 4B shows the first to fifth gear positions 160B of the main transmission, the sub-transmission lever 178 is at the high speed travel position, the main transmission is the second speed in the low speed range H1, and the travel speed is 10 It shows that the car is running at 2 km / h.
FIG. 4 (c) shows from 1 to 6 shift stages 160B of the main transmission, and the maximum speed of the low shift range H1 is widened so that the shift range 160B of the main transmission is expanded to 6 speeds. Is shown.
FIG. 4D shows the 4th to 8th gear stages 160B of the main transmission, the auxiliary transmission lever 178 is traveling at a high speed, the main transmission is 5th in the high transmission range H2, and the traveling speed is 17th. It indicates that the vehicle is traveling at 9 km / h.
FIG. 4 (e) displays from 5 to 8 of the gear stage 160B of the main transmission, and the high speed range H2 in which the auxiliary transmission lever 178 is traveling at high speed and the main transmission has changed the minimum gear stage to 5 speed. It shows that the vehicle is traveling at a sixth speed and a traveling speed of 22.1 km / h.
In FIG. 4 (f), the accelerator shift control is released, and the entire shift range 160B is displayed from the first speed to the eighth speed.
(B), (c), (d), and (e) in FIG. 4 are displays at the time of accelerator shifting. When the sub-shift lever 178 is set to the high speed position, “high speed” is displayed, and when the AT shift road switch 201 is turned on, “road” is displayed, and the accelerator can be shifted. The display of the gear positions in (b), (c), (d), and (e) of FIG. 4 indicates that the accelerator gear shift is possible between the gear positions.

  FIG. 7 shows a first transmission case 3A having a PTO speed change mechanism G (three forward rotations and one reverse rotation) that changes the output rotational speed from the PTO shaft 11 to a plurality of stages and drives at a constant rotation. It is a power transmission diagram.

  The rotational output of the engine 2 is input to the main input shaft 13 connected to the output shaft of the engine 2 by a joint 105. On the main input shaft 13, the first main gear 106, the second main gear 108, and the third main gear 20 are fixed. The first main gear 106 meshes with the forward rotation gear 107 of the hydraulic forward / reverse clutch A, and the second main gear 108 meshes with the reverse rotation gear 19 of the hydraulic forward / backward clutch A via the first counter gear 18. The third main gear 20 meshes with the PTO input gear 21 of the PTO clutch F to transmit power.

  Accordingly, when the forward clutch A1 of the hydraulic forward / reverse clutch A is engaged, the first main shaft 23 to which the hydraulic forward / reverse clutch A is attached rotates in the forward direction, and when the reverse clutch A2 is engaged, the first main shaft 23 reverses and the PTO clutch F Is inserted, the PTO clutch shaft 103 rotates.

  The rotation of the first main shaft 23 includes a transmission clutch device B that shifts to four hydraulic pressures, a high and low hydraulic pressure switching clutch C that shifts to two levels, and a four-speed transmission D (sub-transmission) that mechanically shifts to four steps. ), And is transmitted to the bevel gear shaft 14 which is the final travel transmission shaft. Therefore, since the shift stage is composed of a four-stage shift (shift clutch device B), a two-stage shift (high / low hydraulic pressure switching clutch C), and a four-stage shift (sub-transmission device D), a total of 4 × 2 × 4 = 32. It is the structure shifted by 32 steps. The first to eighth gears of the main transmission described in FIGS. 4, 5, and 6 are a combination of a shift clutch device B that shifts to four hydraulic stages and a high / low hydraulic switching clutch C that shifts to two levels. It shows that the gear position of.

  The rotation of the front wheel 6 transmitted from the bevel gear shaft 14 can be rotated faster than the rear wheel 7 by the speed increasing clutch E. The sub-transmission D can be shifted to 1st speed (ultra-low speed), 2nd speed (low speed), 3rd speed (medium speed), 4th speed (high speed), but 2nd speed (low speed), 3rd speed (medium speed) ), 4th speed (high speed), since the synchro mechanism is included, the speed can be changed without stopping. Further, the auxiliary transmission device D may have a three-stage specification as shown in FIG. For the three-stage specification, depending on the model, 1st speed (low speed), 2nd speed (medium speed), 3rd speed (high speed) specifications, 2nd speed (low speed), 3rd speed (medium speed), 4th speed (high speed) specifications The configuration can be easily changed by changing only the configuration of the auxiliary transmission device D.

  The rotation of the PTO clutch shaft 103 transmitted from the main input shaft 13 by the third main gear 20 and the PTO input gear 21 is transmitted from the PTO clutch F to the first PTO shaft 22, and the PTO speed change mechanism G is rotated in the three forward rotations and the reverse rotation 1. Shifted to a stage.

Hereinafter, the power transmission mechanism will be described in detail.
The rotation of the first main shaft 23 transmitted by the hydraulic forward / reverse clutch A (the forward clutch A1 and the reverse clutch A2) is transmitted from the first gear 15 fixed to the shaft end to the first transmission gear 16 of the first transmission shaft 24. Is transmitted to the first transmission shaft 24. The first speed change shaft 24 is equipped with a first-speed / third-speed shift clutch B1 of a four-speed hydraulic shift clutch device B. Further, the first transmission gear 15 is transmitted to the second transmission shaft 25 via the second transmission gear 17 of the second transmission shaft 25. The second transmission shaft 25 is mounted with a second-speed / four-speed transmission clutch B2 of a transmission clutch device B with a hydraulic four-speed transmission.

A configuration for transmitting the rotation of the first transmission shaft 24 and the second transmission shaft 25 to the second main shaft 42 will be described.
When the first speed clutch B11 is connected, the second main shaft 42 is rotated by being transmitted from the seventh gear 40 to the sixth gear 39 that is spline-fitted to the second main shaft 42. When the second speed clutch B22 is connected, the second main shaft 42 is rotated by being transmitted from the ninth gear 38 to the eighth gear 37 that is spline-fitted to the second main shaft 42.

  When the third speed clutch B13 is connected, the second main shaft 42 is rotated by being transmitted from the eleventh gear 31 to the tenth gear 30 that is spline-fitted to the second main shaft 42. When the fourth speed clutch B24 is connected, the second main shaft 42 is rotated by being transmitted from the thirteenth gear 36 to the twelfth gear 41 that is spline-fitted to the second main shaft 42.

  The rotation of the second main shaft 42 is transmitted to the height switching shaft 44 by the first joint 43. A high / low hydraulic pressure switching clutch C is provided on the high / low switching shaft 44. When the high speed clutch C1 of the high / low hydraulic pressure switching clutch C is connected, the high speed clutch gear 45 is transmitted to the 14th gear 46 of the first countershaft 47, and when the low speed clutch C2 of the high / low hydraulic pressure switching clutch C is connected, the low speed clutch gear 48 is transmitted. To the 16th gear 49 of the counter shaft 47.

  By mounting the hydraulic high / low switching clutch C on the drive side shaft, the inertial rotational force of the hydraulic high / low switching clutch C that is turned off during the shifting of the mechanical four-speed transmission D (sub transmission) can be reduced, and the mechanical four-speed shifting. The synchronization function of the device D (sub transmission) is improved.

  Further, by providing the high / low hydraulic pressure change clutch C between the transmission clutch device B for hydraulic four-speed transmission and the mechanical four-speed transmission device D (sub transmission), two transmission clutch devices B for hydraulic four-speed transmission are provided. By stopping the inertia rotation by heavy biting and disengaging the hydraulic high / low switching clutch C, the sync function of the mechanical four-stage transmission D (sub transmission) works well, and the shift can be performed well.

  The rotation of the first counter shaft 47 is transmitted to the second counter shaft 51 by the second joint 50, and is shifted by the four-stage transmission device D (sub transmission device). When the first transmission clutch D1 of the four-speed transmission D is switched to the 18th gear 53 side, the bevel gear shaft 14 is driven at a high speed by being transmitted from the 17th gear 52 to the 18th gear 53.

  Further, when the first transmission clutch D1 of the four-speed transmission D (sub transmission) is switched to the 20th gear 55 side, the bevel gear shaft 14 is driven at a medium speed by being transmitted from the 19th gear 54 to the 20th gear 55. The

  When the second transmission clutch D2 of the four-speed transmission D (sub transmission) is switched to the 22nd gear 57 side, the transmission is transmitted from the 19th gear 54 to the 20th gear 55, and then from the 25th gear 60 to the 26th gear 61. And the bevel gear shaft 14 is driven at a low speed by being transmitted from the 27th gear 62 to the 28th gear 63.

  Further, when the second speed change clutch D2 is switched to the 24th gear 59 side, it is transmitted from the 19th gear 54 to the 20th gear 55, transmitted from the 25th gear 60 to the 26th gear 61, and from the 27th gear 62 to the 28th gear. The gear 63 is transmitted, the 22nd gear 57 is transmitted to the 21st gear 56, the 23rd gear 58 is transmitted to the 24th gear 59, and the bevel gear shaft 14 is driven at an extremely low speed.

The four-speed transmission D (sub-transmission) has a two-axis configuration of the bevel gear shaft 14 and the second counter shaft 51 by loosely fitting the 21st gear 56 and the 26th gear 61 to the second counter shaft 51. , Space saving.
For the four-speed transmission D (sub-transmission), the 17th gear 52 for shifting, the 19th gear 54, the 26th gear 61, the 27th gear 62, the 21st gear 56, and the 23rd gear. Since the gear 58 is provided on the second counter shaft 51, the synchronization function is improved.

By tightening the shaft end of the bevel gear shaft 14 with a nut 27, it becomes possible to adjust the manufacturing error of the axial width of each gear or clutch, and it is possible to configure with high accuracy.
The rotation of the bevel gear shaft 14 is such that the first bevel gear 64 formed integrally with the bevel gear shaft 14 meshes with the second bevel gear 66 of the rear wheel drive shaft 65, and the rear bevel gear set 83 (differential device) and the rear wheel drive shaft are engaged. The rear wheel shaft 5 to which the rear wheel 7 is mounted is driven through the rear wheel gear set 84 and 65.

  The 29th gear 67 that is spline-fitted to the end portion of the bevel gear shaft 14 is fixed to the first front wheel drive shaft 71 via the 30th gear 68 and the 31st gear 69 (spline fitting) to the 32nd gear 70. The first front wheel drive shaft 71 is configured to be engaged with each other.

  When the front wheel speed change clutch E is attached to the front shaft end of the first front wheel drive shaft 71 and the constant speed clutch E2 of the front wheel speed change clutch E is connected, the rotation of the first front wheel drive shaft 71 remains as it is and the second front wheel drive shaft 71 It is transmitted to 79. When the speed increasing clutch E1 of the front wheel speed change clutch E is connected, the rotation of the first front wheel drive shaft 71 is increased through the 33rd gear 75, the 34th gear 76, the 35th gear 78, and the 36th gear 77 to increase the speed. 2 It is configured to be transmitted to the front wheel drive shaft 79.

The tip of the second front wheel drive shaft 79 drives the front wheel shaft 4 to which the front wheel 6 is mounted via the front bevel gear set 80 (differential device), the front vertical drive shaft 81, and the front planetary gear set 82 as in the prior art. .
The rotation of the PTO input gear 21 is configured to rotate the second PTO shaft 73 from the PTO clutch shaft 103 through the third joint 85, the first PTO shaft 22, and the fourth joint 86 by inserting the PTO clutch F.

  The PTO clutch shaft 104 provided side by side with the second PTO shaft 73 constitutes a PTO transmission mechanism G, and is provided with a first PTO transmission clutch G1 and a second PTO transmission clutch G2.

  When the first PTO speed change clutch G1 is put on the 38th gear 88 side, the rotation of the second PTO shaft 73 is transmitted to the PTO clutch shaft 104 through the 37th gear 87 and the 38th gear 88 at a low speed. When the first PTO speed change clutch G1 is placed on the 40th gear 91 side, the rotation of the second PTO shaft 73 is transmitted to the PTO clutch shaft 104 through the 39th gear 90 and the 40th gear 91 at medium speed.

When the second PTO speed change clutch G2 is placed on the 42nd gear 93 side, the rotation of the second PTO shaft 73 is transmitted to the PTO clutch shaft 104 via the 41st gear 92 and the 42nd gear 93 at a high speed. When the second PTO speed change clutch G2 is placed on the 44th gear 96 side, the rotation of the second PTO shaft 73 is transmitted by the reverse rotation of the PTO clutch shaft 104 via the 43rd gear 95, 45th gear 101 and 44th gear 96. . The 45th gear 101 is supported by the counter shaft 97.
The power transmitted to the PTO clutch shaft 104 is configured to rotationally drive the PTO 11 via the PTO joint 74a and the PTO connection shaft 74.

  FIG. 8 shows a power transmission configuration in the second mission case 3B described above. The configuration in the second mission case 3B is configured by changing a part of the PTO transmission mechanism G in the configuration of the first mission case 3A. The second transmission case 3B also has a sub-speed four-speed specification. However, the rotation of the PTO shaft 11 is a vehicle speed corresponding PTO transmission mechanism H that changes the speed by following the rotation of the PTO shaft 11 according to the vehicle speed of the tractor. I have.

  The 43rd gear 95 of the 2nd PTO shaft 73 which meshes with the 45th gear 101 currently supported by the counter shaft 97 shown in FIG. 8, the 46th gear 98 is provided on the counter shaft 97 to which the 45th gear 101 is fixed (spline fitting). The 46th gear 98 meshes with the 30th gear 68.

  Thus, the rotational power after passing through the auxiliary transmission D is transmitted from the 29th gear 67 of the bevel gear shaft 14 to the 46th gear 98 via the 30th gear 68. Further, as described above, the power transmitted to the 30th gear 68 is also transmitted to the first front wheel drive shaft 71 via the 31st gear 69 and the 32nd gear 70.

  When the second PTO speed change clutch G2 is switched to the 44th gear 96 side, the PTO clutch shaft 104 is transmitted from the 29th gear 67 through the 30th gear 68, the 46th gear 98, the 45th gear 101, and the 44th gear 96. go. As a result, the PTO clutch shaft 104, that is, the PTO shaft 11 rotates and fluctuates in accordance with the rotational fluctuation of the bevel gear shaft 14, resulting in a PTO rotation corresponding to the traveling speed (ground PTO).

The 30th gear 68 that receives the rotation from the 29th gear 67 and the 31st gear 69 that transmits the rotation to the 32nd gear 70 are integrated, and the 30th gear 68 is used to mesh with the 46th gear 98. Thus, since the rotation of the PTO shaft 11 is configured to obtain traveling speed compatible PTO rotation, the first mission case 3A and the second mission case 3B can be shared.
In addition, the 30th gear 68 and the 31st gear 69 which are integrally configured are loosely fitted to the PTO clutch shaft 104 of the coaxial PTO transmission mechanism G, whereby the configuration can be simplified.

As described above, the 44th gear 96 outputs the PTO reverse rotation output and the PTO vehicle speed corresponding rotation output (PTO vehicle speed synchronized rotation) in common. Further, since the PTO speed change mechanism G is provided immediately before the 44th gear, the number of parts is reduced and the structure is compact.
Further, the 29th gear 67 described above is provided close to the mechanical four-speed transmission D (sub-transmission), and both the left and right front wheels 6 and 6 are driven from the 29th gear 67 and the PTO vehicle speed sync drive is driven. Therefore, the number of parts can be reduced and a compact configuration can be achieved.

FIG. 9 is a transmission diagram of a main part of a mission case with a three-stage specification sub-shift.
By integrally configuring the 26th gear 61 and the 23rd gear 58 of the above-described auxiliary transmission device D, it is possible to configure an auxiliary transmission mechanism with a three-stage specification by the first-stage second transmission clutch D2.

Next, the flow of control signals will be described with reference to the control block diagram of FIG.
First, the engine controller 124 receives the exhaust temperature from the engine exhaust temperature sensor 125, the engine speed from the engine rotation sensor 126, the engine lubricating oil pressure from the engine oil pressure sensor 127, and the engine water temperature sensor 128. The temperature of the cooling water enters, the pressure of the common rail enters from the rail pressure sensor 129, the drive signal is output to the fuel high-pressure pump 130, and the fuel supply adjustment control signal is output to the high-pressure injector 131.

Next, the working machine to the lifting controller 132, the working machine lifting signals and raising adjust die up position regulation signal Ya le 120 and lowering speed die Ya of the operating signal and the lift arm sensor 122 of the working machine lifting sensor 123 provided on the lifting lever The lowering speed setting signal of the robot 121 is input, and the work implement raising / lowering signal is outputted to the main raising solenoid 133 and the main lowering solenoid 134 to operate the working implement raising / lowering cylinder 135.

  The engine controller 124, work implement lifting controller 132, and travel system controller 149, which will be described later, communicate with each other, and the meter panel 136 displays the engine status, the lift status of the work implement, the travel speed of the travel device, etc. The operation position of each lever and pedal is displayed on the panel 137.

  The travel system controller 149 receives a clutch engagement signal from the shift 1 clutch pressure sensor 138, the shift 2 clutch pressure sensor 139, the shift 3 clutch pressure sensor 140, and the shift 4 clutch pressure sensor 141. In other words, the gear position of the four-speed hydraulic transmission clutch device B is input. Further, high / low switching signals of the high / low hydraulic pressure switching clutch C are inputted from the high speed clutch pressure sensor 142 and the low speed clutch pressure sensor 143.

  The shift position of the four-speed transmission D (sub-transmission) is input from the auxiliary transmission lever operation position sensor 147, and the forward / neutral / reverse of the hydraulic forward / reverse clutch A is input from the forward clutch pressure sensor 144 and the reverse clutch pressure sensor 145. To do. For forward / reverse movement, a forward / reverse shift operation position signal is input from the forward / reverse lever operation position sensor 146. A mode switching signal is input from the accelerator mode changeover switch 148, and an accelerator instruction signal is input from the accelerator sensor 159 of the throttle lever.

  Further, the travel system controller 149 receives a signal for increasing the shift speed of the low shift range H1 and the high shift range H2 of the accelerator control from the travel shift increase switch 193, and a signal for decreasing the shift speed from the travel shift decrease switch 194, A traveling speed is input from the vehicle speed sensor 163, an oil temperature is input from the mission oil temperature sensor 164, and a switching signal of the four-speed transmission D (sub transmission) is input from the clutch button 162.

  As for the output from the travel system controller 149, the switching signal of the forward / reverse switching clutch 101 is output to the forward / reverse switching solenoid 150, and the hydraulic relief pressure adjustment signal for driving the forward / reverse switching solenoid 150 is output to the linear boost solenoid 151. Reduce the shock of clutch connection.

  An on / off signal is output to the clutch solenoid 152. A first-speed or third-speed input signal is output to the shift 1-3 switching solenoid 153 of the hydraulic cylinder that drives the first shift clutch 102 for switching the 1st / 3rd speed. A hydraulic relief pressure adjustment signal for driving the 1st / 3rd clutch is output to the shift 1-3 boost solenoid 154 to reduce the shock of clutch engagement. A second-speed or fourth-speed input signal is output to the shift 2-4 switching solenoid 155 of the hydraulic cylinder that drives the second shift clutch 103 for 2-speed / 4-speed switching. A relief pressure adjustment signal for hydraulic pressure for driving the 2nd / 4th clutch is output to the shift 2-4 boost solenoid 156 to reduce the shock of clutch engagement. A high-speed clutch engagement signal and a low-speed clutch engagement signal are output to a high-speed clutch switching solenoid 157 and a low-speed clutch switching solenoid 158 that operate a hydraulic cylinder that drives the high / low speed switching clutch 107.

(Transmission system)
Next, a transmission system for a work vehicle will be described.
As shown in the block diagram of FIG. 11, the transmission system includes a sub-transmission device in a traveling system controller 149 that controls the transmission of main transmission devices B1, B2, and C, which are transmission transmission devices that adjust the traveling speed according to multiple shift positions. An accelerator sensor 159 is connected via a position sensor 147, an AT shift switch 301, which is a transmission system switching member for switching to an accelerator transmission system, an engine rotation sensor 126, a vehicle speed sensor 163, and an engine ECU 124, and an accelerator transmission control described below. Thus, the main transmissions B1, B2, and C are configured to be capable of shifting control in accordance with the operation of the accelerator pedal 173.

The console shown in FIGS. 12 to 14 is obtained by changing the layout of switches and levers with respect to the console shown in FIGS.
The AT shift switch 301 is disposed in the vicinity (front) of the auxiliary transmission lever 178, as shown in the perspective view of the main part of the console in FIG. As shown in the perspective view of the main part of the four-stage configuration (a) and the three-stage configuration (b) in FIG. 13, the auxiliary transmission lever 178 is an increase / decrease that is a manual transmission member composed of an acceleration button 302a and a deceleration button 302b. Place a speed switch.

  In addition, a clutch button 162 is disposed on the auxiliary transmission lever 178, and an accelerator lever 175, a control lever 191, a lowering height adjustment dial 303, a work implement up / down switch 192, a PTO rotation switch 304, A PTO selector switch 304a, an accelerator memory switch 305, and a tilling depth adjustment dial 306 are arranged. In addition, an external hydraulic control lever 179, a differential lock switch 190, a tilt adjustment dial 307, a horizontal manual switch 308, an electrohydraulic operation box are provided on the console. 309 is arranged.

  As shown in FIG. 14, the electrohydraulic operation box 309 includes a memory adjustment unit 311, a connection sensitivity setting unit 312, a raising position adjustment dial 313, a lowering speed adjustment dial 314, a brake adjustment dial 315, and a maximum speed. A restriction switch 321, an auto accelerator switch 322, a backup switch 323, an auto lift switch 324, a deserializer switch 325, an auto selector switch 326, a 3P selector switch 327, and a horizontal selector switch 328 are arranged.

(Shift control)
The shift control of the main transmissions B1, B2, and C is determined in accordance with the engine load so as to increase the speed by switching from a predetermined start shift position suitable for starting in road driving or the like to a shift position corresponding to depression of the accelerator pedal. The AT shift switch 301 applies an accelerator shift method that outputs the changed shift position as a main shift, and when the AT shift switch 301 is turned on during traveling, the shift position at that time is used as a new start shift position for main shift output. The continuous transition control to which the accelerator shifting method is applied is configured in the traveling system controller 149.

  That is, as shown in the flowchart of FIG. 15, the accelerator shift continuous transition control is performed by the AT shift switch 301 through step 1 of the sensor reading process when the engine is started (hereinafter abbreviated as “S1”). According to the result of the vehicle speed detection check (S4) when there is an on operation by the on / off check (S2, S3), if the vehicle is stopped, a predetermined start shift position is output as a main shift (S5a). Further, when the vehicle speed is detected, the shift position at that time is output as a main shift (S5b), and the accelerator shift control is applied (S6).

  By switching to the accelerator shift system by operating the AT shift switch 301 that is a shift system switching member during vehicle traveling by the above-described accelerator shift continuous transition control, the shift position at that time is shifted to the accelerator shift position as the start shift position. The shift shock due to the shift can be avoided, and the speed increase adjustment can be performed corresponding to the subsequent accelerator pedal operation. Therefore, it is possible to smoothly shift to the vehicle speed adjustment by the accelerator shifting method without requiring the conventional complicated operation of switching to the accelerator shifting after stopping once and without causing a shift shock at the time of switching.

  Further, at the end of the accelerator shift, the control process is configured so that the changed start shift position is returned to the original position, thereby enabling normal start travel by the next accelerator shift while the original start shift position is changed. If the vehicle is traveling at a lower speed than the position, even if the vehicle is stopped, the same shift state will be reproduced when the vehicle is restarted. It is possible to prevent a sudden start and to ensure stable accelerator speed shifting.

  More specifically, as shown in the flowchart of the stop-time check flag set in FIG. 16, the accelerator shift system is operated by operating the AT shift switch 301 while traveling under the condition that the sub-shift D is in the “high speed” position (S12). When the engine is switched to (S11 to S15), flag processing for setting the stoppage check flag to “ON” as long as the shift positions of the main transmissions B1, B2, and C do not reach the initial start shift position (S16, S17). Further, as shown in the flowchart of resetting the stop-time check flag in FIG. 17, when the stop-time check flag is “ON”, the shift positions of the main transmissions B1, B2, C are the initial start shift positions. (S21), there is an operation for changing the sub-shift position (S22), and there is an operation for turning off the AT shift switch 301 (S23). The stop check flag performs flag reset to "OFF" (S24).

  When the vehicle is stopped, as shown in the flowchart of the stoppage check control in FIG. 18, if it is “ON” according to the stoppage check flag, the shift position at that time is changed to the shift of the main transmissions B1, B2, C. The main shift output is output as the position (S32a), and when it is not "ON", the original shift position is output as the main shift position (S32b).

  The application conditions of the accelerator shift are limited to the case where the sub-shift lever 178 is “high speed”, the AT shift switch 301 is “on”, and the forward / reverse lever 169 is “forward”. From the first speed to the regulated speed in the maximum speed regulation mode described later, from the first speed to the eighth speed in the full speed use mode.

  As for the start shift position, the main shift output position when the AT shift switch 301 is “ON” and the sub-shift lever 178 is “high speed (indicated on the road)” is 1st to 5th speed (the upper limit speed is set in the upper limit regulation mode). If the speed is restricted to the 4th speed, the default position is the 3rd speed. If the main speed change is performed by operating the acceleration / deceleration switches 302a and 302b while the tractor is stopped, the main speed after the change is changed. The position is set as a start shift position.

  The set start shift position is stored in the EEPROM, and when the sub-shift lever 178 is set to “high speed (with AT shift switch 301)” next time, the main shift is output to the storage position. The start shift position is stored separately in the upper limit restriction mode and the full speed use mode. The lower limit shift position of the accelerator shift is assumed to be the start shift position.

The engine rotation instruction value is obtained by calculating an engine rotation instruction calculated from the accelerator opening in the engine ECM, and by CAN communication from the engine ECM. Further, an engine rotation instruction at the time of the accelerator shift control is given by CAN communication from this unit ECU when the AT shift switch 301 is “ON” and the sub-shift lever 178 is “on the road”.

(Highest speed regulation)
Next, the highest speed restriction control and the highest speed restriction switch will be described.
As shown in the flowchart of FIG. 19, the maximum speed restriction switch 321 of the electrohydraulic operation box 309 limits the speed that can be changed (“S42”) by its “ON” operation, and thus appears to be a saddle with a large shake of the aircraft. Even if the accelerator depression becomes unstable due to traveling on uneven roads, shifting to the fast vehicle speed zone will not be performed, so it is necessary to bother the AT shift switch 301 to turn off the accelerator shifting each time Therefore, it is possible to travel safely with the accelerator shifting function on.

  Specifically, the highest speed restriction switch 321 switches between the full speed range shift mode and the highest speed restriction mode in response to the switch operation. In the highest speed restriction mode, the AT shift switch 301 is set to “ “On”, the maximum speed of the main transmissions B1, B2, C when the auxiliary transmission lever 178 is “high speed” is set to the restriction speed set in the memory, and the meter panel 163 displays the range up to the restriction speed of the main transmission. .

  In addition, as shown in the flowchart of FIG. 20, the restriction speed set in the memory can be changed by changing the speed change position restricted when the maximum speed restriction switch 321 is operated (S51, S52). It is possible to regulate at the shift position according to the situation, and it is possible to deal with a wide range even when the shift position to be regulated differs depending on the situation of the bag, the skill level of the worker, or the mounting work machine.

The main transmission liquid crystal display of the maximum speed regulation, to change the display contents of the main transmission display portion 160B of the meter panel 163 in accordance with the mode selected (full speed range shift mode or maximum speed regulation mode). Specifically, as shown in the display example of FIG. 21, the 1st to 8th speeds are displayed numerically in the full speed range shift mode (a), and 1 to 8 in the maximum speed restriction mode (b). Up to the regulation speed is displayed as a number, the current position is displayed in reverse video, and it is possible to check at a glance which mode is in effect due to the difference in display. 21 (a) and 21 (b) are “on the road” because they are in the accelerator shift mode. As described above, when the AT shift switch 301 is set to “ON” when the sub-shift lever 178 is “high speed”, the accelerator shift is performed. However, when the AT shift switch 301 is turned OFF, the accelerator shift is canceled and “high speed” is displayed. Become.

  In addition to the maximum speed restriction switch 321, a setting switch is provided, and the method for setting the shift position to be restricted is the next operation procedure. That is, the sub-transmission lever 178 is set to neutral, the main transmission devices B1, B2, and C are changed to the regulation speed to be set, and the maximum speed regulation switch 321 and the setting switch are both pressed. By this simple setting method, a new regulated speed can be set in the memory without increasing the cost by sharing the switch already equipped.

The restriction speed setting range of the maximum speed restriction mode is the maximum speed restriction from the full speed range shift mode by setting the upper speed to 7th speed and the upper limit to 7th speed when the main speed is 8 steps and the accelerator speed change function is provided. It can be determined at a glance that the mode has been reached by displaying the number of shift stages.

Switching between the full speed range mode and the maximum speed restriction mode is a risk that sudden deceleration will occur when switching to the maximum speed restriction mode while driving at a vehicle speed exceeding the restriction speed of the maximum speed restriction mode. In order to avoid such a danger, the mode is switched by operating the maximum speed restriction switch 321 only when the vehicle is stopped.

As another configuration example of switching between the full speed range shift mode and the maximum speed restriction mode, it is possible to switch modes during traveling, and in the state where deceleration is performed by changing the mode, depending on the vehicle speed By configuring it to gradually decelerate, for example, you can switch to the full speed range mode without stopping once you are running on the road in the fastest speed regulation mode and exit the paved road. It is possible to avoid bothering the temporary stop for switching and to ensure safety.

  In addition, the application of the maximum speed regulation mode is limited to the case of an accelerator shift by the AT shift switch 301, and it is possible to travel on a road or an agricultural road with poor road surface conditions with an auxiliary shift as "on the road" with an accelerator shift. At the same time as the “high speed” work travel where the sub-shift position is the same as “on the road”, switching to manual shift makes it suitable as a full-speed shift without requiring the effort to cancel the maximum speed restriction mode. It is possible to promptly shift to work traveling by manual speed change of the vehicle speed.

149 Driving system controller 173 Accelerator pedal 301 AT shift switch (shifting method switching member)
302a Speed increase switch (manual operation member)
302b Deceleration switch (manual operation member)
B1 Main transmission (transmission transmission)
B2 Main transmission (transmission transmission)
C Main transmission (transmission transmission)
D Sub-transmission

Claims (4)

A transmission device (B1, B2, C) that adjusts the traveling speed according to a multi-stage shift position, a manual shift system that selects the shift position by a manual operation member (302a, 302b), and an accelerator pedal from a predetermined start shift position In a work vehicle including an accelerator shift method for shifting to a shift position corresponding to the depression of (173), and a shift method switching member (301) for switching these shift methods,
While the vehicle is running, when the gear shifting method switching member (301) is used to switch to the accelerator gear shifting method, the gear shifting position of the gear transmission device (B1, B2, C) at that time is applied as a new start gear shifting position, and the accelerator gear shifting method is applied .
A maximum speed restriction switch (321) that can be switched from the full speed range shift mode to the maximum speed restriction mode by turning on the switch is provided, and the speed changeable speed is limited by switching to the highest speed restriction mode by turning on the switch. Feature work vehicle. In the highest speed restriction mode, the highest speed restriction switch (321) of the transmission transmission device (B1, B2, C) when the transmission method switching member (301) is turned on and the auxiliary transmission lever (178) is at a high speed. 2. The work vehicle according to claim 1, wherein the maximum speed is set up to a regulated speed set in a memory, and the meter panel (163) also displays a range up to the regulated speed of the main shift . The work vehicle according to claim 2, wherein the switching between the full speed range shift mode and the maximum speed restriction mode is configured to be switched by operating the maximum speed restriction switch (321) only when the vehicle is stopped. The end of the previous SL speed change transmission apparatus (B1, B2, C) in the secondary shift position of the auxiliary transmission device (D) with switched or accelerator shifting by the shift scheme operating the switching member (301), or until its termination 4. The work vehicle according to claim 3 , wherein the new start shift position is returned to the initial start shift position when the shift position by the accelerator shift during the period reaches the initial start shift position.

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