JP2021055704A - Shift control device for work vehicle - Google Patents

Abstract

To start travelling surely without an engine stalling even when work travelling is performed without performing engine rotation setting by an accelerator lever, in a work vehicle which can set the engine rotational frequency by the accelerator lever by driving a travel device via a hydraulic continuously variable transmission device from the engine.SOLUTION: In a shift control device for a work vehicle which travels by transmitting a driving force to driving wheels via a hydraulic continuously variable transmission device from an engine, and which increases speed by rotating a trunnion shaft of the hydraulic continuously variable transmission device by the step-on of a gear shift pedal, in the case where the gear shift pedal is stepped on without setting the rotation of the engine by an engine setting tool, the speed is increased gradually by lowering the rotation speed to the speed increase of the trunnion shaft as a variation line A2 shown by a dotted line.SELECTED DRAWING: Figure 7

Description

The present invention relates to a shift control device for a work vehicle.

The power transmission mechanism to the drive wheels of the work vehicle connects the hydraulic continuously variable transmission to the output shaft of the engine, and changes the output shaft rotation speed of the engine and the shift rate of the hydraulic continuously variable transmission to change the traveling speed steplessly. It can be changed with. Further, an accelerator lever for setting the engine speed is provided, and the engine speed is set to a predetermined speed by the accelerator lever so that the vehicle can start running while driving the work machine.

In the work vehicle described in Patent Document 1, if the accelerator lever is set to high rotation when traveling on the road, the setting is forcibly released so that the engine starts from low rotation and can start running smoothly. ing.

Further, in the work vehicle described in Patent Document 2, the pedal position corresponding to the depression of the shift pedal is detected in changing the rotation angle of the tranion shaft that shifts the hydraulic stepless transmission by the depression operation of the shift pedal. Based on the pedal position detection unit and the detection value of the pedal position detection unit, the speed change pedal controls the engine speed and the tranny shaft rotation angle of the hydraulic stepless speed changer during normal driving to shift gears. It is disclosed.

Japanese Unexamined Patent Publication No. 10-114236 Japanese Unexamined Patent Publication No. 2016-183681

When working while driving the work machine with a work vehicle, start running by engaging the running clutch while driving the work machine with the engine rotated at high speed with the accelerator lever, but set the high speed with the accelerator lever. If the work running is started without performing the above, the drive load of the work machine and the drive load of the running device are simultaneously applied to the engine, resulting in an excessive load and the engine may stall.

According to the present invention, in a work vehicle in which a traveling device is driven from an engine via a hydraulic continuously variable transmission and the engine rotation speed can be set by an accelerator lever, work traveling is performed without setting the engine rotation by the accelerator lever. Even if there is, it is an issue to ensure that the engine can start running without stalling.

The above-mentioned problem of the present invention is solved by the following technical means.

According to the first aspect of the present invention, the driving force is transmitted from the engine 7 to the drive wheels 4 and 5 via the hydraulic continuously variable transmission 8 to travel, and when the speed change pedal 22 is depressed, the tranny shaft of the hydraulic continuously variable transmission 8 is driven. In the speed change control device of a work vehicle that rotates 87 to accelerate the speed, when the speed change pedal 22 is depressed without setting the rotation of the engine 7 with the engine setting tool 15, the speed of the trunnion shaft 87 is increased. The speed change control device for a work vehicle is characterized in that the rotation speed is reduced and the speed is gradually increased.

According to the second aspect of the present invention, when the stepping speed of the speed change pedal 22 is faster than the predetermined stepping speed in a state where the rotation of the engine 7 is not set by the engine setting tool 15, the speed of the tranion shaft 87 is increased. The shift control device for a work vehicle according to claim 1, wherein the rotation speed is reduced.

In the invention of claim 1, when traveling while driving the work equipment, the engine 7 is operated without stalling by depressing the speed change pedal 22 after setting the rotation of the engine 7 to a high rotation with the engine setting tool 15. However, even if the speed change pedal 22 is depressed without increasing the rotation speed of the engine 7 with the engine setting tool 15, the tranion shaft 87 of the hydraulic continuously variable transmission 8 gradually rotates to increase the speed of the engine 7. The load is gradually applied to the engine, and an excessive load is not suddenly applied to prevent the engine from stalling.

In the invention of claim 2, in addition to the effect of claim 1, even if the rotation of the engine 7 is not set by the engine setting tool 15, when the speed change pedal 22 is slowly depressed, the speed of the tranion shaft 87 of the hydraulic continuously variable transmission 8 is increased. The drive load does not suddenly increase to the engine 7 due to the slow rotation to the engine 7, but the rotation speed of the tranny shaft 87 to increase the speed is reduced even if the stepping speed of the speed change pedal 22 is faster than a predetermined value. Therefore, a smooth start can be performed without applying a sudden load to the engine 7.

It is a top view of the tractor of the embodiment of this invention. It is a side view which shows by omitting a part of the tractor of embodiment in this invention. It is explanatory drawing which shows the power transmission path of the tractor of embodiment in this invention. It is a control block diagram of the tractor of embodiment in this invention. It is explanatory drawing which shows the speed change pedal of the tractor of embodiment in this invention. It is an engine rotation instruction characteristic figure which shows the relationship between the operation amount of the speed change pedal of embodiment of this invention, and the rotation speed of an engine. It is an opening degree instruction characteristic figure which shows the relationship between the operation amount of the speed change pedal of embodiment of this invention, and the drive current applied to a hydraulic continuously variable transmission. It is a partial perspective view which looked at the lower part of the steering wheel of embodiment of this invention from the rear. It is a perspective view which looked at the lower part of the steering wheel of embodiment of this invention from the rear. It is a front view of the one-touch tillage switch of embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The work vehicle according to the embodiment of the present invention will be described as the tractor 1. FIG. 1 is a plan view of the tractor 1 as a work vehicle according to the embodiment, and FIG. 2 is a side view showing a part of the tractor 1 omitted. Further, FIG. 3 is an explanatory diagram showing a power transmission path of the tractor 1, and FIG. 4 is a control block diagram of the tractor 1.

The tractor 1 is a work vehicle that performs work in a field or the like, and as shown in FIGS. 1 and 2, as front wheels 4 provided as steering wheels and driving wheels on the left and right sides of the machine body 2, respectively. A traveling device 17 including the provided rear wheels 5 is provided. An engine 7 (see FIG. 3) is mounted in a bonnet 6 provided at the front of the airframe 2, and the output from the engine 7 is left and right via a power transmission mechanism 3 (see FIG. 3). It is transmitted to the rear wheels 5 and 5. Further, as shown in FIG. 2, a rear PTO (Power Take-Off) shaft 11R to which a work machine such as a rotary (not shown) can be mounted is arranged at the rear portion of the machine body 2. The rotation of the engine 7 can be set to high rotation with the engine rotation setting tool (engine setting tool) 15 such as the accelerator lever, and when starting running while driving the work equipment, the engine 7 is set with the engine rotation setting tool 15. Set to high rotation and start running while driving the work equipment.

As shown in FIG. 3, the power transmission mechanism 3 includes a hydraulic continuously variable transmission 8 using hydraulic oil and an auxiliary transmission 9 for shifting using a mechanical mechanism. That is, the power transmission mechanism 3 appropriately decelerates (shifts) the power generated by the engine 7 by the hydraulic continuously variable transmission 8 and the auxiliary transmission 9, and transmits the power to the rear wheels 5 via the differential case 10. In this way, the rear wheels 5 are driven by the power transmitted by decelerating from the engine 7.

The hydraulic continuously variable transmission 8 is a hydrostatic continuously variable transmission called HST (Hydro Static Transmission), and as will be described in detail later, the driving force from the engine 7 is transmitted to the work machine and the rear wheels 5. Can be done. In the following, the hydraulic continuously variable transmission may be abbreviated as HST.

The tractor 1 according to the present embodiment has a rear wheel 5 attached to a rear wheel drive shaft 51 to which power is transmitted from the engine 7, and is a two-wheel drive traveling device 17 that drives only the rear wheel 5. Four-wheel drive can also be achieved by further transmitting the power generated by the engine 7 and decelerated by the hydraulic continuously variable transmission 8 and the auxiliary transmission 9 to the front wheels 4. Further, it can be configured so that the four-wheel drive state and the two-wheel drive state can be switched. The two-wheel drive may be configured to transmit the power of the engine 7 only to the left and right front wheels 4 and 4 instead of the left and right rear wheels 5 and 5. In the description of the present invention, the front wheels 4 and 4 and the rear wheels may be transmitted. The driving wheels are 5 and 5.

As shown in FIGS. 1 and 2, a driver's seat 12 on which an operator sits when operating the tractor 1 is provided in the central portion of the airframe 2, and a driver's seat 12 is used in front of the driver's seat 12 for steering the front wheels 4. A steering handle 13 is provided. The steering handle 13 is rotatably attached to the upper end side of the handle post 131. The driver's seat 12 is provided with a seating sensor 12S for detecting that the worker is sitting, and when the worker sits down, an output is output to the traveling system ECU 32. If it is detected that the worker is not seated while driving, a warning buzzer sounds to prompt the worker to sit down, and if the seating difference state cannot be confirmed even after a certain period of time, the hydraulic continuously variable transmission 8 is neutralized. When the operator is seated, the speed is increased to the original speed.

The handle post 131 is provided with a forward / backward switching lever 27 for switching the traveling direction of the tractor 1 between forward and reverse, and the engine rotation for setting the rotation of the work equipment elevating lever 14 and the engine 7 shown in FIG. A setting tool 15 and a blinker switching lever 16 and the like are provided. The engine rotation setting tool 15 sets the rotation of the engine 7 to a high rotation when the traveling is started while driving the work machine.

Further, as shown in FIG. 9, a mode changeover switch 18 and a one-touch tillage switch 25 for inputting the work travel mode M2 and the non-work travel mode M3 are provided on the right side of the handle post 131. When the mode changeover switch 18 is pressed during work travel, automatic straight-ahead control is activated to perform straight-ahead travel without the operator performing a maneuvering operation, and when the non-work-travel mode M3 is pressed during work travel, automatic straight-ahead travel is performed. The control does not work and the operator must operate the maneuver.
As shown in FIG. 10, the one-touch tillage switch 25 switches between normal tillage running and discerning tillage.

The forward / backward switching lever 27 can switch between forward and reverse movement of the airframe 2 by tilting the tractor 1 forward when moving the tractor 1 forward and tilting the tractor 1 backward when moving the tractor 1 backward. Further, the forward / backward switching lever 27 has a neutral position between the forward position and the reverse position, and this neutral position can prevent the tractor 1 from moving forward or backward. The forward / backward switching lever 27 is detected by the forward / backward lever sensor 322 (see FIG. 4) at operating positions (forward position, reverse position, neutral position).

Various pedals are arranged on the lower side of the handle post 131, that is, near the driver's feet when the driver sits on the driver's seat 12. That is, as shown in FIG. 1, a clutch pedal 20 is arranged on the left front side of the driver's seat 12, and the left and right rear wheels 5 and 5 are individually braked on the right front side according to a stepping operation as a pedal operation. The left and right brake pedals 21L and 21R are arranged.

Further, a speed change pedal 22 for changing the traveling speed of the machine body 2 is provided so as to be aligned with the brake pedal 21. The traveling speed of the tractor 1 according to the present embodiment adjusts the rotation speed of the engine 7 according to the amount of depression of the speed change pedal 22, and rotates the tranny shaft 87 (see FIG. 3) of the hydraulic continuously variable transmission 8. It is controlled so as to reach the set running speed.

That is, as shown in FIG. 4, the tractor 1 includes a controller 30 that functions as a shift control device in a broad sense. The controller 30 is various engine controllers (ECUs: Electronic Control Units) that communicate control signals by CAN (Controller Area Network) communication, and includes an engine ECU 31, a traveling system ECU 32, and a work equipment elevating system ECU 33. In the following, the engine controller may be referred to as an ECU.

For example, the traveling system ECU 32 has a hydraulic continuously variable transmission at a second pedal position P2 set at a position shallower than the first pedal position P1 at which the rotation speed of the engine 7 is maximized by depressing the speed change pedal 22. The device 8 is controlled so that the tranny axis angle is maximized.

Here, the speed change pedal 22 will be described with reference to FIG. FIG. 5 is an explanatory view showing a speed change pedal 22 of the tractor 1 according to the present embodiment. In the speed change pedal 22, the base end of the pedal body 221 is rotatably connected to the pivot portion 222 on the upper surface side of the bracket 220 attached to the machine body 2. By the driver's pedal operation, the pedal body 221 rotates from the pedal release position A to the pedal maximum depression position B. A stopper 223 is provided below the pedal body 221 and the pedal body 221 stepped on from the pedal release position A abuts on the stopper 223 at the pedal maximum stepping position B to restrict rotation.

Further, on the lower surface side of the bracket 220, a spring 224 for urging the pedal body 221 so as to be in the pedal release position A is provided. Then, on the opposite side of the spring 224, a speed change pedal sensor 321 (see FIG. 4) for detecting a pedal operation (depression operation) of the speed change pedal 22 by the driver is provided. The speed change pedal sensor 321 corresponds to a pedal position detection unit that detects a pedal position according to the amount of depression of the speed change pedal 22 (pedal body 221), and outputs the detection result to the traveling system ECU 32. By the way, in the present embodiment, the rotation fulcrum (not shown) of the speed change pedal sensor 321 is offset from the pivot portion 222 which is the rotation fulcrum of the pedal body 221.

Further, as shown in FIG. 1, on the left side of the driver's seat 12 of the tractor 1, a main shift lever 300 for performing operations related to shifting during traveling, an auxiliary shift lever 310, and a working machine mounted on the rear portion of the tractor 1 are provided. A PTO clutch lever 320 for engaging and disengaging the drive of the rear PTO shaft 11R for driving the rear PTO shaft 11R is arranged.

The main speed change lever 300 can set the speed of the tractor 1 from, for example, 1st speed to 8th speed, and the traveling system ECU 32 adjusts the rotation speed of the engine 7 so that the speed becomes the set speed, and there is no oil pressure. The angle (trunnion shaft angle) of the trunnion shaft 87 of the speed transmission 8 is adjusted.

The auxiliary transmission lever 310 is for shifting the traveling speed of the machine body 2 to three speeds of low speed, medium speed, and high speed by the auxiliary transmission device 9 (see FIG. 3). The auxiliary transmission 9 has a plurality of gear ratios that can be selectively set so that the gear ratios are different from each other in the low speed, medium speed, and high speed states. The low speed and medium speed at which the auxiliary transmission lever 310 shifts are suitable for traveling when working in the field, and the high speed is suitable for traveling on the road when moving between fields.

Further, on the right side of the driver's seat 12, a position lever 330 for adjusting the height of the working machine connected to the rear part of the machine body 2 is arranged. The operating position of the position lever 330 is detected by the position lever sensor 331 (see FIG. 4), and the position lever sensor 331 outputs the detection result to the work equipment elevating system ECU 33.

Here, the power transmission mechanism 3 will be described with reference to FIG. The power transmission mechanism 3 is provided in a mission case (not shown) arranged on the rear stage side of the engine 7. The rotation of the output shaft of the engine 7 is transmitted to the input shaft 80 of the hydraulic continuously variable transmission 8 via the damper 34 via the main clutch (not shown) that is interrupted by the clutch pedal 20 (FIG. 1). That is, the power of the engine 7 is input to the hydraulic continuously variable transmission 8.

The hydraulic continuously variable transmission 8 is composed of a variable capacity type hydraulic pump 81 and a fixed capacity type hydraulic motor 82, and changes the rotation of the hydraulic motor 82 by changing the inclination of the movable diagonal plate 83 of the hydraulic pump 81. The inclination of the movable swash plate 83 is changed by an actuator 84 such as a hydraulic cylinder that operates by detecting the movement of the speed change pedal 22, the main speed change lever 300, and the forward / backward switching lever 27, and the motor output shaft 86 of the hydraulic motor 82. The rotation is changed. The rotation speed of the pump output shaft 85 directly connected to the hydraulic pump 81 is the same as the rotation speed of the input shaft 80.

The rotation of the pump output shaft 85 is transmitted to the PTO shaft 11 via the PTO clutch 35, and is finally taken out of the mission case by the rear PTO shaft 11R and the mid PTO shaft 11M. With this configuration, the power of the engine 7 can be taken out to drive a working machine such as a rotary linked to the rear PTO shaft 11R and a mower linked to the mid PTO shaft 11M.

Further, the motor output shaft 86 of the hydraulic motor 82 drives the rear wheels 5 and 5 via the auxiliary transmission 9 and the differential case 10. The rotation speed of the motor output shaft 86 is detected by the HST output shaft rotation sensor 323 (see FIG. 4). The HST output shaft rotation sensor 323 outputs the detection result to the traveling system ECU 32.

Further, the rotations shifted to low speed, medium speed, and high speed in the auxiliary transmission 9 are output to the differential case 10, but a high speed sensor 324 for detecting the shift to high speed is provided and output to the traveling system ECU 32.
When high-speed switching is detected by the high-speed sensor 324 during traveling, the automatic straight-ahead control is disabled and displayed to notify the operator in operation.

The movable swash plate 83 of the hydraulic continuously variable transmission 8 is connected to a trunnion shaft 87 which is interlocked and connected to a trunnion arm (not shown). In this way, the trunnion shaft 87, the trunnion arm, and the movable swash plate 83 are interlocked with each other. That is, the hydraulic continuously variable transmission 8 according to the present embodiment shifts the power input from the engine 7 and outputs it to the motor output shaft 86 by changing the trunnion shaft angle.

By the way, the rotation angle (position) of the trunnion shaft 87 and the trunnion arm and the inclination angle of the movable swash plate 83 change in correspondence with each other. Therefore, in the present embodiment, a trunnion arm angle sensor for detecting the rotation angle of the trunnion arm is provided to detect the trunnion axis angle.

Further, the power transmission mechanism 3 includes a neutral holding mechanism (not shown) that holds the trunnion arm and the trunnion shaft 87 in a neutral position.

The engine ECU 31, the traveling system ECU 32, and the work equipment elevating system ECU 33 constituting the control unit each have, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), respectively. The controller 30 controls each part of the tractor 1 by executing the program stored in the ROM.

As shown in FIG. 4, the engine rotation setting tool 15, the accelerator sensor 311 and the engine rotation sensor 312 are connected to the engine ECU 31. The engine rotation setting tool 15 sets the rotation speed of the engine 7, the accelerator sensor 311 detects the rotation angle of the speed change pedal 22, and outputs the detection result to the controller 30. The engine rotation sensor 312 detects the rotation speed of the engine 7 and outputs the detection result to the controller 30.

Then, the engine ECU 31 outputs a rail pressure to the fuel high-pressure pump 313 and an injection signal to the high-pressure injector 314. By adjusting the injection timing of the high-pressure injector 314 by the engine ECU 31 based on the detection value of the accelerator sensor 311, the rotation speed of the engine 7 can be arbitrarily adjusted.

The speed change pedal sensor 321, the forward / backward lever sensor 322, the HST output shaft rotation sensor 323, and the high-speed sensor (vehicle speed sensor) 324 are connected to the traveling system ECU 32. The high-speed sensor 324 detects the traveling speed of the machine body 2 from the rotation of the shaft of the rear wheel 5, and outputs the detection result to the traveling system ECU 32.

Further, the traveling system ECU 32 outputs a forward output signal to the HST forward proportional pressure solenoid (HST forward proportional pressure sol) 328, a reverse output signal to the HST reverse proportional pressure solenoid (HST reverse proportional pressure sol) 329, and the like. That is, the traveling system ECU 32 constituting the control unit can control the rotation speed of the engine 7 and the trunnion shaft angle of the hydraulic continuously variable transmission 8 based on the detection value of the speed change pedal sensor 321 (pedal position detection unit). ..

Further, a traveling mode changeover switch 325, an engine rotation set dial 326, and a trunnion axis angle set dial 327 are connected to the traveling system ECU 32, which will be described in detail later.

The position lever sensor 331 and the lift arm position sensor 332 are connected to the work equipment elevating system ECU 33. The lift arm position sensor 332 detects the lift position signal and outputs the detection result to the work equipment elevating system ECU 33. Then, the work equipment elevating system ECU 33 outputs an ascending signal to the main ascending solenoid (main ascending sol) 333 of the hydraulic cylinder (not shown) and outputs a descending signal to the main descending solenoid (main descending sol) 334.

The tractor 1 according to the present embodiment has the above-described configuration, and its operation will be described below. FIG. 6 is an engine rotation instruction characteristic diagram showing the relationship between the operation amount of the speed change pedal 22 and the rotation speed of the engine 7. Further, FIG. 7 is an opening degree instruction characteristic diagram showing the relationship between the operation amount of the speed change pedal 22 and the drive current applied to the hydraulic continuously variable transmission 8. In the engine rotation instruction characteristic diagram shown in FIG. 6, the horizontal axis is shown. Indicates the amount of depression, which is the amount of pedal operation, and the vertical axis indicates the engine speed. A on the horizontal axis corresponds to, for example, the pedal release position A in FIG. 5, and B corresponds to the maximum pedal depression position B in FIG. Further, the amount of depression (operation amount) of the transmission pedal 22 is equivalent to the ratio of the pedal opening degree of the transmission pedal 22 when the pedal is depressed. A pedal play area C is provided from the pedal release position A to the stepping side. The pedal play area C overlaps with the low-speed idle rotation holding position of the engine 7.

As shown in the figure, it can be seen that the engine speed of the tractor 1 according to the present embodiment basically changes linearly depending on the amount of depression of the speed change pedal 22. The engine speed does not necessarily have to change strictly linearly. For example, the configuration may be such that the quadratic curve changes gently.

In the opening degree instruction characteristic diagram shown in FIG. 7, the horizontal axis represents the pedal operation amount and the vertical axis represents the drive current applied to the hydraulic continuously variable transmission 8. A on the horizontal axis corresponds to, for example, the pedal release position A in FIG. 5, and B corresponds to the maximum pedal depression position B in FIG. Here, the detected value of the speed change pedal sensor 321 indicating the pedal release position A is stored in advance in the traveling system ECU 32 as an initial value.

The HST neutral region D is provided from the pedal release position A to the stepping side. The HST neutral region D is a region in which the trunnion shaft angle of the hydraulic continuously variable transmission 8 in the present embodiment is neutral. The start position E to which the drive start point current is applied is set on the stepping side of the HST neutral region D. That is, the hydraulic continuously variable transmission 8 is started from the stepping position side of the speed change pedal 22 with respect to the HST neutral region D. When the speed change pedal 22 is further depressed, the drive current increases, but this is due to the fact that the rotation axis of the speed change pedal 22 and the rotation axis of the speed change pedal sensor 321 are set at offset positions. Therefore, the ratio of the pedal operation amount and the drive current is not constant but changes. In this way, when the speed change pedal 22 is stepped on, the traveling system ECU 32 changes the drive current in a curve from the zero rotation of the hydraulic continuously variable transmission 8.

Further, a maximum maintenance margin angle F for designating the maximum opening degree of the hydraulic continuously variable transmission 8 is provided on the front side of the maximum pedal depression position B. That is, in the section where the maximum maintenance margin angle F at the stepping position is maintained, the hydraulic continuously variable transmission 8 is in the maximum opening state.

The fluctuation line A1 shown by the solid line indicates the drive current value when the tractor 1 starts traveling independently, and linearly increases from the drive start point current to the maximum drive current to accelerate the hydraulic continuously variable transmission 8. The fluctuation line A2 shown by the dotted line is the drive current when the work machine is attached to the tractor 1 and the work machine is driven while the engine rotation setting tool 15 starts running without setting the rotation of the engine 7 to a high speed. By showing the value and increasing from the drive start point current to the maximum drive current in a gentle curve, the hydraulic continuously variable transmission 8 is gradually accelerated so as not to apply a sudden drive load to the engine 7. Prevent engine stall.

The tractor 1 is provided with a work mode switching dial for running / working / sticking / tilling, and in the case of high-speed running, the autobrake is prevented from operating in the sticking / tilling mode. In addition, it is equipped with a straight-ahead assist mechanism that uses GPS so that straight-ahead assist operates only in the discerning and tillage mode. In addition, it detects whether the sub-shift is in the high-speed position, and at the sub-shift high speed, the straight-ahead assist is not activated even in the sticking / tilling mode.

4 Front wheels 5 Rear wheels 7 Engine 8 Hydraulic continuously variable transmission 15 Engine rotation setting tool (engine setting tool)
22 Shift pedal 87 Trunnion shaft

Claims (2)

The driving force is transmitted from the engine (7) to the drive wheels (4) and (5) via the hydraulic continuously variable transmission (8) to travel, and the hydraulic continuously variable transmission (22) is depressed by depressing the speed change pedal (22). In the speed change control device of the work vehicle that rotates the tranion shaft (87) of 8) to accelerate the speed, the speed change pedal (22) is depressed without setting the rotation of the engine (7) with the engine setting tool (15). In this case, the speed change control device for the work vehicle is characterized in that the rotation speed of the tranion shaft (87) for speeding up is reduced so as to gradually increase the speed. When the stepping speed of the speed change pedal (22) is faster than the predetermined stepping speed without setting the rotation of the engine (7) with the engine setting tool (15), the speed of the tranion shaft (87) is increased. The shift control device for a work vehicle according to claim 1, wherein the rotation speed of the work vehicle is reduced.

Images