JP7638757B2 - Work vehicles - Google Patents

Description

The present invention relates to a work vehicle equipped with a control unit that controls the gear shifting operation of the traveling body.

A work vehicle as described in Patent Document 1 has been publicly known which is equipped with a traveling machine body having a control section where an operator operates the traveling machine, a hydraulic transmission (stepless transmission) that changes the traveling power of the traveling machine body, a shift operating device provided on the control section for operating the hydraulic transmission, an operating position detection means for detecting the operating position of the shift operating device, an actuator that operates the hydraulic transmission, and a control unit that shifts the hydraulic transmission to a forward state, a neutral state, or a reverse state depending on the operating position of the shift operating device.

According to the work vehicle in the above document, the continuously variable transmission can be operated by an electric operation method controlled via the electric actuator, and a gear ratio adjustment means is provided that adjusts the gear ratio operated according to the operating position of the gear change operating device, making it easy to adjust the gear change amount according to the operating amount of the gear change operating device. However, compared to when the continuously variable transmission is manually operated through a mechanical linkage, the operating method and operability are roughly the same and cannot be said to have been improved, and there is an issue of increased costs.

Patent No. 3635823

The present invention aims to provide a work vehicle equipped with a control unit that controls a hydraulic transmission via an actuator, which enables smoother and more easy-to-operate gear change operation of the traveling body using a gear change operating device .

In order to solve the above problems, the present invention provides a vehicle having a traveling machine body with a control section where an operator operates the vehicle for traveling, a hydraulic speed change device that changes the traveling power of the traveling machine body, a speed change device that is provided on the control section and operates the speed change device, an operation position detection means that detects the operation position of the speed change device, an actuator that operates the trunnion shaft of the hydraulic speed change device, and a control unit that switches the hydraulic speed change device to a forward state, a neutral state, or a reverse state depending on the operation position of the speed change device, and the speed change device is configured to be swingable in two different directions from a neutral position, and is configured to be capable of being operated to release the swinging operation from the neutral position. The control unit is configured to shift the hydraulic transmission to the forward side when the gearshift operating device is swung from the neutral position to one side, and to shift the hydraulic transmission to the reverse side when the gearshift operating device is swung from the neutral position to the other side. The control unit is configured to change the gear steplessly according to the operating position of the gearshift operating device when the gearshift operating device is operated to the forward or reverse side for a predetermined period of time or more, and to change the gear stepwise according to the operating direction of the gearshift operating device when the gearshift operating device is operated to the forward or reverse side within a predetermined period of time.

Secondly, the control unit is configured to increase or decrease the operating speed of the trunnion shaft operated via the actuator in response to the amount of operation of the speed change device from the neutral position when the speed change device is used for stepless speed change.

Thirdly, the control unit is configured to maintain the neutral state of the hydraulic transmission when the trunnion shaft is operated to a neutral state by the stepless gear shift operation of the gear shift operating device , and to restrict the gear shift operation of the hydraulic transmission device via the gear shift operating device, and when the gear shift operation by the gear shift operating device is restricted, the control unit is configured to release the restriction on the gear shift operation by the gear shift operating device by returning the gear shift operating device to the neutral position.

Fourthly, the control unit is configured to be able to switch between a normal mode in which the hydraulic transmission changes gear in accordance with the amount of operation of the shift operating device, and a low speed mode in which the amount of gear change that can be operated by the shift operating device is smaller than that in the normal mode, when the shift is infinitely variable using the shift operating device.

Fifthly, the control unit is configured to slow down the operating speed of the trunnion shaft operated via the actuator as the amount of operation of the speed change operating device from the neutral position decreases.

The shift operating device is configured to automatically return to a neutral position, and the control unit is configured to continuously change the speed of the hydraulic transmission in accordance with the operating direction when the shift operating device is operated toward the forward or reverse side for a predetermined period of time or more, and to change the speed of the hydraulic transmission in a stepped manner in accordance with the operating position when the shift operating device is operated toward the forward or reverse side within a predetermined period of time.By configuring the shift operating device to automatically return to a neutral position, the control unit is configured to continuously change the speed of the hydraulic transmission in accordance with the operating direction when the shift operating device is operated toward the forward or reverse side for a predetermined period of time or less, and to change the speed of the hydraulic transmission in a stepped manner in accordance with the operating position.This further improves operability because the hydraulic transmission can be operated forward and backward with continuously variable acceleration and deceleration, and forward and backward with stepped acceleration and deceleration, using just the single shift operating device.

Furthermore, when the speed change is performed continuously using the speed change operating device, if the operating speed of the trunnion shaft operated via the actuator is increased or decreased depending on the amount of operation of the speed change operating device from the neutral position, it is possible to intuitively increase or decrease the speed of the traveling body with a similar operating feel to when operating the hydraulic speed change device with a mechanical configuration.

In addition, the control unit is configured to maintain the neutral state of the hydraulic transmission when the trunnion shaft is operated to a neutral state by the stepless speed change operation of the speed change device , and to restrict the speed change operation of the hydraulic transmission device via the speed change device, and the control unit is configured to release the restriction on the speed change operation by the speed change device by returning the speed change device to the neutral position when the speed change operation by the speed change device is restricted.Therefore, when the traveling vehicle body is stopped by operation of the speed change device, the speed change device will stop even if it has been operated from the neutral position to the forward or reverse side, and the traveling vehicle body cannot be moved forward or backward until the speed change device is returned to the neutral state, thereby further improving safety.

Furthermore, if the control unit is configured to be able to switch between a normal mode, in which the hydraulic transmission is changed in accordance with the amount of operation of the shift operating device, and a low-speed mode, in which the amount of gear change that can be performed by the shift operating device is smaller than in the normal mode, it becomes possible to operate the shift operating device to increase or decrease speed at a lower speed, making it easier and smoother to perform work that requires speed control at low speeds, such as when driving for work or when stacking or unloading luggage.

The control unit is configured to slow down the operating speed of the trunnion shaft operated via the actuator as the amount of operation of the speed change operating device from the neutral position decreases, so that the speed of the traveling machine body can be adjusted more finely, improving operability.

1 is an overall plan view of a riding rice transplanter (transplanter) to which the work vehicle of the present invention is applied. 1 is an overall side view of a riding rice transplanter (transplanter) to which the work vehicle of the present invention is applied. FIG. 2 is a side view of a main portion showing a steering mechanism and an HST control mechanism. FIG. 2 is a front perspective view of a main portion showing a steering mechanism and an HST control mechanism. FIG. 2 is a rear perspective view of a main portion showing the steering mechanism and the HST control mechanism. FIG. 4 is an enlarged view of a main portion showing an operating arm for operating the traveling HST. 4A and 4B are side views of the main part of the brake operation linkage mechanism before and during operation of the brake operating tool. FIG. 2 is a block diagram of a control unit. FIG. 1A is a diagram showing the vehicle speed when the shift lever is operated for stepless shifting, FIG. 1B is a diagram showing the vehicle speed when the shift lever is operated for stepped shifting, and FIG. 1C is a diagram showing the difference in vehicle speed between normal mode and low-speed mode.

Figures 1 and 2 are an overall side view and an overall plan view of a riding rice transplanter (transplanter) to which the work vehicle of the present invention is applied. This riding rice transplanter is equipped with a running machine body 3 supported by a pair of left and right front wheels 1, 1 and rear wheels 2, 2, and a planting work machine 6 connected to the rear of the running machine body 3 via a lifting link 4 so that it can be freely raised and lowered.

The vehicle body frame 8 which supports the traveling vehicle body is equipped with an engine (not shown) surrounded by a bonnet 9 at the front, a traveling HST ( hydraulic transmission, hydraulic variable speed device, hydraulic transmission) 10 which continuously changes the engine power input from the engine, and a transmission case 11 to which the power output from the traveling HST 10 is input, and a control section 7 is provided behind the engine where an operator (worker) sits and performs steering operations, etc.

The operating section 7 is provided with a seat 12 on which an operator sits, a steering handle 13 for steering the traveling body 3 (front wheels 1) via a steering mechanism 20 (described later), a main shift lever (shift operation device, forward/reverse switch lever) 14 provided on either the left or right side of the steering handle 13 and operated to swing at least forward and backward, a sub-shift lever 16 for operating the gear shift of the traveling body 3, a floor step 17 below the steering handle 13, and a brake pedal (manual operation device) 18 provided in front of the floor step 17 so as to be stepped on and for operating the brakes (braking) of the traveling body 3.

The main speed change lever 14 is provided with a switch operating device 14a arranged on the upper end of the grip portion so that the operator can press it while holding it. The switch operating device 14a is a changeover switch (changeover operating device) that switches the traveling machine body 3 operated by the main speed change lever 14 to a low speed mode that reduces the amount of speed change. This will be described in detail later.

The main shift lever 14 is also configured to be able to swing back and forth from a basic position (neutral position) that is slightly tilted forward, and is configured to automatically return to the neutral position when the main shift lever is released from its forward and backward swinging operation (see Figure 3, etc.).

The main speed change lever 14 is configured so that the swing operation position in the forward/rearward direction can be detected by an operation position detection potentiometer (operation position detection means, operation position detection sensor) 46. The main speed change lever 14 is also configured so that the traveling machine body 3 can be switched between a forward state, a stopped state, and a reverse state by operating an HST control mechanism 30 that controls the traveling HST 10 (the trunnion shaft 35 that changes the speed) via a control unit 50 described later. The specific configuration of the HST control mechanism 30 will be described later.

Specifically, the control unit 50 is configured to execute HST control such that when the main shift lever 14 is operated to the neutral position, the control unit 50 switches the traveling HST 10 to a neutral state, when the main shift lever 14 is operated to a forward position swung forward from the neutral position, the control unit 50 switches the traveling HST 10 to a forward state shifted forward in accordance with the amount of operation, and when the main shift lever 14 is operated to a reverse position swung backward from the neutral position, the control unit 50 switches the traveling HST 10 to a reverse state shifted backward in accordance with the amount of operation. The HST control will be described later.

The brake pedal 18 has a step portion 18a that the operator steps on, a rod-shaped extension portion 18b that extends downward and rearward in a U-shape from the step portion 18a, and a support portion 18c that supports the rear end of the extension portion 18b on a left-right support shaft 15 located below the floor step, and the step portion 18a is biased to an initial position where it is swung (see FIG. 5, etc.). The brake pedal 18 (support portion 18c) is provided with a brake operation linkage mechanism 40 that switches the traveling HST 10 to a neutral state (neutral state) via the HST control mechanism 30. Details will be described later.

The planting machine 6 has a seedling carrier 22 on which the seedlings to be planted in the field are placed, and a planting section 23 that performs the planting work of the seedlings placed on the seedling carrier 22 in the field. It is raised and lowered relative to the traveling body 3 via the lifting cylinder 4, and the power transmitted from the engine is transmitted intermittently via a planting clutch (not shown).

Next, the steering mechanism and the HST control mechanism will be described with reference to Figures 3 to 6. Figures 3 to 5 are a side view, a front perspective view, and a rear perspective view of the steering mechanism and the HST control mechanism, and Figure 6 is an enlarged view of the operating arm that operates the traveling HST.

The steering mechanism 20 includes the steering shaft extending in the vertical direction, the transmission case 11 that is fitted with a speed change gear for changing the speed of engine power to each part and is arranged between the left and right front wheels 1, 1, a pitman arm (not shown) supported on the underside of the transmission case 11 so as to be able to swing left and right, a power steering device 32 that is arranged below the steering shaft 19 and on the upper side of the transmission case 11, and a cylindrical steering column 31 through which the steering shaft 19 is inserted. A support bracket 33 that is U-shaped and open at the top is provided on the upper side of the power steering device 32.

The HST control mechanism 30 includes a support shaft 36 that is supported so as to penetrate the left and right sides of the support bracket 33 in the left-right direction, a swing arm 37 that is attached to be swingable in the vertical direction around the support shaft 36 and is arranged on the outside of the left side of the support bracket 33, an operation arm 38 that is supported so as to rotate integrally with a trunnion shaft 35 that operates the speed change of the traveling HST 10, a vertical operation rod 39 whose upper end is connected to the swing arm 37 side and whose lower end is connected to the operation arm 38 side, a motor 42 that is installed so as to be able to rotate the support shaft 36 axially via a clutch 41 described later, and the control unit 50. The torque limiter type clutch 41 is provided on the left end side of the support shaft 36 (see Figures 3 to 5, etc.).

The HST control mechanism 30 is provided with a brake operation linkage mechanism 40 that manually operates the traveling HST 10 via the brake pedal 18, and is configured so that the traveling HST 10 can also be directly operated by manual operation by an operator. The specific configuration of the brake operation linkage mechanism 40 will be described later.

According to this configuration, the HST control mechanism 30 is configured to rotate the support shaft 36 by the driving force of the motor 42, to swing the swing arm 37 up and down by the axial rotation of the support shaft 36, to move the operating rod 39 up and down by the up and down swinging movement of the swing arm 37, and to operate the operating position of the operating arm 38 that operates the trunnion shaft 35 by the up and down movement of the operating rod 39 (see Figures 4 to 6, etc.).

At this time, an operating arm detection potentiometer 47 that detects the operating position of the operating arm 38 is provided on the operating arm 38 side, and the control unit 50 is configured to be able to check the gear shifting state of the traveling HST 10 by detecting the operating position of the operating arm 38 (see Figure 6, etc.).

According to the above-mentioned configuration, the control unit 50 is configured to be able to execute the HST shift control by controlling the drive of the motor 42 based on the forward/backward swing operation of the main shift lever 14 detected by the operation position detection potentiometer 46 and the current shift state of the traveling machine body 3 (traveling HST 10) detected by the operation arm detection potentiometer 47.

The clutch 41 is provided on the left end side of the support shaft 36 on the outer left side surface of the support bracket 33 so as to rotate integrally with the support shaft 36, and has a drive gear 41A that rotates freely around the support shaft 36 by meshing with the output gear 42a of the motor 42, a torque limiter type clutch section 41B that interrupts the transmission of power between the drive gear 41A and the support shaft 36, and an elastic member (biasing member) 41C that biases the clutch section 41B toward the drive gear 41A (see FIG. 3, etc.).

As a result, the clutch 41 is configured to cut off the power transmission between the motor 42 and the support shaft 36 when the support shaft 36 (drive gear 41A) rotates with a torque stronger than the driving force of the motor 42 (the biasing force of the elastic member).

In other words, the clutch 41 is configured to operate the swing arm 37 (operating arm 38) via the support shaft 36 when the motor 42 is driven, but to prevent the operating force from being transmitted to the motor 42 when the support shaft 36 (operating arm 37) is operated with a force (torque) greater than the driving force of the motor 42 via the brake operation linkage mechanism 40.

To explain more specifically, the motor 42 is disposed on the upstream side of the clutch 41, while the power is transmitted to the downstream side of the clutch 41 in the order of the support shaft 36 → the swing arm 37 → the operating rod 39 → the operating arm 38 → the trunnion shaft 35, linking the traveling HST 10. The brake operation linkage mechanism 40, which will be described later, operates the support shaft 36 by the operating force generated by depressing the brake pedal 18, thereby operating the trunnion shaft 35 to the neutral state.

Next, the configuration of the brake operation linkage mechanism will be specifically described with reference to Figures 3 to 7. Figures 7(A) and (B) are side views of the main part of the brake operation linkage mechanism before and during operation of the brake operating tool.

The brake operation linkage mechanism 40 includes a swing piece 51 provided on the pivot portion 18c of the brake pedal, a linkage rod 52 extending forward from the swing piece 51 and pushed and pulled in the front-rear direction in response to the operation of the brake pedal 18, a first linkage arm 53 connected to the front end side of the linkage rod 52 and swinging forward and backward, a second linkage arm 54 swinging in the up-down direction in response to the swing operation of the first linkage arm 53, and a linkage arm 55 connecting the first linkage arm and the It is equipped with a linkage arm support shaft 56 that supports the second linkage arm 54, a diamond-shaped brake operation linkage arm 57 that rotates integrally with the support shaft 36 on the right end side of the support shaft 36, a first linkage member 58 in the vertical direction that links the front end side of the brake operation linkage arm 57 with the second linkage arm 54, and a second linkage member 59 in the vertical direction that links the rear end side of the brake operation linkage arm 57 with the second linkage arm 54 (see Figure 7, etc.).

The upper end side of the first linkage member 58 and the upper end side of the second linkage member are formed with through holes 58a, 59a, which are long holes along the vertical direction, and are connected to the front and rear ends of the brake operation linkage arm 57 via the through holes 58a, 59a, respectively (see FIG. 7(A)).

At this time, when the support shaft 36 is rotated via the motor 42 while the brake pedal 18 is not depressed (see FIG. 7A), the brake operation linkage arm 57 is configured to swing within the range of the accommodation holes 58a, 59a.

On the other hand, when the brake pedal 18 is depressed (see FIG. 7B), each of the through holes 58a, 59a is configured to be able to rotate the support shaft 36 in a predetermined direction by linking in the following order: brake pedal 18 → swing piece 51 → link rod 52 → first link arm 53 → link arm support shaft 56 → second link arm 54 → first link member 58 → brake operation link arm 57.

As a result, the brake operation linkage mechanism 40 (and the HST control mechanism 30) is configured to be able to shift the traveling HST 10 to a neutral state by depressing the brake pedal 18.

With this configuration, when the brake pedal 18 is depressed, the brake operation linkage mechanism 40 can forcibly operate the traveling HST 10 to a neutral state (stopped state) regardless of the drive state of the motor 42 controlled by the control unit 50, thereby more reliably stopping the traveling machine body 3.

Incidentally, when the support shaft 36 (traveling HST 10) is operated via the brake operation linkage mechanism 40 by stepping on the brake pedal 18, the clutch 41 can reliably prevent the axial rotation of the support shaft 36 from being transmitted to the motor 42. As a result, when the traveling HST 10 is forcibly shifted by the operator's brake operation (manual operation), the motor 42 is not forcibly rotated, so it is possible to prevent the motor 42 from being subjected to unnecessary load and breaking down.

Next, the control contents of the HST shift control by the control unit will be explained based on Figures 8 and 9. Figure 8 is a block diagram of the control unit, Figure 9 (A) is a diagram showing the vehicle speed when the shift lever is operated to shift continuously forward or reverse, return, and decelerate, Figure 9 (B) is a diagram showing the vehicle speed when the shift lever is operated to shift in a stepped manner forward or reverse, and Figure 9 (C) is a diagram showing the difference in vehicle speed between normal mode and low-speed mode.

The input side of the control unit 50 is connected to the operation position detection potentiometer 46 that detects the operation position of the main shift lever 14, a detection potentiometer (operation arm detection potentiometer) 47 that detects the operation position of the operation arm 38 (trunnion shaft 35), and the switch operation device 14a, and the output side of the control unit 50 is connected to the motor 42 (see Figure 8). The control unit 50 also has a timer and is configured to be able to detect the operation time during which the main shift lever 14 is oscillated.

The operating position detection potentiometer 47 is configured to be able to detect the operating position of the main shift lever 14, specifically the operating direction of the main shift lever 14 (forward or reverse), the amount of operation from the neutral position, and the operating speed (angular velocity of the shaft) when the main shift lever 14 is swung. It is also configured to be able to detect the operating time when the main shift lever 14, which is biased toward the neutral position using the timer or the like, is swung.

The HST shift control by the control unit 50 is configured to shift the travel HST 10 to the forward or reverse side in a stepless manner according to the operating position of the main shift lever 14 when a swing operation (hereinafter, "stepless shift operation") is detected from the neutral position toward the forward or reverse position for a preset period of time or more (see (1) in FIG. 9(A)), and thereafter, when an operation (return operation) of the main shift lever 14 to return to the neutral position is detected, the travel speed at the time the return operation was detected is maintained (see (2) in FIG. 9(A)).

To be more specific, when the stepless speed change operation in the forward direction of the main shift lever 14 is detected and the traveling HST 10 is in a neutral state, the traveling HST 10 (trunnion shaft 35) is shift-controlled so that the traveling machine body 3 increases (or decreases) speed steplessly in a direction corresponding to the operation direction of the main shift lever 14 and toward a traveling speed corresponding to the operation position of the main shift lever 14 (amount of operation from the neutral position).

Incidentally, when the main speed change lever 14 is operated to perform a stepless speed change (stepless deceleration) in the direction opposite to the traveling direction of the traveling machine body 3, the traveling HST 10 is decelerated steplessly (see (3) in Figure 9 (A)).

In response to this, when the traveling HST 10 is operated from a forward or reverse state to a neutral state by the above-mentioned stepless deceleration operation and the traveling machine body 3 is stopped, the control unit 50 is configured to restrict the traveling HST 10 from shifting to the forward or reverse side depending on the operating position of the main shift lever 14, even if the operation of the main shift lever 14 to the forward or reverse position is maintained.

In this case, the control unit 50 is configured to release the state that restricts the main shift lever 14 from shifting the traveling HST 10 from the neutral state to the forward or reverse side when a return operation of the main shift lever 14 to the neutral position is detected.

This configuration reliably prevents the traveling machine body 3 from starting to travel in the reverse direction immediately after stopping when the main speed change lever 14 is used to perform a deceleration operation, thereby improving safety.

On the other hand, the HST shift control is configured to shift the traveling HST 10 in a stepped manner according to the direction of operation of the main shift lever 14 when an operation of swinging the main shift lever 14 back and forth to return it to the neutral position in a time shorter than a predetermined time (hereinafter, a stepped shift operation) is detected (see FIG. 9(B)).

To be more specific, when the traveling HST 10 is in neutral or forward travel and the main shift lever 14 is operated to shift forward (stepped speed increase), the traveling HST 10 is accelerated in the forward travel direction by a preset speed increase amount (see (4) in FIG. 9(B)). Note that when the traveling HST 10 is in reverse travel and the main shift lever 14 is operated to shift forward (stepped speed decrease), the traveling HST 10 is decelerated by a preset speed decrease amount (see (5) in FIG. 9(B)).

Similarly, when the traveling HST 10 is in neutral or reverse and the main shift lever 14 is operated to shift gears in the reverse direction (stepped speed increase operation), the traveling HST 10 is accelerated in the reverse direction by a preset speed increase amount (see (4) in FIG. 9(B)). Note that when the traveling HST 10 is in a forward state and the main shift lever 14 is operated to shift gears in the reverse direction (stepped speed reduction operation), the traveling HST 10 is decelerated by a preset speed reduction amount (see (5) in FIG. 9(B)).

This configuration improves operability by allowing the single main shift lever 14 to selectively operate the traveling machine body 3 (traveling HST 10) for stepless speed change and stepped speed change.

The HST shift control is configured such that, when it is detected that the main shift lever 14 has been swung forward to the front end operating position (reverse stop operation) while the traveling machine body 3 is traveling in reverse, the traveling HST 10 is operated from the reverse state to the neutral state, and, when it is detected that the main shift lever 14 has been swung backward to the rear end operating position (forward stop operation) while the traveling machine body 3 is traveling in forward, the traveling HST 10 is operated from the forward state to the neutral state.

With this configuration, no matter what speed the traveling machine body 3 is traveling at, a simple operation (stopping operation) of the main shift lever 14 can stop the traveling machine body 3 safely and smoothly, improving operability and safety.

The HST shift control is configured so that when the main shift lever 14 is swung forward or backward, the closer the operating position of the main shift lever 14 is to the neutral position, the slower the operating speed of the trunnion shaft 35 operated via the motor 42 becomes.

This configuration allows easy fine adjustment of the running speed of the traveling body 3, and allows the traveling body 3 to be easily and smoothly operated to a slow speed at which it can be stopped immediately and maintained at that slow speed, making it easy to perform delicate tasks such as parking a work vehicle in a garage.

Furthermore, the HST shift control is configured so that it can be switched from normal mode to low-speed mode by pressing the switch operating device 14a, and by swinging the main shift lever 14 back and forth when switched to low-speed mode, the shift range of the traveling HST 10, which is changed according to the operating position of the main shift lever 14, can be made smaller than in normal mode (see FIG. 9(C)).

According to this configuration, by operating the main speed change lever 14 while switched to low-speed mode, the speed range in which the vehicle speed of the traveling machine can be operated is narrowed even with the same operating range, so the vehicle speed cannot be increased, but fine speed adjustments become easier. This prevents the vehicle speed from becoming too fast when traveling for work in a field, and makes it easier and smoother to adjust the desired work traveling speed.

2 Traveling body 7 Control unit 10 Traveling HST (hydraulic variable speed transmission, variable speed transmission)
14. Gear shift lever (gear shifting device)
35 Trunnion axis 42 Motor (actuator)
50 Control unit

Claims (5)

A traveling machine body having a control unit where an operator operates the traveling machine;
A hydraulic transmission that changes the speed of the traveling power of the traveling machine body;
A gear shifting tool provided in the steering section for performing a gear shifting operation of the hydraulic transmission device;
an operating position detection means for detecting an operating position of the gear shift operating tool;
An actuator for operating a trunnion shaft of the hydraulic transmission;
a control unit that switches the hydraulic transmission device to a forward state, a neutral state, or a reverse state according to the operating position of the shift operating tool,
the speed change operating device is configured to be pivotable in two different directions from a neutral position, and is configured to automatically return to the neutral position when the pivoting operation from the neutral position is released;
the control unit is configured to shift the hydraulic transmission to a forward side when the shift operating device is swung to one side from a neutral position, and to shift the hydraulic transmission to a reverse side when the shift operating device is swung to the other side from a neutral position,
The control unit is configured to perform stepless gear change in accordance with the operating position of the gear change device when the gear change device is operated toward the forward or reverse side for a predetermined period of time or more, and to perform stepped gear change in accordance with the operating direction of the gear change device when the gear change device is operated toward the forward or reverse side within a predetermined period of time. The work vehicle according to claim 1, wherein the control unit is configured to increase or decrease the operating speed of the trunnion shaft operated via the actuator in accordance with an amount of operation of the shift operating device from a neutral position, when the shift operating device is used to perform a stepless gear change. the control unit is configured to maintain a neutral state of the hydraulic transmission device when the trunnion shaft is operated to a neutral state by a stepless speed change operation using the speed change device , and to restrict the speed change operation of the hydraulic transmission device via the speed change device ,
3. The work vehicle according to claim 1 or 2, wherein the control unit is configured such that, when the gear shift operation by the gear shift operating device is restricted, the restriction on the gear shift operation by the gear shift operating device is released by returning the gear shift operating device to a neutral position. 4. The work vehicle according to claim 1, wherein the control unit is configured to be able to switch between a normal mode in which the hydraulic transmission is changed in accordance with an amount of operation of the shift operating device, and a low speed mode in which the amount of shifting that can be performed by the shift operating device is smaller than that in the normal mode, when the shift is continuously changed by the shift operating device. 5. The work vehicle according to claim 1, wherein the control unit is configured to slow down the operating speed of the trunnion shaft operated via the actuator as the operation amount of the gear shift operating device from a neutral position decreases.

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