Work vehicle

Abstract

To provide a work vehicle capable of safely executing work even when a safety frame is in a folded attitude.SOLUTION: A work vehicle having an automatic transmission mode for automatically shifting a main transmission 302 depending on the number of revolutions of an engine E and the vehicle speed of a traveling car body 2, and a manual transmission mode by a main gear shift lever 11, includes: a safety frame 14 to ensure a space in which a driver of the traveling car body 1 is present, where the safety frame 14 is configured to be freely switchable between a standing attitude and a folded attitude; and a safety frame sensor 144 for detecting whether the safety frame 14 is in the standing attitude or the folded attitude. The work vehicle is configured to output a warning to warning means 20 when the safety frame 14 is in the folded attitude and in the automatic transmission mode.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a work vehicle.

Background Art

[0002] Conventionally, there is known a rolling machine that includes a safety frame composed of a lower frame and an upper frame, the lower frame is attached to the rear part of the vehicle body so as to straddle the left and right directions of the vehicle body, a hinge is provided to change the state of the upper frame being erected, and when it is detected by a sensor that the upper frame is folded and it is detected that the parking lock is released in a state where the folded state is detected, a warning is given to the operator and surrounding workers by warning means (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in work vehicles such as agricultural tractors, for example, there are cases where work is carried out in workplaces with height restrictions, such as in greenhouses or orchards, and it may be necessary to work and travel with the safety frame in a folded posture.

[0005] However, in the conventional technology as described above, since a function for safely traveling with the upper frame in a folded posture is not installed, if working and traveling with the upper frame in a folded posture, there is a risk of tipping over and it may not be possible to work safely.

[0006] An object of the present invention is to provide a work vehicle capable of safely performing work even when the safety frame is in a folded posture.

Means for Solving the Problems

[0007] The present invention has taken the following technical measures to solve the above problems.

[0008] In the work vehicle having an automatic transmission mode in which the main transmission 302 is automatically shifted according to the engine speed of the engine E and the vehicle speed of the traveling vehicle body 2, and a manual transmission mode by the main transmission lever 11, a safety frame 14 for securing a space where the driver of the traveling vehicle body 1 exists is provided. The safety frame 14 is configured to be switchable between an upright posture and a folded posture, and a safety frame sensor 144 for detecting whether the safety frame 14 is in the upright posture or the folded posture is provided. When the safety frame 14 is in the folded posture and in the automatic transmission mode, a warning output is given to the warning means 20.

[0009] In the invention according to claim 2, in the invention according to claim 1, an operation changeover dial 16 for switching between an operation mode and a non-operation mode is provided. When the safety frame 14 is in the folded posture and the operation changeover dial 16 is set to the non-operation mode, a warning output is given to the warning means 20.

[0010] In the invention according to claim 3, in the invention according to claim 1 or claim 2, a subtransmission lever 18 for shifting the subtransmission 304 is provided. When the safety frame 14 is in the folded posture and the operation position of the subtransmission lever 18 is in the high-speed position, a warning output is given to the warning means 20.

[0011] In the invention according to claim 4, in the invention according to any one of claims 1 to 3, when the safety frame 14 is in the folded posture and the accelerator pedal 19 is operated, a warning output is given to the warning means 20.

[0012] In the invention according to claim 5, in the invention according to any one of claims 1 to 4, when the safety frame 14 is in the folded posture and the detected vehicle speed by the vehicle speed sensor 310 is equal to or higher than a certain vehicle speed, a warning output is given to the warning means 20.

Advantages of the Invention

[0013] According to the present invention, although it is dangerous to fall in a state where the safety frame is folded during road travel, if such road travel is assumed, warning output can prompt an operator to pay attention.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the embodiments shown below.

[0016] A tractor 1 which is a work vehicle is an agricultural tractor that performs work (agricultural work) at work sites such as inside a greenhouse or an orchard in addition to a farm field while self-propelling.

[0017] Also, the tractor 1 performs predetermined work while traveling in a farm field by a driver boarding and driving the tractor 1.

[0018] As shown in FIG. 1, the tractor 1 includes a traveling vehicle body 2 and a working machine 6. The traveling vehicle body 2 can travel not only in the field but also in a vinyl house or an orchard, etc., and includes front wheels 3 and rear wheels 4. The front wheels 3 are a pair of left and right steering wheels (steering wheels). The rear wheels 4 are a pair of left and right driving wheels (drive wheels). Note that the traveling vehicle body 2 may be provided with a crawler device instead of the front wheels 3 and the rear wheels 4. In this case, the traveling crawler is the drive wheel.

[0019] To the rear wheels 4 which are drive wheels, the rotational power generated by the engine E which is a drive source housed in the bonnet 5 is appropriately decelerated and transmitted by a transmission (transmission) incorporated in the power transmission device 12. The rear wheels 4 which are drive wheels are driven by the rotational power transmitted from the engine E.

[0020] As described above, the engine E is mounted on the front part of the traveling vehicle body 2. The rotational power from the engine E is transmitted to the front wheels 3 and the rear wheels 4 via the power transmission device 12. Further, the tractor 1 includes a 4WD clutch 301, and is configured to be switchable between a 2WD mode in which only the rear wheels 4 are driven and a 4WD mode in which both the front wheels 3 and the rear wheels 4 are driven by switching the 4WD clutch 301.

[0021] In FIG. 2, as a power transmission mechanism to the rear wheels 4, a main transmission 302 is disposed behind the engine E via a forward and reverse clutch 303 that switches the forward, reverse, and stop of the tractor 1 (traveling vehicle body 2) between forward connection, reverse connection, and neutral. Further, a sub-transmission 304 which is a transmission is disposed further rearward, and a rear-wheel differential gear device 305 is disposed further rearward. Also, brake devices 306 are respectively disposed at the base of the rear axle 41 that connects the rear-wheel differential gear device 305 and the rear wheels 4. To the power transmission mechanism to the rear wheels 4, power is input to a transmission shaft 307 via an idle gear provided at the rear stage of the sub-transmission 304, and is transmitted to the front wheels 3 via the 4WD clutch 301 and the front-wheel differential gear device 308.

[0022] The transmission device switches the rotational power transmitted from the engine E to any one of a plurality of speed stages by combining the main transmission device 302 and the auxiliary transmission device 304. The main transmission device 302 shifts the rotational power transmitted from the engine E to speeds from 1st to 4th, and the auxiliary transmission device 304 switches to either a low speed stage, a medium speed stage, or a high speed stage.

[0023] The traveling vehicle body 2 can also transmit the power generated by the engine E and decelerated by the main transmission device 302 etc. to the front wheels 3 via the 4WD clutch 301. In this case, when the 4WD clutch 301 transmits power, the four wheels of the front wheels 3 and the rear wheels 4 are driven by the power transmitted from the engine E. Thus, the traveling vehicle body 2 is configured to be able to switch between two-wheel drive (2WD) and four-wheel drive (4WD).

[0024] An implement 6 for performing work is connected to the rear part of the traveling vehicle body 2. A PTO device 7 having a PTO shaft 71 for driving the implement 6 is provided at the rear part of the traveling vehicle body 2.

[0025] Also, a lifting device 13 for raising and lowering the implement 6 is provided at the rear part of the traveling vehicle body 2. The lifting device 13 moves the implement 6 to a non-working position by raising the implement 6. Also, the lifting device 13 moves the implement 6 to a working (ground working) position by lowering the implement 6. The lifting device 13 includes a three-point link mechanism composed of a lower link 134 and a top link 135, a hydraulic lifting cylinder 131, a lift arm 132, and a lift rod 133, and can lift and lower the implement 6 connected via the three-point link mechanism composed of the lower link 134 and the top link 135 in an interlocking manner. A lift arm sensor 136 capable of detecting the rotation angle of the lift arm 132 is provided.

[0026] When hydraulic oil is supplied to the lift arm 132, the lift arm 132 rotates about the rotation axis to raise the working machine 6, and when the hydraulic oil is discharged from the lift cylinder 131, the lift arm 132 rotates about the rotation axis to lower the working machine 6. The lift arm sensor 136 is provided at the base of the lift arm 132 (near the rotation axis) and detects the rotation angle of the lift arm 132. The height of the working machine 6 is detected based on the detection value of the lift arm sensor 136. That is, the lift arm sensor 136 detects the lifting position (height) of the working machine 6.

[0027] Further, the lift arm 132 is connected to the lower link 134 via a lift rod 133. In this way, the lifting device 13 connects the working machine 6 to the traveling vehicle body 2 via the lower link 134 and the top link 135 so that the working machine 6 can be lifted and lowered. Note that FIG. 1 illustrates the case where the working machine 6 is a rotary tiller. The rotary tiller tills the working surface (soil) by rotating the tilling claws 61 by the power transmitted from the PTO shaft 71 of the PTO device 7.

[0028] A driver's seat 8 on which the driver sits when operating the tractor 1 is provided at the center of the traveling vehicle body 2. In front of the driver's seat 8, a steering wheel 9 for steering the front wheels 3, which are steering wheels, is provided. Near the steering wheel 9, there are provided a forward and reverse operation tool (hereinafter referred to as a forward and reverse lever) 10 that is operated when switching the forward and reverse clutch 303 to move the machine forward, backward, and stop (park), and a lifting operation tool (hereinafter referred to as a lifting lever) 15 (see FIG. 3) that is operated when lifting and lowering the working machine 6.

[0029] Further, near the steering wheel 9, there are provided a mode switch 16 (see FIG. 3) and the like that are operated when switching between a working travel mode and a non-working travel mode of the machine body, which will be described later.

[0030] Also, below the steering wheel 9, near the driver's feet when the driver is seated in the driver's seat 8, various operation pedals (such as an accelerator pedal, a brake pedal, a clutch pedal, etc.) are provided. Also, on the right side of the driver's seat 8, a main shift lever 11 that is operated when switching the main transmission 302 to a low speed gear or a high speed gear is provided. Also, on the left side of the driver's seat 8, a sub-shift lever 18 that can be switched among three stages of low speed, medium speed, and high speed is provided. Furthermore, various operation levers and operation switches are provided near the driver's seat 8.

[0031] The tractor 1 has an open area around the driver's seat 8 and is equipped with a safety frame 14 behind the driver's seat 8. The safety frame 14 is a structure for ensuring the safety of the driver in the event of a rollover. The safety frame 14 can be switched between an upright posture for functioning the safety frame 14 and a folded posture which is a stored posture.

[0032] The safety frame 14 has a lower frame 141, an upper frame 142, a hinge portion 143, and a safety frame sensor 144. The safety frame 14 is provided so as to straddle the traveling vehicle body 2 in the left-right direction and is generally U-shaped with the lower side open in a front view. The lower frame 141 constitutes the base of the safety frame 14. The lower frame 141 is a pair on the left and right and is provided along the vertical direction. The upper frame 142 is provided so as to be installed in the left-right direction with respect to the pair of left and right lower frames 141.

[0033] The upper frame 142 is attached to the lower frame 141 via the hinge portion 143. The hinge portion 143 rotatably supports the upper frame 142. The upper frame 142 tilts backward by the hinge portion 143. In the safety frame 14, the state where the upper frame 142 is upright is defined as the upright posture, and the state where the upper frame 142 is tilted (folded) is defined as the folded posture.

[0034] The safety frame sensor 144 detects whether the safety frame 14 is in the upright position or the folded position. The safety frame sensor 144 is provided, for example, at the hinge portion 143 and detects whether the safety frame 14 is in the upright position or the folded position by turning ON, for example, when the upper frame 142 is erected.

[0035] In this way, the tractor 1 equipped with the foldable safety frame 14 can be set in the folded position when working, for example, in a place with a low ceiling height such as inside a vinyl house or in a place with fruit tree branches at a height as low as a person's height such as an orchard, enabling work in places with height restrictions.

[0036] The tractor 1 also includes a control unit 100 (see FIGS. 2 and 3). The control unit 100 controls the engine E and the traveling speed of the traveling vehicle body 2. The control unit 100 also controls the work implement 6.

[0037] Connected to the control unit 100 is a steering wheel cut angle sensor (hereinafter referred to as the front wheel cut angle sensor) 309 that detects the steering angle (hereinafter referred to as the cut angle) of the front wheel 3, which is a steering wheel.

[0038] The brake device 306 provided on the rear wheels 4 functions when the operator depresses the left and right brake pedals 311L and 311R provided on the traveling vehicle body 2, causing the brake cylinder 317 to act by hydraulic pressure. That is, the left brake device 306L provided at the base of the left rear axle 41L is connected to the left brake cylinder 317L, and the right brake device 306R provided at the base of the right rear axle 41R is connected to the right brake cylinder 317R.

[0039] The left and right brake cylinders 317L and 317R are connected to the left and right brake solenoids 312L and 312R connected to the control unit 100. Therefore, when a predetermined brake signal is input to the control unit 100, the control unit 100 can drive the brake solenoid 312 to operate either one or both of the left and right brake devices 306L and 306R. The brake solenoids 312L and 312R form a hydraulic circuit together with a hydraulic pump 314, a relief valve 315, etc. via a proportional pressure regulating valve 313, for example.

[0040] Further, the tractor 1 includes a PTO clutch 316. The PTO clutch 316 is an electronically controlled clutch that connects or disconnects the power to the PTO shaft 71 connected to the working machine 6 (see FIG. 1). The rotational power from the engine E is transmitted to the PTO shaft 71 in a connectable and disconnectable manner by the PTO clutch 316.

[0041] Also, the PTO shaft 71 is provided with a PTO speed change first shifter and a PTO speed change second shifter on the front stage side. By operating each of these shifters, the PTO shaft 71 can be rotated forward from low speed to high speed and can also be reversed.

[0042] Next, the control system of the work vehicle (tractor) 1 will be described with reference to FIG. 3. As shown in FIG. 3, the control unit 100 includes an engine ECU 101, a traveling system ECU 102, and a work implement lifting system ECU 103.

[0043] The engine ECU 101 controls the rotational speed of the engine E. The traveling system ECU 102 controls the rotational speed of the drive wheels (rear wheels 4) to control the traveling speed of the traveling vehicle body 2 (see FIG. 1). The work implement lifting system ECU 103 controls the lifting device 13 to drive the work implement 6 up and down.

[0044] Note that the control unit 100 is a computer provided with a processing device such as a CPU, a storage device such as a ROM, a RAM, and an HDD, and further an input / output device.

[0045] The control unit 100 is electrically connected to an engine speed sensor 17 that detects the rotational speed of the engine E, a front wheel steering angle sensor 309 that detects the steering angle of the front wheels 3 (see FIG. 2), a lift arm sensor 136 that detects the height of the work implement 6, a lift lever 15 that is operated when changing the lifting position of the work implement 6 by the lifting device 13, a work mode change dial 16 that switches between the work running mode and the non-work running mode, a forward / reverse lever 10 that is operated when connecting the forward / reverse clutch 303 to forward, reverse, and neutral, and a safety frame sensor 144 that detects the attitude of the safety frame 14.

[0046] The control unit 100 receives detection signals (such as the rotational speed of the engine E, the angle of the steering angle of the front wheels 3, the height of the work implement 6, and a determination signal as to whether the safety frame 14 is in the upright position or the folded position) from the engine speed sensor 17, the front wheel steering angle sensor 309, the lift arm sensor 136, and the safety frame sensor 144, respectively, operation signals from the lift lever 15 and the forward / reverse lever 10, and a switching signal (a determination signal as to whether it is the work running mode or the non-work running mode) from the work mode change dial 16.

[0047] Furthermore, detection signals obtained by shift operations are input to the control unit 100 from a vehicle speed sensor 310, main shift lever sensors 311a, 311b, 311c, 311d that detect the shift positions of the main shift lever 11, and sub-shift lever sensors 312a, 312b, 312c that detect the shift position of the sub-shift lever 18. Among these, each detection by the main shift lever sensors 311a to 311d outputs a signal to any one of the first-speed clutch 302a to the fourth-speed clutch 302d of the main transmission 302, and is configured to perform a shift change.

[0048] In the guide portion of the main shift lever 11, in addition to the positions of the shift stages from the first speed to the fourth speed, an automatic shift mode position D is provided. When the main shift lever 11 is in this automatic shift mode position D, the shift lever sensor 311d detects this and outputs it to the control unit 100. Then, the control unit 100 executes shifting in the automatic shift mode. That is, the running system ECU 102 inputs the detection signals of the engine speed sensor 17 and the vehicle speed sensor 310, calculates the appropriate shift position, and outputs a signal to any one of the first speed clutch 302a to the fourth speed clutch 302d based on this calculation result. It is configured to be able to automatically set an appropriate shift position according to the change in the engine speed by the operation of the accelerator pedal 19.

[0049] Further, the control unit 100 can execute a front wheel speed increase mode in which the 4WD clutch 301 is operated to change the reduction ratio of the rotational power transmission to the front wheels 3, thereby increasing (for example, doubling) the rotational speed of the front wheels 3. In the front wheel speed increase mode, when the front wheel steering angle sensor 309 detects a steering angle of the front wheels 3 that is a predetermined angle or more, the control unit 100 operates the 4WD clutch 301 to increase the turning speed.

[0050] Further, the control unit 100 can execute a work running mode in which the control settings of the tractor 1 are set to be suitable for running during work. Also, the control unit 100 can execute a non-work running mode in which the control settings of the tractor 1 are set to be suitable for running during non-work (for example, road running). Note that the switching between the work running mode and the non-work running mode can be performed by operating the mode switching switch 16.

[0051] Here, as described above, the tractor 1 may work not only in the field but also in workplaces with height restrictions such as inside a greenhouse or an orchard. In this case, when the safety frame 14 travels in an upright position, the safety frame 14 protruding upward from the machine body may get caught on the ceiling of the greenhouse or the branches of fruit trees, resulting in a decrease in work efficiency and the risk of damage to the greenhouse, fruit trees, or the tractor 1. For this reason, in workplaces with height restrictions such as inside a greenhouse or an orchard, it is preferable to operate and travel with the safety frame 14 in a folded position, but there is a risk that the safety in case of tipping cannot be ensured.

[0052] In the present embodiment, by executing the anti-tipping control when the safety frame 14 is in the folded position, safety can be ensured even when the safety frame 14 is in the folded position and the tractor is operating and traveling. Note that the anti-tipping control when the safety frame 14 is in the folded position may be configured to be performed by switches near the driver's seat 8.

[0053] Next, with reference to FIG. 4, the processing procedure of the anti-tipping control in the folded position of the safety frame 14 will be described. In FIG. 4, when the tractor 1 is operating and traveling in a workplace with height restrictions such as inside a greenhouse or an orchard, as shown in FIG. 4, the control unit 100 determines whether the safety frame 14 is in the folded position (steps S101, S102). Then, when it is detected by the safety frame sensor 144 that the safety frame 14 is in the folded position, it is detected whether the position of the main transmission lever 11 is in the automatic transmission mode position D (S103, S104).

[0054] When the safety frame 14 is in the folded position and in the automatic transmission mode position D, a warning output is given to the warning means 20 (S105). Here, the warning output can be various, such as a buzzer or horn sound output, or a voice warning output. In addition to these, the warning means 20 may employ lighting means such as a hazard lamp.

[0055] With this configuration, when the automatic transmission mode assumed for road travel is selected, attention can be prompted by the warning output.

[0056] In step S104, when the main shift lever 11 is in a position other than the automatic shift mode position D and a manual shift mode is detected by detecting any one of the main shift lever sensors 311a to 311d, the operation position of the work changeover dial 16 is detected and it is determined whether it is in a non-operation mode (S106, S107). If it is determined that it is in the non-operation mode, the process proceeds to S105 and a warning is output. As a specific example of the work changeover dial 16, it has at least "cultivation" and "travel" at the dial switching positions. At the "cultivation" position as the work mode operation position, control functions required for rotary tiller work are set, for example, front wheel speed increase control during turning, automatic raising and lowering control of the work implement during turning, automatic raising control of the work implement during reverse shifting, single brake operation setting,.... At the "travel" position corresponding to the non-operation mode operation position, these functions are reset to avoid risks during high-speed road travel.

[0057] Therefore, when a non-operation mode assuming road travel is selected, attention can be prompted by warning output.

[0058] In step S107, when the work changeover dial 16 does not determine the non-operation mode, the operation position of the sub-shift lever 18 is detected and it is determined whether it is in the high-speed position (S108, S109). That is, when the sub-shift lever sensor 312c detects and outputs and it is determined that it is in the high-speed position, the process proceeds to S105 and a warning is output. With this configuration, when the sub-shift is selected in the high-speed position assuming road travel, attention can be prompted by warning output. Note that work travel is assumed at the low-speed position and the medium-speed position of the sub-shift lever sensor 312, but it may also be configured to proceed to S105 and prompt attention even at the medium-speed position.

[0059] In S109, when the auxiliary shift lever sensor 312 does not determine the high-speed position, it is determined whether the accelerator pedal 19 is being operated (S110, S112). Here, the detection that the accelerator pedal 19 is being operated can be detected by an accelerator pedal sensor 319 such as a potentiometer provided on the accelerator pedal rotation axis or a limit switch arranged at a predetermined depression position of the pedal. When the accelerator pedal 19 is being operated, the process proceeds to S105 and a warning is output. When the accelerator pedal 19 is being operated assuming road driving, attention can be prompted by the warning output.

[0060] If it is determined in S111 that the accelerator pedal 19 is not being operated, the detection of the vehicle speed sensor 310 is determined (S112, S113), and if the vehicle speed is above a certain level, the process proceeds to S105 and a warning is output. With this configuration, when driving at a vehicle speed at which it is easy to tip over, attention can be prompted by the warning output.

[0061] FIG. 5 shows the support configuration of the lower support column 141 of the safety frame 14. Rear axle cases 403 for supporting the rear axles 402 are provided on the left and right of the rear part of the transmission case 401 that constitutes the traveling vehicle body 2, and the lower end of the lower support column 141 of the safety frame 14 is supported by this rear axle case 403. Specifically, a base member 404 is detachably fixed to the outer end of the rear axle case 403, an upward flange portion 405 is provided on this base member 404, and the flange portion 141a on the lower end side of the lower support column 141 is opposed to the above flange portion 405 vertically, and they are fixed with an elastic material interposed therebetween. And a reinforcing member 406 bent in an L shape in plan view is connected to the flange portion 405 on the base member 404 side. Note that the rear end side of the reinforcing member 406 bypasses the rear end corner of the transmission case 401 and is firmly connected to the rear surface. With this configuration, the base of the safety frame 14 can be firmly configured.

[0062] Note that the connection configuration of the base member 404, the flange portion 405, and the reinforcing member 406 can be directly applied to the support configuration of the cabin.

[0063] FIG. 6 shows the support structure of the safety frame 14A as a so-called center post. The lower support column 141A is attached to the side surface of the engine bracket 408 that constitutes the traveling vehicle body 1 by means such as welding to a first flange member 409 that is attached in a superposed state. And the rear side of the first flange member 409 also serves as a second flange member 411 that is attached to the transmission case 401 at the base side of a support bracket 410 provided in a protruding state on the side surface of the transmission case 401. Therefore, the first flange member 409 can be made into a strong rigid structure, and the safety frame 14A can be stably supported. Note that a support hole 410a for an elastic member (not shown) is formed in the support bracket 410 and can be applied to the front support structure of the cabin.

Description of Signs

[0064] 2 Traveling vehicle body 11 Main shift lever 14 Safety frame 144 Safety frame sensor 16 Work switching dial 18 Sub-shift lever 19 Accelerator pedal 20 Warning means 302 Main transmission 304 Sub-transmission 310 Vehicle speed sensor E Engine

Claims

1. In a work vehicle equipped with an automatic transmission mode for automatically shifting a main transmission (302) according to the engine speed (E) and the vehicle speed of the traveling vehicle body (2), and a manual transmission mode by a main transmission lever (11), a safety frame (14) is provided to secure a space for the driver of the traveling vehicle body (2). The safety frame (14) is configured to be switchable between an upright position and a folded position, and a safety frame sensor (144) is provided to detect whether the safety frame (14) is in the upright position or the folded position. When the safety frame (14) is in the folded position and in the automatic transmission mode, a warning means (20) is configured to output a warning. A work vehicle characterized by this.

2. A work switching dial (16) for switching between a work mode and a non-work mode is provided. When the safety frame (14) is in the folded position and the work switching dial (16) is set to the non-work mode, the work vehicle according to claim 1, wherein a warning means (20) is configured to output a warning.

3. A sub-transmission lever (18) for shifting a sub-transmission (304) is provided. When the safety frame (14) is in the folded position and the operating position of the sub-transmission lever (18) is in the high-speed position, the work vehicle according to claim 1 or claim 2, wherein a warning means (20) is configured to output a warning.

4. When the safety frame (14) is in the folded position and the accelerator pedal (19) is operated, the work vehicle according to any one of claims 1 to 3, wherein a warning means (20) is configured to output a warning.

5. When the safety frame (14) is in the folded position and the detected vehicle speed by a vehicle speed sensor (310) is equal to or higher than a certain vehicle speed, the work vehicle according to any one of claims 1 to 4, wherein a warning means (20) is configured to output a warning.

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