JP7521409B2 - Work vehicles - Google Patents

Description

The present invention relates to a work vehicle.

Conventionally, there are work vehicles equipped with a safety frame called a ROPS (Roll-Over Protective Structure), which has an upper frame and a lower frame, is attached to the vehicle body so as to straddle the vehicle body in the left-right direction, and can be moved between an upright position (upright posture) and a folded position (folded posture). By putting the safety frame in an upright position, such work vehicles create space around the driver's seat even if the vehicle rolls over, ensuring the safety of the driver in the event of a rollover.

In addition, in such a work vehicle, a technology is known that issues an alarm to the driver and surrounding workers when it is detected that the safety frame is in a folded position and that the parking lock is also released (see, for example, Patent Document 1).

Patent No. 6646608

However, agricultural tractors and other work vehicles may be required to work in work areas with height restrictions, such as inside greenhouses or in orchards, and may need to be driven with the safety frame in a folded position.

However, the conventional technology described above does not have a function for safely traveling with the safety frame in the folded position, so there is a risk of tipping over when traveling for work with the safety frame in the folded position, and there is a risk of not being able to work safely.

One aspect of the embodiment aims to provide a work vehicle that can prevent tipping over and allow work to be carried out safely even when the safety frame is in a folded position.

In order to solve the above-mentioned problems and achieve the object, the work vehicle (1) according to the embodiment is a structure that ensures the safety of the driver in the event of a rollover, and is a work vehicle (1) equipped with a safety frame (14) that can be switched between an upright position and a folded position, and is equipped with steering wheels (3) and drive wheels (4), an engine (E) that generates rotational power for the drive wheels (4), an engine speed sensor (17) that detects the rotation speed of the engine (E), a control unit (100) that controls the rotation speed of the engine (E), and a control unit (101) that controls the rotation speed of the engine (E). The vehicle is equipped with a safety frame sensor (144) that detects whether the frame (14) is in the upright position or the folded position, and a steering wheel angle sensor (309) that detects the steering angle of the steering wheel (3), and the control unit (100) is characterized in that when the safety frame sensor (144) detects the folded position and the steering wheel angle sensor (309) detects a steering angle of the steering wheel (3) that is equal to or greater than a predetermined angle, the control unit (100) limits the rotation speed of the engine (E) to a predetermined rotation speed or less.

The work vehicle according to the embodiment can prevent tipping over even when the safety frame is in the folded position, allowing work to be carried out safely.

FIG. 1 is a schematic left side view showing a work vehicle according to a first embodiment. FIG. 2 is an explanatory diagram of the power transmission configuration of the work vehicle according to the first embodiment. FIG. 3 is a block diagram showing an example of a control system in the work vehicle according to the first embodiment. FIG. 4 is a flowchart illustrating an example of a processing procedure of the overturn prevention control in the first embodiment. FIG. 5 is a flowchart illustrating an example of a processing procedure of the overturn prevention control in the second embodiment. FIG. 6 is a flowchart illustrating an example of a processing procedure of the overturn prevention control in the third embodiment. FIG. 7 is a flowchart illustrating an example of a processing procedure of the overturn prevention control in the fourth embodiment. FIG. 8 is a flowchart illustrating an example of a processing procedure of the overturn prevention control in the fifth embodiment.

Embodiments of the work vehicle disclosed in this application will be described in detail below with reference to the attached drawings. Note that the present invention is not limited to the embodiments described below.

First Embodiment
<Overall configuration of work vehicle (tractor)>
First, the overall configuration of a work vehicle 1 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic left side view showing the work vehicle 1 according to the first embodiment. In the following, a tractor will be used as an example of the work vehicle 1. The tractor 1, which is a work vehicle, is an agricultural tractor that travels by itself and performs work (agricultural work) in work areas such as farm fields, vinyl greenhouses, orchards, etc.

The tractor 1, which is a work vehicle, is operated by a driver (also called the worker) who rides on the tractor 1 to perform a specified task while traveling around the work site.

In the explanation using the figures including FIG. 1, the forward/rearward direction is the direction of travel of the tractor 1 when traveling straight, with the forward side of the travel direction being defined as "front" and the rear side being defined as "rear." The travel direction of the tractor 1 is the direction from the driver's seat 8 to the steering wheel 9, which will be described later, when the tractor 1 is traveling straight.

The left-right direction is a direction that is horizontally perpendicular to the front-rear direction. In the following, left and right are defined with respect to the "front" side. That is, when the driver is seated in the driver's seat 8 and facing forward, the left hand side is the "left" and the right hand side is the "right". The up-down direction is the vertical direction. The front-rear direction, left-right direction, and up-down direction are perpendicular to each other in three dimensions. Note that in the following explanation, the tractor 1 or the traveling vehicle body 2 described below may be referred to as the "machine body".

As shown in FIG. 1, the tractor 1 comprises a running body 2 and a work implement 6. The running body 2 is capable of running in fields, as well as in vinyl greenhouses and orchards, and comprises front wheels 3 and rear wheels 4. The front wheels 3 are a pair of left and right wheels for steering (steering wheels). The rear wheels 4 are a pair of left and right wheels for driving (driving wheels). The running body 2 may be equipped with a crawler device instead of the wheels (front wheels 3 and rear wheels 4). In this case, the running crawlers are the driving wheels.

The rotational power generated by the engine E, which is the drive source housed inside the bonnet 5, is appropriately reduced in speed by a speed change device (transmission) incorporated in the power transmission device 12 and transmitted to the rear wheels 4, which are the drive wheels. The rear wheels 4, which are the drive wheels, are driven by the rotational power transmitted from the engine E.

The transmission switches the rotational power transmitted from the engine E to one of a number of gears (for example, 1st to 8th gears). In addition, the main transmission 302 (see FIG. 2) of the transmission switches the rotational power transmitted from the engine E to either a low gear or a high gear.

The traveling vehicle body 2 may be configured to transmit the power generated by the engine E and decelerated by the main transmission 302 or the like to the front wheels 3, for example, via a front wheel acceleration clutch (hereinafter referred to as 4WD clutch) 301 (see FIG. 2). In this case, when the 4WD clutch 301 transmits power, the four wheels, the front wheels 3 and the rear wheels 4, are driven by the power transmitted from the engine E. In this way, the traveling vehicle body 2 may be configured to be switchable between two-wheel drive (2WD) and four-wheel drive (4WD).

A work machine 6 that performs work is connected to the rear of the traveling body 2. A PTO device 7 having a PTO (Power Take-Off) shaft 71 that transmits power to drive the work machine 6 is provided to the rear of the traveling body 2.

A lifting device 13 for raising and lowering the working machine 6 is provided at the rear of the traveling vehicle body 2. The lifting device 13 moves the working machine 6 to a non-working position by raising the working machine 6. The lifting device 13 also moves the working machine 6 to a working (ground work) position by lowering the working machine 6. The lifting device 13 includes a hydraulic lifting cylinder 131, a lift arm 132, a lift rod 133, a lower link 134, a top link 135, and a lift arm sensor 136.

When hydraulic oil is supplied to the lift cylinder 131, the lift arm 132 rotates around the pivot shaft to raise the work machine 6, and when hydraulic oil is discharged from the lift cylinder 131, the lift arm 132 rotates around the pivot shaft to lower the work machine 6. The lift arm sensor 136 is provided at the base of the lift arm 132 (near the pivot shaft) and detects the rotation angle of the lift arm 132. The height of the work machine 6 is detected based on the detection value of the lift arm sensor 136. In other words, the lift arm sensor 136 is a lift sensor that detects the lifted position (height) of the work machine 6.

The lift arm 132 is connected to the lower link 134 via the lift rod 133. In this way, the lifting device 13 connects the working machine 6 to the traveling body 2 via the lower link 134 and the top link 135 so that the working machine 6 can be raised and lowered. Note that FIG. 1 illustrates an example in which the working machine 6 is a rotary tiller. The rotary tiller tills the working surface (soil) by rotating the tiller tines 61 using power transmitted from the PTO shaft 71 of the PTO device 7.

A driver's seat 8 is provided in the center of the traveling vehicle body 2, where the driver sits when driving the tractor 1. A steering wheel 9 is provided in front of the driver's seat 8 for steering the front wheels 3, which are the steerable wheels. Near the steering wheel 9, there are provided a forward/reverse operation device (hereafter referred to as a forward/reverse lever) 10 that is operated to move the machine forward, backward, and stop (park), and a lifting operation device (hereafter referred to as a lifting lever) 15 (see Figure 3) that is operated to raise and lower the work machine 6.

Also, near the steering wheel 9, there is provided a mode change switch 16 (see FIG. 3) that is operated to switch the vehicle between a work driving mode and a non-work driving mode, which will be described later.

In addition, various operating pedals (accelerator pedal, brake pedal, clutch pedal, etc.) are provided below the steering wheel 9, near the driver's feet when the driver is seated in the driver's seat 8. In addition, a main shift operating device (hereinafter referred to as a main shift lever) 11 that is operated when switching the main transmission 302 to a low gear or a high gear is provided near the driver's seat 8. In addition to the main shift lever 11, various operating levers and operating switches such as a sub-shift lever are provided near the driver's seat 8.

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 position for enabling the safety frame 14 to function, and a folded position for storage.

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 when viewed from the front. The lower frame 141 forms the base of the safety frame 14. The lower frames 141 are provided in a pair on the left and right, and are provided along the up-down direction. The upper frame 142 is provided so as to span the pair of left and right lower frames 141 in the left-right direction.

The upper frame 142 is attached to the lower frame 141 via hinge parts 143. The hinge parts 143 rotatably support the upper frame 142. The upper frame 142 is tilted backward by the hinge parts 143. In the safety frame 14, the state in which the upper frame 142 is standing is the standing position, and the state in which the upper frame 142 is tilted (folded) is the folded position.

The safety frame sensor 144 detects whether the safety frame 14 is in an upright position or a folded position. The safety frame sensor 144 is provided, for example, on the hinge portion 143, and detects whether the safety frame 14 is in an upright position or a folded position by turning ON, for example, when the upper frame 142 is upright.

In this way, the tractor 1 equipped with the folding safety frame 14 can be folded up when working in places with low ceilings, such as inside a vinyl greenhouse, or in orchards where fruit tree branches are at about the height of a person, making it possible to work in places with height restrictions.

The tractor 1 also includes a control unit 100 (see Figures 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 working implement 6.

<Power transmission configuration of work vehicle (tractor) 1>
Next, the power transmission configuration of the work vehicle (tractor) 1 will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram of the power transmission configuration of the work vehicle (tractor) 1 according to the first embodiment. As shown in Fig. 2, the tractor 1 is equipped with front wheels 3L, 3R attached to left and right front axles 31L, 31R, and left and right rear wheels 4L, 4R attached to left and right rear axles 41L, 41R, on the left and right sides of the traveling body 2, respectively.

In the following explanation, the letters "L" and "R" are used to indicate the left and right sides, respectively, but when there is no need to distinguish between left and right, the letters "L" and "R" are not used, for example, "front wheel 3" and "rear wheel 4".

As described above, the engine E is mounted on the front of the traveling vehicle body 2. Rotational power from the engine E is transmitted to the front wheels 3 and rear wheels 4 via the power transmission device 12. Also, as described above, when the tractor 1 is equipped with a 4WD clutch 301, the tractor 1 is configured to be switchable between a 2WD system in which only the rear wheels 4 are driven and a 4WD system in which both the front wheels 3 and the rear wheels 4 are driven by switching the 4WD clutch 301.

The power transmission mechanism to the rear wheels 4 is provided with a main transmission 302 at the rear of the engine E via a forward/reverse clutch 303 that switches the tractor 1 (traveling body 2) between forward, reverse and stop with forward connection, reverse connection and neutral, and further downstream is a sub-transmission 304, which is a transmission, and further downstream is a rear wheel differential gear device 305. Brake devices 306 are provided at the base of the rear axle 41 that connects the rear wheel differential gear device 305 and the rear wheels 4. The power transmission mechanism to the rear wheels 4 inputs power to the transmission shaft 307 via an idle gear provided at the rear of the sub-transmission 304, and transmits power to the front wheels 3 via the 4WD clutch 301 and the front wheel differential gear device 308.

A steering wheel turning angle sensor (hereafter referred to as the front wheel turning angle sensor) 309 that detects the steering angle (hereafter referred to as the turning angle) of the front wheels 3, which are steered wheels, is connected to the control unit 100.

The brake device 306 provided on the rear wheels 4 functions by hydraulically acting on the brake cylinder 317 when the driver depresses the left and right brake pedals 311L, 311R provided on the traveling body 2. 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.

The left and right brake cylinders 317L, 317R are connected to left and right brake solenoids 312L, 312R that are 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 or both of the left and right brake devices 306L, 306R. The brake solenoids 312L, 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.

The tractor 1 also includes a PTO clutch 316. The PTO clutch 316 is an electronically controlled clutch that connects or disconnects power to a PTO shaft 71 that is connected to the work machine 6 (see FIG. 1). Rotational power from the engine E is transmitted to the PTO shaft 71 by the PTO clutch 316 in an on-off manner.

The PTO shaft 71 is also provided with a first PTO gear shifter and a second PTO gear shifter on the front stage side, and by operating these shifters, the PTO shaft 71 can be rotated forward from low to high speeds, and can also be rotated in reverse.

<Control system of work vehicle (tractor) 1>
Next, the control system of the work vehicle (tractor) 1 will be described with reference to Fig. 3. Fig. 3 is a block diagram showing an example of the control system of the work vehicle (tractor) 1 according to the first embodiment. As shown in Fig. 3, the control unit 100 includes an engine ECU (Electronic Control Unit) 101, a travel system ECU 102, and a work implement lifting system ECU 103.

The engine ECU 101 controls the rotation speed of the engine E. The travel system ECU 102 controls the rotation of the drive wheels (rear wheels 4) to control the travel speed of the travel vehicle body 2 (see FIG. 1). The work machine lifting system ECU 103 controls the lifting device 13 to lift and lower the work machine 6.

The control unit 100 may be a processing device such as a CPU (Central Processing Unit), a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), or a HDD (Hard Disk Drive), or even a computer equipped with an input/output device.

The control unit 100 is electrically connected to an engine speed sensor 17 that detects the speed of the engine E, a front wheel turning angle sensor 309 that detects the turning angle of the front wheels 3 (see Figure 2), a lift arm sensor 136 that detects the height of the work implement 6, a lift lever 15 that is operated to change the lift position of the work implement 6 by the lifting device 13, a mode change switch 16 that switches between work driving mode and non-work driving mode, a forward/reverse lever 10 that is operated to set the forward/reverse clutch 303 to forward connection, reverse connection, and neutral, and a safety frame sensor 144 that detects the posture of the safety frame 14.

The control unit 100 receives detection signals (such as the engine speed sensor 17, the front wheel turning angle sensor 309, the lift arm sensor 136, and the safety frame sensor 144) from the engine speed sensor 17, the front wheel turning angle sensor 309, the lift arm sensor 136, and the safety frame sensor 144, operation signals from the lift lever 15 and the forward/reverse lever 10, and a switching signal (a signal indicating whether the mode is work driving mode or non-work driving mode) from the mode switching switch 16. In addition to the above-mentioned sensors, the control unit 100 is connected to a vehicle speed sensor, a shift sensor, a sub-shift operation device (sub-shift lever), and other devices (not shown).

In addition, in the control unit 100, the engine ECU 101 is connected to the engine E, the driving system ECU 102 is connected to a power transmission device 12 such as the main transmission 302, and the work machine lifting system ECU 103 is connected to the lifting device 13.

The engine ECU 101 outputs a rotation control signal to the engine E. The travel system ECU 102 outputs a gear change control signal to the main transmission 302 and the like. The work machine lifting system ECU 103 outputs a work machine lifting signal to the lifting device 13. The lifting device 13 lifts and lowers the work machine 6 based on the work machine lifting signal output from the work machine lifting system ECU 103.

In addition, the control unit 100 can execute a front wheel acceleration mode in which the rotation speed of the front wheels 3 is increased (e.g., doubled) by activating the 4WD clutch 301 and switching the reduction ratio of the rotational power transmission to the front wheels 3. In the front wheel acceleration mode, when the front wheel turning angle sensor 309 detects a turning angle of the front wheels 3 equal to or greater than a predetermined angle, the control unit 100 activates the 4WD clutch 301 to increase the turning speed.

The control unit 100 can also execute a work driving mode in which the control settings of the tractor 1 are set to settings suitable for driving while working. The control unit 100 can also execute a non-work driving mode in which the control settings of the tractor 1 are set to settings suitable for driving while not working (for example, driving on the road). Note that the work driving mode and non-work driving mode can be switched between by operating the mode change switch 16.

As described above, the tractor 1 may be used to work in fields, as well as in work areas with height restrictions, such as inside a vinyl greenhouse or in an orchard. In this case, if the tractor 1 is driven with the safety frame 14 in an upright position, the safety frame 14 protruding upward from the vehicle body may get caught on the ceiling of the vinyl greenhouse or the branches of a fruit tree, reducing work efficiency and causing damage to the vinyl greenhouse, fruit trees, or the tractor 1. For this reason, it is preferable to drive the tractor 1 with the safety frame 14 in a folded position when driving in work areas with height restrictions, such as inside a vinyl greenhouse or in an orchard; however, this may not ensure safety in the event of a tip-over.

In this embodiment, by executing the anti-tip 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 during work travel. The anti-tip 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.

<Tip-over prevention control in the first embodiment>
Next, a procedure for the anti-toppling control in the first embodiment will be described with reference to Fig. 4. Fig. 4 is a flow chart showing an example of the procedure for the anti-toppling control in the first embodiment. When the tractor 1 is traveling to work in a work area with height restrictions such as a vinyl greenhouse or an orchard, as shown in Fig. 4, the control unit 100 determines whether the safety frame 14 is in the folded position (step S101).

When the safety frame sensor 144 detects that the safety frame 14 is in the folded position, i.e., when the control unit 100 determines that the safety frame 14 is in the folded position (step S101: Yes), the control unit 100 determines whether the turning angle of the front wheels 3, which are the steered wheels, is equal to or greater than a predetermined angle that will result in turning (step S102).

When the front wheel turning angle sensor 309 detects that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle, that is, when the control unit 100 determines that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle (step S102: Yes), the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less so as to limit the driving speed to a low speed (step S103). The control unit 100 controls the rotation speed of the engine E based on the detection result of the engine speed sensor 17.

In addition, if the control unit 100 determines in the processing of step S101 that the safety frame 14 is not in the folded position (step S101: No), in this case the safety frame 14 is in the upright position and anti-tip control is not necessary, so the control unit 100 immediately ends the anti-tip control.

In addition, if the control unit 100 determines in the processing of step S102 that the turning angle of the front wheels 3 is less than the predetermined angle (is not equal to or greater than the predetermined angle) (step S102: No), the control unit 100 repeats the processing of step S102 until it determines that the turning angle of the front wheels 3 is equal to or greater than the predetermined angle.

In addition, when the control unit 100 determines in the process of step S101 that the safety frame 14 is in the folded position, it displays (warns) on the meter panel in front of the driver's seat 8, etc., that the safety frame 14 is in the folded position. In addition, when the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less in the process of step S103, it also displays (warns) on the meter panel, etc., that the driving speed is limited.

In this way, with the tractor 1 according to the first embodiment, if the safety frame 14 were to tip over while in the folded position, it would be dangerous for the driver, so by limiting the rotation speed by limiting the engine E speed to a predetermined speed or less, it is possible to prevent tipping over. This allows work to be carried out safely.

Second Embodiment
Next, a work vehicle (tractor) 1 according to a second embodiment will be described. The second embodiment differs from the first embodiment in the anti-toppling control. The second embodiment has the same overall configuration as the first embodiment. Therefore, the following description of the configuration of each part will be omitted, but the same reference numerals as those in the first embodiment will be used as necessary.

<Tip-over prevention control in the second embodiment>
The procedure of the anti-toppling control in the second embodiment will be described with reference to Fig. 5. Fig. 5 is a flow chart showing an example of the procedure of the anti-toppling control in the second embodiment. When the tractor 1 is traveling to work in a work area with height restrictions such as a vinyl greenhouse or an orchard, as shown in Fig. 5, the control unit 100 determines whether the safety frame 14 is in the folded position (step S201).

When the safety frame sensor 144 detects that the safety frame 14 is in the folded position, i.e., when the control unit 100 determines that the safety frame 14 is in the folded position (step S201: Yes), the control unit 100 determines whether the turning angle of the front wheels 3, which are the steered wheels, is equal to or greater than a predetermined angle that will result in turning (step S202).

When the front wheel turning angle sensor 309 detects that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle, that is, when the control unit 100 determines that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle (step S202: Yes), the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less so as to limit the driving speed to a low speed (step S203). The control unit 100 controls the rotation speed of the engine E based on the detection result of the engine speed sensor 17.

In addition to processing step S203, the control unit 100 prohibits the main transmission 302 from being switched to a high gear (step S204). In this case, the control unit 100 maintains the low gear regardless of the position of the main shift lever 11. Also, in this case, when the main shift lever 11 is operated to a position below a predetermined shift position, the control unit 100 shifts the gear according to the position of the main shift lever 11.

In addition, if the control unit 100 determines in the processing of step S201 that the safety frame 14 is not in the folded position (step S201: No), in this case the safety frame 14 is in the upright position and anti-tip control is not necessary, so the control unit 100 immediately ends the anti-tip control.

In addition, if the control unit 100 determines in the process of step S202 that the turning angle of the front wheels 3 is less than the predetermined angle (is not equal to or greater than the predetermined angle) (step S202: No), the control unit 100 repeats the process of step S202 until it determines that the turning angle of the front wheels 3 is equal to or greater than the predetermined angle.

In addition, when the control unit 100 determines in the process of step S201 that the safety frame 14 is in the folded position, it displays (warns) that the safety frame 14 is in the folded position on the meter panel in front of the driver's seat 8. In addition, when the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less in the process of step S203, it also displays (warns) that the driving speed is limited on the meter panel.

When the control unit 100 performs the process of step S204, it also displays (warns) on the meter panel or the like that the main transmission 302 is maintained in a low gear position.

In addition, even if the safety frame 14 is detected to be in an upright position after the anti-toppling control, the control unit 100 maintains the low gear regardless of the position of the main shift lever 11. This makes it possible to prevent the vehicle speed from increasing suddenly. Note that when the maintenance of the low gear is to be released, the system may be configured to release the low gear when a predetermined time has elapsed, or to be released manually by the driver.

In this way, with the tractor 1 according to the second embodiment, if the safety frame 14 were to tip over while in the folded position, it would be dangerous for the driver, so the main transmission 302 is prohibited from being switched to a higher speed and the maximum speed is limited. In this way, tipping over can be prevented by restricting the travel speed through limiting the maximum speed. This allows work to be carried out even safer.

In the second embodiment described above, when the safety frame sensor 144 detects the folded position, the rotation speed of the engine E is limited to a predetermined rotation speed or less and the main transmission 302 is prohibited from switching to a high speed gear. However, for example, a configuration may be adopted in which the main transmission 302 is only prohibited from switching to a high speed gear when the safety frame sensor 144 detects the folded position. Even with such a configuration, the maximum speed can be limited to regulate the travel speed and prevent tipping, allowing work to be performed safely.

Third Embodiment
Next, a work vehicle (tractor) 1 according to a third embodiment will be described. The third embodiment differs from the first and second embodiments in terms of the anti-toppling control. The third embodiment has the same overall configuration as the first and second embodiments. Therefore, the following description of the configuration of each part will be omitted, but the same reference numerals as those in the first and second embodiments will be used as necessary.

<Tip-over prevention control in the third embodiment>
The procedure of the anti-toppling control in the third embodiment will be described with reference to Fig. 6. Fig. 6 is a flow chart showing an example of the procedure of the anti-toppling control in the third embodiment. When the tractor 1 is traveling to work in a work area with height restrictions such as a vinyl greenhouse or an orchard, as shown in Fig. 6, the control unit 100 determines whether the safety frame 14 is in the folded position (step S301).

When the safety frame sensor 144 detects that the safety frame 14 is in the folded position, i.e., when the control unit 100 determines that the safety frame 14 is in the folded position (step S301: Yes), the control unit 100 determines whether the turning angle of the front wheels 3, which are the steered wheels, is equal to or greater than a predetermined angle that will result in turning (step S302).

When the front wheel turning angle sensor 309 detects that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle, that is, when the control unit 100 determines that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle (step S302: Yes), the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less so as to limit the driving speed to a low speed (step S303). The control unit 100 controls the rotation speed of the engine E based on the detection result of the engine speed sensor 17.

In addition to the process of step S303, the control unit 100 determines whether the front wheel acceleration mode is being executed (step S304). If the control unit 100 determines that the front wheel acceleration mode is being executed (step S304: Yes), it restricts (for example, prohibits) the operation of the 4WD clutch 301 (step S305). In this case, the control unit 100 makes the rotation speed of the front wheels 3 equal to the rotation speed of the rear wheels 4.

In addition, if the control unit 100 determines in the processing of step S301 that the safety frame 14 is not in the folded position (step S301: No), in this case the safety frame 14 is in the upright position and anti-tip control is not necessary, so the control unit 100 immediately ends the anti-tip control.

In addition, if the control unit 100 determines in the process of step S302 that the turning angle of the front wheels 3 is less than the predetermined angle (is not equal to or greater than the predetermined angle) (step S302: No), the control unit 100 repeats the process of step S302 until it determines that the turning angle of the front wheels 3 is equal to or greater than the predetermined angle.

In addition, if the control unit 100 determines in the processing of step S304 that the front wheel acceleration mode is not being executed (step S304: No), the control unit 100 skips the processing of step S305.

In addition, when the control unit 100 determines in the process of step S301 that the safety frame 14 is in the folded position, it displays (warns) that the safety frame 14 is in the folded position on the meter panel in front of the driver's seat 8. In addition, when the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less in the process of step S303, it also displays (warns) that the driving speed is limited on the meter panel.

In addition, if the control unit 100 restricts the operation of the 4WD clutch 301 in the processing of step S305, it displays (warns) that the operation of the 4WD clutch 301 is restricted on the meter panel or the like.

In this way, with the tractor 1 according to the third embodiment, if the safety frame 14 were to tip over while in the folded position, it would be dangerous for the driver, so even if the front wheel acceleration mode is being executed, the operation of the 4WD clutch 301 is limited to regulate the increase in turning speed, thereby preventing tipping over. This allows for even safer work.

In the third embodiment described above, when the safety frame sensor 144 detects the folded position, the engine E speed is limited to a predetermined speed or less, and the operation of the 4WD clutch 301 is limited if the front wheel acceleration mode is being executed. However, for example, when the safety frame sensor 144 detects the folded position, the 4WD clutch 301 may only be limited when the front wheel acceleration mode is being executed. Even with this configuration, by limiting the operation of the 4WD clutch 301, it is possible to prevent tipping by restricting the increase in turning speed, and to perform work safely.

In addition, in the third embodiment described above, the process when the safety frame sensor 144 detects the folded position may further include a process for prohibiting the main transmission 302 from switching to a higher speed (the process of step S204 in FIG. 5).

Fourth Embodiment
Next, a work vehicle (tractor) 1 according to a fourth embodiment will be described. The fourth embodiment differs from the first to third embodiments in terms of the anti-toppling control. The fourth embodiment has the same overall configuration as the first to third embodiments. Therefore, the following description of the configuration of each part will be omitted, but the same reference numerals as those in the first to third embodiments will be used as necessary.

<Tip-over prevention control in the fourth embodiment>
The procedure of the anti-toppling control in the fourth embodiment will be described with reference to Fig. 7. Fig. 7 is a flow chart showing an example of the procedure of the anti-toppling control in the fourth embodiment. When the tractor 1 is traveling to work in a work area with height restrictions such as a vinyl greenhouse or an orchard, as shown in Fig. 7, the control unit 100 determines whether the safety frame 14 is in the folded position (step S401).

When the safety frame sensor 144 detects that the safety frame 14 is in the folded position, i.e., when the control unit 100 determines that the safety frame 14 is in the folded position (step S401: Yes), the control unit 100 determines whether the turning angle of the front wheels 3, which are the steered wheels, is equal to or greater than a predetermined angle that will result in turning (step S402).

When the front wheel turning angle sensor 309 detects that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle, that is, when the control unit 100 determines that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle (step S402: Yes), the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less so as to limit the driving speed to a low speed (step S403). The control unit 100 controls the rotation speed of the engine E based on the detection result of the engine speed sensor 17.

In addition to the process of step S403, the control unit 100 determines whether the lift lever 15 has been operated to raise the working machine 6 above a predetermined height (step S404). When the control unit 100 determines that the lift lever 15 has been operated to raise the working machine 6 above a predetermined height (step S404: Yes), it prohibits the working machine 6 from being raised above the predetermined height (step S405). In this case, the control unit 100 prohibits the working machine 6 from being raised above the predetermined height regardless of the position of the lift lever 15. Also, in this case, when the lift lever 15 is operated to a position where the working machine 6 is below the predetermined height, the control unit 100 raises the working machine 6 in accordance with the position of the lift lever 15.

In addition, if the control unit 100 determines in the processing of step S401 that the safety frame 14 is not in the folded position (step S401: No), in this case the safety frame 14 is in the upright position and anti-tip control is not necessary, so the control unit 100 immediately ends the anti-tip control.

In addition, if the control unit 100 determines in the process of step S402 that the turning angle of the front wheels 3 is less than the predetermined angle (is not equal to or greater than the predetermined angle) (step S402: No), the control unit 100 repeats the process of step S402 until it determines that the turning angle of the front wheels 3 is equal to or greater than the predetermined angle.

In addition, if the control unit 100 determines in the processing of step S404 that the lift lever 15 has not been operated to raise the work implement 6 above the predetermined height (step S404: No), it skips the processing of step S305.

In addition, when the control unit 100 determines in the process of step S401 that the safety frame 14 is in the folded position, it displays (warns) on the meter panel in front of the driver's seat 8, etc., that the safety frame 14 is in the folded position. In addition, when the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less in the process of step S403, it also displays (warns) on the meter panel, etc., that the driving speed is limited.

In addition, if the control unit 100 prohibits the work machine 6 from rising above a predetermined height in the processing of step S405, it displays (warns) on the meter panel or the like that the work machine 6 is prohibited from rising above the predetermined height.

In this way, with the tractor 1 according to the fourth embodiment, even if the lift lever 15 is operated to raise the working implement 6 above a predetermined height, since it would be dangerous for the driver if the safety frame 14 were to tip over while in the folded position, the lift lever 15 is prohibited from raising the working implement 6 above the predetermined height, suppressing the rise of the center of gravity, thereby preventing tipping. This allows for even safer work.

In the fourth embodiment described above, when the safety frame sensor 144 detects the folded position, the engine E is limited to a predetermined rotation speed or less, and the lift lever 15 is operated to raise the working machine 6 above the predetermined height, but the lift lever 15 may be configured to only prohibit the working machine 6 from rising above the predetermined height when the lift lever 15 is operated to raise the working machine 6 above the predetermined height, for example, when the safety frame sensor 144 detects the folded position. Even with this configuration, the lift lever 15 can be configured to prohibit the working machine 6 from rising above the predetermined height, suppress the rise of the center of gravity, and prevent tipping, allowing work to be performed safely.

In addition, in the fourth embodiment described above, the process when the safety frame sensor 144 detects the folded position may further include at least one of the following processes: a process for prohibiting the main transmission 302 from switching to a high speed (the process of step S204 in FIG. 5) and a process for restricting the operation of the 4WD clutch 301 when the front wheel acceleration mode is being executed (the process of steps S304 and S305 in FIG. 6).

Fifth Embodiment
Next, a work vehicle (tractor) 1 according to a fifth embodiment will be described. The fifth embodiment differs from the first to fourth embodiments in terms of the anti-toppling control. The fifth embodiment has the same overall configuration as the first to fourth embodiments. Therefore, the following description of the configuration of each part will be omitted, but the same reference numerals as those in the first to fourth embodiments will be used as necessary.

<Tip-over prevention control in the fifth embodiment>
The procedure of the anti-toppling control in the fourth embodiment will be described with reference to Fig. 8. Fig. 8 is a flow chart showing an example of the procedure of the anti-toppling control in the fifth embodiment. When the tractor 1 is traveling to work in a work area with height restrictions such as a vinyl greenhouse or an orchard, as shown in Fig. 8, the control unit 100 determines whether the safety frame 14 is in the folded position (step S501).

When the safety frame sensor 144 detects that the safety frame 14 is in the folded position, i.e., when the control unit 100 determines that the safety frame 14 is in the folded position (step S501: Yes), the control unit 100 determines whether the turning angle of the front wheels 3, which are the steered wheels, is equal to or greater than a predetermined angle that causes a turn (step S502).

When the front wheel turning angle sensor 309 detects that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle, that is, when the control unit 100 determines that the turning angle of the front wheels 3 is equal to or greater than a predetermined angle (step S502: Yes), the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less so as to limit the driving speed to a low speed (step S503). The control unit 100 controls the rotation speed of the engine E based on the detection result of the engine speed sensor 17.

In addition to the process of step S503, the control unit 100 also determines whether the mode changeover switch 16 has been switched to the non-work driving mode (step S504). If the control unit 100 determines that the mode changeover switch 16 has been switched to the non-work driving mode (step S504: Yes), it further determines whether the forward/reverse lever 10 has been operated to switch the forward/reverse clutch 303 from neutral (step S505).

When the control unit 100 determines that the forward/reverse lever 10 has been operated to switch the forward/reverse clutch 303 from neutral (step S505: Yes), the control unit 100 maintains the forward/reverse clutch 303 in neutral even if the forward/reverse lever 10 is operated to switch from neutral to forward or reverse (step S506).

In addition, if the control unit 100 determines in the processing of step S501 that the safety frame 14 is not in the folded position (step S501: No), in this case the safety frame 14 is in the upright position and anti-tip control is not necessary, so the control unit 100 immediately ends the anti-tip control.

In addition, if the control unit 100 determines in the process of step S502 that the turning angle of the front wheels 3 is less than the predetermined angle (is not equal to or greater than the predetermined angle) (step S502: No), the control unit 100 repeats the process of step S502 until it determines that the turning angle of the front wheels 3 is equal to or greater than the predetermined angle.

In addition, if the control unit 100 determines in the processing of step S504 that the mode changeover switch 16 has not been switched to the non-work driving mode (step S504: No), the processing of steps S505 and S506 is skipped.

In addition, if the control unit 100 determines in the processing of step S505 that the forward/reverse lever 10 has not been operated to switch the forward/reverse clutch 303 from neutral (step S505: No), it skips the processing of step S506.

In addition, when the control unit 100 determines in the processing of step S501 that the safety frame 14 is in the folded position, it displays (warns) that the safety frame 14 is in the folded position on the meter panel in front of the driver's seat 8 or the like. In addition, when the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less in the processing of step S503, it also displays (warns) that the driving speed is limited on the meter panel or the like.

In addition, if the forward/reverse clutch 303 is kept neutral in the processing of step S506, the control unit 100 displays (warns) on the meter panel or the like that the forward/reverse clutch 303 is kept neutral.

In this way, with the tractor 1 according to the fifth embodiment, in the non-work driving mode, which is a control setting that assumes on-road driving when moving from one field to the next, if the safety frame 14 were to tip over while in the folded position, it would be dangerous for the driver, so in the non-work driving mode, forward and backward movement can be prohibited to prevent tipping. This allows for even safer work.

In the fifth embodiment described above, when the safety frame sensor 144 detects the folded position, the engine E is limited to a predetermined rotational speed or less, and the mode changeover switch 16 is switched to the non-work driving mode and the forward/reverse clutch 303 is maintained in neutral when the forward/reverse lever 10 is operated to switch the forward/reverse clutch 303 from neutral. However, for example, when the safety frame sensor 144 detects the folded position, the mode changeover switch 16 is switched to the non-work driving mode and the forward/reverse clutch 303 is only maintained in neutral when the forward/reverse lever 10 is operated to switch the forward/reverse clutch 303 from neutral. Even with this configuration, it is possible to prevent tipping by prohibiting forward/reverse start in the non-work driving mode, and to work safely.

In addition, in the fifth embodiment described above, the processing when the safety frame sensor 144 detects the folded position may further include at least one of the following processing: a processing for prohibiting switching of the main transmission 302 to a high speed gear (processing of step S204 in FIG. 5); a processing for restricting operation of the 4WD clutch 301 when the front wheel acceleration mode is being executed (processing of steps S304 and S305 in FIG. 6); and a processing for prohibiting the work machine 6 from rising above a predetermined height regardless of the position of the lift lever 15 (processing of steps S404 and S404 in FIG. 7).

The above-described embodiment realizes the following work vehicle 1.

(1) A work vehicle 1 that is a structure that ensures the safety of the driver in the event of a rollover and is equipped with a safety frame 14 that can be switched between an upright position and a folded position, and is equipped with steering wheels 3 and driving wheels 4, an engine E that generates rotational power for the driving wheels 4, an engine speed sensor 17 that detects the rotation speed of the engine E, a control unit 100 that controls the rotation speed of the engine E, a safety frame sensor 144 that detects whether the safety frame 14 is in an upright position or a folded position, and a steering wheel turning angle sensor 309 that detects the steering angle of the steering wheels 3, and the control unit 100 is characterized in that when the safety frame sensor 144 detects the folded position and the steering wheel turning angle sensor 309 detects a steering angle of the steering wheels 3 that is equal to or greater than a predetermined angle, the control unit 100 limits the rotation speed of the engine E to a predetermined rotation speed or less.

With this type of work vehicle 1, if the safety frame 14 were to tip over while in the folded position, it would be dangerous for the driver, so by limiting the rotation speed of the engine E to a predetermined number of revolutions or less, it is possible to prevent tipping over. This allows work to be carried out safely.

(2) In the above (1), the work vehicle 1 is equipped with a main transmission 302 that is incorporated in a power transmission device 12 that transmits rotational power from an engine E to drive wheels and switches the rotational power between a low speed and a high speed, and the control unit 100 prohibits the main transmission 302 from switching to the high speed when the safety frame sensor 144 detects the folded position.

In addition to the effect of (1) above, such a work vehicle 1 limits the maximum speed by prohibiting the main transmission 302 from switching to a high speed gear, since it would be dangerous for the driver if the safety frame 14 were to tip over while in the folded position. In this way, tipping over can be prevented by restricting the travel speed through limiting the maximum speed. This allows work to be performed even safer.

(3) In the above (1) or (2), the steering wheels are a pair of left and right front wheels 3, and the vehicle is equipped with a front wheel acceleration clutch 301 that switches the reduction ratio of the rotational power transmission to the front wheels 3 to increase the rotation speed of the front wheels 3, and the control unit 100 can execute a front wheel acceleration mode in which the front wheel acceleration clutch 301 is activated to increase the turning speed when the steering wheel turning angle sensor 309 detects a steering angle of the front wheels 3 equal to or greater than a predetermined angle, and when the safety frame sensor 144 detects a folded position, the work vehicle 1 restricts the operation of the front wheel acceleration clutch 301 even when the front wheel acceleration mode is executed.

In addition to the above effects (1) and (2), such a work vehicle 1 can prevent tipping over by restricting the operation of the front wheel speed-up clutch 301 and regulating the increase in turning speed, even if the front wheel speed-up mode is being executed, since tipping over would be dangerous for the driver if the safety frame 14 were to tip over while in the folded position. This allows for even safer work.

(4) In any one of (1) to (3) above, a work vehicle 1 is provided with a working implement 6 attached to a traveling body 2 traveling by steering wheels 3 and drive wheels 4 and arranged at the rear of the traveling body 2, a lifting device 13 for raising and lowering the working implement 6, a lifting operation tool 15 operated when changing the position at which the working implement 6 is raised or lowered by the lifting device 13, and a lifting sensor 136 for detecting the position at which the working implement 6 is raised or lowered by the lifting device 13, and the control unit 100 prohibits the working implement 6 from being raised above a predetermined height when the safety frame sensor 144 detects the folded position, even if the lifting operation tool 15 is operated to raise the working implement 6 above the predetermined height.

In addition to any one of the effects (1) to (3) above, such a work vehicle 1 can prevent tipping over by prohibiting the work machine 6 from rising above the specified height and suppressing the rise of the center of gravity, even if the lifting operation device 15 is operated to raise the work machine 6 above a specified height, since it would be dangerous for the driver if the safety frame 14 were to tip over while in the folded position. This allows work to be performed even safer.

(5) In any one of (1) to (4) above, the control unit 100 can execute a work driving mode in which the control settings of the work vehicle 1 are set to settings suitable for driving during work, and a non-work driving mode in which the control settings of the work vehicle 1 are set to settings suitable for driving during non-work, and is equipped with a mode changeover switch 16 for switching between the work driving mode and the non-work driving mode, a forward/reverse clutch 303 for switching the forward, reverse, and stop of the work vehicle 1 between forward connection, reverse connection, and neutral, and a forward/reverse operation device 10 that is operated when the forward/reverse clutch 303 is set to forward connection, reverse connection, and neutral, and the control unit 100 maintains the neutral position of the forward/reverse clutch 303 when the safety frame sensor 144 detects the folded position and the mode changeover switch 16 is switched to the non-work driving mode, even if the forward/reverse operation device 10 is operated to switch the forward/reverse clutch 303 from neutral to forward connection or reverse connection.

In addition to any one of the effects (1) to (4) above, such a work vehicle 1 can achieve the following effects: in the non-work driving mode, which is a control setting designed for on-road driving when moving from one field to the next, if the safety frame 14 were to tip over in the folded position, it would be dangerous for the driver. Therefore, in the non-work driving mode, forward and backward movement can be prohibited to prevent tipping. This allows work to be carried out even more safely.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

1. Work vehicle (tractor)
2 Running body 3 Steering wheels (front wheels)
4 Drive wheels (rear wheels)
5 Bonnet 6 Work equipment 7 PTO device 8 Driver's seat 9 Steering wheel 10 Forward/reverse operation device (forward/reverse lever)
11. Main shift lever
12 Power transmission device 13 Lifting device 14 Safety frame 15 Lifting operation tool (lifting lever)
16 Mode changeover switch 17 Engine revolution sensor 31 Front axle 41 Rear axle 61 Cultivator tines 71 PTO shaft 100 Control unit 101 Engine ECU
102 Driving system ECU
103 Work machine lifting system ECU
131 Lift cylinder 132 Lift arm 133 Lift rod 134 Lower link 135 Top link 136 Lift sensor (lift arm sensor)
141 Lower frame 142 Upper frame 143 Hinge portion 144 Safety frame sensor 301 Front wheel acceleration clutch (4WD clutch)
302 Main transmission 303 Forward/reverse clutch 304 Auxiliary transmission 305 Rear wheel differential gear device 306 Brake device 307 Speed change shaft 308 Front wheel differential gear device 309 Steering wheel turning angle sensor (front wheel turning angle sensor)
310 Steering cylinder 311 Brake pedal 312 Brake solenoid 313 Proportional pressure regulating valve 314 Hydraulic pump 315 Relief valve 316 PTO clutch 317 Brake cylinder E Engine

Claims (5)

A work vehicle having a safety frame that is a structure for ensuring the safety of a driver in the event of a rollover and can be switched between an upright position and a folded position,
Steering and driving wheels;
An engine that generates rotational power for the drive wheels;
an engine speed sensor for detecting a speed of the engine;
A control unit for controlling the engine speed;
a safety frame sensor for detecting whether the safety frame is in the standing position or the folded position;
A steering wheel angle sensor that detects the steering angle of the steering wheel,
The control unit is
When the safety frame sensor detects the folded posture and the steering wheel angle sensor detects a steering angle of the steering wheel that is equal to or greater than a predetermined angle, the engine speed is limited to a predetermined speed or less. a main transmission incorporated in a power transmission device that transmits rotational power from the engine to the drive wheels and that switches the rotational power between a low speed stage and a high speed stage;
The control unit is
2. The work vehicle according to claim 1, wherein when the safety frame sensor detects the folded posture, switching of the main transmission to a high speed stage is prohibited. The steering wheels are a pair of left and right front wheels,
a front wheel accelerating clutch that switches a reduction ratio of the rotational power transmission to the front wheels to increase the rotation speed of the front wheels;
The control unit is
a front wheel acceleration mode is executed in which the front wheel acceleration clutch is actuated to increase a turning speed when the steering wheel angle sensor detects a steering angle of the front wheels equal to or greater than a predetermined angle;
3. The work vehicle according to claim 1, wherein when the safety frame sensor detects the folded posture, operation of the front wheel accelerating clutch is restricted even if the front wheel accelerating mode is being executed. a working machine attached to a traveling vehicle body that travels by the steering wheels and the drive wheels and disposed behind the traveling vehicle body;
A lifting device for lifting and lowering the working machine;
a lifting/lowering operation tool that is operated when changing a lifting position of the work machine by the lifting device;
a lifting sensor that detects a lifting position of the working machine by the lifting device,
The control unit is
A work vehicle as described in any one of claims 1 to 3, characterized in that when the safety frame sensor detects the folded posture, even if the lifting operating device is operated to raise the work machine above a predetermined height, the work machine is prohibited from being raised above the predetermined height. The control unit is
A work driving mode in which the control settings of the work vehicle are set to settings suitable for driving when working, and a non-work driving mode in which the control settings of the work vehicle are set to settings suitable for driving when not working, are executable;
a mode changeover switch for changing between the work traveling mode and the non-work traveling mode;
a forward/reverse clutch for switching the forward, reverse and stop of the work vehicle between forward connection, reverse connection and neutral;
a forward/reverse operation device that is operated when the forward/reverse clutch is to be in forward connection, reverse connection, or neutral;
The control unit is
5. The work vehicle according to claim 1, wherein when the safety frame sensor detects the folded posture and the mode changeover switch is switched to the non-work driving mode, the forward/reverse clutch is maintained in neutral even if the forward/reverse operating device is used to change the forward/reverse clutch from neutral to forward connection or reverse connection.

Images