Work vehicle

Abstract

To provide a work vehicle capable of securing safety by automatically switching a farm field mode to a road mode state according to a predetermined condition.SOLUTION: In a work vehicle including a mode selection switch 223 for manually switching between a farm field mode in which the work vehicle travels in a farm field and a road mode in which the work vehicle travels on a road, a horizontal sensor 36 is provided for detecting an inclination of a traveling vehicle body 2 that detects that the work vehicle is traveling a certain distance in a state where a turning angle θ by a steering handle 9 is within a predetermined angle β and a PTO shaft 16 is not rotated, and the farm field mode is automatically switched to the road mode when an accelerator lever 351 is neutral and an accelerator pedal 19 is operated in a state where the inclination of the vehicle body is not detected for a certain period of time.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] Conventionally, a technology has been known that includes a field mode control in which the brakes are activated according to the amount of steering device operation, and a road mode control in which the brakes are not activated even when the steering device is operated (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-96863 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the configuration of Patent Document 1, when traveling in a field, the brake on the inside of the turn is activated in response to the steering operation of the steering device, thereby reducing the turning radius and enabling efficient work. However, since there is no control to switch to road mode when leaving the field onto the road, if the vehicle moves onto the road while maintaining the field mode conditions, it is dangerous because the brake is activated in response to the amount of steering operation of the steering device.

[0005] An object of the present invention is to provide a work vehicle that can ensure safety by automatically switching from a field mode to a road mode under predetermined conditions. [Means for solving the problem]

[0006] The present invention provides the following technical means to solve the above problems.

[0007] The invention described in claim 1 is characterized in that in a work vehicle equipped with a mode selection switch 223 for manually switching between a field mode for traveling in a field and a road mode for traveling on a road, when it is detected that the turning angle θ of the steering handle 9 is within a predetermined angle β, the PTO shaft 16 is not rotating, and the vehicle has traveled a certain distance, the mode is automatically switched from field mode to road mode.

[0008] The invention described in claim 2 is the invention described in claim 1, further comprising a horizontal sensor 36 that detects the inclination of the traveling vehicle body 2, and when the inclination of the vehicle body is not detected for a certain period of time, the mode is automatically switched from field mode to road mode.

[0009] The invention described in claim 3 is configured such that, in the invention described in claim 1, when the PTO switch 34, which can turn the clutch part interposed in the PTO drive part 93 on and off, is operated to the clutch ON side, or when the PTO lever sensor 39 detects that the PTO shift lever 354 is in a specified gear position other than neutral, the mode returns from road mode to field mode.

[0010] The invention described in claim 4 is configured such that, in the invention described in claim 1, when the driving mode selection switch 223, which has been selected for field mode, has been automatically switched from field mode to road mode, and then when field mode is selected again, field mode is given priority. [Effects of the Invention]

[0011] According to the invention described in claim 1, when it is detected that the steering handle 9 is within a predetermined operating range and that the PTO shaft 16 is not rotating and that the vehicle has been traveling a certain distance, it is determined that the vehicle is on the road and the system is configured to automatically switch to traveling mode, thereby preventing unintentional sharp turns and improving safety.

[0012] According to the invention as set forth in claim 2, in addition to the effect as set forth in claim 1, the vehicle can be driven even safer because it is required that the tilt of the vehicle body is not detected for a certain period of time.

[0013] In addition to the effect of claim 1, the invention described in claim 3 has the following advantages: after the control related to the field mode is automatically released, if the PTO switch 34, which can turn the clutch unit in the PTO drive unit 93 on and off, is operated to the clutch-on side, or if the PTO shift lever 354 controlled by the PTO lever sensor 39 is placed in a specified gear position other than neutral, the control related to the field mode can be restored from the control-released state to the control-set state related to the field mode; and when returning to the field to work, the mode can be changed to the mode intended by the operator depending on the driving conditions, allowing for efficient work operation.

[0014] In addition to the effect of claim 1, the invention described in claim 4 has the effect that if the driving mode selection switch 223 is once set to road mode and then the field mode is selected again, the field mode takes priority, so that the driving mode based on the operator's intention can be obtained. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic left side view of a work vehicle according to an embodiment of the present invention. [Figure 2] 1 is a schematic explanatory diagram of power transmission in a work vehicle according to an embodiment of the present invention; [Figure 3] 1 is a schematic perspective view of the right side of a driver's seat of a work vehicle according to an embodiment of the present invention. [Figure 4] 1 is an explanatory diagram of an operating device located in front of a driver's seat of a work vehicle according to an embodiment of the present invention. [Figure 5] 2 is an enlarged view of a portion A of a driver's seat of the work vehicle according to the embodiment of the present invention. FIG. [Figure 6] 3 is a flowchart of a work vehicle according to an embodiment of the present invention. [Figure 7] 1 is a control block diagram of a work vehicle according to an embodiment of the present invention. [Figure 8]6 is a flowchart of another example of the work vehicle according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of a work vehicle disclosed in the present application will be described in detail with reference to the accompanying drawings.

[0017] FIG. 1 is an explanatory diagram of a tractor as a work vehicle 1 according to an embodiment, and is a schematic left side view of the work vehicle 1. As shown in FIG.

[0018] The tractor 1 is an agricultural tractor that travels by itself to perform work in a field, etc. In addition to carrying out predetermined work while an operator rides on the tractor 1 and traveling within the field, the tractor 1 also performs predetermined work while traveling automatically within the field through control of each part by a control system centered on a control device 40, which will be described later.

[0019] The tractor 1 includes a traveling body 2 and a work implement W. The traveling body 2 includes a body frame 3, front wheels 4, rear wheels 5, a bonnet 6, an engine E, a control unit 7, and a transmission case 10. The body frame 3 and the transmission case 10 form the main frame of the traveling body 2.

[0020] The front wheels 4 are a pair of left and right wheels, and are primarily used for steering (steered wheels). The rear wheels 5 are a pair of left and right wheels, and are primarily used for driving (drive wheels). The tractor 1 may be configured to be switchable between two-wheel drive (2WD) in which the rear wheels 5 are driven, and four-wheel drive (4WD) in which both the front wheels 4 and the rear wheels 5 are driven. In this case, both the front wheels 4 and the rear wheels 5 are drive wheels. The traveling body 2 may be equipped with a crawler device instead of wheels (front wheels 4 and rear wheels 5). In this case, the traveling crawler is the drive wheel.

[0021] The hood 6 is provided at the front of the traveling vehicle body 2 so as to be able to be opened and closed freely. The hood 6 can be rotated (opened and closed) in the vertical direction with the rear part as the rotation center. When closed, the hood 6 covers the engine E mounted on the vehicle body frame 3. The engine E is the driving source of the tractor 1 and is a heat engine such as a diesel engine or a gasoline engine.

[0022] The control unit 7 is provided on top of the traveling vehicle body 2 and includes a driver's seat 8, a steering wheel 9, etc. The control unit 7 may be formed by being covered by a cabin 7a provided on top of the traveling vehicle body 2. The driver's seat 8 is the driver's seat. The steering wheel 9 is operated by the driver when steering the front wheels 4, which are steered wheels. The control unit 7 includes a meter panel 11 (display unit) in front of the steering wheel 9 that displays various information.

[0023] The control unit 7 also includes various operation levers such as a forward / reverse lever 201, an accelerator lever, a main speed change operation unit 17, and an auxiliary speed change lever 14, as well as various operation pedals such as a clutch pedal 18, a brake pedal 15, and an accelerator pedal 19.

[0024] The transmission case 10 appropriately reduces the speed of the power (rotational power) transmitted from the engine E and transmits it to the rear wheels 5, which are drive wheels, and to the PTO shaft 16.

[0025] A work implement W that performs work in the field is connected to the rear of the traveling body 2, and a PTO shaft 16 that transmits power to drive the work implement W protrudes rearward from the transmission case 10. The PTO shaft 16 transmits rotational power that has been appropriately reduced by the transmission to the work implement W that is attached to at least the rear of the traveling body 2.

[0026] In addition, a lifting device 12 that raises and lowers the work implement W is provided at the rear of the traveling body 2. The lifting device 12 raises the work implement W to move it to a non-working position. The non-working position is a position where the work implement W is raised when, for example, the traveling body 2 moves backward or turns. In addition, the lifting device 12 lowers the work implement W to move it to a ground work position. The lifting device 12 includes a hydraulic lifting cylinder 121, a lift arm 122, a lift rod 123, a lower link 124, and a top link 125.

[0027] When hydraulic oil is supplied to the lift cylinder 121, the lift arm 122 rotates around the axis AX serving as the rotation fulcrum to raise the work machine W, and when hydraulic oil is discharged from the lift cylinder 121, the lift arm 122 rotates around the axis AX to lower the work machine W. A lift arm sensor 26 that detects the rotation angle of the lift arm 122 is provided at the base of the lift arm 122 (near the axis AX).

[0028] The roof of the cabin 7a is provided with a vehicle body positioning device 30, which is, for example, a GNSS (Global Navigation Satellite System) antenna, and can receive radio waves from a navigation satellite S orbiting in the sky to perform positioning and timing. It can also calculate the travel speed from the history of positioning results and the Doppler effect of radio waves.

[0029] The lift arm 122 is connected to a lower link 124 via a lift rod 123. In this way, the lifting device 12 connects the work implement W to the traveling body 2 via the lower link 124 and the top link 125 so that the work implement W can be raised and lowered. The lower link 124 is attached to the rear of the transmission case 10, and a draft sensor 27 detects the load on the lower link 124. By detecting this load, drag force control can be performed when a plow or other work implement is attached.

[0030] 1, the work implement W is a rotary tiller that performs tilling work in a field. The rotary tiller tills the soil in the field by rotating tiller tines 61 using power transmitted from a PTO shaft 16.

[0031] The tractor 1 also includes a control device 40. The control device 40 controls the engine E and also controls the traveling speed of the traveling vehicle body 2. The control device 40 also controls the lifting and lowering of the work implement W.

[0032] The tractor 1 also allows the operator to set various tasks for a specific field by operating an information processing terminal (a mobile terminal such as a tablet terminal) 100. The information processing terminal 100 includes a storage unit configured with, for example, a hard disk, a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and a display unit and operation unit configured with a touch panel. Note that various keys, buttons, etc. may also be provided separately as the operation unit.

[0033] The tractor 1 also includes an obstacle sensor 20. The obstacle sensor 20 includes a front sensor 21 and a rear sensor 22. The front sensor 21 is disposed at the front of the traveling body 2, for example, by being attached to a sensor mounting stay 13 provided in front of the hood 6, and detects obstacles (people or objects) present in front of the traveling body 2.

[0034] The rear sensor 22 is disposed at the upper rear side of the traveling vehicle body 2, for example, by being attached to the top of the cabin 7a, and detects obstacles present behind the traveling vehicle body 2. The angle of the rear sensor 22 relative to the cabin 7a, i.e., the traveling vehicle body 2, can be changed by a motor (not shown).

[0035] Both the front sensor 21 and the rear sensor 22 are medium-range sensors, preferably infrared sensors. The front sensor 21 and the rear sensor 22 emit infrared beams and detect light reflected from obstacles. The front sensor 21 has a detection area that extends forward. The rear sensor 22 has a detection area that extends backward.

[0036] The front sensor 21 and the rear sensor 22 can detect the distance to an obstacle by, for example, measuring the time it takes to detect the light reflected from the obstacle after emitting an infrared beam. The front sensor 21 and the rear sensor 22, which are infrared sensors, detect obstacles two-dimensionally, with a detection range of, for example, several meters to several tens of meters. Note that, as the obstacle sensor 20, other medium-range sensors such as sonar or millimeter-wave radar can be used or used in combination with other infrared sensors.

[0037] Next, the power transmission of the tractor 1 will be described with reference to Figure 2. This is a schematic explanatory diagram of the power transmission of the tractor 1. The tractor 1 is equipped with a speed change device (transmission) 70 inside a mission case 10. The speed change device 70 is equipped with a power transmission device 71 that transmits rotational power from the engine E to the rear wheels 5 and the like. The power transmission device 71 transmits the rotational power output from the engine E to the front wheels 4, the rear wheels 5, and the work implement W (see Figure 1) connected to the traveling body 2, and drives the front wheels 4, the rear wheels 5, and the work implement W.

[0038] The power transmission device 71 includes a forward / reverse switching unit 72, a main transmission unit 73, an auxiliary transmission unit 74, and a front wheel transmission unit 75. The power transmission device 71 transmits rotational power from the engine E to the rear wheels 5, 5, for example, via an input shaft 76, the forward / reverse switching unit 72, the main transmission unit 73, and the auxiliary transmission unit 74 in this order.

[0039] The power transmission device 71 also transmits rotational power from the engine E to the front wheels 4, 4, for example, via the input shaft 76, forward / reverse switching unit 72, main transmission unit 73, auxiliary transmission unit 74, and front wheel transmission unit 75 in that order. The power transmission device 71 also transmits rotational power from the engine E to the work implement W, for example, via the input shaft 76 and PTO drive unit 93 in that order.

[0040] 2, the input shaft 76 is provided on the output shaft of the engine E, and receives (inputs) rotational power from the engine E. In the following, with regard to the direction of power transmission, the engine E side is defined as the upstream side of the power transmission, and the front wheels 4, 4, rear wheels 5, 5, and work implement W, which are the final output destinations, are defined as the downstream side of the power transmission.

[0041] The forward / reverse clutch unit 72, which serves as a forward / reverse switching unit, switches the rotational power transmitted from the engine E between forward rotation and reverse rotation by rotating the main shaft 77 forward or backward. The forward / reverse clutch unit 72 switches between forward and reverse by hydraulic control via a forward / reverse valve v1, for example, when a forward / reverse lever 201 is operated in the cockpit 8.

[0042] The main transmission section 73 includes a main transmission 92 and a high-low (Hi-Lo) transmission 94. The main transmission 92 changes the speed of the rotational power from the engine E to one of a plurality of gear stages. The main transmission 92 includes a first main transmission clutch 92a and a second main transmission clutch 92b, and includes a plurality of gear stages, for example, first gear to fourth gear.

[0043] The first main transmission clutch 92a is hydraulically controlled by a first main transmission valve v2 controlled by operation of the main transmission operating unit 17, and the second main transmission clutch 92b is hydraulically controlled by a second main transmission valve v3 controlled by operation of the main transmission operating unit 17.

[0044] The main transmission 92 changes the speed of the rotational power from the engine E at one of the speed ratios from first gear to fourth gear depending on the connection state of the first main transmission clutch 92a and the second main transmission clutch 92b, and transmits the power to the subsequent stage, i.e., the power transmission downstream side. The main transmission 92 selects one of the first gear to fourth gear by, for example, operating the main transmission operating unit 17 (see FIG. 3) in the cockpit 8.

[0045] The high-low (Hi-Lo) transmission 94 changes the speed of the rotational power from the engine E between high and low speeds. The high-low (Hi-Lo) transmission 94 is equipped with a high-speed (Hi) side hydraulic multi-plate clutch (Hi clutch), a low-speed (Lo) side hydraulic multi-plate clutch (Lo clutch), a high-speed (Hi) gear, and a low-speed (Lo) gear. The Hi clutch and Lo clutch form a "Hi-Lo clutch."

[0046] The Hi-Lo clutch changes the rotational power that has been changed in speed by the main transmission 92 to a high-speed (Hi) gear ratio or a low-speed (Lo) gear ratio and transmits it to the subsequent stage, i.e., the downstream side of the power transmission. For example, when the main transmission operating unit 17 in the cockpit 8 is operated between fourth and fifth gear, the Hi-Lo clutch automatically switches to the high-speed (Hi) side or the low-speed (Lo) side through hydraulic control via the high-low valve v4. The Hi-Lo clutch has eight speeds, for example, four high-speed (Hi) gears and four low-speed (Lo) gears.

[0047] The auxiliary transmission unit 74 is capable of changing the speed of rotational power transmitted from the engine E, for example, via the forward / reverse clutch unit 72 and the main transmission unit 73 (main transmission, high / low transmission), in this order, to one of a plurality of gear stages. The auxiliary transmission unit 74 includes a first auxiliary transmission clutch 74a and a second auxiliary transmission clutch 74b, and includes a plurality of gear stages, for example, a first gear to a fourth gear.

[0048] The auxiliary transmission unit 74 changes the speed of the rotational power transmitted to the transmission shaft 78 via a first auxiliary transmission clutch 74a, a second auxiliary transmission clutch 74b, and multiple gears, and transmits the changed speed to an output shaft 79. The auxiliary transmission unit 74 changes the speed of the rotational power transmitted from the engine E and further changed in speed by the main transmission unit 73, etc., in four stages, for example, and transmits it to the rear wheels 5, 5. The gear stages of the auxiliary transmission unit 74 are hydraulically controlled by an auxiliary transmission first valve v5 and an auxiliary transmission second valve v6, which are controlled by operation of the auxiliary transmission lever 14.

[0049] That is, the rotation of the main shaft 77 is changed in speed by a main transmission 92 with, for example, four speeds, a high / low (Hi-Lo) transmission 94 with two speeds (high / low), and an auxiliary transmission with, for example, four speeds mechanically, and is finally transmitted to the drive shaft 79. The highest gear of the auxiliary transmission is mainly used for road travel, and allows travel at a predetermined speed or above (for example, 15 km / h or above). Pressing the public road travel button 91 restricts shifting to a gear that allows travel at a predetermined speed or above, so that travel on the road is safe even when traveling with implements attached. The restriction is implemented by restricting the output of signals to valve v5, etc.

[0050] The power transmission device 71 transmits the rotational power transmitted to the drive shaft 79 to the rear wheels 5, 5 via a rear wheel differential gear (rear wheel differential) 81, a rear axle 80, a final reduction gear mechanism, etc. As a result, the rear wheels 5, 5 of the tractor 1 are rotated and driven as drive wheels by the rotational power from the engine E.

[0051] The rotational power transmitted to the drive shaft 79 is transmitted to the front wheels 4,4 via a relay gear and a front wheel transmission unit (4WD clutch unit) 75. The front wheel transmission unit 75 includes a front wheel transmission device, which includes a front wheel speed-up clutch and a front wheel constant speed clutch. The front wheel speed-up clutch and the front wheel constant speed clutch form a 4WD clutch.

[0052] The 4WD clutch is provided on the first front-wheel drive shaft 82, and when the front-wheel constant-speed clutch is engaged, it transmits the rotation of the first front-wheel drive shaft 82 at a constant speed to the second front-wheel drive shaft 83. When the front-wheel speed-up clutch is engaged, the 4WD clutch increases the rotation of the first front-wheel drive shaft 82 and transmits it to the second front-wheel drive shaft 83 via multiple gears.

[0053] The 4WD clutch transmits the rotational power transmitted to the second front wheel drive shaft 83 to the front wheels 4, 4 via a front wheel differential gear (front wheel diff) 84, a front axle 85, a final reduction gear mechanism, etc. As a result, the tractor 1 can travel in four-wheel drive (4WD) mode with the left and right front wheels 4, 4 and the left and right rear wheels 5, 5.

[0054] The tractor 1 is provided with a steering cylinder (not shown) that constitutes a power steering device on the side of the front wheels 4, 4. The tractor 1 is also provided with left and right brakes 56L, 56R that constitute a braking device on the side of the rear wheels 5, 5. The tractor 1 is also provided with a control device 40 that controls the traveling of the traveling body 2.

[0055] Although not shown, the power transmission device 71 further includes a PTO drive device 93. The PTO drive device 93 changes the speed of the rotational power from the engine E and outputs it to the work implement W from the PTO shaft 16 at the rear of the traveling body 2, thereby driving the work implement W with the power from the engine E.

[0056] The PTO drive device includes a PTO clutch device, a PTO transmission, and a PTO shaft 16. The PTO drive device switches between a drive state in which the work implement W at the rear of the traveling body 2 is driven, and a non-drive state in which the drive of the work implement W is stopped.

[0057] 3, various operating devices provided around the cockpit 8 will be described. On the right side of the cockpit 8, a main speed change operating section 17 (main speed increase button 17a, main speed decrease button 17b), an auxiliary speed change lever 14, etc. are provided.

[0058] Next, various operating devices provided around the steering handle 9 will be described with reference to Figures 4 and 5. Figure 4 is an explanatory diagram of the operating devices located in front of the cockpit 8. Figure 5 is an enlarged view of part A in Figure 4.

[0059] As shown in Fig. 4, as described above, the steering handle 9 is provided in front of the driver's seat 8. In addition, the clutch pedal 18 is provided on the lower left side of the handle post 350 to which the steering handle 9 is attached, and the accelerator pedal 19 and the brake pedal 15 are provided on the lower right side of the handle post 350. The brake pedal 15 includes left and right brake pedals 15L and 15R.

[0060] A forward / reverse lever 201 is provided on the upper left of the handle post 350. An accelerator lever 351, a turn signal lever 352, and a one-touch lift lever 353 are provided on the upper right of the handle post 350. The one-touch lift lever 353 operates, with one touch, a lift arm that connects the work implement W to the vehicle body to the operating position of the position lever 152 (see FIG. 3) or the uppermost position; that is, by operating the tip upward with one touch from an unloaded position, the work implement W can be raised to the uppermost position, and by operating the tip downward with one touch, the work implement W can be lowered to the operating position of the position lever 152. A PTO shift lever 354 is provided in the center of the handle post 350.

[0061] As shown in Fig. 4, a dashboard cover 355 is provided in front of the steering wheel 9. The dashboard cover 355 is also provided with a meter panel 11 so as to be visible to the operator in the cockpit 8. The meter panel 11 is also provided with a display unit (liquid crystal monitor) 356, an engine revolution meter (tachometer) 357, and the like. The liquid crystal monitor 356 displays various information such as a gear display that displays the current gear, a fuel consumption rate display, and a traveling speed display, and the fuel consumption rate display and the traveling speed display may be displayed so as to be switched at regular intervals.

[0062] 5, a driving mode selection switch 223 and an engine mode selection switch 192 are provided on the right side of the dashboard cover 355. When the engine mode selection switch 192 is pressed, the engine E is controlled according to a preset engine output curve for low fuel consumption.

[0063] The mode selection switch 223 is configured to allow manual switching between a field mode in which the tractor 1 travels in a field and a road mode in which the tractor 1 travels on a road.

[0064] Field mode is a control mode selected when working in a field. When the vehicle speed is below a set speed (e.g., 10 km / h) and the sub-transmission lever 14 is in a low speed (e.g., first or second gear), autobrake control is activated, allowing work while reducing the turning radius. The pair of brake pedals 15 are configured as a so-called single-brake braking system, where the left brake pedal 15L brakes the left rear wheel 5L, and the right brake pedal 15R brakes the right rear wheel 5R. The autobrake control reduces the turning radius by braking the rear wheel 5 on the steering direction side of the steering wheel 9 during work travel in a field. The vehicle is also equipped with a locking mechanism that connects the left and right brake pedals 15L, 15R to form a unified unit, and a releasing mechanism that releases this connection. In road mode, the system automatically locks the connection or uses a means for confirming the connection status, i.e., the autobrake is released, allowing simultaneous braking of the left and right rear wheels 5L, 5R by depressing the brake pedal 15.

[0065] Incidentally, autobrake control, which is intended for work in fields, allows safe driving when the vehicle speed is slow and the auxiliary transmission is set to a low speed, but if the vehicle remains in field mode, i.e., with the autobrake set, when trying to exit the field onto a road, for example, turning as soon as the vehicle exits the road can cause a sudden turn in which the vehicle on the inside of the turn brakes, creating a dangerous situation. The autobrake safety release control will be explained based on the flowchart in Figure 6 and the control block diagram in Figure 7.

[0066] When the field mode is selected with the travel mode selection switch 223, if the vehicle speed sensor 24 detects that the vehicle speed is below a predetermined speed, autobrake control is set (S101 to S104) on the condition that the sub-transmission lever 14 is in a low-speed position (first or second speed) as detected by the lever sensor 35, and the rear wheel 5 on the steering direction side of the steering wheel 9 can be braked. When the travel mode is selected in S101, the autobrake control is released (S105), and the left and right brakes are locked in connection with each other, or an alarm is issued to prompt connection.

[0067] In S101, field work is performed with the autobrake control set, but if the horizontal sensor 36 mounted on the vehicle body does not detect any tilt for a predetermined period of time (S106), meaning that it is determined that the vehicle body is traveling in a stable state, and if the accelerator lever 351 remains in neutral and the accelerator pedal 19 is depressed (S107, S108), it is determined that the vehicle body is traveling on the road (S109), and the autobrake control is automatically released (S110). The operating position of the accelerator lever 351 can be detected by the accelerator lever sensor 37, and the amount of depression of the accelerator pedal 19 can be detected by the accelerator pedal sensor 38.

[0068] If the horizontal sensor 36 detects tilt in S106, if the accelerator lever 351 is operated in S107, or if the accelerator pedal 19 is not depressed in S108, the autobrake control continues (S112).

[0069] If the driving mode selection switch 223, which was set to the field mode after the processing of S109, is once set to the road mode and then set to the field mode again, the operator's intention is given priority and the field mode is selected (S111), and the autobrake control is continued (S112). After that, when the work is completed, the vehicle is stopped (S113, S114).

[0070] Therefore, when it is detected that the vehicle body has not been tilted for a predetermined period of time, it can be determined that the vehicle is traveling on a relatively flat surface such as a paved surface, and since the vehicle is traveling with the accelerator pedal 19 operated rather than the accelerator lever 351, it can be determined that the vehicle is traveling on the road, and the autobrake control is automatically released, allowing the vehicle to travel safely even if the field mode remains selected with the traveling mode selection switch 223.

[0071] Next, another example of the automatic brake safety release control will be described. This safety control will be described, in which the farmland mode is selected and automatic brake control continues, and the work load is calculated to determine whether the vehicle is traveling on a road. The work load is calculated based on the engine speed. The pedal sensor 38 detects the amount of depression of the accelerator pedal 19, and a pre-stored engine speed corresponding to the amount of pedal depression, such as the engine speed Ns during non-work driving, is retrieved and compared with the actual engine speed Nr detected by the engine speed sensor 23. If the difference |Nr-Ns| between the actual engine speed Nr and the engine speed Ns calculated from the pedal depression amount is equal to or less than a predetermined value α, the vehicle is determined to be traveling on a road. The accuracy of the determination can be improved by adding the condition that |Nr-Ns|<α continues for a predetermined period of time.

[0072] Therefore, it is possible to determine that the vehicle is traveling on a road by calculating the engine speed, and the autobrake control is automatically released, allowing the vehicle to travel safely even if the field mode remains selected with the travel mode selection switch 223.

[0073] In S110, if the vehicle continues to drive after the autobrake control is automatically released, the process returns to S106 and, according to a predetermined decision, when the accelerator pedal 19 is not operated but the accelerator lever 351 is operated, the autobrake control release state can be restored to the autobrake control setting (S112).

[0074] If, in S107 and S108, the accelerator pedal 19 is not operated and the accelerator lever 351 is in an operating range other than neutral, the process proceeds to S112, where the autobrake control is continued or restored. Since the accelerator pedal 19 is normally operated when traveling on the road and the accelerator lever 351 is operated when working in the field, the autobrake control can be restored when it is determined that the vehicle has returned to field work, allowing field work to be carried out safely and efficiently.

[0075] Regarding S110, even under the condition that the mode selection switch 223 is set to the field mode (S101), the auto-brake control is released and the vehicle is placed in the road mode, but if the mode selection switch 223 is switched to the road mode once and then back to the field mode before S110, the vehicle will enter the field mode (S111). Therefore, when it is desired to work in the field again, the situation where the auto-brake control is released and the vehicle is in the road mode can be resolved, and safe and efficient work travel can be achieved.

[0076] Next, a configuration for automatically switching from the field mode to the road mode in another example will be described with reference to the flowchart in FIG.

[0077] When the field mode is selected with the travel mode selection switch 223, if the vehicle speed sensor 24 detects that the vehicle speed is below a predetermined speed, autobrake control is set (S201 to S204) on the condition that the sub-transmission lever 14 is in a low-speed position (first or second speed) as detected by the lever sensor 35, and the rear wheel 5 on the steering direction side of the steering wheel 9 can be braked. When the travel mode is selected in S201, the autobrake control is released (S205), and the left and right brakes are locked in connection with each other, or an alarm is issued to prompt connection.

[0078] In S204, field work is performed with the autobrake control enabled. The system determines whether the steering angle sensor 25 detects a turning angle and the detected angle based on the turning operation of the steering wheel 9 (S206, S207). Specifically, the system recognizes that a turning operation is occurring when the steering angle sensor 25 detects a predetermined angle, and then calculates the turning angle. The absolute value of the turning angle θ (where θ is defined as 0°, with a forward straight-ahead direction as the reference, a right turn being + (plus), and a left turn being - (minus)) is compared with a preset angle β. If the detected angle |θ|<β, i.e., if the turning operation range is small, it is determined that the steering operation is occurring at a relatively high speed. In this case, when rotation of the PTO shaft 16 is detected (S208) and the vehicle has traveled a predetermined distance in this state (S209), it is determined that the vehicle is traveling on a road (S210), and the autobrake control is automatically released (S211). The rotation of the PTO shaft 16 is detected by directly detecting the rotation of the PTO shaft 16 or by using a configuration that can detect the rotation of the power transmission path of the PTO drive unit 93. The travel of the vehicle's predetermined distance is determined by determining whether or not a predetermined distance has been reached based on the relationship between the vehicle speed sensor 24 and the required time.

[0079] In this way, when it is detected that the steering handle 9 is within a predetermined operating range and that the PTO shaft 16 is not rotating and that the vehicle has been traveling a certain distance, it is determined that the vehicle is on the road and the system automatically switches to traveling mode, thereby preventing unintentional sharp turns and ensuring safety.

[0080] Conversely, if the turning operation range is determined to be large enough in S207, it can be determined that a steering operation or turning operation will be performed at low speed in a farm field, and the autobrake control is continued (S213).

[0081] After the processing of S210, if the PTO switch 34, which can turn on and off the clutch unit interposed in the PTO drive unit 93, is operated to the clutch-on side, or if the PTO lever sensor 39 detects that the PTO shift lever 354 is in a predetermined gear position other than neutral (S212), the autobrake control continues (S213). After that, when the work is completed, the vehicle is stopped (S214, S215).

[0082] When returning to the field to work, turning the PTO switch 34 ON again changes the mode from road mode to field mode, allowing the operator to change to the mode they want depending on the driving conditions, enabling efficient work operation. The same effect can be achieved by operating the PTO shift lever 354.

[0083] Furthermore, after processing of S210, if the driving mode selection switch 223, which was selected to the field mode, is once selected to the road mode and then selected to the field mode again, the system can be configured to prioritize the operator's intentions, set to the field mode, and continue auto-brake control, as shown in the flowchart S111 of Figure 6.

[0084] In the various embodiments described above, autobrake control is executed or released as an example of a control mode in the field mode or road mode, but it is also possible to execute or release so-called front wheel acceleration control, which increases the speed of the front wheels when turning in the field mode.Furthermore, it is also possible to execute or release autolift control, which raises or lowers the work implement in conjunction with turning.Furthermore, these may be combined. [Explanation of symbols]

[0085] 2 Running vehicle 9 Steering wheel 16 PTO shaft 34 PTO switch 36 Horizontal sensor 39 PTO lever sensor 93 PTO drive unit 223 Mode selection switch 354 PTO shift lever θ rotation angle β Angle

Claims

1. This work vehicle is equipped with a mode selection switch (223) for manually switching between a field mode for traveling in a field and a road mode for traveling on a road, and is configured to automatically switch from field mode to road mode when it is detected that the turning angle (θ) of the steering handle (9) is within a predetermined angle (β), the PTO shaft (16) is not rotating, and the vehicle has been traveling a certain distance.

2. 2. The work vehicle according to claim 1, further comprising a horizontal sensor (36) for detecting the inclination of the traveling vehicle body (2), and configured to automatically switch from the field mode to the road mode if the inclination of the vehicle body is not detected for a certain period of time.

3. 2. The work vehicle according to claim 1, wherein the work vehicle is configured to return from the road mode to the field mode when a PTO switch (34) that can turn on and off a clutch unit interposed in a PTO drive unit (93) is operated to the clutch-on side, or when a PTO lever sensor (39) detects that a PTO shift lever (354) is in a predetermined gear position other than neutral.

4. 2. The work vehicle according to claim 1, wherein, in a state in which the mode has been automatically switched from the field mode to the road mode, if the traveling mode selection switch (223) that has been selected for the field mode is once selected for the road mode and then the field mode is selected again, the field mode is given priority.

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