Work vehicle

Abstract

To provide a work vehicle capable of executing adjacent working control without reference to an operator's operation and states of a farm field such as a slippery state.SOLUTION: Automatic down control has adjacent working control and normal control other than the adjacent working control. The adjacent working control, in order to perform tilling work of a second path L2 by turning a traveling machine body 2 at 180° from a first path L1 when the first path L1 and the second path L2 are adjacent to each other, makes a rotary tiller automatically lower so as to, relating to a direction along the first path L1, adjust a start position of tilling work on the second path L2 to an end position of tilling work on the first path L1. A control part, in the automatic down control, after starting the turning of the traveling machine body 2, executes the adjacent working control if the machine body angle calculated when the state of the traveling machine body 2 becomes a straight advancing state after a forward state and a turning state in the same direction are kept is within a prescribed range with respect to 180°.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, a work vehicle has been proposed that performs auto-down control to automatically lower a work implement after turning at the edge of a field during work such as plowing or planting in the field (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-102217 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, when the work implement is raised after plowing work on a first path is completed, the traveling machine body is rotated 180° toward the adjacent second path, and the work implement is lowered at a target position on the second path to start plowing work, adjacent plowing control (adjacent work control) may be performed using auto-down control that automatically lowers the work implement at the target position as described above. Adjacent plowing control is executed when it is determined that the traveling machine body has rotated 180°, calculated from the coordinate position of the traveling machine body and the machine body angle, which is the yaw angle of the traveling machine body.

[0005] However, the conditions for the machine body angle are affected by factors such as the driver's operation and the condition of the field, such as whether it is prone to slippage. Therefore, even if the traveling machine body is rotated from the first path to perform adjacent tillage control and moves straight on the second path, the difference between the actual machine body angle and the calculated machine body angle may be large. In this case, the traveling machine body may not be determined to have rotated 180 degrees, and the working machine may pass by without descending to the target position.

[0006] An object of the present invention is to provide a work vehicle that can execute adjacent work control regardless of the driver's operation or the state of the field, such as whether the field is prone to slipping. [Means for solving the problem]

[0007] The present invention relates to a vehicle having a running machine body supported by a pair of left and right front wheels and a pair of left and right running units arranged behind the front wheels; A steering unit that steers the traveling machine body; A switching means for switching between forward and reverse movement of the traveling machine body; Vehicle speed detection means capable of detecting a vehicle speed, which is the speed of the traveling machine body; An angle detection means capable of detecting the angle of the steering unit; a lifting device for lifting and lowering the work machine; a control unit capable of executing auto-down control to automatically lower the working implement at a target position on the second path based on coordinates calculated from the detection results of the vehicle speed detection means and the angle detection means, the coordinates being a reference coordinate position that is the position where the turning of the traveling machine body started, and a machine body angle that is the yaw angle of the traveling machine body, when the traveling machine body is turned from the first path toward the second path to perform work on a second path different from the first path after work on the first path has been completed and the working implement has been raised, The auto-down control includes an adjacent work control for automatically lowering the work machine in a direction along the first path so as to align the start position of work on the second path with the position where work on the first path is completed, in order to rotate the traveling machine body 180° from the first path and perform work on the second path when the first path and the second path are adjacent to each other, and a normal control other than the adjacent work control, The control unit In the auto-down control, after the turning of the traveling machine body is started, During turning, the switching means is maintained in a forward state, and the state of the traveling machine body is When the aircraft is traveling straight ahead, if the calculated aircraft angle is within a predetermined range of 180°, the adjacent work control is executed. death, In the auto-down control, after starting the turning of the traveling machine body, if the switching means is switched from the forward state to the reverse state while the traveling machine body is turning, the normal control is executed. do, This is a work vehicle characterized by the above.

[0008] For example, when the auto-down control is initiated, the control unit simultaneously performs calculations for the adjacent work control and the normal control, and performs the normal control if the conditions for the adjacent work control are not met.

[0009] For example, during the auto-down control, when the traveling machine body goes into a straight traveling state after turning, the control unit corrects the position at which the working machine is lowered based on the calculated machine body angle.

[0010] For example, the control unit can perform an accelerated turning control that increases the circumferential speed of the front wheels relative to the circumferential speed of the traveling part when turning in both forward and reverse states, and an auto-brake control that performs the accelerated turning control when turning only in the forward state and automatically brakes the traveling part on the inside of the turn, and during the auto-down control, the turning fulcrum is changed depending on the settings of forward, reverse, the accelerated turning control, and the auto-brake control. [Effects of the Invention]

[0011] According to the present invention of claim 1, in auto-down control, after the running machine body starts turning, the state of the running machine body is maintained in a forward state and a turning state in the same direction, and then when it changes to a straight-ahead state, adjacent work control is executed if the calculated machine body angle is within a predetermined range of 180°, so adjacent work control can be executed regardless of the driver's operation or the state of the field, such as whether it is prone to slipping.

[0012] According to the present invention as set forth in claim 2, when auto-down control is initiated, calculations for adjacent work control and calculations for normal control are performed simultaneously, and if the conditions for adjacent work control are not met, normal control is performed, thereby enabling a smooth change from adjacent work control to normal control and improving workability.

[0013] According to the present invention as set forth in claim 3, in the auto-down control, when the traveling machine body goes straight after turning, the position at which the working machine is lowered is corrected based on the calculated machine body angle, thereby suppressing deviations in the work start position in the auto-down control and improving workability.

[0014] According to the present invention as set forth in claim 4, during auto-down control, the turning fulcrum is changed by setting forward, reverse, accelerated turning control, and auto-brake control, so that during auto-down control, calculations can be performed with high precision when the traveling machine body is turning according to the situation, and the starting position of the descent of the work machine can be stabilized. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a side view showing a tractor according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 2 is a schematic diagram showing the travel path of the tractor. [Figure 9] 10 is a flowchart showing an auto-down control. [Figure 10] 10 is a flowchart for setting the lowering position of the work implement. [Figure 11] FIG. 10A is an explanatory diagram of the lowering position correction of the work implement in normal control, and FIG. 10B is an explanatory diagram of the lowering position correction of the work implement in adjacent tillage control. [Figure 12] (a) Diagram showing the pivot point when turning right and moving forward, (b) Diagram showing the pivot point when turning right and moving backward. [Figure 13] 10 is a table showing conditions for turning adjustment in auto-down control. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Overall configuration] The present embodiment will be described below with reference to the drawings. As shown in FIG. 1, a tractor 1 serving as a work vehicle according to this embodiment includes a traveling machine body 2 and a rotary tiller 3 serving as a work implement having a rotating rotary 3b and connected to the rear of the traveling machine body 2 so as to be able to ascend and descend. The traveling machine body 2 includes a control unit 52 (shown in FIG. 7) that controls the input and output of various electrical signals, as well as front wheels 5 and rear wheels 6 serving as a traveling unit. The front wheels 5 and rear wheels 6 are provided in pairs, one on each side, and the traveling machine body 2 is steered by steering the front wheels 5 left and right. The traveling machine body 2 also includes a machine body frame 7 supported by the front wheels 5 and rear wheels 6, and a driver's unit 10 having a driver's seat 23 in which an operator sits. In this embodiment, unless otherwise specified, the forward direction facing an operator seated in the driver's seat 23 of the tractor 1 placed on a horizontal surface is defined as the forward direction of the traveling machine body 2, and the front, rear, left, and right directions are defined based on this. An alarm buzzer 53 is provided on the output side of the control unit 52 and is operable by an output signal from the control unit 52 to notify the operator of various types of information by sound emission.

[0017] [Power transmission structure] The vehicle frame 7 includes an engine (not shown) that generates power to drive the front wheels 5 and rear wheels 6, an engine room 9 in which the engine is housed, and a transmission case (not shown) that is positioned between the left and right rear wheels 6.

[0018] The transmission case houses a traveling transmission (not shown) that changes the speed of the engine's power, and the traveling transmission incorporates a main transmission mechanism (not shown) that serves as a speed-changing means for changing the speed of the engine's power in multiple stages, a sub-transmission mechanism (not shown) that serves as a speed-changing means for further changing the speed of the power changed by the main transmission mechanism in multiple stages, and a PTO transmission mechanism (not shown) that changes the speed of the power to the PTO shaft. The rotation of the PTO shaft is transmitted to the rotary tiller 3, and the rotary 3b rotates around the rotary shaft 3a, tilling the field.

[0019] The inside of the transmission case is filled with lubricating oil, which is supplied to a hydraulic pump (not shown) driven by engine power. The hydraulic pressure generated by the hydraulic pump is transmitted to a lift arm cylinder (not shown) that raises and lowers the rotary tiller 3 by operating a lift arm valve 20 shown in Figure 7.

[0020] The power that passes through the main transmission mechanism and the sub-transmission mechanism is distributed to the left and right rear wheels 6 via a rear wheel differential mechanism (not shown) by a rear wheel drive shaft (not shown), and is distributed to the left and right front wheels 5 via a front wheel differential mechanism (not shown) by a front wheel transmission mechanism (not shown) and a front wheel drive shaft (not shown), so that when the running body 2 turns left and right by steering the front wheels 5, a difference in rotation speed between the inner and outer wheels is allowed, enabling smooth running.

[0021] The rear wheel differential mechanism transmits power from the rear drive shaft to the left and right rear wheels 6 via a pair of left and right brake mechanisms (not shown) that can brake the left and right rear wheels 6 independently. The rotation speeds per unit time of the rear drive shaft and either the left or right rear wheel 6 are independently detected by vehicle speed sensors 11 (FIG. 7) serving as vehicle speed detection means, and the vehicle speed as the traveling speed of the traveling vehicle body 2 is calculated based on the rotation speeds per unit time of the rear drive shaft and either the left or right rear wheel 6. Here, the vehicle speed is the travel distance per unit time of a vehicle body reference point 2a, which is the center point of the left and right rear wheels 6 on the rotation axis of the rear wheels 6, as shown in FIG. 8. Information on the vehicle speed at the time of calculation is transmitted to the control unit 52 by an electrical signal. The control unit 52 also integrates the vehicle speed over time to obtain the travel distance of the vehicle body reference point 2a, i.e., the traveling distance of the traveling vehicle body 2.

[0022] The front wheel transmission mechanism is equipped with a friction multi-plate hydraulic clutch (not shown) as a drive state switching means, and by connecting and disconnecting the hydraulic clutch, the running body 2 can be switched between a front wheel double speed on 4WD mode in which front wheel double speed control is performed as a front wheel acceleration control to increase the average peripheral speed of the left and right front wheels 5 relative to the average peripheral speed of the left and right rear wheels 6, a front wheel double speed off 4WD mode in which the average peripheral speed of the left and right front wheels 5 is driven at approximately the same speed relative to the average peripheral speed of the left and right rear wheels 6, and a 2WD mode in which power is not transmitted to the front wheels 5.

[0023] [Steering device] A steering device 12 serving as a steering section is disposed on the vehicle frame 7. The steering device 12 includes a steering wheel 13 that the operator turns to steer the front wheels 5, a steering column 14 (shown in Fig. 6) that turns integrally with the steering wheel 13, a steering mechanism (not shown) that extends to the left and right and converts the turning of the steering column 14 into approximately linear motion in the left and right direction, and tie rods (not shown) that connect both ends of the steering mechanism to the left and right front wheels 5. When the operator turns the steering wheel 13, the steering column 14 turns, and the tie rods move left and right based on the turning angle and turning direction of the steering column 14, thereby steering the left and right front wheels 5.

[0024] The steering device 12 is provided with stoppers (not shown) in both the left and right rotation directions that restrict the steering wheel 13 from being rotated more than a predetermined angle in one direction. The maximum rotation angle α1 of the steering wheel 13 in one direction from the neutral position, when the traveling vehicle body 2 moves substantially straight, is configured to be substantially the same as the maximum rotation angle in the other direction. When the steering wheel 13 is rotated from the neutral position by more than a predetermined angle α2, which is slightly smaller than the maximum rotation angle α1, a steering sensor 15 (shown in FIG. 7 ) serving as angle detection means capable of detecting the angle of the steering device 12, turns on, detecting that the steering wheel 13 has been rotated more than α2 and the direction of rotation of the steering wheel 13. When the rotation angle of the steering wheel 13 is less than α2 from the neutral position, the steering sensor 15 turns off, detecting that the rotation angle of the steering wheel 13 is less than α2. Information on the on / off state of the steering sensor 15 and the direction of rotation of the steering wheel 13 is transmitted to the control unit 52 via an electrical signal. The steering sensor 15 may be one that detects a neutral position and a predetermined rotation angle to the left or right, or one that detects the rotation angle of the steering wheel more precisely than these positions. Also, the angle detection means may be one that can detect the rotation angle of the steering wheel 13 at any position from the steering wheel 13 to the front wheels 5.

[0025] [Lifting link mechanism] A lifting link mechanism 16 is provided at the rear of the traveling body 2, connecting the body frame 7 and the rotary tiller 3 and serving as a lifting device for raising and lowering the rotary tiller 3. The lifting link mechanism 16 has a link bracket (not shown) protruding from the rear of the traveling body 2, a single top link 17 pivotally supported on the link bracket so as to be swingable up and down and extending rearward, and a pair of left and right lower links 18 provided below the top link and pivotally supported on the link bracket so as to be swingable up and down and extending rearward, with the rear ends of the top link 17 and the left and right lower links 18 pivotally supported on the rotary tiller 3 so as to be swingable up and down, forming a three-point link mechanism. The left and right lower links 18 are suspended by lift arms (not shown) via lift rods (not shown) provided on the left and right, respectively. The front end of the lift arm is journalled to a link bracket so that it can swing up and down, and as the lift arm swings up and down due to the extension and contraction of the lift arm cylinder, the lower link 18 swings up and down, raising and lowering the rotary tiller 3. The swing angle of the lift arm is detected by a lift arm sensor 21 (shown in Figure 7) provided on the lift arm and transmitted to the control unit 52 as an electrical signal.

[0026] [Operation section] Next, the driver's section 10 will be described with reference to Figures 2 to 6. As shown in Figure 2, an auxiliary speed change lever 27 that is supported so as to be able to swing freely and that changes the speed of the auxiliary transmission mechanism is provided on the left side of the driver's seat 23. The auxiliary speed change lever 27 is operable to three speed change positions: high speed, medium speed, and low speed, and is configured so that when the auxiliary speed change lever 27 is positioned at the high speed position, the reduction ratio obtained by dividing the engine rotation speed by the rotation speed of the rear wheel drive shaft is the smallest of the three positions, the reduction ratio is the largest at the low speed position, and the reduction ratio at the medium speed position is between that at the high speed position and the low speed position.

[0027] 3, below the operator's seat 23 are provided a work implement descent speed adjustment knob 29 and a differential lock pedal 28 as descent speed setting means that is rotatably supported and can operate a descent speed adjustment valve (not shown) that adjusts the descent speed of the rotary tiller 3. When the operator turns the work implement descent speed adjustment knob 29 clockwise, the descent speed adjustment valve is operated to decrease the descent speed of the rotary tiller 3, and when the operator turns the knob counterclockwise, the descent speed increases. Information on the shift position of the sub-transmission lever 27 and information on the rotation position of the work implement descent speed adjustment knob 29 are transmitted to the control unit 52 by electrical signals.

[0028] 4 and 5, a side panel 26 on which various operating tools and lamps are arranged is provided to the right of the operator's seat 23. On the side panel 26, there are arranged a main speed change lever 30 that is supported so as to be able to swing freely and that changes the speed of the main speed change mechanism, a position lever 31 that operates to raise and lower the rotary tiller 3, a lift height volume 32 as a lift height adjustment means that sets the maximum lift height of the rotary tiller 3, and an auto-down timing volume 33 as a lowering start range adjustment means.

[0029] The main transmission mechanism can be shifted by the main shift lever 30 independently of the sub-transmission mechanism by the sub-transmission lever 27, and is operable to eight shift positions from eighth gear to one first gear, a neutral position in which power is not transmitted to the front wheels 5 and rear wheels 6, and an accelerator shift position in which the main transmission mechanism automatically shifts from eighth gear to fourth gear by operating an accelerator pedal (not shown). Eighth gear is the smallest reduction ratio provided by the main transmission mechanism, and the reduction ratio increases as the gear number decreases. Information on the shift position of the main shift lever 30 is sent to the control unit 52 by electrical signal.

[0030] The position lever 31 is supported so that it can swing back and forth, and is configured to maintain the swing position when the operator releases the lever. When the position lever 31 is swung back and forth, the rotary tiller 3 rises or falls to a height corresponding to the position at which the position lever 31 is held. Information about the position at which the position lever 31 is held is sent to the control unit 52 by an electrical signal.

[0031] The lift height volume 32 is rotatably supported and can be rotated to select between a lift height adjustment position, which is provided within a predetermined rotation range, and a hydraulic pressure take-off position. When the lift height volume 32 is in the lift height adjustment position, the operator rotates the lift height volume 32 clockwise to increase the upper limit height for raising and lowering the rotary tiller 3, and rotates it counterclockwise to decrease the upper limit height. When the lift height volume 32 is in the hydraulic pressure take-off position, hydraulic pressure is transmitted to the traveling machine body 2 from a hydraulic pressure take-off port (not shown), enabling it to operate, for example, a front loader, while hydraulic pressure to the lift cylinder is cut off, preventing the rotary tiller 3 from rising or lowering. Information on the rotation position of the lift height volume 32 is sent to the control unit 52 via an electrical signal.

[0032] The auto-down timing volume 33 is supported rotatably and is changeable between an ON position and an OFF position within a predetermined rotation range. When the auto-down timing volume 33 is rotated to the ON position, the timing at which the rotary tiller 3 starts to descend can be adjusted in accordance with the rotation position in the auto-down control described below. Information on the rotation position of the auto-down timing volume 33 is sent to the control unit 52 by an electrical signal.

[0033] As shown in Figures 2 and 6, a steering wheel 13 is located in front of the driver's seat 23, and below the steering wheel 13 are located a brake pedal 25 for operating the left and right brake mechanisms, an accelerator pedal 38, and the like. Around the steering wheel 13 are located a starter switch 34, which is the main switch for the traveling body 2, a shuttle lever 35 as a switching means by which the operator switches the traveling body 2 between forward and reverse, and a quick-up lever 36, which manually raises and lowers the rotary tiller 3 between preset upper and lower limit heights.

[0034] The shuttle lever 35 is operable to a forward position, a neutral position, and a reverse position, and when the shuttle lever 35 is in the forward position, the traveling machine body 2 moves forward, when in the neutral position, the traveling machine body 2 stops, and when in the reverse position, the traveling machine body 2 moves backward. Information on the operating position of the shuttle lever 35 is sent to the control unit 52 by an electrical signal.

[0035] The quick-up lever 36 is supported so that it can swing between a raised position, a center position, and a lowered position, and is provided with a biasing member (not shown) so that the quick-up lever 36 returns to the center position when the operator raises or lowers the quick-up lever 36 to the raised position or lowers it to the lowered position and then releases the lever. When the rotary tiller 3 is stopped from moving up or down, a short-up operation of the quick-up lever 36 raises the rotary tiller 3 to its upper limit height, and a short-down operation lowers the rotary tiller 3 to its lower limit height, which corresponds to the swing position of the position lever 31. The direction and duration of operation of the quick-up lever 36 are transmitted to the control unit 52 by electrical signals.

[0036] As shown in FIG. 6 , a front panel 24 equipped with various controls, displays, and lamps is located in front of the steering wheel 13. The front panel 24 includes a backup selector switch 37 for switching the backup mode of the traveling machine body 2 between on and off, and a swing up selector switch 39 for switching the swing up mode between on and off. When the traveling machine body 2 is in the backup mode on state, the backup lamp 40 is illuminated. When the rotary tiller 3 is not positioned at its upper limit height, if a reverse operation is performed by switching the shuttle lever 35 from the neutral position to the reverse position, the rotary tiller 3 rises to its upper limit height. When the swing up mode is on, the swing up lamp 41 is illuminated. When the steering sensor 15 is switched from the off state to the on state while the rotary tiller 3 is not positioned at its upper limit height, the rotary tiller 3 rises to its upper limit height. Switching information for the backup selector switch 37 and the swing up selector switch 39 is transmitted to the control unit 52 via an electrical signal.

[0037] The front panel 24 also includes a 4WD selector switch 42 for connecting and disconnecting the hydraulic clutch, and a swing speed selector switch 43 for connecting and disconnecting the hydraulic clutch and for braking by the brake mechanism. Each time the operator operates the 4WD selector switch 42, the traveling machine body 2 switches between a mode in which power is transmitted to the front wheels 5 and a 2WD mode in which power is not transmitted to the front wheels 5, and a 4WD selector lamp 45 lights up when the traveling machine body 2 is in a mode in which power is transmitted to the front wheels 5. Information on the switching operation by the 4WD selector switch 42 and the swing speed selector switch 43 is transmitted to the control unit 52 by an electric signal.

[0038] With the 4WD selector lamp 45 lit, each time the turning double speed selector switch 43 is operated, the traveling vehicle 2 switches between four-wheel drive states: front wheel double speed off 4WD mode, front wheel double speed on 4WD mode, and auto-brake mode (auto-brake control). In the front wheel double speed on 4WD mode, front wheel double speed control (accelerated turning control) is executed to turn by increasing the circumferential speed of the front wheels 5 relative to the circumferential speed of the rear wheels 6, and the turning double speed lamp 46 is lit. In the auto-brake mode, the front wheel double speed control is executed, and auto-brake control is executed by the control unit 52 to automatically brake the rear wheel 6 on the inside of the turn, and the auto-brake turning lamp 47 is lit. Note that the front wheel double speed control can be executed in both forward and reverse travel, while the auto-brake control can only be executed in the forward travel.

[0039] The front panel 24 is equipped with an automatic mode selector switch 49 that can switch the traveling body 2 between a work mode for tilling in a field and a travel mode for traveling on roads or the like outside the field, and an automatic mode selector lamp 50 that indicates whether the traveling body 2 is in work mode or travel mode. Each time the operator operates the automatic mode selector switch 49, the traveling body 2 alternates between work mode and travel mode. When the traveling body 2 switches from work mode to travel mode, both the backup mode and the swing up mode are turned off, and if the traveling body 2 was in front wheel double speed on 4WD mode or auto brake mode, it switches to front wheel double speed off 4WD mode, and if it was in 2WD mode, it maintains 2WD mode, restricting the lifting and lowering of the rotary tiller 3 using the quick-up lever 36. Furthermore, if the main shift lever 30 is in the accelerator shift position, the main transmission mechanism can be shifted by operating the accelerator pedal. When the traveling machine body 2 switches from traveling mode to work mode, it returns to the state it was in before switching from work mode to traveling mode: backup mode, swing up mode, front wheel double speed on 4WD mode, auto brake mode, or 2WD mode, allowing the rotary tiller 3 to be raised or lowered using the quick-up lever 36, and restricting the speed change operation of the main transmission mechanism by operating the accelerator pedal. Information on switching between work mode and traveling mode using the automatic selector switch 49 is sent to the control unit 52 by electric signal.

[0040] The front panel 24 also has a liquid crystal display device 51 that displays various information related to the state of the traveling machine body 2 and tillage work, and the liquid crystal display device 51 has an auto-down status display section 51a and a notification display section 51b. The auto-down status display section 51a displays a temperature / fuel display consisting of an engine temperature display and a remaining fuel display, or information related to the auto-down control described below, and the notification display section 51b displays an engine RPM / usage time display consisting of an engine RPM display and a total usage time display, or notification messages related to the auto-down control.

[0041] FIG. 7 shows a control block diagram of this embodiment. A control unit 52 capable of executing auto-down control, which will be described later, includes a microcomputer 52a having a CPU 52b, a ROM 52c, a RAM 52d, an interface 52e, and the like. The control unit 52 outputs a signal through calculations by the microcomputer 52a based on signals input from the steering sensor 15, lift arm sensor 21, vehicle speed sensor 11, quick-up lever 36, main speed change lever 30, sub-speed change lever 27, position lever 31, automatic selector switch 49, auto-down timing volume 33, lift height volume 32, shuttle lever 35, swing speed double selector switch 43, 4WD selector switch 42, backup selector switch 37, swing-up selector switch 39, implement lowering speed adjustment knob 29, and starter switch 34. The control unit 52 activates the lift arm valve 20 and the alarm buzzer 53, and controls the turning on and off of the lift-up lamp 22, automatic selector lamp 50, swing speed double lamp 46, 4WD selector lamp 45, swing-up lamp 41, backup lamp 40, auto-brake swing lamp 47, and auto-on lamp 48, and displays various information on the liquid crystal display device 51.

[0042] [Auto down control] Next, auto-down control as a turning control that can be executed by the control unit 52 will be described. First, an overview of the auto-down control will be described using FIG. 8. FIG. 8 shows an example of a travel path of the tractor 1 when tilling a field H. The auto-down control is a control that, when the traveling body 2 travels back and forth between two positions, such as straight ahead and turning at the field edge J, when the tractor 1 reaches the field edge J, raises the rotary tiller 3 or other implement and turns, and then automatically starts lowering the rotary tiller 3 or other implement when it reaches a descent start line that serves as the boundary of the implement descent start area. In the following explanation, we will describe a case where tilling is performed as work performed in the field, but this work may also be other work such as ridge making if the work vehicle is a tractor, or rice planting if the work vehicle is a rice transplanter.

[0043] Here, as shown in FIG. 8, a case will be described in which tilling work is performed on a first path L1 and a second path L2 adjacent to each other in a farm field H. First, the tractor 1 performs tilling work while moving forward along the first path L1 from the bottom of FIG. 8. Next, after tilling work on the first path L1 is completed and the rotary tiller (work implement) 3 is raised, the traveling machine body 2 is turned from the first path L1 toward the second path L2 to perform tilling work on a second path L2 different from the first path L1. In the auto-down control, the control unit 52 automatically lowers the rotary tiller 3 at a target position on the second path L2 based on coordinates in which the position where the traveling machine body 2 started to turn is used as a reference coordinate position and the machine body angle, which is the yaw angle of the traveling machine body 2.

[0044] Specifically, after completing tilling work on the first path L1, the driver turns the steering wheel 13 toward the second path L2. In FIG. 8, the steering wheel 13 is turned to the right to make a right turn. If the above-mentioned turn-up mode is on, turning the steering wheel 13 automatically raises the rotary tiller 3. If the turn-up mode is off, the driver manually raises the rotary tiller 3 by operating the quick-up lever 36 before turning the steering wheel 13. The control unit 52 acquires the XY coordinates of the traveling machine body 2 when the steering wheel 13 is turned. In the XY coordinates, the direction along the first path L1 (the up-down direction in FIG. 8) is the Y axis, and the direction perpendicular to the Y axis is the X axis (the left-right direction in FIG. 8).

[0045] The control unit 52 sets the XY coordinate position acquired when the steering wheel 13 is turned, i.e., coordinates with the position where the traveling body 2 starts turning as the reference coordinate position (origin O). Here, the upward direction in FIG. 8 relative to the origin O is the Y-axis direction +, and the downward direction is the Y-axis direction -. That is, on the first path L1, the forward direction is + and the backward direction is -. The origin O is also the center position in the rotation axis direction (X-axis direction) of the pair of left and right rear wheels 6 when the traveling body 2 starts turning, i.e., the body reference point 2a. The position of the traveling body 2 on the coordinate system is specified by the X-coordinate and Y-coordinate of the body reference point 2a.

[0046] In the auto-down control, the control unit 52 sets a descent reference line F, which is defined only by the Y coordinate and serves as a reference for calculating the descent start line, on the set coordinate system. The control unit 52 also calculates a descent travel distance D, which is the distance traveled by the machine body reference point 2a from when the rotary tiller 3 starts to descend until it lands, based on the vehicle speed. If the traveling machine body 2 starts to descend the descent travel distance D before the work restart position G while traveling along the second path L2, tilling work can be resumed from the work restart position G without stopping the traveling machine body 2 when the traveling machine body 2 turns at the field edge J. In this case, the Y coordinate of the descent reference line F is obtained by subtracting the descent travel distance D from the Y coordinate of the work restart position G. In addition, by operating the auto-down timing volume 33, the driver (operator) can set a descent setting line that adjusts the Y coordinate of the position where the rotary tiller 3 starts to descent relative to the descent reference line F within the range of a minimum of -S to a maximum of +S using a predetermined length S.

[0047] Here, when the position of the rotary shaft 3a of the rotary tiller 3 that has landed after turning coincides with the work boundary C, which is the position of the rotary shaft 3a of the rotary tiller 3 in the landed state at the start of the turn, in other words, when the direction of the traveling machine body 2 at the start of the turn is opposite to the direction of the traveling machine body 2 after the turn, the rotary tiller 3 lands at work restart position G where the Y coordinate of the machine body reference point 2a is equal to twice the hitch length A, and tilling work is resumed, tilling work can be performed with the headland width M from the ridge E aligned. The hitch length A is the distance in a plan view between the rotation axis of the rear wheels 6 and the rotary shaft 3a when the rotary 3b lands.

[0048] Therefore, in the auto-down control, the control unit 52 controls the timing at which the rotary tiller 3 starts to be lowered based on the coordinates and the machine body angle, which is the yaw angle of the traveling machine body 2, calculated from the detection results of the vehicle speed sensor 11 and the steering sensor 15, so that the rotary tiller 3 is automatically lowered in the direction along the first path L1, i.e., the Y-axis direction, so that the start position of tilling work on the second path L2 coincides with the position where tilling work on the first path L1 ended. That is, in the auto-down control, the position in the coordinate system of the traveling machine body 2 and the machine body angle are calculated based on fixed data for the turning radius r and turning circumference set in the program, and the rotary tiller 3 is controlled to be lowered so that the start position of tilling work on the second path L2 coincides with the position where tilling work on the first path L1 ended.

[0049] The auto-down control also includes adjacent tillage control, which is adjacent work control that automatically lowers the rotary tiller 3 when the traveling machine body 2 is rotated 180° to perform tilling work on an adjacent path (adjacent tillage), and normal control other than adjacent tillage control (non-adjacent work control). That is, as described above, adjacent tillage control is control that automatically lowers the rotary tiller 3 in the direction along the first path L1 (Y-axis direction) so that the start position of tilling work on the second path L2 aligns with the position where tilling work on the first path L1 ends when the first path L1 is adjacent to the second path L2, in order to rotate the traveling machine body 2 180° from the first path L1 to perform tilling work on the second path L2. Note that adjacent work control when the work is not tillage work, such as ridge making, on an adjacent path is also similar to the above. Normal control is a control that is executed when the conditions for adjacent tillage control are not met, and in this embodiment, it is a control that is executed when the conditions for adjacent tillage control are not met, not only when tillage work is being performed on a non-adjacent path, but also even if tillage work is being performed on an adjacent path.

[0050] Therefore, when auto-down control is initiated, the control unit 52 simultaneously performs calculations for adjacent tillage control and normal control, and performs normal control if the conditions for adjacent tillage control are not met.

[0051] Furthermore, in this embodiment, a 180° turn of the traveling machine body 2 is considered to have occurred if the calculated machine body angle is 180°±30° (180°-30° or more and 180°+30° or less), or -180°±30° (-180°+30° or less and -180°-30° or more). This is because there may be a discrepancy between the actual state of the traveling machine body 2 and the calculation result. Therefore, when the traveling machine body 2 is in a straight-ahead state, if the calculated machine angle is within this range, it is considered to have occurred a 180° turn.

[0052] [Aircraft angle calculation] Here, we will explain how to calculate the machine body angle. The machine body angle is calculated based on the vehicle speed and turning circumference. The turning circumference is set separately for forward and reverse. The turning circumference is set in advance, but as will be described later, it is updated by turning the tractor 1 360°. To explain the calculation of the machine body angle more specifically, first, the change in the machine body angle is calculated based on the vehicle speed during the turn, and the change is then integrated to find the machine body angle. When divided into left and right turns, forward and reverse, the machine body angle is calculated using the following formula. Note that "Δ machine body angle" is the change in the machine body angle during the turn. Also, a right turn is +, a left turn is -, forward is +, and reverse is -.

[0053] (1) Right turn and forward movement ΔFuel cell angle = 360.0° × vehicle speed (mm / s) / forward turning circle (mm) (2) Right turn and reverse ΔFuel cell angle = -360.0° × vehicle speed (mm / s) / reverse turning circle (mm) (3) Left turn and forward movement ΔFuel angle = -360.0° × Vehicle speed (mm / s) / Forward turning circle (mm) (4) When turning left or reversing ΔFuel cell angle = 360.0° × vehicle speed (mm / s) / reverse turning circle (mm) The aircraft angle is calculated by integrating the above-mentioned Δ aircraft angle after the start of the turn.

[0054] [Adjacent tillage control] As described above, the auto-down control calculates the position of the traveling machine body 2 in the coordinate system and the machine body angle to control the descent of the rotary tiller 3. The adjacent tillage control is also executed when it is determined that the traveling machine body has rotated 180° based on these coordinates and the machine body angle. However, as described above, the machine body angle conditions are affected by factors such as the driver's operation and the condition of the field, such as whether the field is prone to slipping. Therefore, even if the traveling machine body is rotated from the first path to perform adjacent tillage control and moves straight on the second path, the difference between the actual machine body angle of the traveling machine body and the calculated machine body angle may be large. In this case, it may not be determined that the traveling machine body has rotated 180°, and the working implement may pass by without descending to the target position.

[0055] Therefore, in this embodiment, the control unit 52 executes adjacent tillage control during auto-down control when the traveling machine body 2 starts turning, maintains a forward movement state and a turning state in the same direction, and then transitions to a straight-ahead state. That is, when the steering wheel 13 is turned and the traveling machine body 2 starts turning in a predetermined direction, if the position of the shuttle lever 35 remains in the forward movement position, the turning direction of the traveling machine body 2 remains in the predetermined direction, and the traveling machine body 2 transitions to a straight-ahead state, the control unit 52 executes adjacent tillage control, assuming that the traveling machine body 2 has turned 180°, even if the calculated machine body angle does not coincide with a 180° turn of the traveling machine body. In other words, even if the calculated machine body angle is not within the range of 180°±30° or −180°±30°, the control unit 52 executes adjacent tillage control as long as the above-mentioned conditions are met.

[0056] This makes it possible to execute adjacent tillage control regardless of the driver's operation or the state of the field, such as whether it is prone to slipping. In other words, even if the calculation result does not match a 180° turn when the traveling machine body 2 is traveling straight, adjacent tillage control will be executed as long as the above-mentioned conditions are met from the start of the turn until the traveling machine body 2 is traveling straight. This prevents adjacent tillage control from being omitted even if the calculation result deviates due to slippage or the like, thereby improving work efficiency.

[0057] However, after the traveling machine body 2 starts turning, and the traveling machine body 2 maintains a forward movement state and a turning state in the same direction, and then transitions to a straight-ahead state, the control unit 52 executes adjacent tillage control if the machine body angle calculated as described above is within a predetermined range of 180°, but does not execute adjacent tillage control if it is outside the predetermined range. For example, if a right turn is defined as +, the predetermined range is a range of 180° -30° to 300° (180 -30° to 300°) and a range of -180 +30° to -300° (-180 +30° to -300°). Specifically, even if the calculated machine body angle exceeds 180° +30°, if it is less than 300°, it is treated as 180° +30°. The same applies to a left turn. This allows for more accurate adjacent tillage control regardless of the driver's operation or field conditions, such as slippage.

[0058] An example of the flow of the above auto-down control will be described with reference to Figure 9. First, the control unit 52 determines whether the traveling machine body 2 is turning or not based on a signal from the steering sensor 15 or the like (S1). If the traveling machine body 2 is not turning (NO in S1), the machine body angle of the traveling machine body 2 is 0° (S2). On the other hand, if the traveling machine body is turning (YES in S1), the control unit 52 calculates the machine body angle of the traveling machine body 2 (S3).

[0059] Then, the control unit 52 determines whether the calculated machine body angle has reached 90°, i.e., whether the traveling machine body 2 has turned 90° (S4). If the 90° turn has not been completed (NO in S4), the control unit 52 stores a "turn not yet reached state" (S5), and if the 90° turn has been completed (YES in S4), the control unit 52 stores a "turn completed state" (S6).

[0060] Next, the control unit 52 determines whether a reverse operation was performed during the turn (S7). In other words, it determines whether the shuttle lever 35 was maintained in the forward position. If a reverse operation was not performed (NO in S7), it determines whether the calculated machine body angle is within a predetermined range relative to 180° (S8). That is, it determines whether the machine body angle is between 180° -30° and 300°, or between -180° +30° and -300°. If the machine body angle is within the predetermined range (YES in S8), it determines that the turn operation is an operation for adjacent tillage control (S9). If the machine body angle is outside the predetermined range (NO in S8), it determines that the turn operation is normal control other than adjacent tillage control (S10). If a reverse operation was performed in S7 (YES in S7), it also determines that the turn operation is normal control (S10).

[0061] Next, the control unit 52 determines whether the machine body angle satisfies the condition (S11). That is, it determines whether the traveling machine body 2 has completed turning and is now in a straight-ahead state. If the condition is not met (NO in S11), the control unit 52 stores a "condition not met state" (S12). If the condition is met (YES in S11), the control unit 52 stores a "condition met state" (S13). The control flow in FIG. 9 is repeatedly executed while the auto-down control is being executed, and the control unit 52 executes adjacent tillage control or normal control during the auto-down control based on the determination result of this control flow.

[0062] [Down position correction] As described above, in this embodiment, in the auto-down control, after the traveling machine body 2 starts turning, the traveling machine body 2 maintains a forward movement state and a turning state in the same direction, and then when it goes into a straight-ahead state, adjacent tilling control is executed. Therefore, there may be a discrepancy between the calculated position of the traveling machine body 2 and the actual position of the traveling machine body 2. In this case, if control is performed to start lowering the rotary tiller 3 as is, there is a risk that the position at which the descent starts will be shifted. For this reason, in this embodiment, when the traveling machine body 2 goes into a straight-ahead state after turning, the control unit 52 corrects the position at which the rotary tiller 3 is lowered based on the calculated machine body angle during the auto-down control.

[0063] This point will be explained using Figures 10 and 11. Correction of the lowering position of the rotary tiller 3 differs between adjacent tilling control and normal control, but first, the flow of calculation of the lowering position will be explained using Figure 10. The "lowering target set value position" appearing in Figure 10 corresponds to, for example, the "lowering reference line F" explained in Figure 8, and the "lowering target reference position" corresponds to, for example, the position of the rotary shaft 3a of the rotary tiller 3 that has landed after turning, explained in Figure 8, which matches the working boundary C, which is the position of the rotary shaft 3a of the rotary tiller 3 in the landed state at the start of turning.

[0064] First, the control unit 52 determines whether adjacent tillage control is in progress (S21). If adjacent tillage control is not in progress (NO in S21), the control unit 52 performs a calculation corresponding to normal control to correct the lowering position (S22). On the other hand, if adjacent tillage control is in progress (YES in S21), the control unit 52 performs a calculation corresponding to adjacent tillage control to correct the lowering position (S23). Next, the control unit 52 determines whether auto-down control is in progress (S24). If auto-down control is not in progress (NO in S24), the control unit 52 sets the lowering position to the "lowering target setpoint position" (S25). If auto-down control is in progress (YES in S24), the control unit 52 determines whether the "lowering target setpoint position" is equal to or greater than the "lowering target reference position," i.e., whether the "lowering target setpoint position" is the same as the "lowering target reference position" in the Y-axis direction in FIG. 8, or whether the "lowering target setpoint position" is below (positive) the "lowering target reference position" (S26).

[0065] In S26, if the "descent target set value position" is equal to or greater than the "descent target reference position" (YES in S26), the descent position is set to the "descent target set value position" (S27). On the other hand, if not (NO in S26), it is determined whether the current position of the traveling body 2 is equal to or less than the "descent target set value position," that is, whether the current position in the Y-axis direction of FIG. 8 is the same as the "descent target set value position," or whether the current position is above (on the negative side of) the "descent target set value position" (S28). In S28, if the current position is equal to or less than the "descent target set value position" (YES in S28), the descent position is set to the "descent target set value position" (S29). On the other hand, if not (NO in S28), it is determined whether the current position of the traveling body 2 is equal to or higher than the "descending target reference position", that is, whether the current position is the same as the "descending target reference position" in the Y-axis direction of Figure 8, or whether the current position is below (on the positive side of) the "descending target reference position" (S30).

[0066] In S30, if the current position is equal to or greater than the "descent target reference position" (YES in S30), the descent position is set to the "descent target reference position" (S31). On the other hand, if this is not the case (NO in S30), it is determined whether the traveling machine body 2 is turning or moving backward (S32). In S32, if the traveling machine body 2 is turning or moving backward (YES in S32), the descent position is set to a position obtained by adding hysteresis to the current position (S33). On the other hand, if this is not the case (NO in S32), the process returns to S21. In this embodiment, the control unit 52 repeatedly executes the flowchart of FIG. 10, and the control unit 52 sets the descent position based on the determination results of this control flow.

[0067] Next, correction of the lowered position of the rotary tiller 3 in normal control and adjacent tilling control will be explained using Figures 11(a) and (b). First, correction of the lowered position in normal control will be explained using Figure 11(a). Correction of the lowered position (ground contact position) in normal control is performed using the following equation. Grounding position Y=A+((A+S)×-cos(θv))

[0068] As described above, A is the distance between the rotation axis (axle) of the rear wheel 6 and the rotary shaft 3a of the rotary tiller 3. S is a value that changes depending on the setting of the adjustment volume (auto-down timing volume 33). θv is the machine body angle.

[0069] FIG. 11(a) shows the case where S = 0. Even if the traveling machine body 2 is in a straight-ahead state after completing a turn, if the calculated body angle on the coordinate system deviates from 180°, the lowered position set by calculation will be different from when the calculated body angle is 180°. Line 100 in FIG. 11(a) shows the case where the calculated body angle is 180° and the actual body angle after the turn matches the calculated body angle. In this case, if the traveling machine body 2 moves forward a distance of 2 × A from the point where the turn ended, the lowered position of the rotary tiller 3 can be made to match the position where the rotary tiller 3 was raised at the start of the turn.

[0070] On the other hand, line 101 in FIG. 11(a) shows a case where the calculated vehicle body angle is less than 180°, and the calculated vehicle body angle is smaller than the actual vehicle body angle after turning. In this case, when attempting to move the traveling machine body 2 forward to the target lowering position on the coordinate system in the Y-axis direction, a distance longer than 2×A is calculated. That is, the control unit 52 calculates the vehicle body angle to be less than 180°, and calculates the lowering position of the rotary tiller 3 in the Y-axis direction to be the position indicated by the tip of line 101 so that the lowering position coincides with the position to which the rotary tiller 3 was raised at the start of turning. Therefore, as is clear from a comparison of the lengths of the lines on the right side of FIG. 11(a), the calculated distance from the end of turning to the target position for starting descent is longer than 2×A. However, in reality, when the driver returns the traveling machine body 2 to a straight-ahead state, the body angle is thought to be approximately 180°, so if the traveling machine body 2 travels the distance calculated by this calculation, the descent position will be shifted. Therefore, by performing a correction based on the calculated body angle using the above formula, the shift in the descent position can be suppressed.

[0071] Next, line 102 in FIG. 11(a) shows the case where the calculated vehicle body angle is greater than 180°, and the calculated vehicle body angle is greater than the actual vehicle body angle after turning. In this case, when attempting to move the traveling machine body 2 forward to the target lowering position on the coordinate system in the Y-axis direction, a distance shorter than 2×A is calculated. That is, the control unit 52 calculates that the vehicle body angle is greater than 180°, and calculates the lowering position of the rotary tiller 3 in the Y-axis direction to be the position indicated by the tip of line 101 so that the lowering position coincides with the position to which the rotary tiller 3 was raised at the start of turning. Therefore, as is clear from a comparison of the lengths of the lines on the right side of FIG. 11(a), the calculated distance from the end of turning to the target position for starting descent is shorter than 2×A. However, in reality, when the driver returns the traveling machine body 2 to a straight-ahead state, the body angle is thought to be approximately 180°, so if the traveling machine body 2 travels the distance calculated by this calculation, the descent position will be shifted. Therefore, by performing a correction based on the calculated body angle using the above formula, the shift in the descent position can be suppressed.

[0072] Next, correction of the lowering position in adjacent tillage control will be described with reference to Fig. 11(b). Correction of the lowering position (ground contact position) in adjacent tillage control is performed using the following equation. Grounding position Y=TY+((-BSY+A+A+S)×-cos(θv))

[0073] BSY is the distance the tractor 1 travels in a straight line after the rotary tiller 3 is raised, and is set to 0 if the rotary tiller 3 is automatically raised during a turn. If the rotary tiller 3 is manually raised, this is the distance from the raised position to the turning start position. TY is the Y coordinate of the traveling vehicle body 2 at the end of the turn. FIG. 11(b) shows the case where S = 0 and BSY = 0. As described above, in this embodiment, during auto-down control, after the traveling vehicle body 2 starts turning, if the traveling vehicle body 2 maintains a forward state and a turning state in the same direction, and then becomes a straight-moving state, adjacent tilling control is executed if the calculated vehicle angle is within the range of 180-30° to 300°, or within the range of -180+30° to -300°. For this reason, there is a risk of a large difference between the actual body angle of the traveling body 2 and the Y coordinate at the end of turning, and the calculated body angle of the traveling body 2 and the Y coordinate at the end of turning. For this reason, by correcting the descent position using the above formula, it is possible to suppress deviation of the descent position even if the calculated body angle of the traveling body 2 and the Y coordinate at the end of turning deviate from the actual ones.

[0074] [Pivot point calculation] As described above, the tractor 1 of this embodiment can execute front wheel double speed control (accelerated turning control) and auto-brake control when turning. Furthermore, front wheel double speed control can be executed in both forward and reverse drive states, while auto-brake control can be executed only in forward drive state. Therefore, in auto-down control, when switching between forward and reverse drive or between right and left drive during a turn, the turning fulcrum changes each time, making calculations difficult. Therefore, in this embodiment, the turning fulcrum is changed during auto-down control depending on the settings of forward drive, reverse drive, front wheel double speed control, and auto-brake control.

[0075] Specifically, the control unit 52 constantly calculates the left and right fulcrums (four locations) for forward and reverse travel, and changes the fulcrum when switching between forward and reverse travel, regardless of whether the vehicle is traveling straight or turning, to calculate the aircraft angle and coordinates. This will be explained using FIGS. 12(a) and 12(b). FIG. 12(a) shows the fulcrum for turning right and forward travel, and FIG. 12(b) shows the fulcrum for turning right and reverse travel. Also, front wheel double speed control is indicated as QT, and autobrake control is indicated as AB. Furthermore, A, B, R, and L in the figures, such as AR0 and BR0, respectively, indicate the order of calculation of each fulcrum: A for QT only, B for QT+AB, L for the left fulcrum relative to the forward direction, and R for the right fulcrum relative to the forward direction. That is, AL indicates the left fulcrum for QT only, AR for the right fulcrum for QT only, BL for the left fulcrum for QT+AB only, and BR for the right fulcrum for QT+AB.

[0076] Also, Figures 12(a) and (b) show the change in the turning fulcrum and coordinates when turning control = QT+AB, turning the steering to the right to turn forward until the vehicle angle reaches 60°, and then reversing to 0° with the steering kept the same. The turning fulcrum for right turning is point BR when moving forward, but changes to point AR when moving backward. Therefore, when turning forward right, the coordinates of AL, BL, and AR are calculated based on C, with BR as the fulcrum. When moving backward, the coordinates of C, AL, BL, and BR are calculated with AR as the fulcrum. With turning control = QT only, the positions of the left and right fulcrums for forward and reverse travel do not change, so when the above operations are performed, they will return to the same positions. In other words, the turning fulcrums are AL and AR for both forward and reverse travel.

[0077] In this embodiment, the coordinate positions of the left and right fulcrums (four points) for forward and backward travel are calculated in real time. Then, the coordinate positions and vehicle body angle are calculated while changing the turning fulcrum. Specifically, the vehicle body angle is calculated, the reference point of the tractor 1 is calculated from the turning fulcrum, and the remaining fulcrums are calculated from the reference point of the tractor 1. This allows highly accurate calculations to be made when the traveling vehicle body is turning according to the situation, that is, highly accurate calculations are possible when operating forward and backward travel and turning left and right, and the descent start position can be stabilized during autobrake control.

[0078] [Turning radius and turning circle calculation] As described above, in the auto-down control, the position of the traveling vehicle 2 in the coordinate system and the vehicle angle are calculated based on the fixed data of the turning radius r and turning circumference set in the program. However, if there is a large discrepancy between the actual state of the traveling vehicle 2 and the calculated state, there is a risk that the lowering position will be shifted or auto-brake control will not be performed. Therefore, in this embodiment, an adjustment mode can be executed to adjust the turning radius and turning circumference. This adjustment mode is executed, for example, by a service technician on-site.

[0079] Specifically, the tractor 1 is made to make one full turn, and the circumference and radius of the turn are calculated based on the vehicle speed and elapsed time during that time, and these are stored in a non-volatile memory such as an EEPROM, and are reflected in subsequent auto-down control. In this type of adjustment mode, depending on the settings, there is a risk that the tractor 1 may tip over while turning, or that sufficient data may not be collected. Examples of such cases include the following conditions: (1) The gears are automatically increased by adjusting the main shift lever. (2) The conditions for auto-down control are not met due to the turning control settings or 4WD switching settings. (3) If the vehicle speed is too slow, the amount of information may be insufficient or the information may be unstable. (4) The vehicle is going too fast, making turning dangerous.

[0080] For this reason, in this embodiment, when the conditions shown in the table of Fig. 13 are not met, the liquid crystal display device 51 as shown in Fig. 6 displays on the screen a message that the condition is not met or information for making the condition met, and sounds a buzzer or the like when a switch (SW) is operated to start or end the adjustment mode or when the calculation is completed. In Fig. 13, first, the conditions before the calculation starts are "automatic turning," "main shift lever," "vehicle speed," "shuttle lever," and "steering angle."

[0081] "Automatic turning" is a condition check to see whether turning is performed using double front wheel speed control (double turning speed) or double turning speed + auto brake control. "Main shift lever" is a condition check to see whether any of the first to fourth gears, in which automatic upshifting does not function, has been selected. In this embodiment, this is done because automatic upshifting functions when the vehicle is in fifth gear or higher.

[0082] "Vehicle speed" is a condition check of the upper limit of a safe vehicle speed and the lower limit of the vehicle speed for obtaining necessary information. In this embodiment, the upper limit is set to 3.0 km / h and the lower limit is set to 0.9 km / h. "Shuttle lever" is a condition check of the shuttle lever 35. Although the table shows "forward", "reverse" may also be selected. However, autobrake control does not function in reverse. "Steering angle" is a condition check of whether the steering wheel 13 is turned.

[0083] Next, the conditions during calculation include "minimum radius," "maximum radius," and "timeout." "Minimum radius" is the lower limit of the turning radius of the tractor 1 for the condition to be met, a value determined depending on the type of tractor 1, and is set to 500 mm in this embodiment. "Maximum radius" is the upper limit of the turning radius of the tractor 1 for the condition to be met, and is set to 3000 mm in this embodiment. "Timeout" is the upper limit of the adjustment mode time, and in this embodiment, the calculation is not met if 75 seconds or more have passed since the start of calculation. Note that the calculation start conditions remain valid even during calculation, and if any of the calculation start conditions are not met during calculation, the calculation is not met. This allows the driver, including the service technician, to execute the adjustment mode by referring to the screen display, etc., even if they do not know the details of the adjustment mode conditions.

[0084] In this embodiment, the turning radius and turning circumference set in the adjustment mode can also be returned to the factory default values. For example, by pressing a specific switch for a specific period of time, the corresponding data is cleared, a buzzer sounds, and the settings are returned to the factory default values. Furthermore, to prevent the rotary tiller 3 from unintentionally lowering while the adjustment mode is being executed, the auto-down control is prohibited when the adjustment mode is being executed.

[0085] The turning radius and turning circumference set by executing the adjustment mode can also be adjusted manually. The data has the following priority order: manually set values, values set in the adjustment mode, and default values (factory default values). However, if the adjustment mode is executed after manual setting, the manually set data is cleared and updated to the data set in the adjustment mode.

[0086] [Other embodiments] Although the vehicle speed is detected by detecting the rotation of one rear wheel 6 and the rotation of the rear wheel drive shaft, the rotation of another part may be detected instead. For example, the rotation of the drive shaft may be detected instead of the rotation of the rear wheel drive shaft, or the rotation of both rear wheels 6 may be detected. Although the main transmission mechanism and the auxiliary transmission mechanism are described as being multi-stage transmission mechanisms, the main transmission mechanism and the auxiliary transmission mechanism may be stepless transmission mechanisms, or a configuration may be provided in which only one of them is provided, as long as the total reduction ratio, which is the ratio of the engine rotation speed to the rear wheel 6 rotation speed, can be detected. The turning start operation may also include operating the position lever 31 to raise the rotary tiller 3.

[0087] While the visual notification to the operator is achieved by changes in the image or message on the LCD display 51, it may be achieved by an organic electroluminescence (EL) display other than an LCD or a dot matrix display such as an LED lamp, or by changes in the color or position of an illuminating display. The various operating tools for inputting information to the control unit 52 may instead be a touch panel provided on the LCD display 51 or an input device provided outside the traveling body 2 that is capable of wireless communication. The tractor 1 may be configured to include a remote control device that enables the operator to operate the tractor 1 from a distance without being on board, and the steering device may be driven by a motor or hydraulic control to steer the front wheels 5. The steering wheel 13 may be a lever or button that can be oscillated or moved horizontally. The operation of the steering wheel 13 is not limited to detecting either an on state or an off state. The control unit 52 may perform calculations based on the turning radius r calculated according to the operation angle, which can be detected numerically. The operation of the steering wheel 13 may be detected directly by detecting the rotation of the steering wheel 13, or may be detected by detecting the amount of movement of a tie rod or the amount of tilt of the front wheels 5. The control unit 52 may be formed by a discrete circuit, or may be formed integrally as a semiconductor integrated circuit element.

[0088] Although the above embodiment has been described with respect to a tractor 1 equipped with a rotary tiller 3, this is not limited to this, and the working implement may be a tiller or plow, etc., and the present invention can also be applied to other work vehicles, such as rice transplanters, that have a working implement that can be raised and lowered on the running body 2. [Explanation of symbols]

[0089] 1 Tractor (work vehicle) 2 Running body 3 Rotary tiller (working machine) 5 front wheels 6 Rear wheels (running part) 12 Steering device (steering section) 16 Lifting link mechanism (lifting device) 35 Shuttle lever (switching means) 52 Control section

Claims

1. A traveling machine body supported by a pair of left and right front wheels and a pair of left and right traveling units arranged behind the front wheels; A steering unit that steers the traveling machine body; A switching means for switching between forward and reverse movement of the traveling machine body; Vehicle speed detection means capable of detecting a vehicle speed, which is the speed of the traveling machine body; An angle detection means capable of detecting the angle of the steering unit; a lifting device for lifting and lowering the work machine; a control unit capable of executing auto-down control to automatically lower the working implement at a target position on the second path based on coordinates calculated from the detection results of the vehicle speed detection means and the angle detection means, the coordinates being a reference coordinate position that is the position where the turning of the traveling machine body started, and a machine body angle that is the yaw angle of the traveling machine body, when the traveling machine body is turned from the first path toward the second path to perform work on a second path different from the first path after work on the first path has been completed and the working implement has been raised, The auto-down control includes an adjacent work control for automatically lowering the work machine in a direction along the first path so as to align the start position of work on the second path with the position where work on the first path is completed, in order to rotate the traveling machine body 180° from the first path to perform work on the second path when the first path and the second path are adjacent to each other, and a normal control other than the adjacent work control, The control unit In the auto-down control, after starting the turning of the traveling machine body, if the switching means is maintained in a forward state while the traveling machine body is turning and the state of the traveling machine body becomes a straight-ahead state, and if the calculated machine body angle is within a predetermined range with respect to 180°, the adjacent work control is executed; In the auto-down control, after starting the turning of the traveling machine body, if the switching means is switched from the forward state to the reverse state while the traveling machine body is turning, the normal control is executed. A work vehicle characterized by:

2. the control unit simultaneously performs a calculation for the adjacent work control and a calculation for the normal control when the auto-down control is started, and performs the normal control when the conditions for the adjacent work control are not satisfied.

2. The work vehicle according to claim 1.

3. The control unit corrects the position at which the work machine is lowered based on the calculated machine body angle when the traveling machine body enters a straight traveling state after turning during the auto-down control.

3. A work vehicle according to claim 1 or 2.

4. The control unit can execute an acceleration turning control that turns by increasing the peripheral speed of the front wheels relative to the peripheral speed of the traveling unit in forward and reverse states, and an auto-brake control that executes the acceleration turning control when turning only in the forward state and automatically brakes the traveling unit on the inside of the turn, and during the auto-down control, changes the turning fulcrum depending on the settings of forward, reverse, the acceleration turning control, and the auto-brake control.

4. A working vehicle according to claim 1, wherein the working vehicle is a work vehicle.

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