Work vehicle

Abstract

To provide a work vehicle capable of preventing unintended automatic lifting / lowering of a work implement, in a work vehicle that controls the lifting / lowering position of the work implement on the basis of positioning information from a positioning device mounted on the work implement.SOLUTION: In a work vehicle in which a work implement W is mounted on a travel vehicle body 2 so as to be liftable via a lift link P, and which includes a work implement positioning device 31 that measures the height position of the work implement W, and has a positioning control mode that controls the lifting / lowering of the work implement W so as to maintain the detection height Hn obtained by the work implement positioning device 31 at a reference height Hs, Hs' in a control device 40, work posture determination means D is provided, and lifting / lowering control by the positioning control mode is performed when it is determined that the work implement W is at or below a predetermined height.SELECTED DRAWING: Figure 10

Description

[Technical field]

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

[0002] A known configuration has a positioning control mode in which the lifting and lowering position of the work machine is controlled based on positioning information obtained by a work machine positioning device attached to the work machine, and a cover control mode in which the lifting and lowering position of the work machine is controlled based on the detection results of a cover sensor, and the lifting and lowering position is controlled using the average height position when working in the cover control mode as the reference value for height control in the positioning control mode (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-193899 Summary of the Invention [Problem to be solved by the invention]

[0004] According to Patent Document 1, the accuracy can be improved by controlling the lifting position in the positioning control mode. However, in the cover control mode in which the lifting position of the working machine is controlled based on the detection result of the cover sensor, the rotation angle of the cover at the rear of the rotary tiller is fed back to control the tilling depth relative to the ground surface to a constant value. Therefore, when the working machine is not on the ground, the angle of the cover does not change basically, so it does not lift or lower automatically. However, when the lifting position of the working machine is controlled based on the positioning information attached to the working machine positioning device, the height position of the vehicle itself changes when the traveling vehicle body travels on a slope, even if the working machine is not on the ground, so there is a risk that the working machine will automatically lift or lower.

[0005] The present invention aims to provide a work vehicle that controls the lifting and lowering position of a work machine based on positioning information from a positioning device attached to the work machine, and that can prevent the work machine from automatically lifting and lowering unintentionally. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides the following technical solutions.

[0007] The invention described in claim 1 is a work vehicle in which a work implement W is mounted on a traveling body 2 so that it can be raised and lowered by a lifting device 12, and which is equipped with a work implement positioning device 31 that measures the height position of the work implement W, and the control device 40 is equipped with a positioning control mode that controls the lifting and lowering of the work implement W to maintain the detected height Hn obtained by the work implement positioning device 31 at the reference height Hs, Hs', and in which a work posture determination means D is provided, and when it is determined that the work implement W is below a predetermined height, lifting and lowering control is performed using the positioning control mode.

[0008] In the invention described in claim 2, in the invention described in claim 1, the working posture determination means D performs lift control in a positioning control mode based on a predetermined angle detected by a lift arm sensor 26 provided on the lift arm 122.

[0009] In the invention described in claim 3, in the invention described in claim 1, the working posture determination means D performs lift control in the positioning control mode when the working implement lift switch 353 is operated to be lowered.

[0010] The invention described in claim 4 is the invention described in claim 1, in which the working posture determination means D performs lifting control in the positioning control mode when the mode selection switch 223, which can select between a field mode for traveling in a field and a road mode for traveling on a road, selects the field mode.

[0011] The invention described in claim 5 is the invention described in claim 1, further comprising an auxiliary transmission 74, and the working posture determination means D is configured to prohibit the execution of lifting / lowering control when the auxiliary transmission 74 is operated to a high-speed position.

[0012] The invention described in claim 6 is the invention described in claim 1, further comprising a vehicle speed sensor 24 for detecting the vehicle speed of the traveling vehicle body, and the working posture determination means D is configured to prohibit the execution of lifting control in the positioning control mode when the vehicle speed is equal to or higher than a predetermined value.

[0013] The invention described in claim 7 is the invention described in claim 1, which is provided with tillage depth control, position control or resistance control as the lifting and lowering control of the work implement W, and the working posture determination means D is configured to prioritize tillage depth control, position control or resistance control and prohibit the execution of lifting and lowering control using the positioning control mode. Effect of the Invention

[0014] According to the inventions recited in claims 1 to 6, it is possible to prevent unintended lifting and lowering of the work machine W while traveling on the road. Furthermore, according to the invention recited in claim 7, execution of multiple lifting and lowering controls is prohibited, thereby preventing hunting. [Brief description 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. [Diagram 2] 1 is a side view of a rotary tilling device of a work vehicle according to an embodiment of the present invention. [Diagram 3] 1 is a perspective view of a rotary tilling device of a work vehicle according to an embodiment of the present invention. [Figure 4] 1 is a schematic explanatory diagram of power transmission in a work vehicle according to an embodiment of the present invention; [Diagram 5] 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 6] 2 is an explanatory diagram of an operating device located in front of a driver's seat of the work vehicle according to the embodiment of the present invention. FIG. [Figure 7] 2 is an enlarged view of a portion A of the work vehicle according to the embodiment of the present invention. FIG. [Figure 8] FIG. 4 is a flow diagram relating to a positioning control mode for a work vehicle according to an embodiment of the present invention. [Figure 9]1 is a control block diagram of a work vehicle according to an embodiment of the present invention. [Figure 10] 3 is a flowchart of a work vehicle according to an embodiment of the present invention. [Figure 11] 1 is a perspective view of a rotary tilling device of a work vehicle according to an embodiment of the present invention. [Figure 12] FIG. 1A is a rear view showing the configuration of an upright position and a lying-down storage position of a work implement positioning device of a work vehicle of an embodiment of the present invention; FIG. 1B and FIG. 1C are rear views showing the configuration of an upright position and a telescopic storage position of a work implement positioning device of a work vehicle of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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] First, the overall configuration of a work vehicle 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram of a work vehicle 1 according to an embodiment, and is a schematic left side view of the work vehicle 1. Note that, in the following, a tractor will be used as an example of the work vehicle 1 to be described.

[0018] The tractor 1, which is a work vehicle, is an agricultural tractor that travels by itself to perform work in fields, etc. In addition to carrying out a predetermined task while an operator rides on the tractor 1 and traveling in a field, the tractor 1 also performs a predetermined task while traveling automatically in a field by controlling each part using a control system centered on a control device 40 (see FIG. 9) described later.

[0019] 1, the tractor 1 includes a traveling body 2 and a working machine W also called a rotary tiller. The traveling body 2 includes a body frame 3, front wheels 4, rear wheels 5, a bonnet 6, an engine E, a steering 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, one on the left and one on the right, and are primarily used for steering (steered wheels). The rear wheels 5 are a pair, one on the left and one on the right, 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 driven wheels. The traveling body 2 may be equipped with a crawler device instead of the wheels (front wheels 4 and rear wheels 5). In this case, the traveling crawlers are the drive wheels.

[0021] The bonnet 6 is provided at the front of the vehicle body 2 so as to be freely opened and closed. The bonnet 6 can be rotated (opened and closed) in the vertical direction with the rear part as the center of rotation. When closed, the bonnet 6 covers the engine E mounted on the vehicle body frame 3.

[0022] The control section 7 is provided on the upper part of the traveling body 2, and includes a cockpit 8 and a steering wheel 9. The control section 7 is covered by a cabin 7a provided on the upper part of the traveling body 2. The cockpit 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 section 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 houses a transmission (speed change mechanism) and transmits the rotational power transmitted from the engine E to the rear wheels 5, which are drive wheels, and a PTO (Power Take-off) shaft 16 after appropriately reducing the speed.

[0025] A work machine W that performs work in a farm field is connected to the rear of the traveling body 2, and a PTO shaft 16 that transmits power to drive the work machine 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 machine W that is attached to at least the rear of the traveling body 2.

[0026] Further, a lifting device 12 for raising and lowering the working machine W is provided at the rear of the traveling body 2. The lifting device 12 moves the working machine W to a non-working position by raising the working machine W. The non-working position is a position where the working machine W is raised when, for example, the traveling body 2 moves backwards or turns. Further, the lifting device 12 moves the working machine W to a ground working position by lowering the working machine W. The lifting device 12 includes a hydraulic lifting cylinder 121, a lift arm 122, a lifting drive device C and a lower link 124 of a lift rod 123, and a lifting link P of 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 a pivot point 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 for detecting the rotation angle of the lift arm 122 is provided at the base (near the axis AX) of the lift arm 122. The height of the work machine W is calculated based on the detection result of the lift arm sensor 26 and a comparison between the height of the work machine W obtained by a work machine positioning device 31, also called a work machine geodetic device, attached to the work machine W and the height of the traveling body 2 obtained by a vehicle body positioning device 30 attached to the traveling body 2. The vehicle body positioning device 30 and the work machine positioning device 31 are, for example, Global Navigation Satellite System (GNSS) antennas, and can receive radio waves from a navigation satellite S orbiting in the sky to perform positioning and timing. It is also possible to calculate the speed of movement from the history of positioning results and the Doppler effect of radio waves.

[0028] Further, the lift arm 122 is connected to a lower link 124 via a lift rod 123. In this manner, the lifting link P 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 control can be performed when a plow or the like is attached.

[0029] 1, the work implement W is a rotary tiller that performs tilling work in a farm field. The rotary tiller tills the farm field (soil) by rotating tiller tines 139 (described later) using power transmitted from a PTO shaft 16.

[0030] The tractor 1 also includes a control device 40 (see FIG. 3). 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.

[0031] The tractor 1 allows the operator to set various tasks in a specific field by operating an information processing terminal (mobile terminal such as a tablet terminal) 100. The information processing terminal 100 includes a storage unit configured with a hard disk, a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and a display unit and an operation unit configured with a touch panel. Note that various keys and buttons may be provided separately as the operation unit.

[0032] 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.

[0033] The rear sensor 22 is disposed on the upper rear side of the traveling body 2, for example, by being attached to the top of the cabin 7a, and detects obstacles present behind the traveling body 2. The rear sensor 22 can change its angle with respect to the cabin 7a, i.e., the traveling body 2, by a motor (not shown).

[0034] Both the front sensor 21 and the rear sensor 22 are mid-range sensors, preferably infrared sensors. The front sensor 21 and the rear sensor 22 emit infrared beams and detect the reflected light from an obstacle. The front sensor 21 has a detection area that extends forward. The rear sensor 22 has a detection area that extends backward.

[0035] The front sensor 21 and the rear sensor 22 can detect the distance to an obstacle by, for example, measuring the time from emitting an infrared beam until detecting the reflected light from the obstacle. The front sensor 21 and the rear sensor 22, which are infrared sensors, detect obstacles two-dimensionally, with a detection area of, for example, several meters to several tens of meters. Note that, as the obstacle sensor 20, other mid-range sensors such as sonar and millimeter wave radar other than an infrared sensor can be used or they can be used in combination.

[0036] 2 and 3, the support structure of the rotary tiller as the rear-mounted working implement W and the working implement positioning device 31 will be described. A gate-shaped hitch frame 128 is installed between the rear ends of the left and right lower links 124, 124, an upper hook 129 is fixed to the upper center position of the hitch frame 128 and the rear end of the top link 125 is connected thereto, and lower hooks 130, 130 are attached to the left and right lower ends of the hitch frame 128 to form the quick hitch device H. A lock plate 133 that rotates due to the forward and backward movement of a lever 132 is pivotally attached to the lower hook 130, and when a lower pin 134 on the rotary tiller W side is fitted into the lower hook 130, the lower pin 134 can be locked by the lock plate 133.

[0037] Meanwhile, a mast 136 is provided at the center of the top of the rotary tilling device R, and an upper pin 137 is provided at the front end of this mast 136. Also, lower pins 134, 134 are provided on the frame 161 of the rotary tilling device W, protruding to the left and right opposite the lower hooks 130, 130. The upper pin 137 is engaged with the upper hook 129 and rotated downward about this upper pin 137, so that the lower pins 134, 134 can engage with the lower hooks 130, 130.

[0038] Furthermore, the upper part of the tilling tines 139 of the rotary tilling device W is covered by a main cover 140, and a rear cover 141 is pivotally attached to the rear part of the main cover 140 so as to be freely rotatable. The main cover 140 and the rear cover 141 are integrally formed so as to be rotatable about the axis of a tilling shaft 143 by the drive of an electric motor (not shown), and when the tilling depth is set to a shallow depth, the main cover 140 and the rear cover 141 rotate backward, and when the tilling depth is set to a deep depth, the main cover 140 and the rear cover 141 rotate forward. A support shaft 145a having a horizontal axis is rotatably provided on a hanger plate 145 protruding from the main cover 140, and a pressure rod 146 having a lower end attached to the rear cover 141 is passed midway through a through hole formed in the support shaft 145a so as to be movable up and down. A lower spring 146a is wound around this pressure rod 146 to allow the rear cover 141 to rise above a predetermined angle but presses downward to prevent it from rising any further, thereby preventing the rear cover 141 from bouncing up. On the other hand, an upper spring 146b is wound around the upper end of the pressure rod 146 to regulate excessive downward swing of the rear cover 141.

[0039] The driving force from the PTO shaft 16 at the rear of the tractor is input via a universal joint 148 to the transmission mechanism in the transmission box 150 via an input shaft 153 in the center of the rotary frame 149, and further passes through the transmission shaft in the rotary frame 149 and the chain in the tillage transmission case 151, etc., to rotate the tillage shaft 162.

[0040] A gate-shaped support frame 155 is fixed to the hitch frame 128 of the quick hitch device H, and the working machine positioning device 31 is provided at a high position on the upper part of the support frame 155 via a vertical support 154. As described above, the height of the working machine W is calculated based on the detection results of the lift arm sensor 26 and a comparison of the height of the working machine W obtained by the working machine positioning device 31 attached to the working machine W and the height of the traveling body 2 obtained by the vehicle body positioning device 30 attached to the traveling body 2. A predetermined tilling depth is set in advance in the control device 40, and the tilling depth can be appropriately controlled while raising and lowering the vertical height of the rotary tilling device W obtained by the working machine positioning device 31 that can move up and down integrally with the rotary tilling device W.

[0041] By providing the working implement positioning device 31 on the quick hitch device H as described above, the working implement W can be appropriately controlled to a predetermined height even when the rotary tilling implement W is replaced.

[0042] A gate-shaped support frame 155 is provided on the hitch frame 128 of the quick hitch device H, and the work machine positioning device 31 is provided on the upper portion thereof, so that the work machine positioning device 31 can be located near the left-right center, and the height obtained by the work machine positioning device 31 can be less affected by the left-right tilt of the work machine W, that is, the left-right rolling of the work machine W. Also, because the work machine positioning device 31 is configured to remain on the vehicle body side rather than on the work machine W side, there is little risk of interference even when the upper pin 137 is engaged with and disengaged from the upper hook 129 to attach and detach the work machine W.

[0043] Next, the power transmission of the tractor 1 will be described with reference to Fig. 4. Fig. 4 is a schematic explanatory diagram of the power transmission of the work vehicle (tractor) 1. As shown in Fig. 4, the tractor 1 is provided with a speed change device (transmission) 70 in a mission case 10. The speed change device 70 is provided 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 Fig. 1) connected to the traveling body 2, and drives the front wheels 4, the rear wheels 5, and the work implement W.

[0044] The power transmission device 71 includes a forward / reverse switching unit 72 also called a forward / reverse clutch, a main transmission unit 73, an auxiliary transmission unit 74 also called an auxiliary transmission, 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.

[0045] The power transmission device 71 also transmits the rotational power from the engine E to the front wheels 4, 4, for example, via the input shaft 76, the forward / reverse switching unit 72, the main transmission unit 73, the auxiliary transmission unit 74, and the front wheel transmission unit 75 in that order. The power transmission device 71 also transmits the rotational power from the engine E to the work machine W, for example, via the input shaft 76 and the PTO drive unit 93 in that order.

[0046] 3, the input shaft 76 is provided on the output shaft of the engine E, and receives (inputs) the 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 side, which are the final output destinations, are defined as the downstream side of the power transmission.

[0047] A forward / reverse switching unit (hereinafter referred to as a forward / reverse clutch unit) 72 switches the rotational power transmitted from the engine E to a forward rotation or a reverse rotation by forward / reverse rotation of the main shaft 77. 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 (see FIG. 1) is operated in the cockpit 8.

[0048] 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, a first gear to a fourth gear.

[0049] The first main shift clutch 92a is hydraulically controlled by a main shift first valve v2 which is controlled by operation of the main shift operating unit 17, and the second main shift clutch 92b is hydraulically controlled by a main shift second valve v3 which is controlled by operation of the main shift operating unit 17.

[0050] 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 operation unit 17 (see FIG. 4) in the cockpit 8.

[0051] The high-low (Hi-Lo) transmission 94 changes the rotational power from the engine E between high and low speed stages. 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 the Lo clutch form a "Hi-Lo clutch."

[0052] The Hi-Lo clutch changes the rotational power 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 power transmission downstream side. For example, when the main transmission operation unit 17 is operated between 4th and 5th gears in the cockpit 8, the Hi-Lo clutch automatically switches to the high-speed (Hi) side or the low-speed (Lo) side by hydraulic control via the high-low valve v4. The Hi-Lo clutch has, for example, 8 speeds, with 4 speeds on the high-speed (Hi) side and 4 speeds on the low-speed (Lo) side.

[0053] The auxiliary transmission unit 74 can change the 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, for example, a first gear to a fourth gear as a plurality of gear stages.

[0054] The sub-transmission unit 74 changes the speed of the rotational power transmitted to the transmission shaft 78 via a first sub-transmission clutch 74a, a second sub-transmission clutch 74b, and a plurality of gears, and transmits the same to an output shaft 79. The sub-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., into, for example, four stages, and transmits the same to the rear wheels 5, 5. The gear stages of the sub-transmission unit 74 are hydraulically controlled by a first sub-transmission valve v5 and a second sub-transmission valve v6, which are controlled by operation of the sub-transmission lever 14.

[0055] 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, and an auxiliary transmission with, for example, four speeds mechanically, and is finally transmitted to the output shaft 79. The highest speed gear of the auxiliary transmission is mainly used when traveling on the road, and allows traveling at a predetermined speed or higher (for example, 15 km / h or higher). Pressing the public road traveling button 91 restricts the shift to a gear that allows traveling at a predetermined speed or higher, so that traveling on the road is safe even when traveling with a work machine attached. The restriction is implemented by restricting the output of a signal to the valve v5, etc.

[0056] The power transmission device 71 transmits the rotational power transmitted to the output shaft 79 to the rear wheels 5, 5 via a rear wheel differential gear (rear wheel differential) 80, an axle (drive shaft) 81, a planetary 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.

[0057] The front wheel transmission section (4WD clutch section) 75 includes a front wheel transmission device, and transmits the rotational power transmitted to the input shaft 76 to the front wheels 4,4. The front wheel transmission device includes a front wheel accelerating clutch and a front wheel constant speed clutch. The front wheel accelerating clutch and the front wheel constant speed clutch form a "front wheel transmission clutch (4WD clutch)."

[0058] 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 transmits the rotation of the first front-wheel drive shaft 82 to the second front-wheel drive shaft 83 at an increased speed via multiple gears.

[0059] 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, an axle (drive shaft) 85, a planetary gear mechanism, etc. As a result, the tractor 1 can run in four-wheel drive (4WD) with the left and right front wheels 4,4 and the left and right rear wheels 5,5.

[0060] The tractor 1 is provided with a steering cylinder 55 constituting 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 constituting 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.

[0061] Although not shown, the power transmission device 71 further includes a PTO drive device. The PTO drive device changes the speed of the rotational power from the engine E and outputs it to the work machine W (see FIG. 1) from the PTO shaft 16 (see FIG. 1) at the rear of the traveling body 2, thereby driving the work machine W with the power from the engine E.

[0062] The PTO drive device includes a PTO clutch device, a PTO transmission device, and a PTO shaft 16. The PTO drive device switches between a drive state in which the work machine W at the rear of the traveling body 2 is driven, and a non-drive state in which the drive of the work machine W is stopped.

[0063] With reference to Fig. 5, the various operating devices provided around the cockpit 8 will be described. Fig. 5 is a schematic perspective view of the right side of the cockpit 8. Note that the various operating devices shown in each figure are merely examples, and the types and arrangements of the operating devices are not limited to these.

[0064] 5, there are provided on the right side of the cockpit 8 a main speed change operation section 17 (main speed increase button 17a, main speed decrease button 17b), sub speed change lever 14, accelerator lever 156, position lever 157, lift position setting means (lift height dial) 90, public road travel button 91, operation panel storage section 62, etc. Among these, the position lever 157 is operated when raising or lowering the lift arm 122.

[0065] In addition, various operation switches such as a PTO automatic / manual changeover switch, a PTO on / off switch, an engine rotation indicator, an RPM increase adjustment switch, and an RPM decrease adjustment switch are provided on the right side of the cockpit 8. The operation panel storage section 62 stores an operation panel on which operation switches other than those described above are provided.

[0066] The lifting position setting means (lifting height dial) 90 is a dial that adjusts the lifting cylinder 121, which is a hydraulic cylinder, to adjust the desired height of the work implement W relative to the traveling vehicle body 2 when the public road driving button 91 is pressed or when the control device 40 determines that the vehicle is traveling on the road, or the desired angle value of the lift arm 122 detected by the lift arm sensor 26.

[0067] Next, various operating devices provided around the steering wheel 9 will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is an explanatory diagram of the operating devices located in front of the cockpit 8. Fig. 7 is an enlarged view of part A in Fig. 4. Fig. 7 shows part A in Fig. 6 viewed from right to left. Also, the types and arrangements of the operating devices shown in each figure are merely examples and are not limited thereto.

[0068] As shown in Fig. 6, as described above, the steering wheel 9 is provided in front of the driver's seat 8 (see Fig. 1). In addition, the clutch pedal 18 is provided on the lower left side of the handle post 350 to which the steering wheel 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, 15R. The configurations of the left and right brake pedals 15L, 15R will be described later with reference to Fig. 9.

[0069] A forward / reverse lever 201 is provided on the upper left of the handle post 350. Also, as shown in Figs. 6 and 7, an accelerator lever 351, a turn signal lever 352, and a one-touch lift lever 353, also called a working machine lift switch or one-touch lift switch, are provided on the upper right of the handle post 350. The one-touch lift lever 353 operates a lift arm that connects the working machine to the vehicle body to the operating position of the position lever 152 (see Fig. 7) or the uppermost position with one touch. In other words, when the tip is operated upward with one touch from an unloaded position, the working machine W can be raised to the uppermost position, and when the tip is operated downward with one touch, the working machine W can be lowered to the operating position of the position lever 152. Also, a PTO shift lever 354 is provided in the center of the handle post 350.

[0070] As shown in Fig. 6, 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.

[0071] As shown in Fig. 7, 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 (see Fig. 1) is controlled according to an engine output curve for low fuel consumption.

[0072] In this embodiment, the tractor 1 is configured to be manually switched between a field mode for traveling in a field and a road mode for traveling on a road by the mode selection switch 223. The field mode is a control mode selected when working in a field, and for example, the vehicle is controlled to travel only at a low speed (1 to 10 km / h). The road mode is a control mode selected when traveling on a road to a field, and for example, the vehicle is controlled to travel at a high speed (15 km / h or higher).

[0073] When the road mode is selected and the sub-transmission lever 14 is operated at high speed, or when the lock operation detection switch 138 detects the locked state, the control device 40 of the embodiment issues a specified notification (audio or screen display) to the worker to inform the worker that the lifted position of the work machine W is not at the specified height (a height at which the work machine can be driven on the road).

[0074] During the period when the notification is being given, the control device 40 automatically raises or lowers the work machine W to the specified height. This reduces the occurrence of the work machine W traveling on the road without being positioned at the specified height.

[0075] Furthermore, when automatically raising or lowering the work implement W to a specified height, the control device 40 according to the embodiment (see FIG. 9) uses the detection status of the lift arm sensor 26 or the vehicle body positioning device 30 and the work implement positioning device 31. Specifically, when the detection status of the lift arm sensor 26 or the vehicle body positioning device 30 and the work implement positioning device 31 is a specific status, the control device 40 determines that the lifted position of the work implement W is at a specified height.

[0076] When the field mode is selected by the mode selection switch 223, the control device 40 executes tillage depth control of the rotary tiller W, which is the working machine W, as shown in Fig. 8. During the field mode (S101), information from the operation levers and sensors of each part of the traveling body 2 is read into the control device 40 (S102). The operator operates the position lever 157 to set the tillage depth of the rotary tiller W (S103, S104). The control device 40 sets and stores the height H0 detected by the working machine positioning device 31 as the reference height Hs (S105, S106). It is preferable to provide a means for recognizing the completion of the setting of the tillage depth based on the operation of the position lever 157 (for example, a setting completion switch).

[0077] Thereafter, in the tilling work, the lifting and lowering control of the work implement W is performed based on the above-mentioned reference height Hs. That is, the control device 40 compares the detected height Hn of the work implement positioning device 31, which is periodically input, with the above-mentioned reference height Hs, and controls the lifting and lowering of the work implement W by supplying and discharging pressure oil to and from the lift arm 122, thereby controlling the height of the work implement W to Hs (S107 to S110).

[0078] During tilling work, when the working implement W is to be raised for a swing operation, the one-touch lift lever 353 is operated upward to raise the working implement W (S111, S112), and immediately after the swing operation, the one-touch lift lever 353 is operated downward to lower the working implement W (S113, S114). During this operation, the reference height Hs is stored, and after the working implement W returns to its lowered position, the reference height Hs is restored (S115), and tilling depth control can be continued.

[0079] If it is desired to change the set cultivation depth during cultivation depth control, the position lever 157 is operated to update the reference height Hs to Hs' (S116, S117). After that, the process returns to S107 and cultivation depth control based on the detection results of the work implement positioning device 31 is continued until the end of work (S118).

[0080] In this way, tillage depth control is performed by controlling the lifting and lowering of the work implement to eliminate the difference between the detected height of the work implement positioning device 31 attached to the work implement W and the reference heights Hs, Hs' based on the position lever 157 in advance (positioning control mode), so that tillage depth control can be performed without measuring the height of the field.

[0081] The mode selection switch 223 is configured to be able to select between a field mode and a traveling mode, and it is preferable that the field mode be configured to be able to select a tilling work mode, and that the tilling work mode be configured to be able to select the positioning control mode configured as described above.

[0082] In the positioning control mode, the reference height Hs can be updated appropriately (Hs→Hs') by updating the setting of the position lever 152, which is convenient because it allows the set cultivation depth to be partially changed according to the field conditions.

[0083] Furthermore, after the one-touch lifting lever 353 is operated to temporarily raise the working machine W to a non-working position, the one-touch lifting lever 353 is operated again to lower the working machine W, which returns it to the reference height Hs. Therefore, the operation is simple even when temporarily raising the working machine W when turning or reversing.

[0084] The tilling control using the positioning control mode in Fig. 8 is performed regardless of the unevenness of the surface of a plot of farmland. Since the reference height Hs or Hs' is maintained regardless of the unevenness of the field surface, it may be difficult to obtain the desired tilling depth in areas with extremely severe unevenness.

[0085] Therefore, if the field surface is made approximately uniform in advance, the desired tillage depth can be achieved. In one plot of field, the operator keeps any conditions (e.g., PTO rotation speed, vehicle speed) constant and tills the entire field once, collecting positioning data from the implement positioning device 31. Based on this positioning data, the soil in higher areas can be moved to lower areas to equalize the field, and tillage depth control in the positioning control mode produces a consistent finish regardless of the operator's level of skill.

[0086] It is preferable to configure the system so that the field averaging mode, which performs the above-mentioned field equalization, and the arbitrary height mode, which does not, can be selected. In the field averaging mode, the accuracy of piling up can be improved by performing combined control of the PTO rotation speed control and the lifting and lowering control of the working implement W based on the positioning data. Furthermore, the accuracy can be further improved by determining the amount of piling up from the data on the opening degree (angle around the upper rotation fulcrum) of the tiller rear cover 141 and correcting the fine adjustment of the lifting and lowering of the working implement W. In addition, the accuracy can be improved by calculating the slip ratio from the engine load and vehicle speed, determining the hardness of the soil from this slip ratio, and finely adjusting the lifting and lowering of the working implement by comparing it with a preset reference soil hardness. If the soil hardness calculated from the slip ratio is higher than the reference soil hardness, the working implement W is corrected to the lower side, and if it is lower than the reference soil hardness, the working implement W is corrected to the higher side.

[0087] Next, a control system of the work vehicle (tractor) 1 centered on the control device 40 will be described with reference to Fig. 9. Fig. 9 is a block diagram showing an example of the control system of the work vehicle 1. As shown in Fig. 9, the control device 40 includes an engine ECU (Electronic Control Unit) 41, a traveling system ECU 42, and a work implement lifting system ECU 43. The engine ECU 41 controls the rotation speed of the engine E. The traveling system ECU 42 controls the rotation of the drive wheels to control the traveling speed of the traveling vehicle body 2 (see Fig. 1). The work implement lifting system ECU 43 controls the lifting device 12 to control the lifting and lowering of the work implement W.

[0088] The control device 40 is capable of controlling each part through electronic control, and is equipped with a processing unit having a CPU (Central Processing Unit) and the like, as well as a memory unit in which various programs and necessary data such as the planned driving route of the traveling vehicle body 2 that is set in advance for each field are stored.

[0089] As shown in FIG. 8, various sensors such as a vehicle body positioning device 30, a work machine positioning device 31, an engine revolution sensor 23, a vehicle speed sensor 24, a steering angle sensor 25, an obstacle sensor 20 (front sensor 21 and rear sensor 22), a lift arm sensor 26, a lever sensor 35, and various switches such as a lock operation detection switch 138, a mode selection switch 223, a public road driving button 91, and a lift height dial 90 are connected to the control device 40. The engine revolution sensor 23 detects the number of revolutions of the engine E. The vehicle speed sensor 24 detects the traveling speed (vehicle speed) of the traveling vehicle body 2 (see FIG. 1). The steering angle sensor 25 detects the steering angle of the front wheels 4 (see FIG. 1), which are steered wheels. The steering angle sensor 25 detects the turning of the vehicle body 2. The lever sensor 35 detects that the sub-transmission lever 14 is operated to at least the high-speed position.

[0090] The control device 40 receives inputs of position information of the traveling vehicle body 2 from the vehicle body positioning device 30, position information of the work machine W from the work machine positioning device 31, the rotation speed of the engine E from the engine rotation sensor 23, the traveling speed of the traveling vehicle body 2 from the vehicle speed sensor 24, the turning angle of the front wheels 4 from the turning angle sensor 25, the detection result of an obstacle from the obstacle sensor 20, the height of the work machine W from the lift arm sensor 26, and the presence or absence of high speed position operation of the sub-transmission lever 14 from the lever sensor 35. When the control device 40 causes the tractor 1 to travel autonomously, it automatically steers the steering wheel 9 by controlling a steering cylinder connected to the steering wheel 9 while feeding back the turning angle of the front wheels 4 using the detection result of the turning angle sensor 25.

[0091] In addition, in the control device 40 , the engine ECU 41 is connected to the engine E, the driving system ECU 42 is connected to the steering device 51 , the transmission 52 , the braking device 53 , etc., and the work implement lifting system ECU 43 is connected to the lifting device 12 .

[0092] Of these, the work machine lifting system ECU 43 outputs a work machine lifting signal to the lifting device 12. The lifting device 12 drives the work machine W to lift or lower based on the work machine lifting signal output from the work machine lifting system ECU 43. The lifting device 12 also controls the horizontal cylinder 33 that adjusts the rolling angle of the work machine W relative to the traveling vehicle body 2. The horizontal cylinder 33 is provided on the right lift rod 123, and adjusts the rolling angle by expanding and contracting to change its length.

[0093] Incidentally, the tilling depth control of the rotary tiller W in Fig. 8 is configured to be performed when the lifting position of the lifting device 12 is below a predetermined height. That is, the control device 40 is configured to determine the detection value of the lift arm sensor 26, and to perform tilling depth control when it is determined that the lift arm 122 is below a predetermined angle and the rotary tiller W is in a working position. With this configuration, it is possible to prevent the rotary tiller W from automatically lifting or lowering unintentionally while traveling on a road, for example.

[0094] The condition for executing the above-mentioned tillage depth control can also be based on the operation of the one-touch lift switch 353. That is, the system is configured so that tillage depth control can be executed when the one-touch lift switch 353 is operated to lower the implement, in other words, when the rotary tiller W is in a lowered state. In this case as well, it is possible to prevent the rotary tiller W from automatically lifting or lowering unintentionally while traveling on a road, for example.

[0095] As described above, the mode selection switch 223 is configured to select between a field mode for traveling in a field and a road mode for traveling on a road. The mode selection switch 223 is configured to be able to execute tillage depth control when the field mode is selected. In this case as well, it is possible to prevent the rotary tilling implement W from automatically raising and lowering unintentionally while traveling on a road.

[0096] In the above, the working machine W has been described as a rotary tiller W, but the same applies when controlling the lifting and lowering of a general working machine W based on detection by the working machine positioning device 31. That is, the control device 40 is provided with a working posture determination means D that determines whether the connected working machine W is in a predetermined working posture or not, and is configured to be able to execute working machine height control when, for example, in Fig. 10, the working machine W height is set to a predetermined or lower level by the lift arm 122 (S201), when the working machine is lowered based on the working machine lift switch operation such as the one-touch lift switch 353 (S202), and when the field mode is selected by the mode selection switch 223 that can select between the field mode and the road mode (S203), thereby making it possible to prevent unintended lifting and lowering of the working machine W while traveling on the road.

[0097] Furthermore, the working posture determination means D has a prohibition determination function for prohibiting the lifting and lowering control of the work implement W in a predetermined case. For example, when the sub-transmission 74 (hereinafter, sub-transmission 74) is set to the fourth speed, which is the highest speed among the first speed to the fourth speed (S204), when the vehicle speed detected by the vehicle speed sensor 24 is equal to or higher than a predetermined value (S205), or when the forward / reverse lever 201 for switching the forward / reverse clutch 72 is operated to the reverse side (206), the lifting and lowering control of the work implement W is prohibited. As a result, in a situation where the sub-transmission 74 is operated to a high speed speed, when the vehicle speed is higher than a predetermined value, or when traveling in reverse, and where it is determined that the vehicle is in a non-working posture, unintended lifting and lowering of the work implement W can be prevented by prohibiting the lifting and lowering control of the work implement W.

[0098] In addition, in the case of a rotary tiller W, a so-called tillage depth control means is provided for controlling lifting and lowering based on detection of the up-down rotation of the rear cover 141 with its lower edge grounded relative to the main cover 140, and when the tillage depth control means is selected, the lifting and lowering control by the working machine positioning device 31 is prohibited (S207). Therefore, although there is a risk of hunting occurring when multiple lifting and lowering controls are executed, the occurrence of hunting can be prevented by prioritizing the tillage depth control when the tillage depth control is executed. Note that, when it is desired to prohibit the tillage depth control and execute the lifting and lowering control by the working machine positioning device 31, a tillage depth control prohibition switch (not shown) is turned ON. Similarly, when multiple lifting and lowering controls, such as the so-called position control and drag control for controlling the lifting and lowering of the working machine W and the lifting and lowering control by the working machine positioning device 31, are executed, hunting can be prevented by prohibiting the lifting and lowering control by the working machine positioning device 31.

[0099] The control device 40 is also wirelessly connected to, for example, an information processing terminal 100 that can be carried by the worker. The control device 40 controls each part of the tractor 1 based on an instruction signal from the information processing terminal 100 operated by the worker. The control device 40 may also be configured to hold a vehicle body information database of the tractor 1, and to be able to receive and transmit information such as the model from the information processing terminal 100, etc.

[0100] Furthermore, the control device 40 stops the traveling vehicle body 2 when an obstacle is detected by the front sensor 21 or the rear sensor 22. Furthermore, the control device 40 stops the engine E or stops the transmission of rotational power to the PTO shaft 16 when an obstacle is detected by the front sensor 21 or the rear sensor 22. Furthermore, the control device 40 may activate an alarm (not shown) to notify the user that an obstacle has been detected when an obstacle is detected by the front sensor 21 or the rear sensor 22.

[0101] The control device 40 also has an "automatic driving mode" in which the tractor 1 performs work while autonomously traveling. In the automatic driving mode, the control device 40 predetermines a planned travel route for each field according to the work content of the work implement W, digitizes it, and stores it in the storage unit, and controls each part such as the engine E, steering device 51, transmission device 52, braking device 53, and lifting device 12 so that the tractor travels along the stored planned travel route based on the measurement results of the positioning device 30. The planned travel route is set according to the shape and size of the field, the width, length, and number of ridges formed in the field, and the type of crop.

[0102] As described above, when the control device 40 detects that the lock operation detection switch 138 is in a locked state, when the sub-speed lever 14 is operated to high speed and the mode selection switch 223 is set to the road mode, or when the control device 40 detects that the work implement W attached to the traveling body 2 is outside the field based on the field position information and shape information preregistered in the control device 40 and the work implement positioning device 31, the control device 40 raises and lowers the work implement W to a predetermined position. At this time, the horizontal cylinder 33 automatically adjusts the rolling angle of the work implement W so that it is approximately horizontal with respect to the traveling body 2, thereby making it possible to put it in a posture more suitable for traveling on the road.

[0103] Furthermore, when it is detected that the work implement W attached to the traveling vehicle body 2 has entered the field from outside the field using preregistered information on the position and range of the field and the work implement positioning device 31, the work implement W can be raised from a predetermined position to the highest position. This allows for tight maneuverability in the field and prevents contact with ridges, etc. Also, by using the work implement positioning device 31 to make a judgment, it is possible to configure the system so that unnecessary raising control is not executed when the traveling vehicle enters the field without a work implement attached.

[0104] Furthermore, the movement speed of the work machine W is calculated from the work machine positioning device 31, and if this speed exceeds a predetermined speed (for example, 15 km / h), a warning is issued to the driver. This makes it possible to prevent high-speed driving with the work machine W attached, and to prevent driving in a state where the vehicle is likely to tip over. By calculating and determining the movement speed of the work machine W from the work machine positioning device 31, it is possible to prevent unnecessary notifications in a state where the vehicle can drive without problems, such as a state where the work machine W is not attached.

[0105] Next, another example of the installation configuration of the work machine positioning device 31 will be described with reference to Figs.

[0106] In Figure 11, the rotary tillage device W has a so-called center drive configuration in which tillage tine shafts 231 are supported on the left and right sides by a central transmission case 230, and cylindrical frames 232, 232 are provided on the left and right sides of the transmission case 230 to make it rigid. Connecting plates 234, 234 with connecting pins 233, 233 are provided on the cylindrical frames 232, 232, and the rear ends of the left and right lower links 124, 124 are connectable to the connecting pins 233, 233. Furthermore, the rear end of the top link 125 is connectable to a connecting pin 236 of an upper bracket 235 provided on the top of the transmission case 230.

[0107] A rotary cover 237 is fixed to a rigid tillage frame consisting of the transmission case 230 and the left and right cylindrical frames 232, 232, etc. This rotary cover 237 is configured to cover the tillage tines 238, 238... provided on the outer periphery of the tillage tine shaft 231. A rear cover 239 that is rotatable about a horizontal axis and covers the rear parts of the tillage tines 238, 238... is disposed at the rear of the rotary cover 237, and side covers 240, 240 are disposed on the left and right side surfaces of the rotary cover 237. In addition, a pressure rod 242, whose lower end is attached to the rear cover 239, is attached to a hanger plate 241 protruding from the rotary cover 237 so as to be movable up and down. A lower spring 243 is wound around this pressure rod 242 to allow the rear cover 239 to rise above a predetermined angle but presses downward to prevent the rear cover 239 from rising any further, thereby preventing the rear cover 239 from bouncing up. On the other hand, an upper spring 244 is wound around the upper end of the pressure rod 242 to regulate excessive downward swing of the rear cover 239.

[0108] In addition, the driving force from the PTO shaft 16 at the rear of the tractor is input to the transmission mechanism inside the transmission case 230 via the input shaft 249 of the transmission case 230 via a universal joint not shown, and is configured to rotate the tiller claw shaft 231 via an interlocking chain, etc.

[0109] Incidentally, a work machine positioning device 31 is provided on the upper surface of the rotary cover 237. That is, when viewed from behind, as shown in FIG.

[0110] The working implement positioning device 31 is disposed via a vertical support 245, also called a support section, so as to be located above the upper end of the rear wheel 5 fender 36 in the working position in which the rotary tiller W is on the ground. Therefore, the working implement positioning device 31 is located at a high position and can receive the positioning signal well. In order to avoid contact with the traveling vehicle body 2, the working implement positioning device 31 is configured so that it can be stored in a lying position together with the support 245 when not performing tilling work (FIG. 12(A)). In order to achieve the stored configuration, the support section 245 is divided into a telescopic configuration so that it is configured so that its height is lowered in the non-working position, thereby preventing the working implement W from contacting the window at the rear of the vehicle when it is raised (FIGS. 12(B)(C)). [Explanation of symbols]

[0111] 2 Running vehicle 12 Lifting device 24 Vehicle speed sensor 26 Lift arm sensor 31 Work equipment positioning device 40 Control device 74 Auxiliary transmission 122 Lift arm 223 Mode selection switch 353 Work equipment lift switch D Working posture determination means Hn Detection height Hs Reference height Hs´ Reference height P Lifting link W Rotary tilling equipment (working machine)

Claims

1. A work vehicle having a working machine (W) mounted on a traveling body (2) via a lifting link (P) so that it can be raised and lowered, a working machine positioning device (31) that measures the height position of the working machine (W), and a control device (40) equipped with a positioning control mode that controls the lifting and lowering of the working machine (W) to maintain a detected height (Hn) obtained by the working machine positioning device (31) at a reference height (Hs, Hs'), characterized in that the work vehicle is provided with a working posture determination means (D) and performs lifting and lowering control using the positioning control mode when it is determined that the working machine (W) is below a predetermined height.

2. 2. The work vehicle according to claim 1, wherein the working posture determining means (D) performs lift control in a positioning control mode based on detection of a predetermined angle by a lift arm sensor (26) provided on the lift arm (122).

3. 2. The work vehicle according to claim 1, wherein the working posture determination means (D) performs lift control in the positioning control mode when the work implement lift switch (353) is operated to lower.

4. 2. The work vehicle according to claim 1, wherein the working posture determination means (D) is configured to perform lifting control in a positioning control mode when a mode selection switch (223) capable of selecting between a field mode for traveling in a field and a road mode for traveling on a road selects the field mode.

5. 2. The work vehicle according to claim 1, further comprising an auxiliary transmission (74), wherein the working posture determination means (D) is configured to prohibit execution of lift control when the auxiliary transmission (74) is operated to a high-speed position.

6. 2. The work vehicle according to claim 1, further comprising a vehicle speed sensor (24) for detecting the speed of the traveling body (2), and the working posture determination means (D) is configured to prohibit the execution of lift control in the positioning control mode when the vehicle speed is equal to or greater than a predetermined value.

7. The work vehicle according to claim 1, further comprising tillage depth control, position control or resistance control as the lifting and lowering control of the work implement (W), and the working posture determination means (D) is configured to prioritize the tillage depth control, position control or resistance control and to prohibit the execution of lifting and lowering control in the positioning control mode.

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