Work vehicle and method

Abstract

To prevent falling of a work object by automatic drive control.SOLUTION: A state determination part determines a work state of a work vehicle on the basis of a tractive force of the work vehicle and a posture of a work machine. An automatic dump determination part determines an automatic dump propriety mode indicating whether or not to execute automatic dump control for automatically driving a bucket up to a predetermined dump angle, according to the work state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to Work vehicle and method .

Background Art

[0002] In a work vehicle such as a wheel loader, automatic drive control (detent control, kick-out control) for automatically driving a work implement to a predetermined position is performed for the purpose of easily and accurately performing the operation of repeatedly operating the work implement to the predetermined position. Patent Document 1 discloses a technique for determining whether or not automatic drive control is possible based on the load state of a work implement specified from the load applied to the work implement.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Automatic drive control can be executed for each of the four operations of boom raising, boom lowering, bucket tilt, and bucket dump. However, when a work object is accommodated in the bucket, if automatic drive control related to bucket dump is performed due to a malfunction or the like, the work object may spill. An object of the present invention is to provide a work implement control device, a work vehicle, and a work implement control method for preventing the fall of a work object due to automatic drive control.

Means for Solving the Problems

[0005] According to one aspect of the present invention, a work implement control device is a work implement control device for a work vehicle including a work implement having a boom and a bucket, the work implement control device including a state determination unit that determines a work state of the work vehicle, and an automatic dump determination unit that determines an automatic dump available mode indicating whether or not to execute automatic dump control for automatically driving the bucket to a predetermined dump angle according to the work state.

Effects of the Invention

[0006] According to the above aspect, the work implement control device prevents the work object from falling due to automatic drive control.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0008] 〈First Embodiment〉 Hereinafter, embodiments will be described in detail with reference to the drawings. FIG. 1 is a side view of a work vehicle according to the first embodiment. The work vehicle 100 according to the first embodiment is a wheel loader. The work vehicle 100 includes a vehicle body 110, a work implement 120, a front wheel portion 130, a rear wheel portion 140, and a cab 150.

[0009] The vehicle body 110 includes a front vehicle body 111, a rear vehicle body 112, and a steering cylinder 113. The front vehicle body 111 and the rear vehicle body 112 are rotatably attached about a steering axis extending in the vertical direction of the vehicle body 110. The front wheel portion 130 is provided at the lower part of the front vehicle body 111, and the rear wheel portion 140 is provided at the lower part of the rear vehicle body 112. The steering cylinder 113 is a hydraulic cylinder. The base end portion of the steering cylinder 113 is attached to the rear vehicle body 112, and the tip end portion is attached to the front vehicle body 111. The steering cylinder 113 defines the angle formed between the front vehicle body 111 and the rear vehicle body 112 by expanding and contracting with hydraulic oil. That is, the steering angle of the front wheel portion 130 is defined by the expansion and contraction of the steering cylinder 113.

[0010] The working machine 120 is used for excavating and transporting work objects such as earth and sand. The working machine 120 is provided at the front part of the vehicle body 110. The working machine 120 includes a boom 121, a bucket 122, a bell crank 123, a lift cylinder 124, and a bucket cylinder 125.

[0011] The base end portion of the boom 121 is attached to the front part of the front vehicle body 111 via a pin. A boom angle sensor 1211 for detecting the boom angle θL is provided at the base end portion of the boom 121. The boom angle θL is represented by the angle formed between a straight line extending forward from the vehicle body 110 and a straight line extending from the base end portion to the tip end portion of the boom 121. The higher the boom angle θL, the higher the position of the tip of the boom 121, and the lower the boom angle θL, the lower the position of the tip of the boom 121. In other embodiments, a lift cylinder stroke sensor for measuring the stroke amount of the lift cylinder 124 may be provided, and the boom angle θL may be detected based on the stroke amount of the lift cylinder 124.

[0012] The bucket 122 includes a blade for excavating a work object and a container for transporting the excavated work object. The base end portion of the bucket 122 is attached to the tip end portion of the boom 121 via a pin.

[0013] The bell crank 123 transmits the power of the bucket cylinder 125 to the bucket 122. The first end of the bell crank 123 is attached to the bottom of the bucket 122 via a link mechanism. The second end of the bell crank 123 is attached to the tip of the bucket cylinder 125 via a pin. A bucket angle sensor 1231 for detecting the bucket angle θB is provided at the central portion of the bell crank 123. The bucket angle θB is represented by the angle formed by a straight line extending forward from the vehicle body 110 and a straight line extending along the bottom surface of the bucket 122. When the bucket angle θB is positive, the bucket 122 tilts toward the tilt side, and when the bucket angle θB is negative, the bucket 122 tilts toward the dump side. The bucket angle θB is obtained by adding the boom angle θL to the angle of the bucket 122 with respect to the boom 121, which is obtained from the measured value of the bucket angle sensor 1231.

[0014] The lift cylinder 124 is a hydraulic cylinder. The base end portion of the lift cylinder 124 is attached to the front portion of the front vehicle body 111. The tip of the lift cylinder 124 is attached to the boom 121. When the lift cylinder 124 expands and contracts by hydraulic oil, the boom 121 is driven in the upward or downward direction.

[0015] The bucket cylinder 125 is a hydraulic cylinder. The base end portion of the bucket cylinder 125 is attached to the front portion of the front vehicle body 111. The tip of the bucket cylinder 125 is attached to the bucket 122 via the bell crank 123. When the bucket cylinder 125 expands and contracts by hydraulic oil, the bucket 122 is driven in the tilt direction or the dump direction.

[0016] The cab 150 is a space for the operator to board and operate the work vehicle 100. The cab 150 is provided on the upper portion of the rear vehicle body 112. FIG. 2 is a top view showing the internal configuration of the driver's cab according to the first embodiment. Inside the driver's cab 150, a seat 151, an accelerator pedal 152, a brake pedal 153, a steering wheel 154, a forward / reverse changeover switch 155, a shift switch 156, a boom lever 157, a bucket lever 158, and a stop switch 159 are provided.

[0017] The accelerator pedal 152 is operated to set the driving force (tractive force) for causing the work vehicle 100 to travel. The brake pedal 153 is operated to set the braking force for causing the work vehicle 100 to travel. The steering wheel 154 is operated to set the steering angle of the work vehicle 100. The forward / reverse changeover switch 155 is operated to set the traveling direction of the work vehicle 100. The shift switch 156 is operated to set the speed range of the power transmission device.

[0018] The boom lever 157 is operated to set the speed of the raising or lowering operation of the boom 121. The boom lever 157 accepts a lowering operation when tilted forward and accepts a raising operation when tilted backward. Hereinafter, the raising and lowering operations of the boom 121 are also referred to as lift operations. Further, when the boom lever 157 is tilted forward by a certain angle or more, it outputs a start command for automatic drive control (automatic lowering control) to the control device 300 to automatically drive the boom 121 to a predetermined lowering position. When the boom lever 157 is tilted backward by a certain angle or more, it outputs a start command for automatic drive control (automatic raising control) to the control device 300 to automatically drive the boom 121 to a predetermined raising position. The lowering position may be, for example, the position when the lift cylinder 124 is fully retracted, or may be a position corresponding to the ground clearance of the work vehicle 100. The raising position may be, for example, the position when the lift cylinder 124 is fully extended. Further, the lowering position and the raising position may be arbitrarily set by the operator. Note that the raising position and the lowering position are not limited to the above examples, but in any case, the raising position is set above the lowering position in the vehicle body coordinate system. After outputting the start command for automatic drive control, the boom lever 157 returns to the neutral position. In other embodiments, after outputting the start command for automatic drive control, the position of the boom lever 157 may be fixed until the automatic drive control ends. Even when the boom lever 157 is fixed, the operator can release the fixation by operating the boom lever 157.

[0019] The bucket lever 158 is operated to set the speed of the dump operation or tilt operation of the bucket 122. The bucket lever 158 accepts a dump operation when tilted forward and accepts a tilt operation when tilted backward. Further, when the bucket lever 158 is tilted forward by a certain angle or more, a start command for automatic drive control (automatic dump control) that automatically drives the bucket 122 to a predetermined dump angle is output to the control device 300. When the bucket lever 158 is tilted backward by a certain angle or more, a start command for automatic drive control (automatic tilt control) that automatically drives the bucket 122 to a predetermined tilt angle is output to the control device 300. The dump angle may be, for example, an angle tilted by a predetermined angle in the dump direction with respect to the horizontal. The tilt angle may be, for example, an angle tilted by a predetermined angle in the tilt direction with respect to the horizontal. The dump angle and the tilt angle may be arbitrarily set by the operator. Note that the dump angle and the tilt angle are not limited to the above examples. Also, the dump angle and the tilt angle may be the same angle (for example, both horizontal). After outputting a start command for automatic drive control, the bucket lever 158 returns to the neutral position. In other embodiments, after outputting a start command for automatic drive control, the position of the bucket lever 158 may be fixed until the automatic drive control ends. Even when the bucket lever 158 is fixed, the operator can release the fixation by operating the bucket lever 158.

[0020] The stop switch 159 is operated to stop various automatic drive controls. The stop switch 159 outputs a stop command to the control device 300 when pressed. The stop switch 159 is provided, for example, on the bucket lever 158.

[0021] 《Power train》 FIG. 3 is a schematic diagram showing the power train of the work vehicle according to the first embodiment. The work vehicle 100 includes an engine 210, a PTO 220 (Power Take Off), a transmission 230, a front axle 240, a rear axle 250, and a variable displacement pump 260.

[0022] The engine 210 is, for example, a diesel engine. The engine 210 is provided with a fuel injection device 211 and an engine tachometer 212. The fuel injection device 211 controls the driving force of the engine 210 by adjusting the amount of fuel injected into the cylinder of the engine 210. The engine tachometer 212 measures the rotational speed of the engine 210. The PTO 220 transmits a part of the driving force of the engine 210 to the variable displacement pump 260. That is, the PTO 220 distributes the driving force of the engine 210 to the transmission 230 and the variable displacement pump 260.

[0023] The transmission 230 shifts the driving force input to the input shaft and outputs it from the output shaft. The input shaft of the transmission 230 is connected to the PTO 220, and the output shaft is connected to the front axle 240 and the rear axle 250. That is, the transmission 230 transmits the driving force of the engine 210 distributed by the PTO 220 to the front axle 240 and the rear axle 250.

[0024] The front axle 240 transmits the driving force output by the transmission 230 to the front wheel portion 130. Thereby, the front wheel portion 130 rotates. The rear axle 250 transmits the driving force output by the transmission 230 to the rear wheel portion 140. Thereby, the rear wheel portion 140 rotates.

[0025] The variable displacement pump 260 is driven by the driving force from the engine 210. The hydraulic oil discharged from the variable displacement pump 260 is supplied to the lift cylinder 124 and the bucket cylinder 125 via the control valve 261. The variable displacement pump 260 is provided with a pump pressure gauge 262 and a pump capacity gauge 263. The pump pressure gauge 262 measures the discharge pressure of the hydraulic oil from the variable displacement pump 260. The pump capacity gauge 263 measures the capacity of the variable displacement pump 260 based on the swash plate angle etc. of the variable displacement pump 260. The control valve 261 controls the flow rate of the hydraulic oil discharged from the variable displacement pump 260 and distributes the hydraulic oil to the lift cylinder 124 and the bucket cylinder 125.

[0026] 《Control Device》 The work vehicle 100 includes a control device 300 for controlling the work vehicle 100. The control device 300 is an example of a work implement control device. The control device 300 outputs a control signal to the control valve 261 according to the operation amounts of the boom lever 157 and the bucket lever 158, and also according to a command for automatic drive control by the operator.

[0027] FIG. 4 is a schematic block diagram showing the configuration of a control device for a work vehicle according to the first embodiment. The control device 300 is a computer including a processor 310, a main memory 330, a storage 350, and an interface 370.

[0028] The storage 350 is a non-transitory tangible storage medium. Examples of the storage 350 include a magnetic disk, a magneto-optical disk, a semiconductor memory, etc. The storage 350 may be an internal medium directly connected to the bus of the control device 300, or may be an external medium connected to the control device 300 via the interface 370 or a communication line. The storage 350 stores a program for controlling the work vehicle 100.

[0029] The program may be for realizing a part of the functions to be exerted by the control device 300. For example, the program may exert functions in combination with other programs already stored in the storage, or in combination with other programs implemented in other devices. In other embodiments, in addition to or instead of the above configuration, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device). Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, part or all of the functions realized by the processor may be realized by the integrated circuit.

[0030] When the program is distributed to the control device 300 via a communication line, the control device 300 that has received the distribution may expand the program in the main memory 330 and execute the above processing. Also, the program may be for realizing a part of the functions described above. Furthermore, the program may be a so-called difference file (difference program) that realizes the functions described above in combination with other programs already stored in the storage 350.

[0031] By executing the program, the processor 310 includes an operation amount acquisition unit 311, a command input unit 312, a measurement value acquisition unit 313, a traction force calculation unit 314, a state determination unit 315, an automatic dump determination unit 316, and a drive control unit 317. Also, when the program is executed, a storage area of the mode storage unit 331 is secured in the main memory 330. The mode storage unit 331 stores an automatic dump enable mode indicating whether automatic dump control can be executed. The automatic dump enable mode takes either a value of an automatic dump permission mode that permits execution of automatic dump control or an automatic dump prohibition mode that prohibits execution of automatic dump control.

[0032] The operation amount acquisition unit 311 acquires the operation amounts of the boom lever 157 and the bucket lever 158. The command input unit 312 receives an input of a start command for automatic drive control from the boom lever 157 and the bucket lever 158. Also, the command input unit 312 receives an input of a stop command for automatic drive control from the stop switch 159.

[0033] The measurement value acquisition unit 313 acquires measurement values from the fuel injection device 211, the engine tachometer 212, the pump pressure gauge 262, the pump capacity gauge 263, the boom angle sensor 1211, and the bucket angle sensor 1231. That is, the measurement value acquisition unit 313 acquires measurement values of the fuel injection amount of the fuel injection device 211, the rotational speed of the engine 210, the discharge pressure of the variable displacement pump 260, the capacity of the variable displacement pump 260, the boom angle θL, and the bucket angle θB.

[0034] The traction force calculation unit 314 calculates the traction force of the work vehicle 100 based on the measurement values acquired by the measurement value acquisition unit 313. For example, when the transmission 230 is a continuously variable transmission, the traction force calculation unit 314 can calculate the traction force according to the following procedure. The traction force calculation unit 314 calculates the output torque of the engine 210 from the measurement value of the fuel injection amount and the rotational speed of the engine 210. Also, the traction force calculation unit 314 calculates the load torque of the variable displacement pump 260 from the discharge pressure and the capacity of the variable displacement pump 260. The traction force calculation unit 314 multiplies the running torque obtained by subtracting the load torque from the output torque by the reduction ratio of the transmission 230, the reduction ratio of the axle, and the torque efficiency, and divides this by the effective diameter of the wheels to calculate the traction force. For example, when the transmission 230 is a torque converter, the traction force calculation unit 314 can calculate the traction force according to the following procedure. The traction force calculation unit 314 calculates the driving torque by multiplying the value obtained by dividing the engine speed of the engine 210 by 1000 rpm and squaring it by the primary torque coefficient and the torque ratio of the transmission 230. The primary torque coefficient and the torque ratio are characteristic values determined by the input / output rotation ratio of the transmission 230. The traction force calculation unit 314 multiplies the driving torque by the reduction ratio of the transmission 230, the reduction ratio of the axle, and the torque efficiency, and divides this by the effective diameter of the wheel to calculate the traction force.

[0035] The state determination unit 315 determines the working state of the work vehicle 100 based on the traction force calculated by the traction force calculation unit 314, the measured values of the boom angle θL and the bucket angle θB acquired by the measurement value acquisition unit 313, and the operation amounts of the boom lever 157 and the bucket lever 158 acquired by the operation amount acquisition unit 311. The working state includes at least an excavation state and a dump state. Specifically, the state determination unit 315 determines that the working state is the excavation state when the traction force is equal to or greater than the traction force threshold, the boom angle θL is equal to or less than the boom angle threshold, the bucket angle θB is within the bucket angle range, and the raising operation of the boom lever or the tilting operation of the bucket lever continues for a certain period of time. The traction force threshold is a threshold corresponding to the traction force exerted during excavation. The boom angle threshold corresponds to the boom angle θL when the base end portion of the bucket 122 is at a position that is a predetermined allowable height higher than the ground contact height. That is, when the boom angle θL is equal to or less than the boom angle threshold, the bucket 122 is located within a predetermined height range including the ground contact height. The height range does not necessarily have a lower limit. The bucket angle range is a range including 0 degrees. That is, when the bucket angle θB is within the bucket angle range, the bottom surface of the bucket 122 is substantially parallel to the front of the vehicle body 110. Further, when the bucket angle θB is less than a predetermined dump threshold value, the state determination unit 315 determines that the working state is the dump state. The dump threshold value is a negative value and is lower than the lower limit value of the bucket angle range. That is, when the bucket angle θB is less than the dump threshold value, the bottom surface of the bucket 122 is inclined in the dump direction.

[0036] When the working state of the work vehicle 100 is the excavation state, the work object is accommodated in the bucket 122. On the other hand, when the working state of the work vehicle 100 is the dump state, the work object is dumped from the bucket 122 and the work object is not accommodated in the bucket 122. That is, there is a high possibility that the work object is accommodated in the bucket 122 from the time when the working state becomes the excavation state until it becomes the dump state. On the other hand, there is a high possibility that the work object is not accommodated in the bucket 122 from the time when the working state becomes the dump state until it becomes the excavation state.

[0037] When it is determined that the working state is the excavation state, the automatic dump determination unit 316 rewrites the value of the automatic dump enable / disable mode stored in the mode storage unit 331 to the automatic dump prohibition mode. On the other hand, when it is determined that the working state is the dump state, the automatic dump determination unit 316 rewrites the value of the automatic dump enable / disable mode stored in the mode storage unit 331 to the automatic dump permission mode.

[0038] When the drive control unit 317 receives a start command for automatic drive control, it generates a drive signal related to the automatic drive control and outputs it to the control valve 261. However, when the drive control unit 317 receives a start command related to the automatic dump control, it outputs a drive signal related to the automatic dump control to the control valve 261 only when the value of the automatic dump enable / disable mode stored in the mode storage unit 331 is the automatic dump permission mode. Further, when the drive control unit 317 is not performing the automatic drive control, it generates a drive signal according to the operation amounts of the boom lever 157 and the bucket lever 158 and outputs it to the control valve 261.

[0039] 《Setting of Automatic Dump Enable / Disable Mode》 Figure 5 is a flowchart showing a method for setting an automatic dump enable / disable mode by the control device according to the first embodiment. The control device 300 executes the following setting process for the automatic dump enable / disable mode at each predetermined control cycle. First, the operation amount acquisition unit 311 acquires the operation amounts of the boom lever 157 and the bucket lever 158 (step S1). Also, the measurement value acquisition unit 313 acquires measurement values from the fuel injection device 211, the engine tachometer 212, the pump pressure gauge 262, the pump capacity gauge 263, the boom angle sensor 1211, and the bucket angle sensor 1231 (step S2).

[0040] Next, the traction force calculation unit 314 calculates the traction force of the work vehicle 100 based on the measurement values acquired in step S2 (step S3). The state determination unit 315 determines whether or not the traction force calculated in step S3 is equal to or greater than the traction force threshold (step S4). If the traction force is equal to or greater than the traction force threshold (step S4: YES), the state determination unit 315 determines whether or not the boom angle θL acquired in step S2 is equal to or less than the boom angle threshold (step S5). If the boom angle θL is equal to or less than the boom angle threshold (step S5: YES), the state determination unit 315 determines whether or not the bucket angle θB acquired in step S2 is within the bucket angle range (step S6). If the bucket angle θB is within the bucket angle range (step S6: YES), it is determined whether or not the duration of the raising operation of the boom 121 or the tilting operation of the bucket 122 is equal to or longer than a certain time based on the operation amount of the boom lever 157 or the bucket lever 158 acquired in step S1 (step S7).

[0041] When the traction force is equal to or greater than the traction force threshold value, the boom angle θL is equal to or less than the boom angle threshold value, the bucket angle θB is within the bucket angle range, and the duration of the raising operation of the boom 121 or the tilting operation of the bucket 122 is equal to or greater than a certain time (step S7: YES), the state determination unit 315 determines that the working state is the excavation state (step S8). When the state determination unit 315 determines that the working state is the excavation state, the automatic dump determination unit 316 rewrites the value of the automatic dump enable / disable mode stored in the mode storage unit 331 to the automatic dump prohibition mode and ends the process (step S9).

[0042] On the other hand, when the traction force is less than the traction force threshold value (step S4: NO), when the boom angle θL is greater than the boom angle threshold value (step S5: NO), when the bucket angle θB is outside the bucket angle range (step S6: NO), or when the duration of the raising operation of the boom 121 and the tilting operation of the bucket 122 is less than a certain time (step S7: NO), the state determination unit 315 determines whether the bucket angle θB is less than the dump threshold value (step S10). When the bucket angle θB is less than the dump threshold value (step S10: YES), the state determination unit 315 determines that the working state is the dump state (step S11). When the state determination unit 315 determines that the working state is the dump state, the automatic dump determination unit 316 rewrites the value of the automatic dump enable / disable mode stored in the mode storage unit 331 to the automatic dump permission mode and ends the process (step S12).

[0043] The control device 300 updates the value of the automatic dump enable / disable mode stored in the mode storage unit 331 by executing the above-described setting process of the automatic dump enable / disable mode at each predetermined control cycle.

[0044] 《Automatic Driving Control》 FIG. 6 is a flowchart showing an automatic driving control method by the control device according to the first embodiment. When the instruction input unit 312 receives an input of a start instruction for automatic drive control, the control device 300 executes the following automatic drive control. First, the drive control unit 317 determines whether the input start instruction is a start instruction related to automatic dump control (step S31). When a start instruction related to automatic dump control is input (step S31: YES), the drive control unit 317 determines whether the value of the automatic dump enable / disable mode stored in the mode storage unit 331 is the automatic dump permission mode (step S32). When the value of the automatic dump enable / disable mode is the automatic dump prohibition mode (step S32: NO), the drive control unit 317 ends the process without performing automatic dump control.

[0045] On the other hand, when a start instruction related to automatic lifting control, automatic lowering control, or automatic tilt control is input (step S31: NO), or when the value of the automatic dump enable / disable mode is the automatic dump permission mode (step S32: YES), the drive control unit 317 outputs a drive command related to a predetermined drive speed to the control valve 261 (step S33).

[0046] The measurement value acquisition unit 313 acquires measurement values from the boom angle sensor 1211 and the bucket angle sensor 1231 (step S34). The drive control unit 317 determines whether or not the angle of the control target (the boom 121 or the bucket 122) has reached a predetermined angle (the raising angle, the lowering angle, the tilt angle, or the dump angle) (step S35). When the angle of the control target has not reached the predetermined angle (step S35: NO), the command input unit 312 determines whether or not an input of a stop instruction has been received (step S36). When no stop instruction has been input (step S36: NO), the operation amount acquisition unit 311 determines whether or not the operation amount of the operation lever (the boom lever 157 or the bucket lever 158) related to the automatic drive control has exceeded the play range again after returning to the predetermined play range immediately after the input of the start command (step S37). When the operation amount of the operation lever does not exceed the play range (step S37: NO), the process returns to step S33 and the output of the drive command is continued. In another embodiment, when the operation lever is fixed after the input of the start command for automatic drive, the operation amount acquisition unit 311 determines in step S37 whether or not the operation amount of the operation lever is within the range where the fixation is released.

[0047] On the other hand, when the angle of the control target has reached the predetermined angle (step S35: YES), when a stop instruction has been input (step S36: YES), or when the operation amount of the operation lever related to the automatic drive control has exceeded the play range (step S37: YES), the drive control unit 317 stops the output of the drive command to the control valve 261 (step S38) and ends the process.

[0048] 《Function and Effect》 As described above, the control device 300 according to the first embodiment determines the working state of the work vehicle 100 based on the traction force of the work vehicle 100 and the posture of the work implement 120, and determines the automatic dump enable / disable mode according to the working state. Thereby, the control device 300 can prevent the object to be worked from falling due to the automatic drive control. More specifically, when it is determined that the working state is the excavation state, the control device 300 switches the automatic dumping permission mode to the automatic dumping prohibition mode. When the work vehicle 100 performs excavation work, thereafter, the work object is accommodated in the bucket 122. Therefore, the control device 300 can prevent the work object from falling due to automatic drive control by setting the automatic dumping permission mode to the automatic dumping prohibition mode after the working state becomes the excavation state.

[0049] Further, when it is determined that the working state is the dumping state, the control device 300 according to the first embodiment switches the automatic dumping permission mode to the automatic dumping permission mode. When the work vehicle 100 performs a dumping operation, the work object is dropped from the bucket 122, and thereafter, there is no work object in the bucket 122. Therefore, the control device 300 can accept automatic drive control in a state where the possibility of the work object falling is low by setting the automatic dumping permission mode to the automatic dumping permission mode after the working state becomes the dumping state.

[0050] The control device 300 according to the first embodiment includes, in the conditions for determining that the traction force is equal to or greater than a predetermined threshold value, the excavation state. This is because the traction force during excavation work is higher than when the work vehicle 100 is not performing excavation work in a state where the bucket 122 is inserted into the work object and moving forward. Further, the control device 300 according to the first embodiment includes, in the conditions for determining the excavation state, that the bucket angle θB is within the bucket angle range and the height of the bucket 122 is within a predetermined height range including the ground contact height of the work vehicle 100. This is because, at the start of excavation, the operator positions the bucket 122 with its bottom surface along the ground. Further, the control device 300 according to the first embodiment includes, in the conditions for determining the excavation state, that the operation of the operating device of the work machine 120 continues for a certain period of time. This is because it is necessary to tilt the bucket 122 while raising the boom 121 during excavation. In other embodiments, the operation of the operating device of the work machine 120 continuing for a certain period of time may not be included in the conditions for determining the excavation state. For example, in other embodiments, instead of this, the driving amount of the work machine 120 being smaller than a predetermined threshold with respect to the operation amount of the operating device of the work machine 120 may be included in the conditions for determining the excavation state.

[0051] Further, the control device 300 according to the first embodiment stops the automatic drive control by pressing the stop switch 159. Thereby, even when the automatic drive control is started due to an operator's misoperation or the like, the operator can easily stop the automatic drive control.

[0052] 〈Other Embodiments〉 Although one embodiment has been described in detail with reference to the drawings above, the specific configuration is not limited to the above, and various design changes and the like are possible. In other embodiments, the order of the above-described processes may be appropriately changed. Also, some processes may be executed in parallel.

[0053] The work vehicle 100 according to the above-described embodiment outputs a start command for automatic drive control by tilting the boom lever 157 or the bucket lever 158 by a predetermined tilt angle or more, but is not limited thereto. For example, the work vehicle 100 according to other embodiments may include a switch for instructing the start of automatic drive control separately from the boom lever 157 and the bucket lever 158. The switch may be used in combination with the stop switch 159.

[0054] Also, the work vehicle 100 according to the above-described embodiment includes the boom lever 157 and the bucket lever 158 separately, but is not limited thereto. For example, in other embodiments, the work vehicle 100 may include one work machine lever that combines the functions of the boom lever 157 and the bucket lever 158.

[0055] Also, the work vehicle 100 according to the above-described embodiment is a wheel loader, but is not limited thereto. For example, in other embodiments, the work vehicle 100 may be a bulldozer and other work vehicles.

[0056] Further, the work vehicle 100 according to the above-described embodiment performs automatic drive control for each of the raising and lowering operations of the boom 121, and the tilt and dump operations of the bucket 122, but is not limited thereto. For example, the work vehicle 100 according to other embodiments may implement at least one automatic drive control including automatic dump control.

[0057] Also, the work vehicle 100 according to the above-described embodiment performs automatic drive control for the tilt and dump operations of the bucket 122 based on the bucket angle θB, but is not limited thereto. For example, the work vehicle 100 according to other embodiments may obtain the stroke amount of the bucket cylinder 125 and perform automatic drive control for the tilt and dump operations based on the stroke amount of the bucket cylinder 125. The stroke amount of the bucket cylinder 125 may be obtained by providing a stroke sensor in the bucket cylinder 125, or may be calculated based on the measured value of the angle sensor provided in the bell crank 123 and the boom angle θL. Further, due to the mechanism of the work implement 120, when the boom 121 is driven, even if the bucket cylinder 125 is not driven, the bell crank angle changes. Therefore, the control device 300 of the work vehicle 100 measures in advance the stroke amount (reference stroke amount) of the bucket cylinder 125 in a state where the bucket 122 is in contact with the ground, and performs automatic drive control for the tilt and dump operations of the bucket 122 based on the difference between the reference stroke amount and the stroke amount of the bucket cylinder 125. Thereby, when the boom 121 is lowered near the ground surface, the bottom surface of the bucket 122 can be made substantially parallel to the ground surface. In this case, the dump angle, the tilt angle, and the bucket angle range used for determining the excavation conditions are compared after being converted into values of the stroke amount with respect to the reference stroke amount.

Explanation of Reference Numerals

[0058] 100... Work vehicle 110... Vehicle body 111... Front vehicle body 112... Rear vehicle body 113... Steering cylinder 120... Working machine 121... Boom 1211... Boom angle sensor 122... Bucket 123... Bell crank 1231... Bucket angle sensor 124... Lift cylinder 125... Bucket cylinder 130... Front wheel section 140... Rear wheel section 150... Cab 151... Seat 152... Accelerator pedal 153... Brake pedal 154... Steering wheel 155... Forward / reverse changeover switch 156... Shift switch 157... Boom lever 158... Bucket lever 159... Stop switch 210... Engine 211... Fuel injection device 212... Engine tachometer 220... PTO 230... Transmission 240... Front axle 250... Rear axle 260... Variable displacement pump 261... Control valve 262... Pump pressure gauge 263... Pump capacity gauge 300... Control device 310... Processor 311... Operation amount acquisition section 312... Command input section 313... Measurement value acquisition section 314... Tractive force calculation section 315... State determination section 316... Automatic dump determination section 317... Drive control section 330... Main memory 331... Mode memory section 350... Storage 370... Interface

Claims

1. A work vehicle equipped with a working machine having a boom and a bucket, comprising a control device having a processor, wherein the control device determines whether the working state of the work vehicle is an excavation state in which the bucket excavates a work object or a dump state in which the work object is unloaded from the bucket, prohibits execution of automatic dump control for automatically driving the bucket to a predetermined dump angle from when the determined working state becomes the excavation state until it becomes the dump state, and permits execution of the automatic dump control from when the determined working state becomes the dump state until it becomes the excavation state, and outputs a drive command for driving the bucket in the dump direction until the angle of the bucket reaches the dump angle when execution of the automatic dump control is permitted. Work vehicle.

2. The control device determines that the working state is the excavation state when the traction force of the work vehicle is equal to or greater than a predetermined threshold value, and the angle of the bucket is within a predetermined angle range including an angle at which the bottom surface of the bucket is parallel to the work vehicle, and the height of the bucket is within a predetermined height range including the ground contact height of the work vehicle. The work vehicle according to claim 1.

3. The control device determines that the working state is the excavation state when the traction force is equal to or greater than a predetermined threshold value, and the angle of the bucket is within a predetermined angle range including an angle at which the bottom surface of the bucket is parallel to the work vehicle, and the height of the bucket is within a predetermined height range including the ground contact height of the work vehicle, and the operation of the operating device of the working machine continues for a certain period of time. The work vehicle according to claim 2.

4. The control device determines that the working state is the dump state when the angle of the bucket is inclined by a predetermined angle or more in the dump direction from an angle at which the bottom surface of the bucket is parallel to the work vehicle. The work vehicle according to any one of claims 1 to 3.

5. A method for controlling a work vehicle equipped with a working machine having a boom and a bucket, the method comprising the step of determining whether the working state of the work vehicle is an excavation state in which the bucket excavates a work object or a dump state in which the work object is unloaded from the bucket. During the period from when the determined working state becomes the excavation state until it becomes the dumping state, prohibit the execution of automatic dumping control for automatically driving the bucket to a predetermined dumping angle, and during the period from when the determined working state becomes the dumping state until it becomes the excavation state, permit the execution of the automatic dumping control; When the automatic dumping control is permitted, output a drive command for driving the bucket in the dumping direction until the angle of the bucket reaches the dumping angle; A method comprising the above steps.

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