Work vehicle

Abstract

The present invention prevents a work vehicle capable of automatic excavation from losing balance while traveling on a slope.　Provided is a work vehicle (100) comprising vehicle bodies (100A, 100B), a cargo handling device (102) provided to the vehicle bodies, an inclination sensor (10) for detecting the inclination angle of the vehicle bodies, and a controller (30) for automatically controlling the cargo handling device (102), wherein the controller (30) stops the automatic control of the cargo handling device (102) when the inclination angle of the vehicle bodies detected by the inclination sensor (10) exceeds a prescribed threshold value.

Description

Work vehicle

[0001] The present invention relates to a work vehicle that performs automatic excavation.

[0002] As background art of the present invention, for example, Patent Document 1 describes a work vehicle that detects a lift force received from a boom (lift arm) and a traveling speed, and starts automatic excavation control by a bucket when at least these detection results satisfy a predetermined condition.

[0003] International Publication No. 2015 / 004809

[0004] In the prior art described in Patent Document 1, when a work vehicle is traveling on a road surface with steep slopes or rough undulations, for example, if a bucket comes into contact with the ground, the lift force received from the boom (lift arm) increases, which may cause automatic excavation control to start unexpectedly. Particularly, in a work vehicle traveling on a slope, if automatic excavation control is mistakenly started, there is a risk that the work vehicle will greatly lose its balance.

[0005] A main object of the present invention is to prevent loss of balance during traveling on a slope in a work vehicle capable of automatic excavation.

[0006] In order to achieve the above object, one aspect of the present invention provides a work vehicle comprising: a vehicle body; a cargo handling device provided on the vehicle body; an inclination sensor that detects an inclination angle of the vehicle body; and a controller that automatically controls the cargo handling device, wherein the controller stops the automatic control of the cargo handling device when the inclination angle of the vehicle body detected by the inclination sensor exceeds a predetermined threshold.

[0007] According to the present invention, in a work vehicle capable of automatic excavation, loss of balance during traveling on a slope can be prevented. Problems, configurations and effects other than those described above will be clarified by the following description of embodiments.

[0008] This is a side view of a wheel loader according to an embodiment of the present invention. This is a block diagram showing the internal configuration of the wheel loader. This is a diagram showing an example of the interior of the driver's cab. This is a diagram showing the transition of the control modes of the wheel loader. This is a diagram showing the digging posture of the wheel loader. This is a flowchart showing the control procedure for digging work. This is a flowchart showing the control procedure for digging work according to modified example 1. This is a flowchart showing the control procedure for digging work according to modified example 2.

[0009] Hereinafter, embodiments of the work vehicle according to the present invention will be described using a wheel loader as an example. Figure 1 is a side view of a wheel loader 100 according to an embodiment of the present invention.

[0010] The wheel loader 100 is an articulated work vehicle that is steered by bending its body in the middle near its center. The front frame 100A, which is the front part of the body, and the rear frame 100B, which is the rear part of the body, are connected by a center joint 103 so as to be rotatable in the left-right direction, and the front frame 100A bends in the left-right direction relative to the rear frame 100B.

[0011] The vehicle body is equipped with four wheels 19. Two of the wheels 19 are front wheels 19A, located on the left and right sides of the front frame 100A, and the remaining two wheels 19 are rear wheels 19B, located on the left and right sides of the rear frame 100B. In Figure 1, only the front wheels 19A and rear wheels 19B located on the left side are shown.

[0012] A hydraulically driven front work implement (cargo handling device) 102 is attached to the front of the front frame 100A for excavating work materials such as soil and minerals and loading them onto dump trucks or hoppers.

[0013] The rear frame 100B is provided with a driver's cab 112 where the operator sits, a machine room 113 that houses the equipment necessary for driving the wheel loader 100, and a counterweight 114 that maintains balance with the front work equipment 102 to prevent the vehicle body from tilting. In the rear frame 100B, the driver's cab 112 is located at the front, the counterweight 114 is located at the rear, and the machine room 113 is located between the driver's cab 112 and the counterweight 114.

[0014] The front work implement 102 includes a lift arm 121 mounted on the front frame 100A so as to be rotatable in the vertical direction, a pair of left and right lift arm cylinders 16 which serve as hydraulic cylinders to drive the lift arm 121, a bucket 123 mounted on the tip of the lift arm 121 so as to be rotatable in the vertical direction, a bucket cylinder 17 which serves as a hydraulic cylinder to drive the bucket 123, and a bell crank 125 which is rotatably connected to the lift arm 121 and constitutes a link mechanism between the bucket 123 and the bucket cylinder 17.

[0015] The lift arm 121 rotates upward relative to the front frame 100A as the rods of the pair of lift arm cylinders 16 extend, and rotates downward relative to the front frame 100A as the rods of the pair of lift arm cylinders 16 retract.

[0016] The bucket 123 rotates upward relative to the lift arm 121 and tilts backward toward the front frame 100A (tilt operation) when the rod of the bucket cylinder 17 extends, and rotates downward relative to the lift arm 121 and tilts forward (dump operation) when the rod of the bucket cylinder 17 retracts. As a result, the bucket 123 can scoop up and discharge (dump) the work material such as soil and minerals.

[0017] Furthermore, the bucket 123 can be replaced with various attachments such as blades, and the wheel loader 100 can perform various tasks such as snow removal and soil pushing in addition to cargo handling using the bucket 123.

[0018] This wheel loader 100 can be operated manually by an operator in the cab 112, as well as in an automatic excavation mode (automatic excavation mode) as described later. Alternatively, the wheel loader 100 may be operated remotely by an operator located some distance away.

[0019] Next, the internal configuration of the wheel loader 100 will be described. Figure 2 is a block diagram showing the internal configuration of the wheel loader 100. In Figure 2, solid lines represent lines through which hydraulic fluid flows, and dotted lines represent electrical signal lines.

[0020] As shown in Figure 2, the wheel loader 100 is equipped with a controller 30 that controls the entire vehicle body. The controller 30 is located, for example, in the driver's cab 112. The controller 30 has a configuration in which a CPU, RAM, ROM, HDD, input I / F, and output I / F are connected to each other via a bus. In this hardware configuration, the CPU reads the calculation program (software) stored in a recording medium such as ROM, HDD, or optical disc, expands it onto RAM, and executes the expanded calculation program. The calculation program and hardware work together to realize the functions of the controller 30.

[0021] The controller 30's input interface is electrically connected to the following: work implement lever 1, accelerator pedal 2, parking switch 3, activation switch 4, automatic excavation start switch 5, forward / reverse lever 6, lift cylinder pressure sensor 7, lift arm angle sensor 8, bucket angle sensor 9, tilt sensor 10, brake pressure sensor 13, vehicle speed sensor 21, and steering angle sensor 25. The lift arm angle sensor 8 and bucket angle sensor 9 are examples of attitude sensors that detect the posture of the front work implement 102.

[0022] An example of an operating device is the work equipment lever 1, which is a component for operating the front work equipment 102, and is composed of, for example, an arm operating lever and a bucket operating lever. The accelerator pedal 2 adjusts the rotational speed of the engine 15 according to the amount it is pressed. The parking switch 3 activates and deactivates the parking brake device (not shown). The parking brake device brakes the propeller shaft when the parking switch 3 is operated.

[0023] The activation switch 4 is a switch for activating the automatic excavation mode, which will be described later. The automatic excavation start switch 5 is a switch for starting the automatic excavation mode. The forward / reverse lever 6, which is an example of a forward / reverse switching device, is a component for switching the wheel loader 100 to forward (F), neutral (N), or reverse (R). When the forward / reverse lever 6 is in the neutral position, the wheel loader 100 is stopped.

[0024] The lift cylinder pressure sensor 7 detects the bottom pressure of the lift arm cylinder 16. The lift arm angle sensor 8 detects the angle of the lift arm 121. The bucket angle sensor 9 detects the angle of the bucket cylinder 17. The brake pressure sensor 13 detects the pressure of the hydraulic fluid supplied to the brake 20.

[0025] The vehicle speed sensor 21 detects the rotational speed of the propeller shaft. The vehicle speed of the wheel loader 100 is calculated from the rotational speed of the propeller shaft. The steering angle sensor 25 detects the steering angle of the steering wheel 28. The steering angle sensor 25 is installed, for example, on the column of the steering wheel 28 and detects the rotational angle of the column. The tilt sensor 10 is, for example, a gyro sensor and detects the tilt angle of the wheel loader 100's body.

[0026] The output interface of the controller 30 is electrically connected to the engine 15, the electromagnetic proportional valve 24, the display device 26, and the alarm device 27.

[0027] The driving force from the engine 15 mounted on the wheel loader 100 is reduced by the transmission 14 and transmitted to the front and rear axles 18 via a propeller shaft (not shown). The driving force transmitted to the axles 18 is then transmitted to the left and right wheels 19 (19A, 19B), which are the running gear, via a differential and final reduction gear (not shown) within the axles 18, causing the wheel loader 100 to move.

[0028] The wheel loader 100 also includes a hydraulic pump 22 for supplying hydraulic fluid and a storage facility for the hydraulic fluid (not shown). The hydraulic pump 22 is driven by the engine 15, and the hydraulic fluid supplied from the hydraulic pump 22 operates the front work implement 102 (lift arm cylinder 16, bucket cylinder 17).

[0029] When the work equipment lever 1 (arm operation lever, bucket operation lever) is operated, the electromagnetic proportional valve 24 is activated and pilot pressure is introduced into the pressure receiving section of the control valve 23. The control valve 23 controls the flow rate and direction of the hydraulic fluid supplied from the hydraulic pump 22 to the lift arm cylinder 16 and the bucket cylinder 17.

[0030] When pilot pressure is introduced into the control valve 23, the spool is switched to a predetermined position. This change in spool position reverses the flow direction of the hydraulic fluid supplied from the hydraulic pump 22. As a result, the lift arm cylinder 16 and the bucket cylinder 17 extend and retract in response to the operator's instructions.

[0031] Note that the electromagnetic proportional valve 24 and the control valve 23 are provided in correspondence with the lift arm cylinder 16 and the bucket cylinder 17, respectively, but their details are omitted in Figure 2.

[0032] Furthermore, the wheel loader 100 brakes the wheels 19 with a brake 20. The brake 20 is, for example, a wet disc brake. The brake 20 is housed in the case of the axle 18. When hydraulic fluid is supplied to the brake 20 via the brake valve 12, the brake 20 generates a braking force corresponding to the pressure of the hydraulic fluid. The wheel loader 100 is equipped with a hydraulic source (not shown) that supplies hydraulic fluid to the brake 20. The hydraulic source is a pressure source with a pressure lower than the discharge pressure of the hydraulic pump 22, and is, for example, composed of an accumulator that stores hydraulic fluid that has been depressurized from the hydraulic pump 22.

[0033] The brake valve 12 is a pressure reducing valve that reduces the hydraulic fluid supplied from the hydraulic source to a pressure corresponding to the compression force of the spring. When the operator presses down the brake pedal 11, the brake valve 12 reduces the pressure of the hydraulic fluid supplied from the hydraulic source to a pressure corresponding to the pressing force (amount of pressing) of the brake pedal 11. The brake valve 12 reduces the pressure of the hydraulic fluid so that the higher the compression force of the spring, that is, the greater the pressing force of the brake pedal 11, the higher the pressure of the hydraulic fluid supplied to the brake 20.

[0034] Next, the internal configuration of the driver's cab 112 will be described. Figure 3 shows an example of the interior of the driver's cab 112.

[0035] As shown in Figure 3, the driver's cab 112 is equipped with a work equipment lever 1, a steering wheel 28 for steering operations, an accelerator pedal 2, a brake pedal 11, a parking switch 3, an activation switch 4, an automatic excavation start switch 5, a forward / reverse lever 6, a display device 26, and an alarm device 27.

[0036] The steering wheel 28 is used to steer the wheel loader 100. The display device 26 displays the travel speed of the wheel loader 100 detected by the vehicle speed sensor 21. The display device 26 also displays the current control mode. Specifically, it displays whether the system is in normal excavation mode 51, automatic excavation mode 52, or automatic excavation mode interrupted 53 (see Figure 4). The alarm device 27 sounds an alarm when automatic excavation is stopped. The display device 26 is, for example, a liquid crystal panel, and the alarm device 27 is, for example, a speaker.

[0037] Next, the control modes of the wheel loader 100 will be described. Figure 4 is a diagram showing the transitions between the control modes of the wheel loader 100. As shown in Figure 4, the controller 30 switches the control mode of the wheel loader 100 between normal excavation mode 51, automatic excavation mode 52, and automatic excavation mode interrupted 53.

[0038] The normal drilling mode 51 is a control mode that allows manual drilling by the operator. In normal drilling mode 51, the operator can perform drilling work with the front work implement 102 by operating the work implement lever 1. In other words, in normal drilling mode 51, automatic drilling is disabled. On the other hand, the automatic drilling mode 52 is a control mode that allows automatic drilling work with the front work implement 102. Switching between normal drilling mode 51 and automatic drilling mode 52 is done by turning the activation switch 4 on or off.

[0039] In the normal drilling mode 51, when the activation switch 4 is turned on, the controller 30 switches the control mode to the automatic drilling mode 52. In this embodiment, in order to avoid unexpected situations, the activation switch 4 is only accepted when the forward / reverse lever 6 is in the neutral position. Of course, it is also possible to configure the system to accept operation of the activation switch 4 regardless of the position of the forward / reverse lever 6.

[0040] In the automatic excavation mode 52, the control state first enters automatic excavation start determination 52A. The automatic excavation start determination 52A is a state of waiting until the start condition for automatic excavation (described later) is satisfied. In this state, when the automatic excavation start switch 5 is pressed and the start condition is satisfied during the automatic excavation start determination 52A, the controller 30 triggered by this event shifts the control state to automatic excavation control 52B, and executes automatic excavation by the front working implement 102.

[0041] Furthermore, when an end condition for automatic excavation (described later) is satisfied during automatic excavation control 52B, the controller 30 triggered by this event ends the automatic excavation performed by the front working implement 102, and shifts the control state back to automatic excavation start determination 52A.

[0042] Furthermore, when an interruption condition for automatic excavation (described later) is satisfied during automatic excavation control 52B, the controller 30 triggered by this event interrupts the automatic excavation performed by the front working implement 102, and shifts the control state to automatic excavation mode suspension 53.

[0043] Then, when a restoration condition for automatic excavation (described later) is satisfied during automatic excavation mode suspension 53, the controller 30 triggered by this event shifts the control state to automatic excavation start determination 52A, and waits for automatic excavation until the start condition for automatic excavation is satisfied.

[0044] Here, the start condition, interruption condition, restoration condition, and end condition are as follows.

[0045] Start condition: All the following conditions are satisfied. (11) The vehicle speed of the wheel loader 100 detected by the vehicle speed sensor 21 is equal to or lower than a predetermined speed. (12) A bucket angle detected by the bucket angle sensor 9 is within a predetermined angle range, and a bucket height calculated from the lift arm angle sensor 8 is equal to or lower than a predetermined height position. That is, the bucket 123 is in an excavation posture (see excavation postures 1 and 2 in FIG. 5). (13) An inclination angle of the wheel loader 100 detected by the inclination sensor 10 is equal to or smaller than a predetermined threshold. (14) The working implement lever 1 is in neutral. That is, the working implement lever 1 is not operated. (15) The forward / backward lever 6 is set to forward (F).

[0046] Interruption condition: At least one of the following conditions is satisfied. (21) The inclination angle of the wheel loader 100 detected by the inclination sensor 10 exceeds a predetermined threshold. (22) The work implement lever 1 exceeds the neutral range. That is, the work implement lever 1 has been operated. (23) The brake pressure detected by the brake pressure sensor 13 is equal to or higher than a predetermined pressure. That is, a braking operation has been performed. (24) The forward / reverse lever 6 is in neutral (N) or reverse (R).

[0047] Reset condition: (31) The automatic excavation start switch 5 is pressed.

[0048] Termination condition: At least one of the following conditions is satisfied. (41) The enabling switch 4 is off. (42) The bucket 123 is not in an excavation posture.

[0049] Next, control of automatic excavation by the controller 30 will be described. FIG. 6 is a flowchart showing a control procedure of excavation work by the controller 30.

[0050] The controller 30 starts the processing shown in FIG. 6 when, for example, a key switch of the engine 15 is turned on. When the processing is started, in step S10, the controller 30 determines whether or not the automatic excavation function is enabled (whether or not the enabling switch 4 is turned on). If the automatic excavation function is enabled (S10 / YES), the controller 30 proceeds to step S20 and determines whether or not the automatic excavation start switch 5 has been pressed. If the automatic excavation start switch 5 has been pressed (S20 / YES), the controller 30 changes the control mode from a normal excavation mode 51 to an automatic excavation mode 52 (see FIG. 4). Then, the controller 30 proceeds to step S30 and determines whether or not a start condition is satisfied (52A during automatic excavation start determination / FIG. 4).

[0051] On the other hand, if the automatic excavation function is not enabled (S10 / NO), the controller 30 waits in step S10 until the automatic excavation function becomes enabled. Also, if the automatic excavation start switch 5 has not been pressed (S20 / NO), the controller 30 waits in step S20 until the automatic excavation start switch 5 is pressed.

[0052] In step S30, if the start condition is met (S30 / YES), the controller 30 proceeds to step S40 and performs automatic excavation (automatic excavation control in progress 52B / Figure 4). The controller 30 then drives the lift arm cylinder 16 and the bucket cylinder 17 to automatically perform a series of operations to raise the bucket 123 from a horizontal position along the ground by raising the lift arm 121 and moving the bucket 123 to a predetermined height. At this time, the controller 30 displays on the display device 26 that automatic excavation control is in progress. On the other hand, if the start condition is not met (S30 / NO), the controller waits in step S30 until the disclosure condition is met.

[0053] Next, the controller 30 proceeds to step S50 to determine whether the conditions for interrupting automatic drilling are met. If the conditions for interruption are not met (S50 / NO), the controller 30 proceeds to step S60 to determine whether the conditions for termination are met. If the conditions for termination are met (S60 / YES), the controller 30 displays a message on the display device 26 indicating that automatic drilling has ended and terminates the process. On the other hand, if the conditions for termination are not met (S60 / NO), the process returns to step S40.

[0054] Furthermore, if the interruption condition is met in step S50 (S50 / YES), the controller 30 proceeds to step S70 and interrupts automatic drilling (automatic drilling mode interrupted in step S53 / Figure 4). The controller 30 then displays on the display device 26 that automatic drilling is interrupted and also emits an alarm via the alarm device 27 indicating that automatic drilling is interrupted. Then, it returns to step S20.

[0055] Therefore, if the controller 30 interrupts (cancels) automatic excavation, it will not resume automatic excavation until the vehicle's tilt is below a threshold and a switch operation is performed.

[0056] As described above, this embodiment can achieve the following effects.

[0057] In this embodiment, the wheel loader 100 uses the tilt angle of the vehicle body detected by the tilt sensor 10 as the start condition for automatic excavation, so that automatic excavation can only be performed when the vehicle body is in a stable position. Furthermore, if the tilt angle of the vehicle body exceeds a threshold, automatic excavation is interrupted, so that the front work implement 102 does not automatically start excavating while the wheel loader 100 is traveling on a slope or the like. This prevents the wheel loader 100 from losing balance while traveling on a slope.

[0058] Furthermore, the display device 26 shows that automatic drilling is in progress, making it user-friendly for the operator. In addition, if automatic drilling is interrupted (Figure 6 / S70), automatic drilling will not resume unless the operator presses the automatic drilling start switch 5, thus ensuring the reliability of the automatic drilling operation. In other words, it prevents drilling operations that the operator did not intend.

[0059] Furthermore, since the system is configured to automatically excavate when the height of the bucket 123 is below a predetermined height, automatic excavation is possible without the bucket 123 touching the ground. Also, by not allowing automatic excavation when the height of the bucket 123 exceeds a predetermined height, it is possible to prevent automatic excavation from being performed with the bucket 123 in an unsuitable position for automatic excavation. In other words, it is possible to avoid automatic excavation being performed when the bucket 123 is not in an excavation position.

[0060] Furthermore, by making it a condition for automatic excavation that the angle of the bucket 123 be within a predetermined angle, it is possible to prevent automatic excavation from being performed while the bucket 123 is tilted too much. In other words, it is possible to avoid automatic excavation being performed when the bucket 123 is not in the correct excavation position.

[0061] (Modification 1) Next, the processing procedure of the controller 30 according to Modification 1 will be described. Figure 7 is a flowchart showing the control procedure for excavation work according to Modification 1. Modification 1 is characterized in that the determination criterion for the start condition of automatic excavation, "(14) The work machine lever 1 is in the neutral position," has been relaxed.

[0062] To explain in more detail, if the automatic drilling start switch 5 is pressed in step S20, the controller 30 proceeds to step S21 and increases the dead zone range of the work implement lever 1. As a result, even if the work implement lever 1 moves slightly from the neutral position, no command is output from the work implement lever 1. Then, if automatic drilling is interrupted (S70), the controller 30 performs a process (S71) to return the dead zone range of the work implement lever 1 to its initial state, and then returns to step S20.

[0063] According to this modified example 1, when the automatic excavation start switch 5 is pressed, automatic excavation can be performed even if the operator does not return the work equipment lever 1 precisely to the neutral position, thus improving work efficiency. To explain in more detail, when starting automatic excavation, the operator may be gripping the work equipment lever 1. Since the wheel loader 100 vibrates during operation, this vibration may cause the work equipment lever 1, which the operator is gripping, to move from the neutral position to the operating position. In that case, the conditions for starting automatic excavation are not met, and automatic excavation will not be performed. To avoid this situation, modified example 1 is designed to increase the dead zone range of the work equipment lever 1 so that even if the work equipment lever 1 moves slightly, the situation in which automatic excavation does not fail to start is prevented.

[0064] (Modification 2) Next, the processing procedure of the controller 30 according to Modification 2 will be described. Figure 8 is a flowchart showing the control procedure for excavation work according to Modification 2. Modification 2 is characterized in that the start condition for automatic excavation, "(13) The inclination angle of the wheel loader 100 detected by the inclination sensor 10 is below a predetermined threshold," and the interruption condition, "(21) The inclination angle of the wheel loader 100 detected by the inclination sensor 10 exceeds a predetermined threshold," are changed according to the steering angle of the wheel loader 100.

[0065] Specifically, the larger the steering angle of the steering wheel 28 detected by the steering angle sensor 25, the smaller the predetermined threshold value is set. More specifically, in step S22, the controller 30 sets the threshold to, for example, the initial value of 20 degrees if the steering angle is small, and sets the threshold to an angle smaller than the initial value, for example, 10 degrees, if the steering angle is large. After automatic excavation is interrupted (S70), the controller 30 returns the threshold to its initial value (S72).

[0066] By doing this, if the wheel loader 100 is steered significantly to the left or right, the threshold is set to, for example, 10 degrees. Therefore, when the wheel loader 100 is steered significantly and traveling on a steep slope, automatic excavation is stopped, which further prevents the wheel loader 100 from losing balance while traveling on a slope.

[0067] The embodiments described above are illustrative for explaining the present invention and are not intended to limit the scope of the present invention to those embodiments only. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the invention.

[0068] For example, in the above embodiment, it was assumed that all of the start conditions (11) to (15) are met, but the fulfillment of any one or more combinations of the conditions may also be considered as fulfillment of the start conditions. Also, for the interruption conditions (21) to (24) and the termination conditions (41) to (42), it was assumed that any of the conditions are met, but it may also be assumed that all of the conditions are met. Furthermore, for the return condition (31), it was assumed that the automatic drilling start switch 5 is pressed, but the function of the automatic drilling start switch may also be combined with that of other switches or levers.

[0069] Furthermore, the present invention is not limited to wheel loaders. The present invention can be applied to any self-propelled work vehicle. For example, it may be applied to hydraulic excavators, forklifts, and the like.

[0070] 4 Activation switch 5 Automatic excavation start switch 10 Tilt sensor 19 Wheel 25 Steering angle sensor 26 Display device 27 Alarm device 28 Handle 30 Controller 100 Wheel loader (work vehicle) 100A Front frame (body) 100B Rear frame (body) 102 Front work implement (cargo handling equipment) 121 Lift arm 123 Bucket

Claims

1. A work vehicle comprising a vehicle body, a cargo handling device provided on the vehicle body, a tilt sensor for detecting the tilt angle of the vehicle body, and a controller for automatically controlling the cargo handling device, wherein the controller discontinues automatic control of the cargo handling device if the tilt angle of the vehicle body detected by the tilt sensor exceeds a predetermined threshold.

2. A work vehicle according to claim 1, characterized in that it is equipped with a display device that displays the control status of the cargo handling device.

3. A work vehicle according to claim 1, wherein the cargo handling device includes a bucket and a lift arm for raising and lowering the bucket, and the controller controls the cargo handling device to automatically perform the operation of raising the lift arm from a horizontal position along the ground to move the bucket to a predetermined height.

4. A work vehicle according to claim 1, comprising: wheels provided on the vehicle body; a handle for steering the wheels; and a steering angle sensor for detecting the steering angle of the handle, wherein the controller changes the setting of the predetermined threshold such that the predetermined threshold decreases as the steering angle increases.

5. A work vehicle according to claim 3, further comprising: a work lever for operating the cargo handling device; a forward / reverse lever for indicating the direction of travel of the vehicle body; and a vehicle speed sensor for detecting the vehicle speed of the work vehicle, wherein the start condition for the automatic control is that all of the following conditions are met: the vehicle speed is below a predetermined speed threshold; the bucket is in an digging position; the inclination angle of the vehicle body is below the predetermined threshold; the work lever is in an unoperated state; and the direction of travel of the vehicle body is indicated to be forward by the forward / reverse lever.

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