Work vehicle

Abstract

A work machine (100) according to the present invention has a function of: performing an automatic excavation operation of automatically moving a front work device (120), which can also be moved by operating a loading / unloading operation lever; and stopping the automatic excavation operation when a deviation from a neutral determination range is detected as a result of the loading / unloading operation lever being operated. During the automatic excavation operation, the neutral determination range for the loading / unloading operation lever is extended in comparison to when normal operation is performed, thereby preventing the automatic excavation operation from being stopped against the operator's intentions due to vehicle body vibrations or the like causing the loading / unloading operation lever to deviate from the neutral determination range.

Description

Working vehicle

[0001] The present invention relates to, for example, a working vehicle that performs excavation work.

[0002] Patent Document 1 is known as a method for automating excavation by a working vehicle. In Patent Document 1, if the neutral state of the cargo handling operation lever is not maintained for a predetermined period of time during automatic excavation operation of the working vehicle, it is considered that the operator has operated the cargo handling operation lever, and the automatic excavation operation is stopped.

[0003] International Publication No. 2015 / 004809

[0004] An operator holds the cargo handling operation lever during normal manual operation, and is considered to release their hand from the cargo handling operation lever during automatic excavation operation. In the technology described in Patent Document 1, when the operator releases their hand from the cargo handling operation lever during automatic excavation operation, if vehicle body vibration caused by road surface conditions or the like is transmitted to the cargo handling operation lever, the cargo handling operation lever vibrates and deviates from the neutral determination range, which may unintentionally stop the automatic excavation operation.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a working vehicle capable of suppressing the stop of automatic excavation operation caused by vibration during automatic excavation operation.

[0006] A working vehicle of the present invention that solves the above problems comprises: a front working device capable of excavating an object to be excavated; a cargo handling operation lever for operating the front working device; and a control device that executes automatic excavation control for causing the front working device to perform automatic excavation operation on the condition that the cargo handling operation lever is positioned within a neutral determination range, wherein the control device stops the automatic excavation control when the cargo handling operation lever deviates from the neutral determination range during execution of the automatic excavation control, and the control device changes the neutral determination range during execution of the automatic excavation control.

[0007] According to the working vehicle of the present invention, it is possible to provide a working vehicle capable of suppressing the stop of automatic excavation operation caused by vibration of the cargo handling operation lever during automatic excavation operation.

[0008] A side view showing one embodiment of the work vehicle relating to this disclosure. A diagram showing the attitude state of the work vehicle relating to this disclosure at the end of automatic excavation operation. A functional block diagram of the control device mounted on the work vehicle relating to this disclosure. A flowchart explaining the control processing of the work vehicle relating to this disclosure. A diagram explaining the neutral determination range of the cargo handling operation lever in the work vehicle relating to this disclosure.

[0009] Hereinafter, an embodiment of the work vehicle relating to this disclosure will be described with reference to the drawings.

[0010] Figure 1 is a side view showing one embodiment of the work vehicle according to the present disclosure, Figure 2 is a diagram showing the attitude state of the work vehicle according to the present disclosure at the end of automatic excavation operation, and Figure 3 is a functional block diagram of the control device mounted on the work vehicle according to the present disclosure.

[0011] The work vehicle 100 in this embodiment is, for example, a wheel loader used to excavate excavation targets Od such as crushed stone, soil, or ore accumulated on the ground surface and load them onto the cargo bed of a transport vehicle such as a dump truck. However, the work vehicle 100 is not limited to a wheel loader and may be other work vehicles or machinery such as a bulldozer or a loading shovel.

[0012] The work vehicle 100 has a body 111 having, for example, a front frame and a rear frame that are pin-connected to each other. The front frame and rear frame of the body 111 are each provided with left and right wheels 112 as a movement mechanism that enables forward and backward movement.

[0013] The rear frame of the vehicle body 111 houses a hydraulic system 130 including a hydraulic pump and electromagnetic proportional valves, a control device 150, as well as an engine, transmission, and fuel tank (not shown). The wheels 112 of the rear frame are, for example, connected to the engine via a transmission and are driven by the engine's rotation via the transmission to propel the work vehicle 100.

[0014] Furthermore, a cabin 113 is provided on the rear frame of the vehicle body 111. Inside the cabin 113, for example, there is a seat for the operator, as well as a brake pedal, an accelerator pedal, a cargo handling lever, a display device 333 with a speaker and screen monitor, multiple switches, instruments, and so on.

[0015] The work vehicle 100 of this embodiment includes, for example, a start switch 326 inside the cabin 113 that instructs the start of automatic excavation control by the control device 150, and an enable switch 327 for activating the automatic excavation control. The start switch 326 and the enable switch 327 are switches operated by an operator, and may be physical switches or touch-operable switch images displayed on a touch panel screen monitor.

[0016] Furthermore, the front frame of the vehicle body 111 is equipped with a front working device 120 capable of excavating the target material Od. The front working device 120 includes, for example, a pair of left and right lift arms 121 whose base ends are attached to the front frame, a bucket 122 attached to the tip of the lift arms 121, a bell crank 123, and a bucket link 124.

[0017] The front work device 120 also includes a lift cylinder 131 for driving the lift arm 121 and a bucket cylinder 132 for driving the bucket 122. The lift cylinder 131 and bucket cylinder 132 are composed of hydraulic cylinders and are driven by hydraulic pressure supplied from the hydraulic system 130. The hydraulic system 130 is mounted, for example, on the rear frame of the vehicle body 111 and includes a hydraulic pump driven by the engine and an electromagnetic proportional valve 332.

[0018] As shown in Figure 1, for example, the tip of the piston rod of the lift cylinder 131 is connected to the lower end of the middle section of the lift arm 121, and the base end of the cylinder tube opposite the piston rod is connected to the front frame of the vehicle body 111. Although not shown in the figures, the work vehicle 100 is equipped with a pair of left and right lift cylinders 131 on both sides in the width direction of the vehicle body 111.

[0019] When the lift cylinder 131 extends, it rotates the lift arm 121 upward around the pivot axis attached to the vehicle body 111. This increases the lift amount of the lift arm 121, allowing the bucket 122 at the tip of the lift arm 121 to be lifted. When the lift cylinder 131 retracts, it rotates the lift arm 121 downward around the pivot axis attached to the vehicle body 111. This decreases the lift amount of the lift arm 121, allowing the bucket 122 attached to the tip of the lift arm 121 to be lowered.

[0020] The bucket cylinder 132 is positioned, for example, between a pair of lift arms 121, as shown in Figures 1 and 2. The bucket cylinder 132 is connected to the bucket 122, for example, at the tip of a piston rod via a bell crank 123 and a bucket link 124, and the base end of the cylinder tube opposite the piston rod is connected to the vehicle body 111. The bell crank 123 is supported, for example, at a connecting part that connects the central parts of a pair of left and right lift arms 121.

[0021] When the bucket cylinder 132 extends, it rotates the bucket 122 upward around a pivot point attached to the tip of the lift arm 121 via the bell crank 123 and bucket link 124. This increases the tilt amount of the bucket 122, causing the opening of the bucket 122 to face upward, allowing the bucket 122 to scoop up the excavated material Od.

[0022] Furthermore, when the bucket cylinder 132 retracts, it rotates the bucket 122 downward around a pivot point attached to the lift arm 121 via the bell crank 123 and bucket link 124. This reduces the tilt of the bucket 122, causing the bucket opening to face downwards, and allowing the excavated material Od scooped up by the bucket 122 to be dumped outwards.

[0023] The control device 150 is a computer system mounted on the vehicle body 111, including firmware and a microcontroller, and performs automatic excavation control (see Figure 4) to drive the bucket 122 and lift arm 121 to automatically excavate the target material Od. The control device 150 includes, for example, a computing device such as a central processing unit (CPU) (not shown), a storage device such as RAM and ROM, a program stored in the storage device, a timer, and an input / output device.

[0024] The control device 150 includes, for example, an input unit 311, a processing unit 312, and an output unit 313, as shown in Figure 3. Each of these parts of the control device 150 is a functional block representing a function of the control device 150, which is realized, for example, by executing a program stored in the storage device of the control device 150 using the arithmetic unit of the control device 150.

[0025] The input unit 311 of the control device 150 receives signals output from the following: a forward / reverse switching device 321 that switches the direction of travel of the work vehicle 100 forward and backward; a vehicle speed sensor 322 that detects the travel speed of the work vehicle 100; a cargo handling angle sensor 323 that detects the operating angle of the bucket 122; a vehicle tilt sensor 324 that detects the tilt angle of the work vehicle 100 with respect to the vertical; a cargo handling lever operating angle sensor 325 that detects the operating angle θ of the cargo handling lever; a start switch 326 that instructs the start of automatic excavation control; and an enable switch 327 that enables automatic excavation control. The input unit 311 outputs the signals received from these sensors and switches to the processing unit 312.

[0026] The processing unit 312 controls normal operation and automatic excavation based on the signal information input to the input unit 311. The processing unit 312 executes automatic excavation control, which causes the front work device 120 to automatically excavate, provided that the cargo handling lever is within the neutral determination range. If the cargo handling lever moves out of the neutral determination range due to operator operation or vehicle vibration while automatic excavation control is being executed (during automatic excavation operation), the processing unit 312 stops the automatic excavation control. While automatic excavation control is being executed, the processing unit 312 changes the neutral determination range to make it wider than normal.

[0027] The output unit 313 outputs the processing result signal from the processing unit 312 to the alarm device 331, the electromagnetic proportional valve 332, and the display device 333. The alarm device 331 notifies the operator that the cargo handling lever has moved out of the neutral determination range during automatic excavation and that the automatic excavation operation has stopped. The electromagnetic proportional valve 332 supplies hydraulic pressure from the hydraulic pump to the lift cylinder 131 and the bucket cylinder 132 in accordance with the control signal from the control device 150. The display device 333 displays information such as the ON / OFF status of the activation switch 327 and the start switch 326, and whether or not automatic excavation operation is in progress.

[0028] Next, the control process by the control device 150 will be explained using Figure 4. The control device 150 determines whether or not the automatic excavation function is enabled (S401). If the activation switch 327 is ON and in the enabled state, it is determined that the automatic excavation function is enabled, that is, that the front work device 120 can be operated for automatic excavation. Then, it determines whether or not the start switch 326 is ON (S402). If the start switch 326 is ON, a process is performed to widen the neutral determination range of the cargo handling operation lever (S403). In the process of S403, the setting of the neutral determination range of the cargo handling operation lever is changed from the neutral determination range θn during normal operation to the wider neutral determination range θa during automatic excavation operation.

[0029] In S403, when the process of widening the neutral determination range of the cargo handling lever is performed, it is determined whether the state of the work vehicle 100 body satisfies the pre-set excavation determination conditions (S404). The excavation determination conditions include, for example, whether the state of the body is in a state where excavation work can be started, such as the body tilt angle being below a threshold, the bucket angle being horizontal to the ground and the bucket being near the ground, the direction of travel being forward, the brakes not being applied, and the vehicle speed being below a threshold.

[0030] If it is determined in S404 that the excavation determination conditions are met, the automatic excavation control of the processing unit 312 is executed, and the automatic excavation operation of the front work device 120 is started (S405). In the automatic excavation operation of the front work device 120, the bucket 122 is inserted into the excavation target Od by moving the vehicle body 111 forward, and the bucket is tilted and the lift arm 121 is raised to scoop up the excavation target Od, and the operation is performed until it is lifted to a height position, for example, as shown in Figure 2.

[0031] During automatic excavation operation, it is determined whether or not a stop operation has been performed to stop the automatic excavation operation (S406). A stop operation in S406 includes intervention operations on the excavation operation by the operator, such as input to the cargo handling operation lever (lever operation exceeding the neutral determination range which is wider than during normal operation in S403), pressing the brake pedal, and setting the direction of travel to something other than forward. Furthermore, if the vehicle tilt sensor 324 detects that the vehicle tilt angle exceeds a threshold, it is also determined that a stop operation has been performed.

[0032] If it is determined in S406 that a stop operation has been performed (Yes in S406), the process of stopping the automatic excavation operation is performed (S407). When the automatic excavation operation is stopped, the neutral determination range setting of the cargo handling operation lever is returned from the neutral determination range θa during automatic excavation operation to the narrower neutral determination range θn, which is the value used during normal operation (S408).

[0033] If it is determined in S406 that no stop operation has been performed (No in S406), it is determined whether the automatic excavation operation has ended (S409). If the automatic excavation operation has not ended, the process returns to S405; if the automatic excavation operation has ended, this flow ends. The conditions for determining whether the automatic excavation operation has ended can be whether the state of the vehicle body, including the arm angle and bucket angle being above a threshold, is in the state of excavation completion (see Figure 2). For example, if the front work device 120, as shown in Figure 2, is in the pre-set excavation completion posture, it is determined that the automatic excavation operation has ended.

[0034] Figure 5 illustrates the neutral position determination range of the cargo handling lever. Figure 5(1) shows an example of the neutral position determination range during automatic excavation operation, and Figure 5(2) shows an example of the neutral position determination range during normal operation. The cargo handling lever 501 is operated by tilting it forward or backward from a state in which it is held in the neutral position C. The cargo handling lever 501 is held in the neutral position C with a predetermined holding force and has a structure that allows the operator to tilt it forward or backward against the holding force. In this embodiment, the case in which the cargo handling lever 501 moves to tilt in two directions, forward and backward, is described as an example, but it is not limited to this, and can also be applied to a configuration that moves to tilt in four directions, for example, forward, backward, left and right.

[0035] The operating angle θ, which is the inclination of the cargo handling lever 501 from the neutral position C, is detected by the cargo handling lever operating angle sensor 325. The neutral determination ranges θa and θn shown in Figures 5(1) and (2) are the ranges in which the cargo handling lever 501 is judged to be in the neutral position (neutral state), and are set to include the neutral position C, respectively. The neutral determination ranges θa and θn are set so that the neutral determination range θa during automatic excavation control is wider and larger than the neutral determination range θn during normal operation (θa > θn).

[0036] During normal operation, as shown in Figure 5(2), the control device 150 determines that the cargo handling lever 501 is in a neutral state until the operating angle θ of the cargo handling lever 501 exceeds the neutral determination range θn, and does not operate the front work device 120. When the operating angle θ of the cargo handling lever 501 exceeds the neutral determination range θn, the control device 150 determines that the cargo handling lever 501 is not in a neutral state, that is, that the cargo handling lever 501 has been operated by the operator, and controls the operation of the front work device 120 according to the tilt angle of the cargo handling lever 501.

[0037] Then, during automatic excavation operation, the control device 150 determines that the cargo handling lever 501 is in a neutral state and continues the automatic excavation operation until the operating angle θ of the cargo handling lever 501 exceeds the neutral determination range θa, as shown in Figure 5(1). When the operating angle θ of the cargo handling lever 501 exceeds the neutral determination range θa, the control device 150 determines that the cargo handling lever 501 is not in a neutral state and determines that a stop operation has been performed to stop the automatic excavation operation. Then, a process to stop the automatic excavation control is performed, and the automatic excavation operation of the front work device 120 is stopped.

[0038] According to the work vehicle 100 described above, during automatic excavation operation, the neutral determination range is changed to be wider than during normal operation. Therefore, even if the cargo handling lever 501 vibrates, it is less likely to deviate from the neutral determination range θa, preventing the automatic excavation operation from stopping unintentionally. Furthermore, during normal operation, the neutral determination range θn is set to be narrower than the neutral determination range θa during automatic excavation operation, allowing the work vehicle 100 to perform quick movements that follow the operator's lever operation.

[0039] In particular, wheel loaders, unlike excavators which perform excavation while the vehicle is stationary, perform excavation while the vehicle is moving, so relatively large vehicle vibrations occur during excavation, making the load handling control lever prone to vibration. For example, if the neutral range of the load handling control lever is set wider than the vibration range to prevent unintended stopping of automatic excavation due to vibration of the load handling control lever, the time until operation stops by lever operation becomes longer during automatic excavation, and a large movement of the load handling control lever is required during normal operation, resulting in poor responsiveness of the excavation operation and reduced operability of the front work device. To address these issues, the work vehicle 100 of this embodiment changes the neutral judgment range during the execution of automatic excavation control, widening the neutral judgment range compared to normal operation. Therefore, even if the load handling control lever 501 vibrates due to vehicle vibration, it is less likely to be judged as a stop operation, and the automatic excavation operation can be prevented from being unintended.

[0040] 100...Work vehicle, 111...Vehicle body, 120...Front work device, 121...Lift arm, 122...Bucket, 326...Start switch, 327...Activation switch, 331...Warning device, 332...Solenoid proportional valve, 333...Display device, 501...Cargo handling operation lever, 150...Control device, θa, θn...Neutral determination range, Od...Excavation target

Claims

1. A work vehicle comprising: a front working device capable of excavating an object to be excavated; a cargo handling operation lever for operating the front working device; and a control device that performs automatic excavation control to cause the front working device to automatically excavate, provided that the cargo handling operation lever is located within a neutral determination range, wherein the control device stops the automatic excavation control if the cargo handling operation lever moves out of the neutral determination range while the automatic excavation control is being performed, and the control device changes the neutral determination range while the automatic excavation control is being performed.

2. The work vehicle according to claim 1, characterized in that the control device widens the neutral determination range while the automatic excavation control is being executed.

3. The work vehicle according to claim 2, further comprising an enable switch for enabling the automatic excavation control and a start switch for instructing the start of the automatic excavation control, wherein the control device executes the automatic excavation control when the automatic excavation control is enabled by operation of the enable switch and the start of the automatic excavation control is instructed by operation of the start switch.

4. The work vehicle according to claim 2, characterized in that the control device returns the neutral determination range when the automatic excavation control is stopped.

5. The work vehicle according to claim 4, further comprising an alarm device that notifies the operator that the automatic excavation control has stopped because the cargo handling lever has moved out of the neutral determination range during the execution of the automatic excavation control.

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