Work machinery

Abstract

To provide a work machine that prevents contact between a bucket and a dump truck etc. while reducing the operational load on an operator during earth dumping work.SOLUTION: A work machine comprises: a vehicle body; an arm supported by the vehicle body and rotatable in the vertical direction; a bucket supported by the arm and performing tilting and dumping operations; an arm actuator vertically rotating the arm; a bucket actuator making the bucket perform the tilting and dumping operations; and a control device that controls the arm actuator and the bucket actuator. The control device determines whether the working machine is in a soil-releasing state in which soil is to be dumped or in a non-soil-releasing state in which soil is not to be dumped, based on a bucket operation signal making the bucket perform the tilting and dumping operations. When it is determined that the work machine is in the soil-releasing state, the arm actuator is controlled to rotate the arm upward.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a work machine such as a wheel loader equipped with a work implement such as a bucket. [Background technology]

[0002] Wheel loaders have been known as work machines used to load earth, sand, crushed stone, and the like onto dump trucks. To perform an earth dumping operation without the bucket coming into contact with the vessel of the dump truck and minimizing impact on the dump truck, an operator must simultaneously move the vehicle forward, raise the arm, and rotate the bucket. To reduce the operator's operational burden during earth dumping, for example, Patent Document 1 describes a control system for controlling the hydraulic cylinder of a wheel loader so that the arm (boom) rises in parallel with at least a portion of the bucket's dumping motion during earth dumping (discharging). The control system described in Patent Document 1 discloses control for raising the arm in parallel with the bucket's dumping motion when the bucket's attitude satisfies a predetermined condition, i.e., when the bucket angle is equal to or less than a threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6208899 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the control system described in Patent Document 1 needs to detect the bucket position in order to raise the arm. Therefore, in this system, the arm actually needs time to rise between when the bucket lever is operated and when the hydraulic cylinder for the bucket is actuated, and time to detect the bucket position (bucket angle) using a sensor or the like. This can lead to cases where the vehicle body moves forward before the hydraulic cylinder for the bucket is actuated, or the vehicle body moves forward before the sensor detects the bucket position. In such cases, there is a delay in the lifting of the arm in response to the bucket dumping operation, which can lead to the bucket coming into contact with the dump truck, soil, or the like.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a work machine that prevents contact between the bucket and a dump truck, etc., while reducing the operational burden on the operator during soil dumping work. [Means for solving the problem]

[0006] In order to achieve the above object, the work machine of the present invention is a work machine comprising a vehicle body, an arm supported on the vehicle body and rotatable in the vertical direction, a bucket supported on the arm and capable of tilting and dumping, an arm actuator that rotates the arm in the vertical direction, a bucket actuator that tilts and dumps the bucket, and a control device that controls the arm actuator and the bucket actuator, wherein the control device determines whether the work machine is in a soil-discharging state in which soil is being discharged, or a non-soil-discharging state in which soil is not being discharged, based on a bucket operation signal that causes the bucket to tilt and dump, and if it is determined that the work machine is in the soil-discharging state, it controls the arm actuator to rotate the arm upward. [Effects of the Invention]

[0007] According to the present invention, when the control device determines that the work machine is in an earth-discharging state in which earth is to be discharged, based on a bucket operation signal that causes the bucket to perform a dumping operation, the control device controls the arm to rotate upward. As a result, the arm can be raised without delay in response to the bucket dumping operation, making it possible to avoid the bucket coming into contact with the target vehicle, earth and sand, etc. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view schematically showing a work machine according to an embodiment of the present invention; [Figure 2] 1 is a system configuration diagram showing a control system for a work machine according to an embodiment of the present invention; [Figure 3] 2 is a schematic diagram illustrating a series of operations performed by the work machine shown in FIG. 1. [Figure 4] FIG. 2 is a schematic diagram illustrating the earth dumping operation performed by the work machine shown in FIG. 1. [Figure 5] FIG. 2 is a functional block diagram of a main controller of the work machine according to the first embodiment. [Figure 6] FIG. 4 is a characteristic diagram showing an example of the relationship between a bucket operation position and an arm correction value in the work machine according to the first embodiment. [Figure 7] 3 is a flowchart showing control processing performed in a main controller of the work machine according to the first embodiment. [Figure 8] FIG. 4 is a diagram illustrating the time series changes of each parameter when performing soil releasing work in the work machine according to the first embodiment. [Figure 9] 6 is a flowchart showing control processing performed in a main controller of a work machine according to a first modification of the first embodiment. [Figure 10] FIG. 10 is a characteristic diagram showing an example of the relationship between the bucket operation position and the arm correction value in a work machine according to a second modification of the first embodiment. [Figure 11A] 10 is a flowchart showing control processing performed in a main controller of a work machine according to a third modification of the first embodiment. [Figure 11B]10 is a flowchart showing control processing performed in a main controller of a work machine according to a third modification of the first embodiment. [Figure 12] FIG. 10 is a functional block diagram of a main controller of a work machine according to a second embodiment. [Figure 13] 10 is a flowchart showing control processing performed in a main controller of a work machine according to a second embodiment. [Figure 14] 10 is a flowchart showing control processing performed in a main controller of a work machine according to a modified example of the second embodiment. [Figure 15] FIG. 11 is a functional block diagram of a main controller of a work machine according to a third embodiment. [Figure 16] 10 is a flowchart showing control processing performed in a main controller of a work machine according to a third embodiment. [Figure 17] FIG. 10 is a functional block diagram of a main controller of a work machine according to a fourth embodiment. [Figure 18] 10 is a flowchart showing control processing performed in a main controller of a work machine according to a fourth embodiment. [Figure 19] FIG. 11 is a functional block diagram of a main controller of a work machine according to a fifth embodiment. [Figure 20] FIG. 13 is a characteristic diagram showing an example of the relationship between the bucket operation position and the arm correction value in the work machine according to the fifth embodiment. [Figure 21A] 10 is a flowchart showing control processing performed in a main controller of a work machine according to a fifth embodiment. [Figure 21B] 10 is a flowchart showing control processing performed in a main controller of a work machine according to a fifth embodiment. [Figure 22] FIG. 13 is a functional block diagram of a main controller of a work machine according to a sixth embodiment. [Figure 23] FIG. 13 is a characteristic diagram showing an example of the relationship between the bucket operation position and the bucket correction value in a work machine according to a sixth embodiment. [Figure 24] 13 is a flowchart showing control processing performed in a main controller of a work machine according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] First, the configuration of a wheel loader as a work machine according to an embodiment of the present invention and the system configuration of a control system will be described with reference to Figures 1 and 2. Figure 1 is a side view showing a schematic view of a wheel loader 1 according to this embodiment. Figure 2 is a system configuration diagram showing the control system for the wheel loader 1 according to this embodiment.

[0011] For ease of explanation, "front," "rear," "left," and "right" are defined as seen from the driver's perspective with reference to the traveling direction of the wheel loader 1 shown in Fig. 1, and "up" and "down" are defined with reference to gravity. That is, the "front" and "rear" arrows shown in Fig. 1 indicate the forward and backward directions of the wheel loader 1, and the "up" and "down" arrows indicate the up and down directions of the wheel loader 1. The left and right (vehicle width) direction of the wheel loader 1 is defined as the direction perpendicular to the fore-and-aft and up and down directions described above.

[0012] As shown in FIG. 1, the wheel loader 1 includes a vehicle body 8 and a working implement 6. The vehicle body 8 is of an articulated steering type (body articulation type) and includes a front vehicle body 8A, a rear vehicle body 8B, and a center joint 10 that connects the front vehicle body 8A and the rear vehicle body 8B. The working implement 6 is attached to the front vehicle body 8A. A driver's cab 12 and an engine compartment 16 are arranged in the rear vehicle body 8B. Inside the driver's cab 12, there is a seat (not shown) for an operator, and operating devices (forward / reverse switch 51, arm operating device 52, bucket operating device 53, parking brake operating device 54, steering operating device 55, accelerator operating device 56, and brake operating device 57 (see FIG. 2)) that are operated by the operator, which will be described later.

[0013] As shown in FIGS. 1 and 2 , the engine compartment 16 is equipped with an engine 20, a fuel injector 23 that supplies fuel to the engine 20, a generator motor 40 mechanically connected to the engine 20, hydraulic pumps 30A, 30B, and 30C mechanically connected to the engine 20 and the generator motor 40, and hydraulic equipment (not shown) such as valves. The engine 20 is configured by an internal combustion engine such as a diesel engine. The fuel injector 23 controls the amount of fuel injected into the engine 20 based on a fuel injection amount command from an engine controller 120 (described later). The generator motor 40 rotates by the torque output from the engine 20 and functions as a generator that generates electricity. The generator motor 40 is controlled by a generator motor inverter (hereinafter referred to as a generator inverter) 41 based on a power generation voltage command input from a main controller 100 (described later). The hydraulic pumps 30A, 30B, and 30C are driven by the torque output from the engine 20 to discharge hydraulic oil. When the generator motor 40 functions as an electric motor, the hydraulic pumps 30A, 30B, and 30C are driven by the torque output by the engine 20 and the generator motor 40. The generator inverter 41 is connected to a DC section (DC bus) 44. The generator inverter 41 controls the bus voltage of the DC section 44 by using the power supplied from the generator motor 40, based on a power generation voltage command from the main controller 100, which will be described later.

[0014] As shown in FIGS. 1 and 2 , the vehicle body 8 is equipped with an electric travel drive device 45 driven by electric power generated by a generator motor 40. The travel drive device 45 includes a travel motor 43 and a travel device 11 to which travel driving force is applied from the travel motor 43. The travel motor 43 is an electric motor that operates the wheels 7 of the travel device 11. The travel motor 43 is driven to rotate by electric power generated by the generator motor 40, which is rotated by the power of the engine 20. The torque of the travel motor 43 is controlled by an inverter for the travel motor (hereinafter referred to as the travel inverter) 42 based on a travel drive torque command input from a main controller 100, which will be described later. The travel inverter 42 is connected to the generator inverter 41 via a DC unit 44. The travel inverter 42 drives the travel motor 43 using the electric power of the DC unit 44 based on the travel drive torque command from the main controller 100, which will be described later.

[0015] The traveling device 11 has front wheels 7A which are wheels 7 attached to the front vehicle body 8A, rear wheels 7B which are wheels 7 attached to the rear vehicle body 8B, and a power transmission device that transmits power from the traveling motor 43 to the wheels 7. The power transmission device may be configured to include an axle, a differential device, a propeller shaft, etc. The wheel loader 1 is steered by a steering device 22 which has a pair of left and right steering hydraulic cylinders 15 provided to connect the front vehicle body 8A and the rear vehicle body 8B. The steering device 22 is driven by hydraulic oil discharged from a hydraulic pump 30C. The wheel loader 1 is also provided with a braking device 21 which includes a braking hydraulic cylinder 17 and a parking brake hydraulic cylinder 18. The braking device 21 is driven by hydraulic oil discharged from a hydraulic pump 30B.

[0016] As shown in FIGS. 1 and 2 , the working device 6 includes an arm 2 supported by a vehicle body 8 and rotatable in the vertical direction, a bucket 3 supported by the arm 2 and capable of tilting and dumping, an arm hydraulic cylinder (arm actuator) 4 that rotates the arm 2 in the vertical direction, and a bucket hydraulic cylinder (bucket actuator) 5 that tilts and dumps the bucket 3. The tilting and dumping operations of the bucket 3 will be described later with reference to FIGS. 3 and 4 . The arm 2 is supported by a front vehicle body 8A and is attached to the front vehicle body 8A so as to be rotatable about an axis extending in the left-right direction. The arm 2 operates when the arm hydraulic cylinder 4 extends and retracts due to hydraulic oil discharged from a hydraulic pump 30A. The bucket 3 is supported at the tip (front side) of the arm 2 and is attached to the arm 2 so as to be rotatable about an axis extending in the left-right direction. The bucket 3 operates when the bucket hydraulic cylinder 5 extends and retracts due to hydraulic oil discharged from the hydraulic pump 30A. The arm 2 and arm hydraulic cylinder 4 are provided one on each side of the front vehicle body 8A. In this embodiment, a Z-link (bell crank) type link mechanism is used as the link mechanism for operating the bucket 3. The working device 6 is driven independently of the traveling drive device 45.

[0017] As shown in FIG. 2 , a front control unit 31 is provided between the hydraulic pump 30A and the working implement 6 in the flow direction of the hydraulic oil. The front control unit 31 controls the pressure, flow rate, and direction of the hydraulic oil supplied from the hydraulic pump 30A to the arm hydraulic cylinder 4 and the bucket hydraulic cylinder 5. This controls the extension and retraction operations of the arm hydraulic cylinder 4 and the bucket hydraulic cylinder 5. Furthermore, a brake control unit 32 is provided between the hydraulic pump 30B and the braking device 21 in the flow direction of the hydraulic oil. The brake control unit 32 controls the pressure, flow rate, and direction of the hydraulic oil supplied from the hydraulic pump 30B to the braking hydraulic cylinder 17 and the parking brake hydraulic cylinder 18. This controls the extension and retraction operations of the braking hydraulic cylinder 17 and the parking brake hydraulic cylinder 18. A steering control unit 33 is provided between the hydraulic pump 30C and the steering device 22 in the flow direction of the hydraulic oil. The steering control unit 33 controls the pressure, flow rate, and direction of the hydraulic oil supplied from the hydraulic pump 30C to the steering hydraulic cylinder 15. This controls the extension and retraction operation of the steering hydraulic cylinder 15.

[0018] As shown in FIGS. 1 and 2, a forward / reverse switch 51, an arm operating device 52, a bucket operating device 53, a parking brake operating device 54, a steering operating device 55, an accelerator operating device 56, and a brake operating device 57 are provided inside the cab 12. The forward / reverse switch 51 is a forward / reverse switching device that switches the vehicle body 8 between forward (F), standby (N), and reverse (R). The arm operating device 52 operates the arm 2 via the arm hydraulic cylinder 4. As an example, the arm operating device 52 is configured as an arm operating lever that is operated by tilting it in a predetermined direction from a neutral position. When this arm operating lever is operated, the arm 2 rotates in the vertical direction (moves up and down) due to the extension and contraction operation of the arm hydraulic cylinder 4. Hereinafter, the arm operating device 52 will also be referred to as an arm operating lever.

[0019] The bucket operating device 53 operates the bucket 3 via the bucket hydraulic cylinder 5. As an example, the bucket operating device 53 is configured as a bucket operating lever of a type that is operated by tilting it in a predetermined direction from a neutral position. When this bucket operating lever is operated, the bucket hydraulic cylinder 5 extends and retracts, causing the bucket 3 to rotate (dump operation or tilt operation). Hereinafter, the bucket operating device 53 is also referred to as a bucket operating lever. In this specification, the explanation will be given on the assumption that the arm operating device 52 is configured as an arm operating lever, and the bucket operating device 53 is configured as a bucket operating lever.

[0020] The accelerator operating device 56 operates the traveling drive device 45. When the accelerator pedal of the accelerator operating device 56 is operated, the wheels 7 are rotated by the drive of the traveling motor 43, and the wheel loader 1 travels. Specifically, when the accelerator pedal of the accelerator operating device 56 is depressed with the forward / reverse switch 51 set to forward (F), the wheels 7 rotate in the forward direction, and the vehicle body 8 travels forward. When the accelerator pedal of the accelerator operating device 56 is depressed with the forward / reverse switch 51 set to reverse (R), the wheels 7 rotate in the reverse direction, and the vehicle body 8 travels backward. When the forward / reverse switch 51 is set to standby (N), the wheels 7 do not rotate, and the vehicle body 8 does not travel, even if the accelerator pedal of the accelerator operating device 56 is depressed. Note that when the switch is set to F or R, the vehicle body travels forward or backward (creeping) at an extremely low speed even if the accelerator pedal is not depressed. The brake operating device 57 operates the brake hydraulic cylinder 17. The parking brake operating device 54 operates the parking brake hydraulic cylinder 18.

[0021] The steering operation device 55 operates a pair of left and right steering hydraulic cylinders 15. When the steering wheel of the steering operation device 55 is operated, the front body 8A is bent (steered) left and right about the center joint 10 relative to the rear body 8B in accordance with the extension and contraction of the steering hydraulic cylinders 15. For ease of explanation, the arm operation device 52, bucket operation device 53, and accelerator operation device 56 will hereinafter also be collectively referred to as operation device 50.

[0022] The wheel loader 1 is equipped with an arm operating lever sensor (arm operation amount sensor) 52a. The arm operating lever sensor 52a detects the operation position (operation amount) of the arm operating device 52 (i.e., the arm operating lever) relative to the neutral position as an arm operation signal, and transmits this arm operation signal to a main controller (control device) 100, which will be described later. Hereinafter, the operation position of the arm operating lever relative to the neutral position will also be referred to as the arm operating position. The arm operating lever sensor 52a is, for example, a potentiometer, and detects a voltage corresponding to the operation position of the arm operating lever.

[0023] For example, the arm operating lever sensor 52a sets the arm operating lever angle when the arm operating lever is tilted to the maximum from the neutral position in a predetermined direction to 100%, and sets the arm operating lever angle when the arm operating lever is tilted to the maximum from the neutral position in the opposite direction to -100%, and detects a voltage (arm operating signal) corresponding to the tilt ratio (percentage) at which the arm operating lever is actually tilted. The tilt ratio of the arm operating lever indicates the arm operating position. The arm operating lever sensor 52a outputs a signal representing the voltage to the main controller 100 (described later) as an arm operating signal for rotating the arm 2 in the up and down direction.

[0024] The wheel loader 1 is equipped with a bucket operation lever sensor (bucket operation amount sensor) 53a. The bucket operation lever sensor 53a detects the operation position (operation amount) of the bucket operation device 53 (i.e., the bucket operation lever) relative to the neutral position as a bucket operation signal, and transmits this bucket operation signal to a main controller (control device) 100, which will be described later. Hereinafter, the operation position of the bucket operation lever relative to the neutral position will also be referred to as the bucket operation position. The bucket operation lever sensor 53a is, as an example, a potentiometer, and detects a voltage corresponding to the operation position of the bucket operation lever. For example, the bucket operation lever sensor 53a sets the bucket operation lever angle when the bucket operation lever is tilted to the maximum in a predetermined direction from the neutral position to 100%, and sets the bucket operation lever angle when the bucket operation lever is tilted to the maximum in the opposite direction from the neutral position to -100%, and detects a voltage (bucket operation signal) corresponding to the tilt rate (percentage) by which the bucket operation lever is actually tilted. The tilt rate of the bucket operation lever means the bucket operation position. The bucket operating lever sensor 53a outputs a signal representing the voltage to a main controller 100, which will be described later, as a bucket operating signal for tilting and dumping the bucket 3. Hereinafter, the arm operating lever sensor 52a and the bucket operating lever sensor 53a will also be collectively referred to as an operating position detection device 150.

[0025] The accelerator operation device 56, the brake operation device 57, and the steering operation device 55 are, for example, an accelerator pedal, a brake pedal, and a steering wheel, respectively. The wheel loader 1 is equipped with an accelerator sensor 56a that detects predetermined information corresponding to the operation amount of the accelerator pedal (hereinafter also referred to as accelerator operation amount), a brake sensor 57a that detects predetermined information corresponding to the operation amount of the brake pedal (hereinafter also referred to as brake operation amount), and a steering sensor 55a that detects predetermined information corresponding to the operation amount of the steering wheel (hereinafter also referred to as steering operation amount). The accelerator sensor 56a, the brake sensor 57a, and the steering sensor 55a are, for example, potentiometers that detect voltages corresponding to the operation positions of operating members (steering wheel or pedals) as the predetermined information. The accelerator sensor 56a, the brake sensor 57a, and the steering sensor 55a output the detected voltages to a main controller 100, which will be described later.

[0026] As shown in FIG. 2, the wheel loader 1 is provided with a main controller (control device) 100 that performs overall control of the wheel loader 1, and an engine controller 120 that controls the fuel injection device 23 based on an engine rotation speed command from the main controller 100.

[0027] The main controller 100 is configured as a microcomputer having a CPU (Central Processing Unit) 101 as an operating circuit, a ROM (Read Only Memory) 102 and a RAM (Random Access Memory) 103 as storage devices, an input interface 104, an output interface 105, and other peripheral circuits. Like the main controller 100, the engine controller 120 is also configured as a microcomputer having an operating circuit, a storage device, an input / output interface, etc. The main controller 100 and the engine controller 120 may each be configured as one microcomputer or as multiple microcomputers.

[0028] The ROM 102 of the main controller 100 is a non-volatile memory such as an EEPROM, and stores programs capable of executing various calculations. In other words, the ROM 102 of the main controller 100 is a storage medium from which the programs that realize the functions of this embodiment can be read. The RAM 103 is a volatile memory, and serves as a work memory that directly inputs and outputs data to and from the CPU 101. The RAM 103 temporarily stores necessary data while the CPU 101 is executing the programs. The main controller 100 may further include a storage device such as a flash memory or a hard disk drive.

[0029] The CPU 101 is a processing device that loads a program stored in the ROM 102 into the RAM 103 and executes the program, and performs predetermined arithmetic processing on signals received from the input interface 104, the ROM 102, and the RAM 103 in accordance with the program.

[0030] Sensor signals from various sensors are input to the input interface 104. The input interface 104 converts the input signals into data that can be calculated by the CPU 101. The output interface 105 generates output signals according to the calculation results of the CPU 101, and outputs the signals to the front control unit 31, the brake control unit 32, the steering control unit 33, the power generation inverter 41, the traveling inverter 42, the engine controller 120, etc.

[0031] Examples of sensor signals input to input interface 104 include a signal representing a voltage corresponding to the amount of accelerator operation detected by accelerator sensor 56a, a signal representing a voltage corresponding to the amount of brake operation detected by brake sensor 57a, a signal representing a voltage corresponding to the arm operation position detected by arm operation lever sensor 52a, a signal representing a voltage corresponding to the bucket position detected by bucket operation lever sensor 53a, a signal representing a voltage corresponding to the amount of steering operation detected by steering sensor 55a, and a signal representing the operation position of forward / reverse switch 51 output from forward / reverse switch 51.

[0032] The sensor signals input to the input interface 104 include a signal representing the angle detected by an arm relative angle sensor 62 provided on the connecting shaft connecting the vehicle body 8 and the arm 2, and a signal representing the angle detected by a bucket relative angle sensor 63 provided on the connecting shaft connecting the arm 2 and the bucket 3. The arm relative angle sensor 62 is a potentiometer that detects the relative angle (tilt angle) of the arm 2 with respect to the vehicle body 8 and outputs a signal representing the detected angle to the input interface 104. The bucket relative angle sensor 63 is a potentiometer that detects the relative angle (tilt angle) of the bucket 3 with respect to the arm 2 and outputs a signal representing the detected angle to the input interface 104. Because the angle of the vehicle body 8 with respect to the ground (traveling surface) is constant, the angle detected by the arm relative angle sensor 62 can be said to correspond to the relative angle (tilt angle) of the arm 2 with respect to the ground.

[0033] Furthermore, the sensor signals input to the input interface 104 include a signal representing the vehicle speed detected by a vehicle speed sensor (vehicle speed detection device) 61. The vehicle speed sensor 61 detects the traveling speed of the vehicle body 8 and outputs a signal representing the detected vehicle speed to the input interface 104. The vehicle speed sensor 61 may be any sensor capable of detecting the vehicle speed of the wheel loader 1. For example, the vehicle speed sensor 61 may be provided on the wheel 7 and detect the vehicle speed of the wheel loader 1 by detecting the number of rotations of the wheel 7, or may be a sensor that detects the vehicle speed of the wheel loader 1 by detecting the ground speed using laser light. Further, the sensor signals input to the input interface 104 include signals from an engine rotation speed sensor 64 that detects the actual rotation speed of the engine 20, and a motor speed sensor 58 such as a resolver that detects the rotation speed of the traveling electric motor 43 (hereinafter also referred to as motor speed). The engine rotation speed sensor 64 is, for example, a rotary encoder provided on the output shaft of the engine 20. The engine rotation speed sensor 64 is not limited to detecting the rotation speed of the output shaft of the engine 20, and may also detect the rotation speed of any shaft constituting the power transmission device. In this case, the main controller 100 calculates the actual engine rotation speed based on the detection result of the engine rotation speed sensor 64. In the illustrated example, the engine rotation speed sensor 64 is connected to the main controller 100, but it may also be connected to the engine controller 120. In this case, the main controller 100 acquires the actual engine rotation speed detected by the engine rotation speed sensor 64 via the engine controller 120.

[0034] Furthermore, signals that are detected by predetermined rotation speed sensors (not shown) and that represent the rotation speeds of hydraulic pumps 30A, 30B, 30C and traveling motor 43 may be input to input interface 104. Furthermore, signals that are detected by second and third discharge pressure sensors 71, 72, 73 and that represent the discharge pressures of hydraulic pumps 30A, 30B, 30C, and signals that are detected by bucket cylinder pressure sensor 74 and arm cylinder pressure sensor 75 and that represent the pressures (load pressures) of bucket hydraulic cylinder 5 and arm hydraulic cylinder 4 are input to input interface 104.

[0035] The main controller 100 calculates a target rotation speed of the engine 20 (hereinafter also referred to as target engine rotation speed) based on the accelerator operation amount, the arm operation position, the bucket operation position, etc. The main controller 100 calculates a rotation speed command value based on the target rotation speed of the engine 20 and outputs it to the engine controller 120. The main controller 100 also outputs an actual engine rotation speed detected by an engine rotation speed sensor 64 to the engine controller 120. The engine controller 120 compares the rotation speed command value acquired from the main controller 100 with the actual engine rotation speed detected by the engine rotation speed sensor 64, and controls the fuel injector 23 so that the actual engine rotation speed becomes the rotation speed command value. The fuel injector 23 controls the fuel injection amount based on the fuel injection amount command output from the engine controller 120, and operates the engine 20. In this way, the main controller 100, the engine controller 120, and the fuel injector 23 cooperate to configure a control device that controls the operation of the engine 20.

[0036] The main controller 100 outputs a front control command to the front control unit 31 via the output interface 105 based on the operation positions (operation amounts) of the arm operation device 52 and the bucket operation device 53 from their neutral positions. The main controller 100 then controls the arm hydraulic cylinder 4 and the bucket hydraulic cylinder 5 via the front control unit 31. Based on the front control command from the main controller 100, the front control unit 31 adjusts the pressure, flow rate, and direction of the hydraulic oil discharged from the hydraulic pump 30A to operate the arm hydraulic cylinder 4 and the bucket hydraulic cylinder 5. The front control unit 31 includes a directional control valve that controls the flow of the hydraulic oil discharged from the hydraulic pump 30A, and a solenoid valve that generates pilot pressure input to a pilot chamber of the directional control valve. Based on the bucket operation signal, the main controller 100 determines whether the wheel loader 1 is in a soil-discharging state in which soil is being discharged, or a non-soil-discharging state in which soil is not being discharged, and if it is determined that the wheel loader 1 is in a soil-discharging state, controls the arm hydraulic cylinder 4 to raise the arm 2, i.e., to rotate it upward. The determination of the soil release state by the main controller 100 will be described in detail later.

[0037] Furthermore, the main controller 100 outputs a brake control command via the output interface 105 based on the operation amount of the brake operating device 57 and the operation position of the operation switch of the parking brake operating device 54. The brake control unit 32 adjusts the pressure, flow rate, and direction of the hydraulic oil discharged from the hydraulic pump 30B based on the brake control command from the main controller 100, and operates the brake hydraulic cylinder 17 and the parking brake hydraulic cylinder 18. The brake control unit 32 has a directional control valve that controls the flow of the hydraulic oil discharged from the hydraulic pump 30B, a solenoid valve that generates pilot pressure that is input to a pilot chamber of the directional control valve, and the like.

[0038] The main controller 100 outputs a steering control command via the output interface 105 based on the operation direction and operation amount of the steering wheel of the steering operation device 55. The steering control unit 33 adjusts the pressure, flow rate, and direction of the hydraulic oil discharged from the hydraulic pump 30C based on the steering control command from the main controller 100, and operates the steering hydraulic cylinder 15. The steering control unit 33 has a directional control valve that controls the flow of the hydraulic oil discharged from the hydraulic pump 30C, a solenoid valve that generates pilot pressure that is input to a pilot chamber of the directional control valve, and the like.

[0039] Next, the work performed by the wheel loader 1 will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram illustrating a series of work performed by the wheel loader 1 shown in Figure 1. Figure 4 is a schematic diagram illustrating the soil dumping work performed by the wheel loader 1 shown in Figure 1.

[0040] As shown in FIG. 3, the wheel loader 1 performs an excavation operation of excavating an excavation target 91 such as earth and sand, minerals, etc., and then transports the excavated material and performs a loading operation of loading the earth and sand into a loading target 92 such as a dump truck.

[0041] As shown by arrow X1 in FIG. 3 , the operator operates the accelerator operating device 56 to move the wheel loader 1 forward toward the excavation target 91 and insert the bucket 3 into the excavation target 91. Next, the operator operates the arm operating device 52 and the bucket operating device 53 to raise the arm 2 and place earth, sand, minerals, etc. into the bucket 3. After that, the operator operates the bucket operating device 53 to tilt the bucket 3. Tilting the bucket 3 means operating the bucket operating device 53 to rotate the bucket 3 rearward. This allows the bucket 3 to be lifted forward to prevent the earth, sand, minerals, etc. that have entered the bucket 3 from spilling. In this way, the excavation work is completed.

[0042] After completing the excavation work, the operator moves the wheel loader 1 backward to return to its original position, as indicated by arrow X2 in FIG. 3 . Then, the operator performs a task called a rise run, in which the operator operates the arm operating device 52 to rotate the arm 2 upward while moving the wheel loader 1 forward toward the loading target 92, as indicated by arrow Y1 in FIG. 3 . Then, the operator stops the wheel loader 1 in front of the loading target 92, as shown in FIG. 4( a). Note that in FIG. 3 , the wheel loader 1 stopped in front of the loading target 92 is shown by a dashed line. Then, as shown in FIG. 4( b), the operator operates the bucket operating device 53 to dump the bucket 3, thereby discharging the material in the bucket 3 onto the loading target 92 bed. The dumping operation of the bucket 3 refers to operating the bucket operating device 53 to rotate the bucket 3 forward. This allows the soil and sand stored in the bucket 3 to be released (discharged). At this time, in order to load the transported materials evenly onto the loading platform, the operator operates the accelerator operation device 56 and the brake operation device 57 to move the wheel loader 1 forward until it is about to come into contact with the loading platform, while discharging the soil. Then, as shown in FIG. 4(c), the soil and sand in the bucket 3 is loaded onto the loading platform of the loading target 92. As shown in FIG. 4(b), discharging the soil and sand in the bucket 3 onto the loading platform of the loading target 92 is called the soil discharging operation. After completing the soil discharging operation, the operator reverses the wheel loader 1 as shown by arrow Y2 in FIG. 3 to return to its original position, thereby completing the loading operation.

[0043] This series of operations, including the dumping operation, is called "V-shape loading" because it is performed while tracing a V-shaped trajectory, and is performed repeatedly. V-shape loading accounts for the majority of the total working time of the wheel loader 1. For this reason, in order to improve the working efficiency of the wheel loader 1, it is effective to quickly perform the series of operations, including the dumping operation, during V-shape loading. Here, working efficiency (t / h) means the weight (t) of transported material loaded onto the loading target 92 per specified time (h).

[0044] Hereinafter, the arm command value C executed by the main controller 100 ARMThe contents of the calculation process will be explained in detail below.

[0045] First Embodiment Fig. 5 is a functional block diagram of the main controller 100 of the wheel loader 1 according to the first embodiment. Fig. 6 is a characteristics diagram showing an example of the relationship between the bucket operation amount and the arm correction value in the wheel loader 1 according to the first embodiment.

[0046] As shown in Fig. 5, the main controller 100 executes the program stored in the ROM 102, thereby functioning as a work state determination unit 110, a correction value calculation unit 111, and an arm command value calculation unit 112. Specifically, the work state determination unit 110 determines whether the wheel loader 1 is in a soil-discharging state where it is performing soil-discharging work (Figs. 4(a) to 4(c)), or whether the wheel loader 1 is in a non-soil-discharging state where it is not performing soil-discharging work, based on the detection result (bucket operation signal) of the bucket operation lever sensor 53a. When the work state determination unit 110 determines that the wheel loader 1 is in a soil-discharging state, it sets a soil-discharging determination flag FL on, and when it determines that the wheel loader 1 is in a non-soil-discharging state, it sets the soil-discharging determination flag FL off.

[0047] The work state determination unit 110 of the main controller 100 calculates the operation position (operation amount) of the bucket operation lever relative to the neutral position based on the bucket operation signal detected by the bucket operation lever sensor 53a (i.e., a signal indicating a voltage corresponding to the operation position of the bucket operation lever), and determines that the wheel loader 1 is in the earth-discharging state when the operation position of the bucket operation lever is equal to or greater than a predetermined first operation threshold R1 that causes the bucket 3 to perform a dumping operation. Specifically, when the earth-discharging determination flag FL is set to off, the work state determination unit 110 switches the earth-discharging determination flag FL from off to on when the bucket operation position becomes equal to or greater than the first operation threshold R1. The first operation threshold R1 corresponds to the bucket operation position when the earth-discharging operation is started and is stored in advance in the ROM 102. For example, the first operation threshold R1 corresponds to an operation position of approximately 10% when the maximum bucket operation position on the dumping operation side from the neutral position is 100% and the maximum bucket operation position on the tilting operation side from the neutral position is -100%. In this embodiment, the operation devices 50 include an accelerator operation device 56, an arm operation device 52, and a bucket operation device 53. Of these, the work state determination unit 110 determines whether the bucket operation position R BKT When the first operation threshold value R1 or more is reached, the release determination flag FL is set to ON.

[0048] When the earth-releasing determination flag FL is set to ON, the work state determination unit 110 switches the earth-releasing determination flag FL from ON to OFF when the bucket operation position becomes equal to or less than the second operation threshold R2. The second operation threshold R2 corresponds to the bucket operation position when the earth-releasing operation is completed, and is stored in advance in the ROM 102. The second operation threshold R2 is equal to or less than the first operation threshold R1, and corresponds to an operation position of about 5% when the maximum bucket operation position on the dump operation side from the neutral position is 100% and the maximum bucket operation position on the tilt operation side from the neutral position is -100%. In this embodiment, the bucket operation position R BKT becomes equal to or less than the second operation threshold R2, the release determination flag FL is set to OFF.

[0049] The correction value calculation unit 111 calculates the bucket operation position R BKTBased on the characteristics of the correlation map shown in Figure 6, the arm correction value K ARM Calculate the arm correction value K ARM As will be described later, the arm operating position R ARM The correlation map characteristic shown in FIG. 6 is obtained by adding the velocity command of the arm hydraulic cylinder 4 to the bucket operating position R BKT As increases beyond the first operation threshold R1, the arm correction value K ARM As a result, when the bucket operation lever as the bucket operation device 53 is operated to dump the bucket 3 during the earth dumping operation of the wheel loader 1, the bucket operation position R BKT Depending on the arm correction value K ARM is arm operation position R ARM , the arm 2 can be rotated upwards quickly. In addition, in the characteristics of the correlation map shown in FIG. 6, the greater the slope is set, the faster the arm 2 can be rotated upwards at a certain bucket operation position R BKT Arm correction value K ARM In other words, the larger the slope of the characteristic, the larger the arm correction value K ARM This allows the arm 2 to be rotated upward more quickly when the bucket 3 is subjected to a dumping operation, so that even if the distance between the bucket 3 and the loading target 92 onto which the wheel loader 1 is discharging soil is short at the start of the soil discharging operation, the bucket 3 can be prevented from coming into contact with the loading target 92, earth and sand, etc. The characteristics of this correlation map are determined in advance by calculation or experiment, and are stored in advance in ROM 102.

[0050] When the release determination flag FL is set to ON, that is, when the work state determination unit 110 determines that the work is in the release state, the correction value calculation unit 111 shown in FIG. 5 calculates the value calculated using the correlation map as the arm correction value K ARM When the soil release determination flag FL is set to OFF, that is, when the work state determination unit 110 determines that the soil is not released, the correction value calculation unit 111 determines the arm correction value K ARMis set to a predetermined value (0 in this embodiment).

[0051] The arm command value calculation unit 112 calculates the arm operation position R ARM and the arm correction value K determined by the correction value calculation unit 111. ARM Using C ARM =R ARM +K ARM (hereinafter referred to as equation (1)), the arm command value C ARM In this way, the arm command value calculation unit 112 calculates the arm correction value K calculated by the correction value calculation unit 111. ARM Arm operation position R ARM Correct the arm operating position R after correction. ARM The arm command value C ARM is output to the front control unit 31 as a speed command for the arm hydraulic cylinder 4. When the earth release determination flag FL is set to OFF, that is, when the work state determination unit 110 determines that the work is in a non-earth release state, the arm correction value K ARM is set to 0. In other words, when it is determined that the arm is in a non-release state, the arm command value calculation unit 112 sets the arm correction value K ARM Arm command value C ARM No correction is made.

[0052] Next, the control processing executed by the main controller 100 will be explained using a flowchart. Figure 7 is a flowchart showing the control processing carried out in the main controller 100 of the wheel loader 1 according to the first embodiment. The processing shown in the flowchart of Figure 7 is started, for example, when the ignition switch (engine key switch) is turned on, and after initial setting (not shown) is performed, it is repeatedly executed at a predetermined control cycle. In the initial setting, the soil release determination flag FL is set to off.

[0053] 7, in S111, the work status determination unit 110 determines whether the currently set release determination flag FL is on. If the currently set release determination flag FL is off (NO in S111), the process proceeds to S113, and if the currently set release determination flag FL is on (YES in S111), the process proceeds to S117.

[0054] In S113, work status determination unit 110 determines whether the operation position of bucket operation device 53 is equal to or greater than first operation threshold R1. If it is determined in S113 that the operation position of bucket operation device 53 is equal to or greater than first operation threshold R1 (YES in S113), the process proceeds to S115, where a decision is made to turn on the soil release determination flag. Thereafter, the process proceeds to S120. On the other hand, if it is determined in S113 that the operation position of bucket operation device 53 is less than first operation threshold R1 (NO in S113), the process proceeds to S120.

[0055] In S117, work status determination unit 110 determines whether the operation position of bucket operation device 53 is equal to or less than second operation threshold R2. If it is determined in S117 that the operation position of bucket operation device 53 is equal to or less than second operation threshold R2 (YES in S117), the process proceeds to S119, where a decision is made to turn off the soil release determination flag. Thereafter, the process proceeds to S120. On the other hand, if it is determined in S117 that the operation position of bucket operation device 53 is greater than second operation threshold R2 (NO in S117), the process proceeds to S120.

[0056] In S120, the work state determination unit 110 determines whether the wheel loader 1 is in a soil-releasing state or a non-soil-releasing state based on the soil-releasing determination flag FL that was set in S115 and S119. If the soil-releasing determination flag FL is set on (YES in S120), the work state determination unit 110 determines that the wheel loader 1 is in a soil-releasing state, and proceeds to S130. If the soil-releasing determination flag FL is set off (NO in S120), the work state determination unit 110 determines that the wheel loader 1 is in a non-soil-releasing state, and proceeds to S140.

[0057] In S130, the correction value calculation unit 111 calculates the bucket operation position R BKT Based on the characteristics of the correlation map shown in Figure 6, the arm correction value K ARM Then, the process proceeds to S150.

[0058] In S140, the correction value calculation unit 111 calculates the arm correction value K ARM is set to an initial value (0 in this embodiment). When the setting process (S140) is completed, the process proceeds to S150.

[0059] In S150, the arm command value calculation unit 112 calculates the arm operation position R ARM , the arm correction value K calculated in S130 or S140 ARM By adding ARM (See the above formula (1)). When the process of S150 is completed, the process of the flowchart for this control cycle ends, and in the next control cycle, the process from S111 to S150 is executed again.

[0060] Next, the operation and effect of the wheel loader 1 according to the first embodiment will be described. FIG. 8 shows the respective parameters (brake operation amount R BRK , bucket operation position R BKT , arm operation position R ARM , arm correction value K ARM , vehicle speed V CRZ , bucket angle θ BKT , arm angle θ ARM ) is a diagram illustrating a time series change in the arm correction value K calculated by the formula (1). An example of the operation of the wheel loader 1 when performing soil dumping work will be described below. In addition, in order to clarify the effects of this embodiment, the arm correction value K calculated by the formula (1) is ARM Arm command value C ARMThis will be explained in comparison with a case where correction is not made (comparative example). That is, the comparative example shows a case where the operator performs earth dumping work while performing combined operations of the brake operating device 57, bucket operating device 53, and arm operating device 52. Note that the wheel loader 1 according to this embodiment and the wheel loader according to the comparative example are assumed to have the same operating procedures and amounts of operation of the various operating devices by the operator other than the arm operating device 52.

[0061] In Fig. 8, the time series changes of each parameter in this embodiment are shown by solid lines, and the time series changes of each parameter in the comparative example are shown by dashed lines. The horizontal axis in Fig. 8(a) to (g) represents time (elapsed time). The vertical axis in Fig. 8(a) represents the brake operation amount R BRK The vertical axis of Fig. 8(b) represents the bucket operation position R BKT The vertical axis of Fig. 8(c) represents the arm operation position R ARM 8(d) represents the arm correction value K calculated by the correction value calculation unit 111. ARM , and the vertical axis of FIG. 8(e) represents the vehicle speed V CRZ The vertical axis of Fig. 8(f) represents the bucket angle θ BKT The vertical axis of Fig. 8(g) represents the arm angle θ ARM Shows.

[0062] In Figure 8, time t0 is the time when the operator operates the control device 50 to start moving the vehicle body 8 forward, lifting the arm 2, and dumping the bucket 3. In other words, time t0 is the time when the earth discharge determination flag FL is switched from off to on. Time t1 is the time when, during earth discharge work, the operator operates the control device 50 to start increasing the lifting speed of the arm 2 and the dumping speed of the bucket 3 while slowing down the forward speed of the vehicle body 8. Time t2 is the time when the operator stops operating the control device 50 to finish discharging earth and sand, and the vehicle body 8, arm 2, and bucket 3 start to stop.

[0063] As shown in FIG. 8(a), the brake operation amount R BRK is large until time t0. This is because the wheel loader 1 is stopped until time t0. At time t0, the brake operation amount RBRK The brake operation amount R decreases suddenly, and the vehicle body 8 starts to move forward by creeping. Note that the operator needs to determine the timing to prevent the wheel loader 1 from contacting the loading target 92, so after time t1, the brake operation amount R BRK By increasing the brake operation amount R, the forward speed of the vehicle body 8 is reduced. BRK The force is suddenly increased, causing the forward movement of the vehicle 8 to stop.

[0064] As shown in Figure 8(b), the bucket operation position R BKT is increased slightly from time t0 to time t1, and the soil and sand in the bucket 3 are dropped without giving a large impact to the loading object 92. From time t1, the bucket operating device 53 is operated to speed up the dumping operation of the bucket 3, and the bucket operating position R BKT After that, the release operation ends at time t2, and the bucket operation position R BKT decreases sharply.

[0065] As shown in FIG. 8(c), in the comparative example (without arm correction), the arm operation position R ARM is increased slightly from time t0 to time t1, and arm 2 is raised in accordance with the dumping operation speed of bucket 3 so that the bottom end of bucket 3 does not drop and so that the distance between bucket 3 and the loading platform of object 92 to be loaded does not become too large. In order to increase the lifting speed of arm 2 in accordance with the acceleration of the dumping operation of bucket 3 from time t1, arm operating device 52 is operated by the operator, and arm operating position R ARM After that, the release operation ends at time t2, so the arm operation position R ARM decreases sharply.

[0066] In contrast, in the present embodiment, the bucket operation position R BKT As the arm operating position R ARM This is because the release judgment flag FL is switched from OFF to ON at time t0, and the arm correction value K is increased quickly from 0 (zero). ARM is the arm command value CARM , the arm 2 rises without operating the arm operating device 52. Therefore, until the time t2 at which the earth-releasing operation is completed, the arm operating position R ARM As shown in FIG. 8(d), in the present embodiment, the bucket operation position R BKT As the arm correction value K increases, ARM At time t1, the bucket operation position R BKT As the arm correction value K ARM As a result, during the soil release operation, the arm operation position R ARM is the arm correction value K ARM As a result, the operator does not need to operate the arm operating device 52, and can focus on operating the vehicle body 8 and the bucket 3.

[0067] As shown in FIG. 8(e), the vehicle speed V CRZ is the brake operation amount R shown in FIG. BRK In both the comparative example (without arm correction) and this embodiment (with arm correction), the main controller 100 moves the vehicle body 8 forward at a slow speed from the start to the middle of the earth dumping operation, and moves the vehicle body 8 forward at an even slower speed from the middle to the end of the earth dumping operation. As shown in FIG. 8(f), the bucket angle θ BKT is the bucket operation position R shown in Figure 8(b). BKT In both the comparative example (without arm correction) and this embodiment (with arm correction), the bucket 3 performs a slow dumping motion from the start to the middle of the earth-releasing operation, and performs a quick dumping motion from the middle to the end of the earth-releasing operation. As shown in FIG. 8(g), the arm angle θ ARM is the arm operation position R shown in Figure 8(c). ARM and the arm correction value K shown in Fig. 8(d) ARM In the example of FIG. 8, the arm operation position R ARM and arm correction value K ARM Arm command value C obtained by adding ARMTherefore, in both the comparative example and this embodiment, the arm 2 rises slowly from the start to the middle of the earth-releasing operation, and rises quickly from the middle to the end of the earth-releasing operation.

[0068] As described above, in the case of earth dumping work in which the forward travel of the vehicle body 8, the lifting operation of the arm 2, and the dumping operation of the bucket 3 are performed simultaneously, in the comparative example (without arm correction), a combined operation of the brake operating device 57, bucket operating device 53, and arm operating device 52 is required. Performing such a combined operation while preventing the wheel loader 1 from coming into contact with the loading target 92 and achieving smooth earth dumping places a heavy operational burden on the operator. Furthermore, performing the combined operation in a situation in which the view from the cab 12 is limited by the work implement 6 and the soil in the bucket 3 also places a heavy operational burden on the operator. Furthermore, smooth earth dumping work itself is difficult for an unskilled operator.

[0069] In contrast to this, in the wheel loader 1 according to this embodiment, the main controller 100 controls the arm 2 to rotate upward when it is determined that the wheel loader 1 is in a dumping state in which soil is to be discharged, based on a bucket operation signal that causes the bucket 3 to perform a dump operation. As a result, the operator of the wheel loader 1 can perform soil discharge operations with the wheel loader 1 by operating the brake operation device 57 and the bucket operation device 53, that is, without operating the arm operation device 52. This reduces the operational burden on the operator when performing smooth soil discharge operations. Furthermore, soil discharge operations become easier for unskilled operators, enabling smoother soil discharge operations.

[0070] Furthermore, in this embodiment, feedforward control is performed to raise the arm 2 based on the operating position of the bucket operating device 53 by the operator, eliminating the need for time until the bucket hydraulic cylinder 5 is driven and time for detecting the attitude of the bucket 3 (bucket angle) using a sensor or the like. For this reason, compared to cases where a sensor or the like is used to determine whether or not earth-discharging operation is being performed, the arm 2 can be raised without delay in response to the dumping operation of the bucket 3. Therefore, even if the distance between the loading target 92 onto which the wheel loader 1 is discharging earth and the bucket 3 is short when the earth-discharging operation starts, or even if the bucket 3 is quickly dumped after the start of earth-discharging operation, it is possible to avoid the bucket 3 coming into contact with the loading target 92, earth and sand, etc.

[0071] Furthermore, in this embodiment, the imaging device and angle sensor are not used to determine whether or not the work is being performed, and the arm correction value is not calculated. Therefore, even if the imaging device or angle sensor becomes unusable or breaks down due to dust or impact, control can be executed to raise the arm 2 during the soil release work, so there is no impact from harsh working environments or deterioration of the equipment over time.

[0072] Next, a first modified example of the wheel loader 1 according to the first embodiment will be described. The wheel loader according to this modified example differs from the wheel loader 1 according to the first embodiment described above in the control processing executed by the main controller. Below, components having the same or similar functions as those in the control processing executed by the main controller 100 of the wheel loader 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and only different parts will be described.

[0073] FIG. 9 is a flowchart showing control processing executed by the main controller of the wheel loader according to Modification 1 of the first embodiment. The main controller according to this modification calculates the operation position of the bucket operation lever based on the bucket operation signal detected by the bucket operation lever sensor 53a. The main controller determines that the wheel loader is in the soil-discharging state if the calculated operation position of the bucket operation lever remains equal to or greater than the first operation threshold R1 for a first duration T1 (a predetermined time). Specifically, as shown in FIG. 9, if it is determined in S113 that the operation position of the bucket operation device 53 is equal to or greater than the first operation threshold R1 (YES in S113), the process proceeds to S114. In S114, the main controller determines whether the operation position of the bucket operation device 53 remains equal to or greater than the predetermined first operation threshold R1 for a first duration T1 or longer. Then, if the state in which the operation position of the bucket operation device 53 is equal to or greater than the first operation threshold R1 continues for the first duration T1 or longer (YES in S114), the main controller determines that the wheel loader is in the earth-releasing state. Thereafter, the process proceeds to S115, where a decision is made to turn on the earth-releasing determination flag, and the process proceeds to S120. On the other hand, if the state in which the operation position of the bucket operation device 53 is equal to or greater than the first operation threshold R1 does not continue for the first duration T1 or longer (NO in S114), the process proceeds to S120.

[0074] Furthermore, in S117, if it is determined that the operation position of bucket operation device 53 is equal to or less than second operation threshold R2 (YES in S117), the process proceeds to S118. In S118, the main controller determines whether the state in which the operation position of bucket operation device 53 is equal to or less than the predetermined second operation threshold R2 continues for equal to or more than a predetermined second duration T2. ​​Then, if the state in which the operation position of bucket operation device 53 is equal to or less than second operation threshold R2 continues for equal to or more than the second duration T2 (YES in S118), the main controller determines that the wheel loader is in a non-discharging state. Thereafter, the process proceeds to S119, where a decision is made to turn off the soil-discharging determination flag, and the process proceeds to S120. On the other hand, in S118, if the state in which the operation position of bucket operation device 53 is equal to or less than second operation threshold R2 has not continued for equal to or more than the second duration T2 (NO in S118), the process proceeds to S120.

[0075] In this way, the wheel loader according to this first modification determines whether the wheel loader is in the earth-releasing state based not only on the operating position of the bucket operating device 53 but also on the durations T1 and T2 of the bucket operating position. As a result, even if the bucket operating device 53 is operated for only a short time during an earth-releasing operation, the main controller determines that the earth-releasing determination flag should be maintained in the off state. Also, even if the bucket operating device 53 is released for only a short time during an earth-releasing operation, the main controller determines that the earth-releasing determination flag should be maintained in the on state. In this way, noise that does not affect the earth-releasing determination can be eliminated to determine whether the earth-releasing determination flag is on or off, thereby improving noise resistance. Furthermore, because the earth-releasing determination flag is not repeatedly turned on and off, hunting can be suppressed. Therefore, according to this first modification, the wheel loader can be operated stably.

[0076] Next, a second modification of the wheel loader 1 according to the first embodiment will be described. The wheel loader according to this modification differs from the wheel loader 1 according to the first embodiment described above in that the bucket operation position R BKT and arm correction value K ARMThe correlation map is different from that stored in the main controller 100 of the wheel loader 1 according to the first embodiment (FIG. 6). Below, components having the same or similar functions as those stored in the main controller 100 of the wheel loader 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and only the differences will be described.

[0077] FIG. 10 shows the bucket operation position R BKT and arm correction value K ARM 10 is a characteristic diagram showing an example of the relationship between the bucket operation position R and the bucket operation position R. As shown in FIG. BKT The bucket operation position R BKT Arm correction value K for changes in ARM Therefore, at the beginning of the dumping operation of the bucket 3, the change in the bucket operating position R BKT Arm correction value K for changes in ARM Since the change in the bucket operating position R is gradual, it is possible to suppress a sudden rise of the arm 2 in response to the dumping operation of the bucket 3. Therefore, the earth dumping operation can be performed without giving the operator any discomfort. BKT Beyond the bucket operating position R BKT When is increased, the more the operator pushes down the bucket operating lever of the bucket operating device 53, the more quickly the main controller 100 controls to raise the arm 2. As a result, it becomes possible to control to raise the arm 2 in accordance with the operator's intention to raise the arm 2 gradually in the early stage of the soil releasing work, and then to raise the arm 2 quickly as the dumping operation speed of the bucket 3 increases.

[0078] Next, a third modified example of the wheel loader 1 according to the first embodiment will be described. The wheel loader according to this modified example differs from the wheel loader 1 according to the first embodiment described above in that it has an external environment information detection device (not shown) such as a camera, and in the control processing executed by the main controller. Below, components having the same or similar functions as those of the wheel loader 1 according to the first embodiment will be given the same reference numerals and their description will be omitted, and only the different parts will be described.

[0079] The wheel loader according to this modified example is equipped with an external environment information detection device (not shown), such as a camera. The main controller according to this modified example monitors the movement of the working implement 6 and the wheels 7, for example, using a camera that captures images in front of the wheel loader, and determines whether the wheel loader is in a soil-releasing state or a non-soil-releasing state based on the movement of the working implement 6 and the wheels 7. The external environment information detection device according to this modified example may be, for example, an infrared sensor. In this case, the main controller determines whether the wheel loader is in a soil-releasing state or a non-soil-releasing state based on information detected by an infrared sensor that monitors the wheel loader's front, for example. Specifically, the main controller determines whether the wheel loader is in a soil-releasing state when the distance between the wheel loader and an object recognized by the infrared sensor is changing, and determines whether the wheel loader is in a non-soil-releasing state when the distance between the wheel loader and an object recognized by the infrared sensor is not changing.

[0080] Fig. 11A shows a part of a flowchart showing the control processing carried out in the main controller of the wheel loader according to Modification 3 of the first embodiment. Fig. 11B shows the rest of the flowchart shown in Fig. 11A.

[0081] 11A, the main controller determines in S100 whether an external information detection device such as a camera or an infrared sensor is normal. If it is determined that the external information detection device is not normal due to a malfunction or the like (NO in S100), the process proceeds to S111 (see FIG. 11B).

[0082] On the other hand, if it is determined that the external information detection device is normal (YES in S100), the process proceeds to S101. In S101, the work state determination unit 110 determines whether the currently set release determination flag FL is on. If the currently set release determination flag FL is off (NO in S101), the process proceeds to S103, and if the currently set release determination flag FL is on (YES in S101), the process proceeds to S107.

[0083] In S103, the work status determination unit 110 determines whether or not the wheel loader is performing earth dumping operation using the external environment information detection device. If it is determined in S103 that the wheel loader is performing earth dumping operation (YES in S103), the process proceeds to S105, where a decision is made to turn on the earth dumping determination flag. Thereafter, the process proceeds to S120. On the other hand, if it is determined in S103 that the wheel loader is not performing earth dumping operation (NO in S103), the process proceeds to S120.

[0084] In S107, the work status determination unit 110 determines whether or not the wheel loader is not performing earth dumping operation using the external environment information detection device. If it is determined in S107 that the wheel loader is not performing earth dumping operation (YES in S107), the process proceeds to S109, where a decision is made to turn off the earth dumping determination flag. Thereafter, the process proceeds to S120. On the other hand, if it is determined in S107 that the wheel loader is performing earth dumping operation (NO in S107), the process proceeds to S120.

[0085] In this way, in the wheel loader according to the present modified example 3, the main controller normally prioritizes the determination of the earth-releasing state by the external information detection device, and if, for example, the camera or infrared sensor fails, switches to prioritize the determination of the earth-releasing state (S111 to S119 in FIG. 11B) based on the operation amount of the bucket operation device 53. This makes it possible to improve the accuracy and redundancy (robustness) of the determination of the earth-releasing state.

[0086] Second Embodiment Next, a wheel loader according to a second embodiment will be described. The wheel loader according to the second embodiment is characterized by preventing the wheel loader from being erroneously determined to be in a soil-discharging state during excavation work or transport work. The wheel loader according to this embodiment differs from the wheel loader 1 according to the first embodiment described above in the control processing executed by the main controller 100A. Below, components having the same or similar functions as those in the control processing executed by the main controller 100 of the wheel loader 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and only different parts will be described.

[0087] Fig. 12 is a functional block diagram of the main controller 100A of the wheel loader according to the second embodiment. Fig. 13 is a flowchart showing the control processing carried out in the main controller 100A of the wheel loader according to the second embodiment.

[0088] The working state determination unit 110A determines the arm operating position R of the arm operating device 52. ARM and the bucket operation position R of the bucket operation device 53 BKT Based on this, it is determined whether the wheel loader 1 is in an earth-releasing state or a non-earth-releasing state, and if it is determined that it is in an earth-releasing state, it sets the earth-releasing determination flag FL to on, and if it is determined that it is in a non-earth-releasing state, it sets the earth-releasing determination flag FL to off. Specifically, the work state determination unit 110A calculates the operation position (operation amount) of the bucket operation lever based on the bucket operation signal detected by the bucket operation lever sensor 53a, and if the calculated operation position of the bucket operation lever is equal to or greater than a predetermined first operation threshold R1 that causes the bucket 3 to perform a dump operation, it determines that the wheel loader 1 is in an earth-releasing state. Hereinafter, the arm operation position R of the arm operation lever ARM The determination of whether the soil is released or not based on the above will now be specifically described.

[0089] Furthermore, the working state determination unit 110A calculates an integrated value of the operation position of the arm operating device 52 (integrated arm operation amount) ΣARM based on the arm operation signal. The integrated value ΣARM of the operation position of the arm operating device 52 is a value obtained by adding, for each operation position, a value obtained by multiplying the operation position of the arm operating device 52 by the time the arm operating device 52 is held at that operation position. For example, if the holding time for the angle of the arm operating lever in a state tilted +5% from the neutral position is 2 seconds, the holding time for the state tilted +7% from the neutral position is 3 seconds, and the holding time for the state tilted -10% from the neutral position is 2 seconds, then the integrated value ΣARM of the operation position of the arm operating device 52 is +11% seconds (= +10% seconds + 21% seconds - 20% seconds), which is the sum of +5% × 2 seconds = +10% seconds, +7% × 3 seconds = +21% seconds, and -10% × 2 seconds = -20% seconds.

[0090] When the release determination flag FL is set to off, the work state determination unit 110A switches the release determination flag FL from off to on when the integrated value ΣARM of the operation position of the arm operating device 52 is equal to or greater than a predetermined integrated threshold Σ1. Furthermore, when the release determination flag FL is set to off, the work state determination unit 110A maintains the release determination flag FL off when the integrated value ΣARM of the operation position of the arm operating device 52 is smaller than a predetermined integrated threshold Σ1. Here, the integrated value ΣARM of the operation position of the arm operating device 52 is measured from the time the engine 20 is started or the switch (not shown) for this function is turned on, and is reset when the switch for this function is turned off or the engine 20 is stopped.

[0091] Furthermore, the predetermined integrated threshold value Σ1 corresponds to the integrated value ΣARM of the operation position of the arm operating device 52 when the arm 2 is in a position higher than the excavation posture or transport posture of the wheel loader 1, and is stored in advance in the ROM 102. The predetermined integrated threshold value Σ1 is set to an integrated value of about +200% seconds when the maximum operation position on the ascending side of the arm 2 is +100% and the maximum operation position on the descending side of the arm 2 is -100%. For example, if the arm operation position of +100% (i.e. the maximum operation position on the ascending side of the arm 2) continues for 2 seconds, the integrated value ΣARM of the operation position of the arm operating device 52 will be +200% seconds.

[0092] When the integrated value ΣARM of the operation position of the arm operation device 52 is equal to or greater than a predetermined integrated threshold Σ1, the arm 2 continues to be in a position higher than the excavation posture or transport posture of the wheel loader 1, and it is estimated that the arm 2 is at a height where earth is to be discharged by the wheel loader 1 (see (a) in FIG. 4, for example). In contrast to this, when the integrated value ΣARM of the operation position of the arm operation device 52 is smaller than the predetermined integrated threshold Σ1 (for example, when ΣARM is 0% seconds or less), it can be estimated, for example, that the arm 2 is at a height where earth is to be discharged by the wheel loader 1. In this way, by comparing the integrated value ΣARM of the operation position of the arm operation device 52 with the predetermined integrated threshold Σ1, it is estimated whether the wheel loader 1 is in a posture where earth is to be discharged to the loading target 92. Note that even if the arm operation position of +10% continues for 20 seconds, for example, the integrated value ΣARM of the operation position of the arm operation device 52 will be +200% seconds. Therefore, in order to improve the accuracy of estimating the posture (height) of the arm 2, the operation position of the arm operation device 52 may be multiplied by an adjustment gain to calculate an integrated value ΣARM of the operation position of the arm operation device 52.

[0093] As shown in FIG. 13, in the second embodiment, if it is determined in S111 that the release determination flag FL is off (NO in S111), the process proceeds to S211.

[0094] In S211, the work state determination unit 110A determines whether the integrated value ΣARM of the operation position of the arm operating device 52 is equal to or greater than a predetermined integrated threshold Σ1. If it is determined in S211 that the integrated value ΣARM of the operation position of the arm operating device 52 is equal to or greater than the integrated threshold Σ1 (YES in S211), the process proceeds to S113. If it is determined in S113 that the operation position of the bucket operating device 53 is equal to or greater than the first operation threshold R1 (YES in S113), the process proceeds to S115, where a decision is made to turn on the soil release determination flag. Thereafter, the process proceeds to S120. On the other hand, if it is determined in S113 that the operation position of the bucket operating device 53 is less than the first operation threshold R1 (NO in S113), the process proceeds to S120. On the other hand, if it is determined in S211 that the integrated value ΣARM of the operation position of the arm operating device 52 is less than the integrated threshold Σ1 (NO in S211), the process proceeds to S120. Thus, in the wheel loader according to the second embodiment, the work status determination unit 110A of the main controller 100A determines that the wheel loader is in a non-earth-discharging state when the integrated value ΣARM of the operation position of the arm operating device 52 is smaller than a predetermined integrated threshold Σ1. In other words, when the integrated value ΣARM of the arm operation position is smaller than a predetermined integrated threshold Σ1, the work status determination unit 110A determines that the arm 2 is not in a position higher than the digging posture or the transport posture (for example, the wheel loader is in an digging posture), and as a result, determines that the wheel loader is in a non-earth-discharging state. Then, when the main controller 100A determines that the wheel loader is in a non-earth-discharging state, it does not perform control to automatically raise the arm 2.

[0095] As described above, in this embodiment, the main controller 100A compares the integrated value ΣARM of the operating position of the arm operating device 52 with a predetermined integrated threshold Σ1 to determine whether or not the wheel loader is in a state to start earth-releasing operation. Therefore, for example, if the operating position of the arm operating device 52 increases instantaneously while the wheel loader is performing excavation or transporting work, it is possible to prevent the wheel loader from being erroneously determined to be in an earth-releasing state and to avoid a situation in which the arm 2 automatically rises further. Therefore, it is possible to prevent the excavation or transporting work of the wheel loader from being hindered.

[0096] Next, a modified example of the wheel loader according to the second embodiment will be described. The wheel loader according to this modified example differs from the wheel loader according to the second embodiment described above in the control processing executed by the main controller. Below, components having the same or similar functions as those of the wheel loader according to the second embodiment will be given the same reference numerals and their description will be omitted, and only the differences will be described.

[0097] Figure 14 is a flowchart showing the control processing performed by the main controller of the wheel loader according to the modified example of Embodiment 2. As shown in Figure 14, in this modified example, if it is determined in S111 that the soil release determination flag FL is off (NO in S111), the processing proceeds to S221.

[0098] In S221, the work status determination unit 110A calculates the integral over time of the speed of the vehicle body 8 detected by, for example, the vehicle speed sensor 61, i.e., the travel distance ΣDST of the vehicle body 8. Then, the work status determination unit 110A determines whether the travel distance ΣDST of the vehicle body 8 is equal to or greater than a predetermined travel distance threshold Σ2. Here, the predetermined travel distance threshold Σ2 corresponds to the travel distance of the vehicle body 8 from the position (initial position) of the wheel loader 1 shown by the solid line in FIG. 3, from when the wheel loader performs excavation work at a preset position (X1), through the transport work of the excavation target (X2, Y1), to when it arrives at the position of the wheel loader 1 shown by the dashed line in FIG. 3 (the soil discharge start position). This predetermined travel distance threshold Σ2 is determined based on the positional relationship between the wheel loader 1, the preset excavation target 91, and the preset loading target 92, and is stored in advance in ROM 102. In other words, the work state determination unit 110A estimates whether the wheel loader has excavated a preset excavation target 91 and is about to start discharging soil onto a preset loading target 92. If the traveling distance ΣDST is smaller than a predetermined traveling distance threshold Σ2, the distance traveled since the wheel loader started a series of operations is short, and therefore, for example, it can be estimated that the wheel loader is performing excavation work on the preset excavation target 91 (i.e., is in a non-discharging state). Also, if the traveling distance ΣDST is smaller than the predetermined traveling distance threshold Σ2, it can be estimated, for example, that the wheel loader is about to start discharging soil onto a loading target other than the preset loading target 92 (a loading target that is positioned closer to the wheel loader 1 than the loading target 92 in FIG. 3). Here, the traveling distance ΣDST of the vehicle body 8 is measured from the time when the wheel loader is at the position indicated by the solid line in FIG. 3, and is reset when the wheel loader returns to the position indicated by the solid line in FIG. 3 after completing the excavation work, transporting work, and soil discharging work.

[0099] If it is determined in S221 that the traveling distance ΣDST of the vehicle body 8 is equal to or greater than the predetermined traveling distance threshold Σ2 (YES in S221), the process proceeds to S113. On the other hand, if it is determined in S221 that the traveling distance ΣDST of the vehicle body 8 is less than the predetermined traveling distance threshold Σ2 (NO in S221), the process proceeds to S120. Thus, in the wheel loader according to the modified example of the second embodiment, the work status determination unit 110A of the main controller 100A determines that the wheel loader is not in a state to discharge earth onto the preset loading target 92 if the integrated value of the speed of the vehicle body 8 over time (i.e., the traveling distance ΣDST) is less than the predetermined traveling distance threshold Σ2. Then, if it is determined that the wheel loader is not in a state to discharge earth onto the preset loading target 92, the main controller 100A does not perform control to raise the arm 2.

[0100] As described above, in this modification, the main controller compares the travel distance ΣDST of the vehicle body 8 with a predetermined travel distance threshold Σ2 to determine whether the wheel loader is in a state to start an earth-discharging operation. Therefore, for example, when the bucket operating device 53 is operated during excavation or transporting operation of the wheel loader, it is possible to prevent the wheel loader from being erroneously determined to be in an earth-discharging state. It is also possible to prevent the wheel loader from being erroneously determined to be in an earth-discharging state for a loading target other than the preset loading target 92. This makes it possible to avoid a situation in which the arm 2 automatically rises even if the bucket operating device 53 is operated, for example, during excavation or transporting operation, or when the wheel loader approaches a loading target other than the preset loading target 92. Therefore, it is possible to avoid interfering with the excavation or transporting operation of the wheel loader, and to make the operator aware that earth is being discharged for a loading target other than the preset loading target 92.

[0101] <Third embodiment> Next, a wheel loader according to a third embodiment will be described. The wheel loader according to the third embodiment is characterized in that the arm 2 is not automatically raised when performing work such as knocking out earth and sand from the inside of the bucket 3. The wheel loader according to this embodiment differs from the wheel loader 1 according to the first embodiment described above in the control processing executed by the main controller 100B. Below, components having the same or similar functions as those in the control processing executed by the main controller 100 of the wheel loader 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and only different parts will be described.

[0102] Fig. 15 is a functional block diagram of the main controller 100B of the wheel loader according to the third embodiment. Fig. 16 is a flowchart showing the control processing carried out in the main controller 100B of the wheel loader according to the third embodiment.

[0103] As shown in FIG. 15, the work state determination unit 110B of the main controller 100B determines whether the bucket operation position R of the bucket operation device 53 is in a predetermined position. BKT and arm cylinder pressure P of arm hydraulic cylinder 4 ARM Specifically, the work state determination unit 110B calculates the operation position (operation amount) of the bucket operation lever based on the bucket operation signal detected by the bucket operation lever sensor 53a, and determines that the wheel loader 1 is in the earth-releasing state if the calculated operation position of the bucket operation lever is equal to or greater than a predetermined first operation threshold R1 that causes the bucket 3 to perform a dumping operation. Hereinafter, the arm cylinder pressure P of the arm hydraulic cylinder 4 ARMThe determination of whether the bucket is in the earth-releasing state or the earth-non-releasing state based on the above will be specifically described. The work state determination unit 110B calculates a state parameter that varies depending on the weight of the load in the bucket 3. Here, examples of the state parameter include the arm cylinder pressure of the arm hydraulic cylinder 4 detected by an arm cylinder pressure sensor (state parameter amount detection device) 75 and the strain of the arm 2 detected by a strain sensor (state parameter amount detection device). The arm cylinder pressure sensor 75 and the strain sensor transmit information on the arm cylinder pressure of the arm hydraulic cylinder 4 and the strain of the arm 2, respectively, to the main controller 100B. The strain sensor is, for example, a piezoelectric element, and is attached to the base of the arm 2 (i.e., the side attached to the vehicle body 8). For example, when the weight of the load in the bucket 3 increases, the arm cylinder pressure of the arm hydraulic cylinder 4 and the strain of the arm 2 increase. Below, an example will be described in which the state parameter is the arm cylinder pressure of the arm hydraulic cylinder 4.

[0104] When the soil release determination flag FL is set to OFF, the work state determination unit 110B determines whether the bucket operation position R BKT becomes equal to or greater than the first operation threshold R1, and the arm cylinder pressure P detected by the arm cylinder pressure sensor 75 ARM When the pressure becomes equal to or greater than a pressure threshold P1 (weight threshold), the release determination flag FL is switched from OFF to ON. The pressure threshold P1 corresponds to the pressure when the load is in the bucket 3, and is stored in advance in the ROM 102. The pressure threshold P1 corresponds to, for example, about 10% of the maximum pressure of the pressure sensor, which is 100%.

[0105] As shown in FIG. 16, in the third embodiment, if it is determined in S111 that the release determination flag FL is off (NO in S111), the process proceeds to S311.

[0106] In S311, the working state determination unit 110B determines the arm cylinder pressure P ARM In step S311, it is determined whether the arm cylinder pressure P ARMIf it is determined that the arm cylinder pressure P is equal to or greater than the pressure threshold P1 (YES in S311), the process proceeds to S113. ARM If it is determined that the pressure is smaller than the pressure threshold P1 (NO in S311), the process proceeds to S120.

[0107] In this way, in the wheel loader according to the third embodiment, the working state determination unit 110B of the main controller 100B determines whether the arm cylinder pressure P ARM If the arm cylinder pressure P ARM is determined to be smaller than the pressure threshold P1, the wheel loader is determined to be not in the earth-releasing state. If it is determined that the wheel loader is not in the earth-releasing state, the main controller 100B does not perform control to raise the arm 2.

[0108] In this manner, in this embodiment, the main controller 100B controls the operation position of the bucket operation device 53 and the arm cylinder pressure P ARM Based on this, it is determined whether or not the state is ready to start releasing soil. As a result, if there is no load in the bucket 3, the arm 2 will not automatically rise when the bucket 3 is subjected to a dumping operation. Therefore, it is possible to prevent the arm 2 from inadvertently automatically rising when the work implement 6 is being positioned for digging or when work is being done to knock off any load remaining in the bucket 3. It is also possible to prevent the amount of pressurized oil flowing to the bucket hydraulic cylinder 5 from being reduced, i.e., to prevent the operation of the bucket 3 from being slowed down. This makes it possible to avoid interfering with the work of knocking off any load remaining in the bucket 3.

[0109] <Fourth embodiment> Next, a wheel loader according to a fourth embodiment will be described. The wheel loader according to the fourth embodiment is characterized by delaying the timing at which the soil release determination flag is turned off. The wheel loader according to this embodiment differs from the wheel loader 1 according to the first embodiment described above in the control processing executed by the main controller 100C1. Below, components having the same or similar functions as those in the control processing executed by the main controller 100 of the wheel loader 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and only different parts will be described.

[0110] Fig. 17 is a functional block diagram of the main controller 100C1 of the wheel loader according to the fourth embodiment. Fig. 18 is a flowchart showing the control processing carried out in the main controller 100C1 of the wheel loader according to the fourth embodiment.

[0111] As shown in FIG. 17, the work state determination unit 110C determines whether the bucket operation position R BKT and vehicle speed V CRZ Specifically, the work state determination unit 110C calculates the operation position (operation amount) of the bucket operation lever based on the bucket operation signal detected by the bucket operation lever sensor 53a, and determines that the wheel loader 1 is in the earth-discharging state if the calculated operation position of the bucket operation lever is equal to or greater than a predetermined first operation threshold R1 that causes the bucket 3 to perform a dumping operation. CRZ When the soil release determination flag FL is set to OFF, the work state determination unit 110C determines whether the bucket is in the soil release state or not based on the soil release determination flag FL. BKT When the vehicle speed V detected by the vehicle speed sensor 61 becomes equal to or greater than the first operation threshold R1, the release determination flag FL is switched from OFF to ON. CRZ The distance traveled calculated based on CRZ Reset to 0.

[0112] When the soil release determination flag FL is set to ON, the work state determination unit 110C of the main controller 100C1 determines whether the calculated travel distance D CRZ When the travel distance D becomes equal to or greater than the distance threshold D1, the earth dumping determination flag FL is switched from on to off. The distance threshold D1 corresponds to a predetermined distance from the position where the earth dumping operation is completed (the position of the wheel loader 1 shown in FIG. 4(c)) to the initial position of the transport operation (the position of the wheel loader 1 shown by the solid line in FIG. 3), and is stored in advance in the ROM 102. The distance threshold D1 corresponds to 1 m in the backward direction, for example, when the position where the earth dumping operation is completed (the position of the wheel loader 1 shown in FIG. 4(c)) is set to 0 m. Travel distance D CRZ corresponds to the actual travel distance of the wheel loader from the position where the above-mentioned earth dumping work was completed to the initial position of the above-mentioned transport work. The work state determination unit (distance detection device) 110C calculates the vehicle speed V detected by the vehicle speed sensor 61 based on the position where the earth dumping work was completed (earth dumping position). CRZ By integrating over time, the distance between the loading target 92 where the wheel loader releases soil and the vehicle body 8 (i.e., the travel distance D CRZ ) is calculated.

[0113] 18, in the fourth embodiment, after the release determination flag FL is set to ON in S115, the process proceeds to S416. In S416, the work state determination unit 110C determines the vehicle speed V detected by the vehicle speed sensor 61. CRZ The distance traveled calculated based on CRZ Reset to 0.

[0114] On the other hand, if it is determined in S111 that the release determination flag FL is on (YES in S111), the process proceeds to S417. CRZ It is determined whether the traveled distance D is equal to or greater than the distance threshold D1. CRZ is not equal to or greater than the distance threshold D1, in other words, CRZ If the distance D is smaller than the distance threshold D1 (NO in S417), the release determination flag remains on and the process proceeds to S120. CRZIf the distance is equal to or greater than the distance threshold D1 (YES in S417), the process proceeds to S119. Then, in S119, the work state determination unit 110C switches the release determination flag to OFF, and the process proceeds to S120.

[0115] That is, in the wheel loader according to the fourth embodiment, after it is determined that the wheel loader is in the earth-releasing state, the working state determination unit 110C determines the distance between the loading target 92 and the vehicle body 8 (i.e., the traveling distance D CRZ ) is equal to or greater than the distance threshold D1, the wheel loader is determined not to be in the earth-releasing state. On the other hand, after the wheel loader is determined to be in the earth-releasing state, the work state determination unit 110C determines that the distance between the loading target 92 and the vehicle body 8 (i.e., the travel distance D CRZ ) is not equal to or greater than the distance threshold D1, it is determined that the wheel loader is in the earth-releasing state.

[0116] In this manner, in this embodiment, the work state determination unit 110C determines the traveled distance D CRZ If the distance D is not equal to or greater than the distance threshold D1, that is, if the vehicle body 8 is located in the vicinity of the loading target 92, the release judgment flag is maintained ON. CRZ The timing at which the earth release determination flag FL is turned off can be delayed until the distance between the vehicle body 8 and the loading target 92 becomes equal to or greater than the distance threshold D1, that is, until the vehicle body 8 moves backward and moves away from the loading target 92. This prevents the earth release flag from being repeatedly turned on and off when the vehicle body 8 is located near the loading target 92, and thus prevents the work state determination unit 110C from malfunctioning.

[0117] Fifth Embodiment Next, a wheel loader according to a fifth embodiment will be described. The wheel loader according to the fifth embodiment is characterized in that the arm 2 is automatically lowered when tilting the bucket 3 after soil-discharging operation. The wheel loader according to this embodiment differs from the wheel loader 1 according to the first embodiment described above in the control processing executed by the main controller 100C2. Below, components having the same or similar functions as those in the control processing executed by the main controller 100 of the wheel loader 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and only different parts will be described.

[0118] Fig. 19 is a functional block diagram of the main controller 100C2 of the wheel loader according to the fifth embodiment. Fig. 20 is a functional block diagram of the main controller 100C2 of the wheel loader according to the fifth embodiment. BKT and arm correction value K ARM Fig. 21A is a characteristic diagram showing an example of the relationship between Fig. 21A and Fig. 21B. Fig. 21A shows part of a flowchart showing the control processing performed in the main controller 100C2 of the wheel loader according to the fifth embodiment. Fig. 21B shows the rest of the flowchart shown in Fig. 21A.

[0119] As shown in FIG. 19, the work state determination unit 110C′ determines whether the bucket operation position R BKT When the soil release determination flag FL is set to ON and the bucket operation position R detected based on the bucket operation lever sensor 53a is set to ON, the work state determination unit 110C' determines the soil release determination flag FL, specifically the preparation flag FL. BKTWhen the load current falls below the third operation threshold R3 that causes the bucket 3 to tilt, the wheel loader's work state determination is changed from the earth-releasing state to the non-earth-releasing state. Specifically, the work state determination unit 110C' changes the earth-releasing determination flag FL from on to off, and then sets the preparation flag FL to on. When the preparation flag FL is set to on, the work state determination unit 110C' determines that the earth-releasing state has ended and that preparation for the next earth-releasing operation has begun. When the preparation flag FL is set to off, the work state determination unit 110C' determines that the earth-releasing state has ended but preparation for the next earth-releasing operation has not begun. The third operation threshold R3 corresponds to the bucket operation position when preparation work (i.e., tilt operation after earth-releasing operation has ended) begins, and is stored in advance in the ROM 102. For example, the third operation threshold R3 corresponds to an operation position of approximately -10% when the maximum bucket operation position on the dump operation side is 100% and the maximum bucket operation position on the tilt operation side is -100%. The third operation threshold value R3 is smaller than the second operation threshold value R2. In this embodiment, the bucket operation position R BKT becomes equal to or less than the third operation threshold R3, the preparation flag FL is set to ON.

[0120] The work state determination unit 110C' calculates the operation position (operation amount) of the bucket operation device based on the bucket operation signal detected by the bucket operation lever sensor 53a. As shown in FIG. 19, the correction value calculation unit 111C calculates the operation position (operation amount) of the bucket operation device based on the calculated bucket operation position R BKT Based on the correlation map characteristics shown in Figure 20, the arm correction value K ARM As shown in Figure 20, the bucket operation position R BKT When the load increases toward the dumping operation side of bucket 3, the arm correction value K is increased to raise arm 2. ARM The characteristic of increasing is the same as that of the first embodiment. BKT When the tilting action of bucket 3 increases, arm correction value K is set to lower arm 2. ARM is reduced.

[0121] 21A and 21B, in the fifth embodiment, after the soil release determination flag FL is switched from ON to OFF in S119, the process proceeds to S510. In S510, the work state determination unit 110C' determines whether the bucket operation position R of the bucket operation device 53 is ON or OFF. BKT is equal to or less than the third operation threshold R3. In the fifth embodiment, S119 is executed after YES in S117, but as shown in FIG. 18, S119 may be executed after YES in S417. In this case, S117 is omitted. Furthermore, S416 shown in FIG. 18 is executed after S115.

[0122] In S510, the bucket operation position R of the bucket operation device 53 BKT is equal to or smaller than the third operation threshold value R3 (YES in S510), the process proceeds to S520, where a determination is made to turn on the preparation flag. BKT If it is determined that the third operation threshold R3 is greater than the third operation threshold R4 (NO in S510), the process proceeds to S530, where a decision is made to turn off the preparation flag.

[0123] After S520 and S530, the processing proceeds to S540. In S540, the work state determination unit 110C' determines whether or not the wheel loader is in a state to start preparation for the next earth-discharging operation, based on the preparation flag FL that was set in S520 and S530. If the preparation flag FL is set on (YES in S540), the work state determination unit 110C' determines that the wheel loader is in a state to start preparation for the next earth-discharging operation, and proceeds to S130a. If the preparation flag FL is set off (NO in S540), the work state determination unit 110C' determines that the wheel loader is not in a state to start preparation for the next earth-discharging operation, and proceeds to S140a.

[0124] In S150a, the arm command value calculation unit 112 calculates the arm operation position R ARM , the arm correction value K calculated in S130a or S140a based on the correlation map shown in FIG. ARMBy adding ARM (See equation (1) above).

[0125] In this way, in the wheel loader according to the fifth embodiment, the work state determination unit 110C′ determines whether the bucket operation device 53 is in the operating position R BKT is equal to or less than the third operation threshold R3, the work state determination unit 110C' changes the work state determination of the wheel loader from the earth-releasing state to the non-earth-releasing state. Specifically, the work state determination unit 110C' determines that the wheel loader is in a state preparing for the next earth-releasing operation. Then, when it is determined that the wheel loader is in a state preparing for the next earth-releasing operation, the main controller 100C2 controls the arm 2 to lower, i.e., to rotate it downward.

[0126] When the operator returns to the initial position for the transporting work (the position of the wheel loader 1 shown by the solid line in FIG. 3 ) after completing the soil dumping work, he tilts the bucket 3 to raise the bottom end of the bucket 3 so that the bucket 3 does not come into contact with the loading target 92, and then performs an operation to lower the arm 2 while moving the vehicle body 8 backward. In this embodiment, after the bucket 3 is dumped during the soil dumping work, the arm automatically lowers in accordance with the tilting of the bucket 3. As a result, when the vehicle body 8 begins to move backward after the soil dumping work, the arm has lowered to an extent that the bucket 3 does not come into contact with the loading target 92, and the work time until the vehicle body 8 returns to the initial position for the transporting work can be shortened. Therefore, a smoother soil dumping work can be achieved, and work efficiency can be improved.

[0127] Sixth Embodiment Next, a wheel loader according to a sixth embodiment will be described. The wheel loader according to the sixth embodiment is characterized in that if the dumping operation of the bucket 3 is too fast during soil discharging work, the dumping speed of the bucket 3 is slowed down. The wheel loader according to this embodiment differs from the wheel loader 1 according to the first embodiment described above in the control processing executed by the main controller 100D. Below, components having the same or similar functions as those in the control processing executed by the main controller 100 of the wheel loader 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and only different parts will be described.

[0128] Fig. 22 is a functional block diagram of the main controller 100D of the wheel loader according to the sixth embodiment. Fig. 23 is an example of a characteristics diagram showing the relationship between the bucket operation amount and the bucket correction value in the wheel loader according to the sixth embodiment. Fig. 24 is a flowchart showing control processing carried out in the main controller 100D of the wheel loader according to the sixth embodiment.

[0129] As shown in FIG. 22, a correction value calculation unit 111D of a main controller 100D calculates a bucket operation position (operation amount) R detected by a bucket operation lever sensor 53a. BKT Based on the arm correction value K ARM In addition to calculating the bucket operation position R BKT Based on the correlation map characteristics shown in Figure 23, the bucket correction value K BKT In the correlation map characteristics shown in FIG. 23, the bucket operation position R BKT The larger the bucket correction value K BKT Specifically, the bucket operation position R BKT The larger the fourth operation threshold R4, the greater the bucket correction value K BKT The fourth operation threshold R4 is a bucket operation position R at which the dumping operation of the bucket 3 becomes relatively faster than the lifting speed of the arm 2. BKT In Figure 23, the bucket operation position R BKT is the bucket correction value K when it is less than the fourth operation threshold R4 (including neutral) BKTis the bucket command value C BKT The bucket operation position R corresponds to an amount that does not affect the value of the bucket operation position R. BKT is less than the fourth operation threshold R4, the bucket correction value K BKT corresponds to 100%, for example.

[0130] The bucket command value calculation unit 113D of the main controller 100D calculates the bucket operation position R BKT and bucket correction value K BKT Based on and C BKT =R BKT ×K BKT (also called equation (2)) based on the bucket command value C BKT Calculate the following.

[0131] As shown in Fig. 24, after S150, the process proceeds to S600. In S600, the main controller 100D determines whether the bucket operation position R BKT is equal to or greater than a fourth operation threshold value R4. BKT is determined to be equal to or greater than the fourth operation threshold R4 (YES in S600), the process proceeds to S610. In S610, the correction value calculation unit 111D calculates the bucket correction value K BKT On the other hand, the bucket operation position R BKT is less than the fourth operation threshold R4 (NO in S600), the process proceeds to S620. In S620, the correction value calculation unit 111D calculates the bucket correction value K BKT is calculated (for example, set to 100%), and the process proceeds to S630.

[0132] In S630, the bucket command value calculation unit 113D calculates the bucket operation position R BKT , the bucket correction value K calculated in S610 or S620 BKT By multiplying by this, the bucket command value C BKT(See the above formula (2)) When the process of S630 is completed, the process of the flowchart for this control cycle ends, and in the next control cycle, the process from S111 to S630 is executed again.

[0133] In this way, in the wheel loader according to the sixth embodiment, the main controller 100D controls the operation position R BKT is equal to or greater than the fourth operation threshold R4, the operation position R BKT is less than the fourth operation threshold R4. BKT Bucket correction value K BKT is multiplied to obtain the bucket command value C BKT As a result, in the case where the dumping operation of the bucket 3 is relatively too fast compared to the lifting of the arm 2 during the soil releasing operation, the dumping operation of the bucket 3 can be slowed down to make it less likely that the bucket 3 will come into contact with the loading target 92 or the load.

[0134] Seventh Embodiment Next, a wheel loader according to a seventh embodiment will be described. The wheel loader according to the seventh embodiment is characterized in that when the arm 2 is manually raised during soil release work, the arm 2 is not suddenly raised. The wheel loader according to this embodiment differs from the wheel loader 1 according to the first embodiment described above in that the arm command value C ARM In this embodiment, the same reference numerals as those used in the main controller 100 of the wheel loader 1 according to the first embodiment will be used for explanation.

[0135] Specifically, instead of the formula (1) in the first embodiment, the arm command value C is calculated using the following formula (3): ARM Calculates C ARM =max(R ARM ,K ARM )(Formula (3))

[0136] In this way, the arm command value calculation unit 112 calculates the arm operation position (operation amount) R ARM and arm correction value KARM The larger value is the arm command value C ARM Here, when the arm 2 is manually raised in accordance with the dumping operation of the bucket 3 during the earth-releasing operation, in the wheel loader according to the first embodiment, the arm operating position R ARM Arm correction value K ARM , which may cause the arm 2 to rise suddenly. In this case, the load in the bucket 3 may fall from a higher position onto the loading target 92, which may result in a greater impact on the loading target 92, for example. There is also a risk that the arm 2 may rise at a speed different from that intended by the operator. In response to this, in the wheel loader according to the seventh embodiment, the arm operating position R ARM Even if the arm operating position R ARM and arm correction value K ARM The larger value is the arm command value C ARM Therefore, it is possible to prevent the lifting speed of the arm 2 from becoming too high. Therefore, it is possible to mitigate the impact of the load in the bucket 3 dropping onto the loading target 92, and to release the soil more exactly as intended by the operator.

[0137] While preferred embodiments of the present invention have been described above, the present invention is not limited to the wheel loaders according to the first to seventh embodiments described above, and includes all aspects encompassed within the concept and scope of the claims of the present invention. Furthermore, the various configurations may be appropriately and selectively combined to achieve at least some of the above-described problems and effects. For example, the shape, material, arrangement, size, etc. of each component in the above-described embodiments may be modified as appropriate depending on the specific aspects of the present invention.

[0138] In the above embodiment, an example has been described in which the work machine is a wheel loader 1, but the present invention is not limited to this. The present invention can be applied to various work machines that are equipped with work implements equivalent to an arm and a bucket, such as forklifts, shovels, and lift trucks. Furthermore, in the above explanation, an example has been given in which a hybrid system using the engine 20 and generator motor 40 as a drive source is employed, but a system that uses only the engine 20 as a drive source may also be employed.

[0139] In the above embodiment, an example has been described in which bucket operation lever sensor 53a is a potentiometer, but the present invention is not limited to this. For example, bucket operation lever sensor 53a may be a pressure sensor that detects the pilot pressure input to a pilot chamber of a directional control valve that controls bucket hydraulic cylinder 5, which constitutes front control section 31.

[0140] In the above embodiment, the main controller 100 may perform moving average processing or low-pass filter processing on the values ​​used in various judgments and calculations to avoid the influence of disturbances and noise. By performing moving average processing or low-pass filter processing, the arm correction value K ARM and bucket correction value K BKT As a result, the stability and operability of the arm lifting during the soil release operation can be improved.

[0141] In the above embodiment, an example has been described in which the wheel loader 1 is equipped with a single traveling motor 43 that supplies power to the traveling device 11, but the present invention is not limited to this. The present invention may also be applied to a wheel loader 1 that is equipped with a plurality of traveling motors 43. For example, the present invention can be applied to a wheel loader 1 that is equipped with a traveling motor 43 that drives the left front wheel 7A and a traveling motor 43 that drives the right front wheel 7A. The present invention can also be applied to a wheel loader 1 that is equipped with four traveling motors 43 that drive each of a pair of left and right front wheels 7A and a pair of left and right rear wheels 7B. The traveling motor 43 may be connected to the wheels 7 via a transmission, or may be configured to be integrated into the wheels 7.

[0142] In the above embodiment, an example was described in which the work machine was an electrically driven wheel loader, but the present invention is not limited to this. The present invention may also be applied to, for example, a torque converter driven wheel loader or a hydraulic static transmission (HST) driven wheel loader in which the power of the engine 20 is converted into hydraulic power and transmitted to the wheels 7.

[0143] In the above embodiment, values ​​used in various determinations and calculations may be subjected to moving average processing or low-pass filtering to avoid the effects of disturbances and noise. By performing moving average processing or low-pass filtering on the engine speed correction value NC, it is possible to suppress a sudden fluctuation in the engine speed correction value NC immediately after the target engine speed NEG_TGT increases, thereby improving the stability and operability of engine control.

[0144] Some or all of the functions of the main controller 100 described in the above embodiment may be realized by hardware (for example, by designing logic for executing each function as an integrated circuit).

[0145] Although the embodiments of the present invention have been described above, these embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. The above-described embodiments and variations are provided as examples to facilitate understanding of the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment or variation with the configuration of another embodiment or variation, and it is also possible to add the configuration of another embodiment or variation to the configuration of one embodiment or variation. Note that the control lines and information lines shown in the figures are those considered necessary for explanation, and do not necessarily represent all control lines and information lines required in the product. In reality, it can be assumed that almost all configurations are interconnected. [Explanation of symbols]

[0146] 1. Wheel loader (work machine) 2 Arms 3 buckets 4 Hydraulic cylinder for arm (actuator for arm) 5. Bucket hydraulic cylinder (bucket actuator) 8. Body 52 Arm operating device 53 Bucket operating device 100 Main controller (control device) D1 distance threshold P1 Pressure threshold (weight threshold) R BKT Bucket operating device operating position (operation amount) R1 First operation threshold R3 Third operation threshold R4 Fourth operation threshold T1 First duration (predetermined time) Σ1 Accumulation threshold Σ2 Mileage threshold

Claims

1. The car body and an arm supported on the vehicle body and rotatable in the vertical direction; a bucket supported by the arm and capable of tilting and dumping; an arm actuator that rotates the arm in the vertical direction; a bucket actuator that causes the bucket to perform a tilt operation and a dump operation; a control device that controls the arm actuator and the bucket actuator; an arm operating device that rotates the arm in the vertical direction; an arm operation amount sensor that detects an operation amount of the arm operation device as an arm operation signal for rotating the arm in the vertical direction; a bucket operation device that causes the bucket to perform a tilt operation and a dump operation; a bucket operation amount sensor that detects an operation amount of the bucket operation device as a bucket operation signal for tilting and dumping the bucket, The control device calculating an integrated arm operation amount, which is a value obtained by multiplying the operation amount of the arm operating device detected by the arm operation amount sensor by a time period during which the operation amount is held, and adding the resultant value for each operation amount of the arm operating device; determining whether the work machine is in an earth-releasing state in which earth is being released, or in a non-earth-releasing state in which earth is not being released, based on the operation amount of the bucket operation device detected by the bucket operation amount sensor and the arm integrated operation amount; A work machine characterized in that, when it is determined that the work machine is in the soil-releasing state, the arm actuator is controlled to rotate the arm upward.

2. The work machine described in Claim 1, characterized in that the control device determines that the work machine is in a soil-releasing state when the operation amount of the bucket operation device detected by the bucket operation amount sensor is equal to or greater than a predetermined first operation threshold value that causes the bucket to perform a dumping operation.

3. 3. The work machine according to claim 2, wherein the control device determines that the work machine is in the soil-releasing state when a state in which the operation amount of the bucket operation device detected by the bucket operation amount sensor is equal to or greater than the first operation threshold continues for a predetermined time.

4. 2. The work machine according to claim 1, wherein the control device determines that the work machine is in the non-earth-releasing state when the arm integrated operation amount is smaller than a predetermined integrated threshold value.

5. a travel drive device that causes the vehicle body to travel; a vehicle speed detection device for detecting a traveling speed of the vehicle body, The control device Calculating a travel distance of the vehicle body from the initial position of the vehicle body to the soil release start position based on the travel speed detected by the vehicle speed detection device; 2. The work machine according to claim 1, wherein a determination is made as to whether the work machine is in the soil-releasing state or a non-soil-releasing state in which soil is not being released, based on the traveling distance of the vehicle body and the operation amount of the bucket operation device detected by the bucket operation amount sensor.

6. The work machine according to claim 5, wherein the control device determines that the work machine is in the non-earth-releasing state when the traveled distance is smaller than a predetermined traveled distance threshold.

7. a state parameter amount detection device for detecting the magnitude of a state parameter that varies in accordance with the weight of the load in the bucket; The control device 2. The work machine according to claim 1, wherein a determination is made as to whether the work machine is in the soil-releasing state or a non-soil-releasing state in which soil is not being released, based on the magnitude of the state parameter detected by the state parameter amount detection device and the operation amount of the bucket operation device detected by the bucket operation amount sensor.

8. 8. The work machine according to claim 7, wherein the control device determines that the work machine is in the non-earth-releasing state when the magnitude of the state parameter detected by the state parameter amount detection device is smaller than a predetermined weight threshold.

9. a travel drive device that causes the vehicle body to travel; a distance detection device that detects the distance between the vehicle body and a soil-releasing position where the work machine releases soil, 2. The work machine according to claim 1, wherein the control device changes the work state determination of the work machine from the soil-releasing state to the non-soil-releasing state when the work machine is determined to be in the soil-releasing state and the distance detected by the distance detection device is equal to or greater than a predetermined distance threshold.

10. A work machine as described in claim 1 or 9, characterized in that when the work machine is determined to be in the soil-releasing state and the operation amount of the bucket operation device detected by the bucket operation amount sensor is equal to or less than a predetermined third operation threshold for tilting the bucket, the control device changes the work state determination of the work machine to the non-soil-releasing state and controls the arm actuator to rotate the arm downward.

11. The control device 2. The work machine according to claim 1, wherein, when the operation amount of the bucket operation device detected by the bucket operation amount sensor is equal to or greater than a predetermined fourth operation threshold, the bucket actuator is controlled to make the dumping operation speed of the bucket slower than when the operation amount of the bucket operation device is less than the fourth operation threshold.

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