Work vehicles

Abstract

To provide a work vehicle which can improve work efficiency even if excavation objects having different grain sizes are excavated.SOLUTION: A work vehicle includes: a hydraulic pump and a power generator driven by an engine; a hydraulic cylinder operated by hydraulic oil from the hydraulic pump; a work device moved by the hydraulic cylinder; an electric motor which is driven by power generated from the power generator and operates a travel device; a pressure sensor for detecting pressure of the hydraulic cylinder; and a control device for calculating an output distribution ratio for distributing the output of the engine to the work device and the travel device, and controlling the hydraulic pump and the electric motor on the basis of the calculated output distribution ratio. The control device calculates a pulsation value indicating magnitude of pulsation of reaction force acting on the work device when the excavation object is excavated by the work device on the basis of the detection result of the pressure sensor, and calculates the output distribution ratio so that a ratio of the output of the travel device to the output of the work device becomes greater as the calculated pulsation value becomes greater.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] There is known a work vehicle including a traveling device for moving a vehicle body, and a work device having a bucket and a lift arm for excavating earth and sand or the like (see Patent Document 1). In such a work vehicle, earth and sand excavated is transported to a transport vehicle such as a dump truck and loaded. The efficiency of a series of operations including excavation, transportation, and loading is one index indicating the performance of the work vehicle. The work efficiency by the work vehicle corresponds to, for example, the weight [ton / h] of the transported material (excavated material) loaded onto the transport vehicle per unit time in a series of operations. That is, the higher the work efficiency value is, the more material can be excavated and transported in a shorter time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a work vehicle, the power (output) of an engine is distributed to the traveling device and the work device to perform excavation work. At this time, if the traveling driving force is small and the work driving force is too large, the bucket cannot be sufficiently penetrated into the earth and sand, or the bucket may be lifted before the earth and sand sufficiently enters the bucket, resulting in a decrease in work efficiency. On the other hand, if the traveling driving force is large and the work driving force is too small, it takes time to lift the bucket, resulting in a decrease in work efficiency. In order to improve work efficiency, it is effective to appropriately perform power distribution (output distribution) between the traveling driving force and the work driving force.

[0005] The size of the material being excavated varies depending on the excavation site. Therefore, if the engine's power distribution ratio to the travel drive force and the work drive force is set to be the same when excavating materials with different size gradations, work efficiency may decrease. For example, when excavating materials with larger size gradations, it is more difficult to penetrate the bucket compared to excavating materials with smaller size gradations, requiring greater travel drive force. Therefore, even if work efficiency is good when excavating materials with smaller size gradations, work efficiency may deteriorate when excavating materials with larger size gradations.

[0006] The present invention aims to provide a work vehicle that can improve work efficiency even when excavating materials with different particle sizes. [Means for solving the problem]

[0007] A work vehicle according to one aspect of the present invention comprises an engine mounted on a vehicle body, a hydraulic pump driven by the engine, a hydraulic cylinder that extends and retracts using hydraulic fluid discharged from the hydraulic pump, a work device that moves in accordance with the extension and retraction of the hydraulic cylinder, a running device that is driven independently of the work device and moves the vehicle body, a generator that is driven by the engine and generates electricity, an electric motor that is driven by the electricity generated by the generator and operates the running device, a pressure sensor that detects the pressure of the hydraulic cylinder, a speed sensor that detects the rotational speed of the electric motor, a current sensor that detects the current of the electric motor, and a control device that calculates an output distribution ratio for distributing the output of the engine to the work device and the running device, and controls the hydraulic pump and the electric motor based on the calculated output distribution ratio. The control device calculates a pulsation value representing the magnitude of the reaction force pulsation acting on the work device when the work device is excavating an object to be excavated, based on at least one of the detection results of the pressure sensor, the speed sensor, and the current sensor, and calculates the output distribution ratio such that the larger the calculated pulsation value, the larger the ratio of the output of the travel device to the output of the work device. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a work vehicle that can improve work efficiency even when excavating materials with different particle sizes. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a side view of a wheel loader. [Figure 2] Figure 2 is a system configuration diagram of a wheel loader. [Figure 3] Figure 3 is a diagram illustrating V-shaped loading using a wheel loader. [Figure 4] Figure 4 is a diagram illustrating the general operation of the excavation work. [Figure 5] Figure 5 is a functional block diagram of the control device according to this embodiment. [Figure 6] Figure 6 is a control block diagram of the excavation operation determination unit. [Figure 7] Figure 7 is a schematic diagram showing the time change of bucket cylinder pressure. [Figure 8] Figure 8 is a control block diagram of the particle size level determination unit 112c. [Figure 9] Figure 9 is a schematic diagram showing the time change of motor speed (vehicle speed). [Figure 10] Figure 10 is a control block diagram of the excavation volume level determination unit. [Figure 11] Figure 11 illustrates the excavation state determination process by the excavation state determination unit according to this embodiment. [Figure 12] Figure 12 is a diagram illustrating the excavation state determination process by the excavation state determination unit according to Modification Example 2. [Figure 13] Figure 13 is a functional block diagram of the control device according to Modification 3. [Modes for carrying out the invention]

[0010] A work vehicle according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, an example will be described in which the work vehicle is a wheel loader equipped with an electric drive system.

[0011] Figure 1 is a side view of the wheel loader 10. As shown in Figure 1, the wheel loader (hereinafter also simply referred to as the vehicle) 10 comprises a body 8 and a multi-jointed working device 6 mounted in front of the body 8. The body 8 employs an articulated steering system (body articulation type). The body 8 comprises a front body (front frame) 8A with front wheels 7A (wheels 7) mounted on the left and right sides, a rear body (rear frame) 8B with rear wheels 7B (wheels 7) mounted on the left and right sides, and a center joint 13 connecting the front body 8A and the rear body 8B. Steering cylinders 9 are provided on both the left and right sides of the center joint 13 to connect the front body 8A and the rear body 8B.

[0012] The working device 6 is attached to the front body 8A. The working device 6 comprises an arm cylinder 4, a lift arm (hereinafter simply referred to as "arm") 2 which moves in accordance with the extension and retraction of the arm cylinder 4, a bucket cylinder 5, and a bucket 3 which moves in accordance with the extension and retraction of the bucket cylinder 5. One arm 2 and one arm cylinder 4 are provided on each side of the front body 8A. A Z-link type (bell crank type) link mechanism is used to operate the bucket 3. The bucket cylinder 5 is included in this link mechanism.

[0013] On the rear body 8B, a driver's cab 12 is mounted in the front and an engine room 16 is mounted in the rear. Inside the driver's cab 12, there are an arm operation device 144 (see Fig. 2) for operating the arm cylinder 4 (arm 2) of the working device 6, a bucket operation device 145 (see Fig. 2) for operating the bucket cylinder 5 (bucket 3) of the working device 6, a forward and reverse switching device 143 (see Fig. 2) for switching the forward (F) and reverse (R) of the vehicle body 8, an accelerator operation device 141 (see Fig. 2) for instructing the vehicle body 8 to accelerate, a brake operation device 142 (see Fig. 2) for instructing the vehicle body 8 to decelerate, and a steering operation device (not shown) for instructing the left and right traveling directions of the vehicle body 8. When the steering operation device is operated, the rear body 8B and the front body 8A are refracted (swiveled) around the center joint 13 as the steering cylinder 9 expands and contracts.

[0014] In the engine room 16, an engine (ENG) 21, a hydraulic pump (PUMP) 24, a control valve (C / V) 25, a generator (GEN) 22, a traveling motor (MOT) 26, etc. shown in Fig. 2 are housed. The engine 21 is constituted by an internal combustion engine such as a diesel engine, for example.

[0015] Fig. 2 is a system configuration diagram of the wheel loader 10. As shown in Fig. 2, the wheel loader 10 is a series hybrid type work vehicle in which the drive part of the traveling device 11 is electrified. The electric drive system of the wheel loader 10 is a system that drives the generator 22 by the engine 21 to generate electricity, operates the traveling motor 26 with the electric power generated by the generator 22, and operates the traveling device 11 with the torque generated by the traveling motor 26.

[0016] The wheel loader 10 includes an engine 21, a control device 100 that controls each part of the vehicle, a generator 22 mechanically connected to the engine 21, a hydraulic pump 24 mechanically connected to the engine 21, hydraulic cylinders (arm cylinder 4, bucket cylinder 5, and steering cylinder 9) driven by the hydraulic oil discharged from the hydraulic pump 24, a power generation inverter (generator inverter) 23 that controls the power generation output (power generation power) of the generator 22 based on the power generation voltage command input from the control device 100, a traveling motor 26 that drives the vehicle body 8 with the power supplied from the generator 22, a traveling inverter (traveling motor inverter) 27 that controls the torque of the traveling motor 26 based on the traveling drive torque command input from the control device 100, and a traveling device 11 that is driven by the traveling motor 26 to cause the vehicle body 8 to travel. The work device 6 and the traveling device 11 are driven independently of each other by the output torque (power) of the engine 21.

[0017] The forward / backward switching device 143 has a forward / backward switch that is selectively operated to any one of a forward (F) position, a neutral (N) position, and a backward (R) position, and an operation position sensor 143a that detects the operation position of the forward / backward switch. The operation position sensor 143a outputs a forward / backward signal (FNR signal) corresponding to the selected operation position to the control device 100. The accelerator operation device 141 includes an accelerator pedal and an accelerator operation amount sensor 141a that detects the operation amount of the accelerator pedal (hereinafter also referred to as the accelerator operation amount). The accelerator operation amount sensor 141a outputs an accelerator signal representing the operation amount (depression amount) of the accelerator pedal to the control device 100. The brake operation device 142 includes a brake pedal and a brake operation amount sensor 142a that detects the operation amount of the brake pedal. The brake operation amount sensor 142a outputs a brake signal representing the operation amount (depression amount) of the brake pedal to the control device 100.

[0018] The arm operating device 144 includes an arm operating lever and an arm operating amount sensor 144a that detects the amount of arm operating lever operation (hereinafter also referred to as arm operating amount). The bucket operating device 145 includes a bucket operating lever and a bucket operating amount sensor 145a that detects the amount of bucket operating lever operation (hereinafter also referred to as bucket operating amount). The arm operating amount sensor 144a, the bucket operating amount sensor 145a, the accelerator operating amount sensor 141a, and the brake operating amount sensor 142a are, for example, potentiometers that output a voltage to the control device 100 according to the operating position of the operating member (operating lever or pedal).

[0019] The wheel loader 10 is equipped with a motor speed sensor 146. The motor speed sensor 146 is, for example, a resolver, which detects the rotational speed of the travel motor 26 (hereinafter also referred to as motor speed) and outputs a motor speed signal representing the detection result to the control device 100. The motor speed detected by the motor speed sensor 146 has a certain relationship with the vehicle speed. Therefore, the motor speed detected by the motor speed sensor 146 can be converted to the vehicle's travel speed (vehicle speed). In other words, the motor speed sensor 146 can also be said to be a vehicle speed sensor that detects vehicle speed.

[0020] The running gear 11 has four wheels 7 and a power transmission device that transmits power from the running motor 26 to the wheels 7. The power transmission device is composed of an axle, a differential device, a propeller shaft, etc. The running motor 26 is an electric motor that is rotationally driven by electricity generated by a generator 22 which is rotated by the torque output by the engine 21, and operates the running gear 11.

[0021] The power generator inverter 23 and the travel inverter 27 are connected by a DC section (power line) 28. The control device 100 drives the generator 22 with the engine 21 while controlling the DC voltage of the DC section 28, and drives the travel motor 26 with the generated power. The power generator inverter 23 controls the bus voltage of the DC section 28 using the power supplied from the generator 22 based on the power generation voltage command from the control device 100. The travel inverter 27 drives the travel motor 26 using the power of the DC section 28 based on the travel drive torque command from the control device 100. When the travel motor 26 is driven and the power of the travel motor 26 is transmitted to the wheels 7 via the power transmission device, the wheel loader 10 moves.

[0022] The hydraulic pump 24 is mechanically connected to the engine 21 and the generator 22, and is driven by the engine 21 to discharge hydraulic fluid as the working fluid. The hydraulic pump 24 is a variable displacement hydraulic pump whose discharge capacity can be changed by controlling the tilt angle of the swash plate or swash axis. The discharge capacity of the hydraulic pump 24 is controlled by a regulator (not shown). The flow rate and direction of the hydraulic fluid discharged from the hydraulic pump 24 are controlled by a control valve 25. The control valve 25 is controlled based on the operating direction and amount of the arm operating device 144, bucket operating device 145, and steering operating device. By controlling the control valve 25, hydraulic fluid is supplied to the hydraulic cylinders (arm cylinder 4, bucket cylinder 5, steering cylinder 9) corresponding to the operating device being operated, and the hydraulic cylinders are driven. The hydraulic cylinders 4, 5, and 9 extend and retract using the hydraulic fluid (pressurized oil) discharged from the hydraulic pump 24, which is rotated by the torque output by the engine 21.

[0023] When the arm operating device 144 is operated, the arm 2 rotates vertically in accordance with the extension and retraction of the arm cylinder 4. When the bucket operating device 145 is operated, the bucket 3 rotates vertically in accordance with the extension and retraction of the bucket cylinder 5. When the steering operating device is operated, the rear body 8B and the front body 8A bend (rotate) around the center joint 13 as the steering cylinder 9 is driven to extend and retract.

[0024] Thus, in the electric drive system according to this embodiment, the generator 22 is driven by the torque output by the engine 21, and the travel motor 26 is driven by the electricity generated by the generator 22. Therefore, torque control is possible independently of the rotational speed of the engine 21. In other words, the control device 100 can independently control the travel device 11 and the work device 6.

[0025] The control device 100 consists of a computer equipped with a processing unit 101 such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), and DSP (Digital Signal Processor), non-volatile memory 102 such as ROM (Read Only Memory), flash memory, and hard disk drive, volatile memory 103 known as RAM (Random Access Memory), an input interface 104, an output interface 105, and other peripheral circuits. The control device 100 may consist of one computer or multiple computers.

[0026] The non-volatile memory 102 stores a program capable of performing various calculations, as well as data such as thresholds used in those calculations. In other words, the non-volatile memory 102 is a storage device (storage medium) from which the program realizing the functions of this embodiment can be read. The processing unit 101 is an arithmetic processing unit that loads the program stored in the non-volatile memory 102 into the volatile memory 103 and executes calculations. The processing unit 101 performs predetermined calculations on signals received from the input interface 104, the non-volatile memory 102, and the volatile memory 103 according to the program.

[0027] The input interface 104 converts operation signals input from the operating device and sensor signals input from the sensors into data that can be processed by the processing unit 101. The operation signals input to the control unit 100 include a signal representing the accelerator operation amount detected by the accelerator operation amount sensor 141a, a signal representing the brake operation amount detected by the brake operation amount sensor 142a, a signal representing the arm operation amount detected by the arm operation amount sensor 144a, a signal representing the bucket operation amount detected by the bucket operation amount sensor 145a, and a signal representing the operating position of the forward / reverse switch detected by the operating position sensor 143a.

[0028] The sensor signals input to the control device 100 include a signal representing the angle detected by the arm relative angle sensor 151, which is provided on the connecting shaft that connects the vehicle body 8 and the arm 2, and a signal representing the angle detected by the bucket relative angle sensor 152, which is provided on the connecting shaft that connects the arm 2 and the bucket 3. The arm relative angle sensor 151 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 detection result to the control device 100. The bucket relative angle sensor 152 is a potentiometer that detects the relative angle of the bucket 3 with respect to the arm 2 and outputs a signal representing the detection result to the control device 100. Since the angle of the vehicle body 8 with respect to the ground (running surface) is constant, the angle detected by the arm relative angle sensor 151 corresponds to the relative angle (tilt angle) of the arm 2 with respect to the ground. The arm relative angle sensor 151 and the bucket relative angle sensor 152 function as attitude sensors that detect the attitude of the work device 6.

[0029] Furthermore, the sensor signals input to the control device 100 include a signal representing the motor speed detected by the motor speed sensor 146, a signal representing the pressure of the bucket cylinder 5 detected by the bucket cylinder pressure sensor (pressure sensor) 153, a signal representing the discharge pressure of the hydraulic pump 24 detected by the discharge pressure sensor 154, and a signal representing the current flowing through the travel motor 26 detected by the current sensor 155.

[0030] The output interface 105 generates an output signal according to the calculation result of the processing unit 101 and outputs that signal to the controlled equipment. Examples of controlled equipment include the power generation inverter 23, the drive inverter 27, an engine controller (not shown) that controls the engine 21, a solenoid valve (not shown) that controls the control valve 25, and a pump controller (not shown) that controls the capacity of the hydraulic pump 24.

[0031] Referring to Figure 3, an example of work performed by the wheel loader 10 will be explained. Figure 3 is a diagram illustrating the V-shaped loading operation of the wheel loader 10. As shown in Figure 3, the wheel loader 10 (1st operation) moves forward toward the object to be excavated 91, such as the ground, (2nd operation) plunges the bucket 3 into the object to be excavated 91, and performs excavation work by operating the bucket 3 and arm 2 to excavate the object to be excavated 91. After the excavation work is completed, the wheel loader 10 (3rd operation) reverses to a predetermined position and stops. Then, the wheel loader 10 (4th operation) moves forward toward the dump truck 92 while raising the bucket 3 (rise run) and stops at the loading position in front of the dump truck 92. Then, (5th operation) performs loading work by releasing the load (excavated material) in the bucket 3 onto the bed of the dump truck 92. After the loading work is completed, the wheel loader 10 (6th operation) reverses to a predetermined position. The wheel loader 10 repeatedly performs a series of operations (1st operation) to (6th operation) while drawing a V-shaped trajectory as described above. In this specification, the series of operations (1st operation) to (6th operation) will also be referred to as the loader operation.

[0032] Loading operations account for the majority of the wheel loader 10's total working time. Therefore, improving the efficiency of loading operations is an effective way to improve the operational efficiency of the wheel loader 10. Operational efficiency is equivalent to, for example, the weight of material (excavated material) loaded onto the transport vehicle per unit time [tons / h] during loader operations. In other words, a higher operational efficiency value means that more material can be excavated and transported in a shorter amount of time.

[0033] Therefore, in order to improve the work efficiency of loader operations, it is possible to increase the amount of soil and other materials loaded into the bucket 3, or to improve the driving performance during operation to shorten the working time. However, if there is a poor balance between the output of the traveling device 11 (also referred to as traction force or driving force) for penetrating the bucket 3 into the object to be excavated 91 and the output of the working device 6 (also referred to as digging force or working force) for digging up the object to be excavated 91, the efficiency of the excavation work will decrease.

[0034] Figure 4 is a diagram illustrating the general operation of the excavation work. As shown in Figure 4, the directions of action of the travel driving force (traction force) and the work driving force (excavation force) are in a phase relationship of approximately 90 degrees, and the performance of the excavation work changes by controlling each force. For example, if the horizontal traction force is insufficient and the vertical excavation force is excessive, the bucket 3 may not be able to penetrate the excavation target 91 sufficiently, or the bucket 3 may be lifted above the excavation target 91 before enough soil and sand enter the bucket 3, thus reducing work efficiency. On the other hand, if the vertical excavation force is insufficient and the horizontal traction force is excessive, it takes time to lift the bucket 3, thus reducing work efficiency. Therefore, in order to improve work efficiency, it is necessary to appropriately set the power distribution ratio for distributing the output (power) of the engine 21 to the work device 6 and the travel device 11.

[0035] However, the particle size of the material to be excavated 91 varies depending on the excavation site. Therefore, if the power distribution ratio of the engine 21 is set assuming a certain particle size of material to be excavated 91, the work efficiency may decrease when excavating material 91 of a different particle size. To address this, the control device 100 according to this embodiment sets the power distribution ratio of the engine 21 according to the particle size of the material to be excavated 91. Specifically, if the particle size of the material to be excavated 91 is relatively large and difficult to excavate, the control device 100 increases the power distribution to the travel device 11. This increases the traction force, allowing the bucket 3 to bite firmly into the material to be excavated 91. On the other hand, if the particle size of the material to be excavated 91 is relatively small and easy to excavate, the control device 100 increases the power distribution to the work device 6. This increases the excavation force, allowing the excavation speed to be improved.

[0036] Furthermore, the control device 100 sets the power distribution ratio of the engine 21, taking into account the weight of the excavated material (hereinafter also referred to as the excavation volume) of soil and other materials excavated by the bucket 3 and loaded into the bucket 3. Specifically, when the excavation volume is large, the control device 100 increases the power distribution to the travel device 11. This increases the traction force, allowing for efficient loading of large amounts of excavated material into the bucket 3. On the other hand, when the excavation volume is small, the control device 100 increases the power distribution to the work device 6. This increases the digging force, allowing for quick excavation of small amounts of material.

[0037] The main contents of the control performed by the control device 100 according to this embodiment will be described below. In this embodiment, without adding any new sensors such as cameras, the output distribution control of the engine 21 according to the particle size of the excavated material and the amount of excavation is performed based on the detection results of various sensors that are equipped in a standard wheel loader 10.

[0038] Figure 5 is a functional block diagram of the control device 100. As shown in Figure 5, the control device 100 functions as an excavation operation determination unit 111, a particle size calculation unit 112, an excavation amount calculation unit 113, an excavation state determination unit 114, an output distribution calculation unit 115, and a power control unit 116 by executing a program stored in the non-volatile memory 102.

[0039] The excavation operation determination unit 111 determines whether or not the excavation operation by the work device 6 has started on the object to be excavated 91, based on the detection results of the arm relative angle sensor (attitude sensor) 151, the bucket relative angle sensor (attitude sensor) 152, the bucket cylinder pressure sensor (pressure sensor) 153, and the motor speed sensor 146. The contents of the excavation operation determination process performed by the excavation operation determination unit 111 will be explained in detail below with reference to Figure 6. Figure 6 is a control block diagram of the excavation operation determination unit 111.

[0040] The excavation operation determination unit 111 determines whether the bucket angle θ is within the angle range of the entry posture (S101). The bucket angle θ is the inclination angle of the bucket 3 from the reference surface 90 (see Figure 1). In this embodiment, the reference surface 90 is a surface set parallel to the ground (traveling surface). When the bottom surface of the bucket 3 is parallel to the reference surface 90, the bucket angle (angle relative to the ground) θ is 0 [°]. When the bucket 3 rotates due to a clouding operation, the bucket angle θ increases with that rotation. In other words, when the bucket 3 rotates due to a dumping operation, the bucket angle θ decreases with that rotation. The bucket angle θ is calculated by the control device 100 based on the relative angle of the arm 2 with respect to the reference surface 90 detected by the arm relative angle sensor 151 and the relative angle of the bucket 3 with respect to the arm 2 detected by the bucket relative angle sensor 152.

[0041] The angle range for the entry posture is set, for example, to determine whether the angle of the bottom surface of the bucket 3 relative to the ground is approximately horizontal. The angle range for the entry posture is the angle range between a first angle threshold θt1 degree and a second angle threshold θt2 degrees. When the angle when the bottom surface of the bucket 3 is horizontal is set to 0 degrees, the first angle threshold θt1 is set to a value of 0 degrees or less, and the second angle threshold θt2 is set to a value of 0 degrees or more. The bucket angle θ threshold determination process (S101) corresponds to the process of determining whether the work device 6 is in an entry posture toward the excavation target 91.

[0042] The excavation operation determination unit 111 determines whether the bucket cylinder pressure Pb detected by the bucket cylinder pressure sensor 153 is equal to or greater than the pressure threshold Pbt (S102). In this embodiment, a Z-link type link mechanism is used as the link mechanism for operating the bucket 3. Therefore, when the wheel loader 10 enters the excavation target 91, the pressure of the hydraulic fluid in the rod-side oil chamber of the bucket cylinder 5 (hereinafter also referred to as rod pressure) increases. For this reason, in the bucket cylinder pressure threshold determination process (S102), the rod pressure is used as the bucket cylinder pressure Pb and compared with the pressure threshold Pbt. The cylinder pressure threshold determination process (S102) corresponds to the process of determining whether a reaction force is acting on the work device 6 from the excavation target 91 as the bucket 3 penetrates the excavation target 91.

[0043] The excavation operation determination unit 111 determines whether the motor speed Vm detected by the motor speed sensor 146 is greater than or equal to the speed threshold Vmt (S103). The speed threshold Vmt is a value greater than 0. The motor speed Vm threshold determination process (S103) corresponds to the process of determining whether the wheel loader 10 is moving forward or not.

[0044] The excavation operation determination unit 111 calculates the rate of change over time of the motor speed Vm detected by the motor speed sensor 146 (S104). The excavation operation determination unit 111 determines whether the rate of change over time Vr of the motor speed Vm is less than or equal to the rate of change threshold Vrt (S105). The rate of change threshold Vrt is a negative value. In other words, the threshold determination process for the rate of change over time Vr of the motor speed Vm (S105) corresponds to the process of determining whether the wheel loader 10 is decelerating or not.

[0045] The angle thresholds θt1, θt2, pressure threshold Pbt, velocity threshold Vmt, and rate of change threshold Vrt are predetermined through experiments and stored in the non-volatile memory 102.

[0046] The excavation operation determination unit 111 determines whether or not the excavation operation by the wheel loader 10 has started (S106). If all of the following conditions (1) to (4) are met, the excavation operation determination unit 111 determines that the excavation operation has started (i.e., the wheel loader 10 has entered the excavation target 91) and turns on the excavation operation flag. If at least one of the following conditions (1) to (4) is not met, the excavation operation determination unit 111 determines that the excavation operation has not started (i.e., the wheel loader 10 has not entered the excavation target 91) and leaves the excavation operation flag at its initial value of off. (Condition 1) The bucket angle θ is greater than or equal to the first angle threshold θt1 and less than or equal to the second angle threshold θt2. (Condition 2) The bucket cylinder pressure Pb is equal to or greater than the pressure threshold Pbt. (Condition 3) The motor speed Vm is equal to or greater than the speed threshold Vmt. (Condition 4) The time rate of change Vr of the motor speed Vm is less than or equal to the rate of change threshold Vrt.

[0047] The excavation operation determination unit 111 determines whether each of (Condition 1) to (Condition 4) is met based on the results of the threshold determination processes (S101) to (S103) and (S105). Although not shown in the figures, after the excavation operation flag is turned on, the excavation operation determination unit 111 determines that the excavation operation has ended and turns off the excavation operation flag when the bucket angle θ becomes greater than or equal to the third angle threshold θt3, which is greater than the second angle threshold θ2.

[0048] Referring to Figures 5, 7, and 8, the contents of the processing performed by the particle size calculation unit 112 will be explained in detail. The particle size calculation unit 112 shown in Figure 5 calculates the particle size of the excavated object 91 when the excavation operation determination unit 111 determines that the excavation operation has started. The particle size of the excavated object 91 has a certain relationship with the magnitude of the pulsation (vibration) of the reaction force acting on the work device 6 when the work device 6 is excavating the excavated object 91. The particle size calculation unit 112 according to this embodiment detects the vibration acting on the work device 6 as the pulsation (fluctuation) of the bucket cylinder pressure Pb that is generated as an excavation reaction force when the bucket 3 hits the excavated object 91, and calculates the particle size of the excavated object 91 based on that pulsation (fluctuation).

[0049] Figure 7 is a schematic diagram showing the time change of the bucket cylinder pressure Pb. As shown in Figure 7, when the excavation operation by the wheel loader 10 starts, the bucket cylinder pressure Pb increases. When the particle size of the material to be excavated 91 is small, the wheel loader 10 can excavate the material 91 with less resistance compared to when the particle size is large. Therefore, as shown in the upper part of Figure 7, there is almost no pulsation (fluctuation) in the bucket cylinder pressure Pb. On the other hand, when the particle size of the material to be excavated 91 is large, the reaction force on the bucket cylinder 5 varies more than when the particle size is small. Therefore, as shown in the lower part of Figure 7, pulsation (fluctuation) occurs in the bucket cylinder pressure Pb.

[0050] In this embodiment, the particle size of the material to be excavated 91 is determined by the content of the pulsation component of the bucket cylinder pressure Pb during excavation. When extracting the pulsation component of the bucket cylinder pressure Pb, it is conceivable to perform frequency analysis such as Fast Fourier Transform (FFT).

[0051] However, in this embodiment, it is necessary to determine the particle size within a short time (for example, a few seconds) between the determination that the excavation operation has started and the start of the excavation lifting operation. For this reason, as shown in Figure 5, the particle size calculation unit 112 in this embodiment has a high-pass filter 112a that can process in a relatively short time. Note that the start of the excavation lifting operation corresponds to the start of the lifting operation of the arm 2.

[0052] The high-pass filter 112a removes frequency components lower than the cutoff frequency. The pulsating component of the bucket cylinder pressure Pb during drilling is typically around a few Hz. Therefore, a value that allows pulsating components of a few Hz to pass through is adopted as the cutoff frequency.

[0053] The particle size calculation unit 112 has an integration processing unit 112b that calculates the integral value of the pulsation component of the bucket cylinder pressure Pb as a pulsation value Pi representing the magnitude of the pulsation (fluctuation) of the reaction force acting on the work device 6. The integration processing unit 112b calculates the integral value of the pulsation component extracted by the high-pass filter 112a as the pulsation value Pi. The integration processing unit 112b integrates the pulsation component extracted by the high-pass filter 112a within a predetermined time t0 between the start of the excavation operation and the start of the excavation operation. In this embodiment, the integration processing unit 112b integrates the pulsation component for a predetermined integration processing time tp (tp ≤ t0) from the time it is determined that the excavation operation has started. In other words, the integration processing unit 112b calculates the pulsation value Pi in the initial stage of the excavation operation (immediately after entering the excavation target 91). Note that this pulsation component may have a negative sign, so in order to detect the magnitude of the pulsation component, it may be necessary to process this extracted amount to make it an absolute value.

[0054] The particle size calculation unit 112 includes a particle size level determination unit 112c that determines the particle size level representing the particle size of the material to be excavated 91. Figure 8 is a control block diagram of the particle size level determination unit 112c. As shown in Figure 8, the particle size level determination unit 112c calculates the particle size level of the material to be excavated 91 currently being excavated based on the pulsation value Pi calculated by the integration processing unit 112b and a predetermined pulsation threshold Pit. The particle size level determination unit 112c determines whether the pulsation value Pi calculated by the integration processing unit 112b is greater than or equal to the pulsation threshold Pit. The pulsation threshold Pit is predetermined data that defines the relationship between multiple particle size levels representing the particle size of the material to be excavated 91 and the pulsation value Pi, and is predetermined by experiments, etc., and stored in the non-volatile memory 102.

[0055] The particle size level determination unit 112c determines that the particle size level of the excavated material 91 is "small (first particle size level)" if the pulsation value Pi is less than the pulsation threshold Pit. The particle size level determination unit 112c determines that the particle size level of the excavated material 91 is "large (second particle size level, which is larger than the first particle size level)" if the pulsation value Pi is equal to or greater than the pulsation threshold Pit.

[0056] Referring to Figures 5, 9, and 10, the contents of the processing performed by the excavation volume calculation unit 113 will be explained in detail. The excavation volume calculation unit 113 shown in Figure 5 calculates the excavation volume when the excavation operation determination unit 111 determines that the excavation operation has started. The excavation volume has a certain relationship with the deceleration of the vehicle speed when the vehicle enters the object to be excavated 91. In this embodiment, the excavation volume calculation unit 113 calculates the excavation volume based on the deceleration of the vehicle speed from the start of the excavation operation. It is preferable to obtain the most accurate information possible regarding the vehicle speed used for the determination. For this reason, in this embodiment, the rotational speed (motor speed) of the travel motor 26 that rotates the wheels 7 is utilized.

[0057] Figure 9 is a schematic diagram showing the time change of motor speed (vehicle speed). As shown in Figure 9, when the wheel loader 10 enters the excavation target 91 and the excavation operation begins, the motor speed Vm decreases. When the excavation amount is small, the change in motor speed Vm is smaller compared to when the excavation amount is large. On the other hand, when the excavation amount is large, the change in motor speed Vm is larger compared to when the excavation amount is small. In this embodiment, this characteristic is utilized to determine the excavation amount based on the deceleration of the motor speed in the initial stage of the excavation operation (immediately after entering the excavation target 91).

[0058] As shown in Figure 5, the excavation volume calculation unit 113 includes a deceleration calculation unit 113a and an excavation volume level determination unit 113b. In this embodiment, the deceleration calculation unit 113a calculates the deceleration D of the travel motor 26 by dividing the decrease in motor speed Vm ΔVm (>0) from the time it is determined that the excavation operation has started until after a predetermined deceleration processing time td (td ≤ t0) has elapsed by the deceleration processing time td (D = ΔVm / td, D > 0). In this embodiment, the deceleration processing time td is the same as the integration processing time tp (td = tp).

[0059] Figure 10 is a control block diagram of the excavation volume level determination unit 113b. As shown in Figure 10, the excavation volume level determination unit 113b calculates the excavation volume level based on the deceleration D calculated by the deceleration calculation unit 113a and a predetermined deceleration threshold Dt. The excavation volume level determination unit 113b determines whether the deceleration D is greater than or equal to the deceleration threshold Dt. The deceleration threshold Dt is predetermined data that defines the relationship between the deceleration D and multiple excavation volume levels, which represent the magnitude of the excavation volume, which is the weight of the excavated material excavated by the work device 6. It is predetermined through experiments, etc., and stored in the non-volatile memory 102.

[0060] The excavation volume level determination unit 113b determines that the excavation volume level is "small (first excavation volume level)" if the deceleration D is less than the deceleration threshold Dt. The excavation volume level determination unit 113b determines that the excavation volume level is "large (second excavation volume level, which is larger than the first excavation volume level)" if the deceleration D is equal to or greater than the deceleration threshold Dt.

[0061] The excavation state determination process by the excavation state determination unit 114 will be explained with reference to Figures 5 and 11. Figure 11 is a diagram illustrating the excavation state determination process by the excavation state determination unit 114. As shown in Figures 5 and 11, the excavation state determination unit 114 determines whether the excavation state by the wheel loader 10 is a light excavation state or a heavy excavation state based on the particle size level determined by the particle size level determination unit 112c and the excavation amount level determined by the excavation amount level determination unit 113b. The excavation state determination unit 114 determines that the excavation state is a light excavation state if the particle size level is "small" and the excavation amount level is "small". The excavation state determination unit 114 determines that the excavation state is a heavy excavation state if the particle size level is "large" or the excavation amount level is "large". A heavy excavation state is an excavation state that requires a greater driving force than a light excavation state.

[0062] The output distribution calculation unit 115 shown in Figure 5 calculates the output distribution ratio for distributing the output of the engine 21 to the work device 6 and the travel device 11 based on the determination result of the excavation state determination unit 114. In this embodiment, the output distribution ratio of the engine 21 corresponds to the ratio (percentage) of the upper limit of the travel driving force and the upper limit of the work driving force.

[0063] The output distribution calculation unit 115 calculates the output distribution ratio of the engine 21 based on both the particle size level calculated by the particle size level determination unit 112c and the excavation volume level calculated by the excavation volume level determination unit 113b.

[0064] The output distribution calculation unit 115 calculates the output distribution ratio such that the ratio of the output of the traveling device 11 to the output of the working device 6 is greater than 1 when the excavation state is determined to be a heavy excavation state (when the particle size level is determined to be "large" or when the excavation volume level is determined to be "large"). The output distribution calculation unit 115 calculates the output distribution ratio such that the ratio of the output of the traveling device 11 to the output of the working device 6 is 1 or less when the excavation state is determined to be a light excavation state (when the particle size level is determined to be "small" and the excavation volume level is determined to be "small").

[0065] In this embodiment, if the output distribution calculation unit 115 determines that the excavation state is a heavy excavation state, it sets the ratio (percentage) of the upper limit of the travel driving force to the upper limit of the work driving force to 7:3. Specifically, the output distribution calculation unit 115 sets the distribution ratio (percentage) ηc of the upper limit of the travel driving force to 70% and the distribution ratio (percentage) ηi of the upper limit of the work driving force to 30%. Note that the numerical values ​​of the distribution ratios are examples. The output distribution calculation unit 115 may, for example, set the distribution ratio ηc of the upper limit of the travel driving force to 60% and the distribution ratio ηi of the upper limit of the work driving force to 40%. In this way, by making the upper limit of the travel driving force greater than the upper limit of the work driving force, the bucket 3 can be driven deeply into the excavated material 91 when the particle size of the material to be excavated 91 is relatively large. In addition, a large amount of excavated material can be excavated efficiently.

[0066] Furthermore, if the output distribution calculation unit 115 determines that the excavation state is a light excavation state, it sets the ratio (percentage) of the upper limit of the travel driving force to the upper limit of the work driving force to 5:5. Specifically, the output distribution calculation unit 115 sets the distribution ratio ηc of the upper limit of the travel driving force and the distribution ratio ηi of the upper limit of the work driving force to 50% each. Note that the numerical values ​​of the distribution ratios are just examples. The output distribution calculation unit 115 may, for example, set the distribution ratio ηc of the upper limit of the travel driving force to 40% and the distribution ratio ηi of the upper limit of the work driving force to 60%. In this way, by setting the upper limit of the work driving force to be greater than or equal to the upper limit of the travel driving force, the excavation speed can be improved when the particle size of the material to be excavated 91 is relatively small and the amount of excavation is relatively small.

[0067] The distribution ratio ηc of the upper limit of the travel driving force and the distribution ratio ηi of the upper limit of the work driving force, calculated by the output distribution calculation unit 115, are held until the excavation operation flag is turned off. When the excavation operation flag is turned off, the output distribution calculation unit 115 sets the distribution ratio ηc of the upper limit of the travel driving force and the distribution ratio ηi of the upper limit of the work driving force to predetermined reference values.

[0068] The output torque of the engine 21 is consumed by the work device 6, the travel device 11, and auxiliary equipment (not shown). The torque consumed by the work device 6 corresponds to the input torque of the hydraulic pump 24. The torque consumed by the travel device 11 corresponds to the output torque of the travel motor 26.

[0069] The power control unit 116 calculates the work drive torque command and the travel drive torque command based on the distribution ratios ηc, ηi calculated by the output distribution calculation unit 115, the engine output torque Te, the work request torque Ti, the travel request torque Tc, and the auxiliary equipment request torque Ta. The engine output torque Te, the work request torque Ti, the travel request torque Tc, and the auxiliary equipment request torque Ta are calculated by the control device 100.

[0070] The engine output torque Te is the maximum torque that can be output at the current engine speed. The control device 100 refers to the engine output torque curve stored in the non-volatile memory 102 and calculates the engine output torque Te based on the engine speed detected by the engine speed sensor 147 (see Figure 2). The auxiliary equipment request torque Ta is calculated according to the operating status of multiple auxiliary equipment that are powered by electricity generated by the generator 22.

[0071] The control device 100 sets a target value for the engine speed (hereinafter also referred to as the target speed) based on the arm operation amount, bucket operation amount, accelerator operation amount, etc. The target speed set by the control device 100 is output to an engine controller (not shown). The engine controller controls the fuel injection system (not shown) so that the engine speed detected by the engine speed sensor 147 becomes the target speed. The engine speed sensor 147 may also be connected to the engine controller.

[0072] The control device 100 calculates the required torque Ti based on the lever operation amount (arm operation amount and bucket operation amount). The non-volatile memory 102 stores a pump request flow rate map. The control device 100 refers to the pump request flow rate map and determines the pump request flow rate based on the lever operation amount (lever signal). The pump request flow rate map is set so that the pump request flow rate is approximately proportional to the lever operation amount. The pump request flow rate increases as the lever operation amount increases. Note that there is a pump request flow rate map based on the arm operation amount and a map based on the bucket operation amount, and the larger of the flow rates determined in each map is determined as the pump request flow rate.

[0073] The control device 100 calculates the required hydraulic power based on the pump flow rate and the discharge pressure of the hydraulic pump 24 detected by the discharge pressure sensor 154, and calculates the required working torque Ti based on the required hydraulic power and the rotational speed of the engine 21 detected by the engine rotational speed sensor 147. The required working torque Ti increases as the lever operation amount increases.

[0074] The control device 100 calculates the required driving torque Tc based on the motor speed and accelerator pedal input. The non-volatile memory 102 stores the torque map of the drive motor 26. This torque map stores multiple torque curves corresponding to the accelerator signal. The torque map is set so that the required driving torque Tc increases as the accelerator signal increases, and decreases as the motor speed increases. The control device 100 selects the torque curve corresponding to the accelerator pedal input and determines the required driving torque Tc based on the motor speed.

[0075] The power control unit 116 calculates a difference value ΔTe, which is the value obtained by subtracting the auxiliary equipment required torque Ta from the engine output torque Te (ΔTe = Te - Ta). The power control unit 116 calculates the upper limit value Tcl of the driving torque by multiplying the distribution ratio ηc of the driving torque calculated by the output distribution calculation unit 115 by the difference value ΔTe. The power control unit 116 calculates the upper limit value Til of the work driving torque by multiplying the distribution ratio ηi of the work driving torque calculated by the output distribution calculation unit 115 by the difference value ΔTe.

[0076] The power control unit 116 determines the smaller of the requested driving torque Tc and the upper limit value of the driving torque Tcl as the target value for the driving torque, and outputs a driving torque command based on that target value. The power control unit 116 determines the smaller of the requested work torque Ti and the upper limit value of the work driving torque Til as the target value for the work driving torque, and outputs a work driving torque command based on that target value.

[0077] The travel drive torque command is output to the travel inverter 27. The travel inverter 27 controls the torque of the travel motor 26 based on the travel drive torque command. As a result, the travel device 11 is driven by the travel drive force generated by the travel motor 26. The work drive torque command is output to a pump controller (not shown). The pump controller generates a control signal to control the discharge capacity (displacement volume) of the hydraulic pump 24 based on the work drive torque command and the discharge pressure of the hydraulic pump 24. The pump controller controls the discharge capacity of the hydraulic pump 24 by outputting the generated control signal to a regulator (not shown). As a result, the work device 6 is driven by the work drive force generated by the hydraulic cylinders 4 and 5.

[0078] As described above, the control device 100 according to this embodiment calculates a pulsation value Pi (in this embodiment, the integral value of the bucket cylinder pressure pulsation over a predetermined period) which represents the magnitude of the pulsation (vibration) of the reaction force acting on the work device 6 as a parameter representing the particle size of the material to be excavated 91. The larger the pulsation value Pi, the larger the upper limit of the travel drive torque (travel driving force) and the smaller the upper limit of the work drive torque (work driving force).

[0079] Therefore, in excavation work, for example, if the operator fully operates the accelerator control device 141 while also fully operating the arm control device 144 and bucket control device 145, the travel driving force and work driving force are controlled to their upper limits, and the travel driving force and work driving force are appropriately adjusted according to the particle size of the material to be excavated 91 and the amount of excavation. This makes it possible to perform good excavation operations. Up to the upper limits, the travel driving force and work driving force can be generated according to the amount of operation performed by the operator.

[0080] According to the above-described embodiment, the following effects are achieved.

[0081] (1) The control device 100 calculates the power distribution ratio for distributing the output of the engine 21 to the work device 6 and the travel device 11, and controls the hydraulic pump 24 and the travel motor (electric motor) 26 based on the calculated power distribution ratio. Based on the detection result of the bucket cylinder pressure sensor (pressure sensor) 153, the control device 100 calculates the pulsation value (integral value of the pulsation component of the bucket cylinder pressure Pb) Pi, which represents the magnitude of the pulsation of the reaction force acting on the work device 6 when the work device 6 is excavating the object to be excavated 91. The control device 100 calculates the power distribution ratio (ηc:ηi) such that the larger the calculated pulsation value Pi, the larger the ratio (ηc / ηi) of the output of the travel device 11 to the output of the work device 6 (work driving force). The control device 100 controls the hydraulic pump 24 and the travel motor (electric motor) 26 based on the calculated power distribution ratio (ηc:ηi).

[0082] The pulsation value Pi is a parameter that represents the particle size of the material to be excavated 91, and the larger the particle size, the larger the pulsation value Pi. Therefore, in this embodiment, the output distribution of the engine 21 is controlled so that the ratio of the output of the traveling device 11 to the output of the working device 6 increases as the particle size of the material to be excavated 91 increases. This makes it possible to provide a wheel loader 10 that can improve work efficiency even when excavating material 91 with different particle sizes.

[0083] (2) The control device 100 calculates the deceleration D of the travel motor 26 based on the detection result of the motor speed sensor (speed sensor) 146. The control device 100 calculates the output distribution ratio (ηc:ηi) such that the larger the calculated deceleration D, the larger the ratio (ηc / ηi) of the output of the travel device 11 to the output of the work device 6 (work driving force).

[0084] Deceleration D is a parameter that represents the amount of excavation, and the larger the amount of excavation, the greater the deceleration D. In this embodiment, the ratio of the output of the traveling device 11 to the output of the working device 6 increases as the amount of excavation increases. Therefore, when the amount of excavation is large, the traveling driving force (traction force) increases. As a result, the operation of loading a large amount of excavated material into the bucket 3 can be performed smoothly. Also, when the amount of excavation is small, the working driving force (excavation force) increases. As a result, a small amount of excavated material can be quickly excavated.

[0085] (3) The control device 100 determines whether or not the excavation operation by the work device 6 has started on the object to be excavated 91 based on the detection results of the arm relative angle sensor (attitude sensor) 151, the bucket relative angle sensor (attitude sensor) 152, the bucket cylinder pressure sensor (pressure sensor) 153, and the motor speed sensor (speed sensor) 146. If the control device 100 determines that the excavation operation has started, it controls the hydraulic pump 24 and the travel motor 26 based on the output distribution ratio (ηc:ηi) calculated based on the pulsation value Pi and the deceleration D. With this configuration, when the excavation operation starts, the hydraulic pump 24 and the travel motor 26 are controlled according to the output distribution ratio suitable for the particle size and excavation amount of the object to be excavated 91. On the other hand, in the stage before the excavation operation starts, the hydraulic pump 24 and the travel motor 26 can be controlled with an output distribution ratio (reference value) different from the output distribution ratio described in this embodiment.

[0086] (4) The non-volatile memory (storage device) 102 stores a pulsation threshold Pit that defines the relationship between a plurality of particle size levels representing the particle size of the material to be excavated 91 and a pulsation value Pi, and a deceleration threshold Dt that defines the relationship between a plurality of excavation volume levels representing the size of the excavation volume and a deceleration D. The control device 100 calculates the particle size level based on the pulsation threshold Pit and the calculated pulsation value Pi. The control device 100 calculates the excavation volume level based on the deceleration threshold Dt and the calculated deceleration D. The control device 100 calculates the output distribution ratio (ηc:ηi) of the engine 21 based on both the calculated particle size level and the excavation volume level. With this configuration, an appropriate output distribution ratio can be calculated according to the plurality of classified particle size levels and excavation volume levels. In this embodiment, the particle size level and the excavation volume level are each classified into two stages. This reduces the computational load on the control device 100, while appropriately adjusting the traction force and excavation force according to the particle size level and excavation volume level, thereby improving work efficiency.

[0087] The following modifications are also within the scope of the present invention, and it is possible to combine the configurations shown in the modifications with the configurations described in the embodiments described above, or to combine the configurations described in the following different modifications.

[0088] <Example 1> The power distribution ratio of the engine 21, that is, the ratio of the upper limit of the driving force for travel to the upper limit of the working force, is not limited to the examples described above. The ratio of the upper limit of the driving force for travel to the upper limit of the working force is determined appropriately according to the type and size of the work vehicle and the location where the work vehicle operates.

[0089] <Modification 2> In the above embodiment, as shown in Figure 11, an example was described in which both the particle size level and the excavation volume level are classified into two stages. However, both the particle size level and the excavation volume level may be classified into three or more stages.

[0090] Referring to Figure 12, an example in which both the particle size level and the excavation volume level are classified into three stages will be explained. Figure 12 is a diagram illustrating the excavation state determination process by the excavation state determination unit 114 according to Modification 2 of this embodiment. In this modification, as shown in Figure 12, the excavation state is determined based on the particle size level, which is classified into three stages: "small," "medium," and "large," and the excavation volume level, which is also classified into three stages: "small," "medium," and "large."

[0091] The particle size level determination unit 112c determines that the particle size level of the excavated material 91 is "small" if the pulsation value Pi is less than the first pulsation threshold Pit1. The particle size level determination unit 112c determines that the particle size level of the excavated material 91 is "medium" if the pulsation value Pi is greater than or equal to the first pulsation threshold Pit1 and less than the second pulsation threshold Pit2. The particle size level determination unit 112c determines that the particle size level of the excavated material 91 is "large" if the pulsation value Pi is greater than or equal to the second pulsation threshold Pit2. Note that the second pulsation threshold Pit2 is greater than the first pulsation threshold Pit1 (Pit2 > Pit1).

[0092] The excavation volume level determination unit 113b determines the excavation volume level to be "small" if the deceleration D is less than the first deceleration threshold Dt1. The excavation volume level determination unit 113b determines the excavation volume level to be "medium" if the deceleration D is greater than or equal to the first deceleration threshold Dt1 and less than the second deceleration threshold Dt2. The excavation volume level determination unit 113b determines the excavation volume level to be "large" if the deceleration D is greater than or equal to the second deceleration threshold Dt2. Note that the second deceleration threshold Dt2 is greater than the first deceleration threshold Dt1 (Dt2 > Dt1).

[0093] The excavation state determination unit 114 determines that the excavation state is light excavation if the particle size level is "small" and the excavation volume level is "small". The excavation state determination unit 114 determines that the excavation state is medium excavation if one of the particle size level and / or excavation volume level is "small" and the other is "medium", or if both the particle size level and / or excavation volume level are "medium". The excavation state determination unit 114 determines that the excavation state is heavy excavation if at least one of the particle size level and / or excavation volume level is "large".

[0094] If the output distribution calculation unit 115 determines that the excavation state is a heavy excavation state, it sets the ratio (percentage) of the upper limit of the travel driving force to the upper limit of the work driving force to 6:4. If the output distribution calculation unit 115 determines that the excavation state is a moderate excavation state, it sets the ratio (percentage) of the upper limit of the travel driving force to the upper limit of the work driving force to 5:5. If the output distribution calculation unit 115 determines that the excavation state is a light excavation state, it sets the ratio (percentage) of the upper limit of the travel driving force to the upper limit of the work driving force to 4:6.

[0095] In this modified example, the number of classifications for particle size level and excavation volume level is greater than in the above embodiment, thus improving the work efficiency of the wheel loader 10.

[0096] In the above embodiment, the particle size level and the excavation volume level are each classified into two stages, and in this modified example, an example in which the particle size level and the excavation volume level are each classified into three stages has been described. However, the particle size level and the excavation volume level may each be classified into four or more stages.

[0097] <Variation 3> As shown in Figure 13, the wheel loader 10 may further include a changeover switch 358, which is a mode switching device that allows manual switching between an AUTO mode (first control mode) that calculates the output distribution ratio based on the pulsation value Pi and deceleration D, and a MANUAL mode (second control mode) that calculates the output distribution ratio regardless of the pulsation value Pi and deceleration D.

[0098] The wheel loader 10 may also be equipped with an output distribution setting dial 359, which is an operating device that allows the output distribution ratio to be set arbitrarily. The changeover switch 358 and the output distribution setting dial 359 are located inside the driver's cab 12.

[0099] The changeover switch 358 has two operating positions: an AUTO mode position and a MANUAL mode position. When the changeover switch 358 is operated to the AUTO mode position, it outputs a signal to the control device 300 indicating that AUTO mode is selected. In this case, the control device 300 sets AUTO mode as the output distribution mode. When the changeover switch 358 is operated to the MANUAL mode position, it outputs a signal to the control device 300 indicating that MANUAL mode is selected. In this case, the control device 300 sets MANUAL mode as the output distribution mode.

[0100] The output distribution setting dial 359 in this modified example sets the distribution ratio ηc used when the output distribution mode is set to MANUAL mode. The control device 300 calculates the distribution ratio ηc of the driving force based on the operating position of the output distribution setting dial 359. Furthermore, the control device 300 calculates the distribution ratio ηi of the work force. The control device 300 calculates the distribution ratio ηi of the work force by subtracting the distribution ratio ηc[%] of the driving force from 100[%] (100-ηc=ηi[%]).

[0101] Thus, according to this modified example, when the output distribution mode is set to MANUAL mode, the distribution ratios ηc and ηi are calculated based on the operating position of the output distribution setting dial 359 operated by the operator. When the output distribution mode is set to AUTO mode, the distribution ratios ηc and ηi are calculated based on the pulsation value Pi and deceleration D, as described in the above embodiment.

[0102] With this modified configuration, the operator can disable the power distribution control function based on the pulsation value Pi and deceleration D at their discretion. In other words, the operator can choose to enable or disable the power distribution control function based on the pulsation value Pi and deceleration D depending on the working conditions and environment.

[0103] The changeover switch 358 may be configured to switch between three modes in AUTO mode: a first AUTO mode that performs output distribution control based on both the pulsation value Pi and the deceleration D; a second AUTO mode that performs output distribution control based only on the pulsation value Pi; and a third AUTO mode that performs output distribution control based only on the deceleration D.

[0104] <Modification 4> The method for determining the start of the excavation operation is not limited to the method described in the above embodiment. Instead of the determination method described in the above embodiment, it is also possible to determine whether or not the excavation operation has started based on image data captured by a camera (image capture device) for monitoring the front of the wheel loader 10. Alternatively, it is possible to determine whether or not the excavation operation has started based on information detected by an infrared sensor that monitors the front of the wheel loader 10. However, cameras and infrared sensors are often provided as options. Therefore, in order to reduce costs, it is preferable that the control device 100 determines whether or not the excavation operation by the work device 6 has started on the object to be excavated 91 based on at least one of the detection results of the standardly equipped attitude sensors (arm relative angle sensor 151 and bucket relative angle sensor 152), pressure sensor (bucket cylinder pressure sensor 153), and speed sensor (motor speed sensor 146).

[0105] <Modification 5> In the above embodiment, an example was described in which, after it was determined that the excavation operation had started, the excavation operation was determined to have ended when the bucket angle θ became equal to or greater than the third angle threshold θt3. However, the present invention is not limited to this. For example, the excavation operation may be determined to have ended when a predetermined time (for example, about 5 seconds) has elapsed since it was determined that the excavation operation had started.

[0106] <Variation 6> In the wheel loader 10 according to the above embodiment, the working device 6 and the traveling device 11 are operated by the operator. For this reason, in the above embodiment, the ratio of the upper limit of the traveling driving force to the upper limit of the working driving force was adjusted according to the pulsation value Pi and the deceleration D. However, the present invention is not limited to this. For example, the wheel loader 10 may be configured to travel by automatic driving control. In this case, the control device 100 calculates the output distribution ratio based on the pulsation value Pi and the deceleration D, and calculates the target value of the traveling driving force and the target value of the working driving force based on the calculated output distribution ratio. In other words, in this modified example, when the excavation operation is started, the output distribution ratio of the engine 21 always corresponds to the ratio (percentage) of the target value of the traveling driving force and the target value of the working driving force. This makes it possible to further improve work efficiency.

[0107] <Example 7> As mentioned above, there is a certain relationship between motor speed and vehicle speed. For this reason, a wheel speed sensor that detects the rotational speed of the wheel 7 may be used instead of the motor speed sensor 146. In other words, the start of the excavation operation and the calculation of the excavation amount may be performed based on the vehicle speed detected by the wheel speed sensor.

[0108] <Differentiation Example 8> In the above embodiment, an example was described in which the pulsation value Pi is calculated based on the detection result of the bucket cylinder pressure sensor (pressure sensor) 153, but the present invention is not limited thereto. The pulsation of the reaction force acting on the work device 6 when the work device 6 is excavating the object to be excavated 91 is also reflected in the detection result of the motor speed sensor 146 and the current sensor 155. Therefore, the control device 100 may calculate the pulsation value Pi based on the detection result of the motor speed sensor 146 or the current sensor 155. The control device 100 is configured to calculate the pulsation value Pi based on at least one of the detection results of the bucket cylinder pressure sensor 153, the motor speed sensor 146, and the current sensor 155.

[0109] <Modification 9> The control device 100 in the above embodiment was described in an example where the output distribution ratio of the engine 21 is calculated based on both the pulsation value Pi and the deceleration D. However, the present invention is not limited thereto. The control device 100 may be configured to calculate the output distribution ratio such that the ratio of the output of the traveling device 11 to the output of the working device 6 increases as the pulsation value Pi increases. It is preferable that the control device 100 has a function to calculate the output distribution ratio such that the ratio of the output of the traveling device 11 to the output of the working device 6 increases as the deceleration increases, as in the above embodiment. By further providing this function, the traveling device 11 and the working device 6 can be operated with an appropriate output distribution according to the amount of excavation.

[0110] <Variation 10> The control device 100 according to the above embodiment was described as a method for determining the excavation level based on the deceleration D. However, the method for determining the excavation level is not limited to this. For example, the excavation level may be determined based on image data of the excavated material loaded into the bucket 3, which is captured by a camera (imaging device).

[0111] <Variation 11> The generator 22 described in the above embodiment may be a generator-motor that operates as an electric motor using power from an energy storage device (not shown).

[0112] <Variation 12> The control device 100 may calculate the work efficiency and display the output distribution ratio set in the previous excavation operation and the work efficiency on the display device.

[0113] <Example 13> The functions of the control device 100 described in the above embodiment may be partially or entirely implemented in hardware (for example, by designing the logic for executing each function using an integrated circuit).

[0114] Although embodiments of the present invention have been described above, these embodiments only represent a portion of the applications of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the embodiments described above. The embodiments and modifications described above are illustrative examples provided to facilitate understanding of the present invention, and are not necessarily limited to those comprising all the configurations described. Furthermore, the control lines and information lines shown in the figures are those deemed necessary for explanation and do not necessarily represent all the control lines and information lines required in the product. In practice, it can be assumed that almost all configurations are interconnected. [Explanation of symbols]

[0115] 2...Arm, 3...Bucket, 4...Arm cylinder (hydraulic cylinder), 5...Bucket cylinder (hydraulic cylinder), 6...Working device, 8...Vehicle body, 10...Wheel loader (working vehicle), 11...Traveling device, 21...Engine, 22...Generator, 23...Generator inverter, 24...Hydraulic pump, 25...Control valve, 26...Travel motor (electric motor), 27...Travel inverter, 91...Excavation target, 100...Control device, 101...Processing device, 102...Non-volatile memory (storage device), 103...Volatile memory (storage device), 111...Excavation operation determination unit, 112...Grain size calculation unit, 112a...High-pass filter, 112b...Integration processing unit, 112c...Grain size level determination unit, 113...Excavation amount calculation unit, 113a...Deceleration calculation unit, 113b...Excavation amount level determination unit, 114...Excavation state determination unit, 115...Output distribution calculation unit, 116...Power control unit, 1 44...Arm operating device, 144a...Arm operating amount sensor, 145...Bucket operating device, 145a...Bucket operating amount sensor, 146...Motor speed sensor (speed sensor), 151...Arm relative angle sensor (attitude sensor), 152...Bucket relative angle sensor (attitude sensor), 153...Bucket cylinder pressure sensor (pressure sensor), 155...Current sensor, 300...Control device, 358...Changeover switch (mode switching operation device), 359...Output distribution setting dial, D...Deceleration, Dt...Deceleration threshold, Dt1...First deceleration threshold, Dt2...Second deceleration threshold, Pb...Bucket cylinder pressure, Pbt...Pressure threshold, Pi...Pulsation value, Pit...Pulsation threshold, Pit...First pulsation threshold, Pit2...Second pulsation threshold, Vm...Motor speed, Vmt...Speed ​​threshold, θ...Bucket angle, θt1...First angle threshold, θt2...Second angle threshold, θt3...Third angle threshold

Claims

1. The engine mounted on the vehicle body, A hydraulic pump driven by the aforementioned engine, A hydraulic cylinder that extends and retracts using hydraulic fluid discharged from the aforementioned hydraulic pump, A work device that moves in accordance with the extension and retraction operation of the hydraulic cylinder, A traveling device that is driven independently of the aforementioned working device and moves the vehicle body, A generator that generates electricity driven by the aforementioned engine, An electric motor driven by the electricity generated by the aforementioned generator operates the aforementioned traction device, A pressure sensor for detecting the pressure of the hydraulic cylinder, A speed sensor for detecting the rotational speed of the electric motor, A current sensor for detecting the current of the electric motor, A work vehicle comprising: a control device that calculates an output distribution ratio for distributing the output of the engine to the work device and the travel device, and controls the hydraulic pump and the electric motor based on the calculated output distribution ratio, The control device is Based on at least one of the detection results of the pressure sensor, the speed sensor, and the current sensor, a pulsation value representing the magnitude of the reaction force pulsation acting on the work device when the work device is excavating the object to be excavated is calculated. The output distribution ratio is calculated such that the larger the calculated pulsation value, the larger the ratio of the output of the travel device to the output of the work device. A work vehicle characterized by the following features.

2. In the work vehicle described in claim 1, The control device is Based on the detection result of the speed sensor, the deceleration of the electric motor is calculated. The output distribution ratio is calculated such that the larger the calculated deceleration, the greater the ratio of the output of the travel device to the output of the work device. A work vehicle characterized by the following features.

3. In the work vehicle described in claim 2, The work device is equipped with a posture sensor that detects the posture of the work device, The control device is Based on at least one of the detection results of the attitude sensor, the pressure sensor, and the speed sensor, it is determined whether or not the excavation operation by the work device has started on the object to be excavated. When it is determined that the excavation operation has started, the hydraulic pump and the electric motor are controlled based on the output distribution ratio calculated based on the pulsation value and the deceleration. A work vehicle characterized by the following features.

4. In the work vehicle described in claim 1, The device includes a storage device that stores a pulsation threshold that defines the relationship between a plurality of particle size levels representing the particle size of the excavated material and the pulsation value, The control device is Based on the pulsation threshold and the calculated pulsation value, the particle size level is calculated. The output distribution ratio is calculated based on the calculated granularity level. A work vehicle characterized by the following features.

5. In the work vehicle described in claim 1, The control device is If the pulsation value is greater than or equal to a predetermined pulsation threshold, the output distribution ratio is calculated such that the ratio of the output of the travel device to the output of the work device is greater than 1. If the pulsation value is less than the pulsation threshold, the output distribution ratio is calculated so that the ratio of the output of the traveling device to the output of the working device is 1 or less. A work vehicle characterized by the following features.

6. In the work vehicle described in claim 2, The control device is The system includes a memory device that stores a deceleration threshold that defines the relationship between multiple excavation volume levels representing the magnitude of the excavation volume and the deceleration, The control device is Based on the deceleration threshold and the calculated deceleration, the excavation level is calculated. The power distribution ratio is calculated based on the calculated drilling volume level. A work vehicle characterized by the following features.

7. In the work vehicle described in claim 2, The control device is If the deceleration is greater than or equal to a predetermined deceleration threshold, the output distribution ratio is calculated such that the ratio of the output of the traveling device to the output of the working device is greater than 1. If the deceleration is less than the deceleration threshold, the output distribution ratio is calculated so that the ratio of the output of the travel device to the output of the work device is 1 or less. A work vehicle characterized by the following features.

8. In the work vehicle described in claim 2, The device includes a storage device that stores a pulsation threshold that defines the relationship between a plurality of particle size levels representing the particle size of the excavated material and the pulsation value, and a deceleration threshold that defines the relationship between a plurality of excavation volume levels representing the size of the excavation volume and the deceleration, The control device is Based on the pulsation threshold and the calculated pulsation value, the particle size level is calculated. Based on the deceleration threshold and the calculated deceleration, the excavation level is calculated. The power distribution ratio is calculated based on both the calculated particle size level and the drilling volume level. A work vehicle characterized by the following features.

9. In the work vehicle described in claim 1, The system further includes a mode switching device that allows manual switching between a first control mode, which calculates the output distribution ratio based on the pulsation value, and a second control mode, which calculates the output distribution ratio regardless of the pulsation value. A work vehicle characterized by the following features.

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