JP7848147B2 - Work vehicles - Google Patents

Description

This invention relates to a work vehicle.

A work vehicle is known that is equipped with a running gear for moving the vehicle body and a work device having a bucket and lift arm for excavating soil and other materials (see Patent Document 1). Such a work vehicle transports the excavated soil and other materials to a transport vehicle such as a dump truck and loads them onto it. The efficiency of this series of operations, including excavation, transport, and loading, is one indicator of the work vehicle's performance. The work efficiency of a work vehicle corresponds, for example, to the weight of transported material (excavated material) loaded onto the transport vehicle per unit time [ton/h] during the series of operations. In other words, a higher work efficiency value means that a larger volume of material can be excavated and transported in a shorter time.

Japanese Patent Publication No. 2021-95710

In such work vehicles, engine power (output) is distributed to the travel mechanism and the work mechanism to perform excavation. If the travel force is too small and the work force too large, the bucket may not penetrate the soil sufficiently, or it may be lifted before enough soil is filled, resulting in reduced work efficiency. Conversely, if the travel force is too large and the work force too small, it takes too long to lift the bucket, also reducing work efficiency. To improve work efficiency, it is effective to appropriately distribute the power (output distribution) between the travel force and the work force.

The excavated material has different particle sizes depending on the excavation site. Therefore, if the engine's power distribution ratio for travel drive and work drive is set the same for excavating materials with different particle sizes, work efficiency may decrease. For example, excavating larger particle sizes requires more travel drive because it is more difficult to penetrate the bucket compared to excavating smaller particle sizes. Therefore, even if work efficiency is good when excavating smaller particle sizes, it may deteriorate when excavating larger particle sizes.

The present invention aims to provide a work vehicle that can improve work efficiency even when excavating materials with different particle sizes.

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, which represents the magnitude of the reaction force pulsation acting on the work device when it is excavating an object, based on at least one of the detection results of the pressure sensor, the speed sensor, and the current sensor. It then calculates the output distribution ratio such that the larger the calculated pulsation value, the greater the ratio of the output of the travel device to the output of the work device.

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.

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

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.

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 on the 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.

The working device 6 is attached to the front vehicle body 8A. The working device 6 comprises an arm cylinder 4, a lift arm (hereinafter simply referred to as "arm") 2 that moves in accordance with the extension and retraction of the arm cylinder 4, a bucket cylinder 5, and a bucket 3 that 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 vehicle body 8A. Furthermore, a Z-link type (bell crank type) link mechanism is employed for operating the bucket 3. This link mechanism includes the bucket cylinder 5.

On the rear body 8B, a driver's cab 12 is mounted at the front and an engine room 16 at the rear. Inside the driver's cab 12 are an arm operating device 144 (see Figure 2) for operating the arm cylinder 4 (arm 2) of the work device 6, a bucket operating device 145 (see Figure 2) for operating the bucket cylinder 5 (bucket 3) of the work device 6, a forward/reverse switching device 143 (see Figure 2) for switching between forward (F) and reverse (R) movement of the body 8, an accelerator operating device 141 (see Figure 2) for instructing the body 8 to accelerate, a brake operating device 142 (see Figure 2) for instructing the body 8 to decelerate, and a steering operating device (not shown) for instructing the left/right direction of travel of the body 8. 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 extends and retracts.

The engine compartment 16 houses the engine (ENG) 21, hydraulic pump (PUMP) 24, control valve (C/V) 25, generator (GEN) 22, and drive motor (MOT) 26, as shown in Figure 2. The engine 21 is, for example, an internal combustion engine such as a diesel engine.

Figure 2 is a system configuration diagram of the wheel loader 10. As shown in Figure 2, the wheel loader 10 is a series hybrid type work vehicle in which the drive unit of the travel device 11 is electrically powered. The electric drive system of the wheel loader 10 is a system in which the engine 21 drives the generator 22 to generate electricity, the electricity generated by the generator 22 operates the travel motor 26, and the torque generated by the travel motor 26 operates the travel device 11.

The wheel loader 10 comprises an engine 21, a control device 100 for controlling various parts 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 fluid discharged from the hydraulic pump 24, a generator inverter (generator inverter) 23 that controls the power output (power generation) of the generator 22 based on a power generation voltage command input from the control device 100, a travel motor 26 that drives the vehicle body 8 with power supplied from the generator 22, a travel inverter (travel motor inverter) 27 that controls the torque of the travel motor 26 based on a travel drive torque command input from the control device 100, and a travel device 11 that is driven by the travel motor 26 to move the vehicle body 8. The work device 6 and the travel device 11 are driven independently of each other by the output torque (power) of the engine 21.

The forward/reverse selector 143 includes a forward/reverse switch that can be selectively operated to one of the forward (F), neutral (N), or reverse (R) positions, and an operating position sensor 143a that detects the operating position of the forward/reverse switch. The operating position sensor 143a outputs a forward/reverse signal (FNR signal) corresponding to the selected operating position to the control device 100. The accelerator control device 141 includes an accelerator pedal and an accelerator operation amount sensor 141a that detects the amount the accelerator pedal is operated (hereinafter also referred to as accelerator operation amount). The accelerator operation amount sensor 141a outputs an accelerator signal representing the amount the accelerator pedal is operated (depression amount) to the control device 100. The brake control device 142 includes a brake pedal and a brake operation amount sensor 142a that detects the amount the brake pedal is operated. The brake operation amount sensor 142a outputs a brake signal representing the amount the brake pedal is operated (depression amount) to the control device 100.

The arm operating device 144 comprises 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 comprises 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).

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 considered a vehicle speed sensor that detects vehicle speed.

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

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 uses the generated power to drive the travel motor 26. 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 from the DC section 28, based on the travel drive torque command from the control device 100. When the travel motor 26 is driven and its power is transmitted to the wheels 7 via the power transmission device, the wheel loader 10 moves.

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.

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 in accordance with the extension and retraction drive of the steering cylinder 9.

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.

The control device 100 consists of a computer equipped with processing units 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 be composed of a single computer or multiple computers.

The non-volatile memory 102 stores a program capable of executing 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) capable of reading the program that realizes the functions of this embodiment. 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 the 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.

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 signals representing the accelerator operation amount detected by the accelerator operation amount sensor 141a, signals representing the brake operation amount detected by the brake operation amount sensor 142a, signals representing the arm operation amount detected by the arm operation amount sensor 144a, signals representing the bucket operation amount detected by the bucket operation amount sensor 145a, and signals representing the operating position of the forward/reverse switch detected by the operating position sensor 143a.

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 connecting 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 connecting 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 posture of the work device 6.

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.

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.

Referring to Figure 3, an example of work performed by the wheel loader 10 will be explained. Figure 3 is a diagram illustrating V-shaped loading by the wheel loader 10. As shown in Figure 3, the wheel loader 10 (first operation) moves forward toward the object to be excavated 91, such as the ground, (second 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 (third operation) reverses to a predetermined position and stops. Then, the wheel loader 10 (fourth 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, (fifth 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 (sixth operation) reverses to a predetermined position. The wheel loader 10 repeatedly performs a series of operations (operation 1) to (operation 6) while tracing a V-shaped trajectory as described above. In this specification, the series of operations (operation 1) to (operation 6) is also referred to as the loader operation.

Loading operations account for the majority of the wheel loader 10's total working time. Therefore, improving the efficiency of loader operations is an effective way to improve the overall work efficiency of the wheel loader 10. Work efficiency, for example, corresponds to the weight of material (excavated material) loaded onto the transport vehicle per unit time [tons/hour] during loader operations. In other words, a higher work efficiency value means that a larger volume of material can be excavated and transported in a shorter time.

Therefore, to improve the efficiency of loader operations, it is conceivable 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 an imbalance between the output of the traveling device 11 (also referred to as traction force or driving force) for penetrating the bucket 3 into the excavation target 91 and the output of the working device 6 (also referred to as excavation force or working force) for digging up the excavation target 91, the efficiency of the excavation work will decrease.

Figure 4 illustrates 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 approximately a 90-degree phase relationship, 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 sufficiently into the excavation target 91, or the bucket 3 may be lifted above the excavation target 91 before enough soil and sand enters 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.

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 with a different particle size. To address this, the control device 100 in 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 sufficiently penetrate 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, improving the excavation speed.

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) that is 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.

The following describes the main contents of the control performed by the control device 100 according to this embodiment. In this embodiment, without adding any new sensors such as cameras, the output distribution control of the engine 21 is performed according to the particle size of the excavated material and the amount of excavation, based on the detection results of various sensors provided by a standard wheel loader 10.

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.

The excavation operation determination unit 111 determines whether or not excavation has started on the object to be excavated 91 by the work device 6, 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.

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.

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 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 defined as 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.

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. Therefore, 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 from the excavation target 91 to the work device 6 as the bucket 3 penetrates the excavation target 91.

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.

The excavation operation determination unit 111 calculates the rate of change 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 of the motor speed Vm Vr 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 of the motor speed Vm Vr (S105) corresponds to the process of determining whether the wheel loader 10 is decelerating.

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

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 greater than or equal to 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.

The excavation operation determination unit 111 determines whether each of conditions (1) to (4) is met based on the results of 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.

Referring to Figures 5, 7, and 8, 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 material 91 when the excavation operation determination unit 111 determines that the excavation operation has started. The particle size of the excavated material 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 material 91. In this embodiment, the particle size calculation unit 112 detects the vibration acting on the work device 6 as the pulsation (fluctuation) of the bucket cylinder pressure Pb generated as the excavation reaction force when the bucket 3 hits the excavated material 91, and calculates the particle size of the excavated material 91 based on that pulsation (fluctuation).

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 begins, 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.

In this embodiment, the particle size of the material to be excavated 91 is determined by the content of the pulsation component in 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 the Fast Fourier Transform (FFT).

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. Therefore, 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 arm 2's raising operation.

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

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, which represents 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). Furthermore, since this pulsation component may have a negative sign, processing such as absolute value conversion may be necessary to detect the magnitude of the pulsation component.

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 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 through experiments, etc., and stored in the non-volatile memory 102.

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. If the pulsation value Pi is equal to or greater than the pulsation threshold Pit, the particle size level of the excavated material 91 is determined to be "large (second particle size level, larger than the first particle size level)."

Referring to Figures 5, 9, and 10, 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 excavation target 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. Therefore, in this embodiment, the rotational speed (motor speed) of the travel motor 26 that rotates the wheels 7 is utilized.

Figure 9 is a schematic diagram illustrating the time variation 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 decelerates. When the excavation volume is small, the change in motor speed Vm is smaller compared to when the excavation volume is large. On the other hand, when the excavation volume is large, the change in motor speed Vm is larger compared to when the excavation volume is small. In this embodiment, this characteristic is utilized to determine the excavation volume based on the deceleration of the motor speed in the initial stage of the excavation operation (immediately after entering the excavation target 91).

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).

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 multiple excavation volume levels, which represent the magnitude of the excavation volume (the weight of the excavated material excavated by the work device 6), and the deceleration D. It is predetermined through experiments, etc., and stored in the non-volatile memory 102.

The excavation volume level determination unit 113b determines the excavation volume level to be "small (first excavation volume level)" if the deceleration D is less than the deceleration threshold Dt. The excavation volume level determination unit 113b determines the excavation volume level to be "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.

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.

The output distribution calculation unit 115 shown in Figure 5 calculates the output distribution ratio for distributing the engine 21's output 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 to the upper limit of the work driving force.

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.

The output distribution calculation unit 115 calculates the output distribution ratio so 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 so 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").

In this embodiment, when 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. For example, the output distribution calculation unit 115 may 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%. By setting the upper limit of the travel driving force to be greater than the upper limit of the work driving force in this way, 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. Furthermore, a large amount of excavated material can be excavated efficiently.

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 examples. For example, the output distribution calculation unit 115 may 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 excavation amount is relatively small.

The distribution ratio ηc for the upper limit of the travel driving force and the distribution ratio ηi for 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 for the upper limit of the travel driving force and the distribution ratio ηi for the upper limit of the work driving force to predetermined reference values.

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.

The power control unit 116 calculates the work drive torque command and the travel drive torque command based on the distribution ratios ηc and 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, work request torque Ti, travel request torque Tc, and auxiliary equipment request torque Ta are calculated by the control device 100.

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 powered by the electricity generated by the generator 22.

The control device 100 sets a target engine speed (hereinafter also referred to as 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.

The control device 100 calculates the work request 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 are two pump request flow rate maps: one based on the arm operation amount and another based on the bucket operation amount. The larger of the flow rates determined in each map is determined as the pump request flow rate.

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. It then 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.

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.

The power control unit 116 calculates a difference value ΔTe, which is the engine output torque Te minus the auxiliary equipment required torque Ta (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 also 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.

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

The travel 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 torque command. As a result, the travel device 11 is driven by the travel driving force generated by the travel motor 26. The work 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 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 driving force generated by the hydraulic cylinders 4 and 5.

Thus, 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 higher the upper limit of the travel drive torque (travel driving force) and the lower the upper limit of the work drive torque (work driving force).

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. Note that the travel driving force and work driving force can be generated according to the operator's input until they exceed the upper limits.

According to the above-described embodiment, the following effects and advantages are achieved.

(1) The control device 100 calculates the output distribution ratio for distributing the engine 21's output 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 output 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 output 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 output distribution ratio (ηc:ηi).

The pulsation value Pi is a parameter representing the particle size of the material to be excavated 91; 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 travel device 11 to the output of the work device 6 increases as the particle size of the material to be excavated 91 increases. This provides a wheel loader 10 that can improve work efficiency even when excavating material 91 with different particle sizes.

(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).

The deceleration rate D is a parameter representing the excavation volume; the larger the excavation volume, the greater the deceleration rate 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 excavation volume increases. Therefore, when the excavation volume 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 efficiently. Conversely, when the excavation volume is small, the working driving force (excavation force) increases. As a result, a small amount of excavated material can be quickly excavated.

(3) The control device 100 determines whether or not the excavation operation by the work device 6 has started on the excavation target 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 an output distribution ratio suitable for the particle size and excavation amount of the excavation target 91. On the other hand, 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.

(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 the 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 the 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.

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.

<Variation 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 example 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.

<Modified Example 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.

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."

The particle size level determination unit 112c determines the particle size level of the excavated material 91 as "small" if the pulsation value Pi is less than the first pulsation threshold Pit1. The particle size level determination unit 112c determines the particle size level of the excavated material 91 as "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 the particle size level of the excavated material 91 as "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).

The excavation volume level determination unit 113b determines the excavation volume level as "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 as "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 as "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).

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 either the particle size level or the excavation volume level is "small" and the other is "medium", or if both the particle size level and the 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 or the excavation volume level is "large".

The output distribution calculation unit 115, when it determines that the excavation state is heavy excavation, 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. When it determines that the excavation state is moderate excavation, the output distribution calculation unit 115 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. When it determines that the excavation state is light excavation, the output distribution calculation unit 115 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.

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.

In the above embodiment, the particle size level and excavation volume level were each classified into two stages, while this modified example describes an example where the particle size level and excavation volume level are each classified into three stages. However, the particle size level and excavation volume level may each be classified into four or more stages.

<Example 3>
As shown in Figure 13, the wheel loader 10 may further include a changeover switch 358, which is a mode switching operation 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.

Furthermore, the wheel loader 10 may 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.

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.

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 work force distribution ratio ηi by subtracting the driving force distribution ratio ηc[%] from 100[%] (100 - ηc = ηi[%]).

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, which is 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.

According to this modified configuration, the operator can disable the power distribution control function based on the pulsation value Pi and deceleration D. In other words, the operator can select whether 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.

Furthermore, 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.

<Modification 4>
The method for determining the start of excavation is not limited to the method described in the above embodiment. Instead of the determination method described in the above embodiment, the start of excavation may be determined based on image data captured by a camera (photography device) for monitoring the front of the wheel loader 10. The start of excavation may also be determined 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 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 attitude sensors (arm relative angle sensor 151 and bucket relative angle sensor 152), pressure sensors (bucket cylinder pressure sensor 153), and speed sensors (motor speed sensor 146) that are standard equipment.

<Example 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 a 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.

<Modification 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.

<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.

<Difference 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.

<Difference 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.

<Modification 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).

<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).

<Modified example 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.

<Modification 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).

The embodiments of the present invention have been described above. However, these embodiments represent only 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.

2...Arm, 3...Bucket, 4...Arm cylinder (hydraulic cylinder), 5...Bucket cylinder (hydraulic cylinder), 6...Working device, 8...Vehicle body, 10...Wheel loader (work 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...Particle size calculation unit, 112a...High-pass filter, 112b...Integration processing unit, 112c...Particle 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 (9)

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.
A work vehicle characterized by calculating 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. 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.
A work vehicle characterized by calculating the output distribution ratio 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. 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.
A work vehicle characterized by controlling the hydraulic pump and the electric motor based on the output distribution ratio calculated based on the pulsation value and the deceleration when it is determined that the excavation operation has started. 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.
A work vehicle characterized by calculating the output distribution ratio based on the calculated particle size level. 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 traveling device to the output of the working device is greater than 1.
A work vehicle characterized in that, when the pulsation value is less than the 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 1 or less. 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.
A work vehicle characterized by calculating the output distribution ratio based on the calculated excavation volume level. 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.
A work vehicle characterized in that, when the deceleration is less than the deceleration 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 1 or less. 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.
A work vehicle characterized by calculating the output distribution ratio based on both the calculated particle size level and the excavation volume level. In the work vehicle described in claim 1,
A work vehicle further comprising a mode switching device that allows manual switching between a first control mode that calculates the output distribution ratio based on the pulsation value and a second control mode that calculates the output distribution ratio regardless of the pulsation value.