Drive system, work vehicle, control method, and computer program

Abstract

The drive system for a work vehicle according to an embodiment comprises: one or more electric motors that generate a driving force for causing the work vehicle to travel and a driving force for rotating a PTO shaft; and a control device that controls the operation of the one or more electric motors. Control modes in which the control device controls the one or more electric motors include: a first mode in which limitation is applied so that electric power supplied to the one or more electric motors is a first upper limit or less; and a second mode in which the limitation is removed. When the work vehicle changes from a state in which the PTO shaft is not rotated to a state in which the PTO shaft is rotated while the one or more electric motors are being controlled in the first mode, the control device controls the one or more electric motors by switching the control mode from the first mode to the second mode.

Description

Drive system, work vehicle, control method, and computer program

[0001] The present invention relates to a drive system, a work vehicle, a control method, and a computer program.

[0002] In the field of automobiles whose main purpose is to move people or objects, electric vehicles (EVs) that generate driving force (traction) for running by an electric motor (hereinafter sometimes simply referred to as "motor") instead of an internal combustion engine are becoming widespread.

[0003] On the other hand, in order to realize a decarbonized society, it is required to reduce the amount of carbon dioxide (CO ２ ) emitted by work vehicles such as tractors used in fields. Different from general automobiles, work vehicles such as tractors need to tow work implements (agricultural implements) to perform farm work such as tilling. Therefore, in order to realize the electrification of work vehicles, there are problems to be solved that are different from the electrification of passenger cars.

[0004] Patent Document 1 discloses an electric tractor that distributes and supplies electric power from a battery to a plurality of electric motors. The electric tractor includes a hydraulic pump, a pump motor, a PTO motor, a traveling motor, a battery, and an electric drive controller. The pump motor is an electric motor that drives the hydraulic pump. The PTO motor is an electric motor that drives the PTO shaft. The traveling motor is an electric motor that drives to run the traveling body. The battery supplies electric power to the pump motor, the PTO motor, and the traveling motor. The electric drive controller controls the distribution of electric power to the pump motor, the PTO motor, and the traveling motor. For example, when an overload state of the battery is detected, the electric drive controller reduces the electric power supplied to the traveling motor. If the overload state continues, the electric drive controller further reduces the electric power supplied to the PTO motor. Thereby, it is possible to prevent the overload of the battery while ensuring the stability of the operation of the hydraulic equipment.

[0005] Japanese Unexamined Patent Application Publication No. 2023-66721

[0006] It is necessary to appropriately control the output of the electric motors equipped in electric work vehicles.

[0007] Embodiments of the present invention include, for example, the drive system, work vehicle, control method, and computer program described in the following items.

[0008] [Item 1] A drive system for a work vehicle, comprising: one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate a PTO (Power Take Off) shaft; and a control device that controls the operation of the one or more electric motors, wherein the control mode in which the control device controls the one or more electric motors includes a first mode in which the power supplied to the one or more electric motors is limited to a first upper limit value and a second mode in which the limitation is removed, and the control device, while controlling the one or more electric motors in the first mode, switches the control mode from the first mode to the second mode and controls the one or more electric motors when the work vehicle changes from a state in which the PTO shaft is not rotating to a state in which it is rotating.

[0009] [Item 2] The drive system according to Item 1, further comprising a switch that accepts user operation for switching the drive of the PTO shaft on and off, wherein when the control device is controlling one or more electric motors in the first mode, if it detects user operation of the switch to turn the drive of the PTO shaft from off to on, it switches the control mode from the first mode to the second mode and controls the one or more electric motors.

[0010] [Item 3] The drive system according to Item 2, wherein the control device maintains control of the one or more electric motors in the first mode while it does not detect the user operating the switch to turn the drive of the PTO shaft from off to on.

[0011] [Item 4] The drive system according to any one of items 1 to 3, wherein the control device sets the upper limit of the power supplied to one or more electric motors in the second mode to a second upper limit that is greater than the first upper limit.

[0012] [Item 5] The drive system according to Item 4, wherein the control device changes the magnitude of the second upper limit depending on the type of work implement connected to the PTO shaft.

[0013] [Item 6] The drive system according to any one of items 1 to 5, wherein the control device slows down the rate at which the power supplied to one or more electric motors is reduced when the control mode is switched from the second mode to the first mode, compared to the rate at which the power supplied to one or more electric motors is increased when the control mode is switched from the first mode to the second mode.

[0014] [Item 7] The drive system according to any one of items 1 to 6, wherein the one or more electric motors include a first electric motor that generates a driving force to move the work vehicle and a second electric motor that generates a driving force to rotate the PTO shaft.

[0015] [Item 8] The drive system according to Item 7, wherein when the control device controls the first and second electric motors in the second mode, it increases the upper limit of the power supplied to the second electric motor compared to when it controls in the first mode.

[0016] [Item 9] The drive system according to Item 8, wherein when the control device controls the first and second electric motors in the second mode, it reduces the upper limit of the power supplied to the first electric motor compared to when it controls in the first mode.

[0017] [Item 10] The drive system according to any one of items 1 to 9, wherein the work vehicle is a mobile agricultural machine.

[0018] [Item 11] The drive system according to any one of items 1 to 10, wherein the work vehicle is a tractor.

[0019] [Item 12] A work vehicle equipped with a drive system as described in any of Items 1 through 11.

[0020] [Item 13] A control method for controlling the operation of a work vehicle, which is executed by one or more computers, wherein the work vehicle is equipped with one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate a PTO (Power Take Off) shaft, and the control mode for controlling the one or more electric motors includes a first mode in which a restriction is set to limit the power supplied to the one or more electric motors to a first upper limit value or less, and a second mode in which the restriction is removed, and the control method includes, when the one or more electric motors are being controlled in the first mode, the work vehicle changing from a state in which the PTO shaft is not rotating to a state in which it is rotating, switching the control mode from the first mode to the second mode and controlling the one or more electric motors.

[0021] [Item 14] A computer program that causes one or more computers to perform a process to control the operation of a work vehicle, wherein the work vehicle is equipped with one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate the PTO (Power Take Off) shaft, and the control mode for controlling the one or more electric motors includes a first mode in which a limit is set to keep the power supplied to the one or more electric motors below a first upper limit, and a second mode in which the limit is removed, and the computer program causes one or more computers to perform the following: when the one or more electric motors are being controlled in the first mode, if the work vehicle changes from a state in which the PTO shaft is not rotating to a state in which it is rotating, the control mode is switched from the first mode to the second mode and the one or more electric motors are controlled.

[0022] [Item 15] A drive system for a work vehicle, comprising: one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate a PTO (Power Take Off) shaft; one or more processors that control the operation of the one or more electric motors; and one or more storage devices that store computer programs that control the operation of the one or more processors, wherein the control modes by the one or more processors that control the one or more electric motors include a first mode in which the power supplied to the one or more electric motors is limited to a first upper limit value and a second mode in which the limitation is removed, and the one or more processors, in accordance with the computer program, when the one or more processors are controlling the one or more electric motors in the first mode and the work vehicle changes from a state in which the PTO shaft is not rotating to a state in which it is rotating, the control mode is switched from the first mode to the second mode and the one or more electric motors are controlled.

[0023] Comprehensive or specific embodiments of the present invention may be realized by apparatus, systems, methods, integrated circuits, computer programs, or computer-readable non-temporary storage media, or any combination thereof. The computer-readable storage media may include volatile storage media or non-volatile storage media. The apparatus may consist of multiple devices. If the apparatus consists of two or more devices, these two or more devices may be located in a single device or in two or more separate devices.

[0024] According to one embodiment of the present invention, the control mode includes a first mode in which the power supplied to one or more electric motors is limited to a first upper limit value, and a second mode in which this limitation is removed. When one or more electric motors are being controlled in the first mode, if the work vehicle changes from a state where the PTO shaft is not rotating to a state where it is rotating, the control mode is switched from the first mode to the second mode to control one or more electric motors. By limiting the output to a small amount when the PTO shaft is not rotating, power consumption is reduced, while the output of one or more electric motors can be increased when the PTO shaft is rotating, thereby preventing insufficient driving force to rotate the PTO shaft.

[0025] This is a schematic plan view showing an example of the basic configuration of a work vehicle according to an exemplary embodiment of the present invention. This is a side view of a work vehicle according to an exemplary embodiment of the present invention. This is a top view of the work vehicle. This is a block diagram showing an example of the main components of the work vehicle and their connection relationships. This is a block diagram showing an example of the configuration of a power converter and its connection to other equipment. This is a block diagram showing an example of the hardware configuration of each ECU. This is a block diagram showing an example of the configuration of a power distribution unit. This is a circuit diagram showing an example of the configuration of a charging circuit. This is a block diagram showing an example of a drive system provided by a work vehicle. This is a flowchart showing an example of the control of the first electric motor and the second electric motor. This is a diagram showing an example of the change in the upper limit of total power when the control mode is switched between the first mode and the second mode.

[0026] Embodiments of the present invention will be described below. However, unnecessarily detailed descriptions may be omitted. For example, detailed descriptions of already well-known matters and redundant descriptions of substantially identical configurations may be omitted. This is to avoid the following description becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The inventors provide the accompanying drawings and the following description so that those skilled in the art can fully understand the present invention, and not to limit the subject matter described in the claims. In the following description, components having the same or similar function are denoted by the same reference numerals.

[0027] The following embodiments are illustrative examples for realizing the technical concept of the present invention, and the present invention is not limited to these embodiments. For example, the numerical values, shapes, materials, steps, and order of steps shown in the following embodiments are merely examples, and various modifications are possible as long as they do not create a technical inconsistency. Furthermore, it is possible to combine one embodiment with other embodiments. The size and positional relationships of the components shown in each drawing may be exaggerated for ease of understanding.

[0028] (Definition of Terms) In this specification, “work vehicle” means a vehicle used for a specific task, such as agricultural work or construction work. “Work” may be, for example, agricultural work, construction work, rubble removal work, or snow removal work. Agricultural work vehicles may be, for example, tractors, combine harvesters, rice transplanters, riding cultivators, vegetable transplanters, vegetable harvesters, lawnmowers, seeders, or fertilizer spreaders. Construction work vehicles may be, for example, backhoes, wheel loaders, or carriers. An agricultural work vehicle such as a tractor or combine harvester, or a construction work vehicle, may function as a “work vehicle” on its own, or the work vehicle and any implements attached to or towed by it may function as a single “work vehicle.” Agricultural work vehicles perform agricultural work on the ground in a field, such as tilling, sowing, pest control, fertilizing, planting crops, or harvesting. Construction work vehicles perform work such as transporting soil, rubble, and other materials at a construction site. These tasks are sometimes referred to as "ground work" or simply "work." The act of a work vehicle moving while performing work is sometimes referred to as "work driving."

[0029] An "electric work vehicle" refers to a work vehicle that runs using an electric motor as its power source. An electric work vehicle may also be equipped with an internal combustion engine as an auxiliary power source in addition to the electric motor. Alternatively, an electric work vehicle may be equipped with an electric motor as an auxiliary power source in addition to the internal combustion engine. An electric work vehicle is equipped with an electrical energy source, such as a battery or fuel cell, to supply power to the electric motor. In the following description, an "electric work vehicle" may be simply referred to as a "work vehicle."

[0030] Electric motors can be synchronous motors such as permanent magnet synchronous motors or reluctance motors, or asynchronous motors such as induction motors.

[0031] A battery is an energy storage device that stores the electrical energy necessary for the operation of electric motors and other electrical components mounted on a work vehicle and / or work machine. A fuel cell is a power generation device that generates such electrical energy from a fuel such as hydrogen. An electrical energy source can be realized by an energy storage device, a power generation device, or a combination of an energy storage device and a power generation device. Furthermore, an electric work vehicle may obtain electrical energy from an electrical energy source located at a distance from the vehicle (e.g., on the ground or on another vehicle) via wired or wireless means.

[0032] When an electric work vehicle performs various "tasks" while moving or stationary, the power required for those tasks may be obtained from electric motors. An electric work vehicle is equipped with one or more electric motors. If an electric work vehicle is equipped with multiple electric motors, certain electric motors may output the driving force required for movement, while other electric motors may output the driving force required for the "tasks." If some or all of the "tasks" are performed by a work machine, the driving force can be mechanically transmitted from one or more electric motors on the electric work vehicle to the work machine. Such mechanical transmission of driving force can be achieved via a power transmission shaft called a power take-off (PTO) shaft.

[0033] The work machine itself may be equipped with an electric motor for the work. In this case, power may be supplied to the electric motor of the work machine from an electrical energy source such as a battery or fuel cell equipped in the electric work vehicle. The work machine may also be equipped with an electrical energy source that stores the power required for the work.

[0034] A "control device" (controller) is a device that controls the operation of part or all of a work vehicle. One example of a "control device" is a computing device comprising at least one processor and at least one memory that stores a computer program (code) that defines the control process executed by the processor. Another example of a "control device" is a computing device with a hardware accelerator such as an FPGA (Field-Programmable Gate Array), ASSP (Application Specific Standard Product), or ASIC (Application-Specific Integrated Circuit) configured or programmed to execute the control process. A control device may also be a collection of multiple devices. For example, several computing devices such as physically separated electronic control units (ECUs) may work together to function as a "control device".

[0035] A "processor" is a hardware electronic circuit such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), ISP (Image Signal Processor), or NPU (Neural Network Processing Unit).

[0036] "Memory" refers to hardware electronic circuits such as ROM (Read Only Memory) or RAM (Random Access Memory). Part of the memory may be a storage medium connected to the processor via wiring or a network. These hardware electronic circuits may be implemented by one or more integrated circuits (ICs) or large-scale integrated circuits (LSIs). Each functional unit or block and associated component within the electronic circuit may be manufactured individually as separate integrated circuit chips, or some or all of these functional units or blocks may be combined and manufactured as a single integrated circuit chip. Memory may store computer programs (hereinafter sometimes simply referred to as "programs") that define the operation of the processor. The programs are designed to cause the processor to perform one or more functions, operations, steps, or processes in embodiments of the present invention.

[0037] (Embodiments) Hereinafter, with reference to the drawings, several embodiments of the present invention applied to an electric agricultural tractor, which is an example of an electric work vehicle, will be described. The various technologies described for tractors in the following description can also be applied to agricultural machinery other than tractors, construction vehicles used at construction sites, work vehicles used at disaster sites, snowplows used in heavy snow areas, and vehicles for transporting goods, etc.

[0038] In the following explanation, the direction of arrow F in the diagram will be referred to as "forward," the direction of arrow B as "backward," the direction of arrow L as "left," the direction of arrow R as "right," the direction of arrow U as "up," and the direction of arrow D as "down."

[0039] <1. Basic Configuration of the Work Vehicle> Figure 1 is a schematic plan view showing an example of the basic configuration of a work vehicle 10 according to an exemplary embodiment of the present invention. The work vehicle 10 shown is an electric tractor for agricultural use. The work vehicle 10 can travel within a field while carrying or towing implements and performing agricultural work according to the type of implement. The work vehicle 10 can also travel within and outside of a field (including roads) with the implement lifted or without the implement attached.

[0040] The work vehicle 10 is equipped with a body (vehicle frame) 11 that rotatably supports the left and right front wheels 14F and the left and right rear wheels 14R. The body 11 includes a front frame 12 on which the front wheels 14F are mounted and a transmission case 13 on which the rear wheels 14R are mounted. The front frame 12 is fixed to the front of the transmission case 13. The front wheels 14F and the rear wheels 14R may be collectively referred to as "wheels 14". Strictly speaking, wheels 14 are wheels, and tires are mounted on the wheels 14. In this disclosure, "wheels" generally means the entire "wheel and tire". One or both of the front wheels 14F and the rear wheels 14R may be replaced with a plurality of wheels (crawlers) equipped with a track instead of wheels with tires.

[0041] The work vehicle 10 in the example shown in Figure 1 is equipped with a battery 20 and an electric motor 30 (hereinafter simply referred to as "motor 30") which are directly or indirectly supported by the front frame 12. The battery 20 may be configured as a battery pack including, for example, multiple cells connected in series. The battery 20 is a rechargeable battery that outputs a relatively high voltage, such as a lithium-ion battery or an all-solid-state battery. The battery 20 stores power to drive the motor 30. The battery 20 may be housed in a front housing, for example, called a "bonnet." The front housing is supported by the front frame 12 located at the front of the vehicle body 11.

[0042] The motor 30 is electrically connected to the battery 20. The motor 30 can convert the electric power output from the battery 20 into mechanical motion (power) to generate the driving force (traction) required for the traveling of the work vehicle 10. The motor 30 can be, for example, an AC synchronous motor. The battery 20 generates a direct current. Therefore, when the motor 30 is an AC synchronous motor, an electric circuit group including an inverter device (hereinafter sometimes simply referred to as an "inverter") may be provided between the battery 20 and the motor 30. The direct current is converted into an alternating current by the inverter device. A part of such an electric circuit group may be inside the battery 20. Also, another part of the electric circuit group may be attached to the motor 30 as a drive circuit of the motor 30.

[0043] The motor 30 has a rotating output shaft 33. The torque of the output shaft 33 is transmitted to the rear wheel 14R via mechanical components such as a transmission (speed change device) provided inside the transmission case 13 and a rear wheel differential device (differential gear device). In other words, the power generated by the motor 30, which is a power source, is transmitted to the rear wheel 14R by a power transmission system (drive train) 34 including a transmission provided inside the transmission case 13. For this reason, the "transmission case" may be called a "mission case". In the four-wheel drive mode, a part of the power of the motor 30 is also transmitted to the front wheel 14F. Thus, the motor 30 drives a traveling device including a plurality of wheels 14.

[0044] The power of the motor 30 may be used not only for the traveling of the work vehicle 10 but also for driving a work implement. A PTO shaft 40 is provided at the rear end of the transmission case 13. A work implement can be connected to the PTO shaft 40. The PTO shaft 40 can be driven by the motor 30 that drives the traveling device or another electric motor not shown in FIG. 1. The torque of the output shaft 33 of the motor 30 or the output shaft of another motor is transmitted to the PTO shaft 40. The work implement mounted on or towed by the work vehicle 10 can receive power from the PTO shaft 40 and execute operations according to various works. The motor 30 and the power transmission system 34 may be collectively referred to as an electric power train.

[0045] As shown in Figure 1, the work vehicle 10 does not have an internal combustion engine such as a diesel engine, but is equipped with a battery 20 and a motor 30. The output shaft 33 of the motor 30 is mechanically coupled to a power transmission system 34, such as a transmission, in a transmission case 13. The motor 30 can efficiently generate torque over a relatively wide range of rotational speeds compared to an internal combustion engine. By using the power transmission system 34, including the transmission, it becomes easy to adjust the torque and rotational speed from the motor 30 over an even wider range by performing multi-stage or continuously variable speed changes. Therefore, it is possible to efficiently perform not only the movement of the work vehicle 10 but also a variety of tasks using work equipment.

[0046] Depending on the intended use or size of the work vehicle 10, some functions of the power transmission system 34 may be omitted. For example, some or all of the transmission responsible for the gear shifting function may be omitted. The number and mounting positions of the motors 30 are not limited to the example shown in Figure 1. Furthermore, the work vehicle may be a hybrid electric vehicle (HEV) equipped with an internal combustion engine such as a diesel engine as a power source in addition to electric motors.

[0047] The work vehicle 10 shown in FIG. 1 includes one motor 30. However, the work vehicle 10 may include a plurality of electric motors. For example, the work vehicle 10 may include a traveling electric motor that drives a traveling device including four wheels 14, and a PTO electric motor that drives a PTO shaft 40. The work vehicle 10 may include a plurality of PTO shafts (for example, a rear PTO shaft, a mid PTO shaft, a front PTO shaft, etc.). In that case, one electric motor may drive a plurality of PTO shafts, or a plurality of electric motors may drive a plurality of PTO shafts. For example, the work vehicle 10 may include a plurality of electric motors each driving a corresponding one of the plurality of PTO shafts. The work vehicle 10 may include a front-wheel electric motor that drives two front wheels 14F, and a rear-wheel electric motor that drives two rear wheels 14R. Alternatively, the work vehicle 10 may include two front-wheel electric motors that respectively drive two front wheels 14F, and two rear-wheel electric motors that respectively drive two rear wheels 14R. That is, the work vehicle 10 may include four electric motors that respectively drive four wheels 14. Thus, the work vehicle 10 may include one or more traveling electric motors that drive the traveling device, and one or more PTO electric motors that drive one or more PTO shafts. By including a plurality of electric motors, the work vehicle 10 can more flexibly control the rotation of the plurality of wheels 14 and one or more PTO shafts. In the following description, the traveling electric motor may be referred to as a "traveling motor", and the PTO electric motor may be referred to as a "PTO motor".

[0048] <2. Specific Example of Work Vehicle> Next, an example of a more specific configuration of the work vehicle 10 will be described.

[0049] FIG. 2 is a side view of the work vehicle 10 according to an exemplary embodiment of the present invention. FIG. 3 is a top view of the work vehicle 10 according to the present embodiment.

[0050] The work vehicle 10 shown in FIGS. 2 and 3 includes a vehicle body 11 and a traveling device supported by the vehicle body 11. The traveling device includes various devices necessary for traveling, such as left and right front wheels 14F, left and right rear wheels 14R, a front axle 15F, a rear axle 15R, and a rear-wheel differential device.

[0051] The vehicle body 11 comprises a front frame 12, a transmission case 13, and a housing frame 16. The front frame 12 is connected to the front of the housing frame 16. The transmission case 13 is connected to the rear of the housing frame 16. A first electric motor 30A and a second electric motor 30B are housed inside the housing frame 16. The first electric motor 30A is a driving motor and drives the running gear via a power transmission system in the transmission case 13. The second electric motor 30B is a PTO motor and drives the PTO shaft 40 and one or more hydraulic pumps. The first electric motor 30A and the second electric motor 30B may be electric motors capable of relatively high efficiency and high torque output, such as permanent magnet synchronous motors.

[0052] The front frame 12 is fitted with a front axle case 17F. The front axle case 17F supports the left and right front wheels 14F. The transmission case 13 includes a rear axle case 17R. The rear axle case 17R supports the left and right rear wheels 14R and transmits power to the rear wheels 14R.

[0053] A battery 20 is mounted on the front frame 12. The battery 20 is supported by the front frame 12 and housed inside the front housing 19 (bonnet). The battery 20 stores the power supplied to the first electric motor 30A and the second electric motor 30B. In other words, the battery 20 stores power for driving, operation, and hydraulic drive. In the following description, the battery 20 may be referred to as the "drive battery 20".

[0054] Above the housing frame 16 and the transmission case 13 are a steering wheel 53, a meter panel unit 54, a group of pedals 55 including the accelerator and brake, a group of switches 56 for work driving, and a driver's seat 52. A safety frame 51 is provided behind the driver's seat 52. The safety frame 51 is attached to the transmission case 13 and has a structure that extends upward. Inside the housing frame 16 are the first electric motor 30A and the second electric motor 30B.

[0055] The switch group 56 includes various operating devices such as switches, levers, and dials for adjusting the operation of the work vehicle 10 and the work implement. The switch group 56 includes various operating devices such as an accelerator lever for adjusting the travel speed, a switch for switching the PTO shaft 40 on and off, a dial for adjusting the rotational speed of the PTO shaft 40, and a lever for adjusting the height of the three-point linkage supporting the work implement. By operating the switch group 56, the driver can give various instructions to the work vehicle 10 for travel and work.

[0056] In the following description, devices used by the user to operate the work vehicle 10, such as the steering wheel 53, pedal group 55, and switch group 56, may be collectively referred to as the "operating device group."

[0057] The meter panel unit 54 displays information regarding the status of the work vehicle 10. For example, the meter panel unit 54 displays various information such as the travel speed, the rotational speed of the PTO shaft 40, the height of the three-point linkage, the output of the motors 30A and 30B, the charge status of the battery 20, and the temperature of the battery 20. The meter panel unit 54 may be equipped with analog meters and / or a digital display (hereinafter sometimes simply referred to as "display") for displaying this information. The display of the meter panel unit 54 may display a graphical user interface (GUI) that allows the user to perform various setting operations related to the work vehicle 10. The user can perform various settings related to the work vehicle 10 on the display screen using an input device connected to the meter panel unit 54 or an input means such as a touchscreen mounted on the display.

[0058] As shown in Figure 3, a charging inlet 57 is provided to the right of the steering wheel 53. The charging inlet 57 is a device that includes a socket configured to allow connection of a charging adapter extending from an external power source or charging device. Near the charging inlet 57, a device for the user to initiate charging, such as a charging start button, may be provided. When the user connects the charging adapter to the charging inlet 57 and performs a predetermined operation, such as pressing the charging start button, charging of the battery 20 begins.

[0059] The battery 20 can be charged using either normal charging or rapid charging. In normal charging, AC power supplied from an external AC power source is converted to high-voltage DC power (e.g., around 350V to 450V), and this DC power is supplied to the battery 20. In rapid charging, high-voltage DC power is directly supplied to the battery 20 from an external DC power source. The charging inlet 57 in this embodiment supports both normal and rapid charging. For normal charging, a commercial AC power source that outputs an AC voltage of, for example, 200V or 100V may be used as the power source. For rapid charging, a DC power source that outputs a DC voltage of, for example, around 350V to 450V may be used as the power source. Rapid charging can be performed using protocols compliant with standards such as CHAdeMO, NACS, CCS1, CCS2, GB / T, or ChaoJi.

[0060] The power stored in the battery 20 can also be output to external electrical equipment via the charging inlet 57. Such external power output is referred to as "external power supply" in this specification. External power supply is performed with an external power supply adapter connected to the charging inlet 57. The DC power from the battery 20 can be converted to AC power by a power converter in the work vehicle 10. This AC power can then be supplied to external equipment via the charging inlet 57 and the external power supply adapter.

[0061] As shown in Figure 3, the first electric motor 30A and the second electric motor 30B in this embodiment are arranged side by side. The first electric motor 30A and the second electric motor 30B are rotated by power supplied from the battery 20. The first electric motor 30A drives the running gear via a power transmission system in the transmission case 13. The second electric motor 30B drives the PTO shaft 40 and the hydraulic pump via a power transmission system in the transmission case 13. As a result, the second electric motor 30B drives the work implement and various hydraulic devices. The hydraulic devices may be used, for example, to change the height of the three-point linkage supporting the work implement. The work vehicle 10 may be equipped with a power steering system that assists the driver's steering wheel operation. In this case, the hydraulic devices may also be used in the power steering system to supply auxiliary force to change the steering angle of the front wheels 104F.

[0062] <3. System Configuration of the Work Vehicle> Figure 4 is a block diagram showing the main components of the work vehicle 10 and an example of their connection relationships. In Figure 4, connection relationships related to power transmission, high-voltage drive power, and low-voltage auxiliary power are represented by solid lines of different thicknesses. Connection relationships related to signals (digital signals and analog signals) are represented by dotted lines. Coolant flow is represented by thick dashed lines.

[0063] As shown in Figure 4, the work vehicle 10 is equipped with a first inverter 35A and a second inverter 35B. The first inverter 35A is connected to the first electric motor 30A. The second inverter 35B is connected to the second electric motor 30B. Each of the first inverter 35A and the second inverter 35B converts the DC voltage from the battery 20 into a three-phase AC voltage. The first inverter 35A supplies the converted three-phase AC voltage to the first electric motor 30A. This causes the first electric motor 30A to rotate and the traction device to be driven. The second inverter 35B also supplies the converted three-phase AC voltage to the second electric motor 30B. This causes the second electric motor 30B to rotate and the hydraulic pump 36 and the PTO shaft 40 to be driven.

[0064] The transmission case 13 houses the power transmission system 34A for driving, the power transmission system 34B for work, and the hydraulic pump 36. The power transmission system 34A for driving may include components such as a reduction gear, a sub-transmission, and a differential brake. The power transmission system 34A for driving transmits power from the rotation of the first electric motor 30A to the rear wheels 14R. In four-wheel drive mode, the power transmission system 34A for driving also transmits a portion of the power from the rotation of the first electric motor 30A to the front wheels 14F. The power transmission system 34B for work may include components such as a reduction gear, a PTO clutch, and a PTO transmission. The power transmission system 34B for work transmits power from the rotation of the second electric motor 30B to the hydraulic pump 36 and the PTO shaft 40. The PTO shaft 40 supplies power for work to the work implement.

[0065] The PTO shaft 40 shown in Figure 4 is the rear PTO shaft. In addition to the rear PTO shaft, the work vehicle 10 may also have a mid-PTO shaft or a front PTO shaft. If the work vehicle 10 has multiple PTO shafts, the power transmission system 34B may be configured to distribute the power generated by the rotation of the second electric motor 30B to the multiple PTO shafts. Alternatively, in addition to the second electric motor 30B that drives the PTO shaft 40, the work vehicle 10 may include other electric motors that drive the other PTO shafts.

[0066] The implements connected to the PTO shaft 40 may include, for example, a rotary tiller, a seeder, a spreader, a transplanter, a mower, a rake, a baler, a harvester, a sprayer, or a harrow. Any implement can be connected to the work vehicle 10 and used.

[0067] The hydraulic pump 36 is driven by power from the second electric motor 30B. The hydraulic pump 36 pressurizes the hydraulic fluid, thereby changing the height of the three-point linkage to which the work equipment is connected. Alternatively, the hydraulic pump 36 may be used in a hydraulic power steering system. If a front loader is mounted as the work equipment, the hydraulic pump 36 may be used in a hydraulic system that enables the lifting and lowering of the front loader. Power from the second electric motor 30B may be transmitted to multiple hydraulic pumps to drive these multiple hydraulic systems. Alternatively, the work vehicle 10 may have one or more electric motors for hydraulics separate from the second electric motor 30B.

[0068] In the example shown in Figure 4, the work vehicle 10 further comprises a power converter 58, a power distribution unit (PDU) 80, an auxiliary battery 21, and a battery temperature control system 70.

[0069] The power converter 58 is positioned between the charging inlet 57 and the battery 20 and performs power conversions such as AC to DC conversion and voltage conversion. Figure 5 shows an example of the configuration of the power converter 58 and its connection to other equipment. The power converter 58 shown in Figure 5 includes an onboard charger (OBC) 81 and a DC-DC converter 82. During normal charging, the OBC 81 converts AC power from the charging inlet 57 to DC power and supplies it to the drive battery 20 via the power distribution unit 80. The drive battery 20 is charged by this DC power. The DC-DC converter 82 is connected to the OBC 81 and also to the battery 20 via the power distribution unit 80. The DC-DC converter 82 converts the relatively high-voltage DC power output from the OBC 81 or the drive battery 20 to lower-voltage DC power (e.g., 12V or 24V). The low-voltage DC power converted by the DC-DC converter 82 is supplied to the auxiliary battery 21 and the auxiliary components 84. The auxiliary components 84 include several devices that operate on the relatively low voltage output from the DC-DC converter 82 or the battery 21. For example, the auxiliary components 84 include several electronic control units (ECUs) and other electrical components. The auxiliary battery 21 is charged by the DC voltage output from the DC-DC converter 82. The auxiliary battery 21 stores the power supplied to the auxiliary components 84, such as each ECU, the meter panel unit 54, the pumps 67, 77, and the air conditioner. The battery 21 may be, for example, a lead-acid battery.

[0070] Refer to Figure 4 again. The work vehicle 10 is equipped with multiple ECUs. The multiple ECUs include a main ECU 61, an electric ECU 62, a charging ECU 63, and a meter ECU 151. The main ECU 61 controls the overall operation of the work vehicle 10 based on signals generated by the user operating the pedal group 55, the switch group 56, and the meter panel unit 54. The electric ECU 62 mainly controls the charging and discharging of the battery 20 and the operation of the electric motors 30A and 30B. The charging ECU 63 communicates with an external charger (external power supply) and performs control to ensure smooth charging by appropriately controlling the relay 64. The meter ECU 151 controls the operation of the meter panel unit 54. For example, the meter ECU 151 controls the display of various information on the meter panel unit 54 and controls various settings in response to user operations on the meter panel unit 54.

[0071] In this embodiment, the combination of the main ECU 61, electric ECU 62, charging ECU 63, and meter ECU 151 functions as a "control device" that controls the operation of the work vehicle 10. Therefore, in the following description, the operations performed by the main ECU 61, electric ECU 62, charging ECU 63, and meter ECU 151 all correspond to operations performed by the "control device". These ECUs can communicate with each other according to a vehicle bus standard such as CAN (Controller Area Network). A faster communication method such as on-board Ethernet (registered trademark) may be used instead of CAN. An on-board computer integrating at least some of the functions of the main ECU 61, electric ECU 62, charging ECU 63, and meter ECU 151 may be provided as the "control device". The control device may include ECUs other than the main ECU 61, electric ECU 62, charging ECU 63, and meter ECU 151. Each ECU may be a computing device including one or more processors and one or more memories. Each ECU can perform the operations described below by having its processor execute a computer program stored in memory.

[0072] The electric ECU 62 sends control signals to the first inverter 35A and the second inverter 35B in response to signals from the pedal group 55 and the switch group 56. The electric ECU 62 can perform motor control based on a rotational speed command value or a torque command value determined, for example, according to the amount of operation of the pedal group 55 by the driver. In this specification, the former control based on the rotational speed command value may be referred to as "speed control," and the latter control based on the torque command value may be referred to as "torque control."

[0073] The electric ECU 62 controls the switching operation of multiple switch elements (e.g., MOSFETs) in the first inverter 35A and the second inverter 35B, respectively. Specifically, the electric ECU 62 generates control signals to control the switching operation of each switch element and outputs them to each inverter. The first inverter 35A converts the DC power from the battery 20 into three-phase AC power, which is a pseudo-sine wave of, for example, u-phase, v-phase, and w-phase, according to the control signals from the electric ECU 62, and supplies this three-phase AC power to the first electric motor 30A. Similarly, the second inverter 35B converts the DC power from the battery 20 into three-phase AC power, which is a pseudo-sine wave of, for example, u-phase, v-phase, and w-phase, according to the control signals from the electric ECU 62, and supplies this three-phase AC power to the second electric motor 30B. As a result, the electric ECU 62 can rotate the electric motors 30A and 30B at appropriate rotational speeds and torques according to the driver's operation.

[0074] While the work vehicle 10 is in operation, the main ECU 61 causes the meter panel unit 54 to display information regarding the status of the work vehicle 10. For example, the main ECU 61 displays information such as the travel speed, the operating status of the motors 30A and 30B, the charge status of the battery 20, and the status of the transmissions included in the power transmission systems 34A and 34B on the meter panel unit 54.

[0075] Figure 6 is a block diagram showing an example of the hardware configuration of each ECU. The main ECU 61, electric ECU 62, charging ECU 63, and meter ECU 151 each include the various components shown in Figure 6. The ECU 400 shown in Figure 6 includes a processor 434, ROM 435, RAM 436, external I / F 437, and communication I / F 438. These components are interconnected via a bus 439.

[0076] ROM 435 is, for example, writable memory (e.g., PROM), rewritable memory (e.g., flash memory), or read-only memory. ROM 435 stores a program that controls the operation of the processor 434. ROM 435 does not have to be a single recording medium; it may be a collection of multiple recording media. Some of the multiple storage media may be removable memory.

[0077] RAM 436 provides a working area for temporarily unpacking the program stored in ROM 435 at boot time. RAM 436 does not need to be a single recording medium; it may be a collection of multiple recording media.

[0078] External I / F 437 is an interface for connecting to external devices. Communication I / F 438 is an interface for communicating with other electronic devices (e.g., sensors and other ECUs). For example, communication I / F 438 can perform wired communication compliant with various protocols such as CAN or Ethernet®. Communication I / F 438 may also perform wireless communication compliant with wireless communication standards such as Bluetooth® and / or Wi-Fi®.

[0079] The ECU 400 may further include a storage device for storing data generated by the processor 434 for a relatively long period of time. Such a storage device may be, for example, a semiconductor storage device, a magnetic storage device, or an optical storage device, or a combination thereof.

[0080] The power distribution unit 80 shown in Figure 4 is a device that electrically connects equipment such as the charging inlet 57, power converter 58, battery 20, inverters 35A and 35B, and heater 72.

[0081] Figure 7 shows an example of the configuration of the power distribution unit 80. The power distribution unit 80 may have a plurality of relay circuits 83 (83a to 83g) that operate under the control of the electric ECU 62. During charging, the power distribution unit 80 is configured to supply power from the charging inlet 57 or the power converter 58 to the battery 20, and to the heater 72 when the temperature is low. On the other hand, during discharging, the power distribution unit 80 is configured to distribute power from the battery 20 to the first inverter 35A, the second inverter 35B, and the power converter 23. The electric ECU 62 may be configured or programmed to control the charging and discharging of the battery 20 by appropriately switching the on and off of the plurality of relay circuits 83a to 83g in the power distribution unit 80. In this specification, relay circuits may be simply referred to as "relays".

[0082] As shown in Figure 4, the battery 20 includes a battery management system (BMS) 22 and a temperature sensor 24. The BMS 22 is configured to monitor the state of the battery 20, such as the input voltage, output voltage, and temperature, and to control the charging and discharging currents to the battery 20 based on these states. The temperature sensor 24 may be configured to measure the temperature of each of the multiple cells contained in the battery 20.

[0083] The work vehicle 10 illustrated in Figure 4 is equipped with a cooling system 60 for high-voltage equipment and a battery temperature control system 70. The cooling system 60 is used to cool equipment to which high voltage is applied (also referred to as "high-voltage equipment"). The cooling system 60 comprises a radiator 65, a reservoir tank 66, a pump 67, and a cooling fan 68. In the example in Figure 4, the cooling system 60 is connected via hoses to the first inverter 35A, the first electric motor 30A, the second electric motor 30B, the second inverter 35B, and the power converter 58 in that order. This forms a flow path through which the coolant circulates. The coolant in the cooling system 60 is, for example, water or oil. The cooling system 60 cools these high-voltage equipment by circulating the coolant through the flow path. The coolant heated by the high-voltage equipment is cooled by heat dissipation in the radiator 65. The cooling fan 68 generates cooling air to cool the refrigerant inside the radiator 65. The cooling air promotes heat dissipation from the radiator 65.

[0084] The battery temperature control system 70 is used to cool or heat (also referred to as "heating") the battery 20. The battery temperature control system 70 comprises a heater 72, a radiator 75, a reservoir tank 76, and a pump 77. The battery temperature control system 70 is connected to the battery 20 via a hose. This creates a passage through which the coolant circulates. The coolant in the battery temperature control system 70 is, for example, water or oil. The battery temperature control system 70 cools the battery 20 by circulating the coolant through the passage. The coolant heated by the battery 20 is cooled by heat dissipation in the radiator 75. Cooling air from the cooling fan 68 also plays a role in cooling the coolant inside the radiator 75. The heater 72 raises the temperature of the battery 20 by warming the coolant. This makes it possible to suppress a decrease in the charge and discharge performance of the battery 20 even in low-temperature environments where the ambient temperature is, for example, below 0 degrees Celsius (°C).

[0085] The operation of the cooling system 60 and the battery temperature control system 70 is controlled by the electric ECU 62. For example, the electric ECU 62 is configured or programmed to maintain the temperature of the battery 20 within an appropriate range by controlling the battery temperature control system 70 based on the temperature of the battery 20 measured by the temperature sensor 24. In addition to the measurement value of the temperature sensor 24, the electric ECU 62 may also control the battery temperature control system 70 based on the measurement value of a temperature sensor 25 that measures the ambient temperature and is installed in the work vehicle 10.

[0086] The flow paths of the coolant in the cooling system 60 and the battery temperature control system 70 are not limited to the illustrated paths and can be changed as appropriate. The cooling method in the cooling system 60 and the battery temperature control system 70 is not limited to water cooling or oil cooling, but may also be air cooling. Alternatively, the refrigerant used in an air conditioner may be used instead of the above-mentioned coolant.

[0087] Next, we will explain an example of a charging circuit configuration that switches between normal charging and fast charging.

[0088] Figure 8 is a circuit diagram showing an example of a charging circuit configuration. The charging circuit 700 illustrated in Figure 8 is a circuit that enables rapid charging in accordance with the NACS standard. The charging circuit 700 comprises a pair of power pins 710a and 710b, a relay circuit 720, a contactor 730, an OBC 81, and a controller 750. The controller 750 may be, for example, the charging ECU 63 or the motor ECU 62 shown in Figure 4. The relay circuit 720 and the contactor 730 operate under the control of the controller 750. The charging circuit 700 is connected to the battery 20 and enables normal and rapid charging of the battery 20. Communication takes place between the charging circuit and the charging station, thereby controlling the charging process.

[0089] When rapid charging is performed, a relatively high DC voltage (e.g., 450V) is applied to a pair of power pins 710a and 710b. If high-voltage DC power is supplied to the OBC 81, the OBC 81 may fail. To avoid this, a relay circuit 720 is provided in the charging circuit 700 in this embodiment. During rapid charging, the controller 750 supplies DC power from an external DC power source to the battery 20 by bringing contact 721a of the relay circuit 720 into contact with contact 721b and closing the contactor 730. On the other hand, during normal charging, the controller 750 inputs AC power from an external AC power source to the OBC 81 by bringing contact 721a of the relay circuit 720 into contact with contact 721c and opening the contactor 730. The controller 750 converts the AC power to DC power by controlling the OBC 81 and supplies the DC power to the battery 20. In this way, a relatively simple circuit like the relay circuit 720 makes it possible to reliably prevent high-voltage DC power from being supplied to the OBC 740 during rapid charging.

[0090] <4. Output Control of Electric Motors> Next, an example of output control for the first electric motor 30A and the second electric motor 30B will be explained.

[0091] Figure 9 is a block diagram showing an example of a drive system 100 provided by a work vehicle 10. The control device 110 shown in Figure 9 is a control unit including a main ECU 61 and an electric ECU 62. The control device 110 may further include a charging ECU 63, a meter ECU 151, or other ECUs. The control device 110 controls the operation of the first electric motor 30A and the second electric motor 30B.

[0092] The current sensor 121 and the voltage sensor 122 are installed at any position in the electrical path between the battery 20 and the first electric motor 30A. The current sensor 121 and the voltage sensor 122 are also installed at any position in the electrical path between the battery 20 and the second electric motor 30B. The control device 110 can calculate the power supplied to the first electric motor 30A and the power supplied to the second electric motor 30B based on the output signals of the current sensor 121 and the voltage sensor 122. The control device 110 may also calculate the power supplied to the first electric motor 30A and the power supplied to the second electric motor 30B based on command values ​​output to the first inverter 35A and the second inverter 35B.

[0093] The control device 110 can control the first and second electric motors 30A and 30B in multiple control modes. The multiple control modes include a first mode in which a restriction is imposed to keep the total power Wo, which is the sum of the power supplied to the first electric motor 30A and the power supplied to the second electric motor 30B, below a first upper limit W1, and a second mode in which this restriction is removed. The multiple control modes may also include modes other than the first and second modes.

[0094] The PTO switch 131 is a user-operated switch for switching the drive of the PTO shaft 40 on and off. For example, when the user turns the PTO switch 131 on, the control device 110 controls the second electric motor 30B and the power transmission system 34B so that the PTO shaft 40 rotates. The PTO switch 131 may be included in the switch group 56.

[0095] Figure 10 is a flowchart showing an example of the control of the first electric motor 30A and the second electric motor 30B. In the example shown in Figure 10, the second mode is turned on based on the user's operation of the PTO switch 131.

[0096] When the PTO shaft 40 is not rotating, the control device 110 controls the first and second electric motors 30A and 30B in first mode (step S101). When the PTO shaft 40 is not rotating, power consumption can be reduced by limiting the total power Wo to a first upper limit W1 or less. In first mode, the PTO shaft 40 is not rotating, but the second electric motor 30B is rotating to drive the hydraulic pump 36.

[0097] The control device 110 determines whether the user has operated the PTO switch 131 to turn on the drive of the PTO shaft 40 (step S102). As long as the control device 110 does not detect operation of the PTO switch 131 to turn on the drive of the PTO shaft 40, it maintains control of the first and second electric motors 30A and 30B in the first mode.

[0098] When the control device 110 determines that the PTO switch 131, which turns on the drive of the PTO shaft 40, has been operated, it switches the control mode from the first mode to the second mode and controls the first and second electric motors 30A and 30B (step S103). The control device 110 sets the upper limit of the total power Wo in the second mode to a second upper limit W2, which is greater than the first upper limit W1. By increasing the upper limit of the total power Wo in the second mode, the output of the first electric motor 30A and / or the second electric motor 30B can be increased. By increasing the output of the second electric motor 30B, the driving force necessary for the proper rotation of the PTO shaft 40 can be supplied to the PTO shaft 40.

[0099] The second upper limit W2 is, for example, 1.2 times or more and 2.0 times or less of the first upper limit W1, but is not limited thereto. For example, the second upper limit W2 may be greater than 2.0 times the first upper limit W1. The values ​​of the first upper limit W1 and the second upper limit W2 are stored in advance in ROM 435, for example.

[0100] The control device 110 determines whether the user has operated the PTO switch 131 to turn off the drive of the PTO shaft 40 (step S104). As long as the control device 110 does not detect operation of the PTO switch 131 to turn off the drive of the PTO shaft 40, it maintains control of the first and second electric motors 30A and 30B in second mode.

[0101] When the control device 110 determines that the PTO switch 131 has been operated to turn off the drive of the PTO shaft 40, it terminates control in the second mode. The control device 110 switches the control mode from the second mode to the first mode and controls the first and second electric motors 30A and 30B (step S105).

[0102] In this embodiment, when the first and second electric motors 30A and 30B are being controlled in the first mode, if the work vehicle 10 changes from a state where the PTO shaft 40 is not rotating to a state where it is rotating, the control mode is switched from the first mode to the second mode to control the first and second electric motors 30A and 30B. When the PTO shaft 40 is not rotating, the output is limited to a small amount, thereby reducing power consumption, while when the PTO shaft 40 is rotating, the output of the first and second electric motors 30A and 30B can be increased, thereby preventing insufficient driving force to rotate the PTO shaft 40.

[0103] The rate at which the upper limit of total power Wo is increased when switching the control mode from the first mode to the second mode may be different from the rate at which the upper limit of total power Wo is decreased when switching the control mode from the second mode to the first mode.

[0104] Figure 11 shows an example of the change in the upper limit of the total power Wo when the control mode is switched between the first mode and the second mode. The vertical axis represents the upper limit, and the horizontal axis represents time.

[0105] In the example shown in Figure 11, at time T1, the control device 110 switches the control mode from the first mode to the second mode and changes the upper limit of the total power Wo from the first upper limit W1 to the second upper limit W2. At time T2, the control device 110 switches the control mode from the second mode to the first mode and changes the upper limit of the total power Wo from the second upper limit W2 to the first upper limit W1.

[0106] As shown in Figure 11, the control device 110 may decrease the upper limit of the total power W when switching from the second mode to the first mode at a slower pace than it increases the upper limit of the total power W when switching from the first mode to the second mode.

[0107] When the control mode is switched from the first mode to the second mode, the upper limit of the total power Wo is quickly increased, thereby quickly meeting the user's requirement to rotate the PTO shaft 40 stably at the desired rotational speed.

[0108] When switching the control mode from the second mode to the first mode, slowly reducing the upper limit of the total power Wo can prevent the motor output from dropping too sharply and causing the user to feel uncomfortable.

[0109] When the control device 110 controls the first and second electric motors 30A and 30B in the second mode, it increases the upper limit of the power supplied to the second electric motor 30B compared to when it controls in the first mode. This increases the output of the second electric motor 30B and prevents insufficient driving force to rotate the PTO shaft 40.

[0110] When the control device 110 controls the first and second electric motors 30A and 30B in the second mode, it may reduce the upper limit of the power supplied to the first electric motor 30A compared to when controlling in the first mode. This helps to prevent the total power consumption from becoming too high.

[0111] The control device 110 may change the size of the second upper limit W2 depending on the type of work implement connected to the PTO shaft 40. For example, the user inputs information about the type of work implement connected to the PTO shaft 40 (e.g., model information) using an input device connected to the meter panel unit 54 or an input means such as a touchscreen mounted on the display. For example, table information showing the relationship between multiple work implements and the second upper limit W2 is pre-stored in the ROM 435. The control device 110 can set the size of the second upper limit W2 based on the information input by the user and the table information.

[0112] Furthermore, for example, if the work vehicle 10 and the work machine are equipped with a communication device that enables data communication between the work vehicle 10 and the work machine, information regarding the type of work machine may be output from the work machine connected to the PTO shaft 40 to the work vehicle 10. The control device 110 can set the size of the second upper limit W2 based on the information output by the work machine and the table information.

[0113] In the example described above, the control mode was switched between a first mode and a second mode in response to user operation on the PTO switch 131, but the present invention is not limited thereto. For example, the control device 110 may detect the state of the PTO clutch provided in the power transmission system 34B and switch the control mode between a first mode and a second mode according to the state of the PTO clutch. When the PTO clutch is engaged, the rotation of the second electric motor 30B is transmitted to the PTO shaft 40, and when the PTO clutch is disengaged, the rotation of the second electric motor 30B is not transmitted to the PTO shaft 40. The control device 110 determines the state of the PTO clutch based on the output signal of the sensor that detects the state of the PTO clutch. The control device 110 may perform control in the first mode when the PTO clutch is disengaged, and perform control in the second mode when the PTO clutch is engaged.

[0114] The control described above can also be applied to a configuration in which a single electric motor generates both the driving force to move the work vehicle 10 and the driving force to rotate the PTO shaft 40. When the control device 110 is controlling the single electric motor in the first mode, if the work vehicle 10 changes from a state where the PTO shaft 40 is not rotating to a state where it is rotating, the control device 110 switches the control mode from the first mode to the second mode and controls the single electric motor. By limiting the output to a small amount when the PTO shaft 40 is not rotating, power consumption is reduced, while the output of the single electric motor can be increased when the PTO shaft 40 is rotating, thereby preventing insufficient driving force to rotate the PTO shaft 40.

[0115] The drive system 100 according to this embodiment can also be retrofitted to a work vehicle that does not have those functions. Such a system can be manufactured and sold independently of the work vehicle. The computer program used in such a system can also be manufactured and sold independently of the work vehicle. The computer program can be provided, for example, stored in a computer-readable non-temporary storage medium. The computer program can also be provided by download via a telecommunications line (e.g., the Internet).

[0116] Embodiments of the present invention include, for example, the drive system, work vehicle, control method, and computer program described in the following items.

[0117] [Item 1] A drive system 100 for a work vehicle 10, comprising: one or more electric motors 30A, 30B that generate a driving force to move the work vehicle 10 and a driving force to rotate the PTO (Power Take Off) shaft 40; and a control device 110 that controls the operation of one or more electric motors 30A, 30B, wherein the control mode for controlling one or more electric motors 30A, 30B by the control device 110 includes a first mode in which the power supplied to one or more electric motors 30A, 30B is limited to a first upper limit W1 or less, and a second mode in which the limitation is removed; and when the control device 110 is controlling one or more electric motors 30A, 30B in the first mode, if the work vehicle 10 changes from a state in which the PTO shaft 40 is not rotating to a state in which it is rotating, the control mode is switched from the first mode to the second mode and the control device 110 controls one or more electric motors 30A, 30B.

[0118] [Item 2] The drive system 100 according to Item 1, comprising a switch 131 that accepts user operation to switch the drive of the PTO shaft 40 on and off, wherein when the control device 110 is controlling one or more electric motors 30A, 30B in the first mode, if it detects user operation of the switch 131 to switch the drive of the PTO shaft 40 from off to on, it switches the control mode from the first mode to the second mode and controls one or more electric motors 30A, 30B.

[0119] [Item 3] The drive system 100 as described in Item 2, wherein the control device 110 maintains control of one or more electric motors 30A, 30B in the first mode while it does not detect user operation of switch 131 to turn the drive of the PTO shaft 40 from off to on.

[0120] [Item 4] The drive system 100 according to any one of items 1 to 3, wherein the control device 110 sets the upper limit of the power supplied to one or more electric motors 30A, 30B in the second mode to a second upper limit W2 which is greater than the first upper limit W1.

[0121] [Item 5] The control device 110 changes the size of the second upper limit W2 according to the type of work implement connected to the PTO shaft 40, the drive system 100 as described in Item 4.

[0122] [Item 6] A drive system 100 according to any one of items 1 to 5, wherein the control device 110 slows down the rate at which the power supplied to one or more electric motors 30A, 30B is reduced when switching the control mode from the second mode to the first mode, compared to the rate at which the power supplied to one or more electric motors 30A, 30B is reduced when switching the control mode from the second mode to the first mode.

[0123] [Item 7] A drive system 100 according to any one of items 1 to 6, wherein one or more electric motors 30A, 30B include a first electric motor 30A that generates a driving force to move the work vehicle 10 and a second electric motor 30B that generates a driving force to rotate the PTO shaft 40.

[0124] [Item 8] The drive system 100 described in Item 7, wherein when the control device 110 controls the first and second electric motors 30A and 30B in the second mode, the upper limit of the power supplied to the second electric motor 30B is increased compared to when it controls in the first mode.

[0125] [Item 9] The drive system 100 described in Item 8, wherein when the control device 110 controls the first and second electric motors 30A and 30B in the second mode, the upper limit of the power supplied to the first electric motor 30A is reduced compared to when it controls in the first mode.

[0126] [Item 10] The work vehicle 10 is a mobile agricultural machine, and the drive system 100 is as described in any of items 1 to 9.

[0127] [Item 11] The work vehicle 10 is a tractor, and the drive system 100 is as described in any of items 1 to 10.

[0128] [Item 12] A work vehicle 10 equipped with a drive system 100 as described in any of items 1 to 11.

[0129] [Item 13] A control method for controlling the operation of a work vehicle 10, which is executed by one or more computers, wherein the work vehicle 10 is equipped with one or more electric motors 30A, 30B that generate a driving force to move the work vehicle 10 and a driving force to rotate the PTO (Power Take Off) shaft 40, and the control mode for controlling one or more electric motors 30A, 30B includes a first mode in which a restriction is set to limit the power supplied to one or more electric motors 30A, 30B to a first upper limit W1 or less, and a second mode in which the restriction is removed, and the control method includes, when controlling one or more electric motors 30A, 30B in the first mode, if the work vehicle 10 changes from a state in which the PTO shaft 40 is not rotating to a state in which it is rotating, switching the control mode from the first mode to the second mode and controlling one or more electric motors 30A, 30B.

[0130] [Item 14] A computer program that causes one or more computers to execute a process to control the operation of a work vehicle 10, wherein the work vehicle 10 is equipped with one or more electric motors 30A, 30B that generate a driving force to move the work vehicle 10 and a driving force to rotate the PTO (Power Take Off) shaft 40, and the control mode for controlling one or more electric motors 30A, 30B includes a first mode in which a restriction is set to limit the power supplied to one or more electric motors 30A, 30B to a first upper limit W1 or less, and a second mode in which the restriction is removed, and the computer program causes one or more computers to execute the following when, while controlling one or more electric motors 30A, 30B in the first mode, the work vehicle 10 changes from a state in which the PTO shaft 40 is not rotating to a state in which it is rotating, the control mode is switched from the first mode to the second mode and the control is set to control one or more electric motors 30A, 30B.

[0131] [Item 15] A drive system 100 for a work vehicle 10, comprising: one or more electric motors 30A, 30B that generate a driving force to move the work vehicle 10 and a driving force to rotate the PTO (Power Take Off) shaft 40; one or more processors 434 that control the operation of one or more electric motors 30A, 30B; and one or more storage devices 435 that store computer programs that control the operation of one or more processors 434, wherein the control modes by one or more processors 434 that control one or more electric motors 30A, 30B include a first mode in which the power supplied to one or more electric motors 30A, 30B is limited to a first upper limit W1 or less, and a second mode in which the limit is removed, and the one or more processors 434, according to the computer program, The drive system 100 switches the control mode from the first mode to the second mode and controls one or more electric motors 30A, 30B when the work vehicle 10 changes from a state where the PTO shaft 40 is not rotating to a state where it is rotating while controlling one or more electric motors 30A, 30B in the first mode.

[0132] The present invention is particularly useful in the field of electric work vehicles such as agricultural tractors and construction vehicles equipped with electric motors for driving.

[0133] 10...Work vehicle, 11...Body, 12...Front frame, 13...Transmission case, 14...Wheels, 14F...Front wheels, 14R...Rear wheels, 15F...Front axle, 15R...Rear axle, 16...Housing frame, 17F...Front axle case, 17R...Rear axle case, 19...Front housing, 20...Battery, 22...Battery management system (BMS), 24...Temperature sensor, 30, 30A, 30B...Electric motor, 33...Output shaft, 34...Power transmission system, 35A, 35B...Inverter, 36...Hydraulic pump, 40...PTO shaft, 51...Loops frame, 52...Driver's seat, 53...Steering wheel, 54...Meter panel unit, 55...Pedal group, 56...Switch group, 57...Charging inlet, 58...Power converter, 60... High-voltage equipment cooling system, 61... Main ECU, 62... Electric ECU, 63... Charging ECU, 64... Relay, 65... High-voltage equipment radiator, 66... ​​Reservoir tank, 67... Pump, 68... Cooling fan, 70... Battery temperature control system, 72... Heater, 75... Battery radiator, 76... Reservoir tank, 77... Pump, 80... Power distribution unit, 81... Onboard charger (OBC), 82... DC-DC converter, 83... Relay circuit, 84... Auxiliary equipment, 100... Drive system, 110... Control device, 121... Current sensor, 122... Voltage sensor, 131... PTO switch

Claims

1. A drive system for a work vehicle, comprising: one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate a PTO (Power Take Off) shaft; and a control device that controls the operation of the one or more electric motors, wherein the control mode in which the control device controls the one or more electric motors includes a first mode in which the power supplied to the one or more electric motors is limited to a first upper limit value and a second mode in which the limitation is removed, and the control device, while controlling the one or more electric motors in the first mode, switches the control mode from the first mode to the second mode and controls the one or more electric motors when the work vehicle changes from a state in which the PTO shaft is not rotating to a state in which it is rotating.

2. The drive system according to claim 1, comprising a switch that accepts user operation for switching the drive of the PTO shaft on and off, wherein when the control device is controlling one or more electric motors in the first mode, if it detects user operation of the switch to turn the drive of the PTO shaft from off to on, it switches the control mode from the first mode to the second mode and controls the one or more electric motors.

3. The drive system according to claim 2, wherein the control device maintains control of the one or more electric motors in the first mode while it does not detect the user operating the switch to turn the drive of the PTO shaft from off to on.

4. The drive system according to claim 1 or 2, wherein the control device sets the upper limit of the power supplied to one or more electric motors in the second mode to a second upper limit that is greater than the first upper limit.

5. The drive system according to claim 4, wherein the control device changes the magnitude of the second upper limit according to the type of work implement connected to the PTO shaft.

6. The drive system according to claim 1 or 2, wherein the control device slows down the rate at which it decreases the power supplied to one or more electric motors when switching the control mode from the second mode to the first mode, compared to the rate at which it increases the power supplied to one or more electric motors when switching the control mode from the first mode to the second mode.

7. The drive system according to claim 1 or 2, wherein the one or more electric motors include a first electric motor that generates a driving force to move the work vehicle and a second electric motor that generates a driving force to rotate the PTO shaft.

8. The drive system according to claim 7, wherein when the control device controls the first and second electric motors in the second mode, it increases the upper limit of the power supplied to the second electric motor compared to when it controls them in the first mode.

9. The drive system according to claim 8, wherein when the control device controls the first and second electric motors in the second mode, it reduces the upper limit of the power supplied to the first electric motor compared to when it controls them in the first mode.

10. The drive system according to claim 1 or 2, wherein the work vehicle is a mobile agricultural machine.

11. The drive system according to claim 1 or 2, wherein the work vehicle is a tractor.

12. A work vehicle equipped with the drive system according to claim 1 or 2.

13. A control method for controlling the operation of a work vehicle, which is executed by one or more computers, wherein the work vehicle is equipped with one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate a PTO (Power Take Off) shaft, and the control mode for controlling the one or more electric motors includes a first mode in which a restriction is set to limit the power supplied to the one or more electric motors to a first upper limit value or less, and a second mode in which the restriction is removed, and the control method includes, when the one or more electric motors are being controlled in the first mode, the work vehicle changing from a state in which the PTO shaft is not rotating to a state in which it is rotating, switching the control mode from the first mode to the second mode and controlling the one or more electric motors.

14. A computer program that causes one or more computers to perform a process to control the operation of a work vehicle, wherein the work vehicle is equipped with one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate the PTO (Power Take Off) shaft, and the control mode for controlling the one or more electric motors includes a first mode in which a limit is set to keep the power supplied to the one or more electric motors below a first upper limit, and a second mode in which the limit is removed, and the computer program causes one or more computers to perform the following: when the one or more electric motors are being controlled in the first mode, if the work vehicle changes from a state in which the PTO shaft is not rotating to a state in which it is rotating, the control mode is switched from the first mode to the second mode and the one or more electric motors are controlled.

15. A drive system for a work vehicle, comprising: one or more electric motors that generate a driving force to move the work vehicle and a driving force to rotate a PTO (Power Take Off) shaft; one or more processors that control the operation of the one or more electric motors; and one or more storage devices that store computer programs that control the operation of the one or more processors, wherein the control modes by the one or more processors that control the one or more electric motors include a first mode in which the power supplied to the one or more electric motors is limited to a first upper limit value and a second mode in which the limitation is removed, and the one or more processors, in accordance with the computer program, when the one or more processors are controlling the one or more electric motors in the first mode and the work vehicle changes from a state in which the PTO shaft is not rotating to a state in which it is rotating, the control mode is switched from the first mode to the second mode and the one or more electric motors are controlled.

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