Work vehicle, control method for cooling system, and computer program

Abstract

This electrically‐powered work vehicle comprises: one or more electric apparatuses; a battery that accumulates electric power to be supplied to the one or more electric apparatuses; a cooling system that is connected to at least one among the battery and the one or more electric apparatuses, includes a flow path for circulating a cooling medium, and is configured to be able to switch the circulation direction of the cooling medium; and a control device that controls the switching of the circulation direction.

Description

Work vehicle, control method for cooling system, and computer program

[0001] The present disclosure relates to a work vehicle, a control method for a cooling system, 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 driving by an electric motor (hereinafter sometimes simply referred to as "motor") instead of an internal combustion engine are becoming popular.

[0003] On the other hand, in order to realize a decarbonized society, it is required to reduce the amount of carbon dioxide (CO , ,

[0006] ,

[0005] ) 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 agricultural work such as tillage. 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 the traveling body to travel. 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.

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

[0007] This disclosure provides an electric work vehicle capable of solving at least one of these problems.

[0008] This disclosure provides solutions as described in the following items.

[0009] [Item 1] An electric work vehicle comprising: one or more electric devices; a battery for storing power to be supplied to the one or more electric devices; a cooling system which is in communication with the battery and at least one of the one or more electric devices and includes a flow path for circulating a cooling medium, and is configured to be able to switch the direction of circulation of the cooling medium; and a control device for controlling the switching of the circulation direction.

[0010] [Item 2] The work vehicle according to Item 1, wherein the cooling system comprises a radiator through which the cooling medium flows, and a pump that circulates the cooling medium flowing through the flow path to the radiator, the flow path connecting the radiator to the battery and at least one of the one or more electric devices, and the control device controls the rotation direction of the pump to switch the circulation direction.

[0011] [Item 3] The work vehicle according to Item 1, wherein the cooling system comprises a radiator through which the cooling medium flows, a pump that circulates the cooling medium flowing through the flow path to the radiator, and a switching valve configured to switch the circulation direction of the cooling medium, and the control device controls the switching valve to switch the circulation direction.

[0012] [Item 4] A work vehicle according to item 2 or 3, comprising: a first temperature sensor for measuring the temperature of a first portion of the battery located on the inlet side of the battery's flow path; and a second temperature sensor for measuring the temperature of a second portion of the battery located on the outlet side of the battery's flow path, wherein the cooling system includes the flow path connecting the radiator and the battery, and the control device switches the circulation direction when the temperature difference between the temperature of the first portion indicated by sensor data output from the first temperature sensor and the temperature of the second portion indicated by sensor data output from the second temperature sensor exceeds a threshold.

[0013] [Item 5] A work vehicle according to item 2 or 3, comprising a running gear, wherein the one or more electric devices include a first electric motor for driving the running gear, and the cooling system includes the flow path connecting the radiator and the first electric motor.

[0014] [Item 6] The work vehicle according to Item 5, comprising a PTO shaft for supplying power to the work machine, wherein the one or more electric devices include a second electric motor that generates power to be transmitted to the PTO shaft, and the cooling system includes the radiator, the first electric motor, and the second electric motor and the flow path connecting them.

[0015] [Item 7] The work vehicle according to Item 6, comprising: a third temperature sensor for measuring the temperature of the first electric motor; and a fourth temperature sensor for measuring the temperature of the second electric motor, wherein the control device switches the circulation direction when the temperature difference between the temperature of the first electric motor indicated by the sensor data output from the third temperature sensor and the temperature of the second electric motor indicated by the sensor data output from the fourth temperature sensor exceeds a threshold.

[0016] [Item 8] The work vehicle according to Item 7, wherein the control device switches the circulation direction so that the cooling medium flows from the other high-temperature side of the first electric motor to the one low-temperature side of the first electric motor when the temperature difference between the temperature of the first electric motor and the temperature of the second electric motor exceeds a threshold, and the temperature of one of the low-temperature side of the first electric motor and the second electric motor falls below the threshold.

[0017] [Item 9] The work vehicle according to any one of items 6 to 8, wherein the cooling system includes a first cooling system and a second cooling system, the first cooling system having a first radiator through which a first cooling medium flows, a first flow path connecting the first radiator and the battery, and a first pump for circulating the first cooling medium flowing through the first flow path to the first radiator, and the second cooling system having a second radiator through which a second cooling medium flows, a second flow path connecting the second radiator, the first electric motor, and the second electric motor, and a second pump for circulating the second cooling medium flowing through the second flow path to the second radiator.

[0018] [Item 10] The work vehicle according to Item 9, wherein the cooling system includes an electric fan that generates cooling air to cool the first cooling medium flowing inside the first radiator and the second cooling medium flowing inside the second radiator.

[0019] [Item 11] The work vehicle according to any one of items 1 to 10, wherein the battery is an immersion-cooled battery.

[0020] [Item 12] The work vehicle according to Item 11, wherein the cooling system has at least one filter separator provided in the flow path.

[0021] [Item 13] The control device comprises one or more processors and one or more memories for storing programs that control the operation of the one or more processors, wherein the one or more processors control the switching of the circulation direction in response to a command that instructs the switching of the circulation direction according to the program, the work vehicle according to any one of items 1 to 11.

[0022] [Item 14] A control method implemented on a computer for controlling a cooling system mounted on an electric work vehicle comprising one or more electric devices and a battery for storing power supplied to the one or more electric devices, wherein the cooling system is a cooling system that communicates with the battery and at least one of the one or more electric devices and includes a flow path for circulating a cooling medium, configured to allow switching of the circulation direction of the cooling medium, waiting until a command instructing the switching of the circulation direction is transmitted, and switching the circulation direction in response to the command when the command is transmitted.

[0023] [Item 15] A computer program used to control a cooling system mounted on an electric work vehicle comprising one or more electric devices and a battery for storing power supplied to the one or more electric devices, wherein the cooling system is a cooling system that communicates with the battery and at least one of the one or more electric devices and includes a flow path for circulating a cooling medium, configured to allow switching of the circulation direction of the cooling medium, and causes the computer to perform the following actions: wait until a command instructing the switching of the circulation direction is transmitted, and when the command is transmitted, switch the circulation direction in response to the command.

[0024] [Item 16] A control device configured to perform the method described in Item 14.

[0025] [Item 17] A computer-readable non-temporary storage medium that stores a computer program containing instructions for causing a computer to perform the method described in Item 14.

[0026] [Item 18] A vehicle system comprising the control device described in Item 16, a cooling system, and two or more electric motors.

[0027] [Item 19] A control device for controlling a cooling system mounted on an electric work vehicle, wherein the work vehicle comprises one or more electric devices and a battery for storing power supplied to the one or more electric devices, the cooling system is a cooling system that communicates with the battery and at least one of the one or more electric devices and includes a flow path for circulating a cooling medium, and is configured to be switchable in the direction of circulation of the cooling medium, the control device comprising: a standby means for waiting until a command instructing the switching of the circulation direction is transmitted, and a switching means for switching the circulation direction in response to the command when the command is transmitted.

[0028] [Item 20] A vehicle system comprising the control device described in Item 19, a cooling system, and two or more electric motors.

[0029] 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.

[0030] According to embodiments of the present disclosure, a work vehicle is provided that can improve the cooling capacity of a cooling system for cooling one or more electric devices.

[0031] 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 a work vehicle according to an exemplary embodiment of the present invention. This is a block diagram showing an example of the main components of a 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 block diagram showing the configuration of a cooling system in an exemplary embodiment of the present invention. This is a block diagram showing another configuration of a cooling system in an exemplary embodiment of the present invention. This is a block diagram showing the configuration of a cooling system according to a first implementation example in an exemplary embodiment of the present invention. This is a flowchart showing the procedure for switching the circulation direction of the cooling medium according to the first implementation example. This is a block diagram showing the configuration of a cooling system according to a second implementation example in an exemplary embodiment of the present invention. This is a flowchart showing the procedure for switching the circulation direction of the cooling medium according to the second implementation example. This is a block diagram showing the configuration of a cooling system according to a third implementation example in an exemplary embodiment of the present invention. This is a block diagram showing the configuration of a cooling system according to a fourth implementation example in an exemplary embodiment of the present invention.

[0032] 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.

[0033] 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.

[0034] (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, mowers, seeders, fertilizer spreaders, sprayers, or broadcasters. 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 tasks on the ground within a field (or work area), such as tilling, sowing, pest control, fertilizing, planting crops, or harvesting. Construction vehicles perform tasks such as transporting soil, rubble, and other materials at construction sites. These tasks are sometimes referred to as "ground work" or simply "work." When a construction vehicle moves while performing work, it is sometimes referred to as "work driving."

[0035] 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."

[0036] Electric motors can be synchronous motors such as permanent magnet synchronous motors or reluctance motors, or asynchronous motors such as induction motors.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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".

[0041] 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).

[0042] "Memory" is a hardware electronic circuit such as a ROM (Read Only Memory) or a RAM (Random Access Memory). A part of the memory may be a storage medium connected to the processor via wiring or a network. These hardware electronic circuits can be implemented by one or more integrated circuits (ICs) or large-scale integrated circuits (LSIs). Each functional unit or block within the electronic circuit, and related components, 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. A computer program (hereinafter sometimes simply referred to as "program") that defines the operation of the processor may be stored in the memory. The program is designed such that the processor executes one or more functions, operations, steps, or processes in the embodiments of the present invention.

[0043] (Embodiment) Hereinafter, several embodiments in which the technology of the present invention is applied to an agricultural electric tractor, which is an example of an electric work vehicle, will be described while referring to the drawings. Various technologies described for the tractor in the following description can also be applied to agricultural machines other than tractors, construction work vehicles used at construction sites, work vehicles used at disaster sites, snow removal vehicles used in heavy snow areas, and vehicles for transporting goods, etc.

[0044] In the following description, the direction of arrow F in the figure is referred to as "front", the direction of arrow B as "rear", 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".

[0045] <1. Basic Configuration of Work Vehicle> FIG. 1 is a plan view schematically showing an example of the basic configuration of a work vehicle 10 according to an exemplary embodiment of the present invention. The illustrated work vehicle 10 is an agricultural electric tractor. The work vehicle 10 can travel within a field while mounting or towing a work implement and performing farm work according to the type of the work implement. The work vehicle 10 can also travel within and outside the field (including roads) with the work implement lifted or without mounting the work implement.

[0046] The work vehicle 10 includes a vehicle body (vehicle frame) 11 that rotatably supports the left and right front wheels 14F and the left and right rear wheels 14R. The vehicle body 11 includes a front frame 12 provided with the front wheels 14F and a transmission case 13 provided with the rear wheels 14R. The front frame 12 is fixed to the front portion of the transmission case 13. The front wheels 14F and the rear wheels 14R may be collectively referred to as "wheels 14". Strictly speaking, the wheels 14 are wheels, and tires are mounted on the wheels 14. In the present disclosure, "wheel" generally means the whole of "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 endless tracks instead of the wheels with tires.

[0047] In the example of FIG. 1, the work vehicle 10 includes a battery 20 and an electric motor 30 (hereinafter simply referred to as "motor 30") that are directly or indirectly supported by the front frame 12. The battery 20 may be configured as a battery pack including a plurality of cells connected in series, for example. The battery 20 is a rechargeable battery that outputs a relatively high voltage, such as a lithium-ion battery or a all-solid-state battery, for example. The battery 20 stores electric power for driving the motor 30. The battery 20 may be housed in a front housing called a "bonnet", for example. The front housing is supported by the front frame 12 at the front portion of the vehicle body 11.

[0048] The motor 30 is electrically connected to the battery 20. The motor 30 can convert the power output from the battery 20 into mechanical motion (power) to generate the driving force (traction) necessary for the work vehicle 10 to move. The motor 30 may be, for example, an AC synchronous motor. The battery 20 generates DC current. For this reason, if the motor 30 is an AC synchronous motor, a group of electrical circuits including an inverter device (hereinafter sometimes simply referred to as "inverter") may be provided between the battery 20 and the motor 30. The inverter device converts the DC current into AC current. Part of such a group of electrical circuits may be located inside the battery 20. Another part of the group of electrical circuits may be attached to the motor 30 as a drive circuit for the motor 30.

[0049] The motor 30 has a rotating output shaft 33. The torque of the output shaft 33 is transmitted to the rear wheels 14R via mechanical components such as a transmission (speed changer) and a rear wheel differential (differential gear device) located inside the transmission case 13. In other words, the power generated by the motor 30, which is the power source, is transmitted to the rear wheels 14R by a power transmission system (drivetrain) 34, including a transmission, located inside the transmission case 13. For this reason, the "transmission case" is sometimes called a "transmission case". In four-wheel drive mode, a portion of the power from the motor 30 is also transmitted to the front wheels 14F. In this way, the motor 30 drives a running gear including multiple wheels 14.

[0050] The power of the motor 30 may be used not only for the movement of the work vehicle 10 but also for driving the 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 may be driven by the motor 30 that drives the travel device, or by another electric motor not shown in Figure 1. Torque from 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 attached to or towed by the work vehicle 10 receives power from the PTO shaft 40 and can perform operations according to various tasks. The motor 30 and the power transmission system 34 are sometimes collectively referred to as the electric powertrain.

[0051] 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.

[0052] 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.

[0053] The work vehicle 10 shown in Figure 1 is equipped with one motor 30. However, the work vehicle 10 may be equipped with multiple electric motors. For example, the work vehicle 10 may be equipped with a drive electric motor that drives a running gear including four wheels 14, and a PTO electric motor that drives the PTO shaft 40. The work vehicle 10 may be equipped with multiple PTO shafts (e.g., a rear PTO shaft, a mid PTO shaft, a front PTO shaft, etc.). In that case, one electric motor may drive multiple PTO shafts, or multiple electric motors may drive multiple PTO shafts. For example, the work vehicle 10 may be equipped with multiple electric motors, each driving a corresponding one of the multiple PTO shafts. The work vehicle 10 may be equipped with 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 be equipped with two electric motors for the front wheels, each driving one of the two front wheels 14F, and two electric motors for the rear wheels, each driving one of the two rear wheels 14R. In other words, the work vehicle 10 may be equipped with four electric motors, each driving one of the four wheels 14. Thus, the work vehicle 10 may be equipped with one or more electric motors for driving the running gear and one or more electric motors for driving one or more PTO shafts. By providing multiple electric motors, the work vehicle 10 can control the rotation of multiple wheels 14 and one or more PTO shafts more flexibly. In the following description, electric motors for driving may be referred to as "driving motors," and electric motors for PTOs may be referred to as "PTO motors."

[0054] <2. Specific Examples of Work Vehicles> Next, we will explain a more specific example of the configuration of work vehicle 10.

[0055] Figure 2 is a side view of a work vehicle 10 according to an exemplary embodiment of the present invention. Figure 3 is a top view of the work vehicle 10 according to this embodiment.

[0056] The work vehicle 10 shown in Figures 2 and 3 comprises a vehicle body 11 and a running gear supported by the vehicle body 11. The running gear includes various devices necessary for driving, such as left and right front wheels 14F, left and right rear wheels 14R, front axle 15F, rear axle 15R, and a rear wheel differential.

[0057] 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.

[0058] 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.

[0059] 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".

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 charger. 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] <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.

[0068] 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.

[0069] 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. 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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, and a charging ECU 63. 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.

[0076] In this embodiment, the combination of the main ECU 61, the electric ECU 62, and the charging ECU 63 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, the electric ECU 62, and the charging ECU 63 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). Instead of CAN, a faster communication method such as on-board Ethernet (registered trademark) may be used. An on-board computer integrating at least some of the functions of the main ECU 61, the electric ECU 62, and the charging ECU 63 may be provided as the "control device". The control device may include ECUs other than the main ECU 61, the electric ECU 62, and the charging ECU 63. Each ECU may be a computing device including one or more processors and one or more memories. Each ECU can perform the operations described later by having the processor execute a computer program stored in the memory.

[0077] 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.

[0078] 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.

[0079] 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 power transmission system 34A and the transmission included in 34A on the meter panel unit 54.

[0080] Figure 6 is a block diagram showing an example of the hardware configuration of each ECU. Each ECU 400 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.

[0081] 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.

[0082] 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.

[0083] 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®.

[0084] The ECU 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.

[0085] 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.

[0086] 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".

[0087] 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.

[0088] 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 coolant inside the radiator 65. The cooling air promotes heat dissipation from the radiator 65.

[0089] 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).

[0090] 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.

[0091] 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.

[0092] <4. Cooling System> As mentioned above, work vehicles are equipped with one or more cooling systems. Conventionally, the circulation direction of the cooling medium (e.g., coolant) flowing through the flow channels formed in the cooling system has been unidirectional, either clockwise or counterclockwise. In this case, during the process of the cooling medium circulating, the inlet side of the flow channel of the object to be cooled may be cooled more than the outlet side, while the outlet side of the flow channel of the object to be cooled may not be cooled as well. As a result, it may be difficult to cool the entire object uniformly. For this reason, improvement of the cooling capacity of the cooling system is desired.

[0093] To solve the above problems, the cooling system in this embodiment includes a flow path that communicates with a battery and at least one of one or more electric devices and circulates a cooling medium, and is configured to allow switching of the circulation direction of the cooling medium. The cooling medium in this embodiment is a coolant, and the cooling method of the cooling system is liquid cooling. However, as mentioned above, the cooling medium includes liquids and gases. The cooling method of the cooling system may be air cooling.

[0094] One or more electric devices may include various electric devices such as a traction motor, a PTO motor, an inverter, a BMS, a heater, and an ECU. In this embodiment, the cooling targets of the cooling system are these electric devices and the battery.

[0095] The cooling system is controlled by a control device. The control device is configured or programmed to control the switching of the circulation direction of the cooling medium. For example, the electric ECU 62 shown in Figure 4 may function as a control device that controls the switching of the circulation direction of the cooling medium. Of course, one or more other ECUs different from the electric ECU 62 may function as the control device, or the electric ECU 62 and one or more other ECUs may cooperate to perform the functions of the control device.

[0096] The control device in this embodiment may include one or more processors and one or more memories that store programs for controlling the operation of the one or more processors. The one or more processors control the switching of the circulation direction of the cooling medium in response to a command instructing the switching of the circulation direction of the cooling medium according to the program. Such a command may be transmitted to the control device, for example, when the temperature difference between two of the one or more electric devices to be cooled exceeds a threshold.

[0097] The control method implemented in a computer for controlling a cooling system mounted on an electric work vehicle, which includes one or more electric devices and a battery for storing power supplied to the one or more electric devices, in this embodiment includes waiting until a command instructing a switch in the circulation direction of the cooling medium is transmitted, and when the command is transmitted, switching the circulation direction in response to the command.

[0098] A computer program containing instructions for causing one or more computers to execute the above-described method of controlling the cooling system may be manufactured and sold independently of the work vehicle. The computer program may be provided, for example, stored on a computer-readable non-temporary storage medium. The computer program may also be provided by download via a telecommunications line (e.g., the Internet).

[0099] According to the work vehicle, cooling system control method, and computer program of this embodiment, the cooling capacity is improved by switching the circulation direction of the cooling medium, and as a result, the entire object to be cooled can be cooled uniformly. Furthermore, depending on the operating state of one or more electric devices or batteries, it is also expected that the heating capacity can be increased.

[0100] Figure 8 is a block diagram showing the configuration of the cooling system in this embodiment.

[0101] The cooling system 100 shown in Figure 8 includes a radiator 110 through which a cooling medium flows, a pump 120 that circulates the cooling medium flowing through the flow path 150 back to the radiator 110, and a reservoir tank (hereinafter simply referred to as "tank") 130.

[0102] Radiator 110 corresponds to radiator 65 or 75 shown in Figure 4. Pump 120 corresponds to pump 67 or 77 shown in Figure 4. Tank 130 corresponds to tank 66 or 76 shown in Figure 4.

[0103] The flow path 150 connects the radiator 110 and the object to be cooled 140. For example, the flow path 150 connects the radiator 110 to the battery and at least one of one or more electric devices. In the example in Figure 8, the cooling system 100 is connected to the radiator 110, tank 130, pump 120 and object to be cooled 140 in this order. This forms a flow path 150 through which the cooling medium circulates.

[0104] The pump 120 illustrated in Figure 8 is a variable displacement pump-motor and a hydraulic pump capable of flowing a cooling medium in two directions. However, the pump 120 is not limited to a variable displacement pump-motor and may be a fixed displacement pump. Furthermore, the pump 120 is not limited to a hydraulic pump.

[0105] The control device 400 controls the switching of the circulation direction of the cooling medium. The control device 400 may be configured or programmed to switch the circulation direction of the cooling medium by controlling the rotation direction of the pump 120. Receiving control from the control device 400, the pump 120 circulates the cooling medium in the flow path 150 by flowing it clockwise (CW) or counterclockwise (CCW).

[0106] In the example shown in Figure 8, if the cooling medium circulates clockwise, the inlet side 140A of the cooling target 140 will be cooled more easily than the outlet side 140B. Conversely, if the cooling medium circulates counterclockwise, the inlet side 140B of the cooling target 140 may be cooled more easily than the outlet side 140A. In this way, a temperature difference can be created between the inlet and outlet sides of the cooling target, potentially leading to an imbalance in cooling capacity. This could result in an increase in the time required to cool the entire cooling target 140.

[0107] According to the cooling system 100 in this embodiment, even if a temperature difference occurs between the inlet and outlet sides of the flow path of the object to be cooled 140, the unevenness of the cooling capacity is improved by controlling the rotation direction of the pump 120 and switching the circulation direction of the cooling medium. Therefore, it becomes possible to cool the entire object to be cooled 140 uniformly, and a reduction in the time required for cooling can be expected.

[0108] Figure 9 is a block diagram showing another configuration of the cooling system in this embodiment.

[0109] The cooling system 101 shown in Figure 9 differs from the cooling system 100 shown in Figure 8 in that it includes a switching valve 160 configured to switch the circulation direction of the cooling medium.

[0110] In the example shown in Figure 9, the cooling system 101 is connected in this order to the radiator 110, tank 130, pump 121, switching valve 160, and the object to be cooled 140. This forms a flow path 150 through which the cooling medium circulates.

[0111] The pump 121 illustrated in Figure 9 is a variable displacement pump-motor and a hydraulic pump capable of flowing a cooling medium in one direction. However, the pump 121 is not limited to a variable displacement pump-motor and may be a fixed displacement pump. Furthermore, the pump 121 is not limited to a hydraulic pump.

[0112] The switching valve 160 illustrated in Figure 9 is a directional control valve. An electromagnetic switching valve may be used as the switching valve 160. The switching valve 160 operates under the control of the control device 400.

[0113] The control device 400 may be configured or programmed to control the switching valve 160 to switch the circulation direction. Under the control of the control device 400, the switching valve 160 circulates the cooling medium in the flow path 150 in either a clockwise or counterclockwise direction.

[0114] In this way, a switching valve can be used as a means to switch the circulation direction of the cooling medium. With a cooling system 101 equipped with a switching valve 160, even if a temperature difference occurs between the inlet side and the outlet side of the flow path of the object to be cooled 140, the unevenness of the cooling capacity can be improved by controlling the switching valve 160 to switch the circulation direction of the cooling medium.

[0115] The battery in this embodiment is, for example, an immersion-cooled battery. However, the battery is not limited to an immersion-cooled battery. An immersion-cooled battery may comprise multiple cell assemblies, each composed of multiple battery cells. Each cell assembly can be independently sealed in a liquid tank and modularized. By immersing each battery cell in a non-conductive coolant, it is possible to directly cool it, thereby uniformly controlling temperature variations within the battery cells. Therefore, compared to a typical air-cooled system, the entire battery can be cooled more reliably and uniformly.

[0116] Next, with reference to Figures 10 to 15, the first to fourth implementation examples of the cooling system in this embodiment will be described.

[0117] Figure 10 is a block diagram showing the configuration of a cooling system according to the first implementation example in this embodiment. The cooling system 102 shown in Figure 10 includes a pump 120 capable of flowing the cooling medium in two directions as a switching means for switching the circulation direction of the cooling medium. Of course, a switching valve can be used as the switching means.

[0118] In the example shown in Figure 10, the object to be cooled is the battery 20. The cooling system 102 includes a flow path 150 that connects the radiator 110 and the battery 20. The cooling system 102 is connected to the radiator 110, the tank 130, the pump 120, and the battery 20 in that order.

[0119] The cooling system 102 includes a first temperature sensor (hereinafter referred to as "temperature sensor 170A") and a second temperature sensor (hereinafter referred to as "temperature sensor 170B").

[0120] The temperature sensor 170A may be configured to measure the temperature of the first portion 20A of the battery 20 located on either the inlet or outlet side of the flow path, and to output sensor data indicating the temperature of the first portion 20A to the control device 400. For example, the temperature sensor 170A may measure the temperature of each of the multiple cells included in the first portion 20A of the battery 20, calculate the average value of the cell temperatures from the temperatures of each cell, and generate sensor data indicating the temperature of the first portion 20A based on the average value of the cell temperatures.

[0121] The temperature sensor 170B may be configured to measure the temperature of a second portion 20B of the battery 20 that is different from the first portion 20A located on the other side of the flow path inlet or outlet, and to output sensor data indicating the temperature of the second portion 20B to the control device 400. For example, the temperature sensor 170B may measure the temperature of each of the multiple cells included in the second portion 20B of the battery 20, calculate the average cell temperature from the temperature of each cell, and generate sensor data indicating the temperature of the second portion 20B based on the average cell temperature.

[0122] In the example shown in Figure 10, when the cooling medium circulates clockwise (CW), the first part 20A and the second part 20B of the battery are located on the inlet and outlet sides of the flow path 150, respectively. When the cooling medium circulates counterclockwise (CCW), the first part 20A and the second part 20B of the battery are located on the outlet and inlet sides of the flow path 150, respectively.

[0123] In Figure 10, the first portion 20A and the second portion 20B of the battery 20 are adjacent and their boundary is defined, but other portions may be located between the first portion 20A and the second portion 20B. In this case, the cooling system may include additional temperature sensors for measuring the temperature of the other portion of the battery 20.

[0124] In the first implementation example, the control device 400 switches the circulation direction when the temperature difference between the temperature of the first part 20A indicated by the sensor data output from the temperature sensor 170A and the temperature of the second part 20B indicated by the sensor data output from the temperature sensor 170B exceeds a threshold.

[0125] Figure 11 is a flowchart showing the procedure for switching the circulation direction of the cooling medium according to the first implementation example.

[0126] The control device 400 obtains the temperature of the first portion 20A of the battery 20 (step S101). For example, the control device 400 receives sensor data indicating the temperature of the first portion 20A, which is output from the temperature sensor 170A. The control device 400 obtains the temperature of the first portion 20A from the sensor data.

[0127] The control device 400 obtains the temperature of the second portion 20B of the battery 20 (step S102). For example, the control device 400 receives sensor data indicating the temperature of the second portion 20B, which is output from the temperature sensor 170B. The control device 400 obtains the temperature of the second portion 20B from the sensor data.

[0128] The control device 400 compares the temperature difference between the first part 20A and the second part 20B of the battery 20 with a first threshold (step S103). The first threshold can be appropriately determined according to the specifications of the battery or the work vehicle.

[0129] When the temperature difference exceeds a first threshold (YES in step S104), the control device 400 controls the pump 120 to switch the circulation direction of the cooling medium (YES in step S105). For example, when the cooling medium is circulating clockwise in the flow path 150, the control device 400 detects that the temperature difference exceeds the first threshold and switches the circulation direction of the cooling medium to circulate it counterclockwise.

[0130] In this way, by switching the circulation direction of the cooling medium using the temperature difference between two different parts of the battery 20 as a trigger, it becomes possible to improve the unevenness in cooling capacity between the battery's flow path inlet and outlet sides. By switching the flow path inlet and outlet sides so that the relatively hotter part of the two different parts is located at the flow path inlet, it becomes possible to efficiently cool the relatively hotter part. Such control is particularly useful for immersion-cooled batteries that can directly cool the battery cells.

[0131] Figure 12 is a block diagram showing the configuration of a cooling system according to a second implementation example in this embodiment. The cooling system 103 shown in Figure 12 includes a pump 120 capable of flowing the cooling medium in two directions as a switching means for switching the circulation direction of the cooling medium. Of course, a switching valve can be used as the switching means.

[0132] In the example shown in Figure 12, the cooling targets are the drive motor 30A and the PTO motor 30B. The cooling system in this embodiment may include a radiator and a flow path connecting the drive motor or the PTO motor. The cooling system 103 illustrated in Figure 12 includes a radiator 110 and a flow path 150 connecting the drive motor 30A and the PTO motor 30B. The cooling system 103 is connected to the radiator 110, tank 130, pump 120, drive motor 30A, and PTO motor 30B in this order. However, although Figure 12 shows an example where the PTO motor 30B is connected closer to the radiator 110, the drive motor 30A may be connected closer to the radiator 110.

[0133] The cooling system 103 includes a third temperature sensor (hereinafter referred to as "temperature sensor 170C") and a fourth temperature sensor (hereinafter referred to as "temperature sensor 170D").

[0134] The temperature sensor 170C may be configured to measure the temperature of the drive motor 30A and output sensor data indicating the temperature of the drive motor 30A to the control device 400. The temperature sensor 170C may be configured to measure the temperature of the cooling medium flowing out from the flow path outlet side of the drive motor 30A. The temperature sensor 170C can estimate the temperature of the drive motor 30A from the measured temperature of the cooling medium.

[0135] The temperature sensor 170D may be configured to measure the temperature of the PTO motor 30B and output sensor data indicating the temperature of the PTO motor 30B to the control device 400. The temperature sensor 170D may be configured to measure the temperature of the cooling medium flowing out from the flow path outlet side of the PTO motor 30B. The temperature sensor 170D can estimate the temperature of the PTO motor 30B from the measured temperature of the cooling medium.

[0136] In the second implementation example, the control device 400 switches the circulation direction of the cooling medium when the temperature difference between the temperature of the drive motor 30A, indicated by the sensor data output from the temperature sensor 170C, and the temperature of the PTO motor 30B, indicated by the sensor data output from the temperature sensor 170D, exceeds a threshold.

[0137] Figure 13 is a flowchart showing the procedure for switching the circulation direction of the cooling medium according to the second implementation example.

[0138] The control device 400 acquires the temperature of the drive motor 30A (step S201). For example, the control device 400 receives sensor data indicating the temperature of the drive motor 30A, which is output from the temperature sensor 170C. The control device 400 acquires the temperature of the drive motor 30A from this sensor data.

[0139] The control device 400 acquires the temperature of the PTO motor 30B (step S202). For example, the control device 400 receives sensor data indicating the temperature of the PTO motor 30B, which is output from the temperature sensor 170D. The temperature of the PTO motor 30B is acquired from this sensor data.

[0140] The control device 400 compares the temperature difference between the travel motor 30A and the PTO motor 30B with a second threshold (step S203). The second threshold can be appropriately determined according to the specifications of the motor or the work vehicle.

[0141] When the temperature difference exceeds the second threshold (YES in step S204), the control device 400 controls the pump 120 to switch the circulation direction of the cooling medium. For example, when the cooling medium is circulating clockwise in the flow path 150, the control device 400 detects that the temperature difference exceeds the second threshold and switches the circulation direction of the cooling medium to circulate it counterclockwise.

[0142] The process described in steps S201 to S204 above allows for the correction of the cooling medium imbalance between the travel motor 30A and the PTO motor 30B by switching the circulation direction of the cooling medium, triggered by the temperature difference between the travel motor 30A and the PTO motor 30B. By switching the inlet and outlet sides of the flow path so that the relatively hotter motor of the travel motor 30A and the PTO motor 30B is located at the flow path inlet, it becomes possible to efficiently cool the relatively hotter motor.

[0143] In one embodiment, the control device can switch the circulation direction so that the cooling medium flows from the other high-temperature side to the other low-temperature side of the drive motor and the PTO motor when the temperature difference between the temperature of the drive motor and the temperature of the PTO motor exceeds a threshold, and the temperature of one of the drive motors or the PTO motor falls below the threshold.

[0144] In the second implementation example, when the temperature difference between the temperature of the travel motor 30A and the temperature of the PTO motor 30B exceeds a second threshold (YES in step S204), and the temperature of the lower-temperature side of the travel motor 30A and the PTO motor 30B falls below a third threshold (YES in step S205), the control device 400 switches the circulation direction of the cooling medium so that the cooling medium flows from the higher-temperature side of the travel motor 30A and the PTO motor 30B to the lower-temperature side (step S206).

[0145] If the temperature of the travel motor 30A is higher than the temperature of the PTO motor 30B, and the temperature difference exceeds a second threshold, and the temperature of the PTO motor 30B is below a third threshold, the control device 400 controls the pump 120 to direct the relatively high-temperature cooling medium flowing out of the travel motor 30A into the PTO motor 30B, thereby switching the circulation direction of the cooling medium.

[0146] If the temperature of the PTO motor 30B is higher than the temperature of the drive motor 30A, and the temperature difference exceeds a second threshold, and the temperature of the drive motor 30A is below a third threshold, the control device 400 controls the pump 120 to allow the relatively high-temperature cooling medium flowing out of the PTO motor 30B to flow into the drive motor 30A, thereby switching the circulation direction of the cooling medium.

[0147] This control method allows the cooling medium to flow from the relatively hotter motor to the relatively colder motor, and as a result, the relatively colder motor can be heated by the cooling medium warmed by the relatively hotter motor. Thus, the cooling system in this embodiment can exhibit not only cooling capacity but also heating capacity.

[0148] In the first implementation example shown in Figure 11, the control device 400 can switch the circulation direction of the cooling medium so that the cooling medium flows from the other high-temperature side to the other low-temperature side of the first part 20A and the second part 20B when the temperature difference between the temperature of the first part 20A and the temperature of the second part 20B exceeds a threshold, and the temperature of one of the lower-temperature sides of the first part 20A and the second part 20B falls below the threshold.

[0149] This type of control makes it possible to flow the cooling medium from the relatively high-temperature part of the battery to the relatively low-temperature part, and as a result, the relatively low-temperature part of the battery can be heated by the cooling medium warmed in the relatively high-temperature part.

[0150] The cooling system in this embodiment may have at least one filter separator provided in the flow path.

[0151] Figure 14 is a block diagram showing the configuration of the cooling system according to the third implementation example in this embodiment.

[0152] The cooling system 104 shown in Figure 14 includes a filter separator 180 provided in the flow path 150. In the illustrated example, the battery 20 is an immersion-cooled battery. The filter separator 180 is provided in the flow path 150 connecting the pump 120 and the battery 20, but the filter separator 180 can be provided at any location in the flow path. For example, the filter separator 180 may be provided in the flow path connecting the battery 20 and the radiator 110, the flow path connecting the radiator 110 and the tank 130, or the flow path connecting the tank 130 and the pump 120. Furthermore, the number of filter separators is not limited to one, but may be two or more.

[0153] The filter separator 180 removes fine impurities, foreign matter, or water from the cooling medium flowing through the flow path 150. It is preferable to use a filter separator 180 that has a bidirectional filtering function, capable of removing impurities, foreign matter, or water from both directions (clockwise and counterclockwise), regardless of the circulation direction of the cooling medium. Alternatively, combining two filter separators, each having a filtering function in only one direction (clockwise or counterclockwise), can achieve a function equivalent to bidirectional filtering.

[0154] The ingress of minute impurities, foreign matter, or water into the cooling pathway of an immersion-cooled battery can cause internal short circuits and subsequent failures. By providing at least one filter separator in the cooling system's flow path for the immersion-cooled battery, contamination can be prevented. As a result, the likelihood of immersion-cooled battery failure can be reduced.

[0155] When a cooling medium circulates in only one direction, uneven flow velocity can occur within the flow path, potentially leading to the accumulation of impurities or foreign matter. In such situations, reversing the circulation direction of the cooling medium using a switching mechanism can eliminate this accumulation, and a filter separator can effectively prevent contamination.

[0156] Figure 15 is a block diagram showing the configuration of the cooling system according to the fourth implementation example in this embodiment.

[0157] The cooling system 105 shown in Figure 15 includes a first cooling system 105A and a second cooling system 105B. The first cooling system 105A includes a first radiator 110A through which a first cooling medium flows, a first flow path 150A connecting the first radiator 110A and the battery 20, and a first pump 120A that circulates the first cooling medium flowing through the first flow path 150A back to the first radiator 110A. The second cooling system 105B includes a second radiator 110B through which a second cooling medium flows, a second flow path 150B connecting the second radiator 110B, the drive motor 30A, and the PTO motor 30B, and a second pump 120B that circulates the second cooling medium flowing through the second flow path 150B back to the second radiator 110B.

[0158] The first cooling system 105A and the second cooling system 105B correspond to the battery temperature control system 70 and the high-voltage equipment cooling system 60 shown in Figure 4, respectively.

[0159] The first pump 120A and the second pump 120B shown in Figure 15 are variable displacement pump motors and hydraulic pumps that enable the flow of a cooling medium in two directions. However, the first pump 120A and the second pump 120B are not limited to variable displacement pump motors, but may be fixed displacement pumps, for example. Also, the first pump 120A and the second pump 120B are not limited to hydraulic pumps.

[0160] As described above, each of the first cooling system 105A and the second cooling system 105B may be equipped with a switching valve as a switching means. The first cooling medium and the second cooling medium may be the same or different.

[0161] The cooling system 105 may include a common electric fan 190 that generates cooling air to cool the first cooling medium flowing inside the first radiator 110A and the second cooling medium flowing inside the second radiator 110B. The electric fan 190 corresponds to the cooling fan 68 shown in Figure 4.

[0162] The battery and motor are electric devices that require special cooling as a measure against heat dissipation. The first cooling system 105A is a system specialized in cooling the battery 20, and the second cooling system 105B is a system specialized in cooling the drive motor 30A and the PTO motor 30B. By providing separate cooling systems in this way, it is possible to increase the cooling capacity of each cooling system. For example, the first cooling system 105A can increase its cooling capacity by switching the circulation direction of the cooling medium triggered by the temperature difference between different parts of the battery 20. The second cooling system 105B can increase its cooling capacity by switching the circulation direction of the cooling medium triggered by the temperature difference between the drive motor 30A and the PTO motor 30B.

[0163] This invention is applicable to electric work vehicles in general.

[0164] 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, 30C...Electric motor, 33...Output shaft, 34...Power transmission system, 35, 35A, 35B...Inverter, 36...Hydraulic pump, 40...PTO shaft, 51...Rops 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... Cooling system for high-voltage equipment, 61... Main ECU, 62... Electric ECU, 63... Charging ECU, 64... Relay, 65... Radiator for high-voltage equipment, 66... ​​Reservoir tank, 67... Pump, 68, 190... Cooling fan, 70... Battery temperature control system, 70A... First power system, 70B... Second power system, 72... Heater, 75... Radiator for battery, 76... Reservoir tank, 77... Pump, 80... Power distribution unit, 81... Onboard charger (OBC), 82...DC-DC converter, 90...Charger, 91...Controller, 100-105...Cooling system, 110...Radiator, 120, 121...Pump, 130...Reservoir tank, 140...Item to be cooled, 150...Flow path, 160...Switching valve, 170A-170D...Temperature sensor, 180...Filter separator, 400...Control device

Claims

1. An electric work vehicle comprising: one or more electric devices; a battery for storing power to supply to the one or more electric devices; a cooling system communicating with the battery and at least one of the one or more electric devices and including a flow path for circulating a cooling medium, the cooling system being configured to be able to switch the direction of circulation of the cooling medium; and a control device for controlling the switching of the circulation direction.

2. The work vehicle according to claim 1, wherein the cooling system comprises a radiator through which a cooling medium flows, and a pump that circulates the cooling medium flowing through the flow path to the radiator, the flow path connects the radiator to the battery and at least one of the one or more electric devices, and the control device controls the rotation direction of the pump to switch the circulation direction.

3. The work vehicle according to claim 1, wherein the cooling system comprises a radiator through which a cooling medium flows, a pump that circulates the cooling medium flowing through the flow path to the radiator, and a switching valve configured to switch the circulation direction of the cooling medium, and the control device controls the switching valve to switch the circulation direction.

4. A work vehicle according to claim 2 or 3, comprising: a first temperature sensor for measuring the temperature of a first portion of the battery located on the flow inlet side of the battery; and a second temperature sensor for measuring the temperature of a second portion of the battery located on the flow outlet side of the battery, wherein the cooling system includes the flow path connecting the radiator and the battery, and the control device switches the circulation direction when the temperature difference between the temperature of the first portion indicated by sensor data output from the first temperature sensor and the temperature of the second portion indicated by sensor data output from the second temperature sensor exceeds a threshold.

5. A work vehicle according to claim 2 or 3, comprising a running device, wherein the one or more electric devices include a first electric motor for driving the running device, and the cooling system includes the flow path connecting the radiator and the first electric motor.

6. The work vehicle according to claim 5, comprising a PTO shaft for supplying power to a work machine, wherein the one or more electric devices include a second electric motor that generates power to be transmitted to the PTO shaft, and the cooling system includes the radiator, the first electric motor, and the second electric motor and the flow path connecting them.

7. The work vehicle according to claim 6, further comprising: a third temperature sensor for measuring the temperature of the first electric motor; and a fourth temperature sensor for measuring the temperature of the second electric motor, wherein the control device switches the circulation direction when the temperature difference between the temperature of the first electric motor indicated by the sensor data output from the third temperature sensor and the temperature of the second electric motor indicated by the sensor data output from the fourth temperature sensor exceeds a threshold.

8. The work vehicle according to claim 7, wherein the control device switches the circulation direction so that the cooling medium flows from the other high-temperature side of the first electric motor to the one low-temperature side of the first electric motor when the temperature difference between the temperature of the first electric motor and the temperature of the second electric motor exceeds a threshold and the temperature of one of the low-temperature side of the first electric motor and the second electric motor falls below the threshold.

9. The work vehicle according to claim 6, wherein the cooling system includes a first cooling system and a second cooling system, the first cooling system having a first radiator through which a first cooling medium flows, a first flow path connecting the first radiator and the battery, and a first pump for circulating the first cooling medium flowing through the first flow path to the first radiator, and the second cooling system having a second radiator through which a second cooling medium flows, a second flow path connecting the second radiator, the first electric motor, and the second electric motor, and a second pump for circulating the second cooling medium flowing through the second flow path to the second radiator.

10. The work vehicle according to claim 9, wherein the cooling system includes an electric fan that generates cooling air to cool the first cooling medium flowing inside the first radiator and the second cooling medium flowing inside the second radiator.

11. The work vehicle according to any one of claims 1 to 3, wherein the battery is an immersion-cooled battery.

12. The work vehicle according to claim 11, wherein the cooling system has at least one filter separator provided in the flow path.

13. The control device comprises one or more processors and one or more memories for storing a program that controls the operation of the one or more processors, wherein the one or more processors control the switching of the circulation direction in response to a command that instructs the switching of the circulation direction according to the program, the work vehicle according to any one of claims 1 to 3.

14. A control method implemented on a computer for controlling a cooling system mounted on an electric work vehicle comprising one or more electric devices and a battery for storing power supplied to the one or more electric devices, wherein the cooling system is a cooling system that communicates with the battery and at least one of the one or more electric devices and includes a flow path for circulating a cooling medium, configured to allow switching of the circulation direction of the cooling medium, waiting until a command instructing the switching of the circulation direction is transmitted, and switching the circulation direction in response to the command when the command is transmitted.

15. A computer program used to control a cooling system mounted on an electric work vehicle comprising one or more electric devices and a battery for storing power supplied to the one or more electric devices, wherein the cooling system is a cooling system that communicates with the battery and at least one of the one or more electric devices and includes a flow path for circulating a cooling medium, configured to allow switching of the circulation direction of the cooling medium, and causes the computer to perform the following actions: wait until a command instructing the switching of the circulation direction is transmitted, and when the command is transmitted, switch the circulation direction in response to the command.

Images