Work vehicle, method for controlling work vehicle, and computer program

Abstract

This electric work vehicle comprises a travel device, an electric motor for driving the travel device, a motive power transmission system for transmitting motive power from the electric motor to the travel device, a rotation sensor for measuring the rotation speed of the electric motor, and a control device for controlling the operation of the work vehicle. The motive power transmission system includes a clutch. When the difference between the measured rotation speed and a command value of the rotation speed satisfies a prescribed condition while the work vehicle is traveling, the control device disconnects the clutch to block the transmission of motive power from the electric motor to the travel device.

Description

Work vehicle, method for controlling a work vehicle, and computer program 【0001】 The present disclosure relates to a work vehicle, a method for controlling a work vehicle, 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 popular. 【0003】 On the other hand, in order to realize a decarbonized society, it is required to reduce the amount of carbon dioxide (CO ２ 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 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. 【0005】 Japanese Unexamined Patent Application Publication No. 2023-66721 【0006】 In a conventional work vehicle equipped with an internal combustion engine, consumption of fossil fuel and emission of greenhouse gases are inevitable. On the other hand, in an electric work vehicle, various problems to be solved such as ensuring safety, improving running performance, reducing environmental load, improving convenience, or reducing costs remain. 【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: a running gear; an electric motor that drives the running gear; a power transmission system that transmits power from the electric motor to the running gear; a rotation sensor that measures the rotational speed of the electric motor; and a control device that controls the operation of the work vehicle, wherein the power transmission system includes a clutch, and the control device, while the work vehicle is running, disengages the clutch to interrupt the transmission of power from the electric motor to the running gear when the difference between the measured rotational speed and the command value of the rotational speed satisfies a predetermined condition. 【0010】 [Item 2] The work vehicle according to Item 1, wherein the control device, while the work vehicle is in motion, disconnects the clutch and cuts off the transmission of power from the electric motor to the travel device when the value obtained by subtracting the command value of the rotational speed from the measured rotational speed remains greater than a threshold for a predetermined period of time. 【0011】 [Item 3] The power transmission system further includes a reduction gear and a transmission, the clutch is positioned between the reduction gear and the transmission, power is transmitted from the reduction gear to the transmission when the clutch is engaged, and the transmission of power from the reduction gear to the transmission is interrupted when the clutch is disengaged, the work vehicle according to item 1 or 2. 【0012】 [Item 4] The control device switches the clutch from a disengaged state to an engaged state when the work vehicle is started, maintains the clutch in the engaged state while the work vehicle is running, and disengages the clutch when the predetermined conditions are met, the work vehicle according to any one of items 1 to 3. 【0013】 [Item 5] The control device stops the rotation of the electric motor when the clutch is disengaged, the work vehicle according to any one of items 1 to 4. 【0014】 [Item 6] A work vehicle according to any one of items 1 to 5, further comprising a display device, wherein the control device causes the display device to display a warning when the clutch is disengaged. 【0015】 [Item 7] The work vehicle according to any one of items 1 to 6, wherein the electric motor is a first electric motor, and the work vehicle further comprises a PTO shaft for supplying power to a work machine, and a second electric motor for driving the PTO shaft. 【0016】 [Item 8] The work vehicle according to Item 6, wherein the power transmission system is a first power transmission system, the clutch is a first clutch, the rotation sensor is a first rotation sensor, the work vehicle further comprises a second power transmission system that transmits power from the second electric motor to the PTO shaft, and a second rotation sensor that measures the rotational speed of the second electric motor, the second power transmission system includes a clutch, and the control device disengages the second clutch to stop the rotation of the PTO shaft when a certain condition is met between the measured rotational speed of the second electric motor and the command value of the rotational speed of the second electric motor. 【0017】 [Item 9] A method performed by a computer controlling an electric work vehicle, wherein the work vehicle comprises a running gear, an electric motor for driving the running gear, a power transmission system for transmitting power from the electric motor to the running gear, and a rotation sensor for measuring the rotational speed of the electric motor, the power transmission system including a clutch, and the method comprising: acquiring information indicating the rotational speed of the electric motor measured by the rotation sensor while the work vehicle is running; determining whether the difference between the measured rotational speed and a command value of the rotational speed satisfies a predetermined condition; and, if the predetermined condition is satisfied, disengaging the clutch to interrupt the transmission of power from the electric motor to the running gear. 【0018】[Item 10] A computer program executed by a computer that controls an electric work vehicle, wherein the work vehicle comprises a travel device, an electric motor that drives the travel device, a power transmission system that transmits power from the electric motor to the travel device, and a rotation sensor that measures the rotational speed of the electric motor, the power transmission system including a clutch, and the computer program causes the computer to: acquire information indicating the rotational speed of the electric motor measured by the rotation sensor while the work vehicle is running; determine whether the difference between the measured rotational speed and the command value of the rotational speed satisfies a predetermined condition; and, if the predetermined condition is satisfied, disengage the clutch to interrupt the transmission of power from the electric motor to the travel device. 【0019】 [Item 11] A control device configured to perform the method described in Item 9. 【0020】 [Item 12] A computer-readable non-temporary storage medium that stores a computer program containing instructions for causing a computer to perform the actions described in Item 9. 【0021】 [Item 13] A system comprising the control device described in Item 11, and an electric motor. 【0022】 [Item 14] A control device for controlling a clutch mounted on a work vehicle equipped with an electric motor, comprising: an acquisition means for acquiring information indicating the rotational speed of the electric motor measured by a rotation sensor while the work vehicle is in motion; a determination means for determining whether the difference between the measured rotational speed and the command value of the rotational speed satisfies a predetermined condition; and a disconnection means for disengaging the clutch and interrupting the transmission of power from the electric motor to the travel device when the predetermined condition is satisfied. 【0023】 [Item 15] A system comprising the control device described in Item 14, and an electric motor. 【0024】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. 【0025】 According to embodiments of this disclosure, an electric work vehicle capable of ensuring safety is provided. 【0026】 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 diagram showing an example of the configuration of the power transmission system for driving and work. This is a diagram showing an example of a warning image that pops up on the display. This is a flowchart showing the control procedure of an electric work vehicle. 【0027】 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. 【0028】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. 【0029】 (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." 【0030】 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." 【0031】Electric motors can be synchronous motors such as permanent magnet synchronous motors or reluctance motors, or asynchronous motors such as induction motors. 【0032】 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. 【0033】 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. 【0034】 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. 【0035】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". 【0036】 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). 【0037】"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. 【0038】 (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. 【0039】 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." 【0040】 <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. 【0041】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. 【0042】 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. 【0043】Motor 30 is electrically connected to battery 20. Motor 30 can convert the electric power output from battery 20 into mechanical motion (power) and generate the driving force (traction) necessary for the running of work vehicle 10. Motor 30 can be, for example, an AC synchronous motor. Battery 20 generates direct current. Therefore, when motor 30 is an AC synchronous motor, an electric circuit group including an inverter device (hereinafter sometimes simply referred to as "inverter") may be provided between battery 20 and motor 30. The inverter device converts direct current into alternating current. A part of such an electric circuit group may be inside battery 20. Also, another part of the electric circuit group may be attached to motor 30 as a drive circuit of motor 30. 【0044】 Motor 30 has a rotating output shaft 33. The torque of output shaft 33 is transmitted to rear wheel 14R through mechanical components such as a transmission (speed change device) provided inside transmission case 13 and a rear wheel differential device (differential gear device). In other words, the power generated by motor 30 which is a power source is transmitted to rear wheel 14R by a power transmission system (drive train) 34 including a transmission provided inside transmission case 13. For this reason, "transmission case" may be called "mission case". In the four-wheel drive mode, a part of the power of motor 30 is also transmitted to front wheel 14F. Thus, motor 30 drives a running device including a plurality of wheels 14. 【0045】 The power of motor 30 may be used not only for the running of work vehicle 10 but also for driving a work implement. A PTO shaft 40 is provided at the rear end of transmission case 13. A work implement can be connected to PTO shaft 40. PTO shaft 40 can be driven by motor 30 that drives the running device or another electric motor not shown in FIG. 1. The torque of output shaft 33 of motor 30 or the output shaft of another motor is transmitted to PTO shaft 40. A work implement mounted on or towed by work vehicle 10 can receive power from PTO shaft 40 and perform operations according to various works. Motor 30 and power transmission system 34 may be collectively referred to as an electric powertrain. 【0046】 As described above, the work vehicle 10 shown in FIG. 1 does not have an internal combustion engine such as a diesel engine, but instead has a battery 20 and a motor 30. Further, the output shaft 33 of the motor 30 is mechanically coupled to a power transmission system 34 such as a transmission within a transmission case 13. The motor 30 can efficiently generate torque within a relatively wide rotational speed range compared to an internal combustion engine. By using the power transmission system 34 including the transmission, it becomes easier to perform a multi-stage or continuously variable speed operation to adjust the torque and rotational speed from the motor 30 over an even wider range. For this reason, not only can the work vehicle 10 travel, but it is also possible to efficiently perform a variety of operations using work implements. 【0047】 Depending on the application or size of the work vehicle 10, some functions of the power transmission system 34 may be deleted. For example, part or all of the transmission responsible for the speed change function may be omitted. The number and mounting positions of the motors 30 are also not limited to the example shown in FIG. 1. Further, the work vehicle may be a hybrid electric vehicle (HEV) having an internal combustion engine such as a diesel engine as a power source in addition to an electric motor. 【0048】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." 【0049】 <2. Specific Examples of Work Vehicles> Next, we will explain a more specific example of the configuration of work vehicle 10. 【0050】 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. 【0051】 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. 【0052】 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. 【0053】 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. 【0054】 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". 【0055】 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. 【0056】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. 【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. 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, 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. 【0071】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. 【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. 【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 power transmission system 34A and the transmission included in 34A on the meter panel unit 54. 【0075】 Figure 6 is a block diagram showing an example of the hardware configuration of each ECU. Each ECU 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 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 coolant 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】 <4. Clutch Control of the Drive Motor> In work vehicles equipped with a drive motor, if the work vehicle operates against the user's will due to an abnormality or failure of the electric motor, it is required that a forced stop or emergency stop function be immediately activated to prevent unintended operation by the user. 【0088】 The electric work vehicle in this embodiment includes a travel device, an electric motor that drives the travel device, a first power transmission system that transmits power from the electric motor to the travel device, a first rotation sensor (see Figure 8) that measures the rotational speed of the electric motor, and a control device that controls the operation of the work vehicle. The rotation sensor is, for example, an angle sensor such as a resolver or a Hall IC. In this embodiment, the rotational speed measured by the rotation sensor is called the "actual rotational speed." The actual rotational speed can also be detected using a speed sensor, for example, in addition to the angle sensor. Therefore, a speed sensor is also an example of a sensor for measuring the rotational speed of an electric motor. 【0089】The control device is configured or programmed to disengage the first clutch and interrupt the transmission of power from the electric motor to the travel device when the difference between the actual rotational speed and the commanded rotational speed meets a predetermined condition while the work vehicle is in motion. For example, the predetermined condition is given by a threshold. The threshold can be determined to be, for example, in the range of 10 rpm (revolutions per minute) to 1000 rpm. As will be described later, it can be determined that the predetermined condition is met when the difference between the actual rotational speed and the commanded rotational speed exceeds the threshold. 【0090】 The control device may include one or more processors and one or more memories that store programs for controlling the operation of the one or more processors. One or more processors, in accordance with the program, execute a process to disconnect the first clutch and interrupt the transmission of power from the electric motor to the travel device when the difference between the actual rotational speed and the commanded rotational speed value satisfies predetermined conditions while the work vehicle is in motion. 【0091】 The method for controlling the electric work vehicle in this embodiment is performed by a computer, or in other words, a method implemented in a computer. The method includes acquiring information indicating the rotational speed of the electric motor measured by a first rotation sensor while the work vehicle is in motion, determining whether the difference between the actual rotational speed and the commanded value of the rotational speed satisfies a predetermined condition, and, if the predetermined condition is satisfied, disengaging the first clutch to interrupt the transmission of power from the electric motor to the travel device. 【0092】 A computer program containing a set of instructions for causing one or more computers to execute the above-described method of controlling an electric work vehicle 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). 【0093】According to the electric work vehicle, electric work vehicle control method, or computer program of this embodiment, if the work vehicle operates against the user's will due to a motor abnormality or failure, the first clutch is disengaged to interrupt the transmission of power from the first electric motor to the travel device, thereby automatically stopping the power transmission system for travel. This makes it possible to forcibly stop the work vehicle. In particular, it is possible to stop the work vehicle even if the electric motor becomes uncontrollable. 【0094】 Unlike diesel engines, electric motors do not inherently require a clutch to interrupt the transmission of power to the running gear. This is because the transmission of power to the running gear can be stopped by directly controlling the drive of the electric motor. In contrast, the electric work vehicle in this embodiment is equipped with a clutch to interrupt the transmission of power to the running gear. The electric work vehicle may further be equipped with a clutch to interrupt the transmission of power to the PTO shaft. 【0095】 Figure 8 shows an example configuration of power transmission systems 34A and 34B. In this example, the power transmission system 34A for driving includes a reduction gear 37A, a clutch 38A, a transmission 39A, and a differential 41. Power transmission system 34A and clutch 38A are examples of a first power transmission system and a first clutch, respectively. 【0096】 In the example shown in Figure 8, the main ECU 61 functions as a control device for controlling the clutch. However, other ECUs may be used to control the clutch. 【0097】 In the power transmission system 34A, the clutch 38A is positioned between the reduction gear 37A and the transmission 39A, and is connected to both the reduction gear 37A and the transmission 39A. Through this mechanical connection, when the clutch 38A is engaged, power is transmitted from the reduction gear 37A to the transmission 39A. The clutch 38A is always engaged unless the above predetermined conditions are met. On the other hand, when the clutch is disengaged, the transmission of power from the reduction gear 37A to the transmission 39A is interrupted. 【0098】As illustrated in Figure 8, the work vehicle may be equipped with a first rotation sensor 31A that measures the rotational speed of the first electric motor 30A, which is a drive motor. 【0099】 In this embodiment, a situation in which a forced stop should be activated is, for example, when the electric motor malfunctions due to a failure. In this situation, the work vehicle may behave contrary to the user's intentions, and it is necessary to activate the forced stop function to immediately stop the work vehicle. In this embodiment, while the work vehicle is in motion, the control device can disconnect the clutch 38A and interrupt the transmission of power from the electric motor to the travel device if the value obtained by subtracting the command value of the rotational speed from the actual rotational speed of the first electric motor 30A measured by the first rotation sensor 31A, or more specifically, the absolute value of this value, remains greater than a threshold for a predetermined time (for example, 1 second). In this way, when a situation in which a forced stop function should be activated occurs, the control device ensures safety by disconnecting the clutch. 【0100】 In this embodiment, the clutch 38A operates, for example, under hydraulic control and is equipped with an ON / OFF solenoid valve. The control device can switch the connected and disconnected state of the clutch 38A by transmitting a control signal to the solenoid valve and controlling the ON / OFF state of the solenoid valve. 【0101】 If the solenoid valve remains in the ON state for an extended period, the solenoid may become stuck in the ON position. To prevent this, the control device in this embodiment may temporarily disengage the clutch 38A when the power switch is turned on and the work vehicle is started, and then switch the clutch 38A from the disengaged state to the engaged state. The control device may maintain the clutch 38A in the engaged state while the work vehicle is running, and disengage the clutch when predetermined conditions are met. Such control can suppress the solenoid becoming stuck in the ON position. 【0102】 It is preferable that the control device stops the rotation of the drive motor when the clutch 38A is disengaged. This control further enhances safety by disengaging the clutch 38A and stopping the rotation of the drive motor in the event of an abnormality or failure in the motor. 【0103】 The work vehicle may be equipped with a display device. An example of a display device is the display on the meter panel unit 54. The control device may cause the display device to show a warning when the clutch 38A is disengaged. For example, the control device may cause a warning image to pop up on the display, which includes a message warning that the forced stop function has been activated and the clutch 38A has been disengaged. Such a display makes it possible to warn the user of the automatic stop of the drive power transmission system. Figure 9 shows an example of a warning image 77 that pops up on the display. 【0104】 In this embodiment, the second power transmission system for work may also be equipped with a second clutch, similar to the first power transmission system for driving. Similar to power transmission system 34A, emergency clutch disengagement control may also be applied to power transmission system 34B. 【0105】 In the example shown in Figure 8, the power transmission system 34B for operation includes a reduction gear 37B, a PTO clutch 38B, and a PTO transmission 39B. The PTO clutch 38B is positioned between the reduction gear 37B and the PTO transmission 39B and connects them. Through this mechanical connection, when the PTO clutch 38B is engaged, power is transmitted from the reduction gear 37B to the PTO transmission 39B. Conversely, when the clutch is disengaged, the transmission of power from the reduction gear 37B to the PTO transmission 39B is interrupted. The power transmission system 34B and the PTO clutch 38B for operation are examples of a second power transmission system and a second clutch, respectively. 【0106】 As illustrated in Figure 8, the work vehicle may be equipped with a second rotation sensor 31B that measures the rotational speed of the second electric motor 30B, which is a PTO motor. 【0107】The control device can disengage the PTO clutch 38B and stop the rotation of the PTO shaft 40 when a certain condition is met in the difference between the actual rotational speed of the second electric motor 30B measured by the second rotation sensor 31B and the commanded value of the rotational speed of the second electric motor 30B. For example, during the operation of the work machine, the control device can disengage the PTO clutch 38B and interrupt the transmission of power from the second electric motor 30B to the PTO shaft 40 when the value obtained by subtracting the commanded value of the rotational speed from the actual rotational speed, or more specifically, the absolute value of this value, remains greater than a threshold for a predetermined period of time. In this way, by applying emergency clutch disengagement control to the power transmission system 34B as well, if a failure occurs in the second electric motor 30B, the PTO clutch 38B can be disengaged and the transmission of power from the second electric motor 30B to the PTO shaft 40 can be interrupted. This makes it possible to automatically stop the power transmission system for work, and as a result, to forcibly stop the work machine. 【0108】 As described above, in this embodiment, by providing separate clutches for the power transmission system for driving and the power transmission system for working, it is possible to control each power transmission system independently and automatically stop them. 【0109】 An example of the operation of the control device will be explained with reference to Figure 10. 【0110】 Figure 10 is a flowchart showing the control procedure for an electric work vehicle. Figure 10 shows an example of the procedure for forcibly stopping the power transmission system for driving. 【0111】 The control device acquires information indicating the actual rotational speed of the electric motor, measured by the rotation sensor while the work vehicle is in motion (step S101). 【0112】Next, the control device determines whether the difference between the actual rotational speed and the commanded rotational speed satisfies a predetermined condition (step S102). For example, the control device determines whether the value obtained by subtracting the commanded rotational speed from the actual rotational speed remains greater than a threshold for a predetermined period of time while the work vehicle is running. If the predetermined condition is not met (for example, the value obtained by subtracting the commanded rotational speed from the actual rotational speed falls below the threshold) (NO in step S103), the control device maintains the clutch engagement state and continues to transmit power from the motor to the travel device (step S104). The control device repeatedly executes the processes from steps S101 to S104 until the power is turned off (NO in step S105). On the other hand, when the power is turned off (YES in step S105), the control device stops the control process. 【0113】 If a predetermined condition is met (for example, if the value obtained by subtracting the command value of the rotational speed from the actual rotational speed exceeds a threshold) (YES in step S103), the control device disengages the clutch and cuts off the transmission of power from the motor to the travel device (step S106). The control device further stops the rotation of the motor (step S107). 【0114】 Thus, the control device can forcibly stop the work vehicle according to the procedure illustrated in Figure 10. 【0115】 The present invention can be applied to agricultural tractors equipped with electric motors for driving, and to electric work vehicles such as construction vehicles. 【0116】10...Work vehicle, 11...Body, 12...Front frame, 13...Transmission case, 14...Wheels, 14F...Front wheel, 14R...Rear wheel, 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, 31A, 31B...Rotation sensor, 33...Output shaft, 34...Power transmission system, 35A, 35B...Inverter, 36...Hydraulic pump, 37A, 37B...Reduction gear, 38A, 38B...Clutch, 39A, 39B...Transmission, 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... 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

Claims

1. An electric work vehicle comprising: a running gear; an electric motor for driving the running gear; a power transmission system for transmitting power from the electric motor to the running gear; a rotation sensor for measuring the rotational speed of the electric motor; and a control device for controlling the operation of the work vehicle, wherein the power transmission system includes a clutch, and the control device, while the work vehicle is running, disengages the clutch to interrupt the transmission of power from the electric motor to the running gear when the difference between the measured rotational speed and the commanded value of the rotational speed satisfies a predetermined condition.

2. The work vehicle according to claim 1, wherein the control device, while the work vehicle is in motion, disconnects the clutch and cuts off the transmission of power from the electric motor to the travel device if the value obtained by subtracting the command value of the rotational speed from the measured rotational speed remains greater than a threshold for a predetermined period of time.

3. The power transmission system further includes a reduction gear and a transmission, the clutch is positioned between the reduction gear and the transmission, power is transmitted from the reduction gear to the transmission when the clutch is engaged, and the transmission of power from the reduction gear to the transmission is interrupted when the clutch is disengaged, the work vehicle according to claim 1 or 2.

4. The work vehicle according to claim 1 or 2, wherein the control device switches the clutch from a disengaged state to an engaged state when the work vehicle is started, maintains the clutch in the engaged state while the work vehicle is running, and disengages the clutch when the predetermined conditions are met.

5. The work vehicle according to claim 1 or 2, wherein the control device stops the rotation of the electric motor when the clutch is disengaged.

6. The work vehicle according to claim 1 or 2, further comprising a display device, wherein the control device causes the display device to display a warning when the clutch is disengaged.

7. The work vehicle according to claim 1 or 2, wherein the electric motor is a first electric motor, and the work vehicle further comprises a PTO shaft for supplying power to a work machine, and a second electric motor for driving the PTO shaft.

8. The work vehicle according to claim 6, wherein the power transmission system is a first power transmission system, the clutch is a first clutch, the rotation sensor is a first rotation sensor, and the work vehicle further comprises a second power transmission system for transmitting power from the second electric motor to the PTO shaft, and a second rotation sensor for measuring the rotational speed of the second electric motor, the second power transmission system includes a clutch, and the control device disengages the second clutch to stop the rotation of the PTO shaft when a certain condition is met by the difference between the measured rotational speed of the second electric motor and the command value of the rotational speed of the second electric motor, the work vehicle according to claim 6.

9. A method performed by a computer controlling an electric work vehicle, wherein the work vehicle comprises a running gear, an electric motor for driving the running gear, a power transmission system for transmitting power from the electric motor to the running gear, and a rotation sensor for measuring the rotational speed of the electric motor, the power transmission system including a clutch, and the method comprising: acquiring information indicating the rotational speed of the electric motor measured by the rotation sensor while the work vehicle is running; determining whether the difference between the measured rotational speed and a command value of the rotational speed satisfies a predetermined condition; and, if the predetermined condition is satisfied, disengaging the clutch to interrupt the transmission of power from the electric motor to the running gear.

10. A computer program executed by a computer that controls an electric work vehicle, wherein the work vehicle comprises a running gear, an electric motor that drives the running gear, a power transmission system that transmits power from the electric motor to the running gear, and a rotation sensor that measures the rotational speed of the electric motor, the power transmission system including a clutch, and the computer program causes the computer to: acquire information indicating the rotational speed of the electric motor measured by the rotation sensor while the work vehicle is running; determine whether the difference between the measured rotational speed and the command value of the rotational speed satisfies a predetermined condition; and, if the predetermined condition is satisfied, disengage the clutch to interrupt the transmission of power from the electric motor to the running gear.

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