Work vehicle, control device for work vehicle, and control method

Abstract

This work vehicle comprises: a fuel cell module having a fuel cell stack; at least one fuel tank that accommodates fuel to be supplied to the fuel cell stack; a motor connected to the fuel cell module; a travel device driven by the motor; a power take-off shaft driven by the motor and to which an implement connects; and a control device. The control device, in response to an operation stop command, stops the supply of the fuel or oxide gas to the fuel cell module, and subsequently rotates the motor in a state in which power transmission from the motor to the travel device is stopped so as to discharge residual charge in a circuit group connected to the motor.

Description

Technical Field

[0001] The present disclosure relates to a work vehicle, a control device for the work vehicle, and a control method therefor.

Background Art

[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 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 also required to reduce the amount of carbon dioxide (CO2) emitted by work vehicles such as tractors used in fields. Different from general automobiles, in work vehicles such as tractors, it is necessary to tow a working machine called an implement to perform agricultural 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 a tractor including a fuel cell (FC) power generation system and a motor without significantly changing the structure of a conventional engine-driven tractor.

[0005] Patent Document 2 discloses a vehicle having a fuel cell system. When the ignition is turned off and the entire vehicle system is turned off, a discharge process is performed to consume the electric charge remaining in the high-voltage system provided in the vehicle. The electric charge remaining in the high-voltage system is the electric charge remaining on the circuit excluding the storage battery, for example, the electric charge remaining in a capacitor included in the circuit. In this discharge process, the electric charge is consumed by a heater that heats the water in a water storage tank for storing the water generated by the power generation of the fuel cell.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-225577 [Patent Document 2] Japanese Patent Publication No. 2022-46376 [Overview of the project] [Problems that the invention aims to solve]

[0007] This disclosure provides a technology for efficiently discharging residual charge when a work vehicle equipped with a fuel cell module is stopped from operation. [Means for solving the problem]

[0008] A work vehicle according to one aspect of the present disclosure, in an exemplary and non-limiting embodiment, comprises a fuel cell module having a fuel cell stack, at least one fuel tank containing fuel to be supplied to the fuel cell stack, a motor connected to the fuel cell module, a running gear driven by the motor, a power take-off shaft driven by the motor and to which an implement is connected, and a control device. The control device, in response to a command to stop operation, stops the supply of the fuel or oxidizing gas to the fuel cell module, and then rotates the motor while stopping the transmission of power from the motor to the running gear to discharge residual charge in a group of circuits connected to the motor.

[0009] The comprehensive or specific embodiments of this disclosure may be implemented by apparatus, systems, methods, integrated circuits, computer programs, or computer-readable non-temporary storage media, or any combination thereof. Computer-readable storage media may include volatile storage media or non-volatile storage media. Apparatus may consist of multiple devices. If 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. [Effects of the Invention]

[0010] According to the embodiments of this disclosure, residual charge can be efficiently discharged when the operation stops. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic plan view showing an example of the basic configuration of a work vehicle according to this disclosure. [Figure 2] This figure shows a basic example configuration of a fuel cell power generation system installed in a work vehicle. [Figure 3] This is a schematic block diagram illustrating an example of electrical connections and power transmission between components of a work vehicle according to this disclosure. [Figure 4] This block diagram schematically shows the electrical signal paths (thin solid lines) and coolant paths (dotted lines) between components in the work vehicle according to this disclosure. [Figure 5] This is a schematic perspective view showing an example of the configuration of a work vehicle in an embodiment of the present disclosure. [Figure 6] This is a schematic side view showing an example of the configuration of a work vehicle in an embodiment of the present disclosure. [Figure 7] This is a flowchart illustrating an example of the discharge process for a work vehicle. [Figure 8] This flowchart shows another example of discharge processing for a work vehicle. [Figure 9] Here is a flowchart showing yet another example of discharge processing for a work vehicle. [Modes for carrying out the invention]

[0012] Embodiments of the present disclosure will be described below. However, detailed descriptions may be omitted where they are not necessary. For example, detailed descriptions of well-known matters and redundant descriptions regarding substantially the same configurations may be omitted. This is to avoid making the following descriptions unnecessarily redundant and to facilitate the understanding of those skilled in the art. Note that the inventors provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend to limit the subject matter described in the claims thereby. In the following description, components having the same or similar functions are denoted by the same reference numerals.

[0013] The following embodiments are examples, and the technology of the present disclosure is not limited to the following embodiments. For example, the numerical values, shapes, materials, steps, the order of those steps, the layout of the display screen, etc. shown in the following embodiments are merely examples, and various modifications are possible as long as there is no technical contradiction. Also, as long as there is no technical contradiction, it is possible to combine one aspect with another aspect.

[0014] The "work vehicle" in the present disclosure means a vehicle used for performing work at a work site. The "work site" is any place where work is performed, such as a farm field, a mountain forest, or a construction site. The "farm field" is any place where agricultural work is performed, such as an orchard, a field, a paddy field, a grain farm, or a pasture. The work vehicle can be, for example, an agricultural machine such as a tractor, a rice transplanter, a combine, a ride-on management machine, or a ride-on lawn mower, or a vehicle used for non-agricultural purposes such as a construction work vehicle or a snow removal vehicle. The work vehicle in the present disclosure can be equipped with an implement (also referred to as a "work machine" or a "work device") corresponding to the work content at at least one of its front and rear parts. The act of the work vehicle traveling while performing work may be referred to as "work traveling".

[0015] Note that "agricultural machinery" means machinery used for agricultural purposes. Examples of agricultural machinery include tractors, harvesters, rice transplanters, ride-on management machines, vegetable transplanters, lawn mowers, seeders, fertilizer spreaders, and agricultural mobile robots. Not only when a work vehicle such as a tractor functions alone as "agricultural machinery", but also when an implement attached to or towed by the work vehicle and the entire work vehicle function as one "agricultural machinery". Agricultural machinery performs farming operations such as tilling, seeding, pest control, fertilizing, planting crops, or harvesting on the ground in the field.

[0016] 1. <Basic configuration of the work vehicle> An example of the basic configuration and operation of the work vehicle in the present disclosure will be described. The work vehicle described below is equipped with a motor and a fuel cell power generation system (hereinafter referred to as the "FC power generation system") that generates electricity required for driving the motor.

[0017] FIG. 1 is a plan view schematically showing an example of the basic configuration of a work vehicle 100 in the present disclosure. In the present disclosure, the traveling direction when the work vehicle 100 travels straight forward will be referred to as the "forward direction", and the traveling direction when it travels straight backward will be referred to as the "backward direction". In a plane parallel to the ground, the direction extending rightward perpendicular to the "forward direction" will be referred to as the "right direction", and the direction extending leftward perpendicular to it will be referred to as the "left direction". In FIG. 1, the "forward direction", "backward direction", "right direction", and "left direction" are indicated by arrows of "front", "back", "right", and "left", respectively. In some cases, both the forward direction and the backward direction may be collectively referred to as the "front-back direction".

[0018] The work vehicle 100 in the illustrated example is, for example, a tractor which is an example of agricultural machinery. The technology of the present disclosure is not limited to work vehicles such as tractors, and can also be applied to other types of work vehicles. The work vehicle 100 can travel in the field while attaching or towing an implement and performing farming operations according to the type of the implement. Also, the work vehicle 100 can travel in the field and outside the field (including roads) in a state where the implement is lifted or not attached.

[0019] The work vehicle 100, like a conventional tractor, is equipped with a body (vehicle frame) 102 that rotatably supports the left and right front wheels 104F and the left and right rear wheels 104R. The body 102 includes a front frame 102A on which the front wheels 104F are mounted and a transmission case 102B on which the rear wheels 104R are mounted. The front frame 102A is fixed to the front of the transmission case 102B. The front wheels 104F and the rear wheels 104R may be collectively referred to as wheels 104. Strictly speaking, wheels 104 are wheels on which tires are mounted. In this disclosure, “wheel” generally means the entire “wheel and tire.” One or both of the front wheels 104F and the rear wheels 104R may be replaced with multiple wheels (crawlers) equipped with tracks instead of wheels with tires. In this specification, the left and right front wheels 104F and left and right rear wheels 104R, the axles that rotate these four wheels, and the braking devices (brakes) that apply braking to each axle may be collectively referred to as the "running gear."

[0020] In the example shown in Figure 1, the work vehicle 100 is equipped with a fuel cell module (FC module) 10 and a motor 70, which are directly or indirectly supported by a front frame 102A. The FC module 10 has a fuel cell stack (FC stack) and functions as an on-board generator that generates electricity from fuel, as will be described later. Hereinafter, "FC module" or "FC stack" may be simply referred to as "fuel cell".

[0021] The motor 70 is electrically connected to the FC module 10. The motor 70 can convert the power generated in the FC module 10 into mechanical motion (power) to generate the driving force (traction) necessary for the work vehicle 100 to move. An example of the motor 70 is an AC synchronous motor. Since the FC stack of the FC module 10 generates DC current, if the motor 70 is an AC synchronous motor, a group of electrical circuits including an inverter device is provided between the FC stack and the motor 70 to convert the DC current to AC current. Some of these electrical circuits may be located inside the FC module 10. Other parts of the electrical circuits may be attached to the motor 70 as a drive circuit for the motor 70.

[0022] The motor 70 has a rotating output shaft 71. The torque of the output shaft 71 is transmitted to the rear wheels 104R via mechanical components such as a transmission (speed changer) and a rear-wheel differential gear, which are located inside the transmission case 102B. In other words, the power generated by the motor 70, which is the power source, is transmitted to the rear wheels 104R by a power transmission system (drivetrain) 74, which includes a transmission, located inside the transmission case 102B. For this reason, the "transmission case" may also be called the "transmission case". In four-wheel drive mode, a portion of the power from the motor 70 is also transmitted to the front wheels 104F. The power from the motor 70 can be used not only for driving the work vehicle 100 but also for driving implements. Specifically, a power take-off (PTO) shaft 76 is provided at the rear end of the transmission case 102B. The PTO shaft 76 is driven by the motor 70 and to which the implement is connected. The torque from the output shaft 71 of the motor 70 is transmitted to the PTO shaft 76. The implement, which is mounted on or towed by the work vehicle 100, receives power from the PTO shaft 76 and can perform various operations according to the task. The motor 70 and the power transmission system 74 may be collectively referred to as the electric powertrain.

[0023] Thus, the work vehicle 100 according to this disclosure is not equipped with an internal combustion engine such as a diesel engine, but is equipped with an FC module 10 and a motor 70. Furthermore, the output shaft 71 of the motor 70 is mechanically coupled to a power transmission system 74, such as a transmission, in a transmission case 102B. The motor 70 can efficiently generate torque over a relatively wide rotational speed range compared to an internal combustion engine. However, by using the power transmission system 74, including the transmission, it becomes easy to adjust the torque and rotational speed from the motor 70 over an even wider range by performing multi-stage or continuously variable speed operation. Therefore, it becomes possible to efficiently perform not only the driving of the work vehicle 100 but also a variety of tasks using implements.

[0024] Furthermore, depending on the intended use or size of the work vehicle 100, some functions of the power transmission system 74 may be omitted. For example, some or all of the transmission responsible for the speed change function may be omitted. The number and mounting positions of the motors 70 are also not limited to the example shown in Figure 1.

[0025] The work vehicle 100 is equipped with at least one fuel tank 50 that contains fuel to be supplied to the FC module 10. In Figure 1, for simplicity, one fuel tank 50 is shown. In one embodiment, multiple fuel tanks 50 are housed in a tank case to constitute a fuel tank module. The fuel tanks 50 are supported by members fixed to the vehicle body 102, as will be described later. The FC module 10 and the fuel tanks 50 are connected by piping and valves, etc., to form an on-board FC power generation system. The configuration and operation of the FC power generation system will be described later.

[0026] The work vehicle 100 in the embodiments described below includes a driver's seat supported by a vehicle body 102. The driver's seat can be surrounded by a cab supported by the vehicle body 102. In the embodiments described below, the FC module 10 is disposed in front of the driver's seat, and the fuel tank 50 is disposed above the driver's seat. Such an FC module 10 and fuel tank 50 are housed in at least one "accommodation body". The "accommodation body" functions as, for example, a housing and serves to protect the FC module 10 and fuel tank 50 from sunlight irradiation and wind and rain. Further, when fuel gas leaks from the FC module 10 or the fuel tank 50, such an accommodation body can also control the spread of the fuel gas into the atmosphere and facilitate the detection of the fuel gas.

[0027] The FC module 10 can be housed in a front housing called a "bonnet" for example. The front housing is part of the "accommodation body". The front housing is supported by the front portion (front frame 102A) of the vehicle body 102. The fuel tank 50 can be housed in a tank case as described above. The tank case is supported directly or indirectly by the vehicle body 102.

[0028] 2. <FC Power Generation System> Next, referring to FIG. 2, a basic configuration example of the FC power generation system 180 mounted on the work vehicle 100 will be described.

[0029] The FC power generation system 180 shown in FIG. 2 functions as an in-vehicle power generation system in the work vehicle 100 of FIG. 1. The electric power generated by the power generation of the FC power generation system 180 is used not only for the running of the work vehicle 100 but also for the operation of an implement towed or mounted by the work vehicle 100.

[0030] <000013?The FC power generation system 180 in the illustrated example includes an FC module 10 and at least one fuel tank 50 that stores fuel to be supplied to the FC module 10. Further, the FC power generation system 180 includes a radiator device 34 for cooling the FC module 10.

[0031] The FC module 10 comprises, as its main components, a fuel cell stack (FC stack) 11, an air compressor 12, a fuel circulation pump 24, a coolant pump 31, a boost circuit 40, and a control device 42. These components are housed within the casing of the FC module 10 and are connected to each other by electrical or fluid communication.

[0032] The FC stack 11 generates electricity through an electrochemical reaction between the fuel, "anode gas," and the oxidizing gas, "cathode gas." In this example, the FC stack 11 is a polymer electrolyte fuel cell. The FC stack 11 has a stack structure in which multiple single cells (fuel cell cells) are stacked. A single cell comprises, for example, an electrolyte membrane formed from an ion exchange membrane, an anode electrode formed on one side of the electrolyte membrane, a cathode electrode formed on the other side of the electrolyte membrane, and a pair of separators that sandwich the anode electrode and cathode electrode from both sides. The voltage generated in a single cell is, for example, less than 1 volt. For this reason, in the FC stack 11, for example, more than 300 single cells are connected in series to generate a voltage of several hundred volts.

[0033] The anode electrode of the FC stack 11 is supplied with an anode gas. The anode gas is called the "fuel gas" or simply "fuel." In embodiments of this disclosure, the anode gas (fuel) is hydrogen gas. The cathode electrode is supplied with a cathode gas. The cathode gas is an oxidizing gas such as air. The anode electrode is called the fuel electrode, and the cathode electrode is called the air electrode.

[0034] At the anode, the electrochemical reaction shown in equation (1) below occurs. 2H2→4H + +4e - ...Equation (1)

[0035] At the cathode electrode, the electrochemical reaction shown in equation (2) below occurs. 4H + +4e - +O2→2H2O...Equation (2)

[0036] Overall, the reaction shown in equation (3) below occurs. 2H2+O2→2H2O...Equation (3)

[0037] The anode gas remaining after being used in the above reaction is called the "anode-off gas," and the cathode gas remaining after being used in the reaction is called the "cathode-off gas."

[0038] The air compressor 12 supplies air taken in from the outside as cathode gas to the cathode electrode of the FC stack 11. The cathode gas supply system, including the air compressor 12, has a cathode gas supply pipe 13, a cathode off gas pipe 14, and a bypass pipe 15. The cathode gas supply pipe 13 flows the cathode gas (air) supplied from the air compressor 12 to the cathode electrode of the FC stack 11. The cathode off gas pipe 14 flows the cathode off gas discharged from the FC stack 11 to the outside air. The bypass pipe 15 branches off from the cathode gas supply pipe 13 downstream of the air compressor 12, bypasses the FC stack 11, and connects to the cathode off gas pipe 14. The bypass pipe 15 is equipped with a control valve 16 that adjusts the flow rate of cathode gas flowing through the bypass pipe 15. The cathode gas supply pipe 13 is equipped with a shut-off valve 17 that selectively blocks the inflow of cathode gas into the FC stack 11. The cathode-off gas pipe 14 is equipped with a pressure regulating valve 18 for adjusting the back pressure of the cathode gas.

[0039] The cathode gas supply system of the FC module 10 is equipped with a rotation speed detection sensor S1 for detecting the rotation speed of the air compressor 12 and a gas flow rate detection sensor S2 for detecting the flow rate of cathode gas flowing through the cathode gas supply pipe 13. The control valve 16, shut-off valve 17, and pressure regulating valve 18 are, for example, solenoid valves.

[0040] The fuel circulation pump 24 supplies fuel gas (anode gas) sent from the fuel tank 50 to the anode electrode of the FC stack 11. The anode gas supply system, including the fuel circulation pump 24, has an anode gas supply pipe 21, an anode off-gas pipe 22, and a circulation passage 23. The anode gas supply pipe 21 flows the anode gas supplied from the fuel tank 50 to the anode electrode of the FC stack 11. In the embodiment of this disclosure, the fuel tank 50 is a hydrogen tank for storing high-pressure hydrogen gas.

[0041] The anode-off gas pipe 22 carries the anode-off gas discharged from the FC stack 11. The anode-off gas is guided through the anode-off gas pipe 22 to the gas-liquid separator 25 where moisture is removed. The anode-off gas from which moisture has been removed is returned to the anode gas supply pipe 21 through the circulation channel 23 by the fuel circulation pump 24. The anode-off gas circulating in the circulation channel 23 can be discharged through the anode-off gas pipe 22 by opening the exhaust valve 26. Moisture stored in the gas-liquid separator 25 can be discharged through the anode-off gas pipe 22 by opening the exhaust valve 26. The exhaust valve 26 is, for example, a solenoid valve. In the example shown in the figure, the anode-off gas pipe 22 is connected to the cathode-off gas pipe 14. By adopting such a configuration, it is possible to improve the utilization efficiency of anode gas by circulating the anode-off gas, including unreacted anode gas that did not contribute to the electrochemical reaction, and supplying it back to the FC stack 11.

[0042] Temperature control is crucial for enhancing the performance of the FC stack 11. Since heat is generated when electricity is produced through the reaction of hydrogen and oxygen gases to create water, cooling is necessary. Figure 2 shows a coolant circulation system including a coolant pump 31 for the FC stack 11, but as will be described later, cooling circulation systems for other electrical components may also be provided. The air compressor 12, fuel circulation pump 24, and coolant pump 31 in the FC module 10 are each operated by their own built-in motors. These motors are also electrical components.

[0043] The coolant circulation system shown in Figure 2, including the coolant pump 31, comprises a coolant supply pipe 32, a coolant discharge pipe 33, a radiator device 34, and a temperature sensor S3. This coolant circulation system can adjust the temperature of the FC stack 11 within a predetermined range by circulating the coolant through the FC stack 11. The coolant is supplied to the FC stack 11 through the coolant supply pipe 32. The supplied coolant flows through coolant flow paths formed between the individual cells and is discharged to the coolant discharge pipe 33. The coolant discharged to the coolant discharge pipe 33 flows to the radiator device 34. The radiator device 34 dissipates heat from the coolant by exchanging heat between the incoming coolant and the outside air, and supplies the cooled coolant back to the coolant supply pipe 32.

[0044] The coolant pump 31 is installed in the coolant supply pipe 32 or the coolant discharge pipe 33 to deliver coolant to the FC stack 11. A coolant bypass passage may be provided between the coolant discharge pipe 33 and the coolant supply pipe 32. In this case, a flow divider valve is provided at the branching point where the coolant bypass passage branches off from the coolant discharge pipe 33. The flow divider valve can adjust the flow rate of coolant flowing through the bypass passage. The temperature sensor S3 detects the temperature of the coolant flowing through the coolant discharge pipe 33.

[0045] The coolant used to cool the FC stack 11 is circulated through a flow path by an electric coolant pump (coolant pump) 31. A coolant control valve may be provided downstream of the FC stack 11. The coolant control valve adjusts the ratio of coolant flowing to the radiator unit 34 to coolant bypassing the radiator unit 34, enabling more precise control of the coolant temperature. Furthermore, by controlling the amount of coolant supplied by the coolant pump, it is also possible to control the temperature difference between the coolant at the inlet and outlet of the FC stack 11 to stay within a desired range. The temperature of the coolant in the FC stack 11 can be controlled to a temperature that maximizes the power generation efficiency of the FC stack 11, for example, around 70°C.

[0046] The coolant flowing through the FC stack 11 preferably has higher insulating properties than the coolant used to cool ordinary electrical components. Since high voltages, for example, exceeding 300 volts, are generated in the FC stack 11, increasing the electrical resistance of the coolant can suppress current leakage through the coolant or the radiator device 34. The electrical resistance of the coolant may decrease as it is used. This is because ions dissolve into the coolant flowing through the FC stack 11. To remove such ions from the coolant and improve its insulating properties, it is desirable to place an ion exchanger in the coolant flow path.

[0047] The boost circuit 40 can raise the voltage output from the FC stack 11 by the power generation operation to a desired level. The downstream stage of the boost circuit 40 is connected to a high-voltage electrical circuit including an inverter device for motor drive. The downstream stage of the boost circuit 40 can also be connected in parallel to a low-voltage electrical circuit via a step-down circuit.

[0048] The control device 42 is an electronic control unit (ECU) that controls power generation by the FC module 10. The control device 42 detects or estimates the operating state of the FC power generation system 180 based on signals output from various sensors. Based on the operating state of the FC power generation system 180 and commands output from a higher-level computer or other ECU, the control device 42 controls the operation of the air compressor 12, fuel circulation pump 24, coolant pump 31, and various valves to control power generation by the FC stack 11. The control device 42 includes, for example, a processor, a memory device, and an input / output interface.

[0049] In the following explanation, for simplicity, "anode gas" will be referred to as "fuel gas" or "fuel," and "anode gas supply pipe" will be referred to as "piping."

[0050] 3. <Example of a work vehicle system configuration> Next, an example of the system configuration of the work vehicle 100 will be described with reference to Figures 3 and 4. Figure 3 is a schematic block diagram showing an example of electrical connections and power transmission between components of the work vehicle 100 according to this disclosure. Figure 4 is a block diagram showing a more detailed configuration than the example in Figure 3. Figure 4 schematically shows the electrical signal paths (thin solid lines) and coolant paths (dotted lines) between components in the work vehicle 100.

[0051] First, with reference to Figure 3, examples of electrical connections and power transmission of components will be described. Electrical connections include both high-voltage and low-voltage systems. High-voltage electrical connections provide, for example, the power supply voltage for an inverter device. Low-voltage electrical connections provide, for example, the power supply voltage for electronic components that operate at relatively low voltages.

[0052] In the example shown in Figure 3, the work vehicle 100 comprises an FC module 10, an inverter device 72, a motor 70, a power transmission system 74, and a PTO shaft 76. The DC voltage of the power generated in the FC stack 11 of the FC module 10 is boosted by a boost circuit 40 and then supplied to the inverter device 72. The inverter device 72 converts the DC voltage to, for example, a three-phase AC voltage and supplies it to the motor 70. The inverter device 72 has a bridge circuit including a plurality of power transistors. The motor 70 has a rotating rotor and a stator having a plurality of coils electrically connected to the inverter device 72. The rotor is coupled to the output shaft 71, for example, via a reduction gear (speed reducer) or directly. The motor 70 rotates the output shaft 71 with torque and rotational speed controlled according to the waveform of the three-phase AC voltage from the inverter device 72.

[0053] The inverter device 72 shown in Figure 4 includes an ECU 73 that controls the motor 70. The ECU 73 controls the switching operation (turn-on or turn-off) of each of the multiple power transistors included in the bridge circuit of the inverter device 72. The ECU 73 may be connected to the multiple power transistors in the bridge circuit via a pre-driver (sometimes called a "gate driver"). The ECU 73 may be configured to operate under the control of a higher-level computer such as a control device 60.

[0054] The torque from the output shaft 71 of the motor 70 is transmitted to the power transmission system 74. The power transmission system 74 operates using the motor 70 as a power source and can drive the wheels 104R, 104F, and / or the PTO shaft 76 in Figure 1. Such a power transmission system 74 may have a structure similar to or identical to that of a power transmission system in a conventional tractor equipped with an internal combustion engine such as a diesel engine. For example, by adopting a power transmission system used in agricultural tractors, it is possible to reduce the design and manufacturing costs for producing an agricultural work vehicle 100 equipped with an FC power generation system. The power transmission system 74 includes a drive system power transmission mechanism that transmits power from the motor 70 to the left and right rear wheels 104R via a clutch, transmission, and rear wheel differential, etc., and a PTO system power transmission mechanism that transmits power from the motor 70 to the PTO shaft 76. The power transmission system 74 includes a PTO clutch that switches between a state in which power from the motor 70 is transmitted to the PTO shaft 76 (connected state) and a state in which power is not transmitted (disconnected state). The PTO clutch can be switched manually by the driver operating a control device, or it can be switched automatically. The transmission case 102B in Figure 1 may be divided into a front case (transmission case) that houses the clutch, such as the PTO clutch and the transmission, and a rear case (differential gear case) that houses the rear wheel differential, etc. The rear case is also called the rear axle case.

[0055] The work vehicle 100 is equipped with a secondary battery (battery pack) 80 that temporarily stores the electrical energy generated by the FC module 10. An example of the battery pack 80 is a lithium-ion battery pack. The battery pack 80 is electrically connected to the FC module 10 and also electrically connected to the motor 70 via an inverter device 72. The battery pack 80 can supply power to the inverter device 72 at the required timing, either in cooperation with the FC module 10 or independently. Various battery packs used in passenger electric vehicles can be used as the battery pack 80. Hereinafter, the battery pack 80 may be simply referred to as "battery 80".

[0056] In addition to the motor 70 and inverter device 72, the work vehicle 100 is equipped with various electrically operated electrical components (on-board electronic components). Examples of electrical components include electromagnetic valves such as the on / off valve 20, the cooling fan of the radiator device 34, the electric pump of the cooling compressor 85, and a temperature control device for heating or cooling the FC stack 11. Such a temperature control device includes an electric heater 86. First and second DC-DC converters 81, 82 and a storage battery 83 for obtaining a power supply voltage suitable for the operation of these electrical components may also be included in the electrical components. Furthermore, various electronic components not shown (such as lamps and electric motors for hydraulic systems) may also be included in the electrical components. These electrical components may be similar to, for example, electronic components installed in conventional agricultural tractors.

[0057] In the example shown in Figure 3, the first DC-DC converter 81 is a circuit that steps down the voltage output from the boost circuit 40 of the FC module 10 to a first voltage, for example, 12 volts. The battery 83 is, for example, a lead-acid battery, and can store electrical energy at the voltage output from the first DC-DC converter 81. The battery 83 can be used as a power source for various electrical components, such as lamps.

[0058] The work vehicle 100 shown in Figure 3 is equipped not only with a first DC-DC converter 81 but also with a second DC-DC converter 82 as a voltage conversion circuit to step down the high voltage output by the FC module 10. The second DC-DC converter 82 is a circuit that steps down the voltage output from the boost circuit 40 of the FC module 10 (for example, several hundred volts) to a second voltage higher than the first voltage, for example, 24 volts. The cooling fan of the radiator unit 34 can operate with the voltage output from the second DC-DC converter 82, for example. Although the radiator unit 34 is shown as a single component in Figure 3, a single work vehicle 100 may be equipped with multiple radiator units 34. In addition, the electric pump of the cooling compressor 85 and the electric heater 86 can also operate with the voltage output from the second DC-DC converter 82.

[0059] The work vehicle 100 shown in Figure 3 is equipped with a temperature control device for cooling or heating the FC stack 11 included in the FC power generation system. Such a temperature control device requires a relatively large amount of power to operate. A relatively high voltage of 24 volts output by the second DC-DC converter 82 is supplied to this temperature control device. In this embodiment, the temperature control device includes a radiator device 34 for dissipating heat from the refrigerant used to cool the FC stack 11, and a relatively high voltage of 24 volts output by the second DC-DC converter 82 is supplied to the radiator device 34. The temperature control device includes a heater 86 for heating the FC stack 11. The relatively high voltage output by the second DC-DC converter 82 may also be supplied to the heater. The relatively high voltage output by the second DC-DC converter 82 may also be supplied to an air conditioning device, such as a cooling compressor 85.

[0060] The work vehicle 100 may also be equipped with a third voltage conversion circuit that converts the high voltage output by the FC module 10 into a third voltage higher than the second voltage. The third voltage is, for example, 48 volts. If the work vehicle 100 is equipped with other motors in addition to the motor 70, the third voltage may be used as a power source for such other motors, for example.

[0061] In agricultural work vehicles equipped with fuel cell power generation systems, in addition to the electrical equipment necessary for agricultural work, there are also electrical equipment necessary for the operation of the fuel cell power generation system, and therefore the appropriate voltage levels for each electrical equipment may differ. According to the embodiments of this disclosure, it becomes possible to supply a voltage of the appropriate magnitude.

[0062] In the example shown in Figure 3, multiple fuel tanks 50 are housed within a single tank case 51. The fuel tanks 50 are connected to a filling port 52 into which fuel is supplied from the outside. This connection is made by piping 21 for carrying fuel gas. The fuel tanks 50 are also connected to the FC module 10 via piping 21 equipped with an on / off valve 20. When hydrogen is used as the fuel gas, these pipes 21 may be made of a material with high resistance to hydrogen embrittlement, such as austenitic stainless steel like SUS316L.

[0063] The tank case 51 is provided with a valve space 53, in which various valves, including a pressure reducing valve, are arranged. Through the various valves provided in the valve space 53, the piping 21 connects the fuel tank 50 and the FC module 10. Fuel gas, whose pressure has been reduced by the pressure reducing valve, flows through the piping 21 connecting the tank case 51 and the FC module 10. When the fuel gas is hydrogen gas, the fuel tank 50 may be filled with high-pressure hydrogen gas of, for example, 35 megapascals or more, but the hydrogen gas after passing through the pressure reducing valve may be reduced to, for example, about 2 atmospheres or less.

[0064] Next, refer to Figure 4. In addition to what is shown in Figure 3, Figure 4 shows multiple ECUs that communicate within the work vehicle 100, and user interface 1. Communication may be performed via CAN bus wiring, which functions as a path for electrical signals (thin solid lines). Figure 4 also shows a cooling system for achieving thermal management of the components. Specifically, the coolant path (dotted lines) is schematically shown.

[0065] As mentioned above, the first and second DC-DC converters 81 and 82 are each capable of outputting voltages of different magnitudes. These first and second DC-DC converters 81 and 82 are also provided with ECUs that control their respective voltage conversion circuits. These ECUs, like other ECUs, are supplied with a relatively low first voltage output by the first DC-DC converter 81.

[0066] In the example shown in Figure 4, the work vehicle 100 is equipped with a cooling system in which coolant is circulated by coolant pumps 31A and 31B. These coolant pumps 31A and 31B are located inside the FC module 10. The cooling system in this example includes a first radiator device 34A responsible for cooling the FC stack 11 and a second radiator device 34B responsible for cooling other electrical components. The cooling system has a flow path (first flow path) through which coolant flows between the FC stack 11 and the first radiator device 34A. The cooling system also has a flow path (second flow path) through which coolant flows between the electrical components, including the motor 70, and the second radiator device 34B. In the example shown in Figure 4, for example, a heater core 87 used for heating the cabin is provided, and the coolant flowing through the first radiator device 34A also flows through this heater core 87.

[0067] The user interface 1 includes an operating device 2 such as an accelerator pedal (or accelerator lever), a main meter 4, and an FC meter 6. The work vehicle 100 shown in Figure 4 further includes a control device 60 and a storage device 7. The control device 60 includes a main ECU 3 and an FC system ECU 5.

[0068] The main ECU 3 is connected to the FC system ECU 5, the control device 2, the main meter 4, and the storage device 7. The main ECU 3 controls the overall operation of the work vehicle 100. The main meter 4 can display various parameters that identify the driving or operating status of the work vehicle 100. The FC system ECU 5 controls the operation of the FC power generation system. The FC system ECU 5 is connected to the FC meter 6. The FC meter 6 can display various parameters that identify the operating status of the FC power generation system.

[0069] The storage device 7 includes one or more storage media, such as flash memory or magnetic disks. The storage device 7 stores various data generated by the main ECU 3 and the FC system ECU 5. The storage device 7 also stores computer programs that cause the main ECU 3 and the FC system ECU 5 to perform desired operations. Such computer programs may be provided to the work vehicle 100 via a storage medium (e.g., semiconductor memory or optical disk) or a telecommunications line (e.g., the internet). Such computer programs may be sold as commercial software.

[0070] The cells of the battery pack 80 are controlled by a battery management unit (BMU). The BMU includes circuits and a CPU (Central Processing Unit) that monitor the voltage of each battery cell, monitor for overcharging and over-discharging, and control cell balance. These circuits and the CPU may be mounted on a battery controller board.

[0071] 4. <Embodiment> (4.1. Basic configuration of work vehicles) Next, the basic configuration of an embodiment of the work vehicle according to this disclosure will be described with reference to Figures 5 and 6. Figure 5 is a schematic perspective view showing an example of the configuration of the work vehicle 200 in this embodiment. Figure 6 is a schematic side view showing an example of the configuration of the work vehicle 200 in this embodiment.

[0072] As shown in Figure 6, the work vehicle 200 in this embodiment includes a running gear including an FC module 10, a fuel tank 50, a motor 70, a driver's seat 107, an operating terminal 400, a control device 60, wheels 104, and a vehicle body 102. The work vehicle 200 has a configuration similar to that of the work vehicle 100 described with reference to Figure 1. The control device 60 includes a main ECU 3 and an FC system ECU 5, as shown in Figure 4. The control device 60 controls the operation of the work vehicle 200 by issuing commands to other ECUs, such as the ECU 73 in the inverter device 72 and the ECU 42 in the FC module 10. Each ECU includes a memory device (ROM) and may further include a processing circuit (or processor), such as an FPGA (Field Programmable Gate Array) and / or a GPU (Graphics Processing Unit). Each ECU, either alone or in cooperation with other ECUs while communicating with them, sequentially executes a computer program stored in the memory device that describes a set of instructions for performing at least one process, thereby performing the desired operation.

[0073] The operating terminal 400 is a terminal for the user to perform operations related to the movement of the work vehicle 200 and the operation of the implement 300, and is also called a virtual terminal (VT). The operating terminal 400 may be equipped with a touchscreen display and / or one or more buttons. The display may be a display such as a liquid crystal or organic light-emitting diode (OLED). By operating the touchscreen of the operating terminal 400, the user can perform various operations such as inputting information about the type of implement 300 and / or the type of work, changing control quantities for the work vehicle 200 such as vehicle speed or engine speed, switching the power of the work vehicle on / off, and switching the implement on / off. The operating terminal 400 may be configured to be detachable from the work vehicle 200. A user located away from the work vehicle 200 may control the operation of the work vehicle 200 by operating the detached operating terminal 400.

[0074] The work vehicle 200 may further include at least one sensing device for sensing the environment surrounding the work vehicle 200, and a processor for processing sensor data output from at least one sensing device. The sensing device may include, for example, multiple cameras, a LiDAR sensor, and multiple obstacle sensors. The sensor data output from the sensing device may be used, for example, for obstacle detection and positioning. Various ECUs mounted on the work vehicle 200 may be configured to cooperate in performing calculations and controls to achieve autonomous driving based on the sensor data output from the sensing device.

[0075] In this embodiment, the fuel tank 50 is supported by a fixed frame 120. The fixed frame 120 is fixed to the vehicle body 102, straddling the driver's seat 107. The fuel tank 50 is located above the driver's seat 107. However, the location of the fuel tank 50 is not limited to the illustrated example, and could be, for example, inside the front housing 110.

[0076] In this embodiment, the fixed frame 120 is a long-axis structure such as a pipe fixed to the vehicle body 102. The fixed frame 120 includes two frames located on the left and right sides of the work vehicle 200 (see Figure 5). The front part of the fixed frame 120 has a curved shape. Note that the shape of the fixed frame 120 shown is merely an example, and the shape of the fixed frame 120 is not limited to this example.

[0077] In this embodiment, the vehicle body 102 has a front frame 102A that rotatably supports the front wheel 104F and a transmission case 102B that rotatably supports the rear wheel 104R. One end (front end) of the fixed frame 120 is fixed to the front frame 102A. The other end (rear end) of the fixed frame 120 is fixed to the transmission case 102B. These fixings can be performed by appropriate methods such as welding or bolting, depending on the material of the fixed frame 120. The fixed frame 120 may be formed from, for example, metal, synthetic resin, carbon fiber, or composite material such as carbon fiber reinforced plastic or glass fiber reinforced plastic. The transmission case 102B includes a rear axle case, and the rear end of the fixed frame 120 may be fixed to the rear axle case. If the fixed frame 120 is formed from metal, part or all of its surface may be covered with synthetic resin.

[0078] As shown in Figure 6, the work vehicle 200 has a cabin 105 surrounding the driver's seat 107, located between the body 102 and the fixed frame 120. The driver's seat 107 is located at the rear of the cabin 105. In front of the driver's seat 107 is a steering handle (steering wheel) 106 for changing the direction of the front wheels 104F, for example. The cabin 105 has a cabin frame that constitutes the framework. A roof 109 is provided on top of the cabin frame. The cabin frame in this embodiment is a four-pillar type. The cabin 105 is supported by the transmission case 102B of the body 102, for example, via vibration-damping mounts. The user interface 1, described with reference to Figure 4, is located inside the cabin 105. Since the cabin 105 does not directly support the fuel tank 50, it does not need to be specially strengthened, and a cabin that has been used in conventional tractors can be used.

[0079] The work vehicle 200 is equipped with a mounting platform 51A that connects the left frame 120 and the right frame 120. The fuel tank 50 may be placed on the mounting platform 51A. If there are multiple fuel tanks 50, the multiple fuel tanks 50 may be housed in a fuel tank module 55. As shown in Figure 6, the fuel tank module 55 is equipped with a tank case 51 that houses the multiple fuel tanks 50. The left and right fixed frames 120 may be connected to each other by members other than the mounting platform 51A.

[0080] A coupling device 108 is provided at the rear end of the transmission case 102B, which is the rear of the vehicle body 102. The coupling device 108 includes, for example, a three-point support device (also referred to as a "three-point link" or "three-point hitch"), a PTO shaft, a universal joint, and a communication cable. The coupling device 108 allows the implement 300 to be attached to and detached from the work vehicle 200. The coupling device 108 can change the position or orientation of the implement 300 by raising and lowering the three-point link, for example, by a hydraulic device. Power can also be supplied from the work vehicle 200 to the implement 300 via the universal joint. The work vehicle 200 can pull the implement 300 and cause the implement 300 to perform a predetermined task (agricultural work). The coupling device 108 may also be provided at the front of the vehicle body 102. In that case, the implement 300 can be connected to the front of the work vehicle 200.

[0081] The implement 300 comprises, for example, a drive unit, a control unit, and a communication unit. The drive unit performs the operations necessary for the implement 300 to perform a predetermined task. The drive unit includes, for example, a hydraulic unit, an electric motor, or a pump, depending on the application of the implement 300. The control unit controls the operation of the drive unit. The control unit causes the drive unit to perform various operations in response to signals transmitted from the work vehicle 200 via the communication unit. It can also transmit signals from the communication unit to the work vehicle 200 according to the status of the implement 300.

[0082] The implement 300 shown in Figure 6 is a rotary tiller, but the implement 300 is not limited to a rotary tiller. For example, any implement such as a seeder, spreader, transplanter, mower, rake, baler, harvester, spreader, or harrow can be connected to the work vehicle 200 and used.

[0083] The work vehicle 200 shown in Figure 6 is capable of being operated by a person, but may also be designed for unmanned operation only. In that case, components necessary only for manned operation, such as the cabin 105, steering wheel 106, and driver's seat 107, do not need to be provided on the work vehicle 200. The unmanned work vehicle 200 can be driven autonomously or by remote control by a user.

[0084] (4.2. Discharge process when operation stops) When a command is issued to stop the operation of the work vehicle 200, the control device 60 of the work vehicle 200 stops the operation of the FC module 10 and performs a discharge process to consume the residual charge of the circuit group in the system. An example of this process will be explained below with reference to Figure 7.

[0085] Figure 7 is a flowchart showing an example of the operation of the control device 60 when stopping the operation of the work vehicle 200. The control device 60 stops the operation of the work vehicle 200 by executing the operations from steps S110 to S150 shown in Figure 7 while the work vehicle 200 is in operation.

[0086] In step S110, the control device 60 determines whether or not a stop command has been issued. A stop command is a command to stop the power supply to each electrical component of the work vehicle 200 and to stop the power generation by the fuel cell. A stop command may be issued, for example, when the user turns off the power switch (e.g., ignition switch) included in the operating device 2. If a stop command is issued, the process proceeds to step S120.

[0087] In step S120, the control device 60 stops the supply of oxidizing gas (e.g., air) to the FC module 10. Specifically, the FC system ECU 5 of the control device 60, in response to the command to stop operation, instructs the ECU 42 of the FC module 10 to close the shut-off valve 17 (see Figure 2). This cuts off the inflow of oxidizing gas to the FC stack 11, and power generation stops. In this embodiment, the supply of oxidizing gas to the FC stack 11 is stopped, but the system may be configured to stop the supply of fuel (hydrogen gas in this embodiment) instead. In step S120, the control device 60 also stops the operation of the air compressor 12.

[0088] Next, in step S130, the control device 60 stops the transmission of power from the motor 70 to the running gear. Specifically, the main ECU 3 of the control device 60 switches the multiple clutches in the power transmission system 74 from the connected state to the disconnected state, thereby stopping the transmission of power from the motor 70 to the running gear, including the axle and wheels 104. At this time, the main ECU 3 may keep the PTO clutch connected to maintain the transmission of power from the motor 70 to the PTO shaft 76, or it may disconnect the PTO clutch to stop the transmission of power from the motor 70 to the PTO shaft 76.

[0089] Next, in step S140, the control device 60 rotates the motor 70 to discharge residual charge in the circuit group connected to the motor 70. Specifically, the main ECU 3 in the control device 60 causes residual charge to be consumed by issuing a command to the ECU 73 in the inverter device 72 to rotate the motor 70. At this time, the motor 70 rotates, but the traction device remains stopped because power transmission from the motor 70 to the traction device is stopped. If power transmission from the motor 70 to the PTO shaft 76 is maintained, the PTO shaft 76 also rotates along with the rotation of the motor 70. By rotating the PTO shaft 76, the energy consumed can be increased compared to the case where the PTO shaft 76 is not rotated. This shortens the time required for discharge. On the other hand, if power transmission from the motor 70 to the PTO shaft 76 is stopped, the PTO shaft 76 does not rotate even if the motor 70 rotates. In this case, the energy consumed is relatively small, and it is possible to avoid the implement 300 connected to the PTO shaft 76 being unnecessarily driven when the operation of the work vehicle 200 is stopped.

[0090] Once the discharge of residual charge is complete, the process proceeds to step S150, in which the control device 60 stops the operation of the motor 70 and other electrical components. This stops the operation of the work vehicle 200.

[0091] The discharge process described above consumes the residual charge in the circuitry connected to the motor 70. The circuitry connected to the motor 70 includes, for example, the bridge circuit, boost circuit 40, and DC-DC converters 81 and 82 in the inverter device 72 shown in Figure 4. The boost circuit 40 functions as a boost converter that increases the DC voltage generated by the FC stack 11. The bridge circuit in the inverter device 72 functions as an inverter that converts the DC voltage output from the boost converter into an AC voltage and supplies it to the motor 70. These circuits may include multiple capacitors. The discharge process allows the residual charge in these capacitors to be discharged. This prevents unnecessary charge from remaining in the circuitry when the power to the work vehicle 200 is turned off.

[0092] In the discharge process of step S140, the control device 60 may discharge residual charge not only by rotating the motor 70, but also by operating other electrical components or charging the battery 80. For example, after stopping the supply of fuel or oxidizing gas to the FC module 10, the control device 60 may rotate the cooling fan in the radiator device 34A, which is responsible for cooling the FC stack 11 as shown in Figure 4, to discharge residual charge from the circuits within the FC module 10. By rotating not only the motor 70 but also the cooling fan for cooling the FC module 10, residual charge within the FC module 10 can be effectively discharged. Furthermore, in response to a command to stop operation, the control device 60 may rotate the cooling fan in the radiator device 34B, which is responsible for cooling electrical components other than the FC stack 11, to discharge residual charge remaining in the DC-DC converter 81, etc. In addition, the control device 60 may be configured to consume residual charge more efficiently by operating a hydraulic system including a hydraulic pump. However, when operating the hydraulic pump, a hydraulic locking mechanism may be used to prevent the lift arm, etc., in the coupling device 108 from operating.

[0093] As shown in Figures 3 and 4, the work vehicle 200 of this embodiment may include a first switch R1 located on the current path between the FC module 10 and the motor 70. The work vehicle 200 may further include a second switch R2 located on the current path between the battery 80 and the motor 70. The first switch R1 and the second switch R2 may be relays, for example. The on / off control of the first switch R1 and the second switch R2, respectively, may be performed by the main ECU 3 in the control device 60. Turning off the first switch R1 cuts off the power supply from the FC module 10 to the motor 70. Turning off the second switch R2 cuts off the power supply from the battery 80 to the motor 70.

[0094] The control device 60 may, in response to a command to stop operation, turn off the first switch R1, and then discharge residual charge by rotating the motor 70 or operating other electrical components. At this time, the control device 60 may also operate other electrical components such as cooling fans in the radiator devices 34A and 34B. By turning off the first switch R1, residual charge discharge can be performed while the power supply from the FC module 10 to the motor 70 is cut off. The control device 60 may also, in response to a command to stop operation, turn off the first and second switches, and then discharge residual charge by rotating the motor 70 or operating other electrical components. This allows residual charge discharge to be performed while the power supply from the FC module 10 and battery 80 to the motor 70 is cut off.

[0095] Figure 8 is a flowchart illustrating an example of an operation in which residual charge is discharged by operating the motor and other electrical components with switches R1 and R2 turned off. The flowchart in Figure 8 is the same as the flowchart in Figure 7, except that step S140 is replaced by steps S240 and S250. In the example in Figure 8, after stopping the transmission of power from the motor 70 to the traction unit in step S130, the process proceeds to step S240, where the control device 60 turns off the first switch R1 and the second switch R2. Next, in step S250, the control device 60 operates the motor 70 and other electrical components (e.g., cooling fans in radiator units 34A and 34B, hydraulic systems, and / or electric pumps, etc.) to discharge residual charge. This operation allows for efficient discharge of the peripheral circuits of the motor 70 and the circuits within the FC module 10.

[0096] The control device 60 may change the discharge process depending on whether the implement 300 is connected to the PTO shaft 76 or not. For example, if the implement 300 is connected to the PTO shaft 76, the control device 60 may rotate the motor 70 with power transmission from the motor 70 to the PTO shaft 76 stopped, and if the implement 300 is not connected to the PTO shaft 76, the control device 60 may rotate the motor 70 with power transmission from the motor 70 to the PTO shaft 76 maintained. Such control allows the discharge method to be appropriately switched depending on the presence or absence of the implement 300.

[0097] Figure 9 is a flowchart showing an example of an operation that changes the discharge process depending on whether or not the implement 300 is connected to the PTO shaft 76. The flowchart shown in Figure 9 is the same as the example shown in step S8 in Figure 8, except that steps S241, S242, and S243 are added between steps S240 and S250. In the example in Figure 9, after turning off switches R1 and R2 in step S240, the control device 60 determines whether or not the implement is connected to the PTO shaft 76. Whether or not the implement 300 is connected to the PTO shaft 76 can be determined, for example, based on a signal transmitted from the implement 300 to the work vehicle 200. If the implement is connected, the process proceeds to step S242. If the implement is not connected, the process proceeds to step S243.

[0098] In step S242, the control device 60 disengages the PTO clutch. This stops the transmission of power from the motor 70 to the PTO shaft 76.

[0099] In step S243, the control device 60 engages the PTO clutch. This maintains power transmission from the motor 70 to the PTO shaft 76.

[0100] In the subsequent step S250, the control device 60 operates the motor 70 and other electrical components to discharge residual charge. Then, in step S150, the operation of the motor 70 and other electrical components is stopped. This stops the operation of the work vehicle 200.

[0101] According to the control shown in Figure 9, when the implement 300 is connected to the work vehicle 200, it is possible to avoid the implement 300 being activated by the unnecessary rotation of the PTO shaft 76 when the work vehicle 200 stops operating. On the other hand, when the implement 300 is connected to the work vehicle 200 do not haveIn this state, rotating the PTO shaft increases energy consumption, allowing for more efficient discharge. Thus, it becomes possible to selectively implement the appropriate discharge method depending on the presence or absence of the implement 300.

[0102] In each of the above embodiments, the discharge process is performed when a command is issued to turn off the power to the work vehicle 100. The same discharge process may be performed not only when the power is turned off, but also, for example, when a command is issued to idle stop the FC module 10 (temporary stop of the FC module 10). By performing the discharge process during idle stop, the deterioration of the fuel cell can be suppressed.

[0103] The configurations and operations of the embodiments described above are illustrative only, and this disclosure is not limited to the embodiments described above. For example, the various embodiments described above may be combined as appropriate to form other embodiments.

[0104] As described above, this disclosure includes a work vehicle, a control device for a work vehicle, and a method for controlling a work vehicle, as described in the following items.

[0105] [Item 1] A fuel cell module having a fuel cell stack, At least one fuel tank for containing fuel to be supplied to the fuel cell stack, A motor connected to the aforementioned fuel cell module, A traveling device driven by the aforementioned motor, The motor drives the power take-off shaft to which the implement is connected, Control device and Equipped with, The control device, in response to a command to stop operation, stops the supply of the fuel or oxidizing gas to the fuel cell stack, and then rotates the motor while stopping the transmission of power from the motor to the traction device to discharge residual charge in the group of circuits connected to the motor. Work vehicle.

[0106] [Item 2] The control device performs the discharge by rotating the motor while maintaining power transmission from the motor to the power take-off shaft. Work vehicles as described in item 1.

[0107] [Item 3] The control device performs the discharge by rotating the motor while stopping the transmission of power from the motor to the power take-off shaft. Work vehicles as described in item 1.

[0108] [Item 4] The system further comprises a first switch provided on the current path between the fuel cell module and the motor, The control device, in response to the command to stop operation, turns off the first switch and then performs the discharge by rotating the motor. A work vehicle listed in any of items 1 through 3.

[0109] [Item 5] The fuel cell module and the battery connected to the motor, A second switch is provided on the current path between the battery and the motor, Furthermore, The control device, in response to the command to stop operation, turns off the first switch and the second switch, and then performs the discharge by rotating the motor. Work vehicles as described in item 4.

[0110] [Item 6] The aforementioned group of circuits A boost converter for boosting the DC voltage generated by the fuel cell stack, An inverter that converts the DC voltage output from the boost converter into an AC voltage and supplies it to the motor, A work vehicle, including any of the vehicles listed in items 1 through 5.

[0111] [Item 7] The fuel cell module is further provided with a cooling fan for cooling the module. The control device, in response to the command to stop operation, stops supplying the fuel or oxidizing gas to the fuel cell module, and then rotates the cooling fan to discharge the residual charge from the fuel cell module. A work vehicle listed in any of items 1 through 6.

[0112] [Item 8] The aforementioned work vehicle is an agricultural machine, or any of the work vehicles listed in items 1 to 7.

[0113] [Item 9] A control device for a work vehicle comprising: a fuel cell module having a fuel cell stack; at least one fuel tank containing fuel to be supplied to the fuel cell stack; a motor connected to the fuel cell module; a running gear driven by the motor; and a power take-off shaft driven by the motor to which an implement is connected, In response to a command to stop operation, the supply of the fuel or oxidizing gas to the fuel cell module is stopped, and then the motor is rotated while the power transmission from the motor to the traction device is stopped to discharge residual charge in the group of circuits connected to the motor. Control device.

[0114] [Item 10] A control method for a work vehicle comprising: a fuel cell module having a fuel cell stack; at least one fuel tank containing fuel to be supplied to the fuel cell stack; a motor connected to the fuel cell module; a running gear driven by the motor; and a power take-off shaft driven by the motor to which an implement is connected, wherein In response to a command to stop operation, the supply of the fuel or oxidizing gas to the fuel cell module is stopped, After stopping the supply of the aforementioned fuel, the motor is rotated while the power transmission from the motor to the traction device is stopped, thereby discharging residual charge in the circuit group connected to the motor. A control method including [Industrial applicability]

[0115] The technology disclosed herein can be applied to work vehicles such as agricultural tractors, harvesters, rice transplanters, riding cultivators, and vegetable transplanters. [Explanation of symbols]

[0116] 1...User interface, 2...Operating device, 3...Main ECU, 4...Main meter, 5...FC system ECU, 6...FC meter, 7...Storage device, 10...Fuel cell module, 11...FC stack, 40...Boost circuit, 34...Radiator device, 40...Boost circuit, 42...Control device (ECU), 50...Fuel tank, 51...Tank case, 60...Control device, 70...Motor, 71...Output shaft, 72...Inverter device 74...Power transmission system, 76...Power take-off (PTO) shaft, 80...Battery pack, 81...First DC-DC converter, 82...Second DC-DC converter, 83...Storage battery, 85...Air conditioning compressor, 86...Heater, 100...Work vehicle, 102...Body, 102A...Front frame, 102B...Transmission case, 104...Wheels, 104F...Front wheels, 104R...Rear wheels, 107...Driver's cab, 120...Fixed frame

Claims

1. A fuel cell module having a fuel cell stack, At least one fuel tank for containing fuel to be supplied to the fuel cell stack, A motor connected to the aforementioned fuel cell module, A traveling device driven by the aforementioned motor, The motor drives the power take-off shaft to which the implement is connected, Control device and Equipped with, The control device is In response to a command to stop operation, the supply of the fuel or oxidizing gas to the fuel cell stack is stopped, and then the motor is rotated while the power transmission from the motor to the traction device is stopped to discharge residual charge in the group of circuits connected to the motor. When performing the discharge, if an implement is connected to the power takeoff shaft, the motor is rotated while the power transmission from the motor to the power takeoff shaft is stopped. When performing the discharge, if an implement is not connected to the power takeoff shaft, the motor is rotated while maintaining power transmission from the motor to the power takeoff shaft. Work vehicle.

2. The system further includes a first switch provided on the current path between the fuel cell module and the motor, The control device, in response to the command to stop operation, turns off the first switch and then performs the discharge by rotating the motor. The work vehicle according to claim 1.

3. The fuel cell module and the battery connected to the motor, A second switch is provided on the current path between the battery and the motor, Furthermore, The control device, in response to the command to stop operation, turns off the first switch and the second switch, and then performs the discharge by rotating the motor. The work vehicle according to claim 2.

4. The aforementioned group of circuits A boost converter for boosting the DC voltage generated by the fuel cell stack, An inverter that converts the DC voltage output from the boost converter into an AC voltage and supplies it to the motor, A work vehicle according to any one of claims 1 to 3, including the work vehicle described in any one of claims 1 to 3.

5. The fuel cell module is further provided with a cooling fan for cooling the module. The control device, in response to the command to stop operation, stops supplying the fuel or oxidizing gas to the fuel cell module, and then rotates the cooling fan to discharge the residual charge from the fuel cell module. A work vehicle according to any one of claims 1 to 3.

6. The work vehicle according to any one of claims 1 to 3, wherein the work vehicle is an agricultural machine.

7. A control device for a work vehicle comprising: a fuel cell module having a fuel cell stack; at least one fuel tank containing fuel to be supplied to the fuel cell stack; a motor connected to the fuel cell module; a running gear driven by the motor; and a power take-off shaft driven by the motor to which an implement is connected, In response to a command to stop operation, the supply of the fuel or oxidizing gas to the fuel cell module is stopped, and then the motor is rotated while the power transmission from the motor to the traction device is stopped to discharge residual charge in the circuit group connected to the motor. When performing the discharge, if an implement is connected to the power takeoff shaft, the motor is rotated while the power transmission from the motor to the power takeoff shaft is stopped. When performing the discharge, if an implement is not connected to the power takeoff shaft, the motor is rotated while maintaining power transmission from the motor to the power takeoff shaft. Control device.

8. A control method for a work vehicle comprising: a fuel cell module having a fuel cell stack; at least one fuel tank containing fuel to be supplied to the fuel cell stack; a motor connected to the fuel cell module; a running gear driven by the motor; and a power take-off shaft driven by the motor to which an implement is connected, wherein In response to a command to stop operation, the supply of the fuel or oxidizing gas to the fuel cell module is stopped, After stopping the supply of the aforementioned fuel, the motor is rotated while the power transmission from the motor to the traction device is stopped, thereby discharging residual charge in the circuit group connected to the motor. Includes, When performing the discharge, if an implement is connected to the power takeoff shaft, the motor is rotated while the power transmission from the motor to the power takeoff shaft is stopped. When performing the discharge, if an implement is not connected to the power takeoff shaft, the motor is rotated while maintaining power transmission from the motor to the power takeoff shaft. Control method.

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