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

Abstract

This work vehicle comprises: a fuel cell module which has a fuel cell stack; at least one fuel tank which accommodates fuel to be supplied to the fuel cell stack; a motor which is connected to the fuel cell module; a power take-off shaft which is driven by the motor and to which an implement is connected; and a control device. The control device can be operated in a plurality of control modes. The plurality of control modes include a normal mode and an output limit mode in which an upper limit value of power supplied to the motor from the fuel cell module is smaller than that in the normal mode. The control device changes the upper limit value of the power supplied to the motor in the output limit mode according to the type of the implement connected to the power take-off shaft and / or the type of work executed by the implement.

Description

Technical Field

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

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 work vehicle equipped with a fuel cell (Fuel Cell: FC) and driven by the generated power of the fuel cell.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a work vehicle equipped with a fuel cell module, there may be a case where it is necessary to suppress the output of the motor, such as when the remaining amount of fuel is low, or when the fuel cell module or the motor becomes high temperature.

[0007] This disclosure provides a technology for appropriately limiting motor output in situations where it is necessary to suppress motor output. [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 power take-off shaft driven by the motor and to which an implement is connected; and a control device for controlling the power supplied from the fuel cell module to the motor. The control device is capable of operating in a plurality of control modes. The plurality of control modes include a normal mode and an output-limiting mode in which the upper limit of the power supplied from the fuel cell module to the motor is smaller than that of the normal mode. The control device modifies the upper limit of the power supplied to the motor in the output-limiting mode depending on the type of implement connected to the power take-off shaft and / or the type of work performed by the implement.

[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 embodiments of the present disclosure, in situations where it is necessary to suppress motor output, it becomes possible to appropriately limit the motor output depending on the type of implement and / or the type of work. [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 7A] This figure shows an example of a table illustrating the relationship between the type of implement and the upper limit of the power supplied to the motor. [Figure 7B] This figure shows an example of a table illustrating the relationship between the type of implement, the type of work, and the upper limit of the power supplied to the motor. [Figure 7C] This figure shows another example of a table illustrating the relationship between the type of implement, the type of work, and the upper limit of the power supplied to the motor. [Figure 8] This flowchart shows an example of an operation performed by the control device. [Figure 9] This diagram schematically illustrates an example of a display on a display device. [Figure 10] This diagram schematically illustrates other examples of displays in display devices. [Modes for carrying out the invention]

[0012] Embodiments of the present disclosure will be described below. However, detailed descriptions may be omitted where not necessary. For example, detailed descriptions of well-known matters and overlapping descriptions of substantially identical 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 so that those skilled in the art can 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 illustrative, 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 for 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 mower, or a ride-on lawn mower, or a vehicle used for non-agricultural purposes such as a construction work vehicle or a snowplow. 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 travel".

[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 can a work vehicle such as a tractor function as "agricultural machinery" alone, but in some cases, the implement attached to or towed by the work vehicle and the entire work vehicle can 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 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 to the right perpendicular to the "forward direction" will be referred to as the "right direction", and the direction extending to the left 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 respectively indicated by arrows of "front", "back", "right", and "left". 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.

[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] In the embodiments described later, the work vehicle 100 includes a driver's seat supported by a vehicle body 102. The driver's seat may be enclosed by a cabin supported by the vehicle body 102. In the embodiments described later, the FC module 10 is located in front of the driver's seat, and the fuel tank 50 is located above the driver's seat. Such an FC module 10 and fuel tank 50 are housed in at least one "container." The "container" functions, for example, as a housing and serves to protect the FC module 10 and fuel tank 50 from sunlight and the elements. Such a containment can also control the spread of fuel gas into the atmosphere if fuel gas leaks from the FC module 10 or fuel tank 50, making it easier to detect the fuel gas.

[0027] The FC module 10 may be housed in a front housing, for example, called a "bonnet." The front housing is part of the "housing." The front housing is supported by the front of the vehicle body 102 (front frame 102A). The fuel tank 50 may 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 FC power generation system 180 is used not only for the running of the work vehicle 100 but also for the operation of implements towed or attached by the work vehicle 100.

[0030] The FC power generation system 180 in the illustrated example includes an FC module 1 ten 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] As main components, the FC module 10 includes 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 "anode gas" which is fuel and "cathode gas" which is an oxidizing gas. The FC stack 11 in this example is a solid polymer fuel cell. The FC stack 11 has a stack structure in which a plurality of single cells (fuel cells) are stacked. A single cell includes, for example, an electrolyte membrane formed from an ion exchange membrane, an anode electrode formed on one surface of the electrolyte membrane, a cathode electrode formed on the other surface of the electrolyte membrane, and a pair of separators that sandwich the anode electrode and the cathode electrode from both sides. The voltage generated in a single cell is, for example, 1 volt or less. For this reason, in the FC stack 11, for example, 300 or more single cells are connected in series so as 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 used in the above reaction is called the "anode-off gas," and the cathode gas 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 (hereinafter also referred to as the "inverter circuit") that includes 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 transmission case 102B in Figure 1 may be divided into a front case (transmission case) that houses the clutch and transmission, etc., and a rear case (differential gear case) that houses the rear differential gear, 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 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.

[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 electrical equipment necessary for agricultural work, electrical equipment necessary for the operation of the fuel cell power generation system is also installed, and therefore the appropriate voltage levels for each electrical equipment may differ. According to the embodiments of this disclosure, it becomes possible to supply an appropriate voltage level.

[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] The fuel tank 50 is equipped with a sensor S4 for measuring the remaining amount of fuel in the fuel tank 50. Furthermore, a temperature sensor may be provided for measuring the temperature inside the fuel tank 50. An example of sensor S4 is a pressure sensor that measures the fuel pressure corresponding to the remaining amount of fuel. The pressure sensor acquires residual pressure data indicating the remaining fuel pressure in the fuel tank 50.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The user interface 1 includes an operating device 2 such as an accelerator pedal (or accelerator lever), an audio output device 8, 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.

[0069] The main ECU 3 is connected to the FC system ECU 5, the control device 2, the audio output device 8, 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.

[0070] 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.

[0071] An example of the audio output device 8 is a buzzer or a speaker. The audio output device 8 may be controlled by the main ECU 3. The audio output device 8 may, for example, output a voice prompting refueling.

[0072] The cells of the battery pack 80 are controlled by a battery management unit (BMU). The BMU includes temperature sensors such as thermistors to measure the cell temperature of the battery, a voltage monitor for each battery cell, circuits and a CPU (Central Processing Unit) for monitoring overcharging and over-discharging, and cell balance control. These circuits and the CPU may be mounted on a battery controller board.

[0073] In the example shown in Figure 4, the inverter device 72 is equipped with a temperature sensor S5. The temperature sensor S5 measures the temperature of the inverter device 72. In addition, a temperature sensor S6 is provided near the motor 70. The temperature sensor S6 measures the temperature of the motor 70.

[0074] 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.

[0075] As shown in Figure 6, the work vehicle 200 in this embodiment includes an FC module 10, a fuel tank 50, a sensor S4 (see Figure 3 or Figure 4), a motor 70, a driver's seat 107, a control device 60, an operating terminal 400, 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.

[0076] 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 variables for the work vehicle 200 such as vehicle speed or engine speed, and switching the implement on / off. The touchscreen of the operating terminal 400 serves as both a display device and an input device. 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. Different input devices and display devices may be used. For example, personal computers (PCs), laptop computers, tablet computers, smartphones, or other computers or their peripherals may be used as input and display devices. Meters 4 and 6 shown in Figure 4 also function as display devices.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] (4.2. Operation in output limit mode) The control device 60 controls the operation of the work vehicle 200. For example, the control device 60 controls the power supplied from the FC module 10 to the motor 70. As shown in Figure 4, the power output from the FC module 10 is supplied to the motor 70 via the inverter device 72. The control device 60 can control the power supplied to the motor 70 by, for example, issuing a command to the ECU 42 to change the amount of power generated by the FC module 10, or by issuing a command to the ECU 73 of the inverter device 72 to change the output power of the inverter circuit. There is a relationship between the power supplied to the motor 70 (i.e., the input power of the motor 70) and the mechanical output of the motor 70 (hereinafter referred to as "motor 70 output" or "motor output"): Input power = Mechanical output + Loss. Therefore, the control device 60 can control the output of the motor 70 by controlling the power supplied from the FC module 10 to the motor 70.

[0088] The control device 60 in this embodiment can operate in multiple control modes. These multiple control modes include a normal mode and an output limit mode. The output limit mode is a mode in which the output of the motor 70 is limited in order to reduce fuel consumption and suppress the temperature rise of the equipment. Since fuel consumption is suppressed in the output limit mode, the output limit mode can also be called the "eco mode". The control device 60 may be configured to switch from the normal mode to the output limit mode, for example, when the amount of fuel remaining in the fuel tank 50 is low, or when the temperature of equipment such as the FC module 10, inverter device 72, or motor 70 becomes high. In the output limit mode, the upper limit of the power supplied from the FC module 10 to the motor 70 and the upper limit of the output of the motor 70 are limited to be lower than in the normal mode. This control can be achieved, for example, by limiting the amount of power generated by reducing the amount of fuel or oxidizing gas supplied to the FC stack 11, or by limiting the output power of the inverter circuit by switching control of the inverter circuit. In the output limit mode, for example, the vehicle speed may not increase much even if the accelerator pedal is pressed hard.

[0089] In this embodiment, the control device 60 is configured to change the upper limit of the power supplied to the motor 70 in output limit mode according to the type of implement 300 connected to the PTO shaft 76 and / or the type of work performed by the implement 300. The control device 60 may be configured to switch from normal mode to output limit mode when, for example, the amount of fuel remaining in the fuel tank 50 measured by the sensor S4 shown in Figure 4 falls below a threshold. Alternatively, the control device 60 may be configured to switch from normal mode to output limit mode when the temperature of the coolant in the FC module 10 measured by the temperature sensor S3 shown in Figure 2 exceeds a threshold (e.g., 90°C or 100°C). Conversely, the control device 60 may switch from normal mode to output limit mode when the temperature of the FC module 10 measured by the temperature sensor S3 falls below another threshold (e.g., 0°C or -10°C). Furthermore, the control device 60 may switch from normal mode to output limit mode not limited to the temperature of the FC module 10, but also when the temperature measured by, for example, the temperature sensor S5 of the inverter device 72 or the temperature sensor S6 of the motor 70 exceeds a threshold. Alternatively, the system may switch from normal mode to output limiting mode if the temperature obtained from a sensor measuring the temperature of equipment or circuits other than the FC module 10, inverter device 72, and motor 70 exceeds a threshold.

[0090] As mentioned above, the types of implements include, for example, rotary tillers, seeders, or spreaders. The types of work performed by the implements include tilling, sowing, or fertilizing. However, there is not necessarily a one-to-one correspondence between the type of implement and the type of work. For example, if the implement is a rotary tiller, the types of work may include multiple types such as tilling, puddling, or ridging. Even when performing the same type of work, the workload may differ depending on the circumstances. For example, even when performing the same work using the same implement, the rotational speed of the PTO shaft 76 may be changed depending on the condition of the work site, etc. In such cases, the control device 60 may change the upper limit of the power supplied to the motor 70 according to the workload.

[0091] The control device 60, for example, obtains identification information of the implement 300 connected to the PTO shaft 76 and identifies the type of implement 300 based on the identification information. The work vehicle 200 and the implement 300 can communicate in accordance with ISOBUS standards, such as ISOBUS-TIM. In this way, the control device 60 of the work vehicle 200 can obtain identification information of the implement 300 by communicating with the implement 300. Alternatively, the control device 60 may identify the type of implement 300 connected to the PTO shaft 76 and / or the type of work performed by the implement 300 based on information about the type of implement 300 and / or the type of work entered by the user, for example, via an input device such as an operation terminal 400.

[0092] The sensor S4 shown in Figure 4 acquires data on the remaining fuel pressure in the fuel tank 50. The control device 60 can estimate the remaining fuel amount based on the remaining pressure data output from the sensor S4. In this embodiment, the remaining fuel amount thus estimated may be referred to as the remaining fuel amount measured by the sensor S4. The remaining fuel amount may be expressed as a percentage (%) of the tank capacity when full. The control device 60 may be configured to determine whether it is necessary to switch from normal mode to output limit mode based on the remaining fuel amount measured by the sensor S4.

[0093] The temperature sensor S3 shown in Figure 2 measures the temperature of the coolant flowing through the coolant discharge pipe 33. The control device 60 may be configured to use the temperature measured by the temperature sensor S3 as the temperature of the FC module 10 and to determine whether it is necessary to transition from normal mode to output limit mode based on this temperature. For example, if the temperature measured by the temperature sensor S3 falls outside a preset temperature range, the control device may transition from normal mode to output limit mode. The temperature of the FC module 10 may be measured not only by the temperature sensor S3 that measures the temperature of the coolant flowing through the coolant discharge pipe 33, but also by temperature sensors that measure the temperature of other parts of the FC module 10. Alternatively, a temperature sensor S5 that measures the temperature of the inverter device 72, or a temperature sensor S6 that measures the temperature of the motor 70 may be used. In that case, the control device 60 may be configured to determine whether it is necessary to transition from normal mode to output limit mode based on the measured temperature of the inverter device 72 or the motor 70.

[0094] The storage device 7 shown in Figure 4 stores data that defines the correspondence between the type of implement and / or the type of operation and the upper limit of the power supplied from the FC module 10 to the motor 70. The control device 60 may be configured to determine the upper limit of the power supplied from the FC module 10 to the motor 70 or the motor output based on this data. This data may be, for example, data such as a lookup table (hereinafter simply referred to as "table").

[0095] Figure 7A is a diagram showing an example table illustrating the relationship between the type of implement and the upper limit of the power supplied to the motor 70 (i.e., the input power of the motor 70). In the example table shown in Figure 7A, the implement types include five types: rotary, spreader, seeder, mower, and harrow. The table lists the corresponding upper limit of power for each type of implement. For example, if the implement 300 attached to the work vehicle 200 is a rotary, the upper limit of power supplied to the motor 70 is P1 (kW), and if the implement 300 is a spreader, the upper limit of power is P2 (kW). In this example, the upper limit of power supplied to the motor 70 may be set to different values ​​depending on the type of implement 300.

[0096] Figure 7B is an example of a table showing the relationship between the type of implement, the type of work, and the upper limit of the power supplied to the motor 70. In the example table shown in Figure 7B, the implement types include five types: rotary tiller, spreader, seeder, mower, and harrow, and the types of work include seven types: tilling, puddling, ridging, fertilizing, seeding, mowing, and soil crushing. The table lists the corresponding upper limit of power for each pair of implement type and type of work. For example, the upper limit of power supplied to the motor 70 when the work vehicle 200 is towing a rotary tiller and performing tilling work is P11 (kW), and the upper limit of power when the work vehicle 200 is towing a spreader and performing fertilizing work is P21 (kW). In this example, the upper limit of power supplied to the motor 70 may be set to different values ​​depending on the type of implement 300 and also depending on the type of work. Alternatively, a table from which information on the type of implement has been removed from the table shown in Figure 7B may be used. In that case, the upper limit of the power supplied to the motor 70 may be set to different values ​​depending on the type of work.

[0097] Figure 7C shows another example of a table illustrating the relationship between the type of implement, the type of work, and the upper limit of the power supplied to the motor 70. In the table shown in Figure 7C, rotary tillage work is classified into three stages according to the magnitude of the load. The rest is the same as the table shown in Figure 7B. For example, when the work vehicle 200 is towing the rotary tillage and performing heavy-load tillage work, the upper limit of the power supplied to the motor 70 is P111 (kW), when performing moderate-load tillage work, the upper limit of the power is P112 (kW), and when performing light-load tillage work, the upper limit of the power is P113 (kW). As in this example, the type of work may be classified into multiple stages according to the load of the work.

[0098] In this embodiment, the control device 60 can determine an upper limit of power corresponding to the type of implement 300 connected to the PTO shaft 76 and / or the type of operation by referring to a table as illustrated in Figures 7A, 7B, or 7C. In output limiting mode, the control device 60 limits the power supplied to the motor 70 so as not to exceed the determined upper limit of power. For example, if the power is likely to exceed the upper limit when the user operates the accelerator pedal or accelerator lever included in the operating device 2 to give an acceleration command or a command to increase the rotational speed of the PTO shaft 76, the control device 60 limits the power to below the upper limit. This limits the motor output and suppresses fuel consumption and heat generation of the equipment.

[0099] While the work vehicle 200 is in operation, the control device 60 may display information on a display device such as an operation terminal 400 indicating whether the current mode is normal mode or output limit mode. In addition, in output limit mode, the control device may display information on the display device indicating that the motor output is actually being limited.

[0100] The work vehicle 200 is equipped with a battery (battery pack 80 shown in Figure 4) connected to the FC module 10 and the motor 70. In output limiting mode, the control device 60 determines whether or not to charge the battery, and if charging is performed, it may increase the power output from the FC module 10 compared to when charging is not performed. For example, if charging is performed, the power output from the FC module 10 may be increased by the amount of power required for charging compared to when charging is not performed. The control device 60 may be configured to determine whether or not to charge the battery based on, for example, the battery's state of charge (SOC) and the battery temperature.

[0101] Figure 8 is a flowchart illustrating an example of an operation performed by the control device 60. The operation shown in Figure 8 begins when the work vehicle 200 is operating in normal mode. In the example shown in Figure 8, the control device 60 first acquires measurement data from each of several sensors in the work vehicle 200. For example, the control device 60 may be configured to acquire data indicating the remaining fuel level measured by the sensor S4 of the fuel tank 50, data indicating the temperature of the FC module 10 measured by the temperature sensor S3 of the FC module 10, and data indicating the state of charge (SOC) and battery cell temperature measured by the BMU of the battery pack 80. The control device 60 may also acquire temperature data measured by the temperature sensor S5 of the inverter device 72 or the temperature sensor S6 of the motor 70.

[0102] In the subsequent step S120, the control device 60 determines whether or not to start the output limit mode based on the acquired data. For example, the control device 60 may be configured to determine to start the output limit mode when the remaining amount of fuel measured by the sensor S4 falls below a first threshold. If the sensor S4 is a pressure sensor that measures the internal pressure in the fuel tank 50, the control device 60 may determine that the remaining amount of fuel has fallen below the first threshold when the measured pressure falls below a predetermined threshold. In addition to, or instead of, the control device 60 may determine to start the output limit mode when the temperature of the FC module 10 measured by the temperature sensor S3 exceeds a second threshold. The second threshold may be set to the upper limit of the appropriate temperature range for the FC module 10, or a value close to it, such as 80°C, 90°C, or 100°C. The control device 60 may also determine to start the output limit mode when the temperature of the FC module 10 measured by the temperature sensor S3 falls below a third threshold that is smaller than the second threshold. The third threshold can be set to the lower limit of an appropriate temperature range or a value close to it, for example, 0°C, -10°C, or -20°C. Alternatively, the control device 60 may determine to start the output limiting mode if the temperature of the inverter device 72 measured by the temperature sensor S5, or the temperature of the motor 70 measured by the temperature sensor S6, falls outside their respective appropriate temperature ranges. If No is determined in step S120, the process returns to step S110. If No is determined in step S120, the process proceeds to step S130.

[0103] In step S130, the control device 60 acquires setting information regarding the type of implement 300 and / or the type of work performed by the implement 300. The setting information may be generated, for example, based on information entered by the user using the operation terminal 400 or other input device. Alternatively, the setting information may be generated based on the identification information of the implement 300 sent from the implement 300 to the work vehicle 200. Based on this setting information, the control device 60 can identify the type of implement 300 connected to the work vehicle 200 and / or the type of work performed by the implement 300.

[0104] In the subsequent step S140, the control device 60 sets an upper limit for the input power of the motor 70 corresponding to the type of implement 300 and / or the type of work identified based on the setting information. For example, the control device 60 can read data from a table such as that shown in Figure 7A, 7B, or 7C from the storage device 7, and by referring to this data, determine an upper limit for the input power of the motor 70 corresponding to the type of implement 300 and / or the type of work installed on the work vehicle 200.

[0105] In the following step S150, the control device 60 determines whether or not to charge the battery. Whether or not to charge the battery depends on the remaining charge and / or the battery temperature. For example, the control device 60 may decide to charge the battery if the state of charge (SOC) of the battery pack 80 shown in Figure 4, which is monitored by the BMU, is below a threshold (e.g., 80% or 90%), and the battery temperature, which is monitored by the BMU, is within a predetermined range (e.g., 0°C to 60°C). Conversely, the control device 60 may decide not to charge the battery if the battery's SOC is above the threshold, or if the battery temperature is outside the predetermined range. If the battery is to be charged, the process proceeds to step S160. If the battery is not to be charged, the process proceeds to step S170.

[0106] In step S160, the control device 60 sets the upper limit of the output power of the FC module 10 to the sum of the upper limit of the input power of the motor 70 and a preset value α. α may be set to a value equivalent to, for example, the sum of the power required to charge the battery and the power required to drive other electrical components such as DC-DC converters 81 and 82.

[0107] In step S170, the control device 60 sets the upper limit of the output power of the FC module 10 to the sum of the upper limit of the input power of the motor 70 and a preset value β (<α). β can be set to, for example, the total power required to drive electrical components other than the battery, such as DC-DC converters 81 and 82. β is smaller than α by the amount of power required to charge the battery.

[0108] After step S160 or S170, the control device 60 limits the amount of power generated by the FC module 10 so as not to exceed the set upper limit of the output power of the FC module 10. For example, even in situations where the amount of power generated should be increased, such as when driving while the implement 300 is performing a heavy load, the control device 60 limits the amount of power generated so as not to exceed the upper limit of the output power of the FC module 10. The control device 60 can control the amount of power generated by the FC stack 11 by sending commands to the control unit (ECU) 42 of the FC module 10 to control the operation of the air compressor 12, fuel circulation pump 24, coolant pump 31, and various valves. When operating in output limit mode, the control device 60 may display information indicating that it is in output limit mode on the operation terminal 400 or on a display device such as meters 4, 6.

[0109] When operating in output limit mode, the control device 60 sequentially acquires measurement data from each sensor and, similar to step S120, determines whether the conditions for operating in output limit mode are met. If these conditions are no longer met, the control device 60 returns from output limit mode to normal mode. For example, if the temperature measured by each temperature sensor is within a specified range and the remaining amount of fuel in the fuel tank 50 is above a threshold, the control device 60 may be configured to return from output limit mode to normal mode. Thereafter, the operation shown in Figure 8 is performed again.

[0110] As described above, the control device 60 in this embodiment switches from normal mode to output limit mode when predetermined conditions are met based on measurement data from one or more sensors. At this time, the control device 60 reduces the upper limit of the power supplied to the motor 70 to a value corresponding to the type of implement 300 connected to the work vehicle 200 and / or the type of work. This allows the system to switch to output limit mode, for example, when the fuel level is low or when the temperature of equipment such as the FC module 10 is not within an appropriate range, thereby suppressing fuel consumption and equipment heat generation. Furthermore, the upper limit of the output power of the FC module 10 in output limit mode can be appropriately set according to the type of implement 300 and / or the type of work. This allows the system to effectively suppress fuel consumption and equipment heat generation according to the magnitude of the work load performed by the implement 300.

[0111] (4.3. Examples of displays on display devices) When the control device 60 switches from normal mode to output limit mode, it may display information on the display device indicating that it is in output limit mode. An example of such information display is described below.

[0112] Figure 9 is a schematic diagram illustrating an example of a display in a display device. The display devices illustrated in Figure 9 are a main meter 4 and an FC meter 6. In this example, both the main meter 4 and the FC meter 6 are digital meters. However, digital meters are not mandatory. The display of the main meter 4 includes, for example, information regarding the speed of the work vehicle 200, the time, fuel consumption, turn signal indicators, parking brake lights, a charge lamp to indicate a charging system malfunction, a water temperature gauge indicator showing the status of the radiator (e.g., temperature measured by temperature sensor S3), and information 19 indicating that the vehicle is in output limit mode.

[0113] In the example shown in Figure 9, FC meters 6 are positioned on both sides of the main meter 4. However, the FC meters 6 may be positioned on only one side of the main meter 4, and the shape of each meter is not limited to the example shown and is arbitrary. The FC meters 6 display information regarding the operating status of the FC power generation system 180. For example, the FC meters 6 may display predictive information estimated from the remaining fuel and the work content. In the example shown in Figure 9, the FC meter 6 on the right displays predictive information for the remaining driving distance, the remaining driving (working) time, and the working area. However, it is not necessary for all of this information to be displayed. For example, the remaining driving distance and driving time may be displayed, but the working area information may not be displayed. The FC meter 6 on the right also displays information on the type of implement and the type of work.

[0114] In the example shown in Figure 9, the display on the left side of the FC meter 6 includes information regarding the battery SOC (state of charge) of the battery pack 80, the remaining fuel level (%) in the fuel tank 50, the temperature of the fuel tank (°C), and the value (kPa) of the sensor S4 (pressure sensor) located in the fuel tank 50. The display on the left side of the FC meter 6 further includes the power generation status of the FC stack 11, a warning light 9 to warn of a malfunction in the fuel tank 50, and indicators corresponding to the battery SOC and remaining fuel level, respectively.

[0115] Figure 10 schematically illustrates another example of a display on a display device. The display device illustrated in Figure 10 is an operating terminal 400. The screen of the operating terminal 400 may also display the same or similar information as the information that may be displayed on the FC meter 6. The screen of the operating terminal 400 illustrated in Figure 10 displays information 19 indicating that it is in output limit mode, implement type, work type, and prediction information, as well as an input interface for setting vehicle speed and tilling depth, and vehicle information.

[0116] In this way, by presenting information indicating that the system is in output limit mode to, for example, the driver seated in the driver's seat or the user using the control terminal, it becomes easier to prompt the driver or user to make decisions such as refueling or stopping the implement's operation. Furthermore, by presenting information regarding the operating status of the FC power generation system to the driver or user, it becomes easier to prompt the driver or user to inspect, for example, the work vehicle or the FC power generation system.

[0117] The control device 60 may cause the audio output device to output an audio message indicating that it has switched to output limit mode, and / or an audio message prompting refueling. For example, the control device 60 may cause the speaker to output an audio message to notify that it has switched to output limit mode, or an audio message prompting refueling. Alternatively, the control device 60 may cause the buzzer to output a buzzer sound indicating that it has switched to output limit mode.

[0118] 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.

[0119] 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.

[0120] [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, The motor drives the power take-off shaft to which the implement is connected, A control device for controlling the power supplied from the fuel cell module to the motor, Equipped with, The control device is capable of operating in multiple control modes, The plurality of control modes include a normal mode and an output limit mode in which the upper limit of the power supplied from the fuel cell module to the motor is smaller than that of the normal mode. The control device changes the upper limit of the power supplied to the motor in the output limiting mode according to the type of implement connected to the power take-off shaft and / or the type of work performed by the implement. Work vehicle.

[0121] [Item 2] The system further includes a sensor for measuring the remaining amount of fuel in the fuel tank, The control device switches from the normal mode to the output limit mode when the measured remaining amount of fuel falls below a threshold. The upper limit of the power supplied to the motor is reduced to a value corresponding to the type of implement and / or the type of work. The work vehicle according to claim 1.

[0122] [Item 3] The fuel cell module is further equipped with a sensor for measuring its temperature. The control device switches from the normal mode to the output limit mode when the measured temperature exceeds a threshold. The upper limit of the power supplied to the motor is reduced to a value corresponding to the type of implement and / or the type of work. A work vehicle according to claim 1 or 2.

[0123] [Item 4] An inverter device connected between the fuel cell module and the motor, A sensor for measuring the temperature of the inverter device or the motor, Furthermore, The control device switches from the normal mode to the output limit mode when the measured temperature exceeds a threshold. The upper limit of the power supplied to the motor is reduced to a value corresponding to the type of implement and / or the type of work. A work vehicle according to claim 1 or 2.

[0124] [Item 5] The device further includes a storage device that stores a table defining the correspondence between the type of implement and / or the type of work and the upper limit of the power supplied to the motor. The control device refers to the table to determine the upper limit of the power corresponding to the type of implement connected to the power takeoff shaft and / or the type of operation. A work vehicle according to claim 1 or 2.

[0125] [Item 6] The work vehicle according to claim 1 or 2, wherein the control device obtains identification information of the implement from the implement connected to the power take-off shaft, and identifies the type of the implement and / or the type of work based on the identification information.

[0126] [Item 7] The work vehicle according to claim 1 or 2, wherein the control device identifies the type of implement connected to the power takeoff shaft based on information about the type of implement and / or the type of work entered by the user via an input device.

[0127] [Item 8] The fuel cell module and the battery connected to the motor are further comprising: In the output limiting mode, the control device, Determine whether or not to charge the aforementioned battery. When the aforementioned charging is performed, the power output from the fuel cell module is increased compared to when the aforementioned charging is not performed. A work vehicle according to claim 1 or 2.

[0128] [Item 9] The work vehicle according to claim 8, wherein the control device determines whether or not to charge the battery based on at least one of the state of charge (SOC) of the battery and the temperature of the battery.

[0129] [Item 10] The work vehicle according to claim 1 or 2, wherein the work vehicle is an agricultural machine.

[0130] [Item 11] A control device for a work vehicle, comprising a power take-off shaft to which an implement is connected, wherein the power take-off shaft is driven by a motor connected to a fuel cell module, It can operate in multiple control modes, The plurality of control modes include a normal mode and an output limit mode in which the upper limit of the power supplied from the fuel cell module to the motor is smaller than that of the normal mode. The upper limit of the power in the output limiting mode is changed according to the type of implement connected to the power takeoff shaft and / or the type of work performed by the implement. Control device.

[0131] [Item 12] A control method for a work vehicle, comprising a power takeoff shaft to which an implement is connected, wherein the power takeoff shaft is driven by a motor connected to a fuel cell module, The control method includes operation in multiple control modes, The plurality of control modes include a normal mode and an output limit mode in which the upper limit of the power supplied from the fuel cell module to the motor is smaller than that of the normal mode. The power limit in the output limiting mode is changed according to the type of implement connected to the power takeoff shaft and / or the type of work performed by the implement, Control method. [Industrial applicability]

[0132] 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]

[0133] 1...User interface, 2...Operating device, 3...Main ECU, 4...Main meter, 5...FC system ECU, 6...FC meter, 7...Storage device, 8...Audio output device, 10...Fuel cell module, 11...FC stack, 40...Boost circuit, 34...Radiator device, 40...Boost circuit, 42...ECU, 50...Fuel tank, 51...Tank case, 60...Control device, 70...Motor, 71...Output shaft, 72...Inverter device, 73...ECU, 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 seat, 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, The motor drives the power take-off shaft to which the implement is connected, A control device for controlling the power supplied from the fuel cell module to the motor, An agricultural tractor work vehicle equipped with, The control device is capable of operating in multiple control modes, The plurality of control modes include a normal mode and an output limit mode in which the upper limit of the power supplied from the fuel cell module to the motor is smaller than that of the normal mode. The control device determines the upper limit of the power supplied to the motor in the output limiting mode based on the combination of the type of implement connected to the power takeoff shaft and the type of work performed by the implement. The type of implement includes at least one of a rotary tiller, spreader, seeder, mower, and harrow. The aforementioned types of work include at least one of tilling, puddling, ridging, fertilizing, sowing, mowing, and soil crushing. Work vehicle.

2. The system further includes a sensor for measuring the remaining amount of fuel in the fuel tank, The control device, when the measured remaining amount of fuel falls below a threshold, switches from the normal mode to the output limit mode and reduces the upper limit of the power supplied to the motor to a value corresponding to the combination of the implement type and the type of work. The work vehicle according to claim 1.

3. The fuel cell module is further equipped with a sensor for measuring its temperature. The control device, when the measured temperature exceeds a threshold, switches from the normal mode to the output limit mode and reduces the upper limit of the power supplied to the motor to a value corresponding to the combination of the implement type and the type of work. A work vehicle according to claim 1 or 2.

4. An inverter device connected between the fuel cell module and the motor, A sensor for measuring the temperature of the inverter device or the motor, Furthermore, When the measured temperature exceeds a threshold, the control device switches from the normal mode to the output limit mode and reduces the upper limit of the power supplied to the motor to a value corresponding to the combination of the implement type and the type of work. A work vehicle according to claim 1 or 2.

5. The device further includes a storage device that stores a table defining the correspondence between the combination of the type of implement and the type of work, and the upper limit of the power supplied to the motor. The control device refers to the table and determines the upper limit of the power corresponding to the combination of the type of implement connected to the power takeoff shaft and the type of operation. A work vehicle according to claim 1 or 2.

6. The work vehicle according to claim 1 or 2, wherein the control device acquires identification information of the implement from the implement connected to the power take-off shaft and identifies the type of the implement based on the identification information.

7. The work vehicle according to claim 1 or 2, wherein the control device identifies the type of implement connected to the power takeoff shaft and the type of work based on information about the type of implement and the type of work input by the user via an input device.

8. The fuel cell module and the battery connected to the motor are further comprising: In the output limiting mode, the control device, Determine whether or not to charge the aforementioned battery. When performing the aforementioned charging, the upper limit of the output power of the fuel cell module is set to a value obtained by adding a first value to the upper limit of the power supplied to the motor. If the aforementioned charging is not performed, the upper limit of the output power of the fuel cell module is set to a value obtained by adding a second value smaller than the first value to the upper limit of the power supplied to the motor. A work vehicle according to claim 1 or 2.

9. The work vehicle according to claim 8, wherein the control device determines whether or not to charge the battery based on at least one of the battery's state of charge (SOC) and the battery's temperature.

10. The work vehicle according to claim 1 or 2, wherein the work vehicle is an agricultural machine.

11. A control device for an agricultural tractor, comprising a power take-off shaft to which an implement is connected, wherein the power take-off shaft is driven by a motor connected to a fuel cell module, It can operate in multiple control modes, The plurality of control modes include a normal mode and an output limit mode in which the upper limit of the power supplied from the fuel cell module to the motor is smaller than that of the normal mode. The upper limit of the power in the output limiting mode is determined based on the combination of the type of implement connected to the power takeoff shaft and the type of work performed by the implement. The type of implement includes at least one of a rotary tiller, spreader, seeder, mower, and harrow. The aforementioned types of work include at least one of tilling, puddling, ridging, fertilizing, sowing, mowing, and soil crushing. Control device.

12. A control method for an agricultural tractor, comprising a power take-off shaft to which an implement is connected, wherein the power take-off shaft is driven by a motor connected to a fuel cell module, The control method includes operation in multiple control modes, The plurality of control modes include a normal mode and an output limit mode in which the upper limit of the power supplied from the fuel cell module to the motor is smaller than that of the normal mode. The power limit in the output limiting mode is determined based on the type of implement connected to the power takeoff shaft and the type of work performed by the implement, The type of implement includes at least one of a rotary tiller, spreader, seeder, mower, and harrow. The aforementioned types of work include at least one of tilling, puddling, ridging, fertilizing, sowing, mowing, and soil crushing. Control method.

Images