tractor

Abstract

To provide a tractor with a fuel cell system which can rapidly and accordingly supply a fuel cell with hydrogen gas supply amount when electric power load is suddenly generated regarding the fuel cell.SOLUTION: A tractor comprises: a vehicle body; an engine hood which is arranged at a front part of the vehicle body; a travel unit which runnably supports the vehicle body; a drive motor which drives the travel unit; a PTO shaft which transmits power to a work device; a fuel cell system which includes a fuel cell and supplies the drive motor with electric power generated by the fuel cell; and a battery which accumulates electric power generated by the fuel cell. The fuel cell and the battery are arranged in the engine hood.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tractor equipped with a fuel cell system. [Background technology]

[0002] In recent years, hydrogen fuel gas has been attracting attention as a clean energy source that prevents air pollution and is used as a fuel for automobiles. Accordingly, fuel cell vehicles (FCVs) have been developed that are equipped with fuel cells that generate electricity through an electrochemical reaction between a fuel gas, such as hydrogen gas, and an oxidant gas, such as air, and that use the electricity generated by the fuel cell as a drive source for the front and rear wheels (see, for example, Patent Document 1). Such fuel cell vehicles are equipped with fuel gas storage tanks, such as hydrogen storage alloy tanks and high-pressure tanks, that store fuel gas, such as hydrogen gas, to be supplied to the fuel cells.

[0003] From the perspective of preventing such air pollution, the technological trend of using fuel cells as a power source is not limited to automobiles; research and development is underway to apply this to various types of work machinery, such as agricultural machinery such as rice transplanters and combine harvesters, and construction machinery such as backhoes, compact track loaders, and skid steer loaders. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-102458 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in industrial machinery (machines) that can be fitted with or have a working implement, while most of the drive power of an automobile is used only as a drive power source for traveling, in working machinery, the drive power source is used not only as a drive power source for traveling but also as a drive power source for the working implement. For this reason, in working machinery, the power load can suddenly increase regardless of the accelerator position for traveling. Therefore, in working machinery equipped with a fuel cell as a drive power source, the supply of fuel gas, such as hydrogen gas, to the fuel cell cannot be increased quickly and swiftly, and a sudden increase in the flow rate of hydrogen gas released from the MH (Metal Hydride) tank causes a sudden drop in pressure within the MH tank, resulting in a problem of reduced responsiveness of the fuel cell's output power.

[0006] Furthermore, to improve safety and comply with the High-Pressure Gas Safety Act, MH tanks made of hydrogen storage alloys that can store hydrogen gas even at pressures of 1.0 MPa or less are commonly used to store hydrogen gas for fuel cells installed in such work machines. Therefore, when the amount of hydrogen stored in the MH tank decreases, the pressure must be further reduced to release the hydrogen gas at a certain temperature. Furthermore, because a hydrogen gas pressure above a certain value is required for fuel cell power generation, the hydrogen gas pressure cannot be further reduced to release the hydrogen gas at a certain temperature. This creates the problem of having to refill the MH tank with the next batch of hydrogen gas, leaving much of the hydrogen gas stored in the MH tank.

[0007] The present invention has been made to solve the problems of the prior art, and aims to provide a tractor equipped with a fuel cell system that, in a work machine equipped with a fuel cell, can quickly adjust the amount of hydrogen gas supplied to the fuel cell without reducing the responsiveness of the fuel cell's output power even if a sudden power load occurs on the fuel cell, and can also reduce the amount of hydrogen gas left unused in the hydrogen storage alloy in the MH tank. [Means for solving the problem]

[0008] A tractor according to one embodiment of the present invention comprises a body, a hood provided at the front of the body, a traveling device that supports the body so that it can travel, a drive motor that drives the traveling device, a PTO shaft that transmits power to a work device, a fuel cell system that includes a fuel cell and supplies electricity generated by the fuel cell to the drive motor, and a battery that stores the electricity generated by the fuel cell, the fuel cell and battery being arranged inside the hood.

[0009] In one aspect of the present invention, the fuel cell system may be disposed at a higher position than the drive motor.

[0010] The fuel cell system may be disposed forward of the drive motor.

[0011] The height of the fuel cell system may be greater than the height of the battery.

[0012] In another aspect of the present invention, the tractor may include an inverter that controls the drive motor, and the inverter may be disposed forward of the drive motor.

[0013] The inverter may be located inside the hood.

[0014] The tractor according to another aspect of the present invention may include an access step for an operator to get on and off the tractor, and the access step may be located rearward of the fuel cell system.

[0015] The step may be disposed between the fuel cell system and the drive motor. [Effects of the Invention]

[0016] A tractor equipped with the fuel cell system of the present invention can quickly adjust the amount of hydrogen gas supply required to match the required fuel cell output power without reducing responsiveness, even if a sudden power load occurs on the fuel cell in a work machine equipped with a fuel cell, and can also reduce the amount of hydrogen gas left unused in the hydrogen storage alloy in the MH tank. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic side view of an agricultural tractor 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a schematic configuration of a fuel cell system 22 of FIG. [Figure 3] FIG. 3 is a vertical cross-sectional view of the hydrogen tank 232A of FIG. 2. [Figure 4] 3 is a flowchart showing a hydrogen gas supply process executed by the fuel cell system 22 of FIG. 2. [Figure 5A] 2. (a) is a time-axis waveform diagram showing the change in flow rate of hydrogen gas flowing from hydrogen tanks 232A, 232B, and 232C to fuel cell 229 via hydrogen gas supply path 27 over time t; (b) is a time-axis waveform diagram using the same elapsed time axis as (a) and showing the change in pressure of hydrogen gas in hydrogen tank 232A of FIG. 2 over time t; (c) is a time-axis waveform diagram using the same time axis as (a) and showing the change in flow rate of the first circulating water (hot water) flowing in hydrogen tanks 232A, 232B, and 232C of FIG. 1 over time t; (d) is a time-axis waveform diagram using the same time axis as (a) and showing the change in temperature of the first circulating water (hot water) over time t; (e) is a time-axis waveform diagram using the same time axis as (a) and showing the change in operating state of fuel cell 229 of FIG. 2 over time t; and (f) is a time-axis waveform diagram using the same time axis as (a) and showing the change in remaining amount of hydrogen gas in hydrogen tank 232A of FIG. 2 over time t. [Figure 5B]2. (a) is a time-axis waveform diagram showing the change in flow rate of hydrogen gas flowing from hydrogen tanks 232A, 232B, and 232C to fuel cell 229 via hydrogen gas supply path 27 over time t; (b) is a time-axis waveform diagram using the same elapsed time axis as (a) and showing the change in pressure of hydrogen gas in hydrogen tank 232A of FIG. 2 over time t; (c) is a time-axis waveform diagram using the same time axis as (a) and showing the change in flow rate of the first circulating water (hot water) flowing in hydrogen tanks 232A, 232B, and 232C of FIG. 1 over time t; (d) is a time-axis waveform diagram using the same time axis as (a) and showing the change in temperature of the first circulating water (hot water) over time t; (e) is a time-axis waveform diagram using the same time axis as (a) and showing the change in operating state of fuel cell 229 of FIG. 2 over time t; and (f) is a time-axis waveform diagram using the same time axis as (a) and showing the change in remaining amount of hydrogen gas in hydrogen tank 232A of FIG. 2 over time t. [Figure 6] 1. FIG. 4 is a block diagram showing a schematic configuration of a fuel cell system 22A according to a modified example of the fuel cell system 22 of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, like components are designated by like reference numerals and will not be described again.

[0019] 1 to 3 illustrate a work machine 1 and its components according to this embodiment. In this embodiment, the work machine 1 is a tractor, and the direction of travel of the vehicle (arrow pointing forward) is referred to as the "forward" of the tractor 1 and its components, the direction opposite to the direction of travel of the vehicle is referred to as the rear, and the left-right direction as seen from the operator riding on the tractor is referred to as the "left-right" of the tractor 1 and its components. The horizontal direction perpendicular to the fore-and-aft direction of the vehicle body is referred to as the width direction of the tractor 1. The tractor 1 is equipped with a fuel cell 229 (see FIG. 2) that generates electricity through an electrochemical reaction between fuel gas and oxidant gas, and is configured to use the electricity generated by this fuel cell 229 as its power source. While this embodiment has been described using an agricultural tractor as the work machine, the present invention is not limited thereto. The work machine may be various other types of work machines, such as agricultural machines such as rice transplanters and combine harvesters, and construction machines such as backhoes, compact track loaders, and skid steer loaders.

[0020] Fig. 1 is a schematic side view of a tractor 1 according to this embodiment. The tractor 1 in Fig. 1 shows the left side of the entire tractor. The tractor 1 in Fig. 1 is configured to include a body 2 that is long in the front-to-rear direction, a hood 3 provided at the front of the body 2, a cabin 5 that is mounted at the rear of the body 2 and houses a driver's seat 4 where an operator sits, a wheeled traveling device 6 that supports the body 2 so that it can travel, a drive unit 7 that drives the traveling device 6, a three-point linkage mechanism 9 provided at the rear end of the body 2, and a PTO shaft (power take-off shaft) 10 that transmits power from the drive unit 7.

[0021] The traveling device 6 in Fig. 1 has a pair of left and right rear wheels 11 and a pair of left and right front wheels 12, with the upper parts of the rear wheels 11 covered by fenders 13. Here, the traveling device 6 is a two-wheel drive / four-wheel switchable four-wheel drive system, and is configured to be switchable between a two-wheel drive state in which only the rear wheels 11 are driven, and a four-wheel drive state in which both the rear wheels 11 and the front wheels 12 are driven. Note that the present invention is also applicable to tractors equipped with a two-wheel drive system in which only the rear wheels are driven, or a track-type (crawler-type) traveling device.

[0022] 1 is configured to include an AC drive motor (electric motor) 21 that is disposed near the rear wheels 11 and drives the wheels or tracks of the traveling unit 6, a fuel cell system 22 that is disposed inside the hood 3 and supplies power to the drive motor 21, and a controller 23 that is disposed inside the hood 3 and controls the power supply from the fuel cell system 22 to the drive motor 21. Furthermore, the vehicle may be configured to be equipped with a hydrogen gas detector that detects hydrogen gas, and in that case, the vehicle may be configured to have an exhaust door on the ceiling wall 43 of the cabin 5 that opens when the hydrogen gas detector detects hydrogen gas to connect the interior space S1 of the cabin 5 to the outside.

[0023] Here, the output shaft of drive motor 21 is indirectly or directly connected to the axle of rear wheels 11 via a transmission mechanism, and is switchably connected to front wheels 12 via a two-wheel drive / four-wheel drive switching mechanism. Furthermore, fuel cell system 22 generates electricity by reacting hydrogen gas supplied from hydrogen tanks 232A-232C (described later) with air (oxygen) taken in from the outside, and supplies this electricity to drive motor 21. Furthermore, controller 23 has an inverter function, converts direct current electricity generated by fuel cell system 22 to alternating current electricity, and controls the frequency to control the rotation of drive motor 21. Furthermore, battery 28 is disposed inside hood 3 to store surplus electricity from the power supplied from fuel cell system 22 to drive motor 21, and controller 23 may be configured to control the rotation of drive motor 21 using the electricity stored in battery 28.

[0024] The three-point linkage mechanism 9 includes a pair of left and right lower links 31 supported on the lower rear end of the vehicle body 2 so as to be vertically rotatable, a pair of left and right lift arms 32 supported on the upper rear end of the vehicle body 2 so as to be vertically rotatable and driven by a hydraulic device, a connecting link 33 connecting the rear ends of the lift arms 32 to the middle parts of the lower links 31 so as to rotate the lower links 31 with the rotation of the lift arms 32, and a bracket 34 for attaching an upper link. Various working devices are supported for vertical movement by upper links connected to the rear ends of the pair of left and right lower links 31 and the bracket 34. In addition, input portions of various working devices are connected to the PTO shaft 10 via a drive shaft. In addition, the PTO shaft 10 rotates by power transmitted from a drive motor 21. Here, the working equipment includes tilling equipment, fertilizer spreading equipment, pesticide spreading equipment, harvesting equipment, reaping equipment, spreading equipment, grass, etc., grass collecting equipment, grass shaping equipment (roll baler), etc.

[0025] The cabin 5 in Fig. 1 is composed of four cabin frames (pillars) 41 rising from the four corners, transparent walls (not numbered) covering the front, right, and rear sides, a transparent boarding door 42 covering the left side, and a ceiling wall 43. Here, a control device 44 including a handle and the like is disposed in front of the cockpit 4, and an air conditioning unit 46 that conditions the interior space S1 of the cabin 5 is disposed below the cockpit 4. In addition, below the cabin 5, there is disposed a boarding step 8 on which the operator places their feet when getting in and out of the cabin 5. Here, the boarding step 8 is provided below each of the boarding doors 42 on the left and right sides.

[0026] FIG. 2 is a block diagram showing a schematic configuration of the fuel cell system 22 of FIG. The fuel cell system 22 in Figure 2 is composed of three hydrogen tanks 232A, 232B, and 232C, each storing hydrogen gas and supplying hydrogen gas for fuel to the fuel cell 229; the fuel cell 229, which generates electricity by receiving hydrogen gas from each of the hydrogen tanks 232A to 232C; a first circulating water supply path 24, which circulates first circulating water (hot water) to adjust the temperature in each of the hydrogen tanks 232A to 232C; a temperature adjustment device 220, which is disposed in the first circulating water supply path 24 and adjusts the temperature of the first circulating water (hot water); a control unit (ECU) 230, which controls the temperature of the temperature adjustment device 220 based on the remaining amount of hydrogen in the hydrogen tanks 232A to 232C; a hydrogen gas supply path 27, which supplies hydrogen gas from each of the hydrogen tanks 232A to 232C to the fuel cell 229; and a second circulating water supply path 25, which circulates second circulating water (cooling water) to cool the fuel cell 229. That is, the fuel cell system 22 further includes a second circulating water supply path 25 that circulates second circulating water (cooling water) that cools the fuel cell 229, and the first circulating water supply path 24 branches off from the second circulating water supply path 25. Here, the temperature adjustment device 220 is configured to include a heater 221 such as a ceramic heater that increases the temperature of the first circulating water, a first radiator 222 that cools the temperature of the first circulating water, and a first fan 223 that blows cooling air through the first radiator 222.

[0027] Additionally, a pressure sensor P is disposed in hydrogen gas supply path 27 to detect the pressure of hydrogen gas stored in hydrogen tank 232. While this embodiment has been described as an example in which three hydrogen tanks are disposed for convenience, the present invention is not limited to this, and may be configured to dispose of, for example, one or a plurality of hydrogen tanks other than three. Here, the plurality of hydrogen tanks may be connected in series or in parallel.

[0028] 2 includes a first flow path 24a that passes the first circulating water sent from the temperature adjustment device 220 through a pipe 233A in the hydrogen tank 232A, a second flow path 24b that connects the pipe 233A in the hydrogen tank 232A with the pipe 233B in the hydrogen tank 232B, a third flow path 24c that connects the pipe 233B in the hydrogen tank 232B with the pipe 233C in the hydrogen tank 232C, and a fourth flow path 24d that connects the pipe 233B in the hydrogen tank 232B with the pipe 233C in the hydrogen tank 232C. A fourth flow path 24d is provided for flowing the first circulating water (hot water), a three-way valve 231B is provided for switching the flow path of the first circulating water (hot water) flowing in the fourth flow path 24d, a fifth flow path 24e is provided for flowing the first circulating water (hot water) sent out from the three-way valve 231B, a three-way valve 231A is provided for switching the flow path of the first circulating water (hot water) flowing in the fifth flow path 24e, and a sixth flow path 24f is provided for returning the first circulating water (hot water) to the temperature adjustment device 220 via the three-way valve 231A.

[0029] Here, first flow path 24a is provided with temperature sensor T1 that measures the temperature of the first circulating water (hot water) sent from temperature adjustment device 220 to pipe 233A of hydrogen tank 232A, and fourth flow path 24d is provided with temperature sensor T2 that measures the temperature of the first circulating water (hot water) sent from pipe 233C of hydrogen tank 232C. Furthermore, sixth flow path 24f is provided with PWM pump 224 that controls the flow rate of the first circulating water (hot water) flowing to temperature adjustment device 220 via three-way valve 231A. Here, the temperature of the first circulating water (hot water) may be determined by acquiring temperature data from either temperature sensor T1 or T2, or by acquiring average data from both temperature sensors T1 and T2. Furthermore, although not shown here, at least one of the hydrogen tanks 232A to 232C may be provided with a temperature sensor that measures the temperature inside the hydrogen tank, and the control unit 230 may be configured to acquire at least one piece of temperature data and use that temperature data to calculate the temperature of the first circulating water (hot water).

[0030] 2 is formed using, for example, piping so that the first circulating water (hot water) delivered from PWM pump 224 flows through temperature adjustment device 220, hydrogen tanks 233A-232C, three-way valve 231B, and three-way valve 231A in this order via flow paths 24a, 24b, 24c, 24d, 24e, and 24f, and piping 233A-233C in each hydrogen tank, before returning to PWM pump 224 and circulating. Here, the first circulating water (hot water) functions as a heat medium, and first circulating water supply path 24 heats hydrogen tanks 233A, 233B, and 233C by circulating the first circulating water (hot water). While this embodiment has been described using water as the heat medium, the present invention is not limited thereto. For example, an antifreeze solution containing ethylene glycol as the main component may be used as the heat medium.

[0031] Furthermore, the second circulating water supply path 25 in Figure 2 is provided with a three-way valve 231A that switches the flow path of the second circulating water (cooling water) sent out from the fuel cell 229, a seventh flow path 25a that flows the second circulating water whose flow path has been switched from the three-way valve 231A, a three-way valve 231B that switches the flow path of the second circulating water flowing in the seventh flow path 25a, a second radiator 226 that cools the second circulating water sent out from the three-way valve 231B, a second blower (FAN) 227 that ventilates cooling air through the second radiator 226, and an eighth flow path 25b that returns the second circulating water (cooling water) sent out from the second radiator 226 to the fuel cell 229. The fifth flow path 24e of the first circulating water supply path 24 and the seventh flow path 25a of the second circulating water supply path 25 are formed by a common pipe. Here, the second radiator 226 dissipates heat from the second circulating water (coolant), and the second blower 227 promotes heat dissipation by the second radiator 226. The eighth flow path 25a is provided with a PWM pump 228 that controls the flow rate of the second circulating water (coolant) flowing into the fuel cell 229. That is, the second circulating water supply path 25 in FIG. 2 is formed using, for example, a pipe so that the second circulating water (coolant) sent from the PWM pump 228 flows through the fuel cell 229, the three-way valve 231A, the three-way valve 231B, and the second radiator 226 in this order via the seventh flow path 25a and the eighth flow path 25b, and then returns to the PWM pump 228 to circulate. Here, the second circulating water (cooling water) functions as a heat medium, and the second circulating water supply path 25 cools the fuel cell 229 by circulating the second circulating water (cooling water).

[0032] The control unit 230 in FIG. 2 controls the temperature regulator 220 based on the amount of hydrogen remaining in the hydrogen tanks 232A-232C. When the amount of hydrogen remaining in the hydrogen tanks 232A-232C is below a predetermined value, the control unit 230 controls the heater 221 to start energizing, thereby raising the temperature of the hydrogen tanks 232A-232C. Furthermore, when the temperature of the hydrogen tank rises due to factors such as high outside temperatures in summer, the control unit 230 monitors the pressure in the hydrogen tank and controls the pressure so that it does not exceed 1.0 MPa. The "1.0 MPa" setting is based on the High-Pressure Gas Safety Act, which requires that the filling pressure in each hydrogen tank be 1.0 MPa or less. The predetermined value is set within a range between the minimum operating pressure PC of hydrogen gas required for operation of the fuel cell 229 and 1.0 MPa. In this embodiment, the minimum operating pressure PC of hydrogen gas required for operation of the fuel cell 229 is set to 0.85 MPa.

[0033] Specifically, the control unit 230 acquires the flow rate value of hydrogen gas supplied to the fuel cell 229 or the current value from the fuel cell 229 to the load, calculates the remaining amount of hydrogen in the hydrogen tanks 232A-232C based on the acquired flow rate value of hydrogen gas or the current value from the fuel cell 229 to the load, and calculates the target temperature from the remaining amount of hydrogen based on a characteristic map of temperature versus the remaining amount of hydrogen. The control unit 230 then controls the heater 221 and the first radiator 222 so that the actual temperature of the first circulating water flowing through the first circulating water supply path 24 becomes the calculated target temperature. Although not shown, a flow meter that measures the flow rate value of hydrogen gas is provided in the hydrogen gas supply path 27, and the control unit 230 is configured to acquire flow rate value data of hydrogen gas from the flow meter as appropriate.

[0034] 2 has a function to detect the value of the current output from the fuel cell 229 to the load, and also has a function to detect the flow rate of the hydrogen gas input from the hydrogen tanks 232A to 232C to the fuel cell 229.

[0035] Here, the characteristic map is a map showing the relationship between the remaining amount of hydrogen in hydrogen tanks 232A-232C, the temperature of the first circulating water (hot water), and the hydrogen gas pressure in hydrogen tanks 232A-232C, and control unit 230 calculates the target temperature of the first circulating water (hot water) from the remaining amount of hydrogen and the hydrogen gas pressure based on this characteristic map, and controls the energization of heater 221 and the operation of first radiator 222 so that the actual temperature of the first circulating water (hot water) becomes the target temperature. In other words, this characteristic map shows the relationship between the integrated value of the current output from fuel cell 229 to an electric load (not shown) and the amount of hydrogen consumed, and it is possible to derive the amount of hydrogen consumed by calculating the integrated value of the current output from fuel cell 229.

[0036] With this configuration, when a sudden increase in the power load on the fuel cell 229 in the tractor 1 (work machine) equipped with the fuel cell 229 occurs, it is possible to increase the flow rate of the first circulating water at a predetermined pressure equal to or higher than the minimum operating pressure PC of the hydrogen gas required for operation of the fuel cell 229, without causing the pressure to drop suddenly to this minimum operating pressure PC. Therefore, when the hydrogen gas pressure in the hydrogen tank reaches a predetermined pressure equal to or higher than the minimum operating pressure PC of the fuel cell 229, it is possible to increase the flow rate of the first circulating water (hot water) and increase the amount of hydrogen gas supplied, so that the amount of hydrogen gas supplied to the fuel cell 229 can be increased quickly in response to the increase in the power load.

[0037] In addition, the control unit 230 in Figure 2 determines the flow rate of the first circulating water flowing through the first circulating water supply path 24 based on the deviation between a predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, and controls the PWM pump 224 so that the flow rate flowing through the first circulating water supply path 24 becomes the determined flow rate.

[0038] Furthermore, the control unit 230 stops power generation by the fuel cell 229 when the pressure of the hydrogen gas detected by the pressure sensor P becomes equal to or lower than the minimum operating pressure PC of the hydrogen gas required for the fuel cell to operate (0.85 MPa in this embodiment).

[0039] FIG. 3 is a longitudinal cross-sectional view of the hydrogen tank 232A of FIG. 2. The hydrogen tank 232A of FIG. 3 is a tank filled with a hydrogen storage material and includes a liner 60 having an internal space filled with hydrogen gas, and a carbon fiber reinforced plastic (CFRP) layer 61 covering the outer surface of the liner 60. Here, the liner 60 is formed of a hydrogen storage material, such as a hydrogen storage alloy, and absorbs hydrogen gas by increasing the pressure or cooling, and releases the hydrogen gas by decreasing the pressure or heating. The structure of each of the hydrogen tanks 232B and 232C of FIG. 2 is the same as that of the hydrogen tank 232A. That is, each of the hydrogen tanks 232A-232C contains a hydrogen storage alloy and releases the hydrogen gas absorbed in the hydrogen storage alloy to supply it to the fuel cell 229. Each of the hydrogen tanks 232A-232C is a low-pressure hydrogen tank capable of absorbing hydrogen gas 1,000 times or more its own volume.

[0040] The following will explain the operation and effects of the fuel cell system 22 configured as above. Figure 4 is a flowchart showing the hydrogen gas supply process executed by the fuel cell system 22 of Figure 2.

[0041] First, in step ST100 of FIG. 4, the control unit 230 starts the supply of hydrogen gas to the fuel cell 229 and simultaneously starts the operation of the fuel cell 229. In the next step ST101, the control unit 230 starts the operation of the PWM pump 224 so as to circulate the first circulating water, which adjusts the temperature in the hydrogen tanks 233A, 233B, and 233C, through the first circulating water supply path 24. Next, the control unit 230 calculates the remaining amount of hydrogen in the hydrogen tanks 233A, 233B, and 233C (step ST102) and proceeds to the next step ST103. In step ST103, the control unit 230 determines whether the remaining amount of hydrogen calculated in step ST102 is equal to or less than a predetermined value VP (see FIGS. 5A(f) and 5B(f) described below). If the remaining amount of hydrogen is equal to or less than the predetermined value VP, the control unit 230 proceeds to step ST108 described below. If the remaining amount of hydrogen is greater than the predetermined value VP, the control unit 230 proceeds to step ST104.

[0042] In step ST104, the control unit 230 acquires the hydrogen gas pressure values ​​in the hydrogen tanks 232A, 232B, and 232C from the pressure sensor P disposed in the hydrogen gas supply path 27. Then, in the next step ST105, it is determined whether the acquired hydrogen gas pressure has dropped to the minimum operating pressure PC, and if the acquired hydrogen gas pressure is equal to or lower than the minimum operating pressure PC, the process proceeds to step ST109, which will be described later, and if the acquired hydrogen gas pressure is higher than the minimum operating pressure PC, the process proceeds to the next step ST106.

[0043] In step ST106, the control unit 230 determines whether the acquired hydrogen gas pressure has dropped to a predetermined value PD (see Figures 5A(b) and 5B(b) described below) set within the range between 1.0 MPa and the minimum operating pressure PC of the fuel cell 229. If the pressure is equal to or less than the predetermined value PD, the control unit 230 proceeds to the next step ST107, and if the pressure is greater than the predetermined value PD, the control unit 230 returns to step ST102 described above. Here, the upper limit of the hydrogen gas pressure, 1.0 MPa, is based on the requirement under the High Pressure Gas Safety Act that the filling pressure in each hydrogen tank must be 1.0 MPa or less.

[0044] In step ST106, if the control unit 230 determines that the acquired hydrogen gas pressure has dropped to a predetermined value PD between 1.0 MPa and the minimum operating pressure PC of the fuel cell 229, it increases the flow rate of the first circulating water (hot water) passing through the pipes 233A, 233B, 233C in each hydrogen tank 232A, 232B, 232C to increase the hydrogen gas pressure in each hydrogen tank 232A, 232B, 232C (step ST107), and proceeds to the above-mentioned step ST104.

[0045] In step ST108, the temperature of the first circulating water (hot water) passing through the pipes 233A, 233B, 233C in the hydrogen tanks 232A, 232B, 232C is increased, and the process returns to step ST104. In step ST109, the control unit 230 stops the operation of the PWM pump 224 to stop the circulation of the first circulating water (hot water), and in the next step ST110, the control unit 230 stops the supply of hydrogen gas to the fuel cell 229 and simultaneously stops the operation of the fuel cell 229, and the process ends.

[0046] Next, the effects of the fuel cell system 22 of FIG. 2 performing the operations shown in the flowchart of FIG. 4 will be described in detail below with reference to the graphs of FIGS. 5A and 5B. Here, Figure 5A explains the effects of using only flow rate control of the first circulating water (hot water), and Figure 5B explains the effects of using flow rate control of the first circulating water (hot water) as well as temperature control of the first circulating water (hot water).

[0047] 5A(a) is a time-axis waveform diagram showing the change in flow rate of hydrogen gas flowing from hydrogen tanks 232A, 232B, and 232C to fuel cell 229 via hydrogen gas supply path 27 over time t. FIG. 5A(b) is a time-axis waveform diagram showing the change in pressure of hydrogen gas in hydrogen tank 232A of FIG. 2 over time t, using the same time axis as FIG. 5A(a). FIG. 5A(c) is a time-axis waveform diagram showing the change in pressure of first circulating water (hot water) flowing to hydrogen tanks 232A, 232B, and 232C of FIG. 1, using the same time axis as FIG. 5A(a). Figure 5A(d) is a time-axis waveform diagram showing the change in flow rate over time t, Figure 5A(d) is a time-axis waveform diagram using the same time axis as Figure 5A(a) and showing the change in temperature of the first circulating water (hot water) over time t, Figure 5A(e) is a time-axis waveform diagram using the same time axis as Figure 5A(a) and showing the change in operating state of the combustion cell 229 of Figure 2 over time t, and Figure 5A(f) is a time-axis waveform diagram using the same time axis as Figure 5A(a) and showing the change in the remaining amount of hydrogen gas in the hydrogen tank 232A of Figure 2 over time t.

[0048] First, an increase in the amount of hydrogen gas supplied to the fuel cell 229 due to an increase in the workload on the work machine will be described using Figure 5A(a). Figure 5A(a) shows changes in the flow rate of hydrogen gas flowing from hydrogen tanks 232A, 232B, 232C to the fuel cell 229 via hydrogen gas supply path 27. Here, it is shown that the flow rate f(t) of hydrogen gas is constant (flow rate f(t) = f0) from time 0 to time t0, but at time t0, the workload on the work machine increases, and accordingly, the hydrogen gas flow rate f(t) increases rapidly to flow rate f1 at time ta.

[0049] Next, a decrease in hydrogen gas pressure in the hydrogen tank due to an increase in the amount of hydrogen gas supplied to the fuel cell 229 will be described using Figure 5A(b). Referring to Figure 5A(b), a sudden increase in the workload on the fuel cell 229 causes the hydrogen gas pressure P(t) in the hydrogen tanks 232A, 232B, and 232C to decrease rapidly around the time ta. This is due to a sudden increase in the amount of hydrogen gas supplied to the fuel cell 229.

[0050] Next, the timing for increasing the flow rate of the first circulating water (hot water) in response to a decrease in the hydrogen gas pressure in the hydrogen tank will be explained using Figures 5A(b) and 5A(c). Figures 5A(b) and 5A(c) show that by increasing the flow rate of the first circulating water (hot water) at time Tb when the hydrogen gas pressure P(t) in the hydrogen tanks 232A, 232B, and 232C has decreased to a predetermined value PD, the hydrogen gas pressure P(t) in the hydrogen tanks 232A, 232B, and 232C begins to increase at time tc (>tb), just before it reaches the minimum operating pressure PC (see Figure 5A(c)).

[0051] Here, referring to FIG. 5A(e), it is shown that at the timing of time tc, the operating state of the fuel cell 229 is in the on state. As a result, the hydrogen gas pressure P(t) in the hydrogen tank does not immediately decrease from the predetermined pressure PD and reach below the minimum operating pressure PC, but once the hydrogen gas pressure P(t) in the hydrogen tank is increased, it is shown that it is possible to continuously supply the fuel cell 229 with hydrogen gas at or above the minimum operating pressure PC required for the operation of the fuel cell 229.

[0052] Note that in FIG. 5A, since temperature control is not performed only by controlling the flow rate of the first circulating water (warm water), the temperature of the first circulating water (warm water) is controlled to be constant (T(t) = T0) (see FIG. 5A(d)).

[0053] Next, the timing at which the operating state of the fuel cell 229 becomes the off state will be described using FIGS. 5A(b) and (e). Referring to FIGS. 5A(b) and (e), it is shown that the hydrogen gas pressure P(t) in the hydrogen tanks 232A, 232B, and 232C starts to decrease at the timing of time td (t5 < td < t6), and the fuel cell 229 is controlled to be in the off state at the timing of time t7 when it becomes below the minimum operating pressure PC which is the lower limit value.

[0054] Next, the amount of hydrogen gas remaining (the remaining amount of hydrogen gas) in the hydrogen tanks 232A, 232B, and 232C when the operating state of the fuel cell 229 becomes the off state will be described using FIG. 5A(f). Referring to FIG. 5A(f), it is shown that the remaining amount V(t) of hydrogen gas in the hydrogen tanks 232A, 232B, and 232C becomes the remaining amount V1 at the timing of time t7 when the fuel cell 229 becomes the off state (see FIG. 5A(e)).

[0055] As described above, the control unit 230 acquires the value (data) of the hydrogen gas pressure in the hydrogen tanks 232A, 232B, 232C from the pressure sensor P disposed in the hydrogen gas supply path 27, and when the acquired hydrogen gas pressure drops to near the minimum operating pressure PC of the fuel cell 229 (a predetermined value PD set within the range between 1.0 MPa and the minimum operating pressure PC of the fuel cell 229), the control unit 230 controls the flow rate of the first circulating water (hot water) passing through the pipes 233A, 233B, 233C in each hydrogen tank 232A, 232B, 232C to increase. This makes it possible to maintain the operating state of the fuel cell 229 in an on state without the hydrogen gas pressure in the hydrogen tanks 232A, 232B, 232C increasing and falling below the minimum operating pressure PC of the fuel cell 229.

[0056] Therefore, according to the fuel cell system 22 of this embodiment, even if a sudden power load occurs on the fuel cell 229, it is possible to quickly adjust the amount of hydrogen gas supply required to meet the required output power of the fuel cell 229 without reducing responsiveness.

[0057] In the above-described FIG. 5A, only the flow rate of the first circulating water (hot water) is controlled. However, the effect of control in which the temperature of the first circulating water (hot water) is further controlled will be described with reference to FIG. 5B.

[0058] FIG. 5B(a) is a time-axis waveform diagram showing the change in the flow rate of hydrogen gas flowing from hydrogen tanks 232A, 232B, and 232C to fuel cell 229 via hydrogen gas supply path 27 with respect to time t. FIG. 5B(b) has the same elapsed time axis as FIG. 5B(a) and is a time-axis waveform diagram showing the change in the pressure of the hydrogen gas in hydrogen tank 232A of FIG. 2 with respect to time t. FIG. 5B(c) has the same time axis as FIG. 5B(a) and is a time-axis waveform diagram showing the change in the flow rate of the first circulating water (warm water) flowing into hydrogen tanks 232A, 232B, and 232C of FIG. 1 with respect to time t. FIG. 5B(d) has the same time axis as FIG. 5B(a) and is a time-axis waveform diagram showing the change in the temperature of the first circulating water (warm water) with respect to time t. FIG. 5B(e) has the same time axis as FIG. 5B(a) and is a time-axis waveform diagram showing the change in the operating state of fuel cell 229 of FIG. 2 with respect to time t. FIG. 5B(f) has the same time axis as FIG. 5B(a) and is a time-axis waveform diagram showing the change in the remaining amount of the hydrogen gas in hydrogen tank 232A of FIG. 2 with respect to time t.

[0059] Here, the temperature control of the first circulating water, which is a difference point from FIG. 5A, will be described. Note that the flow rate control of the first circulating water has been described in FIG. 5A, so it will be omitted.

[0060] As shown in FIG. 5A, when only the flow rate control of the first circulating water is performed, at the timing of time t7 when fuel cell 229 stops, the remaining amount V(t) of the hydrogen gas in hydrogen tanks 232A, 232B, and 232C becomes the remaining amount V1 (see FIG. 5A(f)).

[0061] On the other hand, referring to FIG. 5B(b), due to the continuous state where a rapid working load is applied to fuel cell 229, the hydrogen gas pressure in hydrogen tanks 232A, 232B, and 232C starts to decrease at the timing of time te (t7 < te < t8), and it is shown that it reaches the minimum operating pressure PC at the timing of time t8 and is less than the minimum operating pressure PC thereafter. Therefore, referring to FIG. 5B(e), it is shown that at the timing of time t8, fuel cell 229 switches from the on state to the off state.

[0062] Next, when the operating state of the fuel cell 229 becomes the off state, the amount of hydrogen gas remaining (remaining amount of hydrogen gas) in the hydrogen tanks 232A, 232B, and 232C will be described using FIG. 5B(f). Referring to FIG. 5B(f), at the timing of time t8 (>t7) when the fuel cell 229 becomes the off state (see FIG. 5B(e)), it is shown that the remaining amount V(t) of hydrogen gas in the hydrogen tanks 232A, 232B, and 232C is the remaining amount V2 (<V1).

[0063] This is because, when compared with the control of only the flow rate control of the first circulating water (warm water) (FIG. 5A), due to the continuation of the state where a sudden working load is applied to the fuel cell 229, the start time te (t7 < te < t8) of the decrease in the hydrogen gas pressure in the hydrogen tanks 232A, 232B, and 232C is later than the start time td (t5 < td < t6) in the control of only the flow rate control of the first circulating water. Here, referring to FIG.5B(d), by raising the temperature of the first circulating water (warm water) at the timing of time t4 when the remaining amount V(t) of hydrogen in the hydrogen tanks 232A, 232B, and 232C has decreased to the predetermined value VP, it is shown that the time for continuously supplying the fuel cell 229 with hydrogen gas at a pressure not less than the minimum operating pressure PC required for the operation of the fuel cell 229 becomes longer. Then, at the timing of time t8, the hydrogen gas pressure P(t) in the hydrogen tanks 232A, 232B, and 232C reaches the minimum operating pressure PC, and the fuel cell 229 switches from the on state to the off state (see FIG. 5B(e)).

[0064] As described above, by adding not only the flow rate control but also the temperature control of the first circulating water, it becomes possible to make the operating time of the fuel cell 229 longer, and by extension, it becomes possible to further reduce the waste of the hydrogen gas stored in the hydrogen storage alloy in the hydrogen tank 232 (MH tank).

[0065] According to the fuel cell system 22 of the above embodiment, when a sudden increase in the power load on the fuel cell 229 in the work machine 1 equipped with the fuel cell 229 causes the pressure of the hydrogen gas to reach a predetermined pressure higher than the minimum operating pressure, it is possible to increase the temperature inside the hydrogen tank 232 and increase the amount of hydrogen gas supplied (flow rate), without causing the pressure to suddenly drop to the minimum operating pressure of the hydrogen gas required for operation of the fuel cell 229. Therefore, when a sudden increase in the power load on the fuel cell 229 in the work machine 1 equipped with the fuel cell causes the hydrogen gas pressure inside the hydrogen tank 232 to reach a predetermined pressure higher than the minimum operating pressure of the fuel cell 229, it is possible to increase the amount of hydrogen gas supplied to the fuel cell 229, so that the amount of hydrogen gas supplied to the fuel cell 229 can be increased quickly in response to the increase in the power load.

[0066] Furthermore, in the hydrogen tank 232 (MH tank) that uses a hydrogen storage alloy capable of carrying hydrogen gas, the hydrogen gas is controlled to be released by increasing the temperature without reducing the pressure, which makes it possible to extend the operating time of the fuel cell 229 and further reduce the amount of unused hydrogen gas stored in the hydrogen storage alloy in the hydrogen tank 232 (MH tank).

[0067] In the present embodiment, the PWM pump 224 is used to control the flow rate of the first circulating water flowing through the temperature adjustment device 220, but the present invention is not limited to this. For example, the flow rate of the first circulating water flowing through the temperature adjustment device 220 may be controlled using a flow control valve instead of the PWM pump 224. In particular, the fuel cell system 22 is provided with a flow control valve that adjusts the flow rate of the first circulating water flowing through the first circulating water supply path 24 instead of the PWM pump 224, and the control unit 230 is configured to determine the flow rate of the first circulating water flowing through the first circulating water supply path 24 based on the deviation between a predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, and to control the flow control valve so that the flow rate of the first circulating water flowing through the first circulating water supply path 24 becomes the determined flow rate. In this case, the same operations and effects as those of the present embodiment can be obtained.

[0068] Furthermore, in this embodiment, the remaining amount of hydrogen in hydrogen tanks 232A, 232B, and 232C is calculated based on the current value from fuel cell 229, but the present invention is not limited to this. For example, the present invention may be configured such that hydrogen gas supply path 27 further includes a flow sensor having the function of detecting the flow rate of hydrogen gas supplied from hydrogen tanks 232A, 232B, and 232C to fuel cell 229, and control unit 230 calculates the amount of hydrogen consumed by integrating the flow rate (detected value) obtained from this flow sensor, thereby calculating the remaining amount of hydrogen in hydrogen tanks 232A, 232B, and 232C. In this case, the same operations and effects as those of this embodiment can be obtained.

[0069] Furthermore, in this embodiment, the control unit 230 is configured to have the function of detecting the value of the current output to the load and the function of detecting the flow rate of hydrogen gas supplied to the fuel cell 229, but the present invention is not limited to this. For example, the present invention may be configured such that the control unit 230 is provided with an ammeter that detects the value of the current output to the load, and the control unit 230 appropriately acquires the detected value. In this case, too, the same operations and effects as those of this embodiment can be obtained.

[0070] Furthermore, in this embodiment, the temperature of the hydrogen tanks 232A-232C is adjusted using only the first circulating water flowing through the first circulating water supply path 24, but the present invention is not limited to this. For example, the present invention may be configured such that the control unit 230 controls the switching of the three-way valve 231A to adjust the temperature of the hydrogen tanks 232A-232C using the heat generated by the fuel cell 229, and the second circulating water discharged from the fuel cell 229 flows through the first circulating water supply path 24. Even in this case, the same operation and effects as in this embodiment can be obtained. Furthermore, compared to this embodiment, since residual heat from the fuel cell 229 is used, the operating time of the heater 221 can be shortened, which in turn makes it possible to reduce power consumption.

[0071] Furthermore, in this embodiment, the amount of hydrogen gas supplied to the fuel cell is controlled by determining a sudden increase in load power based on changes in the pressure of hydrogen gas in the hydrogen tank 232, but the present invention is not limited to this. For example, the present invention may also be configured such that the control unit 230 predicts a sudden increase in workload based on the operation of a joystick operated by an operator and controls the amount of hydrogen gas supplied to the fuel cell to increase. In this case, too, the same operations and effects as those of this embodiment can be obtained.

[0072] [Variations] Fig. 6 is a block diagram showing a schematic configuration of a fuel cell system 22A according to a modification of the fuel cell system 22 of Fig. 1. The fuel cell system 22A of Fig. 6 differs from the fuel cell system 22 of Fig. 1 in that a first circulating water supply path 24, which circulates first circulating water that adjusts the temperature in each hydrogen tank 232, and a second circulating water supply path 25, which circulates second circulating water (cooling water) that cools the fuel cell 229, are configured separately. Specifically, in the fuel cell system 22 of Fig. 1, the fifth flow path 24e of the first circulating water supply path 24 and the eighth flow path 25a of the second circulating water supply path 25 are shared, and the three-way valves 231A and 231B are used to switch the flows of the first circulating water (hot water) and the second circulating water (cooling water) through the first circulating water supply path 24 and the second circulating water supply path 25, respectively. In contrast, in the fuel cell system 22A of Fig. 6, the fifth flow path 24e of the first circulating water supply path 24 and the eighth flow path 25a of the second circulating water supply path 25 are configured separately, so there is no need to provide the three-way valve 231A and the three-way valve 231B. Even in this case, the same effects as in the above-described embodiment can be obtained. Furthermore, since there is no need to control the flows of the first and second circulating waters using the three-way valve 231A and the three-way valve 231B as in the fuel cell system 22 of Fig. 1 according to the above-described embodiment, control is made easier than in the fuel cell system 22 according to the above-described embodiment because control for increasing the temperature in the hydrogen tank and control for cooling the fuel cell 229 are performed separately.

[0073] As described above, the fuel cell system 22 according to the first aspect is a fuel cell system 22 comprising a hydrogen tank 232 for storing hydrogen gas and a fuel cell 229 for generating electricity by receiving hydrogen gas from the hydrogen tank 232, and further comprising a temperature adjustment device 220 for adjusting the temperature within the hydrogen tank 232, and a control unit 230 for controlling the temperature adjustment device 220 based on the amount of hydrogen remaining within the hydrogen tank 232, and for raising the temperature of the hydrogen tank 232 when the amount of hydrogen remaining is equal to or less than a first predetermined value.

[0074] With this configuration, temperature adjustment device 220 can be quickly controlled based on the amount of hydrogen remaining in hydrogen tank 232, so the temperature inside hydrogen tank 232 can be adjusted immediately when the amount of hydrogen remaining in hydrogen tank 232 falls below a first predetermined value. Therefore, in a work machine 1 equipped with a fuel cell 229, even if a sudden power load is placed on fuel cell 229, the amount of hydrogen gas output from hydrogen tank 232 to fuel cell 229 can be quickly increased by quickly adjusting the temperature inside hydrogen tank 232 using temperature adjustment device 220. Therefore, the amount of hydrogen gas supply required can be quickly adjusted to match the required output power of fuel cell 229 without reducing responsiveness.

[0075] In addition to the fuel cell system 22 according to the first embodiment, at least one of the following configurations (a) to (m) can be added. (a) further comprising a first circulating water supply path 24 for circulating first circulating water for adjusting the temperature inside the hydrogen tank 232; The temperature control device 220 is arranged in the first circulating water supply path 24 and includes a heater 221 that increases the temperature of the first circulating water, and the control unit 230 starts to energize the heater 221 when the remaining amount of hydrogen is less than or equal to a first predetermined value, thereby increasing the temperature of the hydrogen tank 232.

[0076] According to this configuration, heater 221 can be used to instantly raise the temperature of the first circulating water that adjusts the temperature inside hydrogen tank 232, so that when the remaining amount of hydrogen is below a first predetermined value, heater 221 can be used to instantly raise the temperature inside hydrogen tank 232, allowing the amount of hydrogen gas supply required to match the output power of fuel cell 229 more quickly. Furthermore, the amount of hydrogen gas left unused inside hydrogen tank 232 can be reduced.

[0077] (b) The temperature control device 220 further includes a first radiator 222 arranged in the first circulating water supply path 24 to cool the temperature of the first circulating water, and a first fan 223 that blows cooling air through the first radiator 222.

[0078] According to this configuration, since the first radiator 222 that cools the temperature of the first circulating water is further provided, the temperature inside the hydrogen tank 232 can be adjusted without increasing the temperature inside the hydrogen tank 232 more than necessary. Therefore, it is possible to prevent the supply of more hydrogen gas than necessary for the output power of the fuel cell 229.

[0079] (c) The fuel cell 229 further includes a second circulating water supply path 25 for circulating second circulating water for cooling the fuel cell 229, and the first circulating water supply path 24 branches off from the second circulating water supply path 25.

[0080] According to this configuration, the fuel cell 229 can be cooled using the second circulating water, and therefore it is possible to prevent the fuel cell 229 from becoming too hot due to heat generation.

[0081] (d) The second circulating water supply path 25 further includes a second radiator 226 for cooling the temperature of the second circulating water, and a second fan 227 for blowing cooling air through the second radiator 226.

[0082] According to this configuration, since the second radiator 226 that cools the temperature of the second circulating water that cools the fuel cell 229 is further provided, it is possible to maintain the cooling efficiency of the fuel cell 229 for a long period of time.

[0083] (e) The control unit 230 calculates a target temperature from the calculated remaining hydrogen amount based on a characteristic map of temperature versus remaining hydrogen amount, and controls the heater 221 so that the actual temperature of the first circulating water flowing through the first circulating water supply path 24 becomes the calculated target temperature.

[0084] According to this configuration, the target temperature of the first circulating water is determined using a characteristic map relating temperature to the remaining amount of hydrogen, so the target temperature of the first circulating water can be calculated quickly. Furthermore, if it becomes necessary to change the characteristic map data depending on the work machine 1, the characteristic map data can be easily changed.

[0085] (f) further comprising a hydrogen gas supply path 27 for supplying hydrogen gas from the hydrogen tank 232 to the fuel cell 229; A pressure sensor P for detecting the pressure of the hydrogen gas stored in the hydrogen tank 232 is disposed in the hydrogen gas supply path 27 .

[0086] According to this configuration, the amount of hydrogen remaining in the hydrogen tank 232 can be detected simply by detecting the pressure immediately before it is input to the fuel cell 229 .

[0087] (g) Further provided with a flow control valve for adjusting the flow rate of the first circulating water flowing through the first circulating water supply path 24, the control unit 230 determines the flow rate of the first circulating water flowing through the first circulating water supply path 24 based on the deviation between the second predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, and controls the flow control valve so that the flow rate flowing through the first circulating water supply path 24 becomes the determined flow rate.

[0088] According to this configuration, the flow rate of the first circulating water can be determined based on the deviation between the second predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, so that the flow rate of the first circulating water can be easily determined.

[0089] (h) Further provided is a PWM pump 228 that adjusts the flow rate of the first circulating water flowing through the first circulating water supply path 24, and the control unit 230 determines the flow rate of the first circulating water flowing through the first circulating water supply path 24 based on the deviation between a first predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, and controls the PWM pump 228 so that the flow rate flowing through the first circulating water supply path 24 becomes the determined flow rate.

[0090] According to this configuration, the flow rate of the first circulating water can be determined based on the deviation between the second predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, so that the flow rate of the first circulating water can be easily determined.

[0091] (i) The first predetermined value is located in the range between the minimum operating pressure of hydrogen gas required for the fuel cell 229 to operate and 1.0 MPa.

[0092] According to this configuration, the pressure of the hydrogen gas supplied to the fuel cell 229 is controlled to be less than 1.0 MPa, thereby ensuring safety.

[0093] (j) The minimum operating pressure of hydrogen gas required for the fuel cell 229 to operate is set to 0.85 MPa.

[0094] (k) The control unit 230 stops power generation by the fuel cell 229 when the pressure of the hydrogen gas detected by the pressure sensor P becomes equal to or lower than the minimum operating pressure of the hydrogen gas required for the fuel cell 229 to operate.

[0095] According to this configuration, power generation by the fuel cell 229 is stopped when the pressure of the hydrogen gas falls below the minimum operating pressure, so that unnecessary power generation by the fuel cell 229 can be suppressed.

[0096] (l) The hydrogen tank 232 contains a hydrogen storage alloy, and releases the hydrogen gas stored in the hydrogen storage alloy to supply it to the fuel cell 229 .

[0097] This configuration makes it possible to store a large amount of hydrogen gas at low pressure.

[0098] (m) The control unit 230 calculates the remaining amount of hydrogen based on the flow rate of hydrogen gas or the current value from the fuel cell 229.

[0099] This configuration makes it easy to calculate the amount of hydrogen remaining in the hydrogen tank 232.

[0100] Moreover, the work machine 1 according to the second aspect is equipped with the fuel cell system 22 according to the first aspect.

[0101] Furthermore, a control method for a fuel cell system 22 according to a third aspect is a control method for a fuel cell system 22 including a hydrogen tank 232 that stores hydrogen gas and a fuel cell 229 that generates electricity by receiving a supply of hydrogen gas from the hydrogen tank 232, and includes the steps of circulating first circulating water that adjusts the temperature inside the hydrogen tank 232 through the first circulating water supply path 24, raising the temperature of the first circulating water flowing through the first circulating water supply path 24, and raising the temperature of the first circulating water based on the remaining amount of hydrogen in the hydrogen tank 232. In the step of increasing the temperature of the first circulating water, the remaining amount of hydrogen in the hydrogen tank 232 is calculated, and the temperature of the first circulating water is increased when the calculated remaining amount of hydrogen is equal to or less than a first predetermined value.

[0102] With this configuration, temperature adjustment device 220 can be quickly controlled based on the amount of hydrogen remaining in hydrogen tank 232, so the temperature inside hydrogen tank 232 can be adjusted immediately when the amount of hydrogen remaining in hydrogen tank 232 falls below a first predetermined value. Therefore, in a work machine 1 equipped with a fuel cell 229, even if a sudden power load is placed on fuel cell 229, the amount of hydrogen gas output from hydrogen tank 232 to fuel cell 229 can be quickly increased by quickly adjusting the temperature inside hydrogen tank 232 using temperature adjustment device 220. Therefore, the amount of hydrogen gas supply required can be quickly adjusted to match the required output power of fuel cell 229 without reducing responsiveness.

[0103] In addition to the control method for the fuel cell system 22 according to the third embodiment, at least one of the following configurations (n) to (r) can be added. (n) Calculate the remaining amount of hydrogen based on the flow rate of hydrogen gas or the current value from the fuel cell 229.

[0104] This configuration makes it easy to calculate the amount of hydrogen remaining in the hydrogen tank 232.

[0105] (o) Based on a characteristic map of temperature versus remaining hydrogen amount, the temperature is calculated from the calculated remaining hydrogen amount, and the temperature of the first circulating water flowing through the first circulating water supply path 24 is raised to the calculated temperature.

[0106] According to this configuration, the target temperature of the first circulating water is determined using a characteristic map relating temperature to the remaining amount of hydrogen, so the target temperature of the first circulating water can be calculated quickly. Furthermore, if it becomes necessary to change the characteristic map data depending on the work machine 1, the characteristic map data can be easily changed.

[0107] (p) The method includes the steps of adjusting the flow rate of the first circulating water flowing through the first circulating water supply path 24, detecting the pressure of the hydrogen gas stored in the hydrogen tank 232, and determining the flow rate of the first circulating water flowing through the first circulating water supply path 24 based on the deviation between the second predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, and controlling the flow rate of the first circulating water flowing through the first circulating water supply path 24 to be the determined flow rate.

[0108] According to this configuration, the flow rate of the first circulating water can be determined based on the deviation between the second predetermined value and the pressure of the hydrogen gas detected by the pressure sensor P, so that the flow rate of the first circulating water can be easily determined.

[0109] (q) The second predetermined value is located in the range between the minimum operating pressure of hydrogen gas required for the fuel cell 229 to operate and 1.0 MPa.

[0110] According to this configuration, the pressure of the hydrogen gas supplied to the fuel cell 229 is controlled to be less than 1.0 MPa, thereby ensuring safety.

[0111] (r) The minimum operating pressure of hydrogen gas required for the fuel cell 229 to operate is set to 0.85 MPa.

[0112] Although the present invention has been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0113] 1. Agricultural tractors 2. Body 3. Bonnet 4. Cockpit 5 Cabins 6 Running gear 7. Drive unit 8. Steps for boarding and alighting 9 Three-point linkage mechanism 10 PTO shaft (power take-off shaft) 11 Rear wheel 12 Front wheels 21 Drive motor 22, 22A fuel cell system 23 Controller 24 First circulating water supply route 25 Second circulating water supply route 27 Hydrogen gas supply route 41 Cabin frame 42 Boarding door 43 Ceiling Wall 44 Controls 46 Air conditioner unit 220 Temperature control device 221 Heater 222,226 Radiator 223,227 Fan (FAN) 224,228 PWM pump 229 Fuel Cell 230 Control unit (ECU)

Claims

1. The car body and A bonnet provided at a front part of the vehicle body; A traveling device that supports the vehicle body so that it can travel; A drive motor that drives the traveling device; A PTO shaft that transmits power to a working device; a fuel cell system including a fuel cell and supplying electric power generated by the fuel cell to the drive motor; a battery that stores the power generated by the fuel cell; The fuel cell and the battery are disposed within the hood of the tractor.

2. 2. The tractor according to claim 1, wherein the fuel cell system is disposed at a higher position than the drive motor.

3. The tractor according to claim 1 , wherein the fuel cell system is disposed forward of the drive motor.

4. 2. The tractor according to claim 1, wherein the height of the fuel cell system is greater than the height of the battery.

5. an inverter for controlling the drive motor; 2. The tractor according to claim 1, wherein the inverter is disposed forward of the drive motor.

6. 6. The tractor according to claim 5, wherein the inverter is disposed within the hood.

7. The tractor is provided with a step for an operator to get on and off the tractor, 2. The tractor according to claim 1, wherein the boarding and disembarking step is disposed rearward of the fuel cell system.

8. 8. The tractor according to claim 7, wherein the boarding and disembarking step is disposed between the fuel cell system and the drive motor.

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