Work machine and method

Abstract

In the present invention, a control device causes a power storage device to discharge power stored therein when a stop instruction for a work machine is received. The control device performs stop processing for a fuel cell module after the discharge of the power storage device, and causes the power storage device to be charged with generated power generated as a result of the stop processing.

Description

Work machine and method

[0001] This application claims priority to Japanese Patent Application No. 2024-056246, filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0002] In the technical field of work machines, work machines equipped with fuel cell modules are known. Fuel cells generate electrical energy through a chemical reaction between hydrogen and oxygen. The hydrogen fuel is supplied from a tank filled with hydrogen gas, and the oxygen is supplied from the atmosphere.

[0003] During the shutdown process of a fuel cell, if hydrogen remains in the anode and air remains in the cathode, the air and hydrogen may combine while the fuel cell is shut down, creating an undesirable potential and potentially resulting in oxidation or corrosion. Therefore, it is desirable to completely react the hydrogen and oxygen remaining in the fuel cell. In this case, surplus power is generated when the remaining hydrogen and oxygen react in the fuel cell. Patent Document 1 discloses a technology for charging a capacitor with the surplus power generated when the fuel cell is shut down in order to improve energy efficiency.

[0004] JP 2018-006125 A

[0005] However, the remaining capacity of the power storage device mounted on the work machine is not necessarily sufficient, and it may not be possible to charge all of the surplus power into the power storage device. Patent Document 1 discloses that when the remaining capacity of the power storage device runs out, the power of the power storage device and the power generated by the fuel cell are consumed by the load.

[0006] On the other hand, the power generated by the fuel cell during shutdown processing varies depending on external environmental factors, etc. For example, the power generated by the fuel cell during shutdown processing fluctuates depending on the outside temperature, operating time, etc. Therefore, in order to have the load consume the power generated by the fuel cell during shutdown processing, the control device must perform complex control to balance the power generated and the power consumed.

[0007] An object of the present disclosure is to provide a work machine and method that can absorb the generated power caused by the shutdown process of a fuel cell with simple and robust control.

[0008] According to one aspect of the present invention, a work machine is a work machine equipped with a work implement, and is provided with a fuel cell module, a power storage device, and a control device, wherein the control device discharges the power stored in the power storage device when it receives an instruction to stop the work machine, and after discharging the power storage device, performs a process to stop the fuel cell module, and charges the power storage device with the generated power produced by the stop process.

[0009] The working machine according to the above aspect can absorb the generated power caused by the process of stopping the fuel cell with simple and robust control.

[0010] Fig. 1 is a perspective view of a work machine according to a first embodiment. Fig. 2 is a schematic block diagram showing the configuration of a work machine according to a first embodiment. Fig. 3 is a schematic block diagram showing the configuration of a control system provided in the work machine according to the first embodiment. Fig. 4 is a flowchart showing stop processing of a work machine according to the first embodiment. Fig. 5 is a schematic block diagram showing the configuration of a computer according to the embodiment.

[0011] First Embodiment Configuration of Work Machine 1 Figure 1 is a perspective view of a work machine 1 according to the first embodiment. The work machine 1 according to the first embodiment is, for example, a hydraulic excavator. The work machine 1 includes a traveling body 110, a revolving body 120, a work implement 130, a driver's cab 140, and a machine room 150. The work machine 1, which is a hydraulic excavator, excavates earth and sand and levels the ground at a work site or the like. The traveling body 110 and the revolving body 120 form a vehicle body.

[0012] The running body 110 supports the work machine 1 so that it can travel. The running body 110 has a pair of left and right tracks. The work machine 1 moves forward, swing, or reverse by rotation of the pair of tracks. The rotating body 120 is supported on the running body 110 so that it can swing. The rotating body 120 swings relative to the running body by an electric swing motor 322, which will be described later. The rotating body 120 supports the work implement 130, the operator's cab 140, the machine room 150, and the fuel cell system 20.

[0013] The work implement 130 is operably supported on the body of the work machine 1. The work implement 130 includes a boom 131, an arm 132, and an attachment 133 which is a working tool. The attachment 133 is an example of a working tool. In the example shown in FIG. 1 , the attachment 133 is a bucket. The base end of the boom 131 is rotatably attached to the front end of the rotating unit 120. The base end of the arm 132 is rotatably attached to the tip of the boom 131. The attachment 133 is rotatably attached to the tip of the arm 132.

[0014] The work implement 130 is driven by a plurality of actuators, which include, for example, a boom cylinder 131C, an arm cylinder 132C, and an attachment cylinder 133C.

[0015] The boom cylinder 131C is a hydraulic cylinder for driving the boom 131. The base end of the boom cylinder 131C is attached to the revolving unit 120. The tip end of the boom cylinder 131C is attached to the boom 131. The arm cylinder 132C is a hydraulic cylinder for driving the arm 132. The base end of the arm cylinder 132C is attached to the boom 131. The tip end of the arm cylinder 132C is attached to the arm 132. The attachment cylinder 133C is a hydraulic cylinder for driving the attachment 133. The base end of the attachment cylinder 133C is attached to the arm 132. The tip end of the attachment cylinder 133C is attached to the attachment 133.

[0016] The cab 140 is where the operator of the work machine 1 gets in and operates and pilots the work machine 1. The cab 140 is located, for example, on the left side of the front end of the rotating bed 120. The cab 140 of the work machine 1 is equipped with an operating device 142 for operating the work machine 1, and a power switch 143.

[0017] The operating device 142 is operated by an operator to operate the work machine 1. The operating device 142 outputs an operating signal in response to operation by the operator. The power switch 143 is a switch for starting or terminating operation of the work machine 1. The power switch outputs a signal in response to operation by the operator. The power switch 143 outputs a start request signal when operated on when the power to the work machine is off. The power switch 143 outputs a stop request signal when operated off when the power to the work machine is on. The power switch 143 may be, for example, a switch that outputs a start request signal when pressed by the operator when the power to the work machine 1 is off, and a switch that outputs a stop request signal when pressed by the operator when the power to the work machine 1 is on. Alternatively, for example, the power switch 143 may be a key switch that is operated by turning a key from the off position to the on position and then to the start position. In this case, the power switch 143 outputs a start request signal when the key is turned from the off position to the start position, and outputs a stop request signal when the key is turned from the on position to the off position. Furthermore, for example, the power switch 143 may be a portable operating device carried by an operator, and when the operator operates the portable operating device, wireless communication is established between the portable operating device and the main control device 145, and a start request signal and a stop request signal are output on the condition that communication is established. The portable operating device may be, for example, a remote control key with an embedded electronic chip, or a portable computer device such as a smartphone or a personal digital assistant. Furthermore, the power switch 143 may be configured to be located in a remote location and to output the start request signal and the stop request signal by remote operation, for example.

[0018] The main control device 145 controls the work machine 1. The main control device 145 receives operation signals from the operation device 142. Based on the operation signals from the operation device 142, the main control device 145 controls the travel of the traveling body 110, the drive of the work machine 130, and the swing operation of the swing body 120.

[0019] The main control device 145 acquires a signal from the power switch 143. When the main control device 145 acquires a start request signal from the power switch 143, it starts the work machine 1. When the main control device 145 acquires a start request signal from the power switch 143, it performs start-up processing for each fuel cell module. When the main control device acquires a stop request signal from the power switch 143, it stops the work machine 1. When the main control device 145 acquires a stop request signal from the power switch 143, it performs stop processing for each fuel cell module.

[0020] The fuel cell system 20, which will be described later, is disposed in the machinery room 150. The machinery room 150 is disposed, for example, behind the operator's cab 140. The machinery room 150 forms a space in which the fuel cell system 20 is disposed.

[0021] 2 is a schematic block diagram showing the configuration of a work machine 1 according to the first embodiment. The work machine 1 is equipped with a fuel cell system 20 and a drive system 30. The fuel cell system 20 generates electric power for driving the work machine 1. The fuel cell system 20 generates electric power for driving the drive system 30. The electric power generated by the fuel cell system 20 is output to the drive system 30 via a bus line B. The drive system 30 uses the electric power generated by the fuel cell system 20 to cause the traveling body 110 to travel, drive the work implement 130, and perform the swing operation of the swing body 120.

[0022] The fuel cell system 20 includes a plurality of fuel cell modules 21 and a power storage device module 22 connected in parallel to a bus B.

[0023] Each fuel cell module 21 includes a fuel cell 211, a power converter 212, auxiliary equipment 213, and a fuel cell control device 214. The fuel cell 211 generates electricity by causing an electrochemical reaction between hydrogen and oxygen. The power converter 212 is, for example, a DC-DC converter, and is configured to be able to control the output of the power generated by the fuel cell 211. The power converter 212 converts the power generated by the fuel cell 211 and supplies it to the bus B. The auxiliary equipment 213 is a device for operating the fuel cell 211. The fuel cell module 21 includes, as the auxiliary equipment 213, a hydrogen pump for supplying hydrogen gas to the fuel cell 211, an air compressor for generating compressed air to be supplied to the fuel cell 211, and a water pump for supplying cooling water to cool the fuel cell 211. The fuel cell control device 214 controls the fuel cell module 21 in accordance with commands from the main control device 145. The fuel cell control device 214 monitors the status of the fuel cell 211 and outputs data indicating the status of the fuel cell 211 to the main control device 145. The fuel cell control device 214 is an example of a monitoring device.

[0024] The power storage device module 22 includes a power storage device 221 and a power converter 222. The power storage device 221 is configured to be able to charge or discharge surplus power from the bus B. The power converter 222 is, for example, a DC-DC converter, and controls the input and output of power to and from the power storage device 221. The power converter 222 outputs power from the power storage device 221 in accordance with a command from the main control device 145. The power storage device 221 is, for example, a capacitor.

[0025] The drive system 30 includes a hydraulic drive module 31 and a slewing module 32 .

[0026] The hydraulic drive module 31 includes an inverter 311, an electric pump motor 312, a hydraulic pump 313, and a hydraulic actuator 314. The inverter 311 converts DC current from the bus B into three-phase AC current and supplies it to the electric pump motor 312. The electric pump motor 312 generates power for driving the work machine 130 and the traveling vehicle 110. The electric pump motor 312 is rotated by the supplied three-phase AC current and drives the hydraulic pump 313. The hydraulic pump 313 discharges hydraulic oil to be supplied to the hydraulic actuator 314. The hydraulic oil discharged from the hydraulic pump 313 is supplied to the hydraulic actuator 314 via a control valve (not shown). The hydraulic actuator 314 is driven by the supplied hydraulic oil. The hydraulic actuator 314 includes a boom cylinder 131C, an arm cylinder 132C, an attachment cylinder 133C, and a traveling motor 134. The rotational force generated by the traveling motor 134 is transmitted to the traveling body 110 .

[0027] The swing module 32 includes an inverter 321 and an electric swing motor 322. The inverter 321 converts DC current from the bus B into three-phase AC current and supplies it to the electric swing motor 322. The electric swing motor 322 generates power for swinging the swing unit 120. The electric swing motor 322 rotates by the supplied three-phase AC current, causing the swing unit 120 to swing relative to the traveling unit 110.

[0028] The work machine 1 is equipped with a control system 14. Figure 3 is a schematic block diagram showing the configuration of the control system 14 equipped in the work machine 1 according to the first embodiment. The control system 14 is equipped with a measuring device 141, an operating device 142, a power switch 143, and a main control device 145.

[0029] The measuring device 141 includes a fuel gauge that measures the charging rate of the power storage device, a current sensor that measures the current passing through the inverter 155, and a voltage sensor that measures the voltage of the bus B.

[0030] The main control device 145 includes a receiving unit 501 , a fuel cell control unit 502 , and a drive control unit 503 .

[0031] When the operator turns off the power switch 143, the receiving unit 501 receives the command signal output by the power switch 143 to stop the work machine 1. The receiving unit 501 receives measurement data from the measuring device 141.

[0032] When the receiving unit 501 receives a command signal to stop the work machine 1, the fuel cell control unit 502 outputs a power control command to the fuel cell control devices 214 of the multiple fuel cell modules 21. The fuel cell control unit 502 outputs a power control command to the fuel cell control devices 214 of all of the fuel cell modules 21 to set the output power to zero. As a result, power is no longer supplied from all of the fuel cell modules 21. At this time, the fuel cell control device 214 controls the fuel cell 211 to generate the power required to maintain operation of the auxiliary devices 213. In other words, the power control command to set the output power to zero may be an idling command to put the fuel cell module 21 into an idling state.

[0033] When the load control unit stops driving the electric pump motor, the fuel cell control unit 502 outputs a stop command to the fuel cell control devices 214 of the multiple fuel cell modules 21. Upon receiving the stop command, the fuel cell control device 214 of the fuel cell module 21 executes a predetermined stop process. For example, the fuel cell control device 214 executes the stop process in the following procedure. The fuel cell control device 214 stops the hydrogen pump, which is the auxiliary device 213, and uses the air compressor to compress air to the fuel cell 211, causing the hydrogen remaining in the fuel cell module 21 to react with oxygen in the air. The fuel cell control device 214 controls the power converter 212 to supply the power generated by the fuel cell 211 to the bus B. The fuel cell control device 214 monitors the power generated by the fuel cell 211 and continues generating power until the generated power falls below a predetermined value. When the generated power falls below the predetermined value, the fuel cell control device 214 stops all the auxiliary devices 213 and the power converter 212. This allows the fuel cell control device 214 to completely react the remaining hydrogen in the fuel cell 211. At this time, the fuel cell 211 is shut down. After shutting down all of the auxiliaries 213 and the power converter 212, the fuel cell control device 214 outputs a shutdown process end signal to the receiving unit 501. While the shutdown process for the fuel cell module 21 is being executed, the power converter 222 of the power storage device module 22 performs control to maintain the voltage of the bus B. Therefore, the power generated by the shutdown process for the fuel cell module 21 is charged into the power storage device 221.

[0034] The drive control unit 503 outputs a drive instruction to the inverter 311 to drive the electric pump motor 312 based on the measurement data of the charge rate of the power storage device acquired by the receiving unit 501. The power converter 222 of the power storage device module 22 only needs to perform control to maintain the voltage of the bus B, and therefore does not need complex control to make the electric pump motor 312 consume the power stored in the power storage device 221.

[0035] When the charging rate of the power storage device 221 is equal to or higher than the target charging rate, the drive control unit 503 outputs a drive instruction to the inverter 311 to drive the electric pump motor 312. At this time, the power stored in the power storage device 221 is discharged, and the electric pump motor 312 consumes the power discharged from the power storage device 221. Furthermore, when the charging rate of the power storage device 221 is lower than the target charging rate, the load control unit stops outputting a drive instruction to the inverter 311 to drive the electric pump motor 312. At this time, the discharge of the power stored in the power storage device 221 stops, and the drive of the electric pump motor 312 stops. The target charging rate is a charging rate that is set in advance so that a sufficient capacity is secured to absorb the generated power during shutdown processing of the multiple fuel cell modules 21. Note that when the work machine 1 is stopped, the actuators are not operated, so the control valves provided between the hydraulic pump 313 and the hydraulic actuators 314 are switched to the unload position. Therefore, the hydraulic oil supplied from the hydraulic pump 313 by the rotation of the electric pump motor 312 is returned to the tank by the unloading circuit of the control valve.

[0036] <<Control When Stopping the Work Machine 1>> Figure 4 is a flowchart showing the process for stopping the work machine 1 according to the first embodiment. When the operator turns off the power switch 143, the power switch 143 outputs a command signal to stop the work machine 1 to the receiving unit 501 of the main control device 145. When a command signal to stop the work machine 1 is input from the power switch 143 to the receiving unit 501 by operation of the operator, the main control device 145 stops the fuel cell system 20 in the following procedure.

[0037] First, the fuel cell control unit 502 outputs a power control command to the fuel cell control devices 214 of all fuel cell modules 21 to set the output power to zero (step S1).

[0038] Next, the load control command output unit outputs a drive command to the inverter 311 to drive the electric pump motor 312 so that the electric power stored in the power storage device 221 is consumed by the electric pump motor 312 (step S2).

[0039] The load control command output unit monitors the charge rate of the power storage device 221 and continues to output a drive command for the electric pump motor 312 until the charge rate falls below the target charge rate (step S3). When the charge rate of the power storage device 221 falls below the target charge rate, the load control command output unit stops discharging from the power storage device 221 and driving of the electric pump motor 312 (step S4).

[0040] Next, the fuel cell control unit 502 outputs a stop command to the fuel cell control devices 214 of the plurality of fuel cell modules 21 (step S5). Because the charge rate of the power storage device 221 has already been sufficiently reduced in step S2, all of the power generated by the plurality of fuel cell modules 21 is absorbed by the power storage device 221.

[0041] The main control device 145 waits until the shutdown process is complete for all fuel cell modules 21 (step S6). The main control device 145 may recognize the completion of the shutdown process by, for example, receiving a notification of the completion of the shutdown process from the fuel cell control device 214, or may monitor changes in the output voltage of the fuel cell module 21 and determine that the shutdown process is complete when the output voltage no longer changes. When the shutdown process for all fuel cell modules 21 is complete, the main control device 145 ends the shutdown process for the work machine 1.

[0042] <<Actions and Effects>> As described above, the main control device 145 according to the first embodiment functions as follows. When the main control device 145 receives a command to stop the work machine 1, it discharges the power stored in the power storage device 221. After discharging the power storage device 221, the main control device 145 performs shutdown processing for the fuel cell module 21 and charges the power storage device 221 with the power generated by the shutdown processing. This allows the main control device 145 to keep the capacity of the power storage device 221 available so that the power generated by the shutdown processing can be absorbed before the shutdown processing of the fuel cell module 21. Therefore, the main control device 145 can absorb the power generated by the shutdown processing without performing complex control to have a load such as the electric pump motor 312 consume the power generated by the shutdown processing of the fuel cell module 21. Furthermore, because the work machine 1 can have the power storage device 221 absorb the power generated by the shutdown processing of the fuel cell module 21, a large retarder is not required. Therefore, the work machine 1 may be equipped with a small retarder or may not be equipped with a retarder at all.

[0043] Other Embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design modifications and the like are possible. For example, the main control device 145 according to the embodiment described above may be configured by a single computer, or the configuration of the main control device 145 may be divided into multiple computers that function as the main control device 145 by working together. In this case, some of the computers that make up the main control device 145 may be installed inside the work machine 1, and other computers may be provided external to the work machine 1. The main control device 145 according to the embodiment described above may also have the functionality of the fuel cell control device 214. In this case, each fuel cell module 21 does not need to be equipped with the fuel cell control device 214, and the power converters 212 and auxiliaries 213 of each fuel cell module 21 may operate based on command signals from the main control device 145. The main control device 145 may also function as a monitoring device, having the function of monitoring the status of the fuel cells 211.

[0044] Although the main control device 145 according to the embodiment described above simultaneously executes the shutdown process for the plurality of fuel cell modules 21, this is not limiting. For example, the main control device 145 according to other embodiments may sequentially execute the shutdown process for the plurality of fuel cell modules 21. For example, if the power generated by the shutdown process for the plurality of fuel cell modules 21 exceeds the catalog specifications of the power converter 222, the main control device 145 may divide the plurality of fuel cell modules 21 into several groups and sequentially execute the shutdown process for each group.

[0045] Furthermore, although the work machine 1 according to the embodiment described above is a hydraulic excavator, this is not limiting. For example, the work machine 1 according to other embodiments may be another work machine such as a wheel loader or a dump truck.

[0046] Furthermore, in the work machine 1 according to the embodiment described above, the electric swing motor 322 of the swing module 32 swings the swing unit 120, but this is not limited to this. For example, a work machine 1 according to another embodiment may not be equipped with a swing module 32, and the hydraulic swing motor, which is the hydraulic actuator 314, may swing the swing unit 120.

[0047] Furthermore, in the work machine 1 according to the embodiment described above, the electric pump motor 312 drives the hydraulic actuator 314 to drive the work implement 130 and the traveling body 110, but this is not limited to this. For example, the work machine 1 may be equipped with an electric actuator instead of the electric pump motor 312 and the hydraulic actuator 314, and the work implement 130 may be driven and the traveling body 110 may be traveled by the electric actuator. Furthermore, for example, a work machine 1 according to another embodiment may drive the work implement by hydraulic pressure and the traveling body may be traveled by an electric motor.

[0048] The main control device 145 according to the embodiment described above causes the electric pump motor 312 to consume the power stored in the power storage device 221, but this is not limited to this. For example, the main control device 145 according to other embodiments may cause the electric swing motor 322 or an auxiliary device (such as an air compressor or fan) not shown to consume power. In this case, the main control device 145 may separate the motor from the machine driven by the motor using a clutch not shown so that the rotational force generated by the motor is not transmitted to the machine. Furthermore, for example, the work machine 1 according to other embodiments may be equipped with a retarder, and the retarder may consume power. Furthermore, for example, the work machine 1 according to other embodiments may cause an electric actuator not shown to consume power.

[0049] Furthermore, in the above-described embodiment, a capacitor is given as an example of the power storage device 221, but this is not limiting. For example, the power storage device 221 of the work machine 1 according to other embodiments may be a battery.

[0050] <Computer Configuration> Fig. 5 is a schematic block diagram showing the configuration of a computer according to an embodiment. The computer 90 includes a processor 91, a main memory 92, a storage 93, and an interface 94. The main control device 145 and the fuel cell control device 214 described above are implemented in the computer 90. The operations of the above-described processing units are stored in the storage 93 in the form of a program. The processor 91 reads the program from the storage 93, loads it into the main memory 92, and executes the above-described processing in accordance with the program. The processor 91 also allocates storage areas in the main memory 92 corresponding to the above-described storage units in accordance with the program. Examples of the processor 91 include a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and a microprocessor.

[0051] The program may be for implementing some of the functions to be performed by the computer 90. For example, the program may be implemented in combination with other programs already stored in storage or in combination with other programs implemented in other devices. In another embodiment, the computer 90 may include a custom large-scale integrated circuit (LSI) such as a programmable logic device (PLD) in addition to or instead of the above configuration. Examples of PLDs include programmable array logic (PAL), generic array logic (GAL), complex programmable logic device (CPLD), and field programmable gate array (FPGA). In this case, some or all of the functions implemented by the processor 91 may be implemented by the integrated circuit. Such an integrated circuit is also an example of a processor. In another embodiment, the computer 90 may be virtualized on one or more computers.

[0052] Examples of storage 93 include a magnetic disk, a magneto-optical disk, an optical disk, and a semiconductor memory. Storage 93 may be an internal medium directly connected to the bus of computer 90, or an external medium connected to computer 90 via interface 94 or a communication line. Furthermore, when this program is distributed to computer 90 via a communication line, computer 90 that receives the program may load the program into main memory 92 and execute the above-described processing. In at least one embodiment, storage 93 is a non-transitory tangible storage medium.

[0053] The program may also be a program for realizing some of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-described functions in combination with another program already stored in storage 93.

[0054] The working machine according to the above aspect can absorb the generated power caused by the process of stopping the fuel cell with simple and robust control.

[0055] 1...Work machine 110...Traveling body 120...Swing body 130...Work machine 131...Boom 131C...Boom cylinder 132...Arm 132C...Arm cylinder 133...Attachment 133C...Attachment cylinder 14...Control system 140...Driver's cab 141...Measuring device 142...Operating device 143...Power switch 145...Main control device 150...Machine room 20...Fuel cell system 21...Fuel cell module 211...Fuel cell 212...Power converter 213...Auxiliary equipment 214...Fuel cell control device 22...Power storage device module 221...Power storage device 222...Power converter 30...Drive system 31...Hydraulic drive module 311...Inverter 312...Electric pump motor 312...Electric pump motor 313...Hydraulic pump 314...Hydraulic actuator 32...Swing module 321...Inverter 322: Electric swing motor 501: Receiving unit 502: Fuel cell control unit 503: Drive control unit 90: Computer 91: Processor 92: Main memory 93: Storage 94: Interface B: Bus

Claims

1. A work machine equipped with a work implement, comprising: a fuel cell module; a power storage device; and a control device, wherein the control device discharges the power stored in the power storage device when it receives an instruction to stop the work machine, performs a process to stop the fuel cell module after the power storage device has discharged, and charges the power storage device with the generated power produced by the process to stop the work machine.

2. A work machine according to claim 1, wherein the control device outputs a command to set the output power of the fuel cell module to zero when the control device receives the instruction to stop the work machine.

3. A work machine as claimed in claim 1 or claim 2, wherein the work machine is equipped with a hydraulic pump that pressurizes hydraulic oil for operating the work equipment, and the control device, when receiving the instruction to stop the work machine, operates the hydraulic pump to discharge the electricity stored in the power storage device.

4. A work machine according to claim 1 or claim 2, wherein the control device discharges the power until the charging rate of the power storage device falls below a predetermined value, and performs the stop processing of the fuel cell module after the charging rate of the power storage device falls below the predetermined value.

5. A method relating to a work machine comprising a work implement, a fuel cell module, and a power storage device, comprising discharging the power stored in the power storage device when a stop command for the work machine is received, performing a stop process for the fuel cell module after the power storage device has discharged, and charging the power storage device with the generated power generated by the stop process.

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