Electric work machine

Abstract

Provided is an electric work machine comprising: a fuel cell 110; a secondary battery 135 charged by electric power generated by the fuel cell 110; an electric motor 30 driven by electric power supplied from at least one of the fuel cell 110 and the secondary battery 135; a power mode switch 195 for setting a work mode; and a vehicle body controller 45 for controlling an operation state according to the work mode set by the power mode switch 195, the electric work machine being characterized in that the vehicle body controller 45 drives the electric motor 30 by electric power of the secondary battery 135 when the work mode is set to a mode for suppressing electric power consumption by the electric motor 30 during start preparation of the fuel cell 110. This makes it possible to provide an electric work machine comprising a fuel cell and a secondary battery, wherein overdischarging of the secondary battery is suppressed when an electric motor is to be operated by the secondary battery until the fuel cell is started.

Description

Electric working machine

[0001] The present invention particularly relates to an electric working machine equipped with a fuel cell and a secondary battery and operating on electric power supplied from the fuel cell and the secondary battery.

[0002] In recent years, in consideration of the environment, fuel cells have been mounted on automobiles and commercialized. As a system equipped with a fuel cell in the mobility field, a system is known in which a fuel cell and a secondary battery (battery) are provided, and an electric motor is driven by the electric power output from these.

[0003] Patent Document 1 discloses a moving body including a driving force generating device that generates a driving force for the moving body, a power storage device capable of supplying power to the driving force generating device, a fuel cell capable of supplying power to the driving force generating device, and a control device that controls the driving of the driving force generating device. In this moving body, when it is detected by a front-rear G sensor that the vehicle, which is the moving body, is located on a normal road surface other than a downhill road, it is permitted to start driving a traction motor, which is the driving force generating device, by supplying power only from the power storage device, and when this is executed, the vehicle starts. After that, the power supply to the traction motor is switched from the output of the power storage device to the output of the fuel cell. When overtaking acceleration is started from the steady state, the power of the power storage device is supplied to the traction motor again, and the fuel cell provides assistance.

[0004] Japanese Patent Application Laid-Open No. 2008-72795

[0005] In order to efficiently generate electricity, it is necessary to keep the reaction part where power generation occurs in the fuel cell at an appropriate temperature and humidity. That is, it is necessary to warm up the fuel cell. However, for this reason, the standby time until the fuel cell is started tends to be long. Therefore, in order to quickly start the work by the electric working machine, it is conceivable to operate the electric motor by the secondary battery until the fuel cell is started and perform the work. However, in an electric working machine, since the power consumption due to work is large, if the power stored in the secondary battery is small, the remaining battery level may be insufficient and over-discharge may occur.

[0006] The present invention aims to provide an electric work machine equipped with a fuel cell and a secondary battery, which suppresses over-discharge of the secondary battery when attempting to operate the electric motor using the secondary battery until the fuel cell is started.

[0007] To solve the above problems, the present invention provides an electric work machine comprising a fuel cell, a secondary battery charged by the power generated by the fuel cell, an electric motor driven by power supplied from at least one of the fuel cell and the secondary battery, a mode setting device for setting a work mode, and a control device for controlling the operating state according to the work mode set by the mode setting device, wherein the control device, while preparing to start up the fuel cell, drives the electric motor with the power of the secondary battery if the work mode is set to a mode that reduces the power consumption by the electric motor. In this case, an electric work machine comprising a fuel cell and a secondary battery can be provided that suppresses over-discharge of the secondary battery when attempting to operate the electric motor with the secondary battery until the fuel cell is started up.

[0008] For example, if the control device, while preparing to start the fuel cell, has the remaining capacity of the secondary battery fall below a first threshold or the operating mode set to a mode different from the mode that reduces power consumption by the motor, it will keep the motor stopped until the fuel cell startup preparation is complete. In this case, if the secondary battery is prone to over-discharge, it will suppress over-discharge of the secondary battery by waiting until the fuel cell is started without driving the motor solely with the secondary battery. Also, for example, an operating mode different from the mode that reduces power consumption by the motor includes a mode that prioritizes operating speed. In this case, when prioritizing operating speed, it will suppress over-discharge of the secondary battery by waiting for the fuel cell to start before driving the motor. Furthermore, for example, if the remaining capacity of the secondary battery falls below a predetermined threshold between the time the motor is driven with power from the secondary battery until the fuel cell startup preparation is complete, the control device will stop the motor until the fuel cell startup preparation is complete. In this case, even if the power consumption exceeds the amount expected in advance when operating the motor with the secondary battery until the fuel cell is started, it is possible to prevent the secondary battery from over-discharging. Furthermore, for example, after the fuel cell is ready to start up, the control device drives the electric motor with the power output by the fuel cell, and also controls the charging and discharging of the secondary battery to compensate for any excess or deficiency in the power output by the fuel cell. In this case, it can respond to the output changes required by the electric work machine.

[0009] According to the present invention, it is possible to provide an electric work machine equipped with a fuel cell and a secondary battery that can suppress over-discharge of the secondary battery when attempting to operate the electric motor using the secondary battery until the fuel cell is started.

[0010] This figure shows the overall configuration of the electric work machine in this embodiment. This is an explanatory diagram of the vehicle system provided in the hydraulic excavator shown in Figure 1. This figure shows a flowchart for starting the electric system. This figure explains the thresholds α and β in Figure 3. This figure shows an example of a time chart when step 325 in Figure 3 is set to a mode where only the power from the secondary battery is used as the driving power for the electric motor. This figure shows an example of a time chart when step 335 in Figure 3 is set to standby mode.

[0011] The embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0012] <Description of the overall configuration of the electric work machine> Figure 1 is a diagram showing the overall configuration of the electric work machine in this embodiment. The electric work machine shown is a hydraulic excavator. However, the electric work machine is not limited to this and can be construction machinery such as wheel loaders, bulldozers, and cranes. In addition, the electric work machine can be agricultural machinery such as felling machines, logging machines, tractors, forestry work vehicles, and logging machines.

[0013] The hydraulic excavator comprises a vehicle 3 equipped with a pair of left and right tracks 1 and 2, a slewing body 4 mounted on the vehicle 3, a boom 5 rotatably pinned to one end of the slewing body 4, an arm 6 rotatably pinned to one end of the boom 5, and a bucket 7 rotatably pinned to one end of the arm 6.

[0014] Furthermore, the hydraulic excavator includes a driver's cab 8 mounted on the slewing body 4, a machine room 9 housing a fuel cell, secondary battery, hydraulic pump, etc., and a counterweight 10. In addition, the hydraulic excavator includes travel motors 11 and 12 that drive the tracks 1 and 2, a slewing motor (not shown) that drives the slewing body 4, a pair of left and right boom cylinders 13 and 14 that drive the boom 5, an arm cylinder 15 that drives the arm 6, and a bucket cylinder 16 that drives the bucket 7. In this case, the main working parts correspond to the boom 5, arm 6, and bucket 7, and the posture of these working parts mechanisms is determined by the extension and retraction of the boom cylinders 13 and 14, the arm cylinder 15, and the bucket cylinder 16, respectively.

[0015] Figure 2 is an explanatory diagram of the vehicle body system provided in the hydraulic excavator shown in Figure 1. The main components of the vehicle body system consist of a hydraulic system 180, an electric system 185, an operator system 187, an ambient temperature sensor 205, and a vehicle body controller 45. The hydraulic system 180 consists of a pump 40, a directional control valve 65, a hydraulic actuator (for example, an arm cylinder 15), a hydraulic oil tank 67, a pilot pump 80, a pilot relief valve 90, a lock valve 93, and pilot piping 95.

[0016] The output shaft of the electric motor 30, which constitutes the rotational power generation means, is mechanically connected to the input shaft of the pump 40, and the pump 40 is driven by the electric motor 30. The pump 40 is a variable displacement type, and the volume of the pump 40 is calculated by the vehicle controller 45 and controlled by the pump regulator 50. The pump 40 also draws hydraulic fluid from the hydraulic fluid tank 67 and supplies it to the arm cylinder 15 via the directional control valve 65. When the arm cylinder 15 is driven, the hydraulic fluid is discharged back into the hydraulic fluid tank 67 via the directional control valve 65.

[0017] The electromagnetic proportional valves 65a and 65b appropriately reduce the pressure in the pilot piping 95 (described later) according to the command value of the vehicle controller 45, which is generated based on the operation signal Lv of the electric operation lever 63 (described later), and generate the control pressure of the directional control valve 65. The pilot pump 80 is a device that generates the pressure of the pilot circuit used to control hydraulic equipment. The pilot pump 80 is mechanically connected to the electric motor 30 and driven by the electric motor 30. The hydraulic fluid discharged by the pilot pump 80 maintains the pressure in the pilot piping 95 at a set value (pilot relief pressure) by the pilot relief valve 90. The lock valve 93 opens and closes the valve according to the command of the lock device 200 (described later).

[0018] The electric system 185 consists of an electric motor 30, an inverter 35, a bidirectional converter 130, a step-down converter 115, a step-up converter 112, a fuel cell 110, a fuel cell controller 145, a secondary battery 135, a secondary battery controller 140, an electric-driven A / C (air conditioner) compressor 120, an electric-driven fan 125, an auxiliary controller 147, and a high-voltage circuit 150.

[0019] The high-voltage circuit 150 is connected to a boost converter 112, a bidirectional converter 130, a buck converter 115, and an inverter 35. The fuel cell 110 generates electricity through a chemical reaction between hydrogen and oxygen, and the boost converter 112 increases the voltage to the voltage of the high-voltage circuit 150, supplying power to the high-voltage circuit 150. The inverter 35 converts the voltage of the high-voltage circuit 150 into a three-phase AC voltage to drive the motor 30.

[0020] When surplus power is generated in the high-voltage circuit 150, the bidirectional converter 130 steps down the voltage of the high-voltage circuit 150 to the voltage of the secondary battery 135, charging the secondary battery 135 with the surplus power. In this case, it can be said that the secondary battery 135 is charged by the power generated by the fuel cell 110. When the power of the high-voltage circuit 150 is insufficient, the converter steps up the voltage of the secondary battery 135 to the voltage of the high-voltage circuit 150, discharging the insufficient power into the secondary battery 135. The step-down converter 115 steps down the voltage of the high-voltage circuit 150 to the auxiliary equipment drive voltage, driving the electric-driven A / C compressor 120, the electric-driven fan 125, and auxiliary equipment such as a water pump (not shown). The secondary battery controller 140 transmits information on the remaining capacity of the secondary battery 135 to the vehicle controller 45.

[0021] The operator system 187 consists of an electric operating lever 63, an electric motor control dial 190, a power mode switch (mode switching device) 195, a locking device 200, and a key switch 210. The electric operating lever 63 generates an operating signal Lv according to the operator's operating signal and operating direction. The electric motor control dial 190 sets the target rotational speed of the electric motor 30 by the value of the dial. The power mode switch 195 is a switch that selects an operating mode in which the power consumption of the electric motor 30 differs, and switches between an ECO mode (eco mode) which limits the rotational speed of the electric motor 30 and the volume of the pump 40 in order to prioritize the suppression of the power consumption of the electric motor 30, and a PWR mode (power mode) which does not impose any restrictions in order to prioritize the work performance of the hydraulic system 180. The ECO mode is a mode that prioritizes saving power consumption over work speed. In contrast, the PWR mode is a mode that prioritizes work speed over saving power consumption. The power mode switch 195 functions as a mode switching device that switches the operating mode of the electric motor 30 to set the working mode of the hydraulic excavator. The vehicle controller 45 also functions as a control device that controls the operating state according to the working mode set by the power mode switch 195.

[0022] The locking device 200 shuts off the hydraulic fluid supplied from the pilot pump 80 when the lever is pressed, thereby stopping the operation of the hydraulic excavator. The key switch 210 has three positions: ON, START, and OFF. In the ON position, it sends a start command to the vehicle controller 45 and the electric system 185. In the START position, it sends a drive command to the electric motor 30. Furthermore, in the OFF position, it sends a stop command to the vehicle controller 45 and the electric system 185.

[0023] The ambient temperature sensor 205 measures the ambient temperature. Signals from the electric operating lever 63, motor control dial 190, power mode switch 195, locking device 200, ambient temperature sensor 205, and key switch 210 are transmitted to the vehicle controller 45. The vehicle controller 45 is a higher-level controller that oversees the entire hydraulic excavator system and calculates appropriate command values ​​for the pump regulator 50, electromagnetic proportional valves 65a and 65b, and lower-level controllers (inverter 35, secondary battery controller 140, fuel cell controller 145, and auxiliary equipment controller 147).

[0024] Figure 3 is a flowchart showing the process of starting the electric system 185. In step 300, the key switch 210 is turned ON, and the vehicle controller 45 starts the electric components excluding the fuel cell 110, such as the inverter 35, bidirectional converter 130, secondary battery 135, step-down converter 115, and step-up converter 112. After each component has started up, the process moves to step 305. In step 305, the vehicle controller 45 determines whether the fuel cell 110 has started up. If it has started up, the process moves to step 310; otherwise, it moves to step 315. In step 310, the vehicle controller 45 sets the system to a mode (fuel cell drive mode) where the power from the fuel cell 110 and the secondary battery 135 is used to drive the electric motor 30. In the figure, this is shown as the fuel cell + secondary battery drive mode. In step 310, all components of the electric system 185 are started up, and the process of determining how to supply drive power to the electric motor 30 of the electric system 185 is completed. In this case, after the vehicle controller 45 has finished preparing to start the fuel cell 110, it drives the electric motor 30 with the power output by the fuel cell 110, and controls the charging and discharging of the secondary battery 135 to compensate for any excess or deficiency in the power output by the fuel cell 110.

[0025] In step 315, the vehicle controller 45 determines whether the State of Charge (SOC) of the secondary battery 135 is equal to or greater than the threshold α. If the SOC of the secondary battery 135 is equal to or greater than the threshold α (Yes in step 315), the process proceeds to step 320; otherwise, it proceeds to step 335. The threshold α will be explained in more detail later.

[0026] In step 320, the vehicle controller 45 determines whether the mode switch is set to ECO mode, which prioritizes reducing power consumption over working speed. If it is set to ECO mode (Yes in step 320), the process proceeds to step 325; otherwise, it proceeds to step 335.

[0027] In step 325, the vehicle controller 45 switches to a mode (secondary battery drive mode) where only the power from the secondary battery 135 is used to drive the electric motor 30. After switching to this mode, the process proceeds to step 330. In this case, the vehicle controller 45 can also drive the electric motor 30 with the power from the secondary battery 135 if, while preparing to start the fuel cell 110, the remaining capacity of the secondary battery 135 is above a first threshold (in this case, threshold α) and the work mode is set to a mode that reduces the power consumption of the electric motor 30 (in this case, ECO mode). This allows work by the hydraulic excavator to be started quickly even before the fuel cell 110 has started. Furthermore, the vehicle controller 45 can also maintain the motor 30 in a stopped state until the fuel cell 110 startup preparation is complete if the remaining capacity of the secondary battery 135 is below a first threshold (in this case, threshold α) or if the work mode is set to a mode different from the mode that reduces power consumption by the motor 30 (in this case, ECO mode) while the fuel cell 110 is being prepared to start up. In this case, the work mode that is different from the mode that reduces power consumption by the motor 30 is a mode that prioritizes the work speed of the work equipment (in this case, hydraulic excavator), and this corresponds to the PWR mode. This mode can also be said to be a mode that prioritizes the amount of work. With the above configuration, when attempting to operate the motor 30 with the secondary battery 135 until the fuel cell 110 is started, the secondary battery 135 is less likely to be over-discharged.

[0028] In step 330, the vehicle controller 45 determines whether the State of Charge (SOC) of the secondary battery 135 is below the threshold β. If the SOC is below the threshold β, the process proceeds to step 335; otherwise, it proceeds to step 305. The threshold β will be explained in more detail later.

[0029] In step 335, the vehicle controller 45 switches to a mode in which neither the power from the fuel cell 110 nor the secondary battery 135 is used to drive the electric motor 30. In other words, this mode is a standby mode. After switching to this mode, the vehicle proceeds to step 305. In this case, the vehicle controller 45 can also stop the electric motor 30 until the preparation for starting the fuel cell 110 is complete if, during the preparation for starting the fuel cell 110, the remaining capacity of the secondary battery 135 falls below a predetermined threshold, which is a second threshold (in this case, threshold β), which is smaller than the first threshold (in this case, threshold α). This prevents the secondary battery 135 from being over-discharged even if the power consumption exceeds a predetermined amount (in this case, threshold α) when the electric motor 30 is operated by the secondary battery 135 until the fuel cell 110 is started.

[0030] Steps 310, 325, and 335 are configured to select one of the following work modes. When a work mode is selected within this flow, the previously selected work mode ends, and the system switches to the selected work mode. In this embodiment, the electric motor 30 is driven by power supplied from at least one of the fuel cell 110 and the secondary battery 135. In this embodiment, three work modes are set. These are: step 310, a mode in which the power from the fuel cell 110 and the secondary battery 135 is used to drive the electric motor 30 (fuel cell drive mode); step 325, a mode in which only the power from the secondary battery 135 is used to drive the electric motor 30 (secondary battery drive mode); and a mode in which neither the power from the fuel cell 110 nor the secondary battery 135 is used to drive the electric motor 30 (standby mode).

[0031] Next, we will explain the thresholds α and β in Figure 3. Figure 4 is a diagram illustrating the thresholds α and β in Figure 3. Figure 4 shows the relationship between battery charge and thresholds α and β. As you move upwards in the diagram, the battery charge increases, and as you move downwards, the battery charge decreases. The diagram shows that thresholds α and β are set between the state of full charge and the state of over-discharge. Threshold α is greater than threshold β (α > β).

[0032] The threshold α is set to a value that can secure the amount of power necessary to start up the fuel cell 110. For example, the threshold α is the time it takes for the fuel cell 110 to start up × the power required to drive the hydraulic excavator. The threshold α is set by pre-calculating how much power is needed to drive the hydraulic excavator using only the secondary battery 135 until the fuel cell 110 starts up. The threshold β is set just before the secondary battery 135 becomes over-discharged. In other words, the threshold β is the amount of power beyond which using the secondary battery 135 may result in over-discharge. For example, the threshold β is set to a value that can secure enough power to drive the hydraulic excavator for several tens of minutes.

[0033] Figure 5 shows an example of a time chart when, in step 325 of Figure 3, the mode is set to use only the power from the secondary battery 135 to drive the electric motor 30. Here, the horizontal axis represents time. In Figure 5, the SOC of the secondary battery 135 is above the threshold α in the initial state, and the mode switch is set to ECO mode, which prioritizes reducing power consumption over working speed. Here, the locking device 200 is in the locked state. Also, the electric motor control dial 190 is at its minimum value. From time T0, preparations for starting up electric equipment such as the inverter 35 and secondary battery 135, excluding the fuel cell 110, are made, and at time T1, the startup of these electric equipment is completed.

[0034] At time T2, when the power mode switch 195 changes the mode from PWR mode to ECO mode, the motor 30 becomes capable of being driven by the power of the secondary battery 135, and the system waits for input of a drive command for the motor 30.

[0035] When a drive command for the electric motor 30 is input at time T3, the electric motor 30 is driven by the power of the secondary battery 135, and the system continues in a secondary battery-only drive mode (secondary battery drive mode) until the fuel cell 110 has finished starting up. During this time, no power is generated by the fuel cell 110, so the State of Charge (SOC) of the secondary battery 135 decreases, but because the power mode switch 195 is in ECO mode, power consumption is suppressed and it does not reach the over-discharge range. If the SOC of the secondary battery 135 decreases to a threshold β set just before it reaches the over-discharge range, the system switches to the standby mode described above.

[0036] At time T4, once the fuel cell 110 has finished starting up, the system switches to a fuel cell drive mode in which the electric motor 30 is continuously driven by the power from both the secondary battery 135 and the fuel cell 110. The electric motor 30 is then driven by the power from both the fuel cell 110 and the secondary battery 135. The secondary battery 135 is also charged, increasing its State of Charge (SOC) and preventing over-discharge.

[0037] Figure 6 shows an example of a time chart for when the system enters standby mode at step 335 in Figure 3. Here again, the horizontal axis represents time. The time chart in Figure 6 differs from the time chart in Figure 5 in that the State of Charge (SOC) of the secondary battery 135 is below the threshold α at the initial stage. From time T10, preparations for starting up the electric equipment, such as the inverter 35 and secondary battery 135, excluding the fuel cell 110, are made, and at time T11, the startup of these electric equipment is completed.

[0038] At time T12, the power mode switch 195 is in PWR mode, and the SOC of the secondary battery 135 is below threshold α, so it enters standby mode and remains in standby mode until the fuel cell 110 has finished starting up. In other words, it enters standby mode.

[0039] At time T13, when the fuel cell startup is complete and a drive command for the electric motor 30 is input, the electric motor 30 is driven by the secondary battery 135 and the fuel cell 110, and the system transitions from standby mode to fuel cell drive mode. Since the secondary battery 135 is charged along with the driving of the electric motor 30, the state of charge (SOC) of the secondary battery 135 does not decrease and does not reach the over-discharge range.

[0040] The output response performance of the fuel cell 110 is slower than that of the engine and secondary battery 135, and the fuel cell 110 alone cannot keep up with the speed of output changes required by the hydraulic excavator. For this reason, the secondary battery 135 is also installed to keep up with the speed of output changes required by the hydraulic excavator. In other words, the load fluctuations of the hydraulic excavator are rapid, and when the load increases suddenly and the required output increases suddenly, the fuel cell 110 cannot increase power generation at a speed that can adequately respond to this. In this case, the secondary battery 135 discharges to compensate for the power shortage. Conversely, when the load decreases suddenly and the required output decreases suddenly, the fuel cell 110 cannot decrease power generation at a speed that can adequately respond to this. In this case, the amount of power that the fuel cell 110 has generated in excess is absorbed by charging the secondary battery 135. In other words, the secondary battery 135 charges and discharges to compensate for any surplus or deficit in the power output of the fuel cell 110 when the output response of the fuel cell 110 is slower than the output changes of the electric motor 30. This allows the hydraulic excavator to respond to the power output changes it requires.

[0041] Therefore, it is sufficient for the secondary battery 135 to have a capacity that can cope with this fluctuation, and it is common practice to make the secondary battery 135 have the minimum capacity from the standpoint of space and cost. In other words, in the case of an electric work machine that uses both a fuel cell 110 and a secondary battery 135 as power sources, the capacity of the secondary battery 135 is generally smaller than that of an electric work machine that uses only a secondary battery as a power source. However, because of this, if the electric motor 30 is operated using only the secondary battery 135 while the fuel cell 110 is starting up, over-discharge of the secondary battery 135 is likely to occur.

[0042] In this embodiment, when the remaining capacity of the secondary battery 135 is above a threshold α and the work mode is one that prioritizes reducing power consumption over work speed, the motor 30 is driven using only the power of the secondary battery 135, thereby preventing over-discharge of the secondary battery 135 and shortening the standby time. On the other hand, if neither of the conditions of the remaining capacity of the secondary battery 135 being above a threshold α or the work mode being one that prioritizes reducing power consumption over work speed is met, the motor 30 is not driven using only the power of the secondary battery 135, and the system waits for the fuel cell 110 to start up. This prevents over-discharge of the secondary battery 135. Furthermore, when neither of the conditions of the remaining capacity of the secondary battery 135 being below a threshold β or the work mode being one that prioritizes work speed over reducing power consumption is met, the system enters standby mode, and then the motor 30 is driven using the power of both the secondary battery 135 and the fuel cell 110, thereby preventing over-discharge of the secondary battery 135. With the above configuration, it is possible to provide an electric work machine such as a hydraulic excavator that suppresses over-discharge of the secondary battery 135 when attempting to operate the electric motor 30 using the secondary battery 135 until the fuel cell 110 is started.

[0043] In the example described above, steps 315 and 320 in Figure 3 describe a case where, during the preparation for starting the fuel cell 110, the vehicle controller 45 sets the motor to use only the power from the secondary battery 135 as the driving power for the motor 30 (secondary battery drive mode) if the remaining capacity of the secondary battery 135 is equal to or greater than a first threshold (in this case, threshold α) and the work mode is set to a mode that reduces power consumption by the motor 30 (in this case, ECO mode). However, this is not the only case, and the vehicle controller 45 may also perform a process to drive the motor 30 with the power from the secondary battery 135 during the preparation for starting the fuel cell 110, without considering the remaining capacity of the secondary battery 135, if the work mode is set to a mode that reduces power consumption by the motor 30 (in this case, ECO mode). In other words, step 315 in Figure 3 is not necessary. In this case as well, the motor 30 can be driven with the power from the secondary battery 135 as long as it is not determined in step 330 that the SOC is less than or equal to threshold β.

[0044] 30...Electric motor, 45...Vehicle controller, 110...Fuel cell, 135...Secondary battery, 145...Fuel cell controller, 195...Power mode switch

Claims

1. An electric work machine comprising: a fuel cell; a secondary battery charged by the power generated by the fuel cell; an electric motor driven by power supplied from at least one of the fuel cell and the secondary battery; a mode setting device for setting a work mode; and a control device for controlling the operating state according to the work mode set by the mode setting device, wherein the control device, while preparing to start the fuel cell, drives the electric motor with the power of the secondary battery if the work mode is set to a mode that reduces the power consumption of the electric motor.

2. The electric work machine according to claim 1, characterized in that, during the preparation for starting the fuel cell, if the remaining capacity of the secondary battery is less than a first threshold or the work mode is set to a mode different from the mode that reduces power consumption by the electric motor, the control device maintains the stopped state of the electric motor until the preparation for starting the fuel cell is completed.

3. The electric work machine according to claim 2, characterized in that the work mode, which is different from the mode for reducing power consumption by the electric motor, includes a mode that prioritizes the work speed by the work device.

4. The electric work machine according to claim 1, characterized in that, during the preparation for starting the fuel cell, if the remaining capacity of the secondary battery falls below a predetermined threshold between the time the electric motor is driven with the power of the secondary battery and the preparation for starting the fuel cell is completed, the control device stops the electric motor until the preparation for starting the fuel cell is completed.

5. The electric work machine according to claim 1, characterized in that, after preparation for starting the fuel cell is complete, the control device drives the electric motor with the power output by the fuel cell, and controls the charging and discharging of the secondary battery to compensate for any excess or deficiency in the power output by the fuel cell.

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