Work machine

Abstract

To provide a work machine capable of suppressing frequency of switching actuation and stop of power generation by a fuel cell and suppressing deterioration of the fuel cell.SOLUTION: A shovel comprises: a plurality of fuel cells 32A, 32B; an electric motor 17 for driving the fuel cells 32A, 32B as a power source; a rotational speed dial 20 and a mode switch 21, which indicate a target rotational speed of the electric motor 17; and a vehicle body controller 30 for controlling the number of power generators, which is the number of fuel cells used among the fuel cells 32A, 32B. The vehicle body controller 30 calculates a target value of total generated power generated by the fuel cells 32A, 32B based on a consumption power consumed by the electric motor 17, and calculates a threshold value of the total generated power according to the target rotational speed of the electric motor 17 indicated by the rotational speed dial 20 and the mode switch 21, and controls the number of power generators by the fuel cells based on the calculated target value and threshold value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a work machine such as a shovel. [Background technology]

[0002] Patent document 1 discloses that in general vehicles such as automobiles, a control device is provided that switches between the operating state and stopped state of each fuel cell based on the results of comparing a target value (required power) of the total power generation of multiple fuel cells with a threshold value, in order to suppress deterioration of the multiple fuel cell system as a whole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-043648 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the work load of the work machine fluctuates greatly due to, for example, driving and stopping of the actuators, and accordingly the target value of the total power generation also fluctuates greatly. Furthermore, switching between driving and stopping of the actuators is frequently performed. Therefore, if the conventional technology described in Patent Document 1 is applied to a work machine, the target value of the total power generation will frequently exceed or fall below a predetermined threshold value. In other words, the number of fuel cell power generators will be increased or decreased frequently. Therefore, switching between generating and stopping the fuel cells will be performed frequently, which may hasten the deterioration of the fuel cells.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a work machine that can reduce the frequency of switching between fuel cell power generation and shutdown, and suppress deterioration of the fuel cell. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a work machine including a plurality of fuel cells, an electric motor driven using the plurality of fuel cells as a power source, a target rotation speed indicating device which indicates a target rotation speed of the electric motor, and a control device which controls the number of generators, which is the number of fuel cells to be used among the plurality of fuel cells, wherein the control device calculates a target value for total power generation generated by the plurality of fuel cells based on power consumption consumed by the electric motor, calculates a threshold value for the total power generation in accordance with the target rotation speed of the electric motor indicated by the target rotation speed indicating device, and controls the number of generators of the fuel cells based on the calculated target value and threshold value. Effect of the Invention

[0007] According to the present invention, the frequency of switching between power generation and stop of the fuel cell can be reduced, and deterioration of the fuel cell can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a side view showing a structure of a shovel in one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of a drive system and an electrical system of a shovel in one embodiment of the present invention. [Diagram 3] 2 is a block diagram showing the functional configuration of a vehicle controller related to control of the number of fuel cell power generators, together with related devices, in one embodiment of the present invention. FIG. [Figure 4] FIG. 4 is a characteristic diagram showing the relationship between the indicated value of the rotation speed dial and the target rotation speed of the electric motor in one embodiment of the present invention. [Diagram 5] 5 is a characteristic diagram showing the relationship between the target rotation speed of the electric motor and the threshold value of the total generated power in one embodiment of the present invention. FIG. [Figure 6] 5 is a characteristic diagram showing the relationship between the remaining capacity of a secondary battery and a correction value for a threshold value of total generated power in an embodiment of the present invention. FIG. [Figure 7] 3 is a characteristic diagram showing the relationship between current and voltage and the relationship between current and generated power of a fuel cell in one embodiment of the present invention. FIG. [Figure 8]4 is a time chart showing the target rotation speed of the electric motor, the remaining capacity of the secondary battery, the target value and threshold value of the total generated power, and the change over time of the generated power of each fuel cell in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will be described with reference to the drawings, taking a shovel as an example of an application of the present invention.

[0010] FIG. 1 is a side view showing the structure of a shovel in this embodiment.

[0011] The excavator of this embodiment includes a traveling body 1, a rotating body 2 provided rotatably above the traveling body 1, and a working device 3 connected to the rotating body 2.

[0012] The running body 1 includes an H-shaped track frame 4 when viewed from above, left and right crawler belts 5 rotatably provided on the left side (the front side of the paper in FIG. 1) and the right side (the rear side of the paper in FIG. 1) of the track frame, respectively, and left and right traveling motors 6 for rotating the left and right crawler belts 5, respectively. The running body 1 travels by being driven by the left and right traveling motors 6.

[0013] The working device 3 includes a boom 7 rotatably connected to the rotating body 2, an arm 8 rotatably connected to the tip of the boom 7, and a bucket 9 rotatably connected to the tip of the arm 8. The boom 7 rotates when driven by a boom cylinder 10, the arm 8 rotates when driven by an arm cylinder 11, and the bucket 9 rotates when driven by a bucket cylinder 12.

[0014] The rotating body 2 rotates by being driven by a rotating motor (not shown). The rotating body 2 includes a rotating frame 13 forming a base structure, a cab 14 in which an operator sits and is provided in front of the rotating frame 13 (left side in FIG. 1), a counterweight 15 provided in the rear of the rotating frame 13 (right side in FIG. 1), and a machine room 16 provided between the cab 14 and the counterweight 15 and housing devices such as an electric motor 17 (see FIG. 2 described later).

[0015] The operator's cab 14 is provided with a travel operation device (not shown) that instructs the travel of the travelling body 1, a work operation device (not shown) that instructs the rotation of the boom 7 and the rotation of the bucket 9, a work operation device 18 (see Figure 2 described below) that instructs the rotation of the rotating body 2 and the rotation of the arm 8, and a lock lever device 19 (see Figure 2 described below) that instructs switching between a locked state that prohibits the operation of the shovel and an unlocked state that permits the operation of the shovel.

[0016] The driver's cab 14 is also provided with a rotation speed dial 20 and a mode switch 21. The rotation speed dial 20 has a dial that can be rotated by the driver and a potentiometer that outputs an indication value corresponding to the operation position of the dial, and indicates an increase or decrease in the target rotation speed of the electric motor 17. The mode switch 21 indicates switching between eco mode and power mode. The eco mode is a mode in which the target rotation speed of the electric motor 17 is reduced, and the power mode is a mode in which the target rotation speed of the electric motor 17 is not reduced. The rotation speed dial 20 and the mode switch 21 constitute a target rotation speed indication device that indicates the target rotation speed of the electric motor as described in the claims.

[0017] Fig. 2 is a diagram showing the configuration of the drive system and the electrical system of the excavator in this embodiment. Note that Fig. 2 shows only the configuration related to the drive of the arm cylinder 11 among a plurality of hydraulic actuators (specifically, the left and right traveling motors 6, the boom cylinder 10, the arm cylinder 11, the bucket cylinder 12, and the swing motor).

[0018] The drive system of this embodiment includes an electric motor 17 that is driven by a plurality of fuel cells (described later) as a power source, an inverter device 22 that controls the rotation speed of the electric motor 17, a variable displacement hydraulic pump 23 that is driven by the electric motor 17, a regulator 24 that adjusts the capacity of the hydraulic pump 23 (e.g., the tilt angle of the swash plate), and a control valve 25 that controls the flow of pressure oil (more specifically, the direction and flow rate) from the hydraulic pump 23 to the arm cylinder 11. The inverter device 22 has an inverter and a controller.

[0019] The drive system of the present embodiment includes a pilot pump 26 driven by an electric motor 17, a pilot relief valve 27 that determines the discharge pressure of the pilot pump 26, electromagnetic proportional valves 28A, 28B that generate pilot pressure using the discharge pressure of the pilot pump 26 as a base pressure and output the generated pilot pressure to a pressure-receiving portion of the control valve 25, a lock valve 29 provided between the pilot pump 26 and the electromagnetic proportional valves 28A, 28B, etc., and a vehicle body controller 30.

[0020] The vehicle body controller 30 has a processor that executes processing according to a program, a memory that stores the program and data, and an interface that can communicate with other controllers (specifically, a controller of the inverter device 22, a fuel cell controller described below, a secondary battery controller described below, or an auxiliary controller described below). Note that, like the vehicle body controller 30, the other controllers also have a processor, a memory, and an interface.

[0021] The work operation device 18 includes an operation lever (operation member) that can be operated by the driver, a first potentiometer that generates and outputs a first operation signal in accordance with the amount of operation of one side of the operation lever, and a second potentiometer that generates and outputs a second operation signal in accordance with the amount of operation of the other side of the operation lever.

[0022] The vehicle body controller 30 generates a drive signal in response to a first operation signal from the work operation device 18, and outputs it to the electromagnetic proportional valve 28A. The electromagnetic proportional valve 28A generates a pilot pressure corresponding to the drive signal, and outputs it to a pressure receiving portion on one side of the control valve 25. As a result, the control valve 25 is switched to the switching position on the right side in the figure, and pressure oil from the hydraulic pump 23 is supplied to the upper rod chamber in the figure of the arm cylinder 11 via the control valve 25, and the arm cylinder 11 retracts and contracts.

[0023] The vehicle body controller 30 generates a drive signal in response to a second operation signal from the work operation device 18, and outputs it to the electromagnetic proportional valve 28B. The electromagnetic proportional valve 28B generates a pilot pressure corresponding to the drive signal, and outputs it to a pressure receiving portion on the other side of the control valve 25. As a result, the control valve 25 is switched to the switching position on the left side in the figure, and pressure oil from the hydraulic pump 23 is supplied to the bottom chamber on the lower side in the figure of the arm cylinder 11 via the control valve 25, and the arm cylinder 11 extends.

[0024] The configurations relating to the drive of the other hydraulic actuators (specifically, the travel motor 6, the boom cylinder 10, the bucket cylinder 12, or the swing motor) are substantially the same as the configuration relating to the drive of the arm cylinder 11. That is, the vehicle body controller 30 generates a drive signal in response to an operation signal from a potentiometer of a corresponding operating device, and outputs the drive signal to the corresponding electromagnetic proportional valve. The corresponding control valve is switched by the pilot pressure generated by the electromagnetic proportional valve, and the pressure oil discharged from the hydraulic pump is supplied to the other hydraulic actuators, thereby driving the other hydraulic actuators. The lock valve 29 is provided between all the electromagnetic proportional valves, including the electromagnetic proportional valves 28A and 28B, and the pilot pump 26.

[0025] The lock lever device 19 includes a lock lever that can be operated to a locked position (raised position) and an unlocked position (lowered position), and a lock switch that does not output a signal when the lock lever is operated to the locked position and outputs a signal when the lock lever is operated to the unlocked position.

[0026] When no signal is input from the lock lever device 19, the vehicle body controller 30 does not output a drive signal to the lock valve 29. This causes the lock valve 29 to be in the shutoff position on the right side in the figure, and the discharge pressure of the pilot pump 26 is not introduced to any of the electromagnetic proportional valves. This results in a locked state in which driving of all hydraulic actuators, i.e., operation of the shovel, is prohibited.

[0027] When a signal is input from the lock lever device 19, the vehicle body controller 30 outputs a drive signal to the lock valve 29. This causes the lock valve 29 to move to the communicating position on the left side in the figure, and the discharge pressure of the pilot pump 26 is introduced to all the electromagnetic proportional valves. This results in an unlocked state that allows the drive of all the hydraulic actuators, i.e., the operation of the excavator.

[0028] The vehicle body controller 30 calculates a target rotation speed of the electric motor 17 based on the indication value of the rotation speed dial 20 and the eco mode or power mode selected by the mode switch 21 (details will be described later), and outputs it to the controller of the inverter device 22. The controller of the inverter device 22 controls the inverter so that the rotation speed of the electric motor 17 becomes the target rotation speed.

[0029] The vehicle body controller 30 controls the regulator 24 to adjust the capacity of the hydraulic pump 23 based on the maximum value among the operation amounts of the traveling operation device, the work operation device, and the work operation device 18, and the target rotation speed of the electric motor 17 described above.

[0030] The electrical system of this embodiment includes a high-voltage circuit 31 connected to the electric motor 17 via an inverter device 22, a plurality of fuel cells 32A, 32B which are power sources for the electric motor 17 etc. and generate electricity by chemically reacting hydrogen and oxygen, boost converters 33A, 33B which connect the fuel cells 32A, 32B to the high-voltage circuit 31, a fuel cell controller 34 which controls the fuel cells 32A, 32B, a secondary battery 35 which can be charged and discharged, a bidirectional converter 36 which connects the secondary battery 35 to the high-voltage circuit 31, a secondary battery controller 37 which monitors the secondary battery 35, a step-down converter 40 which connects auxiliary equipment (e.g., an air conditioner compressor 38 and a fan 39, etc.) to the high-voltage circuit 31, and an auxiliary equipment controller 41 which monitors the auxiliary equipment.

[0031] Boost converter 33A boosts the power generated by fuel cell 32A and supplies it to high-voltage circuit 31, and boost converter 33B boosts the power generated by fuel cell 32B and supplies it to high-voltage circuit 31. When the power of high-voltage circuit 31 is excessive relative to the power consumed by electric motor 17 and the auxiliaries (in other words, the power of fuel cells 32A, 32B is excessive), bidirectional converter 36 steps down the power of high-voltage circuit 31 (in other words, the power generated by fuel cells 32A, 32B) and supplies it to secondary battery 35 to charge secondary battery 35. When the power of the high-voltage circuit 31 is insufficient for the power consumed by the electric motor 17 and the auxiliary machinery (in other words, the power of the fuel cells 32A, 32B is insufficient), the bidirectional converter 36 boosts the power discharged from the secondary battery 35 and supplies it to the high-voltage circuit 31 (in other words, to the electric motor 17 via the high-voltage circuit 31 and the inverter device 22). The step-down converter 40 steps down the power of the high-voltage circuit 31 and supplies it to the auxiliary machinery.

[0032] The fuel cell controller 34 calculates the power generated by the fuel cell 32A based on the current and voltage of the fuel cell 32A, calculates the power generated by the fuel cell 32B based on the current and voltage of the fuel cell 32B, and outputs these to the vehicle body controller 30. The secondary battery controller 37 calculates the remaining capacity of the secondary battery 35 based on, for example, the voltage of the secondary battery 35, and outputs this to the vehicle body controller 30.

[0033] The controller of the inverter device 22 calculates the power consumption of the electric motor 17 based on the current and voltage of the electric motor 17, and outputs the calculated power to the vehicle body controller 30. The auxiliary controller 41 calculates the power consumption of the auxiliary based on the current and voltage of the auxiliary, and outputs the calculated power to the vehicle body controller 30.

[0034] The vehicle body controller 30 calculates a target value for the total power generated by the fuel cells 32A, 32B based on the power consumption of the electric motor 17 and the power consumption of the auxiliary devices, calculates a threshold value for the total power generation in accordance with the target rotation speed of the electric motor 17 specified by the rotation speed dial 20 and the mode switch 21, and controls the number of fuel cells to be generated (in other words, the number of fuel cells to be used out of the fuel cells 32A, 32B) based on the calculated target value and threshold value. The vehicle body controller 30 constitutes a control device described in the claims.

[0035] The control of the number of fuel cells generating electricity in this embodiment will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the functional configuration of a vehicle body controller 30 related to the control of the number of fuel cells generating electricity in this embodiment, together with related devices.

[0036] The vehicle body controller 30 has, as its functional configuration, a total generated power calculation unit 42, a target rotation speed calculation unit 43, a threshold value calculation unit 44, a number of generators calculation unit 45, a usage level calculation unit 46, and a command calculation unit 47.

[0037] The total power generation calculation unit 42 of the vehicle body controller 30 calculates a target value for the total power generation based on the power consumption of the electric motor 17 input from the controller of the inverter device 22 and the power consumption of the auxiliary equipment input from the auxiliary equipment controller 41.

[0038] The target rotation speed calculation unit 43 of the vehicle body controller 30 calculates the target rotation speed of the electric motor 17 based on the indicated value of the rotation speed dial 20 and the eco-mode or power mode selected by the mode switch 21. Specifically, when the eco-mode is selected by the mode switch 21, characteristic A (see Fig. 4), which is the relationship between the indicated value of the rotation speed dial 20 and the target rotation speed of the electric motor 17, is selected. When the power mode is selected by the mode switch 21, characteristic B (see Fig. 4), which is the relationship between the indicated value of the rotation speed dial 20 and the target rotation speed of the electric motor 17, is selected. Then, using the selected characteristic A or B, the target rotation speed of the electric motor 17 is obtained from the indicated value of the rotation speed dial 20.

[0039] The threshold value calculation unit 44 of the vehicle body controller 30 calculates the threshold value of the total generated power according to the target rotation speed of the electric motor 17 calculated by the target rotation speed calculation unit 43. Specifically, for example, as shown in Fig. 5, the higher the target rotation speed of the electric motor 17, the lower the threshold value of the total generated power is set.

[0040] The threshold value calculation unit 44 of the vehicle body controller 30 calculates a correction value for the threshold value of the total generated power based on the remaining capacity of the secondary battery 35 input from the secondary battery controller 37. Specifically, for example, as shown in Fig. 6, when the remaining capacity of the secondary battery 35 is within the range of 0 to C1 (where 0 < C1), the correction value is set to (-α). When the remaining capacity of the secondary battery 35 is within the range of C1 to C2 (where C1 < C2), as the remaining capacity of the secondary battery 35 increases from C1 to C2, the correction value increases from (-α) to 0. When the remaining capacity of the secondary battery 35 is within the range of C2 to C3 (where C2 < C3), the correction value is set to 0. When the remaining capacity of the secondary battery 35 is within the range of C3 to C4 (where C3 < C4), as the remaining capacity of the secondary battery 35 increases from C3 to C4, the correction value increases from 0 to (+α). When the remaining capacity of the secondary battery 35 is within the range of C4 to C5 (where C4 < C5 and C5 is the maximum value), the correction value is set to (+α). The threshold value calculation unit 44 corrects the threshold value of the total generated power by adding the above-mentioned correction value.

[0041] The generator number calculation unit 45 of the vehicle body controller 30 compares the target value of the total power generation calculated by the total power generation calculation unit 42 with the threshold value calculated by the threshold value calculation unit 44, and increases or decreases the number of fuel cell generators based on the comparison result. To explain in more detail, when the target value of the total power generation is equal to or greater than the threshold value, the number of fuel cell generators is set to 2, and when the target value of the total power generation is less than the threshold value, the number of fuel cell generators is set to 1.

[0042] The power generation number calculation unit 45 of the vehicle body controller 30 judges whether the lock valve 29 has been switched to the shutoff position (in other words, the locked state). If the lock valve 29 has been switched to the shutoff position, the power generation number of the fuel cells is set to 1, regardless of the target value and threshold value of the total power generation (regardless of the comparison result between the target value of the total power generation and the threshold value).

[0043] The power generation number calculation unit 45 of the vehicle body controller 30 determines whether the time during which the travel operation device, the work operation device, and the work operation device 18 have been in a non-operated state is equal to or greater than a predetermined value, based on operation signals from the travel operation device, the work operation device, and the work operation device 18. If the aforementioned time is equal to or greater than the predetermined value, the number of power generation units of the fuel cells is set to 1, regardless of the target value and threshold value of the total power generation.

[0044] The usage calculation unit 46 of the vehicle body controller 30 calculates the usage of the fuel cell 32A by integrating the product of the generated power and the power generation time of the fuel cell 32A input from the fuel cell controller 34. Also, the usage calculation unit 46 calculates the usage of the fuel cell 32B by integrating the product of the generated power and the power generation time of the fuel cell 32B input from the fuel cell controller 34.

[0045] The command calculation unit 47 of the vehicle body controller 30 generates commands to operate or stop the fuel cells 32A, 32A based on the number of fuel cell generators calculated by the generator number calculation unit 45 and the usage of the fuel cell 32A and the usage of the fuel cell 32B calculated by the usage degree calculation unit 46, and outputs the commands to the fuel cell controller 34. To explain in detail, when the number of fuel cell generators is 2, a command to operate the fuel cells 32A, 32A is generated. When the number of fuel cell generators is 0, a command to stop the fuel cells 32A, 32A is generated. When the number of fuel cell generators decreases from 2 to 1, or when the number of fuel cell generators increases from 0 to 1, a fuel cell to be operated or stopped is selected based on the usage of the fuel cell 32A and the usage of the fuel cell 32B. In other words, a command is generated to operate the fuel cell with a lower usage degree and to stop the fuel cell with a higher usage degree.

[0046] When the number of fuel cells generating electricity continues to be 1, the command calculation unit 47 of the vehicle body controller 30 determines whether the usage of the operating fuel cell is greater than the usage of the stopped fuel cell by a predetermined value or more. If the usage of the operating fuel cell is greater than the usage of the stopped fuel cell by a predetermined value or more, a command is generated to operate the stopped fuel cell and stop the operating fuel cell in order to replace the fuel cell.

[0047] The command calculation unit 47 of the vehicle body controller 30 calculates the target value of the power generation of each fuel cell based on the target value of the total power generation calculated by the total power generation calculation unit 42 and the number of fuel cells generating electricity calculated by the number of fuel cells generating electricity calculation unit 45, and includes the calculated target value in the command described above. To explain in detail, the target value of the power generation of each fuel cell is calculated by dividing the target value of the total power generation by the number of fuel cells generating electricity. Then, the target value of the power generation of each fuel cell is restricted to be equal to or greater than a minimum value. The reason for this is to make the voltage of each fuel cell equal to or less than a maximum value, as shown in FIG. 7. Furthermore, the target value of the power generation of each fuel cell is corrected so that the rate of change is equal to or less than a predetermined value.

[0048] The operation and effects of this embodiment will be described with reference to Fig. 8. Fig. 8 is a time chart showing the target rotation speed of the motor, the remaining capacity of the secondary battery, the target value and threshold value of the total generated power, and the change over time in the generated power of each fuel cell in this embodiment.

[0049] The operator selects the power mode with the mode switch 21 in order to perform high-load work with the shovel from time t0 to time t3. In addition, from time t0 to time t2, the operator operates the rotation speed dial 20 to increase the target rotation speed of the electric motor 17. The vehicle body controller 30 reduces the threshold value of the total power generation in response to the increase in the target rotation speed of the electric motor 17.

[0050] From time t0 to time t1, the target value for the total power generation is less than the threshold, so the vehicle body controller 30 sets the number of fuel cell power generators to 1. That is, fuel cell 32A is operated and fuel cell 32B is stopped. From time t1 to time t3, the target value for the total power generation is equal to or greater than the threshold, so the vehicle body controller 30 sets the number of fuel cell power generators to 2. That is, fuel cells 32A and 32B are operated.

[0051] After time t3, in order to perform low-load work with the shovel, the operator selects the eco mode with the mode switch 21 and lowers the target rotation speed of the electric motor 17. As the target rotation speed of the electric motor 17 decreases, the vehicle body controller 30 increases the threshold value of the total power generation.

[0052] From time t3 to time t4, the target value for the total power generation is equal to or greater than the threshold value, so the vehicle body controller 30 keeps the number of fuel cell power generators at 2. From time t4 to time t6, the target value for the total power generation is less than the threshold value, so the vehicle body controller 30 sets the number of fuel cell power generators to 1. That is, from time t4 to time t5, fuel cell 32A is operated and fuel cell 32B is stopped. At time t5, the usage of fuel cell 32A becomes greater than the usage of fuel cell 32B by a predetermined value or more. Therefore, from time t5 to time t6, fuel cell 32A is stopped and fuel cell 32B is operated.

[0053] The driver operates the lock lever device 19 to the lock position to suspend shovel operation from time t6 to time t8. In response to the operation of the lock lever device 19, the vehicle body controller 30 switches the lock valve 29 to the shutoff position. Accordingly, the number of fuel cell power generators remains at 1, regardless of the target value and threshold value of the total power generation. The secondary battery 35 is charged as the shovel operation is suspended, and the remaining capacity increases. Because the remaining capacity of the secondary battery 35 is equal to or greater than C3 from time t7 to time t8, the vehicle body controller 30 corrects the threshold value of the total power generation accordingly.

[0054] After time t8, the operator operates the lock lever device 19 to the unlocked position in order to resume shovel operation. In response to the operation of the lock lever device 19, the vehicle body controller 30 switches the lock valve 29 to the connected position. As the shovel operation is resumed, the secondary battery 35 is discharged and the remaining capacity decreases. From time t8 to time t10, the remaining capacity of the secondary battery 35 is equal to or greater than C3, so the vehicle body controller 30 corrects the threshold value of the total power generation accordingly.

[0055] From time t8 to time t9, the target value for the total power generation is less than the threshold, so the vehicle body controller 30 keeps the number of fuel cell power generators at 1. After time t9, the target value for the total power generation is equal to or greater than the threshold, so the vehicle body controller 30 sets the number of fuel cell power generators to 2. That is, the vehicle body controller 30 operates fuel cells 32A and 32B.

[0056] In this embodiment, when the target rotation speed of the motor 17 is high (for example, between time t2 and time t3, when the target value of the total power generation is large and fluctuating), the threshold value of the total power generation is made small. This makes it possible to reduce the frequency of increasing or decreasing the number of fuel cells generating electricity, compared to when the threshold value of the total power generation is not made small. Also, when the target rotation speed of the motor 17 is low (for example, after time t3, when the target value of the total power generation is small and fluctuating), the threshold value of the total power generation is made large. This makes it possible to reduce the frequency of increasing or decreasing the number of fuel cells generating electricity, compared to when the threshold value of the total power generation is not made large. Therefore, the frequency of switching between generating and stopping fuel cells can be reduced, and deterioration of the fuel cells can be suppressed.

[0057] In addition, in this embodiment, when the remaining capacity of the secondary battery 35 is large, the threshold value of the total generated power is corrected to be larger, and when the remaining capacity of the secondary battery 35 is small, the threshold value of the total generated power is corrected to be smaller. This makes it possible to reduce the frequency of increasing or decreasing the number of fuel cell power generators compared to when the threshold value of the total generated power is not corrected. This therefore makes it possible to reduce the frequency of switching between generating and stopping fuel cell power, and to suppress deterioration of the fuel cell.

[0058] In the above embodiment, the vehicle body controller 30 corrects the threshold value of the total power generation in accordance with the remaining capacity of the secondary battery 35. However, the present invention is not limited to this. That is, the vehicle body controller 30 does not have to correct the threshold value of the total power generation in accordance with the remaining capacity of the secondary battery 35, although the above-mentioned effect cannot be obtained.

[0059] In the above embodiment, the locking device that switches between a locked state that prohibits the operation of the shovel and an unlocked state that permits the operation of the shovel is the lock valve 29 that switches between a disconnected position and a communicating position, but is not limited to this. The locking device may be, for example, a function of the vehicle body controller 30 that switches between disabling and enabling the operation signal of the operating device.

[0060] In the above embodiment, the vehicle body controller 30 sets the number of fuel cell power generators to 1 when the locking device is switched to the locked state or when the time during which the traveling operation device, the work operation device, and the work operation device 18 have not been operated continues for a predetermined value or more, but this is not limited to the above. For example, if conditions are met such as an auxiliary device not being connected to the high voltage circuit 31 or the capacity of the secondary battery 35 being large, the vehicle body controller 30 may set the number of fuel cell power generators to 0 when the locking device is switched to the locked state or when the time during which the traveling operation device, the work operation device, and the work operation device 18 have not been operated continues for a predetermined value or more.

[0061] In the above embodiment, the target rotation speed indicator for indicating the target rotation speed of the electric motor 17 is the rotation speed dial 20 and the mode switch 21, but is not limited to this. The target rotation speed indicator may be only one of the rotation speed dial 20 and the mode switch 21, or may be another device other than these.

[0062] In the above embodiment, the shovel is provided with two fuel cells, and the vehicle body controller 30 compares the target value of the total power generation with one threshold value. However, the present invention is not limited to this. The shovel may be provided with three or more fuel cells, and the vehicle body controller 30 may compare the target value of the total power generation with multiple threshold values. In this case, the vehicle body controller 30 may vary the multiple threshold values ​​according to the target rotation speed of the electric motor 17.

[0063] In the above embodiment, the controller of the inverter device 22 calculates the power consumption of the electric motor 17 based on the current and voltage of the electric motor 17, but this is not limiting. For example, the vehicle body controller 30 may calculate the power consumption of the electric motor 17 based on the maximum value among the operation amounts of the traveling operation device, the work operation device, and the work operation device 18 and the target rotation speed of the electric motor 17.

[0064] Although the present invention has been described above by taking a shovel as an example of an application of the present invention, the present invention is not limited to this. In other words, the present invention may be applied to other work machines besides shovels. [Explanation of symbols]

[0065] 17 Electric motor 20 Rotation Speed ​​Dial 21 Mode switch 30 Vehicle Controller 32A,32B fuel cell 35 Secondary battery

Claims

1. A work machine including a plurality of fuel cells, an electric motor that is driven using the plurality of fuel cells as a power source, a target rotation speed indicating device that indicates a target rotation speed of the electric motor, and a control device that controls a number of power generating units, which is the number of fuel cells to be used among the plurality of fuel cells, the control device calculates a target value for a total power generation by the plurality of fuel cells based on the power consumption of the electric motor, calculates a threshold value for the total power generation in accordance with the target rotation speed of the electric motor indicated by the target rotation speed indicating device, and controls the number of power generating fuel cells based on the calculated target value and threshold value.

2. 2. The work machine according to claim 1, The control device increases or decreases the number of power generating fuel cells based on a comparison result between the target value of the total power generation and the threshold value.

3. 2. The work machine according to claim 1, The control device sets the threshold value to a smaller value as the target rotation speed of the electric motor indicated by the target rotation speed indicating device increases.

4. 2. The work machine according to claim 1, a secondary battery that is charged with the electric power generated by the plurality of fuel cells and discharged to supply the electric power to the electric motor; The control device corrects the threshold value in accordance with a remaining capacity of the secondary battery.

5. 2. The work machine according to claim 1, a locking device that switches between a locked state in which operation of the work machine is prohibited and an unlocked state in which operation of the work machine is permitted, a control device that sets the number of power generating fuel cells to one or less when the locking device is switched to a locked state, regardless of the target value and the threshold value of the total power generation.

6. 2. The work machine according to claim 1, the control device calculates a usage level for each of the plurality of fuel cells, which is the product of the generated power and the power generation time, and gives priority to operating fuel cells with lower calculated usage levels and gives priority to stopping fuel cells with higher calculated usage levels.

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