Work machine and method for controlling work machine

Abstract

This work machine comprises a traveling body, a turning body, an electric turning motor, and a fuel cell. The turning body is pivotally supported on the traveling body, and the electric turning motor generates power for turning the turning body. The electric power generated by the fuel cell when the turning body is turning is less than the electric power generated by the fuel cell when the turning body is not turning.

Description

Work machine and work machine control method

[0001] This application claims priority to Japanese Patent Application No. 2024-055300, filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0002] As shown in Patent Document 1, a work machine equipped with a fuel cell that uses hydrogen as fuel is being considered. A work machine driven by a fuel cell is equipped with a power storage device such as a battery to limit the amount of fuel cell installed and to charge regenerative power. Therefore, the control device of the work machine needs to perform energy management that appropriately distributes the energy between the fuel cell and the power storage device.

[0003] JP 2023-110969 A

[0004] It is preferable for a work machine to control the amount of power generated by the fuel cell so that the power stored in the power storage device is not depleted. On the other hand, if the power storage device is sufficiently charged by power generation by the fuel cell, the regenerative power generated by the operation of the work machine must be converted into thermal energy and consumed, which may result in poor energy efficiency.

[0005] An object of the present disclosure is to provide a work machine and a control method for a work machine that can improve the energy efficiency of the work machine.

[0006] According to one aspect of the present disclosure, a work machine includes a running body, a rotating body rotatably supported on the running body, an electric swing motor that generates power to rotate the rotating body, and a fuel cell that generates electricity to drive the electric swing motor, and the power generated by the fuel cell when the rotating body is rotating is smaller than the power generated by the fuel cell when the rotating body is not rotating.

[0007] According to the above aspect, the energy efficiency of the work machine can be improved.

[0008] FIG. 1 is a perspective view of a work machine according to a first embodiment. FIG. 2 is a schematic diagram showing the configuration of a cab of a work machine according to the first embodiment. FIG. 3 is a schematic block diagram showing the configuration of a work machine according to the first embodiment. FIG. 4 is a schematic block diagram showing the configuration of a main control device according to the first embodiment. FIG. 5 is a time chart showing an example of control of the main control device according to the first embodiment. FIG. 6 is a block diagram showing a calculation algorithm by a control quantity determination unit according to the first embodiment. FIG. 7 is a flowchart showing a control method of a work machine according to the first embodiment. FIG. 8 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. FIG. 9 is a schematic block diagram showing the configuration of a work machine according to a second embodiment.

[0009] 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 cab 140, and a main control device 145. 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.

[0010] 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 110 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.

[0011] 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 rotating body 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.

[0012] The work machine 1 is equipped with a plurality of actuators for driving the work implement 130. The plurality of actuators includes, for example, a boom cylinder 131C, an arm cylinder 132C, and an attachment cylinder 133C.

[0013] 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.

[0014] 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 provided with an operating device 142 for operating the work machine 1.

[0015] The operating device 142 is operated by an operator to operate the work machine 1. The operating device 142 is configured to output an operating signal in response to an operation by the operator.

[0016] The main control device 145 receives operation signals from the operation device 142. The main control device 145 controls the work machine 1 based on the operation signals from the operation device 142.

[0017] 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.

[0018] <Configuration of the Operator's Cabin> FIG. 2 is a schematic diagram showing the configuration of the operator's cab 140 of the work machine 1 according to the first embodiment.

[0019] As shown in FIG. 2, the driver's cab 140 is provided with the operating devices 142, which include a left operating lever 142LO, a right operating lever 142RO, a left foot pedal 142LF, a right foot pedal 142RF, a left travel lever 142LT, and a right travel lever 142RT.

[0020] The left operating lever 142LO is configured to be able to operate the rotation of the rotating body 120 and the excavation / dumping operation of the arm 132. The right operating lever 142RO is configured to be able to operate the excavation / dumping operation of the attachment 133 and the raising / lowering operation of the boom 131.

[0021] The left travel lever 142LT and the right travel lever 142RT are configured to operate the travel of the work machine 1. The left travel lever 142LT is configured to operate the rotation of the left crawler of the running body 110. The right travel lever 142RT is configured to operate the rotation of the right crawler of the running body 110. The left foot pedal 142LF and the right foot pedal 142RF are linked to the left travel lever 142LT and the right travel lever 142RT, respectively, and the travel of the work machine 1 can also be controlled by the left foot pedal 142LF and the right foot pedal 142RF.

[0022] Figure 3 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 rotates the rotating body 120 using the electric power generated by the fuel cell system 20. The drive system 30 drives the work implement 130 and the traveling body 110 using the electric power generated by the fuel cell system 20.

[0023] 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.

[0024] 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 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.

[0025] 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 commands from the main control device 145. The power storage device 221 is, for example, a lithium-ion battery.

[0026] The drive system 30 includes a hydraulic drive module 31 and a slewing module 32 .

[0027] 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 .

[0028] 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 using the supplied three-phase AC current and swings the swing unit 120 relative to the traveling unit 110. The electric swing motor 322 performs power running to swing the swing unit 120 and regenerative running to generate regenerative power and decelerate the swing of the swing unit 120.

[0029] 4 is a schematic block diagram showing the configuration of the main control device 145 according to the first embodiment. The main control device 145 controls the work machine 1 in accordance with operation signals from the operation device 142. The main control device 145 includes a receiving unit 401, a reference generated power setting unit 402, a vehicle control unit 403, a required power calculation unit 404, a regenerative power calculation unit 405, a power storage device capacity determination unit 406, a control mode determination unit 407, a control variable determination unit 408, a fuel cell control unit 409, and a power storage device control unit 410.

[0030] The receiving unit 401 receives measurement data from a measuring device 161 provided on the work machine 1. The measuring device 161 acquires measurement data related to the operating state of the work machine 1. The measuring device 161 acquires various measurement data indicating the state of the power storage device 221. The measuring device 161 includes an IMU (Inertial Measurement Unit) for measuring the attitude of the work machine 1, a temperature sensor for measuring the temperature of the power storage device 221, a fuel gauge for measuring the charging rate of the power storage device 221, a current sensor for measuring the current passing through the inverter 321, and a voltage sensor for measuring the voltage of the bus bar B. The IMU is an example of an attitude sensor for measuring the attitude of the work machine 1. The receiving unit 401 receives an operation signal from the operation device 142.

[0031] The reference generated power setting unit 402 sets the reference generated power of the fuel cell 211 based on the charging rate of the power storage device 221 that the receiving unit 401 receives from the measuring device 161. Specifically, the reference generated power setting unit 402 sets the reference generated power to a lower value the higher the charging rate of the power storage device 221, and sets the reference generated power to a higher value the lower the charging rate of the power storage device 221. The reference generated power, for example, monotonically decreases (does not monotonically increase) with respect to the charging rate of the power storage device 221.

[0032] The vehicle body control unit 403 generates a control signal for controlling the work machine 1 based on the operation signal of the operation device 142. The vehicle body control unit 403 generates a control signal for controlling, for example, the operation of the work implement 130, the travel of the traveling body 110, and the rotation of the rotating body 120.

[0033] The required power calculation unit 404 calculates the required power required by the drive system 30 based on the control signal generated by the vehicle body control unit 403 .

[0034] The regenerative power calculation unit 405 calculates the regenerative power generated by the work machine 1 based on the measurement data of the voltage of the bus B and the current passing through the inverter 321 received by the receiving unit 401 .

[0035] The power storage device capability determination unit 406 determines the maximum chargeable power and the maximum dischargeable power by using various measurement data indicating the state of the power storage device 221 received by the receiving unit 401. Note that the power storage device capability determination unit 406 may determine the maximum chargeable power and the maximum dischargeable power by inquiring about the maximum chargeable power and the maximum dischargeable power from a monitoring device for the power storage device 221.

[0036] The control mode determination unit 407 determines the control mode of the fuel cell module 21 based on whether the revolving unit 120 is revolving. The control mode determination unit 407 determines whether the revolving unit 120 is revolving based on a revolving operation signal that controls the revolving of the revolving unit 120 and the magnitude of the regenerative power calculated by the regenerative power calculation unit 405, and determines the control mode of the fuel cell module 21. The control modes of the fuel cell module 21 include a normal mode in which the target power generation power of the fuel cell 211 is determined using a reference power generation power, and a limited mode in which the target power generation power of the fuel cell 211 is determined using a limited power generation power that is smaller than the reference power generation power. The limited power generation power may be set by multiplying the reference power generation amount by a coefficient less than 1, or may be a predetermined value smaller than the range that the reference power generation power can take. The control mode determination unit 407 determines the control mode of the fuel cell module 21 so that the power generated by the fuel cell 211 when the revolving unit 120 is revolving is smaller than the power generated by the fuel cell 211 when the revolving unit 120 is not revolving. The limit mode is a mode in which the amount of power generated by the fuel cell 211 is limited, for example, in preparation for regenerative power generated by the electric revolving motor 322 when the revolving unit 120 is decelerated.

[0037] The control mode determination unit 407 determines that the rotation of the rotating unit 120 has started, for example, when the receiving unit 401 receives a rotation operation signal for operating the rotation of the rotating unit 120 from the operating device 142 continuously for a predetermined period. The control mode determination unit 407 determines that the rotation of the rotating unit 120 has stopped, for example, when the receiving unit 401 does not receive a rotation operation signal for operating the rotation of the rotating unit 120 from the operating device 142 continuously for a predetermined period and the regenerative power calculated by the regenerative power calculation unit 405 changes from non-zero to zero. If the control mode determination unit 407 determines that the rotating unit 120 is not rotating, it determines the control mode of the fuel cell module 21 to be the normal mode. If the control mode determination unit 407 determines that the rotating unit 120 is rotating, it determines the control mode of the fuel cell module 21 to be the restricted mode. When the revolving unit 120 is revolving, the control mode determination unit 407 limits the amount of power generated by the fuel cell 211 in preparation for regenerative power generated by the electric revolving motor 322 when the revolving unit 120 is decelerated. This allows the work machine 1 to charge the power storage device 221 with regenerative power generated by the electric revolving motor 322 when the revolving unit 120 is decelerated, without converting the regenerative power into thermal energy and consuming it.

[0038] FIG. 5 is a time chart showing an example of control by the main control device 145 according to the first embodiment. In the example shown in FIG. 5 , the work machine 1 performs excavation work using the work implement 130 until time T1. During this time, the revolving unit 120 does not rotate, so the control mode determination unit 407 determines the control mode of the fuel cell module 21 to be the normal mode. At time T1, when the operator operates the operation device 142 to rotate the revolving unit 120 to the right, the receiving unit 401 receives a rotation operation signal to rotate the revolving unit 120 to the right. As a result, the revolving unit 120 starts rotating to the right. When the rotation operation signal to rotate the revolving unit 120 to the right is received continuously for a predetermined period of time, the control mode determination unit 407 changes the control mode of the fuel cell module 21 to the restricted mode from time T1. At time T2, when the operator operates the operation device 142 to stop the right rotation of the revolving unit 120, the receiver 401 finishes receiving the rotation operation signal to rotate the revolving unit 120 to the right. As a result, the revolving unit 120 decelerates to stop the right rotation, and regenerative power is generated in the electric rotation motor 322. Because the revolving unit 120 is still rotating to the right at time T2, the control mode determination unit 407 maintains the control mode of the fuel cell module 21 in the restricted mode. At time T3, when the rotation of the revolving unit 120 stops, the regenerative power generated by the electric rotation motor 322 disappears. In other words, the regenerative power changes from non-zero to zero. As a result, the control mode determination unit 407 determines that the revolving unit 120 is not rotating, and changes the control mode of the fuel cell module 21 to the normal mode.

[0039] At time T4, when the operator operates the operation device 142 to rotate the rotating body 120 to the left, the receiving unit 401 receives a rotation operation signal to rotate the rotating body 120 to the left. As a result, the rotating body 120 starts rotating to the left. After receiving the rotation operation signal to rotate the rotating body 120 to the left for a predetermined period of time, the control mode determination unit 407 changes the control mode of the fuel cell module 21 to the restricted mode from time T4. At time T5, when the operator operates the operation device 142 to stop the left rotation of the rotating body 120, the receiving unit 401 stops receiving the rotation operation signal to rotate the rotating body 120 to the left. As a result, the rotating body 120 decelerates to stop the left rotation, and regenerative power is generated in the electric rotation motor 322. Because the rotating body 120 is still rotating to the left at time T5, the control mode determination unit 407 maintains the control mode of the fuel cell module 21 in the restricted mode. At time T6, when the rotation of the rotating unit 120 stops, the regenerative power by the electric rotation motor 322 ceases. In other words, the regenerative power changes from non-zero to zero. As a result, the control mode determination unit 407 determines that the rotating unit 120 is not rotating, and changes the control mode of the fuel cell module 21 to the normal mode.

[0040] In either control mode, if the maximum dischargeable power of the power storage device 221 is smaller than the difference between the power generated by the fuel cell 211 and the required power, the fuel cell 211 is controlled to generate power greater than the reference power generation power or the limited power generation power. In either control mode, if the maximum chargeable power of the fuel cell 211 is smaller than the sum of the power generated by the fuel cell 211 and the regenerated power, the fuel cell 211 is controlled to generate power less than the reference power generation power or the limited power generation power.

[0041] The control amount determination unit 408 determines the target power generation of the fuel cell 211 and the target charge power or target discharge power of the power storage device 221 based on the required power, the regenerative power, the reference power generation power or the limited power generation power, the maximum chargeable power and the maximum dischargeable power of the power storage device 221, and the control mode. The method of determining the control amount by the control amount determination unit 408 will be described later.

[0042] The fuel cell control unit 409 controls the amount of power generated by the fuel cell 211 in accordance with the target power generation determined by the control amount determination unit 408. The fuel cell control unit 409 outputs a power generation command to the fuel cell control device 214 so that the fuel cell 211 generates power in accordance with the target power generation determined by the control amount determination unit 408.

[0043] The storage device control unit 410 controls the power converter 222 connected to the storage device 221 so as to discharge the storage device 221 in accordance with the target discharge power determined by the control amount determination unit 408, or to charge the storage device 221 in accordance with the target charge power determined by the control amount determination unit 408.

[0044] Here, the calculation of the control amount determiner 408 according to the first embodiment will be described. Fig. 6 is a block diagram showing a calculation algorithm by the control amount determiner 408 according to the first embodiment. The control amount determiner 408 includes a selection block 420, a first subtraction block 421, a second subtraction block 422, a MAX block 423, a first MIN block 424, a third subtraction block 425, a second MIN block 426, an addition block 427, and a third MIN block 428.

[0045] The selection block 420 selects either the reference generated power or the limited generated power according to the control mode determined by the control mode determination unit 407. The selection block 420 selects the reference generated power when the control mode is the normal mode. The selection block 420 selects the limited generated power when the control mode is the limited mode.

[0046] The first subtraction block 421 subtracts the maximum dischargeable power from the required power. The second subtraction block 422 subtracts the regenerative power from the maximum chargeable power. The regenerative power and the required power shown in FIG. 6 are represented by the difference between the required power calculated by the required power calculation unit 404 and the regenerative power calculated by the regenerative power calculation unit 405. Specifically, the required power is the value obtained by subtracting the regenerative power from the required power, and the regenerative power is the value obtained by subtracting the required power from the regenerative power. In other words, the required power is equal to the value obtained by multiplying the regenerative power by -1.

[0047] The MAX block 423 selects the larger of the reference generated power or the limited generated power, and the calculation result of the first subtraction block 421 .

[0048] The first MIN block 424 selects the smaller of the calculation result of the MAX block 423 and the calculation result of the second subtraction block 422. In other words, the first MIN block 424 outputs the reference generated power or the limited generated power if the subtracted regenerative power can be absorbed within the charging capacity of the power storage device 221. Furthermore, if the subtracted regenerative power cannot be absorbed within the charging capacity of the power storage device 221, the first MIN block 424 outputs the difference between the maximum chargeable power of the power storage device 221 and the subtracted regenerative power. However, if the calculation result is a negative number, the first MIN block 424 outputs zero as the calculation result.

[0049] The third subtraction block 425 subtracts the calculation result of the first MIN block 424 from the net required power. The second MIN block 426 determines the smaller of the calculation result of the third subtraction block 425 or the maximum dischargeable power as the target discharge power of the power storage device 221.

[0050] The addition block 427 adds the subtracted regenerative power to the calculation result of the first MIN block 424. The third MIN block 428 determines the smaller of the maximum chargeable power and the calculation result of the addition block 427 as the target charge power for the power storage device 221.

[0051] At least one of the target discharge power and the target charge power determined by the control amount determination unit 408 is zero.

[0052] 7 is a flowchart showing a control method for the work machine 1 according to the first embodiment. When the work machine 1 according to the first embodiment starts work, the receiving unit 401 of the main control device 145 receives measurement data relating to the charge rate of the power storage device 221, the passing current of the inverter 321, the voltage of the bus bar B, and the attitude of the work machine 1 from the measurement device 161, and receives an operation signal from the operation device 142 (step S1).

[0053] Next, the reference generated power setting unit 402 sets the reference generated power of the fuel cell 211 based on the measurement data of the charging rate of the power storage device 221 acquired in step S1 (step S2). The vehicle body control unit 403 generates a control signal for controlling the work machine 1 based on the operation signal received in step S1 (step S3). The required power calculation unit 404 calculates the required power based on the control signal generated in step S2 (step S4). Furthermore, the regenerative power calculation unit 405 calculates the regenerative power based on the measurement data of the voltage of the bus B and the current passing through the inverter 321 received in step S1 (step S5).

[0054] The power storage device capacity determination unit 406 determines the maximum chargeable power and the maximum dischargeable power of the power storage device 221 using various measurement data indicating the state of the power storage device 221 received in step S1 (step S6). The control mode determination unit 407 determines whether the revolving unit 120 is revolving or not, based on the revolving operation signal for controlling the revolving of the revolving unit 120 received in step S1 and the magnitude of the regenerative power calculated in step S4, and determines the control mode of the fuel cell 211 (step S7).

[0055] If it is determined that the rotating body 120 is not rotating (step S7: NO), the control mode determination unit 407 determines the control mode to be the normal mode, and the control quantity determination unit 408 determines the target generated power of the fuel cell 211 and the target charge power or target discharge power of the storage device 221 based on the reference generated power, the required power calculated in step S3, the regenerated power calculated in step S4, and the maximum chargeable power and maximum dischargeable power determined in step S5 (step S8).

[0056] On the other hand, if it is determined that the rotating body 120 is rotating (step S7: YES), the control mode determination unit 407 determines the control mode to be the limited mode, and the control quantity determination unit 408 determines the target generated power of the fuel cell 211 and the target charge power or target discharge power of the storage device 221 based on the limited generated power, the required power calculated in step S3, the regenerated power calculated in step S4, and the maximum chargeable power and maximum dischargeable power determined in step S5 (step S9).

[0057] The fuel cell control unit 409 controls the amount of power generated by the fuel cell 211 in accordance with the target power generation determined in step S8 or step S9 (step S10). If the target power generation determined in step S8 or step S9 is zero, the fuel cell control unit 409 causes the fuel cell 211 to idle. Idling operation refers to operation in which the fuel cell 211 generates power necessary to operate the auxiliary device 213 and does not supply power to the bus B. If the target power generation is zero, the fuel cell control unit 409 may maintain power generation at the minimum output power of the fuel cell 211. If the target power generation is zero, the fuel cell control unit 409 may stop power generation by the fuel cell 211. The power storage device control unit 410 controls the power converter 222 in accordance with the target discharge power or target charge power determined in step S8 or step S9 (step S11).

[0058] <<Actions and Effects>> As described above, the work machine 1 according to the first embodiment limits the amount of power generated by the fuel cell 211 when the revolving unit 120 is revolving. This makes it possible to suppress the power generated by the fuel cell 211 in preparation for the regenerative power generated by the electric revolving motor 322 when the revolving unit 120 is decelerated. This allows the work machine 1 to charge the power storage device 221 with the regenerative power generated by the electric revolving motor 322 when the revolving unit 120 is decelerated, without converting it into thermal energy and consuming it.

[0059] If the amount of power generated by the fuel cell 211 is not limited while the revolving unit 120 is rotating, the maximum chargeable power of the power storage device 221 needs to be greater than the difference between the reference power generation power and the maximum value of the regenerative power. In other words, even though much of the work performed by the work machine 1 requires power running, the specifications required of the power storage device 221 are determined by the absorption of regenerative power. In contrast, according to the first embodiment, the amount of power generated by the fuel cell 211 is limited while the revolving unit 120 is rotating, so the maximum chargeable power of the power storage device 221 can be determined based on a limited power generation power that is smaller than the reference power generation power. In other words, the work machine 1 according to the first embodiment can be equipped with a power storage device 221 with a smaller capacity than when the amount of power generated by the fuel cell 211 is not limited while the revolving unit 120 is rotating.

[0060] <Computer Configuration> Fig. 8 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. The computer 90 includes a processor 91, a main memory 92, a storage 93, and an interface 94. The main control device 145 described above is implemented in the computer 90. The operations of each of the processing units described above 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 each of the storage units described above in accordance with the program. Examples of the processor 91 include a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and a microprocessor.

[0061] 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.

[0062] 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.

[0063] The program may also be a program for realizing part 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.

[0064] Second Embodiment A second embodiment will be described with reference to Fig. 9. Note that the same or corresponding reference numerals will be used to designate the same components as those in the first embodiment, and the description thereof will be omitted.

[0065] The work machine 1 according to the first embodiment is configured so that the rotating body 120 rotates using an electric rotating motor 322. In contrast, the work machine 1 according to the second embodiment is configured so that the rotating body 120 rotates using a hydraulic rotating motor 326.

[0066] 9 is a schematic block diagram showing the configuration of a work machine 1 according to the second embodiment. The swing module 32 according to the second embodiment includes an electric pump motor 324, a hydraulic pump 325, and a hydraulic swing motor 326, instead of the electric swing motor 322 of the first embodiment.

[0067] The inverter 321 converts the DC current from the bus B into three-phase AC current and supplies it to the electric pump motor 324. The electric pump motor 324 generates power for rotating the rotating body 120. The electric pump motor 324 is rotated by the supplied three-phase AC current and drives the hydraulic pump 325. The hydraulic pump 325 discharges hydraulic oil to be supplied to the hydraulic swing motor 326. The hydraulic pump 325 and the hydraulic swing motor 326 form a closed circuit by a pair of main oil passages. The hydraulic oil discharged from the hydraulic pump 325 is supplied to the hydraulic swing motor 326 via a control valve (not shown). The hydraulic swing motor 326 is driven by the supplied hydraulic oil. The rotational force generated by the hydraulic swing motor 326 is transmitted to the rotating body 120.

[0068] Other Embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some processes may be executed in parallel.

[0069] The control mode determination unit 407 according to the above-described embodiment determines whether the revolving unit 120 is revolving, for example, based on the revolving operation signal received by the receiving unit 401 from the operating device 142 and the magnitude of the regenerative power calculated by the regenerative power calculation unit 405. However, this is not limited to this. The control mode determination unit 407 according to other embodiments may determine whether the revolving unit 120 is revolving based on the control signal for controlling the revolving of the revolving unit 120 generated by the vehicle body control unit 403 and the magnitude of the regenerative power calculated by the regenerative power calculation unit 405. Furthermore, the control mode determination unit 407 according to other embodiments may determine whether the revolving unit 120 is revolving based only on the revolving operation signal received by the receiving unit 401 from the operating device 142. For example, the control mode determination unit 407 may determine that the revolving unit 120 has stopped revolving when the receiving unit 401 does not receive a revolving operation signal for operating the revolving unit 120 from the operating device 142 for a predetermined consecutive period of time. Furthermore, the control mode determination unit 407 according to other embodiments may determine whether the revolving structure 120 is revolving based on measurement data from the IMU. For example, the control mode determination unit 407 may calculate the angular velocity of the yaw angle included in the measurement data from the IMU and determine whether the work machine 1 is revolving. Furthermore, the work machine 1 according to other embodiments may have an angle sensor as the measurement device 161 for detecting the angle of the revolving structure 120 relative to the running structure 110, and the control mode determination unit 407 may determine whether the revolving structure 120 is revolving based on measurement data from the angle sensor. For example, the control mode determination unit 407 may calculate an angular velocity or a revolving angular acceleration from measurement data from the angle sensor and determine whether the work machine 1 is revolving. Furthermore, the control mode determination unit 407 according to other embodiments may determine whether the revolving structure 120 is revolving based on the rotation speed of the electric revolving motor 322.

[0070] The main control device 145 according to the above-described embodiments may be configured by a single computer 90, or the configuration of the main control device 145 may be divided into multiple computers 90, and the multiple computers 90 may function as the main control device 145 by working together. In this case, some of the computers 90 that make up the main control device 145 may be mounted inside the transport vehicle 10, and other computers 90 may be provided outside the work machine 1. For example, when a work machine 1 according to another embodiment is remotely operated, configurations other than the fuel cell control unit 409 and the power storage device control unit 410 may be provided in the remote computer 90.

[0071] A work machine 1 according to another embodiment may be controlled by a control system located in a remote location, and the receiving unit 401 may receive a control signal from the control system for controlling the work machine 1. In this case, the control mode determination unit 407 may determine whether or not the revolving unit 120 is revolving based on the control signal received from the control system, and determine the control mode for the fuel cell 211. Whether or not the work machine 1 is revolving may also be determined by the control system.

[0072] A work machine 1 according to another embodiment may operate by autonomous driving. For example, the work machine 1 may be provided with a measurement device 161 for receiving measurement data relating to the position, orientation, and speed of the work machine 1 and the surrounding terrain, and the vehicle body control unit 403 may generate a control signal for controlling the work machine 1 based on the measurement data and pre-stored design data. In this case, the control mode determination unit 407 may determine whether the revolving bed 120 is revolving or not based on the control signal generated by the vehicle body control unit 403, and determine the control mode of the fuel cell 211.

[0073] The work machine 1 according to other embodiments is not limited to a hydraulic excavator, and may be, for example, another work machine having a rotating body, such as a crane or a crawler dump truck.

[0074] Although the work machine 1 according to the embodiment described above uses the limited power generation power to determine the target power generation of the fuel cell 211 when the swing unit 120 is swinging, this is not limiting. For example, a work machine 1 according to another embodiment may determine the target power generation of the fuel cell 211 using the limited power generation power at least while the electric swing motor 322 is generating regenerative power. For example, if the main control device 145 can predict the start of regenerative power generation by the electric swing motor 322, the control mode determination unit 407 may use the reference power generation power to determine the target power generation of the fuel cell 211 until the time when the electric swing motor 322 is predicted to start generating regenerative power, and may use the limited power generation power to determine the target power generation of the fuel cell 211 from the time when the electric swing motor 322 is predicted to start generating regenerative power.

[0075] The work machine 1 according to the embodiment described above may use the calculation algorithm shown in Fig. 6 to set the target power generation power to a value different from the basic power generation power or the limited power generation power, depending on the remaining capacity of the power storage device 221, but is not limited to this. For example, a work machine 1 according to another embodiment may determine the target power generation power of the fuel cell 211 using the basic power generation power when not turning, regardless of the charge rate of the power storage device 221, and may determine the target power generation power of the fuel cell 211 using the limited power generation power when turning.

[0076] Although the reference generated power setting unit 402 according to the embodiment described above sets the reference generated power of the fuel cell 211 based on the charging rate of the power storage device 221, this is not limiting. For example, the reference generated power setting unit 402 according to another embodiment may set the reference generated power to a constant value regardless of the charging rate of the power storage device 221. In this case, the main control device 145 does not need to include the reference generated power setting unit 402.

[0077] The power storage device module 22 according to the embodiment described above includes the power converter 222, but is not limited to this. The power storage device module 22 may not include the power converter 222, and the power storage device 221 may be directly connected to the bus B. In this case, the charge / discharge amount of the power storage device 221 is determined by subtracting the output of the fuel cell 211 from the power consumption of the drive system 30, and therefore the control of step S11 in FIG. 6 is not necessary.

[0078] According to the above aspect, the energy efficiency of the work machine can be improved.

[0079] REFERENCE SIGNS LIST 1...Work machine 110...Traveling body 120...Swiveling body 130...Work machine 131...Boom 131C...Boom cylinder 132...Arm 132C...Arm cylinder 133...Attachment 133C...Attachment cylinder 134...Travel motor 140...Driver's cab 141...Driver's seat 142...Operation device 142LF...Left foot pedal 142LO...Left operation lever 142LT...Left travel lever 142RF...Right foot pedal 142RO...Right operation lever 142RT...Right travel lever 145...Main control device 150...Machine room 161...Measuring device 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 313... Hydraulic pump 314... Hydraulic actuator 32... Swing module 321... Inverter 322... Electric swing motor 324... Electric pump motor 325... Hydraulic pump 326... Hydraulic swing motor 401... Receiving unit 402... Reference generated power setting unit 403... Vehicle body control unit 404... Required power calculation unit 405... Regenerative power calculation unit 406... Power storage device capacity determination unit 407... Control mode determination unit 408... Control amount determination unit 409... Fuel cell control unit 410... Power storage device control unit 420... Selection block 421... First subtraction block 422... Second subtraction block 423... MAX block 424... First MIN block 425... Third subtraction block 426... Second MIN block 427... Addition block 428...Third MIN block B...Busbar

Claims

1. A work machine comprising: a running body; a rotating body rotatably supported on the running body; a rotating motor that generates power to rotate the rotating body; and a fuel cell that generates electricity to drive the rotating motor, wherein the power generated by the fuel cell when the rotating body is rotating is smaller than the power generated by the fuel cell when the rotating body is not rotating.

2. A work machine as described in claim 1, comprising a control device that outputs a command to cause the fuel cell to generate electricity based on a predetermined first power when the rotating body is not rotating, and outputs a command to cause the fuel cell to generate electricity based on a second power smaller than the first power when the rotating body is rotating.

3. A work machine as described in claim 2, wherein the control device outputs the command based on the second electric power from the time when the rotation of the rotating body starts until the rotation of the rotating body stops.

4. A work machine as described in claim 3, wherein the control device determines that the rotation of the rotating body will begin when it receives a rotation operation signal that controls the rotation of the rotating body, and outputs the command to cause the fuel cell to generate electricity based on the second electric power.

5. A method for controlling a work machine comprising: a work implement; a rotating body; and a fuel cell supported on the rotating body and generating electricity for driving the work implement and rotating the rotating body, the method controlling the amount of power generated by the fuel cell when the rotating body is rotating so that the amount of power generated by the fuel cell is smaller than when the rotating body is not rotating.

Images