Work machine and method

Abstract

According to the present invention, when the power required to drive a work machine is high, a control device sets a target state of charge such that the state of charge of an energy storage device is lower compared to when the required power is low. The control device calculates a control power for bringing the state of charge of the energy storage device closer to the target state of charge on the basis of the current state of charge of the energy storage device and the target state of charge. The control device sets a power generation target for a fuel cell on the basis of the sum of the required power and the control power.

Description

Work machine and method

[0001] This application claims priority to Japanese Patent Application No. 2024-053965, filed on March 28, 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 under consideration. A work machine powered by a fuel cell is equipped with a battery that charges with surplus electricity generated by the fuel cell and discharges to make up for any shortage of electricity generated by the fuel cell.

[0003] Japanese Patent Application Laid-Open No. 2023-144222

[0004] When the power storage device is fully charged, it may not be possible to charge the power storage device with surplus power from the fuel cell. On the other hand, from the standpoint of cost and size, it is desirable for the power storage device mounted on the work machine to have a small capacity.

[0005] An object of the present disclosure is to provide a work machine and method that can absorb surplus power using a small-capacity power storage device.

[0006] According to one aspect of the present disclosure, a work machine is provided with a fuel cell and a power storage device, and is further provided with a control device, wherein the control device determines a target charging rate so that the charging rate of the power storage device is lower when the required power to drive the work machine is high compared to when the required power is low, calculates control power based on the current charging rate of the power storage device and the target charging rate to bring the charging rate of the power storage device closer to the target charging rate, and determines a target generation power for the fuel cell based on the sum of the required power and the control power.

[0007] According to the above aspect, the work machine can absorb surplus power using a small-capacity power storage device.

[0008] 1 is a perspective view of a work machine according to a first embodiment. FIG. 1 is a schematic diagram showing the configuration of a cab of a work machine according to the first embodiment. FIG. 2 is a schematic block diagram showing the configuration of a work machine according to the first embodiment. FIG. 3 is a schematic block diagram showing the configuration of a main control device according to the first embodiment. FIG. 4 is a block diagram showing a calculation algorithm used by a controlled variable determination unit according to the first embodiment. FIG. 5 is a diagram showing an example of a conversion function for calculating a target charging rate from required power according to the first embodiment. FIG. 6 is a diagram showing an example of available capacity to be secured in the first embodiment. FIG. 7 is a flowchart showing a control method for a work machine according to the first embodiment. FIG. 8 is a side view of a work machine according to a second embodiment. FIG. 9 is a schematic diagram showing the configuration of a cab of a work machine according to the second embodiment. FIG. 10 is a schematic block diagram showing the configuration of a work machine according to the second embodiment. FIG. 11 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. FIG. 12 is a first diagram showing an example of a conversion function according to another embodiment. FIG. 13 is a second diagram showing an example of a conversion function according to another embodiment. FIG. 14 is a third diagram showing an example of a conversion function according to another embodiment. FIG. 15 is a fourth diagram showing an example of a conversion function according to another 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 Figure 2, the driver's cab 140 is provided with operating devices 142, including a driver's seat 141, 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 rotating operation 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 track of the running body 110. The right travel lever 142RT is configured to operate the rotation of the right crawler track 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 drives the work implement 130 and the traveling body 110 using the electric power generated by the fuel cell system 20. The drive system 30 rotates the revolving unit 120 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 vehicle body control unit 402, a required power calculation unit 403, a control variable determination unit 404, a fuel cell control unit 405, and a power storage device control unit 406.

[0030] The receiving unit 401 receives measurement data from a measuring device 161 provided on the work machine 1. The measuring device 161 receives measurement data relating to the operating state of the work machine 1. The measuring device 161 receives various measurement data indicating the state of the work machine 1. The measuring device 161 includes a fuel gauge for measuring the charging rate of the power storage device 221, a current sensor for measuring the passing current of the inverter 321, and a voltage sensor for measuring the voltage of the bus bar B. The receiving unit 401 receives an operation signal from the operation device 142.

[0031] The vehicle body control unit 402 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 402 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.

[0032] The required power calculation unit 403 calculates the required power required by the drive system 30 based on the control signal generated by the vehicle body control unit 402. Note that the required power calculation unit 403 may calculate the current power consumption of the drive system 30 based on the measurement data received by the receiving unit 401 from the measurement device 161, or the required power calculation unit 403 may calculate the required power needed by the drive system 30 based on the current power consumption.

[0033] The control amount determination unit 404 determines the next (after one calculation step) target power generation of the fuel cell 211 based on the required power calculated by the required power calculation unit 403, the charging rate of the power storage device 221, and the current target power generation of the fuel cell 211. The calculation method used by the control amount determination unit 404 will be described later.

[0034] The fuel cell control unit 405 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 404. The fuel cell control unit 405 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 404.

[0035] The power storage device control unit 406 controls the power converter 222 so that the power storage device 221 charges or discharges according to the difference between the required power calculated by the required power calculation unit 403 and the power output from the fuel cell module 21. The power storage device control unit 406 outputs a charge / discharge command to the power converter 222.

[0036] <<Determination of Target Power Generation>> Here, a calculation method of the controlled variable determiner 404 according to the first embodiment will be described. Fig. 5 is a block diagram showing a calculation algorithm by the controlled variable determiner 404 according to the first embodiment. The controlled variable determiner 404 includes a conversion block 421, a subtraction block 422, a proportional integral block 423, an addition block 424, and a limit block 425.

[0037] The transformation block 421 uses the transformation function f(P load ) and determines the target charging rate of the power storage device from the required power calculated by the required power calculation unit 403. FIG. 6 shows a conversion function f(P load ) is a diagram showing an example of the conversion function f(P load ) is expressed by the following formula (1): load is the target power generation, P fcslew is the limit rate (allowable rate of change) of the target power generation of the fuel cell, E max indicates the maximum capacity of the storage device.

[0038]

[0039] Here, the transformation function f(P load 7 is a diagram showing an example of the free space to be secured in the first embodiment. As shown in FIG. 7, when the fuel cell 211 has a target generated power P loadAssume that the required power suddenly becomes zero at time t0 while the fuel cell 211 is generating power in accordance with the target power generation rate P [kW]. In order to prevent deterioration of the fuel cell 211, as will be described later, the main control device 145 limits the rate of change of the target power generation to a limit rate P fcslew Therefore, the target power generation is limited according to P load / P fcslew It takes time [h]. The target power output is P load The amount of power generated from gen [kWh] is expressed by the following equation (2).

[0040]

[0041] The amount of power E expressed by equation (2) gen In order to absorb this into the power storage device 221, the power storage device 221 must be charged with the amount of power E gen Therefore, the maximum remaining capacity allowed for the power storage device 221 is E max -E gen This remaining capacity E max -E gen By converting this into the charging rate form, we obtain equation (1). In this way, the target power generation P load When the power storage device 221 is generating power, if the charge rate shown in formula (1) is ensured, the amount of power E shown in FIG. gen can be absorbed by the power storage device 221. Therefore, the control amount determination unit 404 according to the first embodiment uses the conversion function f(P load ) to determine the target charging rate.

[0042] In consideration of the possibility of a sudden increase in required power, there is a lower limit to the charging rate that should be ensured in the power storage device 221. The lower limit of the charging rate that should be ensured in the power storage device 221 is expressed by a lower limit function g(P load ) can be expressed as the lower bound function g(P load ) is expressed by the following equation (3): load_max indicates the maximum expected power requirement.

[0043]

[0044] Therefore, the control amount determination unit 404 can make the power storage device 221 absorb the effects of a sudden increase in load by setting the target charging rate for the power storage device 221 to a charging rate that is equal to or lower than the charging rate indicated by formula (1) and equal to or higher than the charging rate indicated by formula (3). In other words, the target charging rate is equal to or lower than the charging rate at which the power generated by the fuel cell 211 can be charged until the power generated by the fuel cell 211 decreases from the required power to zero. Since the higher the charging rate of the power storage device 221, the higher the efficiency, in the first embodiment, the upper limit of the charging rate to be ensured is determined as the target charging rate.

[0045] The subtraction block 422 subtracts the current charging rate of the power storage device 221 from the target charging rate determined in the conversion block 421 .

[0046] The proportional integral block 423 calculates proportional integral control based on the difference between the target charging rate calculated by the subtraction block 422 and the current charging rate, thereby calculating the control power to be charged or discharged so that the charging rate of the power storage device 221 approaches the target charging rate. Note that a positive control power indicates that the power storage device 221 should be charged with power corresponding to the absolute value of the control power. A negative control power indicates that the power storage device 221 should be discharged with power corresponding to the absolute value of the control power.

[0047] The addition block 424 calculates the total required power by adding the required power calculated by the required power calculation unit 403 and the control power calculated by the proportional-plus-integral block 423 .

[0048] The limit block 425 multiplies the total required power calculated by the addition block 424 by the current target power generation of the fuel cell 211 and a predetermined limit rate P fcslew The target power generation is limited to within the allowable range determined based on the current target power generation. tgt0 , the time interval of one calculation step is T s Then, the allowable range of the target power generation is P tgt0 ±P fcslew ×T s The control amount determination unit 404 determines the output result of the limit block 425 as the target generated power.

[0049] <<Control of Work Machine 1>>

[0050] 8 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, and the voltage of the bus bar B from the measurement device 161, and receives an operation signal from the operation device 142 (step S1).

[0051] The vehicle body control unit 402 generates a control signal for controlling the work machine 1 based on the operation signal received in step S1 (step S2). The required power calculation unit 403 calculates the required power based on the control signal generated in step S2 (step S3).

[0052] The control quantity determination unit 404 determines a target charging rate for the power storage device 221 from the required power calculated in step S3 (step S4). Based on the target charging rate determined in step S4 and the charging rate of the power storage device 221 indicated by the measurement data received in step S1, the control quantity determination unit 404 calculates control power for bringing the charging rate of the power storage device 221 closer to the target charging rate (step S5). Based on the current target power generation of the fuel cell 211 and a predetermined limit rate, the control quantity determination unit 404 determines an allowable range for the next target power generation (step S6). The control quantity determination unit 404 determines the next target power generation by limiting the sum of the required power calculated in step S3 and the control power determined in step S5 to within the allowable range determined in step S6 (step S7).

[0053] The fuel cell control unit 405 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 power determined in step S7 (step S8). The power storage device control unit 406 controls the power converter 222 connected to the power storage device 221 so that the power converter 222 charges or discharges the power that is the difference between the required power calculated in step S3 and the power output from the fuel cell module 21 (step S9). The power storage device control unit 406 may output a command to the power converter 222 to control the voltage of the bus B to be constant.

[0054] <<Actions and Effects>> As described above, the main control device 145 according to the first embodiment functions as follows. The main control device 145 determines a target charging rate such that the charging rate of the power storage device 221 decreases as the power required to drive the work machine 1 increases. The main control device 145 calculates the control power for bringing the charging rate of the power storage device 221 closer to the target charging rate, based on the current charging rate and the target charging rate of the power storage device 221. The main control device 145 determines the target power generation for the fuel cell 211, based on the sum of the required power and the control power. This allows the work machine 1 according to the first embodiment to control the charging rate of the power storage device 221 so that the power storage device 221 can absorb power when the load suddenly decreases. When driving multiple electric motors provided in the work machine 1, the power required to drive the work machine 1 may increase. Furthermore, for example, the power required to drive the work machine 1 increases when the operator performs a combined operation in which the revolving body 120 is rotated and the work implement 130 is operated simultaneously. More specifically, when the revolving unit 120 is rotated while the boom 131 and arm 132 are moving with a load loaded on the attachment 133, the amount of power required to drive the work machine 1 increases. At this time, the main control device 145 controls the amount of power generated by the fuel cell 211 so as to ensure available capacity in the power storage device 221. This allows the power storage device 221 to absorb surplus power generated by the fuel cell 211 when operation of the work machine 1 stops. In other words, the work machine 1 according to the first embodiment can control the charge rate of the power storage device 221 so that the power storage device 221 can absorb power when there is a sudden drop in load. Therefore, the work machine 1 according to the first embodiment can absorb surplus power using a small-capacity power storage device.

[0055] The main control device 145 according to the first embodiment does not reduce the charging rate uniformly regardless of the load output, but rather minimizes the reduction in the target charging rate according to the current load output. In other words, the main control device 145 sets the upper limit of the charging rate that should be ensured as the target charging rate. This enables the work machine 1 to prevent a decrease in efficiency due to the power storage device 221 being charged or discharged at a low charging rate.

[0056] The main control device 145 according to the first embodiment limits the rate of change of the target power generation of the fuel cell 211 to within a predetermined limit rate. This prevents the main control device 145 from using the fuel cell 211 at an excessively high rate of change in output, thereby suppressing deterioration of the fuel cell 211. However, in other embodiments, the present invention is not limited to this, and the main control device 145 may control the fuel cell 211 without limiting the rate of change. However, even if the fuel cell module 21 is instructed to change the target power generation at a high rate of change in output, it takes time for the power generation of the fuel cell 211 to follow the target power generation, and therefore the main control device 145 needs to determine the target charging rate of the power storage device 221 based on the delay in this follow-up. In other words, if the rate of change of the target charging rate is not limited, the main control device 145 will determine the target charging rate of the power storage device 221 based on the delay in this follow-up. fcslew The target charging rate can be calculated by replacing the above with the speed at which the fuel cell 211 follows the change in the target power generation.

[0057] Second Embodiment A second embodiment will be described with reference to Figures 9 to 11. 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.

[0058] <Configuration of Work Machine 1> Figure 9 is a side view of a work machine 1 according to the second embodiment. The work machine 1 according to the second embodiment is, for example, a wheel loader. The work machine 1 comprises a vehicle body 500, a traveling device 520, and a work implement 530.

[0059] The vehicle body 500 supports the work implement 530, a cab 540, a machinery room 550, and the fuel cell system 20. The vehicle body 500 includes a front vehicle body section 501 and a rear vehicle body section 502 that is positioned rearward of the front vehicle body section 501. The front vehicle body section 501 and the rear vehicle body section 502 are flexibly connected via a joint mechanism 503. The joint mechanism 503 has a steering cylinder 503C for steering the work machine 1. The front vehicle body section 501 bends relative to the rear vehicle body section 502 when the steering cylinder 503C extends and retracts. The traveling direction of the work machine 1 is adjusted when the front vehicle body section 501 bends relative to the rear vehicle body section 502.

[0060] The traveling device 520 supports the work machine 1 so that it can travel. The traveling device 520 has an electric traveling motor 522, wheels 523, and a brake 524, which will be described later. The wheels 523 include two front wheels 523F rotatably supported on the front body part 501, and two rear wheels 523R rotatably supported on the rear body part 502. The wheels 523 are rotated by the electric traveling motor 522. The brake 524 generates a braking force that reduces the traveling speed of the work machine 1.

[0061] The work implement 530 is operably supported on the front vehicle body 501. At least a portion of the work implement 530 is disposed forward of the front vehicle body 501. The work implement 530 includes a boom 531, a bell crank 532, and an attachment 533. The attachment 533 is an example of a working tool. In the example shown in FIG. 9 , the attachment 533 is a bucket. The base end of the boom 531 is rotatably attached to the front vehicle body 501. The bell crank 532 is attached to the attachment 533 via a link 534. The attachment 533 is rotatably attached to the tip of the boom 531. The attachment 533 is disposed forward of the front wheels 523F.

[0062] The work machine 1 is equipped with a plurality of actuators for driving the work implement 530. The plurality of actuators include, for example, a boom cylinder 531C and an attachment cylinder 533C.

[0063] The boom cylinder 531C is a hydraulic cylinder for driving the boom 531. A base end of the boom cylinder 531C is attached to the vehicle body front part 501. A tip end of the boom cylinder 531C is attached to the boom 531.

[0064] The attachment cylinder 533C is a hydraulic cylinder for driving the attachment 533. A base end of the attachment cylinder 533C is attached to the front body 501. A tip end of the attachment cylinder 533C is attached to the bell crank 532.

[0065] The cab 540 is where the operator of the work machine 1 rides in and operates and pilots the work machine 1. The cab 140 is located, for example, at the front end of the rear body 502. The cab 540 of the work machine 1 is provided with an operating device 142 for operating the work machine 1.

[0066] <Configuration of Cab> Figure 10 is a schematic diagram showing the configuration of a cab 540 of a work machine 1 according to the second embodiment. As shown in Figure 10, the cab 540 is provided with the following operating devices 142: a steering handle 142SH, a forward / rearward switch 142FR, a boom operating lever 142BL, an attachment operating lever 142AL, ​​an accelerator pedal 142SP, and a brake pedal 142BP.

[0067] The steering handle 142SH is configured to operate the steering angle of the work machine 1. The forward / rearward selector switch 142FR is operated to operate the direction of travel of the work machine 1. The boom control lever 142BL is configured to operate the raising / lowering operation of the boom 531. The attachment control lever 142AL is configured to operate the excavation / dumping operation of the attachment 533. The accelerator pedal 142SP is configured to operate the driving force generated in the work machine 1 for traveling. The brake pedal 142BP is configured to operate the braking force of the brake 524.

[0068] Figure 11 is a schematic block diagram showing the configuration of a work machine 1 according to the second embodiment. The work machine 1 is equipped with a fuel cell system 20 and a drive system 50. The fuel cell system 20 generates electric power for driving the drive system 50. The electric power generated by the fuel cell system 20 is output to the drive system 50 via a bus line B. The drive system 50 drives a work implement 530 using the electric power generated by the fuel cell system 20. The drive system 50 runs the work machine 1 using the electric power generated by the fuel cell system 20.

[0069] The drive system 50 includes a hydraulic drive module 51 and a traveling module 52 .

[0070] The hydraulic drive module 51 includes an inverter 311, an electric pump motor 312, a hydraulic pump 313, and a hydraulic actuator 514. The inverter 311 converts DC current from a 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 implement 530 and the joint mechanism 513. 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 514. The hydraulic oil discharged from the hydraulic pump 313 is supplied to the hydraulic actuator 514 via a control valve (not shown). The hydraulic actuator 514 is driven by the supplied hydraulic oil. The hydraulic actuator 514 includes a boom cylinder 531C, an attachment cylinder 533C, and a steering cylinder 503C.

[0071] The traveling module 52 includes an inverter 321 and an electric traveling motor 522. The inverter 321 converts DC current from the bus B into three-phase AC current and supplies it to the electric traveling motor 522. The electric traveling motor 522 generates power for traveling the work machine 1. The electric traveling motor 522 rotates using the supplied three-phase AC current, causing the wheels 523 of the traveling device 520 to rotate. The electric traveling motor 522 performs power running, which causes the work machine 1 to travel, and regenerative running, which generates regenerative power and decelerates the work machine 1.

[0072] The vehicle body control unit 402 according to the first embodiment 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 402 generates control signals for controlling, for example, the steering, acceleration, and braking of the traveling device 520, and the operation of the work implement 530.

[0073] <<Actions and Effects>> The work machine 1 according to the second embodiment can control the charge rate of the power storage device 221 so that the power storage device 221 can absorb electric power when there is a sudden drop in load. For example, when the operator accelerates the work machine 1, the electric power required to drive the work machine 1 increases. At this time, the main control device 145 controls the amount of power generated by the fuel cell 211 so as to ensure available capacity in the power storage device 221. This allows the power storage device 221 to absorb surplus electric power generated by the fuel cell 211, for example, when the work machine 1 finishes accelerating. In other words, the work machine 1 according to the first embodiment can control the charge rate of the power storage device 221 so that the power storage device 221 can absorb electric power when there is a sudden drop in load. Furthermore, the work machine 1 may require more electric power when driving multiple electric motors. For example, when the operator operates the work implement 530 while moving the work machine 1 forward in order to load a load onto the attachment 533, the electric power required to drive the work machine 1 increases. At this time, the main control device 145 controls the amount of power generated by the fuel cell 211 so as to ensure available capacity in the power storage device 221. This allows the power storage device 221 to absorb surplus power generated by the fuel cell 211 when, for example, loading of a load onto the attachment 533 is complete. In other words, the work machine 1 according to the second embodiment can control the charge rate of the power storage device 221 so that the power storage device 221 can absorb power when there is a sudden drop in load. Therefore, the work machine 1 according to the second embodiment can absorb surplus power using a small-capacity power storage device.

[0074] <Computer Configuration> Fig. 12 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.

[0075] 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.

[0076] 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.

[0077] The program may also be a program for realizing some of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-described functions in combination with another program already stored in storage 93.

[0078] <Other Embodiments> Although several embodiments have been described in detail above with reference to the drawings, the specific configurations are not limited to those described above, and various design changes and the like are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some of the processes may be executed in parallel. 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 control device 163 by cooperating with each other. In this case, some of the computers 90 that make up the main control device 145 may be installed inside the work machine 1, and other computers 90 may be provided outside the work machine 1.

[0079] A work machine 1 according to another embodiment may be remotely operated, and components other than the fuel cell control unit 405 and the power storage device control unit 406 may be provided in a remote computer 90. A work machine 1 according to another embodiment may also be controlled by a control system located in a remote location. In this case, the receiving unit 401 may receive a control signal for controlling the work machine 1 from the control system, and the required power calculation unit 403 may calculate the required power for the drive system 30 based on the control signal received from the control system. A work machine 1 according to another embodiment may also operate by autonomous driving. For example, the work machine 1 may be provided with a measurement device 161 for receiving measurement data related to the position, orientation, and speed of the work machine 1 and the surrounding terrain, and the vehicle body control unit 402 may generate a control signal for controlling the work machine 1 based on the measurement data and pre-stored design data.

[0080] A work machine 1 according to another embodiment may be a hydraulic excavator that rotates the rotating body 120 using a hydraulic rotation motor instead of the rotation module 32. In this case, the hydraulic drive module 31 may include a hydraulic rotation motor that is driven by hydraulic oil discharged from the hydraulic pump 313.

[0081] The work machine 1 according to other embodiments is not limited to a hydraulic excavator, and may be, for example, another work machine such as a wheel loader or a forklift.

[0082] Although the control variable determiner 404 according to the above-described embodiment determines the target charging rate based on Equation (1), this is not limiting. For example, the control variable determiner 404 may determine the target charging rate by incorporating a time delay factor. For example, the control variable determiner 404 may determine the target charging rate with a margin corresponding to the communication delay between when an instruction to change the target power generation is issued to the fuel cell module 21 and when the change is transmitted to the fuel cell module 21, the control delay between when the change in the target power generation is transmitted to the fuel cell module 21 and when the power converter 212 actually starts to change its output, and the fixed control delay required for the output of the fuel cell 211 to be completely reduced to zero after the power generation of the fuel cell 211 has decreased to a certain level. Furthermore, the control variable determiner 404 may determine the target charging rate with a margin corresponding to the amount of regenerative power that can be generated. The regenerative power that can be generated may be calculated based on, for example, the rotation speed, weight, and regenerative efficiency of the rotating unit 120, or may be calculated based on the currently required power.

[0083] As described above, the control amount determination unit 404 determines the upper limit function f(P load ) and the lower limit function g(P load ) or more may be set as the target charging rate of the power storage device 221. Therefore, the conversion function is the upper limit function f(P load ) and the lower bound function g(P load ) is sufficient as long as it falls within the range expressed by the formula (1). FIG. 13 is a first diagram showing an example of a conversion function according to another embodiment. For example, the conversion function h(P load ) is the required power P load When the target charging rate is equal to or less than the threshold value TH1, the target charging rate becomes the first target charging rate, and the required power P load is equal to or greater than the threshold value TH2, the target charging rate becomes the second target charging rate, and when the required power is greater than the threshold value TH1 and less than the threshold value TH2, the target charging rate may follow a predetermined linear function. FIG. 14 is a second diagram showing an example of a conversion function according to another embodiment. For example, the conversion function h(P load ) is the required power P load When the target charging rate is equal to or less than the threshold value TH, the target charging rate becomes the first target charging rate, and the required power P loadmay be a step function in which the target charging rate becomes the second target charging rate when is greater than the threshold TH.

[0084] The conversion function may have a hysteresis characteristic. FIG. 15 is a third diagram showing an example of a conversion function according to another embodiment. The conversion function h(P load ) is the conversion function h(P load ), thresholds TH1' and TH1'', and thresholds TH2' and TH2'', which have hysteresis characteristics, have inflection points (non-differentiable points). FIG. 16 is a fourth diagram showing an example of a conversion function according to another embodiment. The conversion function h(P load ) is the conversion function h(P load ) have inflection points (non-differentiable points) at threshold values ​​TH' and TH'', which have hysteresis characteristics.

[0085] According to the above aspect, the work machine can absorb surplus power using a small-capacity power storage device.

[0086] 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 401... Receiving unit 402... Vehicle body control unit 403... Required power calculation unit 404... Control amount determination unit 405... Fuel cell control unit 406... Storage device control unit 421... Conversion block 422... Subtraction block 423... Proportional integral block 424... Addition block 425... Limit block B... Bus

Claims

1. A work machine equipped with a fuel cell and a power storage device, comprising a control device which, when the power required to drive the work machine is high, determines a target charging rate so that the charging rate of the power storage device is lower than when the required power is low, calculates control power based on the current charging rate of the power storage device and the target charging rate to bring the charging rate of the power storage device closer to the target charging rate, and determines a target generated power for the fuel cell based on the sum of the required power and the control power.

2. A work machine according to claim 1, wherein the control device determines the target charging rate such that the charging rate of the power storage device decreases as the power required to drive the work machine increases.

3. The work machine according to claim 1, wherein the control device outputs a charge / discharge command for the power storage device in accordance with the difference between the required power and the power generated by the fuel cell.

4. The work machine according to claim 1, wherein the control device calculates the target generated power by limiting the sum of the required power and the control power in accordance with an allowable rate of change of the target generated power of the fuel cell.

5. A work machine according to claim 1, wherein the target charging rate is equal to or lower than the charging rate at which the fuel cell can charge the generated power generated until the power generated by the fuel cell decreases from the required power to zero.

6. A method for controlling a work machine equipped with a fuel cell and a power storage device, comprising: determining a target charging rate so that the charging rate of the power storage device is lower when the power required to drive the work machine is high compared to when the required power is low; calculating control power for bringing the charging rate of the power storage device closer to the target charging rate based on the current charging rate of the power storage device and the target charging rate; and determining a target generated power for the fuel cell based on the sum of the required power and the control power.

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