Work machine and control method for work machine

Abstract

This work machine comprises: a power supply device that is connected to an external power supply and outputs supply power; a battery that is charged by the charging power input from the power supply device; an electrical device that consumes load power input from the power supply device and / or the battery; and a controller. The controller determines a first upper limit value on the charging power, changes the first upper limit value to a second upper limit value on the basis of the load power, and controls the power supply device such that the supply power follows the load power and the charging power does not exceed the first upper limit value.

Description

Work machine and work machine control method

[0001] The present disclosure relates to a work machine and a method for controlling a work machine.

[0002] Work machines that operate using power supplied from a battery are known. If a work machine is operated using only power supplied from a battery, the operating time of the work machine may be insufficient. If a large-capacity battery is installed in the work machine to prevent this insufficient operating time, the battery may take up most of the space on the work machine, which may result in the work machine becoming larger. Furthermore, installing a large-capacity battery in a work machine may increase the cost of the work machine. By operating the work machine using a combination of power supplied from an external power source and power supplied from a battery, it is possible to extend the operating time and reduce the battery capacity. Patent Document 1 discloses a construction machine that uses a combination of power supplied from an external power source and power supplied from a battery.

[0003] Japanese Patent Application Laid-Open No. 2022-109029

[0004] Operating a work machine using power supplied from an external power source reduces the charge and discharge rate of the battery, which may reduce the reduction in battery life. On the other hand, if a small-capacity battery is installed in the work machine in order to reduce the space occupied by the battery, the ratio of charge and discharge rate to battery capacity increases, which may reduce the battery life.

[0005] The present disclosure aims to suppress a decrease in battery life in a work machine that uses both an external power source and a battery.

[0006] According to the present disclosure, there is provided a work machine including a power supply device connected to an external power source and outputting supply power, a battery charged with charging power input from the power supply device, an electric device consuming load power input from at least one of the power supply device and the battery, and a controller. The controller determines a first upper limit value of the charging power, changes the first upper limit value to a second upper limit value based on the load power, and controls the power supply device so that the supply power follows the load power and so that the charging power does not exceed the first upper limit value.

[0007] According to the present disclosure, in a work machine that uses both an external power source and a battery, it is possible to suppress a decrease in the battery life.

[0008] FIG. 1 is a diagram schematically showing a work machine according to an embodiment. FIG. 2 is a block diagram showing the work machine according to an embodiment. FIG. 3 is a hardware configuration diagram showing a controller according to an embodiment. FIG. 4 is a diagram for explaining an operation method of a work machine according to an embodiment. FIG. 5 is a block diagram showing a controller according to an embodiment. FIG. 6 is a flowchart showing a control method of a work machine according to an embodiment. FIG. 7 is a diagram showing the relationship between feed power, charging power, and load power according to an embodiment. FIG. 8 is a diagram showing the relationship between feed power, charging power, and load power according to an embodiment. FIG. 9 is a diagram showing the relationship between feed power, charging power, and load power according to an embodiment. FIG. 10 is a diagram showing the relationship between feed power, charging power, and load power when regenerative power is generated according to an embodiment. FIG. 11 is a diagram showing the relationship between feed power, charging power, and load power when regenerative power is generated according to an embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described, but the present disclosure is not limited to the embodiments. The components of each embodiment described below can be combined as appropriate. In addition, some components may not be used.

[0010] [Working Machine] Figure 1 is a diagram that schematically shows a working machine 1 according to an embodiment. In the embodiment, the working machine 1 is an electric working machine that is driven by an external power source 8 and a battery 7. In the embodiment, the working machine 1 is an electric excavator. The working machine 1 includes a lower traveling body 2, an upper rotating body 3, a working implement 4, a hydraulic actuator 5, a power supply unit 6, and a battery 7.

[0011] The undercarriage 2 has a pair of tracks. The undercarriage 2 is capable of traveling on the ground. The upper rotating body 3 is supported on the undercarriage 2. The upper rotating body 3 is capable of swinging. The work implement 4 is supported on the upper rotating body 3. The work implement 4 includes a boom 4A connected to the upper rotating body 3, an arm 4B connected to the boom 4A, and a bucket 4C connected to the arm 4B. The hydraulic actuator 5 includes a boom cylinder 5A that operates the boom 4A, an arm cylinder 5B that operates the arm 4B, and a bucket cylinder 5C that operates the bucket 4C. Each of the boom cylinder 5A, the arm cylinder 5B, and the bucket cylinder 5C is a hydraulic cylinder. The hydraulic actuator 5 also includes a travel motor 5D that rotates the tracks of the undercarriage 2 and a swing motor 5E that swings the upper rotating body 3. Each of the travel motor 5D and the swing motor 5E is a hydraulic motor.

[0012] The power feeder 6 is connected to an external power source 8. The external power source 8 is a commercial power source. The power feeder 6 is arranged on the upper rotating body 3. The external power source 8 is connected to the work machine 1 via a cable 9. A power feed port 10 is provided on the upper rotating body 3. The cable 9 is attached to and detached from the power feed port 10. The power feeder 6 is fed with power from the external power source 8 via the cable 9 and the power feed port 10.

[0013] The battery 7 is an internal battery mounted on the upper rotating body 3. The battery 7 includes a secondary battery. In this embodiment, the battery 7 includes a rechargeable lithium-ion battery. The battery 7 is charged by power output from the power supply device 6.

[0014] 2 is a block diagram showing a work machine 1 according to an embodiment. The work machine 1 has a power supply port 10, a power supply unit 6, a battery 7, an inverter 11, an electric motor 12, a hydraulic pump 13, a main valve 14, a hydraulic actuator 5, high-voltage accessories 15, a DC / DC converter 16, low-voltage accessories 17, a first power sensor 18, a second power sensor 19, and a controller 20.

[0015] The power supply device 6 is connected to an external power supply 8 via a power supply port 10. The power supply device 6 converts AC voltage supplied from the external power supply 8 into DC voltage. The power supply device 6 outputs power supply. The power supply device 6 can supply power supply to at least one of the battery 7, the inverter 11, the high-voltage auxiliary device 15, and the DC / DC converter 16. The power supply output from the power supply device 6 is distributed to each of the battery 7, the inverter 11, the high-voltage auxiliary device 15, and the DC / DC converter 16.

[0016] The battery 7 is charged by charging power input from the power supply device 6. The charging power is at least a portion of the supply power output from the power supply device 6. The charging power is supply power distributed from the power supply device 6 to the battery 7. The battery 7 outputs discharge power. The battery 7 can supply discharge power to at least one of the inverter 11, the high-voltage auxiliary device 15, and the DC / DC converter 16. The discharge power output from the battery 7 is distributed to each of the battery 7, the inverter 11, the high-voltage auxiliary device 15, and the DC / DC converter 16.

[0017] The inverter 11 is supplied with feed power from the power supply device 6 and with discharge power from the battery 7. The inverter 11 converts a DC voltage input from at least one of the power supply device 6 and the battery 7 into an AC voltage. The AC voltage converted by the inverter 11 is input to the electric motor 12.

[0018] The electric motor 12 is an electrical device (load) that consumes load power input from at least one of the power supply 6 and the battery 7 via the inverter 11. The load power input to the electric motor 12 from the power supply 6 is at least a part of the feed power output from the power supply 6. The load power input to the electric motor 12 from the battery 7 is at least a part of the discharge power output from the battery 7. The electric motor 12 is driven by consuming the load power input from at least one of the power supply 6 and the battery 7.

[0019] The hydraulic pump 13 is driven by the electric motor 12. The hydraulic pump 13 discharges hydraulic oil. The hydraulic oil discharged from the hydraulic pump 13 is supplied to the hydraulic actuator 5 via a main valve 14.

[0020] The high-voltage auxiliary machine 15 and the low-voltage auxiliary machine 17 are each an electric device (load) different from the electric motor 12. The high-voltage auxiliary machine 15 is connected in parallel with the inverter 11. The low-voltage auxiliary machine 17 is connected in parallel with the inverter 11. The high-voltage auxiliary machine 15 is driven at a higher voltage than the low-voltage auxiliary machine 17. The high-voltage auxiliary machine 15 is driven by consuming load power input from at least one of the power feeder 6 and the battery 7. The low-voltage auxiliary machine 17 is driven by consuming load power input from at least one of the power feeder 6 and the battery 7.

[0021] The DC / DC converter 16 converts a voltage input from at least one of the power supply device 6 and the battery 7 into a predetermined voltage. In this embodiment, the DC / DC converter 16 steps down the input voltage at a predetermined step-down ratio. The DC / DC converter 16 is connected in parallel with the inverter 11. The low-voltage auxiliary machine 17 is driven based on the power output from the DC / DC converter 16.

[0022] The first power sensor 18 detects the supply power output from the power supply device 6. The first power sensor 18 transmits detection data indicating the current value of the supply power to the controller 20. The supply power includes a supply current output from the power supply device 6. The first power sensor 18 may be a current sensor that detects the current value of the supply current.

[0023] The second power sensor 19 detects the charging power input to the battery 7. The second power sensor 19 detects the discharging power output from the battery 7. The second power sensor 19 transmits detection data indicating the current value of the charging power and detection data indicating the current value of the discharging power to the controller 20. The charging power includes the charging current input to the battery 7. The discharging power includes the discharging current output from the battery 7. The second power sensor 19 may be a current sensor that detects the current value of the charging current and the current value of the discharging current.

[0024] The power supplied from the power supply device 6 and the discharge power output from the battery 7 are consumed not only by the electric motor 12 but also by a plurality of electrical devices including the high-voltage auxiliary machine 15 and the low-voltage auxiliary machine 17. In the following description, for simplicity, it is assumed that the load power is consumed only by the electric motor 12.

[0025] [Controller] FIG. 3 is a hardware configuration diagram showing the controller 20 according to the embodiment. The controller 20 includes a computer system 1000. The computer system 1000 includes a processor 1001 such as a central processing unit (CPU), a main memory 1002 including a nonvolatile memory such as a read-only memory (ROM) and a volatile memory such as a random access memory (RAM), a storage 1003, and an interface 1004 including an input / output circuit. The functions of the controller 20 are stored in the storage 1003 as a computer program. The processor 1001 reads the computer program from the storage 1003, loads it into the main memory 1002, and executes the above-described processing in accordance with the program. The computer program may be distributed to the computer system 1000 via a network.

[0026] 2, the controller 20 receives detection data from the first power sensor 18 indicating the current value of the supplied power. The controller 20 receives detection data from the second power sensor 19 indicating the current value of the charged power. The controller 20 receives detection data from the second power sensor 19 indicating the current value of the discharged power.

[0027] The controller 20 receives as input a current SOC value indicating the current state of charge (SOC) of the battery 7 and a target SOC value indicating a target value for the state of charge of the battery 7. The state of charge of the battery 7 refers to the ratio of the charge amount to the capacity (fully charged capacity) of the battery 7. The current SOC value is calculated, for example, based on detection data from a voltage sensor that detects the output voltage of the battery 7. The target SOC value is a predetermined value, and may be input from a specified input device or may be stored in a storage 1003 mounted on the work machine 1.

[0028] The controller 20 receives battery power limit information indicating the allowable value of the received power (received current) that the power supply device 6 can receive from the external power source 8 and the upper limit of the battery power (charging power). The allowable value of the received power and the upper limit of the battery power are each predetermined values. There is an upper limit to the amount of power that the external power source 8 can output. The allowable value of the received power indicates the upper limit to the amount of power that the external power source 8 can output. It is preferable that the amount of power that the external power source 8 can output is 80% or more of the total load power (total load current). Similarly, there is an upper limit to the amount of power that the battery 7 can input. The battery power limit information indicates the upper limit to the charging power that the battery 7 can input.

[0029] [Operation Method] Figure 4 is a diagram for explaining the operation method of the work machine 1 according to the embodiment. As shown in Figure 4, the work machine 1 can be operated in a combined operation method in which it operates using both feed power (feed current) output from a power feeder 6 connected to an external power source 8, and discharge power (discharge current) output from a battery 7.

[0030] In the combined operation method, the supply power output from the power supply device 6 is distributed to the battery 7 and the inverter 11. The battery 7 is charged by the charging power (charging current) representing the supply power distributed to the battery 7. The electric motor 12 is driven by the load power (load current) representing the supply power distributed to the inverter 11.

[0031] In the combined operation mode, the controller 20 controls the power supply device 6 so that the supply power (supply current) output from the power supply device 6 follows the load power (load current) consumed by the electric motor 12. The load power consumed by the electric motor 12 is the difference between the supply power output from the power supply device 6 and the charging power input to the battery 7. The supply power output from the power supply device 6 is detected by a first power sensor 18. The charging power input to the battery 7 is detected by a second power sensor 19. The controller 20 can calculate the load power based on the detection data of the first power sensor 18 and the detection data of the second power sensor 19. The load power includes a current value of the load power.

[0032] The controller 20 varies the feed power output from the power supply device 6 so as to follow the load power consumed by the electric motor 12. The controller 20 outputs a control command to the power supply device 6 so that the feed power increases as the load power increases. The controller 20 outputs a control command to the power supply device 6 so that the feed power decreases as the load power decreases.

[0033] The power supply power output from the power supply device 6 varies so as to follow the load power of the electric motor 12, thereby suppressing fluctuations in the charge / discharge amount of the battery 7. Suppressing fluctuations in the charge / discharge amount of the battery 7 suppresses a decrease in the lifespan of the battery 7. Even if the capacity of the battery 7 is small, suppressing fluctuations in the charge / discharge amount of the battery 7 reduces the ratio of the charge / discharge amount to the capacity of the battery 7, thereby suppressing a decrease in the lifespan of the battery 7.

[0034] [Charging the Battery] The battery 7 can be charged both when the work machine 1 is operating and when it is at rest. When the work machine 1 is operating, this means that the electric motor 12 is operating. When the work machine 1 is at rest, this means that the electric motor 12 is stopped.

[0035] While the work machine 1 is in operation, the battery 7 is charged with charging power that is part of the supply power output from the power supply device 6. When charging the battery 7, the controller 20 outputs a control command to the power supply device 6 so that the charging rate of the battery 7 does not exceed an allowable value that is lower than 100%. In other words, when charging the battery 7 while the work machine 1 is in operation, the controller 20 controls the charging operation of the battery 7 by the power supply device 6 so that the battery 7 is not fully charged. By keeping the charging rate of the battery 7 at a low value, a decrease in the lifespan of the battery 7 is suppressed.

[0036] The electric motor 12 generates regenerative power (regenerative current) during braking, for example. While the work machine 1 is in operation, the battery 7 is charged by the regenerative power input from the electric motor 12 via the inverter 11.

[0037] When the work machine 1 is at rest, no discharge power is output from the battery 7. When charging the battery 7 while the work machine 1 is at rest, the controller 20 outputs a control command to the power supply device 6 so that the charging rate of the battery 7 becomes 100%. In other words, when charging the battery 7 while the work machine 1 is at rest, the controller 20 controls the charging operation of the battery 7 by the power supply device 6 so that the battery 7 is fully charged.

[0038] In the embodiment, the controller 20 determines a first upper limit value of the charging power. If the charging power for charging the battery 7 is excessively large, there is a possibility that the battery 7 will deteriorate. The first upper limit value of the charging power is set so that the battery 7 will not deteriorate due to charging.

[0039] The charging power allowed for the battery 7 to suppress deterioration of the battery 7 is proportional to the capacity of the battery 7. The charging power allowed for the battery 7 changes based on the charging rate of the battery 7. Battery power limit information is input to the controller 20 as a value that changes based on the charging rate of the battery 7. The controller 20 acquires the battery power limit information for the battery 7. The controller 20 determines a first upper limit value of the charging power as a value equal to the battery power limit information.

[0040] The lower the charging rate of the battery 7, the higher the allowable charging power, and the higher the charging rate of the battery 7, the lower the allowable charging power. In other words, when the charging rate of the battery 7 is low, deterioration of the battery 7 is suppressed even if the charging power is high. When the charging rate of the battery 7 is high, the charging power needs to be reduced because there is a high possibility that the battery 7 will deteriorate if the charging power is high. Based on the battery power limit information, the controller 20 increases the first upper limit value the lower the charging rate of the battery 7, and decreases the first upper limit value the higher the charging rate of the battery 7. The controller 20 controls the power supply device 6 so that the charging power does not exceed the first upper limit.

[0041] In this embodiment, the controller 20 changes the first upper limit value of the charging power to a second upper limit value based on the load power consumed by the electric motor 12. The second upper limit value is a value higher than the first upper limit value. In this embodiment, the second upper limit value is the sum of the first upper limit value and the current value of the load power. The controller 20 controls the power supply device 6 so that the supply power follows the load power and so that the charging power (input to the battery 7) does not exceed the first upper limit value (battery power limit information). The controller 20 controls the power supply device 6 so that the supply power (output from the power supply device 6) does not exceed the second upper limit value.

[0042] [Control Method] Fig. 5 is a block diagram showing a controller 20 according to the embodiment. The controller 20 has a first calculation unit 21, a second calculation unit 22, a third calculation unit 23, a fourth calculation unit 24, a fifth calculation unit 25, a sixth calculation unit 26, a seventh calculation unit 27, and an eighth calculation unit 28. The controller 20 receives as input the charging power, the supply power, the target SOC value, the current SOC value, the first upper limit value of the charging power, and the allowable value of the received power.

[0043] The first calculation unit 21 calculates the load power based on the difference between the feed power and the charging power. The load power is the value obtained by subtracting the charging power from the feed power.

[0044] The second calculation unit 22 calculates the difference between the target SOC value and the current SOC value. The target SOC value is a value lower than 100%. The target SOC value may be, for example, 90%.

[0045] The third calculation unit 23 performs low-pass filtering on the load power.

[0046] The fourth calculation unit 24 calculates a control command value for performing PI control on the current SOC value based on the difference between the target SOC value and the current SOC value so that the current SOC value becomes the target SOC value.

[0047] The fifth calculation unit 25 calculates the charging power for charging the battery 7 based on the current value of the load power output from the third calculation unit 23 and the control command value output from the fourth calculation unit 24 .

[0048] The sixth calculation unit 26 changes the first upper limit value of the charging power to a second upper limit value based on the load power. The sixth calculation unit 26 calculates the second upper limit value based on the sum of the first upper limit value and the current value of the load power. The second upper limit value is the first upper limit value plus the current value of the load power.

[0049] The seventh calculation unit 27 limits the charging power so that the charging power calculated by the fifth calculation unit 25 does not exceed the second upper limit value calculated by the sixth calculation unit 26. The seventh calculation unit 27 outputs the smaller value of the charging power calculated by the fifth calculation unit 25 and the second upper limit value calculated by the sixth calculation unit 26 as the charging power.

[0050] The eighth calculation unit 28 limits the charging power so that the charging power calculated by the seventh calculation unit 27 does not exceed the allowable value of the received power. The eighth calculation unit 28 outputs the smaller value of the charging power calculated by the seventh calculation unit 27 and the allowable value of the received power as the charging power.

[0051] 6 is a flowchart showing a method for controlling the work machine 1 according to this embodiment. The controller 20 determines whether the power feeder 6 is receiving power from the external power source 8 via the power feed port 10 (step S1).

[0052] In step S1, if it is determined that the power supply device 6 is receiving power from the external power source 8 (step S1: Yes), the controller 20 controls the power supply device 6 so that the power supply device 6 outputs supply power (step S4).

[0053] If it is determined in step S1 that the power supply device 6 is not receiving power from the external power source 8 (step S1: No), or if power supply power is output from the power supply device 6 in step S4, the controller 20 determines whether to output a drive command to drive the electric motor 12 (step S2).

[0054] If a drive command is output in step S2 (step S2: Yes), the controller 20 drives the electric motor 12 (step S5).

[0055] If it is determined in step S2 that a drive command is not to be output (step S2: No), or if the electric motor 12 is driven in step S5, the controller 20 determines whether the key is in an off state (step S3).

[0056] If it is determined in step S3 that the key is in the off state (step S3: Yes), the controller 20 terminates the system (step S6).

[0057] If it is determined in step S3 that the key is not in the off state (step S3: No), the controller 20 returns to the process of step S1.

[0058] [Effects] As described above, in a work machine 1 that uses both an external power supply 8 and a battery 7, the controller 20 varies the feed power output from the power supply 6 so as to follow the load power consumed by the electric motor 12. This reduces the charge / discharge amount of the battery 7 (the ratio of the charge / discharge amount to the capacity of the battery 7). It also reduces an increase in the number of cycles in which the battery 7 is repeatedly charged and discharged. This reduces deterioration of the battery 7 and reduces a reduction in the lifespan of the battery 7.

[0059] FIG. 7 is a diagram showing the relationship between the supply power, the charging power, and the load power according to the embodiment. In FIG. 7 , the horizontal axis represents the time the work machine 1 is driven, and the vertical axis represents the power. As shown in FIG. 7 , the load power fluctuates greatly based on, for example, the type of work being performed by the work machine 1. When the supply power output from the power supply device 6 is constant, the charge / discharge amount of the battery 7 increases in accordance with fluctuations in the load power. Note that in FIG. 7 , a positive value for the charging power indicates that charging power is being input to the battery 7 and the battery 7 is being charged. A negative value for the charging power indicates that discharging power is being output from the battery 7. When the charge / discharge amount of the battery 7 is large, the battery 7 is likely to deteriorate. As shown in FIG. 7 , in the embodiment, the supply power output from the power supply device 6 fluctuates to track the load power. Because the supply power fluctuates to track the load power, the charging power input to the battery 7 and the discharging power output from the battery 7 are small. In other words, the charge / discharge amount of the battery 7 is suppressed. This suppresses deterioration of the battery 7 and a reduction in the lifespan of the battery 7.

[0060] Fig. 7 shows a case where the charging rate of the battery 7 is low and the first upper limit value of the charging power is high. In the example shown in Fig. 7, the first upper limit value is higher than the maximum value of the load power. According to the example shown in Fig. 7, since the first upper limit value of the charging power is high, the controller 20 can control the power supply device 6 so that the feeding power follows the load power even if the feeding output is limited so as not to exceed the first upper limit value.

[0061] FIG. 8 is a diagram showing the relationship between the supply power, the charging power, and the load power according to the embodiment. FIG. 8 illustrates a case where the charging rate of the battery 7 is high and the first upper limit value of the charging power is low. As described above, the higher the charging rate of the battery 7, the lower the first upper limit value. When the first upper limit value is low, the load power is more likely to be lower than the maximum value. When the supply power is limited so as not to exceed the first upper limit value, the supply power may not be able to keep up with the load power. Because charging power (discharging power) is the difference between the supply power and the load power, if the supply power cannot keep up with the load power, as shown in FIG. 8, the amount of charge and discharge of the battery 7 will fluctuate greatly, which may result in a shortened lifespan of the battery 7.

[0062] Therefore, in the embodiment, the controller 20 changes the first upper limit value to the second upper limit value based on the load power.

[0063] 9 is a diagram illustrating the relationship between the supply power, the charging power, and the load power according to the embodiment. Fig. 9 illustrates an example in which the first upper limit value is changed to the second upper limit value based on the load power. The second upper limit value is the first upper limit value plus the current value of the load power.

[0064] The controller 20 controls the power supply device 6 so that the supply power follows the load power and so that the charging power does not exceed the first upper limit. The supply power is distributed to the charging power and the load power. As the load power increases, the charging power decreases. When the load power is large, the charging power decreases, leaving room for increasing the supply power. By raising the first upper limit by the amount of the load power to set it as the second upper limit, the supply power can follow the load power. The supply power is controlled so as not to exceed the second upper limit. As the charging power decreases by the amount of the load power, the charging power does not exceed the first upper limit.

[0065] 10 and 11 are diagrams showing the relationship between the feed power, the charging power, and the load power when regenerative power is generated.

[0066] When the electric motor 12 generates regenerative power, the regenerative power from the electric motor 12 is input to the battery 7. That is, the battery 7 is charged with the regenerative power. When the regenerative power is input to the battery 7 as charging power, even if the supply power is limited so as not to exceed the first upper limit, there is a possibility that the charging power (regenerative power) will exceed the first upper limit, as shown in FIG. 10 .

[0067] When the electric motor 12 generates regenerative power, the controller 20 strengthens the limitation on the charging power. As shown in Fig. 11 , the controller 20 controls the power supply device 6 so that the supply power follows the load power and so that the charging power does not exceed the first upper limit.

[0068] [Other Embodiments] In the above-described embodiment, for the sake of simplicity, the load power is assumed to be consumed only by the electric motor 12. The controller 20 may control the power supply device 6 so that the supply power output from the power supply device 6 follows the total load power of a plurality of loads including the electric motor 12, the high-voltage auxiliary device 15, and the low-voltage auxiliary device 17.

[0069] In the above-described embodiment, some or all of the hydraulic actuators 5 may be replaced with electric actuators. The swing motor 5E may be an electric motor. The travel motor 5D may be an electric motor. The boom cylinder 5A, the arm cylinder 5B, and the bucket cylinder 5C may each be an electric cylinder. When all of the hydraulic actuators 5 are replaced with electric actuators, the hydraulic pump 13 and the main valve 14 are omitted.

[0070] In the above-described embodiment, the work machine 1 is an electric shovel. However, the work machine 1 may be, for example, an electric forklift.

[0071] 1...working machine, 2...undercarriage, 3...upper rotating body, 4...working machine, 4A...boom, 4B...arm, 4C...bucket, 5...hydraulic actuator, 5A...boom cylinder, 5B...arm cylinder, 5C...bucket cylinder, 5D...traveling motor, 5E...swing motor, 6...power supply, 7...battery, 8...external power supply, 9...cable, 10...power supply port, 11...inverter, 12...electric motor, 13...hydraulic pump, 14...main valve, 15...high voltage Auxiliary equipment, 16...DC / DC converter, 17...low-voltage auxiliary equipment, 18...first power sensor, 19...second power sensor, 20...controller, 21...first calculation unit, 22...second calculation unit, 23...third calculation unit, 24...fourth calculation unit, 25...fifth calculation unit, 26...sixth calculation unit, 27...seventh calculation unit, 28...eighth calculation unit, 1000...computer system, 1001...processor, 1002...main memory, 1003...storage, 1004...interface.

Claims

1. A work machine comprising: a power supply device connected to an external power source and outputting supply power; a battery charged with charging power input from the power supply device; an electrical device consuming load power input from at least one of the power supply device and the battery; and a controller, wherein the controller determines a first upper limit value of the charging power, changes the first upper limit value to a second upper limit value based on the load power, and controls the power supply device so that the supply power tracks the load power and so that the charging power does not exceed the first upper limit value.

2. The work machine according to claim 1, wherein the controller acquires battery power limit information of the battery, and determines the first upper limit value based on the battery power limit information.

3. The work machine according to claim 2, wherein the second upper limit value is the sum of the first upper limit value and a current value of the load power.

4. The work machine according to claim 1, wherein the electrical equipment includes an electric motor, the battery is charged by regenerative power input from the electric motor, and the controller controls the power supply so that the supply power follows the load power and so that the charging power does not exceed the first upper limit value.

5. A control method for a work machine equipped with a power supply connected to an external power source, a battery charged by the power supply, and an electrical device, comprising: outputting supply power from the power supply connected to the external power source; charging the battery with charging power input from the power supply to the battery; inputting load power from at least one of the power supply and the battery to an electrical device; determining a first upper limit value of the charging power; changing the first upper limit value to a second upper limit value based on the load power; and controlling the power supply so that the supply power follows the load power and so that the charging power does not exceed the first upper limit value.

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