Work machine, power control method, and power control system

Abstract

This work machine, such as an electric excavator 100, is provided with a vehicle body including a work device, an AC / DC converter 111 that is provided to the vehicle body and receives power from a system power source 400, and a high-voltage battery 112 provided to the vehicle body. The work machine runs on received power, which is power received from the system power source 400 by the AC / DC converter 111, as well as power from the high-voltage battery 112. The work machine comprises a vehicle control device 120 for modifying the received power during operation of the vehicle body. Due to this configuration, the work machine can properly distribute power acquired from the system power source, thereby making it possible to provide a work machine, a power control method, and a power control system able to promptly address decrease in load on the system power source.

Description

Work machine, power control method and power control system

[0001] The present invention relates to a work machine, a power control method, and a power control system, and in particular to a work machine that operates using both power from a grid power supply and power from a battery, as well as a power control method and power control system that can be preferably applied to this work machine.

[0002] Recently, from an environmental perspective, electrically operated work machines have been increasingly used. As a method for supplying power to a work machine, there is a method in which power is supplied from both a grid power supply and a battery.

[0003] Patent Document 1 discloses an electric construction machine in which a controller calculates its own required power for driving multiple hydraulic actuators based on operation signals from multiple operating devices, calculates an allowable power as a power limit value that the electric motor can use based on its own required power, the required power of other electric construction machines received via a communication device, and the allowable power of the commercial power receiving equipment, and controls the power consumption of the electric motor so that it does not exceed the allowable power.

[0004] Japanese Patent Application Laid-Open No. 2020-39239

[0005] However, there is an upper limit to the amount of power that can be received from a grid power supply. Meanwhile, the power required within a work site that shares the grid power supply changes from time to time depending on the operating status and number of electrically powered products, such as work machines, operating at the work site. In addition, a request to reduce the amount of power used may be received from the power company depending on the power supply and demand situation of the entire power infrastructure. For example, if a work machine does not change the amount of power it receives despite receiving a request from the power company to reduce its power use, there is a risk that power will not be distributed to other work machines, etc. within the work site. Therefore, it is necessary to quickly change the amount of power received by the work machine in accordance with the upper limit of the power that can be received from the grid power supply and a request to reduce the power used. An object of the present invention is to provide a work machine, a power control method, and a power control system that can quickly respond to a reduction in the load on the grid power supply.

[0006] In order to solve the above problems, the present invention provides a work machine that includes a vehicle body including a work implement, a power receiving device mounted on the vehicle body and receiving power from a power grid, and a battery mounted on the vehicle body, and that operates using received power, which is power received by the power receiving device from the power grid, and power from the battery, and that includes a control device that changes the received power while the vehicle body is operating.In this case, it is possible to provide a work machine that can appropriately allocate power obtained from the power grid, thereby quickly responding to a reduction in the load on the power grid.

[0007] Here, the control device can be configured to be able to change the received power not only while the vehicle is operating, but also while the vehicle is stopped. In this case, charging management within the work site can be performed taking into account the remaining battery power of the work machine when the work machine is stopped, such as at night or during a break, when the remaining battery power is less likely to fluctuate. The control device can also determine the change in received power based on the power consumption, which is the power consumed by the vehicle. In this case, the power received from the grid power supply can be changed depending on the operating status of the vehicle. Furthermore, the control device can store power consumption over a predetermined period and determine the change in received power based on the stored power consumption over the predetermined period. In this case, the power received from the grid power supply can be changed depending on the power most recently used by the control device. Furthermore, the predetermined period can be a period during which the vehicle is operating. In this case, the power most recently used by the control device can be calculated more accurately. The control device can also be provided with a data communication device that receives a signal output by an external device, and the control device can change the received power based on the signal received by the data communication device. In this case, the power received by each work machine from the grid power supply can be changed based on the power used throughout the work site. Furthermore, the signal received by the data communication device can include information on the received power set by an administrator based on the power consumed by multiple work machines, including the vehicle. In this case, the power received from the grid power supply can be allocated according to the power usage status of the multiple work machines. Furthermore, the data communication device can transmit information on power consumption, which is the power consumed by the vehicle body, to an external device, and the external device can receive information on new power to be received from the grid power supply, which is determined from power consumption over a predetermined period based on the power consumption information. The control device can change the received power based on the new power information received by the data communication device. In this case, the power to be received from the grid power supply can be set according to the power most recently used by the device. Furthermore, the data communication device can transmit information on power consumption, which is the power consumed by the vehicle body, to an external device, and receive information on new power to be received from the grid power supply, which is determined by the external device based on the power consumed by multiple work machines, including the vehicle. The control device can change the received power based on the new power information received by the data communication device.In this case, the power received from the grid power supply can be allocated according to the power used by each work machine. The data communication device can then receive new power information determined by the external device so that power is allocated to the multiple work machines within a range that does not exceed the upper limit of power that can be obtained from the grid power supply. In this case, when allocating power received from the grid power supply, it is possible to ensure that the upper limit of power that can be obtained from the grid power supply is not exceeded.

[0008] The present invention also provides a power control method in which, for a work machine that operates on power from a grid power supply and power from a battery, the received power that the work machine receives from the grid power supply is changed while the work machine is operating by having a processor execute a program stored in memory. In this case, it is possible to provide a power control method that can be preferably applied to a work machine that can quickly respond to a reduction in the load on the grid power supply.

[0009] Furthermore, the present invention provides a power control system that includes a management device that determines the received power that a work machine receives from a grid power supply based on the power consumption when the work machine is operating on power from the grid power supply and power from a battery, and a vehicle control device that is mounted on the work machine and changes the power that the work machine receives from the grid power supply to the received power determined by the management device while the work machine is operating.In this case, it is possible to provide a power control system that is preferably applicable to a work machine that can quickly respond to a reduction in the load on the grid power supply.

[0010] According to the present invention, it is possible to provide a work machine, a power control method, and a power control system that can more appropriately allocate power obtained from a system power supply to a work machine, thereby quickly responding to a reduction in the load on the system power supply.

[0011] 1 is a schematic diagram showing the overall configuration of a work site to which the present embodiment is applied. FIG. 2 is a diagram showing a first example of a power control system 1 according to the present embodiment. FIG. 3 is a diagram showing a second example of a power control system 1 according to the present embodiment. FIG. 4 is a flowchart showing a case in which a worker A changes the received power while the electric shovel is stopped. FIG. 5 is a flowchart showing a case in which a vehicle control device calculates and changes the received power while the electric shovel is in operation. FIG. 6 is a sequence diagram showing data exchange between the vehicle control device, the control device, and the database. FIG. 7 is a flowchart showing a case in which a server calculates and changes the received power while the electric shovel is in operation. FIG. 8 is a sequence diagram showing data exchange between the vehicle control device, the control device, and the database. FIG. 9 is a flowchart showing a case in which a server calculates and changes the received power while the electric shovel is in operation. FIG. 10 is a sequence diagram showing data exchange between a power plant, a vehicle control device, the control device, and the database. (a) to (b) are diagrams explaining the most recent predetermined time period. (a) to (e) are diagrams showing transitions in the power state (mode) of the electric shovel. 1A is a diagram illustrating a case where the received power is changed. FIGS. 1B to 1D are diagrams illustrating changes in peak power when the power source is changed. FIGS. 1C to 1D are diagrams illustrating specific examples of distributing received power to a plurality of electric excavators.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0013] <Explanation of Overall Configuration of Work Site> FIG. 1 is a schematic diagram showing the overall configuration of a work site to which this embodiment is applied. Multiple work machines operate at the work site. The work site shown in the figure is a construction site. The illustration shows a case where an electric shovel 100 operates as a work machine at the construction site. Note that the work machine operating at the construction site is not limited to the electric shovel 100, and can be construction machinery such as a wheel loader, bulldozer, or crane truck. The work machine operating at the construction site may also be a truck 190 for transporting gravel or the like. Note that the work site is not limited to a construction site. For example, it can also be an agricultural work site where agricultural machinery operates as work machines. In this case, the agricultural machinery can be a felling machine, a timber processing machine, a tractor, a forestry work vehicle, a logging machine, or the like. Note that FIG. 1 shows a case where operation information of various work machines is collected in a server 500 via wireless communication or the like, and information management is performed for operation, inspection, and maintenance.

[0014] The electric shovel 100 shown in the figure is an example of a work machine that operates using power from a grid power supply and power from a battery. The electric shovel 100 can also be said to be an example of an electric construction machine. A power cable 200 that supplies power to the electric shovel 100 is connected to the electric shovel 100. The power cable 200 is, for example, a high-voltage cable that is capable of transmitting three-phase alternating current. Both ends of the power cable 200 are connected to the electric shovel 100 and a reel-type cable container 300, and power is supplied to the electric shovel 100 via the reel-type cable container 300. The reel-type cable container 300 has the power cable 200 wound around a cable reel (not shown) housed within the container, and the power cable 200 is unwound from the cable reel toward the electric shovel 100.

[0015] The reel-type cable container 300 is supplied with power from a power grid 400. The power grid 400 is also called a commercial power source, and is power generated by a power plant 410 and supplied by a power company. In FIG. 1, power is supplied from two power grids 400.

[0016] The amount of power that can be used from the grid power supply 400 is limited by contract or other factors. The power limit is, for example, 88 VA. Therefore, even when multiple work machines are operating, the total power used cannot exceed this limit. A battery-powered work machine that operates solely on power from its battery needs to receive power from the grid power supply when charging. If multiple work machines are rapidly charging at the same time during a break, for example, this could result in an overload on the grid power supply or interference with rapid charging due to limitations on the available power. Furthermore, a cable-operated work machine that operates solely on power from the grid power supply could be disrupted in its operation or the normal operation of the grid power supply if the power demand based on output fluctuations of the work machines exceeds the available power. Therefore, this embodiment employs a battery-cable combined use work machine that is configured to receive power from the grid power supply while also using power from its own onboard battery. The upper limit of available power can be individually changed for each work machine depending on the conditions at the work site, thereby achieving both a reduction in the load on the grid power supply and a response to the power demands of the work machines.

[0017] However, the power required within a work site that shares a grid power supply changes from time to time depending on the operating status and number of electrically powered products, such as work machines, operating at the work site. Furthermore, there are cases where a request to reduce power usage is received from the power company depending on the power supply and demand situation of the entire power infrastructure. In such cases, a method of setting a fixed upper limit on the power received from the grid power supply for each work machine is not sufficient to achieve both a reduction in the load on the grid power supply and a response to the power requests of the work machines. Therefore, this embodiment aims to solve this problem by adopting a method of changing the power received by each work machine from the grid power supply, at least while the work machine is operating, depending on the operating status of the work machine.

[0018] <Explanation of the configuration of power control system 1> Fig. 2 is a diagram showing a first example of the power control system 1 of the present embodiment. In the power control system 1 shown in Fig. 2, power is supplied from a system power supply 400 to an electric shovel 100 via a power cable 200. Note that, in the following explanation, for the sake of simplicity, a case will be described in which the work machine is the electric shovel 100, but it goes without saying that the invention can also be applied to cases in which the work machine is other than the electric shovel 100.

[0019] The electric shovel 100 includes a high-voltage circuit 110, a vehicle control device 120, a hydraulic circuit 130, and an operation system 140. The electric shovel 100 shown in the figure controls the high-voltage circuit 110 using power supplied from a power cable 200 to drive a drive motor 118, which is a power source. The high-voltage circuit 110 includes an AC / DC converter 111, which is an example of a power receiving device that receives power from a system power supply 400 and converts the AC power supplied from the power cable 200 into DC, a high-voltage storage battery 112, which is an example of a battery and stores power, a pre-charge relay 113 and a main relay 114 that control the ON / OFF of the high-voltage circuit 110, a resistor 115, a capacitor 116, an inverter 117 that converts the DC power into AC power for driving the drive motor 118, and the drive motor 118.

[0020] When the high-voltage circuit 110 is turned on, the pre-charge relay 113 is first turned on. This causes charge to accumulate in the capacitor 116. Then, the main relay 114 is turned on. This prevents an inrush current from occurring when the high-voltage circuit 110 is turned on. It also prevents the terminals of the high-voltage circuit 110 from welding. The high-voltage circuit 110 supplies power to the drive motor 118 using power generated by the AC / DC converter 111 and the high-voltage storage battery 112. In other words, when the load on the drive motor 118 is small, the drive motor 118 is driven by power from the AC / DC converter 111. At this time, if there is a surplus of power supplied from the AC / DC converter 111, the high-voltage storage battery 112 is charged. On the other hand, when the load on the drive motor 118 increases and the power from the AC / DC converter 111 becomes insufficient, the shortfall in power is supplied from the high-voltage storage battery 112. The power supplied from the AC / DC converter 111 and the high-voltage storage battery 112 is converted into stable direct current by repeated charging and discharging by a capacitor 116. Then, an inverter 117 converts the direct current into alternating current at a desired frequency and voltage, and controls the rotation speed of a drive motor 118. This controls the amount of hydraulic pressure generated by a hydraulic pump 131, and operates the electric excavator 100.

[0021] The vehicle control device 120 is an example of a control device that changes the received power (the upper limit of the power that each electric shovel 100 can receive from the grid power supply 400), which is the power received from the grid power supply 400 while the vehicle body is in operation. The vehicle control device 120 is also an example of a vehicle control device that is mounted on the electric shovel 100 and changes the power that the electric shovel 100 receives from the grid power supply 400 to the received power determined by the server 500 while the electric shovel 100 is in operation. The received power is adjusted by the AC / DC converter 111. For example, the received power can be adjusted by adjusting the resistance value in a current limiting circuit of the AC / DC converter 111. The vehicle control device 120 includes a control and calculation function unit 121 (processor), a data recording unit (memory) 122, and a communication function unit 123. The control and calculation function unit 121 performs calculations to control the AC / DC converter 111, the high-voltage storage battery 112, and the inverter 117. The AC / DC converter 111, the high-voltage storage battery 112, and the inverter 117 are each equipped with a control unit (controller) 111C, 112C, and 117C. The control units 111C, 112C, and 117C transmit data representing the states of the AC / DC converter 111, the high-voltage storage battery 112, and the inverter 117 to a control and calculation function unit 121. The control and calculation function unit 121 performs calculations based on the transmitted data and transmits control signals for controlling the AC / DC converter 111, the high-voltage storage battery 112, and the inverter 117 to the control units 111C, 112C, and 117C. When adjusting the received power, the vehicle control device 120 transmits a command, which is received by the control unit 111C of the AC / DC converter 111. The settings of the AC / DC converter 111 are then changed, thereby changing the received power. A data recording unit (memory) 122 records program data used by the control and calculation function unit 121 to perform calculations. The communication function unit 123 is a communication interface used when transmitting control signals to the control units 111C, 112C, and 117C. In addition, a vehicle monitor 124 and a first data transmission / reception unit 125 are connected to the vehicle control device 120. The vehicle monitor 124 can display the status of the electric excavator 100.Furthermore, the vehicle monitor 124 is, for example, a touch panel, and the operator can input settings for the electric shovel 100 through the vehicle monitor 124. In this embodiment, as will be described in detail later, the vehicle monitor 124 is used by the worker A to input the received power of the multiple electric shovels 100. The worker A is, for example, an operator who operates the electric shovel. The first data transmitter / receiver 125 is a communication interface for communicating with an external device.

[0022] The hydraulic circuit 130 includes a hydraulic pump 131 that generates hydraulic pressure, a hydraulic oil tank 132 that stores hydraulic oil, a first directional control valve 133, and a second directional control valve 134. The hydraulic pump 131 is a variable displacement hydraulic pump driven by the drive motor 118. The hydraulic pump 131 draws hydraulic oil from the hydraulic oil tank 132 and supplies the hydraulic oil to the swing motor (not shown), boom cylinder 14, arm cylinder 16, and bucket cylinder 17 of the electric excavator 100 via the first directional control valve 133 and the second directional control valve 134, thereby operating the electric excavator 100. Note that hereinafter, when the boom cylinder 14, arm cylinder 16, and bucket cylinder 17 are not distinguished from one another, they may be simply referred to as the hydraulic cylinders 14, 16, and 17. The hydraulic cylinders 14, 16, and 17, as well as the boom, arm, and bucket (not shown) are examples of working devices.

[0023] The operation system 140 is provided in the driver's cab of the electric shovel 100, and is used by the operator when operating the electric shovel 100. The operation system 140 includes a work mode selection switch, a motor control dial (not shown) for setting the rotation speed of the drive motor 118, operation levers 141A, 141B, etc. The operation levers 141A, 141B correspond to the respective swing motors and arm cylinders, and use, for example, electric levers that output an electric operation signal (lever signal Lv) according to the amount of operation.

[0024] Fig. 3 is a diagram showing a second example of the power control system 1 of this embodiment. The power control system 1 shown in Fig. 3 differs from the power control system 1 shown in Fig. 2 in that a server 500, a power plant 410, and a third data transmission / reception unit 411 of the power plant 410 are added.

[0025] The server 500 is an example of a management device that determines the received power, which is the power that the electric shovel 100 receives from the grid power supply 400, based on the power consumption when the electric shovel 100 is operating. The server 500 is an external device and a server computer that manages the entire power control system 1. The server 500 can be, for example, a cloud server that operates on the cloud. The server 500 includes a second data transmitter / receiver 510, a control device 520, and a database 530. The second data transmitter / receiver 510 is a communication interface that exchanges data such as power with the electric shovel 100. In this case, the second data transmitter / receiver 510 communicates with a first data transmitter / receiver 125 that is connected to the vehicle control device 120 of the electric shovel 100. The control device 520 communicates with the multiple electric shovels 100 and obtains the power used by each electric shovel 100. The received power of each electric shovel 100 is then determined. As will be described in detail later, in a first method for determining the power, worker B determines the received power of each electric shovel 100 based on the acquired power. Worker B is, for example, the manager of the power control system 1. In addition, in a second method for determining the power, the control device 520 determines the received power of each electric shovel 100 using a predetermined calculation method based on the acquired power. The determined power is sent to each electric shovel 100 via the second data transmission / reception unit 510. The database 530 stores the history of the acquired power.

[0026] The third data transmitter / receiver 411 of the power plant 410 transmits the allowable power value of the grid power supply 400 to the server 500, as will be described in detail later.

[0027] <Explanation of Processing Performed by Power Control System 1> FIGS. 4 to 11 are flowcharts and sequence diagrams showing processing performed by the power control system 1. Of these, FIG. 4 is a flowchart showing a case in which an operator A changes the received power (hereinafter, sometimes referred to as the "allowable power value") while the electric shovel 100 (hereinafter, sometimes referred to as the "vehicle body") is stopped. In this case, the electric shovel 100, which is the vehicle body, includes a structure, a drive unit, and the like, and constitutes a work machine. First, the vehicle control device 120 determines whether the vehicle body is stopped (S401). Then, if the vehicle body is operating (No in S401), an error message is displayed on the vehicle monitor 124, and the processing ends (S402). On the other hand, if the vehicle body is stopped (Yes in S401), the operator A manually changes the allowable power value via the vehicle monitor 124 (S403). Next, the allowable power value data is transmitted from the vehicle monitor 124 to the vehicle control device 120 (S404). Furthermore, the vehicle control device 120 transmits the allowable power value as data to the AC / DC converter 111 (S405). Then, the hardware of the AC / DC converter 111 performs power conversion in accordance with the allowable power value (S406). The method of Fig. 4 operates in the power control system 1 shown in Fig. 2. According to the method of Fig. 4, the vehicle control device 120 is configured to be able to change the received power not only while the vehicle body is operating but also while the vehicle body is stopped. Also, according to the method of Fig. 4, the received power is determined in advance and is input by contractor A while the electric shovel 100 is stopped. According to the method of Fig. 4, worker A can manually change the received power of the electric shovel 100 while the electric shovel 100 is stopped.

[0028] 5 is a flowchart showing a case in which the vehicle control device 120 calculates and changes the received power while the electric excavator 100 is operating. First, the control unit 117C of the inverter 117 transmits the power consumption consumed during a predetermined period of time while the key was most recently turned on to the data recording unit (memory) 122 of the vehicle control device 120 (S501). Next, the data recording unit (memory) 122 in the vehicle control device 120 transmits this data to the control and calculation function unit 121 (S502). Furthermore, the control and calculation function unit 121 in the vehicle control device 120 calculates the allowable power value (S503). Next, the vehicle control device 120 transmits the allowable power value data to the AC / DC converter 111 (S504). Then, the hardware of the AC / DC converter 111 performs power conversion in accordance with the allowable power value (S505).

[0029] The method of FIG. 5 operates in the power control system 1 shown in FIG. 2. According to the method of FIG. 5, the vehicle control device 120 determines the received power to be changed based on the power consumption, which is the power consumed by the vehicle body. At this time, the vehicle control device 120 stores the power consumption for a predetermined period and determines the received power to be changed based on the stored power consumption for the predetermined period. More specifically, the vehicle control device 120 stores the power consumption for the predetermined period in the data recording unit 122, and the control and calculation function unit 121 determines the received power to be changed based on the power consumption for the predetermined period stored in the data recording unit 122. In this case, the vehicle control device 120 calculates the received power based on the power used by its own device while it is operating, without taking into account the power of other electric excavators 100. This allows the vehicle control device 120 to automatically change the received power of the electric excavator 100 while it is operating.

[0030] FIG. 6 is a flowchart showing a case where worker B changes the received power while the electric shovel 100 is in operation. First, worker B manually inputs the allowable power value (S601). For example, worker B monitors the power used by multiple electric shovels 100 (vehicle bodies) and changes the allowable power value depending on the work situation. For example, if a certain electric shovel 100 is performing work with a heavy load and using a lot of power, worker B increases the allowable power value of that electric shovel 100. On the other hand, if a certain electric shovel 100 is performing work with a light load and using less power, worker B decreases the allowable power value of that electric shovel 100. In this way, worker B allocates the received power according to the status of power used by each electric shovel 100 while observing the upper limit of the grid power supply 400 used. Next, the control device 520 recognizes the allowable power value (S602). Furthermore, the control device 520 transmits the allowable power value as data to the second data transmitter / receiver 510 (S603). Then, the second data transceiver 510 wirelessly transmits the data to the first data transceiver 125 of the vehicle body (S604). In the electric excavator 100, the first data transceiver 125 of the vehicle body receives the allowable power value data from the second data transceiver 510 of the server 500 (S605). Next, the first data transceiver 125 of the vehicle body transmits the allowable power value data to the vehicle control device 120 (S606). Furthermore, the vehicle control device 120 transmits the allowable power value data to the AC / DC converter 111 (S607). Then, the hardware of the AC / DC converter 111 performs power conversion in accordance with the allowable power value (S608).

[0031] FIG. 7 is a sequence diagram showing data exchange between the vehicle control device 120, the control device 520, and the database 530. When worker B manually inputs the allowable power value, the vehicle control device 120 needs to understand the status of power usage by the multiple electric excavators 100. To this end, each vehicle control device 120 of the multiple electric excavators 100 transmits power consumption data to the control device 520 (S701). The control device 520 transmits the power consumption data to the database 530 and stores the data (S702). The control device 520 also acquires power consumption data for a predetermined period of time from the database 530 (S703). After viewing this data, worker B manually inputs the allowable power value (S704). This corresponds to S601 in FIG. 6. The control device 520 transmits the allowable power value to the vehicle control device 120 (S705). This corresponds to S604 in FIG. 6. The vehicle control device 120 changes the allowable power value (S706). This corresponds to S607 in FIG. 6.

[0032] The methods in Figures 6 to 7 operate in the power control system 1 shown in Figure 3. According to the methods in Figures 6 to 7, the received power is determined by a server 500, which is an external device, and the vehicle control device 120 obtains it from the server 500 via communication. At this time, the received power is determined by worker B, who is the manager, based on the power used by multiple work machines including the device itself (vehicle body). At this time, worker B allocates power to multiple electric excavators 100 within a range that does not exceed the upper limit of power that can be obtained from the system power supply 400 (in this case, the contracted power value). This allows worker B to manually change the received power of the electric excavator 100 while the electric excavator 100 is operating.

[0033] 8 is a flowchart showing a case where the server 500 calculates and changes the received power while the electric excavator 100 is operating. First, the control unit 117C of the inverter 117 transmits key ON / OFF information and power consumption data to the vehicle control device 120 (S801). Next, the first data transmission / reception unit 125 of the vehicle body wirelessly transmits this information to the second data transmission / reception unit 510 of the server 500 (S802).

[0034] In the server 500, the second data transmitter / receiver 510 transmits data to the control device 520 (S803). Next, the control device 520 transmits the data to the database 530 (S804). At this time, the database 530 receives the data from the control device 520 and stores the data (S805). Furthermore, the control device 520 calculates the allowable power value from the most recent power consumed by the electric excavator 100 for a predetermined period of time while the key was ON (S806). Then, the control device 520 transmits the allowable power value to the second data transmitter / receiver 510 (S807). The second data transmitter / receiver 510 wirelessly transmits the data to the first data transmitter / receiver 125 of the vehicle body (S808).

[0035] The first data transmitter / receiver 125 of the vehicle body receives the allowable power value data from the second data transmitter / receiver 510 of the server 500 (S809). The first data transmitter / receiver 125 of the vehicle body transmits the allowable power value data to the vehicle control device 120 (S810). The vehicle control device 120 then receives the allowable power value data (S811). Next, the vehicle control device 120 transmits the allowable power value data to the AC / DC converter 111 (S812). The hardware of the AC / DC converter 111 then performs power conversion in accordance with the allowable power value (S813).

[0036] FIG. 9 is a sequence diagram showing data exchange between the vehicle control device 120, the control device 520, and the database 530. First, power consumption data of the electric excavator 100 is transmitted to the control device 520 (S901). This corresponds to S802 in FIG. 8. The control device 520 transmits the power consumption data to the database 530 and stores the data (S902). This corresponds to S804 to S805 in FIG. 8. The control device 520 also acquires power consumption data for a predetermined period of time from the database 530 (S903), and calculates the allowable power value based on the acquired power consumption data (S904). This corresponds to S806 in FIG. 8. The control device 520 transmits the allowable power value to the vehicle control device 120 (S905). This corresponds to S808 in FIG. 8. The vehicle control device 120 changes the allowable power value (S906). This corresponds to S812 in FIG. 8.

[0037] The methods of Figures 8 to 9 operate in the power control system 1 shown in Figure 3. According to the methods of Figures 8 to 9, the received power is determined by the server 500, which is an external device, and the vehicle control device 120 obtains it from the server 500 via communication. At this time, the server 500, which is an external device, calculates the received power based on the power consumed by the electric excavator 100, which is the device itself, over a predetermined period of time. In this case, the server 500 calculates the received power based on the power used by the device itself while it is operating, without taking into account the power of other electric excavators 100. As a result, the vehicle control device 120 can automatically change the received power calculated by the server 500 while the electric excavator 100 is operating.

[0038] Figure 10 is also a flowchart showing a case in which the server 500 calculates and changes the received power while the electric excavator 100 is operating. However, the method of calculating the received power is different from the case in Figure 8. First, the control unit 117C of the inverter 117 of each of the multiple electric excavators 100 (vehicle bodies) transmits key ON / OFF information and power consumption data to the vehicle control device 120 (S1001). Meanwhile, the control unit 112C of the high-voltage storage battery 112 of each of the multiple vehicle bodies transmits SOC (State Of Charge) data to the vehicle control device 120 (S1002). Next, the first data transmission / reception unit 125 of the vehicle body wirelessly transmits this information to the second data transmission / reception unit 510 of the server 500 (S1003).

[0039] In the server 500, the second data transmission / reception unit 510 transmits data to the control device 520 (S1004). Meanwhile, the second data transmission / reception unit 510 in the server 500 receives the allowable power value of the grid power supply 400 within the construction site from the power plant 410 and transmits this value to the control device 520 (S1005). Next, the control device 520 further transmits the data transmitted in S1004 and S1005 to the database 530 (S1006). The database 530 receives the data from the control device 520 and stores the data (S1007). Furthermore, the control device 520 calculates the distribution power required for each vehicle as the allowable power value for each vehicle from the most recent key ON / OFF, power consumption, SOC, and contracted power value of the grid power supply 400 (S1008). Then, the control device 520 transmits the allowable power value to the second data transmission / reception unit 510 (S1009). Furthermore, the second data transmitter / receiver 510 wirelessly transmits the distributed power required for each vehicle body to the first data transmitter / receiver 125 of each vehicle body (S1010).

[0040] The first data transmitter / receiver 125 of each vehicle body receives the allowable power value data from the second data transmitter / receiver 510 of the server 500 (S1011). The first data transmitter / receiver 125 of each vehicle body transmits the allowable power value data to the vehicle control device 120 (S1012). The vehicle control device 120 then receives the allowable power value data (S1013). Next, the vehicle control device 120 transmits the allowable power value data to the AC / DC converter 111 (S1014). The hardware of the AC / DC converter 111 then performs power conversion in accordance with the allowable power value (S1015).

[0041] FIG. 11 is a sequence diagram showing data exchange between the power plant 410, the vehicle control device 120, the control device 520, and the database 530. First, each vehicle control device 120 of the multiple electric excavators 100 transmits power consumption data and the like to the control device 520 (S1101). This corresponds to S1003 in FIG. 10. The power plant 410 transmits the contracted power value to the control device 520 (S1102). This corresponds to S1005 in FIG. 10. The control device 520 transmits the power consumption data and the contracted power value to the database 530 and stores the data (S1103). This corresponds to S1006 to S1007 in FIG. 10. The control device 520 also acquires power consumption data of the multiple electric excavators 100 from the database 530 (S1104), and calculates the allowable power value based on the acquired power consumption data (S1105). This corresponds to S1008 in FIG. 10. The control device 520 transmits the permissible power value data to the vehicle control device 120 (S1106). This corresponds to S1010 in Fig. 10. The vehicle control device 120 changes the permissible power value (S1107). This corresponds to S1014 in Fig. 10.

[0042] The methods of FIGS. 10 and 11 operate in the power control system 1 shown in FIG. 3. According to the methods of FIGS. 10 and 11, the received power is determined by a server 500, which is an external device, and is acquired by the vehicle control device 120 from the server 500 via communication. At this time, the received power is calculated by the server 500, which is an external device, based on the power consumed by multiple electric excavators 100, including the electric excavator 100 itself. In this case, the server 500 takes into account the power consumption of not only the server 500 itself but also the other electric excavators 100. The server 500 then calculates the allocation of received power based on the power consumption consumed by the multiple electric excavators 100 while the server 500 itself is operating. At this time, the server 500, which is an external device, allocates power to the multiple electric excavators 100 within a range that does not exceed the upper limit of power that can be obtained from the grid power supply 400 (in this case, the contracted power value). As a result, the vehicle control device 120 can automatically change the received power calculated by the server 500 while the electric excavator 100 is operating.

[0043] 6 to 11 can be said to include a first data transmitter / receiver 125 as a data receiver that receives a signal output by a server 500, which is an external device, and the vehicle control device 120 changes the received power based on the signal received by the first data transmitter / receiver 125. Also, in the methods of FIGS. 6 and 7, it can be said that the signal received by the first data transmitter / receiver 125 includes information on the received power that is set by the operator B based on the power consumed by multiple electric excavators 100 including the vehicle itself. Furthermore, in the methods of FIGS. 8 and 9, it can be said that the first data transmitter / receiver 125 transmits information on power consumption, which is the power consumed by the vehicle body, to the server 500, the server 500 receives information on new power to be received from the grid power supply 400 that is determined from the power consumption over a predetermined period based on the power consumption information, and the vehicle control device 120 changes the received power based on the new power information received by the first data transmitter / receiver 125. Furthermore, in the methods of Figures 10 and 11, the first data transmitter / receiver 125 transmits power consumption information, which is the power consumed by the vehicle body, to the server 500, receives information on new power that the server 500 has determined based on the power consumed by multiple electric excavators 100 including the vehicle itself, and the vehicle control device 120 changes the received power based on the information on new power to be received from the system power supply 400 that has been received by the first data transmitter / receiver 125.

[0044] <Explanation of Most Recent Predetermined Time> In FIGS. 5 and 8 , the control device 520 calculates the allowable power value from the power consumption, which is the power consumed by the electric shovel 100 during a predetermined time while the key was most recently ON. The method for determining this most recent predetermined time will be described next. FIGS. 12( a) and 12(b) are diagrams illustrating the most recent predetermined time. In this embodiment, the most recent predetermined time is a predetermined period going back from the current time. FIG. 12(a) illustrates a case where this period can be continuously acquired. That is, during the predetermined period Δt going back from the current time indicated by “present,” the electric shovel 100 has the key turned ON and is operating, and the power consumption can be acquired. FIG. 12(a) illustrates a case where this period cannot be continuously acquired. That is, during the predetermined period Δt going back from the current time indicated by “present,” there is a period when the key of the electric shovel 100 is turned OFF, and during this period, the electric shovel 100 is stopped, and therefore the power consumption cannot be acquired. In this case, the power consumption during the key-on period is obtained by going back further in time, and the total time is set to the predetermined period Δt. In FIG. 12(b), the predetermined period is set so that the sum of the operating periods Δt1 and Δt2 is Δt (Δt1 + Δt2 = Δt). In other words, the predetermined period Δt is the period during which the vehicle body is operating. It can also be said that the predetermined period Δt is set excluding the period during which the device itself is stopped. Alternatively, if the predetermined period Δt includes a period during which the device is stopped, a predetermined initial value may be used.

[0045] <Explanation of Operating and Stopped> In this embodiment, whether the electric shovel 100 is operating or stopped is determined as follows. FIGS. 13( a) to 13(e) are diagrams showing the transition of the power state (mode) of the electric shovel 100. Here, the transition of the power state (mode) of the electric shovel 100 is shown when the electric shovel 100 is turned from key OFF to key ON and then back to key OFF. FIG. 13(a) shows the power state when the key of the electric shovel 100 is removed and the key is OFF. At this time, both the low-voltage circuit and the high-voltage circuit 110 (see FIG. 2) are off. FIG. 13(b) shows the power state when the key is inserted into the electric shovel 100 and the ACC (accessory) switch is turned on. At this time, the low-voltage circuit is turned on, but the high-voltage circuit 110 remains off. In this power state, the vehicle control device 120, vehicle monitor 124, and first data transmission / reception unit 125 of the electric excavator 100 can be operated, but the hydraulic circuit 130 cannot be operated, and the arm of the electric excavator 100 cannot be moved. FIG. 13( c) shows the power state when the main relay 114 of the high-voltage circuit 110 (see FIG. 2) is turned ON. At this time, both the low-voltage circuit and the high-voltage circuit 110 are turned ON. In this power state, the hydraulic circuit 130 of the electric excavator 100 can be operated, and the arm of the electric excavator 100 can be moved. FIG. 13( d) shows the power state when the main relay 114 of the high-voltage circuit 110 is turned OFF. The power state at this time is the same as FIG. 13( b), and the low-voltage circuit is ON but the high-voltage circuit 110 is OFF. FIG. 13( e) shows the power state when the key is removed from the electric excavator 100 and the key is turned OFF. The power state at this time is the same as that shown in FIG. 13A, and both the low voltage circuit and the high voltage circuit 110 are turned off.

[0046] In this embodiment, the electric shovel 100 being in operation refers to the state shown in Fig. 13(c). In other words, this refers to the state when both the low voltage circuit and the high voltage circuit 110 are on. On the other hand, in this embodiment, the electric shovel 100 being stopped refers to the states shown in Figs. 13(a) to 13(b) and 13(d) to 13(e). In other words, this refers to the state when the high voltage circuit 110 is off.

[0047] <Explanation of Effects> Next, the effects of this embodiment will be described. As described above, in this embodiment, the vehicle control device 120 changes the received power. The timing for the change is at least while the electric shovel 100 is in operation, but as shown in FIG. 4 , it can also be while the electric shovel 100 is stopped. In other words, the change can be made at any time as long as the electric shovel 100 can accept it. When the change is made while the electric shovel 100 is stopped, such as at night or during a break when the remaining battery charge is less likely to fluctuate, optimal power distribution can be made from outside the electric shovel 100 (without having to get on to drive the electric shovel 100), taking into consideration the remaining battery charge of the electric shovel 100 and the like, thereby enabling charge management within the work site.

[0048] FIG. 14( a) is a diagram illustrating a case where the received power is changed. In FIG. 14( a), the horizontal axis represents time, and the vertical axis represents the power consumption of the electric shovel 100. In the figure, dotted line L represents the received power. When the power consumption of the electric shovel 100 is equal to or less than dotted line L, the electric shovel 100 is operated using power from the grid power supply 400. At this time, the high-voltage storage battery 112, which is a battery, is charged with surplus power from the grid power supply 400. On the other hand, when the power consumption of the electric shovel 100 exceeds dotted line L, the shortage is replenished from the high-voltage storage battery 112, and the electric shovel 100 is operated using power from both the grid power supply 400 and the high-voltage storage battery 112. In this embodiment, the received power is changed using the method described above. This corresponds to moving the dotted line L up and down in FIG. 14( a). Even if the received power is changed or reduced while the electric shovel 100 is in operation, the shortfall is replenished from the high-voltage storage battery 112, so there is no impact on the operation of the electric shovel 100 or the operability of the operator.

[0049] This makes it possible to level out the peak power of the received power. Figures 14(b) to 14(d) are diagrams showing changes in peak power when the power source is changed. Of these, Figure 14(b) is a diagram showing a case where the electric shovel 100 is operated using only the battery. In this case, when the electric shovel 100 is operated, the received power is zero. However, for example, during a lunch break, it is necessary to charge the battery using power from the grid power supply 400. In this case, charging must be performed in a short period of time, and therefore the peak power becomes high.

[0050] FIG. 14( c ) is a diagram showing a case where the electric shovel 100 is operated using only power from the grid power supply 400. Compared to the case of FIG. 14( a ), power is received from the grid power supply 400 for a longer period of time, and therefore, when considering a case where the same amount of power is received as in FIG. 14( a ), the received power is leveled and the peak power is reduced. However, the power required to operate the electric shovel 100 increases or decreases depending on the type of work, and therefore the received power increases or decreases as shown in the figure. Therefore, the peak power does not decrease significantly, and power leveling is not sufficient. The amount of power corresponds to the area indicated in gray.

[0051] Fig. 14(d) shows the case of this embodiment, where the electric shovel 100 is operated using power from both the grid power supply 400 and the battery. In this case, the presence of the battery makes it possible to further level out the received power and further reduce the peak power compared to Fig. 14(c).

[0052] With regard to the received power, if the peak power can be leveled, the received power can also be leveled. In this case, the received power can be more efficiently allocated in accordance with the power request required by each electric excavator 100. Furthermore, in a method in which the server 500 determines the received power for each electric excavator 100, the received power can be determined in accordance with the power request required by a plurality of electric excavators 100. This makes it possible to allocate the received power even more efficiently. Therefore, even if the grid power supply 400 has an upper limit on the amount of power that can be used, such as contracted power, this power can be used more effectively. As a result, it is possible to achieve both a reduction in the load on the grid power supply 400 and a response to the power request of the electric excavator 100. This makes it possible to quickly respond to a reduction in the load on the grid power supply 400.

[0053] <Example> Fig. 10 will explain an actual example of distributing received power to a plurality of electric shovels 100. Fig. 15 is a diagram showing a specific example of distributing received power to a plurality of electric shovels 100. Here, the amount of distributed received power is determined based on the ratio between the average past power consumption of each electric shovel 100 and the remaining operating time calculated from the remaining SOC. Note that here, a case will be explained in which received power is distributed to four electric shovels A to D. The average past power consumption of electric shovel A can be calculated using the following formula 1. Furthermore, the amount of distributed received power for electric shovel A can be calculated using the following formula 2. Note that the same method can be used for electric shovels B to D.

[0054]

[0055]

[0056] In equations 1 and 2, h Ａ ~h D is the remaining operating time [h] of the electric excavators A to D, h Ａｌｌ Is, h Ａ ~h Ｄ Total remaining operating time [h], SOC Ａ is the remaining battery power of the electric excavator A [kWh], P Ａ ａｖｅis the average power consumption of electric shovel A [kW], P ｌｉｍ is the contracted power [kW] of the system power supply 400, P Ａ is the power [kW] allocated to the electric shovel A, and n is the number of electric shovels.

[0057] When the remaining operating time [h], SOC, and remaining battery capacity of the electric shovels A to D are as shown in the figure, the remaining operating time h of the electric shovels A to D can be calculated by the formula 1. Ａ ~h D are 3h, 2h, 2h, and 6h, respectively. From this, the remaining operating time h of electric excavators A to D is Ａ ~h D The ratio of these is A:B:C:D = 3h:2h:2h:6h, resulting in a distribution ratio of 10:11:11:7. When the contracted power of the system power supply 400 is 88VA, the received power of the electric excavators A to D is A:B:C:D = 22kW:25kW:25kW:16kW. Note that the method of calculating the received power of each electric excavator 100 is not limited to using a formula such as Formula 1 or Formula 2. For example, a method may be used in which a table listing the relationship between power consumption and received power is prepared, and the received power of each electric excavator 100 is determined based on this table.

[0058] <Explanation of Power Control Method> The processing performed by the vehicle control device 120 in this embodiment described above is realized by cooperation between software and hardware resources. That is, a processor such as a CPU (Central Processing Unit) (not shown) provided in the vehicle control device 120 loads into memory and executes a program that realizes each function of the vehicle control device 120, thereby realizing each function performed by the vehicle control device 120.

[0059] Therefore, the processing performed by the vehicle control device 120 described above can be considered to be a power control method in which, for a work machine that operates using power from the system power supply 400 and power from the high-voltage storage battery 112, the received power that the work machine receives from the system power supply 400 is changed while the work machine is operating, by the processor executing a program recorded in memory.

[0060] The program for realizing this embodiment can be provided not only by communication means but also by being stored on a recording medium such as a CD-ROM.

[0061] Although the present embodiment has been described above, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear from the claims that various modifications and improvements to the above embodiment are also included in the technical scope of the present invention.

[0062] 1...power control system, 14, 16, 17...hydraulic cylinder (working device), 100...electric shovel (working machine, vehicle body), 110...high voltage circuit, 111...AC / DC converter (power receiving device), 112...high voltage storage battery (battery), 120...vehicle control device (control device, vehicle control device), 121...control calculation function unit (processor), 122...data recording unit (memory), 125...first data transmission / reception device (data communication device), 130...hydraulic circuit, 200...power cable, 300...reel-type cable container, 400...system power supply, 500...server (external device, management device), 520...control device, 530...database

Claims

1. A work machine comprising: a vehicle body including a work implement; a power receiving device provided on the vehicle body and receiving power from a power grid; and a battery provided on the vehicle body, the work machine operating on received power, which is power received by the power receiving device from the power grid, and power from the battery, and a control device that changes the received power while the vehicle body is operating.

2. A work machine as set forth in claim 1, wherein the control device is configured to be able to change the received power not only while the vehicle body is in operation, but also while the vehicle body is stopped.

3. A work machine according to claim 1, wherein the control device determines the change in the received power based on the power consumption, which is the power consumed by the vehicle body.

4. A work machine according to claim 3, wherein the control device stores the power consumption for a predetermined period, and determines the incoming power to be changed based on the stored power consumption for the predetermined period.

5. A work machine according to claim 4, wherein the predetermined period is a period during which the vehicle body is in operation.

6. A work machine according to claim 1, further comprising a data communication device for receiving a signal output by an external device, said control device changing said received power based on said signal received by said data communication device.

7. A work machine according to claim 6, wherein the signal received by the data communication device includes information about the received power that is set by an administrator based on the power consumed by a plurality of work machines including the own vehicle.

8. A work machine as described in claim 6, wherein the data communication device transmits information about power consumption, which is the power consumed by the vehicle body, to the external device, and the external device receives information about new power to be received from the system power supply, which is determined from the power consumption over a predetermined period based on the power consumption information, and the control device changes the received power based on the new power information received by the data communication device.

9. A work machine as described in claim 6, wherein the data communication device transmits to the external device information on power consumption, which is the power consumed by the vehicle body, and receives information on new power to be received from the system power supply, which information has been determined by the external device based on the power consumed by a plurality of work machines including the vehicle itself, and the control device changes the received power based on the new power information received by the data communication device.

10. A work machine as described in claim 9, wherein the data communication device receives information about the new power determined by the external device so as to allocate power to a plurality of work machines within a range not exceeding an upper limit of power obtainable from the system power source.

11. A power control method in which a processor executes a program recorded in a memory, and, for a work machine that operates using power from a power grid and power from a battery, receives power from the power grid by the work machine while the work machine is in operation.

12. A power control system comprising: a management device that determines received power, which is power that a work machine receives from a system power source, based on power consumption when the work machine is operating using power from a system power source and power from a battery; and a vehicle control device that is mounted on the work machine and changes the power that the work machine receives from the system power source to the received power determined by the management device while the work machine is operating.

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