Electric construction machine

Abstract

The purpose of the present invention is to provide an electric construction machine with which a hydrogen tank for storing fuel of a fuel cell and a heat exchanger for radiating heat of coolant of the fuel cell can be reduced in size. To achieve this purpose, a hydraulic shovel is provided with a vehicle body, an electric motor that is the vehicle body power source, a fuel cell that generates power, and a power control device that controls the power supplied to the electric motor. The hydraulic shovel is provided with an external power receiver that receives power from a commercial power supply device. The power control device controls the power supplied to the electric motor from the fuel cell and the external power receiver.

Description

electric construction machinery

[0001] The present invention relates to an electric construction machine.

[0002] Development of construction machinery with low greenhouse gas emissions has been ongoing, and for example, electric construction machinery equipped with fuel cells has been developed. Patent Document 1, for example, is a document disclosing prior art of electric construction machinery equipped with fuel cells. Patent Document 1 describes an electric construction machine that includes a first swivel unit disposed between a main body and a traveling device that travels on the main body and that rotates the main body, a working device connected to the main body, and a storage unit that can be rotated by a second swivel unit different from the first swivel unit, the storage unit housing a hydrogen tank that stores hydrogen and a fuel cell that generates electricity using the hydrogen supplied from the hydrogen tank, and a hydraulic device that drives the working device disposed in the main body.

[0003] Japanese Patent Application Laid-Open No. 2022-180565

[0004] Hydrogen, the fuel for fuel cells, has a lower energy density than diesel, so to achieve the same continuous operating time as a diesel engine of the same power output with a fuel cell, a huge hydrogen tank would be required, which poses a problem in terms of mountability of the hydrogen tank.Furthermore, the fuel cell's coolant (cooling water) must be maintained at a lower temperature than the coolant in a diesel engine, which requires a larger heat exchanger than a diesel engine of the same power output, which also poses a problem in terms of mountability of the heat exchanger.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide an electric construction machine that can reduce the size of the hydrogen tank that stores fuel for the fuel cell and the heat exchanger that dissipates heat from the fuel cell coolant.

[0006] In order to achieve the above object, the present invention provides an electric construction machine comprising a vehicle body, an electric motor that is a power source for the vehicle body, a fuel cell that generates electricity, and a power control device that controls the power supplied to the electric motor, the machine also comprising an external power receiver that receives power from a commercial power supply, and the power control device controls the power supplied to the electric motor from the fuel cell and the external power receiver.

[0007] According to the present invention, power can be supplied from an external power receiver to an electric motor, thereby reducing the power supplied from the fuel cell to the electric motor. This reduces the fuel consumption and heat generation of the fuel cell, making it possible to reduce the size of the hydrogen tank that stores fuel for the fuel cell and the heat exchanger that dissipates heat from the coolant that cools the fuel cell.

[0008] Schematic diagram of a hydraulic excavator according to an embodiment of the present invention. Configuration diagram of a power control system according to an embodiment of the present invention. Flowchart showing the processing of a power control device according to an embodiment of the present invention. Configuration diagram showing a modified example of the power control system according to an embodiment of the present invention. Flowchart showing a modified example of the processing of a power control device according to an embodiment of the present invention.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a hydraulic excavator is used as an electric construction machine according to the present invention. However, the application of the present invention is not limited to hydraulic excavators, and the present invention can also be applied to other electric construction machines.

[0010] FIG. 1 is a schematic diagram of a hydraulic excavator according to this embodiment. The hydraulic excavator 100 includes a crawler-type undercarriage 101, an upper rotating body 102 rotatably mounted on the undercarriage 101, and a front work implement 103 rotatably attached to the upper rotating body 102. The undercarriage 101, the upper rotating body 102, and the front work implement 103 form the vehicle body of the hydraulic excavator 100. The undercarriage 101, the upper rotating body 102, and the front work implement 103 are each driven by a hydraulic actuator (not shown). A cab 104 for an operator is provided in front of the upper rotating body 102. An operating device 16 for instructing the operation of the vehicle bodies 101 to 103 is arranged inside the cab 104.

[0011] The upper rotating body 102 is equipped with a hydraulic pump 1, an electric motor 2, a fuel cell 3, a battery 4, an external power receiver 5, a power control device 6, a hydrogen tank 7, a heat exchanger 8, a vehicle controller 9, etc. The hydraulic pump 1 is driven by the electric motor 2 and supplies pressure oil to each hydraulic actuator. The external power receiver 5 is connected to a commercial power supply unit 11 via a power cable 10 and receives a supply of power from the commercial power supply unit 11.

[0012] 2 is a configuration diagram of the electric drive system mounted on the hydraulic excavator 100. The power control system 200 includes an electric motor 2, a fuel cell 3, a battery 4, an external power receiver 5, a power control device 6, a hydrogen tank 7, a heat exchanger 8, a vehicle controller 9, an operation device 16, and a battery controller 17. The fuel cell 3 is connected to the hydrogen tank 7 via a hydrogen fuel line 12, and generates electricity by receiving a supply of hydrogen fuel from the hydrogen tank 7. The heat exchanger 8 is connected to the fuel cell 3 via a coolant line 13 that circulates coolant (cooling water), and dissipates heat from the coolant that has cooled the fuel cell 3.

[0013] The power control device 6 is connected to the fuel cell 3, the battery 4, and the external power receiver 5 via a power line 14, and to the fuel cell 3, the battery controller 17, and the vehicle body controller 9 via a signal line 15. A signal notifying the amount of power required by the electric motor 2 is input from the vehicle body controller 9 to the power control device 6. The vehicle body controller 9 calculates the amount of power required by the electric motor 2 based on a signal (operation amount) input from an operation device 16. The battery controller 17 measures the remaining charge and temperature of the battery 4 to determine the state of the battery 4 (whether power can be supplied and whether it can be charged). A signal indicating the state of the battery 4 (battery state signal) is input from the battery controller 17 to the power control device 6. A signal instructing the fuel cell 3 to generate or stop power is input from the power control device 6 to the fuel cell 3. The power control device 6 controls the power supplied to the electric motor 2 from the fuel cell 3, the battery 4, and the external power receiver 5, and the power supplied to the battery 4 from the fuel cell 3 and the external power receiver 5, based on the amount of power required by the electric motor 2 and the state of the battery 4.

[0014] 3 is a flowchart showing the processing of the power control device 6. Each step will be described below.

[0015] The power control device 6 first determines whether the battery 4 is in a state where it can supply power (step S101). Whether the battery 4 is in a state where it can supply power is determined based on a battery state signal from the battery controller 17.

[0016] If the determination result in step S101 is YES, it is determined whether the amount of power required by the electric motor 2 exceeds a first upper limit value (step S102). The first upper limit value is set to, for example, the maximum output value of the external power receiver 5 or a value obtained by subtracting a predetermined margin from the maximum output value.

[0017] If the determination result in step S102 is YES, it is determined whether the amount of power required by the electric motor 2 exceeds a second upper limit value or a third upper limit value (step S103). The second upper limit value is set to, for example, the total maximum output value of the external power receiver 5 and the battery 4, or a value obtained by subtracting a predetermined margin from the total maximum output value. The third upper limit value is set to, for example, the total maximum output value of the external power receiver 5 and the fuel cell 3, or a value obtained by subtracting a predetermined margin from the total maximum output value.

[0018] If the determination result in step S103 is YES, the necessary power is supplied to the electric motor 2 from the battery 4, the fuel cell 3, and the external power receiver 5 (step S104), and the flow ends. As a result, when the load on the electric motor 2 is high, the necessary power can be supplied to the electric motor 2 from the external power receiver 5, the battery 4, and the fuel cell 3.

[0019] If the determination result in step S103 is NO, it is determined whether the battery 4 is in a chargeable state (step S105). Whether the battery 4 is in a chargeable state is determined based on a battery state signal from the battery controller 17.

[0020] If the determination result in step S105 is YES, power is supplied from the fuel cell 3 and the external power receiver 5 to the electric motor 2 and the battery 4 (step S106), and the flow ends. This makes it possible to charge the battery 4 while supplying the necessary power to the electric motor 2.

[0021] If the determination result in step S105 is NO, the fuel cell 3 is stopped, and power is supplied from the battery 4 and the external power receiver 5 to the electric motor 2 (step S107), and the flow ends. This makes it possible to supply the necessary power to the electric motor 2 with the fuel cell 3 stopped.

[0022] If the determination result in step S102 is NO, it is determined whether the battery 4 is in a chargeable state (step S108). Whether the battery 4 is in a chargeable state is determined based on a battery state signal from the battery controller 17.

[0023] If the determination result in step S108 is YES, the fuel cell 3 is stopped, and power is supplied from the external power receiver 5 to the electric motor 2 and the battery 4 (step S109), and the flow ends. This makes it possible to charge the battery 4 while supplying necessary power to the electric motor 2 with the fuel cell 3 stopped.

[0024] If the determination result in step S108 is NO, the battery 4 and fuel cell 3 are stopped, and power is supplied from the external power receiver 5 to the electric motor 2 (step S110), and the flow ends. This makes it possible to supply the necessary power to the electric motor 2 with the fuel cell 3 stopped.

[0025] If the determination result in step S101 is NO, power is supplied from the fuel cell 3 to the electric motor 2 and the battery 4, and power is also supplied from the external power receiver 5 to the electric motor 2 and the battery 4 (step S111), and the flow ends. This makes it possible to prevent the battery 4 from being over-discharged.

[0026] Fig. 4 is a configuration diagram showing a modified example of a power control system 200. The configuration differs from that shown in Fig. 1 in that the battery controller 17 is omitted. A signal indicating the remaining battery capacity (battery remaining capacity signal) is input from the battery 4 to the power control device 6.

[0027] Fig. 5 is a flowchart showing a modified example of the processing of the power control device 6. The differences from the flow shown in Fig. 3 are that steps S101, S105, and S108 are replaced with steps S101A, S105A, and S108A, and that step S112 is added immediately after step S111.

[0028] In step S101A, it is determined whether the remaining battery charge is greater than 10%. If the determination result in step S101A is YES, it is determined that the battery 4 is in a state where it can supply power, and the process proceeds to step S102. If the determination result in step S101A is NO, it is determined that the battery 4 is in a state where it cannot supply power, and the process proceeds to step S111.

[0029] In step S105A, it is determined whether the remaining battery charge falls below 30%, or whether the previous determination result in step S105A was YES and the remaining battery charge falls below 40%. If the determination result in step S105A is YES, the process proceeds to step S106. If the determination result in step S105A is NO, the process proceeds to step S107. As a result, charging of battery 4 and power generation by fuel cell 3 (step S106) continue from the time the remaining battery charge falls below 30% until the remaining battery charge reaches 40%, so it is possible to prevent hunting between charging of battery 4 and power generation by fuel cell 3 (step S106) and discharging of battery 4 and stopping of fuel cell 3 (step S107).

[0030] In step S108A, it is determined whether the remaining battery charge falls below 70%, or whether the previous determination result in step S108A was YES and the remaining battery charge falls below 80%. If the determination result in step S108A is YES, the process proceeds to step S109. If the determination result in step S108A is NO, the process proceeds to step S110. As a result, charging of battery 4 (step S109) continues from the time the remaining battery charge falls below 70% until the remaining battery charge reaches 80%, which prevents a loop between charging battery 4 (step S109) and stopping battery 4 (step S110) and also prevents overcharging of battery 4.

[0031] In step S112, it is determined whether the remaining battery charge is greater than 20%. While the determination result in step S112 is NO, the determination in step S112 is repeated, and when the determination result in step S112 is YES, the flow ends. As a result, charging of battery 4 (step S111) continues until the remaining battery charge reaches 20%, making it possible to prevent a hunting between charging of battery 4 (step S111) and discharging of battery 4 (step S104).

[0032] (Summary) In this embodiment, the hydraulic excavator 100 includes vehicle bodies 101 to 103, an electric motor 2 that is a power source for the vehicle bodies 101 to 103, a fuel cell 3 that generates electric power, and a power control device 6 that controls the electric power supplied to the electric motor 2. The hydraulic excavator 100 also includes an external power receiver 5 that receives electric power from a commercial power supply unit 11, and the power control device 6 controls the electric power supplied to the electric motor 2 from the fuel cell 3 and the external power receiver 5.

[0033] According to the present embodiment configured as described above, power can be supplied from the external power receiver 5 to the electric motor 2, thereby reducing the power supplied from the fuel cell 3 to the electric motor 2. This reduces the fuel consumption and heat generation of the fuel cell 3, making it possible to reduce the size of the hydrogen tank 7 that stores fuel for the fuel cell 3 and the heat exchanger 8 that dissipates heat from the coolant that cools the fuel cell 3.

[0034] Furthermore, the hydraulic excavator 100 in this embodiment is equipped with an operating device 16 for instructing the operation of the vehicle bodies 101 to 103, and the power control device 6 determines the amount of power to be supplied from the fuel cell 3 to the electric motor 2 and the amount of power to be supplied from the external power receiver 5 to the electric motor 2 based on the amount of required power calculated based on the amount of operation of the operating device 16. This makes it possible to supply the required power from the fuel cell 3 and the external power receiver 5 to the electric motor 2.

[0035] Furthermore, the hydraulic excavator 100 in this embodiment is equipped with a battery 4 capable of supplying power to the electric motor 2, and when the required amount of power exceeds a first power threshold (second upper limit) set based on the total maximum output value of the external power receiver 5 and the battery 4, or when the required amount of power exceeds a second power threshold (third upper limit) set based on the total maximum output value of the external power receiver 5 and the fuel cell 3, the power control device 6 supplies power to the electric motor 2 from the battery 4, the fuel cell 3, and the external power receiver 5. This makes it possible to supply required power to the electric motor 2 from the battery 4, the fuel cell 3, and the external power receiver 5 when the load on the electric motor 2 is high.

[0036] Furthermore, when the remaining charge of the battery 4 is equal to or less than a predetermined first battery threshold (10%) while the electric motor 2 is being driven, the power control device 6 in this embodiment supplies power from the fuel cell 3 to the electric motor 2 and the battery 4, and also supplies power from the external power receiver 5 to the electric motor 2 and the battery 4. This makes it possible to prevent the battery 4 from being over-discharged.

[0037] Furthermore, in this embodiment, when the required amount of power is equal to or less than a third power threshold (first upper limit) set based on the maximum output value of the external power receiver 5, the power control device 6 determines whether the remaining charge of the battery 4 is less than a second battery threshold (70%) set higher than the first battery threshold (10%), and when it determines that the remaining charge of the battery 4 is less than the second battery threshold, it stops the power supply from the fuel cell 3 and supplies power from the external power receiver 5 to the electric motor 2 and the battery 4. When it determines that the remaining charge of the battery 4 is equal to or greater than the second battery threshold, it stops the power supply from the battery 4 and the fuel cell 3 and supplies power from the external power receiver 5 to the electric motor 2. This makes it possible to supply the required power from the external power receiver 5 to the electric motor 2 while supplying surplus power from the external power receiver 5 to the battery 4, thereby maintaining the battery 4 in a highly charged state, with the fuel cell 3 stopped.

[0038] Furthermore, in this embodiment, when the required amount of power exceeds the third power threshold (first upper limit), is equal to or less than the first power threshold (second upper limit), and is equal to or less than the second power threshold (third upper limit), the power control device 6 determines whether the remaining charge of the battery 4 is less than a third battery threshold (30%) that is set to be greater than the first battery threshold and less than the second battery threshold (70%). If it determines that the remaining charge of the battery 4 is less than the third battery threshold, the power control device 6 supplies power from the fuel cell 3 and the external power receiver 5 to the electric motor 2 and the battery 4. If it determines that the remaining charge of the battery 4 is equal to or greater than the third battery threshold, the power control device 6 stops the power supply from the fuel cell 3 and supplies power from the battery 4 and the external power receiver 5 to the electric motor 2. This makes it possible to prevent the battery 4 from entering a low charge state while supplying the required power to the electric motor 2.

[0039] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the described configurations.

[0040] 1...hydraulic pump, 2...electric motor, 3...fuel cell, 4...battery, 5...external power receiver, 6...power control device, 7...hydrogen tank, 8...heat exchanger, 9...vehicle controller, 10...power cable, 11...commercial power supply unit, 12...hydrogen fuel line, 13...coolant line, 14...power line, 15...signal line, 16...operation device, 17...battery controller, 100...hydraulic excavator (electric construction machinery), 101...lower running body (vehicle body), 102...upper rotating body (vehicle body), 103...front work equipment (vehicle body), 200...power control system.

Claims

1. An electric construction machine comprising: a vehicle body; an electric motor which is a power source for the vehicle body; a fuel cell which generates electric power; and a power control device which controls the power supplied to the electric motor; further comprising an external power receiver which receives electric power from a commercial power supply device; and the power control device controls the power supplied to the electric motor from the fuel cell and the external power receiver.

2. An electric construction machine as described in claim 1, further comprising an operating device for instructing the operation of the vehicle body, and wherein the power control device determines the amount of power to be supplied from the fuel cell to the electric motor and the amount of power to be supplied from the external power receiver to the electric motor based on the required amount of power calculated based on the amount of operation of the operating device.

3. An electric construction machine as described in claim 2, further comprising a battery capable of supplying power to the electric motor, and wherein the power control device supplies power from the battery, the fuel cell, and the external power receiver to the electric motor when the required amount of power exceeds a first power threshold set based on a total maximum output value of the external power receiver and the battery, or when the required amount of power exceeds a second power threshold set based on a total maximum output value of the external power receiver and the fuel cell.

4. An electric construction machine as described in claim 3, characterized in that, when the remaining charge of the battery is equal to or less than a predetermined first battery threshold when the electric motor is being driven, the power control device supplies power from the fuel cell to the electric motor and the battery, and supplies power from the external power receiver to the electric motor and the battery.

5. An electric construction machine as described in claim 4, wherein the power control device, when the required amount of power is equal to or less than a third power threshold set based on the maximum output value of the external power receiver, determines whether the remaining charge of the battery is less than a second battery threshold set greater than the first battery threshold, when it determines that the remaining charge of the battery is less than the second battery threshold, stops the power supply from the fuel cell and supplies power from the external power receiver to the electric motor and the battery, and when it determines that the remaining charge of the battery is equal to or greater than the second battery threshold, stops the power supply from the battery and the fuel cell and supplies power from the external power receiver to the electric motor.

6. An electric construction machine as described in claim 5, wherein the power control device, when the required amount of power exceeds the third power threshold and is equal to or less than the first power threshold and the required amount of power is equal to or less than the second power threshold, determines whether the remaining charge of the battery is less than a third battery threshold which is set to be greater than the first battery threshold and less than the second battery threshold; when it determines that the remaining charge of the battery is less than the third battery threshold, supplies power from the fuel cell and the external power receiver to the electric motor and the battery; and when it determines that the remaining charge of the battery is equal to or greater than the third battery threshold, stops the power supply from the fuel cell and supplies power from the battery and the external power receiver to the electric motor.

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