Electric construction machine

Abstract

To provide an electric construction machine with which a hydrogen tank storing fuel of a fuel cell and a heat exchanger radiating heat of coolant of a fuel cell can be reduced in size.SOLUTION: A hydraulic shovel 100 comprises: vehicle bodies 101 to 103; an electric motor 2 that is a power source of the vehicle bodies 101 to 103; a fuel cell 3 generating power; a power control device 6 controlling the power supplied to the electric motor 2; and an external power receiver 5 receiving power from a commercial power supply device 11. The power control device 6 controls the power supplied from the fuel cell 3 and the external power receiver 5 to the electric motor 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Construction machines with low greenhouse gas emissions have been developed, and for example, electric construction machines equipped with fuel cells have been developed. Patent Document 1, for example, is a document disclosing prior art of electric construction machines equipped with fuel cells. Patent Document 1 describes an electric construction machine that includes a first swivel unit that is provided between a main body unit and a traveling device that travels on the main body unit and that rotates the main body unit, a working device connected to the main body unit, 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 is disposed in the main body unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-180565 A Summary of the Invention [Problem to be solved by the invention]

[0004] Hydrogen, the fuel for fuel cells, has a lower energy density than diesel, so to obtain the same continuous operating time with a fuel cell as a diesel engine of the same power output, a huge hydrogen tank is required, which makes the installation of the hydrogen tank an issue.Furthermore, the fuel cell's coolant (cooling water) needs to be maintained at a lower temperature than the coolant for a diesel engine, which requires a larger heat exchanger than a diesel engine of the same power output, which also makes the installation of the heat exchanger an issue.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide an electric construction machine that makes it possible to miniaturize the hydrogen tank that stores fuel for the fuel cell and the heat exchanger that dissipates heat from the fuel cell coolant. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides 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 electricity, and a power control device which controls the power supplied to the electric motor, the machine also comprising an external power receiver which receives power from a commercial power supply unit, and the power control device which controls the power supplied to the electric motor from the fuel cell and the external power receiver. Effect of the Invention

[0007] According to the present invention, since it is possible to supply power from an external power receiver to an electric motor, it is possible to reduce 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 the fuel for the fuel cell and the heat exchanger that dissipates the heat of the coolant that cools the fuel cell. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hydraulic excavator according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a configuration diagram of a power control system according to an embodiment of the present invention. [Diagram 3] 10 is a flowchart showing the process of the power control device according to the embodiment of the present invention. [Figure 4] FIG. 1 is a configuration diagram showing a modification of a power control system according to an embodiment of the present invention. [Diagram 5] 1 is a flowchart showing a modified example of the process of the power control device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, but the application of the present invention is not limited to hydraulic excavators and can 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 lower traveling body 101, an upper rotating body 102 rotatably mounted on the lower traveling body 101, and a front work unit 103 rotatably attached to the upper rotating body 102. The lower traveling body 101, the upper rotating body 102, and the front work unit 103 form a vehicle body of the hydraulic excavator 100. The lower traveling body 101, the upper rotating body 102, and the front work unit 103 are each driven by a hydraulic actuator (not shown). A cab 104 in which an operator rides 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 provided in 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 an electric drive system mounted on a 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 power 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 a 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 is connected 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 the operation device 16. The battery controller 17 determines the state of the battery 4 (whether or not power can be supplied and whether or not it can be charged) by measuring the remaining charge and temperature of the battery 4. 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 from the fuel cell 3, the battery 4, and the external power receiver 5 to the electric motor 2, and the power supplied from the fuel cell 3 and the external power receiver 5 to the battery 4, 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 explained below.

[0015] The power control device 6 first determines whether the battery 4 is in a state capable of supplying power (step S101). Whether the battery 4 is in a state capable of supplying 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 the second upper limit value or the 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. This makes it possible to supply the necessary power to the electric motor 2 from the external power receiver 5, the battery 4, and the fuel cell 3 when the electric motor 2 is under high load.

[0019] If the determination result in step S103 is NO, it is determined whether or not the battery 4 is in a chargeable state (step S105). Whether or not 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 necessary power to the electric motor 2 with the fuel cell 3 stopped.

[0022] If the result of the determination in step S102 is NO, it is determined whether or not the battery 4 is in a chargeable state (step S108). Whether or not 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 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 the power control system 200. The difference from the configuration shown in Fig. 1 is 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 process of the power control device 6. The difference from the flow shown in Fig. 3 is that steps S101, S105, and S108 are replaced with steps S101A, S105A, and S108A, and 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 is 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 the battery 4 and power generation of the 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 the battery 4 and power generation of the fuel cell 3 (step S106) and discharging of the battery 4 and stopping of the 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 is 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 the battery 4 (step S109) continues from when the remaining battery charge falls below 70% until the remaining battery charge reaches 80%, so that it is possible to prevent hunting between charging of the battery 4 (step S109) and stopping of the battery 4 (step S110) and to prevent overcharging of the battery 4.

[0031] In step S112, it is determined whether the remaining battery charge exceeds 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 is terminated. As a result, charging of the battery 4 (step S111) continues until the remaining battery charge reaches 20%, so that it is possible to prevent hunting between charging of the battery 4 (step S111) and discharging of the battery 4 (step S104).

[0032] (summary) In this embodiment, a hydraulic excavator 100 is provided with vehicle bodies 101-103, an electric motor 2 which is the power source for the vehicle bodies 101-103, a fuel cell 3 which generates electricity, and a power control device 6 which controls the power supplied to the electric motor 2. The hydraulic excavator 100 is also provided with an external power receiver 5 which receives power from a commercial power supply unit 11, and the power control device 6 controls the 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 the 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 101-103, 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 required amount of power calculated based on the amount of operation of the operating device 16. This makes it possible to supply 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 includes 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 motor 2 is being driven, the power control device 6 in this embodiment supplies power from the fuel cell 3 to the motor 2 and the battery 4, and also supplies power from the external power receiver 5 to the motor 2 and the battery 4. This makes it possible to prevent the battery 4 from being over-discharged.

[0037] In addition, in the power control device 6 in this embodiment, when the required amount of power is equal to or less than a third power threshold (first upper limit value) set based on the maximum output value of the external power receiver 5, the power control device 6 judges whether or not the remaining amount of the battery 4 is less than a second battery threshold (70%) set to be greater than the first battery threshold (10%), and when it is judged that the remaining amount 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, and when it is judged that the remaining amount 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. As a result, it becomes 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 and maintain the battery 4 in a highly charged state while keeping the fuel cell 3 stopped.

[0038] In addition, in the power control device 6 in this embodiment, when the required amount of power exceeds the third power threshold (first upper limit value), and the required amount of power is equal to or less than the first power threshold (second upper limit value), and the required amount of power is equal to or less than the second power threshold (third upper limit value), the power control device 6 determines whether the remaining amount 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%), and when it determines that the remaining amount of the battery 4 is less than the third battery threshold, it supplies power from the fuel cell 3 and the external power receiver 5 to the electric motor 2 and the battery 4, and when it determines that the remaining amount of the battery 4 is equal to or greater than the third battery threshold, it 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 becoming in a low charge state while supplying the required power to the electric motor 2.

[0039] Although the embodiment of the present invention has been described above in detail, the present invention is not limited to the above-mentioned embodiment and includes various modified examples. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations. [Explanation of symbols]

[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...operating 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. The car body and An electric motor that is a power source for the vehicle body; A fuel cell for generating electrical power; In an electric construction machine including a power control device that controls the power supplied to the electric motor, An external power receiver is provided for receiving 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. An electric construction machine characterized by:

2. The electric construction machine according to claim 1, An operation device for instructing an operation of the vehicle body, 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 a required amount of power calculated based on an amount of operation of the operating device. An electric construction machine characterized by:

3. The electric construction machine according to claim 2, A battery capable of supplying power to the electric motor is provided, 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, the power control device supplies power from the battery, the fuel cell, and the external power receiver to the electric motor. An electric construction machine characterized by:

4. The electric construction machine according to claim 3, When the remaining charge of the battery is equal to or less than a predetermined first battery threshold value while the electric motor is being driven, the power control device supplies electric power from the fuel cell to the electric motor and the battery, and supplies electric power from the external power receiver to the electric motor and the battery. An electric construction machine characterized by:

5. The electric construction machine according to claim 4, When the required amount of power is equal to or less than a third power threshold set based on a maximum output value of the external power receiver, the power control device determines whether or not a remaining amount of the battery is less than a second battery threshold set to be greater than the first battery threshold; When it is determined that the remaining charge of the battery is less than the second battery threshold, the power supply from the fuel cell is stopped and power is supplied from the external power receiver to the electric motor and the battery; When it is determined that the remaining charge of the battery is equal to or greater than the second battery threshold, the power supply from the battery and the fuel cell is stopped, and power is supplied from the external power receiver to the electric motor. An electric construction machine characterized by:

6. The electric construction machine according to claim 5, when the required amount of power exceeds the third power threshold, and the required amount of power 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, the power control device determines whether or not a remaining amount of the battery is less than a third battery threshold that is set to be greater than the first battery threshold and smaller than the second battery threshold; When it is determined that the remaining charge of the battery is less than the third battery threshold, power is supplied from the fuel cell and the external power receiver to the electric motor and the battery; When it is determined that the remaining charge of the battery is equal to or greater than the third battery threshold, the power supply from the fuel cell is stopped, and power is supplied from the battery and the external power receiver to the electric motor. An electric construction machine characterized by:

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