Electric dump truck

Abstract

The purpose of the present invention is to realize a practical application of a battery-driven electric dump truck in which a battery can be charged by both a trolley charging system and a stationary charging system. This electric dump truck comprises: a pantograph that receives electric power from a trolley line; a battery that is charged with electric power from the pantograph; a traveling motor that causes a vehicle body to travel by means of electric power from the battery or the pantograph; an electric power path that connects the pantograph and the battery; a DC / DC converter that is connected between the pantograph and the battery, and that converts electric power from the pantograph and supplies the same to the battery; a switch that is connected between the pantograph and the DC / DC converter, and that switches between conduction and non-conduction on the electric power path on the basis of the voltage of the electric power path; and a power reception terminal that is connected between the pantograph and the switch, and that receives electric power from an external power source different from the trolley line.

Description

Electric dump truck

[0001] The present invention relates to an electric dump truck.

[0002] Conventionally, for the transportation work of mineral resources in mines, mining dump trucks (hereinafter also referred to as "dump trucks") equipped with high-output engines have been used. Dump trucks usually carry out transportation work almost without rest except for service times such as maintenance. Since dump trucks are one of the most operating machines at the mine site, it can be said that they are one of the machines that have the greatest impact on the environment at the mine site. Therefore, as an effort to reduce the environmental load at the mine site, the electrification of dump trucks has attracted attention.

[0003] On the other hand, in the field of passenger cars, efforts towards electrification are being actively carried out. Patent Document 1 discloses an electric vehicle having a highly flexible battery charging and discharging function.

[0004] Japanese Patent Application Laid-Open No. 2018-11460

[0005] The electrification of dump trucks has bottlenecks in the improvement of the charging environment and the securing of necessary power, and it is difficult to proceed with electrification in the same way as passenger cars. For example, a trolley charging method dump truck that receives power from an overhead trolley wire with a pantograph and charges the battery has been developed. However, it is difficult to lay trolley wires throughout the mine site, so it is difficult to cover all the power required for the transportation work of dump trucks only with the trolley charging method. Therefore, at present, when promoting the electrification of dump trucks, the engine cannot be eliminated from the dump trucks.

[0006] Meanwhile, at mining sites, in order to realize the introduction of battery-powered, engineless electric dump trucks, the installation of stationary charging facilities, similar to electric vehicle charging stations, is being considered. Electric dump trucks are required to be compatible not only with the conventional trolley charging method, but also with a stationary charging method that receives power from stationary charging facilities to charge the battery. This will facilitate the practical application of battery-powered electric dump trucks.

[0007] In view of the circumstances described above, the present invention aims to commercialize a battery-powered electric dump truck capable of charging its battery using both a trolley charging method and a stationary charging method.

[0008] To solve the aforementioned problems, the electric dump truck of the present invention is characterized by comprising: a pantograph that receives power supplied from a trolley wire; a battery that is charged by the power received by the pantograph; a driving motor that drives the vehicle body using power supplied from the battery or power received by the pantograph; a power path connecting the pantograph, the battery and the driving motor; a DC / DC converter connected to the power path between the pantograph and the battery, which converts the power received by the pantograph and supplies it to the battery; a switch connected to the power path between the pantograph and the DC / DC converter, which switches the power path between a conductive state and a non-conductive state based on the voltage of the power path; and a power receiving terminal connected to the power path between the pantograph and the switch, which receives power supplied from an external power source different from the trolley wire.

[0009] According to the present invention, it is possible to commercialize a battery-powered electric dump truck that can be charged using both a trolley charging method and a stationary charging method.

[0010] Side view of an electric dump truck. Front view of an electric dump truck receiving power supplied from a trolley wire. Front view of an electric dump truck receiving power supplied from a stationary charging facility. Diagram showing the electrical circuit of an electric dump truck. Diagram explaining the flow of power when the battery is charged by the trolley charging method. Diagram explaining the flow of power when the battery is charged by the stationary charging method. Timing chart explaining an example of the operation of a control device when the battery is charged by the trolley charging method. Timing chart explaining an example of the operation of a control device when the battery is charged by the stationary charging method. Timing chart explaining another example of the operation of a control device when the battery is charged by the stationary charging method. Diagram explaining a modified version of an electric dump truck.

[0011] Embodiments of the present invention will be described below with reference to the drawings. Components denoted by the same reference numerals in each embodiment are similar in each embodiment unless otherwise specified, and their descriptions will be omitted.

[0012] The configuration of the electric dump truck 1 will be explained using Figures 1 to 4. Figure 1 is a side view of the electric dump truck 1.

[0013] The electric dump truck 1 is a work machine used at mining sites to load minerals or soil excavated by a hydraulic excavator and transport them to the unloading area. The electric dump truck 1 is a battery-powered electric dump truck that is equipped with a battery 5 instead of an engine and generator, and runs using the electricity stored in the battery 5 as its power source.

[0014] The electric dump truck 1 has a body frame 1a on which a battery 5 is mounted, a cab 1b attached to the body frame 1a and configured for the operator to sit in and equipped with various operating devices, a vessel 1c attached to the body frame 1a on which cargo is loaded, and a body 1f including running wheels 1d, 1e consisting of front wheels (right front wheel and left front wheel) 1d and rear wheels (right rear wheel and left rear wheel) 1e attached to the body frame 1a.

[0015] Furthermore, the electric dump truck 1 includes a pantograph 3 mounted on the front of the vehicle frame 1a and connected to the trolley wire T, a power receiving socket 4 mounted on the side of the vehicle frame 1a and to which a cable extending from a stationary charging facility S is attached, and a switch box 2 that houses a switch 8 provided on the power path 6 connecting the pantograph 3 and the power receiving socket 4 to the battery 5.

[0016] Figure 2 is a front view of an electric dump truck 1 that receives power supplied from a trolley wire T.

[0017] The trolley wire T is connected to an external power source and installed on part (for example, an uphill road) or all of the electric dump truck 1's travel path, and is an overhead power supply wire stretched above the electric dump truck 1 as it travels. The electric dump truck 1 receives power from the trolley wire T by pressing the pantograph 3 against the trolley wire T. The electric dump truck 1 is also configured to run while charging the battery 5 by distributing the power supplied from the trolley wire T to the wheels 1d, 1e and the battery 5. In this embodiment, the method of receiving power supplied from the trolley wire T via the pantograph 3 and thereby charging the battery 5 is also called the "trolley charging method".

[0018] Figure 3 is a front view of an electric dump truck 1 receiving power supplied from a stationary charging facility S.

[0019] The stationary charging equipment S is a charging facility installed in a location away from the road where the trolley wire T is installed (for example, near a flat section included in the road). The charging equipment S is an external power source different from the trolley wire T. The electric dump truck 1 has its battery 5 charged by power supplied from the charging equipment S when a cable extending from the charging equipment S is attached to a power receiving socket 4 located on the side of the vehicle body 1f. The electric dump truck 1 has its battery 5 charged while parked within the movable range of the cable extending from the charging equipment S. In this embodiment, the method in which power supplied from the charging equipment S is received by the power receiving socket 4 and the battery 5 is charged by this is also called the "stationary charging method".

[0020] Figure 4 shows the electrical circuit of the electric dump truck 1.

[0021] The electric dump truck 1 includes a pantograph 3 that receives power supplied from a trolley wire T, a battery 5 that is charged by the power received by the pantograph 3, and a power path 6 that connects the pantograph 3 and the battery 5. The electric dump truck 1 includes driving motors 16 and 17 that propel the vehicle body 1f using power supplied from the battery 5 or power received by the pantograph 3. The electric dump truck 1 includes a DC / DC converter 7 connected to the power path 6 between the pantograph 3 and the battery 5, which converts the power received by the pantograph 3 and supplies it to the battery 5. The electric dump truck 1 includes a switch 8 connected to the power path 6 between the pantograph 3 and the DC / DC converter 7, which switches the power path 6 between a conductive state and a non-conductive state based on the voltage of the power path 6. The electric dump truck 1 includes a power receiving terminal 9 connected to the power path 6 between the pantograph 3 and the switch 8, which receives power supplied from a charging facility S, which is an external power source different from the trolley wire T.

[0022] Specifically, the power receiving terminal 9 is a terminal provided on the power receiving socket 4. The power receiving terminal 9 is electrically connected to the cable when the cable extending from the charging equipment S is attached to the power receiving socket 4.

[0023] Furthermore, the electric dump truck 1 is equipped with a first voltage sensor 11 connected to a first power path 61, which is a power path 6 between the power receiving terminal 9 and the switch 8, and which detects the voltage of the first power path 61. The electric dump truck 1 is equipped with a second voltage sensor 12 connected to a second power path 62, which is a power path 6 between the switch 8 and the DC / DC converter 7, and which detects the voltage of the second power path 62. The electric dump truck 1 is equipped with a third voltage sensor 13 connected to a third power path 63, which is a power path 6 between the DC / DC converter 7 and the battery 5, and which detects the terminal voltage of the battery 5.

[0024] Furthermore, the electric dump truck 1 is connected to a first power path 61 between a power receiving terminal 9 and a first voltage sensor 11, and includes a circuit breaker 10 that switches the first power path 61 to a non-conducting state when the voltage of the first power path 61 detected by the first voltage sensor 11 reaches the allowable limit value of the first voltage sensor 11.

[0025] Furthermore, the electric dump truck 1 is connected to a fourth power path 64, which is a power path 6 between the switch 8 and the DC / DC converter 7, and is equipped with drive inverters 14 and 15 that convert the power received by the pantograph 3 or the power supplied from the battery 5. The electric dump truck 1 is housed in a grid box and is connected to the drive motors 16 and 17, and is equipped with resistors 19 that convert the regenerative power of the drive motors 16 and 17 into heat, and a chopper 18 that is connected between the drive motors 16 and 17 and the resistors 19, and controls the amount of regenerative power supplied to the resistors 19.

[0026] The drive motors 16 and 17 are connected to drive inverters 14 and 15, and are driven by the power converted by drive inverter 14 to rotate the wheels 1d and 1e. The drive motors 16 and 17 include drive motor 16, which rotates the left rear wheel 1e, which is a drive wheel of the electric dump truck 1, and drive motor 17, which rotates the right rear wheel 1e, which is a drive wheel of the electric dump truck 1. The drive inverters 14 and 15 include drive inverter 14, which converts the power supplied to drive motor 16, and drive inverter 15, which converts the power supplied to drive motor 17.

[0027] Furthermore, the electric dump truck 1 is equipped with a hydraulic inverter 20 connected to a DC / DC converter 7, which converts the power received by the pantograph 3 or the power supplied from the battery 5. The electric dump truck 1 is equipped with a hydraulic motor 21 connected to the hydraulic inverter 20, which is driven by the power converted by the hydraulic inverter 20. The electrical circuit of the electric dump truck 1 is equipped with an auxiliary system 23 connected to the DC / DC converter 7, which is driven by the power received by the pantograph 3 or the power supplied from the battery 5.

[0028] The hydraulic motor 21 rotates the hydraulic pump 22 that supplies pressurized oil to the hydraulic cylinders of the electric dump truck 1 (for example, the hoist cylinder that operates the vessel 1c). The hydraulic inverter 20 is connected to the DC / DC converter 7 via the fifth power path 65. The auxiliary equipment system 23 is, for example, an air conditioning system or lighting system for the electric dump truck 1. The auxiliary equipment system 23 is connected to the DC / DC converter 7 via the sixth power path 66.

[0029] Furthermore, the electric dump truck 1 is equipped with a control device 30 that controls each component of the electric dump truck 1 shown in Figure 4. Based on the detection results of the voltage sensors 11 to 13, the control device 30 controls the switch 8, DC / DC converter 7, circuit breaker 10, travel inverters 14 and 15, chopper 18, hydraulic inverter 20, and auxiliary equipment system 23.

[0030] The control device 30 is comprised of a processor such as a CPU, and memory such as ROM and RAM. The control device 30 realizes its various functions by having the processor execute programs stored in the memory.

[0031] The operation of the electric dump truck 1 in relation to the charging of the battery 5 will be explained using Figures 5 to 8. Figure 5 is a diagram illustrating the flow of electricity when the battery 5 is charged by the trolley charging method.

[0032] When the battery 5 is charged by the trolley charging method, the control device 30 performs the following control. Specifically, as shown in Figure 5, the control device 30 controls the switch 8, DC / DC converter 7, traction inverters 14, 15 and hydraulic inverter 20 so that the power received by the pantograph 3 is supplied to the battery 5, the traction motors 16, 17, the hydraulic motor 21 and the auxiliary equipment system 23. Specifically, the control device 30 controls the switch 8 so that the power path 6 becomes conductive. The control device 30 controls the DC / DC converter 7 so that the battery 5 is charged by the power received by the pantograph 3 and the auxiliary equipment system 23 and hydraulic motor 21 are driven. The control device 30 controls the traction inverters 14, 15 so that the traction motors 16, 17 are driven by the power received by the pantograph 3.

[0033] Figure 6 illustrates the flow of electricity when the battery 5 is charged using a stationary charging method.

[0034] When charging the battery 5 using the stationary charging method, the control device 30 performs the following control. Specifically, as shown in Figure 6, the control device 30 controls the switch 8, DC / DC converter 7, drive inverters 14, 15 and hydraulic inverter 20 so that the power received by the power receiving terminal 9 is supplied to the battery 5 and the auxiliary system 23, but the power received by the power receiving terminal 9 is not supplied to the drive motors 16, 17 and the hydraulic motor 21. Specifically, the control device 30 controls the switch 8 so that the power path 6 becomes conductive. The control device 30 controls the DC / DC converter 7 so that the battery 5 is charged by the power received by the power receiving terminal 9 and the auxiliary system 23 is driven. The control device 30 controls the drive inverters 14, 15 and hydraulic inverter 20 so that the power received by the power receiving terminal 9 does not drive the drive motors 16, 17 and the hydraulic motor 21.

[0035] As a result, when the electric dump truck 1 is charged using the stationary charging method, it can take advantage of the fact that the electric dump truck 1 is stationary, and the power supply can be limited compared to the trolley charging method, thus shortening the charging time of the battery 5. In particular, when the electric dump truck 1 is charged using the stationary charging method, the hydraulic motor 21, which is usually driven at all times except when the key is off, is not driven, so power does not need to be supplied to the hydraulic motor 21. Therefore, when the electric dump truck 1 is charged using the stationary charging method, the power that was conventionally supplied to the hydraulic motor 21 can be allocated to charging the battery 5, thus shortening the charging time of the battery 5. Consequently, the electric dump truck 1 can reduce downtime (non-operating time) and improve productivity.

[0036] Figure 7 is a timing chart illustrating an example of the operation of the control device 30 when the battery 5 is charged by the trolley charging method.

[0037] The upper graph in Figure 7 shows the time variation of the voltage in the second power path 62, which is the power path 6 between the switch 8 and the DC / DC converter 7. The voltage in the second power path 62 is detected by the second voltage sensor 12. The middle graph in Figure 7 shows the time variation of the charge level (SOC) of the battery 5. The charge level of the battery 5 is calculated by the control device 30 according to the terminal voltage of the battery 5. The terminal voltage of the battery 5 is detected by the third voltage sensor 13. The lower graph in Figure 7 shows the time variation of the ON / OFF state of the switch 8. When the switch 8 is ON, the power path 6 becomes conductive. When the switch 8 is OFF, the power path 6 becomes non-conductive. The ON / OFF state of the switch 8 is controlled by the control device 30.

[0038] When charging the battery 5 using the trolley charging method, the control device 30 raises the pantograph 3 so that it is connected to the trolley wire T. Before the pantograph 3 is connected to the trolley wire T, the switch 8 is in the OFF state and the power path 6 is in a non-conductive state. Before the pantograph 3 is connected to the trolley wire T, the voltage of the second power path 62 detected by the second voltage sensor 12 is the initial voltage V0.

[0039] When the pantograph 3 is connected to the trolley wire T (time t0 in Figure 7), the control device 30 acquires the voltage of the first power path 61 detected by the first voltage sensor 11 and stores it as the first predetermined voltage V1. The first predetermined voltage V1 represents the power received by the pantograph 3. The control device 30 also acquires the voltage of the second power path 62 detected by the second voltage sensor 12 and the terminal voltage of the battery 5 detected by the third voltage sensor 13, and monitors these voltages.

[0040] Then, until the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the first predetermined voltage V1 (until time t1 in Figure 7), the control device 30 controls the DC / DC converter 7 to boost the voltage of the second power path 62 and controls the switch 8 to the OFF state so that the power path 6 becomes non-conductive.

[0041] When the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the first predetermined voltage V1 (after time t1 in Figure 7), the control device 30 controls the DC / DC converter 7 to reduce the voltage of the second power path 62 and controls the switch 8 to the ON state so that the power path 6 becomes conductive.

[0042] As a result, the electric dump truck 1 can generate a desired potential difference between the first power path 61 upstream of the switch 8 (pantograph 3 side) and the second power path 62 downstream of the switch 8 (battery 5 side). Therefore, the electric dump truck 1 can prevent the charging voltage of the battery 5 from becoming excessive and a large current from being suddenly supplied to the battery 5, thus enabling the battery 5 to be charged safely. The charge level of the battery 5 increases.

[0043] Here, when the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the first predetermined voltage V1 (after time point t1 in FIG. 7), the control device 30 controls the DC / DC converter 7 to step down the voltage of the second power path 62 until the voltage of the second power path 62 detected by the second voltage sensor 12 reaches a second predetermined voltage V2 that is lower than the first predetermined voltage V1 and corresponds to the allowable current of the battery 5 (until time point t2 in FIG. 7).

[0044] Thereby, the electric dump truck 1 can surely prevent the charging voltage of the battery 5 from becoming excessive, so that the battery 5 can be charged more safely.

[0045] When the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the second predetermined voltage V2 (after time point t2 in FIG. 7), the control device 30 controls the DC / DC converter 7 to maintain the voltage of the second power path 62 until the inter-terminal voltage of the battery 5 detected by the third voltage sensor 13 reaches a third predetermined voltage V3 corresponding to the target charge rate C of the battery 5 (until time point t3 in FIG. 7).

[0046] When the inter-terminal voltage of the battery 5 detected by the third voltage sensor 13 reaches the third predetermined voltage V3 (at time point t3 in FIG. 7), the control device 30 controls the switch 8 to be in the OFF state so that the power path 6 becomes non-conductive. Further, the control device 30 lowers the pantograph 3 so that the connection between the pantograph 3 and the trolley wire T is released.

[0047] Thereby, the electric dump truck 1 can charge the battery 5 so that the charge rate of the battery 5 reaches the target charge rate C while preventing the charging voltage of the battery 5 from becoming excessive, so that the battery 5 can be charged safely and surely up to the target charge rate C.

[0048] After the inter-terminal voltage of the battery 5 detected by the third voltage sensor 13 reaches the third predetermined voltage V3 (after time t3 in FIG. 7), the control device 30 controls the DC / DC converter 7 to step down the voltage of the second power path 62 until the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the initial voltage V0 (until time t4 in FIG. 7). When the voltage of the second power path 62 detected by the second voltage sensor 12 is stepped down to the initial voltage V0 (at time t4 in FIG. 7), the control device 30 ends the operation related to the charging of the battery 5.

[0049] In FIG. 7, time t0 represents the start timing of the operation related to the charging of the control device 30. Time t1 represents the start timing of the charging of the battery 5. Time t3 represents the end timing of the charging of the battery 5. Time t4 represents the end timing of the operation related to the charging of the control device 30. In FIG. 7, the time from time t1 to time t3 represents the charging time of the battery 5.

[0050] FIG. 8 is a timing chart for explaining an example of the operation of the control device 30 when the battery 5 is charged by the stationary charging method. FIG. 8 is a diagram corresponding to FIG. 7.

[0051] When charging the battery 5 by the stationary charging method, the control device 30 notifies the operator of information prompting the operator to attach the cable of the charging facility S to the power receiving socket 4 including the power receiving terminal 9 so that the power receiving terminal 9 is connected to the charging facility S. Before the power receiving terminal 9 is connected to the charging facility S, the switch 8 is in the OFF state and the power path 6 is in the non-conductive state. Before the power receiving terminal 9 is connected to the charging facility S, the voltage of the second power path 62 detected by the second voltage sensor 12 is the initial voltage V0.

[0052] When the power receiving terminal 9 is connected to the charging equipment S (time t0 in Figure 8), the control device 30 acquires the voltage of the first power path 61 detected by the first voltage sensor 11, as shown in Figure 7, and stores it as the first predetermined voltage V1. The first predetermined voltage V1 represents the power receiving voltage of the charging equipment S. The control device 30 also acquires the voltage of the second power path 62 detected by the second voltage sensor 12 and the terminal voltage of the battery 5 detected by the third voltage sensor 13, as shown in Figure 7, and monitors these voltages.

[0053] Then, after the power receiving terminal 9 is connected to the charging equipment S (from time t0 onward), the control device 30 performs the same operations as shown in Figure 7 until the charging operations shown in Figure 8 are completed (until time t4).

[0054] For example, when the power receiving terminal 9 is connected to the charging equipment S (after time t0 in Figure 8), the control device 30 controls the DC / DC converter 7 to boost the voltage of the second power path 62 until the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the first predetermined voltage V1 (until time t1 in Figure 8), and controls the switch 8 to the OFF state so that the power path 6 becomes non-conductive. Then, when the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the first predetermined voltage V1 (after time t1 in Figure 8), the control device 30 controls the DC / DC converter 7 to lower the voltage of the second power path 62, and controls the switch 8 to the ON state so that the power path 6 becomes conductive.

[0055] As a result, the electric dump truck 1 can charge the battery 5 by standardizing the operation of the control device 30 regardless of whether it is using a trolley charging method or a stationary charging method, eliminating the need to prepare a separate operating program for the control device 30 for each charging method. Therefore, the electric dump truck 1 can charge the battery 5 using both the trolley charging method and the stationary charging method by adding only a minimum number of components.

[0056] As described above, the electric dump truck 1 of this embodiment includes a pantograph 3 that receives power supplied from a trolley wire T, a battery 5 that is charged by the power received by the pantograph 3, driving motors 16 and 17 that move the vehicle body 1f using power supplied from the battery 5 or power received by the pantograph 3, a power path 6 connecting the pantograph 3 and the battery 5, a DC / DC converter 7 connected to the power path 6 between the pantograph 3 and the battery 5 and converting the power received by the pantograph 3 and supplying it to the battery 5, a switch 8 connected to the power path 6 between the pantograph 3 and the DC / DC converter 7 and switching the power path 6 to a conductive or non-conductive state based on the voltage of the power path 6, and a power receiving terminal 9 connected to the power path 6 between the pantograph 3 and the switch 8 and receiving power supplied from a charging facility S, which is an external power source different from the trolley wire T.

[0057] As a result, the electric dump truck 1 can charge the battery 5 using a stationary charging method with a trolley charging electrical circuit simply by connecting the power receiving terminal 9 to the power path 6 between the pantograph 3 and the switch 8. Therefore, according to this embodiment, it is possible to put into practical use a battery-powered electric dump truck 1 that can charge the battery 5 using both a trolley charging method and a stationary charging method with a simple configuration.

[0058] Furthermore, the electric dump truck 1 of this embodiment is connected to a first power path 61 between a power receiving terminal 9 and a first voltage sensor 11, and includes a circuit breaker 10 that switches the first power path 61 to a non-conducting state when the voltage of the first power path 61 detected by the first voltage sensor 11 reaches the allowable limit value of the first voltage sensor 11.

[0059] As a result, the electric dump truck 1 does not need to separately prepare a circuit breaker 10 for stationary charging. Therefore, according to this embodiment, it is possible to put into practical use a battery-powered electric dump truck 1 that can charge the battery 5 using both trolley charging and stationary charging methods with a simple configuration.

[0060] Figure 9 is a timing chart illustrating another example of the operation of the control device 30 when the battery 5 is charged by the stationary charging method. Figure 9 corresponds to Figure 8.

[0061] In the example shown in Figure 8, when the power receiving terminal 9 is connected to the charging equipment S (from time t0 onwards in Figure 8), the control device 30 controls the DC / DC converter 7 to boost the voltage of the second power path 62 until the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the first predetermined voltage V1 (up to time t1 in Figure 8), and also controls the switch 8 to the OFF state so that the power path 6 becomes non-conductive.

[0062] In contrast, in the example shown in Figure 9, when the power receiving terminal 9 is connected to the charging equipment S (from time t0 onwards in Figure 9), the control device 30 controls the DC / DC converter 7 to boost the voltage of the second power path 62 until the voltage of the second power path 62 detected by the second voltage sensor 12 reaches a second predetermined voltage V2 corresponding to the allowable current of the battery 5, which is lower than the first predetermined voltage V1, and controls the switch 8 to the OFF state so that the power path 6 becomes non-conductive. Then, when the voltage of the second power path 62 detected by the second voltage sensor 12 reaches the second predetermined voltage V2 (from time t2 onwards in Figure 9), the control device 30 controls the DC / DC converter 7 to maintain the voltage of the second power path 62 until the terminal voltage of the battery 5 detected by the third voltage sensor 13 reaches a third predetermined voltage V3 corresponding to the target charge rate C of the battery 5 (until time t3 in Figure 9), and controls the switch 8 to the ON state so that the power path 6 becomes conductive.

[0063] As a result, in the example shown in Figure 9, the electric dump truck 1 can shorten the voltage boosting time (time from time t0 to time t2 in Figure 9) after the power receiving terminal 9 is connected to the charging equipment S (after time t0 in Figure 9) compared to the voltage boosting time in the example shown in Figure 8 (time from time t0 to time t1 in Figure 8). Furthermore, in the example shown in Figure 9, the electric dump truck 1 does not require a voltage reduction time (time from time t1 to time t2 in Figure 8), so the battery charging time (time from time t2 to time t3 in Figure 9) can be shortened compared to the charging time in the example shown in Figure 8 (time from time t1 to time t3 in Figure 8). Therefore, in the example shown in Figure 9, the electric dump truck 1 can further reduce downtime and further improve productivity.

[0064] Figure 10 illustrates a modified example of the electric dump truck 1.

[0065] The electric dump truck 1 of this embodiment includes a GNSS receiver 31 for detecting the position of the electric dump truck 1, a storage device 32 for storing the position of the charging equipment S, and a notification device 33 for notifying the operator riding in the electric dump truck 1 of the information.

[0066] The control device 30 shown in Figure 10 controls the notification device 33 to notify information prompting the charging of the battery 5 by the charging equipment S when the distance between the position of the electric dump truck 1 detected by the GNSS receiver 31 and the position of the charging equipment S stored in the storage device 32 falls below a predetermined distance. The notification device 33 consists of a display and a speaker, and displays information prompting the charging of the battery 5 by the charging equipment S on the display or emits it from the speaker.

[0067] With the current performance of the battery 5, the electric dump truck 1 needs to be charged at least once using the stationary charging method during one lap of the driving route. However, in actual mines, engine-driven dump trucks rarely stop this frequently, so when an operator is in the electric dump truck 1, they may forget to charge it using the stationary charging method. In this embodiment, the electric dump truck 1 can prompt the operator to charge the battery 5 when the distance between the electric dump truck 1 and the charging equipment S falls below a predetermined distance, thus preventing the operator from forgetting to charge and running out of power during driving.

[0068] Furthermore, if the performance of the battery 5 improves in the future and it becomes unnecessary for the electric dump truck 1 to be charged by the stationary charging method at least once during one lap of the road, the control device 30 may control the notification device 33 as follows: Specifically, the control device 30 may control the notification device 33 to notify information prompting the charging equipment S to charge the battery 5 when the distance between the electric dump truck 1 and the charging equipment S falls below a predetermined distance and the terminal voltage detected by the third voltage sensor 13 drops to a voltage corresponding to the charge level of the battery 5, which is prone to running out of power.

[0069] This allows the electric dump truck 1 to prompt the operator to charge the battery 5 without causing any inconvenience, effectively preventing the battery from running out during operation.

[0070] Furthermore, in the electric dump truck 1 of this embodiment, when charging by the trolley charging method is performed after charging by the stationary charging method, the control device 30 slows down the charging speed of the battery 5 compared to the charging speed when charging by the stationary charging method. That is, when the control device 30 charges the battery 5 with the power received by the power receiving terminal 9 and then charges the battery 5 with the power received by the pantograph 3, it slows down the charging speed of the battery 5 compared to the charging speed when charging the battery 5 with the power received by the power receiving terminal 9.

[0071] When charging by trolley charging is performed after charging by stationary charging, the charge level of the battery 5 is relatively high, and there is still some remaining charge in the battery 5. Therefore, when charging by trolley charging, it is not necessary to increase the charging speed. If the charging speed is too high, the amount of heat generated by the battery 5 will increase, shortening the lifespan of the battery 5. In this embodiment, the electric dump truck 1 slows down the charging speed of the battery 5 when charging by trolley charging after charging by stationary charging, so the lifespan of the battery 5 can be extended compared to when the battery 5 is charged by stationary charging alone.

[0072] Furthermore, in the electric dump truck 1 of this embodiment, when charging by the trolley charging method is performed after charging by the stationary charging method, the control device 30 sets the travel speed of the electric dump truck 1 to be faster than the travel speed when charging by the trolley charging method. That is, when the control device 30 charges the battery 5 with the power received by the power receiving terminal 9 and then charges the battery 5 with the power received by the pantograph 3, it sets the travel speed of the electric dump truck 1 to be faster than the travel speed when charging the battery 5 with the power received by the pantograph 3.

[0073] If the electric dump truck 1 is driven too fast when charging using the trolley charging method, the connection time of the pantograph 3 to the trolley wire T will be shortened, and the battery 5 will not be able to be fully charged. However, when charging using the trolley charging method is performed after charging using the stationary charging method, there is sufficient charge remaining in the battery 5, so the battery 5 can be fully charged without ensuring a long connection time of the pantograph 3 to the trolley wire T. Therefore, when charging using the trolley charging method is performed after charging using the stationary charging method, the electric dump truck 1 can be driven at a faster speed than when charging the battery 5 using only the trolley charging method.

[0074] This is particularly effective in mines where "trolley wires T cannot be installed over long distances" and "under trolley wires T, battery-powered electric dump trucks must travel at a slower speed than engine-powered dump trucks to charge their batteries." This is because it eliminates the problem of engine-powered dump trucks having to overtake battery-powered electric dump trucks, or causing congestion when overtaking is not possible.

[0075] Although embodiments of the present invention have been described in detail above, the present invention is not limited to each embodiment, and various modifications can be made without departing from the spirit of the invention. The present invention can be modified by adding components of one embodiment to components of another embodiment, replacing components of one embodiment with components of another embodiment, or deleting parts of components of one embodiment.

[0076] 1...Electric dump truck, 1a...Body frame, 1b...Cab, 1c...Vessel, 1d...Front wheels, 1e...Rear wheels, 1f...Body, 2...Switch box, 3...Pantograph, 4...Power receiving socket, 5...Battery, 6...Power path, 61...First power path, 62...Second power path, 63...Third power path, 64...Fourth power path, 65...Fifth power path, 66...Sixth power path, 7...DC / DC converter, 8...Switch, 9...Power receiving terminal, 10...Circuit breaker, 11...First voltage sensor , 12...Second voltage sensor, 13...Third voltage sensor, 14, 15...Traction inverter, 16, 17...Traction motor, 18...Chopper, 19...Resistor, 20...Hydraulic inverter, 21...Hydraulic motor, 22...Hydraulic pump, 23...Auxiliary system, 30...Control device, 31...GNSS receiver, 32...Storage device, 33...Notification device, C...Target charge rate, T...Trolley wire, S...Charging equipment, V0...Initial voltage, V1...First predetermined voltage, V2...Second predetermined voltage, V3...Third predetermined voltage

Claims

1. An electric dump truck comprising: a pantograph that receives power supplied from a trolley wire; a battery that is charged by the power received by the pantograph; a traction motor that moves the vehicle body using power supplied from the battery or power received by the pantograph; a power path connecting the pantograph, the battery and the traction motor; a DC / DC converter connected to the power path between the pantograph and the battery, which converts the power received by the pantograph and supplies it to the battery; a switch connected to the power path between the pantograph and the DC / DC converter, which switches the power path between a conductive state and a non-conductive state based on the voltage of the power path; and a power receiving terminal connected to the power path between the pantograph and the switch, which receives power supplied from an external power source different from the trolley wire.

2. The electric dump truck according to claim 1, further comprising: a first voltage sensor connected to a first power path which is the power path between the power receiving terminal and the switch, for detecting the voltage of the first power path; a second voltage sensor connected to a second power path which is the power path between the switch and the DC / DC converter, for detecting the voltage of the second power path; and a control device that controls the switch and the DC / DC converter based on the detection results of the first voltage sensor and the second voltage sensor, wherein when the battery is charged by the power received by the pantograph, the control device controls the DC / DC converter to boost the voltage of the second power path until the voltage of the second power path detected by the second voltage sensor reaches a first predetermined voltage detected by the first voltage sensor, and controls the switch so that the power path becomes non-conductive; and when the voltage of the second power path detected by the second voltage sensor reaches the first predetermined voltage, the DC / DC converter to lower the voltage of the second power path and controls the switch so that the power path becomes conductive.

3. The electric dump truck according to claim 2, characterized in that when the power receiving terminal charges the battery, the control device controls the DC / DC converter to boost the voltage of the second power path until the voltage of the second power path detected by the second voltage sensor reaches the first predetermined voltage, and controls the switch so that the power path becomes non-conductive, and when the voltage of the second power path detected by the second voltage sensor reaches the first predetermined voltage, the DC / DC converter controls the voltage of the second power path to decrease, and controls the switch so that the power path becomes conductive.

4. The electric dump truck according to claim 3, characterized in that when the voltage of the second power path detected by the second voltage sensor reaches the first predetermined voltage, the control device controls the DC / DC converter to reduce the voltage of the second power path until the voltage of the second power path detected by the second voltage sensor reaches a second predetermined voltage lower than the first predetermined voltage and corresponding to the allowable current of the battery.

5. The electric dump truck according to claim 4, further comprising a third voltage sensor connected to a third power path which is the power path between the DC / DC converter and the battery, for detecting the terminal voltage of the battery, wherein the control device controls the DC / DC converter to maintain the voltage of the second power path when the voltage of the second power path detected by the second voltage sensor reaches a second predetermined voltage, until the terminal voltage detected by the third voltage sensor reaches a third predetermined voltage corresponding to the target charge rate of the battery, and controls the switch to cause the power path to become non-conductive when the terminal voltage detected by the third voltage sensor reaches a third predetermined voltage.

6. The electric dump truck according to claim 2, characterized in that when the power receiving terminal charges the battery, the control device controls the DC / DC converter to boost the voltage of the second power path until the voltage of the second power path detected by the second voltage sensor reaches a second predetermined voltage corresponding to the allowable current of the battery, which is lower than the first predetermined voltage, and controls the switch to make the power path non-conductive, and when the voltage of the second power path detected by the second voltage sensor reaches the second predetermined voltage, the control device controls the DC / DC converter to maintain the voltage of the second power path and controls the switch to make the power path conductive.

7. The system further comprises: a traction inverter connected to the power path between the switch and the DC / DC converter, which converts power received by the pantograph or power supplied from the battery; a hydraulic inverter connected to the DC / DC converter, which converts power received by the pantograph or power supplied from the battery; a hydraulic motor connected to the hydraulic inverter and driven by the power converted by the hydraulic inverter; an auxiliary system connected to the DC / DC converter and driven by power received by the pantograph or power supplied from the battery; and a control device that controls the switch, the DC / DC converter, the traction inverter, and the hydraulic inverter, wherein the traction motor is connected to the traction inverter and driven by the power converted by the traction inverter; the external power source is a stationary charging device installed away from the trolley wire; and the control device charges the battery with the power received by the power receiving terminal. The electric dump truck according to claim 1, characterized in that the power received by the power receiving terminal is supplied to the battery and the auxiliary equipment system, and the switch, the DC / DC converter, the drive inverter, and the hydraulic inverter are controlled so that the power received by the power receiving terminal is not supplied to the drive motor and the hydraulic motor.

8. The electric dump truck according to claim 7, characterized in that when the control device charges the battery with the power received by the power receiving terminal and then charges the battery with the power received by the pantograph, the charging speed of the battery is slower than the charging speed when the battery is charged with the power received by the power receiving terminal.

9. The electric dump truck according to claim 7, characterized in that when the control device charges the battery with the power received by the power receiving terminal and then charges the battery with the power received by the pantograph, the driving speed of the electric dump truck is faster than the driving speed when charging the battery with the power received by the pantograph.

10. The electric dump truck according to claim 2, further comprising a circuit breaker connected to the first power path between the power receiving terminal and the first voltage sensor, which switches the first power path to the non-conducting state when the voltage of the first power path detected by the first voltage sensor reaches the permissible limit value of the first voltage sensor.

11. The electric dump truck according to claim 1, wherein the external power supply is a stationary charging facility installed at a location away from the trolley wire, the electric dump truck further comprises a GNSS receiver for detecting the position of the electric dump truck, a storage device for storing the position of the charging facility, a notification device for notifying an operator riding in the electric dump truck, and a control device for controlling the notification device, and the control device controls the notification device to notify information prompting the charging facility to charge the battery when the distance between the position of the electric dump truck detected by the GNSS receiver and the position of the charging facility stored in the storage device falls below a predetermined distance.

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