dump truck

Abstract

To provide a dump truck capable of securing travelling performance by preventing overdischarge of a rechargeable battery in a travelling cycle of a mine.SOLUTION: A controller 30 detects a charging rate of a rechargeable battery 16 at a starting point of a travelling cycle as an initial SoC, detects a charging rate of the rechargeable battery 16 at an ending point of the travelling cycle as a final SoC, corrects a first electric power threshold P1 to a plus side or corrects a second electric power threshold P2 to a minus side when the final SoC is higher than the initial SoC, and corrects the first electric power threshold P1 to a minus side or corrects the second electric power threshold P2 to a plus side when the final SoC is lower than the initial SoC.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a dump truck.

Background Art

[0002] As a countermeasure against global warming, systems utilizing storage batteries have become widespread in the fields of automobiles and railways. For example, a hybrid vehicle is equipped with an engine and a storage battery, and can reduce the fuel consumption of the engine by storing the regenerative energy generated during vehicle braking in the storage battery and providing electric power assist during acceleration. In addition, since the output of the engine can be reduced by the electric power assist of the storage battery, the engine can be miniaturized.

[0003] Large work vehicles such as dump trucks used for transportation at mining sites also drive a motor using the electric power generated by a generator driven by an engine, similar to automobiles. The regenerative energy generated during dump truck braking was consumed as heat by a resistor, but by installing a storage battery, the fuel consumption of the engine can be reduced like that of a hybrid vehicle. On the other hand, when miniaturizing the engine by installing a storage battery, it is necessary to run using both the engine and the storage battery when a large amount of power is required, such as when climbing a slope of a dump truck.

[0004] Patent Document 1 is a prior art document disclosing the background technology of this field. Patent Document 1 states that "a driving control device is installed in a vehicle equipped with an electric motor and an internal combustion engine as power sources, and a battery that stores the energy that drives the electric motor and the regenerative energy recovered by the regenerative braking of the electric motor. The driving control device comprises a creation unit that creates a speed profile predicting the vehicle's speed, an estimation unit that estimates the expected amount of recoverable regenerative energy based on the speed profile, and a determination unit that determines the power source to be used for driving based on the expected amount of regenerative energy and thermal information representing the vehicle's heat requirements." According to the driving control device described in Patent Document 1, by determining the driving energy to be supplied to the electric motor based on the expected amount of recovered regenerative energy and thermal information representing the vehicle's heat requirements, thermal management such as heat generation by the internal combustion engine and cooling or heating of the battery can be suitably performed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-91318 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, Patent Document 1 does not describe a method for managing the remaining charge of the storage battery. If the remaining charge of the storage battery in a dump truck is insufficient, power assistance from the battery may not be available when climbing hills, potentially leading to a decrease in driving performance.

[0007] This invention has been made in view of the above problems, and its purpose is to provide a dump truck that can ensure driving performance by preventing over-discharge of the storage battery during the driving cycle in a mine. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides an electric motor as a power source and a generator that supplies power to the electric motor, The engine that drives the aforementioned generator, A dump truck comprising a battery that stores power supplied to the electric motor and regenerative power of the electric motor, a bidirectional converter that adjusts the output power of the battery, and a controller that controls the bidirectional converter, which repeatedly travels in a travel cycle consisting of a travel path between a loading area and a loading area, wherein the controller, when the required power of the dump truck is less than a predetermined first power threshold, A mode is set in which the necessary power is supplied using only the battery among the engine and the battery, The output power command value of the storage battery is set to the required power, and if the required power is greater than the second power threshold, which is set to a value greater than the first power threshold, A mode is set in which the necessary power is supplied using both the engine and the battery, The aforementioned Battery The output power command value is set to the difference obtained by subtracting the second power threshold from the required power, and if the required power is greater than or equal to the first power threshold and less than the second power threshold, A mode is set in which the necessary power is supplied using only the engine among the engine and the storage battery, The aforementioned Battery The output power command value is set to a value smaller than the first power threshold, the charge level of the battery at the start of the driving cycle is detected as the initial SoC, the charge level of the battery at the end of the driving cycle is detected as the final SoC, if the final SoC is higher than the initial SoC, the first power threshold is corrected to the positive side, or the second power threshold is corrected to the negative side, if the final SoC is lower than the initial SoC, the first power threshold is corrected to the negative side, or the second power threshold is corrected to the positive side. Furthermore, if the final SoC is equal to the initial SoC and higher than a predetermined reference SoC, the first power threshold is corrected to the positive side, or the second power threshold is corrected to the negative side. If the final SoC is equal to the initial SoC and lower than the reference SoC, the first power threshold is corrected to the negative side, or the second power threshold is corrected to the positive side. It shall be done.

[0009] According to the present invention configured as described above, the first or second power threshold is corrected so that the initial SoC and the final SoC of each driving cycle match (so that the charge / discharge balance of the battery becomes zero). This prevents over-discharge of the battery, thereby ensuring the driving performance of the dump truck. [Effects of the Invention]

[0010] According to the present invention, it is possible to ensure the driving performance of a dump truck by preventing over-discharge of the battery during the driving cycle in a mine. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing the configuration of a dump truck in the first embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of a power conversion system in the first embodiment of the present invention. [Figure 3] This is a schematic diagram illustrating power control during dump truck acceleration by a power conversion system in the first embodiment of the present invention. [Figure 4] This is a diagram showing the configuration of a bidirectional converter in the first embodiment of the present invention. [Figure 5] This is a flowchart showing the processing of the controller involved in the control of the bidirectional converter in the first embodiment of the present invention. [Figure 6] This figure shows an example of a method for calculating the correction amount in the first embodiment of the present invention. [Figure 7] This is a timing chart showing the changes in the SoC of the storage battery during operation of a dump truck in the first embodiment of the present invention. [Figure 8] This flowchart shows an example of the process by which the controller updates the 1-cycle completion flag in the first embodiment of the present invention. [Figure 9] This flowchart shows another example of the process by which the controller updates the cycle completion flag in the first embodiment of the present invention. [Figure 10] This is a flowchart illustrating the controller processing involved in the control of the bidirectional converter in a second embodiment of the present invention. [Figure 11] This is a timing chart showing the change in the State of C of the battery during operation of a dump truck in a second embodiment of the present invention. [Figure 12] This is a flowchart showing the processing of the controller involved in the control of the bidirectional converter in the third embodiment of the present invention.

Best Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same reference numerals are given to equivalent elements, and redundant descriptions are omitted as appropriate.

Examples

[0013] FIG. 1 is a configuration diagram of a dump truck in a first embodiment of the present invention. The dump truck is equipped with a body 5 for loading earth and sand or the like on a frame 1, and the two are connected by a hoist cylinder 6. Further, a front wheel 2, a rear wheel 3, a fuel tank 9, etc. are attached to the frame 1 via mechanical components (not shown). In the rotating shaft portion of the rear wheel 3, a motor 10 as an electric motor for driving the rear wheel 3 and a speed reducer (not shown) for adjusting the rotational speed of the rear wheel 3 are housed.

[0014] The frame 1 is further provided with a deck on which an operator can walk. The deck is equipped with a cab 4 for the operator to board to operate the dump truck, a control cabinet 8 in which various electric devices are housed, and a plurality of grid resistors 7 for dissipating surplus energy as heat.

[0015] Also, in the portion hidden by the front wheel 2 in FIG. 1, an engine 11 (shown in FIG. 2), a main generator 12 (shown in FIG. 2) mainly as a power source for the traveling motor, an auxiliary generator (not shown) mainly as a power source for auxiliary equipment, a main pump (not shown) mainly as a hydraulic source for hydraulic equipment, etc. are mounted. Note that a storage battery 16 (shown in FIG. 2) and a bidirectional converter 17 (shown in FIG. 2) described later are attached to the body of the dump truck (on the deck or the frame 1, etc.).

[0016] Next, the operator will explain how to operate the dump truck. Inside cab 4 are an accelerator pedal, a brake pedal, a hoist pedal, and a steering wheel (none of which are shown). The operator can also control the acceleration and braking force of the dump truck by the amount they press the accelerator and brake pedals inside cab 4.

[0017] Furthermore, the operator performs hydraulic steering by rotating the steering wheel left and right, and hydraulic dumping by pressing the hoist pedal. However, the steering and dumping systems are the same as in conventional systems, so they will not be described in detail.

[0018] Figure 2 is a diagram showing the configuration of the power conversion system mounted on the dump truck in this embodiment. The power conversion system consists of an engine 11, a main generator (hereinafter referred to as the generator) 12, a rectifier 13, a voltage sensor 21 for detecting DC voltage, an inverter 14, a motor 10, current sensors 22a and 22b for detecting the current of the motor 10, a speed sensor 15 for the motor 10, a storage battery 16, a current sensor 22c for detecting the current of the storage battery 16, an SoC detection device 31 for detecting the charge level (hereinafter referred to as SoC: State of Charge) of the storage battery 16, a bidirectional converter 17 for controlling the power of the storage battery 16, a grid resistor 7, a grid chopper 18 for controlling the power of the grid resistor 7, and a controller 30. In addition, the power consumption of auxiliary equipment (not shown) is supplied from the storage battery 16 or from the DC side of the rectifier 13 and inverter 14 via a converter (not shown).

[0019] The following describes the power flow during acceleration of a dump truck. Fuel is supplied from the fuel tank 9 to the engine 11, generating rotational power for the engine. This rotational power is input to the generator 12, converting mechanical energy into electrical energy and obtaining three-phase AC power. The obtained three-phase AC power is converted from AC to DC by the rectifier 13. Here, the rectifier 13 may be either a diode rectifier or a PWM converter using a switching element.

[0020] The inverter 14 converts DC power to AC power to drive the motor 10. The inverter circuit configuration can be either a 2-level circuit or a 3-level circuit. The battery 16 is connected to the DC side of the rectifier 13 and inverter 14 via a bidirectional converter 17. That is, the power output from the battery 16 during dump truck acceleration is controlled by the bidirectional converter 17. The grid resistor 7 is connected to the DC side of the rectifier 13 and inverter 14 via a grid chopper. The grid chopper starts operating in response to the DC voltage of the rectifier 13 and inverter 14.

[0021] In this embodiment, the dump truck is equipped with a generator 12 driven by the engine 11 and a storage battery 16 as power sources for the motor 10. Because the power assist from the storage battery reduces the output of the engine, the engine 11 can be made smaller compared to a dump truck with the same maximum power output for the motor 10 but without a storage battery 16.

[0022] The following describes the power flow during braking of a dump truck. When a dump truck brakes, the motor 10 acts as a generator, generating regenerative energy and converting the kinetic energy of the dump truck into electrical energy. The inverter converts the generated AC power into DC power. The converted DC power is used to charge the battery 16 via the bidirectional converter 17 or to dissipate as heat through the grid resistor 7 via the grid chopper 18.

[0023] The regenerative energy charged in the battery 16 is used as power to assist the engine 11 when accelerating the dump truck. At this time, the greater the regenerative energy charged in the battery 16, that is, the smaller the energy consumed by the grid resistor 7, the lower the output of the engine 11 when accelerating the dump truck can be, and thus the lower the fuel consumption of the engine 11 can be.

[0024] The configuration of the controller 30 is described below. The controller 30 outputs command values ​​to the engine 11, generator 12, inverter 14, bidirectional converter 17, and grid chopper 18 based on the DC voltage detected by the voltage sensor 21 connected to the DC side of the rectifier 13 and inverter 14, the motor current detected by current sensors 22a and 22b, the motor speed detected by the speed sensor 15, the battery current detected by the current sensor 22c, the battery's SoC, and the operator's pedal input.

[0025] Figure 3 is a schematic diagram showing power control during dump truck acceleration by a power conversion system. In this embodiment, the power conversion system has two power thresholds P1 and P2 for the required power P of the dump truck, and has three modes depending on the relationship between the required power P and the power thresholds P1 and P2. In this embodiment, power threshold P1 is set to a value less than power threshold P2. The required power P is calculated by the controller 30 based on the amount of pedal operation by the operator. The controller 30 also compares the required power P with the power thresholds P1 and P2.

[0026] The following describes the three modes. First, Mode 1 is when the required power P of the dump truck is higher than the power threshold P2. In this embodiment, the power threshold P2 is set to a value equal to the rated output of the engine 11. That is, in Mode 1, the required power P is higher than the power threshold P2, which is the rated output of the engine 11, and the engine 11 alone cannot supply the required power P, so the dump truck is driven using both the engine 11 and the battery 16.

[0027] One example of a case where the required power P is high is when a dump truck is climbing an uphill slope while loaded with soil or other materials. In such a case, the rated output of the engine 11 (=power threshold P2) falls below the required power P, so the power command value of the battery 16, i.e., the bidirectional converter 17, becomes the insufficient power, "P-P2". Furthermore, if the battery 16 cannot output the desired power due to insufficient SoC in the battery 16, even though operation in Mode 1 is required, the torque of the motor 10 will be insufficient, and the acceleration performance of the dump truck will decrease. In other words, in order to adhere to the operating cycle time of the dump truck, it is necessary to output the desired power in Mode 1.

[0028] Next, Mode 2 is the case when the required power P of the dump truck is greater than or equal to the power threshold P1 and less than the power threshold P2. If the power threshold P2 is set to the rated output of the engine 11, then if the required power P is lower than the power threshold P2, the required power P can be supplied by the engine 11 alone. For this reason, in Mode 2, the output from the battery 16 is not required, and the power command value of the bidirectional converter 17 becomes "0". Note that the power command value in Mode 2 does not necessarily have to be "0"; the effects of the present invention, which will be described later, can be obtained if it is a sufficiently small value relative to the required power P (for example, a few percent or less of the power threshold P1).

[0029] Finally, Mode 3 is the case when the power required by the dump truck P is less than the power threshold P1. In order to improve the fuel efficiency of a dump truck equipped with a battery 16, it is desirable to make the charge-discharge balance of the battery 16 zero throughout one or more cycles of mining operation. The charge-discharge balance here refers to the difference obtained by subtracting the amount of power output from the battery 16 during dump truck acceleration or auxiliary equipment drive (output power) from the amount of power charged to the battery 16 from the regenerative energy generated when the dump truck is braking (regenerative energy).

[0030] In Mode 1 described above, the vehicle runs using the output power of the battery 16. However, if Mode 1 is the only mode in which the vehicle runs using the output power of the battery 16, the amount of regenerated power may exceed the amount of output power, resulting in a positive charge-discharge balance. In this case, in order to improve the fuel efficiency, it is necessary to increase the opportunities to drive the motor 10 using the power of the battery 16. Therefore, in Mode 3 as well, the motor 10 will be driven using the output power of the battery 16. In Mode 3, as in Mode 2, the required power P can be supplied by the output of the engine 11 alone. However, generally, the fuel consumption of the engine 11 is high when the output is low, so the fuel efficiency of the dump truck tends to worsen. In other words, in the range where the fuel efficiency of the engine 11 is poor, driving the motor 10 using only the battery 16 can improve fuel efficiency. Therefore, in Mode 3, the output of the engine 11 is set to zero, and the power command value of the bidirectional converter 17 is set to the required power "P".

[0031] Furthermore, if the SoC of the battery 16 deteriorates, it is conceivable to charge the battery 16 using the engine 11. In that case, the battery 16 would be charged from the engine 11 via the bidirectional converter 17, and power would be supplied from the battery 16 to the inverter 14 via the bidirectional converter 17. However, considering the losses incurred in the bidirectional converter 17, there are cases where it is better not to use the mode of charging the battery 16 from the engine 11 in order to improve fuel efficiency.

[0032] Figure 4 is a diagram showing the configuration of the bidirectional converter 17. In this embodiment, the bidirectional converter 17 is configured as a non-isolated chopper circuit, but an isolated bidirectional converter may also be used. The circuit configuration of the bidirectional converter 17 will be described below.

[0033] The bidirectional converter 17 consists of a reactor 24, switching elements Q1 and Q2, diodes D1 and D2 connected in antiparallel to switching elements Q1 and Q2, respectively, and a capacitor 23. The reactor 24 may be air-core or iron-core. The switching elements Q1 and Q2 may be voltage-driven semiconductor devices such as IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0034] If the switching elements Q1 and Q2 are MOSFETs, external diodes D1 and D2 may not be connected, and body diodes for the switching elements Q1 and Q2 may be used instead. By using body diodes, the external diodes D1 and D2 can be eliminated, and the bidirectional converter 17 can be miniaturized. Alternatively, the semiconductor base material for the switching elements Q1 and Q2 and diodes D1 and D2 may be Si (silicon), or SiC (silicon carbide) or GaN (gallium nitride), which have a wider band gap than Si. By using SiC or GaN, the losses generated in the bidirectional converter 17 can be reduced compared to Si, and the bidirectional converter 17 can be miniaturized by simplifying the coolers for the switching elements Q1 and Q2 and diodes D1 and D2.

[0035] The operation of the bidirectional converter 17 and the battery 16 will be described below. Here, we will describe the operation during dump truck acceleration, that is, the operation of supplying power from the battery 16 to the inverter 14 (shown in Figure 2) via the bidirectional converter 17. Based on the current of the battery 16 detected by the current sensor 22c, the DC voltage of the rectifier 13 and inverter 14 detected by the voltage sensor 21, and the SoC of the battery 16 detected by the SoC detection device 31, the controller 30 outputs gate signals for switching elements Q1 and Q2 so that the output voltage, output current, and output power of the bidirectional converter 17 become desired values. Note that a dead time is inserted so that switching elements Q1 and Q2 are not turned ON at the same time.

[0036] When an ON signal is input to switching element Q2, a current path is formed through the battery 16, reactor 24, and switching element Q2. That is, energy is stored in reactor 24. Next, when an OFF signal is input to switching element Q2 and an ON signal is input to switching element Q1, a current path is formed through the battery 16, reactor 24, diode D1, and inverter 14 (shown in Figure 2). By operating in this manner, even when the voltage of the battery 16 is lower than the DC voltage of the rectifier 13 and inverter 14, the voltage of the battery 16 can be boosted by utilizing the energy of the reactor, and power can be supplied to the inverter 14. As mentioned above, the power supplied to the inverter 14 can be controlled by the ON ratio of switching elements Q1 and Q2.

[0037] Figure 5 is a flowchart showing the processing of the controller 30 involved in the control of the bidirectional converter 17. Each step will be explained in order below.

[0038] First, the initial SoC of the battery 16 is obtained (step 100). The initial SoC is the SoC at the start of one cycle of mining travel by the dump truck. One cycle of mining travel consists of a travel route between the loading area and the unloading area. The method for detecting the start and end points of one cycle will be described later.

[0039] Following step 100, power thresholds P1 and P2 are set (step 101). In this embodiment, power threshold P2 is set to a value equal to the rated output of the engine 11, and power threshold P1 is set to zero. Note that power threshold P1 may be set to a value that results in a zero charge / discharge balance of the battery 16 using the calculation results of mine operation, or data from the same dump truck or a different dump truck that has previously operated in the same mine may be referenced. By setting power threshold P1 to an appropriate value instead of zero in this way, it is possible to shorten the correction period for power threshold P1, which will be described later.

[0040] Following step 101, it is determined whether the required power P of the dump truck is higher than the power threshold P2 (step 102). If the required power P is higher than the power threshold P2, Mode 1 operation is performed, and the power command value of the bidirectional converter 17 is set to "P-P2" (step 103). If the required power P is less than or equal to the power threshold P2, the process proceeds to step 104.

[0041] In step 104, it is determined whether the required power P of the dump truck is equal to or greater than the power threshold P1. If the required power P is equal to or greater than the power threshold P1, Mode 2 operation is performed, and the power command value of the bidirectional converter 17 is set to "0" (step 105). If the required power P is less than the power threshold P1, Mode 3 operation is performed, and the power command value of the bidirectional converter 17 is set to "P1" (step 106).

[0042] Following steps 103, 105, or 106, it is determined whether the dump truck has completed one cycle of travel (step 107). This determination is made using the cycle completion flag, which will be described later. If the cycle completion flag is OFF, the process returns to step 102. In other words, while the dump truck is traveling, steps 102 to 106 are repeatedly executed to generate power commands for the bidirectional converter 17. If the cycle completion flag is ON, the process proceeds to step 108.

[0043] Step 108 retrieves the final SoC of battery 16. The final SoC is the SoC at the point when the dump truck completes one cycle of mining travel.

[0044] Following step 108, the correction amount α for the power threshold P1 is calculated based on the initial SoC and the final SoC (step 109). The correction amount α may be a constant value, but as shown in Figure 6, the correction amount α may be increased as the absolute value of the difference between the initial SoC and the final SoC increases. In this way, the charge / discharge balance of the battery 16 can be reduced to zero with a small number of driving cycles.

[0045] Following step 109, it is determined whether the initial SoC is higher than the final SoC (step 110). If the initial SoC is higher than the final SoC, the output power of the battery 16 exceeds the regenerated power, so the output power of the battery 16 needs to be reduced in the next cycle. If the output power of the battery 16 exceeds the regenerated power in the next cycle without reducing the output power, the SoC of the battery 16 may reach its lower limit, and the battery 16 may not be able to output power. Therefore, in this embodiment, if the initial SoC is higher than the final SoC, the power threshold P1 for the next cycle is corrected to the negative side to reduce the output power. Specifically, the power threshold P1 for the next cycle is set to "P1-α" (step 111). If the initial SoC is less than or equal to the final SoC, the process proceeds to step 112.

[0046] In step 112, it is determined whether the initial SoC is lower than the final SoC. If the initial SoC is lower than the final SoC, the output power of the battery 16 will be lower than the regenerated power, so it is necessary to increase the output power of the battery 16 in the next cycle. If the output power is not increased and the output power remains lower than the regenerated power in the next cycle, the SoC of the battery 16 may reach its upper limit, and it may become impossible to charge the battery 16. Therefore, in this embodiment, if the initial SoC is lower than the final SoC, the power threshold P1 for the next cycle is corrected to the positive side to increase the output power. Specifically, the power threshold P1 for the next cycle is set to "P1 + α" (step 113).

[0047] If step 112 determines that the initial SoC is less than or equal to the final SoC, the power threshold P1 is not corrected and the previous value is retained (step 114) because the initial SoC and the final SoC are the same. In this case, the charge-discharge balance of the battery 16 is zero in one cycle of mining operation, and Mode 1 to Mode 3 operation is possible without a shortage of battery charge in the battery 16, thus ensuring the driving performance of the dump truck.

[0048] After the corrected power threshold P1 is stored in the controller 30, the process returns to step 100 and starts another cycle of mine operation. By correcting the power threshold P1 in this way for each cycle, the bidirectional converter 17 can be controlled so that the charge / discharge balance of the battery 16 becomes zero, even if the output power and regenerated power amount for each cycle fluctuate depending on the road surface conditions, etc.

[0049] Figure 7 is a timing chart showing the change in the SoC of the battery 16 during dump truck operation. From top to bottom, it shows the required power P, the output power of the battery 16, and the SoC of the battery 16. This is an example of driving through a mine for three cycles, and the required power P is the same pattern for all three cycles, assuming driving through the same mine. Also, auxiliary power is not considered.

[0050] The operating modes of the dump truck during one cycle are described below. In the first cycle, the power threshold P1 is set to zero, and P2 is set to the rated output of the engine 11. During period (1), the required power P is higher than the power threshold P2. At this time, the power P-P2 exceeding the power threshold P2 is output from the battery 16. As a result, the SoC of the battery 16 decreases.

[0051] During period (2), the required power P is greater than or equal to the power threshold P1 and less than or equal to the power threshold P2. At this time, since the vehicle is running using only the engine 11, the output power of the battery 16 is zero, and the SoC of the battery 16 does not change.

[0052] During period (3), the vehicle is traveling downhill. At this time, the regenerative energy generated by the braking action of the dump truck is charged into the battery 16, and the SoC of the battery 16 increases.

[0053] During period (4), the required power P is higher than the power threshold P2, similar to period (1). At this time, the power P-P2 exceeding the power threshold P2 is output from the battery 16. As a result, the SoC of the battery 16 decreases.

[0054] During periods (5) and (6), the required power P is equal to or greater than the power threshold P1 and less than or equal to the power threshold P2, similar to period (2). At this time, since the vehicle is running using only the engine 11, the output power of the battery 16 is zero, and the SoC of the battery 16 does not change.

[0055] Comparing the initial SoC of the battery 16 in the first cycle with the final SoC, the final SoC is higher than the initial SoC. In other words, the output power of the battery 16 is lower than the regenerated power, so in the next cycle, the second cycle, the power threshold P1 is corrected to the positive side.

[0056] The operation of the second cycle is described below. During period (1), the required power P is higher than the power threshold P2. At this time, the power P-P2 that exceeds the power threshold P2 is output from the battery 16. As a result, the SoC of the battery 16 decreases.

[0057] During period (2), the required power P is lower than the power threshold P1. At this time, since the vehicle is running using only the battery 16, the output power of the battery 16 is equal to the required power P. As a result, the SoC of the battery 16 decreases. In the first cycle, period (2) was a mode in which the vehicle ran using only the engine 11, but in the second cycle, the power threshold P1 was corrected to the positive side, so this period switches to a mode in which the vehicle runs using only the battery 16.

[0058] During period (3), the vehicle is traveling downhill. At this time, the regenerative energy generated by the braking action of the dump truck is charged into the battery 16, and the SoC of the battery 16 increases.

[0059] During period (4), the required power P is higher than the power threshold P2, similar to period (1). At this time, the power P-P2 exceeding the power threshold P2 is output from the battery 16. As a result, the SoC of the battery 16 decreases.

[0060] During periods (5) and (6), the required power P is equal to or greater than the power threshold P1 and less than or equal to the power threshold P2, similar to period (2). At this time, since the vehicle is running using only the engine 11, the output power of the battery 16 is zero, and the SoC of the battery 16 does not change.

[0061] Comparing the initial SoC and final SoC of the battery 16 in the second cycle, the final SoC is higher than the initial SoC. In other words, the output power of the battery 16 is lower than the regenerated power, so in the next cycle, the third cycle, the power threshold P1 is corrected to the positive side.

[0062] The operation of the third cycle is described below. During period (1), the required power P is higher than the power threshold P2. At this time, the power P-P2 that exceeds the power threshold P2 is output from the battery 16. As a result, the SoC of the battery 16 decreases.

[0063] During period (2), the required power P is lower than the power threshold P1. At this time, since the vehicle is running using only the battery 16, the output power of the battery 16 is equal to the required power P. As a result, the SoC of the battery 16 decreases.

[0064] During period (3), the vehicle is traveling downhill. At this time, the regenerative energy generated by the braking action of the dump truck is charged into the battery 16, and the SoC of the battery 16 increases.

[0065] During period (4), the required power P is higher than the power threshold P2, similar to period (1). At this time, the power P-P2 exceeding the power threshold P2 is output from the battery 16. As a result, the SoC of the battery 16 decreases.

[0066] During period (5), the required power P is equal to or greater than the power threshold P1 and less than or equal to the power threshold P2, similar to period (2). At this time, since the vehicle is running using only the engine 11, the output power of the battery 16 is zero, and the SoC of the battery 16 does not change.

[0067] During period (6), the required power P is lower than the power threshold P1. At this time, since the vehicle is running using only the battery 16, the output power of the battery 16 is equal to the required power P. As a result, the SoC of the battery 16 decreases. In the second cycle, period (6) was running using only the engine 11, but in the second cycle, the power threshold P1 was corrected to the positive side, so this period switches to a mode where the vehicle runs using only the battery 16.

[0068] Comparing the initial and final SoC values ​​of the battery 16 in its third cycle, the final SoC and initial SoC are equal. This means that the charge-discharge balance of the battery 16 is zero, and the battery 16 is outputting the appropriate amount of power. Furthermore, it is able to supply power without excess or deficiency to meet the required power P, and driving performance is ensured.

[0069] Figure 8 is a flowchart showing an example of the process by which the controller 30 updates the cycle completion flag. The cycle completion flag indicates when the dump truck has completed one cycle of travel. In the example shown in Figure 7, the cycle completion flag is updated based on the dump truck's current position. Each step will be explained in order below.

[0070] First, the current location of the dump truck is detected (step 200). The current location is detected using a location detection device 32 (shown in Figure 2), such as a GPS.

[0071] Following step 200, it is determined whether the dump truck's current position matches the reference position (step 201). The reference position is any pre-set point on the travel cycle. If the current position does not match the reference position, the cycle completion flag is turned OFF (step 202). If the current position matches the reference position, the cycle completion flag is turned ON (step 203).

[0072] Figure 9 is a flowchart showing another example of the process by which the controller 30 updates the cycle completion flag. Mining dump trucks typically load or unload cargo at a specific location within the mine. Therefore, by setting the location where loading or unloading takes place as the reference position on the travel cycle, the timing of the end of a cycle can be detected based on the change in load volume. In the example shown in Figure 8, the location where loading takes place is used as the reference position. Each step will be explained in order below.

[0073] First, the load capacity of the dump truck is detected (step 300). The load capacity is detected using a load capacity detection device 33 (shown in Figure 2), such as a pressure sensor that detects the pressure of the hoist cylinder 6. Following step 300, it is determined whether or not the load capacity is increasing (step 301). If the load capacity is not increasing, the cycle completion flag is turned OFF (step 302). If the load capacity is increasing, the cycle completion flag is turned ON (step 303). If the point where the soil is discharged is used as the reference position, step 301 can be replaced with determining whether or not the load capacity is decreasing.

[0074] Figures 8 and 9 show a method for detecting the end of one cycle, but since the end of one cycle is also the start of the next cycle, this can be interpreted as a method for detecting the start of one cycle. Furthermore, the cycle completion flag update processes shown in Figures 8 and 9 may be used in combination. By selectively performing either one, the cycle completion flag update can be continued even if the position detection device 32 or the load amount detection device 33 fails. In addition, by comparing the update results of both, erroneous updates of the cycle completion flag can be prevented. Note that other methods for updating the cycle completion flag are not limited to these.

[0075] (summary) In this embodiment, a dump truck is equipped with an electric motor 10 as a power source, a generator 12 that supplies power to the electric motor 10, a battery 16 that stores the power supplied to the electric motor 10 and the regenerative power of the electric motor 10, a bidirectional converter 17 that adjusts the input and output power of the battery 16, and a controller 30 that controls the bidirectional converter 17, and the dump truck repeatedly travels in a travel cycle consisting of a travel path between a loading area and a dumping area. In this embodiment, if the required power P of the dump truck is less than a predetermined first power threshold P1, the controller 30 sets the output power command value of the battery 16 to the required power P, and if the required power P is set to a value greater than the first power threshold P1, the second power threshold P If the value is greater than 2, the output power command value is set to the difference between the required power P and the second power threshold P2. If the required power P is greater than or equal to the first power threshold P1 and less than the second power threshold P2, the output power command value is set to a value smaller than the first power threshold P1 (for example, a few percent or less of the first power threshold P1). The SoC of the battery 16 at the start of the driving cycle is detected as the initial SoC, and the charge level of the battery 16 at the end of the driving cycle is detected as the final SoC. If the final SoC is higher than the initial SoC, the first power threshold P1 is corrected to the positive side, and if the final SoC is lower than the initial SoC, the first power threshold P1 is corrected to the negative side.

[0076] In this embodiment configured as described above, the first power threshold P1 is corrected so that the initial SoC and the final SoC of each driving cycle match (so that the charge / discharge balance of the battery 16 becomes zero). This prevents over-discharge of the battery 16, thereby ensuring the driving performance of the dump truck.

[0077] Furthermore, the dump truck in this embodiment is equipped with a position detection device 32 that detects the current position of the dump truck, and the controller 30 detects the timing when the current position coincides with a predetermined reference position on the travel path as the end of the travel cycle. This makes it possible to detect the end of the travel cycle based on the position of the dump truck.

[0078] Furthermore, the controller 30 in this embodiment detects the timing when the load capacity of the dump truck increases as the end of the travel cycle. This makes it possible to detect the end of the travel cycle based on the load capacity of the dump truck.

[0079] Furthermore, in this embodiment, the controller 30 increases the positive correction amount α of the first power threshold P1 as the difference between the final SoC and the initial SoC increases when the final SoC is higher than the initial SoC, and increases the negative correction amount α of the first power threshold P1 as the difference between the initial SoC and the final SoC increases when the final SoC is lower than the initial SoC. This makes it possible to reduce the charge / discharge balance of the battery 16 to zero with a small number of driving cycles. [Examples]

[0080] Figure 10 is a flowchart showing the process related to the control of the bidirectional converter 17 of the controller 30 in the second embodiment of the present invention. The differences from the first embodiment (shown in Figure 5) will be explained below.

[0081] First, a reference SoC for the battery 16 is set (step 400). The reference SoC is an SoC capable of maximizing the performance of the battery 16. Specifically, it is an SoC capable of suppressing the degradation of the battery 16 and is set to a value (for example, 50%) that avoids full charge and over-discharge states.

[0082] Following step 400, the initial SoC is acquired and power thresholds P1 and P2 are set (step 401). Power threshold P2 is set to a value equal to the rated output of engine 11, and power threshold P1 is set to zero.

[0083] Following step 401, steps 102 to 110 are executed. If step 110 determines that the initial SoC is less than or equal to the final SoC, it is determined whether the initial SoC and the final SoC match (step 402). If the initial SoC and the final SoC do not match, in light of step 107, the final SoC is higher than the initial SoC, and the output power of the battery 16 is lower than the regenerated power, so it is necessary to increase the output power of the battery 16 in the next cycle. Therefore, in this embodiment, the power threshold P1 is corrected to the positive side to increase the output power of the next cycle. Specifically, the power threshold P1 for the next cycle is set to "P1 + α" (step 113). In this embodiment, the power threshold P1 is corrected to the positive side, but the power threshold P2 may also be corrected to the negative side to increase the output power. If the initial SoC and the final SoC match, proceed to step 403.

[0084] In step 403, it is determined whether the final SoC is lower than the reference SoC. If the final SoC is lower than the reference SoC, the output power of the battery 16 must be reduced in order to make the final SoC match the reference SoC. Therefore, in this embodiment, the power threshold P1 is corrected to the negative side to reduce the output power. Specifically, the power threshold P1 for the next cycle is set to "P1-α" (step 111). In this embodiment, the power threshold P1 is corrected to the negative side, but the power threshold P2 may also be corrected to the positive side to reduce the output power. If the final SoC is equal to or better than the reference SoC, the process proceeds to step 404.

[0085] In step 404, it is determined whether the final SoC matches the reference SoC. If the final SoC does not match the reference SoC, in light of step 403, the final SoC is higher than the reference SoC, and therefore the output power of the battery 16 needs to be increased in the next cycle. In this embodiment, the power threshold P1 is corrected to the positive side to increase the output power of the next cycle. Specifically, the power threshold P1 for the next cycle is set to "P1 + α" (step 113). In this embodiment, the power threshold P1 is corrected to the positive side, but the power threshold P2 may also be corrected to the negative side to increase the output power. If the final SoC matches the reference SoC, in light of step 402, the initial SoC and the final SoC also match. That is, the reference SoC, the initial SoC, and the final SoC match, and a power threshold P1 has been set that ensures zero charge / discharge balance for the battery 16 and driving performance. Therefore, the power threshold P1 for the next cycle follows the power threshold P1 of the previous cycle (step 114).

[0086] Figure 11 is a timing chart showing the change in the SoC of the battery 16 during dump truck operation. In the third cycle, the initial SoC and the final SoC coincide, and the charge-discharge balance becomes zero, thus ensuring the vehicle's driving performance. However, generally, if the SoC is too high or too low, the battery tends to degrade. To prevent degradation of the battery 16, it is desirable to keep the battery's SoC near the reference SoC. Therefore, in this embodiment, after the initial SoC and the final SoC coincide, the power threshold P1 is corrected so that the initial SoC and the final SoC coincide with the reference SoC.

[0087] Specifically, since the initial and final SoCs in the third cycle exceed the reference SoC, it is necessary to increase the output power of the battery 16 in order to make the initial and final SoCs match the reference SoC. Therefore, the first power threshold P1 is corrected to the positive side to increase the output power. In this way, the final SoC can be made to match the reference SoC at the end of the fourth cycle, and the initial and final SoCs can be made to match the reference SoC from the fifth cycle onward.

[0088] (summary) In this embodiment, the controller 30 corrects the first power threshold P1 to the positive side or the second power threshold P2 to the negative side if the final SoC is equal to the initial SoC and higher than a predetermined reference SoC, and corrects the first power threshold P1 to the negative side or the second power threshold P2 to the positive side if the final SoC is equal to the initial SoC and lower than the reference SoC.

[0089] In this embodiment configured as described above, it is possible to ensure the driving performance of the dump truck, similar to the first embodiment. Furthermore, by matching the initial SoC and the final SoC to a reference SoC, it is possible to suppress the degradation of the storage battery 16. [Examples]

[0090] Figure 12 is a flowchart showing the processing of the controller 30 involved in the control of the bidirectional converter 17 in the third embodiment of the present invention. The differences from the first embodiment (shown in Figure 5) will be explained below.

[0091] In the power conversion system of the first embodiment, the first power threshold P1 was corrected and the second power threshold P2 was fixed. However, in the power conversion system of this embodiment, the first power threshold P1 is fixed and the second power threshold P2 is corrected. Specifically, if it is determined in step 110 that the initial SoC is higher than the final SoC, the second power threshold P2 is set to "P2 + α" (step 500). This reduces the output power of the battery 16 in the next cycle.

[0092] If step 112 determines that the initial SoC is lower than the final SoC, the second power threshold P2 is set to "P2-α" (step 501). This increases the output power of the battery 16 in the next cycle.

[0093] If step 112 determines that the initial SoC is equal to or better than the final SoC, then the second power threshold P2 is not corrected and the previous value is retained because the initial SoC and the final SoC are the same (step 502).

[0094] By correcting the second power threshold P2 in this way, it is possible to ensure the vehicle's driving performance while keeping the charge / discharge balance of the battery 16 at zero, similar to the power conversion system in the first embodiment. However, the upper limit of the second power threshold P2 must be less than or equal to the rated output of the engine 11. In Figure 3, when the required power P is greater than or equal to the first power threshold P1 and less than or equal to the second power threshold P2, it becomes Mode 2, a mode in which the vehicle runs using only the output of the engine 11. Here, if the second power threshold P2 is set higher than the rated output of the engine 11, the engine 11 alone will not have enough power. For example, if the first power threshold P1 is 500kW and the rated output of the engine 11 is 2000kW, then if the second power threshold P2 is 2500kW, the vehicle will run using only the engine 11 when the required power P is between 500kW and 2500kW. However, since the rated output of the engine 11 is 2000kW, there will be a 500kW shortage when the required power P is 2500kW, resulting in reduced driving performance. Therefore, in this embodiment of the power conversion system, it is desirable to set the upper limit of the second power threshold P2 to be less than or equal to the rated output of the engine 11, so that the corrected second power threshold P2 does not exceed the rated output of the engine 11.

[0095] (summary) In this embodiment, a dump truck is equipped with an electric motor 10 as a power source, a generator 12 that supplies power to the electric motor 10, a battery 16 that stores the power supplied to the electric motor 10 and the regenerative power of the electric motor 10, a bidirectional converter 17 that adjusts the input and output power of the battery 16, and a controller 30 that controls the bidirectional converter 17, and the dump truck repeatedly travels in a travel cycle consisting of a travel path between a loading area and a dumping area. The controller 30 sets the output power command value of the battery 16 to the required power P if the required power P of the dump truck is less than a predetermined first power threshold P1, and sets the second power threshold to a value greater than the first power threshold P1. If the output power command value is greater than P2, the output power command value is set to the difference between the required power P and the second power threshold P2. If the required power P is greater than or equal to the first power threshold P1 and less than the second power threshold P2, the output power command value is set to a value smaller than the first power threshold P1 (for example, a few percent or less of the power threshold P1). The SoC of the battery 16 at the start of the driving cycle is detected as the initial SoC, and the charge rate of the battery 16 at the end of the driving cycle is detected as the final SoC. If the final SoC is higher than the initial SoC, the second power threshold P2 is corrected to the negative side, and if the final SoC is lower than the initial SoC, the second power threshold P2 is corrected to the positive side.

[0096] In this embodiment configured as described above, the second power threshold P2 is corrected so that the initial SoC and the final SoC of each driving cycle match (so that the charge / discharge balance of the battery 16 becomes zero). This prevents over-discharge of the battery 16, thereby ensuring the driving performance of the dump truck.

[0097] Furthermore, in this embodiment, the controller 30 increases the negative correction amount α of the second power threshold P2 as the difference between the final SoC and the initial SoC increases when the final SoC is higher than the initial SoC, and increases the positive correction amount α of the second power threshold P2 as the difference between the initial SoC and the final SoC increases when the final SoC is lower than the initial SoC. This makes it possible to reduce the charge / discharge balance of the battery 16 to zero with a small number of driving cycles.

[0098] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible to add parts of the configuration of one embodiment to the configuration of another embodiment, and it is also possible to delete parts of the configuration of one embodiment or replace parts of parts of another embodiment. [Explanation of symbols]

[0099] 1...Frame, 2...Front wheel, 3...Rear wheel, 4...Cab, 5...Body, 6...Hoist cylinder, 7...Grid resistor, 8...Control cabinet, 9...Fuel tank, 10...Motor (electric motor), 11...Engine, 12...Generator, 13...Rectifier, 14...Inverter, 15...Speed ​​sensor, 16...Battery, 17...Bidirectional converter, 18...Grid chopper, 21...Voltage sensor, 22a,22b,22c...Current sensor, 23...Capacitor, 24...Reactor, 30...Controller, 31...SoC detection device, 32...Position detection device, 33...Load detection device, D1,D2...Diode, Q1,Q2...Switching element.

Claims

1. The electric motor is the power source, A generator that supplies power to the aforementioned electric motor, The engine that drives the aforementioned generator, A battery that stores the power supplied to the electric motor and the regenerative power of the electric motor, A bidirectional converter that adjusts the output power of the aforementioned battery, The system includes a controller that controls the bidirectional converter, In a dump truck that repeatedly travels a driving cycle consisting of a driving route between a loading area and a loading area, The aforementioned controller, If the power required by the dump truck is less than a predetermined first power threshold, a mode is set in which only the battery among the engine and the battery is used to supply the required power, and the output power command value of the battery is set to the required power. If the required power is greater than a second power threshold set to a value greater than the first power threshold, a mode is set to supply the required power using both the engine and the storage battery, and the output power command value of the storage battery is set to the difference between the required power and the second power threshold. If the required power is equal to or greater than the first power threshold and less than the second power threshold, a mode is set in which the required power is supplied using only the engine among the engine and the storage battery, and the output power command value of the storage battery is set to a value smaller than the first power threshold. The charge level of the battery at the start of the aforementioned driving cycle is detected as the initial SoC. The charge level of the battery at the end of the aforementioned driving cycle is detected as the final SoC. If the final SoC is higher than the initial SoC, the first power threshold is corrected to the positive side, or the second power threshold is corrected to the negative side. If the final SoC is lower than the initial SoC, the first power threshold is corrected to the negative side, or the second power threshold is corrected to the positive side, and If the final SoC is equal to the initial SoC and higher than a predetermined reference SoC, the first power threshold is corrected to the positive side, or the second power threshold is corrected to the negative side. If the final SoC is equal to the initial SoC and lower than the reference SoC, the first power threshold is corrected to the negative side, or the second power threshold is corrected to the positive side. A dump truck characterized by the following features.

2. In the dump truck according to claim 1, The dump truck is equipped with a position detection device that detects its current position, The controller detects the timing when the current position coincides with a predetermined reference position on the travel path as the end of the travel cycle. A dump truck characterized by the following features.

3. In the dump truck according to claim 1, The controller detects the timing when the load capacity of the dump truck is increasing as the end of the driving cycle. A dump truck characterized by the following features.

4. In the dump truck according to claim 1, The aforementioned controller, If the final SoC is higher than the initial SoC, the positive correction amount of the first power threshold is increased as the difference obtained by subtracting the initial SoC from the final SoC increases, or the negative correction amount of the second power threshold is increased. If the final SoC is lower than the initial SoC, the negative correction amount of the first power threshold is increased, or the positive correction amount of the second power threshold is increased, as the difference obtained by subtracting the final SoC from the initial SoC increases. A dump truck characterized by the following features.

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