dump truck

Abstract

This electric dump truck ensures a hydraulic source necessary when being towed without depending on an external hydraulic source, while preventing early deterioration of a battery. The electric dump truck 1 comprises: a travel motor 16; a hydraulic pump 20 that supplies pressure oil to at least one among a brake device 17 and a steering device 18; a hydraulic pump drive motor 23 that drives the hydraulic pump 20; a battery 24 that supplies power to the travel motor 16 and the hydraulic pump drive motor 23; and a control device 37 that controls power supply from the battery 24 to the travel motor 16 and the hydraulic pump drive motor 23. In a towed mode in which the dump truck 1 is towed, the control device 37 performs control to supply the power of the battery 24 only to the hydraulic pump drive motor 23.

Description

Technical Field

[0001] The present invention relates to an electric dump truck powered by a battery.

Background Art

[0002] When a dump truck becomes unable to move on its own due to some abnormality including equipment failure and power outage, it is towed to a target location such as a work base.

[0003] As a method of towing a dump truck that has become unable to move on its own, a towing method in which it is towed while being connected by a wire rope to another vehicle is common. In the case of this towing method, a passenger is also required on the side of the dump truck that has become unable to move on its own, and braking operation and steering operation by the passenger are also required.

[0004] A dump truck that has become unable to move on its own often cannot drive a hydraulic pump that sends pressure oil to the braking device and the steering device. In order to send pressure oil to the braking device and the steering device, it is necessary to connect the hydraulic circuit of another vehicle and the hydraulic circuit of the dump truck that has become unable to move on its own with a hydraulic hose, and there are problems such as it taking a lot of time and effort. Therefore, a method of sending pressure oil to the braking device and the steering device of a dump truck that has become unable to move on its own without taking much time and effort during towing has been studied (for example, Patent Document 1).

[0005] Patent Document 1 discloses a dump truck including an accumulator that accumulates pressure oil, and a bleed-down control prohibition device that prohibits releasing the pressure stored in the accumulator during towing.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] However, in the dump truck disclosed in Patent Document 1, situations could arise where the brake and steering systems could not be driven, such as when the accumulator did not store sufficient pressure. As a result, the dump truck disclosed in Patent Document 1 may not be able to stably tow to a target location such as a work base.

[0008] In addition, electric dump trucks use their onboard motors to drive the hydraulic pumps. This meant that if the motors in electric dump trucks were kept running until the battery ran out, the batteries could deteriorate prematurely.

[0009] In view of the above circumstances, the present invention aims to prevent premature deterioration of the battery in an electric dump truck while ensuring that the hydraulic power source necessary for towing is not reliant on an external hydraulic power source. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides an electric dump truck comprising: a travel motor; a hydraulic pump that supplies pressurized oil to at least one of a brake system and a steering system; a hydraulic pump drive motor that drives the hydraulic pump; a battery that supplies power to the travel motor and the hydraulic pump drive motor; and a control device that controls the power supply from the battery to the travel motor and the hydraulic pump drive motor, wherein the control device controls the supply of power from the battery only to the hydraulic pump drive motor when the dump truck is in towing mode. [Effects of the Invention]

[0011] According to the present invention, in an electric dump truck, it is possible to prevent premature degradation of the battery while securing the hydraulic power required when being towed without relying on an external hydraulic power source. [Brief explanation of the drawing]

[0012] [Figure 1] A side view showing the schematic configuration of a dump truck when being towed according to this embodiment. [Figure 2] This figure shows a schematic configuration of the hydraulic circuit in a dump truck according to this embodiment. [Figure 3] A schematic electrical circuit diagram of the dump truck according to this embodiment. [Figure 4] A flowchart illustrating an example of the operation of the control device for towing a dump truck according to this embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. Components denoted by the same reference numerals in each embodiment have the same function in each embodiment unless otherwise specified, and their description will be omitted.

[0014] Figure 1 is a side view showing the schematic configuration of the dump truck 1 when being towed according to this embodiment. The dump truck 1 shown in Figure 1 is connected to another vehicle 3 by a wire rope 2. The other vehicle 3, while connected to the dump truck 1 by the wire rope 2, tows the dump truck 1, which has become unable to move under its own power, to a target location such as a work base. The other vehicle 3 may be the same type of vehicle as the dump truck 1, or it may be a vehicle specifically designed for towing, as long as it is capable of towing the dump truck 1 that has become unable to move under its own power.

[0015] Dump truck 1 is an electric dump truck powered by a battery. Dump truck 1 is used, for example, to transport excavated soil or minerals in an open-pit mine.

[0016] As shown in FIG. 1, the dump truck 1 is composed of front wheels 11, rear wheels 12, and a body 13 which is a sturdy frame connected to the front wheels 11 and rear wheels 12. A loading platform 14 for loading earth and sand is mounted on the body 13. The body 13 and the loading platform 14 are connected by a hoist device 15.

[0017] Among the front and rear wheels 11 and 12 of the dump truck 1, the rear wheels 12, which are the left and right wheels on the rear side, serve as drive wheels, and the front wheels 11, which are the left and right wheels on the front side, serve as driven wheels. The dump truck 1 operates in a rear-wheel drive mode. A traveling motor 16 is provided on the rotating shaft portion of the rear wheels 12. The dump truck 1 includes brake devices 17 attached to each of the front and rear wheels 11 and 12, and a steering device 18 interposed between the front and rear wheels 11 and 12 and the body 13.

[0018] The dump truck 1 has a normal mode which is an operation mode in which it travels by rotating the rear wheels 12 as drive wheels by the traveling motor 16, and a towing mode which is an operation mode when the rear wheels 12 are not driven and all the wheels 11 and 12 become driven wheels and the dump truck 1 is towed by another vehicle or the like. The dump truck 1 drives the brake device 17 and the steering device 18 in either the normal mode or the towing mode.

[0019] FIG. 2 is a diagram showing a schematic configuration of a hydraulic circuit in the dump truck 1 according to the present embodiment.

[0020] The hoist device 15 including a hoist cylinder, the brake device 17 including a brake piston, and the steering device 18 including a steering cylinder are part of the hydraulic actuators provided in the dump truck 1. As shown in FIG. 2, the dump truck 1 has a hydraulic circuit for driving the hydraulic actuators.

[0021] As devices constituting the hydraulic circuit, the dump truck 1 includes a hydraulic oil tank 19, a hydraulic pump 20, a control valve 21, and an accumulator 22.

[0022] The hydraulic oil tank 19 is connected to hydraulic actuators such as the brake device 17 and the steering device 18, the hydraulic pump 20, the control valve 21, and the accumulator 22.

[0023] The hydraulic pump 20 is connected to the control valve 21 and supplies pressure oil to the hoist device 15, the brake device 17, the steering device 18, and the accumulator 22 via the control valve 21. Further, the hydraulic pump 20 is connected to a hydraulic pump drive motor 23, which will be described later, and is driven by the hydraulic pump drive motor 23.

[0024] The control valve 21 is connected to the hydraulic pump 20, the hoist device 15, the brake device 17, the steering device 18, and the accumulator 22. The control valve 21 distributes the pressure oil supplied from the hydraulic pump 20 to the hoist device 15, the brake device 17, the steering device 18, and the accumulator 22. Further, the control valve 21 is connected to the hydraulic oil tank 19 and returns the surplus hydraulic oil that is not distributed to any of the above devices to the hydraulic oil tank 19.

[0025] The hoist device 15 is driven by the pressure oil supplied from the hydraulic pump 20 via the control valve 21, and extends or contracts the hoist cylinder.

[0026] The brake device 17 is a hydraulic brake device driven by the pressure oil supplied from the hydraulic pump 20 via the control valve 21.

[0027] The steering device 18 is a hydraulic steering device driven by the pressure oil supplied from the hydraulic pump 20 via the control valve 21.

[0028] The accumulator 22 is a device that stores pressure from pressurized oil supplied from the hydraulic pump 20 via the control valve 21. The accumulator 22 is connected to the brake system 17 and the steering system 18, and together with the hydraulic pump 20, it may supply pressurized oil (pressure) that has been stored in the brake system 17 or the steering system 18.

[0029] Figure 3 is a schematic electrical circuit diagram of the dump truck 1 according to this embodiment.

[0030] As shown in Figures 2 and 3, the dump truck 1 is equipped with a hydraulic pump drive motor 23 to drive the hydraulic pump 20. As shown in Figure 3, the dump truck 1 has an electrical circuit to drive the travel motor 16 and the hydraulic pump drive motor 23.

[0031] The dump truck 1 is equipped with the following devices that constitute its electrical circuit: a battery 24, a first sensor 25, a DC / DC converter 26, an inverter 27 for the drive motor, a first switch 28, an inverter 29 for the hydraulic pump drive motor, and a control device 37. Furthermore, the dump truck 1 is equipped with a resistor 31, a chopper 32, a pantograph 33, a second sensor 34, and a second switch 35.

[0032] Furthermore, the dump truck 1 is equipped with a towing switch 30, which is a switch that accepts input operations to switch the setting between normal mode and towing mode. The towing switch 30 is located in the driver's cab of the dump truck 1 and is connected to the control device 37. The towing switch 30 transmits a signal to the control device 37 to set the vehicle to normal mode or towing mode according to the input operation of the driver.

[0033] Furthermore, the dump truck 1 is equipped with a notification device 36 that includes a display, speaker, buzzer, indicator lamp, and rotating light, and that informs the occupant of the status of the dump truck 1 based on control signals from the control device 37.

[0034] The battery 24 supplies power to the travel motor 16 and the hydraulic pump drive motor 23. The battery 24 is connected to the travel motor 16 via a DC / DC converter 26 and an inverter 27 for the travel motor. The battery 24 is connected to the hydraulic pump drive motor 23 via a DC / DC converter 26 and an inverter 29 for the hydraulic pump drive motor.

[0035] The drive motor 16 is an electric motor powered by electricity supplied from the battery 24. The drive motor 16 is an AC motor and is connected to the drive motor inverter 27. The drive motor 16 is driven by electricity supplied from the battery 24 via the DC / DC converter 26 and the drive motor inverter 27.

[0036] Furthermore, the drive motor 16 acts as a generator when it rotates, generating regenerative power. The regenerative power generated by the drive motor 16 is supplied to the battery 24. The drive motor 16 also functions as a regenerative braking mechanism, generating rotational resistance as regenerative power is generated.

[0037] The hydraulic pump drive motor 23 is an electric motor powered by electricity supplied from the battery 24. The hydraulic pump drive motor 23 is an AC motor and is connected to the inverter 29 for the hydraulic pump drive motor. The hydraulic pump drive motor 23 is driven by electricity supplied from the battery 24 via the DC / DC converter 26 and the inverter 29 for the hydraulic pump drive motor.

[0038] The first sensor 25 is located between the battery 24 and the DC / DC converter 26. The first sensor 25 is a voltage sensor that detects the voltage across the battery 24 (the voltage output by the battery 24). The first sensor 25 transmits the detected battery 24 voltage to the control device 37.

[0039] The DC / DC converter 26 is installed between the battery 24 and the inverter 27 for the drive motor. Based on a control command from the control device 37, the DC / DC converter 26 boosts or lowers the DC power supplied from the battery 24 to a predetermined voltage and supplies it to the inverter 27 for the drive motor. The DC / DC converter 26 is also installed between the battery 24 and the inverter 29 for the hydraulic pump drive motor. Based on a control command from the control device 37, the DC / DC converter 26 boosts or lowers the DC power supplied from the battery 24 to a predetermined voltage and supplies it to the inverter 29 for the hydraulic pump drive motor. Based on a control command from the control device 37, the DC / DC converter 26 boosts or lowers the DC power supplied from the inverter 27 for the drive motor to a predetermined voltage and charges the battery 24.

[0040] The travel motor inverter 27 is installed between the DC / DC converter 26 and the travel motor 16. Based on control commands from the control device 37, the travel motor inverter 27 converts the DC power supplied from the DC / DC converter 26 into AC power and supplies it to the travel motor 16. In addition, based on control commands from the control device 37, the travel motor inverter 27 converts the AC power, which is regenerative power generated by the travel motor 16, into DC power and supplies it to the DC / DC converter 26.

[0041] The first switch 28 is a switch that allows or stops the supply of power from the battery 24 to the travel motor 16. The first switch 28 is located between the DC / DC converter 26 and the travel motor inverter 27. Based on a control signal from the control device 37, the first switch 28 closes or opens to allow or stop the supply of power from the battery 24 to the travel motor 16.

[0042] The inverter 29 for the hydraulic pump drive motor is installed between the DC / DC converter 26 and the hydraulic pump drive motor 23. Based on control commands from the control device 37, the inverter 29 converts the DC power supplied from the DC / DC converter 26 into AC power and supplies it to the hydraulic pump drive motor 23.

[0043] The resistor 31 and the chopper 32 are connected in parallel to the travel motor inverter 27 connected to the travel motor 16, with the resistor 31 converting the regenerative power generated by the travel motor 16 into heat. The chopper 32 controls the amount of regenerative power supplied to the resistor 31 based on control commands from the control device 37.

[0044] As shown in Figure 1, the pantograph 33 is mounted on the front upper part of the dump truck 1 and is configured to extend and retract vertically by operation by the driver of the dump truck 1. When the pantograph 33 extends upward, it comes into contact with the trolley wire or the like and receives power from the trolley wire or the like. When the pantograph 33 retracts downward, it moves away from the trolley wire or the like and stops receiving power from the trolley wire or the like. As shown in Figure 3, the pantograph 33 is connected to the traction motor 16 via the traction motor inverter 27 and to the battery 24 via the DC / DC converter 26.

[0045] A dump truck 1 equipped with a pantograph 33 can also use a location where it can receive power via the pantograph 33, such as a trolley wire, as a target point when being towed.

[0046] The second sensor 34 is located between the pantograph 33 and the DC / DC converter 26. The second sensor 34 is also located between the pantograph 33 and the inverter 27 for the traction motor. The second sensor 34 is a voltage sensor that detects the voltage of power supplied via the pantograph 33 from the trolley wire or the like, or the voltage of regenerative power generated by the traction motor 16. The second sensor 34 transmits the detected voltage of power supplied from the trolley wire or the regenerative power generated by the traction motor 16 to the control device 37.

[0047] The second switch 35 is a switch that allows or stops the supply of power from the pantograph 33 to the battery 24 or the running motor 16. The second switch 35 is located between the pantograph 33 and the inverter 27 for the running motor. The second switch 35 is also located between the pantograph 33 and the DC / DC converter 26. Based on a control signal from the control device 37, the second switch 35 opens or closes in conjunction with the vertical extension and retraction of the pantograph 33 to allow or stop the supply of power from the pantograph 33 to the battery 24 or the running motor 16.

[0048] The control device 37 is comprised of a processor such as a CPU, memory, and input / output interfaces. Based on signals from each component shown in Figure 3, the control device 37 controls the operation of each component of the dump truck 1 by executing a program stored in memory using the CPU.

[0049] The control device 37 estimates the remaining capacity of the battery 24 based on the voltage of the battery 24 transmitted from the voltage sensor provided by the first sensor 25. The remaining capacity of the battery 24 is expressed as a percentage of the remaining capacity after the battery 24 has been fully charged to 100% capacity and then discharged.

[0050] The control device 37 controls the supply of power from the battery 24 to the drive motor 16 to stop if the estimated remaining charge of the battery 24 is less than or equal to a first specified value D1. The first specified value D1 is a preset remaining charge value of the battery 24 that indicates the dump truck 1 is unable to move under its own power. The first specified value D1 is a remaining charge value of the battery 24 that is greater than 0%. The first specified value D1 is a remaining charge value of the battery 24 that is capable of driving the hydraulic pump drive motor 23. The first specified value D1 is a value that can be changed depending on the driving environment, etc. For example, the first specified value D1 may be 10%.

[0051] Furthermore, the control device 37 preferably opens the first switch 28 to stop the power supply from the battery 24 to the travel motor 16 when the estimated remaining charge of the battery 24 is less than or equal to the first specified value D1. In addition, the control device 37 may control the inverter 29 for the hydraulic pump drive motor to stop the power supply from the battery 24 to the hydraulic pump drive motor 23 when the estimated remaining charge of the battery 24 is less than or equal to the first specified value D1.

[0052] The control device 37 sets the operating mode of the dump truck 1 to either normal mode or towing mode based on the signal transmitted from the towing switch 30. Specifically, when the remaining charge of the battery 24 is less than or equal to a first specified value D1, the control device 37 sets the operating mode of the dump truck 1 to towing mode when it receives a signal from the towing switch 30 to set it to towing mode. Also, when the remaining charge of the battery 24 is less than or equal to the first specified value D1, and the operating mode of the dump truck 1 is set to towing mode, the control device 37 sets the operating mode of the dump truck 1 to normal mode when it receives a signal from the towing switch 30 to set it to normal mode, i.e., to cancel the towing mode.

[0053] When the dump truck 1 is in towing mode, the control device 37 controls the supply of power from the battery 24 only to the hydraulic pump drive motor 23, which is one of the electric components that perform rotational or linear motion using the battery 24 as a power source in normal mode. The control device 37 does not prevent the supply of power to necessary devices when power is required for the operation of the notification device or regenerative power in normal mode or in towing mode.

[0054] The control device 37 may also control the inverter 27 for the traction motor to constantly generate regenerative braking to an extent that does not hinder traction when in traction mode.

[0055] In towing mode, the control device 37 controls the regenerative power generated by the drive motor 16 to charge the battery 24. Specifically, in towing mode, the control device 37 controls the drive motor inverter 27 and the DC / DC converter 26 to charge the battery 24 with the regenerative power generated by the drive motor 16.

[0056] The control device 37 issues an alarm to the notification device 36 when the vehicle is in towing mode and the remaining charge of the battery 24 is less than or equal to a second specified value D2, which is less than a first specified value D1. Specifically, the control device 37 controls the notification device 36 to issue an alarm to inform the passenger that the battery 24 is running low when the vehicle is in towing mode and the remaining charge of the battery 24 is less than or equal to a second specified value D2, which is less than a first specified value D1. The second specified value D2 is a preset value for the remaining charge of the battery 24 that is greater than 0% and less than the first specified value D1. The second specified value D2 is a value that can be changed depending on the driving environment, etc. For example, the second specified value D2 may be 3% to 5%.

[0057] The control device 37 sets the upper limit L of the rotational speed of the hydraulic pump drive motor 23 to a lower value than in the normal mode when the vehicle is driven by the travel motor 16, in the towing mode. Specifically, the control device 37 controls the inverter 29 for the hydraulic pump drive motor to set the upper limit L of the rotational speed of the hydraulic pump drive motor 23 to an upper limit L1 or L2, which is lower than the upper limit L0 in the normal mode, in the towing mode. Upper limit L1 is an upper limit L that is lower than the upper limit L0 in the normal mode. Also, upper limit L2 is an upper limit L that is lower than the upper limit L1. Preferably, in the towing mode, the control device 37 changes the upper limit L of the rotational speed of the hydraulic pump drive motor 23 according to the remaining charge of the battery 24. Specifically, the control device 37 controls the inverter 29 for the hydraulic pump drive motor to set the upper limit L of the rotational speed of the hydraulic pump drive motor 23 to an upper limit L1 or L2, which is lower than the upper limit L0 in the normal mode, according to the remaining charge of the battery 24, in the towing mode. The control device 37 sets the upper limit L in the order of upper limit L0, upper limit L1, and upper limit L2, so that the upper limit L of the rotational speed becomes lower than the current value as the remaining charge of the battery 24 decreases.

[0058] Figure 4 is a flowchart showing an example of the operation of the control device 37 related to the towing of the dump truck 1 according to this embodiment.

[0059] In the example shown in Figure 4, the default open / closed state of the first switch 28 is pre-set to the closed state, which allows power supply from the battery 24 to the travel motor 16. In the example shown in Figure 4, the default open / closed state of the second switch 35 is pre-set to the open state, which stops power supply from the pantograph 33 to the battery 24 or the travel motor 16.

[0060] The control device 37 estimates the remaining charge of the battery 24 based on the voltage of the battery 24 received from the first sensor (step S1).

[0061] The control device 37 determines whether the remaining charge of the battery 24 is less than or equal to a first specified value D1 (step S2). The control device 37 repeats the process of step S1 and the determination of step S2 until it determines that the remaining charge of the battery 24 is less than or equal to the first specified value D1 (if No in step S2).

[0062] If the control device 37 determines that the remaining charge of the battery 24 is less than or equal to a first specified value D1 (Yes in step S2), it controls the inverter 27 for the travel motor to stop supplying power from the battery 24 to the travel motor 16 (step S3).

[0063] After stopping the power supply from the battery 24 to the drive motor 16, the control device 37 checks whether it has received a signal from the traction switch 30 to set the traction mode (step S4).

[0064] When the control device 37 receives a signal from the towing switch 30 to set the towing mode (Yes in step S4), it sets the operating mode of the dump truck 1 to towing mode. Subsequently, the control device 37 controls the DC / DC converter 26 and the inverter 29 for the hydraulic pump drive motor to supply power to the hydraulic pump drive motor 23 from the battery 24 (step S5).

[0065] As a result of the process in step S5, power is supplied from the battery 24 to the hydraulic pump drive motor 23, enabling the brake system 17 and steering system 18 to be driven. Then, the dump truck 1 begins towing while coupled to the other vehicle 3.

[0066] When towing begins, the drive motor 16 of the dump truck 1 rotates in accordance with the rotation of the tires. In this case, the control device 37 controls the inverter 27 for the drive motor to constantly generate regenerative braking to an extent that does not hinder towing (step S6). As a result, the drive motor 16 functions as a generator and generates regenerative power.

[0067] In traction mode, the control device 37 controls the drive motor inverter 27 and the DC / DC converter 26 so that the regenerative power generated by the drive motor 16 is used to charge the battery 24 (step S7).

[0068] The control device 37 determines, in the towing mode, whether the remaining charge of the battery 24 is less than or equal to a second specified value D2, which is less than a first specified value D1 (step S8).

[0069] If the control device 37 determines that the remaining charge of the battery 24 is less than or equal to the second specified value D2 (Yes in step S8), it controls the notification device 36 to issue an alarm to inform the passenger that the remaining charge of the battery 24 is low (step S9).

[0070] In towing mode, the control device 37 checks whether it has received a signal from the towing switch 30 to cancel towing mode if the remaining charge of the battery 24 is greater than the second specified value D2 (No in step S8), or after an alarm has been issued by the notification device 36 (step S10).

[0071] If the control device 37 receives a signal from the towing switch 30 to cancel the towing mode (Yes in step S10), it cancels the towing mode, which is the operating mode of the dump truck 1, and terminates the control device 37's operation processing related to towing. The control device 37 repeats the determination in step S8, the processing in step S9, and the determination in step S10 (No in step S10) until it receives a signal from the towing switch 30 to cancel the towing mode.

[0072] As described above, the dump truck 1 according to this embodiment includes a travel motor 16, a hydraulic pump 20 that supplies pressurized oil to at least one of the brake device 17 and the steering device 18, and a hydraulic pump drive motor 23 that drives the hydraulic pump 20. The dump truck 1 according to this embodiment is an electric dump truck that includes a battery 24 that supplies power to the travel motor 16 and the hydraulic pump drive motor 23, and a control device 37 that controls the power supply from the battery 24 to the travel motor 16 and the hydraulic pump drive motor 23. In the dump truck 1 according to this embodiment, the control device 37 controls the supply of power from the battery 24 only to the hydraulic pump drive motor 23 when the dump truck 1 is in towing mode.

[0073] With this configuration, the dump truck 1 according to this embodiment supplies power from the battery 24 to the hydraulic pump drive motor 23 when in towing mode. As a result, the dump truck 1 according to this embodiment can drive the brake device 17 and steering device 18, which are the minimum necessary when being towed, using the remaining capacity of its own battery 24 without relying on external devices. Furthermore, since the dump truck 1 according to this embodiment limits the power supply from the battery 24 to the hydraulic pump drive motor 23 when in towing mode, unnecessary consumption of the battery 24 can be suppressed. As a result, the dump truck 1 according to this embodiment can suppress the premature deterioration of the battery 24. Therefore, according to the dump truck 1 according to this embodiment, in an electric dump truck, it is possible to secure the hydraulic power source necessary when being towed without relying on an external hydraulic power source, while preventing the premature deterioration of the battery.

[0074] Furthermore, in this embodiment, the dump truck 1 has a control device 37 that, when in towing mode, controls the regenerative power generated by the drive motor 16 to charge the battery 24.

[0075] With this configuration, the dump truck 1 according to this embodiment can effectively utilize the regenerative power generated by the drive motor 16 to charge the battery 24, thereby providing the power for the battery 24, which is the main source of the hydraulic power required when being towed. As a result, the dump truck 1 according to this embodiment can extend the towing time while preventing the battery 24 from reaching 0% charge, thanks to the regenerative power charged in the battery 24. Therefore, the dump truck 1 according to this embodiment makes it easy to secure the hydraulic power required when being towed without relying on an external hydraulic power source, while preventing premature deterioration of the battery.

[0076] Furthermore, in this embodiment, the dump truck 1 has a control device 37 that, when in towing mode, sets the upper limit L of the rotational speed of the hydraulic pump drive motor 23 to a lower value than in normal mode when the truck is driven by the travel motor 16.

[0077] This configuration allows the dump truck 1 according to this embodiment to maintain the minimum necessary braking and steering performance while suppressing unnecessary consumption of the battery 24. Therefore, according to the dump truck 1 according to this embodiment, it is easy to secure the hydraulic power source necessary when being towed without relying on an external hydraulic power source, while preventing premature deterioration of the battery.

[0078] Furthermore, in the dump truck 1 according to this embodiment, the control device 37 changes the upper limit L of the rotational speed of the hydraulic pump drive motor 23 according to the remaining charge of the battery 24.

[0079] With this configuration, the dump truck 1 according to this embodiment can appropriately suppress unnecessary consumption of the battery 24 according to the remaining charge of the battery 24 while ensuring the minimum necessary braking and steering performance. Therefore, the dump truck 1 according to this embodiment makes it easy to secure the hydraulic power source necessary when being towed without relying on an external hydraulic power source, while preventing premature deterioration of the battery.

[0080] Furthermore, in this embodiment, the dump truck 1 has a control device 37 that stops supplying power from the battery 24 to the drive motor 16 when the remaining charge of the battery 24 is less than or equal to a first specified value D1.

[0081] With this configuration, the dump truck 1 according to this embodiment stops supplying power from the battery 24 to the drive motor 16 when the remaining charge of the battery 24 is less than or equal to the first specified value D1, thereby preventing the discharge of the battery 24 when the remaining charge of the battery 24 is greater than 0%. As a result, the dump truck 1 according to this embodiment makes it easy to prevent premature deterioration of the battery 24. Therefore, the dump truck 1 according to this embodiment makes it easy to secure the hydraulic power source necessary when being towed without relying on an external hydraulic power source, while preventing premature deterioration of the battery.

[0082] Furthermore, the dump truck 1 according to this embodiment is further equipped with an alarm device 36 that issues an alarm. In the dump truck 1 according to this embodiment, the control device 37 causes the alarm device 36 to issue an alarm when the towing mode is in operation and the remaining charge of the battery 24 is less than or equal to a second specified value D2, which is less than a first specified value D1.

[0083] With this configuration, the dump truck 1 according to this embodiment can prevent excessive discharge of the battery 24 by notifying the occupant not to completely drain the battery 24 until its remaining charge reaches 0%. Therefore, according to the dump truck 1 according to this embodiment, premature battery degradation is further reduced.

[0084] The dump truck 1 according to this embodiment may also be equipped with a towing switch 30 that accepts an input operation to switch the setting between normal mode and towing mode. The control device 37 may set the operating mode to towing mode by receiving the input signal from the towing switch 30 and supply power from the battery 24 only to the hydraulic pump drive motor 23.

[0085] As a result, the dump truck 1 according to this embodiment sets its operating mode to towing mode when the control device 37 receives a signal from the towing switch 30 to set it to towing mode. In other words, the dump truck 1 according to this embodiment does not automatically switch from normal mode to towing mode until it receives a signal from the towing switch 30 to set it to towing mode. This suppresses the occurrence of unintended switching to an operating mode, and allows the operating mode to be switched at the timing intended by the occupant. As a result, the dump truck 1 according to this embodiment operates in an operating mode that aligns with the occupant's intentions. Therefore, the dump truck 1 according to this embodiment can improve safety.

[0086] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention as described in the claims. The present invention can be made by adding the configuration of one embodiment to the configuration of another embodiment, replacing the configuration of one embodiment with that of another embodiment, or deleting a part of the configuration of one embodiment. [Explanation of Symbols]

[0087] 1...Dump truck, 16...Traction motor, 17...Brake system, 18...Steering system, 20...Hydraulic pump, 23...Hydraulic pump drive motor, 24...Battery, 30...Towing switch, 36...Notification device, 37...Control device, D1...First specified value, D2...Second specified value, L, L0, L1, L2...Upper limit of rotational speed of hydraulic pump drive motor

Claims

1. An electric dump truck comprising: a travel motor; a hydraulic pump that supplies pressurized oil to at least one of a brake system and a steering system; a hydraulic pump drive motor that drives the hydraulic pump; a battery that supplies power to the travel motor and the hydraulic pump drive motor; and a control device that controls the power supply from the battery to the travel motor and the hydraulic pump drive motor, A towing switch that accepts an input operation to switch the operating mode of the dump truck between a normal mode in which power is supplied from the battery to the hydraulic pump drive motor and the travel motor, and a towing mode in which power is supplied from the battery only to the hydraulic pump drive motor, It has a first sensor for detecting the voltage of the battery, The control device is characterized in that, when the towing switch sets the towing mode based on the remaining battery level determined by the voltage of the battery as measured by the first sensor, it controls the supply of battery power only to the hydraulic pump drive motor, thereby enabling the dump truck.

2. The dump truck according to claim 1, characterized in that the control device, in the towing mode, controls the regenerative power generated by the drive motor to charge the battery.

3. The dump truck according to claim 1, characterized in that the control device sets the upper limit of the rotational speed of the hydraulic pump drive motor to a lower value than in the normal mode in which the truck is driven by the travel motor when in the towing mode.

4. The dump truck according to claim 3, characterized in that the control device changes the upper limit of the rotational speed of the hydraulic pump drive motor according to the remaining charge of the battery.

5. The dump truck according to claim 1, characterized in that the control device performs control to stop supplying power from the battery to the drive motor when the remaining charge of the battery is less than or equal to the first specified value.

6. The aforementioned dump truck is further equipped with an alarm device that emits a warning, The dump truck according to claim 5, characterized in that the control device causes the notification device to issue an alarm when the towing mode is in place and the remaining battery level is less than or equal to a second specified value which is less than the first specified value.

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