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

Dump truck

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

[0002] When a dump truck becomes unable to move under its own power due to some abnormality, such as equipment failure or energy shortage, the dump truck is towed to a target location such as a work base.

[0003] The most common method for towing a disabled dump truck is to connect it to another vehicle with a wire rope, which requires a driver to drive the disabled dump truck and also to brake and steer the truck.

[0004] In dump trucks that have become unable to move, the hydraulic pump that supplies pressurized oil to the braking and steering devices is often also unable to operate. In order to supply pressurized oil to the braking and steering devices, it is necessary to connect the hydraulic circuit of another vehicle to the hydraulic circuit of the disabled dump truck with hydraulic hoses, which requires a great deal of effort. Therefore, a method for supplying pressurized oil to the braking and steering devices of a disabled dump truck without requiring much effort when being towed has been studied (for example, Patent Document 1).

[0005] Patent Document 1 discloses a dump truck that includes an accumulator that accumulates pressure with pressurized oil, and a bleed-down control prohibition device that prohibits the release of the pressure accumulated in the accumulator when the dump truck is being towed.

[0006] Japanese Patent Application Laid-Open No. 2019-48522

[0007] However, the dump truck disclosed in Patent Document 1 may encounter a situation where the brake device and steering device cannot be driven when sufficient pressure is not stored in the accumulator, etc. This may cause the dump truck disclosed in Patent Document 1 to be unable to be towed stably to a target point such as a work base.

[0008] In addition, electric dump trucks also use a motor to drive a hydraulic pump, which can lead to early battery deterioration if the motor is kept running until the battery runs out.

[0009] In view of the above circumstances, an object of the present invention is to prevent early deterioration of the battery in an electric dump truck while ensuring the hydraulic power source required when being towed without relying on an external hydraulic power source.

[0010] In order to solve the above problems, the dump truck of the present invention is an electric dump truck that includes a travel motor, a hydraulic pump that supplies pressurized oil to at least one of a brake device and a steering device, 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 supply of power from the battery to the travel motor and the hydraulic pump drive motor, and is characterized in that when the dump truck is in a towing mode in which it is towed, the control device controls the supply of power from the battery only to the hydraulic pump drive motor.

[0011] According to the present invention, in an electric dump truck, early deterioration of the battery can be prevented, and the hydraulic pressure source required when being towed can be secured without relying on an external hydraulic pressure source.

[0012] A side view showing a schematic configuration of a dump truck when being towed according to the present embodiment. A diagram showing a schematic configuration of a hydraulic circuit in the dump truck according to the present embodiment. A schematic electrical circuit diagram of the dump truck according to the present embodiment. A flowchart showing an example of the operation of a control device related to towing of the dump truck according to the present embodiment.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Components with the same reference numerals in each embodiment have the same functions in each embodiment unless otherwise specified, and description thereof will be omitted.

[0014] Fig. 1 is a side view showing a schematic configuration of a dump truck 1 according to this embodiment when being towed. The dump truck 1 shown in Fig. 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, to a target point such as a work base. The other vehicle 3 may be a vehicle similar to the dump truck 1, or may be a dedicated towing vehicle, as long as it is capable of towing the dump truck 1, which has become unable to move.

[0015] The dump truck 1 is an electric dump truck powered by a battery, and is used to transport, for example, earth and sand or minerals excavated in an open-cut mine.

[0016] As shown in Fig. 1, the dump truck 1 is composed of front wheels 11, rear wheels 12, and a vehicle 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 vehicle body 13. The vehicle body 13 and the loading platform 14 are connected by a hoist device 15.

[0017] The dump truck 1 operates by rear-wheel drive in which the rear wheels 12, which are the left and right rear wheels of the front and rear wheels 11, 12, are drive wheels and the front wheels 11, which are the left and right front wheels, are driven wheels. A travel motor 16 is provided on the rotating shaft of the rear wheels 12. The dump truck 1 is equipped with brake devices 17 attached to each of the front and rear wheels 11, 12, and a steering device 18 interposed between the front and rear wheels 11, 12 and the vehicle body 13.

[0018] The dump truck 1 can operate in a normal mode, which is an operation mode in which the rear wheels 12 are rotated as drive wheels by the travel motor 16 to travel, and a towing mode, which is an operation mode in which the rear wheels 12 are not driven and all the wheels 11, 12 serve as driven wheels and are towed by another vehicle, etc. In either the normal mode or the towing mode, the dump truck 1 drives the brake device 17 and the steering device 18.

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

[0020] The hoist device 15 including the hoist cylinder, the brake device 17 including the brake piston, and the steering device 18 including the steering cylinder are parts 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] The dump truck 1 is equipped with a hydraulic oil tank 19, a hydraulic pump 20, a control valve 21, and an accumulator 22 as devices that constitute a hydraulic circuit.

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

[0023] The hydraulic pump 20 is connected to a control valve 21, and supplies pressure oil to the hoist device 15, the brake device 17, the steering device 18, and an accumulator 22 via the control valve 21. The hydraulic pump 20 is also connected to a hydraulic pump drive motor 23 (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 pressurized oil supplied from the hydraulic pump 20 to the hoist device 15, the brake device 17, the steering device 18, and the accumulator 22. The control valve 21 is also connected to a hydraulic oil tank 19, and returns any excess 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 pressure oil supplied from a hydraulic pump 20 via a control valve 21 to extend or retract the hoist cylinder.

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

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

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

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

[0030] 2 and 3, the dump truck 1 is provided with a hydraulic pump drive motor 23 for driving the hydraulic pump 20. The dump truck 1 has an electric circuit for driving the travel motor 16 and the hydraulic pump drive motor 23, as shown in FIG.

[0031] The dump truck 1 is equipped with a battery 24, a first sensor 25, a DC / DC converter 26, a travel motor inverter 27, a first switch 28, a hydraulic pump drive motor inverter 29, and a control device 37 as devices that make up an electric circuit. 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] The dump truck 1 also includes a towing switch 30, which is a switch that accepts an input operation to switch the setting between the normal mode and the towing mode. The towing switch 30 is provided in a driver's cab mounted on the dump truck 1, and is connected to a control device 37. The towing switch 30 transmits a signal to the control device 37 to set the mode to the normal mode or the towing mode, according to an input operation by the occupant.

[0033] The dump truck 1 is also equipped with an alarm device 36 that includes a display, speaker, buzzer, indicator lamp, rotating light, etc., and notifies the occupant of the status of the dump truck 1 based on a control signal 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 a travel motor inverter 27. The battery 24 is connected to the hydraulic pump drive motor 23 via the DC / DC converter 26 and a hydraulic pump drive motor inverter 29.

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

[0036] Furthermore, the traveling motor 16 functions as a generator by rotating, generating regenerative power. The regenerative power generated by the traveling motor 16 is supplied to the battery 24. The traveling motor 16 functions as a regenerative braking mechanism that generates rotational resistance as the regenerative power is generated.

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

[0038] The first sensor 25 is provided 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 voltage of the battery 24 to the control device 37.

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

[0040] The traction motor inverter 27 is provided between the DC / DC converter 26 and the traction motor 16. Based on a control command from the control device 37, the traction motor inverter 27 converts the DC power supplied from the DC / DC converter 26 into AC power and supplies it to the traction motor 16. Based on a control command from the control device 37, the traction motor inverter 27 also converts AC power, which is regenerated power generated by the traction 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 traveling motor 16. The first switch 28 is provided between the DC / DC converter 26 and the traveling motor inverter 27. The first switch 28 closes or opens based on a control signal from the control device 37 to allow or stop the supply of power from the battery 24 to the traveling motor 16.

[0042] The hydraulic pump drive motor inverter 29 is provided between the DC / DC converter 26 and the hydraulic pump drive motor 23. Based on a control command from the control device 37, the hydraulic pump drive motor 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 chopper 32 are connected in parallel to the travel motor inverter 27 connected to the travel motor 16, and the resistor 31 converts 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 a control command from the control device 37.

[0044] As shown in Fig. 1, the pantograph 33 is provided at the upper front part of the dump truck 1, and is configured to extend and retract up and down by operation by a rider of the dump truck 1. When the pantograph 33 extends upward, it comes into contact with a trolley wire or the like and receives power supply from the trolley wire or the like. When the pantograph 33 contracts downward, it separates from the trolley wire or the like and stops the power supply from the trolley wire or the like. As shown in Fig. 3, the pantograph 33 is connected to the traveling motor 16 via a traveling motor inverter 27, and is connected to the battery 24 via a DC / DC converter 26.

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

[0046] The second sensor 34 is provided between the pantograph 33 and the DC / DC converter 26. The second sensor 34 is also provided between the pantograph 33 and the traction motor inverter 27. The second sensor 34 is a voltage sensor that detects the voltage of the power supplied from the trolley wire or the like via the pantograph 33, or the voltage of the regenerative power generated by the traction motor 16. The second sensor 34 transmits the detected voltage of the power supplied from the trolley wire or the like, or the voltage of 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 traction motor 16. The second switch 35 is provided between the pantograph 33 and the traction motor inverter 27. The second switch 35 is also provided between the pantograph 33 and the DC / DC converter 26. The second switch 35 closes or opens in conjunction with the extension and contraction of the pantograph 33 up and down, based on a control signal from the control device 37, so as to allow or stop the supply of power from the pantograph 33 to the battery 24 or the traction motor 16.

[0048] The control device 37 is configured to include a processor such as a CPU, a memory, an input / output interface, etc. The control device 37 controls the operation of each component of the dump truck 1 by causing the CPU to execute a program stored in the memory based on signals from each component shown in FIG.

[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 included in the first sensor 25. The remaining capacity of the battery 24 is expressed as a percentage of the remaining capacity when the battery 24 is fully charged to 100% capacity and then discharged.

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

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

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

[0053] In the towing mode in which the dump truck 1 is towed, the control device 37 controls the supply of power from the battery 24 only to the hydraulic pump drive motor 23 among the electric components that perform rotational or linear motion operations using the battery 24 as a power source in the normal mode. Note that in the normal mode or in the towing mode, when power is required for the operation of an alarm device and for operations related to regenerative power, the control device 37 does not prevent power from being supplied to the necessary devices.

[0054] In the towing mode, the control device 37 may control the travel motor inverter 27 so as to always generate regenerative braking to the extent that it does not interfere with towing.

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

[0056] The control device 37 causes the notification device 36 to issue an alarm when the vehicle is in towing mode and the remaining charge of the battery 24 is equal to or less than a second specified value D2 that is less than the first specified value D1. Specifically, when the vehicle is in towing mode and the remaining charge of the battery 24 is equal to or less than the second specified value D2 that is less than the first specified value D1, the control device 37 controls the notification device 36 to issue an alarm to notify the occupant that the remaining charge of the battery 24 is low. The second specified value D2 is a preset remaining charge value 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. The second specified value D2 may be, for example, 3% to 5%.

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

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

[0059] 4, the default open / close state of the first switch 28 is preset to a closed state that allows power to be supplied from the battery 24 to the traction motor 16. In the operation example shown in FIG. 4, the default open / close state of the second switch 35 is preset to an open state that stops power supply from the pantograph 33 to the battery 24 or the traction motor 16.

[0060] The control device 37 estimates the remaining capacity 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 equal to or less than the 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 equal to or less than the first specified value D1 (if the result of step S2 is No).

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

[0063] After stopping the power supply from the battery 24 to the traveling motor 16, the control device 37 checks whether or not a signal to set the mode to the towing mode has been received from the towing switch 30 (step S4).

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

[0065] In the dump truck 1, power is supplied from the battery 24 to the hydraulic pump drive motor 23 through the processing of step S5, thereby enabling the brake device 17 and the steering device 18 to be driven. Then, the dump truck 1 starts towing in a state where it is coupled to the other vehicle 3.

[0066] When the dump truck 1 starts towing, the travel motor 16 is rotated in accordance with the rotation of the tires. In this case, the control device 37 controls the travel motor inverter 27 so as to always generate regenerative braking to the extent that towing is not hindered (step S6). As a result, the travel motor 16 functions as a generator and generates regenerative power.

[0067] In the towing mode, the control device 37 controls the travel motor inverter 27 and the DC / DC converter 26 so that the regenerative power generated by the travel motor 16 is charged into the battery 24 (step S7).

[0068] In the towing mode, the control device 37 determines whether the remaining charge of the battery 24 is equal to or less than a second specified value D2 that is lower than the 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 alarm device 36 to issue an alarm to notify the passenger that the remaining charge of the battery 24 is low (step S9).

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

[0071] When the control device 37 receives a signal to cancel the towing mode from the towing switch 30 (Yes in step S10), it cancels the towing mode, which is the operation mode of the dump truck 1, and terminates the towing-related operation processing of the control device 37. 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 to cancel the towing mode from the towing switch 30.

[0072] As described above, the dump truck 1 according to this embodiment includes the travel motor 16, the hydraulic pump 20 that supplies pressure oil to at least one of the brake device 17 and the steering device 18, and the 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 the battery 24 that supplies power to the travel motor 16 and the hydraulic pump drive motor 23, and the control device 37 that controls the supply of power 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 a towing mode in which it is towed.

[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 required when towed, using the remaining capacity of its own battery 24 without relying on an external device. Furthermore, the dump truck 1 according to this embodiment limits the supply destination of power from the battery 24 to the hydraulic pump drive motor 23 when in towing mode, thereby reducing wasteful consumption of the battery 24. As a result, the dump truck 1 according to this embodiment can prevent early deterioration of the battery 24. Therefore, with the dump truck 1 according to this embodiment, an electric dump truck can secure the hydraulic source required when towed without relying on an external hydraulic source, while preventing early deterioration of the battery.

[0074] Furthermore, in the dump truck 1 according to this embodiment, the control device 37 performs control to charge the battery 24 with regenerative power generated by the traveling motor 16 when in the towing mode.

[0075] With this configuration, the dump truck 1 according to this embodiment can effectively utilize the regenerative power generated by the travel motor 16 as power for the battery 24, which is the main source of the hydraulic power required when being towed, by charging the battery 24 with the regenerative power generated by the travel motor 16. As a result, the dump truck 1 according to this embodiment can extend the towing time while preventing the remaining charge of the battery 24 from reaching 0% by using the regenerative power charged in the battery 24. Therefore, the dump truck 1 according to this embodiment can easily secure the hydraulic power required when being towed without relying on an external hydraulic power source, while preventing early deterioration of the battery.

[0076] Furthermore, in the dump truck 1 according to this embodiment, when in towing mode, the control device 37 sets the upper limit value L of the rotation speed of the hydraulic pump drive motor 23 to a value lower than in the normal mode in which travel is performed using the travel motor 16.

[0077] With this configuration, the dump truck 1 according to this embodiment can ensure the minimum necessary braking performance and steering performance while suppressing unnecessary consumption of the battery 24. Therefore, the dump truck 1 according to this embodiment can easily ensure the hydraulic source required when being towed without relying on an external hydraulic source, while preventing early 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 rotation speed of the hydraulic pump drive motor 23 in accordance with the remaining charge of the battery 24 .

[0079] With this configuration, the dump truck 1 according to this embodiment can ensure the minimum necessary braking performance and steering performance, while appropriately suppressing unnecessary consumption of the battery 24 in accordance with the remaining charge of the battery 24. Therefore, the dump truck 1 according to this embodiment can easily ensure the hydraulic source required when being towed without relying on an external hydraulic source, while preventing early deterioration of the battery.

[0080] Furthermore, in the dump truck 1 according to this embodiment, the control device 37 performs control to stop the supply of power from the battery 24 to the traveling motor 16 when the remaining charge of the battery 24 is equal to or less than the first specified value D1.

[0081] With this configuration, the dump truck 1 according to this embodiment stops the supply of power from the battery 24 to the travel motor 16 when the remaining charge of the battery 24 is equal to or less than the first specified value D1, and therefore it is possible to suppress the discharge of the battery 24 at a stage when the remaining charge of the battery 24 is greater than 0%. This makes it easy for the dump truck 1 according to this embodiment to prevent early deterioration of the battery 24. Therefore, with the dump truck 1 according to this embodiment, it is easy to ensure the hydraulic source required when being towed without relying on an external hydraulic source, while preventing early deterioration of the battery.

[0082] Furthermore, the dump truck 1 according to this embodiment is further provided 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 dump truck 1 is in the towing mode and the remaining charge of the battery 24 is equal to or less than a second specified value D2 that is less than the 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 informing the occupant not to use up the remaining charge of the battery 24 until it reaches 0%. Therefore, the dump truck 1 according to this embodiment makes it even more difficult for early deterioration of the battery to occur.

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

[0085] As a result, in the dump truck 1 according to this embodiment, when the control device 37 receives a signal from the towing switch 30 to set the operation mode to the towing mode, the control device 37 sets the operation mode to the towing mode. That is, the dump truck 1 according to this embodiment does not automatically switch from the normal mode to the towing mode until it receives a signal from the towing switch 30 to set the operation mode. As a result, the dump truck 1 according to this embodiment can suppress unintended switching to the operation mode, and switches the operation mode at the timing intended by the occupant. As a result, the dump truck 1 according to this embodiment operates in an operation mode that is in line with the occupant's intention. Therefore, the dump truck 1 according to this embodiment can improve safety.

[0086] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention as defined in the claims. In the present invention, the configuration of one embodiment can be added to the configuration of another embodiment, the configuration of one embodiment can be replaced with the configuration of another embodiment, or part of the configuration of one embodiment can be deleted.

[0087] 1...dump truck, 16...travel motor, 17...brake device, 18...steering device, 20...hydraulic pump, 23...hydraulic pump drive motor, 24...battery, 30...traction switch, 36...alarm device, 37...control device, D1...first specified value, D2...second specified value, L, L0, L1, L2...upper limit value of rotation speed of hydraulic pump drive motor

Claims

1. An electric dump truck comprising: a travel motor; a hydraulic pump that supplies pressure oil to at least one of a brake device and a steering device; 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 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 operation 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 traveling motor, and a towing mode in which power is supplied from the battery only to the hydraulic pump drive motor; a first sensor that detects the voltage of the battery; When the towing mode is set by the towing switch in a case where the remaining charge of the battery based on the voltage of the battery measured by the first sensor is equal to or less than a first specified value, the control device controls the supply of power from the battery only to the hydraulic pump drive motor.

2. 2. The dump truck according to claim 1, wherein the control device performs control such that, in the towing mode, regenerative power generated by the traveling motor is charged into the battery.

3. 2. The dump truck according to claim 1, wherein, in the towing mode, the control device sets an upper limit value of the rotation speed of the hydraulic pump drive motor to a value lower than that in a normal mode in which travel is performed by the travel motor.

4. 4. The dump truck according to claim 3, wherein the control device changes an upper limit value of the rotation speed of the hydraulic pump drive motor in accordance with the remaining charge of the battery.

5. 2. The dump truck according to claim 1, wherein the control device performs control to stop the supply of power from the battery to the traveling motor when the remaining charge of the battery is equal to or less than the first specified value.

6. The dump truck further includes an alarm device that issues an alarm, The dump truck according to claim 5, wherein the control device causes the alarm device to issue an alarm when the dump truck is in the towing mode and the remaining charge of the battery is equal to or less than a second specified value that is lower than the first specified value.