Dump truck

Abstract

The purpose of the present invention is to prevent early deterioration of a battery in an electric dump truck, and to secure a hydraulic pressure source required when the electric dump truck is towed without depending on an external hydraulic pressure source. An electric dump truck (1) is provided with: 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); 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 the supply of power from the battery (24) to the travel motor (16) and the hydraulic pump drive motor (23). The control device (37) performs control for supplying only the power of the battery (24) to the hydraulic pump drive motor (23) in a traction mode in which the dump truck (1) is towed.

Description

Technical Field

[0001] The present invention relates to an electric dump truck using a battery as a power source. Background Art

[0002] When a dump truck becomes unable to operate on its own due to some abnormality including equipment failure or energy exhaustion, it is towed to a target location such as a work base.

[0003] A common method of towing a disabled dump truck is to tow it by connecting it to another vehicle with a wire rope. This method requires a passenger on the disabled dump truck and requires braking and steering operations by the passenger.

[0004] Many disabled dump trucks are also unable to operate the hydraulic pumps that supply pressurized oil to the brakes and steering systems. Supplying pressurized oil to the brakes and steering systems requires connecting the hydraulic circuits of other vehicles to the hydraulic circuits of the disabled dump truck using hydraulic hoses, which presents a significant effort. Therefore, research has been conducted to minimize the effort required to supply pressurized oil to the brakes and steering systems of disabled dump trucks while being towed (e.g., Patent Document 1).

[0005] Patent Document 1 discloses a dump truck including an accumulator for storing pressure using pressurized oil and a discharge control prohibition device for prohibiting the release of pressure stored in the accumulator when the truck is being towed.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-48522 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, the dump truck disclosed in Patent Document 1 may fail to actuate the brakes and steering if the accumulator does not accumulate sufficient pressure. Consequently, the dump truck disclosed in Patent Document 1 may not be stably towed to a target location such as a work site.

[0011] In addition, electric dump trucks use an onboard motor to drive a hydraulic pump. Therefore, if the motor is continuously driven until the battery is exhausted, the battery may deteriorate prematurely.

[0012] In view of the above circumstances, an object of the present invention is to prevent premature deterioration of a battery in an electric dump truck and to ensure a hydraulic source required for towing without relying on an external hydraulic source.

[0013] Means for solving problems

[0014] In order to solve the above-mentioned problems, the dump truck of the present invention is an electric dump truck, which has: a traveling motor; a hydraulic pump, which supplies pressure oil to at least one of a braking device and a steering device; a hydraulic pump drive motor, which drives the hydraulic pump; a battery, which supplies power to the traveling motor and the hydraulic pump drive motor; and a control device, which controls the power supply from the battery to the traveling motor and the hydraulic pump drive motor, and is characterized in that the control device controls the power of the battery to be supplied only to the hydraulic pump drive motor in a towing mode in which the dump truck is towed.

[0015] Effects of the Invention

[0016] According to the present invention, in an electric dump truck, premature deterioration of a battery can be prevented and a hydraulic pressure source required for towing can be ensured without relying on an external hydraulic pressure source. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a side view showing a schematic structure of the dump truck when being towed according to the present embodiment.

[0018] Figure 2 This is a diagram showing a schematic configuration of a hydraulic circuit of a dump truck according to the present embodiment.

[0019] Figure 3 This is a schematic circuit diagram of a dump truck according to this embodiment.

[0020] Figure 4 This is a flowchart showing an example of the operation of the control device related to traction of the dump truck according to the present embodiment. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. Components denoted by the same reference numerals in each embodiment have the same functions in each embodiment unless otherwise specified, and their description will be omitted.

[0022] Figure 1 It is a side view showing a schematic structure of the dump truck 1 when being towed according to the present embodiment. Figure 1The dump truck 1 shown is connected to another vehicle 3 via a wire rope 2. The other vehicle 3, while connected to the dump truck 1 via the wire rope 2, tows the immobile dump truck 1 to a target location such as a work base. The other vehicle 3 can be a vehicle similar to the dump truck 1 or a dedicated towing vehicle, as long as it can tow the immobile dump truck 1.

[0023] The dump truck 1 is an electric dump truck using a battery as a power source. The dump truck 1 is a dump truck for transporting soil, minerals, etc. excavated in an open-pit mine, for example.

[0024] like Figure 1 As shown, the dump truck 1 is composed of front wheels 11, rear wheels 12, and a body 13 which is a strong frame connected to the front wheels 11 and rear wheels 12. A cargo box 14 for loading sand and soil is mounted on the body 13. The body 13 and the cargo box 14 are connected by a lifting device 15.

[0025] The dump truck 1 operates in a rear-wheel drive mode, with the rear left and right wheels (rear wheels 12) serving as driving wheels and the front left and right wheels (front wheels 11) serving as driven wheels. A travel motor 16 is provided on the rotating shaft of the rear wheel 12. The dump truck 1 has a brake system 17 mounted on each of the front and rear wheels 11, 12, and a steering system 18 interposed between the front and rear wheels 11, 12 and the vehicle body 13.

[0026] The dump truck 1 can operate in a normal mode, in which the rear wheels 12 are rotated as driving wheels by the travel motor 16, and a towing mode, in which the rear wheels 12 are not driven, and all wheels 11 and 12 are driven wheels, while the dump truck 1 is towed by another vehicle or the like. In both the normal mode and the towing mode, the brake system 17 and the steering system 18 are driven.

[0027] Figure 2 This is a diagram showing a schematic configuration of a hydraulic circuit in the dump truck 1 according to the present embodiment.

[0028] The lifting device 15 including the lifting cylinder, the braking device 17 including the braking piston, and the steering device 18 including the steering cylinder are part of the hydraulic actuator of the dump truck 1. Figure 2 As shown, the dump truck 1 has a hydraulic circuit for driving a hydraulic actuator.

[0029] The dump truck 1 includes a hydraulic oil tank 19 , a hydraulic pump 20 , a control valve 21 , and an accumulator 22 as devices constituting a hydraulic circuit.

[0030] 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 .

[0031] The hydraulic pump 20 is connected to a control valve 21 and supplies pressurized oil to the lifting device 15, the brake device 17, the steering device 18, and the accumulator 22 via the control valve 21. The hydraulic pump 20 is also connected to a hydraulic pump drive motor 23 described below and is driven by the hydraulic pump drive motor 23.

[0032] The control valve 21 is connected to the hydraulic pump 20, the lifting 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 lifting device 15, the brake device 17, the steering device 18, and the accumulator 22. Furthermore, the control valve 21 is connected to the hydraulic oil tank 19 to return any remaining hydraulic oil not distributed to any of the above devices to the hydraulic oil tank 19.

[0033] The lifting device 15 is driven by pressurized oil supplied from a hydraulic pump 20 via a control valve 21 , thereby extending or contracting a lift cylinder.

[0034] The brake device 17 is a hydraulic brake device driven by pressurized oil supplied from a hydraulic pump 20 via a control valve 21 .

[0035] The steering device 18 is a hydraulic steering device driven by pressurized oil supplied from a hydraulic pump 20 via a control valve 21 .

[0036] The accumulator 22 is a device that accumulates pressure using the pressurized oil supplied from the hydraulic pump 20 via the control valve 21. The accumulator 22 may also be connected to the brake device 17 and the steering device 18, and supplies the accumulated pressurized oil (pressure) to the brake device 17 or the steering device 18 together with the hydraulic pump 20.

[0037] Figure 3 This is a schematic circuit diagram of the dump truck 1 according to the present embodiment.

[0038] like Figure 2 and Figure 3 As shown, the dump truck 1 has a hydraulic pump drive motor 23 for driving the hydraulic pump 20. Figure 3 As shown, the dump truck 1 has an electric circuit for driving the travel motor 16 and the hydraulic pump drive motor 23 .

[0039] The dump truck 1 includes, as components constituting a circuit, 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. Furthermore, the dump truck 1 includes a resistor 31, a chopper 32, a pantograph 33, a second sensor 34, and a second switch 35.

[0040] The dump truck 1 also includes a traction switch 30, which receives an input operation to switch the setting to normal mode or traction mode. The traction switch 30 is installed in the cab of the dump truck 1 and is connected to a control device 37. The traction switch 30 sends a signal to the control device 37 to set the setting to normal mode or traction mode in response to the input operation of the passenger.

[0041] The dump truck 1 also includes a display, a speaker, a buzzer, an indicator light, a rotating light, and the like, and has a notification device 36 for notifying passengers of the state of the dump truck 1 based on a control signal from a control device 37 .

[0042] 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 a DC / DC converter 26 and a hydraulic pump drive motor inverter 29.

[0043] The travel motor 16 is an electric motor powered by power supplied from the battery 24. The travel motor 16 is an AC motor connected to a travel motor inverter 27. The travel motor 16 is driven by power supplied from the battery 24 via the DC / DC converter 26 and the travel motor inverter 27.

[0044] The travel motor 16 rotates to become a generator and generates regenerative power. The regenerative power generated by the travel motor 16 is supplied to the battery 24. The travel motor 16 also serves as a regenerative braking mechanism that generates rotational resistance as the regenerative power is generated.

[0045] 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.

[0046] 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.

[0047] The DC / DC converter 26 is provided between the battery 24 and the travel motor inverter 27. The DC / DC converter 26 steps up or steps down the DC power supplied from the battery 24 to a predetermined voltage in response to control commands from the control device 37, and supplies the power to the travel motor inverter 27. Furthermore, the DC / DC converter 26 is provided between the battery 24 and the hydraulic pump drive motor inverter 29. The DC / DC converter 26 steps up or steps down the DC power supplied from the battery 24 to a predetermined voltage in response to control commands from the control device 37, and supplies the power to the hydraulic pump drive motor inverter 29. The DC / DC converter 26 steps up or steps down the DC power supplied from the travel motor inverter 27 to a predetermined voltage in response to control commands from the control device 37, thereby charging the battery 24.

[0048] The travel motor inverter 27 is provided 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 the power to the travel motor 16. Furthermore, 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 the power to the DC / DC converter 26.

[0049] 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 provided between the DC / DC converter 26 and the travel motor inverter 27. The first switch 28 is closed or opened to allow or stop the supply of power from the battery 24 to the travel motor 16 in response to a control signal from the control device 37.

[0050] The hydraulic pump drive motor inverter 29 is provided between the DC / DC converter 26 and the hydraulic pump drive motor 23. The hydraulic pump drive motor inverter 29 converts DC power supplied from the DC / DC converter 26 into AC power according to a control command from the control device 37 and supplies the AC power to the hydraulic pump drive motor 23.

[0051] The resistor 31 and the chopper 32 are connected in parallel to the travel motor inverter 27 connected to the travel motor 16. 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 control commands from the control device 37.

[0052] like Figure 1As shown, the pantograph 33 is provided at the front upper portion of the dump truck 1 and is configured to be extended and retracted up and down by the operation of the passengers of the dump truck 1. The pantograph 33 is extended upward to contact with the trolley wire, etc., and receives power supply from the trolley wire, etc. On the other hand, the pantograph 33 is retracted downward to separate from the trolley wire, etc., and the power supply from the trolley wire, etc. is stopped. Figure 3 As shown, the pantograph 33 is connected to the travel motor 16 via the travel motor inverter 27 , and is connected to the battery 24 via the DC / DC converter 26 .

[0053] A location where the dump truck 1 having the pantograph 33 can receive power supply from a trolley wire or the like via the pantograph 33 can also be used as a target location when being towed.

[0054] The second sensor 34 is provided between the pantograph 33 and the DC / DC converter 26. Furthermore, the second sensor 34 is provided between the pantograph 33 and the travel 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 travel 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 travel motor 16, to the control device 37.

[0055] The second switch 35 is a switch that enables or disables the supply of power from the pantograph 33 to the battery 24 or the travel motor 16. The second switch 35 is provided between the pantograph 33 and the travel motor inverter 27. Furthermore, the second switch 35 is provided between the pantograph 33 and the DC / DC converter 26. Based on a control signal from the control device 37, the second switch 35 closes or opens in conjunction with the upward and downward extension and retraction of the pantograph 33, thereby enabling or disabling the supply of power from the pantograph 33 to the battery 24 or the travel motor 16.

[0056] The control device 37 is composed of a processor such as a CPU, a memory, and an input / output interface. Figure 3 The CPU executes a program stored in a memory using signals from the components shown, thereby controlling the operation of the components of the dump truck 1 .

[0057] The control device 37 estimates the remaining capacity of the battery 24 based on the voltage of the battery 24 sent from the voltage sensor of the first sensor 25. The remaining capacity of the battery 24 is the remaining capacity expressed in % when the battery 24 is fully charged to 100% capacity and then discharged.

[0058] When the estimated remaining charge of the battery 24 is less than or equal to the first predetermined value D1, the control device 37 controls the battery 24 to stop supplying power to the travel motor 16. The first predetermined value D1 is a predetermined value indicating the remaining charge of the battery 24 at which the dump truck 1 cannot travel on its own. The first predetermined value D1 is a value greater than 0% of the remaining charge of the battery 24. The first predetermined value D1 is a value at which the remaining charge of the battery 24 is sufficient to drive the hydraulic pump drive motor 23. The first predetermined value D1 can be changed depending on the driving environment, etc. For example, the first predetermined value D1 can be 10%.

[0059] Furthermore, it is preferred that the control device 37 open the first switch 28 to stop the power supply from the battery 24 to the travel motor 16 when the estimated remaining power of the battery 24 is less than or equal to the first predetermined value D1. Furthermore, the control device 37 may control the hydraulic pump drive motor inverter 29 to stop the power supply from the battery 24 to the hydraulic pump drive motor 23 when the estimated remaining power of the battery 24 is less than or equal to the first predetermined value D1.

[0060] The control device 37 sets the operation mode of the dump truck 1 to the normal mode or the traction mode based on a signal sent from the traction switch 30. Specifically, when the remaining charge of the battery 24 is less than or equal to the first predetermined value D1, and upon receiving a signal from the traction switch 30 to set the operation mode to the traction mode, the control device 37 sets the operation mode of the dump truck 1 to the traction mode. Alternatively, when the remaining charge of the battery 24 is less than or equal to the first predetermined value D1, and the operation mode of the dump truck 1 is set to the traction mode, and upon receiving a signal from the traction switch 30 to set the operation mode to the normal mode, i.e., to release the traction mode, the control device 37 sets the operation mode of the dump truck 1 to the normal mode.

[0061] In the towing mode, in which the dump truck 1 is being towed, the control device 37 controls the supply of power from the battery 24 to only the hydraulic pump drive motor 23, among the electrically powered components that, in the normal mode, perform rotational or linear motion using the battery 24 as a power source. Furthermore, in the normal mode or in the towing mode, when power is notified for the operation of a device or for an operation related to regenerative power, the control device 37 does not prevent the supply of power to the required devices.

[0062] In the case of the traction mode, the control device 37 may control the travel motor inverter 27 so as to always generate regenerative braking to an extent that does not hinder traction.

[0063] In the traction mode, the control device 37 controls the battery 24 to be charged with the regenerative power generated by the travel motor 16. Specifically, in the traction mode, the control device 37 controls the travel motor inverter 27 and the DC / DC converter 26 to charge the battery 24 with the regenerative power generated by the travel motor 16.

[0064] When the vehicle is in towing mode and the remaining charge of battery 24 is less than or equal to a second predetermined value D2, which is less than first predetermined value D1, control device 37 controls notification device 36 to issue an alarm. Specifically, when the vehicle is in towing mode and the remaining charge of battery 24 is less than or equal to second predetermined value D2, which is less than first predetermined value D1, control device 37 controls notification device 36 to issue an alarm to notify passengers that the remaining charge of battery 24 is low. Furthermore, second predetermined value D2 is a preset value of the remaining charge of battery 24 that is greater than 0% and less than first predetermined value D1. Second predetermined value D2 is adjustable depending on the driving environment and other factors. For example, second predetermined value D2 can be between 3% and 5%.

[0065] In towing mode, the control device 37 sets the upper limit L of the rotational speed of the hydraulic pump drive motor 23 to a value lower than that in the normal mode in which the vehicle is driven by the travel motor 16. Specifically, in towing mode, the control device 37 controls the hydraulic pump drive motor inverter 29 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 normal mode. Upper limit L1 is an upper limit L lower than the upper limit L0 in normal mode. Furthermore, upper limit L2 is an upper limit L lower than upper limit L1. Preferably, in towing mode, the control device 37 changes the upper limit L of the rotational speed of the hydraulic pump drive motor 23 based on the remaining charge in the battery 24. Specifically, in towing mode, the control device 37 controls the hydraulic pump drive motor inverter 29 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 normal mode, based on the remaining charge in the battery 24. The control device 37 sets the upper limit value L in the order of upper limit value L0, upper limit value L1, and upper limit value L2 so that the upper limit value L of the rotation speed is lower than the current value according to the decrease in the remaining charge of the battery 24.

[0066] Figure 4 This is a flowchart showing an example of the operation of the control device 37 related to traction of the dump truck 1 according to the present embodiment.

[0067] exist Figure 4 In the illustrated operation example, the default open / close state of the first switch 28 is preset to a closed state that allows the supply of electric power from the battery 24 to the travel motor 16. Figure 4In the illustrated operation example, the default open / close state of the second switch 35 is preset to an open state in which the power supply from the pantograph 33 to the battery 24 or the travel motor 16 is stopped.

[0068] The control device 37 estimates the remaining amount of the battery 24 based on the voltage of the battery 24 received from the first sensor (step S1 ).

[0069] The control device 37 determines whether the remaining amount of the battery 24 is less than or equal to the first predetermined value D1 (step S2). The control device 37 repeats the processing of step S1 and the determination of step S2 until it determines that the remaining amount of the battery 24 is less than or equal to the first predetermined value D1 (if the answer is No in step S2).

[0070] When the control device 37 determines that the remaining power of the battery 24 is equal to or less than the first predetermined value D1 (Yes in step S2 ), it controls the travel motor inverter 27 to stop the power supply from the battery 24 to the travel motor 16 (step S3 ).

[0071] After stopping the power supply from the battery 24 to the travel motor 16 , the control device 37 checks whether a signal for setting the traction mode is received from the traction switch 30 (step S4 ).

[0072] When the control device 37 receives a signal from the traction switch 30 to set the traction mode (Yes in step S4), the operation mode of the dump truck 1 is set to the traction mode. Thereafter, the control device 37 controls the DC / DC converter 26 and the hydraulic pump drive motor inverter 29 to supply power from the battery 24 to the hydraulic pump drive motor 23 (step S5).

[0073] The dump truck 1 supplies power from the battery 24 to the hydraulic pump drive motor 23 through the process of step S5, thereby driving the brake device 17 and the steering device 18. Then, the dump truck 1 starts towing while being coupled to the other vehicle 3.

[0074] When the dump truck 1 starts towing, the travel motor 16 rotates in response to the rotation of the tires. In this case, the control device 37 controls the travel motor inverter 27 to always generate regenerative braking to a level that does not hinder towing (step S6). This causes the travel motor 16 to function as a generator, generating regenerative power.

[0075] In the case of the traction 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 charges the battery 24 (step S7 ).

[0076] In the case of the traction mode, the control device 37 determines whether the remaining amount of the battery 24 is equal to or less than a second predetermined value D2 that is smaller than the first predetermined value D1 (step S8 ).

[0077] When the control device 37 determines that the remaining amount of the battery 24 is less than or equal to the second predetermined value D2 (Yes in step S8 ), it controls the notification device 36 to issue an alarm to notify the passenger that the remaining amount of the battery 24 is low (step S9 ).

[0078] In the traction mode, when the remaining charge of the battery 24 is greater than the second predetermined value D2 (step S8: No) or after the notification device 36 issues an alarm, the control device 37 checks whether a signal to release the traction mode is received from the traction switch 30 (step S10).

[0079] When the control device 37 receives a signal from the traction switch 30 to cancel the traction mode (YES in step S10), the traction mode, which is the operating mode of the dump truck 1, is canceled, and the traction-related operation processing of the control device 37 is terminated. The control device 37 repeats the determination in step S8, the processing in step S9, and the determination in step S10 until the control device 37 receives a signal from the traction switch 30 to cancel the traction mode (NO in step S10).

[0080] As described above, the dump truck 1 of this embodiment includes a travel motor 16, a hydraulic pump 20 that supplies pressurized oil to at least one of the brake system 17 and the steering system 18, and a hydraulic pump drive motor 23 that drives the hydraulic pump 20. The dump truck 1 of 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 towing mode, in which the dump truck 1 of this embodiment is being towed, the control device 37 controls the supply of power from the battery 24 only to the hydraulic pump drive motor 23.

[0081] With this configuration, the dump truck 1 of this embodiment supplies power from the battery 24 to the hydraulic pump drive motor 23 in towing mode. Thus, the dump truck 1 of this embodiment can use the remaining power in its own battery 24 to drive the brake system 17 and steering system 18, which are minimally required for towing, without relying on external devices. Furthermore, the dump truck 1 of this embodiment limits the supply of power from the battery 24 to the hydraulic pump drive motor 23 in towing mode, thereby suppressing wasteful consumption of the battery 24. Thus, the dump truck 1 of this embodiment can suppress premature degradation of the battery 24. Therefore, according to the dump truck 1 of this embodiment, in an electric dump truck, premature battery degradation can be prevented, and the hydraulic power required for towing can be secured without relying on an external hydraulic power source.

[0082] Furthermore, regarding the dump truck 1 of the present embodiment, in the case of the towing mode, the control device 37 performs control to charge the battery 24 with the regenerative electric power generated by the travel motor 16 .

[0083] With this configuration, the dump truck 1 of this embodiment charges the battery 24 with regenerative power generated by the travel motor 16, effectively utilizing the power of the battery 24 as a power source for the hydraulic pressure required for towing. Consequently, the dump truck 1 of this embodiment can prevent the remaining charge in the battery 24 from reaching 0% by using the regenerative power charged to the battery 24, thereby extending the towing time. Therefore, the dump truck 1 of this embodiment easily prevents premature battery degradation and secures the hydraulic pressure required for towing without relying on an external hydraulic pressure source.

[0084] Furthermore, regarding the dump truck 1 of this embodiment, in the towing mode, the control device 37 sets the upper limit L of the rotation speed of the hydraulic pump drive motor 23 to a value lower than that in the normal mode in which the vehicle travels using the travel motor 16 .

[0085] With this configuration, the dump truck 1 of this embodiment can ensure the minimum required braking and steering performance while suppressing wasteful consumption of the battery 24. Therefore, the dump truck 1 of this embodiment can easily prevent premature battery degradation and ensure the hydraulic power required for towing without relying on an external hydraulic power source.

[0086] Furthermore, in the dump truck 1 of the present embodiment, the control device 37 changes the upper limit value L of the rotation speed of the hydraulic pump drive motor 23 according to the remaining charge of the battery 24 .

[0087] With this configuration, the dump truck 1 of this embodiment can ensure the minimum required braking and steering performance, and can appropriately suppress wasteful consumption of the battery 24 according to the remaining charge of the battery 24. Therefore, according to the dump truck 1 of this embodiment, premature degradation of the battery can be easily prevented, and the hydraulic pressure required for towing can be ensured without relying on an external hydraulic pressure source.

[0088] Furthermore, in the dump truck 1 of the present embodiment, the control device 37 performs control to stop the power supply from the battery 24 to the travel motor 16 when the remaining power of the battery 24 is equal to or less than the first predetermined value D1.

[0089] With this configuration, the dump truck 1 of this embodiment stops supplying power from the battery 24 to the travel motor 16 when the remaining charge in the battery 24 falls below the first predetermined value D1. This prevents discharge of the battery 24 when the remaining charge in the battery 24 exceeds 0%. Consequently, the dump truck 1 of this embodiment easily prevents premature degradation of the battery 24. Therefore, the dump truck 1 of this embodiment easily prevents premature degradation of the battery and secures the hydraulic power required for towing without relying on an external hydraulic power source.

[0090] The dump truck 1 of this embodiment further includes a notification device 36 for issuing an alarm. In the dump truck 1 of this embodiment, the control device 37 causes the notification device 36 to issue an alarm when the remaining charge of the battery 24 is less than or equal to a second predetermined value D2, which is less than the first predetermined value D1, in the towing mode.

[0091] With this configuration, the dump truck 1 of this embodiment can prevent overdischarge of the battery 24 by notifying passengers not to use up the battery 24 until the remaining charge reaches 0%. Therefore, the dump truck 1 of this embodiment further reduces the risk of premature battery deterioration.

[0092] Furthermore, the dump truck 1 of this embodiment may also include a traction switch 30 that receives an input operation to switch the setting between the normal mode and the traction mode. The control device 37 may also set the operating mode to the traction mode by receiving the input signal from the traction switch 30, and supply power from the battery 24 only to the hydraulic pump drive motor 23.

[0093] Thus, in the dump truck 1 of this embodiment, upon receiving a signal from the traction switch 30 to set the mode to traction, the control device 37 sets the operating mode to traction mode. That is, the dump truck 1 of this embodiment does not automatically switch from normal mode to traction mode until the traction switch 30 has received a signal to set the mode to traction. Thus, the dump truck 1 of this embodiment can suppress the occurrence of unintended switching to an unintended operating mode and switch the operating mode at the desired timing according to the passenger's wishes. As a result, the dump truck 1 of this embodiment operates in an operating mode that matches the passenger's intention. Therefore, the dump truck 1 of this embodiment can improve safety.

[0094] While the embodiments of the present invention have been described above, the present invention is not limited to the aforementioned embodiments and various modifications may be made without departing from the spirit of the present invention as described in the scope of the claims. The present invention may add the structure of a certain embodiment to the structure of another embodiment, replace the structure of a certain embodiment with that of another embodiment, or delete a portion of the structure of a certain embodiment.

[0095] Explanation of symbols

[0096] 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…notification device, 37…control device, D1…first specified value, D2…second specified value, L, L0, L1, L2…upper limit of the rotational speed of the 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 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. It is characterized in that The control device performs control to supply the power of the battery only to the hydraulic pump drive motor in a towing mode in which the dump truck is towed.

2. The dump truck according to claim 1, characterized in that The control device controls the battery to be charged with regenerative electric power generated by the travel motor in the traction mode.

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

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

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

6. The dump truck according to claim 5, characterized in that The dump truck also has a notification device that sounds an alarm. The control device causes the notification device to issue an alarm when the vehicle is in the towing mode and the remaining battery level is equal to or less than a second predetermined value that is smaller than the first predetermined value.

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