Dump truck

Abstract

A power collection device 10 includes: a first collector shoe 15A and a second collector shoe 15B that contact an overhead wire 100; a hydraulic first lifting device 20A for lifting the first collector shoe 15A; a hydraulic second lifting device 20B for lifting the second power collector shoe 15B; a first hydraulic circuit device 30A having a first direction control valve 32A and a first pump 31A for supplying hydraulic oil to the first lifting device 20A; a second hydraulic circuit device 30B having a second direction control valve 32B and a second pump 31B for supplying hydraulic oil to the second lifting device 20B; and a controller 60 for controlling the first hydraulic circuit device 30A and the second hydraulic circuit device 30B.

Description

Dump truck

[0001] The present invention relates to a dump truck equipped with a current collector that collects electric power from an overhead line.

[0002] Conventionally, as a dump truck equipped with a current collector (pantograph) that collects electric power from an overhead line, Patent Document 1 describes a dump truck that moves two current collector boats arranged side by side left and right by a hydraulic lifting device.

[0003] Japanese Patent No. 5844452

[0004] However, in the structure described in Patent Document 1, hydraulic oil is branched and supplied to a lifting device that moves two current collector boats from one hydraulic drive source mounted on the vehicle body. Therefore, due to differences in the pipe lengths from the branch point to each lifting device and individual differences in the operability of each device, slight differences may occur in the operation of each lifting device. In this case, each current collector boat may not perform the intended lifting operation, which may affect the power reception state.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a dump truck that can receive power more stably by causing the left and right current collector boats to perform the intended lifting operation.

[0006] To achieve the above objective, the dump truck of the present invention comprises a vehicle body and a current collector provided on the vehicle body for collecting power from an overhead wire, wherein the current collector comprises a first current collector shoe and a second current collector shoe arranged side by side in the width direction of the vehicle and in contact with the overhead wire; a first hydraulic lifting device for raising and lowering the first current collector shoe between a contact position in contact with the overhead wire and a separation position away from the overhead wire; a second hydraulic lifting device for raising and lowering the second current collector shoe between the contact position and the separation position; a first pump for supplying hydraulic fluid to the first lifting device; and a first directional control valve for switching the communication state between the first pump and the first lifting device; a second hydraulic circuit device for supplying hydraulic fluid to the second lifting device; and a second directional control valve for switching the communication state between the second pump and the second lifting device; and a control device for controlling the first hydraulic circuit device and the second hydraulic circuit device.

[0007] According to the dump truck of the present invention, by allowing the left and right current collector shoes to perform the intended raising and lowering movements, more stable power reception becomes possible.

[0008] This is a side view showing a dump truck according to an embodiment. This is a perspective view showing the front of the dump truck. This is a schematic diagram showing the outline of the current collector. This is a schematic diagram showing the current collector in a folded state and its operation restricted. This is a schematic diagram showing the current collector in a raised state. This is a timing chart showing an example of the operation of each component of the current collector. This is an explanatory diagram showing the rotational speed control of the first pump and the second pump according to a modified example. This is a schematic diagram showing an example of how the hydraulic fluid circulates when the current collector is folded and its operation is restricted.

[0009] An embodiment of the present invention will be described below with reference to the drawings. In the following description, the vehicle's longitudinal direction, vehicle width direction (left-right direction), and vertical direction are defined with reference to the driver riding in the dump truck 1.

[0010] (Dump Truck) Figure 1 is a side view showing a dump truck according to an embodiment. The dump truck 1 is used as a vehicle for transporting cargo such as ore and soil loaded on a cargo bed 6 at work sites such as large-scale mines. As shown in Figure 1, the dump truck 1 comprises a body 2, a pair of left and right front wheels 3 and a pair of left and right rear wheels 4 as drive wheels, which are provided on the body 2. The front of the body 2 is provided with a driver's cab 5 where the driver sits, a deck 7 on which the driver's cab 5 is located, and steps 9 and handrails 8 for users of the dump truck 1 to board the deck 7. The rear of the body 2 is provided with a cargo bed 6 that is mounted so as to be rotatable in the vertical direction.

[0011] Furthermore, the dump truck 1 is an electrically driven vehicle that controls AC power from a power source using control equipment such as an inverter and supplies it to an electric motor, which then transmits the driving force of the electric motor to the left and right rear wheels 4 to propel the vehicle. The dump truck 1 is configured to allow selection between a power generation mode and a trolley mode. The power generation mode is a mode in which the vehicle runs by supplying the electric motor with power obtained by driving a generator with an engine such as a diesel engine. The trolley mode is a mode in which the vehicle runs by supplying the electric motor with power obtained from an overhead wire 100 installed on the road. In trolley mode, for example, the climbing speed can be increased when going uphill. However, the dump truck 1 may also drive the electric motor using both the power obtained from the engine and the power obtained from the overhead wire 100.

[0012] (Current Collector) Next, the configuration of the dump truck 1 for operating in trolley mode will be described. The dump truck 1 is equipped with a current collector (pantograph) 10 mounted on the front of the vehicle body 2 in order to obtain power from the overhead line 100. Figure 2 is a perspective view showing the front of the dump truck 1. Figure 3 is a schematic diagram showing the general shape of the current collector 10. Figure 4 is a schematic diagram showing the current collector 10 in a folded state and its operation restricted. Figure 5 is a schematic diagram showing the current collector 10 in a state where the current collector shoe 15 is raised. Note that when the current collector 10 is folded, it means that the lower frame 22 and upper frame 23, which will be described later, are folded.

[0013] As shown in the figure, the current collector 10 includes a pantograph support 11, two current collector shoes 15, two lifting devices 20, two hydraulic circuit devices 30 (first hydraulic circuit device 30A, second hydraulic circuit device 30B), two locking devices 40, a third hydraulic circuit device 50 corresponding to each locking device 40, and a controller (control device) 60.

[0014] (Pantograph Support) As shown in Figures 1 and 2, the pantograph support 11 is a support frame attached to the deck 7 that supports each component of the current collector 10. A frame 12 extending in the vehicle width direction is provided on the upper part of the pantograph support 11.

[0015] (Current collector shoes) The current collector shoes 15 include a first current collector shoe 15A and a second current collector shoe 15B, which are spaced apart from each other in the vehicle width direction and arranged as a pair on the left and right sides. Each current collector shoe 15 collects power from the overhead wire 100 by sliding into contact with the overhead wire 100. Each current collector shoe 15 is connected to an electrical circuit provided inside the vehicle body 2 via a power line (not shown) and supplies the power collected from the overhead wire 100 to the electric motor. Each current collector shoe 15 is supported on a frame 12 via a lifting device 20. The current collector shoes 15 are connected to each other by connecting plates 14. This prevents the overhead wire 100 from getting between the left and right current collector shoes 15. Note that the connecting plates 14 do not electrically connect the current collector shoes 15 to each other.

[0016] (Lifting device) The lifting device 20 is arranged on the frame 12 at intervals from each other in the vehicle width direction and includes a first lifting device 20A that supports the first current collector shoe 15A and a second lifting device 20B that supports the second current collector shoe 15B. Each lifting device 20 supports the corresponding current collector shoe 15 and moves the current collector shoe 15 up and down relative to the overhead line 100. As shown in Figures 3 to 5, each lifting device 20 includes a frame 21 attached to the frame 12 (Figure 2), a lower frame 22, an upper frame 23, a hydraulic cylinder 24, and a spring member 25.

[0017] The lower frame 22 is rotatably connected to the base frame 21 at its base end 22a (Figure 5). The upper frame 23 is rotatably connected to the tip end 22b (Figure 5) of the lower frame 22 at its base end 23a (Figure 5), and a current collector shoe 15 corresponding to the tip end 23b (Figure 5) is connected to it. The hydraulic cylinder 24 includes the first hydraulic cylinder 24A of the first lifting device 20A and the second hydraulic cylinder 24B of the second lifting device 20B, but will be referred to as "hydraulic cylinder 24" without distinction as appropriate. Each hydraulic cylinder 24 has oil chambers 241 and 242 to which hydraulic fluid is supplied from the hydraulic circuit device 30, and a piston 24p that moves in accordance with the hydraulic pressure supplied to the oil chambers 241 and 242. The piston 24p is connected to the lower frame 22. The spring member 25 is connected between the base frame 21 and the base end 23a of the upper frame 23. Furthermore, the lifting device 20 is equipped with a parallel link mechanism (not shown) that can maintain the position of the current collector shoe 15 regardless of the position of the lower frame 22 or the upper frame 23.

[0018] As shown in Figures 3 and 4, when the piston 24p of the hydraulic cylinder 24 is retracted, the lower frame 22 and upper frame 23 are folded and extend in a substantially horizontal direction, and each current collector shoe 15 is separated from the overhead wire 100. In contrast, as shown in Figure 5, when the piston 24p of the hydraulic cylinder 24 is extended, the lower frame 22 is pressed by the hydraulic cylinder 24, and its tip 22b stands upright relative to its base end 22a. As a result, the spring member 25 connected to the base end 23a of the upper frame 23 pulls the base end 23a toward the frame 21, and the tip 23b of the upper frame 23 stands upright relative to the base end 23a. Consequently, the position of the current collector shoe 15 rises, and it comes into contact with the overhead wire 100. In the contact state, the force of the spring member 25 presses the current collector shoe 15 against the overhead wire 100 via the upper frame 23, making it possible to make the current collector shoe 15 follow changes in the height of the overhead wire 100.

[0019] (Hydraulic circuit device: for lifting device) The hydraulic circuit device 30 includes a first hydraulic circuit device 30A corresponding to the first lifting device 20A and a second hydraulic circuit device 30B corresponding to the second lifting device 20B. As shown in Figure 2, the first hydraulic circuit device 30A and the second hydraulic circuit device 30B are arranged on the frame 12 between the left and right current collector shoes 15 and the lifting device 20. In this embodiment, the length of the hydraulic fluid passage from each hydraulic circuit device 30 to each lifting device 20 is set to be the same. The first hydraulic circuit device 30A has a first pump (hydraulic pump) 31A and a first directional control valve 32A, and the second hydraulic circuit device 30B has a second pump (hydraulic pump) 31B and a second directional control valve 32B. As appropriate, the first pump 31A and the second pump 31B will be referred to as "pump 31" without distinction, and the first directional control valve 32A and the second directional control valve 32B will be referred to as "directional control valve 32" without distinction.

[0020] Each pump 31 is a hydraulic pump that is rotationally driven by a corresponding electric motor M and sucks and discharges hydraulic fluid stored in a tank (hydraulic fluid tank) 70 mounted on the vehicle body 2. Here, one tank 70 is provided for each hydraulic circuit device 30 and the third hydraulic circuit device 50, but all tanks 70 may be shared. The hydraulic fluid discharged from the pump 31 is supplied to at least one of the oil chambers 241 and 242 of the hydraulic cylinder 24 via a directional control valve 32. A relief valve 33 is connected to the discharge side of the pump 31 upstream of the directional control valve 32, which returns at least a portion of the hydraulic fluid to the tank 70 when the discharge pressure exceeds a predetermined value.

[0021] The directional control valve 32 is a double solenoid type three-position valve that switches the communication state between the pump 31, the tank 70, and the hydraulic cylinder 24, and is controlled by the controller 60. As shown in Figures 3 and 4, when the solenoid sections 321 and 322 are de-energized, the directional control valve 32 connects the pump 31, the tank 70, and the oil chambers 241 and 242 of the hydraulic cylinder 24. In this case, no force acts on the piston 24p due to the hydraulic pressure from the pump 31. As a result, the entire lower frame 22 and upper frame 23 are pulled in a direction that folds due to the spring member 25, and the piston 24p of the hydraulic cylinder 24 is pushed by the lower frame 22 and contracts. This creates the separated state of the current collector shoe 15 described above.

[0022] In contrast, as shown in Figure 5, the directional control valve 32, when energized at one solenoid section 321, connects the pump 31 to the oil chamber 241 and the oil chamber 242 to the tank 70. As a result, the hydraulic pressure supplied to the oil chamber 241 extends the piston 24p, and the piston 24p presses against the lower frame 22, causing the lower frame 22 and the upper frame 23 to stand upright and form the contact state of the current collector shoe 15 described above. A variable throttle valve 34 with a check valve is positioned between the directional control valve 32 and the hydraulic cylinder 24. In this embodiment, the variable throttle valve 34 is configured to adjust the flow rate of hydraulic fluid from the oil chamber 241 of the hydraulic cylinder 24 to the tank 70 when the current collector shoe 15 is lowered. This slows down the speed (time) at which the hydraulic cylinder 24 retracts, and mitigates the vibration and shock acting on the current collector 10 when it is fully retracted.

[0023] (Locking device) The locking device 40 includes a first locking device 40A provided in correspondence with the first lifting device 20A, and a second locking device 40B provided in correspondence with the second lifting device 20B. The locking device 40 is a device that restricts (locks) the operation of each lifting device 20 when the current collector 10 is folded, and is arranged adjacent to the corresponding lifting device 20. Each locking device 40 has a locking part 41 and a third hydraulic cylinder 42.

[0024] The hook portion 41 is a member that presses the tip portion 23b of the upper frame 23 downward when the current collector 10 is folded. The third hydraulic cylinder 42 is attached to the base frame 21. The third hydraulic cylinder 42 has oil chambers 421 and 422 and a piston 42p that moves in accordance with the hydraulic pressure supplied to the oil chambers 421 and 422. Detailed illustration and description of the structure are omitted, but the hook portion 41 is rotatably attached to the tip of the piston 42p, and the hook portion 41 is configured to rotate in accordance with the extension and retraction state of the piston 42p.

[0025] Specifically, as shown in Figure 3, when the piston 42p of the locking device 40 is retracted, the lock portion 41 is positioned away from the upper frame 23. In this state, the movement of the upper frame 23 is not restricted by the locking device 40. In contrast, as shown in Figure 4, when the piston 42p of the third hydraulic cylinder 42 extends, the lock portion 41 of the locking device 40 rotates and pushes the tip of the upper frame 23 downward. As a result, the upright movement of the upper frame 23 is restricted, and the current collector 10 is firmly fixed in a folded state so as to suppress shaking caused by vibration.

[0026] (Hydraulic circuit device: for locking device) The third hydraulic circuit device 50 includes a third pump 51 and a third directional control valve 52. As shown in Figure 2, the third hydraulic circuit device 50 is positioned on a frame 12 between the left and right current collector shoes 15 and the lifting device 20. The third pump 51 is rotationally driven by a correspondingly provided electric motor M and sucks and discharges hydraulic fluid stored in a tank 70 mounted on the vehicle body 2. The hydraulic fluid discharged from the third pump 51 is supplied to either the oil chamber 421 or 422 of the third hydraulic cylinder 42 via the third directional control valve 52. A relief valve 53 is connected to the discharge side of the third pump 51 upstream of the third directional control valve 52, which returns at least a portion of the hydraulic fluid to the tank 70 when the discharge pressure exceeds a predetermined value.

[0027] The third directional control valve 52 is a double solenoid type three-position valve that switches the communication state between the third pump 51, the tank 70, and each of the third hydraulic cylinders 42 of the two locking devices 40, and is controlled by the controller 60. As shown in Figure 3, the directional control valve 32 connects the third pump 51, the tank 70, and each of the oil chambers 421 and 422 when the solenoid sections 521 and 522 are de-energized. In this case, no force acts on the piston 42p due to the hydraulic pressure from the third pump 51. Figure 3 shows an example of the state in which the piston 42p is retracted.

[0028] In contrast, when the third directional control valve 52 is energized at one solenoid section 521, it connects the third pump 51 to each oil chamber 421 and also connects each oil chamber 422 to the tank 70, as shown in Figure 4. As a result, the hydraulic pressure supplied to each oil chamber 421 extends each piston 42p, causing each hook section 41 to rotate as shown by the solid arrows in Figure 4, and restricting the upright movement of each upper frame 23. Furthermore, when the other solenoid section 522 of the third directional control valve 52 is energized, it connects the third pump 51 to the oil chamber 422 and also connects the oil chamber 421 to the tank 70, as shown in Figure 5. As a result, the hydraulic pressure supplied to the oil chamber 422 causes each piston 42p to retract, causing each hook section 41 to rotate in a direction away from each upper frame 23, as shown by the solid arrows in Figure 5. As a result, the restriction on the upright movement of each upper frame 23 is released.

[0029] (Controller) The controller 60 is mounted, for example, in the driver's cab 5 and consists of a central processing unit, ROM (Read Only Memory), RAM (Random Access Memory), non-volatile RAM, etc. The controller 60 receives signals from the trolley switch 80. The trolley switch 80 is a switch used to instruct the driver whether to select power generation mode or trolley mode, and is located in the driver's cab 5. The controller 60 also receives detection results from a temperature sensor 90 that detects the temperature of the hydraulic fluid stored in each tank 70. Based on the instruction via the trolley switch 80 to select either power generation mode or trolley mode, the controller 60 controls the first pump 31A, the second pump 31B, the first directional control valve 32A, the second directional control valve 32B, the third pump 51, and the third directional control valve 52.

[0030] (Control of the current collector) Next, the control of the current collector 10 when driving the dump truck 1 while switching between power generation mode and trolley mode will be explained. Figure 6 is a timing chart showing an example of the operation of each component of the current collector 10. (a) in the figure indicates the driving mode instruction state. (b) is the rotational speed Np1 of the first pump 31A and the rotational speed Np2 of the second pump 31B. (c) is the rising signal of the current collector 10, that is, the energizing signal to the solenoid section 321 of the first directional control valve 32A and the second directional control valve 32B of the lifting device 20. (d) is the extension and retraction state of the first hydraulic cylinder 24A and the second hydraulic cylinder 24B. (e) is the rotational speed Np3 of the third pump 51. (f) is the unlocking signal indicating the release of the restriction on the operation of the upper frame 23 by the locking device 40, that is, the energizing signal to the solenoid section 522 of the third directional control valve 52. (g) is a signal that restricts the movement of the upper frame 23 by the locking device 40, that is, an energizing signal to the solenoid section 521 of the third direction control valve 52. (h) is the extension / retraction state of the third hydraulic cylinder 42.

[0031] First, when the dump truck 1 is running in power generation mode (before time t1), the controller 60 (b) sets the rotational speed Np1 of the first pump 31A and the rotational speed Np2 of the second pump 31B to a predetermined minimum value Nmin1. The controller 60 also (c) sets the first directional control valve 32A and the second directional control valve 32B to a non-energized state, not outputting an energizing signal to the solenoid section 321 (pantograph raising signal "off"). As a result, (d) the first hydraulic cylinder 24A and the second hydraulic cylinder 24B are retracted, and as shown in Figure 4, the current collector 10 is folded, creating a separated state where the first current collector shoe 15A and the second current collector shoe 15B are separated from the overhead line 100. Furthermore, the controller 60 (e) sets the rotational speed Np3 of the third pump 51 to a predetermined minimum value Nmin2, (f) does not output an energizing signal to the solenoid section 522 of the third directional control valve 52 (the "off" signal for unlocking in the figure), and (g) outputs an energizing signal to the solenoid section 521 of the third directional control valve 52 (the "on" signal for locking in the figure). As a result, (h) the third hydraulic cylinder 42 is extended, and the operation of each upper frame 23 is restricted by each locking device 40 as shown in Figure 4.

[0032] Next, assume that at time t1, the trolley switch 80 is operated by the driver, and (a) the driving mode indication state switches from power generation mode to trolley mode. At this time, the controller 60 (b) starts to increase (change) the rotational speed Np1 of the first pump 31A and the rotational speed Np2 of the second pump 31B in a manner that generates hydraulic pressure to position the first and second current collector shoes 15A and 15B in contact positions. However, the controller 60 (c) does not output an energizing signal to the solenoid section 321, and maintains the first directional control valve 32A and the second directional control valve 32B in the state shown in Figure 4. As a result, (d) the first hydraulic cylinder 24A and the second hydraulic cylinder 24B remain in the contracted state.

[0033] Furthermore, the controller 60 (e) starts increasing the rotational speed Np3 of the third pump 51, (f) outputs an energizing signal to the solenoid section 522 of the third directional control valve 52 (locking signal "on"), and (g) stops outputting an energizing signal to the solenoid section 521 of the third directional control valve 52 (locking signal "off"). As a result, (h) the third hydraulic cylinder 42 starts to retract. Then, at time t2, (e) the rotational speed Np3 of the third pump 51 reaches a predetermined maximum value Nmax2, and (h) the third hydraulic cylinder 42 is in its most retracted state, and the restriction on the operation of each upper frame 23 by each locking device 40 is released. The controller 60 detects the retracted state of the third hydraulic cylinder 42 and recognizes, based on the detection result, that the restriction on the operation of each upper frame 23 by each locking device 40 has been released.

[0034] When the controller 60 recognizes that the restriction on the operation of each upper frame 23 by each locking device 40 has been released (time t2), it (c) outputs an energizing signal to the solenoid section 321 of the first directional control valve 32A and the second directional control valve 32B (pantograph raising signal "on"), and (d) starts the extension of the first hydraulic cylinder 24A and the second hydraulic cylinder 24B. Here, as described above, (b) the rotational speed Np1 of the first pump 31A and the rotational speed Np2 of the second pump 31B have been increasing since time t1, and as a result, they are maintained at a predetermined maximum value Nmax1 from time t2 onward. This makes it possible to supply sufficiently high hydraulic pressure to the first hydraulic cylinder 24A and the second hydraulic cylinder 24B at time t2, and to extend them quickly.

[0035] In this example, the magnitudes of the rotational speeds Np1 and Np2, the flow rate supplied to each hydraulic cylinder 24, and the output timing of the energization signals to the first directional control valve 32A and the second directional control valve 32B are all synchronized. However, the controller 60 may adjust the rotational speeds Np1 and Np2, the flow rate, and the output timing of the energization signals so that each current collector shoe 15 contacts the overhead line 100 as simultaneously as possible, depending on individual differences in the operability of each lifting device 20 and each hydraulic circuit device 30, and the length of the hydraulic fluid passage (same setting in this embodiment).

[0036] Subsequently, at time t3, when the first hydraulic cylinder 24A and the second hydraulic cylinder 24B are fully extended, the first current collector shoe 15A and the second current collector shoe 15B rise, as shown in Figure 5, and a contact state is formed where they are in contact with the overhead line 100. As a result, the dump truck 1 can be driven by the power from the overhead line 100.

[0037] Next, at time t4, the driver operates the trolley switch 80, and (a) the instruction state of the driving mode switches from trolley mode to power generation mode. At this time, the controller 60 (b) starts to decrease the rotational speed Np1 of the first pump 31A and the rotational speed Np2 of the second pump 31B, and (c) stops the output of the energizing signal to the solenoid section 321 of the first directional control valve 32A and the second directional control valve 32B (pantograph raising signal "off"). As a result, (d) the first hydraulic cylinder 24A and the second hydraulic cylinder 24B start to contract. Also, at time t4, the controller 60 (e) starts to decrease (change) the rotational speed Np3 of the third pump 51 in a manner that tends to generate hydraulic pressure to restrict the operation of the first lifting device 20A and the second lifting device 20B by the first locking device 40A and the second locking device 40B.

[0038] Subsequently, at time t5, when the first hydraulic cylinder 24A and the second hydraulic cylinder 24B have fully retracted, the current collector 10 is folded, as shown in Figure 4. As a result, the first current collector shoe 15A and the second current collector shoe 15B are separated from the overhead wire 100. This ends the trolley mode operation and starts the power generation mode operation.

[0039] Furthermore, when the controller 60 recognizes that the current collector 10 is folded based on the state of the first hydraulic cylinder 24A and the second hydraulic cylinder 24B at time t5, it (f) stops outputting the energizing signal to the solenoid section 522 of the third directional control valve 52 (locking signal "off"), and (g) outputs an energizing signal to the solenoid section 521 of the third directional control valve 52 (locking signal "on"). As a result, (h) the third hydraulic cylinder 42 begins to extend, and when it reaches its maximum extension at time t6, the operation of the upper frame 23 is restricted by each locking device 40, as shown in Figure 4. As described above, since the rotational speed Np3 of the third pump 51 is started to decrease at time t4, the third hydraulic cylinder 42 can be quickly extended and the restriction of the operation of the upper frame 23 by each locking device 40 can be completed. This ensures that the current collector 10 remains folded when running in power generation mode.

[0040] (Effects of the Embodiment) As described above, the dump truck 1 according to the embodiment comprises a vehicle body 2 and a current collector 10 provided on the vehicle body 2 for collecting power from the overhead wire 100. The current collector 10 comprises a first current collector shoe 15A and a second current collector shoe 15B arranged side by side in the vehicle width direction and in contact with the overhead wire 100, a hydraulic first lifting device 20A for raising and lowering the first current collector shoe 15A between a contact position in contact with the overhead wire 100 and a separation position away from the overhead wire 100, a hydraulic second lifting device 20B for raising and lowering the second current collector shoe 15B between the contact position and the separation position, a first pump 31A for supplying hydraulic fluid to the first lifting device 20A, and a first pump The system includes a first hydraulic circuit device 30A having a first directional control valve 32A for switching the communication state between pump 31A and the first lifting device 20A; a second hydraulic circuit device 30B having a second pump 31B for supplying hydraulic fluid to the second lifting device 20B and a second directional control valve 32B for switching the communication state between the second pump 31B and the second lifting device 20B; and a controller (control device) 60 for controlling the first hydraulic circuit device 30A and the second hydraulic circuit device 30B.

[0041] With this configuration, hydraulic pressure can be supplied from the first hydraulic circuit device 30A to the first lifting device 20A that raises and lowers the first current collector boat 15A, and hydraulic pressure can be supplied from the second hydraulic circuit device 30B to the second lifting device 20B that raises and lowers the second current collector boat 15B. Therefore, compared with a configuration in which hydraulic oil is branched and supplied from a hydraulic circuit device including a single pump and a direction control valve to the first lifting device 20A and the second lifting device 20B, it is possible to individually control the hydraulic circuit device with a higher degree of freedom. Therefore, even if there are individual differences in the length of the flow path and the operability of each device, for example, it becomes easier to drive the first lifting device 20A and the second lifting device 20B so that the current collector boats 15 move synchronously. Thus, according to the dump truck 1 of the embodiment, it is possible to cause the left and right current collector boats 15 to perform intended lifting operations. Therefore, for example, the influence of the difference in the operating speed of the left and right current collector boats 15 due to individual differences in parts and circuits, the operating environment, and the deterioration status can be reduced, and power reception can be performed more stably.

[0042] In the present embodiment, the current collector boats 15 are connected to each other by the connecting plate 14 and are configured to be able to move following each other. However, if the movements of the current collector boats 15 by hydraulic pressure are not synchronized, the load on the connecting plate 14 will increase. According to the configuration of the present embodiment, it is also possible to reduce the load on the connecting plate 14.

[0043] Furthermore, even when there are changes in the vehicle compartment of the dump truck 1 or the specifications and sizes of the components of the current collector device 10, it can be dealt with by adjusting the rotational speeds Np1, Np2 of the pumps 31 and the rotational speed Np3 of the third pump 51. As a result, there is no need to select hydraulic equipment corresponding to the above changes, and parts can be made common.

[0044] The current collector device 10 includes a gantry 12 that extends in the vehicle width direction on the vehicle body 2 and supports the first current collector boat 15A, the second current collector boat 15B, the first lifting device 20A, and the second lifting device 20B, and the first hydraulic circuit device 30A and the second hydraulic circuit device 30B are mounted on the gantry 12.

[0045] With this configuration, the hydraulic circuit device 30 can be arranged close to the lifting device 20. As a result, the distance from the first hydraulic circuit device 30A to the first lifting device 20A (that is, the length of the hydraulic oil flow path) and the distance from the second hydraulic circuit device 30B to the second lifting device 20B (that is, the length of the hydraulic oil flow path) are less likely to differ. Therefore, it becomes easier to synchronize the operations of the respective current collectors 15 better. Note that each hydraulic circuit device 30 and the third hydraulic circuit device 50 may be mounted at locations other than the gantry 12.

[0046] Further, the current collector device 10 includes a hydraulic first locking device 40A that restricts the operation of the first lifting device 20A in a separated state where the first current collector 15A is separated from the overhead line 100, a hydraulic second locking device 40B that restricts the operation of the second lifting device 20B in a separated state where the second current collector 15B is separated from the overhead line 100, a third pump 51 that supplies hydraulic oil to the first locking device 40A and the second locking device 40B, and a third direction control valve 52 that switches the communication state between the third pump 51, the tank 70, the first locking device 40A, and the second locking device 40B. The current collector device 10 further includes a third hydraulic circuit device 50.

[0047] With this configuration, when the dump truck 1 travels in a state where each current collector 15 is separated from the overhead line 100 (in the power generation mode), the operation of each lifting device 20 can be restricted by each locking device 40, and it is possible to prevent each current collector 15 from accidentally contacting the overhead line 100.

[0048] Further, while the controller 60 is executing the release process of restricting the operations of the first lifting device 20A and the second lifting device 20B by the first locking device 40A and the second locking device 40B (at times t1 to t2 in FIG. 6), the controller 60 increases (changes) in advance the rotational speeds Np1 and Np2 of the first pump 31A and the second pump 31B so as to generate the hydraulic pressure for positioning the first current collector 15A and the second current collector 15B at the contact position while not supplying hydraulic oil to the first lifting device 20A and the second lifting device 20B.

[0049] With this configuration, when the restriction on the operation of each lifting device 20 by each locking device 40 is released, each lifting device 20 can be quickly driven to position each current collector shoe 15 in contact with the target. If the configuration requires reducing the hydraulic pressure supplied to each lifting device 20 in order to position each current collector shoe 15 in contact with the target, the rotational speeds Np1 and Np2 of the first pump 31A and the second pump 31B should be reduced in advance.

[0050] Furthermore, while the controller 60 is performing the process of separating the first current collector shoe 15A and the second current collector shoe 15B from the overhead line 100 using the first lifting device 20A and the second lifting device 20B (times t4 to t5 in Figure 6), the controller 60 pre-decreases (changes) the rotational speed Np3 of the third pump 51 so as to generate hydraulic pressure to restrict the operation of the first lifting device 20A and the second lifting device 20B, while refraining from supplying hydraulic fluid to the first locking device 40A and the second locking device 40B.

[0051] With this configuration, once the process of separating each current collector shoe 15 from the overhead line 100 is completed, each locking device 40 can be quickly driven to restrict the operation of each lifting device 20. In the case of a configuration in which the hydraulic pressure supplied to each locking device 40 is increased in order to restrict the operation of each lifting device 20, the rotational speed Np3 of the third pump 51 can be increased in advance.

[0052] In this embodiment, when the current collector shoes 15 are in a separated position and the current collector 10 is folded and its operation is restricted (Figure 4), the rotational speed Np1 of the first pump 31A and the rotational speed Np2 of the second pump 31B are set to a predetermined minimum value Nmin. However, the values ​​of the rotational speeds Np1 and Np2 when the current collector 10 is folded and its operation is restricted are not limited to these values. Figure 7 is an explanatory diagram showing the rotational speed control of the first pump 31A and the second pump 31B according to a modified example. Figure 8 is a schematic diagram showing an example of how the hydraulic fluid circulates when the current collector 10 is folded and its operation is restricted.

[0053] As shown in Figure 7, the controller 60 is set to tend to increase the rotational speeds Np1 and Np2 as the hydraulic fluid temperature detected by the temperature sensor 90 decreases. In the example shown in Figure 7, when the hydraulic fluid temperature is below the first predetermined temperature T1, the rotational speeds Np1 and Np2 are set to the first predetermined value N1. When the hydraulic fluid temperature is greater than the first predetermined temperature T1 and below the second predetermined temperature T2, the rotational speeds Np1 and Np2 are set to tend to decrease as the hydraulic fluid temperature increases. When the hydraulic fluid temperature is greater than the second predetermined temperature T2, the rotational speeds Np1 and Np2 are set to the second predetermined value N0, which is lower than the first predetermined value N1. The rotational speed Np1 should be set based on the temperature of the hydraulic fluid in the first hydraulic circuit device 30A, and the rotational speed Np2 should be set based on the temperature of the hydraulic fluid in the second hydraulic circuit device 30A.

[0054] In this configuration, when the current collector 10 is folded and its operation is restricted, the hydraulic fluid is circulated between the tank 70 and the directional control valve 32 by the pump 31, for example, as shown by the thick arrow in Figure 8. At this time, the pump 31, the tank 70, and the oil chambers 241 and 242 of the hydraulic cylinder 24 are all in communication and in a balanced state, so no force acts on the piston 24p due to the hydraulic pressure from the pump 31. Note that even when the rotational speeds Np1 and Np2 are set to the predetermined minimum value Nmin, the hydraulic fluid circulates in the same way, but this is omitted in Figure 4 above for the sake of simplicity. As mentioned above, the lower the hydraulic fluid temperature, the larger the rotational speeds Np1 and Np2 tend to be, so the lower the hydraulic fluid temperature, the faster the hydraulic fluid circulates.

[0055] Thus, the dump truck 1 is further equipped with a temperature sensor (temperature detection device) 90 that detects the temperature of the hydraulic fluid stored in each tank 70, that is, the temperature of the hydraulic fluid in the first hydraulic circuit device 30A and the second hydraulic circuit device 30B. When the first current collector shoe 15A and the second current collector shoe 15B are in a separated position, the controller 60 controls the first hydraulic circuit device 30A and the second hydraulic circuit device 30B to circulate the hydraulic fluid faster the lower the temperature of the hydraulic fluid detected by the temperature sensor 90, without operating the first lifting device 20A and the second lifting device 20B. As a result, it becomes possible to suppress the decrease in the temperature of the hydraulic fluid more effectively. Note that the temperature sensor 90 may be provided in a location other than the tank 70.

[0056] This concludes the description of the embodiments, but the embodiments of the present invention are not limited to these embodiments.

[0057] 1 Dump truck 2 Body 10 Current collector (pantograph) 11 Pantograph support 12 Frame 15 Current collector shoe 15A First current collector shoe 15B Second current collector shoe 20 Lifting device 20A First lifting device 20B Second lifting device 24 Hydraulic cylinder 24A First hydraulic cylinder 24B Second hydraulic cylinder 30 Hydraulic circuit device 30A First hydraulic circuit device 30B Second hydraulic circuit device 31 Pump 31A First pump 31B Second pump 32 Directional control valve 32A First directional control valve 32B Second directional control valve 40 Locking device 40A First locking device 40B Second locking device 50 Third hydraulic circuit device 51 Third pump 52 Third directional control valve 60 Controller (control device) 90 Temperature sensor (temperature detection device) 100 overhead lines

Claims

1. A dump truck comprising a vehicle body and a current collector provided on the vehicle body for collecting power from an overhead wire, wherein the current collector comprises: a first current collector shoe and a second current collector shoe arranged side by side in the vehicle width direction and in contact with the overhead wire; a hydraulic first lifting device for raising and lowering the first current collector shoe between a contact position in contact with the overhead wire and a separation position away from the overhead wire; a hydraulic second lifting device for raising and lowering the second current collector shoe between the contact position and the separation position; a first hydraulic circuit device having a first pump for supplying hydraulic fluid to the first lifting device and a first directional control valve for switching the communication state between the first pump and the first lifting device; a second hydraulic circuit device having a second pump for supplying hydraulic fluid to the second lifting device and a second directional control valve for switching the communication state between the second pump and the second lifting device; and a control device for controlling the first hydraulic circuit device and the second hydraulic circuit device.

2. The dump truck according to claim 1, characterized in that the current collector extends in the width direction on the vehicle body and comprises a frame that supports the first current collector shoe, the second current collector shoe, the first lifting device and the second lifting device, and the first hydraulic circuit device and the second hydraulic circuit device are mounted on the frame.

3. The dump truck according to claim 1, further comprising: a hydraulic first locking device that restricts the operation of the first lifting device when the first current collector shoe is separated from the overhead wire; a hydraulic second locking device that restricts the operation of the second lifting device when the second current collector shoe is separated from the overhead wire; a third pump that supplies hydraulic fluid to the first locking device and the second locking device; and a third directional control valve that switches the communication state between the third pump and the first locking device and the second locking device; 4. The dump truck according to claim 1, further comprising a temperature detection device for detecting the temperature of the hydraulic fluid in the first hydraulic circuit device and the second hydraulic circuit device, wherein the control device controls the first hydraulic circuit device and the second hydraulic circuit device to circulate the hydraulic fluid faster the lower the temperature of the hydraulic fluid detected by the temperature detection device is, without operating the first lifting device and the second lifting device, when the first and second current collector shoes are in the separated position.

5. The dump truck according to claim 3, characterized in that the control device pre-varies the rotational speeds of the first pump and the second pump so as to generate hydraulic pressure to position the first and second current collector shoes at the contact position, while the control device is performing a process to release the restriction on the operation of the first and second lifting devices by the first and second locking devices, while not supplying the hydraulic fluid to the first and second lifting devices.

6. The dump truck according to claim 3, characterized in that the control device pre-varies the rotational speed of the third pump so as to generate hydraulic pressure to restrict the operation of the first lifting device and the second lifting device, while the first lifting device and the second lifting device are performing the process of separating the first and second current collector shoes from the overhead line, while the control device is not supplying the hydraulic fluid to the first locking device and the second locking device.

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