Work vehicles

Abstract

To provide a work vehicle that can consume regenerative electric power.SOLUTION: A work vehicle comprises an electric motor, a travelling body, a hydraulic oil tank, a hydraulic pump and an accumulator. The hydraulic pump is driven by regenerative electric power of the electric motor generated by braking the travelling body to pressure-feed hydraulic oil in the hydraulic oil tank. The accumulator accumulates pressure of the hydraulic oil pressure-fed from the hydraulic pump.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This disclosure relates to a work vehicle.

Background Art

[0002] In an open-pit mine, a transport vehicle may continuously descend a slope in a loaded state for a long time. In such a case, in order to keep the downhill speed constant, it is necessary to keep the brake operating during the downhill. Patent Document 1 discloses an electric drive dump truck that converts the regenerative power generated by braking into thermal energy by a resistor (retarder grid).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to exert braking force by converting regenerative power into heat by a retarder grid, a large retarder grid capable of consuming a large amount of energy generated during downhill is required. The retarder grid mounted on a large dump truck is installed on a platform. The platform is a flat plate portion provided above the front wheels of the vehicle body. However, when installing a structure other than the retarder grid on the platform, it is preferable to miniaturize the retarder grid. For example, in order to install a hydrogen tank on the platform of a transport vehicle driven by a fuel cell, it is preferable to reduce the proportion occupied by the retarder grid on the platform. In order to miniaturize the retarder grid, it is necessary to reduce the power consumed by the retarder grid.

[0005] An object of the present disclosure is to provide a work vehicle capable of consuming regenerative power. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, the work vehicle comprises an electric motor, a traveling body driven by the electric motor, a hydraulic oil tank for storing hydraulic fluid, a hydraulic pump driven by regenerative power from the electric motor generated by braking the traveling body and for pressurizing the hydraulic fluid in the hydraulic oil tank, and an accumulator for accumulating the pressure of the hydraulic fluid pressurized by the hydraulic pump. [Effects of the Invention]

[0007] According to the above embodiment, the work vehicle can consume regenerative power. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic perspective view showing a transport vehicle according to the first embodiment. [Figure 2] This is a schematic block diagram showing the configuration of the hydraulic system provided in the transport vehicle according to the first embodiment. [Figure 3] This is a schematic block diagram showing the configuration of the electric system provided in the transport vehicle according to the first embodiment. [Figure 4] This is a schematic block diagram showing the configuration of the control device according to the first embodiment. [Figure 5] This is a flowchart showing retarder control by the control device according to the first embodiment. [Modes for carrying out the invention]

[0009] <First Embodiment> 《Configuration of transport vehicle 10》 The embodiments will be described in detail below with reference to the drawings. The transport vehicle 10 according to the first embodiment is a rigid-frame dump truck used to transport crushed stone and other materials excavated in mines, etc. The transport vehicle 10 is driven by a fuel cell 41 that uses hydrogen gas as fuel. The transport vehicle 10 is an example of a work vehicle. Figure 1 is a schematic perspective view showing a transport vehicle 10 according to the first embodiment. The transport vehicle 10 comprises a dump body 11, a vehicle body 12, and a running gear 13.

[0010] The dump body 11 is the component on which the cargo is loaded. At least a portion of the dump body 11 is positioned above the vehicle body 12. The dump body 11 performs dumping and lowering operations. Through the dumping and lowering operations, the dump body 11 is adjusted to a dumping position and a loading position. The dumping position refers to the position in which the dump body 11 is raised. The loading position refers to the position in which the dump body 11 is lowered.

[0011] The dumping operation refers to the movement of separating the dump body 11 from the vehicle body 12 and tilting it in the dumping direction. The dumping direction is towards the rear of the vehicle body 12. In this embodiment, the dumping operation includes raising the front end of the dump body 11 and tilting the dump body 11 backward. Due to the dumping operation, the loading surface of the dump body 11 is tilted downward toward the rear.

[0012] The lowering operation refers to the operation of bringing the dump body 11 closer to the vehicle body 12. In this embodiment, the lowering operation includes lowering the front end of the dump body 11.

[0013] When performing soil removal operations, the dump body 11 performs a dumping operation to change from a loading position to a dumping position. If there is cargo loaded on the dump body 11, the cargo is discharged backward from the rear end of the dump body 11 by the dumping operation. When performing loading operations, the dump body 11 is adjusted to a loading position.

[0014] The vehicle body 12 includes a vehicle frame (not shown). The vehicle body 12 rotatably supports the dump body 11 via hinge pins provided on the vehicle frame. The vehicle body 12 is supported by the running gear 13. A platform 121 is provided on the vehicle frame above the front wheels of the running gear 13. The platform 121 is a flat plate that forms the upper surface of the vehicle frame. A driver's cab 122, a control cabinet 123, and a retarder grid 46 are provided on the platform 121. A fuel cell 41 is also provided on the vehicle frame. An opening is provided on the front of the vehicle body 12 in the portion in front of the fuel cell 41, and a grille 124 is provided in the opening. A fan 125 for cooling the fuel cell 41 is provided between the grille 124 and the fuel cell 41. The fan 125 cools the fuel cell 41 by drawing outside air into the vehicle frame through the grille 124.

[0015] The control cabinet 123 performs power conversion. Specifically, the control cabinet 123 controls the power between the fuel cell 41, various motors, and the retarder grid 46. The retarder grid 46 is a resistor that absorbs the regenerative power generated by the braking of the traction unit 13. The retarder grid 46 converts the regenerative power into thermal energy.

[0016] The running gear 13 supports the vehicle body 12. The running gear 13 moves the transport vehicle 10. The running gear 13 moves the transport vehicle 10 forward or backward. At least a portion of the running gear 13 is positioned below the vehicle body 12. The running gear 13 comprises a pair of front wheels and a pair of rear wheels. The front wheels are steering wheels, and the rear wheels are drive wheels.

[0017] Configuration of the hydraulic system 20 Figure 2 is a schematic block diagram showing the configuration of the hydraulic system 20 provided in the transport vehicle 10 according to the first embodiment. As shown in FIG. 2, the hydraulic system 20 of the transport vehicle 10 includes a hydraulic oil tank 21, a hydraulic pump 22, an accumulator 23, a control valve 25, a steering cylinder 26, and a work implement cylinder 27.

[0018] The discharge port of the hydraulic pump 22 is connected to the accumulator 23 via a first flow path P1. A first check valve 28 is provided in the first flow path P1. The first check valve 28 allows the flow of hydraulic oil from the hydraulic pump 22 to the accumulator 23 and blocks the flow of hydraulic oil from the accumulator 23 to the hydraulic pump 22. Thereby, the pressure of the hydraulic oil output by the hydraulic pump 22 is accumulated in the accumulator 23.

[0019] The hydraulic system 20 includes a second flow path P2 that connects an intermediate portion between the accumulator 23 and the first check valve 28 in the first flow path P1 and the hydraulic oil tank 21. In the second flow path P2, a 2-port solenoid valve 29, a throttle 30, a second check valve 31, and an oil cooler 32 are provided in order from the first flow path P1 side. The 2-port solenoid valve 29 is configured to be able to switch between conducting and blocking the first flow path P1. The 2-port solenoid valve 29 conducts the first flow path P1 when regenerative power is generated and the hydraulic pump 22 is operating. The throttle 30 restricts the flow rate of the hydraulic oil flowing through the first flow path P1 and generates a pressure loss. The temperature of the hydraulic oil passing through the throttle 30 rises due to the pressure loss. The second check valve 31 allows the flow of hydraulic oil from the first flow path P1 to the hydraulic oil tank 21 and blocks the flow of hydraulic oil from the hydraulic oil tank 21 to the first flow path P1. The oil cooler 32 cools the hydraulic oil flowing through the second flow path P2 by heat exchange with a refrigerant. The refrigerant of the oil cooler 32 is cooled by a radiator 35. The radiator 35 is provided between the grill 124 and the fan 125 shown in FIG. 1. That is, the fan 125 according to the first embodiment is a cooling device that cools the fuel cell 41 and is also a cooling device that cools the hydraulic oil.

[0020] The hydraulic system 20 includes a third flow path P3 that connects the intermediate section of the first flow path P1 between the hydraulic pump 22 and the first check valve 28, and the intermediate section of the second flow path P2 between the oil cooler 32 and the second check valve 31. The third flow path P3 is equipped with a relief valve 33 and a flow meter 34. The relief valve 33 opens when the pressure in the first flow path P1 exceeds a predetermined relief pressure. This keeps the pressure in the accumulator 23 below the relief pressure. The relief valve 33 also closes when the pressure in the first flow path P1 falls below a predetermined pressure. This keeps the pressure in the accumulator 23 above the predetermined pressure. The flow meter 34 measures the flow rate of the hydraulic fluid flowing through the third flow path P3.

[0021] The control valve 25 is connected to the intermediate portion of the first flow path P1 between the accumulator 23 and the first check valve 28.

[0022] The control valve 25 adjusts the flow rate of hydraulic fluid supplied to the steering cylinder 26 and the work machine cylinder 27 in response to the operation of an operating device (not shown) by the operator. The steering cylinder 26 controls the direction of travel of the travel device 13 by changing the angle of the front wheels of the travel device 13. The first port of the control valve 25 is connected to the intermediate part of the first flow path P1 between the accumulator 23 and the first check valve 28. Hydraulic fluid is supplied to the first port from the hydraulic pump 22 and the accumulator 23, whichever has the higher pressure. The second port of the control valve 25 is connected to the hydraulic fluid tank 21. Return hydraulic fluid from the steering cylinder 26 and the work machine cylinder 27 is supplied to the hydraulic fluid tank 21 via the second port. The third and fourth ports of the control valve 25 are connected to the steering cylinder 26. The fifth and sixth ports of the control valve 25 are connected to the work machine cylinder 27. The implement cylinder 27 has its head attached to the dump body 11 and its rod attached to the vehicle body 12. As the implement cylinder 27 extends and retracts, the posture of the dump body 11 relative to the vehicle body 12 changes. In other words, by driving the implement cylinder 27, the dumping and lowering movements of the dump body 11 can be achieved.

[0023] 《Configuration of the Electric System 40》 Figure 3 is a schematic block diagram showing the configuration of the electric system 40 provided in the transport vehicle 10 according to the first embodiment. The electric system 40 comprises a fuel cell 41, a battery 42, a pump motor 43, a fan motor 44, a drive motor 45, a retarder grid 46, a first DC-DC converter 47, a second DC-DC converter 48, a third DC-DC converter 49, a fourth DC-DC converter 50, an inverter 51, and a control device 60. The first DC-DC converter 47, the second DC-DC converter 48, the third DC-DC converter 49, the fourth DC-DC converter 50, the inverter 51, and the control device 60 are housed in a control cabinet 123.

[0024] The fuel cell 41 generates electricity by reacting hydrogen gas supplied from a hydrogen tank (not shown) with oxygen contained in the outside air. The first DC-DC converter 47 supplies the DC power generated by the fuel cell 41 to busbar B. The second DC-DC converter 48 supplies power charged in the battery 42 to bus B. The second DC-DC converter 48 also charges the battery 42 by adjusting the voltage of the DC power flowing to bus B and supplying it to the battery 42. In other words, the second DC-DC converter 48 is an example of a charging device. The battery 42 is equipped with a Battery Management Unit (BMU) (not shown) that monitors the state of the battery 42. The BMU measures the charge rate of the battery 42 and outputs the measurement data to the control device 60. The pump motor 43 drives the hydraulic pump 22 shown in Figure 2. The third DC-DC converter 49 adjusts the voltage of the DC power flowing through busbar B and supplies it to the pump motor 43. The fan motor 44 drives the fan 125 shown in Figure 1. The fourth DC-DC converter 50 adjusts the voltage of the DC power flowing through busbar B and supplies it to the fan motor 44. The traction motor 45 is a three-phase AC electric motor that drives the traction device 13. The inverter 51 converts the DC power flowing to the busbar B into three-phase AC power and supplies it to the traction motor 45. The inverter 51 also converts the regenerative power generated in the traction motor 45 by the braking of the traction device 13 into DC power and supplies it to the busbar B. A voltmeter 52 is provided on the traction motor 45. The voltmeter 52 measures the voltage related to the traction motor 45. The voltmeter 52 transmits the measurement data to the control device 60.

[0025] The control device 60 controls the first DC-DC converter 47, the second DC-DC converter 48, the third DC-DC converter 49, the fourth DC-DC converter 50 and inverter 51, as well as the two-port solenoid valve 29 shown in Figure 2, based on measurement data received from the flow meter 34, the battery 42's BMU and voltmeter 52.

[0026] Configuration of the control device 60 Figure 4 is a schematic block diagram showing the configuration of the control device 60 according to the first embodiment. The control unit 60 is a computer equipped with a processor 61, main memory 62, storage 63, and interface 64. The processor 61 reads the program from the storage 63, loads it into the main memory 62, and executes processing according to the program. Examples of processors 61 include CPUs (Central Processing Units), GPUs (Graphics Processing Units), and microprocessors.

[0027] The program may be for implementing a part of the functions to be performed by the control device 60. For example, the program may perform functions in combination with other programs already stored in storage, or in combination with other programs implemented in other devices. In other embodiments, the control device 60 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor 61 may be implemented by the integrated circuit. Such an integrated circuit is also included as an example of a processor.

[0028] Examples of storage 63 include magnetic disks, magneto-optical disks, optical disks, and semiconductor memory. Storage 63 may be an internal medium directly connected to the bus, or an external medium connected to the control device 60 via interface 64 or a communication line. Furthermore, if this program is delivered to the control device 60 via a communication line, the receiving control device 60 may expand the program into main memory 62 and execute the above processing. In at least one embodiment, storage 63 is a tangible storage medium that is not temporary.

[0029] Furthermore, the program may be intended to implement some of the functions described above. In addition, the program may be a so-called differential file (differential program) that implements the functions described above in combination with other programs already stored in storage 63.

[0030] Retarder control by a control device Figure 5 is a flowchart showing the retarder control by the control device 60. The control device 60 performs the retarder control shown in Figure 5 at regular intervals. First, the control device 60 determines whether or not regenerative power is being generated in the drive motor 45 based on the measurement data received from the voltmeter 52 (step S1). The control device 60 determines the presence or absence of regenerative power by, for example, the sign of the voltage value. If no regenerative power is being generated (step S1: NO), the control device 60 terminates the retarder control.

[0031] On the other hand, if regenerative power is being generated (step S1: YES), the control device 60 determines whether the charge level of the battery 42 is above the upper limit based on the measurement data received from the battery 42's BMU (step S2). If the charge level of the battery 42 is below the upper limit (step S2: NO), the control device 60 outputs a charge command for the battery 42 to the second DC-DC converter 48 (step S3). This allows the control device 60 to absorb the regenerative power into the battery 42 and reduce the power consumed by the retarder grid 46. Therefore, if the charge level of the battery 42 is below the upper limit, the control device 60 terminates the retarder control.

[0032] On the other hand, if the charge level of the battery 42 is above the upper limit (step S2: YES), the control device 60 outputs a drive command for the pump motor 43 to the third DC-DC converter 49 (step S4). As a result, the pump motor 43 drives the hydraulic pump 22.

[0033] Next, the control device 60 determines whether or not hydraulic fluid is flowing through the third channel P3 based on the measurement data from the flow meter 34 (step S5). If hydraulic fluid is not flowing through the third channel P3 (step S5: NO), it is understood that the hydraulic fluid pressure is being accumulated in the accumulator 23 by the hydraulic pump 22. In this case, the pump motor 43 can absorb regenerative power due to the load generated by the pressure accumulation in the accumulator 23. Therefore, if hydraulic fluid is not flowing through the third channel P3 (step S5: NO), the control device 60 terminates the retarder control.

[0034] On the other hand, if hydraulic fluid is flowing through the third flow path P3 (step S5: YES), the pressure in the accumulator 23 exceeds the relief pressure of the relief valve 33, indicating that no further pressure can be accumulated in the accumulator 23. If hydraulic fluid is flowing through the third flow path P3 (step S5: YES), the control device 60 energizes the 2-port solenoid valve 29 (step S6) to start the flow of hydraulic fluid to the second flow path P2. The control device 60 also outputs a drive command for the fan motor 44 to the fourth DC-DC converter 50 (step S7). As a result, the pump motor 43 can absorb regenerative power due to the load generated by the throttle 30. The fan motor 44 can also absorb regenerative power. Furthermore, the rotation of the fan 125 cools the refrigerant in the oil cooler 32 via the radiator 35, thereby cooling the hydraulic fluid whose temperature has risen due to the throttle 30.

[0035] Action / Effect As described above, the control device 60 of the transport vehicle 10 according to the first embodiment operates the hydraulic pump 22 using the regenerative power of the travel motor 45 generated by the braking of the travel device 13, thereby accumulating hydraulic fluid pressure in the accumulator 23. As a result, the transport vehicle 10 can recover regenerative power by accumulating pressure in the accumulator 23 by the hydraulic pump 22. The hydraulic energy accumulated in the accumulator 23 can be used to drive the steering cylinder 26 and the work machine cylinder 27 via the control valve 25.

[0036] Furthermore, the transport vehicle 10 according to the first embodiment includes a two-port solenoid valve 29 that is controlled to be open when the travel motor 45 is outputting regenerative power and the hydraulic pump 22 is driven, and a throttle 30 provided downstream of the two-port solenoid valve 29. This allows the regenerative power to be converted into thermal energy by the pressure loss of the hydraulic fluid in the throttle 30, even after the accumulator 23 has finished filling with pressure. In addition, when no regenerative power is being generated or when regenerative power is being recovered by the battery 42, closing the two-port solenoid valve 29 prevents the pressure accumulated in the accumulator 23 from being unnecessarily consumed. Note that the transport vehicle 10 according to the other embodiment may not have a second flow path P2.

[0037] Furthermore, the transport vehicle 10 according to the first embodiment is equipped with an oil cooler 32 that is driven by regenerative power from the travel motor 45 and cools the hydraulic fluid downstream of the throttle 30. This allows the transport vehicle 10 to recover regenerative power by driving the oil cooler 32 and further reduce the temperature of the hydraulic fluid that has risen due to pressure loss. Note that the transport vehicle 10 according to other embodiments may not be equipped with an oil cooler 32. Also, the oil cooler 32 according to the first embodiment cools the hydraulic fluid with a refrigerant cooled by a fan 125 and a radiator 35, but is not limited to this. For example, the oil cooler 32 according to other embodiments may be a refrigerator that transfers heat from the refrigerant by compression and expansion of the refrigerant. In this case, the compressor included in the refrigerator is driven by regenerative power.

[0038] Furthermore, the transport vehicle 10 according to the first embodiment is equipped with a second DC-DC converter 48 that charges the battery 42 with regenerative power, and the control device 60 drives the hydraulic pump 22 when the charge level of the battery 42 exceeds an upper limit. As a result, the transport vehicle 10 can absorb regenerative power in two stages: charging the battery 42 and accumulating pressure in the accumulator 23.

[0039] Furthermore, the fan 125 of the transport vehicle 10 according to the first embodiment is driven by regenerative power from the drive motor 45 to cool the fuel cell 41. This allows the regenerative power to be absorbed by the rotation of the fan 125. The control device 60 according to the first embodiment rotates the fan 125 when the charge level of the battery 42 is above the upper limit and the pressure of the accumulator 23 is above the relief pressure, but is not limited to this. For example, the control device 60 according to another embodiment may drive the fan motor 44 when the drive motor 45 generates regenerative power, regardless of the charge level of the battery 42 and the pressure of the accumulator 23.

[0040] As described above, the transport vehicle 10 according to the first embodiment can reduce the regenerative power consumed by the retarder grid 46. If the travel route of the transport vehicle 10 is known in advance, the size of the retarder grid 46 can be designed based on the amount of power that can be absorbed by the battery 42, accumulator 23, throttle 30, oil cooler 32, and fan 125. This makes it possible to miniaturize the retarder grid 46 and secure space for other structures on the platform 121. Examples of other structures to be installed on the platform 121 include a hydrogen tank filled with hydrogen gas to be supplied to the fuel cell 41.

[0041] Furthermore, since the hydraulic pump 22 and accumulator 23 are configured to be widely mounted on electric transport vehicles 10, the transport vehicle 10 according to the first embodiment can be easily manufactured by modifying an existing transport vehicle 10.

[0042] <Other Embodiments> Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes are possible. In other embodiments, the order of the above-described processes may be changed as appropriate. Also, some processes may be executed in parallel. The control device 60 according to the above embodiment may be composed of a single computer, or the configuration of the control device 60 may be divided among multiple computers, and the multiple computers may cooperate with each other to function as the control device 60.

[0043] In the embodiments described above, a transport vehicle 10 was described as an example of a work machine, but it is not limited to this. For example, the work machine in other embodiments may be other work machines such as a hydraulic excavator, a wheel loader, or a motor grader. [Explanation of Symbols]

[0044] 10…Transport vehicle 11…Dump body 12…Vehicle body 121…Platform 122…Driver's cab 123…Control cabinet 124…Grille 125…Fan 13…Running gear 20…Hydraulic system 21…Hydraulic oil tank 22…Hydraulic pump 23…Accumulator 25…Control valve 26…Steering cylinder 27…Working equipment cylinder 28…First check valve 29…2-port solenoid valve 30…Throttle 31…Second check valve 32…Oil cooler 33…Relief valve 34…Flow meter 35…Radiator 40…Electric system 41…Fuel cell 42…Battery 43…Pump motor 44…Fan motor 45…Running motor 46…Retarder grid 47…First DC-DC converter 48…Second DC-DC converter 49…Third DC-DC converter 50…Fourth DC-DC converter 51…Inverter 52…Voltmeter 60...Control device 61...Processor 62...Main memory 63...Storage 64...Interface B...Bus P1...First channel P2...Second channel P3...Third channel

Claims

1. Electric motor and, The electric motor drives the vehicle, A hydraulic oil tank for storing hydraulic fluid, A hydraulic pump, driven by the regenerative power of the electric motor generated by the braking of the aforementioned vehicle, pumps the hydraulic fluid in the hydraulic fluid tank, An accumulator that stores the pressure of the hydraulic fluid pumped from the aforementioned hydraulic pump, A first flow path connecting the accumulator and the hydraulic pump, A second flow path connects the intermediate portion of the first flow path to the hydraulic fluid tank, A solenoid valve is provided in the second flow path and is controlled to be in an open state while the electric motor is outputting the regenerative power and the hydraulic pump is operating. A throttle provided downstream of the solenoid valve, A work vehicle equipped with the following features.

2. A cooling device driven by the regenerative power of the electric motor, which cools the hydraulic fluid downstream of the throttle. A work vehicle according to claim 1, comprising:

3. Battery and A charging device that charges the battery using the regenerative power of the electric motor. Equipped with, The hydraulic pump is activated when the battery's charge level reaches a predetermined value or higher. A work vehicle according to claim 1 or claim 2.

4. An electric motor and The electric motor drives the vehicle, A hydraulic oil tank for storing hydraulic fluid, A hydraulic pump, driven by the regenerative power of the electric motor generated by the braking of the aforementioned vehicle, pumps the hydraulic fluid in the hydraulic fluid tank, An accumulator that stores the pressure of the hydraulic fluid pumped from the aforementioned hydraulic pump, A fuel cell that supplies power to the electric motor, When the pressure of the accumulator is above a predetermined threshold, a cooling device is driven by the regenerative power of the electric motor to cool the fuel cell. A work vehicle equipped with the following features.

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