High and cold closed type lifting hydraulic system, control method and mining dump truck

Abstract

The invention relates to a high and cold closed type lifting hydraulic system, a control method and a mining dump truck, the high and cold closed type lifting hydraulic system comprises a lifting pump, a lifting slide valve, a balance valve group, a lifting oil cylinder and a lifting electro-hydraulic control handle, the oil return end of the lifting slide valve is connected with the oil suction end of the lifting pump through a cold start electromagnetic valve, and an oil supplementing valve is arranged between the oil suction end and the oil outlet end of the lifting pump; the oil supplementing valve is connected with an oil supplementing energy accumulator; the system further comprises a controller, the input end of the controller is connected with an oil temperature sensor, a lifting maximum position sensor and a cargo compartment falling position sensor, and the output end of the controller is connected with a lifting electro-hydraulic control handle and a cold start electromagnetic valve. The closed type lifting hydraulic system has the advantages of being fast in system temperature rise, small in structural size and good in pump self-suction performance, can stably operate in the low-temperature environment, provides oil suction back pressure for the hydraulic pump, meanwhile, improves the corresponding performance of the system in combination with intelligent temperature control and measurement, has intelligent lifting limiting / floating control, and is high in reliability. And the lifting action of the mining dump truck is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering machinery, and in particular to a high-cold closed lifting hydraulic system, a control method and a mining dump truck. Background Art

[0002] Mining dump trucks are specialized heavy-duty vehicles used for short-distance transport of rock, earth, and ore on dedicated roads, such as those in open-pit mines or large-scale civil construction sites. These vehicles often operate in high-altitude and frigid regions. Due to their high latitudes and altitudes, these regions experience low pressure, low temperatures, and severe cold weather for a significant portion of the year. Operating in these regions often requires a heating system to improve vehicle starting performance. Adding a pre-load tank to address the pump's self-priming performance also increases the size and complexity of the hydraulic tank. Conventional lifting hydraulic systems utilize open-loop hydraulic systems, resulting in slow temperature cycles and the need for a large-capacity tank to meet the lifting system's requirements. These characteristics increase the overall vehicle hydraulic system space and complexity. To address these limitations, a compact hydraulic system was required that could operate stably in low-temperature environments and provide suction backpressure for the hydraulic pump. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a high-cold closed lifting hydraulic system, a control method and a mining dump truck with a simple structure and good effect.

[0004] The present invention is implemented by the following technical solution: a high-altitude closed-type lifting hydraulic system, comprising a lifting pump, the lifting pump being connected to a lifting cylinder via a lifting slide valve and a balancing valve group, the control end of the lifting slide valve being connected to a lifting electro-hydraulic control handle, the oil return end of the lifting slide valve being connected to the oil suction end of the lifting pump via a cold start solenoid valve, an oil replenishment valve being provided between the oil suction end and the oil discharge end of the lifting pump, the oil replenishment valve being connected to a hydraulic oil tank via a relief valve, and an oil replenishment accumulator being provided between the oil replenishment valve and the relief valve; The cold start solenoid valve connects the oil return end of the lift slide valve and the oil suction end of the lift pump through the throttle valve when it is energized; An oil supply valve, comprising a low-pressure relief valve and a plurality of one-way valves. When the oil supply valve is in the oil supply state for the system, the oil supply valve is connected to the oil suction end and the oil discharge end of the lift pump through the one-way valve. When the oil supply valve is in the oil supply accumulator state, the oil supply valve is connected to the oil suction end and the oil discharge end of the lift pump through the one-way valve and the low-pressure relief valve. It also includes a controller, the input end of which is connected to an oil temperature sensor, a maximum lifting position sensor and a cargo compartment landing position sensor, the oil temperature sensor is arranged on the oil return pipeline of the system, the maximum lifting position sensor and the cargo compartment landing position sensor are arranged at the tail and front of the cargo compartment, and the output end of the controller is connected to a lifting electro-hydraulic control handle and a cold start solenoid valve.

[0005] It is further characterized in that: the oil suction end of the lifting pump is connected with an oil suction coarse filter, and the oil discharge end of the lifting pump is connected with an oil discharge fine filter.

[0006] The lifting slide valve is provided with four working positions: slide valve descending position, slide valve floating position, slide valve holding position and slide valve lifting position; the lifting electro-hydraulic control handle is provided with four operating positions: pilot descending position, pilot floating position, pilot holding position and pilot lifting position.

[0007] A lifting pilot accumulator is provided at one control end of the lifting electro-hydraulic control handle, and the lifting pilot accumulator is connected to the hydraulic oil tank through a one-way valve. The other control end of the lifting electro-hydraulic control handle is connected to the controller.

[0008] A sequence valve and a lifting relief valve are provided on the oil inlet pipeline connecting the balancing valve group and the rodless chamber of the lifting cylinder, and the hydraulic control end of the sequence valve is connected to another oil inlet pipeline of the balancing valve group.

[0009] The cold start solenoid valve includes a solenoid valve one-way valve core and a solenoid valve throttle valve core. When the cold start solenoid valve is de-energized, the solenoid valve one-way valve core is in the conduction position. When the cold start solenoid valve is energized, the solenoid valve throttle valve core is in the conduction position.

[0010] The oil replenishment valve includes a one-way valve, a one-way valve, a one-way valve, a one-way valve and a low-pressure relief valve. The oil inlet end of the low-pressure relief valve is connected to the oil outlet end and the oil suction end of the lifting pump through the one-way valve and the one-way valve respectively. The one-way valve is arranged between the oil suction end of the lifting pump and the oil replenishment accumulator, and the one-way valve is arranged between the oil outlet end of the lifting pump and the oil replenishment accumulator.

[0011] A control method for a high-altitude closed-loop lifting hydraulic system includes six operating conditions: low-temperature cold start, power lift, hold, power drop, floating drop, and performance improvement. The details are as follows: In low-temperature cold start conditions, when the system temperature is lower than the preheating temperature T°C, the controller issues a control command to place the lifting electro-hydraulic control handle in the pilot float position, and controls the cold start solenoid valve to be energized, forming a closed heating circuit to increase the system oil temperature and simultaneously alert the driver; when the system temperature is greater than or equal to the preheating temperature T°C, the cold start solenoid valve loses power and the driver's alarm is released; In the power lift condition, the driver operates the lift electro-hydraulic control handle to the pilot lift position, forming a closed hydraulic cycle for the lift condition. At this time, the oil replenishment accumulator outputs hydraulic oil to the oil replenishment valve, opening the one-way valve, and the hydraulic oil enters the lift pump suction port. When the cargo box is lifted to the maximum angle, the lift maximum position sensor is triggered, and the controller issues a control command to place the lift electro-hydraulic control handle in the pilot hold position. To maintain the working condition, the driver operates the lifting electro-hydraulic control handle to the pilot holding position, and the lifting slide valve switches to the holding position, performing a closed cycle in the idle state; In the power-down condition, the driver operates the lift electro-hydraulic control handle to the pilot down position, and the lift slide valve switches to the slide valve down position, forming a closed hydraulic cycle for the down condition. At this time, the lift pump suction port releases pressure through the oil replenishment valve, the one-way valve and the low-pressure relief valve open, and the oil replenishment accumulator is filled with fluid; when the cargo box is lowered to the frame, the cargo box landing position sensor is triggered, and the controller issues a control command to place the lift electro-hydraulic control handle in the pilot floating position; In the floating lowering condition, the system performs powered lowering in the early stage of lowering and floating lowering in the later stage. The driver actively places the lifting electro-hydraulic control handle in the pilot floating position in the later stage of lowering the cargo compartment, and the system performs a closed cycle in the idle state. At this time, the lifting pump suction port releases pressure through the oil replenishment valve, the one-way valve and the low-pressure relief valve open, and the oil replenishment accumulator is filled with fluid. In the performance improvement working condition, when pressure accumulates at the oil outlet of the lift pump, the one-way valve and the low-pressure relief valve are opened to charge the oil-making accumulator; when the oil suction pressure at the oil suction port of the lift pump is insufficient, the one-way valve is opened and the oil-making accumulator outputs hydraulic oil to the oil suction port of the lift pump.

[0012] In various working conditions, the controller has a higher control priority than the lifting electro-hydraulic control handle.

[0013] A mining dump truck comprises the above-mentioned high-cold closed lifting hydraulic system and is used to execute the above-mentioned control method of the high-cold closed lifting hydraulic system.

[0014] The present invention has the following advantages: a high-cold closed lifting hydraulic system, a control method and a mining dump truck, providing a closed lifting hydraulic system with the characteristics of fast system heating, small structural volume, and good pump self-priming performance. It can operate stably in a low-temperature environment and provide a hydraulic system with oil suction back pressure for the hydraulic pump. At the same time, it combines intelligent temperature control to improve the corresponding performance of the system, has intelligent lifting limit / floating control, and optimizes the lifting action of the mining dump truck. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, as part of this disclosure, are intended to provide a further understanding of the disclosure. The exemplary embodiments of the disclosure and their descriptions are intended to explain the disclosure and do not constitute undue limitations thereon. Obviously, the drawings described below are merely examples, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0016] In the attached figure: Figure 1 It is the hydraulic principle diagram of the present invention; Figure 2 It is a structural schematic diagram of the lifting slide valve of the present invention; Figure 3 It is the control principle diagram of the system of the present invention; Figure 4 This invention Figure 3 The control principle diagram corresponding to low temperature working conditions; Figure 5 This invention Figure 3 The control principle diagram for lifting and oil replenishment conditions; Figure 6 This invention Figure 3 The control principle diagram corresponding to the holding working condition; Figure 7 This invention Figure 3 The control principle diagram of the lowering and oil discharge conditions; Figure 8 This invention Figure 3 The control principle diagram corresponding to the floating working condition; Figure 9 This invention Figure 3 Control principle diagram corresponding to performance improvement working condition; Figure 10 This invention Figure 5 Logic diagram of the priority of lifting action between the central controller and the driver; Figure 11 This invention Figure 7 Logic diagram of the priority of the descent action between the central controller and the driver; Figure 12 It is a logic diagram of the operating status of the lifting system of the present invention.

[0017] In the figure: 1. Lifting cylinder, 2. Lifting pilot accumulator, 3. Lifting electro-hydraulic control handle, 3.1. Pilot lowering position, 3.2. Pilot floating position, 3.3. Pilot holding position, 3.4. Pilot lifting position, 4. Balancing valve group, 5. Sequence valve, 6. Lifting relief valve, 7. Lifting slide valve, 7.1. Slide valve lowering position, 7.2. Slide valve floating position, 7.3. Slide valve holding position, 7.4. Slide valve lifting position, 8. , oil supply valve, 8.1, one-way valve, 8.2, one-way valve, 8.3, one-way valve, 8.4, one-way valve, 8.5, low-pressure relief valve, 9, relief valve, 10, oil supply accumulator, 11, hydraulic oil tank, 12, lifting pump, 13, one-way valve, 14, cold start solenoid valve, 14.1, solenoid valve one-way valve core, 14.2, solenoid valve throttle valve core, 15, one-way valve, 16, oil suction coarse filter, 17, oil outlet fine filter, 18, oil temperature sensor, 19, lifting maximum position sensor, 20, cargo compartment landing position sensor, 21, controller.

[0018] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0020] In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0021] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; and direct or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0022] like Figures 1 to 12The figure shows a high-cold closed lifting hydraulic system, including a lifting pump 12, the lifting pump 12 is connected to the lifting cylinder 1 through the lifting slide valve 7 and the balance valve group 4, the control end of the lifting slide valve 7 is connected to the lifting electro-hydraulic control handle 3, the return oil end of the lifting slide valve 7 is connected to the oil suction end of the lifting pump 12 through the cold start solenoid valve 14, and an oil replenishment valve 8 is provided between the oil suction end and the oil discharge end of the lifting pump 12, and the oil replenishment valve 8 is connected to the hydraulic oil tank 11 through the overflow valve 9. An oil replenishment accumulator 10 is provided between the oil valve 8 and the overflow valve 9; it also includes a controller 21, the input end of which is connected to an oil temperature sensor 18, a maximum lifting position sensor 19 and a cargo compartment landing position sensor 20, the oil temperature sensor 18 is arranged on the return oil pipeline of the system, the maximum lifting position sensor 19 and the cargo compartment landing position sensor 20 are arranged at the rear and front of the cargo compartment, and the output end of the controller 21 is connected to the lifting electro-hydraulic control handle 3 and the cold start solenoid valve 14. The high-altitude closed lifting hydraulic system of the present invention is composed of a lifting pump, a lifting slide valve, a balancing valve group, a lifting cylinder, a cold start solenoid valve, an oil replenishment valve and an oil replenishment accumulator, wherein the lifting slide valve is controlled by the lifting electro-hydraulic control handle to control the reversing, and the oil replenishment accumulator replenishes oil or relieves pressure for the system through the oil replenishment valve. It also includes a controller, which detects the operating status of the system through an oil temperature sensor, a lifting maximum position sensor and a cargo compartment landing position sensor. The oil temperature sensor is used to detect the oil temperature of the system, and the lifting maximum position sensor and the cargo compartment landing position sensor are used to detect the maximum extension displacement state and the minimum retraction displacement state of the lifting cylinder. The controller controls the lifting electro-hydraulic control handle and the cold start solenoid valve according to the detected signal, so that the system meets the use requirements, overcomes the characteristics of poor starting performance and poor oil absorption performance of mining dump pumps in high altitude areas, and improves the adaptability of the system.

[0023] like Figure 1 The illustrated embodiment shows a high-altitude closed lifting hydraulic system, wherein the oil suction end of the lifting pump 12 is connected to an oil suction coarse filter 16 , and the oil discharge end of the lifting pump 12 is connected to an oil discharge fine filter 17 .

[0024] like Figure 1 The figure shows a high-cold closed lifting hydraulic system, wherein the lifting slide valve 7 is provided with four working positions, namely, slide valve descending position 7.1, slide valve floating position 7.2, slide valve holding position 7.3 and slide valve lifting position 7.4; the lifting electro-hydraulic control handle 3 is provided with four operating positions, namely, pilot descending position 3.1, pilot floating position 3.2, pilot holding position 3.3 and pilot lifting position 3.4.

[0025] like Figure 1The figure shows a high-cold closed lifting hydraulic system, in which one control end of the lifting electro-hydraulic control handle 3 is provided with a lifting pilot accumulator 2, and the lifting pilot accumulator 2 is connected to the hydraulic oil tank 11 through a one-way valve 15, and the other control end of the lifting electro-hydraulic control handle 3 is connected to the controller 21.

[0026] like Figure 1 The figure shows a high-cold closed lifting hydraulic system, in which a sequence valve 5 and a lifting overflow valve 6 are provided on the oil inlet pipeline connecting the balancing valve group 4 and the rodless chamber of the lifting cylinder 1, and the hydraulic control end of the sequence valve 5 is connected to another oil inlet pipeline of the balancing valve group 4.

[0027] like Figure 1 The figure shows a high-cold closed lifting hydraulic system, a cold start solenoid valve 14, which connects the return oil end of the lifting slide valve 7 and the oil suction end of the lifting pump 12 through a throttle valve when powered; the cold start solenoid valve 14 includes a solenoid valve one-way valve core 14.1 and a solenoid valve throttle valve core 14.2. When the cold start solenoid valve 14 is de-energized, the solenoid valve one-way valve core 14.1 is in the conduction position, and when the cold start solenoid valve 14 is energized, the solenoid valve throttle valve core 14.2 is in the conduction position.

[0028] like Figure 1 The oil supply valve 8 is a closed type lifting hydraulic system for high-altitude cold-weather vehicles, comprising a low-pressure relief valve 8.5 and a plurality of one-way valves. When the oil supply valve 8 is in the oil supply state for the system, it is connected to the oil suction end and the oil discharge end of the lifting pump 12 through the one-way valve. When the oil supply valve 8 is in the oil supply state for the oil supply accumulator 10, it is connected to the oil suction end and the oil discharge end of the lifting pump 12 through the one-way valve and the low-pressure relief valve 8.5. The oil supply valve 8 comprises a one-way valve 8 .1, one-way valve 8.2, one-way valve 8.3, one-way valve 8.4 and low-pressure relief valve 8.5, the oil inlet end of the low-pressure relief valve 8.5 is connected to the oil outlet end and oil suction end of the lifting pump 12 through the one-way valve 8.1 and the one-way valve 8.2 respectively, the one-way valve 8.3 is arranged between the oil suction end of the lifting pump 12 and the oil replenishing accumulator 10, and the one-way valve 8.4 is arranged between the oil outlet end of the lifting pump 12 and the oil replenishing accumulator 10.

[0029] like Figures 1 to 12The control method of a high-altitude closed lifting hydraulic system shown in the figure is that before performing the lifting action, the electric drive dump truck in the high-altitude area must perform a low-temperature start-up self-inspection process. When the temperature reaches the allowable vehicle operating temperature, the lifting action is performed to protect the lifting system components. When the system allows the vehicle to perform the lifting action continuously, the lifting work can be divided into the vehicle arriving at the unloading location and performing the lifting work to unload the material; after the vehicle cargo compartment is lifted to the maximum position, the lifting cylinder performs a fixed position maintenance work to ensure that the cargo compartment is completely unloaded; after the material in the cargo compartment is unloaded, the lifting cylinder retracts and lowers the cargo compartment back to the frame; after the cargo compartment returns to the frame, the lifting cylinder is in a floating state to cope with the impact of the road surface when the dump truck is driving. During the operation of the dump truck lifting system, a system buffer function and a function to improve the self-priming performance of the lifting pump in high-altitude areas are also set, as follows: Low temperature and cold start process When the system temperature is lower than the preheating temperature T℃, the controller 21 sends a control instruction to make the lifting electro-hydraulic control handle 3 located at the pilot floating position 3.2, and controls the cold start solenoid valve 14 to be energized, forming a closed heating circuit, increasing the system oil temperature, and at the same time alarming the driver; when the system temperature is greater than or equal to the preheating temperature T℃, the cold start solenoid valve 14 loses power, and the alarm to the driver is released.

[0030] As attached Figure 3 and Figure 4 As shown in the figure, after the high-cold closed-loop lift hydraulic system (hereinafter referred to as the "system") is activated, the controller receives real-time hydraulic oil temperature data from the oil temperature sensor installed in the system's return oil line. When the oil temperature falls below the system's preset temperature, T°C, the cold-start solenoid valve is energized, throttling oil return flow to raise the system temperature. At this point, the controller alerts the driver, "Please idle the vehicle engine," prompting the driver to idle to protect the hydraulic components during low-temperature startup. During system operation, if the temperature exceeds the preset temperature, the cold-start solenoid valve loses power, and the system returns oil normally through the high-flow check valve, clearing the system's preheat alarm.

[0031] The detailed steps are as follows: After the system is operational, controller 21 receives real-time oil temperature feedback from oil temperature sensor 18 installed in the lift return line. When the feedback temperature falls below the preheating temperature T°C, the controller issues a control command, alerting the driver: "Hydraulic oil temperature is low. Please float and idle the vehicle." This ensures safe operation of the hydraulic components during low-temperature system startup. At this point, the lift electro-hydraulic control handle 3 is in pilot float position 3.2, and the lift spool valve 7, driven by the pilot valve core, is in spool float position 7.2. The lift pump 12 transfers hydraulic oil through the outlet fine filter 17 and spool float position 7.2 to the return line. At this point, the cold start solenoid valve 14, under the control of controller 21, is energized, opening the cold start solenoid valve throttle spool 14.2. Oil returns through the throttle valve to the coarse suction filter 16 and is supplied to the lift pump 12 intake port, forming a closed heating circuit to raise the system oil temperature.

[0032] During system operation, controller 21 receives real-time oil temperature feedback from oil temperature sensor 18 installed in the lift oil return line. When the feedback temperature is greater than or equal to the preheating temperature T°C, the controller issues a control command to deactivate the low hydraulic oil temperature alarm. At this point, cold start solenoid valve 14 loses power, and the cold start solenoid valve spool 14.1 conducts, allowing oil to return through the large-diameter check valve. This means that the throttling and heating function is no longer in effect. Active heating of the system hydraulic oil is now disabled.

[0033] Power lift, oil replenishment and automatic limit working conditions The driver operates the lifting electro-hydraulic control handle 3 to the pilot lifting position 3.4, forming a closed hydraulic cycle for the lifting condition. At this time, the oil replenishment accumulator 10 outputs hydraulic oil to the oil replenishment valve 8, opening the one-way valve 8.3, and the hydraulic oil enters the oil suction port of the lifting pump 12; when the cargo box is lifted to the maximum angle, the lifting maximum position sensor 19 is triggered, and the controller 21 issues a control command to place the lifting electro-hydraulic control handle 3 in the pilot holding position 3.3.

[0034] As attached Figure 3 、 Figure 5 and Figure 10 As shown in the figure, after the system is started, the lifting pump runs and supplies pressure oil to the lifting slide valve, and the lifting slide valve is in floating standby state as shown in the attached figure. Figure 8 As shown, at this time, the oil supply of the lifting pump returns the hydraulic oil to the oil suction port of the lifting pump through the floating valve core of the sliding valve.

[0035] The vehicle reaches the unloading area, and the driver operates the electro-hydraulic lift control handle to the lift position. Under the pilot action of the lift control handle, the lift spool valve switches to the lift conduction state. Hydraulic oil is supplied to the rodless chamber of the lift cylinder through the counterbalance valve. Return oil from the rod chamber of the lift cylinder flows through the counterbalance valve's return oil passage and is supplied to the lift spool's return oil passage. This return oil passage then connects to the lift pump's suction port, forming a closed hydraulic circuit for the lift operation.

[0036] During lifting, the lift cylinder supplies oil to the rodless chamber and returns oil to the rod chamber. Because the lifting system is a closed hydraulic system, relying solely on the hydraulic oil returning from the rod chamber is insufficient to meet the lifting requirements of the rodless chamber. At this time, the charge accumulator delivers hydraulic oil to the charge valve, causing it to open and supply the lift pump suction port, ensuring sufficient oil supply and achieving the lifting action.

[0037] When the cargo box is lifted to the maximum angle, the lift maximum position sensor is triggered and sends a signal to the controller, which then issues an electronic hold command to the lift electro-hydraulic control handle, as shown in the attached figure. Figure 10 As described in the logic, the hold-position pilot spool in the lift electro-hydraulic control handle is forced open. At this point, the lift spool valve spool, under the control of the pilot oil from the lift electro-hydraulic control handle, returns to its hold position. This disconnects the upward oil supply from the lift pump port to the lift spool valve. The hold-position lift spool valve seals the rod and rodless chambers of the lift cylinder, causing the cylinder to enter a limited hold state. The oil replenishment valve closes the replenishment check valve, and the replenishment accumulator no longer replenishes oil to the lift pump intake port, leading to a closed cycle at idle.

[0038] The detailed steps are as follows: When the vehicle reaches the unloading area, the driver operates the lifting electro-hydraulic control handle 3 to the pilot lift position 3.4. Pilot oil moves the lifting spool valve 7 to the spool lift position 7.4, switching the lifting spool valve 7 to the lift conduction state. The lifting pump 12 pumps hydraulic oil through the outlet fine filter 17, which then passes through the spool lift position 7.4 and connects it to the rodless chamber oil port of the counterbalance valve 4. The counterbalance valve 4 then delivers the hydraulic oil to the rodless chamber of the lifting cylinder 1, actuating the lifting cylinder. Simultaneously, the oil in the rod chamber of the lifting cylinder 1 is connected to the return oil port of the lifting spool valve 7 through the rod chamber port of the counterbalance valve. The oil then flows through the cold start solenoid valve one-way spool 14.1 (closed during the cold start operation) and through the suction filter 16 to the suction port of the lifting pump 12, forming a closed hydraulic circuit for the lifting operation.

[0039] During the lifting process, the oil pressure in the rod chamber of sequence valve 5 overcomes the action of the valve core return spring, allowing the hydraulic oil in the rodless chamber to act on the top of the lifting relief valve 6 through the valve core of sequence valve 5. When the lifting pressure of the hydraulic oil in the rodless chamber exceeds the set pressure of the lifting relief valve 6, the relief valve 6 opens, overflowing the rodless chamber flow back to the oil tank 11, thus protecting the system.

[0040] During lifting, the oil replenishment accumulator 10 outputs hydraulic oil to the oil replenishment valve 8, opening the one-way valve 8.3, and the oil flows through the oil suction coarse filter 16 and enters the oil suction port of the lifting pump 12. This ensures sufficient oil supply to achieve the lifting action.

[0041] When the cargo compartment is lifted to its maximum angle, the maximum lift position sensor 19 triggers, sending a signal to the controller 21. Controller 21 then issues a command to the lift electro-hydraulic control handle 3, opening the pilot hold position 3.3. Under the control of the pilot oil, the spool of the lift spool valve 7 returns to the spool hold position 7.3, disconnecting the upward oil supply from the lift pump 12 to the lift spool valve 7. At this point, the rod chamber and rodless chamber of the lift cylinder 1 are sealed at the upper end of the lift spool valve 7, implementing the cylinder hold function. The hydraulic oil at the bottom of the lift spool valve 7 flows through the internal passageway of the lift spool valve 7 to the return oil circuit and connect to the cold start solenoid valve 14. The oil passes through the oil suction filter 16 and returns to the suction port of the lift pump 12, forming a closed-loop circulation system.

[0042] When the valve core holding position 7.3 is triggered, the oil replenishment valve 8 closes the oil replenishment check valve 8.3, and the oil replenishment accumulator 10 no longer replenishes oil to the oil suction port of the lifting pump 12.

[0043] The present invention has a closed circulation circuit for the lifting working condition of the high-cold closed lifting hydraulic system. The lifting action is achieved by controlling the lifting slide valve through the electro-hydraulic control lifting control handle, and the closed lifting oil replenishment function is achieved through the oil replenishment valve and the oil replenishment accumulator. The electro-hydraulic control handle is preferentially controlled through the maximum position sensor and controller to achieve the intelligent limit holding function.

[0044] Maintain working conditions The driver operates the lifting electro-hydraulic control handle 3 to the pilot holding position 3.3, and the lifting slide valve 7 switches to the holding position 7.3, performing a closed cycle in the idle state.

[0045] As attached Figure 6 As shown in the figure, after the system is activated and the dump truck is lifted, the cargo compartment must be held at the appropriate angle for unloading. The driver manipulates the lift electro-hydraulic control handle to the hold position. Under the pilot action of the lift electro-hydraulic control handle, the lift spool valve switches to the hold position, disconnecting the upward oil supply from the lift pump port to the lift spool valve. At this point, the rod and rodless chambers of the lift cylinder are sealed due to the lift spool valve's hold position, causing the cylinder to enter the limit hold state. Hydraulic oil from the lift pump's pressure port returns to the lift pump's suction port through the drain line in the lift spool valve's hold position, forming a closed circulation system at idle speed.

[0046] The detailed steps are as follows: After the system is activated, the driver operates the lift electro-hydraulic control handle 3 to the pilot hold position 3.3. Under the action of the pilot oil, the lift spool valve 7 switches to the hold position 7.3, disconnecting the upward oil supply from the lift pump 12 port to the lift spool 7. At this point, the rod and rodless chambers of the lift cylinder 1 are sealed at the upper end of the lift spool valve 7, implementing the cylinder hold function. Hydraulic oil at the bottom of the lift spool valve 7 passes through the check valve 13 and the internal passageway of the lift spool valve 7 to the return oil circuit, connecting to the cold start solenoid valve 14. The oil then passes through the oil suction filter 16 and returns to the suction port of the lift pump 12, forming a closed-loop circulation system.

[0047] Power reduction, oil drain and frame floating work The driver operates the lifting electro-hydraulic control handle 3 to the pilot lowering position 3.1, and the lifting slide valve 7 switches to the slide valve lowering position 7.1, forming a closed hydraulic cycle for the lowering working condition. At this time, the oil suction port of the lifting pump 12 is depressurized through the oil replenishing valve 8, the one-way valve 8.2 and the low-pressure relief valve 8.5 are opened and the oil replenishing accumulator 10 is filled with fluid; when the cargo box is lowered to the frame, the cargo box landing position sensor 20 is triggered, and the controller 21 issues a control command to make the lifting electro-hydraulic control handle 3 located in the pilot floating position 3.2.

[0048] When the cargo box is lowered, the lifting cylinder supplies oil to the rod chamber and returns oil to the rodless chamber. Figure 7 As shown in the figure, after the vehicle has finished unloading materials, the cargo box needs to be lowered onto the vehicle frame. At this point, the driver operates the lift electro-hydraulic control handle to the down position. Under the pilot action of the lift electro-hydraulic control handle, the lift spool valve switches to the down conduction state. The standby hydraulic oil flows through the down position spool of the lift spool valve, through the rod chamber oil passage of the lift counterbalance valve, and into the rod chamber of the lift cylinder. Simultaneously, the return oil in the rodless chamber of the lift cylinder passes through the return oil passage of the counterbalance valve and is supplied to the return oil passage of the down position spool of the lift spool valve. The return oil passage is then connected to the lift pump suction port, forming a closed hydraulic circuit for the down position. This operating condition causes the lift cylinder to compress, driving the cargo box down onto the vehicle frame, completing the down position function.

[0049] Because the lifting system is a closed hydraulic system, the oil supply demand of the rod chamber is less than the oil return volume of the rodless chamber. At this time, the hydraulic oil at the pump suction port accumulates pressure, opening the oil charging check valve of the oil replenishment valve. The oil continues to accumulate pressure, opening the low-pressure relief valve in the oil replenishment valve, and the excess oil is discharged through the oil replenishment valve into the oil replenishment accumulator.

[0050] When lowering the cargo box to the frame, if Figure 11 As described in the logic, the cargo compartment landing position sensor is triggered and sends a signal to the controller. The controller sends an electronic floating command to the lifting electro-hydraulic control handle, forcing the floating position pilot valve core in the lifting electro-hydraulic control handle to open, triggering the attached Figure 8Floating operating condition command logic. At this point, the lift spool valve returns to the floating position under the pilot oil control of the lift electro-hydraulic control handle. The floating position spool of the lift spool valve connects the rodless and rod chamber oil circuits of the lift cylinder to the lift pump outlet and suction circuit, creating a closed circulation system at idle.

[0051] When the cargo box falls onto the frame, oil no longer returns to the large chamber of the lifting cylinder, the flow rate at the lifting pump outlet is equal to the flow rate at the lifting pump suction port, the low-pressure relief valve in the oil replenishing valve is closed, and no oil is discharged to the oil replenishing accumulator.

[0052] The detailed steps are as follows: After unloading the vehicle, the driver operates the lift electro-hydraulic control handle 3 to the pilot lowering position 3.1. Under the piloting action of the pilot oil, lift spool valve 7 switches to the open state (spool lowering position 7.1). Hydraulic oil at the outlet of lift pump 12 passes through the outlet fine filter 17, out through the oil passage within the spool in the lowering position 7.1, flows through the rod chamber oil passage of lift counterbalance valve 4, and enters the rod chamber of lift cylinder 1. Simultaneously, return oil from the rodless chamber of lift cylinder 1 passes through the return oil passage of the counterbalance valve and supplies the return oil passage of the lowering position 7.1 of lift spool valve 7. The oil then flows through the cold start solenoid valve one-way spool 14.1 (closed during cold start operation) and through the suction filter 16 to the suction port of lift pump 12, forming a closed hydraulic circuit for the lowering operation. Lift cylinder 1 contracts, driving the cargo compartment down onto the vehicle frame, completing the lowering function.

[0053] During the descending working condition, the hydraulic oil at the oil suction port of the lifting pump 12 accumulates pressure to open the oil charging check valve 8.2 of the oil replenishing valve 8. The oil continues to be pressurized, opening the low-pressure relief valve 8.5, and the excess oil is discharged to the oil replenishing accumulator 10 through the oil replenishing valve.

[0054] When the cargo box is lowered onto the vehicle frame, the cargo box landing position sensor 20 triggers, sending a signal to the controller 21. This instructs the lift electro-hydraulic control handle 3 to open the pilot float position 3.2 valve spool. Under the control of the pilot oil, the lift spool 7 returns to the float position 7.2. At this point, the rod chamber and rodless chamber of the lift cylinder 1 communicate within the lift spool 7.2 with the lift pump 12 suction circuit, establishing a closed circulation system at idle speed.

[0055] When the valve core floating position 7.2 is triggered, the oil supply valve 8 closes the oil supply check valve 8.2, closes the low-pressure relief valve 8.5, and stops the oil discharge function of the rodless chamber of the lifting cylinder 1 to the oil supply accumulator 10.

[0056] This invention features a closed-loop hydraulic system for lowering, utilizing a closed loop circuit. Lowering is achieved through an electro-hydraulic lift control handle, which controls the lift slide valve. A supplemental oil valve and supplemental oil accumulator are used to achieve closed-loop oil discharge. Furthermore, a landing position sensor and controller prioritize control of the electro-hydraulic control handle, enabling intelligent floating cushioning.

[0057] Floating down, oil draining and frame floating working conditions Power descent is performed in the early stage of descent, and floating descent is performed in the later stage. In the later stage of lowering the cargo compartment, the driver actively places the lifting electro-hydraulic control handle 3 in the pilot floating position 3.2, and the system performs a closed cycle in the idle state; at this time, the oil suction port of the lifting pump 12 is depressurized through the oil replenishment valve 8, the one-way valve 8.2 and the low-pressure relief valve 8.5 are opened and the oil replenishment accumulator 10 is filled with liquid.

[0058] There are two ways to lower the cargo compartment. You can actively lower the cargo compartment to quickly force it down until it lands on the vehicle frame, as described in the "power down, oil drain and vehicle frame floating working conditions" section above. You can also lower the cargo compartment to a certain initial speed in the early stages of the descent, and then lower it to the vehicle frame using the weight of the cargo compartment. This working condition can protect the hydraulic system from impact during descent to the greatest extent possible. Figure 8 As shown in the figure, the driver actively places the lift electro-hydraulic control handle in the floating position while the cargo compartment is lowering. At this point, the lift spool valve is in the floating position under the pilot action of the handle. The hydraulic fluid from the pilot float valve spool connects the rodless and rod chamber oil circuits of the lift cylinder to the lift pump outlet and suction circuit, creating a closed circuit at idle speed. The lift cylinder then slowly descends back onto the vehicle frame under the weight of the cargo compartment. Thereafter, the vehicle remains in the floating position while driving.

[0059] Because the lifting system is a closed hydraulic system, during the floating descent process, the oil supply demanded by the rod chamber is less than the oil return flow from the rodless chamber. At this point, the hydraulic oil at the pump suction port accumulates pressure, opening the oil-charging check valve of the replenishing valve. The oil continues to accumulate pressure, opening the low-pressure relief valve in the replenishing valve. Excess return oil then flows out of the replenishing valve to charge the replenishing accumulator. When the cargo box drops onto the vehicle frame, oil no longer returns from the main chamber of the lifting cylinder. The flow rate at the lift pump outlet equals the flow rate at the lift pump suction port, causing the low-pressure relief valve in the replenishing valve to close, and no more oil is discharged to the replenishing accumulator.

[0060] The detailed steps are as follows: While lowering the cargo compartment, the driver actively places the lift electro-hydraulic control handle 3 in the pilot float position 3.2. The pilot hydraulic oil positions the lift spool valve 7 in the spool float position 7.2. Hydraulic oil at the outlet of the lift pump 12 passes through the outlet fine filter 17, directly through the spool at the spool float position 7.2, through the cold start solenoid valve, and through the oil suction filter 16 before returning to the lift pump 12 suction port. This forms a closed loop at idle speed.

[0061] Lift cylinder 1 retracts under the weight of the cargo compartment. A portion of the return oil from the rodless chamber of lift cylinder 1 flows through the rodless chamber opening of balancing valve 4 and into the internal channel of the valve core at float position 7.2, supplying the rod chamber of lift cylinder 1. A portion of the oil merges with the output of lift pump 12 within float position 7.2, passes through the cold start solenoid valve, and flows through suction filter 16 back to the suction port of lift pump 12. Oil pressure accumulates at the suction port of lift pump 12, opening one-way valve 8.2 of charge valve 8 and low-pressure relief valve 8.5 to charge charge accumulator 10.

[0062] When the cargo box falls onto the frame, the large chamber of the lifting cylinder no longer returns oil, the oil replenishment one-way valve 8.2 is closed, the low-pressure relief valve 8.5 is closed, and the rodless chamber of the lifting cylinder 1 is closed to discharge oil to the oil replenishment accumulator 10.

[0063] System buffering and pump self-priming performance improvement function When pressure accumulates at the oil outlet of the lift pump 12, the one-way valve 8.1 and the low-pressure relief valve 8.5 are opened to charge the oil-making accumulator 10; when the oil suction pressure at the oil suction port of the lift pump 12 is insufficient, the one-way valve 8.3 is opened, and the oil-making accumulator 10 outputs hydraulic oil to the oil suction port of the lift pump 12.

[0064] As attached Figure 9 As shown in the figure, during system operation, valve group switching or vehicle vibration can cause pressure to accumulate at the lift pump inlet. To protect the pump from damage, the charge valve's low-pressure relief path is opened, directing the pressure-shocked oil to the charge accumulator to absorb the shock. If insufficient suction pressure is detected at the lift pump's suction port, the charge valve's anti-cavitation check valve opens, directing hydraulic oil from the charge accumulator to the lift pump's suction port, further enhancing the pump's self-priming performance.

[0065] The detailed steps are as follows: When pressure accumulates at the oil outlet of the lift pump 12, the one-way valve 8.1 of the oil replenishment valve 8 is opened, and the pressure accumulates at the top of the low-pressure relief valve 8.5, and the low-pressure relief valve 8.5 is opened. The accumulated oil fills the oil replenishment accumulator 10 to absorb the impact pressure.

[0066] When the oil suction pressure at the oil suction port of the lift pump 12 is insufficient, the one-way valve 8.3 of the oil replenishment valve 8 opens, and the hydraulic oil in the oil replenishment accumulator 10 is output to the oil suction port of the lift pump 12 to replenish the oil.

[0067] The high-cold closed lifting hydraulic system, control method and mining dump truck of the present invention realize the insulation and heating functions of mining trucks used in high-cold areas through a closed + intelligent cold start system; the dynamic lifting oil replenishment / oil discharge system composed of an oil replenishment accumulator and an oil replenishment valve meets the closed system's working conditions for oil replenishment / oil discharge of the lifting cylinder, and at the same time absorbs hydraulic shocks during system operation and enhances the pump's oil suction performance; the present invention optimizes the conventional lifting system's requirements for large-capacity boosting and heating hydraulic oil tanks, reducing the overall structure of the system.

[0068] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0069] Furthermore, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are also intended to fall within the scope of protection of the present invention and form different embodiments. For example, in the above embodiments, those skilled in the art will be able to use them in combination based on the known technical solutions and the technical problems to be solved by this application.

[0070] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with this patent can make slight changes or modifications to equivalent embodiments using the above-mentioned technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A closed hydraulic lifting system for high-altitude and cold conditions, characterized by: The invention comprises a lifting pump (12), wherein the lifting pump (12) is connected to the lifting cylinder (1) through a lifting slide valve (7) and a balancing valve group (4), the control end of the lifting slide valve (7) is connected to a lifting electro-hydraulic control handle (3), the return oil end of the lifting slide valve (7) is connected to the oil suction end of the lifting pump (12) through a cold start solenoid valve (14), an oil replenishing valve (8) is provided between the oil suction end and the oil discharge end of the lifting pump (12), the oil replenishing valve (8) is connected to the hydraulic oil tank (11) through an overflow valve (9), and an oil replenishing accumulator (10) is provided between the oil replenishing valve (8) and the overflow valve (9); The cold start solenoid valve (14) connects the oil return end of the lift slide valve (7) and the oil suction end of the lift pump (12) through the throttle valve when it is energized; An oil replenishing valve (8) comprising a low-pressure relief valve (8.5) and a plurality of one-way valves. When the oil replenishing valve (8) is in the oil replenishing state for the system, the oil replenishing valve (8) is connected to the oil suction end and the oil discharge end of the lifting pump (12) through the one-way valve. When the oil replenishing valve (8) is in the oil charging state for the oil replenishing accumulator (10), the oil replenishing valve (8) is connected to the oil suction end and the oil discharge end of the lifting pump (12) through the one-way valve and the low-pressure relief valve (8.5); The system further includes a controller (21), the input end of which is connected to an oil temperature sensor (18), a maximum lifting position sensor (19) and a cargo compartment landing position sensor (20), the oil temperature sensor (18) being arranged on the oil return line of the system, the maximum lifting position sensor (19) and the cargo compartment landing position sensor (20) being arranged at the rear and front of the cargo compartment, and the output end of the controller (21) being connected to a lifting electro-hydraulic control handle (3) and a cold start solenoid valve (14).

2. The high-altitude closed lifting hydraulic system according to claim 1, characterized in that: The oil suction end of the lifting pump (12) is connected to an oil suction coarse filter (16), and the oil discharge end of the lifting pump (12) is connected to an oil discharge fine filter (17).

3. The high-altitude closed lifting hydraulic system according to claim 1, characterized in that: The lifting slide valve (7) is provided with a slide valve lowering position ( The lifting electro-hydraulic control handle (3) is provided with four operating positions, namely, a pilot lowering position (3.1), a pilot floating position (3.2), a pilot holding position (3.3) and a pilot lifting position (3.4).

4. The high-altitude closed lifting hydraulic system according to claim 1, characterized in that: One control end of the lifting electro-hydraulic control handle (3) is provided with a lifting pilot accumulator (2), and the lifting pilot accumulator (2) is connected to a hydraulic oil tank (11) via a one-way valve (15). The other control end of the lifting electro-hydraulic control handle (3) is connected to a controller (21).

5. The high-altitude closed lifting hydraulic system according to claim 1, characterized in that: A sequence valve (5) and a lifting overflow valve (6) are provided on the oil inlet pipeline connecting the balancing valve group (4) and the rodless chamber of the lifting oil cylinder (1), and the hydraulic control end of the sequence valve (5) is connected to another oil inlet pipeline of the balancing valve group (4).

6. The high-altitude closed lifting hydraulic system according to claim 1, characterized in that: The cold start solenoid valve (14) comprises a solenoid valve one-way valve core (14.1) and a solenoid valve throttle valve core (14.2). When the cold start solenoid valve (14) loses power, the solenoid valve one-way valve core (14.1) is in a conducting position. When the cold start solenoid valve (14) is energized, the solenoid valve throttle valve core (14.2) is in a conducting position.

7. The high-altitude closed lifting hydraulic system according to claim 1, characterized in that: The oil replenishment valve (8) comprises a one-way valve (8.1), a one-way valve (8.2), a one-way valve (8.3), a one-way valve (8.4) and a low-pressure relief valve (8.5). The oil inlet end of the low-pressure relief valve (8.5) is connected to the oil outlet end and the oil suction end of the lifting pump (12) through the one-way valve (8.1) and the one-way valve (8.2), respectively. The one-way valve (8.3) is arranged between the oil suction end of the lifting pump (12) and the oil replenishment accumulator (10), and the one-way valve (8.4) is arranged between the oil outlet end of the lifting pump (12) and the oil replenishment accumulator (10).

8. A control method using the high-altitude closed lifting hydraulic system according to claim 1, characterized in that: It includes six operating conditions: low temperature cold start, power lift, hold, power drop, floating drop and performance improvement, as follows: In the low-temperature cold start condition, when the system temperature is lower than the preheating temperature T°C, the controller (21) issues a control command to place the lifting electro-hydraulic control handle (3) in the pilot floating position (3.2), and controls the cold start solenoid valve (14) to be energized, thereby forming a closed heating circuit to increase the system oil temperature and simultaneously alarm the driver; when the system temperature is greater than or equal to the preheating temperature T°C, the cold start solenoid valve (14) loses power, and the alarm to the driver is released; In the power lifting condition, the driver operates the lifting electro-hydraulic control handle (3) to be in the pilot lifting position (3.4), forming a closed hydraulic cycle in the lifting condition. At this time, the oil replenishment accumulator (10) outputs hydraulic oil to the oil replenishment valve (8), opens the one-way valve (8.3), and the hydraulic oil enters the oil suction port of the lifting pump (12); when the cargo box is lifted to the maximum angle, the lifting maximum position sensor (19) is triggered, and the controller (21) issues a control command to make the lifting electro-hydraulic control handle (3) be in the pilot holding position (3.3); In the holding condition, the driver operates the lifting electro-hydraulic control handle (3) to the pilot holding position (3.3), and the lifting slide valve (7) switches to the holding position (7.3), performing a closed cycle in the idle state; In the power down condition, the driver operates the lifting electro-hydraulic control handle (3) to the pilot down position (3.1), and the lifting slide valve (7) switches to the slide valve down position ( 7.1), forming a closed hydraulic cycle in the descending working condition, at this time, the oil suction port of the lifting pump (12) is depressurized through the oil replenishing valve (8), the one-way valve (8.2) and the low-pressure relief valve (8.5) are opened and the oil replenishing accumulator (10) is filled with liquid; when the cargo box is lowered to the frame, the cargo box landing position sensor (20) is triggered, and the controller (21) issues a control command to make the lifting electro-hydraulic control handle (3) located in the pilot floating position (3.2); In the floating lowering condition, the power lowering is performed in the early stage of the lowering, and the floating lowering is performed in the later stage. The driver actively places the lifting electro-hydraulic control handle (3) in the pilot floating position (3.2) in the later stage of lowering the cargo compartment, and the system performs a closed cycle in the idle state; at this time, the oil suction port of the lifting pump (12) is depressurized through the oil replenishing valve (8), the one-way valve (8.2) and the low-pressure relief valve (8.5) are opened, and the oil replenishing accumulator (10) is filled with liquid; In the performance improvement working condition, when the pressure accumulates at the oil outlet of the lifting pump (12), the one-way valve (8.1) and the low-pressure relief valve (8.5) are opened to charge the oil-making accumulator (10); when the oil suction pressure at the oil suction port of the lifting pump (12) is insufficient, the one-way valve (8.3) is opened, and the oil-making accumulator (10) outputs hydraulic oil to the oil suction port of the lifting pump (12).

9. The control method of the high-altitude closed lift hydraulic system according to claim 8, characterized in that: In various working conditions, the control priority of the controller (21) is higher than that of the lifting electro-hydraulic control handle (3).

10. A mining dump truck, characterized in that: It comprises a high-cold closed lifting hydraulic system as described in any one of claims 1-7, and is used to execute the control method of the high-cold closed lifting hydraulic system as described in any one of claims 8-9.

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