Hydraulic system for mobile lift truck with gravity energy storage

Abstract

The application discloses a mobile lifting vehicle hydraulic system for gravity energy storage, comprising an oil tank, the oil tank is connected to an oil pump, the oil outlet of the oil pump is connected to a first branch and a second branch; the second branch is connected to a second check valve, the other end of the second check valve is connected to a second switch valve and a second reversing valve, the other end of the second switch valve is connected to an energy accumulator; the other three interfaces of the second reversing valve are connected to the oil tank, a first passage and a second passage respectively, and the first passage and the second passage are switched to oil inlet or oil return; the other end of the first passage and the second passage is connected to a third reversing valve, the other two interfaces of the third reversing valve are connected to the rodless cavity and the rod cavity of a second oil cylinder respectively, and the first passage is switched to be connected to the rodless cavity and the rod cavity of the second oil cylinder for oil inlet, or the first passage and the second passage are connected to the rodless cavity or the rod cavity of the second oil cylinder for oil inlet or oil return. The effect that a small oil pump supplies oil for the system and drives a large-volume heavy-load oil cylinder to run at high speed and be accurately controlled is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic control, in particular to a hydraulic system for a mobile lifting vehicle for gravity energy storage. BACKGROUND

[0002] In a gravity energy storage power generation system, there is a need for lifting and carrying heavy objects. In order to realize the lifting of heavy objects from a low position to a high position and the sequential placement, a lifting system is needed. The system can lift / descend the heavy objects and place them on the high / low load beam through the transverse movement system. In order to realize this function, a hydraulic system is needed to realize the lifting and transverse movement of the heavy objects. Since the lifting and transverse movement of the heavy objects are short in time, the hydraulic system needs to provide high flow pressure oil for the extension and retraction of multiple oil cylinders in a short time, and the cost of the system needs to be considered.

[0003] The above-mentioned transverse movement and lifting functions are realized by different oil cylinders. The transverse movement and lifting functions require high pressure and high flow. Since the equipment is operated in an intermittent manner, the use of an oil pump for oil supply will result in excessive power of the oil pump and high system cost and high energy consumption.

[0004] For example, in the patent "Hydraulic system for high-pressure pump of leveler" with application number CN201820756517.7, a hydraulic system is disclosed, which includes an oil inlet pipe, an oil outlet pipe, a pressure relief pipe, a first hydraulic pump, a second hydraulic pump, and two motors. The hydraulic system continuously provides stable pressure for the external control system through the setting of auxiliary elements and accumulators, so that the leveling effect of the strip is better, and the product quality is improved. However, it relies on two hydraulic pumps to provide pressure oil, and the accumulator is mainly used for pressure maintaining and stabilizing. When high flow is needed, the cost of the system is high. SUMMARY

[0005] The purpose of the present application is to provide a hydraulic system for a mobile lifting vehicle for gravity energy storage, which is used to drive multiple working oil cylinders of a heavy load transverse lifting device to run quickly, efficiently and energy-savingly, realize the use of a small oil pump to supply oil to the system, drive large-volume heavy oil cylinders to run at high speed and accurately control, save equipment investment, and has the advantages of high control precision, low cost, simple control, etc.

[0006] The above technical purpose of the present application is realized by the following technical scheme:

[0007] A hydraulic system for a mobile lifting vehicle for gravity energy storage, comprising an oil tank, the oil tank being connected to an oil pump, the oil outlet of the oil pump being connected to a first branch and a second branch, respectively supplying oil to a first oil cylinder and a second oil cylinder, realizing lifting and transverse movement;

[0008] The second branch is connected to the inlet end of the second check valve, the other end of the second check valve is connected to the second switch valve and the second reversing valve, the other end of the second switch valve is connected to the second accumulator;

[0009] The other three interfaces of the second reversing valve are respectively connected to the oil tank, the first passage and the second passage, for switching oil inlet or oil return to the first passage and the second passage, the other ends of the first passage and the second passage are connected to the third reversing valve, the other two interfaces of the third reversing valve are respectively connected to the rodless chamber and the rod chamber of the second oil cylinder, for switching the first passage to simultaneously connect to the rodless chamber and the rod chamber of the second oil cylinder for oil inlet, or the first passage and the second passage respectively to the rodless chamber or the rod chamber of the second oil cylinder for oil inlet or oil return.

[0010] Further, the first branch is connected to the inlet end of the first check valve, the other end of the first check valve is connected to the first reversing valve, the first reversing valve is also connected to the rodless chamber of the first oil cylinder and the oil tank, for switching oil inlet from the first branch and oil return to the oil tank.

[0011] Further, the first reversing valve is connected to the rodless chamber of the first oil cylinder through a hydraulic control check valve, the oil inlet of the hydraulic control check valve is connected to the A interface of the first reversing valve, and the control circuit is connected to the B interface of the first reversing valve.

[0012] Further, the rodless chamber of the first oil cylinder is also connected to the first switch valve, the other end of the first switch valve is connected to the first accumulator and the outlet end of the first check valve.

[0013] Further, the end of the first switch valve away from the first oil cylinder is also connected to the first overflow valve, and the other end of the first overflow valve is connected to the oil tank.

[0014] Further, the oil inlet and outlet of the rod chamber of the first oil cylinder is connected to the third switch valve, the other end of the third switch valve is connected to the fourth reversing valve, the fourth reversing valve is also connected to the first reversing valve and the oil tank, for switching the rod chamber to return oil to the oil tank or to return part of the oil in the rodless chamber to the rod chamber when the first oil cylinder is retracting.

[0015] Further, the fourth reversing valve is a proportional reversing valve, for controlling the extension speed of the oil cylinder.

[0016] Further, a first displacement sensor is installed inside or outside the first oil cylinder to feedback the extension amount of the oil rod.

[0017] Further, the third reversing valve is a hydraulic control reversing valve, when the pressure in the first passage exceeds a set value, the third reversing valve switches to oil inlet to the rod chamber of the second oil cylinder, so that the oil rod retracts to release pressure.

[0018] Further, the P interface of the third reversing valve is connected to a one-way overflow valve, the oil outlet of the one-way overflow valve is connected to the control oil path at one end of the third reversing valve, and the control oil path controls the oil inlet of the second passage to the rod cavity of the second oil cylinder and the oil return of the rodless cavity to the second passage.

[0019] In summary, the present application has the following advantages:

[0020] 1. The second accumulator provides power oil for the second oil cylinder. When the oil cylinder is working, the oil pump and the second accumulator jointly provide pressure oil for the second oil cylinder, which can meet the large flow requirement of the oil cylinder in a short time. The pressure oil is mainly provided by the accumulator, thereby greatly reducing the rated power of the oil pump, saving system cost and energy consumption.

[0021] Similarly, the working oil of the second oil cylinder is mainly provided by the second accumulator, realizing high-speed operation in a short time without increasing the installed power of the oil pump, thereby saving investment.

[0022] 2. In the hydraulic oil cylinder of a heavy load device, the volume of the rodless cavity is usually much larger than that of the rod cavity. In the present application, when the first oil cylinder is extended, the third switch valve is connected, at which time the oil in the rod cavity of the first oil cylinder enters the fourth reversing valve through the third switch valve, and then returns to the oil tank through the radiator and the oil return filter.

[0023] The fourth reversing valve is used to control the extension speed of the oil cylinder, and in cooperation with the position signal fed back by the first position sensor of the oil cylinder, the extension amount of the first oil cylinder can be accurately controlled.

[0024] Since the volume of the rod cavity of the first oil cylinder is smaller than that of the rodless cavity, the first reversing valve is used in the oil path entering and exiting the rodless cavity, and the fourth reversing valve is used in the oil path entering the rod cavity. Since the cost of the reversing valve is much lower than that of the proportional reversing valve, the flow of the fourth reversing valve can be reduced, thereby reducing the cost of the system.

[0025] 3. When the lifting device is descending, the load weight is used for descending without additional power but with the need for speed and flow control. That is, when the first oil cylinder needs to retract the oil rod, the oil rod is mainly retracted by relying on the external load without the need for pressure oil driving.

[0026] At this time, the left electromagnet of the first reversing valve is connected, and the hydraulic control one-way valve is connected under the action of the pressure oil, so that a large amount of oil in the rodless cavity of the first oil cylinder can directly return to the oil tank from the first reversing valve through the throttle valve, the radiator and the oil return filter.

[0027] At the same time, a part of the oil returns to the rod cavity of the first oil cylinder from the first reversing valve through the fourth reversing valve and the third switch valve, further accelerating the working speed of the first oil cylinder; and the throttle valve can avoid the too fast retraction speed of the oil cylinder.

[0028] The design can realize accurate control of the position and speed of the oil cylinder, and can reduce the flow requirement of the proportional valve and the system cost.

[0029] 4. When the second oil cylinder needs to extend for work, first, the second switch valve is turned on, so that the oil pump supplies oil to the second accumulator, when the pressure reaches the working pressure, the second reversing valve is turned on, and the left side function is used, the pressure oil in the oil pump and the second accumulator enters the rodless chamber and the rod chamber of the second oil cylinder through the middle mechanism of the third reversing valve, because the pressure on both sides of the oil cylinder is different, the oil rod extends, and the oil in the oil rod chamber directly returns to the rodless chamber, realizing the rapid extension movement of the oil rod;

[0030] When the pressure is too large, the one-way overflow valve starts to overflow, so that the third reversing valve is in the left side mechanism, the oil rod retracts to release pressure, and the function of protecting the equipment is realized;

[0031] The design realizes the rapid movement of the oil cylinder, and does not need to provide a large amount of hydraulic oil by the hydraulic pump or the accumulator, but realizes the differential of the oil in the rodless chamber and the rod chamber, so that the installed power and flow requirement of the power source are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the overall structure schematic diagram of the present application;

[0033] Figure 2 is the structure schematic diagram of the first reversing valve part in the present application;

[0034] Figure 3 is the structure schematic diagram of the fourth reversing valve part in the present application;

[0035] Figure 4 is the structure schematic diagram of the second reversing valve and the third reversing valve part in the present application.

[0036] In the figure, 1 is an oil pump, 2 is an oil tank, 3 is a second overflow valve, 4 is a radiator, 401 is a third one-way valve, 5 is a high-pressure filter, 6 is a second accumulator, 601 is a second gas pressure sensor, 7 is a fourth reversing valve, 8 is a third switch valve, 9 is a first reversing valve, 901 is a hydraulic control one-way valve, 10 is a throttle valve, 1101 is a first one-way valve, 1102 is a second one-way valve, 12 is a first oil cylinder, 1201 is a first displacement sensor, 13 is a first switch valve, 14 is a first accumulator, 1401 is a first gas pressure sensor, 15 is a second reversing valve, 16 is a one-way overflow valve, 17 is a third reversing valve, 18 is a second oil cylinder, 1801 is a second displacement sensor, 20 is a second switch valve, 22 is a first overflow valve, 23 is an oil return filter, 242 is a first pressure sensor, and 243 is a second pressure sensor. DETAILED DESCRIPTION

[0037] The specific embodiments of the present application are further described below with reference to the drawings, which do not constitute limitation to the present application.

[0038] A mobile lifting truck hydraulic system for gravity energy storage, as shown in Figure 1 The oil tank 2 is connected to the oil pump 1, the oil outlet of the oil pump 1 is connected to the high-pressure filter 5, the oil outlet of the high-pressure filter 5 is connected to the first branch and the second branch, and the first oil cylinder 12 and the second oil cylinder 18 are supplied with oil respectively to realize lifting and transverse movement.

[0039] As shown in Figure 1 and Figure 2 The first branch is connected to the inlet end of the first one-way valve 1101, the outlet end of the first one-way valve 1101 is connected to the P interface of the first reversing valve 9, and the first reversing valve 9 is also connected to the rodless cavity of the first oil cylinder 12 and the oil tank 2, which is used to switch the oil inlet from the first branch and the oil return to the oil tank 2.

[0040] Specifically, as shown in Figure 2 The A interface of the first reversing valve 9 is connected to the oil inlet of the hydraulic control one-way valve 901, the oil outlet of the hydraulic control one-way valve 901 is connected to the rodless cavity of the first oil cylinder 12, and the control loop of the hydraulic control one-way valve 901 is connected to the B interface of the first reversing valve 9.

[0041] The first reversing valve 9 is a three-position four-way electromagnetic reversing valve, when in the neutral state, the P interface is not connected, the T interface is connected with the A and B interfaces at the same time, and the first oil cylinder does not work; when the right electromagnet is powered on, the hydraulic oil flows from the P interface to the A interface, the B interface is connected with the T interface, and the rodless cavity of the first oil cylinder 12 is supplied with oil; when the left electromagnet is powered on, the hydraulic oil flows from the P interface to the B interface, so that the hydraulic control one-way valve 901 is connected under the action of the pressure oil, a large amount of oil in the rodless cavity of the first oil cylinder 12 flows out from the A interface to the T interface of the first reversing valve 9, and returns to the oil tank 2.

[0042] As shown in Figure 1 The rodless cavity of the first oil cylinder 12 is also connected to the first on-off valve 13 (solenoid valve), the other end of the first on-off valve 13 is connected to the first accumulator 14, the first overflow valve 22 and the outlet end of the first one-way valve 1101; the other end of the first overflow valve 22 is connected to the oil tank 2, and the first gas pressure sensor 1401 is connected to the first accumulator 14; when the gas pressure in the accumulator is insufficient, the sensor sends a low-pressure alarm, and the oil is supplied to the first accumulator 14 through the outlet end of the first one-way valve 1101.

[0043] As shown in Figure 1 and Figure 3As shown, the rod cavity inlet and outlet of the first oil cylinder 12 is connected to the first pressure sensor 242 and the third switch valve 8 (electromagnetic switch valve), the other end of the third switch valve 8 is connected to the B interface of the fourth reversing valve 7 (the fourth reversing valve 7 is a three-position four-way proportional reversing valve, used to control the speed of the oil cylinder extension), the fourth reversing valve 7 is also connected to the first reversing valve 9 and the oil tank 2, used to switch the rod cavity back to the oil tank 2 or return part of the oil in the rodless cavity to the rod cavity when the first oil cylinder 12 retracts;

[0044] Specifically, as shown in the figure Figure 3 As shown, the A interface of the fourth reversing valve 7 is not connected, the P interface is connected to the T interface of the first reversing valve 9, the T interface of the first reversing valve 9 is also connected to the throttle valve 10, the other end of the throttle valve 10 is connected to the T interface of the fourth reversing valve 7 and the radiator 4, the other end of the radiator 4 is connected to the oil return filter 23, and the other end of the oil return filter 23 is connected to the oil tank 2 (the outlet of the oil pump 1 is also connected to the second overflow valve 3, the other end of the second overflow valve 3 is connected to the inlet end of the radiator 4, improving safety; The two ends of the radiator 4 are also connected in parallel with the third check valve 401, when the amount of oil return exceeds the rated flow of the radiator 4, the excess oil can flow back to the oil tank 2 directly through the third check valve 401).

[0045] When the fourth reversing valve 7 is in the middle position or the upper side function (the functions of the two positions are similar), the oil in the rod cavity enters the fourth reversing valve 7 through the third switch valve 8, and the oil flows from the fourth reversing valve 7 B→T oil way, back to the oil tank 2 from the radiator 4 and the oil return filter 23;

[0046] When the first oil cylinder 12 retracts the oil rod, part of the large amount of oil in the rodless cavity returns to the oil tank 2 through the throttle valve 10, and the other part returns to the rod cavity of the oil cylinder through the P→B oil way of the fourth reversing valve 7 when the fourth reversing valve 7 is in the lower side function.

[0047] As shown in the figure Figure 1 The first displacement sensor 1201 is installed inside or outside the first oil cylinder 12 to feedback the extension amount of the oil rod, so as to facilitate the position feedback control of the oil cylinder by the control system; the fourth reversing valve 7 is used to control the extension speed of the oil cylinder, and cooperates with the position signal fed back by the first position sensor of the oil cylinder to accurately control the extension amount of the first oil cylinder 12.

[0048] Working process:

[0049] When the first oil cylinder 12 needs to work, the oil rod needs to be extended;

[0050] For the rodless cavity: the pressure oil output by the oil pump 1 enters the first reversing valve 9 through the first check valve 1101, when the right side electromagnet of the first reversing valve 9 is powered on, the hydraulic oil enters the rodless cavity of the first oil cylinder 12 through the P→A oil way of the first reversing valve 9;

[0051] At the same time, the first switch valve 13 is opened, and the pressure oil in the first accumulator 14 enters the rodless chamber of the first cylinder 12 through the first switch valve 13; the pressure oil of the oil pump 1 and the first accumulator 14 jointly pushes the first cylinder 12 to extend the oil rod; since the first accumulator 14 can output a large amount of pressure oil in a short time, the power and flow of the oil pump 1 can be reduced under the premise of the same working speed, and the system cost is reduced.

[0052] When the first accumulator 14 needs to be refilled, the first switch valve 13 is closed, and the first directional valve 9 is in the neutral state; the oil output by the oil pump 1 enters the first accumulator 14 through the first check valve 1101.

[0053] The rod chamber: the third switch valve 8 is opened, and the oil in the rod chamber of the first cylinder 12 enters the fourth directional valve 7 through the third switch valve 8; the fourth directional valve 7 is in the neutral state, and the oil returns to the oil tank 2 from the radiator 4 and the oil return filter 23 through the fourth directional valve 7B→T oil path.

[0054] Since the rod chamber of the first cylinder 12 has a smaller capacity than the rodless chamber, the first directional valve 9 is used in the oil path entering and exiting the rodless chamber, and the fourth directional valve 7 is used to control the speed in the oil path entering the rod chamber; since the cost of the directional valve is much lower than that of the proportional directional valve, the flow of the fourth directional valve 7 can be reduced, and the system cost is reduced.

[0055] When the first cylinder 12 needs to retract the oil rod,

[0056] The oil rod is mainly retracted by the external load, and does not need to be driven by the pressure oil; at this time, the left electromagnet of the first directional valve 9 is opened, and the hydraulic control check valve 901 is opened under the action of the pressure oil, so that a large amount of oil in the rodless chamber of the first cylinder 12 can directly return to the oil tank 2 from the first directional valve 9 through the throttle valve 10, the radiator 4 and the oil return filter 23. At the same time, a part of the oil returns to the oil tank 2 through the fourth directional valve 7 and the third switch valve 8, further accelerating the working speed of the first cylinder 12; the throttle valve 10 can avoid the oil cylinder from retracting too fast.

[0057] As shown in Figure 1 and Figure 4 The second branch is connected to the inlet end of the second check valve 1102, the other end of the second check valve 1102 is connected to the P interface of the second pressure sensor 243, the second switch valve 20 and the second directional valve 15, the other end of the second switch valve 20 is connected to the second accumulator 6,

[0058] The second switching valve 15 has three other interfaces connected to the oil tank 2, the first passage and the second passage respectively, for switching the oil inlet or return to the first passage and the second passage, and the first passage and the second passage are connected to the third switching valve 17 at the other end, and the third switching valve 17 has two other interfaces connected to the rodless chamber and the rod chamber of the second oil cylinder 18 respectively, for switching the first passage to simultaneously connect to the rodless chamber and the rod chamber of the second oil cylinder 18 for oil inlet, or the first passage and the second passage to separately connect to the rodless chamber or the rod chamber of the second oil cylinder 18 for oil inlet or return;

[0059] Specifically, the A and B interfaces of the second switching valve 15 are connected to the T and P interfaces of the third switching valve 17 respectively, the A and B interfaces of the third switching valve 17 are connected to the rodless chamber and the rod chamber of the second oil cylinder 18 respectively, and the T interface of the second switching valve 15 is connected to the inlet of the radiator 4.

[0060] As shown in the figure, Figure 4 When the pressure in the first passage exceeds the set value, the third switching valve 17 switches to oil inlet to the rod chamber of the second oil cylinder 18, so that the oil rod retracts to release pressure;

[0061] Specifically, the P interface of the third switching valve 17 is connected to the one-way overflow valve 16, and the oil outlet of the one-way overflow valve 16 is connected to the control oil way of one end of the third switching valve 17, which controls the oil inlet to the rod chamber of the second oil cylinder 18 from the first passage and the oil return from the rodless chamber to the second passage; the control oil way of the other end of the third switching valve 17 is connected to the T interface thereof.

[0062] As shown in the figure, Figure 4 When the second switching valve 15 is in the neutral state, the four interfaces thereof are not connected to each other, and there is no pressure oil flowing in the second passage branch;

[0063] When the left position state, the P interface of the second switching valve 15 is connected to the B interface, and is connected to the P interface of the third switching valve 17 through the first passage, so that the oil inlet to the rodless chamber and the rod chamber of the second oil cylinder 18 is controlled when the third switching valve 17 is in the neutral state, and the T interface of the second switching valve 15 is connected to the A interface, and is connected to the T interface of the third switching valve 17 through the second passage;

[0064] When the right position state, the P interface of the second switching valve 15 is connected to the A interface, and is connected to the T interface of the third switching valve 17 through the second passage, and under the action of the hydraulic oil, the third switching valve 17 switches to the right position to control the oil inlet to the rod chamber of the second oil cylinder 18, and the rodless chamber enters the first passage through the third switching valve 17, and then enters the oil tank 2 through the second switching valve 15 for oil return.

[0065] As shown in the figure, Figure 4The second accumulator 6 is used to provide power oil for the second oil cylinder 18, and is connected to the second gas pressure sensor 601 to detect the pressure therein. When the gas pressure in the second accumulator 6 is insufficient, the second gas pressure sensor 601 sends a low pressure alarm. When the second oil cylinder 18 is working, the oil pump 1 and the second accumulator 6 jointly provide pressure oil for the second oil cylinder 18, which can meet the large flow requirement of the second oil cylinder 18 in a short time, reduce the power of the oil pump 1, and save energy.

[0066] As shown in the drawings, Figure 4 The second displacement sensor 1801 is installed inside or outside the second oil cylinder 18, which can feedback the oil rod extension amount, so as to perform oil cylinder position feedback control by the control system

[0067] Working process:

[0068] When the second oil cylinder 18 needs to be extended for work, first, the second on-off valve 20 (solenoid valve) is turned on, the oil pump 1 supplies oil to the second accumulator 6, and the real-time pressure in the system oil circuit and the pressure in the accumulator are detected by the second pressure sensor 243 in the circuit. When the pressure reaches the working pressure, the system enters the standby state.

[0069] When the pressure reaches the working pressure, the second reversing valve 15 is turned on, and the pressure oil in the oil pump 1 and the second accumulator 6 enters the rodless chamber and the rod chamber of the second oil cylinder 18 through the middle mechanism of the third reversing valve 17. Due to the pressure difference on both sides of the oil cylinder, the oil rod is extended, and the oil discharged from the oil rod chamber directly returns to the rodless chamber, realizing the rapid extension movement of the oil rod.

[0070] When the pressure is too large, the one-way overflow valve 16 starts to overflow, so that the third reversing valve 17 is in the left mechanism, the oil rod is retracted to relieve pressure, and the equipment is protected.

[0071] When the oil rod needs to be retracted, the right mechanism of the second reversing valve 15 is used, the pressure oil in the oil pump 1 and the second accumulator 6 enters the rod chamber of the second oil cylinder 18 through the right mechanism of the third reversing valve 17, the oil rod is retracted, and the oil in the rodless chamber returns to the oil return circuit through the third reversing valve 17 and the second reversing valve 15, and finally to the oil tank 2.

[0072] The above is only a preferred embodiment of the present application, which is not used to limit the present application. Those skilled in the art can make various modifications or equivalent replacements to the present application within the spirit and protection scope of the present application, and such modifications or equivalent replacements shall also be considered to fall within the protection scope of the technical scheme of the present application.

Claims

1. A hydraulic system for a mobile lift vehicle for gravity energy storage, characterized by: It includes an oil tank connected to an oil pump, and an oil outlet of the oil pump is connected to a first branch and a second branch, respectively supplying oil to the first oil cylinder and the second oil cylinder to achieve lifting and lateral movement; The second branch is connected to the inlet end of the second one-way valve, the other end of the second one-way valve is connected to the second switch valve and the second reversing valve, and the other end of the second switch valve is connected to the second accumulator; The other three interfaces of the second reversing valve are respectively connected to the oil tank, the first passage and the second passage, for switching oil inlet or oil return to the first passage and the second passage, the other ends of the first passage and the second passage are connected to the third reversing valve, and the other two interfaces of the third reversing valve are respectively connected to the rodless chamber and the rod chamber of the second oil cylinder, for switching the first passage to be connected to the rodless chamber and the rod chamber of the second oil cylinder for oil inlet at the same time, or the first passage and the second passage to supply oil to or return oil to the rodless chamber or the rod chamber of the second oil cylinder respectively; The first branch is connected to the inlet end of the first one-way valve, and the other end of the first one-way valve is connected to the first reversing valve. The first reversing valve is also connected to the rodless chamber of the first oil cylinder and the oil tank, and is used to switch the oil inlet from the first branch and the oil return to the oil tank; the first reversing valve and the rodless chamber of the first oil cylinder are connected via a hydraulically controlled one-way valve, the oil inlet of the hydraulically controlled one-way valve is connected to the A interface of the first reversing valve, and the control circuit is connected to the B interface of the first reversing valve; The oil inlet and outlet of the rod chamber of the first oil cylinder are connected to the third switching valve, the other end of the third switching valve is connected to the fourth reversing valve, and the fourth reversing valve is also connected to the first reversing valve and the oil tank, which is used to switch the rod chamber to return oil to the oil tank or to return part of the oil in the rodless chamber to the rod chamber when the first oil cylinder retracts; the fourth reversing valve is a proportional reversing valve, which is used to control the speed of extension of the oil cylinder.

2. A hydraulic system for a mobile lift vehicle for gravity energy storage according to claim 1, characterized in that: The rodless chamber of the first oil cylinder is also connected to the first switch valve, and the other end of the first switch valve is connected to the first accumulator and the outlet end of the first one-way valve.

3. A hydraulic system for a mobile lift vehicle for gravity energy storage according to claim 2, characterized in that: One end of the first switch valve away from the first oil cylinder is also connected to the first overflow valve, and the other end of the first overflow valve is connected back to the oil tank.

4. The hydraulic system for a mobile lift vehicle for gravity energy storage according to claim 1, characterized in that: A first displacement sensor is installed inside or outside the first oil cylinder to feedback the extension amount of the oil rod.

5. The hydraulic system for a mobile lift vehicle for gravity energy storage according to claim 1, characterized in that: The third reversing valve is a hydraulically controlled reversing valve. When the pressure in the first passage exceeds a set value, it switches to supply oil to the rod chamber of the second oil cylinder, causing the oil rod to retract and release pressure.

6. The hydraulic system for a mobile lift vehicle for gravity energy storage according to claim 5, characterized in that: The P interface of the third reversing valve is connected to the one-way relief valve, and the oil outlet of the one-way relief valve is connected to the control oil circuit at one end of the third reversing valve, controlling the first passage to supply oil to the rod chamber of the second oil cylinder and the rodless chamber to return oil to the second passage.

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