A potential energy recovery oil circuit with a composite speed regulation function

Abstract

The present invention discloses a potential energy recovery oil circuit with a composite speed regulation function, comprising: a lifting oil cylinder; a fuel supply module provided with a fuel tank and a fuel supply component for supplying oil to the potential energy recovery oil circuit; a valve control module provided with a pressure reducing component and a throttle reversing valve, the pressure reducing component being used for reducing the pressure of the pressurized oil provided by the fuel supply module and controlling the reversing of the throttle reversing valve; an energy recovery module provided with a recovery switching valve, a hydraulic motor and a generator; when the lifting oil cylinder descends, it is possible to select to simultaneously open the valve control module and the recovery switching valve or select to open one of the valve control module and the recovery switching valve. The potential energy recovery oil circuit provided by the present invention has multiple speed control modes, which can be freely selected according to the actual working conditions, avoiding energy loss caused by energy recovery itself; the hydraulic motor is only used for energy recovery, with high reliability, and can effectively improve the potential energy recovery efficiency and the control accuracy during the descent of the lifting oil cylinder.

Description

Technical Field

[0001] The present invention relates to the technical field of energy recovery, and more specifically, to a potential energy recovery oil circuit with a composite speed regulation function. Background Art

[0002] Handling equipment such as industrial vehicles (forklifts), excavators, loaders, stackers, aerial work platforms, etc. generally use hydraulic systems to drive their lifting components to lift and lower. During frequent lifting and lowering processes, the gravitational potential energy of the load cannot be effectively utilized. To control the descending speed, in the prior art, a valve control system such as a speed limiting valve, a throttle valve, and a reversing valve is usually set in the descending circuit, and the descending speed is controlled by throttling. The valve control system has advantages such as fast response and good control performance. However, valve control causes most of the potential energy to be directly or indirectly consumed as heat in the hydraulic system, resulting in an increase in oil temperature, further accelerating the oxidation rate of the oil, reducing the oil viscosity, and even decreasing the overall working efficiency of the hydraulic system. It will also accelerate the aging of related components and affect the service life and transmission efficiency of the hydraulic system.

[0003] In the prior art solutions, a forklift potential energy recovery system and control method that are adaptive according to the load weight are disclosed. This solution controls the pump motor speed through motor speed regulation to achieve the speed control of the system, and switches the lifting and lowering actions by changing the rotation direction of the motor. However, during the working process, due to the complex working conditions, the motor needs to be frequently started and stopped, and even switched between the electric and power generation modes. The moment of inertia of the motor is relatively large, resulting in a slow response speed during action switching and affecting the user experience satisfaction. In addition, the current fluctuates greatly during the working process, and the working temperature is relatively high, resulting in a low working life of the pump motor and often accompanied by problems such as large vibration and noise.

[0004] Based on the potential energy recovery system with variable speed and variable displacement speed regulation in the prior art, although it has a good energy-saving effect, the control effect is worse than that of the valve control system. Especially during the low-speed descent process, the generator will be in the low-speed region, and the motor has poor control accuracy of the speed at low speeds, which will inevitably affect the control of the descending speed. At the same time, when the motor is at low speed, it usually enters the low-efficiency region, and the system recovery efficiency will be relatively low. At this time, it is no longer suitable to use potential energy recovery. During the descent, to control the descending speed, the system also needs to provide a certain amount of energy. When the recovery power during the descent is not enough to overcome the minimum loss of the system, if potential energy recovery is still used, the system will instead be in an energy-consuming state.

[0005] In summary, how to improve the control accuracy of the descending speed and the potential energy recovery efficiency during potential energy recovery is an urgent problem to be solved by those skilled in the art at present. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a potential energy recovery oil circuit with a composite speed regulation function, which can control the lifting and lowering of the lifting cylinder, and during the lowering process of the lifting cylinder, it is possible to select to simultaneously open the valve control module and the recovery switching valve or select to open one of the valve control module and the recovery switching valve; the potential energy recovery efficiency and the lowering accuracy of the lifting cylinder can be effectively improved.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A potential energy recovery oil circuit with a composite speed regulation function, comprising:

[0009] A lifting cylinder, the rodless cavity of which is connected to the fuel tank;

[0010] An oil supply module, provided with the fuel tank and an oil supply assembly, and the oil supply assembly is used to supply oil to the potential energy recovery oil circuit with a composite speed regulation function;

[0011] A valve control module, provided with a pressure reducing assembly and a throttle reversing valve, the pressure reducing assembly is used to reduce the pressure of the pressure oil provided by the oil supply assembly and control the reversing of the throttle reversing valve, and the throttle reversing valve is connected to the fuel tank;

[0012] An energy recovery module, provided with a recovery switching valve, a hydraulic motor and a generator, the pressure reducing assembly, the hydraulic motor and the rodless cavity of the lifting cylinder are all connected to the recovery switching valve, and the hydraulic motor drives the generator to rotate;

[0013] When the lifting cylinder descends, it is possible to select to simultaneously open the valve control module and the recovery switching valve or select to open one of the valve control module and the recovery switching valve.

[0014] Optionally, the energy recovery module includes a make-up oil check valve arranged in parallel at the oil inlet and oil outlet of the hydraulic motor. When the hydraulic motor sucks air, the pressure oil is supplied from the fuel tank to the hydraulic motor through the make-up oil check valve.

[0015] Optionally, the recovery switching valve is a two-position two-way electro-hydraulic proportional throttle valve. The oil inlet of the recovery switching valve is connected to the rodless cavity of the lifting cylinder, the oil outlet of the recovery switching valve is connected to the oil inlet of the hydraulic motor, and the pressure reducing assembly provides pilot oil with reduced pressure for the recovery switching valve.

[0016] Optionally, the oil supply assembly includes a motor, a variable pump and a first check valve arranged at the oil outlet of the variable pump. The first check valve is connected to the pressure reducing assembly, and the motor is connected to the variable pump and drives the variable pump to rotate.

[0017] Optionally, the pressure relief assembly includes a pressure compensator, a pilot pressure reducing valve, a first electro-hydraulic proportional pressure reducing valve, and a second electro-hydraulic proportional pressure reducing valve. The pressure compensator and the pilot pressure reducing valve are both connected to the oil supply assembly. The first electro-hydraulic proportional pressure reducing valve, the second electro-hydraulic proportional pressure reducing valve, and the recovery switching valve are all connected to the outlet of the pilot pressure reducing valve;

[0018] The working oil ports of the first electro-hydraulic proportional pressure reducing valve and the second electro-hydraulic proportional pressure reducing valve are respectively connected to the upper end and the lower end of the throttle reversing valve to drive the throttle reversing valve to reverse. The pressure compensator is connected to the throttle reversing valve.

[0019] Optionally, a second check valve and a first accumulator are provided at the output end of the pilot pressure reducing valve. One end of the second check valve is connected to the output end of the pilot pressure reducing valve, and the other end is connected to the first accumulator. The first electro-hydraulic proportional pressure reducing valve and the second electro-hydraulic proportional pressure reducing valve are both connected to the first accumulator.

[0020] Optionally, a relief valve connected in parallel with the throttle reversing valve is further included. The relief valve is used to limit the pressure of the working oil port of the throttle reversing valve.

[0021] Optionally, a load holding valve and a speed limiting valve connected to the rodless cavity of the lifting cylinder are further included. One end of the load holding valve is connected to the throttle reversing valve, and the other end is connected to the speed limiting valve.

[0022] Optionally, a stop valve is connected in parallel between the load holding valve and the speed limiting valve. When the lifting cylinder descends emergently, the pressure oil in the rodless cavity flows through the speed limiting valve and the stop valve in sequence and enters the fuel tank.

[0023] Optionally, a second accumulator is connected in parallel between the speed limiting valve and the load holding valve.

[0024] During the process of using the potential energy recovery oil circuit with a composite speed regulation function provided by the present invention, when the lifting cylinder rises, the oil supply assembly in the oil supply module is controlled to extract pressure oil from the fuel tank and supply the pressure oil to the pressure relief assembly. The pressure relief assembly reduces the pressure of the pressure oil provided by the oil supply assembly and supplies the pressure-reduced pressure oil to the recovery switching valve. The pressure relief assembly controls the throttle reversing valve to communicate with the rodless cavity of the lifting cylinder, so that the pressure-reduced pressure oil enters the rodless cavity of the lifting cylinder through the throttle reversing valve, increasing the pressure in the rodless cavity of the lifting cylinder and driving the lifting cylinder to rise. When the lifting cylinder rises to a preset height, the throttle reversing valve stops supplying oil to the rodless cavity of the lifting cylinder, so that the lifting cylinder remains stationary at the preset height.

[0025] When the lifting cylinder needs to descend, it is possible to select to open the valve control module and the recovery switching valve simultaneously or select to open one of the valve control module and the recovery switching valve according to actual needs.

[0026] When the lifting cylinder needs to descend slowly and there are high requirements for the control precision of the descending speed during the descent process, or the load is lower than the minimum value required for potential energy recovery, the throttle reversing valve can be opened only, and the throttle descent mode can be adopted without energy recovery; the pressure oil in the rodless cavity of the lifting cylinder flows to the throttle reversing valve and returns to the fuel tank through the throttle reversing valve. After the lifting cylinder descends a certain distance, the throttle reversing valve can be controlled to move to a position that prevents the pressure oil from continuing to flow into the fuel tank, so that the lifting cylinder can be maintained at the required height; during this process, the opening degree of the throttle reversing valve can be controlled through the pressure reducing component, thereby controlling the descending speed of the lifting cylinder. This is applicable to the situation where the descending speed of the lifting cylinder is slow and there are high requirements for the control precision of the descending speed, and it can effectively improve the control of the descending precision of the lifting cylinder.

[0027] When the lifting cylinder needs to descend quickly and there are low requirements for the control precision of the descending speed, the recovery switching valve can be opened only to enter the variable speed volume control descent mode; the pressure oil in the rodless cavity of the lifting cylinder flows to the hydraulic motor through the recovery switching valve and drives the hydraulic motor to rotate, converting the potential energy into kinetic energy. The hydraulic motor drives the generator to rotate, converting the kinetic energy into electrical energy for storage, realizing the recovery of potential energy. After the lifting cylinder descends a certain distance and needs to be maintained at a specific position, the hydraulic fluid in the rodless cavity of the lifting cylinder is controlled to not flow out, so that the position of the lifting cylinder is fixed, and at the same time the recovery switching valve loses power and resets; this descending process is applicable to the situation where the descending speed of the lifting cylinder is fast and there are low requirements for the control precision of the descending speed of the lifting cylinder. The descending speed of the lifting cylinder can be adjusted by adjusting the control speed of the generator, and the recovery efficiency of potential energy can be effectively improved.

[0028] When the descending speed of the lifting cylinder is relatively fast and there are high requirements for the control precision of the descending speed, the valve control module and the recovery switching valve can be opened simultaneously to enter the compound speed control descent mode; at this time, the descending speed of the lifting cylinder is relatively fast, and at the same time there are certain requirements for the control precision of the descending speed of the lifting cylinder. Part of the pressure oil of the lifting cylinder flows to the throttle reversing valve and returns to the fuel tank through the throttle reversing valve, and the other part of the pressure oil flows to the hydraulic motor through the recovery switching valve and drives the hydraulic motor to rotate, converting the potential energy into kinetic energy. The hydraulic motor drives the generator to rotate, converting the kinetic energy into electrical energy for storage, realizing the recovery of potential energy; during this process, the descending speed of the lifting cylinder can be adjusted by adjusting the opening degree of the throttle reversing valve and the control speed of the generator. It can improve the control precision of the descending speed of the lifting cylinder when the descending speed of the lifting cylinder is relatively fast; after the lifting cylinder descends a certain distance and needs to be maintained at a specific position, the hydraulic fluid in the rodless cavity of the lifting cylinder is controlled to not flow out, so that the position of the lifting cylinder is fixed, and at the same time the recovery switching valve loses power and resets; the throttle reversing valve is controlled to move to a position that prevents the pressure oil from continuing to flow into the fuel tank, so that the lifting cylinder can be maintained at the required height.

[0029] Compared with the prior art, the potential energy recovery oil circuit with a composite speed regulation function provided by the present invention has multiple speed control modes, which can be freely selected according to the actual working conditions, avoiding energy loss caused by energy recovery itself; the hydraulic motor is only used for energy recovery, with high reliability, and can effectively improve the potential energy recovery efficiency and the control accuracy during the descending process of the lifting cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0031] Figure 1 It is a schematic structural diagram of a specific embodiment of the potential energy recovery oil circuit with a composite speed regulation function provided by the present invention.

[0032] Figure 1 Wherein:

[0033] Oil tank 1, variable pump 2, electric motor 3, first check valve 4, throttle reversing valve 5, pressure compensator 6, overflow valve 7, first electro-hydraulic proportional relief valve 8, second electro-hydraulic proportional relief valve 9, first accumulator 10, second check valve 11, pilot relief valve 12, load holding valve 13, speed limiting valve 14, lifting cylinder 15, second accumulator 16, stop valve 17, recovery switching valve 18, generator 19, oil replenishing check valve 20, hydraulic motor 21. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] The core of the present invention is to provide a potential energy recovery oil circuit with a composite speed regulation function, which can control the lifting of the lifting cylinder, and during the descending process of the lifting cylinder, it is possible to select to simultaneously open the valve control module and the recovery switching valve or select to open one of the valve control module and the recovery switching valve as needed; it can effectively improve the potential energy recovery efficiency and the descending accuracy of the lifting cylinder.

[0036] It should be noted that during the potential energy recovery process, when performing refined operations on the load, the system often requires good fine motion performance. When the lifting cylinder performs a fine motion descent, the descent speed is slow, and the control accuracy requirement for the speed is high. Since the generator has poor control accuracy and low power generation efficiency at low speeds, it is not suitable for potential energy recovery. The energy recovery system composed of a hydraulic motor, a generator, and an energy storage device itself has certain energy losses. Here, the energy storage device can be a device for storing the electric energy of the generator. When the energy that can be recovered by the external load and its own weight is less than the losses generated by the energy recovery system itself, potential energy recovery will generate additional energy losses. Therefore, potential energy recovery has certain requirements for the minimum value of the load.

[0037] Please refer to Figure 1 。

[0038] This specific embodiment discloses a potential energy recovery oil circuit with a composite speed regulation function, including:

[0039] A lifting cylinder 15, whose rodless cavity is connected to a fuel tank 1;

[0040] An oil supply module, provided with a fuel tank 1 and an oil supply component, and the oil supply component is used to supply oil to the potential energy recovery oil circuit with a composite speed regulation function;

[0041] A valve control module, provided with a pressure reducing component and a throttle reversing valve 5. The pressure reducing component is used to reduce the pressure of the pressure oil provided by the oil supply component and control the reversing of the throttle reversing valve 5, and the throttle reversing valve 5 is connected to the fuel tank 1;

[0042] An energy recovery module, provided with a recovery switching valve 18, a hydraulic motor 21, and a generator 19. The pressure reducing component, the hydraulic motor 21, and the rodless cavity of the lifting cylinder 15 are all connected to the recovery switching valve 18, and the hydraulic motor 21 drives the generator 19 to rotate;

[0043] When the lifting cylinder 15 descends, it is possible to select to simultaneously open the valve control module and the recovery switching valve 18 or select to open one of the valve control module and the recovery switching valve 18.

[0044] Preferably, the generator 19 is coaxially connected to the hydraulic motor 21, and the rotational speeds of the generator 19 and the hydraulic motor 21 are the same. The hydraulic motor 21 can be set as a fixed-displacement motor, and the generator 19 is equipped with a rotational speed sensor to read the real-time rotational speed of the generator 19 in real time.

[0045] In the process of the potential energy recovery oil circuit with composite speed regulation function provided by this specific embodiment, when the lifting cylinder 15 rises, it enters the rising mode. The oil supply component in the oil supply module is controlled to extract oil from the oil tank 1 and supply the oil to the pressure reducing component. The pressure reducing component reduces the pressure of the pressurized oil provided by the oil supply component and supplies the depressurized pressurized oil to the recovery switching valve 18. The pressure reducing component controls the throttle reversing valve 5 to communicate with the rodless cavity of the lifting cylinder 15, so that the pressurized oil enters the rodless cavity of the lifting cylinder 15 through the throttle reversing valve 5, increasing the pressure in the rodless cavity of the lifting cylinder 15 and driving the lifting cylinder 15 to rise. When the lifting cylinder 15 rises to the preset height, the throttle reversing valve 5 stops supplying oil to the rodless cavity of the lifting cylinder 15, keeping the lifting cylinder 15 stationary at the preset height.

[0046] When the lifting cylinder 15 needs to descend, it is possible to choose to simultaneously open the valve control module and the recovery switching valve 18 or choose to open one of the valve control module and the recovery switching valve 18 according to actual needs.

[0047] When the lifting cylinder 15 needs to descend slowly and the control accuracy of the descending speed is required to be high during the descending process, or the load is lower than the minimum value required for potential energy recovery, only the throttle reversing valve 5 can be opened to adopt the throttle descending mode without energy recovery; the pressurized oil in the rodless cavity of the lifting cylinder 15 flows to the throttle reversing valve 5 and returns to the oil tank 1 through the throttle reversing valve 5. After the lifting cylinder 15 descends a certain distance, the throttle reversing valve 5 can be controlled to move to a position that prevents the pressurized oil from continuing to flow into the oil tank 1, keeping the lifting cylinder 15 at the required height; during this process, the opening degree of the throttle reversing valve 5 can be controlled through the pressure reducing component, thereby controlling the descending speed of the lifting cylinder 15. This is applicable to the situation where the descending speed of the lifting cylinder 15 is slow and the control accuracy of the descending speed is high, and can effectively improve the control of the descending accuracy of the lifting cylinder 15.

[0048] When the lifting cylinder 15 needs to descend quickly and the control accuracy of the descending speed is required to be low, only the recovery switching valve 18 can be opened to enter the variable speed volume speed regulation descending mode; the pressurized oil in the rodless cavity of the lifting cylinder 15 flows through the recovery switching valve 18 to the hydraulic motor 21 and drives the hydraulic motor 21 to rotate, converting potential energy into kinetic energy. The hydraulic motor 21 drives the generator 19 to rotate, converting kinetic energy into electrical energy for storage, realizing the recovery of potential energy. After the lifting cylinder 15 descends a certain distance and needs to be kept at a specific position, the hydraulic fluid in the rodless cavity of the lifting cylinder 15 is controlled to not flow out, keeping the position of the lifting cylinder 15 fixed, and at the same time the recovery switching valve 18 loses power and resets; this descending process is applicable to the situation where the descending speed of the lifting cylinder 15 is fast and the control accuracy of the descending speed of the lifting cylinder 15 is not high. The descending speed of the lifting cylinder 15 can be adjusted by adjusting the control speed of the generator 19, and the recovery efficiency of potential energy can be effectively improved.

[0049] When the lowering speed of the lifting oil cylinder 15 is relatively fast and a high control precision for the lowering speed is required, the valve control module and the recovery switching valve 18 can be opened simultaneously to enter the compound speed regulation lowering mode; at this time, the lowering speed of the lifting oil cylinder 15 is relatively fast, and at the same time, there is a certain requirement for the control precision of the lowering speed of the lifting oil cylinder 15. Part of the pressure oil of the lifting oil cylinder 15 flows to the throttle reversing valve 5 and returns to the fuel tank 1 through the throttle reversing valve 5, and the other part of the pressure oil flows to the hydraulic motor 21 through the recovery switching valve 18 and drives the hydraulic motor 21 to rotate, converting potential energy into kinetic energy. The hydraulic motor 21 drives the generator 19 to rotate, converting kinetic energy into electrical energy for storage, realizing the recovery of potential energy; during this process, the lowering speed of the lifting oil cylinder 15 can be adjusted by adjusting the opening degree of the throttle reversing valve 5 and the control speed of the generator 19. When the lowering speed of the lifting oil cylinder 15 is relatively fast, the control precision of the lowering speed of the lifting oil cylinder 15 can be improved; after the lifting oil cylinder 15 descends a certain distance and needs to be maintained at a specific position, the hydraulic fluid in the rodless cavity of the lifting oil cylinder 15 is controlled not to flow out, so that the position of the lifting oil cylinder 15 is fixed, and at the same time, the recovery switching valve 18 is powered off and reset; control the throttle reversing valve 5 to move to a position that prevents the pressure oil from continuing to flow into the fuel tank 1, so that the lifting oil cylinder 15 is maintained at the required height.

[0050] It should be noted that the number of the lifting oil cylinders 15 in this specific embodiment can be one, two or more, which is specifically determined according to the actual situation. When there are multiple lifting oil cylinders 15, generally, multiple lifting oil cylinders 15 are arranged in parallel.

[0051] Compared with the prior art, the potential energy recovery oil circuit with compound speed regulation function provided by this specific embodiment has multiple speed control modes, which can be freely selected according to the actual working conditions, avoiding energy loss caused by energy recovery itself; the hydraulic motor 21 is only used for energy recovery, with high reliability, and can effectively improve the potential energy recovery efficiency and the control precision during the lowering process of the lifting oil cylinder 15.

[0052] In a specific embodiment, as Figure 1 shown, the energy recovery module includes a make-up oil check valve 20 arranged in parallel at the oil inlet and outlet of the hydraulic motor 21. One end of the make-up oil check valve 20 is connected to the oil inlet of the hydraulic motor 21, and the other end is connected to the oil outlet of the hydraulic motor 21. When the hydraulic motor 21 sucks air, the pressure oil is supplied from the fuel tank 1 to the hydraulic motor 21 through the make-up oil check valve 20.

[0053] During the downward movement of the lifting oil cylinder 15, it may encounter other resistances. Under the action of the resistance, the downward speed of the lifting oil cylinder 15 will decrease. If the rotational speed of the hydraulic motor 21 remains the previous speed, it will cause the pressure at the inlet of the hydraulic motor 21 to drop sharply, and then lead to the phenomenon of cavitation in the hydraulic motor 21. To prevent cavitation in the hydraulic motor 21, a make-up oil check valve 20 is connected in parallel at the inlet and outlet of the hydraulic motor 21. When cavitation occurs, oil can be replenished from the fuel tank 1 into the inlet of the hydraulic motor 21, avoiding a sharp drop in the pressure at the inlet of the hydraulic motor 21 and effectively preventing the occurrence of cavitation.

[0054] As Figure 1 shown, the recovery switching valve 18 is a two-position two-way electro-hydraulic proportional throttle valve. The inlet of the recovery switching valve 18 is connected to the rodless cavity of the lifting oil cylinder 15, and the outlet of the recovery switching valve 18 is connected to the inlet of the hydraulic motor 21. The decompression component provides pilot oil after decompression for the recovery switching valve 18;

[0055] During use, when the recovery switching valve 18 is energized, the opening of the valve core can be adjusted according to the magnitude of the electrical signal. When the recovery switching valve 18 is de-energized, the recovery switching valve 18 is in the right position and is blocked at both ends, effectively preventing pressure oil from flowing into the hydraulic motor 21.

[0056] Of course, the recovery switching valve 18 can also be other valve body structures that meet the requirements, which will not be elaborated here.

[0057] In this specific embodiment, the recovery switching valve 18 is set as a two-position two-way electro-hydraulic proportional throttle valve, which has a simple connection and is convenient to control.

[0058] As Figure 1 shown, the oil supply component includes a motor 3, a variable pump 2, and a first check valve 4 provided at the outlet of the variable pump 2. The first check valve 4 is connected to the decompression component. The motor 3 is connected to the variable pump 2 and drives the variable pump 2 to rotate.

[0059] Preferably, the motor 3 is coaxially connected to the variable pump 2. The motor 3 drives the variable pump 2 to supply oil, and their rotational speeds are the same. The variable pump has a load-sensing function and can automatically adjust the displacement according to the required flow rate of the work, achieving an energy-saving effect; a first check valve 4 is provided at the outlet of the variable pump 2 to effectively prevent the reverse flow of pressure oil into the variable pump 2.

[0060] In a specific embodiment, as Figure 1 shown, the decompression component includes a pressure compensator 6, a pilot-operated pressure reducing valve 12, a first electro-hydraulic proportional pressure reducing valve 8, and a second electro-hydraulic proportional pressure reducing valve 9. The pressure compensator 6 and the pilot-operated pressure reducing valve 12 are both connected to the oil supply component. The first electro-hydraulic proportional pressure reducing valve 8, the second electro-hydraulic proportional pressure reducing valve 9, and the recovery switching valve 18 are all connected to the outlet of the pilot-operated pressure reducing valve 12;

[0061] The working oil ports of the first electro-hydraulic proportional pressure reducing valve 8 and the second electro-hydraulic proportional pressure reducing valve 9 are respectively connected to the upper end and the lower end of the throttle reversing valve 5 to drive the throttle reversing valve 5 to reverse, and the pressure compensator 6 is connected to the throttle reversing valve 5.

[0062] A second check valve 11 and a first accumulator 10 are arranged at the output end of the pilot-operated pressure reducing valve 12. One end of the second check valve 11 is connected to the output end of the pilot-operated pressure reducing valve 12, and the other end is connected to the first accumulator 10. Both the first electro-hydraulic proportional pressure reducing valve 8 and the second electro-hydraulic proportional pressure reducing valve 9 are connected to the first accumulator 10.

[0063] When the motor 3 does not rotate, the first accumulator 10 can provide a pilot oil source for the first electro-hydraulic proportional pressure reducing valve 8 and the second electro-hydraulic proportional pressure reducing valve 9 to realize the lowering function of the lifting cylinder 15; the setting of the second check valve 11 can effectively prevent the pressure oil in the first accumulator 10 from flowing back into the pilot-operated pressure reducing valve 12.

[0064] It further includes a relief valve 7 connected in parallel with the throttle reversing valve 5, and the relief valve 7 is used to limit the working oil port pressure of the throttle reversing valve 5.

[0065] The setting of the relief valve 7 can effectively limit the pressure of the working oil port of the throttle reversing valve 5. When the oil pressure is greater than the preset value of the relief valve 7, the pressure oil flows back to the oil tank 1 through the relief valve 7.

[0066] During use, the variable pump 2 provides pressure oil for the pilot-operated pressure reducing valve 12 and the pressure compensator 6. The pressure oil provided by the variable pump 2 enters the throttle reversing valve 5 through the pressure compensator 6, and the working oil port of the throttle reversing valve 5 is connected to the load holding valve 13. Further, the pressure of the working oil port of the throttle reversing valve 5 is introduced into one side of the spring chamber of the pressure compensator 6 through a pipeline, and the pressure oil at the oil outlet of the pressure compensator 6 is introduced into the side without a spring chamber of the pressure compensator 6 through a pipeline to form a load sensing system, so that the flow rate provided by the throttle reversing valve 5 is proportional to the spool displacement, ensuring the control accuracy of the flow rate.

[0067] The pressure oil provided by the variable pump 2 is reduced in pressure by the pilot-operated pressure reducing valve 12 and then provides pilot oil for the recovery switching valve 18, the first electro-hydraulic proportional pressure reducing valve 8 and the second electro-hydraulic proportional pressure reducing valve 9; the first electro-hydraulic proportional pressure reducing valve 8 and the second electro-hydraulic proportional pressure reducing valve 9 are pilot valves of the throttle reversing valve 5. When the first electro-hydraulic proportional pressure reducing valve 8 is energized, it can drive the spool of the throttle reversing valve 5 to move downward, and when the second electro-hydraulic proportional pressure reducing valve 9 is energized, it can drive the spool of the throttle reversing valve 5 to move upward, and the displacement size is determined by the obtained electrical signal (current or voltage).

[0068] On the basis of the above embodiments, it further includes a load holding valve 13 and a speed limiting valve 14 connected to the rodless chamber of the lifting cylinder 15. One end of the load holding valve 13 is connected to the throttle reversing valve 5, and the other end is connected to the speed limiting valve 14.

[0069] Preferably, the load holding valve 13 is a two-position two-way one-way cut-off valve 17, which is arranged between the throttle reversing valve 5 and the speed limiting valve 14. When the lifting cylinder 15 needs to be held at a specific position, the load holding valve 13 loses power and is located at the right position to prevent the lifting cylinder 15 from sliding down. When pressure oil needs to be conducted, the load holding valve 13 is energized and located at the left position, so that the pressure oil can flow back from the rodless cavity of the lifting cylinder 15 to the throttle reversing valve 5, or the pressure oil can flow from the throttle reversing valve 5 to the rodless cavity of the lifting cylinder 15.

[0070] The setting of the speed limiting valve 14 can effectively prevent the lifting cylinder 15 from stalling and can be used to limit the maximum speed of the descent of the lifting cylinder 15.

[0071] As Figure 1 shown, a cut-off valve 17 is connected in parallel between the load holding valve 13 and the speed limiting valve 14. When the lifting cylinder 15 makes an emergency descent, the pressure oil in the rodless cavity flows through the speed limiting valve 14 and the cut-off valve 17 in sequence and enters the oil tank 1.

[0072] When the lifting cylinder 15 needs to descend rapidly, the opening degree of the spool of the cut-off valve 17 can be adjusted manually, so that the pressure oil inside the lifting cylinder 15 directly flows back to the oil tank 1 through the speed limiting valve 14 and the cut-off valve 17, avoiding excessive oil pressure inside the lifting cylinder 15 and playing a certain protective role.

[0073] Preferably, a second accumulator 16 is connected in parallel between the speed limiting valve 14 and the load holding valve 13; the setting of the second accumulator 16 can effectively buffer the load fluctuation and make the descent process of the lifting cylinder 15 more stable.

[0074] As Figure 1 shown, the potential energy recovery oil circuit with a composite speed regulation function includes an oil tank 1, a variable pump 2, a motor 3, a first one-way valve 4, a throttle reversing valve 5, a pressure compensator 6, an overflow valve 7, a first electro-hydraulic proportional reducing valve 8, a second electro-hydraulic proportional reducing valve 9, a first accumulator 10, a second one-way valve 11, a pilot reducing valve 12, a load holding valve 13, a speed limiting valve 14, a lifting cylinder 15, a second accumulator 16, a cut-off valve 17, a recovery switching valve 18, a generator 19, a make-up oil one-way valve 20, and a hydraulic motor 21.

[0075] The specific connection relationship is as follows:

[0076] The motor 3 is coaxially connected to the variable pump 2 and rotates at the same speed. A first one-way valve 4 is installed at the oil outlet of the variable pump 2 to prevent the pressure oil in the system from flowing back into the variable pump 2. After the pressure oil provided by the variable pump 2 passes through the first one-way valve 4, it is connected to the oil inlet of the pilot pressure reducing valve 12 and the oil inlet of the pressure compensator 6 through pipelines respectively. After the pressure oil is reduced in pressure by the pilot pressure reducing valve 12, it is connected to the oil inlet of the first electro-hydraulic proportional pressure reducing valve 8, the oil inlet of the second electro-hydraulic proportional pressure reducing valve 9, and the oil inlet of the recovery switching valve 18 through pipelines respectively, providing the pilot pressure oil required for the operation of the first electro-hydraulic proportional pressure reducing valve 8, the second electro-hydraulic proportional pressure reducing valve 9, and the recovery switching valve 18. The working oil ports of the first electro-hydraulic proportional pressure reducing valve 8 and the second electro-hydraulic proportional pressure reducing valve 9 are connected to the upper end and the lower end of the throttle reversing valve 5 respectively, used to drive the throttle reversing valve 5 to move up and down. A first accumulator 10 and a second one-way valve 11 are provided in the pilot oil pipeline provided by the pilot pressure reducing valve 12. When the motor 3 is not working, if the lifting cylinder 15 needs to descend, the oil stored in the first accumulator 10 can ensure that the lifting cylinder 15 can descend normally; the second one-way valve 11 can prevent the oil in the first accumulator 10 from entering the pilot pressure reducing valve 12. The pressure compensator 6 is connected to the oil inlet of the throttle reversing valve 5 through a pipeline. The working oil port of the throttle reversing valve 5 is connected to the rodless cavity of the lifting cylinder 15 through a pipeline. The outlet pressure of the pressure compensator 6 is introduced into the side of the springless cavity of the pressure compensator 6 through a pipeline, and the outlet pressure of the throttle reversing valve 5 is introduced into the spring cavity side of the pressure compensator 6, forming a load sensing system, so that the flow rate provided by the throttle reversing valve 5 is proportional to the spool displacement, ensuring the control accuracy of the flow rate. An overflow valve 7 is connected in parallel at the working oil port of the throttle reversing valve 5, used to limit the maximum working pressure of the throttle reversing valve 5. A load holding valve 13 and a speed limiting valve 14 are connected in series in sequence on the pipeline at the bottom of the rodless cavity of the throttle reversing valve 5 and the lifting cylinder 15. The rod end of the lifting cylinder 15 is connected to the oil tank 1 through a pipeline. A second accumulator 16 is connected in parallel on the pipeline between the load holding valve 13 and the speed limiting valve 14 and is connected to the stop valve 17. The oil inlet of the recovery switching valve 18 is connected to the oil outlet of the load holding valve 13. The oil outlet of the recovery switching valve 18 is connected to the oil inlet of the hydraulic motor 21. The oil outlet of the hydraulic motor 21 is connected to the oil tank 1 through a pipeline. The generator 19 is coaxially connected to the hydraulic motor 21 and rotates at the same speed. At the same time, oil replenishing one-way valves 20 are connected in parallel on both sides of the oil inlet and the oil outlet of the hydraulic motor 21, which can effectively prevent the hydraulic motor 21 from sucking air.

[0077] Use as Figure 1When the potential energy recovery oil circuit with a compound speed regulation function as shown is in operation, when the lifting cylinder 15 needs to rise, it enters the rising mode. The motor 3 drives the variable pump 2 to rotate. The variable pump 2 sucks oil from the oil tank 1. The pressure oil is reduced in pressure by the pilot relief valve 12 and provides pilot oil for the first electro-hydraulic proportional relief valve 8. Under the action of the control electric signal, the spool of the first electro-hydraulic proportional relief valve 8 will generate a corresponding displacement. The load holding valve 13 is energized and located in the left position. The first electro-hydraulic proportional relief valve 8 is energized and opened. The pilot oil is reduced in pressure by the pilot pressure valve and acts on the upper end of the throttle reversing valve 5 by the first electro-hydraulic proportional relief valve 8, driving the throttle reversing valve 5 to move downward, so that the throttle reversing valve 5 operates in the upper position. At this time, the pressure oil sequentially passes through the variable pump 2, the first check valve 4, the pressure compensator 6, the throttle reversing valve 5, the load holding valve 13, and the speed limiting valve 14 and enters the rodless cavity of the lifting cylinder 15, driving the lifting cylinder 15 to rise. When the lifting cylinder 15 has risen a certain distance and needs to be held at a specific position, the first electro-hydraulic proportional relief valve 8 is de-energized and reset to the lower position. At the same time, the upper end of the throttle reversing valve 5 loses pressure and, under the action of its own spring, resets to the middle position. The throttle reversing valve 5 no longer supplies oil, and the lifting cylinder 15 remains stationary.

[0078] During the rising process of the lifting cylinder 15, the speed of the motor 3 can be set to a fixed value, and the displacement is adjusted by the variable mechanism of the variable pump 2 to achieve the matching of flow supply and demand. In this way, it is necessary to ensure that the product of the speed of the motor 3 and the maximum displacement of the variable pump 2 is greater than the lifting required flow rate. The lifting speed is determined by the opening of the spool of the throttle reversing valve 5, with high control accuracy and good operating performance. It is also possible to adjust the speed of the motor 3 to achieve the matching of flow supply and demand, so that the product of the speed of the motor 3 and the maximum displacement of the variable pump 2 should be equal to the lifting required flow rate. In this way, the throttle reversing valve 5 can be fully opened to reduce the throttling loss, and the lifting speed is controlled by changing the speed of the motor 3.

[0079] If a higher control accuracy of the speed is required during the rising process, the method of setting a fixed speed of the motor 3 can be adopted. If the control accuracy of the speed is not required to be high, the method of changing the speed of the motor 3 can be adopted to reduce the throttling loss.

[0080] Use as Figure 1When the potential energy recovery oil circuit with compound speed regulation function as shown is in use, when the lifting cylinder 15 needs to descend slowly and the control accuracy of the descending speed is required to be very high, or the load is lower than the minimum value required for potential energy recovery, the throttling descent mode is adopted and no energy recovery is carried out. The load holding valve 13 is energized and works in the left position. Under the action of the control electrical signal, the spool of the second electro-hydraulic proportional relief valve 9 will generate a corresponding displacement. The pilot oil acts on the lower end of the throttle reversing valve 5, driving the throttle reversing valve 5 to move upward, so that the throttle reversing valve 5 works in the lower position; at this time, the pressure oil in the rodless cavity of the lifting cylinder 15 sequentially passes through the speed limiting valve 14, the load holding valve 13, and the throttle reversing valve 5 and enters the oil tank 1, enabling the lifting cylinder 15 to descend. When the lifting cylinder 15 has descended a certain distance and needs to be held at a specific position, the load holding valve 13 is de-energized and works in the right position. The oil in the rodless cavity of the lifting cylinder 15 cannot flow out, and the position is fixed. At the same time, the second electro-hydraulic proportional relief valve 9 is de-energized and reset.

[0081] During the process of controlling the descent of the lifting cylinder 15, according to the target speed V during the descent j the target flow rate Q required for descent is obtained j , and the specific calculation process is as follows:

[0082] Q j = a·A1·V j

[0083] where a is the number of lifting cylinders 15, and A1 is the effective acting area of the bottom of the rodless cavity of the lifting cylinder 15. Under the working pressure, the relationship between the descending target flow rate Q j and the electrical signal of the second electro-hydraulic proportional relief valve 9 can be obtained through experiments, and V j is the target speed during the descent of the lifting cylinder 15.

[0084] When using the potential energy recovery oil circuit with compound speed regulation function as shown in Figure 1 , when the lifting cylinder 15 needs to descend quickly and the control accuracy of the speed is not required to be high, it enters the variable speed volume speed regulation descent mode. The load holding valve 13 is energized and works in the left position, and the recovery switching valve 18 is energized and fully opened to work in the left position. The pressure oil in the rodless cavity of the lifting cylinder 15 sequentially passes through the speed limiting valve 14, the load holding valve 13, and the recovery switching valve 18 and enters the hydraulic motor 21, driving the hydraulic motor 21 to rotate. The hydraulic motor 21 drives the generator 19 to rotate for power generation, and the electric energy is stored in the battery pack to achieve the purpose of potential energy recovery. The pressure oil flows back to the oil tank 1 through the oil outlet of the hydraulic motor 21. When the lifting cylinder 15 has descended a certain distance and needs to be held at a specific position, the load holding valve 13 is de-energized and works in the right position. The pressure oil in the rodless cavity of the lifting cylinder 15 cannot flow out, and the position is fixed. At the same time, the recovery switch is de-energized and reset.

[0085] In the variable-speed displacement speed control descent mode, the descent speed of the lifting cylinder 15 is controlled by adjusting the rotational speed n of the generator 19 g to achieve

[0086] That is

[0087] wherein, V m is the displacement of the hydraulic motor 21, and η mv is the volume of the hydraulic motor 21

[0088] When using the potential energy recovery oil circuit with a compound speed control function as shown Figure 1 in the figure, when the descent speed of the lifting cylinder 15 is relatively high and there are certain requirements for the descent speed, the compound speed control descent mode can be adopted. To improve the control accuracy of the descent speed, compound speed control can be achieved by adjusting the flow rate of the hydraulic motor 21 and the flow rate of the throttle reversing valve 5. During this process, the load holding valve 13 is energized and works in the left position. Under the action of the control electrical signal, the spool of the second electro-hydraulic proportional pressure reducing valve 9 will generate a corresponding displacement. The pilot oil acts on the lower end of the throttle reversing valve 5, driving the throttle reversing valve 5 to move upward, causing the throttle reversing valve 5 to work in the lower position; at this time, the pressure oil in the rodless cavity of the lifting cylinder 15 sequentially passes through the speed limiting valve 14, the load holding valve 13, and the throttle reversing valve 5 and enters the fuel tank 1; the recovery switching valve 18 is energized and fully opened to work in the left position. The pressure oil in the rodless cavity of the lifting cylinder 15 sequentially passes through the speed limiting valve 14, the load holding valve 13, and the recovery switching valve 18 and enters the hydraulic motor 21, driving the hydraulic motor 21 to rotate. The hydraulic motor 21 drives the generator 19 to rotate for power generation, and the electric energy is stored in the battery pack to achieve the purpose of potential energy recovery. The pressure oil flows back to the fuel tank 1 through the oil outlet of the hydraulic motor 21; enabling the lifting cylinder 15 to descend. When the lifting cylinder 15 has descended a certain distance and needs to be held at a specific position, the load holding valve 13 is de-energized and works in the right position. The oil in the rodless cavity of the lifting cylinder 15 cannot flow out, and the position is fixed. At the same time, the second electro-hydraulic proportional pressure reducing valve 9 is de-energized and reset, and the recovery switch is de-energized and reset

[0089] In the compound speed control descent mode, similar to the variable-speed displacement speed control descent mode, the control rotational speed n of the generator 19 is set according to the target descent speed g , if the control rotational speed n of the generator 19 g is greater than the actual rotational speed n of the motor m due to external forces, friction, etc., according to the actual rotational speed n of the hydraulic motor 21 m the flow rate Q flowing back to the fuel tank 1 through the hydraulic motor 21 can be obtained j1 .

[0090]

[0091] Further calculation can obtain the insufficient descent flow rate Qj2 is: Q j2 = Q j -Q j1

[0092] That is

[0093] According to the descending target flow rate Q j2 and the pressure in the rodless chamber of the lifting cylinder 15, set the electrical signal of the second electro-hydraulic proportional pressure reducing valve 9, so that the throttle reversing valve 5 is partially opened. In this way, most of the descending flow enters the hydraulic motor 21 for energy recovery. Q j2 The flow rate of size flows back to the oil tank 1 through the throttle reversing valve 5 to adjust the descending speed to ensure the control accuracy. When the lifting cylinder 15 descends a certain distance and needs to be held at a specific position, the load holding valve 13 is de-energized and works in the right position. The pressure oil in the rodless chamber of the lifting cylinder 15 cannot flow out, and the position is fixed. At the same time, the recovery switching valve 18 and the second electro-hydraulic proportional pressure reducing valve 9 are de-energized and reset.

[0094] When switching from the throttle descending mode to the variable speed volume control descending mode or the compound speed control descending mode, the generator 19 is energized to participate in the control, and the recovery switching valve 18 is first slowly opened and then quickly fully opened. When switching from the variable speed volume control descending mode or the compound speed control descending mode to the throttle descending mode, the generator 19 is de-energized, and the valve port of the recovery switching valve 18 is first quickly closed and then slowly closed. When switching from the compound speed control descending mode to the variable speed volume control descending mode, if n g = n m , it indicates that it is consistent with the variable speed volume control descending mode at this time, and the control state remains unchanged. If n g > n m , it indicates that at this time, part of the descending pressure oil flows back to the oil tank 1 through the throttle reversing valve 5. The second electro-hydraulic proportional pressure reducing valve 9 should be de-energized, the throttle reversing valve 5 returns to the middle position, and all the descending oil flows back to the oil tank 1 through the motor for potential energy recovery.

[0095] When the lifting cylinder 15 cannot descend due to a fault, the stop valve 17 can be manually opened, and the pressure oil in the rodless chamber of the lifting cylinder 15 flows back to the oil tank 1 through the speed limiting valve 14 and the stop valve 17 in sequence to realize the lowering of the lifting cylinder 15.

[0096] In the first electro-hydraulic proportional pressure reducing valve 8 and the second electro-hydraulic proportional pressure reducing valve 9, the first one-way valve 4 and the second one-way valve 11, the first accumulator 10 and the second accumulator 16 mentioned in this application document, the "first" and "second" are only used to distinguish different positions and there is no order of precedence.

[0097] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. Any combination of all the embodiments provided by the present invention falls within the protection scope of this invention, and will not be elaborated herein.

[0098] The above has introduced in detail the potential energy recovery oil circuit with a composite speed regulation function provided by the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A potential energy recovery oil circuit with a composite speed regulation function, characterized in that, Comprising: A lifting oil cylinder (15), whose rodless cavity is connected to an oil tank (1); An oil supply module, provided with the oil tank (1) and an oil supply component, and the oil supply component is used to supply oil to a potential energy recovery oil circuit with a compound speed regulation function; A valve control module, provided with a pressure reducing component and a throttle reversing valve (5), the pressure reducing component is used to reduce the pressure of the pressure oil provided by the oil supply component and control the reversing of the throttle reversing valve (5), and the throttle reversing valve (5) is connected to the oil tank (1); An energy recovery module, provided with a recovery switching valve (18), a hydraulic motor (21) and a generator (19), the pressure reducing component, the hydraulic motor (21), and the rodless cavity of the lifting oil cylinder (15) are all connected to the recovery switching valve (18), and the hydraulic motor (21) drives the generator (19) to rotate; When the lifting oil cylinder (15) descends, it is possible to select to simultaneously open the valve control module and the recovery switching valve (18) or select to open one of the valve control module and the recovery switching valve (18); The pressure reducing component includes a pressure compensator (6), a pilot pressure reducing valve (12), a first electro-hydraulic proportional pressure reducing valve (8) and a second electro-hydraulic proportional pressure reducing valve (9), the pressure compensator (6) and the pilot pressure reducing valve (12) are both connected to the oil supply component, and the first electro-hydraulic proportional pressure reducing valve (8), the second electro-hydraulic proportional pressure reducing valve (9) and the recovery switching valve (18) are all connected to the oil outlet of the pilot pressure reducing valve (12); The working oil port of the first electro-hydraulic proportional pressure reducing valve (8) and the working oil port of the second electro-hydraulic proportional pressure reducing valve (9) are respectively connected to the upper end and the lower end of the throttle reversing valve (5) to drive the throttle reversing valve (5) to reverse, and the pressure compensator (6) is connected to the throttle reversing valve (5).

2. The potential energy recovery oil circuit with a composite speed regulation function according to claim 1, characterized in that, The energy recovery module includes a make-up oil check valve (20) connected in parallel to the oil inlet and the oil outlet of the hydraulic motor (21). When the hydraulic motor (21) sucks air, the pressure oil is supplied from the oil tank (1) to the hydraulic motor (21) through the make-up oil check valve (20).

3. The potential energy recovery oil circuit with a composite speed regulation function according to claim 1, characterized in that, The recovery switching valve (18) is a two-position two-way electro-hydraulic proportional throttle valve. The oil inlet of the recovery switching valve (18) is connected to the rodless cavity of the lifting oil cylinder (15), the oil outlet of the recovery switching valve (18) is connected to the oil inlet of the hydraulic motor (21), and the pressure reducing component provides pilot oil with reduced pressure for the recovery switching valve (18).

4. The potential energy recovery oil circuit with a composite speed regulation function according to claim 1, characterized in that, The oil supply component includes a motor (3), a variable pump (2) and a first check valve (4) arranged at the oil outlet of the variable pump (2). The first check valve (4) is connected to the pressure reducing component, and the motor (3) is connected to the variable pump (2) and drives the variable pump (2) to rotate.

5. The potential energy recovery oil circuit with a composite speed regulation function according to claim 1, characterized in that, The output end of the pilot pressure reducing valve (12) is provided with a second one-way valve (11) and a first accumulator (10). One end of the second one-way valve (11) is connected to the output end of the pilot pressure reducing valve (12), and the other end is connected to the first accumulator (10). The first electro-hydraulic proportional pressure reducing valve (8) and the second electro-hydraulic proportional pressure reducing valve (9) are both connected to the first accumulator (10).

6. The potential energy recovery oil circuit with a composite speed regulation function according to claim 1, wherein It further includes an overflow valve (7) connected in parallel with the throttle reversing valve (5). The overflow valve (7) is used to limit the working oil port pressure of the throttle reversing valve (5).

7. The potential energy recovery oil circuit with a composite speed regulation function according to any one of claims 1-4, characterized in that It further includes a load holding valve (13) and a speed limiting valve (14) connected to the rodless cavity of the lifting oil cylinder (15). One end of the load holding valve (13) is connected to the throttle reversing valve (5), and the other end is connected to the speed limiting valve (14).

8. The potential energy recovery oil circuit with a composite speed regulation function according to claim 7, characterized in that, A shut-off valve (17) is connected in parallel between the load holding valve (13) and the speed limiting valve (14). When the lifting oil cylinder (15) descends emergently, the pressure oil in the rodless cavity flows through the speed limiting valve (14) and the shut-off valve (17) in sequence and enters the fuel tank (1).

9. The potential energy recovery oil circuit with a composite speed regulation function according to claim 7, characterized in that, A second accumulator (16) is connected in parallel between the speed limiting valve (14) and the load holding valve (13).

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