A hydraulic control system and method for recovering gravitational potential energy

Abstract

The present invention relates to a hydraulic control system and method for recovering gravitational potential energy, belonging to the technical field of hydraulic control. When lifting a heavy object, the piston rod of the lifting hydraulic cylinder extends, and the accumulator and the servo motor pump unit jointly supply oil, which can reduce the installed volume of the accumulator; when the heavy object descends, the piston rod of the lifting hydraulic cylinder retracts, a part of the hydraulic oil is stored in the accumulator, and the other part of the hydraulic oil enters the rod chamber of the hydraulic cylinder through the servo motor pump unit. The suction port pressure of the servo motor pump unit is greater than the discharge port pressure, and the servo motor pump unit is in a power generation state. The gravitational potential energy is converted into hydraulic energy and electrical energy through the accumulator and the servo motor pump unit; the telescopic speed of the piston rod of the lifting hydraulic cylinder is controlled by the pump-controlled volume speed regulation of the servo motor pump unit, without the energy loss of throttle speed regulation, reducing the operating energy consumption; the oil in the accumulator is replaced through the valve control circuit, and the constant pressure oil source only needs to design the flow rate required by the hydraulic cylinder of the valve control circuit and the flow rate for supplementing system leakage, reducing the installed power.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic control, and relates to a hydraulic control system and method for recovering gravitational potential energy. Background Art

[0002] In the field of hydraulic control, accumulators are often used for energy recovery. When a heavy object descends, the oil in the rodless chamber of the hydraulic cylinder compressed by the load is discharged from the rodless chamber, enters the accumulator connected in parallel with the rodless chamber, and compresses the gas on the gas side of the accumulator, so that the pressurized oil is stored in the accumulator for use when driving the heavy object or load next time.

[0003] Due to the diversity of working conditions in the same system, the gravitational potential energy is not stable. The inflation pressure of the accumulator needs to be designed according to the maximum load force, so that the pressure in the rod chamber has to be designed and operated at the maximum working pressure all the time.

[0004] When the conventional accumulator recovers gravitational potential energy, almost all the oil pressure on the pressure-bearing side is pressed into the accumulator, resulting in a large volume requirement for the accumulator.

[0005] During the process of recovering or releasing gravitational potential energy, since the oil pressure in the accumulator needs to be matched with the load and the counter-chamber pressure in real time to control the speed, the valve control mode is often adopted, which will cause energy loss of throttle speed regulation and increase energy consumption. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a hydraulic control system and method for recovering gravitational potential energy to reduce energy consumption.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A hydraulic control system for recovering gravitational potential energy, comprising a servo motor pump unit. The first oil port of the servo motor pump unit is connected to the rodless cavity of the lifting hydraulic cylinder through a first oil circuit, and the second oil port of the servo motor pump unit is connected to the rod cavity of the lifting hydraulic cylinder through a second oil circuit. Overflow valves are connected to both the first oil circuit and the second oil circuit. A energy storage branch is also provided on the pipeline between the servo motor pump unit and the overflow valve in the first oil circuit. The energy storage branch includes an accumulator and a first two-position two-way directional control valve. The oil side of the accumulator is connected to the first two-position two-way directional control valve, and the first two-position two-way directional control valve is connected to the first branch. The oil side of the accumulator is connected to a constant pressure oil source through a three-position three-way directional control valve, and the middle position of the three-position three-way directional control valve is in a cut-off state. The constant pressure oil source is connected to the first oil circuit and the second oil circuit, and a pressure reducing valve and a check valve are provided on the pipeline connecting the constant pressure oil source to the first oil circuit and the second oil circuit to prevent the servo motor pump unit from sucking air. The accumulator is connected with a first displacement sensor to monitor the piston position thereof in real time, and the lifting hydraulic cylinder is connected with a second displacement sensor to detect the piston position thereof in real time. The first displacement sensor, the second displacement sensor, the servo motor pump unit, the first two-position two-way directional control valve, the three-position three-way directional control valve, and the second two-position two-way directional control valve are all connected to the controller, so that when the piston of the lifting hydraulic cylinder is at the high position, the piston of the accumulator descends to the low position, and when the piston of the lifting hydraulic cylinder is at the low position, the piston of the accumulator rises to the high position.

[0009] Optionally, when the oil suction port pressure of the servo motor pump unit is greater than the oil discharge port pressure, the servo motor pump unit is in a power generation state.

[0010] Optionally, the oil side of the accumulator is connected to a valve control circuit through a second two-position two-way directional control valve to replace the oil in the accumulator.

[0011] Optionally, the valve control circuit is a double-rod hydraulic cylinder circuit for horizontal expansion and contraction controlled by a three-position four-way directional control valve.

[0012] Optionally, the oil side of the accumulator is connected with a first pressure sensor connected to the controller to monitor the oil side pressure. The controller calculates the current gas side pressure of the accumulator based on the piston position, the current oil side pressure, the gas side pre-charge pressure, the gas side volume, and the ambient temperature of the accumulator to determine whether the current gas side pressure is within a safe range and whether the gas side needs to be inflated or deflated.

[0013] Optionally, the first oil circuit and the second oil circuit are connected with an exhaust pressure measuring element.

[0014] Optionally, pressure sensors connected to the controller are provided in both the oil suction chamber and the oil discharge chamber of the servo motor pump unit to monitor the pressures of the two chambers.

[0015] A hydraulic control method for recovering gravitational potential energy provides the gravitational potential energy recovery hydraulic control system as described above. When lifting a heavy object, the piston rod of the lifting hydraulic cylinder extends, and the accumulator and the servo motor pump unit jointly supply oil. When the heavy object descends, the piston rod of the lifting hydraulic cylinder retracts, a part of the hydraulic oil is stored in the accumulator, and the other part of the hydraulic oil enters the rod chamber of the hydraulic cylinder through the servo motor pump unit. The telescopic speed of the piston rod of the lifting hydraulic cylinder is controlled by the pump-controlled volume speed regulation of the servo motor pump unit.

[0016] Optionally, the oil side of the accumulator is connected to the valve control circuit through a second two-position two-way directional control valve to replace the oil in the accumulator. After the lifting hydraulic cylinder stops, the solenoid valve a of the first two-position two-way directional control valve loses power to cut off the oil circuit between the lifting hydraulic cylinder and the accumulator, and the solenoid valve a of the second two-position two-way directional control valve loses power to cut off the oil circuit between the valve control circuit and the accumulator. The controller adjusts the piston position of the accumulator by controlling the three-position three-way directional control valve to meet the requirements of the next action of the lifting hydraulic cylinder.

[0017] The beneficial effects of the present invention are as follows: When the gravitational potential energy falls, the gravitational potential energy can be converted into hydraulic energy and electrical energy through the accumulator and the servo motor pump unit. When lifting a heavy object, the rodless chamber of the lifting hydraulic cylinder is jointly supplied with oil by the accumulator and the servo motor pump unit, which can reduce the design volume of the accumulator. The telescopic speed of the lifting hydraulic cylinder is controlled by the servo motor pump unit, without the control and pressure loss of additional hydraulic valves, reducing the operating energy consumption. The oil in the accumulator supplies oil to the valve control circuit, and through the action of the hydraulic cylinder in the valve control circuit, the oil flows back to the oil tank, which not only ensures the cleanliness and temperature of the oil in the pump-controlled closed circuit, but also does not directly drain oil from the accumulator, reusing the hydraulic energy of the accumulator and further saving energy. For the gravitational potential energy lifting circuit, the constant pressure oil source only needs to provide the flow rate required to supplement the leakage of this circuit, reducing the installed power of the constant pressure oil source pump station.

[0018] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent description, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. Brief Description of the Drawings

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0020] Figure 1 It is a schematic diagram of a gravitational potential energy recovery hydraulic control system of the present invention.

[0021] Reference numerals: constant pressure oil source 1, three-position three-way directional control valve 2, accumulator 3, first displacement sensor 4.1, second displacement sensor 4.2, first pressure sensor 5.1, second pressure sensor 5.2, third pressure sensor 5.3, first two-position two-way directional control valve 6.1, second two-position two-way directional control valve 6.2, servo motor pump unit 7, first overflow valve 8.1, second overflow valve 8.2, lifting hydraulic cylinder 9, pressure reducing valve 10, first check valve 11.1, second check valve 11.2, first exhaust pressure measuring joint 12.1, second exhaust pressure measuring joint 12.2, controller 13, four-way three-position directional control valve 14, double-rod hydraulic cylinder 15. Detailed implementation manners

[0022] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0023] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, and do not represent the dimensions of actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0024] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0025] Please refer to Figure 1, a gravity potential energy recovery hydraulic control system, includes a servo motor pump unit 7. The first oil port of the servo motor pump unit 7 is connected to the rodless cavity of the lifting hydraulic cylinder 9 through a first oil circuit, and the second oil port of the servo motor pump unit 7 is connected to the rod cavity of the lifting hydraulic cylinder 9 through a second oil circuit. Both the first oil circuit and the second oil circuit are connected with overflow valves. A energy storage branch is also provided on the pipeline between the servo motor pump unit 7 and the overflow valve in the first oil circuit. The energy storage branch includes an accumulator 3 and a first two-position two-way directional control valve 6.1. The oil side of the accumulator 3 is connected to the first two-position two-way directional control valve 6.1, and the first two-position two-way directional control valve 6.1 is connected to the first branch. The oil side of the accumulator 3 is connected to a constant pressure oil source 1 through a three-position three-way directional control valve 2. The middle position of the three-position three-way directional control valve 2 is in a cut-off state. The oil side of the accumulator 3 is connected to a valve control circuit through a second two-position two-way directional control valve 6.2 to replace the oil in the accumulator 3. When the suction port pressure of the servo motor pump unit 7 is greater than the discharge port pressure, the servo motor pump unit 7 is in a power generation state. The accumulator 3 is connected with a first displacement sensor 4.1 to monitor its piston position in real time, and the lifting hydraulic cylinder 9 is connected with a second displacement sensor 4.2 to detect its piston position in real time. The first displacement sensor 4.1, the second displacement sensor 4.2, the servo motor pump unit 7, the first two-position two-way directional control valve 6.1, the three-position three-way directional control valve 2, and the second two-position two-way directional control valve 6.2 are all connected to a controller 13, so that when the piston of the lifting hydraulic cylinder 9 is at the high position, the piston of the accumulator 3 descends to the low position, and when the piston of the lifting hydraulic cylinder 9 is at the low position, the piston of the accumulator 3 rises to the high position. The valve control circuit can be any valve control circuit supplied with oil by the constant pressure oil source 1. For example, a double-rod hydraulic cylinder 15 that controls horizontal expansion and contraction through a three-position four-way directional control valve 14 is used to meet the replacement of the pressurized oil in the accumulator 3 and ensure the cleanliness and temperature of the oil.

[0026] When lifting a heavy object, the piston rod of the lifting hydraulic cylinder 9 extends, and the accumulator 3 and the servo motor pump unit 7 jointly supply oil, which can reduce the installed volume of the accumulator 3; when the heavy object descends, the piston rod of the lifting hydraulic cylinder 9 retracts, a part of the hydraulic oil is stored in the accumulator 3, and the other part of the hydraulic oil enters the rod chamber of the lifting hydraulic cylinder 9 through the servo motor pump unit 7; the telescopic speed of the lifting hydraulic cylinder 9 is controlled by the pump-controlled volume speed regulation of the servo motor pump unit 7, without the energy loss of throttle speed regulation, reducing the operating energy consumption; when the oil suction port pressure of the servo motor pump unit 7 is greater than the oil discharge port pressure, the servo motor pump unit 7 is in the power generation state; the servo motor pump unit 7 does work or generates electricity according to the pressure requirement on the rod chamber side of the lifting hydraulic cylinder 9, and has strong adaptability to load changes; the oil in the accumulator 3 is replaced by supplying oil to other valve-controlled circuits, which not only replaces the oil, ensures the cleanliness and temperature of the oil, but also makes full use of the hydraulic energy of the replaced oil, rather than directly returning it to the fuel tank from the accumulator, and can achieve better energy-saving effects. In the present invention, the gravitational potential energy can be converted into hydraulic energy and electrical energy through the accumulator 3 and the servo motor pump unit 7. For the gravitational potential energy lifting circuit, the constant pressure oil source 1 only needs to design the flow rate required to supplement the leakage of this circuit, reducing the installed power of the constant pressure source pump station.

[0027] Optionally, a first pressure sensor 5.1 connected to the controller 13 is connected to the oil side of the accumulator 3 to monitor the oil side pressure. The controller 13 calculates the current gas side pressure of the accumulator 3 based on the piston position, the current oil side pressure, the gas side pre-charge pressure, the gas side volume, and the ambient temperature of the accumulator 3 to determine whether the current gas side pressure is within the safe range and to judge whether the gas side needs to be charged or discharged; the constant pressure oil source 1 is connected to the first oil circuit and the second oil circuit, and pressure reducing valves 10 and check valves are provided on the pipelines connecting the constant pressure oil source 1 to the first oil circuit and the second oil circuit to replenish the oil in real time to prevent the servo motor pump unit from sucking air; the first oil circuit and the second oil circuit are connected with exhaust pressure measuring elements; pressure sensors connected to the controller 13 are provided in both the oil suction chamber and the oil discharge chamber of the servo motor pump unit 7 to monitor the pressures of the two chambers.

[0028] A gravitational potential energy recovery hydraulic control method provides the gravitational potential energy recovery hydraulic control system as described above. When lifting a heavy object, the piston rod of the lifting hydraulic cylinder 9 extends, and the accumulator 3 and the servo motor pump unit 7 jointly supply oil; when the heavy object descends, the piston rod of the lifting hydraulic cylinder 9 retracts, a part of the hydraulic oil is stored in the accumulator 3, and the other part of the hydraulic oil enters the rod chamber of the hydraulic cylinder through the servo motor pump unit 7; the telescopic speed of the piston rod of the lifting hydraulic cylinder 9 is controlled by the pump-controlled volume speed regulation of the servo motor pump unit 7; the oil in the accumulator 3 is replaced by supplying oil to other valve-controlled circuits.

[0029] Optionally, after the lifting hydraulic cylinder 9 stops, the solenoid valve a of the first two-position two-way directional valve 6.1 loses power to cut off the oil circuit between the lifting hydraulic cylinder 9 and the accumulator 3, and the solenoid valve a of the second two-position two-way directional valve 6.2 loses power to cut off the oil circuit between the valve control loop and the accumulator 3. The controller 13 adjusts the piston position of the accumulator 3 by controlling the three-position three-way directional valve 2 to meet the requirements of the next action of the lifting hydraulic cylinder 9.

[0030] Embodiment

[0031] A hydraulic control system for recovering gravitational potential energy, please refer to Figure 1 , including a constant pressure oil source 1, a three-position three-way directional valve 2, an accumulator 3, a first displacement sensor 4.1, a second displacement sensor 4.2, a first pressure sensor 5.1, a second pressure sensor 5.2, a third pressure sensor 5.3, a first two-position two-way directional valve 6.1, a second two-position two-way directional valve 6.2, a servo motor pump unit 7, a first relief valve 8.1, a second relief valve 8.2, a lifting hydraulic cylinder 9, a pressure reducing valve 10, a first check valve 11.1, a second check valve 11.2, a first exhaust pressure measuring joint 12.1, a second exhaust pressure measuring joint 12.2, a controller 13, a three-position four-way directional valve 14, and a double-rod hydraulic cylinder 15. The specific connection relationship is as follows: The lifting hydraulic cylinder 9 is provided with a displacement sensor 4.2, and its two chambers are connected to the two chambers of the servo motor pump unit 7; A first relief valve 8.1, a first exhaust pressure measuring joint 12.1, a second relief valve 8.2, and a second exhaust pressure measuring joint 12.2 are respectively connected to the oil circuits of the two chambers of the lifting hydraulic cylinder 9; Second pressure sensors 5.2, first check valves 11.1, third pressure sensors 5.3, and second check valves 11.2 are respectively provided on the oil circuits of the two chambers of the servo motor pump unit 7. A pressure reducing valve 10 is connected in series in front of the first check valve 11.1 and the second check valve 11.2 and is connected to the constant pressure oil source 1; The signals of the second displacement sensor 4.2, the second pressure sensor 5.2, and the third pressure sensor 5.3 are connected to the controller 13, and the servo motor pump unit 7 is controlled according to the requirements of the lifting hydraulic cylinder 9; The rodless chamber of the lifting hydraulic cylinder 9 is connected to the accumulator 3 and is connected to and disconnected from the rodless chamber of the lifting hydraulic cylinder 9 through the first two-position two-way directional valve 6.1; The accumulator 3 is connected with a first displacement sensor 4.1, and the oil side of the accumulator 3 is connected with a first pressure sensor 5.1; The oil side of the accumulator 3 is connected to the constant pressure oil source 1 through a three-position three-way directional valve 2; The signals of the first displacement sensor 4.1 and the first pressure sensor 5.1 are connected to the controller 13, and the three-position three-way directional valve 2 is commutated according to the requirements to further control the accurate position of the piston of the accumulator 3; The accumulator 3 is connected with a second two-position two-way directional valve 6.2 to provide a pressure oil source for the control loop of the conventional double-rod hydraulic cylinder 15.

[0032] The lifting hydraulic cylinder 9 always bears the downward heavy load F. Under the combined action of the accumulator 3 and the servo motor pump unit 7, the lifting hydraulic cylinder 9 controls the lifting or falling of the heavy object.

[0033] When there is no pressure on the oil side of the accumulator 3, nitrogen gas with a certain pre-charge pressure P0 is filled in the gas side, and the charging volume is the volume V0 of the accumulator. The constant pressure oil source 1 fills the oil into the system through the pressure reducing valve 10, the first one-way valve 11.1, and the second one-way valve 11.2, and discharges the gas in the pipeline through the first exhaust pressure measuring joint 12.1 and the second exhaust pressure measuring joint 12.2. At this time, the a electromagnets of the three-position three-way directional control valve 2 and the a electromagnet of the second two-position two-way directional control valve 6.2 are both de-energized, and the two valves are in the cut-off state; the a electromagnet of the first two-position two-way directional control valve 6.1 is energized and in the conducting state.

[0034] Assume that the initial position of the lifting hydraulic cylinder 9 is in the fully retracted state. After the system is filled with oil, the controller 13 controls the a electromagnet of the first two-position two-way directional control valve 6.1 to be de-energized, cutting off the oil circuit between the accumulator 3 and the rodless cavity of the lifting hydraulic cylinder 9. The controller 13 controls the a electromagnet of the three-position three-way directional control valve 2 to be energized and the b electromagnet to be de-energized, so that the constant pressure oil source 1 fills the oil into the accumulator 3, and then controls the piston position and the oil side pressure of the accumulator 3 to meet the requirements of the oil volume and oil pressure provided by the accumulator 3 when the lifting hydraulic cylinder 9 extends next time.

[0035] When the lifting hydraulic cylinder 9 drives the heavy object to lift, the pressure oil of the accumulator 3 supplies oil to the rodless cavity, pushing the lifting hydraulic cylinder 9 to extend. The oil discharged from the rodless cavity enters the rodless cavity of the hydraulic cylinder through the servo motor pump unit 7, and supplies oil jointly with the accumulator 3. The rising speed of the lifting hydraulic cylinder 9 is controlled by the servo motor pump unit 7. By controlling the rotation speed of the servo motor pump unit 7, the flow rate discharged from the rodless cavity of the lifting hydraulic cylinder 9 is controlled to achieve this. When the lifting hydraulic cylinder 9 extends to the highest position, the piston of the accumulator 3 descends to the lowest position, so as to store the oil discharged from the rodless cavity when the lifting hydraulic cylinder 9 retracts next time.

[0036] When the lifting hydraulic cylinder 9 drives the heavy object to fall, the oil discharged from the rodless cavity of the lifting hydraulic cylinder 9 is divided into two paths. One part enters the rodless cavity of the lifting hydraulic cylinder 9 through the servo motor pump unit 7 again, and the remaining part of the oil enters the accumulator 3 to be stored as hydraulic energy. The retracting speed of the lifting hydraulic cylinder 9 is controlled by the servo motor pump unit 7. By controlling the rotation speed of the servo motor pump unit 7, the oil inlet flow rate of the rodless cavity of the lifting hydraulic cylinder 9 is controlled to achieve this. When the lifting hydraulic cylinder 9 retracts to the lowest position, the piston of the accumulator 3 rises to the highest position to store hydraulic energy for use when the lifting hydraulic cylinder 9 extends next time.

[0037] During the extension or retraction of the lifting hydraulic cylinder 9, if the pressure at the suction port of the servo motor pump unit 7 is greater than that at the discharge port, the servo motor pump unit 7 is in a power generation state. Therefore, the gravitational potential energy is completely converted into hydraulic energy and electrical energy, thus saving energy.

[0038] During the extension or retraction of the lifting hydraulic cylinder 9, neither the a nor b electromagnets of the three-position three-way directional control valve 2 are energized, and the valve ports A are disconnected from both P and T. The electromagnet a of the first two-position two-way directional control valve 6.1 is energized and in a conducting state.

[0039] When the oil in the closed oil cavity composed of the accumulator 3, the lifting hydraulic cylinder 9, and the servo motor pump unit 7 needs to be replaced, control the a electromagnet of the second two-position two-way directional control valve 6.2 to be energized to provide an oil source for other valve-controlled hydraulic circuits. After driving the hydraulic cylinder through the four-position four-way directional control valve 14, the hydraulic oil is drained back to the fuel tank to ensure the cleanliness and temperature of the oil in the accumulator and the pump-controlled closed oil cavity.

[0040] The lifting hydraulic cylinder 9 is connected with a second displacement sensor 4.2. The controller 13 detects the position of the lifting hydraulic cylinder 9 in real time. After the lifting hydraulic cylinder 9 stops, the oil circuit between the hydraulic cylinder and the accumulator 3 is cut off. The controller 13 adjusts the piston position of the accumulator 13 by controlling the three-position three-way directional control valve 2 to meet the requirements of the next action of the lifting hydraulic cylinder 9. Therefore, when the lifting hydraulic cylinder 9 stops at a certain position, the connection between the accumulator 3 and the lifting hydraulic cylinder 9 and the double-rod hydraulic cylinder 15 can be cut off, and the piston position of the accumulator can be readjusted to ensure that there is sufficient pressure oil or storage volume in the accumulator 3 during the next action.

[0041] Due to leakage or changes in ambient temperature, the initial pressure P0 on the gas side of the accumulator 3 will change. When leakage occurs or the ambient temperature decreases, the initial pressure will drop. At the same oil-side pressure, the piston of the accumulator 3 will be compressed to a higher position. Conversely, when the ambient temperature rises, the initial pressure will rise, and at the same oil-side pressure, the piston of the accumulator 3 will be in a lower position. Given the pre-charge pressure P0, volume V0, current oil-side pressure, piston position, and ambient temperature of the gas side of the accumulator 3, the controller 13 can calculate whether the gas-side pressure of the accumulator 3 is still within the safe range to remind the maintenance personnel to perform the operations of refilling or discharging gas to avoid hitting the top or bottom during the operation of the accumulator 3.

[0042] The two chambers of the servo motor pump unit 7 are equipped with a second pressure sensor 5.2 and a third pressure sensor 5.3 to detect the pressure. The controller 13 judges whether the pressures in the two chambers are normal and controls the servo motor pump unit 7 to avoid damage to the equipment due to pump cavitation or overpressure. The two chambers of the servo motor pump unit 7 are equipped with overflow valves 8.1 and 8.2 to avoid overpressure in the two chambers.

[0043] Both chambers of the servo motor pump unit 7 are provided with an oil replenishing circuit. The pressurized oil from the constant pressure oil source 1 passes through the pressure reducing valve 10, the first one-way valve 11.1 and the second one-way valve 11.2 to pressurize both chambers of the servo motor pump unit 7. When the pressure in any chamber of the servo motor pump unit 7 is less than the pressure set by the pressure reducing valve 10, the oil enters this chamber to prevent the servo motor pump unit 7 from sucking air.

[0044] Both chambers of the servo motor pump unit 7 are provided with overflow valves to prevent overpressure, so as to protect the pump unit, hydraulic cylinder and pipeline.

[0045] Since the constant pressure oil source 1 no longer needs to directly supply oil to the lifting hydraulic cylinder 9, the requirements for equipment such as the installed power of the constant pressure oil source pump station and the volume of the fuel tank are reduced, and the energy consumption and fuel consumption are decreased.

[0046] The gravitational potential energy of the load of the present invention can be converted into hydraulic energy and electrical energy. While meeting the recovery of gravitational potential energy, it adapts to the variable gravitational potential energy of the load, reduces the designed volume of the accumulator, adopts volume speed control, has no energy loss of throttle speed control, reduces the operating energy consumption, and saves energy.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A hydraulic control system for recovering gravitational potential energy, characterized in that: It includes a servo motor pump unit. The first oil port of the servo motor pump unit is connected to the rodless cavity of the lifting hydraulic cylinder through a first oil circuit, and the second oil port of the servo motor pump unit is connected to the rod cavity of the lifting hydraulic cylinder through a second oil circuit. Overflow valves are connected to both the first oil circuit and the second oil circuit. A energy storage branch is also provided on the pipeline between the servo motor pump unit and the overflow valve in the first oil circuit. The energy storage branch includes an accumulator and a first two-position two-way directional control valve. The oil side of the accumulator is connected to the first two-position two-way directional control valve, and the first two-position two-way directional control valve is connected to the first branch. The oil side of the accumulator is connected to a constant pressure oil source through a three-position three-way directional control valve, and the middle position of the three-position three-way directional control valve is in a cut-off state. The constant pressure oil source is connected to the first oil circuit and the second oil circuit. A pressure reducing valve and a check valve are provided on the pipeline connecting the constant pressure oil source to the first oil circuit and the second oil circuit to prevent the servo motor pump unit from sucking air. The accumulator is connected with a first displacement sensor to monitor the piston position in real time, and the lifting hydraulic cylinder is connected with a second displacement sensor to detect the piston position in real time. The first displacement sensor, the second displacement sensor, the servo motor pump unit, the first two-position two-way directional control valve, the three-position three-way directional control valve, and the second two-position two-way directional control valve are all connected to the controller, so that when the piston of the lifting hydraulic cylinder is at the high position, the piston of the accumulator drops to the low position, and when the piston of the lifting hydraulic cylinder is at the low position, the piston of the accumulator rises to the high position.

2. The gravity potential energy recovery hydraulic control system according to claim 1, wherein: When the oil suction port pressure of the servo motor pump unit is greater than the oil discharge port pressure, the servo motor pump unit is in a power generation state.

3. The gravity potential energy recovery hydraulic control system according to claim 1, wherein: The oil side of the accumulator is connected to a valve control circuit through a second two-position two-way directional control valve to replace the oil in the accumulator.

4. The gravity potential energy recovery hydraulic control system according to claim 3, wherein: The valve control circuit is a double-rod hydraulic cylinder circuit for horizontal expansion and contraction controlled by a three-position four-way directional control valve.

5. The hydraulic control system for recovering gravitational potential energy according to claim 1, wherein: The oil side of the accumulator is connected with a first pressure sensor connected to the controller to monitor the oil side pressure. The controller calculates the current gas side pressure of the accumulator through the piston position of the accumulator, the current oil side pressure, the gas side pre-charge pressure, the gas side volume, and the ambient temperature, so as to judge whether the current gas side pressure is within the safe range and whether the gas side needs to be charged or discharged.

6. The hydraulic control system for recovering gravitational potential energy according to claim 1, wherein: Exhaust pressure measuring elements are connected to the first oil circuit and the second oil circuit.

7. The hydraulic control system for recovering gravitational potential energy according to claim 1, wherein: Pressure sensors connected to the controller are provided in both the oil suction chamber and the oil discharge chamber of the servo motor pump unit to monitor the pressures of the two chambers.

8. A hydraulic control method for recovering gravitational potential energy, providing the gravitational potential energy recovery hydraulic control system as described in any one of claims 1 to 7, characterized in that: When lifting a heavy object, the piston rod of the lifting hydraulic cylinder extends, and the accumulator and the servo motor pump unit jointly supply oil. When the heavy object descends, the piston rod of the lifting hydraulic cylinder retracts. Part of the hydraulic oil is stored in the accumulator, and the other part of the hydraulic oil enters the rod cavity of the hydraulic cylinder through the servo motor pump unit. The telescopic speed of the piston rod of the lifting hydraulic cylinder is controlled by the pump-controlled volume speed regulation of the servo motor pump unit.

9. The hydraulic control method for recovering gravitational potential energy according to claim 8, characterized in that: The oil side of the accumulator is connected to a valve control circuit through a second two-position two-way directional control valve to replace the oil in the accumulator. After the lifting hydraulic cylinder stops, the solenoid valve a of the first two-position two-way directional control valve loses power to cut off the oil circuit between the lifting hydraulic cylinder and the accumulator, and the solenoid valve a of the second two-position two-way directional control valve loses power to cut off the oil circuit between the valve control circuit and the accumulator. The controller adjusts the piston position of the accumulator by controlling the three-position three-way directional control valve to meet the requirements of the next action of the lifting hydraulic cylinder.

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