An electro-hydraulic cylinder hydraulic system with potential energy recovery

Abstract

This invention relates to the field of hydraulic transmission and control technology, and discloses an electro-hydraulic cylinder hydraulic system with potential energy recovery. The system includes a servo motor, a bidirectional piston pump motor, a single-rod electro-hydraulic cylinder, a dynamic energy routing valve group, a high-pressure hydraulic energy storage unit, and an ejector anti-cavitation network. The bidirectional piston pump motor and the single-rod electro-hydraulic cylinder are connected to form a pure volumetric speed regulation closed-loop circuit. Under load reduction conditions, the fluid discharged from the rodless chamber enters the dynamic energy routing valve group and is divided into two paths: the first path flows into the rod chamber; the second path draws fluid from the atmospheric pressure replenishment tank via a fluid ejector, mixing to form a pressurized mixed fluid. Part of this mixed fluid is injected into the high-pressure hydraulic energy storage unit for physical energy storage, while the other part is guided to the bidirectional piston pump motor via a bypass pressure stabilizing circuit to provide suction pressure. This invention utilizes the volume difference fluid generated by the area difference between the two chambers as a self-excitation power source, combined with a momentum exchange mechanism to simultaneously complete hydraulic potential energy recovery and anti-cavitation compensation actions, reducing the system's power consumption.

Description

Technical Field

[0001] This invention relates to the field of hydraulic transmission and control technology, specifically to an electro-hydraulic cylinder hydraulic system with potential energy recovery. Background Technology

[0002] In the field of engineering machinery and heavy industrial equipment manufacturing, electro-hydraulic servo systems often use servo motors to drive bidirectional piston pump motors to directly control the movement of actuators. Single-rod electro-hydraulic cylinders, due to their long stroke and high load-bearing capacity, have become the main actuators. The system usually uses them to form a closed-loop volumetric speed regulation circuit with the bidirectional piston pump motor, relying entirely on the pump's volumetric displacement and speed regulation to control the speed of the hydraulic cylinder, thus avoiding the inherent energy loss of traditional valve control systems.

[0003] However, the inherent difference in effective working area between the rodless and rod chambers within a single-rod electro-hydraulic cylinder leads to asymmetrical fluid flow during operation of the closed-loop circuit. When the system is under load reduction or piston retraction conditions, the large flow rate of fluid discharged from the rodless chamber cannot match the smaller flow rate required by the rod chamber, resulting in a significant volumetric fluid difference within the closed loop. To eliminate this physical volumetric difference, conventional technical approaches involve forcibly intervening with an overflow valve assembly for unloading or configuring an independent external oil replenishment pump assembly for forced flow intervention. The external oil replenishment pump source requires continuous consumption of a large amount of electrical energy to maintain operation, while the intervention of the throttle valve disrupts the physical topology of the pure volumetric speed regulation circuit, causing the fluid to generate severe heat at the throttling point. This forces the gravitational potential energy carried during load reduction to be converted into heat energy and completely dissipated. The above operating architecture leads to a dual degradation of the overall system energy efficiency and the lifespan of core components. When the asymmetrical fluid is converted within the closed-loop circuit, the fluid deficiency area will cause severe cavitation and cavitation phenomena on the suction side of the bidirectional plunger pump motor, directly eroding the precision metal structure inside the pump body. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an electro-hydraulic cylinder hydraulic system with potential energy recovery, which solves the problems of cavitation on the suction side of the bidirectional plunger pump motor caused by the volume difference fluid due to the difference in the area of ​​the two chambers in the closed-loop system of a single-rod electro-hydraulic cylinder, as well as the energy dissipation caused by the inability to self-excite and recover the potential energy of the load gravity.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an electro-hydraulic cylinder hydraulic system with potential energy recovery, comprising a servo motor, a bidirectional piston pump motor drivenly connected to the servo motor, and a single-rod electro-hydraulic cylinder including a rodless chamber and a rod chamber. The effective working area of ​​the rodless chamber is larger than the effective working area of ​​the rod chamber. The system also includes a dynamic energy routing valve group, a high-pressure hydraulic energy storage unit, and an ejector anti-cavitation network.

[0006] The two working ports of the bidirectional plunger pump motor are respectively connected to the rodless chamber and the rod chamber to form a closed-loop circuit. The closed-loop circuit is a pure volumetric speed regulation circuit without throttling elements. The system controls the operating speed of the single-rod electro-hydraulic cylinder by adjusting the volumetric displacement of the bidirectional plunger pump motor. The dynamic energy routing valve group has an inlet connected to the rodless chamber, a first branch port connected to the working port of the bidirectional plunger pump motor connected to the rod chamber, and a second branch port. The ejector anti-cavitation network includes an atmospheric pressure replenishment tank and a fluid ejector. The high-pressure main inlet of the fluid ejector is connected to the second branch port, the negative pressure suction inlet is connected to the atmospheric pressure replenishment tank, and the diffuser mixing port is connected to the high-pressure hydraulic energy storage unit, and is connected to the working port of the bidirectional plunger pump motor connected to the rod chamber via a bypass pressure stabilizing circuit.

[0007] The core innovation of this invention lies in utilizing the inherent difference in the effective working area of ​​the two chambers of a single-rod electro-hydraulic cylinder to obtain the volume difference fluid as the self-excitation power source of the system, and combining the fluid momentum exchange mechanism to achieve the synchronous operation of anti-cavitation and hydraulic potential energy recovery.

[0008] Under load reduction conditions, the fluid discharged from the rodless chamber enters the dynamic energy routing valve assembly and is divided into two paths. The effective working area of ​​the rodless chamber is set to... The effective working area of ​​the rod cavity is The piston retraction speed of the single-rod electro-hydraulic cylinder is... The first stream of fluid drives the bidirectional piston pump motor in hydraulic mode via the first branch port and flows into the rod chamber. Its flow rate is equal to the fluid flow rate required for the rod chamber to expand due to piston retraction, denoted as [missing information]. The total flow rate of the fluid discharged from the rodless cavity is denoted as . The physical conversion relationships of the above parameters satisfy: ; ; Since the effective working area of ​​the rodless cavity is larger than that of the rod cavity, the total flow rate of the fluid discharged from the rodless cavity is... The fluid flow rate is always greater than that required for the expansion of the rod cavity. The second flow path, representing the flow difference between the two chamber volumes, is denoted as [flow rate]. The mathematical model for the difference between the total flow rate of the fluid discharged from the rodless cavity and the flow rate of the first fluid path is as follows: ; The second fluid, acting as a volumetric differential fluid, enters the fluid ejector through the high-pressure main inlet, drawing in the replenishing fluid from the atmospheric pressure replenishing tank and mixing to form a pressurized mixed fluid. The pressurized mixed fluid flows out from the diffuser mixing port. A first portion of the mixed fluid passes through a one-way filling valve on the filling oil line, filling the high-pressure hydraulic energy storage unit to recover potential energy; the second portion of the mixed fluid is guided through the bypass pressure stabilizing circuit to the bidirectional plunger pump motor to provide suction pressure.

[0009] For the control and switching logic of the fluid pipeline, the dynamic energy routing valve group contains a routing matrix composed of logic valves and check valves. The fluid pressure within the rodless chamber is set to... The fluid pressure inside the rod cavity is The fluid pressure difference between the two chambers is denoted as The internal physical state of the system always satisfies: ; The routing matrix represents the fluid pressure difference between the rodless cavity and the rod cavity. As a switching drive source, it enables the separation and guidance of the first fluid path and the second fluid path.

[0010] Under load lifting conditions, the controller configured in the system drives the servo motor to operate the bidirectional piston pump motor in hydraulic pump mode, pumping pressurized oil into the rodless chamber. At this time, the release channel inside the dynamic energy routing valve group opens, and the pressurized oil stored in the high-pressure hydraulic energy storage unit flows out through the release channel. The pressurized oil flowing out of the high-pressure hydraulic energy storage unit through the release channel physically merges with the return fluid drawn from the rod chamber by the bidirectional piston pump motor, together forming the total input fluid injected into the rodless chamber, filling the volumetric flow gap and constructing a complete hydraulic potential energy closed-loop reuse path.

[0011] Under steady-state pressure maintenance, the system's multi-channel pressure sensors detect pressure at multiple points in the closed-loop circuit and feed it back to the controller. The dynamic energy routing valve group cuts off the flow path of the high-pressure hydraulic energy storage unit. When the controller detects a pressure drop in the closed-loop circuit through the multi-channel pressure sensors, the controller sends a power generation signal to control the servo motor to output static holding torque, driving the bidirectional piston pump motor to output directional compensation fluid to the closed-loop circuit. This blocks the fluid pressure attenuation caused by leakage from the hydraulic component's volumetric gap, thus maintaining the position of the single-rod electro-hydraulic cylinder.

[0012] This invention provides an electro-hydraulic cylinder hydraulic system with potential energy recovery. It has the following beneficial effects: 1. In this invention, the system utilizes the effective working area difference between the two chambers of a single-rod electro-hydraulic cylinder to obtain the volume difference fluid. The volume difference fluid is introduced into the fluid ejector to draw the fluid from the atmospheric pressure replenishment tank. The resulting mixed fluid is injected into the suction side of the bidirectional plunger pump motor through the bypass pressure stabilizing circuit to fill the flow gap in the closed loop and eliminate the cavitation induction conditions on the pump suction side.

[0013] 2. In this invention, the fluid discharged from the rodless cavity is divided into two streams by a dynamic energy routing valve. The second stream of fluid undergoes momentum exchange in the fluid ejector to generate a pressurized mixed fluid. The pressurized mixed fluid is then charged into the high-pressure hydraulic energy storage unit. The system uses the volume difference fluid as a power source to simultaneously complete the hydraulic potential energy conversion and recovery without any additional mechanical power input device.

[0014] 3. In this invention, the first fluid directly drives the bidirectional plunger pump motor to flow into the rod chamber. The closed-loop circuit eliminates the throttling element to avoid flow throttling and heat generation. The fluid energy recovered by the high-pressure hydraulic energy storage unit is released and injected into the rodless chamber when the operating conditions change. The fluid reuse mechanism replaces part of the mechanical work output by the servo motor, reducing the power consumption of the pressure reduction system during the entire machine's operating cycle. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall hydraulic principle of the electro-hydraulic cylinder hydraulic system with potential energy recovery according to the present invention. Figure 2 This is a schematic diagram of the internal oil circuit of the dynamic energy routing valve assembly of the present invention; Figure 3 This is a schematic diagram of the internal structure of the fluid ejector of the present invention; Figure 4 This is a schematic diagram of the fluid flow direction and flow distribution under load reduction conditions according to the present invention; Figure 5 This is a schematic diagram illustrating the coupling of fluid direction and flow rate under load lifting conditions according to the present invention; Figure 6 This is a schematic diagram of the electro-hydraulic combined control logic under steady-state pressure-holding conditions according to the present invention. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see the appendix Figure 1 To be continued Figure 6This invention provides an electro-hydraulic cylinder hydraulic system with potential energy recovery. The system utilizes the volume difference fluid generated by the asymmetric cylinder during its movement as a self-excitation power source, and combines the fluid momentum exchange mechanism to achieve simultaneous operation of anti-cavitation and hydraulic potential energy recovery.

[0018] This electro-hydraulic cylinder hydraulic system with potential energy recovery includes a servo motor, a bidirectional plunger pump motor, and a single-rod electro-hydraulic cylinder. The power output shaft of the servo motor and the input shaft of the bidirectional plunger pump motor form a physical transmission connection. The single-rod electro-hydraulic cylinder is equipped with a piston assembly, which tightly seals the internal space of the single-rod electro-hydraulic cylinder into two independent regions: a rodless chamber and a rod chamber. Due to the structural characteristics of the single-rod electro-hydraulic cylinder, the piston rod only occupies the internal space on the rod chamber side, resulting in a physical difference in the actual working area of ​​the fluid in the two chambers.

[0019] The effective working area of ​​the rodless cavity is set as follows: The effective working area of ​​the rod cavity is The internal area properties of a single-rod electro-hydraulic cylinder always satisfy the following absolute inequality:

[0020] When the system undergoes displacement motion, the bidirectional piston pump motor exchanges fluid with the actuator through two independent internal working ports; one working port connects to the rodless chamber, and the other working port connects to the rod chamber. The system is configured as a pure volumetric speed regulation circuit without throttling elements, excluding damping orifices or throttling valves in the oil circuit; when the servo motor drives the bidirectional piston pump motor to rotate, the system relies entirely on the volumetric displacement adjustment of the bidirectional piston pump motor to achieve quantitative control of the operating speed of the single-rod electro-hydraulic cylinder.

[0021] Peripheral to this basic closed-loop architecture, the system also includes a dynamic energy routing valve assembly, a high-pressure hydraulic energy storage unit, and an ejector anti-cavitation network. The dynamic energy routing valve assembly, as the core component for fluid diversion and node switching, has an inlet, a first branch port, and a second branch port on its exterior. The inlet of the dynamic energy routing valve assembly is directly connected to the fluid interaction end of the rodless chamber; the first branch port connects to the working port of the bidirectional plunger pump motor, which connects to the rod chamber; and the second branch port leads to the inlet of the ejector anti-cavitation network.

[0022] The ejector anti-cavitation network consists of an atmospheric pressure replenishment tank and a fluid ejector. The fluid ejector body contains three fluid interaction interfaces: a high-pressure mains inlet, a negative pressure suction inlet, and a diffuser mixing inlet. The high-pressure mains inlet of the fluid ejector is connected to the second branch port of the dynamic energy routing valve group, and the negative pressure suction inlet is connected to the liquid level below the atmospheric pressure replenishment tank via a hydraulic pipeline. The diffuser mixing inlet of the fluid ejector is equipped with two fluid branching branches. The first branch is connected to the high-pressure hydraulic energy storage unit, and the second branch is connected to the working oil port of the bidirectional plunger pump motor connected to the rod chamber via a bypass pressure stabilizing circuit. Thus, the anti-cavitation replenishment flow path and the high-pressure energy storage flow path are physically connected.

[0023] In this embodiment, the dynamic energy routing valve assembly contains a routing matrix composed of interconnected logic valves and check valves. The logic valves, acting as the main control switching elements, are arranged on the main passage, while the check valves are connected in series at the first branch port to block backflow. The dynamic energy routing valve assembly is internally configured with a first pilot oil circuit and a second pilot oil circuit. The first pilot oil circuit connects the rodless chamber to the positive control terminal of the logic valve, and the second pilot oil circuit connects the rod chamber to the negative control terminal of the logic valve. The system uses these pilot oil circuits to directly introduce the fluid pressure difference between the rodless and rod chambers into the control terminal of the routing matrix, using it as the driving source for internal flow path switching.

[0024] Set the fluid pressure inside the rodless cavity as The fluid pressure inside the rod cavity is The fluid pressure difference between the two chambers is denoted as The internal physical state of the system always satisfies:

[0025] When the system generates a fluid pressure difference Furthermore, when the pressure difference reaches the opening threshold set by the logic valve, the fluid pressure transmitted through the first pilot oil circuit... The fluid pressure is greater than that transmitted through the second pilot oil circuit. The sum of the spring preload and the fluid pressure difference It directly overcomes the spring resistance inside the logic valve and pushes the valve core to generate displacement, thereby opening the internal fluid channel; the fluid discharged from the rodless chamber flows into the dynamic energy routing valve group through the inlet, and the routing matrix divides the fluid into the first fluid and the second fluid by relying on the open fluid channel, realizing the separation and guidance of the two fluids. The first fluid is guided to the first branch port, and the second fluid is guided to the second branch port.

[0026] In this invention, the fluid ejector serves as the physical field for momentum exchange, and its interior contains a flow channel with a continuously varying cross-sectional area. The high-pressure main inlet narrows at its end to form a nozzle structure, while the diffuser mixing port expands at its front end to form a diffuser structure. The negative-pressure suction port is located in the throat region between the nozzle and diffuser structures. The second stream of fluid enters the fluid ejector through the high-pressure main inlet; as it flows through the nozzle structure, the cross-sectional area decreases sharply, causing a significant increase in fluid velocity.

[0027] According to Bernoulli's equation in fluid mechanics, in the throat region of a fluid ejector, the relationship between fluid pressure and fluid velocity satisfies the following equation: ; In the formula, The density of the hydraulic fluid. This represents the initial pressure at the inlet of the second fluid stream entering the high-pressure mains. This represents the initial flow velocity of the fluid at that location; This represents the internal pressure of the fluid as it travels through the throat region. This represents the flow velocity after the fluid in the throat region increases. Due to the flow velocity... Much greater than the initial flow velocity This leads to increased internal pressure. A precipitous drop is generated, creating a negative pressure state. The negative pressure state in the throat region causes the replenishing fluid in the normal pressure replenishing tank to rush in through the negative pressure suction port, where it exchanges momentum and mixes with the second fluid inside the fluid ejector. Subsequently, it flows through the diffuser structure, causing its flow velocity to decrease and its pressure to rise, ultimately forming a pressurized mixed fluid at the diffuser mixing port.

[0028] After flowing out of the diffuser mixing port, the pressurized mixed fluid splits into a first part and a second part. The first part is guided to the high-pressure hydraulic energy storage unit. A one-way filling valve is installed on the filling oil line of the high-pressure hydraulic energy storage unit. The first part of the mixed fluid, relying on its own fluid pressure, forces open the valve core inside the one-way filling valve and flows into the high-pressure hydraulic energy storage unit for physical energy storage. The one-way filling valve prevents the high-pressure fluid inside the high-pressure hydraulic energy storage unit from flowing back towards the diffuser mixing port.

[0029] The second part of the mixed fluid enters the bypass pressure regulating circuit, which is internally connected to a constant pressure reducing valve. This constant pressure reducing valve limits the pressure of the second part of the mixed fluid by throttling and reducing the pressure using its internal pressure reducing valve core, thus limiting the fluid pressure to the safe threshold that the suction side of the bidirectional plunger pump motor can withstand. After pressure limitation, the second part of the mixed fluid is guided through the bypass pressure regulating circuit to the working port connected to the rod chamber of the bidirectional plunger pump motor. This second part of the mixed fluid acts as a compensation source injected into the suction side of the bidirectional plunger pump motor, eliminating the physical conditions that induce cavitation and forming a closed-loop fluid compensation system for the entire machine.

[0030] In this embodiment, the piston of the single-rod electro-hydraulic cylinder retracts under the load, forcing the fluid in the rodless chamber to be discharged and enter the dynamic energy routing valve assembly. The dynamic energy routing valve assembly uses an internal routing matrix to divide the inflowing fluid into a first fluid path and a second fluid path. The first fluid path is guided to the bidirectional plunger pump motor through the first branch port. The fluid pressure acts on the inside of the bidirectional plunger pump motor to do work, driving the bidirectional plunger pump motor to operate in hydraulic motor mode. This operating state causes the servo motor to enter the power generation mode. After passing through the bidirectional plunger pump motor, the first fluid path flows into the rod chamber to fill the cavity expansion volume caused by the piston retraction.

[0031] In this invention, to clarify the quantitative relationship between the first and second fluid streams, the displacement velocity of the piston retraction is introduced as a parameter. The operating speed of the piston retraction in the single-rod electro-hydraulic cylinder is set as follows: The total flow rate of fluid discharged from the rodless chamber is denoted as . The fluid flow rate required for the rod chamber to expand due to piston retraction is denoted as . The physical conversion relationship between the two satisfies: ; ; Based on the aforementioned effective working area of ​​the two chambers of the single-rod electro-hydraulic cylinder The physical properties set by the rodless chamber result in a certain total flow rate of fluid discharged. Always greater than the fluid flow rate required for rod cavity expansion The system records the flow rate of the first fluid stream as... It is required that it equals the fluid flow rate required for the rod cavity to expand: ; Total fluid flow rate discharged from the rodless chamber Flow rate of the first fluid The difference in flow rate between the two flows constitutes the second flow path; the flow rate of the second flow path is set as... Its mathematical model is expressed as: ; The second fluid, representing the volumetric difference fluid derived from the above formula, carries the fluid energy from the rodless cavity side and enters the fluid ejector through the high-pressure mains inlet. Based on fluid dynamics, the fluid ejector draws replenishment fluid from the atmospheric pressure replenishment tank through the negative pressure suction inlet; the flow rate of this replenishment fluid is set as... The replenishing fluid and the second-path fluid converge and mix inside the fluid ejector to form a pressurized mixed fluid. The total flow rate of the pressurized mixed fluid is set to... According to the law of conservation of fluid mass, the flow rate relationship satisfies: ; After the pressurized mixed fluid flows out of the diffuser mixing port, it branches into a first part and a second part. The system guides the first part of the mixed fluid to open the one-way filling valve and fill the high-pressure hydraulic energy storage unit, completing the hydraulic potential energy recovery action. At the same time, the system guides the second part of the mixed fluid into the bypass pressure stabilizing circuit. Due to the asymmetrical flow characteristics of the single-rod electro-hydraulic cylinder, there is a fluid deficiency on the suction side of the bidirectional plunger pump motor. The second part of the mixed fluid is guided through the bypass pressure stabilizing circuit to the working port connected to the rod chamber of the bidirectional plunger pump motor, providing suction pressure. The second part of the mixed fluid is injected into the pump body suction side as a compensation source, eliminating the physical conditions that induce cavitation and forming a fluid compensation closed loop for the entire system.

[0032] In this embodiment, the electro-hydraulic cylinder hydraulic system with potential energy recovery includes a controller, the electrical output of which is connected to the control terminal of the servo motor; a backup fluid passage, i.e., a release channel, is opened inside the dynamic energy routing valve group. During load lifting, the controller sends an electrical signal command; upon receiving the command, the servo motor outputs rotational torque, driving the bidirectional piston pump motor connected in the transmission. Under this condition, the bidirectional piston pump motor operates as a hydraulic pump, establishing a fluid pressure differential and pumping pressurized oil into the rodless chamber of the single-rod electro-hydraulic cylinder, driving the piston to overcome the load's gravity and generate a lifting displacement.

[0033] During the piston lift displacement of the single-rod electro-hydraulic cylinder, the internal space of the rod chamber is compressed, generating backflow fluid. The bidirectional piston pump motor uses its internal working port to draw this backflow fluid from the rod chamber. Simultaneously, the dynamic energy routing valve assembly also has a reverse opening pilot control circuit. One end of this reverse opening pilot control circuit is connected to the high-pressure output port of the bidirectional piston pump motor, and the other end is connected to the reset control terminal of the logic matrix. The high-pressure fluid flow generated by the bidirectional piston pump motor in hydraulic pump mode serves as the hydraulic pilot control signal. This signal acts directly on the logic matrix inside the dynamic energy routing valve assembly via the reverse opening pilot control circuit. The reverse fluid pressure overcomes the spring resistance of the internal valve core and switches the flow state, causing the aforementioned release channel to switch to the open position. The pressure oil previously stored in the high-pressure hydraulic energy storage unit under load reduction conditions obtains a physical path for outward release, flowing out from the high-pressure hydraulic energy storage unit through the hydraulic pipeline and the release channel.

[0034] In this invention, to reveal the physical essence of the flow coupling process, a quantitative fluid model for the lifting operation is established. The lifting speed of the single-rod electro-hydraulic cylinder piston is set as follows: Based on the closed-loop properties of a pure volumetric speed regulation system, the flow rate of the return fluid drawn from the rod chamber by the bidirectional plunger pump motor is equal to the rate of compression change of the internal space of the rod chamber. Let the flow rate of this return fluid be... The total input fluid flow rate required to generate the spatial increment by expanding the rodless cavity is denoted as . The mathematical equations for both satisfy the following: ; ; Based on the aforementioned effective working area of ​​the two chambers of the single-rod electro-hydraulic cylinder The physical premise is that the total input fluid flow rate required for the rodless cavity is... Numerically greater than the return fluid flow rate drawn from the rod chamber by the motor of the double-acting piston pump. The system connects to the topology via pipelines, guiding the pressurized oil flowing out of the high-pressure hydraulic energy storage unit through the release channel to physically merge with the return fluid output from the bidirectional plunger pump motor; after the two fluids merge, they together form the aforementioned total input fluid and are injected into the rodless chamber.

[0035] The flow rate of the pressure oil released by the high-pressure hydraulic energy storage unit is set as follows: The fluid confluence process follows the principle of flow superposition, and its nodal flow equation is: ; By substituting the aforementioned physical parameters into the derivation, the quantitative demand relationship for the release flow of the high-pressure hydraulic energy storage unit is obtained: ; The pressure oil released by the high-pressure hydraulic energy storage unit directly fills the volumetric flow gap caused by the difference in the area of ​​the two chambers of the single-rod electro-hydraulic cylinder, forming a flow coupling between the pressure oil and the return fluid; the reuse of the energy storage oil replaces the flow requirement of an external additional pump source, and a complete hydraulic potential energy closed-loop circulation path is built within the overall system framework.

[0036] In this embodiment, the electro-hydraulic cylinder hydraulic system with potential energy recovery is configured with multiple pressure sensors at the hardware level. The measuring ends of the multiple pressure sensors are distributed at multiple fluid nodes in the closed loop, specifically including the main oil circuit monitoring point connected to the rodless chamber and the main oil circuit monitoring point connected to the rod chamber, which detects the physical quantity of fluid pressure at multiple points inside the closed loop in real time. The signal output ends of the multiple pressure sensors are connected to the controller through electrical wiring harnesses, feeding back real-time pressure data to the controller. When the system enters the steady-state pressure holding condition, the single-rod electro-hydraulic cylinder stops physical displacement to bear the static load; at this time, the internal logic control flow path of the dynamic energy routing valve group is closed, cutting off the fluid flow path between the high-pressure hydraulic energy storage unit and the closed loop, thereby blocking the internal leakage channel generated by the high-pressure fluid.

[0037] In this invention, a pressure closed-loop monitoring model is established under steady-state pressure holding conditions. The nominal pressure holding threshold of the closed-loop circuit is set internally by the controller. The real-time node pressure values ​​collected and transmitted by multiple pressure sensors are recorded as follows: The controller sets the nominal holding pressure threshold. Real-time node pressure values Perform continuous difference calculations to obtain the pressure deviation change, and set this pressure deviation change as... Its operational logic satisfies the following equation: ; When fluid leakage occurs inside the closed-loop circuit due to the volume gap of hydraulic components, the real-time node pressure value The decrease causes a change in pressure deviation. A value greater than zero is generated. At this time, the controller determines that a pressure drop event has occurred inside the closed loop through data feedback from multiple pressure sensors. After the controller detects the pressure drop event, it immediately sends a control signal command to the electrical actuator of the servo motor; after receiving the command, the servo motor outputs static holding torque and drives the bidirectional plunger pump motor to run through the mechanical transmission shaft; this operation causes the bidirectional plunger pump motor to output compensating fluid to the closed loop.

[0038] Introducing the inherent physical parameters of the bidirectional piston pump motor, its internal volumetric displacement is set as follows: Set the static holding torque of the servo motor output to... The mechanical transmission efficiency of the bidirectional plunger pump motor is set to be Based on the principle of fluid transmission torque balance, the static holding torque that the servo motor needs to output... Change in pressure deviation The following mathematical calculations are related between them: ; Set the total fluid leakage within the closed loop as The compensated fluid flow rate output by the bidirectional plunger pump motor is set to... Under the controller-dominated closed-loop control mechanism, the system is required to compensate for fluid flow rate to cover the total fluid leakage, and the flow rate substitution relationship satisfies: ; Compensating fluid is injected into the closed-loop circuit through the working port to fill the fluid loss caused by the volume gap. This physical compensation action prevents the load from dropping due to the loss of internal pressure in the single-rod electro-hydraulic cylinder, maintains a constant fluid volume between the rodless and rod chambers, and thus achieves the position holding function of the single-rod electro-hydraulic cylinder; in this state, the system completes the cross-linking and cooperation between pure electrical control commands and hydraulic volume flow compensation.

[0039] In this embodiment, the system utilizes the inherent difference in the effective working area of ​​the two chambers of the single-rod electro-hydraulic cylinder to obtain the volumetric fluid difference generated between the rodless and rod chambers. The fluid ejector uses this volumetric fluid difference as a power source for internal energy conversion, completing momentum exchange without adding an additional power input device. The negative pressure region at the throat generated by momentum exchange causes the replenishment fluid in the atmospheric pressure replenishment tank to flow into the main circulation loop. This convergence of multiple fluids directly replenishes the fluid loss on the suction side of the bidirectional plunger pump motor, physically eliminating the conditions that induce fluid cavitation and cavitation phenomena on the pump suction side, and maintaining the material conservation state of the overall fluid volume within the closed loop.

[0040] In this invention, an energy flow model is established based on the system's energy efficiency conversion mechanism; the total power of gravitational potential energy released by the load during the descent phase is set as follows: The hydraulic potential energy power captured and stored inside the high-pressure hydraulic energy storage unit is set as follows: According to the work law of fluid physics, the hydraulic potential energy power... node pressure with energy storage fluid and the charging flow rate of the first part of the mixed fluid entering the high-pressure hydraulic energy storage unit. The product of these quantities has the following corresponding equality relationship: ; Based on this, the overall energy recovery rate of the entire system is set to be... Its physical calculation and evaluation model satisfies: ; The system guides the first portion of the mixed fluid into the high-pressure hydraulic energy storage unit to accumulate pressure. The high-pressure hydraulic energy storage unit locks in this fluid energy and releases it during subsequent load lifting operations to fill the fluid flow gap required for spatial expansion on the rodless cavity side. This physical energy transfer and reuse cycle replaces the mechanical work input directly provided by external energy sources such as servo motors, significantly reducing the power consumption of the entire system during its operation cycle.

[0041] In this embodiment, the fluid interaction loop composed of the bidirectional plunger pump motor and the single-rod electro-hydraulic cylinder constitutes a pure volumetric speed regulation closed-loop topology without throttling elements. The servo motor outputs rotational torque to directly change the input speed of the bidirectional plunger pump motor, thereby achieving volumetric displacement control of the operating speed of the single-rod electro-hydraulic cylinder. The closed-loop loop eliminates the fluid throttling and heat generation phenomenon caused by the throttling valve, controlling the overall system's heat dissipation to the external environment.

[0042] Simultaneously, multiple pressure sensors perform real-time quantitative data acquisition at the fluid interaction nodes; the controller then uses the acquired pressure deviation changes as the basis for its actions. A pulse signal command is sent to the servo motor to generate static holding torque. The servo motor drives the bidirectional piston pump motor to output directional compensation fluid, blocking the fluid pressure attenuation trend caused by leakage from microscopic gaps in the hydraulic components; the system uses this control logic to build a correlation network between pure electric command feedback and fluid volume compensation, thereby achieving steady-state maintenance of the static load position.

Claims

1. A hydraulic system for an electro-hydraulic cylinder with potential energy recovery, comprising a servo motor, a bidirectional piston pump motor drivenly connected to the servo motor, and a single-rod electro-hydraulic cylinder including a rodless chamber and a rod chamber, wherein the effective working area of ​​the rodless chamber is larger than the effective working area of ​​the rod chamber, characterized in that, It also includes a dynamic energy routing valve assembly, a high-pressure hydraulic energy storage unit, and an ejector anti-cavitation network; The two working ports of the bidirectional plunger pump motor are respectively connected to the rodless chamber and the rod chamber to form a closed loop circuit; The dynamic energy routing valve assembly has an inlet connecting to the rodless chamber, a first branch port connecting the bidirectional plunger pump motor to the rod chamber, and a second branch port. The ejector anti-cavitation network includes an atmospheric pressure replenishment tank and a fluid ejector. The high-pressure main inlet of the fluid ejector is connected to the second branch port, the negative pressure suction port is connected to the atmospheric pressure replenishment tank, the diffuser mixing port is connected to the high-pressure hydraulic energy storage unit, and is connected to the working oil port of the bidirectional plunger pump motor and the rod chamber via a bypass pressure stabilizing circuit. Under load reduction conditions, the fluid discharged from the rodless chamber enters the dynamic energy routing valve group and is divided into two paths; the first path of fluid drives the bidirectional plunger pump motor to operate in hydraulic motor mode through the first branch port and flows into the rod chamber; the second path of fluid enters the fluid ejector through the high-pressure main inlet and draws the replenishing fluid from the atmospheric pressure replenishing tank, and mixes to form a pressurized mixed fluid. The pressurized mixed fluid flows out from the diffuser mixing port. The first part of the mixed fluid is charged into the high-pressure hydraulic energy storage unit to recover potential energy, and the second part of the mixed fluid is guided through the bypass pressure stabilizing circuit to the bidirectional plunger pump motor to provide oil suction pressure.

2. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 1, characterized in that, Under the load reduction condition, the flow rate of the first fluid path is equal to the fluid flow rate required for the rod chamber to expand due to piston retraction; the flow rate of the second fluid path is equal to the difference between the total fluid flow rate discharged from the rodless chamber and the flow rate of the first fluid path.

3. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 2, characterized in that, Since the effective working area of ​​the rodless cavity is greater than that of the rod cavity, the total flow rate of the fluid discharged from the rodless cavity is always greater than the flow rate of the fluid required for the expansion of the rod cavity, and the difference in flow rate between the two constitutes the second fluid path.

4. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 1, characterized in that, The system also includes a controller electrically connected to the servo motor, and the dynamic energy routing valve group is further provided with a release channel; Under load lifting conditions, the controller drives the servo motor to drive the bidirectional piston pump motor to operate in hydraulic pump mode, pumping pressurized oil into the rodless chamber; at this time, the release channel opens, and the pressurized oil stored in the high-pressure hydraulic energy storage unit flows out through the release channel.

5. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 4, characterized in that, Under the load lifting condition, the pressure oil flowing out of the high-pressure hydraulic energy storage unit through the release channel merges with the return fluid drawn from the rod chamber by the bidirectional piston pump motor, and together they form the total input fluid injected into the rodless chamber.

6. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 4, characterized in that, The system also includes multiple pressure sensors, which detect the pressure at multiple points in the closed loop and feed it back to the controller; under steady-state pressure maintenance conditions, the dynamic energy routing valve group cuts off the flow path of the high-pressure hydraulic energy storage unit.

7. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 6, characterized in that, Under the steady-state pressure-holding condition, when the controller detects a pressure drop in the closed loop through the multi-channel pressure sensor, the controller controls the servo motor to output static holding torque, driving the bidirectional plunger pump motor to output compensating fluid to the closed loop to maintain the position of the single-rod electro-hydraulic cylinder.

8. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 1, characterized in that, The dynamic energy routing valve group contains a routing matrix composed of logic valves and check valves. The routing matrix uses the fluid pressure difference between the rodless chamber and the rod chamber as a switching drive source to achieve the separation and guidance of the first fluid path and the second fluid path.

9. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 1, characterized in that, The high-pressure hydraulic energy storage unit is equipped with a one-way filling valve on the filling oil line. The first part of the mixed fluid is filled into the high-pressure hydraulic energy storage unit by opening the one-way filling valve.

10. The electro-hydraulic cylinder hydraulic system with potential energy recovery according to claim 1, characterized in that, The closed-loop circuit is a pure volumetric speed regulation circuit without throttling elements. The system controls the operating speed of the single-rod electro-hydraulic cylinder by adjusting the volumetric displacement of the bidirectional plunger pump motor.

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