Energy storage and recycling system for single-rod electric static hydraulic actuator

Abstract

The invention discloses an energy storage and reutilization system for a single-rod electric static hydraulic actuator, and relates to the technical field of hydraulic systems, the energy storage and reutilization system comprises an EHA assembly, an ESR assembly and an alternating current servo motor, the alternating current servo motor is used for synchronously driving the EHA assembly and the ESR assembly to operate, and the EHA assembly is connected with the alternating current servo motor. The ESR component can realize switching of four operation modes of storage, reutilization, discharge and flow recirculation according to the operation state of the EHA component, so that the operation efficiency of the EHA component is improved; the ESR assembly is established to store and reuse energy of the EHA system, and through four operation modes of storage, reuse, discharge and flow recirculation, evaluation shows that the designed ESR assembly can improve the efficiency of the EHA system by 20%, which proves that the ESR assembly has high feasibility in load operation of the heavy-duty hydraulic mechanical arm, and the ESR assembly can be applied to the load operation of the heavy-duty hydraulic mechanical arm. And the system is simple to implement and configure and wide in application range.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic systems, and particularly to an energy storage and reuse system for a single-rod electro-hydrostatic actuator. Background Art

[0002] Currently, there have been studies on using energy storage components such as hydraulic accumulators, batteries, supercapacitors, and flywheels to capture and reuse potentially wasted energy in excavators. Research shows that about 50%-75% of the gravitational potential energy can be captured when the boom part descends. However, it is difficult to apply similar technologies to other parts of the excavator, and the capture amount is only 10%-13% of that of the boom part, which is due to the short electric operation time of the pump and the uncertainty of the load mass (such as soil, rock, etc.). It is found that there is less research on the hybrid power of the excavator EHA system, and previous research has mostly focused on the excavator boom and has not involved the forearm (single-rod hydraulic cylinder). The pump-controlled actuator system controls the flow rate by changing the pump displacement or the prime mover speed, which can eliminate throttling losses and improve efficiency. Among them, the single-rod electro-hydrostatic actuator (EHA) system is widely used. The EHA system has the advantages of easy maintenance, light weight, simple structure, high reliability, and small heat loss compared with the valve-controlled actuator. However, due to the asymmetry of the single-rod hydraulic cylinder, it is a challenge to handle the imbalance of the pump inlet and outlet flows. Currently, the application of the EHA system in heavy machinery is in the experimental stage. Although the preliminary results show that its system efficiency is 2.5 times higher than that of the traditional valve-controlled actuator system, the efficiency still needs to be further improved. Summary of the Invention

[0003] The purpose of the present invention is to provide an energy storage and reuse system for a single-rod electro-hydrostatic actuator to solve the problems existing in the prior art as mentioned in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] An energy storage and reuse system for a single-rod electro-hydrostatic actuator includes an EHA component, an ESR component, and an AC servo motor. The AC servo motor is used to synchronously drive the EHA component and the ESR component to operate. The ESR component can switch between four operating modes of storage, reuse, discharge, and flow recirculation according to the operating state of the EHA component, thereby improving the operating efficiency of the EHA component.

[0006] Preferably, the EHA component includes a first fixed-displacement bi-directional pump-motor, a single-rod hydraulic cylinder, and a makeup oil pump. The two ports of the first fixed-displacement bi-directional pump-motor are correspondingly connected to the two ports of the single-rod hydraulic cylinder. A first safety valve and a second safety valve are connected between the two connecting pipelines of the single-rod hydraulic cylinder. A first check valve and a second check valve are also connected between the two connecting pipelines of the single-rod hydraulic cylinder. The connection ends of the first check valve and the second check valve are connected to a first oil tank through a pipeline. A safety relief valve is connected between the outlet end of the makeup oil pump and the first oil tank. The makeup oil pump provides flow through a three-position four-way directional control valve and a one-way throttle valve to compensate for the differential cylinder effect.

[0007] Preferably, the ESR component includes a second fixed-displacement bi-directional pump-motor, a floating center directional control valve, and an electro-hydraulic proportional pressure reducing valve. The two ports of the second fixed-displacement bi-directional pump-motor are connected to the two ports of the floating center directional control valve. An electro-hydraulic proportional pressure reducing valve, a reuse valve, and two hydraulic accumulators are sequentially connected to another port of the floating center directional control valve. Storage check valves are connected to both ends of the electro-hydraulic proportional pressure reducing valve. One end of the storage check valve is connected to a second oil tank through a relief valve;

[0008] A third check valve and a fourth check valve are connected to the two ports of the second fixed-displacement bi-directional pump-motor. The connection ends of the third check valve and the fourth check valve are communicated with the second oil tank through a pipeline. One end of the reuse valve is communicated with the second oil tank through a flow discharge valve. Third safety valves are connected to both ends of the flow discharge valve. Pressure sensors are installed on the ports of the hydraulic accumulator and the electro-hydraulic proportional pressure reducing valve to measure the pressure stored in the hydraulic accumulator and the pressure after pressure reduction from the electro-hydraulic proportional pressure reducing valve during the energy reuse process.

[0009] Preferably, the AC servo motor is drivingly connected to the first fixed-displacement bi-directional pump-motor through a drive belt.

[0010] Preferably, the AC servo motor is drivingly connected to the second fixed-displacement bi-directional pump-motor through a drive belt.

[0011] Preferably, the outlet pressure of the makeup oil pump is set to 5.5 kg / cm 2 .

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] The present invention stores and reuses the energy of the EHA system by establishing an ESR component, and through four operating modes of storage, reuse, discharge, and flow recirculation. After evaluation, it is shown that the designed ESR component can increase the efficiency of the EHA system by 20%, which proves that the ESR component is highly feasible in the load operation of heavy-duty hydraulic robotic arms, and the system is simple to implement and configure, and has a wide range of applications. Brief Description of the Drawings

[0014] Figure 1 This is a schematic diagram of the overall structure of the present invention: the EHA component is on the left; the ESR component is on the right.

[0015] Figure 2 This is a schematic diagram of the operation mode of the ESR component of the present invention: (a), (b) storage; (c), (d) reuse.

[0016] Figure 3 This is a schematic diagram of the operation mode of the ESR component of the present invention: (a) discharge; (b) flow recirculation.

[0017] Figure 4 This is a schematic diagram of the energy storage mode of the present invention: (a) the second quadrant; (b) the fourth quadrant.

[0018] Figure 5 This is a schematic diagram of the energy reuse mode of the present invention: (a) the first quadrant; (b) the third quadrant.

[0019] Figure 6 This is the efficiency diagram of the existing EHA system.

[0020] Figure 7 This is the efficiency of the EHA system of the present invention during energy reuse.

[0021] Figure 8 This is the specification table of each component of the system in the embodiment of the present invention.

[0022] In the figure: 1, AC servo motor; 2, first fixed-displacement bi-directional pump-motor; 3, single-rod hydraulic cylinder; 4, piston and piston rod; 5, first oil tank; 6, make-up oil pump; 7, first safety valve; 8, second safety valve; 9, first check valve; 10, second check valve; 11, safety relief valve; 12, second fixed-displacement bi-directional pump-motor; 13, flow discharge valve; 14, second oil tank; 15, electro-hydraulic proportional pressure reducing valve; 16, hydraulic accumulator; 17, storage check valve; 18, three-way check valve; 19, fourth check valve; 20, third safety valve; 21, relief valve; 22, pressure sensor; V1, three-position four-way directional control valve; V2, one-way throttle valve; V3, floating center directional control valve; V4, reuse valve. Detailed Description of the Invention

[0023] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0024] Please refer to Figure 1-7 , the present invention provides the following technical solutions:

[0025] A single-rod electric hydrostatic actuator energy storage and recycling system includes an EHA component, an ESR component and an AC servo motor 1, wherein the AC servo motor 1 is used to synchronously drive the EHA component and the ESR component to operate, and the AC servo motor 1 is connected to a first fixed-displacement bidirectional pump-motor 2 and a second fixed-displacement bidirectional pump-motor 12 through a transmission belt; the ESR component can switch between four operating modes of storage, recycling, discharge and flow recirculation according to the operating status of the EHA component, thereby improving the operating efficiency of the EHA component.

[0026] The EHA component includes a first fixed-displacement bidirectional pump-motor 2, a single-rod hydraulic cylinder 3 and an oil replenishment pump 6. The two ports of the first fixed-displacement bidirectional pump-motor 2 are correspondingly connected to the two ports of the single-rod hydraulic cylinder 3. A first safety valve 7 and a second safety valve 8 are connected between the two connecting pipelines of the single-rod hydraulic cylinder 3. A first check valve 9 and a second check valve 10 are also connected between the two connecting pipelines of the single-rod hydraulic cylinder 3. The connecting ends of the first check valve 9 and the second check valve 10 are connected to the first oil tank 5 through pipelines. A safety overflow valve 11 is connected between the oil outlet end of the oil replenishment pump 6 and the first oil tank 5. The oil replenishment pump 6 provides flow through a three-position four-way reversing valve V1 and a one-way throttle valve V2 to compensate for the differential cylinder effect.

[0027] The ESR component includes a second fixed-flow bidirectional pump-motor 12, a floating center reversing valve V3 and an electric proportional pressure reducing valve 15, wherein two ports of the second fixed-flow bidirectional pump-motor 12 are connected to two ports of the floating center reversing valve V3, and the other port of the floating center reversing valve V3 is connected in sequence to the electric proportional pressure reducing valve 15, a recycling valve V4 and two hydraulic accumulators 16, and both ends of the electric proportional pressure reducing valve 15 are connected to a storage check valve 17, and one end of the storage check valve 17 is connected to the second oil tank 14 through a relief valve 21;

[0028] The two ports of the second fixed-displacement bidirectional pump-motor 12 are connected to a third one-way valve 18 and a fourth one-way valve 19. The connecting ends of the third one-way valve 18 and the fourth one-way valve 19 are connected to the second oil tank 14 through pipelines. One end of the recycling valve V4 is connected to the second oil tank 14 through a flow discharge valve 13. Both ends of the flow discharge valve 13 are connected to a third safety valve 20. Pressure sensors 22 are installed on the ports of the hydraulic accumulator 16 and the ports of the electric proportional pressure reducing valve 15, which are used to measure the pressure stored in the hydraulic accumulator 16 and the pressure after pressure reduction from the electric proportional pressure reducing valve 15 during the energy recycling process.

[0029] The working process of the present invention is as follows:

[0030] Hydraulic cylinder speed It is calculated using a 100-point regression algorithm based on the encoder readings. The outlet pressure of the makeup oil pump 6 is set to 5.5 kg / cm by the safety relief valve 11 2 .

[0031] To define the quadrants, a sign convention for the hydraulic cylinder force F (F = P A A a -P B A b ) and the hydraulic cylinder speed is established. The hydraulic cylinder speed is positive when the hydraulic cylinder extends and negative when it retracts. Similarly, the hydraulic cylinder force F is positive when it extends and vice versa. Based on the signs of the hydraulic cylinder speed and the hydraulic cylinder force F, four quadrants are defined, namely I, II, III, and IV. Quadrant I is defined as F > 0 and Quadrant III is defined as F < 0 and These are the pumping quadrants where energy flows from the circuit to the load. On the other hand, the electric quadrants (II and IV) are the quadrants where energy flows from the load to the circuit. Quadrant II is defined as F < 0 and while quadrant IV is defined as F > 0 and

[0032] During quadrants I and III, the pump consumes energy from the prime mover to extend and retract the hydraulic cylinder. In quadrants II and IV, the load assists the movement of the hydraulic cylinder. Therefore, the energy from the load drives the pump, and at this time the pump operates as a motor. Additionally, the load pressure P L can also be used to define the quadrants because it is proportional to the hydraulic cylinder force F (F = P L A a ).

[0033] There are four operating modes, namely storage, reuse, discharge, and flow recirculation, which can be seen from Figure 2 and Figure 3 . The storage and reuse modes are both operated by the floating center directional valve V3 and the reuse valve V4. In terms of discharging the hydraulic accumulator 16, a built-in check valve ensures that the oil can only flow in one direction when storing energy in the hydraulic accumulator 16. When the reuse valve V4 is opened, the oil can flow bidirectionally, and by opening either side of the floating center directional valve V3, the hydraulic accumulator 16 can discharge oil to the second fixed-displacement bi-directional pump-motor 12. The function of the floating center directional valve V3 is similar to that of an ordinary three-position directional valve, but the oil ports in the neutral position of the floating center directional valve V3 are set to provide flow recirculation in the neutral position.

[0034] The two storage operation modes are carried out when the reuse valve V4 is in the right position, so that the fluid from the hydraulic accumulator 16 remains closed. The floating center reversing valve V3 is set in the left position or the right position according to the rotation direction of the second fixed-displacement bi-directional pump-motor 12. The fluid flowing out of the floating center reversing valve V3 flows through the storage check valve 17, bypasses the electro-hydraulic proportional pressure reducing valve 15, and then reaches the reuse valve V4; subsequently, the fluid is guided to the hydraulic accumulator 16, as Figure 2 (a) and (b) show.

[0035] The reuse operation mode is as shown in Figure 2 (c) and (d). When the hydraulic accumulator 16 is full and the main pump requires auxiliary power, the reuse mode is started. During the reuse mode, the reuse valve V4 is moved to the left position, so that the fluid from the hydraulic accumulator 16 drives the second fixed-displacement bi-directional pump-motor 12. Then, the fluid passes through the electro-hydraulic proportional pressure reducing valve 15, so that a constant reduced pressure is applied to the inlet of the second fixed-displacement bi-directional pump-motor 12. According to the rotation direction of the AC servo motor 1, the floating center reversing valve V3 is operated to make the second fixed-displacement bi-directional pump-motor 12 assist the AC servo motor 1.

[0036] The discharge and flow recirculation operation modes are as shown in Figure 3 . During the discharge operation mode, the main valve in the ESR component circuit is set to its initial (rest) position. Then the flow discharge valve 13 is opened to connect the hydraulic accumulator 16 with the second oil tank 14 to release the pressure in the ESR component circuit; in the idle flow circulation mode ( Figure 3 (b)), the flow discharge valve 13 is closed, while the floating center reversing valve V3 and the reuse valve V4 remain in the rest position. Regarding these two operation modes, the discharge mode is used when it is necessary to cut off the power supply of the ESR component, while the idle mode only separates the EHA from the ESR circuit. In the latter case, the accumulator remains charged.

[0037] The electric operation of the first fixed-displacement bi-directional pump-motor 2 is used to store the gravitational potential energy into the hydraulic accumulator 16, which is as shown in Figure 4 (a) and (b). When the cylinder auxiliary force drives the first fixed-displacement bi-directional pump-motor 2 in the counterclockwise direction (the second quadrant), the ESR circuit charges the hydraulic accumulator 16 through the second fixed-displacement bi-directional pump-motor 12. In the ESR circuit, the floating center reversing valve V3 is displaced from its initial middle position to the left position, and the reuse valve remains in the same position, which connects the second fixed-displacement bi-directional pump-motor 12 with the hydraulic accumulator 16.

[0038] During the fourth quadrant, the cylinder auxiliary force drives the first fixed-displacement bi-directional pump-motor 2 in a clockwise direction. In this case, in order to store energy, the floating center reversing valve V3 is moved to the right position and then held in the same position by valve V4, which enables the second fixed-displacement bi-directional pump-motor 12 to charge the hydraulic accumulator 16 through the storage check valve 17. The amount of stored energy depends on the pressure setting of the third safety valve 20.

[0039] As Figure 5 shown, during the energy reuse process, the auxiliary power stored in the hydraulic accumulator 16 is used to assist the AC servo motor 1 in operating the actuator.

[0040] During the operation in the first quadrant (cylinder extending), the valves in the ESR circuit are adjusted so that the second fixed-displacement bi-directional pump-motor 12 is continuously in the electric state. Before starting this process, the flow discharge valve 13 is closed, and the reuse valve V4 is moved to the left position, allowing the fluid from the hydraulic accumulator 16 to flow to the electro-hydraulic proportional reducing valve 15 to generate a controllable pressure output. Then, the floating center reversing valve V3 is moved to the right position, and the regulated pressurized fluid from the electro-hydraulic proportional reducing valve 15 causes the second fixed-displacement bi-directional pump-motor 12 to rotate counterclockwise, as shown in Figure 5 (a). Figure 5 (b) shows the operation in the third quadrant (cylinder retracting). Contrary to the extending process, the floating center reversing valve is moved to the left position, prompting the second fixed-displacement bi-directional pump-motor 12 to rotate clockwise to reuse the stored energy.

[0041] By Figure 6 and Figure 7 evaluation, it is shown that the designed ESR system can increase the efficiency of the EHA system by 20%, which proves the high feasibility of the ESR system in the load operation of heavy-duty hydraulic robotic arms. In addition, due to its easy implementation and simple configuration, it can also be used in other application scenarios of energy storage and reuse.

[0042] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A single-rod electro-hydrostatic actuator energy storage and reuse system, characterized in that The invention comprises an EHA component, an ESR component and an AC servo motor (1), wherein the AC servo motor (1) is used to synchronously drive the EHA component and the ESR component to operate, and the ESR component can switch between four operating modes of storage, reuse, discharge and flow recirculation according to the operating state of the EHA component, thereby improving the operating efficiency of the EHA component.

2. The energy storage and reuse system of the single-rod electro-hydrostatic actuator according to claim 1, wherein: The EHA assembly comprises a first fixed-displacement bidirectional pump-motor (2), a single-rod hydraulic cylinder (3) and an oil replenishment pump (6); two ports of the first fixed-displacement bidirectional pump-motor (2) are correspondingly connected to two ports of the single-rod hydraulic cylinder (3); a first safety valve (7) and a second safety valve (8) are connected between two connecting pipelines of the single-rod hydraulic cylinder (3); a first check valve (9) and a second check valve (10) are also connected between the two connecting pipelines of the single-rod hydraulic cylinder (3); the connecting ends of the first check valve (9) and the second check valve (10) are connected to a first oil tank (5) through a pipeline; a safety overflow valve (11) is connected between the oil outlet end of the oil replenishment pump (6) and the first oil tank (5); the oil replenishment pump (6) provides flow through a three-position four-way reversing valve (V1) and a one-way throttle valve (V2) to compensate for the differential cylinder effect.

3. The single-rod electro-hydrostatic actuator energy storage and reuse system according to claim 1, characterized in that: The ESR component comprises a second fixed-displacement bidirectional pump-motor (12), a floating center reversing valve (V3) and an electric proportional pressure reducing valve (15); two ports of the second fixed-displacement bidirectional pump-motor (12) are connected to two ports of the floating center reversing valve (V3); the other port of the floating center reversing valve (V3) is connected in sequence to the electric proportional pressure reducing valve (15), a recycling valve (V4) and two hydraulic accumulators (16); two ends of the electric proportional pressure reducing valve (15) are connected to a storage check valve (17); one end of the storage check valve (17) is connected to the second oil tank (14) via a relief valve (21); The two ports of the second fixed-displacement bidirectional pump-motor (12) are connected to a third one-way valve (18) and a fourth one-way valve (19); the connecting ends of the third one-way valve (18) and the fourth one-way valve (19) are connected to the second oil tank (14) through pipelines; one end of the recycling valve (V4) is connected to the second oil tank (14) through a flow discharge valve (13); the two ends of the flow discharge valve (13) are connected to a third safety valve (20); and pressure sensors (22) are installed on the ports of the hydraulic accumulator (16) and the electric proportional pressure reducing valve (15) for measuring the pressure stored in the hydraulic accumulator (16) and the pressure after the pressure reduction from the electric proportional pressure reducing valve (15) during the energy recycling process.

4. The single-rod electro-hydrostatic actuator energy storage and reuse system according to claim 2, characterized in that: The AC servo motor (1) is drivingly connected to the first quantitative bidirectional pump-motor (2) via a transmission belt.

5. The single-rod electro-hydrostatic actuator energy storage and reuse system according to claim 3, characterized in that: The AC servo motor (1) is drivingly connected to the second quantitative bidirectional pump-motor (12) via a transmission belt.

6. The energy storage and reuse system of the single-rod electro-hydrostatic actuator according to claim 2, characterized in that: The outlet pressure of the supplementary oil pump (6) is set to 5.5 kg / cm by the safety overflow valve (11). 2 .

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