A servo-pump-controlled hydraulic power unit with energy recovery and its control method

Abstract

This invention discloses a servo pump-controlled hydraulic power device with energy recovery and its control method. The device includes an electro-hydraulic bidirectional servo pump assembly, a hydraulic cylinder, an oil tank, and an accumulator. The hydraulic cylinder drives the reciprocating motion of a hydraulic press or punch press slide. An oil chamber is formed in the oil tank and connected to the upper chamber of the hydraulic cylinder through a filling valve. Preferably, this invention employs a top-mounted oil tank structure positioned above the end of the hydraulic cylinder. The suction side of the bidirectional hydraulic pump is connected to the oil chamber of the oil tank, and two working ports are respectively connected to the upper and lower chambers of the hydraulic cylinder and the accumulator branch. During the rapid downward movement of the slide due to its own weight, the pressure oil in the lower chamber drives the bidirectional hydraulic pump to fill the accumulator, achieving energy recovery. During the slide return phase, the accumulator releases high-pressure oil, which, combined with the output of the bidirectional hydraulic pump, drives the hydraulic cylinder. This, along with displacement and / or force feedback, achieves servo control, thereby reducing the power demand of the servo motor and improving system energy efficiency and structural integration.

Description

Technical Field

[0001] This invention belongs to the field of servo hydraulic pump control technology, and particularly relates to a servo pump-controlled hydraulic power device with energy recovery and its control method. Background Technology

[0002] Existing large hydraulic presses, punch presses, and other hydraulic equipment typically employ a traditional hydraulic system consisting of a motor, a variable displacement pump, and a valve assembly. The hydraulic power unit generally includes: a variable displacement pump driven by a power frequency motor, an independent oil tank, a relief valve assembly, multiple solenoid directional valves, a filling valve, and numerous external pipelines. This type of system suffers from the following problems:

[0003] 1. Numerous pipelines, joints, and leak points result in a large workload for installation and maintenance, and require a large footprint.

[0004] 2. The speed and pressure are regulated by throttling and overflow, but the energy-saving performance is poor, the system generates a lot of heat, and a large cooling capacity is required.

[0005] 3. During the rapid descent of the slider due to its own weight, the oil squeezed out of the lower chamber of the hydraulic cylinder is usually throttled or returned directly to the oil tank. The gravitational potential energy is difficult to recover and is mostly wasted as heat energy.

[0006] 4. To achieve rapid depressurization and rapid return, it is often necessary to install large-diameter solenoid directional valves, pre-depressurization valves and other components, which results in high costs, complex control circuits and long return times.

[0007] In recent years, servo pump-controlled hydraulic systems have emerged, employing servo motors to drive fixed displacement pumps. These systems achieve on-demand flow and pressure output by adjusting the servo motor's speed, offering energy savings compared to traditional throttling systems. However, existing servo pump-controlled systems still have limitations in applications such as large-tonnage hydraulic presses and punch presses.

[0008] 1. Hydraulic stations and hydraulic cylinders are mostly arranged separately, with long connecting pipelines and limited integration.

[0009] 2. During the rapid descent phase due to the slider's own weight, the potential energy utilization of the oil in the lower chamber is insufficient, and there is a lack of systematic coordination between energy recovery and servo pump control.

[0010] 3. To meet the maximum speed and pressure requirements, the rated power of the servo motor and hydraulic pump is relatively large, resulting in high system peak power and relatively high overall equipment cost and operating energy consumption.

[0011] Therefore, there is a need for a servo pump-controlled hydraulic power unit and its control method that is compact, highly integrated, and capable of recovering energy during the rapid downward movement of the slider and reusing that energy during the return movement, in order to further improve the energy efficiency and control performance of large hydraulic presses and punch presses. Summary of the Invention

[0012] The purpose of this invention is to provide a servo pump-controlled hydraulic power device with energy recovery and its control method, through:

[0013] 1. A bidirectional hydraulic pump driven by a servo drive mechanism is used to form a specific oil circuit connection between the upper and lower working chambers of the hydraulic cylinder, as well as the oil tank and accumulator. The pressure oil generated by the slider and its connected load during the downward phase drives the bidirectional hydraulic pump to charge the accumulator, thereby realizing the recovery of potential energy or external load energy.

[0014] 2. During the slide return phase, the accumulator releases high-pressure oil, which is superimposed on the oil output by the bidirectional hydraulic pump to supply oil to the working chamber of the hydraulic cylinder, thereby compensating for energy during the return process.

[0015] 3. With the help of the filling valve installed between the upper chamber of the hydraulic cylinder and the oil tank, a high-flow passage is established between the two when needed, so as to realize the rapid filling and rapid depressurization of the upper chamber of the hydraulic cylinder;

[0016] The aim is to recover gravitational potential energy and / or external load energy while maintaining servo control precision, thereby reducing the power demand of the servo motor and improving the system's energy utilization efficiency and structural integration. This invention is preferably applied to large hydraulic equipment such as hydraulic presses and punch presses.

[0017] To achieve the above objectives, the present invention adopts the following technical solution:

[0018] A servo pump-controlled hydraulic power unit with energy recovery includes an electro-hydraulic bidirectional servo pump assembly, a hydraulic cylinder, an oil tank, an oil circuit assembly, and an accumulator.

[0019] An oil chamber for storing working oil is formed inside the oil tank. A filling valve is installed between the oil tank and the upper chamber of the hydraulic cylinder. The filling valve is used to establish a high-flow passage between the upper chamber and the oil chamber during rapid filling and / or return of the hydraulic cylinder.

[0020] The electro-hydraulic bidirectional servo pump assembly includes a bidirectional hydraulic pump driven by a servo drive mechanism. The oil suction side of the bidirectional hydraulic pump is connected to the oil chamber of the oil tank via a first channel. One of the two working ports of the bidirectional hydraulic pump is connected to the upper chamber of the hydraulic cylinder via a second channel, and the other working port is connected to the lower chamber of the hydraulic cylinder via a third channel.

[0021] The accumulator is connected to at least one working port of the bidirectional hydraulic pump and / or the lower chamber of the hydraulic cylinder through the accumulator branch, and a control valve group is provided in the accumulator branch.

[0022] As a further explanation of the present invention, the hydraulic cylinder includes a cylinder body and a piston and piston rod assembly disposed in the cylinder body, wherein the free end of the piston and piston rod assembly is rigidly connected to the slider of a hydraulic press or punch press.

[0023] The oil tank is arranged along the axis of the hydraulic cylinder. The bottom plate of the oil tank is rigidly fixed to the cylinder body by bolts or welding. The filling valve is fastened to the bottom, inside and / or on the hydraulic cylinder housing of the oil tank.

[0024] As a further explanation of the present invention, the oil circuit assembly is composed of channels and / or external connecting pipes disposed inside the cylinder body, connectors and / or the housing of the bidirectional hydraulic pump, including at least a first channel, a second channel, a third channel and a fourth channel, wherein the fourth channel connects any working port of the bidirectional hydraulic pump to the control chamber of the filling valve.

[0025] The oil circuit assembly also includes an accumulator branch, which is connected to the control valve group and then to the accumulator.

[0026] As a further explanation of the present invention, the accumulator is a diaphragm accumulator and / or a bladder accumulator and / or a piston accumulator.

[0027] As a further explanation of the present invention, the upper chamber and / or lower chamber of the hydraulic cylinder are jointly formed by the working chambers of at least two single-acting hydraulic cylinders. The piston rods of the at least two single-acting hydraulic cylinders are rigidly connected to the slider. The working chamber of at least one single-acting hydraulic cylinder is connected to the working port of the bidirectional hydraulic pump through a third channel and to the accumulator through an accumulator branch, for recovering potential energy under the condition of rapid downward movement of the slider by its own weight and releasing potential energy under the condition of return movement of the slider.

[0028] As a further explanation of the present invention, the hydraulic cylinder is a cylinder group consisting of at least two hydraulic cylinders. The piston rod of each hydraulic cylinder in the cylinder group is rigidly connected to the slider. The upper chamber and / or lower chamber of at least one hydraulic cylinder in the cylinder group is connected to the working port of the bidirectional hydraulic pump through a second channel and / or a third channel. The lower chamber of at least one hydraulic cylinder in the cylinder group is connected to the accumulator through an accumulator branch, so that each hydraulic cylinder drives the slider to move in concert and realizes the recovery and release of potential energy.

[0029] As a further explanation of the present invention, the servo drive mechanism is a servo motor, and the bidirectional hydraulic pump is one of a bidirectional piston type, gear type, or screw type hydraulic pump.

[0030] The servo motor is driven by a servo driver. The servo driver body is equipped with an input interface for receiving feedback signals from displacement sensors and / or force sensors. Based on externally given position and / or force and speed commands and feedback signals, it performs closed-loop control on the rotation direction and speed of the servo motor and servo control on the displacement and / or output force of the hydraulic cylinder.

[0031] As a further explanation of the present invention, the servo drive mechanism, bidirectional hydraulic pump, oil circuit assembly, accumulator and oil tank are integrally mounted on the frame or cylinder body connected to the hydraulic cylinder to form an integrated hydraulic power unit for driving the reciprocating motion of the slide of a hydraulic press or punch press.

[0032] A control method for a servo-pump-controlled hydraulic power unit with energy recovery includes the following steps:

[0033] Rapid downward movement of the slider due to its own weight: When the slider is not in contact with the workpiece and is in the condition of rapid downward movement due to its own weight, the oil in the lower chamber of the hydraulic cylinder enters the bidirectional hydraulic pump through the third channel. Under the control of the servo drive mechanism, it rotates in the first direction under low load conditions, pressurizing the pressure oil in the lower chamber of the hydraulic cylinder and delivering it to the accumulator for energy storage.

[0034] The rotational speed of the bidirectional hydraulic pump is adjusted by regulating the rotational speed of the servo motor, thereby enabling continuous and adjustable control of the downward speed of the slider due to its own weight.

[0035] Slider pressing or pressurizing stage: After the slider stops descending rapidly, the servo motor is controlled to drive the bidirectional hydraulic pump to work in the first direction of rotation. Oil is drawn from the oil chamber of the oil tank through the first channel and supplied to the upper chamber of the hydraulic cylinder through the second channel to drive the slider to descend slowly and pressurize the workpiece.

[0036] Slider depressurization and return phase: When it is necessary to depressurize the upper chamber of the hydraulic cylinder and return the slider, the servo motor is controlled to drive the bidirectional hydraulic pump in the second rotation direction. Oil is drawn from the upper chamber of the hydraulic cylinder through the second channel to achieve instantaneous depressurization of the upper chamber. Pressure is supplied to the control chamber of the filling valve through the fourth channel to open the filling valve, so that the upper chamber is connected to the oil chamber of the oil tank through the filling valve. At the same time, the accumulator is controlled to release high-pressure oil to the lower chamber of the hydraulic cylinder and / or the working port side of the bidirectional hydraulic pump through the control valve group to achieve energy compensation during the slider return process.

[0037] As a further explanation of the present invention, during the rapid downward movement of the slider due to its own weight, the pressing or pressurizing stage, and the depressurization and return stage, the servo driver performs closed-loop control of the position and / or force value of the servo motor based on the feedback signals from the displacement sensor and / or force sensor, so as to improve the control accuracy of the slider position and output force.

[0038] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0039] (1) Integrated structure, reducing pipelines

[0040] In the preferred embodiment, the electro-hydraulic bidirectional servo pump assembly, hydraulic cylinder, and oil tank are integrated into a single unit with a top-mounted oil tank. This significantly shortens the oil circuit length, reduces the number of external pipes and joints, lowers the risk of leakage and installation space requirements, and improves the overall reliability and integration of the machine.

[0041] (2) Energy recovery is achieved by using gravity to descend.

[0042] When the slider moves rapidly downwards under its own weight, the oil in the lower chamber of the hydraulic cylinder drives the bidirectional hydraulic pump to fill the accumulator under the action of gravity, realizing the conversion of the slider's own weight potential energy into the pressure energy in the accumulator, effectively recovering the energy that might have been wasted through throttling or depressurization.

[0043] (3) The accumulator assists the return stroke, reducing drive energy consumption.

[0044] During the slide return process, the accumulator releases high-pressure oil to assist in driving the hydraulic cylinder upward, reusing the energy recovered in the previous working condition. This reduces the power requirement of the servo motor and improves the system's energy utilization efficiency.

[0045] (4) Selecting the pre-charge pressure of the accumulator is conducive to the participation of its own weight in energy storage and reduces the work done by the motor.

[0046] By selecting the pre-charge pressure of the accumulator to be close to the pressure of the lower chamber of the hydraulic cylinder under the condition of rapid downward movement of the slider's own weight, part of the pressure is provided by the pressure of the lower chamber generated by the slider's own weight during the initial stage of accumulator oil filling. The bidirectional hydraulic pump rotates under low load conditions, and the servo motor only needs to compensate for the pressure difference between the accumulator pressure and the lower chamber pressure, thereby reducing the work demand of the servo motor during the energy storage process. This is more energy-efficient than replenishing the accumulator with oil from a near-zero or negative pressure oil source.

[0047] (5) The downlink speed is adjustable and the throttling loss is small.

[0048] The equivalent flow rate when the slider descends rapidly is determined by the displacement of the bidirectional hydraulic pump and the speed of the servo motor. By adjusting the speed of the servo motor, the downward speed of the slider due to its own weight can be continuously and adjustablely controlled, reducing the dependence on throttling elements and thus reducing throttling losses and system heat generation.

[0049] (6) Compatible with low-speed, high-torque servo motors and bidirectional hydraulic pumps

[0050] Because the oil tank is located above the end of the cylinder, the oil suction passage of the bidirectional hydraulic pump is short and the oil suction port has a certain static pressure height. Even if a low-speed, high-torque servo motor is used to drive a large-displacement bidirectional hydraulic pump, good oil suction conditions can be guaranteed, which is conducive to the hydraulic cylinder achieving stable operation and high-precision control under low-speed and high-pressure conditions.

[0051] (7) Facilitates the implementation of position / force servo control

[0052] By setting displacement sensors and / or force sensors, the servo driver can directly perform closed-loop control of the servo motor based on feedback signals, thereby achieving precise control of the slider position and output force, and meeting the speed, position and pressure requirements of different processes. Attached Figure Description

[0053] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0054] Figure 1 This is a schematic diagram of the device of the present invention;

[0055] Figure 2 This is a hydraulic schematic diagram of the device of the present invention;

[0056] Figure 3 This is a schematic diagram of the hydraulic principle of an embodiment of the present invention;

[0057] Figure 4 This is a schematic diagram of the structure of the present invention applied to a hydraulic press.

[0058] Figure 5 This is a schematic diagram of the vertical cross-sectional structure of the present invention applied to a punch press.

[0059] The reference numerals in the attached figures are explained as follows:

[0060] 1. Electro-hydraulic bidirectional servo pump assembly; 101. Servo drive mechanism; 102. Bidirectional hydraulic pump; 2. Hydraulic cylinder; 2a. Main actuating cylinder; 2b. Auxiliary single-acting cylinder; 201. Cylinder body; 202. Piston and piston rod assembly; 203. Upper chamber; 204. Lower chamber; 3. Oil tank; 301. Oil chamber; 4. Filling valve; 5. Oil circuit assembly; 501. First channel; 502. Second channel; 503. Third channel; 504. Fourth channel; 505. Accumulator branch; 6. Accumulator; 601. Control valve group; 7. Displacement sensor; 8. Force sensor; 9. Slider. Detailed Implementation

[0061] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0062] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0063] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0064] A servo-pump controlled hydraulic power unit with energy recovery includes an electro-hydraulic bidirectional servo pump assembly 1, a hydraulic cylinder 2 (which can be a cylinder group), an oil tank 3, and an accumulator 6; wherein the hydraulic cylinder 2 can also be a large vertical hydraulic cylinder 2 used to drive a hydraulic press or punch press slide 9, and the oil tank 3 is preferably located near the hydraulic cylinder 2 and is connected to the upper chamber 203 and / or lower chamber 204 of the hydraulic cylinder 2 through an oil circuit. Wherein:

[0065] The hydraulic cylinder 2 includes a cylinder body 201 and a piston and piston rod assembly 202 disposed within the cylinder body 201. The free end of the piston rod assembly is rigidly connected to the slide block 9 of the hydraulic press or punch press. The hydraulic cylinder 2 is preferably of a vertical structure, and the slide block 9 moves rapidly downward under its own weight and load.

[0066] The oil tank 3 is preferably fixed to the end of the cylinder body 201 of the hydraulic cylinder 2 and arranged above it, along the axial direction of the hydraulic cylinder 2. Its bottom plate is rigidly fixed to the cylinder body 201 by bolt connection or welding. In this embodiment, the oil tank 3 adopts a top-mounted structure.

[0067] An oil chamber 301 for storing working oil is formed inside the oil tank 3. A filling valve 4 is provided between the oil tank 3 and the upper chamber 203 of the hydraulic cylinder 2. The filling valve 4 is used to establish a high flow passage between the upper chamber 203 and the oil chamber 301 when the hydraulic cylinder 2 is rapidly filled and returned.

[0068] The filling valve 4 is preferably a large-diameter hydraulically controlled check valve or a pilot-operated filling valve 4, used to open the high-flow-rate channel between the upper chamber 203 of the hydraulic cylinder 2 and the oil chamber 301 of the oil tank 3 when the control port is pressurized. In other embodiments, the filling valve 4 may also be a cartridge logic valve with a pilot control oil circuit, an electro-hydraulic control check valve, or other valves that can achieve openable and closed connection between the upper chamber 203 and the large-diameter oil tank 3 under the action of a control signal. This invention does not limit this type of valve.

[0069] In other embodiments, the oil tank 3 can also be arranged on the side or bottom of the hydraulic cylinder 2 or set as an independent oil tank 3, as long as it can be connected to the hydraulic cylinder 2 and the bidirectional hydraulic pump 102 through the oil circuit. The present invention is not limited to a specific installation location.

[0070] Electro-hydraulic bidirectional servo pump assembly 1

[0071] The bidirectional hydraulic pump 102 is preferably fixed to the side of the cylinder body 201 and / or the oil tank 3 via a rigid connector, so that the electro-hydraulic bidirectional servo pump assembly 1, the hydraulic cylinder 2, and the oil tank 3 form an integrated assembly. This embodiment adopts this integrated structure to shorten the oil circuit length and reduce external pipelines.

[0072] Of course, in other embodiments, the electro-hydraulic bidirectional servo pump assembly 1 can also be mounted on the frame in a separate form and connected to the hydraulic cylinder 2 and the oil tank 3 through pipelines, and the present invention is equally applicable.

[0073] The suction side of the bidirectional hydraulic pump 102 is connected to the oil chamber 301 of the oil tank 3 via the first channel 501. One of its two working ports is connected to the upper chamber 203 of the hydraulic cylinder 2 via the second channel 502, and the other working port is connected to the lower chamber 204 of the hydraulic cylinder 2 via the third channel 503. One of the working ports of the bidirectional hydraulic pump 102 is also connected to the control chamber of the filling valve 4 via the fourth channel 504, which is used to control the filling valve 4 when needed.

[0074] The servo drive mechanism 101 is preferably a servo motor. The servo motor is driven by a servo driver and its speed and direction of rotation are adjusted. The servo driver can control the working state of the bidirectional hydraulic pump 102 according to externally given displacement, speed and / or force commands to achieve servo control of the hydraulic cylinder 2.

[0075] Accumulator 6 and its branches

[0076] Accumulator 6 is connected to the working port of bidirectional hydraulic pump 102 and / or the lower chamber 204 of hydraulic cylinder 2 via accumulator branch 505. Control valve group 601 is installed in accumulator branch 505. Accumulator 6 can be a diaphragm type, bladder type or piston type accumulator 6, and its pre-charge pressure and volume are selected according to the pressure of the lower chamber 204 of hydraulic cylinder 2 and the desired energy recovery.

[0077] The accumulator 6 is used to store and release hydraulic energy through a compressible medium, and is preferably a gas accumulator 6, such as a diaphragm accumulator 6, a bladder accumulator 6, or a piston accumulator 6. In other embodiments, the accumulator 6 may also be a weighted, spring-loaded, or other energy storage device capable of storing hydraulic energy under pressure and releasing it when needed, and the present invention is not limited thereto.

[0078] Multi-cylinder cylinder group arrangement

[0079] In the single-cylinder embodiment, hydraulic cylinder 2 is a single double-acting hydraulic cylinder 2;

[0080] In the cylinder group embodiment, the hydraulic cylinder 2 can be composed of a cylinder group consisting of at least two hydraulic cylinders 2, such as the main actuating cylinder 2a and the auxiliary single-acting cylinder 2b, etc. In this specification, the hydraulic cylinder 2 can also be understood as the overall number of the cylinder group.

[0081] In some embodiments, a cylinder group can be formed by 2 to N hydraulic cylinders 2 arranged independently. Each hydraulic cylinder 2 has an independent electro-hydraulic bidirectional servo pump assembly 1, an accumulator 6 and an oil tank 3. The piston rod of each hydraulic cylinder 2 in the cylinder group is rigidly connected to the integral slider 9 or connected to the corresponding separate slider 9.

[0082] Corresponding to the cylinder group of 2 to N hydraulic cylinders 2 mentioned above, a corresponding pump group and / or accumulator group 6 can be set up. The upper chamber 203 and / or lower chamber 204 of each hydraulic cylinder 2 are connected to their respective bidirectional hydraulic pump 102 and / or accumulator 6 through independent oil circuits. Corresponding to multiple servo drive mechanisms 101, each drives its respective bidirectional hydraulic pump 102 to work. The output speed and start / stop of each servo motor are synchronously controlled by the servo driver to realize the synchronization of the stroke of each hydraulic cylinder 2 in the cylinder group, thereby realizing the balanced force and synchronous movement of the slider 9.

[0083] In other embodiments, the cylinder group consists of 2 to N hydraulic cylinders 2. The upper chamber 203 and / or lower chamber 204 of each hydraulic cylinder 2 in the cylinder group are connected to a common upper chamber 203 main pipe and lower chamber 204 main pipe through an integrated oil circuit block or pipeline. The upper chamber 203 main pipe is connected to the oil chamber 301 of the bidirectional hydraulic pump 102 and / or oil tank 3 through the second channel 502. The lower chamber 204 main pipe is connected to another working port of the bidirectional hydraulic pump 102 and the accumulator branch 505 through the third channel 503. The accumulator branch 505 is connected to the accumulator 6 through the control valve group 601.

[0084] In this arrangement, only one electro-hydraulic bidirectional servo pump assembly 1 can be set up. A single servo drive mechanism 101 drives a single bidirectional hydraulic pump 102 to simultaneously drive all hydraulic cylinders 2 in the cylinder group to work together through the upper chamber 203 main pipe and the lower chamber 204 main pipe. Alternatively, two or more sets of electro-hydraulic bidirectional servo pump assemblies 1 can be set up according to the tonnage and flow requirements. Multiple sets of bidirectional hydraulic pumps 102 are connected in parallel to the upper chamber 203 main pipe and the lower chamber 204 main pipe. The servo drive driver performs speed and phase synchronization control on multiple servo drive mechanisms 101 to achieve synchronous pressurization, synchronous energy recovery and synchronous return of the cylinder group.

[0085] In another arrangement of the cylinder group, the piston rods of each hydraulic cylinder 2 in the cylinder group are rigidly connected to the slider 9, and the following structure can also be adopted:

[0086] The cylinder assembly includes at least one single-acting main actuating cylinder 2a disposed above the slider 9 and at least one auxiliary single-acting cylinder 2b disposed below the slider 9;

[0087] The upper chamber 203 of the single-acting main actuator cylinder 2a is connected to the first working port of the bidirectional hydraulic pump 102 through the second channel 502, and is mainly used to drive the slider 9 to pressurize the workpiece;

[0088] The auxiliary single-acting cylinder 2b is located below the slider 9. Its lower chamber 204 is connected to the second working port of the bidirectional hydraulic pump 102 through the third channel 503, and is connected to the accumulator 6 through the accumulator branch 505. When the slider 9 moves rapidly downwards due to its own weight, the oil in the lower chamber 204 drives the bidirectional hydraulic pump 102 to rotate through the third channel 503 under the action of the slider 9's own weight, and is stored in the accumulator 6 through the accumulator branch 505 to realize potential energy recovery. When the slider 9 returns, the accumulator 6 releases energy to the lower chamber 204 of the auxiliary single-acting cylinder 2b and / or the oil suction side of the bidirectional hydraulic pump 102 through the accumulator branch 505. This energy is superimposed with the oil supply from the servo drive mechanism 101 driving the bidirectional hydraulic pump 102 to provide return thrust for the slider 9's return stroke.

[0089] With the above structural configuration, the following can be achieved:

[0090] In the rapid downward working condition of the piston rod of hydraulic cylinder 2 and its connected load under its own weight, the oil discharged from the lower chamber 204 of hydraulic cylinder 2 enters the bidirectional hydraulic pump 102 through the third channel 503 and is transported to the accumulator 6 to compress the gas in the accumulator 6, thereby realizing the storage of oil energy generated by the potential energy of the lower chamber 204.

[0091] During the upward return stroke of hydraulic cylinder 2, accumulator 6 releases high-pressure oil to the lower chamber 204 of hydraulic cylinder 2 and / or the working port side of bidirectional hydraulic pump 102 through accumulator branch 505. This oil is superimposed on the output of bidirectional hydraulic pump 102 to assist in driving the return stroke of hydraulic cylinder 2, thereby increasing the return speed and reducing the energy consumption of servo motor.

[0092] Servo Driver and Detection

[0093] The servo drive can be equipped with an input interface for receiving feedback signals from displacement sensor 7 and / or force sensor 8. Displacement sensor 7 can be installed inside the piston rod of hydraulic cylinder 2 or in a follow-up external mechanism to detect the displacement of slider 9; force sensor 8 can be installed at the end of piston rod or on an external structure connected to slider 9 to detect the output force value. The servo drive performs closed-loop position and / or force control on the servo motor according to external commands and feedback signals.

[0094] Example 1: A servo-pump controlled hydraulic power unit with energy recovery, such as... Figure 1-5 As shown, it includes: a hydraulic cylinder 2, an oil tank 3, an electro-hydraulic bidirectional servo pump assembly 1, an accumulator 6, and an oil circuit assembly 5, etc. In this embodiment, the hydraulic cylinder 2 is a large, vertically arranged hydraulic cylinder 2 used to drive the reciprocating motion of the slide block 9 of a hydraulic press or punch press.

[0095] The hydraulic cylinder 2 is arranged vertically, with its cylinder body 201 housing fixed to the frame, and the free end of the piston and piston rod assembly 202 rigidly connected to the slider 9 through a connector.

[0096] In this embodiment, the oil tank 3 is arranged above the cylinder body 201, and its bottom plate is rigidly connected to the cylinder body 201 by bolts or welding. An oil chamber 301 is formed inside the oil tank 3. The filling valve 4 is fastened to the housing of the hydraulic cylinder 2. The main oil port of the filling valve 4 is connected to the upper chamber 203 of the hydraulic cylinder 2, and the other side is connected to the oil chamber 301.

[0097] The electro-hydraulic bidirectional servo pump assembly 1 includes a servo drive mechanism 101 and a bidirectional hydraulic pump 102, which are fixed to the side of the cylinder body 201 and / or the oil tank 3 by a bracket or rigid connector, so that it forms an integral structure with the hydraulic cylinder 2 and the oil tank 3.

[0098] The accumulator 6 is connected to the lower chamber 204 of the hydraulic cylinder 2 and / or the working port of the bidirectional hydraulic pump 102 through the accumulator branch 505. A control valve group 601 is provided in the accumulator branch 505 to control the energy storage and release process of the accumulator 6.

[0099] Example 2: Figure 2 As shown, the oil circuit assembly 5 includes:

[0100] First channel 501: Connects the oil chamber 301 of the oil tank 3 to the oil suction side of the bidirectional hydraulic pump 102;

[0101] Second channel 502: connects the first working port of the bidirectional hydraulic pump 102 to the upper chamber 203 of the hydraulic cylinder 2;

[0102] Third channel 503: connects the second working port of the bidirectional hydraulic pump 102 to the lower chamber 204 of the hydraulic cylinder 2;

[0103] Fourth channel 504: Connects any working port of the bidirectional hydraulic pump 102 to the control chamber of the filling valve 4;

[0104] Accumulator branch 505: It is led out from the oil circuit of the lower chamber 204 of the hydraulic cylinder 2 and connected to the accumulator 6 via the control valve group 601.

[0105] The servo drive mechanism 101 can be a low-speed, high-torque servo motor, whose speed and direction of rotation are controlled by a servo driver. The servo driver can receive feedback signals from the displacement sensor 7 and / or the force sensor 8 to achieve closed-loop control of the position and output force of the slider 9.

[0106] Example 3: Rapid descent of slider 9 due to its own weight and energy recovery stage

[0107] When the slider 9 is not in contact with the workpiece and is in the stage of rapid downward movement due to its own weight, the bidirectional hydraulic pump 102 is driven by the pressure of the lower chamber 204 of the hydraulic cylinder 2 and rotates in the first direction under low load conditions.

[0108] The hydraulic fluid in the lower chamber 204 of the hydraulic cylinder 2 enters the bidirectional hydraulic pump 102 through the third channel 503 under the action of the slider 9's own weight. After being pressurized by the bidirectional hydraulic pump 102, it enters the accumulator branch 505. At the same time, the control valve group 601 is opened, and the hydraulic fluid in the lower chamber 204 enters the accumulator 6 through the accumulator branch 505 and the control valve group 601. The gas in the accumulator 6 is compressed to achieve energy storage. By adjusting the speed of the bidirectional hydraulic pump 102 driven by the servo motor, the downward speed of the slider 9 can be continuously and adjustablely controlled, while reducing throttling losses.

[0109] Suppression or pressure stage

[0110] During the loading and pressure holding stage of slider 9, the control servo motor drives the bidirectional hydraulic pump 102 in the first rotation direction to work, drawing oil from the oil chamber 301 of the oil tank 3 through the first channel 501 and supplying oil to the upper chamber 203 of the hydraulic cylinder 2 through the second channel 502, so as to drive slider 9 to descend slowly and pressurize the workpiece; the control valve group 601 of the accumulator branch 505 can be closed to improve the rigidity of the lower chamber 204; the servo driver implements position and / or force closed-loop control of the servo motor according to the feedback signal of displacement sensor 7 and / or force sensor 8 to ensure the stability and control accuracy of slider 9 position and pressure.

[0111] Decompression and return and energy release phases

[0112] When it is necessary to depressurize and return slider 9, the servo driver controls the servo motor to drive the bidirectional hydraulic pump 102 in the second rotation direction:

[0113] The bidirectional hydraulic pump 102 draws oil and relieves pressure from the upper chamber 203 of the hydraulic cylinder 2 through the second channel 502;

[0114] Pressure is supplied to the control chamber of the filling valve 4 through the fourth channel 504, the filling valve 4 is opened, and the upper chamber 203 is connected to the oil chamber 301 of the oil tank 3 through the filling valve 4, so as to realize the rapid depressurization and oil return of the upper chamber 203.

[0115] At the same time, the control valve group 601 is turned on, and the accumulator 6 releases high-pressure oil to the lower chamber 204 of the hydraulic cylinder 2 and / or the working port side of the bidirectional hydraulic pump 102 through the accumulator branch 505. The oil supply from the bidirectional hydraulic pump 102 is superimposed to push the piston and slider 9 together, so as to realize energy compensation during the return process of the slider 9, achieve rapid return, and reduce the output power requirement of the servo motor.

[0116] Example 4: Without departing from the spirit and essence of the present invention, those skilled in the art can make various modifications to the above embodiments, for example:

[0117] The bidirectional hydraulic pump 102 can be an axial piston pump, a radial piston pump, or other reversible positive displacement pump.

[0118] The accumulator 6 can adopt different structural forms, and there can be one or more of them, which can be arranged on different branches;

[0119] The control valve assembly 601 can be a solenoid valve, a cartridge valve, a check valve, a hydraulic check valve, or other forms of switching control element;

[0120] The shape and installation method of the oil tank 3 can be adjusted according to the overall structure of the machine. It can be top-mounted, side-mounted, bottom-mounted, or an independent oil tank 3, as long as it can be connected to the hydraulic cylinder 2 and the bidirectional hydraulic pump 102 through the oil circuit.

[0121] To better illustrate the function and effect of the present invention, the following experimental scheme is provided:

[0122] Experimental materials and specifications

[0123] Table 1

[0124]

[0125] 2.2 Comparison with traditional systems

[0126] To compare the performance of this device with that of a traditional servo hydraulic system, the following comparison configuration was selected:

[0127] Comparison system: Traditional servo hydraulic pump station + valve control system, without energy recovery circuit;

[0128] Pump type: Displacement pump (Italian Marzucci gear pump);

[0129] Control method: Throttling and rapid unloading + conventional unloading / return loop;

[0130] The remaining mechanical parts (slider, frame, tooling) are tested under the same conditions as the device under test.

[0131] The motor power is uniformly set at 18KW, using Huichuan servo motors.

[0132] 2.3 Measurement and Acquisition System

[0133] Pressure sensor: range 0~40 MPa, accuracy ±0.5 %FS, located in the upper cylinder chamber, lower cylinder chamber, accumulator branch, pump outlet, etc.

[0134] Flow sensor: can be left unconnected; the theoretical flow rate can be calculated using the actual motor speed.

[0135] Displacement sensor: with a range greater than the full stroke of the slider, used to detect the slider position and calculate speed;

[0136] Power analyzer: records the instantaneous power and power consumption of the servo motor;

[0137] Temperature sensors: placed in the oil tank and key areas to monitor changes in oil temperature;

[0138] Data acquisition system: Adjust the appropriate sensor sampling frequency and record the curves of each channel changing over time.

[0139] 3. Test conditions and methods

[0140] 3.1 Test Condition Setting

[0141] To test the temperature rise, two cycle conditions are selected, for example:

[0142] Operating condition A: 3 times / minute, 200 tests;

[0143] Operating condition B: 8 times / minute, 200 tests;

[0144] In actual testing, different cycles can be set as needed and energy consumption can be calculated separately.

[0145] 3.2 Test Procedure

[0146] 3.2.1 Rapid descent of the slider due to its own weight and energy recovery stage

[0147] 1) Set the bidirectional hydraulic pump circuit to energy recovery mode;

[0148] 2) When the slider is not in contact with the workpiece and is in the downward phase due to its own weight, the lower chamber of the hydraulic cylinder is allowed to build up pressure under the action of external loads (including its own weight);

[0149] 3). The pressure oil in the lower chamber of the hydraulic cylinder enters the bidirectional hydraulic pump 102 through the third channel 503, driving it to rotate under low load conditions;

[0150] 4). The pressure oil in the lower chamber enters the accumulator 6 through the bidirectional hydraulic pump 102 and the accumulator branch 505, compressing the gas in the accumulator and realizing the recovery of the potential energy of the slider.

[0151] 5) By adjusting the servo motor speed setting, the speed of the bidirectional hydraulic pump can be changed, thereby achieving continuous and adjustable control of the slider's self-weight rapid descent speed.

[0152] 3.2.2 Slider pressing / pressurizing stage

[0153] 1) The servo driver controls the bidirectional hydraulic pump 102 to draw oil from the oil chamber 301 of the oil tank 3;

[0154] 2) Oil is supplied and pressurized to the upper chamber 203 of the hydraulic cylinder through the second channel 502, driving the slider to press against the workpiece at a set speed;

[0155] 3) Record the changes in pressure, displacement, speed, and motor power during the pressurization phase.

[0156] 3.2.3 Slider pressure relief and return stage

[0157] 1) When pressure relief and return are required, the servo drive controls the bidirectional hydraulic pump 102 to work in the opposite direction, drawing oil from the upper chamber 203 of the hydraulic cylinder through the second channel 502 to quickly relieve pressure;

[0158] 2). At the same time, pressure is supplied to the control chamber of the filling valve 4 through the fourth channel 504 to open the filling valve 4, so that the upper chamber 203 is connected to the oil chamber 301 of the oil tank, thereby realizing a large flow of oil return;

[0159] 3). When the control valve group 601 is opened, the accumulator 6 releases high-pressure oil to the lower chamber 204 of the hydraulic cylinder and / or the suction side of the bidirectional hydraulic pump through the accumulator branch 505, which, together with the oil supplied by the pump, drives the slider to return.

[0160] 4) Record the slider speed, power consumption, and accumulator pressure changes during the return phase.

[0161] 4. Experimental Data and Results

[0162] Table 2. Record of key parameters for a single work cycle

[0163]

[0164] 4.2 Comparison of energy consumption and temperature rise under different cycle times

[0165] Table 3

[0166]

[0167] 5. Experimental Conclusions

[0168] 1. Compared to traditional throttling and rapid descent methods, this device can convert almost all potential energy into accumulator pressure energy. The motor energy consumption during the rapid descent phase is only slightly higher than in traditional throttling and rapid descent modes. However, during the return phase, the upward speed is significantly increased and the motor energy consumption is significantly reduced.

[0169] 2. The motor speed is controlled by a servo driver, and the downward speed of the slider due to its own weight is continuously adjustable within the range of 0 to 300 mm / s, which is convenient for balancing production efficiency and impact control.

[0170] 3. After continuous operation for 0.4-1 hour, the system temperature rise is approximately 2-3℃, which is significantly lower than that of a system without energy recovery.

[0171] 4. Effectively recover the pressure energy of the lower chamber of the hydraulic cylinder during the rapid downward movement of the slider due to its own weight, and perform energy compensation for the system during the pressure relief and return phase.

[0172] 5. Compared with traditional hydraulic systems without energy recovery, this device significantly reduces energy consumption per cycle and per hour under the same working conditions, achieving energy savings of approximately 30%, while also significantly reducing the peak power requirement of the servo motor.

[0173] In summary, after passing the durability test, this device is suitable for widespread application in medium and large servo hydraulic presses and punch presses, and has good engineering application value and energy-saving and emission-reduction benefits.

[0174] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A servo pump controlled hydraulic power device with energy recovery, characterized in that: comprising an electro-hydraulic bidirectional servo pump assembly (1), a hydraulic cylinder (2), an oil tank (3), an oil circuit assembly (5) and an accumulator (6); the oil tank (3) is provided with an oil cavity (301) for storing working oil, and a liquid filling valve (4) is arranged between the oil tank (3) and an upper cavity (203) of the hydraulic cylinder (2), the liquid filling valve (4) is used to establish a large flow path between the upper cavity (203) and the oil cavity (301) when the hydraulic cylinder (2) is rapidly filled with liquid and / or returns; the electro-hydraulic bidirectional servo pump assembly (1) comprises a bidirectional hydraulic pump (102) driven by a servo driving mechanism (101), the oil suction side of the bidirectional hydraulic pump (102) is communicated with the oil cavity (301) of the oil tank (3) through a first channel (501), one of the two working ports of the bidirectional hydraulic pump (102) is communicated with the upper cavity (203) of the hydraulic cylinder (2) through a second channel (502), and the other working port is communicated with a lower cavity (204) of the hydraulic cylinder (2) through a third channel (503); the accumulator (6) is communicated with at least one working port of the bidirectional hydraulic pump (102) and / or the lower cavity (204) of the hydraulic cylinder (2) through an accumulator branch (505), and the accumulator branch (505) is provided with a control valve group (601). 2.A servo pump controlled hydraulic power device with energy recovery according to claim 1, characterized in that: the hydraulic cylinder (2) comprises a cylinder body (201) and a piston and piston rod assembly (202) arranged in the cylinder body (201), and the free end of the piston and piston rod assembly (202) is rigidly connected with a slider (9) of a hydraulic press or a punch. 3.A servo pump controlled hydraulic power device with energy recovery according to claim 1, characterized in that: the accumulator (6) is a diaphragm accumulator, a bladder accumulator and / or a piston accumulator. 4.A servo pump controlled hydraulic power device with energy recovery according to claim 1, characterized in that: ​ ​ ​ ​ ​ ​ ​ ​ ​ The upper chamber (203) and / or the lower chamber (204) of the hydraulic cylinder (2) is formed by the working chambers of at least two single-acting hydraulic cylinders (2), the piston rods of the single-acting hydraulic cylinders (2) are rigidly connected with the slider (9), the working chamber of at least one single-acting hydraulic cylinder (2) is communicated with the working port of the bidirectional hydraulic pump (102) through the third channel (503) and is communicated with the accumulator (6) through the accumulator branch (505), and is used for recovering potential energy in the condition that the slider (9) rapidly descends under its own weight and releasing the potential energy in the condition that the slider (9) returns.

5. The servo pump controlled hydraulic power device with energy recovery according to claim 1, characterized in that: The hydraulic cylinder (2) is a cylinder group composed of at least two hydraulic cylinders (2), the piston rods of the hydraulic cylinders (2) in the cylinder group are rigidly connected with the slider (9), the upper chamber (203) and / or the lower chamber (204) of at least one hydraulic cylinder (2) in the cylinder group is communicated with the working port of the bidirectional hydraulic pump (102) through the second channel (502) and / or the third channel (503), and the lower chamber (204) of at least one hydraulic cylinder (2) in the cylinder group is communicated with the accumulator (6) through the accumulator branch (505), so that the hydraulic cylinders (2) cooperatively drive the slider (9) to move and recover and release the potential energy.

6. The servo pump controlled hydraulic power device with energy recovery according to claim 1, characterized in that: The servo driving mechanism (101) is a servo motor, and the bidirectional hydraulic pump (102) is one of a bidirectional plunger type, a gear type or a screw type hydraulic pump; The servo motor is driven by a servo driver, the servo driver is provided with an input interface for receiving feedback signals of a displacement sensor (7) and / or a force value sensor (8), and the rotation direction and rotation speed of the servo motor are closed-loop controlled and the displacement and / or output force value of the hydraulic cylinder (2) is servo controlled according to the externally given position and / or force value and speed instructions and the feedback signals.

7. The servo pump controlled hydraulic power device with energy recovery according to claim 1, characterized in that: The servo driving mechanism (101), the bidirectional hydraulic pump (102), the accumulator (6) and the oil tank (3) are integrally installed on a frame or a cylinder body (201) connected with the hydraulic cylinder (2) to form an integrated hydraulic power unit for driving the slider (9) of a hydraulic press or a punch press to reciprocate.

8. A control method of a servo-pump-controlled hydraulic power device with energy recovery, applied to a servo-pump-controlled hydraulic power device with energy recovery according to any one of claims 1-7, characterized in that: The method comprises the following steps: Slider (9) rapid descending stage under its own weight: when the slider (9) does not contact a workpiece and is in the condition of rapidly descending under its own weight, the oil in the lower chamber (204) of the hydraulic cylinder (2) enters the bidirectional hydraulic pump (102) through the third channel (503), is rotated in a first rotation direction under the cooperation control of the servo driving mechanism (101) in a low load condition, and is pressurized and delivered to the accumulator (6) to store energy. The rotation speed of the bidirectional hydraulic pump (102) is adjusted by adjusting the rotation speed setting value of the servo drive mechanism (101), so as to continuously and adjustably control the self-weight down speed of the sliding block (9); The sliding block (9) pressing or pressurizing stage: after the sliding block (9) stops fast descending, the servo motor drives the bidirectional hydraulic pump (102) to work in the first rotation direction, oil in the oil cavity (301) of the oil tank (3) is sucked through the first channel (501), and oil is supplied to the upper cavity (203) of the hydraulic cylinder (2) through the second channel (502), so that the sliding block (9) slowly descends and pressurizes the workpiece; The sliding block (9) pressure relief and return stage: when it is needed to make the upper cavity (203) of the hydraulic cylinder (2) pressure relief and make the sliding block (9) return, the servo motor drives the bidirectional hydraulic pump (102) to work in the second rotation direction, oil in the upper cavity (203) of the hydraulic cylinder (2) is sucked through the second channel (502), so that the upper cavity (203) is instantaneously pressure relieved, the filling valve (4) is opened by supplying pressure to the control cavity of the filling valve (4) through the fourth channel (504) to make the upper cavity (203) communicate with the oil cavity (301) of the oil tank (3) through the filling valve (4), and the accumulator (6) releases high-pressure oil to the lower cavity (204) of the hydraulic cylinder (2) and / or the working port side of the bidirectional hydraulic pump (102) through the control valve group (601), so as to realize energy compensation in the return process of the sliding block (9).

9. The control method of the servo pump-controlled hydraulic power device with energy recovery according to any one of claim 8, characterized in that: In the self-weight fast descending stage, the pressing or pressurizing stage, and the pressure relief and return stage of the sliding block (9), the servo motor is subjected to position and / or force value closed-loop control according to the feedback signals of the displacement sensor (7) and / or the force value sensor (8) by the servo driver, so as to improve the control accuracy of the position and output of the sliding block (9).

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