Electro-hydrostatic drive system

Abstract

The application discloses an electro-hydraulic driving system, comprising: a hydraulic cylinder for realizing power output; an accumulator for storing hydraulic medium; a main pump for pumping the hydraulic medium in the accumulator into the hydraulic cylinder; an electric motor for driving the main pump; a controller for controlling the operation of the electric motor; the hydraulic cylinder comprises a cylinder body, a piston and a piston rod, the piston is accommodated in the cylinder body and separates the internal space of the cylinder body into a first chamber and a second chamber, the piston rod is connected to one side of the piston in the second chamber and can move synchronously with the piston, and the piston rod is at least partially arranged outside the cylinder body; the electro-hydraulic driving system further comprises a liquid supplementing device for supplementing the hydraulic medium into one of the first chamber or the second chamber to balance the flow balance on both sides of the piston when the piston moves. The electro-hydraulic driving system can effectively realize the flow balance of the hydraulic cylinder.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electro-hydraulic drive, in particular to an electro-hydraulic drive system. BACKGROUND

[0002] The excavator and other engineering machinery used diesel engine as power source, although through several technical innovation, mature development, but in the operation process of burning fuel pollution is inevitable.

[0003] In the related art, electric power is used as a power source, such as using a general motor to replace a diesel engine, but the system efficiency of the general motor is low, and in the related art, an electro-hydraulic drive system is used to replace a traditional hydraulic drive system driven by a diesel engine. With the development of electro-hydraulic technology, the electro-hydraulic technology overcomes the problems of oil leakage, maintenance, complex pipe laying and high energy consumption of the traditional hydraulic servo system.

[0004] However, the existing electro-hydraulic drive technology often does not consider the asymmetric structure of the hydraulic cylinder, resulting in unstable electro-hydraulic drive. SUMMARY

[0005] The summary part of the present application is used to introduce the concept in a simple form, which will be described in detail in the specific embodiment part. The summary part of the present application is not intended to identify the key features or essential features of the claimed technical solution, nor is it intended to limit the scope of the claimed technical solution.

[0006] Some embodiments of the present application propose an electro-hydraulic drive system, comprising: a hydraulic cylinder for realizing power output; an accumulator for at least storing hydraulic medium; a main pump for pumping the hydraulic medium in the accumulator into the hydraulic cylinder; an electric motor for driving the main pump; a controller for at least controlling the operation of the electric motor; the hydraulic cylinder comprises a cylinder body, a piston and a piston rod, the piston is accommodated in the cylinder body and separates the internal space of the cylinder body into a first chamber and a second chamber, the piston rod is connected to one side of the piston located in the second chamber and can move synchronously with the piston, and the piston rod is at least partially arranged outside the cylinder body; the electro-hydraulic drive system further comprises: a liquid supplementing device for supplementing hydraulic medium into one of the first chamber or the second chamber to balance the flow balance on both sides of the piston when the piston moves.

[0007] Further, the liquid supplementing device comprises: a medium container for arranging a liquid supplementing space containing hydraulic medium independently of the accumulator.

[0008] Further, the liquid supplementing device further comprises: an auxiliary pump for pumping the hydraulic medium in the liquid supplementing space into the first chamber or the second chamber.

[0009] Further, the liquid supplement device further comprises a backflow valve for connecting the liquid supplement space with the first chamber or the second chamber when the pressure of the hydraulic medium input into the medium container is greater than or equal to a preset value.

[0010] Further, the liquid supplement device further comprises a switching valve for switching the communication relationship between the first chamber or the second chamber and the auxiliary pump and the backflow valve.

[0011] Further, the cylinder is provided with a first medium channel in communication with the first chamber, and the liquid supplement device further comprises a first hydraulic control pressure reducing valve for forming one-way communication from the first medium channel to the switching valve when the pressure of the first medium channel is greater than a preset value.

[0012] Further, the cylinder is provided with a second medium channel in communication with the second chamber, and the liquid supplement device further comprises a second hydraulic control pressure reducing valve for forming one-way communication from the second medium channel to the switching valve when the pressure of the second medium channel is greater than a preset value.

[0013] Further, the electro-hydrostatic drive system further comprises a first hydraulic control one-way valve for forming one-way communication from the first liquid outlet of the main pump to the accumulator when the pressure of the first liquid outlet of the main pump is greater than a preset value.

[0014] Further, the electro-hydrostatic drive system further comprises a second hydraulic control one-way valve for forming one-way communication from the second liquid outlet of the main pump to the accumulator when the pressure of the second liquid outlet of the main pump is greater than a preset value.

[0015] Further, the electro-hydrostatic drive system further comprises an isolation device for isolating the communication between the first liquid outlet or / and the second liquid outlet of the main pump and the first chamber or / and the second chamber; the accumulator is in communication with the liquid inlet of the main pump; the first liquid outlet and the second liquid outlet of the main pump are respectively in communication with the isolation device, and the isolation device comprises at least one isolation valve.

[0016] The application has the beneficial effect of providing an electro-hydrostatic drive system capable of effectively balancing the flow of the hydraulic cylinder. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings, which form a part of this application, are intended to provide further understanding of the application and are incorporated herein in their entirety. The schematic embodiment drawings of the application and their descriptions serve to explain the application, and do not constitute an improper limitation on the application.

[0018] In addition, throughout the drawings, the same or similar reference signs represent the same or similar elements. It should be understood that the drawings are schematic, and the elements and elements are not necessarily drawn to scale.

[0019] In the drawings:

[0020] Figure 1 This is a schematic diagram of the structure of an electro-hydrostatic drive system according to an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of the structure of an electro-hydrostatic drive system according to another embodiment of this application;

[0022] The meanings of the reference numerals in the attached figures are as follows:

[0023] 200. Electro-hydraulic drive system;

[0024] 201, Hydraulic cylinder; 2011, Cylinder body; 2012, Piston; 2013, Piston rod; 201a, First chamber; 201b, Second chamber; 201c, First medium passage; 201d, Second medium passage;

[0025] 202. Accumulator;

[0026] 203, Active pump; 203a, First outlet; 203b, Second outlet;

[0027] 204. Motor; 205. Controller;

[0028] 206. Liquid replenishment device;

[0029] 207. Medium container; 208. Auxiliary pump; 209. Return valve;

[0030] 210. Switching valve; A1. First switching port; A2. Second switching port; A3. Third switching port; A4. Fourth switching port;

[0031] 211. First hydraulic pressure reducing valve; B1. First inlet; B2. First outlet;

[0032] 212. Second hydraulic pressure reducing valve; C1. Second inlet; C2. Second outlet;

[0033] 213. First hydraulic control check valve; D1. First inlet; D2. First delivery port; D3. First hydraulic control port;

[0034] 214. Second hydraulic control check valve; E1. Second inlet; E2. Second delivery port; E3. Second hydraulic control port;

[0035] 215. Isolation device; 216. Isolation valve; F1. First isolation port; F2. Second isolation port; F3. Third isolation port; F4. Fourth isolation port;

[0036] 217. First pressure sensor; 218. Second pressure sensor; 219. Rotational speed sensor; 220. Speed ​​sensor. Detailed Implementation

[0037] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0038] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0039] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0040] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0041] The names of messages or information exchanged between multiple devices in the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of such messages or information.

[0042] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] like Figure 1 As shown, the electro-hydraulic drive system of this application adopts the following scheme. The electro-hydraulic drive system 200 mainly includes: hydraulic cylinder 201, accumulator 202, active pump 203, motor 204 and controller 205, etc.

[0044] Specifically, the hydraulic cylinder 201 is used to realize power output; the hydraulic cylinder 201 includes a cylinder body 2011, a piston 2012 and a piston rod 2013. The piston 2012 is housed in the cylinder body 2011 and divides the internal space of the cylinder body 2011 into a first chamber 201a and a second chamber 201b. The piston rod 2013 is connected to the piston 2012 on one side of the second chamber 201b and can move synchronously with the piston 2012. The piston rod 2013 is at least partially disposed outside the cylinder body 2011. Accumulator 202 is used to store hydraulic medium at least. Accumulator 202 is connected to the inlet of active pump 203. Active pump 203 is used to pump the hydraulic medium in accumulator 202 into hydraulic cylinder 201. Active pump 203 is a fixed displacement pump and has at least a first outlet D2203a and a second outlet 203b. The first outlet D2203a is directly or indirectly connected to the first chamber 201a, and the second outlet 203b is directly or indirectly connected to the second chamber 201b. Motor 204 is used to drive active pump 203. Controller 205 is used to control the operation of motor 204 (motor direction and speed, etc.), the operation strategy of hydraulic cylinder, flow balance, overload protection, and precision control, etc.

[0045] Because of the presence of piston rod 2013, the first chamber 201a and the second chamber 201b have an asymmetrical structure, which makes the maximum volume of the first chamber 201a greater than the maximum volume of the second chamber 201b. The hydraulic cylinder 201 is an asymmetrical hydraulic cylinder 201. When the piston 2012 moves, the inflow and outflow of the medium in the first chamber 201a and the second chamber 201b are not the same, which makes the piston rod 2013 unstable when driven.

[0046] To address the aforementioned problem of unstable piston rod 2013 drive, this application proposes the following solution: When oil is transported from the first chamber 201a to the second chamber 201b, the outflow of oil from the first chamber 201a is greater than the inflow of oil into the second chamber 201b, resulting in excess oil. This excess oil needs to be stored in the accumulator 202. Conversely, when oil is transported from the second chamber 201b to the first chamber 201a, the oil in the accumulator 202 needs to be replenished in the first chamber 201a.

[0047] As a preferred embodiment, the electro-hydraulic drive system 200 of this application further includes a fluid replenishment device 206, used to replenish or recover hydraulic medium to one of the first chamber 201a or the second chamber 201b when the piston 2012 moves, in order to balance the flow on both sides of the piston 2012. Specifically, the fluid replenishment device 206 includes a medium container 207, an auxiliary pump 208, a return valve 209, and a switching valve 210.

[0048] As a specific embodiment, the medium container 207 is used to provide a replenishment space for hydraulic medium, independent of the accumulator 202. The auxiliary pump 208 has two operating modes: motor mode and flow balance mode. When the auxiliary pump operates in motor mode, it pumps the hydraulic medium in the replenishment space into the first chamber 201a or the second chamber 201b. When the auxiliary pump operates in flow balance mode, i.e., when the flow in the first chamber, the second chamber, or the drive circuit is saturated, it recovers the hydraulic medium back to the replenishment space. Specifically, the auxiliary pump 208 is a hydraulic pump driven by a low-power motor (not shown). The return valve 209 is used to connect the replenishment space with the first chamber 201a or the second chamber 201b when the pressure of the hydraulic medium input to the medium container 207 is greater than or equal to a preset value. Specifically, the return valve 209 is a hydraulically controlled relief valve. The switching valve 210 is used at least to switch the connection relationship between the first chamber 201a or the second chamber 201b and the auxiliary pump 208 and the return valve 209. Specifically, the switching valve 210 is a three-position four-way solenoid directional valve. The switching valve 210 is used to change the position to achieve flow replenishment / return to different oil circuits and achieve active flow balance. The switching valve 210 is electrically connected to the controller 205, and the switching valve 210 receives electrical signals from the controller 205 to change its position.

[0049] Specifically, the switching valve 210 has: a first switching port A1, a second switching port A2, a third switching port A3, and a fourth switching port A4; the first switching port A1 is connected to the first chamber 201a, the second switching port A2 is connected to the second chamber 201b, the third switching port A3 is directly or indirectly connected to the replenishment space, and the fourth port is sealed. When the switching valve 210 is in the left position, the replenishment space is connected to the second chamber 201b; when the switching valve 210 is in the right position, the replenishment space is connected to the first chamber 201a; when the switching valve 210 is in the middle position, the replenishment space is not connected to either the first chamber 201a or the second chamber 201b.

[0050] As a more specific embodiment, the cylinder body 2011 is provided with a first medium channel 201c, which is connected to the first chamber 201a; the liquid replenishment device 206 further includes a first hydraulically controlled pressure reducing valve 211, which is used to establish a one-way connection between the first medium channel 201c and the switching valve 210 when the pressure in the first medium channel 201c is greater than a preset value. The first hydraulically controlled pressure reducing valve 211 includes a first inlet B1 and a first outlet B2; the first inlet B1 is connected to the first chamber 201a, so that the pressure at the first inlet B1 is equal to the pressure in the first chamber 201a, and the first outlet B2 is connected to the second chamber 201b, or the first outlet B2 is directly / indirectly connected to the active pump 203; when the pressure in the first chamber 201a is greater than the set pressure of the first hydraulically controlled pressure reducing valve 211, the first outlet B2 of the first hydraulically controlled pressure reducing valve 211 opens, and the first hydraulically controlled pressure reducing valve 211 is activated, so that the pressure in the first chamber 201a is maintained within a safe pressure range.

[0051] The cylinder body 2011 is provided with a second medium channel 201d, which is connected to the second chamber 201b. The replenishing device 206 further includes a second hydraulically controlled pressure reducing valve 212, which is used to establish a one-way connection between the second medium channel 201d and the switching valve 210 when the pressure in the second medium channel 201d is greater than a preset value. The second hydraulically controlled pressure reducing valve 212 includes a second inlet C1 and a second outlet C2. The second inlet C1 is connected to the second chamber 201b, so that the pressure at the second inlet C1 is equal to the pressure in the second chamber 201b. The second outlet C2 is connected to the first chamber 201a, or the second outlet C2 is directly / indirectly connected to the active pump 203. When the pressure in the second chamber 201b is greater than the set pressure of the second hydraulically controlled pressure reducing valve 212, the second outlet C2 of the second hydraulically controlled pressure reducing valve 212 opens, and the second hydraulically controlled pressure reducing valve 212 is activated, so that the pressure in the second chamber 201b is maintained within a safe pressure range.

[0052] As a more specific embodiment, the electro-hydraulic drive system 200 of this application further includes: a first hydraulically controlled check valve 213 and a second hydraulically controlled check valve 214. The first hydraulically controlled check valve 213 is used to establish a one-way connection between the first outlet 2023a and the accumulator 202 when the pressure at the first outlet 203a of the active pump 203 is greater than a preset value. Specifically, the first hydraulically controlled check valve 213 includes: a first inlet D1, a first delivery port D2, and a first hydraulically controlled control port D3; the first inlet D1 is connected to the first outlet 203a of the active pump 203, the first delivery port D2 is connected to the accumulator 202, and the first hydraulically controlled control port D3 is connected to the second outlet 203b.

[0053] The second hydraulically controlled check valve 214 is used to establish a one-way connection between the second outlet 203b and the accumulator 202 when the pressure at the second outlet 203b of the active pump 203 exceeds a preset value. Specifically, the second hydraulically controlled check valve 214 includes: a second inlet E1, a second outlet E2, and a second hydraulically controlled port E3; the second inlet E1 is connected to the second outlet 203b of the active pump 203, the second outlet is connected to the accumulator 202, and the second hydraulically controlled port E3 is connected to the first outlet 203a.

[0054] In this scheme, the first hydraulically controlled check valve 213 and the second hydraulically controlled check valve 214 are used to achieve flow balance between the first chamber 201a and the second chamber 201b. Since the hydraulically controlled check valves can achieve bidirectional flow through the hydraulic control port, the pressure values ​​of the first hydraulically controlled check valve 213 and the second hydraulically controlled check valve 214 are preset to be equal. When the pressure in the first chamber 201a exceeds the preset pressure value, the second hydraulically controlled control port E3 automatically opens, conducting the second hydraulically controlled check valve 214 to regulate the flow, thereby achieving flow balance between the first chamber 201a and the second chamber 201b. Similarly, when the pressure in the second chamber 201b exceeds the preset pressure value, the first hydraulically controlled control port D3 automatically opens, conducting the first hydraulically controlled check valve 213 to regulate the flow, thereby achieving flow balance between the first chamber 201a and the second chamber 201b.

[0055] As a preferred embodiment, the electro-hydraulic drive system 200 of this application further includes: a first pressure sensor 217, a second pressure sensor 218, a speed sensor 219, and a velocity sensor 220; the first pressure sensor 217 is used to monitor the pressure of the first chamber 201a, and is electrically connected to the controller 205 to output a pressure signal to the controller 205; the second pressure sensor 218 is used to monitor the pressure of the second chamber 201b, and is electrically connected to the controller 205 to output a pressure signal to the controller 205; the speed sensor 219 is electrically connected to the controller 205 and is used to monitor the speed of the motor 204; the velocity sensor 220 is electrically connected to the controller 205 and is used to monitor the displacement velocity of the piston rod. Alternatively, a displacement sensor can be used to monitor the displacement of the piston rod, and the displacement velocity can be calculated from the displacement per unit time.

[0056] When the pressure value of the first pressure sensor 217 is greater than the pressure value of the second pressure sensor 218, and the value monitored by the speed sensor 220 is less than a specified value (i.e., the pressure of the first chamber 201a is greater than the pressure of the second chamber 201b), the switching valve 210 is placed in the left position, and the replenishment space is connected to the second chamber 201b; when the pressure value of the first pressure sensor 217 is less than the pressure value of the second pressure sensor 218, and the displacement speed monitored by the speed sensor 220 is less than a specified value (i.e., the pressure of the second chamber 201b is greater than the pressure of the first chamber 201a), the switching valve 210 is placed in the right position, and the replenishment space is connected to the first chamber 201a.

[0057] The switching valve 210, auxiliary pump 208 and return valve 209 achieve active flow balance. The auxiliary pump 208 has the functions of outputting and recovering flow. The return valve 209 is opened when the pressure reaches the preset value, and the oil flow can return to the oil tank through the return valve 209.

[0058] The aforementioned oil tank is a specific embodiment of a medium container 207. The medium container 207, auxiliary pump 208, return valve 209, and switching valve 210 constitute the fluid replenishment device 206 of this application. The fluid replenishment device 206 of this application is used to replenish hydraulic medium to one of the first chamber 201a or the second chamber 201b when the piston 2012 moves, in order to balance the flow rate on both sides of the piston 2012.

[0059] The electro-hydrostatic drive system 200 of this application operates under the following four conditions:

[0060] Operating Condition 1: When the pressure in the second chamber 201b is less than the pressure in the first chamber 201a, the piston rod 2013 moves towards the second chamber 201b. The controller 205 controls the motor 204 to drive the active pump 203, which transports the oil in the second chamber 201b to the first chamber 201a. The direction of the second hydraulic pressure is the same as the direction of the piston rod 2013's movement speed. The inflow rate into the first chamber 201a is greater than the outflow rate from the second chamber 201b. The pressure value of the first pressure sensor 217 is greater than the pressure value of the second pressure sensor 218. The switching valve 210 is in the left position, the second hydraulic control port E3 is opened, and the second hydraulic check valve 214 is activated. The oil in the accumulator 202 and the oil discharged from the auxiliary pump 208 flow into the oil flowing out of the second chamber 201b, so that the return flow rate to the active pump 203 is equal to the output flow rate.

[0061] Operating Condition 2: When the pressure in the second chamber 201b is greater than the pressure in the first chamber 201a, the piston rod 2013 moves toward the second chamber 201b. The controller 205 controls the motor 204 to drive the active pump 203, which transports the oil in the second chamber 201b to the first chamber 201a. The pressure direction is opposite to the direction of the piston rod 2013's movement speed. At this time, the oil discharged from the accumulator 202 and the auxiliary pump 208 is also needed to replenish the first chamber 201a. When the pressure value of the first pressure sensor 217 is less than the pressure value of the second pressure sensor 218, the switching valve 210 is placed in the right position, the first hydraulic control port D3 is opened, and the first hydraulic check valve 213 is turned on. The oil in the accumulator 202 and the oil discharged by the auxiliary pump 208 flow into the first chamber 201a, realizing the flow balance between the first chamber 201a and the second chamber 201b. At the same time, the potential energy of the load is transferred to the piston 2012, which then drives the active pump 203 to generate electricity through the hydraulic circuit and recycles it, saving energy.

[0062] Operating Condition 3: When the pressure in the second chamber 201b is greater than the pressure in the first chamber 201a, the piston rod 2013 moves towards the first chamber 201a. At this time, the oil in the first chamber 201a is transported to the second chamber 201b through the active pump 203. The pressure direction is the same as the direction of the piston rod 2013's movement speed. The outflow rate of the first chamber 201a is greater than the inflow rate of the second chamber 201b. The pressure value of the first pressure sensor 217 is less than the pressure value of the second pressure sensor 218. The switching valve 210 is in the right position, the first hydraulic control port D3 is opened, and the first hydraulic check valve 213 is opened. The excess oil in the first chamber flows from the switching valve 210 and the auxiliary pump into the oil tank, thereby driving the auxiliary pump to generate electricity and recycle it, saving energy. At the same time, a portion of the excess oil in the first chamber flows from the first hydraulic check valve 213 into the accumulator 202, achieving flow balance between the first chamber 201a and the second chamber 201b.

[0063] Operating condition 4: The pressure in the second chamber 201b is less than the pressure in the first chamber 201a, and the piston rod 2013 moves toward the first chamber 201a; the oil in the first chamber 201a is transported to the second chamber 201b through the active pump 203. The pressure direction is opposite to the direction of the piston rod 2013's movement speed. The outflow rate of the first chamber 201a is greater than the inflow rate of the second chamber 201b. The pressure value of the first pressure sensor 217 is greater than the pressure value of the second pressure sensor 218. The switching valve 210 is in the left position, the second hydraulic control port E3 is opened, and the second hydraulic check valve 214 is activated. Excess oil that is about to enter the second chamber 201b will flow into the oil tank through the switching valve 210 and the auxiliary pump, thereby driving the auxiliary pump to generate electricity and recover it for reuse, saving energy. At the same time, some excess oil in the second chamber 201b flows into the accumulator 202 through the second hydraulic check valve 214, achieving flow balance between the first chamber 201a and the second chamber 201b. Simultaneously, the potential energy of the load is transferred to the piston 2012, which then drives the active pump 203 to generate electricity through the hydraulic circuit and recover it for reuse, saving energy.

[0064] Based on the above working conditions, the hydrostatic drive system of this application can realize variable displacement control of asymmetric cylinders. The first and second hydraulic pressure reducing valves, auxiliary pump, active pump and accumulator all play the role of energy recovery during operation, optimize system energy consumption, and enable the electro-hydrostatic drive system of this application to have low energy consumption characteristics (energy recovery, overflow optimization).

[0065] For example Figure 1 As shown, in a specific implementation, the electro-hydraulic drive system 200 also includes an isolation device 215, which is used to isolate the communication between the first outlet 203a and / or the second outlet 203b of the active pump 203 and the first chamber 201a and / or the second chamber 201b.

[0066] Specifically, the first outlet 203a and the second outlet 203b of the active pump 203 are respectively connected to the isolation device 215. The isolation device 215 includes at least one isolation valve 216. The isolation valve 216 is electrically connected to the controller 205, and thus the isolation valve 216 receives an electrical signal from the controller 205 to change its position, thereby opening and closing the oil circuit between the hydraulic cylinder 201 and the active pump 203, preventing slippage caused by leakage of the active pump 203. At the same time, it prevents hydraulic shock effects on the drive circuit under sudden load changes, such as emergency stop, rapid unloading, and loading obstacles, ensuring the safety of the drive circuit components. Overall, it has the functions of safety, stability, and improved accuracy.

[0067] Specifically, the isolation valve 216 is a two-position four-way solenoid directional valve, which can isolate the connection between the liquid replenishment device 206 and the accumulator 202. The isolation valve 216 includes a first isolation port F1, a second isolation port F2, a third isolation port F3, and a fourth isolation port F4; the first isolation port F1 is connected to the first outlet 203a of the active pump 203, the second isolation port F2 is connected to the second outlet 203b of the active pump 203, the third isolation port F3 is connected to the first chamber 201a, and the fourth isolation port F4 is connected to the second chamber 201b. When the isolation valve 216 is switched to the first position, the first isolation port F1 is connected to the third isolation port F3 along the internal passage of the isolation valve 216, and the first outlet 203a is connected to the first chamber 201a. When the isolation valve 216 is switched to the second position, the first isolation port F1 is connected to the second isolation port F2 along the internal passage of the isolation valve 216, and the oil passages of the third isolation port F3 and the fourth isolation port F4 are switched on and off. At this time, the switching valve 210 is placed in the neutral position, so that the hydraulic medium in the first chamber 201a and the second chamber 201b cannot flow in or out, and the position of the piston rod 2013 can be stably maintained.

[0068] like Figure 2 As shown, as another embodiment of the isolation device, the isolation device 315 includes an isolation valve 316 and a shuttle valve 317. The isolation valve 316 is electrically connected to the controller 205. The isolation valve 316 receives an electrical signal from the controller 205 and changes its position to realize the connection and disconnection of the oil circuit between the hydraulic cylinder 201 and the active pump 203, thereby avoiding slippage caused by leakage of the active pump 203.

[0069] During normal operation, the shuttle valve 317 on the high-pressure side opens and acts on the hydraulic control unit of the isolation valve 316. At this time, the pressure is adjusted by the electrical control side of the isolation valve 316, and the isolation valve 316 is normally opened and in the upper position.

[0070] When a hydraulic shock effect occurs, the pressure on the high-pressure side of the drive circuit rises sharply, which will act on the hydraulic control unit of the isolation valve. The isolation valve closes and is in the lower position, isolating the drive circuit, thereby protecting the active pump, motor, and accumulator. At the same time, it limits the hydraulic cylinder to ensure the stability and accuracy of the hydraulic cylinder and prevent accidents caused by high-amplitude vibration.

[0071] Once the pressure is released, the controller activates the electromagnetic signal unit to open the isolation valve, restoring the circuit to normal operation.

[0072] The above description is merely a selection of preferred embodiments of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. An electro-hydraulic drive system, comprising: Hydraulic cylinders are used to achieve power output; Accumulators, at least for storing hydraulic fluid; An active pump is used to pump the hydraulic medium in the accumulator into the hydraulic cylinder; An electric motor is used to drive the active pump; A controller, at least for controlling the operation of the motor; Its features are: The hydraulic cylinder includes: a cylinder body, a piston, and a piston rod. The piston is housed in the cylinder body, dividing the internal space of the cylinder body into a first chamber and a second chamber. The piston rod is connected to the piston and located on one side of the second chamber, and can move synchronously with the piston. The piston rod is at least partially disposed outside the cylinder body. The electro-hydraulic drive system further includes: A fluid replenishment device is used to replenish hydraulic medium to one of the first or second chambers when the piston moves, so as to balance the flow on both sides of the piston. The fluid replenishment device also includes: A medium container, used to provide a replenishment space for containing hydraulic medium, separate from the accumulator; An auxiliary pump is used to pump the hydraulic medium in the replenishment space into the first chamber or the second chamber. The auxiliary pump has two operating modes: motor mode and flow balance mode. When the auxiliary pump operates in motor mode, it pumps the hydraulic medium in the replenishment space into the first chamber or the second chamber. When the auxiliary pump operates in flow balance mode, that is, when the flow in the first chamber or the second chamber or the drive circuit is saturated, it recovers the hydraulic medium to the replenishment space. The electro-hydrostatic drive system also includes: A first hydraulically controlled check valve is used to establish a one-way connection between the first outlet of the active pump and the accumulator when the pressure at the first outlet of the active pump is greater than a preset value; the electro-hydraulic drive system further includes: The second hydraulic check valve is used to establish a one-way connection between the second outlet of the active pump and the accumulator when the pressure at the second outlet of the active pump is greater than a preset value. The first and second hydraulically controlled check valves are used to achieve flow balance between the first and second chambers. Since the hydraulically controlled check valves can achieve bidirectional flow through the hydraulic control port, the pressure values ​​of the first and second hydraulically controlled check valves are preset to be equal. When the pressure in the first chamber exceeds the preset pressure value, the second hydraulic control port automatically opens, opening the second hydraulically controlled check valve to regulate the flow and thus achieve flow balance between the first and second chambers. Similarly, when the pressure in the second chamber exceeds the preset pressure value, the first hydraulic control port automatically opens, opening the first hydraulically controlled check valve to regulate the flow and thus achieve flow balance between the first and second chambers. The electro-hydraulic drive system also includes an isolation device for isolating the communication between the first outlet and / or the second outlet of the active pump and the first chamber and / or the second chamber; the accumulator is connected to the inlet of the active pump; the first outlet and the second outlet of the active pump are respectively connected to the isolation device, and the isolation device includes at least one isolation valve.

2. The electro-hydraulic drive system according to claim 1, characterized in that: The fluid replenishment device also includes: A reflux valve is used to connect the replenishment space to the first chamber or the second chamber when the pressure of the hydraulic medium input to the medium container is greater than or equal to a preset value. A switching valve is used at least to switch the connection between the first chamber or the second chamber and the auxiliary pump and the return valve; The cylinder body is equipped with: The first medium channel is connected to the first chamber; the liquid replenishment device further includes: a first hydraulic pressure reducing valve, used to make the first medium channel and the switching valve form a one-way connection when the pressure of the first medium channel is greater than a preset value; The second medium channel is connected to the second chamber; the replenishment device further includes a second hydraulic pressure reducing valve, which is used to establish a one-way connection between the second medium channel and the switching valve when the pressure in the second medium channel is greater than a preset value.

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