An automatically compensating low speed stability control hydraulic system and method of use thereof

Abstract

This invention discloses an automatic compensation low-speed stable control hydraulic system and its usage method, belonging to the technical field of hydraulic control systems. It includes a hydraulic cylinder, a first pipeline, a second pipeline, and a proportional directional valve. A third and fourth pipeline are connected in parallel on the second pipeline. A first relief valve and a first check valve are respectively installed on the third and fourth pipelines. A throttle valve, an automatic compensation valve, and a second check valve are sequentially installed on the fifth pipeline towards the first pipeline. This invention achieves the up-and-down movement of the hydraulic cylinder and adjusts the downward speed by switching the proportional directional valve. The first check valve controls the oil inlet to the cylinder rod chamber, and the first relief valve controls the oil outlet and back pressure adjustment of the cylinder rod chamber. The combination of the throttle valve, automatic compensation valve, and second check valve controls the flow rate to the cylinder rod chamber during low-speed downward movement, achieving stable low-speed downward control. The second relief valve sets a safety pressure, preventing high pressure from being generated in the cylinder rod chamber and causing equipment damage.

Description

Technical Field

[0001] This invention relates to the field of hydraulic system technology, specifically to an automatic compensation low-speed stability control hydraulic system and its usage method. Background Technology

[0002] With the rapid development of hydraulic equipment in China, the hydraulic control systems of large hydraulic presses, large lifting platforms, and isothermal forging presses still rely on traditional control concepts. Both the working and low-speed downward movement of the cylinder are achieved through back pressure discharge from the cylinder rod chamber. During working downward movement, the discharge volume from the rod chamber is relatively large, and the discharge can be stably controlled through the back pressure valve without pressure fluctuations. However, when switching to low-speed downward movement, which is about twenty times slower than the working downward movement, the discharge flow from the rod chamber is very small. Discharge through the back pressure valve cannot be stably controlled, and pressure fluctuations occur. During low-speed operation, the hydraulic cylinder creeps, causing significant equipment vibration. To achieve smooth control of the hydraulic cylinder during low-speed downward movement and completely solve the problem of hydraulic cylinder creep, there is an urgent need to develop an automatic compensation low-speed stable control hydraulic system.

[0003] Especially in large isothermal forging presses, the downward speed and low-speed downward speed of the hydraulic cylinder must be controlled within a single hydraulic system, and rapid switching is required within a single work cycle. This process requirement cannot be adjusted manually. It must be achieved through an automatic compensation low-speed stabilization control hydraulic system. With automatic compensation low-speed stabilization control hydraulic system as its core function, this control method has always been the preferred approach. It utilizes the magnitude of the back pressure discharge pressure in the hydraulic cylinder rod chamber as the opening and closing control of the automatic compensation valve. By compensating the cylinder plug chamber, it increases the discharge flow in the cylinder rod chamber, achieving stable back pressure control and solving the technical problem of vibration caused by cylinder creep during low-speed operation in large isothermal forging presses. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an automatic compensation low-speed stable control hydraulic system and its usage method. This system solves the problems of large isothermal forging press equipment hydraulic systems being unable to achieve automatic compensation control for low-speed operation, complex control oil circuits, unstable speed switching during automatic control, high failure rate, and low production efficiency, thereby improving equipment operating efficiency and control stability.

[0005] To achieve the above objectives, the present invention provides the following solution: An automatic compensation low-speed stability control hydraulic system includes a hydraulic cylinder, a first pipeline with its two ends connected to the cylinder plug chamber and the oil tank port of the hydraulic cylinder, respectively, a second pipeline with its two ends connected to the cylinder rod chamber and the oil pump outlet of the hydraulic cylinder, respectively, and a proportional directional valve disposed on the first pipeline and the second pipeline. A third pipeline and a fourth pipeline are disposed in parallel on the second pipeline. A first relief valve and a first check valve are disposed on the third pipeline and the fourth pipeline, respectively. A fifth pipeline is disposed connecting the first pipeline and the second pipeline. A throttle valve, an automatic compensation valve, and a second check valve are disposed sequentially on the fifth pipeline in the direction closer to the first pipeline.

[0006] Preferably, the connection point between the fifth pipeline and the first pipeline is closer to the hydraulic cylinder relative to the first relief valve.

[0007] Preferably, a sixth pipeline is provided between the automatic compensation valve and the first pipeline.

[0008] Preferably, a seventh pipeline is provided between the first pipeline and the second pipeline. One end of the seventh pipeline is connected to the area between the oil outlet and the proportional directional valve on the second pipeline, and the other end of the first pipeline is connected to the area between the hydraulic cylinder and the sixth pipeline on the first pipeline.

[0009] Preferably, a second overflow valve is provided on the seventh pipeline.

[0010] Preferably, a back pressure valve is also provided between the first pipeline and the oil tank to maintain a back pressure of not less than 0.1 to 0.5 MPa in the first pipeline to prevent gas from entering the plug cavity during the compensation process.

[0011] Preferably, it also includes an auxiliary controller, which receives the displacement sensor or speed sensor signal of the hydraulic cylinder. When the actual speed is detected to be lower than a set threshold and the opening degree of the proportional directional valve is lower than the minimum stable opening degree, the auxiliary controller actively increases the opening frequency or opening time of the automatic compensation valve to form a pulsed compensation flow.

[0012] Preferably, the opening pressure setting of the automatic compensation valve changes linearly with the control signal of the proportional directional valve.

[0013] A method of using an automatic compensation low-speed stability control hydraulic system includes the following steps: The oil pump outlet is connected to the P port of the proportional directional valve through the first pipeline, while ports A, B, P and T are closed. When the hydraulic cylinder moves upward, the oil pump outlet oil enters the P port of the proportional directional valve. Through the proportional directional valve, it connects from port A to port A of the first check valve and port T of the first relief valve. The oil cannot pass through port T of the first relief valve to port P. Instead, the oil passes through port A of the first check valve to port B, connecting to port P of the first relief valve, the cylinder rod chamber, port B of the second check valve, and port P of the second relief valve. Port T of the first relief valve is subjected to pressure from port A of the proportional directional valve. Therefore, port P of the first relief valve cannot connect to port T, and port B of the second check valve cannot connect to port A. The second relief valve is set... When the safety pressure is reached, the P port of the second relief valve cannot be connected to the T port of the second relief valve. At this time, the oil can only enter the cylinder rod chamber to push the hydraulic cylinder to move upward. The oil in the cylinder plug chamber is connected to the A port of the throttle valve and the B port of the proportional directional valve. The A port of the throttle valve is connected to the B port of the throttle valve and then to the P port of the automatic compensation valve and then to the A port of the automatic compensation valve. The A port of the automatic compensation valve is connected to the A port of the second check valve. Because the B port of the second check valve is closed by the hydraulic oil pressure connected to the A port of the proportional directional valve, the A port of the second check valve cannot be connected to the B port of the second check valve. Under the right position function, the B port of the proportional directional valve is connected to the T port of the proportional directional valve and flows back to the oil tank. When the hydraulic cylinder moves downwards, the oil pump outlet enters the P port of the proportional directional valve, and then flows through the proportional directional valve from port B to the cylinder piston chamber and the throttle valve port A. The hydraulic oil pushes the cylinder piston chamber to achieve the downward movement of the hydraulic cylinder. At this time, the cylinder rod chamber is connected to the P port of the second relief valve, the B port of the first check valve, and the P port of the first relief valve. The second relief valve is set with a safety pressure and will not open, so the oil will not flow to the T port of the second relief valve. The B port of the first check valve will not connect to the A port of the first check valve. The first relief valve, according to the set back pressure value, connects its P port to its T port to control the oil discharge from the cylinder rod chamber. The T port of the first relief valve connects to the A port of the proportional directional valve, at which point the proportional directional valve is in its left-position function. The A port of the proportional directional valve connects to its T port and flows back to the oil tank. The throttle valve port A is connected to... The flow is directed to port B of the throttle valve. The size of the throttle orifice is adjusted to control the flow from port A to port B, limiting the maximum flow to the cylinder rod chamber. Port B of the throttle valve is connected to port P of the automatic compensation valve. Port P of the automatic compensation valve is connected to port A of the automatic compensation valve. Port A of the automatic compensation valve is connected to port A of the second check valve. Port A of the second check valve is connected to port B of the second check valve. Port B of the second check valve is connected to port P of the first relief valve. Port Y of the automatic compensation valve is connected to port P of the first relief valve. The pressure value is fed back to the automatic compensation valve, controlling the automatic compensation valve to disconnect port P from port A. The pressure at port P of the first relief valve is connected to port B of the second check valve, causing the second check valve to close. At this time, because the pressure in the cylinder rod chamber is stable and has reached the set value, the automatic compensation valve cuts off the oil from the cylinder plug chamber to the cylinder rod chamber for compensation. When the hydraulic cylinder moves downwards at low speed, the oil pump outlet enters the P port of the proportional directional valve, and then flows through the proportional directional valve from port B to the cylinder piston chamber and the throttle valve port A. The hydraulic oil pushes the cylinder piston chamber to achieve the low-speed downward movement of the hydraulic cylinder. At this time, the cylinder rod chamber is connected to the P port of the second relief valve, the B port of the first check valve, and the P port of the first relief valve. The second relief valve is set with a safety pressure and will not open, so the oil will not flow to the T port of the second relief valve. The B port of the first check valve will not connect to the A port of the first check valve. The first relief valve controls the oil discharge from the cylinder rod chamber by connecting port P to port T according to the set back pressure value. The T port of the first relief valve connects to the A port of the proportional directional valve, at which time the proportional directional valve is in its left-position function. The A port of the proportional directional valve connects to the T port of the proportional directional valve and flows back to the oil tank. The A port of the throttle valve connects to the B port of the throttle valve. The throttle orifice size adjustment controls the flow rate from port A to port B, limiting the maximum flow rate to the cylinder rod chamber for compensation. Port B of the throttle valve is connected to port P of the automatic compensation valve, port P of the automatic compensation valve is connected to port A of the automatic compensation valve, port A of the automatic compensation valve is connected to port A of the second check valve, port A of the second check valve is connected to port B of the second check valve, port B of the second check valve is connected to port P of the first relief valve, and port Y of the automatic compensation valve is connected to port P of the first relief valve. When the pressure is lower than the set value, feedback is sent to the automatic compensation valve, controlling the connection between port P and port A of the automatic compensation valve. At this time, because the pressure in the cylinder rod chamber has not reached the set value, it cannot be stably controlled and is prone to hydraulic cylinder creep, causing vibration. Relying on the automatic compensation valve to connect the oil from the cylinder plug chamber to the cylinder rod chamber for compensation, the cylinder rod chamber has a stable oil flow to reach the set value of the first relief valve.

[0014] Preferably, when the pressure in the cylinder rod chamber exceeds the safety set pressure, the second relief valve opens, the cylinder rod chamber is connected to the P port of the second relief valve, and flows back to the oil tank through the T port of the second relief valve.

[0015] The present invention achieves the following technical effects compared to the prior art: This invention achieves the up-and-down movement of the hydraulic cylinder and adjusts the downward speed by switching the proportional directional valve; controls the oil inlet to the cylinder rod chamber by the first check valve and controls the oil outlet and back pressure adjustment by the first relief valve; controls the flow rate to the cylinder rod chamber to compensate for the low-speed downward movement of the hydraulic cylinder by the combination of the throttle valve, the automatic compensation valve and the second check valve, so as to achieve stable control of the low-speed downward movement; and sets a safety pressure by the second relief valve to prevent high pressure from being generated in the cylinder rod chamber, which could cause equipment damage. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a system schematic diagram of the present invention; Among them, 1. proportional directional valve; 2. first check valve; 3. first relief valve; 4. throttle valve; 5. automatic compensation valve; 6. second check valve; 7. second relief valve; 8. hydraulic cylinder; 9. cylinder plug chamber; 10. cylinder rod chamber; 11. first pipeline; 12. second pipeline; 13. third pipeline; 14. fourth pipeline; 15. fifth pipeline; 16. sixth pipeline; 17. seventh pipeline. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides an automatic compensation low-speed stable control hydraulic system and its usage method, which solves the problems of large isothermal forging press equipment hydraulic system being unable to achieve automatic compensation control for low-speed operation, complex control oil circuit, unstable speed switching during automatic control, high failure rate, and low production efficiency, thereby improving equipment operating efficiency and control stability.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] refer to Figure 1An automatic compensation low-speed stability control hydraulic system includes a hydraulic cylinder 8, a first pipeline 11 with its two ends connected to the cylinder piston chamber 9 and the oil tank opening of the hydraulic cylinder 8 respectively, a second pipeline 12 with its two ends connected to the cylinder rod chamber 10 and the oil pump outlet of the hydraulic cylinder 8 respectively, and a proportional directional valve 1 installed on the first pipeline 11 and the second pipeline 12. A third pipeline 13 and a fourth pipeline 14 are connected in parallel on the second pipeline 12. A first relief valve 3 and a first check valve 2 are installed on the third pipeline 13 and the fourth pipeline 14 respectively. A fifth pipeline 15 is connected between the first pipeline 11 and the second pipeline 12. A throttle valve 4, an automatic compensation valve 5, and a second check valve 6 are sequentially arranged towards the first pipeline 11. This invention uses a proportional directional valve 1 to switch the hydraulic cylinder 8 up and down and adjust its downward speed. The first check valve 2 controls the oil inlet to the cylinder rod chamber 10, and the first relief valve 3 controls the oil outlet and back pressure adjustment of the cylinder rod chamber 10. The combination of the throttle valve 4, automatic compensation valve 5, and second check valve 6 controls the flow to the cylinder rod chamber 10 when the hydraulic cylinder 8 descends at low speed, achieving stable control during low-speed descent. The second relief valve 7 sets a safety pressure, preventing high pressure from being generated in the cylinder rod chamber 10 and thus avoiding equipment damage.

[0022] refer to Figure 1 The connection point between the fifth pipeline 15 and the first pipeline 11 is closer to the hydraulic cylinder 8 than the first relief valve 3; this is to ensure that the compensation oil is not bypassed by the relief valve and is directly and quickly replenished into the cylinder plug chamber 9, while avoiding pressure interference and flow loss, thereby ensuring the effectiveness and stability of low-speed compensation.

[0023] refer to Figure 1 A sixth pipeline 16 is also provided between the automatic compensation valve 5 and the first pipeline 11. The core purpose is to introduce pressure feedback or pilot control so that the automatic compensation valve 5 can dynamically adjust the opening state according to the actual pressure of the cylinder plug chamber 9, thereby improving the accuracy and response speed of compensation. At the same time, it can also realize extended functions such as load sensitivity, anti-oscillation, remote control and fault diagnosis, further enhancing the adaptability and reliability of the low-speed stability control system.

[0024] refer to Figure 1 A seventh pipeline 17 is also provided between the first pipeline 11 and the second pipeline 12. One end of the seventh pipeline 17 is connected to the area between the oil outlet and the proportional directional valve 1 on the second pipeline 12, and the other end of the first pipeline 11 is connected to the area between the hydraulic cylinder 8 and the sixth pipeline 16 on the first pipeline 11.

[0025] refer to Figure 1 A second overflow valve 7 is installed on the seventh pipeline 17.

[0026] Furthermore, a back pressure valve is also provided between the first pipeline 11 and the oil tank to maintain a back pressure of not less than 0.1 to 0.5 MPa in the first pipeline 11, so as to prevent gas from entering the plug cavity during the compensation process.

[0027] Furthermore, it also includes an auxiliary controller that receives signals from the displacement sensor or speed sensor of the hydraulic cylinder 8. When the actual speed is detected to be lower than the set threshold and the opening degree of the proportional directional valve 1 is lower than the minimum stable opening degree, the auxiliary controller actively increases the opening frequency or opening time of the automatic compensation valve 5 to form a pulse-type compensation flow.

[0028] Furthermore, the opening pressure setting of the automatic compensation valve 5 changes linearly with the control signal of the proportional directional valve 1.

[0029] A method of using an automatic compensation low-speed stability control hydraulic system includes the following steps: The oil pump outlet is connected to the P port of the proportional directional valve 1 through the first pipeline 11. At this time, the proportional directional valve 1 is in the neutral position, and ports A, B, P and T are closed. Therefore, the oil connected to the oil pump outlet is sealed inside, and the hydraulic cylinder 8 remains stationary.

[0030] When the hydraulic cylinder 8 moves upward, the right-hand function of the proportional directional valve 1 is activated. The opening degree of the directional valve core is controlled by the magnitude of the signal command. Generally, when speed control is not performed, a 100% command is given. The oil pump outlet oil enters the P port of the proportional directional valve 1, and then connects from the A port of the proportional directional valve 1 to the A port of the first check valve 2 and the T port of the first relief valve 3. The oil cannot pass through the T port of the first relief valve 3 to the P port of the first relief valve 3. The oil passes through the A port of the first check valve 2 to the B port of the first check valve 2, connecting to the P port of the first relief valve 3, the cylinder rod chamber 10, the B port of the second check valve 6, and the P port of the second relief valve 7. The T port of the first relief valve 3 is subjected to pressure from the A port of the proportional directional valve 1. The P port of the first relief valve 3 cannot connect to the T port of the first relief valve 3, and the B port of the second check valve 6 cannot connect to the A port of the second check valve 7. Valve 7 is set with a safety pressure, and the P port of the second relief valve 7 cannot be connected to the T port of the second relief valve 7. At this time, the oil can only enter the cylinder rod chamber 10 to push the hydraulic cylinder 8 to move upward. The oil in the cylinder plug chamber 9 is connected to the throttle valve 4A port and the proportional directional valve 1B port. The throttle valve 4A port is connected to the throttle valve 4B port and then to the automatic compensation valve 5P port, which is connected to the automatic compensation valve 5A port. The automatic compensation valve 5A port is connected to the A port of the second check valve 6. Because the B port of the second check valve 6 is closed by the hydraulic oil pressure connected to the proportional directional valve 1A port, the A port of the second check valve 6 cannot be connected to the B port of the second check valve 6. Under the right-position function, the B port of the proportional directional valve 1 is connected to the T port of the proportional directional valve 1 and flows back to the oil tank. In this way, the pressure oil in the cylinder rod chamber 10 pushes the hydraulic cylinder 8 to move upward quickly. The upward speed is determined by the command of the proportional directional valve 1.

[0031] When the hydraulic cylinder 8 moves downwards, the proportional directional valve 1 operates in its left position. The opening of the directional valve core is controlled by the magnitude of the control signal command. During downward movement, the speed control is given according to the 100% command. The oil pump outlet enters the P port of the proportional directional valve 1, and through the proportional directional valve 1, it connects from the B port to the cylinder plug chamber 9 and the throttle valve 4A port. The hydraulic oil pushes the cylinder plug chamber 9 to achieve the downward movement of the hydraulic cylinder 8. At this time, the cylinder rod chamber 10 is connected to the P port of the second relief valve 7 and the first... The B port of check valve 2 and the P port of the first relief valve 3 are connected. The second relief valve 7 is set with a safety pressure and will not open, so oil will not flow to the T port of the second relief valve 7. The B port of the first check valve 2 will not connect to the A port of the first check valve 2. The first relief valve 3 connects its P port to its T port according to the set back pressure value to control the oil discharge of the cylinder rod chamber 10. The T port of the first relief valve 3 connects to the A port of the proportional directional valve 1. At this time, the proportional directional valve 1 is in its left position and the A port of the proportional directional valve 1 is open. The flow returns to the oil tank via port T of the proportional directional valve 1; port A of throttle valve 4 is connected to port B of throttle valve 4, and the throttle orifice size adjustment controls the flow from port A to port B, limiting the maximum flow to the cylinder rod chamber 10 for compensation; port B of throttle valve 4 is connected to port P of automatic compensation valve 5, port P of automatic compensation valve 5 is connected to port A of automatic compensation valve 5, port A of automatic compensation valve 5 is connected to port A of second check valve 6, and port A of second check valve 6 is connected to port B of second check valve 6. The B port of valve 6 is connected to the P port of the first relief valve 3, and the Y port of the automatic compensation valve 5 is connected to the P port of the first relief valve 3. The pressure value is fed back to the automatic compensation valve 5, controlling the automatic compensation valve 5 to disconnect the P port from the A port. The pressure of the P port of the first relief valve 3 is connected to the B port of the second check valve 6, causing the second check valve 6 to close. At this time, because the pressure in the cylinder rod chamber 10 is stable and has reached the set value, the automatic compensation valve 5 cuts off the oil from the cylinder plug chamber 9 to compensate the cylinder rod chamber 10.

[0032] When the hydraulic cylinder 8 moves downwards at low speed, the proportional directional valve 1 operates in its left position. The opening degree of the directional valve core is controlled by the magnitude of the control signal command. During downward movement, the speed control is given according to the 5% command. The oil pump outlet oil enters the P port of the proportional directional valve 1, and through the proportional directional valve 1, it connects to the cylinder plug chamber 9 and the throttle valve 4A port from the B port. The hydraulic oil pushes the cylinder plug chamber 9 to achieve the low-speed downward movement of the hydraulic cylinder 8. At this time, the cylinder rod chamber 10 is connected to the P port of the second relief valve 7, the B port of the first check valve 2, and the first relief valve. Port P of valve 3 is set with a safety pressure, so the second relief valve 7 will not open. Oil will not flow to port T of the second relief valve 7, and port B of the first check valve 2 will not connect to port A. The first relief valve 3 connects port P to port T according to the set back pressure value to control the oil discharge from cylinder rod chamber 10. Port T of the first relief valve 3 connects to port A of the proportional directional valve 1, at which point the proportional directional valve 1 is in its left-position function. Port A of the proportional directional valve 1 connects to port T of the proportional directional valve 1, flowing back to the oil tank. Port A of the throttle valve 4 is connected... The flow rate from port A to port B of throttle valve 4 is controlled by adjusting the size of the throttle orifice, limiting the maximum flow rate to the cylinder rod chamber 10. Port B of throttle valve 4 is connected to port P of automatic compensation valve 5, port P of automatic compensation valve 5 is connected to port A of automatic compensation valve 5, port A of automatic compensation valve 5 is connected to port A of second check valve 6, port A of second check valve 6 is connected to port B of second check valve 6, port B of second check valve 6 is connected to port P of first relief valve 3, and port Y of automatic compensation valve 5 is connected to first relief valve 3. When the pressure at port P is lower than the set value, feedback is sent to the automatic compensation valve 5, which controls the connection between port P and port A. At this time, because the pressure in the cylinder rod chamber 10 has not reached the set value, it cannot be stably controlled and is prone to causing vibration due to the creeping of the hydraulic cylinder 8. The automatic compensation valve 5 connects the cylinder plug chamber 9 to the cylinder rod chamber 10 to compensate for the oil, so that the cylinder rod chamber 10 has a stable oil flow to reach the set value of the first relief valve 3, which can stabilize the back pressure regulation function and make the hydraulic cylinder 8 stably controlled during low-speed downward movement.

[0033] Preferably, when the pressure in the cylinder rod chamber 10 exceeds the safety set pressure, the second relief valve 7 opens, the cylinder rod chamber 10 is connected to the P port of the second relief valve 7, and flows back to the oil tank through the T port of the second relief valve 7, thereby protecting the cylinder rod chamber 10 from overpressure damage.

[0034] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. An automatic compensation low-speed stability control hydraulic system, characterized in that, The system includes a hydraulic cylinder, a first pipeline with its two ends connected to the cylinder plug chamber and the oil tank opening of the hydraulic cylinder, a second pipeline with its two ends connected to the cylinder rod chamber and the oil pump outlet of the hydraulic cylinder, and a proportional directional valve disposed on the first pipeline and the second pipeline. A third pipeline and a fourth pipeline are disposed in parallel on the second pipeline. A first relief valve and a first check valve are disposed on the third pipeline and the fourth pipeline, respectively. A fifth pipeline is disposed between the first pipeline and the second pipeline. A throttle valve, an automatic compensation valve, and a second check valve are disposed sequentially on the fifth pipeline toward the first pipeline.

2. The automatically compensating low speed stability control hydraulic system of claim 1, wherein, The connection point between the fifth pipeline and the first pipeline is closer to the hydraulic cylinder relative to the first relief valve.

3. The automatically compensating low speed stability control hydraulic system of claim 1, wherein, A sixth pipeline is also provided between the automatic compensation valve and the first pipeline.

4. The automatically compensating low speed stability control hydraulic system of claim 3, wherein, A seventh pipeline is also provided between the first pipeline and the second pipeline. One end of the seventh pipeline is connected to the area between the oil outlet and the proportional directional valve on the second pipeline, and the other end of the first pipeline is connected to the area between the hydraulic cylinder and the sixth pipeline on the first pipeline.

5. The automatically compensating low speed stability control hydraulic system of claim 4, wherein, A second overflow valve is installed on the seventh pipeline.

6. The automatic compensation low-speed stability control hydraulic system according to claim 1, characterized in that, A return oil back pressure valve is also installed between the first pipeline and the oil tank to maintain a back pressure of not less than 0.1 to 0.5 MPa in the first pipeline, so as to prevent gas from entering the plug cavity during the compensation process.

7. The automatically compensating low speed stability control hydraulic system of claim 1, wherein, It also includes an auxiliary controller, which receives signals from the displacement sensor or speed sensor of the hydraulic cylinder. When the actual speed is detected to be lower than a set threshold and the opening degree of the proportional directional valve is lower than the minimum stable opening degree, the auxiliary controller actively increases the opening frequency or opening time of the automatic compensation valve to form a pulse-type compensation flow.

8. The automatically compensating low speed stability control hydraulic system of claim 1, wherein, The opening pressure setting of the automatic compensation valve changes linearly with the control signal of the proportional directional valve.

9. A method of use of an automatic compensation low speed stability control hydraulic system, characterized in that, The automatic compensation low-speed stability control hydraulic system according to any one of claims 1 to 8 includes the following steps: The oil pump outlet is connected to the P port of the proportional directional valve through the first pipeline, while ports A, B, P and T are closed. When the hydraulic cylinder moves upward, the oil pump outlet oil enters the P port of the proportional directional valve. Through the proportional directional valve, it connects from port A to port A of the first check valve and port T of the first relief valve. The oil cannot pass through port T of the first relief valve to port P. Instead, the oil passes through port A of the first check valve to port B, connecting to port P of the first relief valve, the cylinder rod chamber, port B of the second check valve, and port P of the second relief valve. Port T of the first relief valve is subjected to pressure from port A of the proportional directional valve. Therefore, port P of the first relief valve cannot connect to port T, and port B of the second check valve cannot connect to port A. The second relief valve is set... When the safety pressure is reached, the P port of the second relief valve cannot be connected to the T port of the second relief valve. At this time, the oil can only enter the cylinder rod chamber to push the hydraulic cylinder to move upward. The oil in the cylinder plug chamber is connected to the A port of the throttle valve and the B port of the proportional directional valve. The A port of the throttle valve is connected to the B port of the throttle valve and then to the P port of the automatic compensation valve and then to the A port of the automatic compensation valve. The A port of the automatic compensation valve is connected to the A port of the second check valve. Because the B port of the second check valve is closed by the hydraulic oil pressure connected to the A port of the proportional directional valve, the A port of the second check valve cannot be connected to the B port of the second check valve. Under the right position function, the B port of the proportional directional valve is connected to the T port of the proportional directional valve and flows back to the oil tank. When the hydraulic cylinder moves downwards, the oil pump outlet enters the P port of the proportional directional valve, and then flows through the proportional directional valve from port B to the cylinder piston chamber and the throttle valve port A. The hydraulic oil pushes the cylinder piston chamber to achieve the downward movement of the hydraulic cylinder. At this time, the cylinder rod chamber is connected to the P port of the second relief valve, the B port of the first check valve, and the P port of the first relief valve. The second relief valve is set with a safety pressure and will not open, so the oil will not flow to the T port of the second relief valve. The B port of the first check valve will not connect to the A port of the first check valve. The first relief valve, according to the set back pressure value, connects its P port to its T port to control the oil discharge from the cylinder rod chamber. The T port of the first relief valve connects to the A port of the proportional directional valve, at which point the proportional directional valve is in its left-position function. The A port of the proportional directional valve connects to its T port and flows back to the oil tank. The throttle valve port A is connected to... The flow is directed to port B of the throttle valve. The size of the throttle orifice is adjusted to control the flow from port A to port B, limiting the maximum flow to the cylinder rod chamber. Port B of the throttle valve is connected to port P of the automatic compensation valve. Port P of the automatic compensation valve is connected to port A of the automatic compensation valve. Port A of the automatic compensation valve is connected to port A of the second check valve. Port A of the second check valve is connected to port B of the second check valve. Port B of the second check valve is connected to port P of the first relief valve. Port Y of the automatic compensation valve is connected to port P of the first relief valve. The pressure value is fed back to the automatic compensation valve, controlling the automatic compensation valve to disconnect port P from port A. The pressure at port P of the first relief valve is connected to port B of the second check valve, causing the second check valve to close. At this time, because the pressure in the cylinder rod chamber is stable and has reached the set value, the automatic compensation valve cuts off the oil from the cylinder plug chamber to the cylinder rod chamber for compensation. When the hydraulic cylinder moves downwards at low speed, the oil pump outlet enters the P port of the proportional directional valve, and then flows through the proportional directional valve from port B to the cylinder piston chamber and the throttle valve port A. The hydraulic oil pushes the cylinder piston chamber to achieve the low-speed downward movement of the hydraulic cylinder. At this time, the cylinder rod chamber is connected to the P port of the second relief valve, the B port of the first check valve, and the P port of the first relief valve. The second relief valve is set with a safety pressure and will not open, so the oil will not flow to the T port of the second relief valve. The B port of the first check valve will not connect to the A port of the first check valve. The first relief valve controls the oil discharge from the cylinder rod chamber by connecting port P to port T according to the set back pressure value. The T port of the first relief valve connects to the A port of the proportional directional valve, at which time the proportional directional valve is in its left-position function. The A port of the proportional directional valve connects to the T port of the proportional directional valve and flows back to the oil tank. The A port of the throttle valve connects to the B port of the throttle valve. The throttle orifice size adjustment controls the flow rate from port A to port B, limiting the maximum flow rate to the cylinder rod chamber for compensation. Port B of the throttle valve is connected to port P of the automatic compensation valve, port P of the automatic compensation valve is connected to port A of the automatic compensation valve, port A of the automatic compensation valve is connected to port A of the second check valve, port A of the second check valve is connected to port B of the second check valve, port B of the second check valve is connected to port P of the first relief valve, and port Y of the automatic compensation valve is connected to port P of the first relief valve. When the pressure is lower than the set value, feedback is sent to the automatic compensation valve, controlling the connection between port P and port A of the automatic compensation valve. At this time, because the pressure in the cylinder rod chamber has not reached the set value, it cannot be stably controlled and is prone to hydraulic cylinder creep, causing vibration. Relying on the automatic compensation valve to connect the oil from the cylinder plug chamber to the cylinder rod chamber for compensation, the cylinder rod chamber has a stable oil flow to reach the set value of the first relief valve.

10. The method of using an automatic compensating low speed stability control hydraulic system of claim 9, wherein, When the pressure in the cylinder rod chamber exceeds the safety set pressure, the second relief valve opens, and the cylinder rod chamber is connected to the P port of the second relief valve, flowing back to the oil tank through the T port of the second relief valve.

Images