Two-section hydraulic control valve

Abstract

A two-section type hydraulic control valve can accurately balance the pressure difference between an upper cavity part and a lower cavity part through adjustment of a control pipeline. When the runner needs to be cut off, the pressure of the upper cavity part is increased by controlling the adjusting device on the pipeline, and the valve rod device is pushed to drive the piston assembly to move towards the lower cavity part until the runner is completely cut off by the piston assembly, so that the fluid in the runner is effectively cut off. And when the flow channel needs to be conducted, the pressure of the upper cavity part is reduced through the control pipeline, the piston assembly moves towards the upper cavity part under the combined action of the pressure of the fluid in the flow channel and the pressure of the lower cavity part, and the flow channel is conducted again. Due to the two-section type design, the control valve can keep a stable working state under different flow and pressure conditions.

Description

Technical Field

[0001] This utility model relates to the field of valve technology, specifically to a two-stage hydraulic control valve. Background Technology

[0002] Currently available hydraulic control valves suffer from several defects, including valve jamming (failure to activate when check valves are needed), seal leakage, valve position oscillation, and high flow resistance coefficients. These defects reduce the reliability of hydraulic control valves in practical applications, making them unsuitable for scenarios with high fluid control requirements. For example, in some water conservancy projects, valve jamming can affect the normal operation of the entire water system, leading to untimely water flow regulation and even safety accidents. Seal leakage not only wastes water resources but can also pollute the surrounding environment. Valve position oscillation reduces the valve's control accuracy, making it difficult to accurately regulate fluid flow and pressure. A high flow resistance coefficient increases energy consumption in fluid transport, raising operating costs. Utility Model Content

[0003] In view of this, the present invention provides a two-stage hydraulic control valve.

[0004] To achieve the above objectives, this utility model provides the following technical solution:

[0005] A two-stage hydraulic control valve includes a control valve body, within which a valve cavity and a flow channel are formed. A piston assembly is disposed within the valve cavity, dividing the valve cavity into an upper chamber and a lower chamber. The flow channel communicates with the lower chamber. A valve stem device is disposed on the control valve body, one end of which extends into the upper chamber and abuts against the piston assembly, causing the piston assembly to move towards the lower chamber to isolate the flow channel. A control pipeline is disposed on the control valve body, connecting the upper chamber and the lower chamber, and the control pipeline controls the flow rate and pressure within the valve cavity.

[0006] Preferably, the piston assembly includes a piston disc and a sealing plate. The sealing plate is disposed on the end face of the piston disc near the lower cavity. A valve seat is formed by protrusion on the inner wall of the lower cavity. As the piston assembly moves toward the lower cavity, the sealing plate gradually approaches and abuts against the valve seat, forming a sealing connection with the valve seat. The valve stem device extends into the upper cavity and abuts against the piston disc.

[0007] Preferably, a valve stem drive groove is formed by recessing the piston disc on one end face near the valve stem device. One end of the valve stem device extends into the valve stem drive groove and abuts against the piston disc. A return spring is sleeved on the part of the valve stem that extends into the valve stem drive groove. The two ends of the return spring abut against the groove wall of the valve stem drive groove and the inner wall of the upper cavity, respectively.

[0008] Preferably, the piston disc has a frustum-shaped structure on the side near the sealing pressure plate. The frustum-shaped structure has an annular inclined surface. The bottom of the frustum-shaped structure is concave to form a connecting groove. The top of the sealing pressure plate protrudes from the connecting groove to form a connecting end. The connecting end extends into the connecting groove and connects with the piston disc.

[0009] Preferably, the sealing plate has a plate body and a plurality of sheet-like guide portions disposed on the plate body. The guide portions are disposed on one end face of the plate body near the lower cavity. The plurality of guide portions are spaced apart and are trapezoidal or triangular in shape.

[0010] Preferably, the flow channel has an inlet and an outlet, and the control pipeline includes a first branch connecting the inlet and the upper cavity and a second branch connecting the outlet and the upper cavity, with a T-joint connecting the first branch and the second branch.

[0011] Preferably, a ball valve is installed on the first branch, and a check valve and a needle valve are installed sequentially from the upper cavity to the outlet on the second branch.

[0012] Preferably, the valve stem device includes a valve stem body and a handwheel. The valve stem body has a piston drive end and a handwheel connection end. The piston drive end extends into the valve cavity and abuts against the piston assembly. The handwheel is disposed on the handwheel connection end. Rotating the handwheel thereby drives the piston assembly to move downward into the cavity through the valve stem body.

[0013] Preferably, the control valve body includes a valve body and a valve cover, the valve cavity is formed between the valve cavity and the valve cover, a cylinder liner is disposed in the upper cavity, the cylinder liner has a fixing part and a guiding part, the fixing part is formed in an annular structure on the outer wall of the guiding part near the valve cover, the valve cover presses the fixing part onto the valve body, the valve cover and the valve body are fixedly connected by screws, a guiding channel is formed in the guiding part of the cylinder liner, and the piston assembly is disposed in the guiding channel.

[0014] Preferably, a first sealing ring is provided between the piston disc and the sealing pressure plate, a first sealing ring groove is formed on the piston disc, the first sealing ring is disposed in the first sealing ring groove, and the two sides of the first sealing ring are respectively sealed and connected to the inner wall of the first sealing ring groove and the sealing pressure plate. The piston disc and the sealing pressure plate are fixedly connected by screws.

[0015] The beneficial effects of this invention are as follows: By adjusting the control pipeline, the pressure difference between the upper and lower chambers can be precisely balanced. When it is necessary to isolate the flow channel, the pressure in the upper chamber is increased by the adjustment device on the control pipeline, pushing the valve stem device to move the piston assembly towards the lower chamber until the piston assembly completely blocks the flow channel, effectively cutting off the fluid in the flow channel. When it is necessary to open the flow channel, the pressure in the upper chamber is reduced by the control pipeline. Under the combined action of the fluid pressure in the flow channel and the pressure in the lower chamber, the piston assembly moves towards the upper chamber, and the flow channel is reopened. This two-stage design allows the control valve to maintain a stable working state under different flow and pressure conditions. In small flow applications, the control pipeline can be finely adjusted, slightly adjusting the position of the piston assembly to achieve precise control of small flow rates in the flow channel, meeting the requirements of high-precision adjustment for small flow rates. In large flow conditions, the control pipeline can quickly adjust the pressure difference between the upper and lower chambers, causing the piston assembly to move rapidly, achieving rapid opening or closing of the flow channel, ensuring efficient operation of the system at high flow rates. Attached Figure Description

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

[0017] Appendix Figure 1 This is a schematic diagram of the control valve body and control piping;

[0018] Appendix Figure 2 This is a schematic diagram of the control valve body. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] The present invention will now be further described with reference to the accompanying drawings.

[0021] This utility model provides the following technical solution:

[0022] As attached Figure 1-2As shown, this utility model discloses a two-stage hydraulic control valve, including a control valve body 1. The control valve body 1 forms a valve cavity 2 and a flow channel 3. A piston assembly 4 is disposed within the valve cavity 2, dividing the valve cavity 2 into an upper cavity 5 and a lower cavity 6. The flow channel 3 communicates with the lower cavity 6. A valve stem device is disposed on the control valve body 1. One end of the valve stem device extends into the upper cavity 5 and abuts against the piston assembly 4, causing the piston assembly 4 to move towards the lower cavity 6, thus isolating the flow channel 3. A control pipeline 7 is disposed on the control valve body 1, connecting the upper cavity 5 and the lower cavity 6. The control pipeline 7 controls the flow rate and pressure within the valve cavity 2. Specifically, in this design, by adjusting the control pipeline 7, the pressure difference between the upper cavity 5 and the lower cavity 6 can be precisely balanced. When flow channel 3 needs to be isolated, the pressure in the upper chamber 5 is increased by the regulating device on the control line 7, pushing the valve stem device to move the piston assembly 4 towards the lower chamber 6 until the piston assembly 4 completely blocks flow channel 3, effectively cutting off the fluid in flow channel 3. Conversely, when flow channel 3 needs to be opened, the pressure in the upper chamber 5 is reduced by the control line 7. Under the combined action of the fluid pressure in flow channel 3 and the pressure in the lower chamber 6, the piston assembly 4 moves towards the upper chamber 5, reopening flow channel 3. This two-stage design allows the control valve to maintain stable operation under different flow and pressure conditions. In low-flow applications, the control line 7 can be finely adjusted, slightly modifying the position of the piston assembly 4 to achieve precise control of the small flow rate in flow channel 3, meeting the requirements of high-precision regulation at low flow rates. In high-flow situations, the control line 7 can quickly adjust the pressure difference between the upper chamber 5 and the lower chamber 6, causing the piston assembly 4 to move rapidly, quickly opening or closing flow channel 3, ensuring efficient system operation at high flow rates.

[0023] Furthermore, the piston assembly 4 includes a piston disc 8 and a sealing plate 9. The sealing plate 9 is disposed on the end face of the piston disc 8 near the lower cavity 6. A valve seat 10 protrudes from the inner wall of the lower cavity 6. As the piston assembly 4 moves towards the lower cavity 6, the sealing plate 9 gradually approaches and abuts against the valve seat 10, sealing it in contact with the valve seat 10. The valve stem device extends into the upper cavity 5 and abuts against the piston disc 8. Specifically, in this embodiment, when the valve stem device drives the piston disc 8 to move towards the lower cavity 6, the sealing plate 9 approaches the valve seat 10 accordingly. At the moment of contact with the valve seat 10, a tight seal can be quickly formed, effectively preventing fluid leakage in the flow channel 3. At the same time, the edge of the sealing plate 9 is chamfered to avoid scratching the valve seat 10 during movement, extending the service life of the valve seat 10. With the tight fit between the sealing plate 9 and the valve seat 10, the flow channel 3 is completely isolated. At this time, the pressure in the upper cavity 5 remains at a high level, ensuring that the piston assembly 4 is stably in the state of isolating the flow channel 3. Even if the fluid pressure within flow channel 3 fluctuates, the effective isolation remains unaffected due to the strong seal between the sealing plate 9 and the valve seat 10. This combination of piston assembly 4 and valve seat 10 not only ensures effective isolation and conduction of flow channel 3 but also improves the reliability and stability of the control valve. It maintains excellent performance under frequent switching operations and long-term use. Furthermore, the replaceability of the sealing plate 9 and valve seat 10 allows for easy replacement when wear or damage occurs, reducing maintenance costs and downtime.

[0024] Furthermore, a valve stem drive groove 11 is formed by recessing the piston disc 8 on one end face near the valve stem device. One end of the valve stem device extends into the valve stem drive groove 11 and abuts against the piston disc 8. A return spring 12 is fitted on the portion of the valve stem extending into the valve stem drive groove 11. The two ends of the return spring 12 abut against the groove wall of the valve stem drive groove 11 and the inner wall of the upper cavity 5, respectively. Specifically, in this embodiment, when the flow channel 3 needs to be opened, the control pipe 7 reduces the pressure in the upper cavity 5. Under the combined action of the fluid pressure in the flow channel 3 and the pressure in the lower cavity 6, the piston disc 8 is subjected to an upward thrust. At this time, the return spring 12 begins to function, releasing its stored elastic potential energy to assist the piston disc 8 in moving towards the upper cavity 5. During the upward movement of the piston disc 8, the return spring 12 ensures that the valve stem device and the piston disc 8 always maintain good contact and transmission relationship. Even under conditions of large pressure fluctuations, the return spring 12 can buffer the impact of pressure changes on the valve stem device and the piston disc 8, avoiding component damage or jamming caused by instantaneous pressure changes. As the piston disc 8 moves upward, the sealing plate 9 gradually moves away from the valve seat 10, and the flow channel 3 reopens. The return spring 12 continues to function, maintaining the piston disc 8 in the appropriate position and ensuring the flow channel 3 remains stably open. This design with a return spring 12 makes the two-stage hydraulic control valve more stable and reliable during operation, adapting to various complex working environments and changing conditions. Whether it's fine adjustment of small flow rates or rapid opening and closing of large flow rates, the return spring 12 effectively assists the piston assembly 4 in completing the corresponding actions, improving the overall performance and service life of the control valve.

[0025] Furthermore, a frustum-shaped structure 13 is provided on the side of the piston disc 8 near the sealing plate 9. The frustum-shaped structure 13 has an annular inclined surface 14, and the bottom of the frustum-shaped structure 13 is concave to form a connecting groove 15. The top of the sealing plate 9 protrudes corresponding to the connecting groove 15 to form a connecting end 16, which extends into the connecting groove 15 and connects with the piston disc 8. Specifically, in this embodiment, in order to prevent the connection between the sealing plate 9 and the piston disc 8 from loosening due to long-term scouring by the liquid in the flow channel 3, the annular inclined surface 14 of the frustum-shaped structure 13 plays an important buffering role. When the liquid in the flow channel 3 impacts, the annular inclined surface 14 can disperse the impact force of the liquid, reducing the direct pressure on the connection part. Moreover, this frustum-shaped design can also guide the flow of liquid, avoiding the formation of vortices at the connection part, further reducing the risk of loosening of the connection.

[0026] Furthermore, the sealing plate 9 has a plate body 17 and several sheet-like flow guides 18 disposed on the plate body 17. The flow guides 18 are disposed on the end face of the plate body 17 near the lower cavity 6, and are spaced apart. The flow guides 18 are trapezoidal or triangular in shape. Specifically, in this embodiment, the unique shape and spacing of the flow guides 18 play an important role. The trapezoidal or triangular flow guides 18 can effectively guide the flow direction of the fluid in the flow channel 3, allowing the fluid to pass through the flow channel 3 more smoothly. When the fluid flows through the sealing plate 9, the flow guides 18 divide the fluid into multiple small streams. These streams flow in an orderly manner under the guidance of the flow guides 18, reducing turbulence and lowering the resistance to fluid flow. The multiple spaced flow guides 18 also increase the contact area between the fluid and the sealing plate 9, allowing the fluid pressure to be distributed more evenly on the sealing plate 9. This helps improve the sealing effect between the sealing plate 9 and the valve seat 10, preventing fluid leakage at the seal. Even when the fluid pressure in the flow channel 3 is high, the guide part 18 can ensure a tight fit between the sealing plate 9 and the valve seat 10 by properly guiding the fluid and dispersing the pressure.

[0027] Furthermore, the flow channel 3 has an inlet 19 and an outlet 20. The control pipeline 7 includes a first branch 21 connecting the inlet 19 and the upper cavity 5, and a second branch 22 connecting the outlet 20 and the upper cavity 5. A T-joint 23 is provided between the first branch 21 and the second branch 22 for connection. Specifically, in this embodiment, the first branch 21 and the second branch 22 are connected by the T-joint 23, realizing a flexible connection between the inlet 19 and the outlet 20 and the upper cavity 5. When the fluid pressure in the flow channel 3 changes, this connection method enables the upper cavity 5 to obtain the pressure information of the inlet 19 and the outlet 20 in a timely manner. With the flow channel 3 open, the fluid pressure at the inlet 19 is transmitted to the upper chamber 5 via the first branch 21, and the fluid pressure at the outlet 20 is transmitted to the upper chamber 5 via the second branch 22. Through the adjustment of the tee fitting 23, the upper chamber 5 can adjust its pressure according to the pressure difference between the inlet 19 and the outlet 20, ensuring that the piston assembly 4 is in the appropriate position and maintaining the stable flow of the flow channel 3. When it is necessary to cut off the flow channel 3, the adjusting device on the control pipe 7 can precisely control the flow rates of the first branch 21 and the second branch 22 according to the actual pressure conditions of the inlet 19 and the outlet 20, thereby quickly adjusting the pressure in the upper chamber 5, causing the piston assembly 4 to move rapidly and effectively cut off the flow channel 3.

[0028] Furthermore, a ball valve 24 is installed on the first branch 21, and a check valve 25 and a needle valve 26 are sequentially installed on the second branch 22 from the upper cavity 5 to the outlet 20. Specifically, in this embodiment, the ball valve 24 provides a convenient flow control method for the first branch 21. By rotating the ball of the ball valve 24, the first branch 21 can be quickly opened or closed, realizing the on / off control of the fluid flow from the inlet 19 to the upper cavity 5. When it is necessary to inspect or maintain the control valve, the ball valve 24 can be closed to prevent the fluid from the inlet 19 from entering the upper cavity 5, ensuring the safe conduct of maintenance work. At the same time, the ball valve 24 has good sealing performance, which can effectively prevent fluid leakage and ensure the sealing and stability of the entire system. The check valve 25 and the needle valve 26 on the second branch 22 have different functions. The function of the check valve 25 is to prevent fluid backflow. When the fluid in the flow channel 3 flows from the outlet 20 to the upper cavity 5, the check valve 25 allows the fluid to pass in one direction, ensuring that the fluid can only flow towards the upper cavity 5. If the fluid shows a tendency to flow backward, the check valve 25 will quickly close, preventing reverse flow and ensuring the normal operation of the system. The needle valve 26 can finely regulate the flow rate of the second branch 22. The fit between the valve needle and the valve seat 10 of the needle valve 26 is very precise; by rotating the valve needle, the flow rate of the fluid can be accurately controlled. Under different operating conditions, the opening of the needle valve 26 can be adjusted according to actual needs to meet the requirements of the upper cavity 5 for accurate acquisition and pressure adjustment of pressure information from the outlet 20.

[0029] Furthermore, the valve stem device includes a valve stem body 27 and a handwheel 28. The valve stem body 27 has a piston drive end 29 and a handwheel connecting end 30. The piston drive end 29 extends into the valve chamber 2 and abuts against the piston assembly 4. The handwheel 28 is mounted on the handwheel connecting end 30. Rotating the handwheel 28 causes the piston assembly 4 to move towards the lower chamber 6 via the valve stem body 27. Specifically, in this embodiment, rotating the handwheel 28 moves the valve stem body 27, thereby pushing the piston assembly 4 towards the lower chamber 6. This manual operation provides an additional control method for the use of the control valve. In some special cases, such as when the automatic control system malfunctions or when emergency operation is required, the operator can directly rotate the handwheel 28 to isolate or open the flow channel 3. The design of the handwheel 28 makes the operation more intuitive and convenient, allowing the operator to flexibly control the moving distance and speed of the piston assembly 4 according to actual needs. When it is necessary to quickly cut off the flow channel 3, the operator can quickly turn the handwheel 28, causing the valve stem body 27 to rapidly push the piston assembly 4 towards the lower chamber 6, thereby quickly cutting off the flow channel 3. When fine adjustment is required, the operator can slowly turn the handwheel 28 to precisely control the position of the piston assembly 4 to meet the adjustment requirements under different flow and pressure conditions.

[0030] Furthermore, the control valve body 1 includes a valve body 31 and a valve cover 32. The valve cavity 2 is formed between the valve cavity 2 and the valve cover 32. A cylinder sleeve 33 is provided in the upper cavity 5. The cylinder sleeve 33 has a fixing part 34 and a guide part 35. The fixing part 34 is formed in an annular structure on the outer wall of the guide part 35 near the valve cover 32. The valve cover 32 presses the fixing part 34 onto the valve body 31. The valve cover 32 and the valve body 31 are fixedly connected by screws. A guide channel 36 is formed in the guide part 35 of the cylinder sleeve 33. The piston assembly 4 is disposed in the guide channel 36. Specifically, in this embodiment, the cylinder liner 33 is configured to provide guidance for the movement of the piston assembly 4. The piston assembly 4 can move along the guide channel 36 within the cylinder liner 33, thereby preventing the piston assembly 4 from deviating during the movement driven by the valve stem device. The fixing part 34 of the cylinder liner 33 is pressed against the valve body 31 by the valve cover 32, thereby fixing the position of the cylinder liner 33 within the valve cavity 2 and preventing the cylinder liner 33 from loosening.

[0031] Furthermore, a first sealing ring 37 is provided between the piston disc 8 and the sealing pressure plate 9. A first sealing ring groove 38 is formed on the piston disc 8, and the first sealing ring 37 is disposed within the first sealing ring groove 38. The two sides of the first sealing ring 37 are respectively sealed and connected to the inner wall of the first sealing ring groove 38 and the sealing pressure plate 9. The piston disc 8 and the sealing pressure plate 9 are fixedly connected by screws. Specifically, in this embodiment, the edge of the end face of the first sealing ring 37 near the sealing pressure plate 9 protrudes away from the piston disc 8 to form a sealing lip, which has good elasticity. When the sealing pressure plate 9 and the piston disc 8 are fixedly connected by screws, the sealing lip fits tightly against the sealing pressure plate 9, further enhancing the sealing effect between the two. Even when the fluid pressure in the flow channel 3 is high, the sealing lip can effectively prevent fluid leakage from the connection gap between the piston disc 8 and the sealing pressure plate 9. Moreover, this structural design of the sealing lip allows the first sealing ring 37 to better adapt to pressure changes and mechanical vibrations during long-term use, maintaining stable sealing performance.

[0032] Furthermore, a second sealing ring 40 is provided between the piston assembly 4 and the cylinder liner 33. A second sealing ring groove 41 is formed on the piston assembly 4, and the second sealing ring 40 is disposed within the second sealing ring groove 41. The two sides of the second sealing ring 40 are respectively sealed to the inner wall of the second sealing ring groove 41 and the inner wall of the cylinder liner 33. Specifically, in this embodiment, the provision of the second sealing ring 40 further enhances the sealing performance between the piston assembly 4 and the cylinder liner 33. When the piston assembly 4 moves within the guide channel 36 of the cylinder liner 33, the second sealing ring 40 can effectively prevent fluid in the flow channel 3 from leaking into the upper cavity 5 from the gap between the piston assembly 4 and the cylinder liner 33. During the operation of the control valve, the fluid pressure in the flow channel 3 may fluctuate, and the second sealing ring 40, with its good elasticity and sealing performance, can adapt to such pressure changes and always maintain a tight fit with the inner wall of the cylinder liner 33 and the inner wall of the second sealing ring groove 41. Even with frequent movement of the piston assembly 4, the second sealing ring 40 provides both cushioning and sealing, reducing wear between the piston assembly 4 and the cylinder liner 33 and extending their service life. Furthermore, because the second sealing ring 40 is located within the second sealing ring groove 41, its installation position is relatively fixed, making it less prone to displacement or detachment during piston assembly 4 movement, thus ensuring the reliability and stability of the seal. Whether under normal operating conditions or in the event of sudden pressure changes or other abnormal situations, the second sealing ring 40 provides strong protection for the control valve's sealing performance, ensuring the stable operation of the entire system.

[0033] Specifically, the working principle of this design is as follows:

[0034] When handwheel 28 is opened, the opening, closing, and opening / closing time of the valve can be controlled by the needle valve 26 and ball valve 24 on control line 7. With needle valve 26 fully closed and ball valve 24 partially open, the medium flows from right to left through flow channel 3 as indicated by the arrow in the diagram. This medium pushes open the spring, sealing plate 9, and piston disc 8 assembly. The medium in the upper space of piston disc 8 flows away through ball valve 24 on control line 7, causing the valve to open rapidly. If needle valve 26 is opened slowly, the opening speed of the valve can be reduced. Conversely, if ball valve 24 is closed, the medium enters the upper space of piston disc 8 through needle valve 26 and check valve 25 on control line 7, creating a piston effect with the lower space, closing the valve. The closing time of the main valve can be controlled by adjusting the opening degree of ball valve 24.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A two-stage hydraulic control valve, comprising a control valve body, wherein a valve cavity and a flow channel are formed within the control valve body, characterized in that: A piston assembly is installed inside the valve chamber, which divides the valve chamber into an upper chamber and a lower chamber. The flow channel is connected to the lower chamber. A valve stem device is installed on the control valve body. One end of the valve stem device extends into the upper chamber and abuts against the piston assembly, causing the piston assembly to move towards the lower chamber to isolate the flow channel. A control pipeline is installed on the control valve body to connect the upper chamber and the lower chamber. The control pipeline controls the flow rate and pressure in the valve chamber.

2. The two-stage hydraulic control valve according to claim 1, characterized in that: The piston assembly includes a piston disc and a sealing plate. The sealing plate is disposed on the end face of the piston disc near the lower cavity. A valve seat is formed by protrusion on the inner wall of the lower cavity. As the piston assembly moves toward the lower cavity, the sealing plate gradually approaches and abuts against the valve seat, forming a sealing connection with the valve seat. The valve stem device extends into the upper cavity and abuts against the piston disc.

3. The two-stage hydraulic control valve according to claim 2, characterized in that: The piston disc has a concave end face near the valve stem device to form a valve stem transmission groove. One end of the valve stem device extends into the valve stem transmission groove and abuts against the piston disc. A return spring is sleeved on the part of the valve stem that extends into the valve stem transmission groove. The two ends of the return spring abut against the groove wall of the valve stem transmission groove and the inner wall of the upper cavity, respectively.

4. The two-stage hydraulic control valve according to claim 2, characterized in that: The piston disc is provided with a frustum-shaped structure on the side near the sealing pressure plate. The frustum-shaped structure has an annular inclined surface. The bottom of the frustum-shaped structure is concave to form a connecting groove. The top of the sealing pressure plate protrudes from the connecting groove to form a connecting end. The connecting end extends into the connecting groove and connects with the piston disc.

5. The two-stage hydraulic control valve according to claim 2, characterized in that: The sealing plate has a plate body and several sheet-like flow guides disposed on the plate body. The flow guides are disposed on one end face of the plate body near the lower cavity. The flow guides are spaced apart from each other and are trapezoidal or triangular in shape.

6. The two-stage hydraulic control valve according to claim 1, characterized in that: The flow channel has an inlet and an outlet, and the control pipeline includes a first branch connecting the inlet and the upper cavity and a second branch connecting the outlet and the upper cavity. A T-joint is provided between the first branch and the second branch for connection.

7. The two-stage hydraulic control valve according to claim 6, characterized in that: A ball valve is installed on the first branch, and a check valve and a needle valve are installed sequentially from the upper cavity to the outlet on the second branch.

8. The two-stage hydraulic control valve according to claim 1, characterized in that: The valve stem device includes a valve stem body and a handwheel. The valve stem body has a piston drive end and a handwheel connection end. The piston drive end extends into the valve cavity and abuts against the piston assembly. The handwheel is disposed on the handwheel connection end. Rotating the handwheel will drive the piston assembly to move downward into the cavity through the valve stem body.

9. The two-stage hydraulic control valve according to claim 1, characterized in that: The control valve body includes a valve body and a valve cover. The valve cavity is formed between the valve cavity and the valve cover. A cylinder liner is provided in the upper cavity. The cylinder liner has a fixing part and a guiding part. The fixing part is an annular structure protruding from the outer wall of the guiding part near the valve cover. The valve cover presses the fixing part onto the valve body. The valve cover and the valve body are fixedly connected by screws. A guiding channel is formed in the guiding part of the cylinder liner. The piston assembly is disposed in the guiding channel.

10. The two-stage hydraulic control valve according to claim 2, characterized in that: A first sealing ring is provided between the piston disc and the sealing pressure plate. A first sealing ring groove is formed on the piston disc. The first sealing ring is disposed in the first sealing ring groove. Both sides of the first sealing ring are respectively sealed and connected to the inner wall of the first sealing ring groove and the sealing pressure plate. The piston disc and the sealing pressure plate are fixedly connected by screws.

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