An electro-hydraulic speed control valve for a hydraulic support push cylinder in an underground coal mine and its working method

Abstract

This invention discloses an electro-hydraulic speed control valve and its working method for a hydraulic support push cylinder in coal mines, belonging to the technical field of electro-hydraulic speed control valves for hydraulic support push cylinders. It includes an electromagnetic pilot valve and a main valve. The inlet of the main valve is connected to the inlet of the pilot valve and the outlet of the electromagnetic directional valve of the push cylinder. The outlet of the pilot valve is connected to a high-water-based hydraulic system. The outlet of the main valve is connected to the nozzle of the push cylinder. The electromagnetic pilot valve is connected to the main valve through a flow channel outlet. The inlet of the main valve is connected to the inlet of the pilot valve and the outlet of the electromagnetic directional valve of the push cylinder. The outlet of the pilot valve is connected to a high-water-based hydraulic system. The outlet of the main valve is connected to the nozzle of the push cylinder. The electromagnetic pilot valve is a three-way two-way valve controlled by an electromagnet, and the main valve is a spring valve that opens or closes under the pressure of the flow channel outlet of the electromagnetic pilot valve. Its structure is simple, enabling precise control of the movement speed and position of the push cylinder, improving the straightening accuracy of the underground working face, and simultaneously reducing the pressure impact on the push cylinder.

Description

Technical Field

[0001] This invention relates to an electro-hydraulic speed control valve and its working method for a hydraulic support push cylinder in underground coal mines, belonging to the technical field of electro-hydraulic speed control valves for hydraulic support push cylinders. Background Technology

[0002] The construction of intelligent coal mining faces has become a key focus of coal mine intelligentization. However, the straightness control of the working face is the primary factor affecting the efficient and safe operation of intelligent working faces, and it is the most fundamental and critical technology for achieving intelligent working faces. Electro-hydraulic control technology for hydraulic supports has been successfully applied in coal mine production. As the core of the electro-hydraulic control system, the performance of the electro-hydraulic directional valve directly affects the entire support electro-hydraulic control system and even the intelligent production of the entire fully mechanized mining face, making it crucial for safe, high-yield, and intensive coal mine production.

[0003] The pusher cylinder of the hydraulic support is mainly used to push the scraper conveyor and move the hydraulic support during face adjustment. Due to the complex operating load of the hydraulic support pusher cylinder and the coupling between adjacent cylinders, the working medium of the hydraulic system at the working face is a high-water-based fluid. Currently, the pusher cylinder is controlled by an electro-hydraulic directional valve. When the electro-hydraulic directional valve operates, only the valve port is open or closed, making it difficult to achieve precise real-time flow control. The pusher stroke of the hydraulic support relies on visual estimation by on-site personnel, resulting in low face straightening accuracy. After multiple cycles of operation, the machine needs to be stopped for adjustment, significantly impacting coal mine safety and mining efficiency. Furthermore, the cyclical movement of the support and the pusher action at the working face cause frequent on / off switching of the electro-hydraulic directional valve in the existing fluid supply system. The complex and harsh operating conditions of the pusher cylinder, coupled with the rapid and frequent on / off switching of the electro-hydraulic directional valve, inevitably lead to severe pressure fluctuations at the valve port and inside the cylinder, resulting in severe hydraulic shock and easily causing malfunctions and damage to the electro-hydraulic directional valve, pusher cylinder, and related mechanisms. Therefore, there is an urgent need to develop an electro-hydraulic speed control system that can adapt to high water-based media and downhole push cylinder operating conditions, so as to achieve position control and impact pressure buffering of the hydraulic support push cylinder. Summary of the Invention

[0004] Purpose of the invention: Addressing the problems of hydraulic shock and difficulty in speed control in existing hydraulic support push cylinders, this invention proposes an electro-hydraulic speed control valve and its operating method for underground hydraulic support push cylinders in coal mines. The main valve is controlled by an electromagnetic pilot valve, causing the multi-hole throttling orifice on the main valve core to open slowly. The flow area increases proportionally to the number of flow holes on the main valve core, achieving proportional flow regulation and thus precisely controlling the movement speed and position of the push cylinder. After the hydraulic support electromagnetic directional valve opens, the multi-hole throttling orifice opens slowly, allowing high-pressure flow to pass through the multi-hole throttling orifice of the main valve core, reducing pressure shock in the hydraulic system, improving the straightening accuracy of the underground working face, and mitigating pressure shock in the push cylinder. This invention relates to the application of the electro-hydraulic speed control valve for underground hydraulic support push cylinders in coal mines.

[0005] Technical Solution: To achieve the above-mentioned technical objectives, the present invention provides an electro-hydraulic speed control valve for a push cylinder of a hydraulic support in a coal mine, comprising an electromagnetic pilot valve and a main valve. The electromagnetic pilot valve includes a pilot valve outlet and a pilot valve inlet. The main valve includes a main valve inlet and a main valve outlet. The main valve inlet is connected to the pilot valve inlet and the electromagnetic directional valve outlet of the push cylinder. The pilot valve outlet is connected to a high-water-based hydraulic system. The main valve outlet is connected to the oil nozzle of the push cylinder. The electromagnetic pilot valve is connected to the main valve through a flow channel outlet. The main valve inlet is connected to the pilot valve inlet and the electromagnetic directional valve outlet of the push cylinder. The pilot valve outlet is connected to a high-water-based hydraulic system. The main valve outlet is connected to the oil nozzle of the push cylinder.

[0006] The electromagnetic pilot valve is a three-way two-way valve controlled by an electromagnet. The electromagnetic pilot valve is controlled by an electromagnet to select whether the pilot valve outlet or the pilot valve inlet is connected to the electromagnetic pilot valve flow channel outlet.

[0007] The main valve is a spring valve that is opened or closed by the outlet pressure of the solenoid pilot valve. When the outlet pressure of the solenoid pilot valve is greater than the threshold of the spring valve, the main valve is connected to the main valve inlet and the main valve outlet. When the outlet pressure of the solenoid pilot valve is less than the threshold of the spring valve, the main valve is closed to the main valve inlet and the main valve outlet.

[0008] Furthermore, the electromagnetic pilot valve includes an electromagnetic pilot valve block, within which a pilot valve chamber is laterally arranged. Within the pilot valve chamber, a double-ball valve core structure capable of left and right movement is provided. The pilot valve chamber is designed in a left-right direction, with a three-stage variable diameter structure from small to large on both sides. Within the three-stage variable diameter pilot valve chamber, from right to left, are arranged a valve seat, ball valve seat II, and ball valve seat III. The pilot valve inlet communicates with the pilot valve chamber at ball valve seat I, and the pilot valve outlet communicates with the pilot valve chamber at ball valve seat III. The flow channel outlet connecting the electromagnetic pilot valve to the main valve communicates with the pilot valve chamber at ball valve seat II. The left side of the valve seat has a spring groove for mounting spring I. The ball valve seat I is mounted in the spring groove via spring I. Between ball valve seat I and ball valve seat II... A ball valve core I is provided, and a ball valve seat II is located between a ball valve seat II and a ball valve seat III. A push rod I is provided between the ball valve core I and the ball valve core II, passing through the ball valve seat II. Both ends of the ball valve seat II are provided with flow channels communicating with the flow channel outlet. A valve core push rod II is provided inside the ball valve seat III. The right side of the valve core push rod II is in contact with the ball valve core II, and the left side of the valve core push rod II is pressed against the electromagnet under the action of spring I. There is no mechanical connection between the two. The electromagnet pushes the ball valve core II, and the ball valve core II pushes the ball valve core I through the push rod I, thus opening the flow channel blocked by the ball valve core I. At this time, the pilot valve inlet is connected to the flow channel outlet. When the electromagnet stops pushing, the ball valve core I pushes the push rod I to move under the action of spring I, thereby disconnecting the flow channel outlet from the pilot valve inlet and connecting the pilot valve outlet.

[0009] Furthermore, sealing rings are provided between push rod I and ball valve seat III, between ball valve seat III and electromagnetic pilot valve block, between ball valve seat II and electromagnetic pilot valve block, and between valve seat and electromagnetic pilot valve block.

[0010] Furthermore, the main valve includes a main valve block, within which a main valve chamber runs vertically upwards. A main valve end cap, sealing the main valve chamber, is located at the lower end of the main valve block. A damping orifice is located at the top of the main valve block. The flow channel outlet of the electromagnetic pilot valve is connected to the damping orifice on the main valve. A main valve core, capable of vertical movement, is located within the main valve chamber. A main valve sleeve is located on the outer side of the main valve core and the inner side of the main valve chamber. The main valve inlet and outlet are connected to the main valve block and the main valve sleeve, and are in contact with the main valve core. A connecting cavity, facilitating communication between the main valve inlet and outlet, is located within the main valve core. A spring cavity is located at the bottom of the main valve core, and a connection is provided between the end cap and the main valve end cap within the spring cavity. A main valve spring is provided, and a flow channel connecting the conduction cavity and the spring cavity is provided on the axis. The top of the conduction cavity is provided with a main valve plug, and multiple main valve core inlets matching the main valve inlet are opened on the side of the top of the conduction cavity. The bottom of the conduction cavity is provided with a multi-hole throttling orifice matching the main valve outlet. When the main valve core moves to the upper position of the main valve cavity, the conduction cavity is not connected to the main valve inlet and the main valve outlet. When the main valve core moves to the lower position of the main valve cavity, the conduction cavity is connected to the main valve inlet and the main valve outlet. The area of ​​the main valve plug on the upper side of the main valve core, which serves as the high water-based liquid action surface, is larger than the high water-based liquid action area on the lower side of the main valve core.

[0011] Furthermore, the inlet diameter of the main valve core meets the requirements for the flow of high-water-based liquids, and the diameter of the multi-hole throttling orifice is 1-3mm. Under high flow rates, the number of flow holes on the multi-hole throttling orifice gradually increases, thereby achieving flow regulation.

[0012] Furthermore, a displacement sensor for measuring the position of the main valve core is connected to the lower end of the valve core.

[0013] Furthermore, the main valve sleeve is equipped with a sealing ring for sealing the high-pressure liquid; the outer diameter of the main valve core is respectively provided with guide band 1 and guide band 2 to prevent the valve core from eccentric wear after being subjected to eccentric load; a sealing ring is provided between the main valve core and the main valve sleeve to prevent leakage of high-pressure high-water-based liquid; the main valve end cover is connected to the bottom end of the main valve block by bolts; a leakage port is machined on the main valve end cover to prevent liquid trapping during the movement of the main valve core.

[0014] A method for operating an electro-hydraulic speed control valve for a hydraulic support push cylinder in an underground coal mine includes the following steps:

[0015] When the electro-hydraulic speed control valve of the hydraulic support push cylinder in the coal mine is closed, the electromagnet is not energized. The main valve spring causes the main valve core to move to the uppermost side of the main valve cavity. High water-based liquid with working pressure P enters both the main valve inlet and the pilot valve inlet. The main valve core inlet and the main valve inlet are isolated, and the multi-hole throttling port is isolated from the main valve outlet. At this time, the high water-based liquid with working pressure P enters the cavity where the ball valve core I is located through the pilot valve inlet and the flow channel on the electromagnetic pilot valve block. Under the action of hydraulic pressure, the ball valve core I is pressed against the ball valve seat II. The ball valve seat II is disengaged from the ball valve core II by the push rod I. The high water-based liquid with working pressure P cannot enter the damping orifice through the electromagnetic pilot valve. The damping orifice is connected to the pilot valve outlet through the flow channel on the ball valve seat II. The high water-based liquid pressure on the right side of the main valve core I is zero. At this time, the electro-hydraulic speed control valve of the hydraulic support push cylinder in the coal mine is completely closed, and the hydraulic support push cylinder is stationary.

[0016] When the electromagnet is energized, the valve core push rod II is pushed by the electromagnetic force of the electromagnet to push the ball valve core II. The ball valve core II is pressed against the ball valve seat II, and the damping orifice is isolated from the pilot valve outlet. At the same time, the ball valve core II pushes the push rod I to move, further opening the ball valve core I. At this time, the high-pressure water-based liquid with working pressure P flows through the valve port at the ball valve core I and the flow channel on the ball valve seat II into the damping orifice. At this time, the high-pressure high-pressure water-based liquid overcomes the main valve spring and pushes the main valve core downward. The main valve core inlet is connected to the main valve inlet, and as the main valve core moves downward, the flow rate gradually increases. At the same time, the multi-hole throttling orifice is also gradually connected to the main valve outlet. During this process, the number of multi-hole throttling orifices connected to the main valve outlet increases linearly to avoid the violent impact pressure caused by the instantaneous maximum flow rate of the high-pressure water-based liquid, thus improving the efficiency. Controllability of the pusher cylinder position: High-pressure high-water-based fluid flows into the pusher cylinder from the main valve outlet through the main valve core inlet and the multi-hole throttling port. The flow rate of the pusher cylinder is controlled by the number of flow holes on the multi-hole throttling port, which can accurately control the movement speed and position of the pusher cylinder, improve the straightening accuracy of the downhole working face, and at the same time reduce the pressure shock of the pusher cylinder. After the electromagnetic reversing valve in the hydraulic system of the hydraulic support pusher cylinder is opened, the high-pressure high-water-based fluid enters the pusher cylinder through the main valve core inlet and the multi-hole throttling port. At this time, the main valve core inlet and the multi-hole throttling port are equivalent to two hydraulic dampers in the hydraulic system. The main valve core inlet has a larger diameter and smaller damping, while the multi-hole throttling port has a smaller diameter and larger damping, which can effectively reduce the pressure shock of the high-water-based fluid.

[0017] High-pressure high-water-based liquid enters the lower side of the main valve core through the flow channel on the axis of the main valve core. The high-water-based liquid action area on the upper side of the main valve core is larger than that on the lower side of the main valve core. When the main valve core is subjected to downward liquid pressure, it moves downward. The hydraulic pressure on the upper side of the main valve core must overcome the spring force of the main valve spring, the friction of the sealing ring on the main valve core, guide belt 1, guide belt 2, and the hydraulic pressure on the lower side of the main valve core.

[0018] Furthermore, the displacement of the main valve core is dynamically measured by a displacement sensor. The hydraulic system controls the valve opening of the electro-hydraulic speed control valve of the underground hydraulic support push cylinder by controlling whether the electromagnet of the electromagnetic pilot valve is energized. When the main valve core moves, a leakage port is machined on the main valve end cover to prevent fluid from being trapped in the closed space formed by the main valve core, the main valve end cover, and the main valve sleeve.

[0019] Beneficial Effects: This invention achieves flow control and pressure buffering for the pusher cylinder. By controlling the displacement of the main valve core through an electromagnetic pilot valve, the flow area of ​​the multi-hole throttling orifice is controlled, thus achieving flow control of the pusher cylinder and ultimately precisely controlling the speed of the hydraulic support pusher cylinder. This improves the straightening accuracy of the scraper conveyor and hydraulic support in the fully mechanized mining face. The displacement sensor of the main valve core provides real-time feedback on the position of the main valve core, improving the position control accuracy of the main valve core. When the pusher cylinder operates, the multi-hole throttling orifice slowly opens, allowing flow into the pusher cylinder, effectively reducing the instantaneous pressure impact in the working chamber of the pusher cylinder. Simultaneously, the electro-hydraulic speed control valve for the pusher cylinder of the underground hydraulic support in this invention allows for a certain degree of leakage, reducing the machining accuracy requirements of the main valve core and valve sleeve. This invention is applicable to the speed regulation and pressure buffering of the pusher cylinder of the underground hydraulic support in coal mines, achieving straightening accuracy control and reducing hydraulic shock during the pusher process in the working face. Attached Figure Description

[0020] Figure 1 This is a structural diagram of the closed state of the electro-hydraulic speed control valve of the underground hydraulic support push cylinder in an embodiment of the present invention.

[0021] Figure 2 This is a structural diagram of the open state of the electro-hydraulic speed control valve for the push cylinder of an underground hydraulic support in a coal mine, according to an embodiment of the present invention.

[0022] In the diagram, 1. Ball valve core I, 2. Ball valve seat I, 3. Electromagnetic pilot valve block, 4. Spring I, 5. Valve seat, 6. Ball valve seat II, 7. Push rod I, 8. Ball valve core II, 9. Ball valve seat III, 10. Valve core push rod II, 11. Electromagnet, 12. Damping orifice, 13. Main valve plug, 14. Main valve core, 15. Main valve sleeve, 16. Main valve block, 17. Main valve core inlet, 18. Multi-hole throttling orifice, 19. Main valve spring, 20. Main valve end cap, 21. Bolt, 22. Displacement sensor. Detailed Implementation

[0023] The invention will now be explained in further detail with reference to the accompanying drawings.

[0024] like Figure 1 and Figure 2As shown, the present invention discloses an electro-hydraulic speed control valve for a hydraulic support push cylinder in a coal mine. It comprises an electromagnetic pilot valve and a main valve. The electromagnetic pilot valve includes a ball valve core I1, a ball valve seat I2, an electromagnetic pilot valve block 3, a spring I4, a valve seat 5, a ball valve seat II6, a push rod I7, a ball valve core II8, a ball valve seat III9, a valve core push rod II10, and an electromagnet 11. The main valve includes a damping orifice 12, a main valve plug 13, a main valve core 14, a main valve sleeve 15, a main valve block 16, a main valve core inlet 17, a multi-hole throttling orifice 18, a main valve spring 19, a main valve end cap 20, a bolt 21, and a displacement sensor 22.

[0025] The electromagnet 11 is mounted on the electromagnetic pilot valve block 3. The valve core push rod II 10, ball valve seat III 9, ball valve core II 8, push rod I 7, ball valve seat II 6, ball valve core I 1, ball valve seat I 2, spring I 4, and valve seat 5 are sequentially installed inside the electromagnetic pilot valve block 3. Sealing rings are provided between push rod I 7 and ball valve seat III 9, between ball valve seat III 9 and electromagnetic pilot valve block 3, between ball valve seat II 6 and electromagnetic pilot valve block 3, and between valve seat 5 and electromagnetic pilot valve block 3.

[0026] The damping hole 12 is installed in the end hole of the main valve block 16, and the main valve sleeve 15 is installed in the hole of the main valve block 16. The main valve sleeve 15 is equipped with a sealing ring for sealing high-pressure liquid. The main valve plug 13 is installed on the main valve core 14 by threaded connection. The main valve core 14 is installed in the hole of the main valve sleeve 15. At the same time, the guide band 1 and the guide band 2 are installed on the outer circle of the main valve core 14 to prevent the valve core 14 from eccentric wear after being subjected to eccentric load. A sealing ring is provided between the main valve core 14 and the main valve sleeve 15 to prevent leakage of high-pressure high-water-based liquid. The displacement sensor 22 is installed at the end of the main valve core 14 to measure the displacement of the main valve core 14. The main valve spring 19 is installed in the hole of the main valve core 14. The main valve end cover 20 is installed on the main valve block 16 by bolts 21. The main valve end cover 20 is machined with a leakage port to prevent liquid trapping during the movement of the main valve core 14.

[0027] The main valve block 15 is machined with a main valve inlet and a main valve outlet, and the electromagnetic pilot valve block 3 is machined with a pilot valve inlet and a pilot valve outlet. The main valve inlet is connected to the pilot valve inlet and the electromagnetic directional valve outlet of the push cylinder. The pilot valve outlet is connected to the high-water-based hydraulic system, and the main valve outlet is connected to the oil nozzle of the push cylinder. The flow channel outlet of the electromagnetic pilot valve is connected to the damping orifice 12 on the main valve.

[0028] Combination Figure 1The working principle of the electro-hydraulic speed control valve for the push cylinder of a hydraulic support in a coal mine, as described in this invention, in its closed state is explained in detail. When the electro-hydraulic speed control valve for the push cylinder of the hydraulic support in a coal mine is in the closed state, the electromagnet 11 is not energized. Under the action of the main valve spring 19, the main valve core 14 moves to its uppermost position. The hydraulic system working pressure P simultaneously enters the main valve inlet and the pilot valve inlet. The main valve core inlet 17 is isolated from the main valve inlet, and the multi-hole throttling port 18 is isolated from the main valve outlet. At this time, the high-water-based fluid with working pressure P enters the upper part of the ball valve core I1 through the flow channel on the pilot valve inlet and the electromagnetic pilot valve block 3. In the cavity, under the action of hydraulic pressure, the ball valve core I1 is pressed onto the ball valve seat II6. The ball valve seat II6 is disengaged from the ball valve core II8 by the push rod I7. The high water-based liquid with working pressure P cannot enter the damping orifice 12 through the electromagnetic pilot valve. At this time, the damping orifice 12 is connected to the pilot valve outlet through the flow channel on the ball valve seat II. The high water-based liquid pressure on the right side of the main valve core 14 is zero. At this time, the electro-hydraulic speed control valve of the hydraulic support push cylinder in the coal mine is completely closed, and the hydraulic support push cylinder is stationary.

[0029] Combination Figure 2 The working principle of the electro-hydraulic speed control valve for the push cylinder of a hydraulic support in a coal mine is described in detail below. When the electromagnet 11 is energized, the valve core push rod II 10 is pushed by the electromagnet 11 to push the ball valve core II 8. The ball valve core II 8 is pressed against the ball valve seat II 6, and the damping orifice 12 is isolated from the pilot valve outlet. At the same time, the ball valve core II 8 pushes the push rod I 7 to move, further opening the ball valve core I 1. At this time, the high-pressure water-based liquid with working pressure P flows through the valve port at the ball valve core I 1 and the flow channel on the ball valve seat II 6 into the damping orifice 12. At this time, the high-pressure high-pressure water-based liquid pushes the main valve core 14 downward. The main valve core inlet 17 is connected to the main valve inlet, and the flow area gradually increases. The multi-hole throttling orifice 18 is also connected to the main valve outlet. The number of through-holes increases proportionally. High-pressure high-water-based liquid flows into the push cylinder from the main valve outlet through the main valve core inlet 17 and the multi-hole throttling port 18. The flow rate of the push cylinder is controlled by the number of through-holes on the multi-hole throttling port 18. At the moment the electromagnetic directional valve in the hydraulic system of the hydraulic support push cylinder opens, the high-pressure high-water-based liquid enters the push cylinder after passing through the main valve core inlet 17 and the multi-hole throttling port 18 of the electro-hydraulic speed control valve of the underground hydraulic support push cylinder. The main valve core inlet 17 and the multi-hole throttling port 18 can be equivalent to two hydraulic damping points, which can effectively reduce the pressure impact of the high-water-based liquid.

[0030] At the same time, the high-pressure high-water-based liquid enters the lower side of the main valve core 14 through the hole on the axis of the main valve core 14. The high-water-based liquid action area on the upper side of the main valve core 14 is larger than that on the lower side of the main valve core 14. The hydraulic pressure on the upper side of the main valve core 14 must overcome the spring force of the main valve spring 19, the friction of the sealing ring on the main valve core 14, the guide belt 1, the guide belt 2, and the hydraulic pressure on the lower side of the main valve core 14.

[0031] The displacement of the main valve core 14 is dynamically measured by the displacement sensor 22. The hydraulic system controller controls whether the electromagnet 11 of the electromagnetic pilot valve is energized, thereby controlling the valve opening of the electro-hydraulic speed control valve of the coal mine underground hydraulic support push cylinder of the present invention.

[0032] When the main valve core 14 moves, in order to prevent liquid from being trapped in the closed space formed by the main valve core 14, the main valve end cover 20, and the main valve sleeve 15, a leakage port is machined on the main valve end cover 20.

Claims

1. An electro-hydraulic speed control valve for a hydraulic support push cylinder in an underground coal mine, characterized in that: It includes an electromagnetic pilot valve and a main valve. The electromagnetic pilot valve includes a pilot valve outlet and a pilot valve inlet. The main valve includes a main valve inlet and a main valve outlet. The main valve inlet is connected to the pilot valve inlet and the electromagnetic directional valve outlet of the push cylinder. The pilot valve outlet is connected to a high-water-based hydraulic system. The main valve outlet is connected to the oil nozzle of the push cylinder. The electromagnetic pilot valve is connected to the main valve through the flow channel outlet. The electromagnetic pilot valve is a three-way two-way valve controlled by an electromagnet (11). The electromagnetic pilot valve is controlled by an electromagnet (11) to achieve the selection of the pilot valve outlet or pilot valve inlet and the electromagnetic pilot valve flow channel outlet. The main valve is a spring valve that is opened or closed by the outlet pressure of the solenoid pilot valve. When the outlet pressure of the solenoid pilot valve is greater than the threshold of the spring valve, the main valve is connected to the main valve inlet and the main valve outlet. When the outlet pressure of the solenoid pilot valve is less than the threshold of the spring valve, the main valve is closed to the main valve inlet and the main valve outlet. The main valve includes a main valve block (16), which has a main valve chamber running vertically. The main valve block (16) has a main valve end cap (20) at its lower end that blocks the main valve chamber. The main valve block (16) has a damping hole (12) at its top. The flow outlet of the electromagnetic pilot valve is connected to the damping hole (12) on the main valve. The main valve chamber has a main valve core (14) that can move vertically. The outer side of the main valve core (14) and the inner side of the main valve chamber have a main valve sleeve (15). The main valve inlet and the main valve outlet are connected to the main valve block (16) and the main valve sleeve (15) and are in contact with the main valve core (14). The main valve core (14) has a connecting cavity for communicating the main valve inlet and the main valve outlet. The bottom of the main valve core (14) has a spring cavity. The spring cavity has an end cap. A main valve spring (19) is provided between the main valve part and the main valve end cover (20), and a flow channel connecting them is provided on the axis between the conduction cavity and the spring cavity; a main valve plug (13) is provided in the top of the conduction cavity, and multiple main valve core liquid inlets (17) matching the main valve inlet are opened on the side of the top of the conduction cavity, and a multi-hole throttling port (18) matching the main valve outlet is opened on the side of the bottom of the conduction cavity. When the main valve core (14) moves to the upper position of the main valve cavity, the conduction cavity is not connected with the main valve inlet and the main valve outlet. When the main valve core (14) moves to the lower position of the main valve cavity, the conduction cavity is connected with the main valve inlet and the main valve outlet. The area of ​​the main valve plug (13) on the upper side of the main valve core (14) as the high water-based liquid action surface is larger than the high water-based liquid action area on the lower side of the main valve core (14).

2. The electro-hydraulic speed control valve for the push cylinder of a hydraulic support in an underground coal mine according to claim 1, characterized in that: The electromagnetic pilot valve includes an electromagnetic pilot valve block (3), and a pilot valve chamber is provided laterally inside the electromagnetic pilot valve block (3). The pilot valve chamber is provided with a double ball valve core structure that can move left and right. The pilot valve chamber is designed in a left-right direction. The left and right sides of the pilot valve chamber are designed as a three-stage variable diameter structure from small to large. The pilot valve chamber of the three-stage variable diameter structure is provided with valve seat (5), ball valve seat II (6) and ball valve seat III (9) in sequence from right to left. The pilot valve inlet is located at the ball valve seat I (2). The pilot valve chamber is connected, the pilot valve outlet is connected to the pilot valve chamber at ball valve seat Ⅲ (9), and the flow channel outlet of the electromagnetic pilot valve connected to the main valve is connected to the pilot valve chamber at ball valve seat Ⅱ (6); wherein the left side of the valve seat (5) is provided with a spring groove for installing spring Ⅰ (4), and the spring groove is used to install ball valve seat Ⅰ (2) through spring Ⅰ (4). A ball valve core Ⅰ (1) is provided between ball valve seat Ⅰ (2) and ball valve seat Ⅱ (6), and ball valve seat Ⅱ (6) and ball valve seat Ⅲ (9) are connected. 9) A ball valve core II (8) is provided between the ball valve core I (1) and the ball valve core II (8). A push rod I (7) is provided between the ball valve core I (1) and the ball valve core II (8). Both ends of the ball valve seat II (6) are provided with flow channels that communicate with the flow channel outlet. A valve core push rod II (10) is provided inside the ball valve seat III (9). The right side of the valve core push rod II (10) is in contact with the ball valve core II (8). The left side of the valve core push rod II (10) is pressed on the electromagnet (11) under the action of the spring I (4). There is no mechanical connection between the two. The electromagnet (11) pushes the ball valve core II (8), and the ball valve core II (8) pushes the ball valve core I (1) through the push rod I (7) to open the flow channel blocked by the ball valve core I (1). At this time, the pilot valve inlet is connected to the flow channel outlet. When the electromagnet (11) stops pushing, the ball valve core I (1) pushes the push rod I (7) to move under the action of the spring I (4), thereby disconnecting the pilot valve inlet from the flow channel outlet and connecting the pilot valve outlet.

3. The electro-hydraulic speed control valve for the push cylinder of a hydraulic support in an underground coal mine according to claim 2, characterized in that: A sealing ring is provided between push rod I (7) and ball valve seat III (9), between ball valve seat III (9) and electromagnetic pilot valve block (3), between ball valve seat II (6) and electromagnetic pilot valve block (3), and between valve seat (5) and electromagnetic pilot valve block (3).

4. The electro-hydraulic speed control valve for the push cylinder of a coal mine underground hydraulic support according to claim 1, characterized in that: The diameter of the main valve core inlet (17) meets the requirements for the flow of high water-based liquid. The diameter of the multi-hole throttling port (18) is 1~3mm. Under high flow rate, the number of flow holes on the multi-hole throttling port (18) gradually increases, thereby achieving flow regulation.

5. The electro-hydraulic speed control valve for the push cylinder of a hydraulic support in an underground coal mine according to claim 2, characterized in that: The main valve core (14) is connected to a displacement sensor (22) at its lower end to measure its position.

6. The electro-hydraulic speed control valve for the push cylinder of a coal mine underground hydraulic support according to claim 5, characterized in that: The main valve sleeve (15) is equipped with a sealing ring for sealing high-pressure liquid; the outer diameter of the main valve core (14) is provided with guide belt 1 and guide belt 2 to prevent the main valve core (14) from eccentric wear after being subjected to eccentric load; a sealing ring is provided between the main valve core (14) and the main valve sleeve (15) to prevent leakage of high-pressure high-water-based liquid; the main valve end cover (20) is connected to the bottom end of the main valve block (16) by bolts (21); a leakage port is machined on the main valve end cover (20) to prevent liquid trapping during the movement of the main valve core (14).

7. A method for operating the electro-hydraulic speed control valve for the push cylinder of a coal mine underground hydraulic support according to claim 6, characterized in that... The steps are as follows: When the electro-hydraulic speed control valve of the hydraulic support push cylinder in the coal mine is closed, the electromagnet (11) is not energized. The main valve spring (19) causes the main valve core (14) to move to the uppermost side of the main valve cavity. The high water-based liquid with working pressure P enters the main valve inlet and the pilot valve inlet at the same time. The main valve core inlet (17) is isolated from the main valve inlet, and the multi-hole throttling port (18) is isolated from the main valve outlet. At this time, the high water-based liquid with working pressure P enters the cavity where the ball valve core I (1) is located through the pilot valve inlet and the flow channel on the electromagnetic pilot valve block (3). Under the action of hydraulic pressure, the ball valve core I (1) is pressed on the ball valve seat II (6), and the ball valve seat II (6) is disengaged from the ball valve core II (8) by the action of the push rod I (7). The high water-based liquid with working pressure P cannot enter the damping hole (12) through the electromagnetic pilot valve. At this time, the damping hole (12) is connected to the pilot valve outlet through the flow channel on the ball valve seat II (6). The high water-based liquid pressure on the right side of the main valve core (14) is zero. At this time, the electro-hydraulic speed control valve of the hydraulic support push cylinder in the coal mine is completely closed, and the hydraulic support push cylinder is stationary. When the electromagnet (11) is energized, the valve core push rod II (10) is pushed by the electromagnetic force of the electromagnet (11) to push the ball valve core II (8). The ball valve core II (8) is pressed onto the ball valve seat II (6), and the damping hole (12) is isolated from the pilot valve outlet. At the same time, the ball valve core II (8) pushes the push rod I (7) to move, further opening the ball valve core I (1). At this time, the high water-based liquid with working pressure P flows through the valve port at the ball valve core I (1) and enters the damping hole (12) through the flow channel on the ball valve seat II (6). At this time, the high-pressure high water-based liquid overcomes the main valve spring (19) and pushes the main valve core (14) downward. The main valve core inlet (17) is connected to the main valve inlet, and as the main valve core (14) moves downward, the flow rate gradually increases. At the same time, the multi-hole throttling port (18) is also gradually connected to the main valve outlet. During this process, the number of multi-hole throttling ports (18) connected to the main valve outlet increases linearly to avoid the instantaneous flow of the high water-based liquid. The high pressure of the push cylinder is maximized, which improves the controllability of the position of the push cylinder. The high pressure high water base liquid flows into the push cylinder from the main valve outlet through the main valve core inlet (17) and the multi-hole throttle port (18). The flow rate of the push cylinder is controlled by the number of flow holes on the multi-hole throttle port (18). The movement speed and position of the push cylinder can be precisely controlled, which improves the straightening accuracy of the downhole working face and reduces the pressure impact of the push cylinder. After the electromagnetic reversing valve is opened in the hydraulic system of the hydraulic support push cylinder, the high pressure high water base liquid enters the push cylinder through the main valve core inlet (17) and the multi-hole throttle port (18). At this time, the main valve core inlet (17) and the multi-hole throttle port (18) are equivalent to two hydraulic dampers in the hydraulic system. The main valve core inlet (17) has a larger diameter and smaller damping, while the multi-hole throttle port (18) has a smaller diameter and larger damping, which can effectively reduce the pressure impact of the high water base liquid. High-pressure high-water-based liquid enters the lower side of the main valve core (14) through the flow channel on the axis of the main valve core (14). The high-water-based liquid action area on the upper side of the main valve core (14) is larger than the high-water-based liquid action area on the lower side of the main valve core (14). When the main valve core (14) is subjected to downward liquid pressure, it moves downward. The hydraulic pressure on the upper side of the main valve core (14) must overcome the spring force of the main valve spring (19), the friction of the sealing ring on the main valve core (14), the guide belt 1, the guide belt 2, and the hydraulic pressure on the lower side of the main valve core (14).

8. The working method according to claim 7, characterized in that: The displacement of the main valve core (14) is dynamically measured by the displacement sensor (22). The hydraulic system controls the valve opening of the electro-hydraulic speed control valve of the coal mine hydraulic support push cylinder by controlling whether the electromagnet (11) of the electromagnetic pilot valve is energized. When the main valve core (14) moves, in order to prevent the liquid from being trapped in the closed space formed by the main valve core (14), the main valve end cover (20), and the main valve sleeve (15), a leakage port is machined on the main valve end cover (20).

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