An electromagnetic pilot valve and method capable of achieving self-buffering

Abstract

The present invention discloses an electromagnetic pilot valve capable of realizing self-buffering and a method thereof, belonging to the field of main steam valve stations. The electromagnetic pilot valve includes an electromagnetic device, a valve body, an intake pipeline and an outlet pipeline; the valve body is divided into a left chamber and a right chamber, and the electromagnetic device is fixed at the top; a compression spring is fixed at the top of the left chamber, and a ferromagnetic piston is fixed at the bottom of the compression spring; a buffer assembly, a valve core limiting member, a sleeve and a valve core are arranged in the right chamber; the buffer assembly includes a fixing plate, a buffer spring and a sealing plate. When the pressure in the main valve reaches the setting pressure, the electromagnetic pilot valve starts to relieve pressure. While ensuring the pressure relief efficiency, through the characteristics of its own structure, the valve core is buffered in the latter 50% of the opening degree, avoiding the rapid collision of the static iron core and the moving iron core, reducing noise and vibration, and increasing its service life; at the same time, the self-buffering time of the electromagnetic pilot valve can be changed by adjusting the stiffness of the spring to adapt to various different working conditions.

Description

Technical Field

[0001] The present invention belongs to the field of main steam valve stations, and particularly relates to an electromagnetic pilot valve and method capable of achieving self-buffering. Background Art

[0002] As one of the key overpressure protection devices in the secondary circuit of a nuclear power plant, the main steam valve station is of great significance for the safe and reliable operation of the main steam system. When faults occur upstream and downstream, the main steam valve station opens the pre-isolation valve through pilot control to discharge steam to atmospheric pressure, and closes the discharge function when the system pressure returns to normal. Therefore, ensuring that the pre-isolation valve opens within the specified time is the key to ensuring the safety of the main steam system and the safety of personnel.

[0003] Currently, the pilot control of the pre-isolation valve is mainly controlled by an electromagnetic valve. When analyzing the opening process of the pre-isolation valve, that is, the pressure relief process of the electromagnetic valve, it is found that, as Figure 6 shown, the flow rate discharged by the electromagnetic valve basically reaches the maximum at the first 50% opening, and changes little at the last 50% opening. However, the electromagnetic valve is a quick-opening device. Under the action of electromagnetic force, it realizes from closed to maximum opening in a short time, which will cause a large collision between the moving iron core and the static iron core, easily cause vibration of the valve core and generate a large noise, reducing the service life of the electromagnetic valve.

[0004] Therefore, it is of great significance to study an electromagnetic pilot valve and method that can achieve self-buffering without affecting the pressure relief efficiency of the electromagnetic valve. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects in the prior art and provide an electromagnetic pilot valve and method capable of achieving self-buffering. The electromagnetic pilot valve of the present invention is connected to the pre-isolation valve of the main steam valve station. When the pressure in the pre-isolation valve reaches the set pressure, the electromagnetic pilot valve starts to relieve pressure. While ensuring the pressure relief efficiency, through the characteristics of its own structure, it realizes buffering the valve core in the second half of the opening, avoiding the rapid collision between the static iron core and the moving iron core, reducing noise and vibration, and increasing its service life; at the same time, the self-buffering time of the electromagnetic pilot valve can be changed by adjusting the stiffness of the spring to adapt to various different working conditions.

[0006] The specific technical solutions adopted by the present invention are as follows:

[0007] In the first aspect, the present invention provides an electromagnetic pilot valve capable of achieving self-buffering, including an electromagnetic device, a valve body, an intake pipe and an outlet pipe;

[0008] The interior of the valve body is divided into a left chamber and a right chamber, and an electromagnetic device is fixed at the top; a compressible spring capable of vertical expansion and contraction is fixed at the top of the left chamber, and a ferromagnetic piston is fixed at the bottom of the compressible spring. The piston can slide vertically and sealingly along the inner wall of the left chamber; a buffer assembly, a valve core position limiter, a sleeve and a valve core are arranged in the right chamber; the sleeve is fixed at the bottom of the right chamber, and the buffer assembly is fixed at the top; a plurality of first through holes are circumferentially formed in the side wall of the sleeve and can be communicated with the upper valve chamber of the pre-isolation valve through an air inlet pipe, and the bottom is communicated with the outside through an air outlet pipe. A ferromagnetic valve core capable of sliding up and down along the sleeve to open and close the electromagnetic pilot valve is arranged in the sleeve; the main body of the valve core is of a cylindrical structure, and a ring-shaped ear with a plurality of second through holes is circumferentially connected to the edge of the top surface; in the initial state of the valve core, the air outlet pipe can be closed, and the top is connected to a valve core position limiter with a plurality of third through holes; the valve core position limiter is located above the sleeve and can slide vertically along the inner wall of the right chamber to radially limit the valve core; the buffer assembly includes a fixing plate, a buffer spring and a sealing plate; the buffer spring can expand and contract vertically, one end is fixed to the top of the right chamber through the fixing plate, and the other end is fixed with the sealing plate; the sealing plate is located above the valve core position limiter and can slide vertically and sealingly along the inner wall of the right chamber; a vertical acting force can be generated by the contact between the sealing plate and the valve core position limiter; the right chamber located above the sealing plate is communicated with the left chamber and jointly serves as a first cavity, and the right chamber located below the sealing plate serves as a second cavity, and the first cavity and the second cavity are not communicated with each other.

[0009] Preferably, the electromagnetic device is a static iron core externally wound with a coil, covering the top of the entire left chamber and right chamber, and can generate an electromagnetic attraction force on the valve core and the piston when energized.

[0010] Preferably, in the initial state, the compressible spring is in its original length, and the piston is located at the bottom of the left chamber.

[0011] Preferably, the top of the sleeve protrudes outward in the circumferential direction, and is fixed by the friction force between the protruding structure and the inner wall of the valve body.

[0012] Preferably, the fixing plate and the sealing plate are made of plexiglass, and the buffer spring is made of rubber.

[0013] Preferably, the ring-shaped ear is in sealing sliding connection with the inner wall of the sleeve.

[0014] Preferably, the valve core position limiter is of a circular plate structure, is bolt-connected to the valve core, and the outer periphery is in sealing sliding connection with the inner wall of the right chamber.

[0015] Preferably, the air inlet pipe is arranged obliquely downward.

[0016] Preferably, the buffer spring is in a stretched state initially.

[0017] Second aspect, the present invention provides a self-buffering adjustment method using any of the electromagnetic pilot valves in the first aspect, specifically as follows:

[0018] Connect the electromagnetic pilot valve to the upper valve cavity of the pre-isolation valve through the intake pipeline;

[0019] When the pressure in the pre-isolation valve does not reach the set pressure, the electromagnetic pilot valve is in the closed state; the valve core is at the bottom of the sleeve and blocks the outlet pipeline, the compression spring is in a non-expanded state, the buffer spring is in an extended state under the action of the gravity of the sealing plate, and the air pressures in the first cavity and the second cavity are stable;

[0020] When the pressure in the pre-isolation valve reaches the set pressure, turn on the electromagnetic device to generate an electromagnetic force to attract the valve core and the piston to move upward; the valve core moves upward together with it under the limiting action of the valve core limiting member, and the valve core limiting member gradually approaches the sealing plate; the piston moves upward and compresses the compression spring, and part of the gas in the first cavity enters the right chamber from the left chamber, making the air pressure above the right chamber increase, the sealing plate is subjected to a downward pressure and stretches the buffer spring to move downward; during the opening process of the valve core, the sealing plate contacts the valve core limiting member and generates a downward force on it, and the valve core begins to gradually decelerate and continue to move upward slowly; during the process of the valve core continuing to move upward, the buffer spring is gradually compressed, the downward force on the valve core is further increased, the valve core further decelerates and finally stops moving; during the upward movement of the valve core, the gas in the pre-isolation valve flows out from the outlet pipeline through the intake pipeline and the first through hole of the sleeve, and the pre-isolation valve realizes pressure relief and gradually opens;

[0021] When the pre-isolation valve reaches the fully open state, turn off the electromagnetic device; the piston moves downward and resets under the action of the elastic force of the compression spring and its own gravity; the valve core gradually moves downward under the action of the elastic force of the buffer spring and its own gravity, and through the radial limiting action of the valve core limiting member, the valve core falls into the sleeve and blocks the outlet pipeline; the sealing plate gradually resets under the action of the buffer spring; the electromagnetic pilot valve returns to the closed state;

[0022] By adjusting the stiffness of the compression spring and the buffer spring to change the contact time between the sealing plate and the valve core limiting member, thereby controlling the time when the electromagnetic pilot valve starts self-buffering.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The electromagnetic pilot valve of the present invention is connected to the pre-isolation valve of the main steam valve station. While ensuring the pressure relief efficiency, through the characteristics of its own structure, it realizes buffering of the valve core in the latter 50% opening degree, avoids the rapid collision of the static iron core and the moving iron core, reduces noise and vibration, and increases its service life;

[0025] 2) The self-buffering time of the electromagnetic pilot valve of the present invention can be changed by adjusting the spring stiffness. The specific principle is to change the speed of the piston compressing the spring by adjusting the spring stiffness, thereby changing the time when the sealing plate contacts the valve core limiting member, and finally achieving the purpose of changing the self-buffering time, enhancing the adaptability of the device to different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of the electromagnetic pilot valve;

[0027] Figure 2 is a schematic sectional structural diagram of the electromagnetic pilot valve;

[0028] Figure 3 is a schematic structural diagram of the buffer assembly;

[0029] Figure 4 is a schematic structural diagram of the valve core;

[0030] Figure 5 is a schematic structural diagram of the electromagnetic pilot valve assembled on the pre-isolation valve;

[0031] Figure 6 is the relationship between the discharge flow and the opening of the solenoid valve;

[0032] In the figure: 1, static iron core; 2, valve body; 3, buffer assembly; 31, fixing plate; 32, buffer spring; 33, sealing plate; 4, valve core limiting member; 5, sleeve; 6, valve core; 7, outlet pipeline; 8, piston; 9, compression spring; 10, inlet pipeline. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The present invention will be further described and explained below in conjunction with the drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined correspondingly without conflict.

[0034] As Figure 1 and 2 shown, a self-buffering electromagnetic pilot valve provided by the present invention mainly includes an electromagnetic device 1, a valve body 2, an inlet pipeline 10, and an outlet pipeline 7. The electromagnetic pilot valve of the present invention is mainly used on the pre-isolation valve of the main steam valve station. When the pressure of the pre-isolation valve reaches the set pressure, the electromagnetic pilot valve can be used to relieve pressure to achieve opening. At the same time, the electromagnetic pilot valve also has a self-buffering function, which can avoid the rapid collision of the static iron core and the moving iron core without affecting the pressure relief efficiency, reduce noise and vibration, and increase its service life. The structure and connection method of each component will be specifically described below.

[0035] The valve body 2 is divided into a left chamber and a right chamber, and an electromagnetic device 1 is fixed at the top. In this embodiment, the electromagnetic device 1 can adopt a static iron core with a coil wound around the outside. When the coil is energized, the static iron core can generate an electromagnetic attraction force on the valve core 6 and the piston 8. The static iron core should cover the tops of the entire left chamber and right chamber so as to make the acting force on the valve core 6 and the piston 8 more uniform.

[0036] A compression spring 9 and a piston 8 are arranged in the left chamber. The compression spring 9 can stretch vertically. One end of it is fixed to the top of the left chamber, and the other end is fixedly connected to the top of the piston 8. The piston 8 has ferromagnetism and can be attracted by the energized electromagnetic device 1. In the initial state, the piston 8 is located at the bottom of the left chamber and is in sealed sliding connection with the inner wall of the left chamber, that is, while there is a seal between the piston 8 and the inner wall of the left chamber, it can also slide up and down along the inner wall of the left chamber. In this embodiment, the compression spring 9 is in its original length in the initial state and does not have telescopic elastic force.

[0037] A buffer assembly 3, a valve core limiting member 4, a sleeve 5 and a valve core 6 are arranged in the right chamber. A sleeve 5 is fixed at the bottom of the right chamber. In this embodiment, the top of the sleeve 5 protrudes outward in the circumferential direction, and the fixing of the sleeve 5 and the valve body 2 is realized through the frictional force between the protruding structure and the inner wall of the valve body 2. A circle of first through holes is circumferentially opened on the side wall of the sleeve 5. The sleeve 5 at the location of the first through holes is communicated with the upper valve chamber of the pre-isolation valve through an air inlet pipe 10, and the bottom of the sleeve 5 is communicated with the outside through an air outlet pipe 7. A ferromagnetic valve core 6 is coaxially arranged in the sleeve 5 and can block the air outlet pipe 7 at the bottom in the initial state. The valve core 6 can slide up and down along the sleeve 5 to change the opening and closing state of the electromagnetic pilot valve. When the valve core moves upward, gas can flow through the inner cavity of the sleeve to the air outlet and finally flow out of the valve body through the air outlet pipe.

[0038] As Figure 4 shown, the main body of the valve core 6 is of a cylindrical structure, and a ring-shaped ear is circumferentially externally connected to the edge of the top surface. A number of second through holes for air flow are evenly circumferentially opened on the ring-shaped ear. The valve core 6 is connected to the valve core limiting member 4, and a number of third through holes are provided on the valve core limiting member 4. The valve core limiting member 4 is located above the sleeve 5 and can slide vertically along the inner wall of the right chamber to radially limit the valve core 6. In this embodiment, the ring-shaped ear is in sealed sliding connection with the inner wall of the sleeve 5; the valve core limiting member 4 is of a circular plate structure, is bolted to the valve core 6, and is in sealed sliding connection with the inner wall of the right chamber at the outer circumference. In actual application, since a lot of small holes are opened on the valve core limiting member 4, when the valve core 6 moves upward to exceed the upper end of the sleeve 5, under the constraint of the valve core limiting member 4, the valve core can still move on the original track, avoiding the vibration and instability of the valve core 6.

[0039] A buffer assembly 3 is fixed at the top of the right chamber. As Figure 3As shown in the figure, the buffer assembly 3 includes a fixed plate 31, a buffer spring 32, and a sealing plate 33. The buffer spring 32 can be vertically telescoped. One end is fixed to the top of the right chamber through the fixed plate 31, and the other end is fixed with the sealing plate 33. The sealing plate 33 is located above the valve core limiting member 4 and can slide vertically and sealingly along the inner wall of the right chamber. Here, the sealing slide means that the sealing plate 33 is hermetically connected to the inner wall of the right chamber and can completely cover the inner cavity of the right chamber at the place where it is located. However, the sealing plate 33 can slide up and down along the inner wall of the right chamber to achieve an effect similar to that of a piston. A vertical acting force can be generated by the contact between the sealing plate 33 and the valve core limiting member 4. The right chamber located above the sealing plate 33 is communicated with the left chamber and together serves as the first chamber, and the right chamber located below the sealing plate 33 serves as the second chamber. The first chamber and the second chamber are not communicated with each other.

[0040] In this embodiment, the fixed plate 31 is connected to the static iron core by bolts, the static iron core is connected to the valve body 2 by bolts, the upper end of the buffer spring 32 is suspended into the fixed plate 31, and the lower end is also suspended into the sealing plate 33, so that the three form an integral component. The valve core limiting member 4 is connected to the valve core 6 by threads and can move together. The buffer assembly 3 is entirely made of non-metallic materials. Specifically, the fixed plate 31 and the sealing plate 33 are both made of plexiglass, and the buffer spring 32 is made of rubber. The intake pipe 10 is arranged obliquely downward and is communicated with the upper chamber of the pre-isolation valve through the openings on the pre-isolation valve body and the valve cover. The buffer spring 32 is initially in a stretched state.

[0041] The self-buffering adjustment method of the above electromagnetic pilot valve is as follows:

[0042] As Figure 5 shown, the electromagnetic pilot valve is communicated with the upper valve chamber of the pre-isolation valve through the intake pipe 10. When the pressure in the pre-isolation valve does not reach the set pressure, the electromagnetic pilot valve is in a closed state. In this state, the valve core 6 is at the bottom of the sleeve 5 and blocks the outlet pipe 7. The compression spring 9 is in a non-telescopic state, and the buffer spring 32 is in an extended state under the action of the gravity of the sealing plate 33. The air pressures in the first chamber and the second chamber are stable.

[0043] When the pressure in the pre-isolation valve is greater than the set pressure, the pre-isolation valve needs to be opened. At this time, the coil on the static iron core of the electromagnetic pilot valve is energized, and the device will start to act. Specifically as follows:

[0044] When the pressure inside the pre-isolation valve reaches the set pressure, the electromagnetic device 1 is turned on to generate an electromagnetic force, attracting the valve core 6 and the piston 8 to move upward. The valve core 6 moves upward together with it under the limiting action of the valve core limiting member 4, and the valve core limiting member 4 gradually approaches the sealing plate 33. The piston 8 moves upward and compresses the compression spring 9, and the compression spring 9 will generate a reverse elastic force on the piston 8, but this elastic force is much smaller than the electromagnetic attraction force of the static iron core on the piston 8. As the piston 8 rises, part of the gas in the first chamber gathers from the left chamber into the right chamber, increasing the air pressure above the right chamber and giving a downward pressure to the sealing plate 33. The sealing plate 33 is subjected to the downward pressure and stretches the buffer spring 32 to move downward.

[0045] During the opening process of the valve core 6, the sealing plate 33 contacts the valve core limiting member 4 and generates a downward acting force on it, and the valve core 6 begins to gradually decelerate and continue to move upward slowly. In this embodiment, by adjusting the stiffness of the compression spring 9 and the buffer spring 32, the sealing plate 33 and the valve core limiting member 4 contact when the valve core moves to half of its opening. During the process of the valve core 6 continuing to move upward, the buffer spring 32 is gradually compressed, and the downward acting force on the valve core 6 further increases, and the valve core 6 further decelerates and finally reaches the maximum achievable opening and stops moving. During the upward movement of the valve core 6, the gas in the pre-isolation valve flows out from the outlet pipe 7 through the intake pipe 10 and the first through hole of the sleeve 5. The pressure in the upper chamber of the pre-isolation valve continues to decrease, realizing pressure relief and gradually opening.

[0046] When the pre-isolation valve reaches the fully open state, the electromagnetic device 1 is turned off, and there is no longer an electromagnetic force acting on the valve core 6 and the piston 8. The piston 8 moves downward and quickly resets under the action of the elastic force of the compression spring 9 and its own gravity. The valve core 6 gradually moves downward under the action of the elastic force of the buffer spring 32 and its own gravity. During the movement process, due to the action of the valve core limiting member 4, the valve core 6 always moves vertically in the axial direction and will not deviate from the axis, so it will just fall into the sleeve, making the upper end fit with the inner wall of the sleeve to ensure the stability of the device. The valve core 6 will finally fall into the sleeve 5 and block the outlet pipe 7. The sealing plate 33 gradually returns to a stable state and resets under the action of the buffer spring 32. The electromagnetic pilot valve finally returns to the closed state.

[0047] When the pressure of the pre-isolation valve reaches the set pressure again, repeat the above process to realize the pressure relief and opening of the pre-isolation valve through the electromagnetic pilot valve. At the same time, in practical applications, by adjusting the stiffness of the compression spring 9 and the buffer spring 32, the contact time between the sealing plate 33 and the valve core limiting member 4 can be changed, and then the time when the electromagnetic pilot valve starts self-buffering can be controlled to adapt to various different working conditions.

[0048] The embodiments described above are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. An electromagnetic pilot valve capable of achieving self-buffering, characterized in that, it includes an electromagnetic device (1), a valve body (2), an intake pipe (10) and an outlet pipe (7); the interior of the valve body (2) is divided into a left chamber and a right chamber, and an electromagnetic device (1) is fixed at the top; a compressible spring (9) capable of vertical expansion and contraction is fixed at the top of the left chamber, and a ferromagnetic piston (8) is fixed at the bottom of the compressible spring (9), and the piston (8) can slide vertically and sealingly along the inner wall of the left chamber; a buffer assembly (3), a valve core limiting member (4), a sleeve (5) and a valve core (6) are arranged in the right chamber; the sleeve (5) is fixed at the bottom of the right chamber, and the buffer assembly (3) is fixed at the top; a plurality of first through holes are circumferentially formed on the side wall of the sleeve (5) and can be communicated with the upper valve chamber of the pre-isolation valve through the intake pipe (10), and the bottom is communicated with the outside through the outlet pipe (7), and a ferromagnetic valve core (6) capable of sliding up and down along it to open and close the electromagnetic pilot valve is arranged in the sleeve (5); the main body of the valve core (6) is of a cylindrical structure, and a ring-shaped ear with a plurality of second through holes is circumferentially connected to the edge of the top surface; in the initial state, the valve core (6) can close the outlet pipe (7), and the top is connected to a valve core limiting member (4) with a plurality of third through holes; the valve core limiting member (4) is located above the sleeve (5) and can slide vertically along the inner wall of the right chamber to radially limit the valve core (6); the buffer assembly (3) includes a fixing plate (31), a buffer spring (32) and a sealing plate (33); the buffer spring (32) can expand and contract vertically, one end is fixed to the top of the right chamber through the fixing plate (31), and the other end is fixed with a sealing plate (33); the sealing plate (33) is located above the valve core limiting member (4) and can slide vertically and sealingly along the inner wall of the right chamber; a vertical force can be generated by the contact between the sealing plate (33) and the valve core limiting member (4); the right chamber located above the sealing plate (33) is communicated with the left chamber and jointly serves as a first cavity, and the right chamber located below the sealing plate (33) serves as a second cavity, and the first cavity and the second cavity are not communicated with each other.

2. An electromagnetic pilot valve capable of achieving self-buffering according to claim 1, characterized in that, the electromagnetic device (1) is a static iron core externally wound with a coil, covering the top of the entire left chamber and right chamber, and can be energized to generate an electromagnetic attraction force on the valve core (6) and the piston (8).

3. An electromagnetic pilot valve capable of achieving self-buffering according to claim 1, characterized in that, in the initial state, the compressible spring (9) is in its original length, and the piston (8) is located at the bottom of the left chamber.

4. An electromagnetic pilot valve capable of achieving self-buffering according to claim 1, characterized in that, the top of the sleeve (5) protrudes outward in the circumferential direction, and is fixed by the friction force between the protruding structure and the inner wall of the valve body (2).

5. An electromagnetic pilot valve capable of achieving self-buffering according to claim 1, characterized in that, the fixing plate (31) and the sealing plate (33) are made of plexiglass, and the buffer spring (32) is made of rubber.

6. An electromagnetic pilot valve capable of achieving self-buffering according to claim 1, It is characterized in that the annular ear is in a closed sliding connection with the inner wall of the sleeve (5).

7. An electromagnetic pilot valve capable of realizing self-buffering according to claim 1, It is characterized in that the valve core limiting member (4) is in a circular plate structure, is connected to the valve core (6) by bolts, and is in a closed sliding connection with the inner wall of the right chamber at the outer periphery.

8. An electromagnetic pilot valve capable of realizing self-buffering according to claim 1, It is characterized in that the intake pipe (10) is arranged obliquely downward.

9. An electromagnetic pilot valve capable of realizing self-buffering according to claim 1, It is characterized in that the buffer spring (32) is initially in a stretched state.

10. A self-buffering adjustment method using the electromagnetic pilot valve according to any one of claims 1 to 9, It is characterized in that specifically as follows: Connect the electromagnetic pilot valve to the upper valve chamber of the pre-isolation valve through the intake pipe (10); When the pressure in the pre-isolation valve does not reach the setting pressure, the electromagnetic pilot valve is in a closed state; the valve core (6) is at the bottom of the sleeve (5) and blocks the outlet pipe (7), the compression spring (9) is in a non-telescopic state, the buffer spring (32) is in an extended state under the gravity of the sealing plate (33), and the air pressures in the first chamber and the second chamber are stable; When the pressure in the pre-isolation valve reaches the setting pressure, turn on the electromagnetic device (1) to generate an electromagnetic force, attracting the valve core (6) and the piston (8) to move upward; the valve core (6) moves upward together with it under the limiting action of the valve core limiting member (4), and the valve core limiting member (4) gradually approaches the sealing plate (33); the piston (8) moves upward and compresses the compression spring (9), and part of the gas in the first chamber enters the right chamber from the left chamber, making the air pressure above the right chamber increase, the sealing plate (33) is subjected to a downward pressure and stretches the buffer spring (32) to move downward; during the opening process of the valve core (6), the sealing plate (33) contacts the valve core limiting member (4) and generates a downward acting force on it, and the valve core (6) begins to gradually decelerate and continues to move upward slowly; during the process of the valve core (6) continuing to move upward, the buffer spring (32) is gradually compressed, the downward acting force on the valve core (6) is further increased, the valve core (6) further decelerates and finally stops moving; during the upward movement of the valve core (6), the gas in the pre-isolation valve flows out from the outlet pipe (7) through the intake pipe (10) and the first through hole of the sleeve (5), and the pre-isolation valve realizes pressure relief and gradually opens; When the pre-isolation valve reaches the fully open state, turn off the electromagnetic device (1); the piston (8) moves downward and resets under the action of the elastic force of the compression spring (9) and its own gravity; the valve core (6) gradually moves downward under the action of the elastic force of the buffer spring (32) and its own gravity, and through the radial limiting action of the valve core limiting member (4), the valve core (6) falls into the sleeve (5) and blocks the outlet pipe (7); the sealing plate (33) gradually resets under the action of the buffer spring (32); the electromagnetic pilot valve returns to the closed state; By adjusting the stiffness of the compression spring (9) and the buffer spring (32) to change the contact time between the sealing plate (33) and the valve core stopper (4), thereby controlling the time when the electromagnetic pilot valve starts self-buffering.

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