A gas pressure driven pilot valve of a negative stiffness structure, system and control method

Abstract

The application discloses a kind of negative stiffness structure's air pressure drive pilot valve, system and control method, the pilot valve includes first partition and second partition, pneumatic piston is arranged in first partition, second partition is below pneumatic piston, and negative stiffness pneumatic elastic element is connected below second partition;Air pressure rises, and the air pressure in second valve cavity drives pneumatic piston to move up to cut off atmospheric pressure gas path, and the air pressure in third valve cavity drives outer ring convex surface to deform and pull plug to move up to open negative pressure communication port;Air pressure drops, and reset spring drives pneumatic piston to move down to make atmospheric pressure gas path communication, and negative pressure port pre-tightening spring drives plug to move down to block negative pressure communication port.The application is controlled by pure mechanical type, does not rely on power control, can work in humid, high temperature, many mosquitoes and power supply difficult and so on harsh working conditions, improves the working stability of pilot valve;By using air pressure as control signal, the automatic control of pilot valve is realized, and the control accuracy is improved.

Description

Technical Field

[0001] This invention relates to a pneumatically driven pilot valve with a negative stiffness structure, a system, and a control method, belonging to the field of valve automation control technology. Background Technology

[0002] A pilot valve is an auxiliary valve that controls the airflow to and from the main circuit valves by opening and closing it. Common pilot valves use an electrical signal to drive a two-position, three-way solenoid valve to control the main circuit valves. While solenoid valves offer fast response, high precision, and automatic control, they rely on a power supply and are unsuitable for humid, high-temperature, or power-scarce environments. Manually controlled pilot valves, although simple in structure and adaptable to various harsh environments, require manual intervention, resulting in slow signal transmission, susceptibility to human error, and difficulty in ensuring timely control. Therefore, existing pilot valve designs have the following shortcomings:

[0003] 1. Electromagnetically driven pilot valves rely on power supplies, making them unsuitable for harsh operating conditions such as power supply difficulties. Patent CN108844268B, "A Liquid Level Control Device for a Low-Pressure Circulating Tank in a Refrigeration System," discloses an electromagnetically driven pilot valve that automatically switches on and off based on liquid level. This device uses a host computer system to control the conduction and cutoff of a magnetic coil based on the liquid level signal collected by a sensor, thereby opening and closing the valve. This device has high requirements for the working environment and cannot maintain stable operation under harsh conditions such as high temperature, humidity, insect infestation, and power supply difficulties.

[0004] 2. Although manually controlled pilot valves are disconnected from power supplies, they cannot achieve automatic control and have poor control timeliness. Patent CN101782151B, "Manual Control Valve," discloses a pilot valve for pneumatic conveying and gas supply systems. Gas delivery is controlled by manually rotating the valve handle. This device has low control precision, is highly susceptible to human error, and has poor control timeliness. Summary of the Invention

[0005] To address the problems of existing pilot valves, which mostly rely on dedicated power supplies and struggle to maintain operational stability under harsh conditions such as humidity, high temperatures, insect infestations, and power supply difficulties; and mechanical pilot valves, which are independent of electrical circuits, are mostly manually controlled, making automation difficult and resulting in poor control timeliness, this invention provides a pneumatically driven pilot valve with a negative stiffness structure, a system, and a control method. This invention uses pneumatic signals to control the movement of a pneumatic piston and the deformation of a negative stiffness elastic element, thereby opening and closing the valve's two channels. The pilot valve can serve as an auxiliary valve to the main drain valve in sewage pipeline systems. The main valve port of the pilot valve is connected to the pneumatic control interface of the main drain valve. When the pilot valve outputs negative pressure, the main drain valve opens, and sewage discharge begins; when the pilot valve outputs atmospheric pressure, the main drain valve closes, and sewage discharge stops. Compared to existing pilot valves, this invention achieves automated control while being independent of power supplies and control circuits, maintaining accuracy and stability under various harsh conditions.

[0006] The first objective of this invention is to provide a pneumatically driven pilot valve with a negative stiffness structure. The pilot valve includes a valve body shell and a first top cover and a second top cover respectively connected to both ends of the valve body shell. A first partition and a second partition located below the first partition are provided inside the valve body shell. A movable pneumatic piston is disposed inside the first partition, and a return spring is provided between the pneumatic piston and the first partition. The second partition is located below the pneumatic piston. A first valve chamber is formed between the first top cover and the first partition, a second valve chamber is formed between the first partition and the second partition, and a third valve chamber is formed between the second partition and the second top cover.

[0007] The valve body shell has an atmospheric pressure connection port, a liquid level rise gas pressure conduction port, and a main valve connection port; the atmospheric pressure connection port is connected to atmospheric pressure and communicates with the first valve chamber; the liquid level rise gas pressure conduction port communicates with the second valve chamber and the third valve chamber; there are two main valve connection ports, one of which communicates with the first valve chamber and the other of which communicates with the third valve chamber. The atmospheric pressure connection port, the first valve chamber, and the main valve connection port communicating with the first valve chamber constitute an atmospheric pressure air path.

[0008] A negative stiffness pneumatic elastic element is connected below the second partition; the second top cover has a negative pressure port for communicating with negative pressure, and the negative stiffness pneumatic elastic element includes an elastic outer ring convex surface and a plug connected below the outer ring convex surface. The plug is used to block the negative pressure port, and a negative pressure port preload spring is provided between the plug and the second partition.

[0009] Air pressure enters the second and third valve chambers through the liquid level rise air pressure conduction port; as the air pressure rises, the air pressure in the second valve chamber drives the pneumatic piston to move upward to the upper limit position to cut off the atmospheric pressure air path, and the air pressure in the third valve chamber drives the outer ring convex surface to undergo expansion deformation and pulls the plug upward to open the negative pressure connection port; as the air pressure drops, the reset spring drives the pneumatic piston downward to open the atmospheric pressure air path, and the negative pressure port pre-tightening spring drives the plug downward to seal the negative pressure connection port.

[0010] In one embodiment of the present invention, the pneumatic piston includes a piston rod and a piston head and a piston bottom respectively disposed at both ends of the piston rod. The piston head is located in the first valve chamber, and the piston bottom is located in the second valve chamber. The piston rod is movably inserted through the first partition. A return spring is sleeved on the piston rod, with one end abutting against a spring seat disposed below the first partition and the other end abutting against a spring seat disposed above the piston bottom. A first limiting seat is disposed below the first top cover, and a second limiting seat is disposed above the first partition. A through hole is formed between the first limiting seat and the second limiting seat. A sealing gasket is disposed on the upper surface of the piston head. The piston head can move upward to abut against the first limiting seat and the second limiting seat to block the through hole between the first limiting seat and the second limiting seat, thereby cutting off the atmospheric pressure air path.

[0011] In one embodiment of the present invention, the second partition has a first through hole connecting the second valve chamber and the third valve chamber; the second partition is a disc-shaped structure with an annular recess on its outer edge, and the negative stiffness pneumatic elastic element is embedded in the annular recess; the interior of the second partition has a channel connecting the liquid level rise gas pressure conduction port and the first through hole, and the channel extends from the edge of the second partition to its center; the first through hole is located at one end of the channel near the center of the second partition.

[0012] In one embodiment of the present invention, a protrusion is provided above the second top cover; the negative stiffness pneumatic elastic element is located in the third valve cavity, the edge of the outer ring convex surface is bent inward and fixedly connected to the second partition; the outer ring convex surface is made of elastic material, air pressure is introduced into the third valve cavity from the liquid level rise air pressure conduction port and drives the negative stiffness pneumatic elastic element to undergo expansion deformation and move downward, the protrusion abuts against the outer ring convex surface and drives the negative stiffness pneumatic elastic element to be recessed inward, the elastic material outer ring convex surface undergoes expansion deformation and drives the plug to rise, so as to open the negative pressure communication port.

[0013] In one embodiment of the present invention, the negative stiffness pneumatic elastic element is made of rubber material and has an overall hemispherical shape. The central axis of the negative stiffness pneumatic elastic element coincides with the central axis of the pilot valve body. The plug is located at the center of the negative stiffness pneumatic elastic element. One end of the negative pressure port preload spring abuts against the top of the plug and the other end abuts against the bottom of the center of the second partition.

[0014] In one embodiment of the present invention, the air pressure sensitivity of the negative stiffness pneumatic elastic element is adjusted according to its shape and thickness to adjust the displacement of the plug; the curvature of the outer ring convex surface varies from 0.52 to 1.40.

[0015] In one embodiment of the present invention, the first top cover and the valve body shell are sealed together by a first top cover sealing ring, the first partition and the valve body shell are sealed together by a first partition sealing ring, the piston bottom and the valve body shell are sealed together by a sealing ring, the second partition and the valve body shell are sealed together by a second partition sealing ring, and the second top cover and the valve body shell are sealed together by a second top cover sealing ring; the first top cover and the valve body shell are connected by a first fastening bolt, and the second top cover and the valve body shell are connected by a second fastening bolt.

[0016] A second objective of the present invention is to provide a pneumatically driven pilot valve system with a negative stiffness structure, the system comprising the aforementioned pneumatically driven pilot valve with the negative stiffness structure.

[0017] The system also includes a sewage tank, a level sensor, a negative pressure tank, and a main drain valve; the pilot valve's atmospheric pressure port is connected to atmospheric pressure; the sewage tank stores sewage, the level sensor is fixed to the inner wall of the sewage tank, its bottom is connected to the sewage tank, and the upper end of the level sensor is connected to a pressure transmission pipe, the other end of which is connected to the pilot valve's level rise pressure transmission port; when the liquid level in the sewage tank rises, the liquid level in the level sensor rises synchronously, the air in the pipe is compressed by the liquid surface, and through the opening at the upper end of the level sensor, it is transmitted through the pressure transmission pipe. The liquid enters the pilot valve through the pressure transmission port for the rising liquid level; the bottom of the sewage tank is a drain outlet connected to a drain pipe, the other end of which is connected to a main drain valve. The main drain valve has a pressure control interface, which is connected to the two main valve ports of the pilot valve through a pressure pipe; the main drain valve is connected to the negative pressure tank through a sewage pipe, and the negative pressure port of the pilot valve is connected to a negative pressure pipe. The other end of the negative pressure pipe is connected to the sewage pipe between the main drain valve and the negative pressure tank, and the negative pressure tank provides continuous negative pressure to the pilot valve through the negative pressure pipe.

[0018] A third objective of this invention is to provide a liquid level control method employing a pneumatically driven pilot valve system with a negative stiffness structure, the method comprising the following steps:

[0019] Step 1: As the liquid level in the sewage tank rises, the liquid level in the liquid level sensing tube rises synchronously, compressing the gas inside the liquid level sensing tube and transmitting it to the pilot valve;

[0020] Step 2: The gas inside the liquid level sensing tube is conducted into the second and third valve chambers through the liquid level rising pressure conduction port and the first through hole of the second partition. As the gas pressure rises above 20 kPa, the pneumatic piston gradually rises under the action of the gas pressure until the piston head reaches the upper limit position. The sealing gasket abuts against the first and second limit seats to block the through hole between the first and second limit seats, thus closing the atmospheric pressure air path. At the same time, when the gas pressure rises, the outer ring convex surface of the negative stiffness pneumatic elastic element is subjected to positive pressure and undergoes expansion deformation. The plug of the negative stiffness pneumatic elastic element is lifted, opening the negative pressure connection port. The main drain valve is connected to the negative pressure and opens to start draining.

[0021] Step 3: When the sewage tank level drops, the liquid level in the level sensing tube drops synchronously, the air pressure drops, the pneumatic piston drops under the elastic force of the return spring, the atmospheric pressure connection port and the main valve connection port are connected, the atmospheric pressure air circuit is connected to the sewage discharge main valve, the negative stiffness pneumatic elastic element returns to its original state, the plug seals the negative pressure connection port under the elastic force of the negative pressure port pre-tightening spring, the negative pressure connection is closed, the sewage discharge main valve is closed, and sewage discharge stops.

[0022] In one embodiment of the present invention, the flow rate of wastewater injected into the liquid level sensing tube is controlled at 1 to 3 m / s. 3 / h, in the pilot valve, connects to the third valve chamber of the negative pressure tank, where the air flow rate is 5 to 10 L / min.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) The pilot valve provided by the present invention is a purely mechanical structure and does not rely on electric control; it uses the air pressure generated by the change in liquid level in the liquid level sensing tube as the control signal, is independent of the control circuit, has low manufacturing cost, and is simple to maintain and repair; it can also work continuously, adapt to harsh working conditions, and can work in harsh environments such as humidity, high temperature, many mosquitoes and difficult power supply, and can maintain its working stability.

[0025] (2) The present invention uses air pressure as a control signal to achieve automatic control; the pilot valve uses air pressure as a control signal to control the connection and disconnection of the negative pressure and the main drain valve. When the liquid level in the liquid level sensing tube rises, the air pressure is transmitted to the valve chamber of the pilot valve, and the pressure gradually increases. When the air pressure exceeds a certain threshold, the negative pressure is connected, the atmospheric pressure is closed, and the main drain valve is opened; when the water level in the sewage tank drops, the liquid level in the liquid level sensing tube drops, the air pressure drops, the negative pressure is closed, the atmospheric pressure is connected, and the main drain valve is closed, thereby realizing the automatic control of the main drain valve by the pilot valve.

[0026] (3) The present invention uses a negative stiffness pneumatic elastic element as the main control element to control the negative pressure connection; when the negative stiffness pneumatic elastic element is subjected to positive pressure, the element undergoes expansion deformation, the plug of the negative stiffness pneumatic elastic element is lifted, the negative pressure port is opened, the negative pressure is connected to the main drain valve, and the main drain valve is opened; when the negative stiffness pneumatic elastic element retracts, the plug of the negative stiffness pneumatic elastic element falls back to block the negative pressure port, the negative pressure is shut off, and the main drain valve is closed; thereby achieving precise control of the main drain valve.

[0027] (4) The negative stiffness pneumatic elastic element provided by the present invention has adjustable air pressure sensitivity; the air pressure sensitivity of the negative stiffness pneumatic elastic element is adjusted according to its shape and thickness. The negative stiffness pneumatic elastic element can be manufactured by 3D printing. According to the magnitude of air pressure transmission, a negative stiffness pneumatic elastic element with corresponding sensitivity can be manufactured, and air pressure control with different sensitivities can be achieved. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the pilot valve provided by the present invention.

[0030] Figure 2 This is a schematic diagram of the pilot valve in its initial state as provided by the present invention.

[0031] Figure 3 This is a schematic diagram of the pilot valve in the intermediate process provided by the present invention.

[0032] Figure 4 This is a schematic diagram of the pilot valve in the draining state provided by the present invention.

[0033] Figure 5 This is a schematic diagram of the structure of the negative stiffness aeroelastic element provided by the present invention.

[0034] Figure 6This is a schematic diagram of the system provided by the present invention.

[0035] Figure 7 A flowchart illustrating the control method provided by this invention.

[0036] In the diagram: 1. Sewage tank; 2. Liquid level sensor; 3. Pilot valve; 4. Negative pressure tank; 5. Main drain valve; 310. First top cover; 3101. First limit seat; 311. First fastening bolt; 312. First top cover sealing ring; 321. First partition; 3211. Second limit seat; 322. Second partition; 3221. First through hole; 323. First partition sealing ring; 324. Second partition sealing ring; 325. First valve chamber; 326. Second valve chamber; 327. Third valve chamber; 330. Valve body shell; 331. Atmospheric pressure connection 332. Liquid level rise air pressure conduction port; 333. Main valve connection port; 340. Pneumatic piston; 341. Piston head; 342. Sealing gasket; 343. Piston rod; 344. Piston bottom; 345. Sealing ring; 350. Return spring; 360. Negative pressure port preload spring; 370. Negative stiffness pneumatic elastic element; 371. Plug; 372. Outer ring convex surface; 380. Second top cover; 381. Second fastening bolt; 382. Negative pressure connection port; 383. Second top cover sealing ring; 384. Protrusion; 510. Air pressure control interface. Detailed Implementation

[0037] The invention is described in detail below. In the following paragraphs, different aspects of the embodiments are defined in more detail. The aspects so defined may be combined with any other aspect or aspects unless explicitly stated otherwise. In particular, any feature considered preferred or advantageous may be combined with one or more other features considered preferred or advantageous.

[0038] The terms "first" and "second" used in this invention are merely for ease of description and to distinguish different components with the same name, and do not indicate a sequential or primary / secondary relationship.

[0039] Furthermore, when an element is referred to as being "on" another element, the element may be directly on the other element, or it may be indirectly on the other element with one or more intermediate elements inserted between them. Additionally, when an element is referred to as being "connected" to another element, the element may be directly connected to the other element, or it may be indirectly connected to the other element with one or more intermediate elements inserted between them. In the following drawings, the same reference numerals denote the same elements.

[0040] The present invention uses terms such as "upper", "lower", "top", "bottom", "front", "rear", "inner" and "outer" to indicate orientation or positional relationships. This is only for the convenience of describing the present invention and is not intended to indicate or imply that the device referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the scope of protection of the present invention.

[0041] like Figure 1-5 As shown, the present invention provides a pneumatically driven pilot valve with a negative stiffness structure. In some embodiments, the pilot valve 3 includes a valve body shell 330 and a first top cover 310 and a second top cover 380 respectively connected to both ends of the valve body shell 330. A first partition 321 and a second partition 322 located below the first partition 321 are provided inside the valve body shell 330. A movable pneumatic piston 340 is disposed inside the first partition 321. A return spring 350 is disposed between the pneumatic piston 340 and the first partition 321. The second partition 322 is located below the pneumatic piston 340. A negative stiffness pneumatic elastic element 370 is connected below the second partition 322. A negative pressure port preload spring 360 is disposed between the negative stiffness pneumatic elastic element 370 and the second partition 322.

[0042] Furthermore, a first valve chamber 325 is formed between the first top cover 310 and the first partition 321, a second valve chamber 326 is formed between the first partition 321 and the second partition 322, and a third valve chamber 327 is formed between the second partition 322 and the second top cover 380.

[0043] Optionally, the first top cover 310 is connected to the valve body housing 330 by a first fastening bolt 311, and the second top cover 380 is connected to the valve body housing 330 by a second fastening bolt 381; the first top cover 310 and the second top cover 380 can also be connected to the valve body housing 330 by threads or other means, and there is no specific limitation on this.

[0044] Optionally, in one embodiment, the pneumatic piston 340 includes a piston rod 343 and a piston head 341 and a piston bottom 344 respectively disposed at both ends of the piston rod 343. The piston head 341 is located in the first valve chamber 325, and the piston bottom 344 is located in the second valve chamber 326. The piston rod 343 is movably inserted into the first partition 321. The return spring 350 is sleeved on the piston rod 343, with one end abutting against a spring seat disposed below the first partition 321 and the other end abutting against a spring seat disposed above the piston bottom 344. The second partition 322 has an opening for communicating with the second... The valve chamber 326 and the third valve chamber 327 have a first through hole 3221; a first limiting seat 3101 is provided below the first top cover 310, and a second limiting seat 3211 is provided above the first partition 321. A through hole is formed between the first limiting seat 3101 and the second limiting seat 3211. A sealing gasket 342 is provided on the upper surface of the piston head 341. The piston head 341 with the sealing gasket 342 on the upper surface can move upward to abut against the first limiting seat 3101 and the second limiting seat 3211 to block the through hole between the first limiting seat 3101 and the second limiting seat 3211, thereby cutting off the atmospheric pressure air path.

[0045] Optionally, the first top cover 310 is sealed to the valve body housing 330 via a first top cover sealing ring 312, the first partition 321 is sealed to the valve body housing 330 via a first partition sealing ring 323, the piston bottom 344 is sealed to the valve body housing 330 via a sealing ring 345, the second partition 322 is sealed to the valve body housing 330 via a second partition sealing ring 324, and the second top cover 380 is sealed to the valve body housing 330 via a second top cover sealing ring 383. This pilot valve 3 is an airtight device. Through the above arrangement, all components in contact with the inner wall of the valve body housing 330 are sealed with sealing rings, ensuring the airtightness of the valve body.

[0046] In this embodiment, the return spring 350 is always compressed, causing the pneumatic piston 310 to always tend to move downwards. When there is no air pressure transmission, the pneumatic piston 340 is at the lower limit position. The piston bottom 344 is sealed to the valve body housing 330 by a sealing ring 345, ensuring the airtightness of the valve body when the pneumatic piston 310 moves. When the liquid level in the liquid level sensing tube 2 rises, air pressure is transmitted, causing the air pressure in the second valve chamber 326 and the third valve chamber 327 to rise, and the pneumatic piston 340 moves upwards to the upper limit position, cutting off the atmospheric pressure air path. The upper limit position of the pneumatic piston 340 refers to the sealing gasket 342 provided above the piston head 341 moving upwards to abut against the first limit seat 3101 and the second limit seat 3211. By abutting against the first limiting seat 3101 and the second limiting seat 3211 with the sealing gasket 342, the through hole between the first limiting seat 3101 and the second limiting seat 3211 can be completely sealed to prevent air leakage from the through hole, thereby cutting off the atmospheric pressure air path.

[0047] Optionally, in one embodiment, the valve body housing 330 has an atmospheric pressure connection port 331, a liquid level rise pressure conduction port 332, and a main valve connection port 333; the atmospheric pressure connection port 331 is connected to atmospheric pressure, and there are two main valve connection ports 333, which are vertically distributed, one of which is connected to the first valve chamber 325, and the other is connected to the third valve chamber 327; the atmospheric pressure connection port 331 and the liquid level rise pressure conduction port 332 are vertically distributed, and the atmospheric pressure connection port 331... The liquid level rise air pressure conduction port 332 is located on one side of the valve body shell 330, and the two main valve connection ports 333 are located on the other side of the valve body shell 330; the atmospheric pressure connection port 331 is connected to the first valve chamber 325, and the atmospheric pressure connection port 331, the first valve chamber 325 and the main valve connection port 333 connected to the first valve chamber 325 form an atmospheric pressure air path; the liquid level rise air pressure conduction port 332 is connected to the through hole 3221 in the second partition 322, and is connected to the second valve chamber 326 and the third valve chamber 327 respectively.

[0048] Optionally, the second partition 322 has a disc-shaped structure with an annular notch on its outer edge, into which the negative stiffness pneumatic elastic element 370 is embedded; the interior of the second partition 322 has a channel connecting the liquid level rise gas pressure conduction port 332 and the first through hole 3221, the cross-section of the channel is a circular hole with a diameter of 5mm, the channel extends from the edge of the second partition 322 to its center, and the length of the channel is in the ratio of the radius of the second partition 322 to 2:3; the first through hole 3221 is located at one end of the channel near the center of the second partition 322, the first through hole 3221 is a circular through hole with a diameter of 5mm and is arranged perpendicular to the second partition 322.

[0049] Optionally, in one embodiment, the second top cover 380 has a negative pressure communication port 382 for communicating with negative pressure, and a protrusion 384 is provided on the upper part of the second top cover 380; the negative stiffness pneumatic elastic element 370 is located in the third valve chamber 327, and the negative stiffness pneumatic elastic element 370 includes an outer ring convex surface 372 and a plug 371 connected below the outer ring convex surface 372. The plug 371 is used to block the negative pressure communication port 382. The edge of the outer ring convex surface 372 is bent inward and fixedly connected to the second partition 322. The plug 371 and the second partition 322 are pre-tightened through the negative pressure port. A spring 360 is connected, and the plug 371 can seal the negative pressure connection port 382 under the elastic force of the pre-tightening spring 360 at the negative pressure port. The outer ring convex surface 372 is made of elastic material. Air pressure rises from the liquid level and enters the third valve chamber 327 through the air pressure transmission port 332, driving the negative stiffness pneumatic elastic element 370 to move downward. The protrusion 384 abuts against the outer ring convex surface 372 and drives the negative stiffness pneumatic elastic element 370 to be recessed inward. The elastic material outer ring convex surface 372 can undergo expansion deformation and drive the plug 371 to rise, so as to open the negative pressure connection port 382.

[0050] Preferably, the curvature of the outer ring convex surface 372 varies from 0.52 to 1.40 mm, the distance between the inwardly recessed apex of the negative stiffness pneumatic elastic element 370 and the second partition 322 ranges from 10 mm to 15 mm, and the upward displacement of the plug 371 ranges from 0 to 4 mm. The ratio of the diameter of the plug 371 to the overall diameter of the negative stiffness pneumatic elastic element 370 is 1:5, and its thickness is 5 mm. The thickness of the outer ring convex surface 372 ranges from 0.3 mm to 0.6 mm. Different thicknesses affect the sensitivity of the negative stiffness pneumatic elastic element 370, and the thickness of the outer ring convex surface 372 can be adjusted according to actual usage requirements.

[0051] Optionally, the negative stiffness pneumatic elastic element 370 is made of rubber material and can be manufactured using 3D printing technology. Its overall shape is hemispherical. The central axis of the negative stiffness pneumatic elastic element 370 coincides with the central axis of the pilot valve 3 body. The plug 371 is located at the center of the negative stiffness pneumatic elastic element 370. One end of the negative pressure port preload spring 360 abuts against the top of the plug 371, and the other end abuts against the bottom of the center of the second partition 322.

[0052] like Figure 5As shown, optionally, the elastic modulus E of the negative stiffness pneumatic elastic element 370 is set to 7.8 MPa and the Poisson's ratio μ = 0.47 according to the properties of the rubber material. When the control air pressure rises from 0 to 0.36 MPa, the outer ring convex surface 372 of the negative stiffness pneumatic elastic element 370 undergoes significant expansion deformation, pulling the lower plug 371 upward, thereby opening and closing the negative pressure connection port 382. By changing the shape and thickness of the negative stiffness pneumatic elastic element 370, the air pressure sensitivity of the negative stiffness pneumatic elastic element 370 can be changed, and the displacement of the plug 371 can be adjusted to meet the actual design requirements.

[0053] In this embodiment, when there is no air pressure transmission, the plug 371 of the negative stiffness pneumatic elastic element 370 seals the negative pressure connection port 382 under the elastic force of the negative pressure port pre-tightening spring 360. Since the edge of the negative stiffness pneumatic elastic element 370 is bent inward and fixedly connected to the second partition 322, and the negative stiffness pneumatic elastic element 370 is made of rubber, it can also act as a sealing element to form a seal between the valve body and the second partition 322, making the third valve chamber 327 an airtight space. During air pressure transmission, the outer convex surface 372 of the negative stiffness pneumatic elastic element 370 is subjected to positive pressure, causing it to undergo expansion deformation. According to the generalized Hooke's law, the plug 371 of the negative stiffness pneumatic elastic element 370 is lifted, opening the negative pressure connection port 382. The main drain valve 5 and the negative pressure connection port 382 are connected, and draining begins.

[0054] Preferably, the valve body of the pilot valve 3 is made of 304 stainless steel. 304 stainless steel has good machinability, high strength, and high toughness, which improves the machining accuracy and pressure resistance of the pilot valve 3 body, and also extends its service life. Of course, in addition to 304 stainless steel, other materials can be used for the valve body of the pilot valve 3; no specific limitation is made thereto.

[0055] like Figure 2 , Figure 3 , Figure 4 and Figure 6 As shown, Figure 2 , Figure 3 and Figure 4 These are schematic diagrams showing the pilot valve 3 in its initial state, intermediate process, and sewage discharge state, respectively.

[0056] First, the air pressure rises from the liquid level through the air pressure transmission port 332 and passes through the first through hole 3221 in the second partition 322 into the third valve chamber 327 and the second valve chamber 326 respectively. As the air pressure slowly rises, the pneumatic piston 340 gradually rises under the action of the air pressure until the piston head 341 reaches the upper limit position. The sealing gasket 342 abuts against the first limit seat 3101 and the second limit seat 3211 to block the through hole between the first limit seat 3101 and the second limit seat 3211, thereby sealing the air passage and closing the atmospheric pressure channel.

[0057] At the same time, when the air pressure rises, the outer ring convex surface 372 of the negative stiffness pneumatic elastic element 370 is subjected to positive pressure and undergoes expansion deformation. According to the generalized Hooke's law, the plug 371 of the negative stiffness pneumatic elastic element 370 is lifted, opening the negative pressure connection port 382, ​​and the main valve connection port 333 is connected to the negative pressure, starting to discharge sewage.

[0058] When the main drain valve 5 is open for a period of time, the sewage level in the sewage tank 1 drops, and the liquid level in the liquid level sensing tube 2 drops at the same time. At this time, the air pressure in the valve chamber is transmitted back to the liquid level sensing tube 2 through the liquid level rising air pressure transmission port 332. The air pressure in the valve chamber drops, and the pneumatic piston 340 drops to the lower limit under the elastic force of the piston return spring 350. The atmospheric pressure connection port 331 and the main valve connection port 333 are connected. The plug 371 of the negative stiffness pneumatic elastic element 370 blocks the negative pressure connection port 382 under the elastic action of the negative pressure port pre-tightening spring 360. The negative pressure air circuit is closed, the main drain valve 5 is closed, and the sewage discharge stops.

[0059] In addition, such as Figure 6 As shown, the present invention also provides a pneumatically driven pilot valve system with a negative stiffness structure. The system includes a pneumatically driven pilot valve 3 with the aforementioned negative stiffness structure, a sewage tank 1, a liquid level sensing tube 2, a negative pressure tank 4, and a main discharge valve 5. The atmospheric pressure connection port 331 of the pilot valve 3 is connected to atmospheric pressure. The sewage tank 1 stores sewage. The liquid level sensing tube 2 is fixed to the inner wall of the sewage tank 1, and its bottom is connected to the sewage tank 1. The upper end of the liquid level sensing tube 2 is connected to a pneumatic pressure transmission tube, and the other end of the pneumatic pressure transmission tube is connected to the liquid level rise pneumatic pressure transmission port 332 of the pilot valve 3. The bottom of the sewage tank 1 is a sewage outlet connected to a sewage pipe. The other end of the sewage pipe is connected to a main sewage valve 5. The main sewage valve 5 has a pneumatic control interface 510, which is connected to the two main valve ports 333 of the pilot valve 3 via a pneumatic pipe. The main sewage valve 5 is connected to the negative pressure tank 4 via a sewage pipe. The negative pressure port 382 of the pilot valve 3 is connected to a negative pressure pipe. The other end of the negative pressure pipe is connected to the sewage pipe between the main sewage valve 5 and the negative pressure tank 4. The negative pressure tank 4 provides continuous negative pressure to the pilot valve 3 through the negative pressure pipe.

[0060] The sewage in the sewage tank 1 enters the liquid level sensing tube 2. The liquid level sensing tube 2 is an airtight element. When the liquid level in the liquid level sensing tube 2 rises, the air in the tube is compressed by the liquid surface and enters the pilot valve 3 through the air pressure transmission tube via the liquid level rise air pressure transmission port 332 through the opening at the upper end of the liquid level sensing tube 2. When the liquid level in the sewage tank 1 rises, according to the principle of communicating vessels, the liquid level in the liquid level sensing tube 2 rises synchronously, compressing the air in the liquid level sensing tube 2 and entering the second valve chamber 326 and the third valve chamber 327 through the liquid level rise air pressure transmission port 332 of the pilot valve 3. When the air pressure exceeds the operating pressure, the pneumatic piston 340 gradually rises under the action of air pressure until the piston head 341 reaches the upper limit position. The sealing gasket 342 abuts against the first limit seat 3101 and the second limit seat 3211 to close the gap between the first limit seat 3101 and the second limit seat 3211. The through-hole is sealed, closing the atmospheric pressure air path. Simultaneously, when the air pressure rises, the outer ring convex surface 372 of the negative stiffness pneumatic elastic element 370 is subjected to positive pressure, causing expansion deformation. According to the generalized Hooke's law, the plug 371 of the negative stiffness pneumatic elastic element 370 is lifted, opening the negative pressure connection port 382. The main drain valve 5 is connected to the negative pressure, and the main drain valve 5 is opened, starting the sewage discharge. The liquid level in the sewage tank 1 drops, and the liquid level in the liquid level sensing tube 2 drops synchronously. The air pressure drops, and the pneumatic piston 340 descends to the lower limit under the elastic force of the piston return spring 350. The atmospheric pressure connection port 331 and the main valve connection port 333 are connected, and the atmospheric pressure air path is connected. The negative stiffness pneumatic elastic element 370 returns to its original position, and the plug 371, under the elastic action of the negative pressure port pre-tightening spring 360, seals the negative pressure connection port 382, ​​closing the negative pressure connection. The main drain valve 5 is closed, and the sewage discharge stops.

[0061] The preferred operating pressure is 20 kPa, but those skilled in the art can adjust it according to actual usage requirements without making specific limitations.

[0062] Finally, as Figure 7 As shown, the present invention also provides a liquid level control method, which utilizes the pneumatically driven pilot valve of the negative stiffness structure or the pneumatically driven pilot valve system of the negative stiffness structure, the method comprising the following steps:

[0063] Step 1: As the liquid level in sewage tank 1 rises, the liquid level in liquid level sensing tube 2 rises synchronously, compressing the gas inside liquid level sensing tube 2 and transmitting it to pilot valve 3;

[0064] Step 2: The gas inside the liquid level sensing tube 2 is conducted into the second valve chamber 326 and the third valve chamber 327 through the liquid level rising air pressure conduction port 332 and the first through hole 3221 of the second partition 322. As the air pressure rises above 20 kPa, the pneumatic piston 340 gradually rises under the action of air pressure until the piston head 341 reaches the upper limit position. The sealing gasket 342 abuts against the first limit seat 3101 and the second limit seat 3211 to block the through hole between the first limit seat 3101 and the second limit seat 3211, thus closing the atmospheric pressure air path. At the same time, when the air pressure rises, the outer ring convex surface 372 of the negative stiffness pneumatic elastic element 370 is subjected to positive pressure and undergoes expansion deformation. The plug 371 of the negative stiffness pneumatic elastic element 370 is lifted, opening the negative pressure connection port 382. The main drain valve 5 is connected to the negative pressure and opens to start draining.

[0065] Step 3: When the liquid level in sewage tank 1 drops, the liquid level in the liquid level sensing tube 2 drops synchronously, the air pressure drops, the pneumatic piston 340 drops under the elastic force of the return spring 350, the atmospheric pressure connection port 331 and the main valve connection port 333 are connected, the atmospheric pressure air circuit is connected to the sewage discharge main valve 5, the negative stiffness pneumatic elastic element 370 returns to its original position, the plug 371 seals the negative pressure connection port 382 under the elastic force of the negative pressure port pre-tightening spring 360, the negative pressure connection is closed, the sewage discharge main valve 5 is closed, and sewage discharge stops.

[0066] Optionally, the flow rate of the sewage injection level sensing tube 2 is controlled at 1-3 m / s. 3 / h, in the pilot valve 3, the third valve chamber 327 of the negative pressure tank 4 is connected, where the air flow rate is 5 to 10 L / min.

[0067] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pneumatically driven pilot valve with a negative stiffness structure, characterized in that, The pilot valve (3) includes a valve body shell (330) and a first top cover (310) and a second top cover (380) respectively connected to both ends of the valve body shell (330). A first partition (321) and a second partition (322) located below the first partition (321) are provided inside the valve body shell (330). A movable pneumatic piston (340) is provided inside the first partition (321). A return spring (350) is provided between the pneumatic piston (340) and the first partition (321). The second partition (322) is located below the pneumatic piston (340). A first valve chamber (325) is formed between the first top cover (310) and the first partition (321). A second valve chamber (326) is formed between the first partition (321) and the second partition (322). A third valve chamber (327) is formed between the second partition (322) and the second top cover (380). The valve body shell (330) is provided with an atmospheric pressure connection port (331), a liquid level rise gas pressure conduction port (332), and a main valve connection port (333); the atmospheric pressure connection port (331) is connected to atmospheric pressure and communicates with the first valve chamber (325); the liquid level rise gas pressure conduction port (332) communicates with the second valve chamber (326) and the third valve chamber (327); there are two main valve connection ports (333), one of which communicates with the first valve chamber (325), and the other of which communicates with the third valve chamber (327). The atmospheric pressure connection port (331), the first valve chamber (325), and the main valve connection port (333) communicating with the first valve chamber (325) form an atmospheric pressure air path. A negative stiffness pneumatic elastic element (370) is connected below the second partition (322); the second top cover (380) has a negative pressure communication port (382) for communicating negative pressure, the negative stiffness pneumatic elastic element (370) includes an elastic outer ring convex surface (372) and a plug (371) connected below the outer ring convex surface (372), the plug (371) is used to block the negative pressure communication port (382), and a negative pressure port preload spring (360) is provided between the plug (371) and the second partition (322); Air pressure enters the second valve chamber (326) and the third valve chamber (327) through the liquid level rise air pressure conduction port (332); the air pressure rises, the air pressure in the second valve chamber (326) drives the pneumatic piston (340) to move up to the upper limit to cut off the atmospheric pressure air path, the air pressure in the third valve chamber (327) drives the outer ring convex surface (372) to undergo expansion deformation and pulls the plug (371) to move up to open the negative pressure connection port (382); the air pressure drops, the reset spring (350) drives the pneumatic piston (340) to move down to make the atmospheric pressure air path open, the negative pressure port preload spring (360) drives the plug (371) to move down to block the negative pressure connection port (382).

2. The pneumatically driven pilot valve with a negative stiffness structure according to claim 1, characterized in that, The pneumatic piston (340) includes a piston rod (343) and a piston head (341) and a piston bottom (344) respectively disposed at both ends of the piston rod (343). The piston head (341) is located in the first valve chamber (325), and the piston bottom (344) is located in the second valve chamber (326). The piston rod (343) is movably inserted into the first partition (321). The return spring (350) is sleeved on the piston rod (343), with one end abutting against a spring seat disposed below the first partition (321), and the other end abutting against a spring seat disposed above the piston bottom (344). The first limiting seat (3101) is provided below the first top cover (310), and the second limiting seat (3211) is provided above the first partition (321). A through hole is formed between the first limiting seat (3101) and the second limiting seat (3211). A sealing gasket (342) is provided on the upper surface of the piston head (341). The piston head (341) can move upward to abut against the first limiting seat (3101) and the second limiting seat (3211) to block the through hole between the first limiting seat (3101) and the second limiting seat (3211) and cut off the atmospheric pressure air path.

3. The pneumatically driven pilot valve with a negative stiffness structure according to claim 1, characterized in that, The second partition (322) has a first through hole (3221) connecting the second valve chamber (326) and the third valve chamber (327); the second partition (322) is a disc-shaped structure with an annular recess on its outer edge, and the negative stiffness pneumatic elastic element (370) is embedded in the annular recess; the interior of the second partition (322) has a channel connecting the liquid level rise gas pressure conduction port (332) and the first through hole (3221), and the channel extends from the edge of the second partition (322) to its center; the first through hole (3221) is located at one end of the channel near the center of the second partition (322).

4. The pneumatically driven pilot valve with a negative stiffness structure according to claim 1, characterized in that, A protrusion (384) is provided above the second top cover (380); the negative stiffness pneumatic elastic element (370) is located in the third valve chamber (327), the edge of the outer ring convex surface (372) is bent inward and fixedly connected to the second partition (322); the outer ring convex surface (372) is made of elastic material, the air pressure is introduced into the third valve chamber (327) from the liquid level rise air pressure conduction port (332) and drives the negative stiffness pneumatic elastic element (370) to undergo expansion deformation and move downward, the protrusion (384) abuts against the outer ring convex surface (372) and drives the negative stiffness pneumatic elastic element (370) to be recessed inward, the elastic material outer ring convex surface (372) undergoes expansion deformation and drives the plug (371) to rise, so as to open the negative pressure communication port (382).

5. The pneumatically driven pilot valve with a negative stiffness structure according to claim 4, characterized in that, The negative stiffness pneumatic elastic element (370) is made of rubber material and has a hemispherical shape. The central axis of the negative stiffness pneumatic elastic element (370) coincides with the central axis of the pilot valve (3) body. The plug (371) is located at the center of the negative stiffness pneumatic elastic element (370). One end of the negative pressure port preload spring (360) abuts against the top of the plug (371), and the other end abuts against the bottom of the center of the second partition (322).

6. The pneumatically driven pilot valve with a negative stiffness structure according to claim 5, characterized in that, The air pressure sensitivity of the negative stiffness pneumatic elastic element (370) is adjusted according to its shape and thickness to adjust the displacement of the plug (371); the curvature of the outer ring convex surface (372) varies from 0.52 to 1.

40.

7. A pneumatically driven pilot valve with a negative stiffness structure according to claim 2, characterized in that, The first top cover (310) is sealed to the valve body shell (330) by a first top cover sealing ring (312), the first partition (321) is sealed to the valve body shell (330) by a first partition sealing ring (323), the piston bottom (344) is sealed to the valve body shell (330) by a sealing ring (345), the second partition (322) is sealed to the valve body shell (330) by a second partition sealing ring (324), and the second top cover (380) is sealed to the valve body shell (330) by a second top cover sealing ring (383); the first top cover (310) is connected to the valve body shell (330) by a first fastening bolt (311), and the second top cover (380) is connected to the valve body shell (330) by a second fastening bolt (381).

8. A pneumatically driven pilot valve system with a negative stiffness structure, characterized in that, The system includes a pneumatically driven pilot valve with a negative stiffness structure as described in any one of claims 1-7; The system also includes a sewage tank (1), a liquid level sensing tube (2), a negative pressure tank (4), and a main drain valve (5); the atmospheric pressure connection port (331) of the pilot valve (3) is connected to atmospheric pressure; the sewage tank (1) stores sewage, the liquid level sensing tube (2) is fixed to the inner wall of the sewage tank (1), its bottom is connected to the sewage tank (1), the upper end of the liquid level sensing tube (2) is connected to a pressure transmission tube, and the other end of the pressure transmission tube is connected to the liquid level rise pressure transmission port (332) of the pilot valve (3); when the liquid level in the sewage tank (1) rises, the liquid level in the liquid level sensing tube (2) rises synchronously, the air in the tube is squeezed by the liquid surface, and through the opening at the upper end of the liquid level sensing tube (2), it is transmitted through the pressure transmission tube to the liquid level tank (1). The rising air pressure conduction port (332) enters the pilot valve (3); the bottom of the sewage tank (1) is a sewage outlet, which is connected to a sewage pipe. The other end of the sewage pipe is connected to a sewage main valve (5). The sewage main valve (5) has an air pressure control interface (510). The air pressure control interface (510) is connected to the two main valve communication ports (333) of the pilot valve (3) through the air pressure pipe. The sewage main valve (5) is connected to the negative pressure tank (4) through a sewage pipe. The negative pressure communication port (382) of the pilot valve (3) is connected to a negative pressure pipe. The other end of the negative pressure pipe is connected to the sewage pipe between the sewage main valve (5) and the negative pressure tank (4). The negative pressure tank (4) provides continuous negative pressure to the pilot valve (3) through the negative pressure pipe.

9. A liquid level control method, characterized in that, The pneumatically driven pilot valve system with a negative stiffness structure as described in claim 8, the method comprising the following steps: Step 1: The liquid level in the sewage tank (1) rises, and the liquid level in the liquid level sensing tube (2) rises synchronously, squeezing the gas in the liquid level sensing tube (2) and transmitting it to the pilot valve (3); Step 2: The gas inside the liquid level sensing tube (2) is conducted into the second valve chamber (326) and the third valve chamber (327) through the liquid level rising gas pressure conduction port (332) and the first through hole (3221) of the second partition (322). As the gas pressure rises above 20 kPa, the pneumatic piston (340) gradually rises under the action of the gas pressure until the piston head (341) reaches the upper limit position. The sealing gasket (342) and the first limit seat (3101) and the second limit seat (321) are then connected. 1) Abutting, to block the through hole between the first limiting seat (3101) and the second limiting seat (3211), closing the atmospheric pressure air passage; at the same time, when the air pressure rises, the outer ring convex surface (372) of the negative stiffness pneumatic elastic element (370) is subjected to positive pressure, undergoes expansion deformation, the plug (371) of the negative stiffness pneumatic elastic element (370) is lifted, opening the negative pressure connection port (382), the sewage discharge main valve (5) is connected to the negative pressure, the sewage discharge main valve (5) is opened, and sewage discharge begins; Step 3: When the liquid level in the sewage tank (1) drops, the liquid level in the liquid level sensing tube (2) drops synchronously, the air pressure drops, the pneumatic piston (340) drops under the elastic force of the return spring (350), the atmospheric pressure connection port (331) and the main valve connection port (333) are connected, the atmospheric pressure air path is connected to the sewage discharge main valve (5), the negative stiffness pneumatic elastic element (370) returns to its original state, the plug (371) seals the negative pressure connection port (382) under the elastic action of the negative pressure port pre-tightening spring (360), the negative pressure connection is closed, the sewage discharge main valve (5) is closed, and sewage discharge stops.

10. A liquid level control method according to claim 9, characterized in that, The flow rate of wastewater injected into the liquid level sensing tube (2) is controlled at 1-3 m / s. 3 / h, in the pilot valve (3), the third valve chamber (327) of the negative pressure tank (4) is connected, where the air flow rate is 5 to 10 L / min.

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