Gas-liquid isolation sealing method for piston accumulator

Abstract

The present invention discloses a gas-liquid isolation sealing method for a piston accumulator, which aims to solve the problem that it is difficult to ensure the extreme dynamic sealing of the accumulator piston seal ring and the problem of the seal tilting and damage under high pressure. The present invention is implemented through the following technical scheme: according to the cylindrical piston, the clamping nut and the seal assembled in the cylinder for bidirectional movement, and the end covers at both ends of the cylinder, the piston accumulator end cover and the cylinder are threadedly connected, and three to four annular rectangular ring grooves are arranged on the outer circle of the piston, wherein the first rectangular ring groove and the fourth rectangular ring groove are assembled with a guide ring, the second ring groove is assembled with an O-ring, and a sealing ring pressed on the O-ring is assembled on the O-ring, and the third rectangular ring groove is assembled with a triangular sealing ring, and triangular protective rings are arranged on both sides of the triangular sealing ring. The present invention avoids the pressure trapped between the combined seal formed by the O-ring and the sealing ring and the triangular seal.

Description

Technical Field

[0001] The invention relates to a hydraulic sealing system and a sealing method for gas-liquid isolation in a piston accumulator in the hydraulic and pneumatic fields. Background Art

[0002] The accumulator is an energy storage device that can store hydraulic pressure in a pressure-resistant container and release it when needed. The accumulator is an important auxiliary component in the hydraulic system, and plays an important role in ensuring the normal operation of the system, improving its dynamic performance, maintaining working stability, extending working life, and reducing noise. The piston accumulator is a high-pressure piston accumulator, which relates to the technical field of hydraulic auxiliary components. It can be used in the hydraulic systems of die-casting machines, metallurgy and other industries as an auxiliary power source to reduce power consumption and achieve energy saving. The piston accumulator is a common hydraulic accessory in the hydraulic system. It is an energy conversion device. It is mainly used in the hydraulic system to store energy, absorb pulsation pressure, eliminate pulsation, reduce noise and recover energy. The piston accumulator uses a piston to separate gas and liquid. There is a seal between the piston and the inner wall of the cylindrical accumulator, so the oil is not easy to oxidize. The piston accumulator has a long life, light weight, easy installation, simple structure and convenient maintenance, but the disadvantage is that the mass block has a large inertia, poor reaction sensitivity, and is not easy to seal; it is not suitable for low-pressure absorption of pulsation. The piston accumulator uses the compressibility of gas to store hydraulic oil, which can be quickly released when needed, and improve the effective power of the hydraulic pump under less power. The cylindrical piston of the piston accumulator separates the gas and liquid, and there is a seal between the piston and the inner wall of the accumulator cylinder. Due to the large inertia of the piston and the friction resistance of the seal, when the end face of the piston is just close to the end face of the lower end cover, the starting pressure is too high, especially for small accumulators. The starting pressure and sealing of the piston accumulator often have poor action sensitivity during use, and the nitrogen end cannot maintain pressure. The technical problem solved is to improve the service life and sealing. The sealing form of the piston ensures the reliability of the seal, which is the key to ensure the safe and reliable operation of the piston accumulator. The consequences of seal failure can sometimes be very serious.

[0003] The structure of the piston accumulator is mainly composed of a cylinder, a piston, a lower end cover, an upper end cover, and a compression nut seal. The lower end cover is connected to the cylinder by threads, and the upper end cover is compressed by a compression nut. The compression nut is connected by threads. The hydraulic oil chamber and the nitrogen chamber are separated by the piston, and the internal and external seals are guaranteed by the seal. When working, the hydraulic pump injects high-pressure oil into the hydraulic oil chamber, and the piston moves upward and compresses the nitrogen in the nitrogen chamber. When the set pressure, also known as the maximum working pressure, is reached, the hydraulic pump stops, and the hydraulic valve is closed to maintain pressure. At this time, a certain amount of high-pressure oil has been stored in the accumulator. When needed, the hydraulic valve is opened, and the accumulator can quickly discharge the high-pressure oil to supply the hydraulic system. The reason for the high starting pressure of the hydraulic system: mainly when the nitrogen chamber is connected to the atmosphere, the hydraulic oil chamber is connected to the hydraulic oil, and the overflow valve of the pressure test system gradually increases the pressure from zero. The pressure reflected by the pressure gauge when the piston starts is called the minimum starting pressure. The minimum starting pressure is related to the friction coefficient and the selected seal. Different types of seals have different friction coefficients, so the minimum starting pressure varies. In addition, when the piston end face is in contact with the end face of the lower end cover, the hydraulic oil cannot directly enter the cylinder of the accumulator. In this case, the minimum starting pressure will increase a lot. The high starting pressure of the accumulator is due to the small diameter of the oil inlet hole of the small accumulator and the internal leakage. The existing technology usually uses a Yx sealing ring at each end of the piston seal structure of the piston accumulator, and an O-shaped sealing ring and a Yx-shaped sealing ring with double retaining rings in the middle. Although the dynamic and static sealing performance is good, due to the limitations of the seal structure and the seal material, the suitable reciprocating speed is 0.5m / s. The piston (material LD10) is in direct contact with the cylinder, and a Yx sealing ring near the nitrogen chamber end is always in a dry friction or semi-dry friction state. The friction resistance will increase, and the action sensitivity of the piston accumulator will deteriorate. In this case, the high-speed movement of the piston will generate high temperature, causing the seal to age, become black, harden, and become brittle. The seal loses its sealing function, and internal leakage will naturally occur, affecting the sealing performance of the seal and shortening its service life. In addition, the dimensional accuracy and surface roughness of the inner surface of the cylinder; the dimensional accuracy and surface roughness of the piston seal groove processing; the protection of the seal during installation and the cleanliness of the hydraulic oil used, etc., all these factors affect the internal leakage.

[0004] High-speed accumulator structure The piston of a high-speed piston accumulator moves fast, causing the piston to violently collide with the end cover, which is more common in high-power hydraulic systems. The high-speed accumulator controls the pre-charge pressure of the accumulator through a high-pressure gas source and a pressure reducing valve. In the initial state, the main valve is in a closed state, and the oil source first fills the accumulator with liquid. After the filling is completed, the servo valve core position is switched to open the main valve. The oil stored in the accumulator enters the hydraulic cylinder through the main valve to achieve high-speed movement of the piston. According to the requirements of the accumulator piston for gas-liquid sealing, buffering requirements, and whether there is relative movement between the piston sealing surfaces, it is divided into rotary seals and reciprocating seals. When the sliding speed is very small, the friction force when the piston rod retracts is greater than the friction force when it extends outward because the shear flow of the piston rod during retraction will bring a small amount of leaked oil back to the pressure chamber. Reciprocating seals are all changes in the sealing gap caused by the deformation of the contact seal and the cylinder sleeve. The elasticity and wear resistance required by the seal are difficult to be simultaneously available on one part. In the hydraulic seal system, piston accumulators can be mainly divided into three types of accumulators: gas, spring, and heavy hammer. The most common of these three types is the gas structure accumulator. Among the gas-filled accumulators, the piston accumulator and the bladder accumulator are the most widely used. The piston accumulator of this type of hydraulic seal system ( Figure 2 The piston accumulator structure of the hydraulic seal system shown in the figure uses a piston in the cylinder to isolate the gas and oil. The piston can float in the cylinder. The gas is inflated into the accumulator air chamber through the charging valve. The oil port of the accumulator liquid chamber is connected to the system and filled with pressure oil. The piston accumulator of this type of hydraulic seal system will be affected by the inertia of the piston and the friction between the seal and the cylinder, so the reaction is not sensitive enough. The cylinder processing and piston seal requirements are high. The piston accumulator is mainly composed of three main parts: the cylinder, the piston in the cylinder, and the end covers at both ends of the cylinder, and other accessories such as seals and compression nuts. The closed end face of the piston bears the pressure of the working fluid and forms a combustion chamber or compression volume with the cylinder head and cylinder wall. The piston is equipped with a piston ring or a colloid seal to prevent fluid leakage. The piston can be made of cast iron, forged steel, cast steel or aluminum alloy. The inner cavity at the inner end of the oil cylinder head body is provided with a retaining ring, a dirt retaining ring, a sealing ring, a shaft sleeve and a retaining ring in sequence; the outer end of the oil cylinder head body is provided with an O-ring; one side of the oil cylinder head body is provided with an oil channel interface; the key points are that a buffer sealing ring is provided between the sealing ring and the shaft sleeve, a buffer chamber connected to the oil channel interface is provided on the outer side of the retaining ring, a throttle valve connecting hole connected to the buffer chamber is provided on the other side of the oil cylinder head body, and a buffer oil channel is provided at the inner end of the throttle valve connecting hole. During operation, the piston of the piston accumulator is in a frequent movement process. When storing oil, the internal pressure at the piston is required to quickly reach the system pressure value. When discharging oil, the internal sealing pressure of the piston will not be too high, and the high pressure on the air side acts on the seal, causing the seal to tilt and destroy the sealing function. Figure 2The accumulator piston seal structure shown is a conventional seal structure, which is sealed by two O-rings. Since the O-ring is made of rubber, the friction coefficient is large, the heat generated by friction is large, and the mechanical seal loses elasticity, is easy to wear, and may produce coke. These solid particles will cause scratches on the sealing end face, causing the seal to fail. At the same time, the O-ring is prone to twisting off, which also affects the service life of the piston accumulator.

[0005] When the accumulator is used as a large flow oil output source, a certain pressure of nitrogen is pre-charged before work. The hydraulic pump with a high flow outputs high-pressure oil into the oil chamber of the accumulator and pushes the piston to compress the gas to store energy. When working, the gas expands and pushes the piston to move quickly. Output large flow oil. During use, a small number of products have poor action sensitivity, and the nitrogen end cannot maintain pressure. After removing the upper end cover, it is found that there is a small amount of hydraulic oil at the nitrogen end. There are two problems with the product: 1) The starting pressure is too high; 2) Internal leakage occurs. After disassembling and inspecting the faulty products, the following situations are found: 1) There are traces of strain on the inner surface of the cylinder; 2) The groove surface of the piston where the seal is installed has knife marks caused by vibration during processing; 3) When the end face of the piston is close to the end face of the lower end cover, the starting pressure is too high, especially for small accumulators, and it is slightly better for large accumulators; when the piston leaves the end face of the lower end cover, the starting pressure becomes normal; 4) The seal becomes black, hard, and brittle. Reasons for high starting pressure: When the nitrogen chamber is open to the atmosphere, hydraulic oil is introduced into the hydraulic oil chamber, and the overflow valve of the pressure test system gradually increases the pressure from zero. The pressure reflected by the pressure gauge when the piston starts is called the minimum starting pressure. The piston seal structure of the original piston accumulator adopts a Yx seal ring at each end and an O-ring with a double retaining ring in the middle. Although the Yx seal ring and the O-ring have good dynamic and static sealing performance, due to the limitations of the seal structure and the seal material, the suitable reciprocating speed is ≤0.5m / s. The piston (material LD10) is in direct contact with the cylinder barrel, and the Yx seal ring at the nitrogen chamber end is always in a dry friction or semi-dry friction state. The friction resistance will increase, and the action sensitivity of the piston accumulator will deteriorate. In this case, the high-speed movement of the piston will generate high temperature, causing the seal to age, affecting the sealing performance of the seal and shortening the service life of the seal. This verifies that the seal appears black, hard, and brittle. The seal loses its sealing function, and internal leakage will naturally occur.

[0006] In the aircraft hydraulic control system, the compressibility of the sealing gas at the end of the accumulator air chamber is used to work, and the functions of oil absorption and discharge are achieved through the compression, expansion and pressure of the air chamber volume. The piston sealing performance is required to be high. When the accumulator piston moves quickly, the temperature of the hydraulic oil rises rapidly, and the extreme working temperature reaches 150℃ or even higher. At the same time, the accumulator sometimes works at an extreme low temperature of -55℃. Therefore, the seal on the accumulator piston must be guaranteed to work normally in a large temperature range. The two O-rings on the accumulator piston that are currently commonly used are difficult to guarantee dynamic sealing when the number of extreme low temperature operations increases. Therefore, it is particularly important to ensure the dynamic sealing of the accumulator at extreme low and high temperatures. Summary of the invention

[0007] In order to ensure the effect of absorbing pulsating pressure, the piston of the accumulator has small starting friction, the dynamic and static sealing performance of the seal on the piston is good, the piston should move smoothly, and the reliability is increased. In addition, the service life of the piston accumulator is improved. In view of the shortcomings of the prior art, the present invention provides a piston accumulator sealing method with small friction, smoother movement, superior dynamic sealing and good wear resistance, so as to solve the problems of seal twisting, large piston starting friction, poor dynamic sealing and wear resistance in the piston sealing structure of conventional piston accumulators, and also avoid the pressure trapped between the combined seal formed by the O-ring and the sealing ring and the triangular seal.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a gas-liquid isolation sealing method for a piston accumulator, which has the following technical features: according to a cylindrical piston, a clamping nut and a seal assembled in a cylinder for bidirectional movement, and end covers at both ends of the cylinder, a piston accumulator end cover and a cylinder 1 are threadedly connected, and three to four annular rectangular ring grooves are arranged on the outer circle of the piston 2, wherein the first rectangular ring groove and the fourth rectangular ring groove are assembled with a guide ring 3, the second ring groove is assembled with an O-type sealing ring 6, and a sealing ring 7 pressed on the O-type sealing ring 6 is assembled on the O-type sealing ring 6, the third rectangular ring groove is assembled with a triangular sealing ring 4, and triangular protective rings 5 ​​are arranged on both sides of the triangular sealing ring 4.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] The piston has low starting friction, good dynamic sealing effect, the seal has anti-torsion ability, and the sealing ring has good wear resistance. The present invention adopts a triangular sealing structure between the two sealing lines in front and behind the bidirectional motion piston. The triangular sealing ring used has high contact stress with the cylinder barrel, low friction resistance, and good dynamic sealing performance. The triangular protective rings are installed on both sides of the triangular sealing ring assembled through the second ring groove to prevent the twisting and extrusion of the triangular sealing ring, which solves the problem of twisting and extrusion of the seals of the two O-ring sealing structure of the piston in the conventional piston accumulator, and the problem that the dynamic sealing performance of the two O-rings on the accumulator piston in the prior art is difficult to ensure at extreme working temperatures.

[0011] The movement is smoother. The present invention adopts the method of installing guide rings 3 in the first ring groove and the fourth ring groove assembled in the front and rear ends of the bidirectional motion piston generatrix as the first gas sealing defense line between the gas cavity end and the liquid cavity end. The guide rings on both sides of the piston are used to make the start and movement of the piston smoother, which not only avoids the phenomenon of unstable piston movement caused by excessive gap between the piston and the cylinder, but also reduces the friction force of piston start-up and improves the stability of piston movement.

[0012] Increased reliability. The present invention uses a third ring groove to install the O-ring 6, and assembles a sealing ring 7 pressed on the O-ring 6 on the O-ring 6. The one-way sealing ring and the O-ring form a combined seal as the liquid cavity end sealing oil. When the accumulator is working, the sealing ring 7 is in direct contact with the cylinder body, which increases the wear resistance and reliability of the seal, reduces the friction, and concentrates the O-ring 6 on the dynamic sealing surface. The liquid film has good wiping performance and a small friction coefficient, which well meets the requirements of the piston seal in the gas-liquid accumulator, and solves the problem that the high pressure on the liquid cavity side acts on the seal, causing the seal to tilt and destroy the sealing function.

[0013] The present invention adopts a double-layer seal that sequentially arranges a guide ring, a triangular sealing ring, and a sealing ring 7 pressed on a one-way sealing O-ring 6. The double-layer seal has good air tightness and no leakage, effectively ensures the sealing of the piston and the cylinder barrel, and solves the problem of excessive starting pressure when the end face of the piston just contacts the end face of the lower end cover. The air pressure of the four-line sealing defense oil groove forms an oil seal that can prevent the nitrogen in the nitrogen chamber from leaking into the hydraulic system. This triangular sealing ring has a triangular protective ring structure on both sides, which can make the piston receive a damping effect of a buffering effect before reaching the lower end cover, and can prevent the piston from being impacted. In addition, the guide rings installed in the first ring groove and the fourth ring groove assembled at the front and rear ends of the piston can prevent the piston from directly contacting the cylinder barrel, and the bearing capacity is high, the friction is small, the wear resistance is good, and the service life is long. If the two sealing ring oil grooves are filled with lubricating oil, not only will the friction resistance be small and the static sealing performance be good, but also the lubricating oil can be prevented from creeping. It can not only isolate the nitrogen in the nitrogen chamber from leaking into the hydraulic oil chamber, but also lubricate the inner surface of the nitrogen chamber, preventing the gas end sealing ring from being in a dry friction or semi-dry friction state, and improving the action sensitivity of the piston accumulator. Due to the special structure of the one-way sealing ring with the "pump backflow" function, the high-pressure area between the seals is avoided, thereby effectively solving the problem of trapped pressure between the triangular sealing ring and the combined seal. Compared with the prior art, by providing three to four annular rectangular groove sealing structures, the starting pressure is further reduced, the action sensitivity of the piston accumulator and the service life of the sealing ring are improved, and the speed requirements of the instantaneous rapid movement of the piston in the accumulator can be met. The test results show that the piston sealing structure and the overall structure are reasonably designed, which can improve the action sensitivity of the piston accumulator and enable the designed piston accumulator to meet the actual use requirements well. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a partial cross-sectional schematic diagram of the gas-liquid isolation seal of the piston accumulator of the present invention.

[0015] Figure 2 This is a schematic diagram of a conventional piston seal structure.

[0016] In the figure: 1 cylinder, 2 piston, 3 guide ring, 4 triangular sealing ring, 5 triangular protection ring, 6 O-ring, 7 sealing ring.

[0017] The present invention is further described below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0018] See also Figure 1According to the present invention, based on the cylindrical piston, the clamping nut and the seal assembled in the cylinder for bidirectional movement, and the end covers at both ends of the cylinder, the piston accumulator end cover and the cylinder 1 are threadedly connected, and three to four annular rectangular ring grooves are arranged on the outer circle of the piston 2, wherein the first rectangular ring groove and the fourth rectangular ring groove are assembled with the guide ring 3, the second ring groove is assembled with the O-type sealing ring 6, and the sealing ring 7 pressed on the O-type sealing ring 6 is assembled on the O-type sealing ring 6, the third rectangular ring groove is assembled with the triangular sealing ring 4, and triangular protective rings 5 ​​are arranged on both sides of the triangular sealing ring 4.

[0019] In the preferred embodiment described below, a gas-liquid isolation sealing method for a piston accumulator includes: a cylindrical piston, a clamping nut and a seal assembled in a cylinder for bidirectional movement, and end covers at both ends of the cylinder, the piston accumulator end covers and the cylinder are threadedly connected, wherein: three to four annular rectangular ring grooves are arranged on the outer circle of the piston 2, the first rectangular ring groove and the fourth rectangular ring groove are equipped with a guide ring 3, the second ring groove is equipped with an O-ring 6, and a sealing ring 7 pressed on the O-ring 6 is assembled on the O-ring 6, and the third rectangular ring groove is equipped with a triangular sealing ring 4, and triangular protective rings 5 ​​are arranged on both sides of the triangular sealing ring 4.

[0020] Furthermore, the first annular groove and the fourth annular groove are provided with guide rings 3, and the function of the support guide rings is to prevent the gap between the piston and the cylinder from being too large, thereby causing the piston to move unsteadily.

[0021] Furthermore, an O-ring 6 is installed in the second ring groove, and a one-way sealing ring 7 is assembled on the O-ring, wherein the O-ring serves as a force-applying element of the sealing ring to provide sufficient sealing force, and the sealing ring 7 is a stepped trapezoidal structure, and the trapezoidal sealing edge has a steep contact stress gradient on the high-pressure side, and the trapezoidal sealing edge on the low-pressure side has a gentle contact pressure gradient, thereby ensuring that the oil film attached to the cylinder barrel returns to the liquid chamber when the piston moves toward the liquid chamber, preventing the leakage of a trace amount of oil layer on the inner surface of the cylinder body in the liquid chamber during the movement of the piston, and also avoiding the pressure trapped between the combined seal formed by the O-ring and the sealing ring and the triangular seal.

[0022] Furthermore, the third ring groove is provided with a triangular sealing ring 4, and triangular protective rings 5 ​​are installed on both sides of the triangular sealing ring 4. The triangular sealing ring 4 is used to seal the gas in the air cavity, and triangular protective rings 5 ​​are installed on both sides to prevent the triangular sealing ring from turning over and squeezing out. When designing the triangular sealing ring, the appropriate rubber material is selected according to the high and low temperature environment of the accumulator, and the triangular sealing ring is designed with a compression rate of 12% to 18%. After the triangular sealing ring is installed, the sealing band with the cylinder barrel is narrower, but the contact stress between the triangular sealing ring and the cylinder barrel is higher, and the dynamic sealing performance is better.

[0023] Working principle of piston accumulator: The piston separates the cylinder into the air chamber and the liquid chamber. When in use, a certain pressure of inert gas is pre-filled into the air chamber. When the accumulator is pressurized, the oil pressure acts on the end face of the piston, pushing the piston to compress the gas, so that the volume of the oil chamber increases and the volume of the air chamber decreases, thereby storing oil and increasing the pressure of the air chamber. The upper part of the piston is compressed gas, and the lower part is pressurized oil. The pressurized oil enters from the lower oil inlet, pushes the piston, and compresses the gas in the upper chamber of the piston to store energy; when the system pressure is lower than the pressure in the accumulator, the gas pushes the piston and releases the pressurized oil. When the accumulator is depressurized, the gas pressure acts on the end face of the piston, and the gas expands to push the piston to move, thereby discharging the oil and reducing the pressure in the air chamber.

[0024] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A gas-liquid isolation sealing method for a piston accumulator, having the following technical features: according to a cylindrical piston, a compression nut and a seal assembled in a cylinder for bidirectional movement, and end covers at both ends of the cylinder, a piston accumulator end cover and a cylinder (1) are threadedly connected, and four annular rectangular grooves are arranged on the outer circle of the piston (2), wherein: The first rectangular ring groove and the fourth rectangular ring groove are equipped with guide rings (3), the function of the guide rings is to prevent the gap between the piston and the cylinder from being too large, which may cause the piston to move unsteadily. The second rectangular ring groove is equipped with an O-type sealing ring (6), and a sealing ring (7) pressed on the O-type sealing ring (6) is assembled on the O-type sealing ring (6) to perform a one-way sealing. The third rectangular ring groove is equipped with a triangular sealing ring (4), and triangular protective rings (5) are arranged on both sides of the triangular sealing ring (4); The sealing ring (7) is a stepped trapezoidal structure. The trapezoidal sealing edge has a steep contact stress gradient on the high-pressure side and a gentle contact pressure gradient on the low-pressure side, thereby ensuring that the oil film attached to the cylinder barrel returns to the liquid chamber when the piston moves toward the liquid chamber, thereby preventing the leakage of a trace amount of oil layer on the inner surface of the cylinder body in the liquid chamber brought out by the piston during movement. The sealing structure composed of the O-ring (6) and the one-way sealing ring (7) can avoid pressure trapped between the O-ring and the triangular sealing ring.

2. The gas-liquid isolation and sealing method for a piston accumulator according to claim 1, characterized in that: The triangular sealing ring (4) is used to seal the gas in the air cavity, and the triangular protection rings (5) installed on both sides of the triangular sealing ring prevent the triangular sealing ring from turning over and squeezing out.

3. The gas-liquid isolation and sealing method for a piston accumulator according to claim 1, characterized in that: The triangular sealing ring (4) is selected from rubber materials according to the high and low temperature environment in which the accumulator is used, and is designed with a compression rate of 12% to 18%.

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