Self-lubricating pneumatic actuator

Abstract

This application discloses a self-lubricating pneumatic actuator, including a cylinder body and a piston seat. The outer wall of the piston seat is provided with a support ring and two sets of sealing rings. An annular lubricating oil groove is formed between the two sets of sealing rings. A lubricating oil piston chamber is formed inside the piston seat. A through hole communicating with the lubricating oil piston chamber is formed on the annular lubricating oil groove. A small piston is slidably fitted inside the lubricating oil piston chamber, and the small piston is exposed on the end face of the piston seat opposite to the piston rod. Under the action of the cylinder's intake pressure, the small piston makes a micro-stroke sliding motion within the lubricating oil piston chamber, pushing the lubricating oil in the lubricating oil piston chamber through the through hole to the annular lubricating oil groove, thus lubricating the two sets of sealing rings. By using the cylinder's own intake pressure to drive the small piston to make a micro-stroke sliding motion, lubricating oil can be automatically delivered to the annular lubricating oil groove, achieving continuous lubrication of the sealing rings, effectively reducing friction and wear of the sealing rings, and improving the sealing life and operational stability of the actuator.

Description

Technical Field

[0001] This application belongs to the field of pneumatic and hydraulic actuators, and in particular relates to a self-lubricating pneumatic actuator. Background Technology

[0002] The piston cylinder of a pneumatic actuator is the core power component that drives the valve. It mainly consists of a cylinder body, a piston, an O-ring seal, and a guide ring. The piston is fitted inside the cylinder body, and the O-ring seal embedded on the outer circumference seals the two cavities on both sides of the piston. The guide ring fits against the inner wall of the cylinder body to guide the piston, bear lateral forces, and prevent direct metal-to-metal friction between the piston and the cylinder body. The two work together to ensure that the piston moves stably back and forth along the cylinder axis under air pressure, and then transmits power through the piston rod to drive the valve to open and close.

[0003] In the actual use of piston cylinders, lubrication is crucial for maintaining their normal operation. Before installation, grease must be applied to the inner wall of the cylinder to reduce the frictional resistance between the O-rings, guide rings, and the inner wall of the cylinder, thereby reducing wear on the seals and preventing problems such as seal leakage and insufficient thrust caused by dry friction. However, the existing lubrication method for piston cylinders has significant defects. As the piston reciprocates, the O-rings and guide rings, which are tightly fitted to the inner wall of the cylinder, act like scrapers, continuously pushing the grease on the cylinder wall surface towards both ends of the cylinder. Over time, the grease on the inner wall of the cylinder in the high-frequency piston movement area gradually disappears. This not only significantly increases the frictional resistance between the seals and the cylinder but also accelerates the wear and aging of the O-rings, ultimately leading to seal failure, air leakage between the piston and the cavities on both sides, and the inability of the pneumatic actuator to provide sufficient driving force to the valve. This results in valves not opening and closing properly, and malfunctions such as stuck movements, seriously affecting the reliability of equipment operation.

[0004] To address the lubrication failure problem caused by grease loss, patent CN206017311U proposes a self-lubricating piston cylinder structure. This structure features a lubrication groove on the outer circumference of the piston between the O-ring and the guide ring, and a lubrication channel communicating with the lubrication groove inside the piston. One end of the lubrication channel communicates with the lubrication channel, while the other end penetrates the piston surface and communicates with the cylinder body cavity. Grease is filled into the lubrication channel and the lubrication groove, and the air pressure in the cylinder cavity is used to squeeze the grease from the lubrication channel into the lubrication channel, thus achieving continuous lubrication replenishment. However, this self-lubricating piston cylinder structure still has insurmountable technical defects and cannot achieve the expected lubrication effect: Since the two ends of the lubrication groove form passages in the cylinder cavity, during the operation of the pneumatic actuator, the intake pressure of the cylinder cavity will act on the port connecting the lubrication groove and the cavity at the same time, causing the intake pressure and outlet pressure inside the lubrication groove to tend to be consistent; according to the law of conservation of energy and the principle of fluid dynamics transmission, when the pressure difference on both sides of the grease is zero, the grease in the lubrication groove loses its driving force and remains in a static state, and cannot be effectively squeezed into the lubrication groove, so it is impossible to achieve lubrication replenishment of the cylinder wall and seals.

[0005] Another patent, CN120027114B, discloses a hydraulic cylinder with a self-lubricating system. It features two sets of piston seals forming a lubrication zone on the outer wall of the piston seat. An annular oil filter chamber and an annular compression chamber are located inside the piston seat. The annular compression chamber is divided into an oil injection zone and an action zone by an annular piston. A sliding groove is provided at the center of the piston seat shaft, which works in conjunction with a plunger rod fixed to the end cap. The piston rod's compression of the gas medium in the action zone during the reciprocating motion of the piston seat pushes the annular piston, forcing lubricating oil from the oil injection zone into the lubrication zone. Simultaneously, the negative pressure created by the reverse motion of the piston seat allows the annular piston to return to its original position and for lubricating oil to circulate and replenish. However, when this self-lubricating structure is applied to an actuator... This design completely relies on the main driving power of the actuator piston seat for the driving power of the lubrication system. Originally, the power to drive the piston seat only needed to overcome the friction between the piston seat and the cylinder and the external load. However, under this design, the main driving power also needs to bear multiple resistances, such as squeezing the gas medium in the action zone, pushing the lubricating oil to flow in the narrow oil passage, and driving the annular piston to slide. These multiple resistances are directly superimposed on the main motion resistance, resulting in a significant decrease in the main thrust of the actuator. Moreover, when there is a slight blockage in the oil passage, the annular piston gets stuck, or the gas medium is overpressurized, the additional resistance will suddenly soar. Once it exceeds the upper limit of the main driving power, the piston seat will be directly locked and unable to move, causing the main function of the actuator to be completely paralyzed. Meanwhile, the annular piston of this structure relies solely on the passive negative pressure generated by the reverse movement of the piston seat for return, without any auxiliary return or pressure compensation structure. In actual operation, it is prone to problems such as untimely, incomplete, or even jammed return due to gas leakage and check valve sticking, which further leads to the failure of the lubrication system. Moreover, it does not have a structure for venting, depressurizing, and pressurizing the gas medium. During assembly, residual air in the cavity cannot be discharged. Under high and low temperature conditions, the thermal expansion and contraction of the gas will cause pressure runaway, aggravating the damage of the seals and gas leakage, forming a vicious cycle of insufficient power, movement jamming, lubrication failure, increased friction, and even more insufficient power. Not only can it not achieve effective lubrication, but it also seriously hinders the main movement of the actuator, making it unsuitable for lubrication scenarios of pneumatic actuator piston cylinders.

[0006] Therefore, a novel self-lubricating structure for piston cylinders is urgently needed to overcome the pressure balance bottleneck of existing structures, achieve effective grease driving and continuous replenishment, and fundamentally solve the lubrication failure problem in the reciprocating motion of piston cylinders. It is evident that existing technologies require further improvement and enhancement. Summary of the Invention

[0007] This invention provides a self-lubricating pneumatic actuator, which solves the problems of complex internal lubrication integration, superimposed resistance, and easy failure in existing pneumatic actuators, or at least provides a beneficial alternative.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A self-lubricating pneumatic actuator includes a cylinder body and a piston seat. The outer wall of the piston seat is provided with a support ring and two sets of sealing rings. An annular lubricating oil groove is formed between the two sets of sealing rings. A lubricating oil piston chamber is formed inside the piston seat. A through hole is formed on the annular lubricating oil groove to communicate with the lubricating oil piston chamber. A small piston is slidably fitted in the lubricating oil piston chamber. The small piston is exposed on the end face of the piston seat away from the piston rod. Under the action of the cylinder intake pressure, the small piston slides slightly in the lubricating oil piston chamber, pushing the lubricating oil in the lubricating oil piston chamber through the through hole to the annular lubricating oil groove to lubricate the two sets of sealing rings.

[0009] By employing the self-lubricating pneumatic actuator of this application, the small piston is driven by the cylinder's own intake pressure to perform a micro-stroke sliding motion, which automatically delivers lubricating oil to the annular lubricating oil groove, achieving continuous lubrication of the sealing ring, effectively reducing friction and wear of the sealing ring, and improving the sealing life and working stability of the actuator. The movement direction of the small piston is consistent with the reciprocating direction of the piston seat, without adding additional movement resistance or affecting the original movement characteristics of the piston. The overall structure is integrated inside the piston seat, eliminating the need for external lubrication components, resulting in a simple structure, convenient processing and assembly, and low cost. At the same time, the self-lubricating structure is an add-on design, so even if a failure occurs, it will not affect the basic driving and sealing functions of the pneumatic actuator, providing high safety redundancy, strong reliability, and wide applicability.

[0010] In a preferred embodiment, the micro-stroke sliding direction of the small piston is parallel to the reciprocating motion direction of the piston seat, and the cylinder intake pressure acts synchronously on the force-bearing end face of the piston seat and the exposed end face of the small piston, driving the piston seat to move while simultaneously driving the small piston to slide micro-stroke.

[0011] The micro-stroke sliding direction of the small piston is parallel to the reciprocating motion direction of the piston seat. The cylinder intake pressure can be applied synchronously to the force-bearing end face of the piston seat and the exposed end face of the small piston. While driving the piston seat to reciprocate normally, it simultaneously drives the small piston to complete a micro-oil replenishment action. The two movements are coordinated and consistent, without generating additional radial force, lateral force, or additional motion resistance. It does not change the original power characteristics and motion stability of the pneumatic actuator. The structure is reasonably stressed, the response is synchronous, the operation is reliable, and it does not increase the system energy consumption.

[0012] In a preferred embodiment, the depth of the lubricating oil piston chamber is the maximum micro-stroke of the small piston, and the small piston is stopped when it slides to the bottom of the lubricating oil piston chamber.

[0013] In a preferred embodiment, the lubricating oil piston chamber is pre-set with an initial air pressure, which is less than the cylinder's intake pressure. The cylinder's intake pressure drives the small piston to slide into the lubricating oil piston chamber. When the cylinder's intake pressure is released, the small piston slides outward and resets under the action of the initial air pressure in the lubricating oil piston chamber. After resetting, the end face of the small piston is flush with the end face of the piston seat away from the piston rod.

[0014] By pre-setting an initial air pressure lower than the cylinder intake pressure in the lubricating oil piston chamber, automatic oil replenishment can be achieved by driving the small piston to slide into the chamber during air intake using the air pressure difference. Alternatively, after the intake pressure is removed, the initial air pressure in the chamber can be used to push the small piston to slide outward and reset, keeping the end face of the small piston flush with the end face of the piston seat, thus realizing an automatic cycle of oil replenishment and reset. This structure can reliably reset without additional elastic or driving components, with stable operation and timely response. It can continuously provide lubrication for the sealing ring over a long period of time, further ensuring the continuity and stability of the actuator's operation.

[0015] In a preferred embodiment, the lubricating oil piston chamber is filled with lubricating oil, but the lubricating oil does not completely fill the entire lubricating oil piston chamber. A gas space is reserved above the lubricating oil to maintain the initial gas pressure. The gas is an inert gas that is insoluble in the lubricating oil.

[0016] In a preferred embodiment, the piston seat protrudes outward from the end face away from the piston rod to form a sleeve portion, the lubricating oil piston chamber is opened inside the sleeve portion, and the small piston is adapted to be installed in the lubricating oil piston chamber inside the sleeve portion.

[0017] In a preferred embodiment, the outer wall of the small piston is fitted with a micro support ring and a micro sealing ring at intervals, and the micro sealing ring is located on the side of the small piston near the bottom of the lubricating oil piston cavity.

[0018] The outer wall of the small piston is equipped with a micro support ring and a micro sealing ring at intervals. The micro support ring ensures the guiding fit between the small piston and the lubricating oil piston cavity, effectively preventing the small piston from wobble or jamming during sliding and improving the smoothness of movement. The micro sealing ring located near the bottom of the cavity forms a reliable seal inside the cavity, preventing oil and gas leakage, ensuring the initial gas pressure inside the cavity is stable, and ensuring that the small piston can normally perform oil replenishment and reset actions. The structure is reasonably matched, and the sealing and guiding effects are excellent.

[0019] In a preferred embodiment, a connecting section cavity is provided inside the piston seat, the inner diameter of the connecting section cavity is smaller than the inner diameter of the lubricating oil piston cavity, and the connecting section cavity connects the lubricating oil piston cavity and the through hole.

[0020] In a preferred embodiment, the lubricating oil piston chamber is provided with an axially sliding intermediate piston, which divides the lubricating oil piston chamber into a non-communicating gas chamber and an oil chamber; the gas chamber is formed between the small piston and the intermediate piston, and the gas chamber is pre-filled with gas at a certain initial pressure; the side of the intermediate piston away from the gas chamber forms the oil chamber with the piston seat, and the oil chamber is connected to the through hole and the annular lubricating oil groove and is completely filled with lubricating oil and free of gas.

[0021] By setting an axially sliding intermediate piston in the lubricating oil piston chamber, the chamber is divided into an independent and non-communicating air chamber and an oil chamber. The air chamber is only used to contain gas with initial pressure, and the oil chamber is dedicated to filling with lubricating oil. This achieves complete isolation between air and oil, preventing gas from entering the oil chamber and lubrication area and affecting the main sealing performance. The air chamber can use the compressibility of gas to buffer and reduce the intake pressure, preventing high pressure from directly and rigidly acting on the lubricating oil. The oil chamber ensures that the lubricating medium is stable, free of air bubbles, and supplied evenly. While achieving automatic oil replenishment, it greatly improves the sealing reliability and structural working stability.

[0022] In a preferred implementation, when the cylinder is intake, the small piston compresses the air chamber under the intake pressure, increasing the air chamber pressure and acting on the intermediate piston. When there is no loss of lubricating oil in the annular lubricating oil groove, there is no room for the lubricating oil in the oil chamber to move, and the intermediate piston remains stationary. When the lubricating oil in the annular lubricating oil groove is consumed, the intermediate piston moves to one side of the oil chamber under the pressure of the air chamber to replenish the lubricating oil. After the intake pressure of the cylinder is released, the small piston resets under the action of the gas in the air chamber. The intermediate piston remains in its current position because the lubricating oil inside the oil chamber is incompressible and has no room for movement.

[0023] In a preferred embodiment, the through holes are opened radially along the piston seat, and there are multiple through holes that are evenly distributed circumferentially along the annular lubricating oil groove.

[0024] The above structure has the following beneficial effects: 1. The self-lubricating pneumatic actuator of this application utilizes the cylinder's own intake pressure to drive a small piston to complete micro-stroke oil replenishment. The sliding direction of the small piston is parallel to the reciprocating direction of the piston seat, with coaxial force and no lateral force component, thus not increasing additional motion resistance and not affecting the original dynamic characteristics and motion stability of the piston. It requires no complex lubrication components, has a high degree of structural integration, is simple in overall design, is easy to process and assemble, and has low production costs.

[0025] 2. The self-lubricating pneumatic actuator of this application can continuously supply lubricating oil to the sealing ring, significantly reducing the friction and wear of the sealing ring, delaying the aging of the seal, extending the service life of the pneumatic actuator, and improving operational stability.

[0026] 3. The self-lubricating pneumatic actuator of this application has an additional redundant design for the self-lubricating structure. Even if the small piston fails due to jamming, it will not affect the normal movement of the piston and the main sealing function. It has high safety redundancy and strong reliability. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and, together with their description, serve to explain this application and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A perspective view illustrating one embodiment of the self-lubricating pneumatic actuator of this application is shown; Figure 2 The illustration shows an internal structural view of a schematic embodiment of the self-lubricating pneumatic actuator of this application. Figure 3 The illustration shows an internal structural view of a schematic embodiment of the self-lubricating pneumatic actuator of the present application. Figure 4 A perspective view illustrating a schematic embodiment of the piston seat of the self-lubricating pneumatic actuator of this application is shown. Label Explanation: 1. Cylinder; 10. Air port; 2. Piston rod; 3. Piston seat; 30. Support ring; 31. Sealing ring; 32. Sleeve section; 33. Lubricating oil piston chamber; 34. Through hole; 35. Annular lubricating oil groove; 36. Connecting section chamber; 4. Upper end cover; 5. Lower end cover; 6. Small piston; 60. Miniature support ring; 61. Miniature sealing ring; 7. Intermediate piston; 70. Air chamber; 71. Oil chamber. Detailed Implementation

[0028] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit and scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0029] The present invention will now be described with reference to the accompanying drawings.

[0030] The specific solution adopted is as follows: like Figure 1-4As shown, the present invention provides a self-lubricating pneumatic actuator, including a cylinder body and a piston seat 3. The outer wall of the piston seat 3 is provided with a support ring 30 and two sets of sealing rings 31. An annular lubricating oil groove 35 is formed between the two sets of sealing rings 31. A lubricating oil piston cavity 33 is formed inside the piston seat 3. A through hole 34 is formed on the annular lubricating oil groove 35 to connect the lubricating oil piston cavity 33. A small piston 6 is slidably fitted in the lubricating oil piston cavity 33. The small piston 6 is exposed on the end face of the piston seat 3 away from the piston rod 2. Under the action of the cylinder intake pressure, the small piston 6 slides slightly in the lubricating oil piston cavity 33, pushing the lubricating oil in the lubricating oil piston cavity 33 to the annular lubricating oil groove 35 through the through hole 34 to lubricate the two sets of sealing rings 31.

[0031] The micro-stroke sliding direction of the small piston 6 is parallel to the reciprocating motion direction of the piston seat 3. The cylinder intake pressure acts synchronously on the force-bearing end face of the piston seat 3 and the exposed end face of the small piston 6, driving the piston seat 3 to move while simultaneously driving the small piston 6 to slide micro-stroke. The cavity depth of the lubricating oil piston chamber 33 is the maximum micro-stroke of the small piston 6, and the small piston 6 is limited when it slides to the bottom of the lubricating oil piston chamber 33.

[0032] The self-lubricating pneumatic actuator of this application utilizes the cylinder's own intake pressure to drive the small piston 6 to slide with a micro-stroke, automatically pushing the lubricating oil in the lubricating oil piston chamber 33 through the through hole 34 to the annular lubricating oil groove 35, achieving continuous and uniform lubrication of the two sets of sealing rings 31. The lubrication action is synchronized with the cylinder's intake action, requiring no additional power drive, and has a high degree of structural integration, avoiding the problems of complicated assembly and high failure rate caused by complex lubrication structures. It will not generate any additional resistance to the main movement of the piston seat 3, and will not affect the original movement speed, output force, and working efficiency of the pneumatic actuator. Even if the small piston 6 experiences malfunctions such as jamming, wear, or failure, the piston seat 3 can still reciprocate normally under the action of the cylinder's intake pressure; it will only lose the automatic oil replenishment effect, without serious malfunctions such as the entire machine jamming, stopping, or being damaged, greatly improving the working reliability and safety redundancy of the actuator.

[0033] To further clarify the technical solution, working principle, and applicable working conditions of this application, the self-lubricating pneumatic actuator of this application is described in further detail below with reference to three different implementation methods: Example 1: The piston chamber 33 is completely filled with lubricating oil. The actuator in this example mainly includes a cylinder barrel 1, a piston seat 3, a piston rod 2, a sealing assembly, and a lubrication assembly. The cylinder barrel 1 is a cylindrical hollow shell structure. The two ends of the cylinder barrel 1 are respectively equipped with an upper end cover 4 and a lower end cover 5. The upper end cover 4 and the lower end cover 5 are fixedly connected to the cylinder barrel 1 by fasteners, and cylinder body seals are provided on the mating end faces to ensure that a sealed pressure-bearing cavity is formed inside the cylinder body, avoiding external air leakage and pressure relief during cylinder operation, and ensuring the output pressure and motion stability of the pneumatic actuator.

[0034] Both the upper end cover 4 and the lower end cover 5 are provided with airflow channels and air ports 10. An external air source introduces compressed air into the pressure-bearing cavity inside the cylinder body through the airflow channels. The pressure difference within the cavity drives the piston seat 3 to reciprocate linearly along the axial direction of the cylinder body. The piston seat 3 is assembled in the internal cavity of the cylinder body, and the outer circular surface of the piston seat 3 is clearance-fitted with the inner wall of the cylinder body to ensure that the piston seat 3 can slide smoothly along the axial direction without jamming, uneven wear, abnormal noise, or other phenomena. The outer wall of the piston seat 3 is provided with a support ring 30 mounting groove, a first sealing ring 31 mounting groove, an annular lubricating oil groove 35, and a second sealing ring 31 mounting groove in sequence along the axial direction. The support ring 30 is fixedly installed in the mounting groove. The outer circular surface of the support ring 30 slides against the inner wall of the cylinder, which is used to radially position and guide the piston seat 3, counteract the lateral force and overturning force generated by the piston seat 3 during reciprocating motion, avoid direct rigid contact between the piston seat 3 and the inner wall of the cylinder, reduce the wear between the outer wall of the piston seat 3 and the cylinder, and improve the coaxiality and stability of the piston seat 3 movement.

[0035] The first sealing ring 31 and the second sealing ring 31 are respectively installed in the mounting groove of the first sealing ring 31 and the mounting groove of the second sealing ring 31. The outer circular surfaces of the first sealing ring 31 and the second sealing ring 31 are tightly fitted to the inner wall of the cylinder, forming two independent axial dynamic sealing structures. The two seals block the high-pressure gas inside the cylinder, preventing gas from leaking along the mating gap between the piston seat 3 and the cylinder body, ensuring stable internal pressure in the cylinder, and thus ensuring that the piston seat 3 outputs sufficient driving force. Between the first sealing ring 31 and the second sealing ring 31, there is an annular lubricating oil groove 35. The annular lubricating oil groove 35 is arranged in a closed loop around the circumference of the piston seat 3 to store and uniformly supply lubricating oil to the outer walls of the first sealing ring 31 and the second sealing ring 31. At the bottom of the annular lubricating oil groove 35, multiple through holes 34 are evenly provided along the radial direction of the piston seat 3. The multiple through holes 34 are arranged in a circumferential array with the axis of the piston seat 3 as the center, so as to ensure that the lubricating oil can flow evenly and synchronously to each circumferential position of the annular lubricating oil groove 35, avoiding the problems of insufficient local lubrication and local dry friction.

[0036] The inner end of the through hole 34 is connected to the lubricating oil piston chamber 33 inside the piston seat 3. The lubricating oil piston chamber 33 is opened along the axial direction of the piston seat 3. The end face of the piston seat 3 away from the piston rod 2 protrudes outward to form a sleeve portion 32. The lubricating oil piston chamber 33 is opened inside the sleeve portion 32. The small piston 6 is adapted to be installed in the lubricating oil piston chamber 33 inside the sleeve portion 32. A connecting section cavity 36 is opened in the piston seat 3. The inner diameter of the connecting section cavity 36 is smaller than the inner diameter of the lubricating oil piston chamber 33. The connecting section cavity 36 connects the lubricating oil piston chamber 33 and the through hole 34.

[0037] The lubricating oil piston cavity 33 is a cylindrical blind hole structure. The bottom end of the blind hole forms the piston cavity bottom, which constitutes the limit limiting surface for the inward sliding of the small piston 6. This limit restricts the maximum sliding stroke of the small piston 6, preventing excessive displacement of the small piston 6 and squeezing of the internal oil. It also limits the endpoint of the movement of the small piston 6, ensuring the controllability of the structure's movement. The open end of the lubricating oil piston cavity 33 is located on the end face of the piston seat 3 away from the piston rod 2. A constriction limiting structure is provided at the open end. The constriction limiting structure is an annular retaining edge formed by the inward contraction of the piston seat 3 body at the open end. The inner diameter of the annular retaining edge is smaller than the inner diameter of the lubricating oil piston cavity 33, thus forming an axial limiting surface at the open end. This surface restricts the small piston 6 from dislodging outward, ensuring that the small piston 6 is always confined inside the lubricating oil piston cavity 33 and will not fall off during movement, pressure relief, or reset, thereby improving the assembly stability and operational reliability of the structure.

[0038] The small piston 6 is fitted with a clearance fit inside the lubricating oil piston cavity 33. Specifically, a miniature support ring 60 and a miniature sealing ring 61 are spaced apart on the outer wall of the small piston 6. The miniature sealing ring 61 is located on the side of the small piston 6 near the bottom of the lubricating oil piston cavity 33. Through the contact between the miniature support ring 60 and the miniature sealing ring 61 with the inner wall of the lubricating oil piston cavity 33, the small piston 6 can slide freely along the axial direction of the lubricating oil piston cavity 33 and prevents lubricating oil from leaking outward from the fit clearance. The end face of the piston seat 3 facing the piston rod 2 is a fixed connection end face, and one end of the piston rod 2 is fixedly connected to this fixed connection end face. The two can be fixed into a single structure by welding, which will not damage the sealed structure inside the piston seat 3, such as the lubricating oil piston chamber 33, the connecting hole 34, and the annular lubricating oil groove 35. There is no need to open a through shaft hole in the center of the piston seat 3, avoiding the sealing difficulties, air leakage, and oil leakage problems caused by through structures. The piston rod 2 does not pass through the piston seat 3 or the lubricating oil piston chamber 33, so that the lubricating oil passage and pressure-bearing cavity inside the piston seat 3 remain intact and sealed, making the structure simpler and more reliable.

[0039] The end face of the small piston 6, furthest from the bottom of the piston chamber, protrudes from the end face of the piston seat 3, remaining flush with or slightly concave to the end face of the piston seat 3. The cylinder intake pressure acts on the entire force-bearing end face of the piston seat 3, and also directly on the exposed end face of the small piston 6. In this embodiment, the lubricating oil piston chamber 33 is completely filled with lubricating oil, with no pre-existing gas or initial pressure. The lubricating oil fills the lubricating oil piston chamber 33, the connecting hole 34, and the annular lubricating oil groove 35, forming a complete sealed oil body. When the cylinder is working, external high-pressure gas enters the cylinder body, and the gas pressure acts synchronously on the force-bearing end face of the piston seat 3 and the exposed end face of the small piston 6, driving the piston seat 3 to reciprocate axially. Simultaneously, under the action of gas pressure, the small piston 6 slides slightly axially within the lubricating oil piston chamber 33. The sliding direction of the small piston 6 is parallel to the reciprocating direction of the piston seat 3, maintaining coaxiality and preventing the generation of radial or lateral forces, thus avoiding interference with the main motion of the piston seat 3.

[0040] When the small piston 6 slides towards the bottom of the piston chamber, the volume inside the lubricating oil piston chamber 33 is compressed. Since the lubricating oil is an incompressible liquid, after the lubricating oil inside is scraped and worn by the sealing ring 31, and a spare space appears, the internal oil is pushed into the annular lubricating oil groove 35 through the connecting hole 34 under the squeezing action of the small piston 6. The lubricating oil is evenly distributed in the annular lubricating oil groove 35 and continuously wets the contact surface between the first sealing ring 31 and the second sealing ring 31, forming a continuous and stable oil film between the sealing ring 31 and the inner wall of the cylinder, reducing the frictional loss of the sealing ring 31, reducing heat generation, delaying aging, and improving the sealing life and sealing reliability.

[0041] The axial depth of the lubricating oil piston cavity 33 is the maximum micro-stroke of the small piston 6. When the small piston 6 slides inward to fit against the bottom of the piston cavity, the bottom of the piston cavity forms a rigid limit on the small piston 6. When the small piston 6 reaches the limit position, it can no longer slide inward, thus limiting the maximum displacement of the small piston 6. The closing limit structure at the opening end of the lubricating oil piston cavity 33 forms a limit when the small piston 6 moves outward, preventing the small piston 6 from coming out of the lubricating oil piston cavity 33 during depressurization, vibration, and reversal, ensuring that the small piston 6 always moves reliably within the set stroke.

[0042] This embodiment adopts a fully oil-based self-lubricating structure, which is extremely simple in overall structure and has few parts. The piston seat 3 is an integral main structure, and the main body can be manufactured by machining only the lubricating oil piston cavity 33, the radial connecting hole 34, and various external mounting grooves. The processing technology is simple, the manufacturing cost is low, and the assembly difficulty is small, making it suitable for mass industrial production. Since there is only lubricating oil inside and no gas-bearing structure, there are no problems such as gas leakage, gas crossflow, gas pressure attenuation, or gas dissolving in oil. It will not interfere with the airtightness of the cylinder's main seal, and there will be no situation where the sealing effect is damaged due to gas entering the lubrication area. The small piston 6 and the lubricating oil piston cavity 33 have a sliding fit structure, and its movement resistance is extremely low. During the normal reciprocating motion of the piston seat 3, the small piston 6 only makes a small adaptive sliding under the action of oil pressure and gas pressure. It will not generate additional resistance to the main motion of the piston seat 3, will not increase the load on the cylinder, and will not affect the original movement speed, output force, and working efficiency of the pneumatic actuator.

[0043] The self-lubricating structure in this embodiment is an additional, redundant safety design. Even if the small piston 6 fails to slide or becomes completely stuck due to wear, impurities, or lubrication failure, the piston seat 3 can still independently complete reciprocating motion under the action of cylinder air pressure. The support ring 30, the first sealing ring 31, and the second sealing ring 31 can still achieve their original support and sealing functions. The basic functions of the pneumatic actuator are completely unaffected, only losing the automatic oil replenishment lubrication effect. There will be no serious failures such as machine jamming, shutdown, or damage. This greatly improves the working reliability, environmental adaptability, and safety redundancy of the pneumatic actuator.

[0044] Meanwhile, since the piston rod 2 is fixed to the end face of the piston seat 3 by welding without passing through the interior of the piston seat 3, it does not damage the lubricating oil piston cavity 33 and the oil passage structure, avoiding the multiple sealing problems caused by the central through hole 34, reducing leakage points, and improving the overall airtightness and stability of the structure. The bidirectional limiting structure of the small piston 6 limits the bottom of the inner piston cavity and limits the outer opening end, ensuring that the movement stroke of the small piston 6 is precise and controllable, and there will be no problems such as overtravel, disengagement, offset, or jamming. The movement is smooth and the coaxiality is high, further ensuring the stability and continuity of the oil replenishment action.

[0045] When the lubricating oil in the annular lubricating oil groove 35 is consumed by the sealing ring 31 due to scraping and friction, the oil level in the lubricating oil piston chamber 33 drops. Each compression action of the small piston 6 can replenish the lost oil, thus achieving continuous lubrication.

[0046] This embodiment is suitable for pneumatic actuators with relatively low intake pressure. Under conditions where the system supply pressure and working pressure are not high, the pressure load on the lubricating oil is small, and excessive upward thrust on the main sealing ring 31 will not occur due to excessive oil pressure, thus achieving stable self-lubrication. Because the cylinder intake pressure is low, the rigid force transmission problem caused by the incompressibility of the oil is significantly weakened. The oil pressure will not exceed the pressure bearing range of the sealing ring 31, and phenomena such as the seal being lifted, flipped outward, or leaking will not occur. It can work reliably for a long time in a low-pressure environment.

[0047] From an operational perspective, this embodiment is more suitable for operating conditions with slower speeds and lower reciprocating frequencies. Under low-speed operating conditions, the friction frequency between the sealing ring 31 and the inner wall of the cylinder is low, resulting in minimal heat generation. The lubricating oil consumption rate is gradual, eliminating the need for frequent and rapid oil replenishment, thus fully meeting continuous lubrication requirements. In low-frequency operating scenarios, the small piston 6 does not require frequent movement. Oil replenishment is completed only after the lubricating oil is gradually consumed and a small displacement occurs in the oil chamber 71, creating an oil-free space. This avoids issues such as delayed oil replenishment or dry friction.

[0048] Example 2: The main structure of the overall pneumatic actuator remains the same, still including cylinder 1, upper end cover 4, lower end cover 5, piston seat 3, piston rod 2, support ring 30, two sets of main sealing rings 31, and lubrication-related components. The assembly method of cylinder body and end cover, sealing structure, airflow channel layout, and piston rod 2 welding and fixing method in Example 1 are used to ensure basic assembly compatibility and motion logic uniformity. The cylinder body is still a cylindrical hollow shell, and both ends are sealed and locked by upper end cover 4 and lower end cover 5. A rubber cylinder body sealing ring 31 is provided at the mating point of the end cover and cylinder body to improve the airtightness under high pressure conditions. External compressed air is accurately introduced into the cylinder cavity through the airflow channel of the end cover to form a controllable air pressure drive environment.

[0049] The piston seat 3 is coaxially assembled inside the cylinder body, with its outer surface slidingly fitted to the inner wall of the cylinder. The outer wall still sequentially has mounting grooves for the support ring 30, the first sealing ring 31, the annular lubricating oil groove 35, and the second sealing ring 31. The dimensions, spacing, and machining accuracy of each groove are consistent with those in Embodiment 1. The assembly method and sealing mechanism of the support ring 30, the first sealing ring 31, and the second sealing ring 31 are exactly the same as in Embodiment 1, ensuring that the radial support and axial sealing functions of the piston seat 3 are not affected by the optimized lubrication structure, maintaining the basic stability of the piston's reciprocating motion. The annular lubricating oil groove 35 is formed in a closed loop around the piston seat 3. Multiple evenly distributed connecting holes 34 are radially opened at the bottom of the groove. The number, diameter, and arrangement of the connecting holes 34 are the same as in Embodiment 1, ensuring that the lubricating oil is evenly delivered to the contact surface of the sealing ring 31. The inner end of the connecting holes 34 connects to the lubricating oil piston cavity 33 inside the piston seat 3.

[0050] The core improvement of this embodiment lies in the internal medium filling of the lubricating oil piston chamber 33. The lubricating oil piston chamber 33 is not completely filled with lubricating oil; instead, it uses a mixture of lubricating oil and a pre-placed inert gas. For example, nitrogen is used as the pre-placed gas because it is chemically stable and extremely difficult to dissolve in conventional lubricating oil, preventing the gas from dissolving in the oil and causing a loss of reset pressure. It also prevents gas oxidation from accelerating lubricating oil aging. During assembly, a measured amount of lubricating oil is first injected into the lubricating oil piston chamber 33, filling 70%-80% of the chamber volume. The remaining 20%-30% is reserved as a gas chamber. Atmospheric pressure nitrogen is then injected through a dedicated gas injection port, and the port is subsequently sealed, creating a stable initial gas pressure within the chamber. This initial gas pressure is strictly set lower than the cylinder's working intake pressure, forming the basis for pressure differential drive.

[0051] The small piston 6 is coaxially assembled inside the lubricating oil piston cavity 33. A miniature support ring 60 and a miniature sealing ring 61 are added to the outer wall, spaced apart along the axial direction of the small piston 6. The miniature sealing ring 61, located near the bottom of the lubricating oil piston cavity 33, is press-fitted against the inner wall of the cavity, achieving a seal and isolation of the oil-gas cavity 70, preventing leakage of pre-installed gas and lubricating oil. The miniature support ring 60, located near the exposed end face of the small piston 6, is clearance-fitted against the inner wall of the cavity, providing radial guidance and preventing the small piston 6 from wobbling or jamming during sliding, ensuring smooth axial sliding. The exposed end face of the small piston 6 is initially flush with the end face of the piston seat 3. The cylinder intake pressure acts synchronously on the force-bearing end face of the piston seat 3 and the exposed end face of the small piston 6, with the force-bearing surfaces coaxially aligned, avoiding lateral force interference with movement.

[0052] When the cylinder is working, external air rushes into the cylinder cavity instantly. The intake air pressure is greater than the initial air pressure inside the lubricating oil piston chamber 33. The pressure difference pushes the small piston 6 to slide slightly towards the bottom of the cavity. The sliding direction is parallel to the reciprocating motion direction of the piston seat 3. During the sliding process of the small piston 6, the pre-placed nitrogen in the cavity is first compressed. The compressibility of the gas is used to achieve pressure buffering, avoiding the direct rigid action of high-pressure intake air on the lubricating oil and greatly reducing the oil pressure peak. As the gas is compressed, the pressure in the cavity gradually increases, squeezing the lubricating oil. The lubricating oil is then smoothly pushed through the connecting hole 34 to the annular lubricating oil groove 35, uniformly wetting the two sets of main sealing rings 31 to form a lubricating oil film.

[0053] After the cylinder intake pressure is released, the compressed nitrogen gas in the lubricating oil piston chamber 33 rapidly expands and rebounds, releasing its compressed energy and pushing the small piston 6 to slide in the opposite direction until it is blocked by the limiting stop at the open end, returning to its initial flush position and completing the automatic reset. This reset action requires no additional power drive, relying entirely on the gas expansion force, and the reset process is smooth and shock-free, without interfering with the main movement of the piston seat 3. Lubricating oil is automatically replenished with each intake.

[0054] This embodiment retains the core advantages of embodiment 1: simple structure, easy assembly, and redundant safety. Simultaneously, it solves the problems of high-pressure hard-locking and inability to reset in a fully oil-based structure through an oil-gas hybrid design. The compressibility of pre-placed nitrogen plays a crucial buffering and decompression role, preventing high-pressure intake from the cylinder from being directly and rigidly transmitted to the lubricating oil. This avoids excessive oil pressure from lifting the main sealing ring 31 and compromising its airtightness, effectively extending the service life of the sealing ring 31 and ensuring the cylinder's sealing stability. Furthermore, the small piston 6 can automatically reset after pressure relief due to gas expansion force, requiring no manual intervention and enabling multiple oil replenishment cycles.

[0055] Example 2 has a significantly wider applicable pressure range than Example 1, maintaining stable sealing performance and lubrication even under medium-pressure conditions. Regarding operating frequency and speed, this example is suitable for medium-speed, medium-frequency operation. As the operating frequency increases, the lubricant consumption of the sealing ring 31 increases, requiring the small piston 6 to perform more frequent oil replenishment. The oil-gas mixing structure makes the small piston 6 more responsive, achieving minute displacement through gas compression with each intake, promptly replenishing lubricant without significant lag. Simultaneously, the gas buffering effect reduces the impact of the small piston 6's movement, preventing significant vibration and noise during medium-speed operation and avoiding interference with the piston's main motion.

[0056] Example 3: Based on Examples 1 and 2, a deep structural upgrade is made, retaining the advantages of the first two examples. The cylinder body is a high-precision cylindrical hollow structure, with an upper end cover 4 and a lower end cover 5 respectively installed at both ends. Similarly, the piston seat 3 is coaxially located in the cylinder cavity, with its outer surface precisely sliding with the inner wall of the cylinder. The outer wall is axially machined with the mounting groove of the support ring 30, the mounting groove of the first sealing ring 31, the annular lubricating oil groove 35, and the mounting groove of the second sealing ring 31. The support ring 30, the first sealing ring 31, and the second sealing ring 31 are respectively assembled. The support ring 30 achieves radial guidance and wear reduction. The two sets of main sealing rings 31 form a double axial seal to block high-pressure gas inside the cylinder. The annular lubricating oil groove 35 is a circumferential closed-loop groove on the outer wall of the piston seat 3. Multiple evenly arranged through holes 34 are radially opened at the bottom of the groove. The inner wall of the through holes 34 is smoothed to reduce the flow resistance of the lubricating oil. The piston seat 3 faces away from the end face of the piston rod 2 and integrally protrudes outward to form a sleeve portion 32. The sleeve portion 32 and the piston seat 3 are coaxial integral structures with smooth inner walls and are coaxial with the lubricating oil piston chamber 33. The sleeve portion 32 is designed to provide independent assembly space for the small piston 6, without occupying the main cavity of the piston seat 3, thus avoiding damage to the internal oil and gas passage layout. The piston rod 2 is still fixed to the end face of the piston seat 3 facing the piston rod 2 by welding. The non-through design does not damage the internal sealed structure of the piston seat 3. The weld joint is ground and polished to ensure connection strength and appearance flatness. The sealing mechanism is the same as in Examples 1 and 2, ensuring the basic stability of piston movement.

[0057] The difference lies in the fact that the piston seat 3 has a three-section coaxial cavity: the inner cavity of the sleeve section 32, the lubricating oil piston cavity 33, and the connecting section cavity 36. The connecting section cavity 36 is radially connected to the through hole 34 of the annular lubricating oil groove 35, and the inner diameter of the connecting section cavity 36 is smaller than the inner diameter of the lubricating oil piston cavity 33, forming a stepped cavity structure to achieve flow and pressure control. The connecting section cavity 36 is equipped with an intermediate piston 7, which completely separates the lubricating oil piston cavity 33 into two independent sealed chambers: a gas chamber and an oil chamber 71. The two are not connected to each other and there is no medium crossing, thus completely achieving oil and gas isolation.

[0058] A small piston 6 is assembled inside the sleeve section 32. The outer wall of the small piston 6 is also equipped with a miniature support ring 60 and a miniature sealing ring 61. The miniature sealing ring 61, located near the gas chamber, seals the gas chamber and prevents gas leakage. The miniature support ring 60 acts as a radial guide, ensuring smooth sliding of the small piston 6. The chamber between the small piston 6 and the intermediate piston 7 is a gas chamber filled only with pre-filled nitrogen, without any lubricating oil. The initial gas pressure is set lower than the cylinder's working intake pressure. The side of the intermediate piston 7 away from the gas chamber, the connecting section cavity 36, the connecting hole 34, and the annular lubricating oil groove 35 together form a pure oil chamber 71. The oil chamber 71 is completely filled with lubricating oil, without any gas. The sliding stroke of the intermediate piston 7 is limited by the chamber depth. When the oil chamber 71 is full of oil, there is no room for the intermediate piston 7 to move forward; only after the lubricating oil is consumed can a slight displacement occur. The cylinder intake pressure acts synchronously on the force-bearing end face of the piston seat 3 and the exposed end face of the small piston 6, driving the piston seat 3 to reciprocate while simultaneously generating an axial thrust on the small piston 6.

[0059] When the cylinder is working, the high-pressure intake pushes the small piston 6 to slide towards the air chamber, compressing the nitrogen in the air chamber. After the gas is compressed, the pressure increases, forming a flexible thrust that acts on the intermediate piston 7. At this time, the oil chamber 71 is completely filled with lubricating oil, with no gaps or compression space. If there is no loss of lubricating oil in the annular lubricating oil groove 35, the isolation piston remains stationary due to the oil in front, and will not produce any unnecessary movements. It does not supply oil for lubrication every time air is intake, avoiding excessive oil supply that could lead to oil overflow, seal lifting, or premature consumption of lubricating oil. Only when the sealing ring 31 scrapes and rubs to consume the lubricating oil, a small gap appears at the front end of the oil chamber 71. Under the pressure of the air chamber, the intermediate piston 7 makes a slight displacement, pushing the lubricating oil in the oil chamber 71 through the connecting section cavity 36 and the connecting through hole 34 to the annular lubricating oil groove 35 to replenish the lost oil and maintain the stability of the oil film.

[0060] After the cylinder intake pressure is released, the compressed nitrogen in the cylinder chamber rapidly expands and rebounds, pushing the small piston 6 to slide in the opposite direction until it is stopped by the retaining edge of the sleeve 32, returning to its initial position and completing the automatic reset. Meanwhile, the intermediate piston 7, with its oil chamber 71 full of oil and no additional oil intake, remains stationary in its current position and does not require reset. This reduces wear and tear on the moving parts and prevents oil backflow that could interrupt lubrication. Throughout the entire operation, the nitrogen in the cylinder chamber is completely blocked inside the isolation piston, preventing it from entering the oil chamber 71, the connecting hole 34, and the annular lubricating oil groove 35. This completely eliminates the problem of gas crosstalk to the main seal, ensuring that the sealing effect of the sealing ring 31 is not affected in any way.

[0061] In this embodiment, self-lubrication, sealing safety, pressure buffering, and automatic reset are achieved. The air chamber 70 is only responsible for buffering pressure and driving reset, while the oil chamber 71 is responsible for storing and transporting lubricating oil. This retains the buffering and pressure reduction advantages of gas compressibility, preventing high pressure from damaging the sealing ring 31, while also eliminating the sealing failure problem caused by gas leakage and cross-contamination, thus achieving optimal cylinder airtightness.

[0062] The oil chamber 71 is designed to be full of oil, and in conjunction with the micro-oil replenishment logic of the intermediate piston 7, it achieves on-demand oil replenishment. It only moves when the lubricating oil is consumed and remains stationary when there is no consumption, avoiding unnecessary work and preventing over-supply, overflow, and leakage, resulting in more precise and efficient lubrication. The small piston 6 automatically resets by the expansion force of the air chamber, with sensitive cyclic response, suitable for pneumatic actuators that operate at high frequency and for long periods. This embodiment still retains redundant safety features. Even if the small piston 6 or the intermediate piston 7 malfunctions and becomes stuck, the piston seat 3 can still independently complete the reciprocating motion, and the support and sealing functions are not affected. The one-piece sleeve part 32, the welded piston rod 2, and the non-through-cavity structure reduce the risk of sealing points and leakage, and the processing and assembly difficulty is moderate, making it suitable for mass production.

[0063] Under high pressure conditions, the internal pressure of the oil chamber 71 remains at a low and stable level, and will not damage the sealing ring 31. It can work stably in the high pressure pneumatic system, and the upper limit of the applicable pressure is higher than that of Example 1 and Example 2.

[0064] Regarding movement speed and operating frequency, this embodiment is suitable for high-speed reciprocating and high-frequency start-stop conditions. High-speed and high-frequency operation will increase the friction of the sealing ring 31 and consume lubricating oil quickly. This embodiment adopts an on-demand oil replenishment mode, replenishing only the amount of lubricating oil consumed. The oil replenishment response is fast and accurate, and a stable oil film can be maintained continuously during high-speed movement, avoiding dry friction, high temperature, and aging. At the same time, the small piston 6 can quickly reset, and the isolated piston only makes a slight movement. The overall moving parts have low inertia and low resistance, and will not have problems such as jamming, lag, or impact due to high frequency and high speed.

[0065] For any parts not mentioned in this invention, existing technologies can be used or referenced.

[0066] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A self-lubricating pneumatic actuator, comprising a cylinder body and a piston seat (3), characterized in that, The piston seat (3) has a support ring (30) and two sets of sealing rings (31) on its outer wall. An annular lubricating oil groove (35) is provided between the two sets of sealing rings (31). A lubricating oil piston cavity (33) is provided inside the piston seat (3). A through hole (34) is provided on the annular lubricating oil groove (35) to connect the lubricating oil piston cavity (33). A small piston (6) is slidably fitted inside the lubricating oil piston cavity (33). The small piston (6) is exposed on the end face of the piston seat (3) away from the piston rod (2). Under the action of the cylinder intake pressure, the small piston (6) makes a micro-stroke sliding in the lubricating oil piston cavity (33) to push the lubricating oil in the lubricating oil piston cavity (33) through the through hole (34) to the annular lubricating oil groove (35) to lubricate the two sets of sealing rings (31).

2. The self-lubricating pneumatic actuator according to claim 1, characterized in that, The micro-stroke sliding direction of the small piston (6) is parallel to the reciprocating motion direction of the piston seat (3). The cylinder intake pressure acts synchronously on the force-bearing end face of the piston seat (3) and the exposed end face of the small piston (6), driving the piston seat (3) to move while driving the small piston (6) to slide in a micro-stroke.

3. The self-lubricating pneumatic actuator according to claim 1, characterized in that, The depth of the lubricating oil piston chamber (33) is the maximum micro-stroke of the small piston (6), and the small piston (6) forms a limit when it slides to the bottom of the lubricating oil piston chamber (33).

4. The self-lubricating pneumatic actuator according to claim 1, characterized in that, The lubricating oil piston chamber (33) is preset with an initial air pressure. The initial air pressure is less than the cylinder's intake pressure. The cylinder's intake pressure drives the small piston (6) to slide into the lubricating oil piston chamber (33). When the cylinder's intake pressure is removed, the small piston (6) slides outward and resets under the action of the initial air pressure in the lubricating oil piston chamber (33). After reset, the end face of the small piston (6) is flush with the end face of the piston seat (3) away from the piston rod (2).

5. The self-lubricating pneumatic actuator according to claim 4, characterized in that, The lubricating oil piston chamber (33) is filled with lubricating oil, but the lubricating oil does not fill the entire lubricating oil piston chamber (33). A gas space is reserved above the lubricating oil to maintain the initial gas pressure. The gas is an inert gas that is insoluble in the lubricating oil.

6. The self-lubricating pneumatic actuator according to claim 1, characterized in that, The piston seat (3) is convex outward from the end face away from the piston rod (2) to form a sleeve portion (32). The lubricating oil piston cavity (33) is opened inside the sleeve portion (32). The small piston (6) is adapted to be installed in the lubricating oil piston cavity (33) inside the sleeve portion (32).

7. The self-lubricating pneumatic actuator according to claim 6, characterized in that, The outer wall of the small piston (6) is fitted with a micro support ring (60) and a micro sealing ring (61) at intervals. The micro sealing ring (61) is located on the side of the small piston (6) near the bottom of the lubricating oil piston chamber (33).

8. The self-lubricating pneumatic actuator according to claim 5, characterized in that, The piston seat (3) has a connecting section cavity (36) inside. The inner diameter of the connecting section cavity (36) is smaller than the inner diameter of the lubricating oil piston cavity (33). The connecting section cavity (36) connects the lubricating oil piston cavity (33) and the through hole (34).

9. The self-lubricating pneumatic actuator according to claim 1, characterized in that, The lubricating oil piston chamber (33) is provided with an axially sliding intermediate piston (7), which divides the lubricating oil piston chamber (33) into a non-communicating gas chamber (70) and an oil chamber (71); the small piston (6) and the intermediate piston (7) form the gas chamber (70), which is pre-filled with gas at a certain initial pressure; the side of the intermediate piston (7) away from the gas chamber (70) forms the oil chamber (71) with the piston seat (3), which is connected to the through hole (34) and the annular lubricating oil groove (35) and is completely filled with lubricating oil and free of gas.

10. The self-lubricating pneumatic actuator according to claim 9, characterized in that, When the cylinder is intake, the small piston (6) compresses the air chamber (70) under the intake pressure, and the pressure in the air chamber (70) increases and acts on the intermediate piston (7). When there is no loss of lubricating oil in the annular lubricating oil groove (35), there is no room for the lubricating oil in the oil chamber (71), and the intermediate piston (7) remains stationary. When the lubricating oil in the annular lubricating oil groove (35) is consumed, the intermediate piston (7) moves to the side of the oil chamber (71) under the pressure of the air chamber (70) to replenish the lubricating oil. After the intake pressure of the cylinder is removed, the small piston (6) resets under the action of the gas in the air chamber (70). The intermediate piston (7) remains in its current position because the lubricating oil inside the oil chamber (71) is incompressible and has no room for retraction.

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