Piston blind hole structure

Abstract

The utility model relates to a piston blind hole structure in the technical field of hydraulic transmission, which comprises a cylinder barrel, a piston and a piston rod, and the piston is fixed at one end of the piston rod and positioned in the cylinder barrel. A bottom groove is formed in the cylinder bottom of the cylinder barrel, the edge of the bottom face of the bottom groove is an arc transition face, the edge of the piston is in an arc shape, and when the piston makes contact with the cylinder bottom, an annular cavity is formed between the bottom groove and the piston. Compared with the prior art, through an annular cavity formed by the integrated piston head and the bottom groove and a simplified low-friction and high-sealing dynamic sealing structure, the piston blind hole structure which does not need an external device and is buffered, light in weight and efficient in sealing is provided, stress dispersion and cylinder bottom movement buffering are achieved, and the service life of the piston is prolonged. And the application range of the blind hole piston under the high-pressure and high-frequency working conditions of a lightweight structure is expanded.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic transmission technology, and in particular to a piston blind hole structure. Background Technology

[0002] In hydraulic cylinder design, the piston, as the core component for power transmission, directly determines the cylinder's working efficiency and service life through its sealing performance and structural reliability. Traditional through-hole pistons primarily bear pressure at the connection between the piston and piston rod, typically requiring O-ring seals and serving as the main pressure point. However, under high pressure conditions, this connection is prone to extrusion, leading to piston failure. To address this issue, existing technologies have proposed blind-hole piston structures. For example, Chinese utility model patent CN201020674611 discloses a novel blind-hole piston structure for push-type cylinders, directly fixing the piston and piston rod together to reduce leakage points and eliminate sealing failure caused by damage to the sealing structure between the piston and piston rod.

[0003] However, because the piston in this design collides directly with the cylinder bottom at high speed when it reaches the bottom of the cylinder, the force on the piston end face is increased significantly due to the combined forces of the high-pressure hydraulic oil and the impact force from the collision with the cylinder bottom. Simultaneously, the piston edge is prone to stress concentration due to abrupt structural changes. Especially under high pressure or alternating loads, fatigue cracks are easily generated in these stress concentration areas, leading to piston damage over time and significantly reducing piston life. Therefore, there is an urgent need for a piston blind bore structure that balances stress dispersion and shock absorption to expand the applicability of blind bore pistons. Utility Model Content

[0004] This invention overcomes the shortcomings of existing piston blind hole structures. By integrating the annular cavity formed by the piston head and the bottom groove, and a simplified low-friction, high-sealing dynamic sealing structure, it provides a piston blind hole structure that requires no external device and is lightweight and highly efficient in sealing. This achieves stress dispersion and cylinder bottom movement buffering, and expands the applicability of blind hole pistons in high-pressure, high-frequency operating conditions with lightweight structures.

[0005] This utility model is achieved by the following technical solution: a piston blind hole structure, including a cylinder 1, a piston 2, and a piston rod 3. The piston 2 is fixed to one end of the piston rod 3 and located inside the cylinder 1. The bottom 11 of the cylinder 1 is provided with a bottom groove 12. The bottom edge of the bottom groove 12 is a rounded transition surface (R≥1mm) to disperse stress. The edge of the piston 2 is rounded to disperse stress and avoid edge cracking damage caused by stress concentration. When the piston 2 contacts the bottom 11, a narrow annular cavity 13 is formed between the bottom groove 12 and the piston 2 for buffering.

[0006] Preferably, the piston 2 includes a piston head 23 and a piston tail 24. The edge of the piston tail 24 is a stepped arc shape. The radius of the first arc near the bottom of the cylinder 11 is larger than the radius of the second arc near the other end. Through the phased transition, the stress peak is dispersed. The larger radius of the first segment is used to initially alleviate stress concentration. The smaller radius of the second segment is mainly to avoid the moving parts with different coefficients of thermal expansion from getting stuck due to the shrinkage of their mating clearance caused by thermal expansion, which would cause cylinder scoring and damage to the oil cylinder.

[0007] Preferably, there are gaps between the piston head 23 and the cylinder bottom 11 and the cylinder barrel 1 to form a cavity 25, so as to prevent vacuum suction between the piston 2 and the cylinder barrel 1, and to serve as an additional channel for oil flow, so as to remove frictional heat through oil circulation and achieve the effect of heat dissipation.

[0008] Preferably, the piston 2 has two sets of dynamic sealing structures, piston guide rings 21 and composite sealing rings 22, arranged at intervals on its radial outer circumference and tightly connected to the inner wall of the cylinder 1. The piston guide rings 21 are located on the high-pressure side near the cylinder bottom 11 to prevent extrusion, while the composite sealing rings 22 are located on the low-pressure side near the piston rod 3 to enhance sealing. The piston guide rings 21 act as a barrier between the high-pressure hydraulic oil and the composite sealing rings 22, dissipating some pressure and preventing direct contact between the high-pressure hydraulic oil and the composite sealing rings, thus protecting the composite sealing rings 22. Through this simplified dynamic sealing structure, the piston 2 achieves a balance between pressure on both sides of the piston blind hole structure and between low friction and high sealing reliability.

[0009] Preferably, the composite sealing ring 22 is composed of a wear-resistant guide ring 221 and an elastic sealing ring 222. The wear-resistant guide ring 221 is located on the outer side near the cylinder 1 and together with the piston 2, it compresses the elastic sealing ring 222 to absorb radial pressure fluctuations. Its compression amount is 10%-20% of the thickness of the elastic sealing ring 222. The sealing performance of the composite sealing ring 22 is improved by the rebound effect of the elastic sealing ring 222, and it also has a structural compensation function to make up for processing errors.

[0010] Preferably, the piston guide ring 21 and the composite sealing ring 22 are respectively embedded in the piston guide groove 210 and the piston sealing groove 220 opened in the piston 2. Both the piston guide ring 21 and the wear-resistant guide ring 221 are made of elastic self-lubricating wear-resistant materials. The piston guide ring 21 mainly bears the contact between the piston and the inner wall of the cylinder, avoids hard friction between metals, reduces wear and heat generation, and ensures the linearity of piston movement. To improve the pressure-bearing, guiding and extrusion-resistant capacity of the piston guide ring 211, the width of the piston guide groove 210 is greater than its depth. To improve the radial sealing strength of the piston and increase the resistance of the wear-resistant guide ring 221 to the extrusion deformation of the elastic sealing ring 222 by high-pressure oil, the depth of the piston sealing groove 220 is greater than its width.

[0011] Preferably, the piston 2 and piston rod 3 are connected by a thread or an interference fit to form a blind hole structure, which is easy to disassemble and assemble, does not require O-ring seals, eliminates the risk of O-ring extrusion, reduces leakage points, and extends the service life of the hydraulic cylinder. At the same time, it reduces the internal space of the piston and makes it easier to program the stroke dimensions of the hydraulic cylinder.

[0012] Preferably, a guide sleeve 4 is installed at the top of the cylinder 1, and there is an oil inlet 5 at each end of the cylinder 1. The end of the guide sleeve 4 near the piston 2 is chamfered, which plays a guiding role in the installation, avoids damage caused by edge collision, reduces the accuracy requirements of the initial alignment, and reduces friction or jamming during the assembly process. The inner wall of the guide sleeve 4 is tightly connected to the piston rod 3.

[0013] Preferably, the inner wall of the guide sleeve 4 is provided with an annular groove, and a piston rod guide ring 41, a piston rod sealing unit 42 and a dustproof ring 43 with a dynamic sealing structure are installed and tightly connected to the piston rod 3; the outer wall of the guide sleeve 4 has an external thread, and the two ends of the external thread are provided with annular grooves, and elastic retaining rings 44 with a static sealing structure are installed and tightly contacted with the cylinder 1.

[0014] Preferably, the inner wall of the cylinder 1 has an internal thread at the connection point with the guide sleeve 4. The guide sleeve 4 and the cylinder 1 are connected by a composite thread-ring connection. The external thread of the guide sleeve 4 is pre-tightened with the internal thread of the cylinder 1. The elastic ring restricts the axial movement of the guide sleeve 4, so that the guide sleeve 4 has both the detachability of the threaded connection and the anti-loosening reliability of the ring connection, which is suitable for high-frequency vibration conditions.

[0015] The beneficial effects of this utility model are:

[0016] 1. Through the coordinated action of the piston head and the bottom groove, the flow cross-section automatically shrinks from the larger cavity to the narrower annular cavity as the piston approaches the end of its stroke, achieving smooth deceleration. At the same time, the arc transition surface between the piston head and the bottom groove disperses collision stress.

[0017] 2. By integrating a guide support ring and a composite sealing ring into a dual asymmetric dynamic sealing structure, a balance is achieved between low friction, high sealing reliability, and low-cost maintenance while simplifying the structure.

[0018] 3. The stepped rounded chamfer at the piston tail prevents cylinder scoring caused by the difference in thermal expansion coefficients between the piston and cylinder materials when the piston heats up during piston movement.

[0019] 4. The structure is simple and easy to process, resulting in good economic benefits. Attached Figure Description

[0020] Figure 1 This utility model relates to a blind hole structure for a hydraulic cylinder piston.

[0021] Figure 2This is a magnified view of part A in the diagram;

[0022] Figure 3 This is a magnified view of part B in the diagram.

[0023] In the diagram: 1. Cylinder; 11. Cylinder bottom; 12. Bottom groove; 13. Annular cavity; 14. U-shaped weld; 2. Piston; 21. Piston guide ring; 210. Piston guide groove; 22. Composite sealing ring; 220. Piston sealing groove; 221. Wear-resistant guide ring; 222. Elastic annular sealing ring; 23. Piston head; 24. Piston tail; 25. Cavity; 3. Piston rod; 4. Guide sleeve; 41. Piston rod guide ring; 42. Piston rod sealing unit; 43. Dustproof ring; 44. Elastic retaining ring; 5. Oil inlet. Detailed Implementation

[0024] To make the technical solution and advantages of this utility model clearer, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. This embodiment takes the application of hydraulic cylinders under high pressure (35-50MPa) and high frequency (10-20Hz) conditions as an example, but the protection scope of this utility model is not limited thereto.

[0025] like Figure 1 As shown, this utility model is a piston blind hole structure, including a cylinder 1, a piston 2, and a piston rod 3. The piston 2 is fixed to one end of the piston rod 3 and located inside the cylinder 1. The tail of the piston rod 3 is equipped with a guide sleeve 4 to support and ensure the coaxiality of the piston rod 3 and the cylinder 1. At the same time, the guide sleeve 4 acts as a cover to seal the hydraulic cylinder, preventing oil leakage and external contaminants from entering the hydraulic cylinder. There is an oil inlet 5 at each end of the cylinder 1.

[0026] like Figure 2 As shown, the cylinder barrel 1 and cylinder bottom 11 are welded using a U-shaped weld 14. Compared with traditional V-shaped welds or double V-shaped welds, the U-shaped weld 14 can improve welding strength, facilitate welding operation, make it easier to control welding quality, and reduce welding deformation and residual stress, making it more suitable for welding hydraulic cylinders under high pressure. The cylinder bottom 11 is provided with a bottom groove 12 with a diameter of 25mm and a depth of 5mm. The bottom edge of the bottom groove 12 is a rounded transition surface with R=2mm.

[0027] The piston 2 and piston rod 3 are connected by threads and secured with sealant, forming a blind-hole structure that eliminates the need for O-ring seals, thus reducing the risk of O-ring extrusion, minimizing leakage points, and extending the hydraulic cylinder's service life. Simultaneously, this reduces the internal space of the hydraulic cylinder, resulting in a more compact internal structure, enabling lightweight design, and facilitating the programming of the cylinder's stroke dimensions. In terms of installation, the simple sealing structure on the piston makes disassembly and assembly easier.

[0028] Piston 2 includes piston head 23 and piston tail 24. Piston head 23 refers to the end of the piston near the cylinder bottom 11, and piston tail 24 refers to the end of the piston near the guide sleeve 4. The piston head 23 has a radius of 11mm and a height of 9mm. The piston 2 has a radius of 15.5mm and a height of 30mm. The height of piston head 23 is about 1 / 3 of the height of piston 2, and the depth of bottom groove 12 is about 1 / 2 of the height of piston head 23.

[0029] Both the piston head 23 and piston tail 24 have rounded edges to disperse stress and prevent edge cracking and damage caused by stress concentration. The rounded chamfer of the piston head 23 makes the oil pressure distribution at the piston edge more uniform, avoiding pressure abrupt changes caused by right-angled edges. The piston tail 24 is a stepped rounded shape. The first segment of the rounded arc near the cylinder bottom 11 of both the piston head 23 and piston tail 24 has a radius of R=2mm, while the second segment of the rounded arc near the other end of the piston tail 24 has a radius of R=1mm. The piston tail 24 disperses stress peaks through a phased transition. The larger radius of the first segment is used to initially alleviate stress concentration, while the smaller radius of the second segment is mainly to prevent the moving parts with different coefficients of thermal expansion from jamming due to reduced clearance caused by thermal expansion, which could damage the cylinder. The piston head 23 has the same radius of rounded arc as the bottom groove 12, making the stress distribution more uniform during their fit.

[0030] When the end face of the piston head 23 contacts the bottom groove 12, there is a 1.5mm wide gap in the radial direction, which forms a narrow annular cavity 13. As the piston approaches the bottom of the cylinder, the space of the bottom groove 12 is gradually occupied by the piston head 23, the volume is reduced, and the oil is forced to be squeezed out through the narrow annular cavity 13 formed between the piston 2 and the bottom groove 12, forming a damping effect, which buffers the movement of the piston rod 3, reduces the peak impact pressure, and avoids component damage caused by direct high-speed collision between the piston 2 and the bottom of the cylinder 11.

[0031] The piston head 23 has a 5mm gap with the cylinder bottom 11 and the cylinder barrel 1, forming a cavity 25. This cavity, along with the rounded chamfer, accelerates oil filling and reduces the formation of vacuum areas. This prevents the formation of a localized vacuum between the piston 2 and the cylinder barrel 1 due to insufficient oil return speed during rapid piston retraction, which could lead to increased motion resistance or even jamming. It also serves as an additional channel for oil flow, carrying away frictional heat through oil circulation to achieve a cooling effect.

[0032] Typically, through-hole pistons have a symmetrical sealing structure. However, since piston 2 has a blind-hole structure, the pressure and main pressure-bearing positions of the rod chamber and rodless chamber at both ends of the piston are different. Therefore, the sealing structure of piston 2 is set as an asymmetrical seal. A complete radial circumferential groove piston guide groove 210 and piston sealing groove 220 are formed on the piston 2, used to embed piston guide ring 21 and composite sealing ring 22 respectively, forming an asymmetrical double dynamic seal structure. This reduces the number of seals used while ensuring sealing performance, simplifies the sealing structure, makes it easier to process and install, meets the requirements of lightweight design, saves internal space, and simplifies the internal structure of the hydraulic cylinder. Piston guide ring 21 and composite sealing ring 22 are tightly connected to the inner wall of cylinder 1 to guide and support piston movement and seal the piston to prevent oil leakage.

[0033] The piston guide groove 210 has a rectangular cross-section of 6mm wide and 2mm deep. The piston guide ring 21 has a rectangular cross-section of 6mm wide and 2.5mm thick, and is made of polytetrafluoroethylene composite material. As the main support and guiding structure of the piston 2, the piston guide ring 21 is nested around the outer circumference of the piston 2 and tightly connected to the cylinder 1, located on the high-pressure side near the cylinder bottom 11. It bears the contact between the piston and the inner wall of the cylinder, avoiding hard friction between metals, reducing wear and heat generation, and ensuring the linearity of piston movement. Its width is greater than its thickness, which can be used to block the axial force from the high-pressure hydraulic oil on the piston 2 and reduce the pressure exerted by the high-pressure hydraulic oil on the composite sealing ring 22.

[0034] The piston sealing groove 220 has a rectangular cross-section with a width of 3.2 mm and a depth of 3.25 mm. The composite sealing ring 22 consists of a wear-resistant guide ring 221 and an elastic sealing ring 222, and is mainly subjected to the radial force of the piston 2, thus playing a sealing role. The wear-resistant guide ring 221 is a circular ring with a width of 3.2 mm and a thickness of 2 mm, with a rectangular cross-section, and is made of polytetrafluoroethylene. The elastic sealing ring 222 is an elliptical nitrile rubber with a major axis of 3.2 mm and a minor axis of 2 mm. The wear-resistant guide ring 221 is fitted onto the outside of the elastic sealing ring 222, and together with the piston 2, it compresses the elastic sealing ring 222 with a compression of 0.25 mm. The annular groove is 3.2 mm wide and 3.25 mm deep. The rebound effect of the elastic sealing ring 222 improves the sealing performance of the composite sealing ring 22. Under further high-pressure and high-frequency conditions, the hydraulic cylinder design parameters can be optimized by increasing the compression of the elastic sealing ring 222 to ensure that the leakage of the piston under high-pressure conditions meets the sealing requirements.

[0035] The long axis of the elastic sealing ring 222 is parallel to the piston rod 3, and the short axis is perpendicular to the piston rod 3. When high-pressure hydraulic oil enters the rodless chamber of the cylinder 1, the piston 2 is subjected to a force in the axial direction parallel to the piston rod 3. The piston sealing groove 220 compresses the long axis of the elastic sealing ring 222, forcing the elastic sealing ring 222 to expand and deform in the short axis direction. This causes the wear-resistant guide ring 221 to move in the short axis direction of the elastic sealing ring, i.e., the radial direction of the piston 2, which compresses the cylinder 1 and improves the sealing effect of the composite sealing ring when the piston 2 is pushed by high-pressure hydraulic oil.

[0036] Both the piston guide ring 21 and the composite sealing ring 22 extend 0.5 mm above the piston guide groove 210 and the piston sealing groove 2200. This portion serves as the assembly space between the piston 2 and the cylinder 1, providing structural compensation to accommodate manufacturing tolerances. Simultaneously, this reserved space allows for the installation of seals, permitting appropriate deformation under pressure to ensure sealing performance.

[0037] The wider piston guide ring 21 acts as a barrier between the high-pressure hydraulic oil and the composite sealing ring 22, bearing most of the axial pressure. This prevents direct contact between the high-pressure hydraulic oil and the composite sealing ring, reduces the force exerted by the hydraulic oil on the composite sealing ring 22, and decreases the axial compression of the composite sealing ring 22 by the hydraulic oil. This prevents the composite sealing ring 22 from failing due to high-pressure extrusion, effectively extending its service life. Simultaneously, the cooperation between the piston guide ring 21 and the composite sealing ring 22 improves the piston sealing effect.

[0038] like Figure 3 As shown, the top of the cylinder 1 is equipped with a guide sleeve 4 that integrates guiding and sealing functions. The end of the guide sleeve 4 near the piston 2 is chamfered, which guides the installation, avoids damage caused by edge collision, reduces the accuracy requirements of initial alignment, and reduces friction or jamming during assembly.

[0039] The inner wall of the guide sleeve 4 is provided with an annular groove, on which two piston rod guide rings 41, piston rod sealing unit 42 and dustproof ring 43 are installed in sequence, which are in close contact with the piston rod 3 to form a three-level protection to ensure the sealing performance of the guide sleeve.

[0040] The piston rod guide ring 41 is a rectangular cross-section polytetrafluoroethylene ring. Two piston rod guide rings 41, by tightly fitting against the piston rod surface, guide the piston rod 3 to move linearly, reducing radial sway or bending deformation, preventing friction between the piston 2 and the inner wall of the cylinder 1, and distributing the radial load on the piston rod to prevent localized stress concentration that could lead to wear or jamming. The piston rod sealing unit 42 is a U-shaped nitrile rubber seal with the U-shaped opening facing towards the piston 2, forming a dynamic seal with the piston rod 3 to prevent hydraulic oil leakage and ensure stable system pressure.

[0041] Since the guide sleeve 4 also serves as a cylinder cover, a dustproof ring 43 is provided at the contact position between the piston rod 3 and the outer end of the guide sleeve 4. The end of the dustproof ring 43 near the piston 2 is a U-shaped sealing opening to enhance the sealing performance of the guide sleeve 4, and the other end is a sharp lip opening to ensure a tight fit with the piston rod surface. It is made of rigid polyurethane material, which has both elasticity and wear resistance, and scrapes off dust, dirt, moisture and other contaminants attached to the surface of the piston rod 3 to prevent them from entering the hydraulic system.

[0042] The guide sleeve 4 and cylinder 1 are connected by a composite thread-ring connection. The guide sleeve 4 has external threads on its outer wall, and the part of the cylinder 1 that connects to the guide sleeve has internal threads that mate with the external threads. Both ends of the external threads have annular grooves 3.6mm wide and 2mm deep, each fitted with two elastic retaining rings 44 that are in close contact with the cylinder 1. The guide sleeve 4 and cylinder 1 are pre-tightened through the threaded connection, and the elastic retaining rings restrict the axial movement of the guide sleeve 4. This combination of the detachability of the threaded connection and the anti-loosening reliability of the retaining ring connection makes it suitable for high-frequency vibration conditions.

[0043] The working process of this utility model embodiment is as follows:

[0044] High-pressure hydraulic fluid is injected into the rodless chamber through the inlet 5 near the bottom of cylinder 1. Initially, the fluid mainly flows through the gap (4-10mm) between piston head 23 and cylinder 1, entering cavity 25 to form an initial fluid circulation. The hydraulic system can dissipate frictional heat through this circulation, achieving a cooling effect. During operation, the high-pressure hydraulic fluid pushes piston 2 towards guide sleeve 4. Piston guide ring 21 initially bears the axial load of the high-pressure hydraulic fluid and ensures that piston 2 moves linearly without deviation. The elastic sealing ring 222 of composite sealing ring 22 expands and compresses towards the short axis under the axial pressure of the oil on the piston, pushing the wear-resistant guide ring 221 tightly against the inner wall of cylinder 1, further enhancing the sealing effect and blocking the oil leakage path. When the fluid switches to the rod chamber, piston 2 moves in the opposite direction, and elastic sealing ring 222 recovers its deformation under back pressure, maintaining dynamic sealing.

[0045] As piston 2 moves close to the cylinder bottom 11, piston head 23 gradually enters the bottom groove 12. The volume of the cavity formed between piston head 23 and bottom groove 12 gradually decreases as the piston moves. Oil is forced to exit through the 1.5mm wide annular cavity 13 between piston head 23 and bottom groove 12. Due to the sudden decrease in flow channel cross-sectional area, the oil flow velocity increases, generating a throttling damping effect, which creates reverse resistance on piston 2, causing its movement speed to decrease linearly.

[0046] When piston 2 is fully inserted into the bottom groove 12, the volume of the annular cavity 13 reaches its minimum. At this time, the damping force reaches its peak, and the kinetic energy of piston 2 is fully dissipated. Finally, it contacts the cylinder bottom 11 at a lower speed, reducing its rigid impact. At the same time, the cavity 25 between piston head 23 and cylinder bottom 11 continuously guides oil circulation, carrying away frictional heat through oil inlet 5.

[0047] This embodiment achieves a lightweight and miniaturized piston blind hole design through the collaborative design of a buffer cavity and an asymmetric structure composite sealing unit, as well as the optimization of the cavity's anti-vacuum suction and hot runner layout. It also meets the requirements of low impact, low leakage, and long-term durability under high pressure and high speed conditions, which is significantly better than existing piston blind hole technology.

Claims

1. A piston blind hole structure, comprising a cylinder (1), a piston (2), and a piston rod (3), wherein the piston (2) is fixed to one end of the piston rod (3) and located inside the cylinder, characterized in that: The cylinder bottom (11) of the cylinder barrel (1) is provided with a bottom groove (12), and the bottom edge of the bottom groove (12) is a rounded transition surface; The piston (2) includes a piston head (23) and a piston tail (24). The edge of the piston (2) is arc-shaped. When the piston (2) contacts the cylinder bottom (11), an annular cavity (13) is formed between the bottom groove (12) and the piston (2).

2. The piston blind hole structure according to claim 1, characterized in that: The edge of the piston tail (24) is a stepped arc shape.

3. The piston blind hole structure according to claim 1, characterized in that: The piston head (23) has gaps with the cylinder bottom (11) and the cylinder barrel (1), forming a cavity (25).

4. The piston blind hole structure according to claim 1, characterized in that: The piston (2) is provided with a piston guide ring (21) and a composite sealing ring (22) that are in close contact with the inner wall of the cylinder (1) on its outer periphery; the piston guide ring (21) is located on the high-pressure side near the bottom of the cylinder (11), and the composite sealing ring (22) is located on the low-pressure side near the piston rod (3).

5. A piston blind hole structure according to claim 4, characterized in that: The composite sealing ring (22) is composed of a wear-resistant guide ring (221) and an elastic sealing ring (222), with the wear-resistant guide ring (221) sleeved on the outer side near the cylinder (1).

6. A piston blind hole structure according to claim 4, characterized in that: The piston guide ring (21) and the composite sealing ring (22) are respectively embedded in the piston guide groove (210) and piston sealing groove (220) opened in the piston (2).

7. A piston blind hole structure according to claim 1, characterized in that: The piston (2) and piston rod (3) are connected by a thread or an interference fit.

8. A piston blind hole structure according to claim 1, characterized in that: The top of the cylinder (1) is fitted with a guide sleeve (4), and each end of the cylinder (1) has an oil inlet (5); the end of the guide sleeve (4) near the piston (2) is chamfered, and the inner wall of the guide sleeve (4) is tightly connected to the piston rod (3).

9. A piston blind hole structure according to claim 8, characterized in that: The inner wall of the guide sleeve (4) is provided with an annular groove, and a piston rod guide ring (41), a piston rod sealing unit (42), and a dustproof ring (43) with a dynamic sealing structure are installed; and The outer wall of the guide sleeve (4) has external threads, and the two ends of the external threads are provided with annular grooves and are fitted with elastic retaining rings (44) with static sealing structure, which are in close contact with the cylinder (1).

10. A piston blind hole structure according to claim 8 or 9, characterized in that: The inner wall of the cylinder (1) has an internal thread at the connection with the guide sleeve (4); the guide sleeve (4) and the cylinder (1) are connected by a composite thread-ring connection.

Images