A hydraulic cylinder piston sealing device with variable sealing gap and a hydraulic cylinder

Abstract

The present invention discloses a hydraulic cylinder piston sealing device with variable sealing gap and a hydraulic cylinder, belonging to the technical field of hydraulic cylinders. The device adopts a split piston, and the piston comprises a first retaining ring (102, 202) and a second retaining ring (9) located at both ends of the piston, and an inner piston body (103, 203), a thin-walled sleeve (104, 204) and an outer piston body (5) located at the axial middle position of the piston and arranged in sequence in the radial direction from the outer edge of the piston rod (10) to the inner wall of the cylinder barrel (11). During the one-way stroke operation of the hydraulic cylinder, when the oil pressure increases, the pressure oil enters the inner cavity (6) of the thin-walled sleeve through the oil passage (16), causing the thin-walled part of the thin-walled sleeve (104, 204) to produce radial elastic deformation, driving the outer circular surface of the outer piston body (5) to also produce an overall radial outward expansion, thereby reducing the sealing gap between the piston and the inner wall of the cylinder barrel (11), reducing the leakage, and solving the problem of increased leakage caused by increased pressure. The device is suitable for occasions with high oil pressure and high requirements for sealing performance.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic cylinders, and in particular relates to a hydraulic cylinder piston sealing device with a variable sealing gap and a hydraulic cylinder. Background Art

[0002] The hydraulic cylinder is an important power transmission component in the hydraulic transmission system. The sealing performance of the hydraulic cylinder directly affects the working performance, efficiency and life of the hydraulic cylinder, and even the normal operation of the whole machine. Among them, the seal between the hydraulic cylinder piston and the inner wall of the cylinder barrel is the key seal in the hydraulic cylinder, which directly determines whether the typical failure of leakage in the hydraulic cylinder will occur. The common sealing devices and structures between the hydraulic cylinder piston and the cylinder barrel mainly include sealing ring seals, gap seals and piston ring seals.

[0003] Among them, gap seals are increasingly gaining attention as a non-contact sealing structure. Gap seals include two situations: fixed and variable sealing gaps. For gap seals with fixed sealing gaps, it cannot completely eliminate leakage, especially in situations with high oil pressure. Moreover, the leakage will increase with the increase of oil pressure, which will reduce the volumetric efficiency and make it difficult to meet the needs of practical applications. The situation where the sealing gap is variable can alleviate the problem of leakage increasing with the increase of oil pressure to a certain extent. In the article "Research on Low-friction High-frequency Response Variable Gap Seal Hydraulic Cylinder" in the Journal of Mechanical Engineering, Vol. 51, No. 24, 2015, a gap seal structure with variable gap is given, that is, a thin layer of deformable lip is processed on the left and right ends of the hydraulic cylinder piston. The piston lip can produce elastic deformation when the working pressure increases, so that the sealing gap between the inner wall of the cylinder and the piston lip is reduced, thereby reducing the leakage to compensate for the increase in leakage caused by the increase in pressure. This deformation of the piston lip is a deformation of a local area of ​​the piston, and the load on this type of hydraulic cylinder cannot exceed the critical value of elastic deformation of the deformed lip, otherwise the piston lip will produce plastic deformation, affecting the gap change and leakage adjustment capabilities.

[0004] So far, among the existing hydraulic cylinder gap sealing devices and structures, there are few that can automatically adjust the sealing gap when the pressure changes. Therefore, it is necessary to further study other practical sealing gap changing methods and structures to eliminate or reduce the problem of increased leakage caused by increased pressure and improve the hydraulic cylinder gap sealing effect. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a sealing gap adjustment technical solution different from the prior art. The sealing gap can be adaptively adjusted according to pressure changes, thereby eliminating or reducing the problem of increased leakage caused by increased pressure, thereby improving the volumetric efficiency and obtaining an excellent sealing effect.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a hydraulic cylinder piston sealing device with a variable sealing gap, which is used for sealing the gap between the hydraulic cylinder piston and the inner wall of the cylinder barrel.

[0008] The piston of the hydraulic cylinder piston sealing device with variable sealing gap adopts a split combined structure, which is composed of a first retaining ring, a second retaining ring, an inner piston body, an outer piston body, and a thin-walled sleeve, and is axially fixed to one end of the piston rod located in the cylinder barrel by a locking nut; the first retaining ring and the second retaining ring are respectively located at both ends of the piston; the inner piston body, the thin-walled sleeve and the outer piston body are sequentially installed in the axial middle position of the piston and in the radial direction from the outer circumference of the piston rod to the inner wall of the cylinder barrel. The outer piston body includes an inner hole surface with a larger inner diameter and an inner hole surface with a smaller inner diameter. Among them, the inner piston body is sleeved on the corresponding axial diameter of the piston rod through its inner hole, and a thin-walled sleeve is installed on the outer circumference of the inner piston body, and the outer cylindrical surface of the thin-walled part of the thin-walled sleeve is matched and contacted with the inner hole surface of the larger inner diameter in the outer piston body; the inner piston body is fixedly connected to the second retaining ring through a threaded connection at one end, and is fixedly connected to the first retaining ring through a connecting screw at the other end; the inner piston body is provided with a first annular groove on the outer circular surface in contact with the inner hole surface of the smaller inner diameter in the outer piston body, and a first sealing ring is installed in the first annular groove; a second sealing ring is installed between the inner hole of the inner piston body and the piston rod; a small radial annular gap is provided between the outer circular surface of the outer piston body and the inner wall of the cylinder to form a gap seal; a number of annular pressure-equalizing grooves parallel to each other are also provided on the outer circular surface of the outer piston body; The longitudinal cross-section of each annular pressure-equalizing groove is semicircular, or non-semicircular arc, V-shaped, U-shaped, or a shape formed by a combination of a semicircle, V-shape, U-shape, trapezoid, or rectangle; the first retaining ring is evenly distributed with three arc-shaped through holes of the same shape and size along the circumferential direction, and these three arc-shaped through holes penetrate the first retaining ring and continue to enter the inner piston body to form three arc-shaped groove holes respectively; the three arc-shaped through holes have the same cross-sectional shape as the three arc-shaped groove holes, and their internal cavities are directly opposite and connected front to back to form a continuous oil channel, which connects the rodless cavity on one side of the first retaining ring and the internal cavity of the thin-walled sleeve; and the central angles corresponding to the arc-shaped through holes and the arc-shaped groove holes are both 60°, the radial widths are both 7 mm, and the distances from the inner margins to the center of the circle are both 35 mm.

[0009] As a preferred structure of the present invention, the hydraulic cylinder piston sealing device with variable sealing gap has an outer piston body axially located between the end flange of the thin-walled sleeve and the second retaining ring, and the end flange of the thin-walled sleeve and the first retaining ring are fixedly connected by a threaded connection.

[0010] As another preferred structure of the present invention, the outer piston body is axially located between the first retaining ring and the second retaining ring; a second annular groove is also provided on the outer circumference of the inner piston body close to the first retaining ring, and a positioning retaining ring is installed in the second annular groove, and a thin-walled sleeve is axially fixed between the positioning retaining ring and the bottom surface of the inner hole of the outer piston body.

[0011] In the hydraulic cylinder piston sealing device with variable sealing gap, when the longitudinal cross-section shape of each annular pressure equalizing groove is semicircular, the corresponding groove radius size is 0.25mm-0.5mm, the depth is 0.5mm-1mm, and the spacing between each annular pressure equalizing groove is 2mm-5mm.

[0012] The material of the thin-walled sleeve of the hydraulic cylinder piston sealing device with variable sealing gap can be No. 45 carbon structural steel commonly used in engineering; or tin bronze alloy, aluminum bronze alloy.

[0013] In a second aspect, the present invention further provides a hydraulic cylinder, comprising the hydraulic cylinder piston sealing device described in any one of the first aspects.

[0014] The prior art mainly changes the sealing gap by locally elastically deforming the deformed lips at the left and right ends of the piston. The present invention adopts a solution different from the prior art, which changes the sealing gap by radially expanding the outer surface of the piston close to the inner wall of the cylinder. Compared with the background art, the present invention has the following beneficial effects:

[0015] (1) The present invention allows working oil of a certain pressure to enter the internal cavity of the thin-walled sleeve, so that the thin-walled portion of the thin-walled sleeve expands radially as a whole and produces uniform radial elastic deformation, causing the outer piston body in contact with the outer cylindrical surface of the thin-walled portion of the thin-walled sleeve to also produce an overall radial outward displacement, so that the gap between the outer cylindrical surface of the outer piston body and the inner wall of the cylinder is reduced, thereby achieving the purpose of reducing leakage. In this way, as the oil pressure increases, the gap between the outer cylindrical surface of the outer piston body and the inner wall of the cylinder will adaptively decrease, thereby eliminating or reducing the problem of increased leakage caused by increased pressure and improving the volumetric efficiency of the hydraulic cylinder. Moreover, this method of changing the sealing gap by radially expanding the outer cylindrical surface of the piston as a whole can withstand a higher critical load value of elastic deformation than the method of local elastic deformation of the deformable lip in the prior art, is suitable for working conditions with high oil pressure, and its operation is more reliable.

[0016] (2) The outer circular surface of the outer piston body is provided with a plurality of annular pressure equalizing grooves parallel to each other. When the longitudinal cross-section of the annular pressure equalizing groove is semicircular, compared with the annular pressure equalizing groove with a rectangular longitudinal cross-section in the prior art, it is beneficial to reduce oil turbulence, vortex and other phenomena, reduce energy loss, and thus reduce the adverse effects of oil heating.

[0017] In short, the first aspect of the present invention provides a hydraulic cylinder piston sealing device with a variable sealing gap. The technical solution of changing the sealing gap and adjusting the leakage volume by transmitting pressure to make the piston expand radially as a whole can eliminate or reduce the problem of increased leakage volume caused by increased pressure, improve the volumetric efficiency of the hydraulic cylinder, have good sealing effect, high reliability, and is suitable for occasions with high oil pressure and high requirements for sealing performance. The second aspect of the present invention provides a hydraulic cylinder piston sealing device with a variable sealing gap provided by the first aspect of the present invention, so that the hydraulic cylinder has all the beneficial effects of the hydraulic cylinder piston sealing device with a variable sealing gap provided by the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a first embodiment of a hydraulic cylinder piston sealing device with a variable sealing gap and a hydraulic cylinder of the present invention.

[0019] Figure 2 It is a schematic diagram of the three-dimensional structure of the first retaining ring part in the first embodiment.

[0020] Figure 3 It is a schematic diagram of the three-dimensional structure of the inner piston body part in the first embodiment.

[0021] Figure 4 It is a schematic diagram of the full cross-section structure of the inner piston body part in the first embodiment.

[0022] Figure 5 It is a full cross-sectional structural view of the outer piston body part of the present invention.

[0023] Figure 6 It is a structural schematic diagram of a second embodiment of a hydraulic cylinder piston sealing device with a variable sealing gap and a hydraulic cylinder of the present invention.

[0024] Figure 7 It is a schematic diagram of the full cross-section structure of the inner piston body part in the second embodiment.

[0025] Figure 1 to Figure 7 In the figure: oil inlet and outlet 1, first retaining ring 102 and 202, arc-shaped through hole 2A, inner piston body 103 and 203, arc-shaped groove hole 3A, thin-walled sleeve 104 and 204, outer piston body 5, inner hole surface with larger inner diameter 5A, inner hole surface with smaller inner diameter 5B, inner hole bottom surface 5C, inner cavity 6 of thin-walled sleeve, annular pressure-equalizing groove 7, first sealing ring 8, second retaining ring 9, piston rod 10, cylinder 11, oil inlet and outlet 12, guide sleeve 13, end cover 14, second sealing ring 15, oil channel 16, locking nut 17, positioning retaining ring 18, first annular groove 109 and 209, second annular groove 20, connecting screw 21. DETAILED DESCRIPTION

[0026] The following is a further description of a hydraulic cylinder piston sealing device with a variable sealing gap and a hydraulic cylinder according to the present invention in conjunction with the accompanying drawings and embodiments. It should be noted that in the description of the present invention, the terms "left", "right", "inside", "outside" and the like indicate directions or positional relationships based on the attached drawings. Figure 1 or attached Figure 6 The orientation or positional relationship shown is only for the convenience of describing the present invention, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and do not indicate or imply their relative importance.

[0027] Implementation Method 1

[0028] Figure 1 FIG. 1 is a schematic diagram showing a first embodiment of the present invention. Figure 2-Figure 5 It is a structural diagram of some key parts. Figure 1-Figure 5In the embodiment, a combined piston capable of reciprocating linear motion in the hydraulic cylinder is installed in the cylinder barrel 11 of the hydraulic cylinder, which is composed of a first retaining ring 102, a second retaining ring 9, an inner piston body 103, an outer piston body 5, and a thin-walled sleeve 104. The first retaining ring 102 and the second retaining ring 9 are respectively located at both ends of the piston, and the inner piston body 103, the outer piston body 5, and the thin-walled sleeve 104 are axially located between the first retaining ring 102 and the second retaining ring 9; the inner piston body 103, the thin-walled sleeve 104, and the outer piston body 5 are sequentially installed along the radial direction from the outer circumference of the piston rod 10 to the inner wall of the cylinder barrel 11. The outer piston body 5 includes an inner hole surface 5A with a larger inner diameter, an inner hole surface 5B with a smaller inner diameter, and an inner hole bottom surface 5C. The inner piston body 103 is sleeved on the corresponding axial diameter of the piston rod 10 through its inner hole, and a thin-walled sleeve 104 is installed on the outer circumference of the inner piston body 103. The outer cylindrical surface of the thin-walled part of the thin-walled sleeve 104 is matched with the inner hole surface 5A of the larger inner diameter in the outer piston body 5. The outer piston body 5 is axially located between the end flange of the thin-walled sleeve 104 and the second retaining ring 9, and the end flange of the thin-walled sleeve 104 is fixedly connected to the first retaining ring 102 through a threaded connection. The inner piston body 103 is fixedly connected to the second retaining ring 9 through a threaded connection at the end thereof that contacts the second retaining ring 9. The inner piston body 103 is provided with a first annular groove 109 on the outer circumferential surface in contact with the inner hole surface 5B of the smaller inner diameter in the outer piston body 5. The first sealing ring 8 is installed in the first annular groove 109 to prevent the oil entering the inner cavity 6 of the thin-walled sleeve from penetrating into the contact surface between the second retaining ring 9 and the outer piston body 5, and the gap between the outer piston body 5, the second retaining ring 9 and the inner wall of the cylinder; the first sealing ring 8 can be in the form of an O-ring or the like. A second sealing ring 15 is installed between the inner hole of the inner piston body 103 and the outer diameter of the piston rod 10 to prevent the oil from penetrating and leaking through the piston rod. The second sealing ring 15 can also be in the form of an O-ring or the like.

[0029] A small radial annular gap is provided between the outer circular surface of the outer piston body 5 and the inner wall of the cylinder barrel 11 to form a non-contact gap seal of the hydraulic cylinder piston. The outer circular surface of the outer piston body 5 is also provided with a number of annular equalizing pressure grooves 7 parallel to each other, which can make the piston radial force more balanced. The longitudinal section shape of each annular equalizing pressure groove 7 is semicircular, or a non-semicircular arc, V-shaped, U-shaped, or a shape formed by a combination of a semicircular and a V-shaped, U-shaped, trapezoidal, or rectangular. As a preferred structure of the present invention, when the longitudinal section shape of each annular equalizing pressure groove 7 is semicircular, the corresponding groove radius size is 0.25mm~0.5mm, the depth is 0.5mm~1mm, and the spacing between each annular equalizing pressure groove is 2mm~5mm. Studies have found that when an annular equalizing pressure groove structure with a semicircular longitudinal section shape is adopted, relative to the annular equalizing pressure groove structure with a rectangular longitudinal section shape in the prior art, it is beneficial to reduce phenomena such as oil turbulence and vortex, reduce energy loss, and reduce the adverse effects of oil heating.

[0030] The first retaining ring 102 is evenly distributed with three arc-shaped through holes 2A of the same shape and size along the circumferential direction. The three arc-shaped through holes 2A penetrate the first retaining ring 102 and continue to enter the inner piston body 103 to form three arc-shaped groove holes 3A respectively. The three arc-shaped through holes 2A have the same cross-sectional shape as the three arc-shaped groove holes 3A. Their internal cavities are directly opposite and connected to form a continuous oil passage 16 from front to back. The oil passage 16 connects the rodless cavity on one side of the first retaining ring 102 and the internal cavity 6 of the thin-walled sleeve. The inner piston body 103 and the first retaining ring 102 are fixedly connected by connecting screws 21 to avoid relative rotation between the inner piston body 103 and the first retaining ring 102, ensuring that the arc-shaped through holes 2A and the internal cavities of the arc-shaped groove holes 3A are directly opposite to each other, and the flow cross section of the oil passage 16 connected is maximized. The number of connecting screws 21 can be 1 to 3, and the corresponding figure of the first embodiment shows the case where there is only one connecting screw 21. In addition, the arc-shaped through hole 2A on the first retaining ring 102 and the arc-shaped groove hole 3A in the inner piston body 103 have corresponding central angles of 60°, radial widths of 7 mm, and inner margins at a distance of 35 mm from the center of the circle.

[0031] Figure 1 In the embodiment, the piston of the split combined structure is axially fixed to one end of the piston rod 10 located in the cylinder 11 by a locking nut 17, and is coaxial with the piston rod 10; the other end of the piston rod 10 passes through the center holes of the guide sleeve 13 and the end cover 14 in sequence and extends to the outside of the cylinder 11. The left and right ends of the cylinder 11 are provided with oil inlet and outlet ports 1 and 12, and the oil enters and exits the inner cavity of the hydraulic cylinder through these two oil inlet and outlet ports when the hydraulic cylinder is working.

[0032] In the design of the thin-walled sleeve 104, material selection is a key factor. The thin-walled sleeve 104 can be made of No. 45 carbon structural steel commonly used in engineering; other materials with good elastic deformation and recovery properties, such as tin bronze alloy, aluminum bronze alloy, etc., can also be considered. In addition, the thickness dimension design of the thin-walled part is also very important. In the present invention, a preferred solution for the thickness dimension of the thin-walled part of the thin-walled sleeve 104 is 1.5mm to 1.8mm. In addition, the oil pressure value during the operation of the hydraulic cylinder cannot exceed the critical load value of elastic deformation that the thin-walled sleeve can withstand, so as to avoid radial plastic deformation of the thin-walled part of the thin-walled sleeve and cause the gap adjustment to fail.

[0033] Implementation Method 2

[0034] Figure 6 The schematic diagram of the structure of the second embodiment of the present invention is shown, wherein the same components as the first embodiment are used as the first embodiment. Figure 1 The same reference numerals refer to corresponding parts of different structures, such as the first retaining ring, the inner piston body, and the thin-walled sleeve. Figure 6 The second embodiment is also different from the first embodiment in that the outer piston body 5 is axially located between the first retaining ring 202 and the second retaining ring 9. The inner piston body 203 is not only provided with a first annular groove 209 on the outer circumference of the side close to the second retaining ring 9, but also provided with a second annular groove 20 on the outer circumference of the side close to the first retaining ring 202, and a positioning retaining ring 18 is installed in the second annular groove 20, and a thin-walled sleeve 204 is axially fixed between the positioning retaining ring 18 and the inner hole bottom surface 5C of the outer piston body 5.

[0035] The first embodiment and the second embodiment mentioned above both include a corresponding hydraulic cylinder piston sealing device with a variable sealing gap, and a hydraulic cylinder provided with the hydraulic cylinder piston sealing device with a variable sealing gap.

[0036] The working process of the first embodiment of the present invention is briefly described as follows:

[0037] In the initial state, the working oil is at low pressure, and the pressure oil enters the rodless chamber of the hydraulic cylinder from the oil inlet and outlet 1, driving the piston and the piston rod 10 to move rightward relative to the cylinder 11, and returns the oil from the other oil inlet and outlet 12. At this time, the pressure oil enters the inner cavity 6 of the thin-walled sleeve through the oil passage 16, but the thin-walled part of the thin-walled sleeve 104 remains in its original shape, and the outer cylindrical surface of the outer piston body 5 and the inner wall of the cylinder 11 maintain the original initial gap. The hydraulic cylinder implements gap sealing through this initial gap. When the oil pressure in the rodless chamber increases, the pressure oil in the inner cavity 6 of the thin-walled sleeve evenly transmits the pressure to the thin-walled sleeve 104, causing the thin-walled part to produce radial elastic deformation, and driving the outer cylindrical surface of the outer piston body 5 to produce an overall radial outward displacement, reducing the sealing gap between the piston and the inner wall of the cylinder 11, thereby reducing the leakage, overcoming the deficiency that the leakage of the constant gap sealing hydraulic cylinder increases with the increase of pressure, so that the hydraulic cylinder maintains a high volumetric efficiency and achieves a good and reliable seal.

[0038] It is necessary to point out that when the pressure oil enters the rod chamber of the hydraulic cylinder from the oil inlet and outlet 12 and returns through the oil inlet and outlet 1, the piston and the piston rod 10 move to the left relative to the cylinder barrel 11. This process cannot change the sealing gap and affect the leakage. That is, the present invention is suitable for automatically adjusting the sealing gap in the unidirectional movement stroke of the hydraulic cylinder to eliminate or reduce the problem of increased leakage caused by increased pressure.

[0039] The working process of the second embodiment of the present invention is similar to the working process of the first embodiment of the present invention, and will not be repeated here.

[0040] The above specific implementation modes are used to explain the present invention rather than to limit the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements are all within the protection scope of the present invention.

Claims

1. A hydraulic cylinder piston sealing device with a variable sealing gap, used for sealing the gap between the hydraulic cylinder piston and the inner wall of the cylinder barrel (11), characterized in that: The piston adopts a split combined structure, which is composed of a first retaining ring (102, 202), a second retaining ring (9), an inner piston body (103, 203), an outer piston body (5), and a thin-walled sleeve (104, 204), and is axially fixed to one end of a piston rod (10) located in a cylinder barrel (11) through a locking nut (17); the first retaining ring (102, 202) and the second retaining ring (9) are respectively located at two ends of the piston; the inner piston body (103, 203), the thin-walled sleeve (104, 204) and the outer piston body (5) are sequentially installed in the axial middle position of the piston and in the radial direction from the outer circumference of the piston rod (10) to the inner wall of the cylinder barrel (11); the outer piston body (5) comprises an inner hole surface (5A) with a larger inner diameter and a smaller inner hole surface (5B) with a smaller inner diameter. The inner piston body (103, 203) is sleeved on the corresponding axial diameter of the piston rod (10) through its inner hole, and a thin-walled sleeve (104, 204) is installed on the outer circumference of the inner piston body (103, 203). The outer cylindrical surface of the thin-walled part of the thin-walled sleeve (104, 204) is in contact with the inner hole surface (5A) of the larger inner diameter in the outer piston body (5); the inner piston body (103, 203) is fixedly connected to the second retaining ring (9) through a threaded connection at one end, and is fixedly connected to the first retaining ring (102, 202) through a connecting screw (21) at the other end; the outer cylindrical surface of the inner piston body (103, 203) in contact with the inner hole surface (5B) of the smaller inner diameter in the outer piston body (5) A first annular groove (109, 209) is provided on the inner surface of the inner piston body (103, 203), and a first sealing ring (8) is installed in the first annular groove (109, 209); a second sealing ring (15) is installed between the inner hole of the inner piston body (103, 203) and the piston rod (10); a small radial annular gap is provided between the outer circular surface of the outer piston body (5) and the inner wall of the cylinder barrel (11) to form a gap seal; the outer circular surface of the outer piston body (5) is also provided with a plurality of annular pressure equalizing grooves (7) parallel to each other; the longitudinal cross-section shape of each annular pressure equalizing groove (7) is semicircular, or a non-semicircular arc, V-shaped, U-shaped, or a shape formed by combining a semicircular shape with a V-shaped, U-shaped, trapezoidal, or rectangular shape; the first retaining ring (102, 202) is evenly distributed along the circumferential direction with three parallel shapes. The three circular arc through holes (2A) are of the same shape and size; the three circular arc through holes (2A) penetrate the first retaining ring (102, 202) and then continue to enter the inner piston body (103, 203) to form three circular arc groove holes (3A) respectively; the three circular arc through holes (2A) and the three circular arc groove holes (3A) have the same cross-sectional shape, and their internal cavities are directly opposite and penetrate and communicate with each other from front to back to form a continuous oil passage (16), and the oil passage (16) communicates with the rodless cavity on one side of the first retaining ring (102, 202) and the internal cavity (6) of the thin-walled sleeve; and the central angles of the circular arc through holes (2A) and the circular arc groove holes (3A) are both 60°, the radial widths are both 7 mm, and the distances of the inner edges from the center of the circle are both 35 mm.

2. The hydraulic cylinder piston sealing device with variable sealing gap according to claim 1, characterized in that: The outer piston body (5) is axially located between the end flange of the thin-walled sleeve (104) and the second retaining ring (9), and the end flange of the thin-walled sleeve (104) and the first retaining ring (102) are fixedly connected via a threaded connection.

3. The hydraulic cylinder piston sealing device with variable sealing gap according to claim 1, characterized in that: The outer piston body (5) is axially located between the first retaining ring (202) and the second retaining ring (9); the inner piston body (203) is also provided with a second annular groove (20) on the outer circumference of the side close to the first retaining ring (202), and a positioning retaining ring (18) is installed in the second annular groove (20), and the thin-walled sleeve (204) is axially fixed between the positioning retaining ring (18) and the bottom surface (5C) of the inner hole of the outer piston body (5).

4. The hydraulic cylinder piston sealing device with variable sealing gap according to claim 1, characterized in that: Each annular pressure equalizing groove (7) has a semicircular longitudinal cross-section shape, a groove radius of 0.25 mm to 0.5 mm, and a depth of 0.5 mm to 1 mm; and the spacing between each annular pressure equalizing groove (7) is 2 mm to 5 mm.

5. The hydraulic cylinder piston sealing device with variable sealing gap according to claim 1, 2 or 3, characterized in that: The material of the thin-walled sleeve (104, 204) can be No. 45 carbon structural steel commonly used in engineering; or tin bronze alloy, aluminum bronze alloy.

6. A hydraulic cylinder, characterized in that: A hydraulic cylinder piston sealing device with a variable sealing gap comprising any one of claims 1 to 5.

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