Hydraulic machine self-locking cylinder

Abstract

The application relates to the technical field of hydraulic oil cylinders, in particular to a self-locking oil cylinder of a hydraulic machine, which comprises a cylinder body, detachable intermediate end covers and rear end covers are connected to the two ends of the cylinder body, an oil inlet pipe is arranged on the inner wall of the intermediate end cover, an oil outlet pipe is arranged on the inner wall of the rear end cover, and an oil return pipe is through-connected on the inner wall of the cylinder body. Through detachable cooperation of the front end cover and the rear end cover, a variable-diameter self-locking assembly is installed in the inner cavity of the rear end cover, self-locking of the piston when the piston restores the initial stroke is realized, the potential energy impact on the piston can be buffered, and the damage to the piston rod and the piston is reduced; through cooperation of the piston sleeve rod and the lock block, the piston rod can be double-locked, and the convenience of unlocking is reserved; and through cooperation of the central oil channel designed at the end of the piston rod and the transmission hole, a lubricating channel is formed during self-locking, so that the oil can enter the friction surface between the piston rod and the piston, thereby reducing the friction.

Description

Technical Field

[0001] This invention relates to the field of hydraulic cylinder technology, specifically to a self-locking hydraulic cylinder for a hydraulic press. Background Technology

[0002] Hydraulic self-locking cylinders are an important component of hydraulic systems, used to maintain load and prevent accidental movement at specific positions or under specific conditions. In hydraulic systems, when hydraulic cylinders act as actuators, they sometimes need to remain stationary at any position or a certain point and bear a certain load force. Traditionally, this requirement is achieved through hydraulic locking circuits, but this method may have problems such as insufficient stability or high complexity.

[0003] In the prior art, such as the self-locking hydraulic cylinder installed on a lifting device with publication number CN107120333A, there are cylinder bottoms, pistons, cylinder barrels, cylinder heads, and piston rods. The piston and piston rod are both located inside the cylinder barrel. The piston is sleeved on the piston rod, and the cylinder head seals the piston rod inside the cylinder barrel. The cylinder bottom is welded to the cylinder barrel. A rodless chamber and a rod chamber are formed between the piston, the cylinder bottom, and the cylinder head, respectively. A sleeve is provided on the piston rod, which is sleeved on the outer wall of the piston rod and can rotate around the axis of the piston rod. The sleeve is also provided with a locking groove. A second groove is provided on the inner wall of the cylinder barrel. A connecting element and a locking pin matching the locking groove are provided in the second groove. One end of the connecting element is connected to the second groove, and the other end is connected to the locking pin. The locking pin can move along the axial direction of the connecting element.

[0004] However, in actual operation, when the hydraulic cylinder completes a working cycle and the piston returns to its initial position, if the kinetic energy accumulated during its sliding process is not completely consumed, the piston will strike the cylinder head with residual speed, reducing the service life of the hydraulic cylinder. Furthermore, as the usage time increases, the locking spring may gradually lose its elastic stress due to fatigue, corrosion, or material aging, leading to the failure of the locking mechanism, which in turn causes the piston rod to move or fall off unexpectedly, resulting in serious consequences.

[0005] Therefore, this invention proposes a self-locking hydraulic cylinder for hydraulic presses to solve the problems of impact loss caused by improper piston kinetic energy management and insufficient reliability of locking mechanisms in traditional hydraulic cylinder systems. It can achieve multiple self-locking at the end of the piston rod stroke while retaining the ability to unlock easily, improving the compactness and maintenance convenience of the overall structure and extending the overall service life. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a self-locking cylinder for a hydraulic press, which has multiple self-locking capabilities at the end of the piston rod stroke while retaining the ability to unlock easily, thus improving the overall compactness and ease of maintenance.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a self-locking hydraulic cylinder for a hydraulic press, comprising a cylinder body, with a middle end cover and a rear end cover detachably connected to both ends of the cylinder body. An oil inlet pipe is provided on the inner wall of the middle end cover, and an oil outlet pipe is provided on the inner wall of the rear end cover. A return oil pipe is connected through the inner wall of the cylinder body. A front end cover is detachably connected to the outer side of the middle end cover. A pre-reserved groove is provided on the central inner wall of the middle end cover. A support ring seat and a U-shaped groove plate are fixedly installed on the inner surface of the pre-reserved groove. A piston rod is disposed at the center of the U-shaped groove plate. A central oil passage is formed on the inner wall of one end of the piston rod. A piston sleeve is fitted onto the outer surface of the piston rod. A pressure boosting hole is formed on the inner wall of the piston sleeve. A piston is fixedly connected to one end of the piston rod. A variable diameter self-locking assembly is provided on the side of the piston near the middle end cover for locking and braking after the piston rod returns to its stroke. A buffer groove is formed on the inner wall of the cylinder. A buffer ring is movably embedded inside the buffer groove. The buffer ring is fixedly installed on the surface of the piston. A contact switch is provided between the buffer groove and the buffer ring for activating the variable diameter self-locking assembly.

[0008] Preferably, a controller is fixedly installed on the inner surface of the support ring seat. The controller is electrically connected to a contact switch. A hollow shaft is fixedly connected to the output shaft of the controller. The hollow shaft has a hollow columnar structure. Oil inlet holes are evenly opened on the inner wall of the hollow shaft. A solenoid valve is provided on the inner wall of the hollow shaft.

[0009] Preferably, the variable diameter self-locking assembly includes a rotating plate and a base plate. The base plate is rotatably installed inside the rotating plate. The diameter of the base plate is larger than the diameter of the rotating plate. A protective cover is fixedly connected to the outer surface of the rotating plate. An arc-shaped groove is formed on the inner wall of the rotating plate. A sliding groove for auxiliary limiting is formed on the inner wall of the base plate. There are nine sets of both the arc-shaped groove and the sliding groove.

[0010] Preferably, a locking rod is slidably connected to the inner surface of the groove, and a protruding post is fixedly installed on the surface of the locking rod. The outer surface of the protruding post is movably connected to the inner surface of the arc-shaped groove.

[0011] Preferably, a support wing arm is fixedly connected to the outer surface of the base plate near the rotating plate. The support wing arm is provided in two sets and is in an "L"-shaped plate structure. The two sets of support wing arms are mirror-distributed about the central axis of the base plate. One end of the support wing arm is fixedly connected to the inner wall of the reserved groove.

[0012] Preferably, one end of the piston rod is fixedly connected to a rod end limiting ring, and the inner wall of the rod end limiting ring is provided with equally spaced locking grooves, the inner surface of the locking grooves being movably inserted into the outer surface of the locking rod.

[0013] Preferably, the spiral groove plate has a hollow annular plate structure, and an annular cavity is provided inside the spiral groove plate. An abutment spring is fixedly connected to the inner surface of the annular cavity, and a pressure block is fixedly connected to the other end of the abutment spring. The side of the pressure block away from the abutment spring is rounded, and the rounded end of the pressure block is in movable contact with the outer surface of the piston rod.

[0014] Preferably, a transfer hole is provided through the inner wall of the central oil passage for the transfer of lubricating oil. The transfer hole is provided in multiple sets and is distributed in a circular array about the central axis of the central oil passage.

[0015] Preferably, the pressure boosting holes are provided in multiple sets and are arranged in an equidistant array about the central axis of the piston rod.

[0016] Preferably, a locking groove is formed on the inner wall of the cylinder, and a locking block is movably connected to the inner surface of the locking groove. Two sets of locking blocks are provided and symmetrically distributed about the central axis of the piston rod. A spring is fixedly connected to the inner side of the locking block. A receiving groove is formed on the surface of the piston rod, and the spring is located inside the receiving groove. One end of the spring is fixedly connected to the inner wall of the receiving groove.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention proposes a self-locking hydraulic cylinder for a hydraulic press. Through the detachable connection of the front and rear covers, a variable-diameter self-locking component is installed inside the rear cover cavity. This achieves self-locking when the piston returns to its initial stroke, while also buffering the potential energy impact on the piston, reducing damage to the piston rod and piston. The cooperation between the piston sleeve rod and the locking block allows for double locking of the piston rod while retaining convenient unlocking capability. Furthermore, the central oil passage designed at the piston rod end, in conjunction with the transmission hole, forms a lubrication channel during self-locking, allowing oil to enter the friction surface between the piston rod and piston, thereby reducing friction. This further solves the problems of impact loss caused by improper piston kinetic energy management and the risk of insufficient reliability of the locking mechanism in traditional hydraulic cylinder systems. It can achieve multiple self-locking at the end of the piston rod stroke while improving the overall structural compactness and maintenance convenience. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0020] Figure 2 This is a schematic diagram of the half-section structure of the present invention;

[0021] Figure 3 For the present invention Figure 2 A magnified structural diagram at point A;

[0022] Figure 4 For the present invention Figure 3Enlarged structural diagram at point A1;

[0023] Figure 5 This is a partial cross-sectional structural diagram of the cylinder block of the present invention;

[0024] Figure 6 This is a schematic diagram of the connection structure between the piston rod and the piston of the present invention;

[0025] Figure 7 This is a schematic cross-sectional view of the connection between the piston rod and the piston of the present invention;

[0026] Figure 8 For the present invention Figure 7 A magnified structural diagram at point B;

[0027] Figure 9 This is a schematic diagram of the structure of the variable diameter self-locking assembly of the present invention;

[0028] Figure 10 This is a schematic diagram of the disassembled structure of the rotating plate and the base plate of the present invention.

[0029] In the diagram: 1. Cylinder block; 11. Intermediate end cover; 13. Front end cover; 12. Rear end cover; 110. Reserved groove; 2. Piston rod; 3. Piston; 31. Buffer ring; 10. Buffer groove; 4. Oil inlet pipe; 5. Oil outlet pipe; 8. Oil return pipe; 21. Rod end limiting ring; 210. Locking groove; 6. Support ring seat; 61. Controller; 611. Hollow shaft; 6110. Oil inlet hole; 612. Rotating plate; 6 121. Protective cover; 6120. Arc groove; 613. Base plate; 614. Support wing arm; 6130. Slide groove; 6131. ​​Protruding column; 6132. Locking rod; 7. Recessed groove plate; 71. Abutment spring; 72. Pressure block; 20. Central oil passage; 200. Transmission hole; 22. Piston sleeve rod; 220. Pressure boosting hole; 230. Receiving groove; 23. Locking block; 231. Spring; 24. Locking groove. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1, please refer to Figure 1-10The present invention provides a technical solution: a self-locking cylinder for a hydraulic press, comprising a cylinder body 1, with a middle end cover 11 and a rear end cover 12 detachably connected to both ends of the cylinder body 1. An oil inlet pipe 4 is provided on the inner wall of the middle end cover 11, and an oil outlet pipe 5 is provided on the inner wall of the rear end cover 12. A return oil pipe 8 is connected through the inner wall of the cylinder body 1. A front end cover 13 is detachably connected to the outer side of the middle end cover 11. A reserved groove 110 is provided on the inner wall of the center of the middle end cover 11. A support ring seat 6 and a return groove plate 7 are fixedly installed on the inner surface of the reserved groove 110. A piston rod 2 is provided at the center of the return groove plate 7. A piston 3 is fixedly connected to one end of the piston rod 2. A variable diameter self-locking assembly is provided on the side of the piston 3 near the middle end cover 11 for locking and braking after the piston rod 2 returns to its stroke.

[0032] Example 2, see attached document Figure 1-10 Based on Embodiment 1, in order to achieve the self-locking trigger of the variable diameter self-locking assembly after the piston 3 resumes its stroke: a buffer groove 10 is provided on the inner wall of the cylinder 1, a buffer ring 31 is movably embedded inside the buffer groove 10, the buffer ring 31 is fixedly installed on the surface of the piston 3, and a contact switch is provided between the buffer groove 10 and the buffer ring 31 for starting the variable diameter self-locking assembly; a controller 61 is fixedly installed on the inner surface of the support ring seat 6, the controller 61 is electrically connected to the contact switch, a hollow shaft 611 is fixedly connected on the output shaft of the controller 61, the hollow shaft 611 has a hollow columnar structure, oil inlet holes 6110 are evenly provided on the inner wall of the hollow shaft 611, and a solenoid valve is provided on the inner wall of the hollow shaft 611;

[0033] A buffer groove 10 is made on the inner wall of one end of the cylinder 1, and a contact switch is installed inside it for activating the variable diameter self-locking assembly. When the piston rod 2 drives the piston 3 to reset to the initial position, the kinetic energy accumulated during the sliding process is not completely consumed. At this time, the buffer ring 31 connected to one end of the piston 3 enters the buffer groove 10 first. The piston 3 will not directly contact the cylinder 1 due to the obstruction of the buffer ring 31. In this way, the dynamic potential energy of the piston 3 is reduced by the elastic force of the buffer ring 31. When the buffer ring 31 touches the contact switch inside the buffer groove 10, the piston 3 fully reaches the initial position, and the variable diameter self-locking assembly is activated in time.

[0034] Example 3, refer to Appendix Figure 1-10Based on Embodiment 2, in order to achieve automatic locking of the piston 3 in the initial position: the variable diameter self-locking assembly includes a rotating plate 612 and a base plate 613. The base plate 613 is rotatably mounted inside the rotating plate 612, and the diameter of the base plate 613 is larger than the diameter of the rotating plate 612. A protective cover 6121 is fixedly connected to the outer surface of the rotating plate 612. An arc-shaped groove 6120 is formed on the inner wall of the rotating plate 612, and a sliding groove 6130 for auxiliary limiting is formed on the inner wall of the base plate 613. Both the arc-shaped groove 6120 and the sliding groove 6130 have nine sets. A locking rod 6132 is slidably connected to the inner surface of the sliding groove 6130, and the surface of the locking rod 6132 is fixed. A protruding post 6131 is fixedly installed, and the outer surface of the protruding post 6131 is movably connected to the inner surface of the arc-shaped groove 6120; a support wing arm 614 is fixedly connected to the outer surface of the base plate 613 near the rotating plate 612. The support wing arm 614 is provided in two sets and is in an "L"-shaped plate structure. The two sets of support wing arms 614 are mirror-distributed about the central axis of the base plate 613. One end of the support wing arm 614 is fixedly connected to the inner wall of the reserved groove 110; a rod end limiting ring 21 is fixedly connected to one end of the piston rod 2. The inner wall of the rod end limiting ring 21 is provided with equally spaced locking grooves 210. The inner surface of the locking groove 210 is movably inserted into the outer surface of the locking rod 6132.

[0035] When the controller 61 receives the drive signal and starts, its output shaft rotates, causing the hollow shaft 611 to rotate. It should be noted that at this time, the oil inlet pipe 4 is in a state of stopping oil supply, and one end of the piston 3 is blocked at one end of the reserved groove 110. When the hollow shaft 611 rotates, it synchronously drives the rotating plate 612 and the protective cover 6121 to rotate. The reason for adding the protective cover 6121 to the outside of the rotating plate 612 is to avoid the hydraulic oil flowing through the oil inlet pipe 4 from impacting the rotating plate 612. At this time, the arc-shaped grooves 6120 evenly opened on the rotating plate 612 drive the internal protrusions 6131 to move. Thus, multiple sets of locking rods 6132 synchronously change diameter and finally match with the locking grooves 210 opened on the rod end limit ring 21 to achieve mechanical locking of the piston rod 2 as a whole.

[0036] Example 4, see attached document Figure 1-10 Based on Example 3, in order to enable the oil to penetrate into the friction surface between the piston rod 2 and the piston 3 during the self-locking process: a central oil passage 20 is provided on the inner wall of one end of the piston rod 2, and a transmission hole 200 is provided through the inner wall of the central oil passage 20 for the transmission of lubricating oil. Multiple sets of transmission holes 200 are provided and distributed in a circular array about the central axis of the central oil passage 20.

[0037] As Figure 3As shown, after piston 3 completes self-locking, a small amount of oil exists in the lubrication channel formed by the central oil passage 20 and the transmission hole 200 through the oil inlet hole 6110 on the hollow shaft 611. At this time, the oil will penetrate into the friction surface between piston rod 2 and piston 3 through multiple small channels, thus achieving dynamic lubrication, which greatly reduces running resistance and wear. Lubrication can reduce energy loss during friction, improve mechanical transmission efficiency, enable hydraulic cylinder to work more efficiently, and further extend the service life of hydraulic cylinder. It is worth noting that by designing the central oil passage 20 at the end of piston rod 2 near the oil inlet pipe 4 and connecting it to the dispersed transmission hole 200, piston rod 2 and piston 3 can be connected to the hollow shaft 611 through the input port of the central oil passage 20 when self-locking is completed. After the two are connected, not only is the limiting support of piston rod 2 and piston 3 during self-locking satisfied, but a small amount of oil can also be guided to the friction surface between piston rod 2 and piston 3 to form a dynamic lubrication effect.

[0038] Example 5, see attached document Figure 1-10 Based on embodiment four, in order to achieve double locking of piston rod 2: the back groove plate 7 is a hollow annular plate structure, the back groove plate 7 is provided with an annular cavity, the inner surface of the annular cavity is fixedly connected to the abutment spring 71, the other end of the abutment spring 71 is fixedly connected to the pressure block 72, the side of the pressure block 72 away from the abutment spring 71 is set as rounded corner, and the rounded corner end of the pressure block 72 is movably abutting against the outer surface of piston rod 2;

[0039] As Figure 7 and Figure 8 As shown, when the piston rod 2 passes through the center position of the abutment spring 71, the rounded corner of the pressure block 72 contacts the surface of the piston rod 2. During the movement of the piston rod 2 to return to its initial position, the pressure block 72 is always pushed by the surface of the piston rod 2, and the abutment spring 71 is in a compressed state at this time. When the piston 3 fully reaches the locking position, the elastic potential energy of the abutment spring 71 drives the pressure block 72 to clamp the surface of the piston rod 2, realizing double-layer locking of the piston rod 2 while avoiding fluctuations between the piston rod 2 and the piston 3, maintaining the overall stability of the piston 3 when it resets, and further solving the problem of impact loss caused by improper piston kinetic energy management and the risk of insufficient reliability of the locking mechanism in traditional hydraulic cylinder systems.

[0040] Example 6, see attached document Figure 1-10Based on Embodiment 5, in order to achieve convenient unlocking capability between piston rod 2 and piston 3: a piston sleeve 22 is sleeved and connected to the outer surface of piston rod 2, and a pressure boosting hole 220 is opened on the inner wall of piston sleeve 22. Multiple sets of pressure boosting holes 220 are arranged in an equidistant array about the central axis of piston sleeve 22; a locking groove 24 is opened on the inner wall of cylinder 1, and a locking block 23 is movably connected to the inner surface of locking groove 24. Two sets of locking blocks 23 are arranged and symmetrically distributed about the central axis of piston rod 2. A spring 231 is fixedly connected to the inner side of locking block 23. A receiving groove 230 is opened on the surface of piston rod 2, and the spring 231 is located inside the receiving groove 230. One end of the spring 231 is fixedly connected to the inner wall of receiving groove 230.

[0041] As Figure 5 and Figure 6 As shown, a piston sleeve 22 is added to the surface of the piston rod 2. Pressure boosting holes 220 are evenly distributed on the inner wall of the piston sleeve 22 for introducing hydraulic oil during the return flow of the return oil pipe 8. Specifically, the return oil pipe 8 is connected to an external return oil channel. At this time, the hydraulic oil flows towards the locking block 23 side through the pressure boosting holes 220. When the pressure inside the cylinder 1 increases, the locking groove 24 fills with hydraulic oil, pushing the locking block 23 outwards. At this time, the spring 231 is compressed by the external force, causing deformation. The locking block 23 and spring 231 are received into the receiving groove 230, and the locking groove 24 releases its restriction on the locking block 23. This achieves rapid unlocking of the piston rod 2. The pressure-boosting hole 220 on the piston sleeve 22 can guide some of the oil, allowing the hydraulic oil to flow towards the locking block 23 through the pressure-boosting hole 220. Here, the piston sleeve 22 not only provides structural support for the piston rod 2 during use, but also guides the flow of hydraulic oil, and achieves the effect of assisting in unlocking the locking block 23, thus realizing the effect of multiple uses. It should be noted that when the spring 231 gradually loses its elastic stress due to fatigue, corrosion, or material aging after long-term use, causing the locking mechanism to fail, the piston rod 2 can be automatically unlocked by the reverse drive of the variable diameter self-locking component, thereby restoring the normal use of the piston rod 2 and piston 3.

[0042] The working principle and usage process of this invention are as follows: First, the self-locking cylinder of the hydraulic press is in a non-working state, and the piston 3 and its piston rod 2 are located in a certain working position of the cylinder. When the hydraulic cylinder starts working, hydraulic oil enters the cylinder through the oil supply system such as the oil inlet pipe 4, pushing the piston 3 and piston rod 2 to move in the working direction to complete the work task. After the work is completed, the piston 3 and piston rod 2 need to return to their initial positions. During this process, the piston 3 enters the buffer groove 10 through the buffer ring 31, and the elastic force of the buffer ring 31 reduces the dynamic potential energy of the piston 3. Subsequently, when the buffer ring 31... When the contact switch inside the buffer groove 10 is touched, the contact switch sends a signal to the controller 61. The controller 61 receives the drive signal and starts, and at the same time, the hollow shaft 611 begins to rotate. At this time, because the oil inlet pipe 4 stops supplying oil and the piston 3 blocks one end of the reserved groove 110, it is ensured that the rotation of the hollow shaft 611 is not affected by the hydraulic oil. As the hollow shaft 611 rotates, the rotating plate 612 and the base plate 613 in the diameter-changing self-locking assembly begin to work. The arc groove 6120 drives the protrusion 6131 to move, so that multiple sets of locking rods 6132 change diameter synchronously, and finally... The locking grooves 210 on the rod end limiting ring 21 are matched to achieve mechanical locking of the piston 3 and its connected component, the piston rod 2. During the variable diameter self-locking process, due to the structure of the abutment spring 71 and pressure block 72 inside the return groove plate 7, when the piston rod 2 returns to its initial position, the rounded end of the pressure block 72 moves against the outer surface of the piston rod 2, and further clamps the piston rod 2 through the elastic potential energy of the abutment spring 71, achieving double locking. During the self-locking process, a small amount of oil enters the central oil passage 20 and the transmission hole 200 through the oil inlet hole 6110 on the hollow shaft 611. Within the formed lubrication channel, fluid permeates between the friction surfaces of piston rod 2 and piston 3, achieving dynamic lubrication and reducing friction and wear. When unlocking is required, hydraulic oil fills the lock groove 24 through external control or pressure changes in the hydraulic system, pushing the lock block 23 outward. Simultaneously, the spring 231 undergoes compression deformation, causing the lock block 23 and spring 231 to be received into the receiving groove 230, thereby releasing the restriction on piston rod 2 and achieving rapid unlocking. If the spring 231 loses its elastic stress due to prolonged use, automatic unlocking can also be achieved through the reverse drive of the variable diameter self-locking assembly.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hydraulic machine self-locking oil cylinder, comprising a cylinder body (1), detachable connection of both ends of the cylinder body (1) has a middle end cover (11) and a rear end cover (12), an oil inlet pipe (4) is arranged on the inner wall of the middle end cover (11), and an oil outlet pipe (5) is arranged on the inner wall of the rear end cover (12), characterized in that: The inner wall of the cylinder body (1) is connected with an oil return pipe (8), the outer side of the middle end cover (11) is detachably connected with a front end cover (13), the central inner wall of the middle end cover (11) is provided with a reserved groove (110), the inner surface of the reserved groove (110) is fixedly installed with a support ring seat (6) and a return type groove plate (7), the center of the return type groove plate (7) is provided with a piston rod (2), one end of the piston rod (2) is fixedly connected with a piston (3), the side of the piston (3) close to the middle end cover (11) is provided with a variable-diameter self-locking assembly, which is used for locking and braking after the piston rod (2) restores the stroke, the inner wall of the cylinder body (1) is provided with a buffer groove (10), the inner part of the buffer groove (10) is movably connected with a buffer ring (31), the buffer ring (31) is fixedly installed on the surface of the piston (3), and a touch switch is arranged between the buffer groove (10) and the buffer ring (31), which is used for starting the variable-diameter self-locking assembly. The inner surface of the support ring seat (6) is fixedly installed with a controller (61), the controller (61) is electrically connected with the touch switch, and the output shaft of the controller (61) is fixedly connected with a hollow shaft rod (611). The inner wall of one end of the piston rod (2) is provided with a central oil channel (20), and the inner wall of the central oil channel (20) is provided with a transmission hole (200) in a penetrating manner, which is used for the transmission of lubricating oil. The outer surface of the piston rod (2) is sleeved with a piston sleeve rod (22), the inner wall of the piston sleeve rod (22) is provided with a booster hole (220), and the booster hole (220) is provided with a plurality of groups and is arranged in an equidistant array about the central axis of the piston sleeve rod (22). The inner wall of the cylinder body (1) is provided with a lock groove (24), the inner surface of the lock groove (24) is movably connected with a lock block (23), the inner side of the lock block (23) is fixedly connected with a spring (231), the surface of the piston rod (2) is provided with a receiving groove (230), the spring (231) is arranged on the inner side of the receiving groove (230), and one end of the spring (231) is fixedly connected with the inner wall of the receiving groove (230). The variable-diameter self-locking assembly comprises a rotating plate (612) and a base plate (613), the inner wall of the rotating plate (612) is provided with an arc-shaped groove (6120), and the inner wall of the base plate (613) is provided with a sliding groove (6130) for auxiliary limiting. The inner surface of the sliding groove (6130) is slidably connected with a locking rod (6132), the surface of the locking rod (6132) is fixedly installed with a convex column (6131), and the outer surface of the convex column (6131) is movably connected with the inner surface of the arc-shaped groove (6120). The outer surface of the side of the base plate (613) close to the rotating plate (612) is fixedly connected with a support wing arm (614), and one end of the support wing arm (614) is fixedly connected with the inner wall of the reserved groove (110). One end of the piston rod (2) is fixedly connected with a rod end limiting ring (21), an inner wall of the rod end limiting ring (21) is equally divided to form locking grooves (210), and inner surfaces of the locking grooves (210) are movably connected with outer surfaces of locking rods (6132); an output shaft of the controller (61) rotates to drive the hollow shaft rod (611) to rotate, and when the hollow shaft rod (611) rotates, the rotating plate (612) is synchronously rotated.

2. The self-locking hydraulic cylinder of claim 1, wherein: The hollow shaft rod (611) has a hollow columnar structure, and an inner wall of the hollow shaft rod (611) is provided with an electromagnetic valve.

3. The self-locking hydraulic cylinder of claim 1, wherein: The base plate (613) is rotatably installed on the inner side of the rotating plate (612), the diameter of the base plate (613) is greater than the diameter of the rotating plate (612), an outer surface of the rotating plate (612) is fixedly connected with a protective cover (6121), and the arc-shaped grooves (6120) and the sliding grooves (6130) are each provided with nine groups.

4. The self-locking hydraulic cylinder of claim 3, wherein: The support wing arms (614) are provided with two groups and have overall "L" shaped plate structures, and the two groups of support wing arms (614) are mirror image distributed about the central axis of the base plate (613).

5. The self-locking hydraulic cylinder of claim 1, wherein: The return type groove plate (7) has a hollow annular plate structure, an inner portion of the return type groove plate (7) is provided with an annular cavity, an inner surface of the annular cavity is fixedly connected with an abutting spring (71), the other end of the abutting spring (71) is fixedly connected with a pressing block (72), a side, away from the abutting spring (71), of the pressing block (72) is provided with a rounded corner, and the rounded corner end of the pressing block (72) is movably abutted with an outer surface of the piston rod (2).

6. The self-locking hydraulic cylinder of claim 1, wherein: The transmission holes (200) are provided with multiple groups and are circularly arrayed about the central axis of the central oil channel (20).

7. The self-locking hydraulic cylinder of claim 1, wherein: The locking blocks (23) are provided with two groups and are symmetrically distributed about the central axis of the piston rod (2).

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