Bidirectional self-locking hydraulic cylinder suitable for underwater equipment hydraulic system and use method thereof

Abstract

A bidirectional self-locking hydraulic cylinder suitable for underwater equipment hydraulic system and a use method thereof, comprising a cylinder barrel, both ends of which are provided with cylinder end covers, and a piston rod is arranged in the cylinder barrel, a spaced a oil port, a b oil port and a p oil port are arranged on the cylinder barrel, and a plurality of oil channels and cavities are arranged on the cylinder barrel, specifically, an X1 cavity is communicated with a q oil channel and a m oil channel, an X2 cavity is communicated with a g oil channel and a h oil channel, a Y1 cavity is communicated with a q oil channel and a n oil channel, a Y2 cavity is communicated with a g oil channel and an i oil channel, a f oil channel is communicated with the b oil channel and the a oil port or a f oil channel is communicated with a d oil channel and an e oil port, the m oil channel is communicated with the q oil channel and the p oil port, the n oil channel is communicated with the q oil channel and the p oil port, and the f oil channel is communicated with the g oil channel, the h oil channel and the i oil channel. By arranging a hydraulic control logic element in the cylinder, and by automatically detecting the oil supply or non-oil supply state of the cylinder, the piston rod of the cylinder can be locked or unlocked at any position.

Description

Technical Field

[0001] This invention relates to the field of hydraulic system technology, and in particular to a bidirectional self-locking hydraulic cylinder suitable for underwater equipment hydraulic systems and its usage method. Background Technology

[0002] Hydraulic systems are widely used in various underwater equipment, such as manned submersibles and underwater robots, due to their advantages of high energy density and reliability. Hydraulic cylinders, as the most commonly used actuators, are widely used as drive components in various mechanical devices. When underwater equipment operates in complex sea conditions, it often requires the mechanical device to have good position-holding capabilities; using a self-locking mechanism with hydraulic cylinders is the simplest and easiest method to achieve this.

[0003] Currently, there are three main methods for self-locking of hydraulic cylinders in existing technologies:

[0004] (i) The most common method is to achieve self-locking of the hydraulic cylinder at any position by setting a balance valve or a hydraulic control check valve in the hydraulic circuit. This method requires connecting valve blocks and valves to the outside of the cylinder circuit, making the hydraulic circuit more complex and increasing the weight. The increase in hydraulic components also leads to an increase in pipeline connection points, increasing the risk of hydraulic circuit leakage. At the same time, domestic manufacturers currently do not have balance valves or hydraulic control check valves that can effectively prevent seawater corrosion.

[0005] (ii) After the hydraulic cylinder reaches its position, an external mechanical self-locking method is used. However, this method often requires manual operation or additional mechanical structures, making it relatively complex.

[0006] (iii) Install a self-locking device inside the hydraulic cylinder, such as a steel ball tension self-locking device. However, this method can only be used when the piston rod is fully extended or retracted, and cannot achieve self-locking at any position.

[0007] In summary, conventional hydraulic cylinder self-locking methods are currently unsuitable for underwater equipment due to their complex structure, low integration, inconvenient operation, or inability to achieve self-locking at any position. Summary of the Invention

[0008] To address the shortcomings of existing manufacturing technologies, the applicant provides a bidirectional self-locking hydraulic cylinder and its usage method suitable for underwater equipment hydraulic systems. This cylinder incorporates a hydraulic control logic element that automatically detects whether the cylinder is supplied with or not, allowing the piston rod to lock or unlock at any position. Furthermore, the cylinder is made of seawater-resistant materials, enabling long-term use in marine environments and exhibiting extremely high reliability and environmental adaptability.

[0009] The technical solution adopted in this invention is as follows:

[0010] A bidirectional self-locking hydraulic cylinder suitable for underwater equipment hydraulic systems includes a cylinder barrel. A first cylinder end cap and a second cylinder end cap are respectively installed at both ends of the cylinder barrel via sealing devices. A piston rod is fitted inside the cylinder barrel, with both ends extending out of the first and second cylinder end caps respectively. The cylinder barrel is provided with spaced oil ports a, b, and p, and multiple oil passages and cavities are provided on the cylinder barrel. Specifically: cavity X1 is connected to oil passage q via oil passage m; cavity X2 is connected to oil passage g via oil passage h; cavity Y1 is connected to oil passage q via oil passage n; cavity Y2 is connected to oil passage g via oil passage i; oil passage f is connected to oil port a via oil passage b or oil port e via oil passage d; oil passage m is connected to oil port p via oil passage q; oil passage n is connected to oil port p via oil passage q; and oil passage f is connected to oil passage h and oil passage i via oil passage g.

[0011] It also includes an oil port self-locking piston, one end of which is connected to an oil port self-locking piston pin. The oil port self-locking piston pin contacts the oil port self-locking piston pin support seat. The oil port self-locking piston seals with the oil port through the oil port self-locking piston rod sealing ring, thus isolating the oil passage. The oil port self-locking piston is pressed against the inner conical surface of the cylinder by a return spring, so that the oil port X3 cavity is sealed and the oil passage is isolated.

[0012] The mounting structure of the e-port self-locking piston is the same as that of the a-port self-locking piston.

[0013] It also includes a logic valve core, which is pressed against the inner conical surface of the cylinder by a logic valve core reset spring, and the f oil passage is connected to the e oil port.

[0014] As a further improvement to the above technical solution:

[0015] Ports a, e, and p are all equipped with internal threads, allowing them to be directly connected to pipe fittings.

[0016] The oil inlet a is the oil supply port or oil return port on the left side of the oil cylinder.

[0017] The oil port b is the oil supply port or oil return port on the right side of the oil cylinder.

[0018] The p-port is the drain port for the self-locking piston pins on both sides.

[0019] The end caps of the No. 1 and No. 2 cylinders and the cylinder barrels are all made of titanium alloy or high-strength aluminum alloy.

[0020] The piston rod is made of double-sided stainless steel or precipitation-hardening stainless steel.

[0021] The logic valve core, the e-port self-locking piston, the a-port self-locking piston, the e-port self-locking piston pin, and the a-port self-locking piston pin are all made of 45 steel.

[0022] A method for using a two-way self-locking hydraulic cylinder suitable for underwater equipment hydraulic systems includes the following operating steps:

[0023] Step 1: Connect port a and port e to ports A and B of the Y-type solenoid directional valve in the hydraulic system, and connect port p to the main return oil circuit of the hydraulic system;

[0024] Step 2: When the solenoid valve is energized in the left position, high pressure is applied to port a, and port e is connected to the oil tank. High-pressure oil flows through port a and oil passage b, and the hydraulic pressure acts on the lower end face of the logic valve core, thereby overcoming the preload of the logic valve core return spring. This causes the logic valve core to move upward until the logic valve core return spring is fully compressed. At this time, oil passage f is connected to oil passage b. High-pressure oil from port a flows through oil passage f and oil passage g into oil passage h and oil passage i, respectively. High-pressure oil flows from oil passage h and oil passage i into the X2 and Y2 cavities, respectively. High-pressure oil acts on the piston ends of the self-locking piston pins of port a and port e, thereby pushing the self-locking pistons of port a and port e towards the self-locking piston return springs of port a and port e, until the springs are fully compressed.

[0025] Oil port a connects to cavity X3, allowing high-pressure oil to enter the left piston rod cavity; oil port e connects to cavity Y3, allowing oil to return from the right piston rod cavity; the cylinder piston rod moves to the right; oil drains from both cavity X1 and cavity Y1 through oil port p.

[0026] Both port a and port e are connected to the oil tank. The logic valve core is pressed against the conical surface inside the cylinder by the logic valve core return spring. The X2 cavity is connected to port e through oil passages h, g, f, and d. Therefore, the piston end of the self-locking piston pin at port a has no force, and the self-locking piston at port a is pressed against the conical surface inside the cylinder by the self-locking piston return spring. Hydraulic oil cannot flow into or out of the piston rod cavity X3. Similarly, the Y2 cavity is connected to port e through oil passages i, g, f, and d. Therefore, the piston end of the self-locking piston pin at port e has no force, and the self-locking piston at port e is pressed against the conical surface inside the cylinder by the self-locking piston return spring. Hydraulic oil cannot flow into or out of the piston rod cavity Y3. Thus, the cylinder can achieve self-locking at any position when there is no oil supply.

[0027] When the solenoid valve is energized in the right position, high pressure is supplied to port e, and port a is connected to the oil tank. High-pressure oil flows through port e and oil passage d, and the hydraulic pressure acts on the upper end face of the logic valve core, causing the logic valve core to be pressed more tightly against the inner cone surface in the cylinder. At this time, oil passage f and oil passage d are connected. High-pressure oil from port e flows through oil passage f and oil passage g, and then flows into oil passage h and oil passage i respectively. High-pressure oil flows from oil passage h and oil passage i into the X2 and Y2 cavities respectively. High-pressure oil acts on the piston ends of the self-locking piston pins of port a and port e, thereby pushing the self-locking pistons of port a and port e towards the return springs of the self-locking pistons of port a and port e, until the springs are fully compressed.

[0028] Oil port a connects to cavity X3, allowing oil to return from the left piston rod cavity; oil port e connects to cavity Y3, allowing high-pressure oil to enter the right piston rod cavity; the cylinder piston rod moves to the left, and both cavity X1 and cavity Y1 drain oil through oil port p.

[0029] Step 4: When the electromagnet is de-energized, the cylinder continues to self-lock as described above.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention features a compact and rational structure, and is easy to operate. By incorporating a hydraulic control logic element within the cylinder and automatically detecting whether the cylinder is supplied with or not, the piston rod can be locked or unlocked at any position. This hydraulic cylinder is suitable for applications where the piston rod must be locked and free from displacement when extended or retracted to any position. Underwater equipment hydraulic systems are limited by layout space and weight, requiring the minimization of hydraulic components, improved system reliability, and reduced system weight. Because this cylinder integrates a self-locking device, it eliminates the need for external hydraulic locking elements, greatly simplifying the hydraulic system design. Furthermore, the self-locking device's simple and ingenious design effectively reduces its weight.

[0032] In addition, the present invention also has the following advantages:

[0033] (1) The present invention has a simple overall structure and is relatively easy to process and obtain materials;

[0034] (2) The present invention adopts a universal interface, which can be conveniently and quickly connected to various conventional and unconventional submersible pipeline systems;

[0035] (3) The present invention realizes the connection and disconnection between the external hydraulic oil circuit and the two cavities on both sides of the oil cylinder by means of built-in logic elements;

[0036] (4) When the high-pressure oil is not connected, the two cavities on both sides of the oil cylinder are not connected to the outside, thereby realizing the self-locking of the oil cylinder at any position.

[0037] (5) This invention can work normally in deep marine environments. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the present invention.

[0039] Figure 2 This is the front view of the present invention.

[0040] Figure 3 for Figure 2 Top view.

[0041] Figure 4 for Figure 2 Side view.

[0042] Figure 5 for Figure 3 Full sectional view along section AA (I) (self-locking state of the oil port on the left side of the cylinder).

[0043] Figure 6 for Figure 3 Full sectional view along section AA (II) (left oil port of the cylinder in open state).

[0044] Figure 7 for Figure 3 Full sectional view along section BB (I) (self-locking state of the oil port on the right side of the cylinder).

[0045] Figure 8 for Figure 3 Full sectional view along section BB (II) (oil port on the right side of the cylinder is open).

[0046] Figure 9 for Figure 4 Full sectional view along section CC (I) (when the piston rod moves to the left).

[0047] Figure 10 for Figure 4 Full sectional view along section CC (II) (when the piston rod moves to the right).

[0048] Figure 11 for Figure 4 Full sectional view along section DD.

[0049] Figure 12 for Figure 4 Full sectional view along section EE.

[0050] Figure 13 for Figure 2 Full sectional view along section FF.

[0051] Figure 14 This is a schematic diagram of the hydraulic cylinder connected to the hydraulic system according to the present invention.

[0052] The components are: 1. Piston rod; 2. End cap of cylinder 1; 3. Cylinder barrel; 4. End cap of cylinder 2; 5. Logic valve core; 6. Logic valve core return spring; 7. Logic valve core return spring seat; 8. E-port self-locking piston pin support seat; 9. E-port self-locking piston pin; 10. E-port self-locking piston; 11. E-port self-locking piston return spring; 12. E-port self-locking piston return spring seat; 13. A-port self-locking piston pin support seat; 14. A-port self-locking piston pin; 15. A-port self-locking piston; 16. A-port self-locking piston return spring; 17. A-port self-locking piston return spring seat; 18. A-port self-locking piston rod sealing ring; 19. E-port self-locking piston rod sealing ring. Detailed Implementation

[0053] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0054] like Figures 1-14 As shown, the bidirectional self-locking hydraulic cylinder applicable to the hydraulic system of underwater equipment in this embodiment includes a cylinder barrel 3. A first cylinder end cap 2 and a second cylinder end cap 4 are respectively installed at both ends of the cylinder barrel 3 via sealing devices. A piston rod 1 is installed inside the cylinder barrel 3, with both ends of the piston rod 1 extending out of the first cylinder end cap 2 and the second cylinder end cap 4 respectively. The cylinder barrel 3 is provided with spaced oil ports a, b, and p, and multiple oil passages and cavities are provided on the cylinder barrel 3. Specifically: cavity X1 is connected to oil passage q via oil passage m; cavity X2 is connected to oil passage g via oil passage h; cavity Y1 is connected to oil passage q via oil passage n; cavity Y2 is connected to oil passage g via oil passage i; oil passage f is connected to oil port a via oil passage b or oil port e via oil passage d; oil passage m is connected to oil port p via oil passage q; oil passage n is connected to oil port p via oil passage q; and oil passage f is connected to oil passage h and oil passage i via oil passage g.

[0055] It also includes an oil port self-locking piston 15, one end of which is connected to an oil port self-locking piston pin 14. The oil port self-locking piston pin 14 contacts the oil port self-locking piston pin support seat 13. The oil port self-locking piston 15 is sealed to the oil port and isolates the oil passage through the oil port self-locking piston rod sealing ring 18. The oil port self-locking piston 15 is pressed against the inner conical surface of the cylinder 3 by the return spring 16, so that the oil port X3 cavity is sealed and isolates the oil passage.

[0056] The mounting structure of the e-port self-locking piston 10 is the same as that of the a-port self-locking piston 15.

[0057] It also includes a logic valve core 5, which is pressed against the inner conical surface of the cylinder 3 by a logic valve core reset spring 6, and the f oil passage is connected to the e oil port.

[0058] Ports a, e, and p are all equipped with internal threads, allowing them to be directly connected to pipe fittings.

[0059] a. Oil port: Oil supply port or oil return port on the left side of the oil cylinder.

[0060] Port b is the oil supply port or oil return port on the right side of the oil cylinder.

[0061] The p-port is the drain port for the self-locking piston pins on both sides.

[0062] The end cap 2 of cylinder No. 1, the end cap 4 of cylinder No. 2, and the cylinder barrel 3 are all made of titanium alloy or high-strength aluminum alloy.

[0063] Piston rod 1 is made of double-sided stainless steel or precipitation hardening stainless steel.

[0064] The logic valve core 5, the e-port self-locking piston 10, the a-port self-locking piston 15, the e-port self-locking piston pin 9, and the a-port self-locking piston pin 14 are all made of 45 steel.

[0065] The specific structure and function of the bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems described in this invention are as follows:

[0066] It mainly includes piston rod 1, cylinder end cap 2, cylinder end cap 4, cylinder barrel 3, logic valve core 5, logic valve core return spring 6, logic valve core return spring seat 7, e-port self-locking piston pin support seat 8, e-port self-locking piston pin 9, e-port self-locking piston 10, e-port self-locking piston return spring 11, e-port self-locking piston return spring seat 12, a-port self-locking piston pin support seat 13, a-port self-locking piston pin 14, a-port self-locking piston 15, a-port self-locking piston return spring 16, a-port self-locking piston return spring seat 17, a-port self-locking piston rod sealing ring 18, and e-port self-locking piston rod sealing ring 19.

[0067] The logic valve core return spring 6, the e-port self-locking piston return spring 11, and the a-port self-locking piston return spring 16 are all compression springs, which are always in a compressed state.

[0068] Ports a, e, and p are all equipped with internal threads, allowing for direct connection of pipe fittings.

[0069] One end of the self-locking piston 15 at the oil port is connected to the self-locking piston pin 14 at the oil port. The self-locking piston pin 14 at the oil port contacts the self-locking piston pin support seat 13 at the oil port. The self-locking piston 15 at the oil port seals and isolates the oil passage from the oil port through the self-locking piston rod sealing ring 18 at the oil port. The self-locking piston 15 at the oil port is pressed against the inner conical surface of the cylinder 3 by the self-locking piston return spring 16 at the oil port, so that the cavity of the oil port X3 is sealed and the oil passage is isolated.

[0070] The logic valve core 5 is pressed against the inner conical surface of the cylinder 3 by the logic valve core reset spring 6, and the f oil passage is connected to the e oil port.

[0071] Port a is the oil supply or return port on the left side of the oil cylinder, port b is the oil supply or return port on the right side of the oil cylinder, and port p is the drain port for the self-locking piston pins on both sides.

[0072] Cavity X1 is connected to oil channel q via oil channel m. Cavity X2 is connected to oil channel g via oil channel h.

[0073] Cavity Y1 is connected to oil channel q via oil channel n. Cavity Y2 is connected to oil channel g via oil channel i.

[0074] Oil passage f is connected to oil port a via oil passage b, or oil passage f is connected to oil port e via oil passage d.

[0075] Oil channel m is connected to oil port p via oil channel q; oil channel n is connected to oil port p via oil channel q.

[0076] Oil channel f is connected to oil channels h and i via oil channel g.

[0077] In summary, cavity X1 and cavity Y1 are connected to port p; cavity X2 and cavity Y2 are connected to oil passage f.

[0078] The main function of this invention is to enable self-locking at any position.

[0079] The first cylinder end cap 2, the second cylinder end cap 4, and the cylinder barrel 3 described in this invention are all made of titanium alloy or high-strength aluminum alloy.

[0080] The piston rod 1 described in this invention is made of biaxially oriented stainless steel or precipitation-hardening stainless steel.

[0081] The logic valve core 5, the oil port self-locking piston, and the oil port self-locking piston pins 9 and 14 described in this invention are made of 45 steel.

[0082] The compression spring described in this invention uses carbon spring steel wire, indicating that it is coated or made of stainless steel or titanium alloy.

[0083] In actual work process:

[0084] Connect oil ports a and e to ports A and B of the Y-type solenoid directional valve in the hydraulic system, and connect oil port p to the main return oil circuit of the hydraulic system.

[0085] When the solenoid valve is energized in the left position, high pressure is supplied to port a, and port e is connected to the oil tank. High-pressure oil flows through port a and oil passage b, and the hydraulic pressure acts on the lower end face of the logic valve core 5, thus overcoming the preload of the logic valve core return spring 6. This causes the logic valve core 5 to move upwards until the logic valve core return spring 6 is fully compressed. At this time, oil passage f is connected to oil passage b. (See attached...) Figure 6As shown, high-pressure oil from port a flows through oil passages f and g, then into oil passages h and i respectively. The high-pressure oil then flows from oil passages h and i into cavities X2 and Y2 respectively. The high-pressure oil acts on the piston ends of the self-locking piston pins 14 (port a) and 9 (port e), thereby pushing the self-locking pistons 15 (port a) and 10 (port e) towards the compression return springs 16 and 11 until the springs are fully compressed. At this time, port a connects to cavity X3, and high-pressure oil enters the left piston rod cavity; port e connects to cavity Y3, and oil returns from the right piston rod cavity; the cylinder piston rod moves to the right. Both cavities X1 and Y1 drain oil through port p.

[0086] When the solenoid valve is not energized, both port a and port e are connected to the oil tank. Logic valve core 5 is pressed against the inner conical surface of cylinder 3 by logic valve core return spring 6. The X2 cavity is connected to port e via oil passages h, g, f, and d. Therefore, the piston end of the self-locking piston pin 14 at port a has no force, and the self-locking piston 15 at port a is pressed against the inner conical surface of cylinder 3 by the self-locking piston return spring 16. Hydraulic oil cannot flow into or out of the piston rod cavity X3. Similarly, the Y2 cavity is connected to port e via oil passages i, g, f, and d. Therefore, the piston end of the self-locking piston pin 9 at port e has no force, and the self-locking piston 10 at port e is pressed against the inner conical surface of cylinder 3 by the self-locking piston return spring 11. Hydraulic oil cannot flow into or out of the piston rod cavity Y3. Thus, the cylinder can achieve self-locking at any position when no oil is supplied.

[0087] When the solenoid valve is energized in the right position, high pressure is supplied to port e, and port a is connected to the oil tank. High-pressure oil flows through port e and oil passage d, and the hydraulic pressure acts on the upper surface of the logic valve core 5, causing the logic valve core 5 to press more tightly against the inner conical surface of the cylinder 3. At this time, oil passage f and oil passage d are connected. (See attached...) Figure 6 As shown, high-pressure oil from port e flows through oil passages f and g, then into oil passages h and i respectively. The high-pressure oil then flows from oil passages h and i into cavities X2 and Y2 respectively. This high-pressure oil acts on the piston ends of the self-locking piston pins 14 and 9 at ports a and e, respectively, pushing the self-locking pistons 15 and 10 at ports a and e towards the compression return springs 16 and 11 until the springs are fully compressed. At this point, port a connects to cavity X3, and oil returns from the left piston rod cavity; port e connects to cavity Y3, and high-pressure oil enters the right piston rod cavity; the cylinder piston rod moves to the left. Both cavities X1 and Y1 drain oil through port p.

[0088] When the electromagnet is de-energized, the cylinder continues to self-lock as described above.

[0089] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A bidirectional self-locking hydraulic cylinder suitable for underwater equipment hydraulic systems, characterized in that: The cylinder (3) includes a cylinder barrel (3), and the two ends of the cylinder barrel (3) are respectively fitted with a first cylinder end cap (2) and a second cylinder end cap (4) through a sealing device. A piston rod (1) is fitted inside the cylinder barrel (3), and the two ends of the piston rod (1) extend out of the first cylinder end cap (2) and the second cylinder end cap (4) respectively. The cylinder (3) is provided with a left oil supply port (a), a right oil supply port (e), and an oil drain port (p) spaced apart. The cylinder (3) contains: a first pressure relief chamber (X1) and a second pressure relief chamber (Y1) connected to the oil drain port (p), a left working chamber (X3) connected to the left oil supply port (a), a right working chamber (Y3) connected to the right oil supply port (e), a first control chamber (X2) for controlling the left self-locking, and a second control chamber (Y2) for controlling the right self-locking. The cylinder (3) is also provided with oil passages connecting each cavity, including: The first oil passage (m) connects the first pressure relief chamber (X1) and the oil drain port (p), the second oil passage (n) connects the second pressure relief chamber (Y1) and the oil drain port (p), the third oil passage (h) connects the first control chamber (X2) and the logic control oil circuit (g), and the fourth oil passage (i) connects the second control chamber (Y2) and the logic control oil circuit (g). It also includes an oil port self-locking piston (15), one end of which is connected to an oil port self-locking piston pin (14). The oil port self-locking piston pin (14) contacts the oil port self-locking piston pin support seat (13). The oil port self-locking piston (15) is sealed and isolated from the oil port by the oil port self-locking piston rod sealing ring (18). The oil port self-locking piston (15) is pressed against the inner conical surface of the cylinder (3) by the oil port self-locking piston return spring (16), so that the left working chamber (X3) is sealed and isolated from the oil passage. The mounting structure of the e-port self-locking piston (10) is the same as that of the a-port self-locking piston (15); It also includes a logic valve core (5), which is pressed against the inner conical surface of the cylinder (3) by a logic valve core reset spring (6), and the oil passage is connected to the right oil supply port.

2. The bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The left oil inlet, right oil inlet, and drain port are all equipped with internal threads, which can be directly connected to the pipeline connector.

3. The bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The left oil supply port (a) is the oil supply port or oil return port on the left side of the oil cylinder.

4. The bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The right-side oil supply port (e) is the oil supply port or oil return port on the right side of the oil cylinder.

5. The bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The oil drain port (p) is the oil drain port of the self-locking piston pin on both sides.

6. The bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The end cap (2) of the first cylinder, the end cap (4) of the second cylinder, and the cylinder barrel (3) are all made of titanium alloy or high-strength aluminum alloy.

7. The bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The piston rod (1) is made of double-sided stainless steel or precipitation-hardening stainless steel.

8. The bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The logic valve core (5), e-port self-locking piston (10), a-port self-locking piston (15), e-port self-locking piston pin (9), and a-port self-locking piston pin (14) are all made of 45 steel.

9. A method of using a bidirectional self-locking hydraulic cylinder for underwater equipment hydraulic systems as described in claim 1, characterized in that: The following steps are included: Step 1: Connect the left and right oil supply ports to ports A and B of the Y-type solenoid directional valve in the hydraulic system, and connect the drain port to the main return oil circuit of the hydraulic system. Step 2: When the solenoid valve is energized in the left position, high pressure is supplied to the left oil port, and the right oil port is connected to the oil tank. High pressure oil flows through the left oil port, and the hydraulic pressure acts on the lower end face of the logic valve core (5), thereby overcoming the preload of the logic valve core reset spring (6), causing the logic valve core (5) to move up until the logic valve core reset spring (6) is fully compressed. At this time, the f oil passage is connected to the b oil passage; the high pressure oil from the left oil port flows through the f oil passage and the g oil passage into the h oil passage and the i oil passage, respectively. The high pressure oil flows from the h oil passage and the i oil passage into the X2 and Y2 cavities, respectively. The high pressure oil acts on the lower end face of the logic valve core (5), thereby overcoming the preload of the logic valve core reset spring (6), causing the logic valve core (5) to move up until the logic valve core reset spring (6) is fully compressed. At this time, the f oil passage and the b oil passage are connected. The high pressure oil from the left oil port flows through the f oil passage and the g oil passage into the h oil passage and the i oil passage, respectively. At the piston ends of the self-locking piston pin (14) at port a and the self-locking piston pin (9) at port e, the self-locking pistons (15) at port a and port e are pushed towards the return springs (16) at port a and port e, respectively, until the springs are fully compressed. At this time, the left oil supply port is connected to the X3 cavity, and high-pressure oil enters the left piston rod cavity; the right oil supply port is connected to the Y3 cavity, and oil returns from the right piston rod cavity; the cylinder piston rod moves to the right; both the X1 cavity and the Y1 cavity drain oil through the drain port. Step 3: When the solenoid valve is not energized, both the left and right oil supply ports are connected to the oil tank; the logic valve core (5) is pressed against the inner conical surface of the cylinder (3) by the logic valve core return spring (6), and the X2 cavity is connected to the right oil supply port through the h oil passage, g oil passage, f oil passage, and d oil passage. Then, the piston end of the self-locking piston pin (14) of the a oil port has no force, and the self-locking piston (15) of the a oil port is pressed against the inner conical surface of the cylinder (3) by the self-locking piston return spring (16). Hydraulic oil cannot flow into or out of the piston rod cavity X3; similarly, the Y2 cavity is connected to the e oil port through the i oil passage, g oil passage, f oil passage, and d oil passage, so the piston end of the e oil port self-locking piston pin (9) has no force, and the e oil port self-locking piston (10) is pressed against the inner conical surface of the cylinder (3) by the e oil port self-locking piston return spring (11), so hydraulic oil cannot flow into or out of the piston rod cavity Y3; thus, the cylinder can achieve self-locking at any position when there is no oil supply. When the solenoid valve is energized in the right position, the right oil supply port is supplied with high pressure, and the left oil supply port is connected to the oil tank. The high-pressure oil flows through the right oil supply port and the d oil passage. The hydraulic pressure acts on the upper end face of the logic valve core (5), making the logic valve core (5) press more tightly against the inner cone surface of the cylinder (3). At this time, the f oil passage is connected to the d oil passage. The high-pressure oil from the e oil port flows through the f oil passage and the g oil passage into the h oil passage and the i oil passage, respectively. The high-pressure oil flows from the h oil passage and the i oil passage into the X2 and Y2 cavities, respectively. The high-pressure oil acts on the self-locking piston pin (1) at the a oil port. 4) The piston end of the self-locking piston pin (9) of the e-port pushes the self-locking piston (15) of the a-port and the self-locking piston (10) of the e-port towards the return spring (16) of the self-locking piston of the a-port and the return spring (11) of the self-locking piston of the e-port until the spring is fully compressed. At this time, the oil supply port on the left is connected to the X3 cavity, and the oil returns to the left piston rod cavity; the e-port is connected to the Y3 cavity, and the high-pressure oil enters the right piston rod cavity; the piston rod of the oil cylinder moves to the left, and the X1 cavity and the Y1 cavity both drain oil through the drain port; Step 4: When the electromagnet is de-energized, the cylinder continues to self-lock as described above.

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