Single-rod hydraulic cylinder closed type hydraulic system

Abstract

The closed hydraulic system of the single-rod hydraulic cylinder comprises the hydraulic cylinder, a single-rod hydraulic cylinder and a single-rod hydraulic cylinder, wherein the hydraulic cylinder is provided with a rodless cavity and a rod cavity; an oil tank containing hydraulic oil; the pump is a two-way pump and is arranged in the oil tank, and the pump is provided with a first oil port and a second oil port; the main valve block and the oil tank are assembled together, a first oil way, a second oil way and an auxiliary oil way are formed in the main valve block, the first oil way is connected between the first oil port and the rodless cavity, the second oil way is connected between the second oil port and the rod cavity, and the auxiliary oil way starts from the oil tank; wherein the main valve block comprises a plurality of mechanical hydraulically-driven hydraulic valves. The hydraulic system is compact and high in integration level.

Description

Technical Field

[0001] The present application relates to a single-rod hydraulic cylinder closed hydraulic system. Background Art

[0002] Hydraulic transmission has the advantages of large driving force and suitable for heavy-load direct drive. However, the power part, control part and actuator of the traditional open hydraulic system are separated and independent, occupying a large space area. In some places where the space is relatively small and a large force output is required, it is difficult to install and arrange the hydraulic equipment.

[0003] A closed hydraulic system may be designed to occupy a smaller space. For a closed hydraulic system, when the actuator is a single-rod hydraulic cylinder, due to the difference in area between the rodless chamber and the rod chamber, when the rod chamber is filled with oil and the rodless chamber is returned to oil, a portion of the oil returned from the rodless chamber is used to supply the hydraulic pump with hydraulic oil, and the excess hydraulic oil needs to be returned to the oil tank through high-pressure overflow, resulting in energy waste and system heating. In addition, the existing closed hydraulic system has too serious redundant design of system principles, which makes the hydraulic system principle too complicated. Utility Model Content

[0004] An object of the present application is to provide an improved single-rod hydraulic cylinder closed hydraulic system, which can realize closed-type driving of the single-rod hydraulic cylinder in a compact structure.

[0005] To this end, the present application provides, in one aspect, a single-rod hydraulic cylinder closed hydraulic system, comprising:

[0006] A hydraulic cylinder having a rodless chamber and a rod chamber;

[0007] an oil tank containing hydraulic oil;

[0008] A pump, which is a bidirectional pump, is arranged in the oil tank, and has a first oil port and a second oil port;

[0009] A main valve block is assembled with the oil tank, wherein a first oil circuit, a second oil circuit and an auxiliary oil circuit are formed in the main valve block, wherein the first oil circuit is connected between the first oil port and the rodless chamber, the second oil circuit is connected between the second oil port and the rod chamber, and the auxiliary oil circuit leads to the oil tank;

[0010] The main valve block comprises:

[0011] a first one-way valve, disposed between the first oil circuit and the auxiliary oil circuit, and oriented to allow only the hydraulic oil in the auxiliary oil circuit to flow toward the first oil circuit;

[0012] a second one-way valve, disposed between the second oil circuit and the auxiliary oil circuit, and oriented to allow only the hydraulic oil in the auxiliary oil circuit to flow toward the second oil circuit;

[0013] a first hydraulic lock, disposed between an upstream section and a downstream section of the first oil circuit, oriented to allow only hydraulic oil in the upstream section of the first oil circuit to flow to the downstream section under normal conditions, a control end of the first hydraulic lock being connected to the second oil circuit;

[0014] a second hydraulic lock, disposed between an upstream section and a downstream section of the second oil circuit, oriented to allow only the hydraulic oil in the upstream section of the second oil circuit to flow to the downstream section under normal conditions, and a control end of the second hydraulic lock connected to the first oil circuit;

[0015] an unloading valve, disposed between the first oil circuit and the auxiliary oil circuit, oriented to allow only the hydraulic oil in the auxiliary oil circuit to flow toward the first oil circuit under normal conditions, and a control end of the unloading valve is connected to the second oil circuit;

[0016] The shuttle valve has two inlets connected to the downstream section of the first oil circuit and the downstream section of the second oil circuit respectively, and an outlet connected to the auxiliary oil circuit.

[0017] In one embodiment, the first hydraulic lock is the only hydraulic element in the first oil circuit.

[0018] In one embodiment, the control end of the first hydraulic lock is connected to the upstream section of the second oil circuit.

[0019] In one embodiment, the second hydraulic lock is the only hydraulic element in the second oil circuit.

[0020] In one embodiment, the control end of the second hydraulic lock is connected to the upstream section of the first oil circuit.

[0021] In one embodiment, the unloading valve is arranged between the upstream section of the first oil circuit and the auxiliary oil circuit.

[0022] In one embodiment, the single-rod hydraulic cylinder closed hydraulic system further includes:

[0023] A pressure regulating valve is provided in the auxiliary oil circuit;

[0024] a first safety valve, arranged between the upstream section of the first oil circuit and the auxiliary oil circuit;

[0025] The second safety valve is arranged between the upstream section of the second oil circuit and the auxiliary oil circuit.

[0026] In one embodiment, the pump is immersed in hydraulic oil in an oil tank, and the hydraulic cylinder is integrated on the oil tank.

[0027] In one embodiment, a bladder is provided inside the oil tank.

[0028] In one embodiment, the first one-way valve, the second one-way valve, the first hydraulic lock, the second hydraulic lock, the unloading valve, the shuttle valve, and the pressure regulating valve are all mechanically hydraulically driven.

[0029] According to the single-rod hydraulic cylinder closed hydraulic system of the present application, the hydraulic cylinder is an asymmetric hydraulic cylinder. During the operation of the system, the return oil of the rodless chamber of the hydraulic cylinder is more than the inlet oil of the rod chamber. The excess hydraulic oil returns to the oil tank without pressure through the hydraulic unloading valve, and does not need to return to the oil tank through the high-pressure safety valve, which reduces heat generation and has high system stability. The closed hydraulic system includes an integrated structure, in which the power part and the transmission part are integrated into one, and the system is compact and highly integrated.

[0030] The hydraulic valves in the closed hydraulic system can all be driven by mechanical hydraulics without any electrical signals. When the system is working, only the drive motor needs to be powered, which makes the hydraulic system stable and simple in structure.

[0031] The closed hydraulic system can ensure the safety protection of the hydraulic cylinder when it is impacted by a large external force through a combined circuit of a shuttle valve and a pressure regulating valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The foregoing and other aspects of the present application will be more fully understood and appreciated through the following detailed description made with reference to the accompanying drawings, in which:

[0033] Figure 1 It is a schematic diagram of the hydraulic principle of the single-rod hydraulic cylinder closed hydraulic system of the present application;

[0034] Figure 2 is a schematic diagram of the single-rod hydraulic cylinder closed hydraulic system performing an extension operation;

[0035] Figure 3 It is a schematic diagram of the single-rod hydraulic cylinder closed hydraulic system performing a retraction operation. DETAILED DESCRIPTION

[0036] The present application generally relates to a single-rod hydraulic cylinder closed hydraulic system. The hydraulic system has a compact structure and is particularly suitable for narrow space applications, such as the latch positioning of a ship's cabin door, for realizing the opening and closing of the ship's cabin door.

[0037] Figure 1 An exemplary structure of a single-rod hydraulic cylinder closed hydraulic system of the present application is schematically shown. The hydraulic system includes a bidirectional pump P and a drive motor M integrated in a closed oil tank 1. The oil tank 1 contains hydraulic oil, and a bladder 3 is provided inside the oil tank 1. The bladder 3 is inflated and retracts and bulges with the increase or decrease of the amount of hydraulic oil in the oil tank 1, so that a substantially constant oil pressure is maintained in the oil tank 1. The side wall of the oil tank 1 may be provided with an air release valve 4 and an oil filling valve 5.

[0038] The driving motor M is configured to drive the pump P to rotate bidirectionally to supply hydraulic oil to the single-rod hydraulic cylinder C. The pump P may be installed inside the oil tank 1, and the driving motor M may be installed outside the oil tank 1. For example, the pump P may be installed on the inner surface of a wall of the oil tank 1, and the driving motor M may be exposed from the wall and arranged outside. For some pumps and motors of an integrated structure, both the pump P and the driving motor M may be arranged inside the oil tank 1.

[0039] The pump P is preferably immersed in the hydraulic oil in the oil tank 1 , so that the hydraulic oil leaked from the pump P can directly return to the oil tank 1 , and the hydraulic oil in the oil tank 1 can cool and lubricate the pump P.

[0040] The main valve block 2 is assembled with the oil tank 1. The main valve block 2 is formed with a first oil path L1, a second oil path L2 and an auxiliary oil path L3.

[0041] The starting end of the first oil circuit L1 is connected to the A port (first oil port) of the pump P, and the starting end of the second oil circuit L2 is connected to the B port (second oil port) of the pump P. The ends of the first oil circuit L1 and the second oil circuit L2 both terminate at corresponding ports on the surface of the main valve block 2. The single-rod hydraulic cylinder C has a rodless chamber C1 and a rod chamber C2. The rodless chamber C1 is connected to the end port of the first oil circuit L1, and the rod chamber C2 is connected to the end port of the second oil circuit L2. Thus, a closed-loop hydraulic circuit is formed between the pump P and the hydraulic cylinder C through the first oil circuit L1 and the second oil circuit L2.

[0042] The main valve block 2 includes various hydraulic valves for controlling the supply of hydraulic oil from the pump P to the hydraulic cylinder C. These hydraulic valves are usually composed of valve cores installed in valve chambers formed in the main valve block 2. These hydraulic valves are all mechanically hydraulically driven, and the action is purely driven by the oil pressure in the main valve block 2, without any electromagnetic drive element, and no electrical signal input. The following is an introduction to the various hydraulic valves in the main valve block 2.

[0043] First, the auxiliary oil circuit L3 is connected to the first oil circuit L1 through a one-way valve 6 (first one-way valve), and the one-way valve 6 is oriented to allow the hydraulic oil in the auxiliary oil circuit L3 to flow to the first oil circuit L1 and prohibit reverse flow. The auxiliary oil circuit L3 is connected to the second oil circuit L2 through a one-way valve 7 (second one-way valve), and the one-way valve 7 is oriented to allow the hydraulic oil in the auxiliary oil circuit L3 to flow to the second oil circuit L2 and prohibit reverse flow.

[0044] In the first oil circuit L1, a hydraulic lock 8 (first hydraulic lock) is arranged downstream of the connection point of the one-way valve 6. The hydraulic lock 8 divides the first oil circuit L1 into an upstream section (the section connected to the A port of the pump P) and a downstream section (the section away from the A port of the pump P). The hydraulic lock 8 is a hydraulically controlled one-way valve, which is oriented to allow the hydraulic oil in the first oil circuit L1 to flow from the upstream section to the downstream section in the normal state (non-forced opening state), prohibit reverse flow in the normal state, but allow reverse flow when forced opening.

[0045] In the second oil circuit L2, a hydraulic lock 9 (second hydraulic lock) is arranged downstream of the connection point of the one-way valve 7. The hydraulic lock 9 divides the second oil circuit L2 into an upstream section (the section connected to the B port of the pump P) and a downstream section (the section away from the B port of the pump P). The hydraulic lock 9 is a hydraulically controlled one-way valve, which is oriented to allow the hydraulic oil in the second oil circuit L2 to flow from the upstream section to the downstream section under normal conditions (non-forced opening state), prohibit reverse flow under normal conditions, but allow reverse flow when forced opening.

[0046] The control end of the hydraulic lock 8 is connected to the second oil circuit L2 (preferably connected to the upstream section of the second oil circuit L2), that is, the opening oil pressure of the hydraulic lock 8 is taken from the second oil circuit L2 (preferably taken from the upstream section of the second oil circuit L2), and the opening degree of the hydraulic lock 8 when forced to open depends on the oil pressure in the second oil circuit L2. The control end of the hydraulic lock 9 is connected to the first oil circuit L1 (preferably connected to the upstream section of the first oil circuit L1), that is, the opening oil pressure of the hydraulic lock 9 is taken from the first oil circuit L1 (preferably taken from the upstream section of the first oil circuit L1), and the opening degree of the hydraulic lock 9 when forced to open depends on the oil pressure in the first oil circuit L1. The hydraulic lock 8 can be the only hydraulic element in the first oil circuit L1, that is, there are no other hydraulic elements in the upstream and downstream sections of the first oil circuit L1. The hydraulic lock 9 can be the only hydraulic element in the second oil circuit L2, that is, there are no other hydraulic elements in the upstream and downstream sections of the second oil circuit L29.

[0047] An unloading valve 10 is provided between the first oil circuit L1 and the auxiliary oil circuit L3. The unloading valve 10 is a hydraulically controlled one-way valve, which is oriented to allow the hydraulic oil in the auxiliary oil circuit L3 to flow to the first oil circuit L1 under normal conditions (non-forced opening state), prohibit reverse flow under normal conditions, but allow reverse flow when forced to open. The inlet of the unloading valve 10 is connected to the auxiliary oil circuit L3, and the outlet of the unloading valve 10 is connected to the first oil circuit L1 (preferably connected to the upstream section of the first oil circuit L1). The control end of the unloading valve 10 is connected to the second oil circuit L2 (preferably connected to the upstream section of the second oil circuit L2), that is, the opening oil pressure of the unloading valve 10 is taken from the second oil circuit L2 (preferably taken from the upstream section of the second oil circuit L2). The opening degree of the unloading valve 10 when forced to open depends on the oil pressure in the second oil circuit L2. The opening pressure of the unloading valve 10 is higher than the opening pressure of the one-way valves 6 and 7.

[0048] A safety valve 11 (first safety valve) is provided between the first oil circuit L1 and the auxiliary oil circuit L3. The inlet of the safety valve 11 is connected to the first oil circuit L1 (preferably connected to the upstream section of the first oil circuit L1), and the outlet of the safety valve 11 is connected to the auxiliary oil circuit L3.

[0049] A safety valve 12 (second safety valve) is provided between the second oil circuit L2 and the auxiliary oil circuit L3. The inlet of the safety valve 12 is connected to the second oil circuit L2 (preferably connected to the upstream section of the second oil circuit L2), and the outlet of the safety valve 12 is connected to the auxiliary oil circuit L3.

[0050] The safety valves 11 and 12 are substantially overflow valves, and preferably have adjustable opening pressures.

[0051] A shuttle valve 13 is provided between the downstream section of the first oil circuit L1 and the downstream section of the second oil circuit L2. The two inlets of the shuttle valve 13 are respectively connected to the downstream section of the first oil circuit L1 and the downstream section of the second oil circuit L2, and the outlet of the shuttle valve 13 is connected to the end of the auxiliary oil circuit L3. The starting end of the auxiliary oil circuit L3 is connected to the oil tank 1.

[0052] A pressure regulating valve 14 is provided in the auxiliary oil circuit L3 (preferably near the end of the auxiliary oil circuit L3). The inlet of the pressure regulating valve 14 is connected to the outlet of the shuttle valve 13, and the outlet of the pressure regulating valve 14 is preferably located downstream of the connection point of the unloading valve 10, the safety valves 11, 12, and the one-way valves 6, 7 on the auxiliary oil circuit L3. The pressure regulating valve 14 is essentially a relief valve, preferably with an adjustable opening pressure. The pressure regulating valve 14 can be the only hydraulic component in the auxiliary oil circuit L3.

[0053] The downstream sections of the first oil circuit L1 and the second oil circuit L2 can be connected to valves 15 and 16 through corresponding ports located on the surface of the main valve block 2, so as to inject hydraulic oil into the downstream sections of the first oil circuit L1 and the second oil circuit L2 and the hydraulic cylinder C before the initial use of the system and after maintenance. The upstream sections of the first oil circuit L1 and the second oil circuit L2 can be connected to corresponding ports 17 and 18 located on the surface of the main valve block 2, so as to connect similar valves (not shown) so as to inject hydraulic oil into the upstream sections of the first oil circuit L1 and the second oil circuit L2 before the initial use of the system and after maintenance.

[0054] Refer to the following Figure 2 , Figure 3 describe Figure 1 The operation of the hydraulic system is shown. Figure 2 , Figure 3 In the figure, only the components directly related to the operation are drawn, and the direction of hydraulic oil flow is indicated by arrows.

[0055] First see Figure 2When the hydraulic cylinder C is extended, the driving motor M drives the pump P to rotate in a first direction, so that the pump P sucks hydraulic oil from the B port and outputs hydraulic oil from the A port.

[0056] At this time, the B port of the pump P generates negative pressure, and the hydraulic oil is sucked from the oil tank 1 through the starting end of the auxiliary oil circuit L3 through the one-way valve 7. The hydraulic oil output from the A port of the pump P flows into the rodless chamber C1 of the hydraulic cylinder C in the first oil circuit L1 (the hydraulic lock 8 allows flow in this direction under normal conditions), causing the cylinder rod of the hydraulic cylinder C to extend. The hydraulic oil output from the A port of the pump P generates high pressure in the first oil circuit L1, which causes the hydraulic lock 9 to be forced to open, thereby allowing the hydraulic oil in the rod chamber C2 of the hydraulic cylinder C to return to the B port of the pump P through the second oil circuit L2. During the extension operation of the hydraulic cylinder C, part of the hydraulic oil sucked from the B port of the pump P comes from the oil tank 1, and part comes from the rod chamber C2 of the hydraulic cylinder C.

[0057] During the extension operation of the hydraulic cylinder C, when the oil pressure in the first oil circuit L1 exceeds the opening pressure of the safety valve 11, the safety valve 11 opens, so that part of the hydraulic oil in the first oil circuit L1 flows into the auxiliary oil circuit L3 through the safety valve 11 and returns to the oil tank 1, thereby avoiding excessive oil pressure in the first oil circuit L1 to protect the pump P.

[0058] Next, see Figure 3 When the hydraulic cylinder C is retracted, the drive motor M drives the pump P to rotate in the second direction, so that the pump P sucks hydraulic oil from the A port and outputs hydraulic oil from the B port.

[0059] At this time, the A port of the pump P generates negative pressure, and the hydraulic oil is sucked from the oil tank 1 through the starting end of the auxiliary oil circuit L3 through the one-way valve 6. The hydraulic oil output from the B port of the pump P flows into the rod chamber C2 of the hydraulic cylinder C in the second oil circuit L2 (the hydraulic lock 9 allows flow in this direction under normal conditions), causing the cylinder rod of the hydraulic cylinder C to retract. The hydraulic oil output from the B port of the pump P generates high pressure in the second oil circuit L2, which causes the hydraulic lock 8 to be forcibly opened, thereby allowing a portion of the hydraulic oil in the rodless chamber C1 of the hydraulic cylinder C to return to the A port of the pump P through the first oil circuit L1, so that the A port only obtains hydraulic oil from the rodless chamber C1, and no longer draws hydraulic oil from the oil tank 1 through the one-way valve 6. At the same time, the high pressure in the second oil circuit L2 also causes the unloading valve 10 to be forcibly opened, so that another portion of the hydraulic oil in the rodless chamber C1 of the hydraulic cylinder C can flow into the auxiliary oil circuit L3 through the unloading valve 10 and return to the oil tank 1.

[0060] During the retraction operation of the hydraulic cylinder C, when the oil pressure in the second oil circuit L2 exceeds the opening pressure of the safety valve 12, the safety valve 12 opens, so that part of the hydraulic oil in the second oil circuit L2 flows into the auxiliary oil circuit L3 through the safety valve 12 and returns to the oil tank 1, thereby avoiding excessive oil pressure in the second oil circuit L2 to protect the pump P.

[0061] When the extension or retraction operation of the hydraulic cylinder C needs to be stopped, the drive motor M stops rotating, and the A port and the B port of the pump P do not output oil pressure, causing the pressure in the upstream sections of the first oil circuit L1 and the second oil circuit L2 to drop, and the hydraulic locks 8 and 9 return to normal, prohibiting the hydraulic oil in the downstream sections of the first oil circuit L1 and the second oil circuit L2 from flowing to the upstream sections, thereby locking the hydraulic oil in the rodless chamber C1 and the rod chamber C2 of the hydraulic cylinder C, so that the cylinder rod of the hydraulic cylinder C remains stationary.

[0062] When the hydraulic cylinder C is stationary, the pressure generated by the external load in the rodless chamber C1 or the rod chamber C2 of the hydraulic cylinder C acts on the corresponding inlet of the shuttle valve 13 through the downstream section of the first oil circuit L1 or the second oil circuit L2, and is transmitted to the inlet of the pressure regulating valve 14 through the shuttle valve 13. When the external load is too large and the pressure difference between the two inlets transmitted to the pressure regulating valve 14 is higher than the opening pressure of the pressure regulating valve 14, the pressure regulating valve 14 opens and the hydraulic oil in the downstream section of the first oil circuit L1 or the second oil circuit L2 flows into the auxiliary oil circuit L3 and returns to the oil tank 1, thereby realizing the unloading of the high pressure in the rodless chamber C1 or the rod chamber C2 of the hydraulic cylinder C to protect the hydraulic cylinder C.

[0063] In the closed hydraulic system of the present application, the hydraulic cylinder C is an asymmetric hydraulic cylinder with a single rod. When the hydraulic cylinder C is extended, the return oil of the rod chamber C1 circulates to the rodless chamber C2, so that the cylinder rod can be quickly extended. When the hydraulic cylinder C is retracted, the return oil volume of the rodless chamber C2 is greater than the inlet oil volume of the rod chamber C1, and the excess hydraulic oil returns to the oil tank 1 without pressure through the unloading valve 10, and does not need to return to the oil tank through the high-pressure safety valve like the closed hydraulic system of the prior art, thereby reducing energy consumption, reducing heat, and improving system stability.

[0064] In addition, the closed hydraulic system of the present application includes an integrated structure, in which the power part (motor M, pump P, oil tank 1) and the transmission part (main valve block 2 and the oil circuit and hydraulic valve therein) are integrated into one, and the system is compact and highly integrated. Furthermore, the actuator (hydraulic cylinder C) hydraulic cylinder can be integrated with the power part and the transmission part to make the system more compact and more integrated. For example, the hydraulic cylinder C can be directly mounted on the wall of the oil tank 1. For example, the hydraulic cylinder C can be fixedly mounted on the oil tank 1 through the head or tail flange of the hydraulic cylinder C, fixedly mounted on the oil tank 1 through the base, pivotally mounted on the oil tank 1 through the pivots, earrings, etc. at the head, middle, and tail, rotatably mounted on the oil tank 1 through the tail ball head, and so on.

[0065] In addition, the hydraulic valves used in the closed hydraulic system of the present application are all mechanical hydraulically driven valves without any electrical signals. When the hydraulic system is working, it only needs to power the drive motor. Therefore, the hydraulic system is stable and reliable, and has a simple structure, simple layout, and simple operation, which is further suitable for applications in narrow spaces.

[0066] In addition, a bladder is added to the closed oil tank 1 of the closed hydraulic system of the present application, which can be freely expanded and contracted to automatically adapt to changes in the amount of hydraulic oil in the closed oil tank 1.

[0067] In addition, hydraulic locks 8 and 9 are used in the closed hydraulic system of the present application to ensure that the hydraulic cylinder C is stationary.

[0068] In addition, the closed hydraulic system of the present application ensures the safety protection of the hydraulic cylinder C1 when it is impacted by a large external force through the combined circuit of the shuttle valve 13 and the pressure regulating valve 14, thereby improving the safety of the hydraulic system.

[0069] Although the present application is described herein with reference to specific exemplary embodiments, the scope of the present application is not limited to the details shown. Various modifications may be made to these details without departing from the basic principles of the present application.

Claims

1. A single-rod hydraulic cylinder closed hydraulic system, comprising: A hydraulic cylinder (C) having a rodless chamber (C1) and a rod chamber (C2); An oil tank (1) containing hydraulic oil; A pump (P), which is a bidirectional pump, is arranged in the oil tank (1), and the pump (P) has a first oil port (A) and a second oil port (B); A main valve block (2) is assembled with an oil tank (1), wherein a first oil circuit (L1), a second oil circuit (L2) and an auxiliary oil circuit (L3) are formed in the main valve block (2), wherein the first oil circuit (L1) is connected between the first oil port (A) and the rodless chamber (C1), the second oil circuit (L2) is connected between the second oil port (B) and the rod chamber (C2), and the auxiliary oil circuit (L3) leads to the oil tank (1); Characterized in that the main valve block (2) comprises: A first one-way valve (6) is arranged between the first oil circuit (L1) and the auxiliary oil circuit (L3) and is oriented to only allow the hydraulic oil in the auxiliary oil circuit (L3) to flow into the first oil circuit (L1); A second one-way valve (7) is arranged between the second oil circuit (L2) and the auxiliary oil circuit (L3) and is oriented to only allow the hydraulic oil in the auxiliary oil circuit (L3) to flow into the second oil circuit (L2); A first hydraulic lock (8) is arranged between the upstream section and the downstream section of the first oil circuit (L1), and is oriented to allow only the hydraulic oil in the upstream section of the first oil circuit (L1) to flow to the downstream section under normal conditions, and a control end of the first hydraulic lock (8) is connected to the second oil circuit (L2); A second hydraulic lock (9) is arranged between the upstream section and the downstream section of the second oil circuit (L2), and is oriented to allow only the hydraulic oil in the upstream section of the second oil circuit (L2) to flow to the downstream section under normal conditions, and a control end of the second hydraulic lock (9) is connected to the first oil circuit (L1); An unloading valve (10) is arranged between the first oil circuit (L1) and the auxiliary oil circuit (L3), and is oriented to allow only the hydraulic oil in the auxiliary oil circuit (L3) to flow into the first oil circuit (L1) under normal conditions, and a control end of the unloading valve (10) is connected to the second oil circuit (L2); The shuttle valve (13) has two inlets connected to the downstream section of the first oil circuit (L1) and the downstream section of the second oil circuit (L2) respectively, and an outlet connected to the auxiliary oil circuit (L3).

2. The single-rod hydraulic cylinder closed hydraulic system according to claim 1, characterized in that: The first hydraulic lock (8) is the only hydraulic element in the first oil circuit (L1).

3. The single-rod hydraulic cylinder closed hydraulic system according to claim 1, characterized in that: The control end of the first hydraulic lock (8) is connected to the upstream section of the second oil circuit (L2).

4. The single-rod hydraulic cylinder closed hydraulic system according to claim 1, characterized in that: The second hydraulic lock (9) is the only hydraulic element in the second oil circuit (L2).

5. The single-rod hydraulic cylinder closed hydraulic system according to claim 1, characterized in that: The control end of the second hydraulic lock (9) is connected to the upstream section of the first oil circuit (L1).

6. The single-rod hydraulic cylinder closed hydraulic system according to any one of claims 1 to 5, characterized in that: The unloading valve (10) is arranged between the upstream section of the first oil circuit (L1) and the auxiliary oil circuit (L3).

7. The single-rod hydraulic cylinder closed hydraulic system according to any one of claims 1 to 5, characterized in that: The single-rod hydraulic cylinder closed hydraulic system also includes: A pressure regulating valve (14) is arranged in the auxiliary oil circuit (L3); A first safety valve (11) is arranged between an upstream section of the first oil circuit (L1) and the auxiliary oil circuit (L3); The second safety valve (12) is arranged between the upstream section of the second oil circuit (L2) and the auxiliary oil circuit (L3).

8. The single-rod hydraulic cylinder closed hydraulic system according to any one of claims 1 to 5, characterized in that: The pump (P) is immersed in the hydraulic oil in the oil tank (1), and the hydraulic cylinder (C) is integrated on the oil tank (1).

9. The single-rod hydraulic cylinder closed hydraulic system according to any one of claims 1 to 5, characterized in that: The oil tank (1) is provided with a bladder (3) inside.

10. The single-rod hydraulic cylinder closed hydraulic system according to any one of claims 1 to 5, characterized in that: The first one-way valve (6), the second one-way valve (7), the first hydraulic lock (8), the second hydraulic lock (9), the unloading valve (10), and the shuttle valve (13) are all mechanically hydraulically driven.

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