Hydraulic system and control method for leveling cylinder of front shovel hydraulic excavator

Abstract

The present invention belongs to the technical field of excavators, and specifically relates to a hydraulic system and control method for a leveling cylinder of a front shovel hydraulic excavator. The hydraulic system includes a two-position four-way reversing valve, a three-position four-way reversing valve I, and a three-position four-way reversing valve II. The first working oil port of the three-position four-way reversing valve I is connected to the large chamber of the boom cylinder, and the second working oil port of the three-position four-way reversing valve I is connected to the small chamber of the boom cylinder. A two-position four-way reversing valve is provided between the boom cylinder and the leveling cylinder. When the leveling cylinder is in the initial position, the large chamber of the boom cylinder is connected to the large chamber of the leveling cylinder, and the small chamber of the boom cylinder is connected to the small chamber of the leveling cylinder. When the leveling cylinder is in the working position, the large chamber of the boom cylinder is connected to the small chamber of the leveling cylinder, and the small chamber of the boom cylinder is connected to the large chamber of the leveling cylinder. The present invention uses the two-position four-way reversing valve to precisely control the movement of the leveling cylinder, fully utilizing the auxiliary function of the leveling cylinder in different excavator operations.

Description

Technical Field

[0001] The present invention belongs to the technical field of excavators, and in particular relates to a hydraulic system and a control method for a leveling cylinder of a front shovel hydraulic excavator. Background Art

[0002] On a traditional face shovel, when the excavator's boom extends, oil flows into the large chamber of the boom cylinder and returns to the small chamber. Therefore, the hydraulic pressure in the large chamber of the boom cylinder is greater than the hydraulic pressure in the small chamber. When the excavator's boom retracts, the regeneration valve comes into play. Since the regeneration valve connects the large and small chambers of the boom cylinder, only when the hydraulic oil pressure in the large chamber of the boom cylinder is greater than that in the small chamber can the hydraulic oil in the large chamber of the boom cylinder pass through the regeneration valve and enter the small chamber of the boom cylinder, thereby retracting the boom cylinder. Therefore, when the excavator's boom retracts, the hydraulic oil pressure in the large chamber of the boom cylinder is greater than that in the small chamber of the boom cylinder.

[0003] Because the large chamber of the boom cylinder in a traditional face shovel is always connected to the large chamber of the leveling cylinder, and the small chamber of the boom cylinder is always connected to the small chamber of the leveling cylinder, the hydraulic oil pressure in the large chamber of the leveling cylinder is always greater than that in the small chamber. Furthermore, because the force-bearing area of ​​the large chamber of the leveling cylinder is greater than that of the small chamber, the leveling cylinder always tends to extend. Therefore, the leveling cylinder only provides positive support when the arm cylinder is extending forward. When the arm cylinder is retracting, the leveling cylinder hinders the retraction process, creating a negative effect, resulting in slower operating speeds and lower efficiency in traditional face shovels. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a hydraulic system and control method for a leveling cylinder of a face shovel hydraulic excavator. Through precise control of the reversing valve, the leveling cylinder can realize both the push function and the second boom cylinder function of the auxiliary boom cylinder.

[0005] The present invention is achieved through the following technical solutions: A hydraulic system for a leveling cylinder of a front shovel hydraulic excavator comprises a two-position four-way reversing valve, a three-position four-way reversing valve I and a three-position four-way reversing valve II;

[0006] The first working oil port of the three-position four-way reversing valve I is connected to the large chamber of the boom cylinder, and the second working oil port of the three-position four-way reversing valve I is connected to the small chamber of the boom cylinder; the large chamber and the small chamber of the boom cylinder are respectively connected to the two-position four-way reversing valve, and the two-position four-way reversing valve is also respectively connected to the large chamber and the small chamber of the leveling cylinder;

[0007] When the leveling cylinder does not receive any signal, it is in the initial position. When the leveling cylinder is in the initial position, the large cavity of the boom cylinder is connected to the large cavity of the leveling cylinder, and the small cavity of the boom cylinder is connected to the small cavity of the leveling cylinder; when the leveling cylinder receives a signal, it is in the working position. When the leveling cylinder is in the working position, the large cavity of the boom cylinder is connected to the small cavity of the leveling cylinder, and the small cavity of the boom cylinder is connected to the large cavity of the leveling cylinder;

[0008] The first working oil port of the three-position four-way reversing valve II is connected to the large chamber of the boom cylinder, and the second working oil port of the three-position four-way reversing valve II is connected to the small chamber of the boom cylinder;

[0009] The oil inlet of the three-position four-way reversing valve II and the oil inlet of the three-position four-way reversing valve I are both connected to the oil outlet of the hydraulic pump; the oil return port of the three-position four-way reversing valve II and the oil return port of the three-position four-way reversing valve I are both connected to the hydraulic oil tank.

[0010] Furthermore, the three-position four-way directional reversing valve I is in the initial position when no signal is received. When the three-position four-way directional reversing valve I is in the initial position, all oil ports of the three-position four-way directional reversing valve I are in a closed state; the left control end of the three-position four-way directional reversing valve I is in the left working position when receiving a signal. When the three-position four-way directional reversing valve I is in the left working position, the oil inlet of the three-position four-way directional reversing valve I is connected to the first working oil port of the three-position four-way directional reversing valve I, and the second working oil port of the three-position four-way directional reversing valve I is connected to the oil return port of the three-position four-way directional reversing valve I; the right control end of the three-position four-way directional reversing valve I is in the right working position when receiving a signal. When the three-position four-way directional reversing valve I is in the right working position, the oil inlet of the three-position four-way directional reversing valve I is connected to the second working oil port of the three-position four-way directional reversing valve I, and the first working oil port of the three-position four-way directional reversing valve I is connected to the oil return port of the three-position four-way directional reversing valve I;

[0011] The three-position four-way directional reversing valve II is in the initial position when no signal is received. When the three-position four-way directional reversing valve II is in the initial position, all oil ports of the three-position four-way directional reversing valve II are in a closed state; the left control end of the three-position four-way directional reversing valve II is in the left working position when receiving a signal. When the three-position four-way directional reversing valve II is in the left working position, the oil inlet of the three-position four-way directional reversing valve II is connected to the first working oil port of the three-position four-way directional reversing valve II, and the second working oil port of the three-position four-way directional reversing valve II is connected to the oil return port of the three-position four-way directional reversing valve II; the right control end of the three-position four-way directional reversing valve II is in the right working position when receiving a signal. When the three-position four-way directional reversing valve II is in the right working position, the oil inlet of the three-position four-way directional reversing valve II is connected to the second working oil port of the three-position four-way directional reversing valve II, and the first working oil port of the three-position four-way directional reversing valve II is connected to the oil return port of the three-position four-way directional reversing valve II.

[0012] Furthermore, the control end of the two-position four-way directional valve, the left control end of the three-position four-way directional valve I, the right control end of the three-position four-way directional valve I, the left control end of the three-position four-way directional valve II and the right control end of the three-position four-way directional valve II are all connected to the controller signal.

[0013] Furthermore, the hydraulic pump is a swash plate plunger hydraulic pump.

[0014] Furthermore, two boom cylinders are provided, and the two boom cylinders are connected in parallel.

[0015] The present invention also provides a method for controlling a leveling cylinder of a front shovel hydraulic excavator, which adopts any one of the above-mentioned hydraulic systems for a leveling cylinder of a front shovel hydraulic excavator;

[0016] When the three-position four-way directional valve I is in the initial position, and the three-position four-way directional valve II is in the left working position, the two-position four-way directional valve is controlled to be in the initial position;

[0017] When the three-position four-way directional valve I is in the left working position, and the three-position four-way directional valve II is also in the left working position, the two-position four-way directional valve is controlled to be in the initial position;

[0018] When the three-position four-way directional valve I is in the left working position, and the three-position four-way directional valve II is in the right working position, the two-position four-way directional valve is controlled to be in the working position;

[0019] When the three-position four-way directional valve I is in the right working position, and the three-position four-way directional valve II is in the left working position, the two-position four-way directional valve is controlled to be in the working position;

[0020] When the three-position four-way directional valve I is in the right working position and the three-position four-way directional valve II is also in the right working position, the two-position four-way directional valve is controlled to be in the initial position.

[0021] The beneficial effects of the present invention are as follows: when the excavator requires horizontal pushing operations, the two-position four-way reversing valve and the three-position four-way reversing valve I are both in the initial position, and the three-position four-way reversing valve II is in the left working position, allowing the leveling cylinder to follow the arm cylinder in performing normal horizontal pushing operations. When the excavator requires other complex operations, the valve position of the two-position four-way reversing valve is controlled according to the complex movements of the boom cylinder and arm cylinder to achieve coordinated movements of the leveling cylinder and arm cylinder, allowing the leveling cylinder to assist the arm cylinder, accelerating the extension and retraction speed of the arm cylinder, improving the operating efficiency of the excavator, and creating greater economic benefits for the user. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the hydraulic principle diagram of the present invention;

[0023] Figure 2 This is a hydraulic diagram of the bucket cylinder of the present invention when performing a horizontal push operation;

[0024] Figure 3 This is a hydraulic diagram of the boom cylinder and the arm cylinder of the present invention when they operate together (compound action 1);

[0025] Figure 4 This is a hydraulic diagram of the present invention when the boom cylinder and the arm cylinder operate together (compound action 2);

[0026] Figure 5 This is a hydraulic diagram of the boom cylinder and the arm cylinder of the present invention when they operate together (compound action 3);

[0027] Figure 6 This is a hydraulic diagram of the present invention when the boom cylinder and the arm cylinder operate together (compound action 4);

[0028] Figure 7 It is a structural schematic diagram of the present invention;

[0029] In the figure, 1. leveling cylinder, 2. two-position four-way reversing valve, 3. boom cylinder, 4. three-position four-way reversing valve I, 5. hydraulic pump, 6. hydraulic oil tank, 7. controller, 8. three-position four-way reversing valve II, 9. arm cylinder, 10. boom, 11. arm. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and examples.

[0031] like Figure 7 As shown, a front shovel hydraulic excavator includes a leveling cylinder 1, a boom cylinder 3 and a stick cylinder 9. The boom cylinder 3 is arranged between the frame and the boom 10 of the front shovel hydraulic excavator, and the leveling cylinder 1 and the stick cylinder 9 are both arranged between the boom 10 and the stick 11.

[0032] like Figures 1 to 6 As shown, a hydraulic system for a leveling cylinder of a front shovel hydraulic excavator includes a two-position four-way reversing valve 2, a three-position four-way reversing valve I4 and a three-position four-way reversing valve II8.

[0033] Specifically, the first working oil port of the three-position four-way reversing valve I4 is connected to the large chamber of the boom cylinder 3, and the second working oil port of the three-position four-way reversing valve I4 is connected to the small chamber of the boom cylinder 3. The three-position four-way reversing valve I4 is in its initial position when no signal is received. When the three-position four-way reversing valve I4 is in its initial position, all oil ports of the three-position four-way reversing valve I4 are closed. The left control end of the three-position four-way reversing valve I4 is in its left working position when a signal is received. When the three-position four-way reversing valve I4 is in the left working position, the oil inlet of the three-position four-way reversing valve I4 is connected to the large chamber of the boom cylinder 3 through the first working oil port of the three-position four-way reversing valve I4, and the small chamber of the boom cylinder 3 is connected to the oil return port of the three-position four-way reversing valve I4 through the second working oil port of the three-position four-way reversing valve I4. When the right control end of the three-position four-way reversing valve I4 receives a signal, it is in the right working position. When the three-position four-way reversing valve I4 is in the right working position, the oil inlet of the three-position four-way reversing valve I4 is connected to the small chamber of the boom cylinder 3 through the second working oil port of the three-position four-way reversing valve I4, and the large chamber of the boom cylinder 3 is connected to the oil return port of the three-position four-way reversing valve I4 through the first working oil port of the three-position four-way reversing valve I4.

[0034] There are two boom cylinders 3 , which are connected in parallel, that is, the large cavity of the first boom cylinder 3 is connected to the large cavity of the second boom cylinder 3 , and the small cavity of the first boom cylinder 3 is connected to the small cavity of the second boom cylinder 3 .

[0035] The two-position, four-way reversing valve 2 is installed between the boom cylinder 3 and the leveling cylinder 1. Specifically, when the leveling cylinder 1 receives no signal, it is in the initial position. When the leveling cylinder 1 is in the initial position, the large chamber of the boom cylinder 3 is connected to the large chamber of the leveling cylinder 1, and the small chamber of the boom cylinder 3 is connected to the small chamber of the leveling cylinder 1. When the leveling cylinder 1 receives a signal, it is in the working position. When the leveling cylinder 1 is in the working position, the large chamber of the boom cylinder 3 is connected to the small chamber of the leveling cylinder 1, and the small chamber of the boom cylinder 3 is connected to the large chamber of the leveling cylinder 1.

[0036] The first working oil port of the three-position, four-way directional control valve II8 communicates with the large chamber of the boom cylinder 9, while the second working oil port of the three-position, four-way directional control valve II8 communicates with the small chamber of the boom cylinder 9. When receiving no signal, the three-position, four-way directional control valve II8 is in its initial position. When in this initial position, all oil ports of the three-position, four-way directional control valve II8 are closed. When receiving a signal, the left control port of the three-position, four-way directional control valve II8 is in its left working position. When in this position, the oil inlet of the three-position, four-way directional control valve II8 communicates with the large chamber of the boom cylinder 9 via its first working oil port, while the small chamber of the boom cylinder 9 communicates with its return port via its second working oil port. When the right control end of the three-position four-way directional reversing valve II8 receives a signal, it is in the right working position. When the three-position four-way directional reversing valve II8 is in the right working position, the oil inlet of the three-position four-way directional reversing valve II8 is connected with the small chamber of the boom cylinder 9 through the second working oil port of the three-position four-way reversing valve II8, and the large chamber of the boom cylinder 9 is connected with the return oil port of the three-position four-way reversing valve II8 through the first working oil port of the three-position four-way reversing valve II8.

[0037] The oil inlet of the three-position, four-way directional valve II 8 and the oil inlet of the three-position, four-way directional valve I 4 are both connected to the oil outlet of the hydraulic pump 5; the hydraulic pump 5 is a swash plate type plunger hydraulic pump. The oil return port of the three-position, four-way directional valve II 8 and the oil return port of the three-position, four-way directional valve I 4 are both connected to the hydraulic oil tank 6.

[0038] The control end of the two-position four-way directional valve 2, the left control end of the three-position four-way directional valve I4, the right control end of the three-position four-way directional valve I4, the left control end of the three-position four-way directional valve II8 and the right control end of the three-position four-way directional valve II8 are all connected to the controller 7 by signal, and the valve positions of the two-position four-way directional valve 2, the three-position four-way directional valve I4 and the three-position four-way directional valve II8 are controlled by the controller 7.

[0039] The present invention also provides a method for controlling a leveling cylinder of a front shovel hydraulic excavator, which adopts any one of the above-mentioned hydraulic systems for a leveling cylinder of a front shovel hydraulic excavator;

[0040] like Figure 2As shown, when the three-position four-way directional valve I4 is in its initial position and the three-position four-way directional valve II8 is in its left working position, the controller 7 controls the two-position four-way directional valve 2 to its initial position. The leveling cylinder 1, the two-position four-way directional valve 2, and the boom cylinder 3 form a closed circulation system. In this case, when the three-position four-way directional valve II8, which controls the arm cylinder 9, is in its left working position, hydraulic oil from the outlet of the hydraulic pump 5 enters the large chamber of the arm cylinder 9 through the three-position four-way directional valve II8, causing the arm cylinder 9 to begin to push forward. The boom cylinder 3 begins to contract due to gravity. Since the two-position four-way directional valve 2 is in its initial position, the hydraulic oil in the large chamber of the boom cylinder 3 enters the large chamber of the leveling cylinder 1 through the two-position four-way directional valve 2, causing the leveling cylinder 1 to also follow the arm cylinder 9 in its forward movement.

[0041] like Figure 3 As shown, when the three-position four-way directional valve I4 is in the left working position, and the three-position four-way directional valve II8 is also in the left working position, the controller 7 controls the two-position four-way directional valve 2 to its initial position. In this situation, hydraulic oil from the outlet of the hydraulic pump 5 flows through the three-position four-way directional valve I4 into the large chamber of the boom cylinder 3, causing the boom cylinder 3 to begin extending. The hydraulic oil from the outlet of the hydraulic pump 5 flows through the three-position four-way directional valve II8 into the large chamber of the arm cylinder 9, causing the arm cylinder 9 to begin extending. When the two-position four-way directional valve 2 is controlled by the controller 7 to its initial position, the hydraulic oil in the large chamber of the boom cylinder 3 flows through the two-position four-way directional valve 2 into the large chamber of the leveling cylinder 1, causing the leveling cylinder 1 to also begin extending. At this point, the leveling cylinder 1 and the arm cylinder 9 operate in unison, acting as a secondary arm cylinder and accelerating the extension of the arm cylinder 9.

[0042] like Figure 4 As shown, when the three-position four-way directional valve I4 is in the left working position and the three-position four-way directional valve II8 is in the right working position, the controller 7 controls the two-position four-way directional valve 2 to the working position. In this situation, hydraulic oil from the outlet of the hydraulic pump 5 flows through the three-position four-way directional valve I4 into the large chamber of the boom cylinder 3, causing the boom cylinder 3 to extend. The hydraulic oil from the outlet of the hydraulic pump 5 flows through the three-position four-way directional valve II8 into the small chamber of the arm cylinder 9, causing the arm cylinder 9 to retract. When the two-position four-way directional valve 2 is controlled by the controller 7 to the working position, the hydraulic oil in the large chamber of the boom cylinder 3 flows through the two-position four-way directional valve 2 into the small chamber of the leveling cylinder 1, causing the leveling cylinder 1 to also retract. At this point, the leveling cylinder 1 and the arm cylinder 9 operate in unison, acting as a second arm cylinder and accelerating the retraction of the arm cylinder 9.

[0043] like Figure 5As shown, when the three-position four-way directional valve I4 is in the right working position and the three-position four-way directional valve II8 is in the left working position, the controller 7 controls the two-position four-way directional valve 2 to the working position. In this situation, hydraulic oil from the outlet of the hydraulic pump 5 flows through the three-position four-way directional valve I4 into the small chamber of the boom cylinder 3, causing the boom cylinder 3 to retract. The hydraulic oil from the outlet of the hydraulic pump 5 flows through the three-position four-way directional valve II8 into the large chamber of the arm cylinder 9, causing the arm cylinder 9 to extend. When the two-position four-way directional valve 2 is controlled by the controller 7 to the working position, the hydraulic oil in the small chamber of the boom cylinder 3 flows through the two-position four-way directional valve 2 into the large chamber of the leveling cylinder 1, causing the leveling cylinder 1 to also extend. At this point, the leveling cylinder 1 and the arm cylinder 9 operate in unison, acting as a second arm cylinder and accelerating the extension of the arm cylinder 9.

[0044] like Figure 6 As shown, when the three-position four-way directional valve I4 is in the right working position, and the three-position four-way directional valve II8 is also in the right working position, the controller 7 controls the two-position four-way directional valve 2 to its initial position. In this situation, hydraulic oil from the hydraulic pump 5 outlet passes through the three-position four-way directional valve I4 and enters the small chamber of the boom cylinder 3, causing the boom cylinder 3 to begin retracting. The hydraulic oil from the hydraulic pump 5 outlet passes through the three-position four-way directional valve II8 and enters the small chamber of the arm cylinder 9, causing the arm cylinder 9 to begin retracting. When the two-position four-way directional valve 2 is controlled by the controller 7 to its initial position, the hydraulic oil in the small chamber of the boom cylinder 3 passes through the two-position four-way directional valve 2 and enters the small chamber of the leveling cylinder 1, causing the leveling cylinder 1 to also begin retracting. At this point, the leveling cylinder 1 and the arm cylinder 9 operate in unison, acting as a second arm cylinder and accelerating the retraction of the arm cylinder 9.

[0045] The present invention realizes precise control of the leveling cylinder action through a two-position four-way reversing valve, fully exerts the auxiliary role of the leveling cylinder under different actions of the face shovel excavator, accelerates the extension and retraction speed of the bucket cylinder, and improves the working efficiency of the excavator.

[0046] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A hydraulic system for a leveling cylinder of a front shovel hydraulic excavator, characterized by: It includes a two-position four-way directional valve (2), a three-position four-way directional valve I (4), and a three-position four-way directional valve II (8); The first working oil port of the three-position four-way reversing valve I (4) is communicated with the large chamber of the boom oil cylinder (3), and the second working oil port of the three-position four-way reversing valve I (4) is communicated with the small chamber of the boom oil cylinder (3); the large chamber of the boom oil cylinder (3) and the small chamber of the boom oil cylinder (3) are respectively communicated with the two-position four-way reversing valve (2), and the two-position four-way reversing valve (2) is also respectively communicated with the large chamber of the leveling oil cylinder (1) and the small chamber of the leveling oil cylinder (1); When the leveling oil cylinder (1) does not receive a signal, it is in the initial position. When the leveling oil cylinder (1) is in the initial position, the large cavity of the boom oil cylinder (3) is connected to the large cavity of the leveling oil cylinder (1), and the small cavity of the boom oil cylinder (3) is connected to the small cavity of the leveling oil cylinder (1); when the leveling oil cylinder (1) receives a signal, it is in the working position. When the leveling oil cylinder (1) is in the working position, the large cavity of the boom oil cylinder (3) is connected to the small cavity of the leveling oil cylinder (1), and the small cavity of the boom oil cylinder (3) is connected to the large cavity of the leveling oil cylinder (1); The first working oil port of the three-position four-way reversing valve II (8) is connected to the large chamber of the boom cylinder (9), and the second working oil port of the three-position four-way reversing valve II (8) is connected to the small chamber of the boom cylinder (9); The oil inlet of the three-position four-way reversing valve II (8) and the oil inlet of the three-position four-way reversing valve I (4) are both connected to the oil outlet of the hydraulic pump (5); the oil return port of the three-position four-way reversing valve II (8) and the oil return port of the three-position four-way reversing valve I (4) are both connected to the hydraulic oil tank (6); The three-position four-way directional reversing valve I (4) is in the initial position when no signal is received. When the three-position four-way directional reversing valve I (4) is in the initial position, all the oil ports of the three-position four-way directional reversing valve I (4) are in a closed state. The left control end of the three-position four-way directional reversing valve I (4) is in the left working position when a signal is received. When the three-position four-way directional reversing valve I (4) is in the left working position, the oil inlet of the three-position four-way directional reversing valve I (4) is connected to the first working oil port of the three-position four-way directional reversing valve I (4). The second working oil port of the reversing valve I (4) is communicated with the return oil port of the three-position four-way reversing valve I (4); when the right control end of the three-position four-way reversing valve I (4) receives a signal, it is in the right working position. When the three-position four-way reversing valve I (4) is in the right working position, the oil inlet of the three-position four-way reversing valve I (4) is communicated with the second working oil port of the three-position four-way reversing valve I (4), and the first working oil port of the three-position four-way reversing valve I (4) is communicated with the return oil port of the three-position four-way reversing valve I (4); The three-position four-way directional valve II (8) is in the initial position when no signal is received. When the three-position four-way directional valve II (8) is in the initial position, all the oil ports of the three-position four-way directional valve II (8) are in a closed state. The left control end of the three-position four-way directional valve II (8) is in the left working position when a signal is received. When the three-position four-way directional valve II (8) is in the left working position, the oil inlet of the three-position four-way directional valve II (8) is connected to the first working oil port of the three-position four-way directional valve II (8). The second working oil port of the reversing valve II (8) is communicated with the return oil port of the three-position four-way reversing valve II (8); when the right control end of the three-position four-way reversing valve II (8) receives a signal, it is in the right working position. When the three-position four-way reversing valve II (8) is in the right working position, the oil inlet of the three-position four-way reversing valve II (8) is communicated with the second working oil port of the three-position four-way reversing valve II (8), and the first working oil port of the three-position four-way reversing valve II (8) is communicated with the return oil port of the three-position four-way reversing valve II (8).

2. The hydraulic system for a leveling cylinder of a front shovel hydraulic excavator according to claim 1, characterized in that: The control end of the two-position four-way directional valve (2), the left control end of the three-position four-way directional valve I (4), the right control end of the three-position four-way directional valve I (4), the left control end of the three-position four-way directional valve II (8), and the right control end of the three-position four-way directional valve II (8) are all connected to the controller (7) for signal transmission.

3. The hydraulic system for a leveling cylinder of a front shovel hydraulic excavator according to claim 1 or 2, characterized in that: The hydraulic pump (5) is a swash plate type plunger hydraulic pump.

4. The hydraulic system for a leveling cylinder of a front shovel hydraulic excavator according to claim 1 or 2, characterized in that: Two boom oil cylinders (3) are provided, and the two boom oil cylinders (3) are connected in parallel.

5. A method for controlling a leveling cylinder of a front shovel hydraulic excavator, characterized in that: A hydraulic system for a leveling cylinder of a front shovel hydraulic excavator according to any one of claims 2 to 4; When the three-position four-way directional valve I (4) is in the initial position and the three-position four-way directional valve II (8) is in the left working position, the two-position four-way directional valve (2) is controlled to be in the initial position; When the three-position four-way directional valve I (4) is in the left working position, and the three-position four-way directional valve II (8) is also in the left working position, the two-position four-way directional valve (2) is controlled to be in the initial position; When the three-position four-way directional valve I (4) is in the left working position and the three-position four-way directional valve II (8) is in the right working position, the two-position four-way directional valve (2) is controlled to be in the working position; When the three-position four-way directional valve I (4) is in the right working position and the three-position four-way directional valve II (8) is in the left working position, the two-position four-way directional valve (2) is controlled to be in the working position; When the three-position four-way directional valve I (4) is in the right working position and the three-position four-way directional valve II (8) is also in the right working position, the two-position four-way directional valve (2) is controlled to be in the initial position.

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