Unloading valve and hydraulic system

Abstract

The present application relates to the technical fields of hydraulic valve, and provides an unloading valve and a hydraulic system, the unloading valve comprising: a valve sleeve, the valve sleeve being provided with an oil inlet channel, an oil outlet channel and a control channel, the valve sleeve being internally provided with a valve cavity, the valve cavity comprising a first cavity and a second cavity, the inner diameter of the second cavity being greater than the inner diameter of the first cavity; the control channel being communicated to the second cavity, the oil inlet channel and the oil outlet channel being communicated to the first cavity, the inner diameter of the oil inlet channel being smaller than the inner diameter of the first cavity; a valve core comprising a first core and a second core, the diameter of the second core being greater than the diameter of the first core, the first core being inserted into the first cavity, and the second core being inserted into the second cavity. The diameter of the second core of the valve core in the unloading valve is greater than the diameter of the first core, so that even if the system pressure suddenly rises, the force received by the first core is difficult to exceed the force received by the second core, greatly reducing the risk of abnormal conduction of the oil inlet channel and the oil outlet channel, and improving the stability of the unloading valve state.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic valves, more particularly to an unloading valve and a hydraulic system. BACKGROUND

[0002] A hydraulic system is a system that uses liquid (usually oil) as a working medium to transfer and control energy through the pressure energy of the liquid, and is widely used in various industrial and engineering fields. An oil motor is a device that uses hydraulic energy to produce mechanical movement, and the main function of the oil motor is to convert the pressure energy of the hydraulic system into linear motion or rotary motion to drive mechanical equipment.

[0003] An unloading valve is also an important control element in a hydraulic system, mainly used to guide part or all of the hydraulic oil from the high-pressure side back to the oil tank when the system pressure reaches a certain value, to reduce the system pressure and prevent overload and protect other components in the system. Specifically, after the unloading valve operates, the valve core moves, allowing the pressure oil to enter the lower end of the oil cylinder, and the oil motor can be quickly closed; when the system pressure drops to the preset recovery pressure, the valve core is reset under the action of a spring or an electromagnetic valve, the unloading channel is closed, and the system returns to normal operation.

[0004] However, when using a traditional unloading valve, once the system pressure of the oil motor fluctuates, it is easy to cause the valve core of the unloading valve to be insufficient in pressure and thus cause the unloading valve to open, causing the oil motor to close and thus causing abnormal operation of the unit, that is, due to fluctuations in the system pressure, the state of the unloading valve is extremely unstable, the unloading valve may be opened, which will interfere with the stable state of the oil motor and cause serious safety hazards to the operation of the unit.

[0005] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0006] The purpose of the present application is to provide an unloading valve and a hydraulic system to solve the technical problem that the valve core of the unloading valve in the prior art is easy to open under the influence of the system pressure.

[0007] To achieve the above-mentioned purpose, the first aspect of the present application provides an unloading valve, which comprises:

[0008] A valve sleeve is provided with an oil inlet channel, an oil outlet channel and a control channel, and a valve cavity is provided inside the valve sleeve, the valve cavity comprises a first cavity and a second cavity arranged coaxially, the inner diameter of the second cavity is greater than the inner diameter of the first cavity; the control channel is connected to the second cavity, the oil inlet channel and the oil outlet channel are connected to the first cavity, and the inner diameter of the oil inlet channel is smaller than the inner diameter of the first cavity;

[0009] The valve core comprises a first core body and a second core body arranged coaxially, the diameter of the second core body is larger than that of the first core body, the first core body is inserted into the first cavity, and the second core body is inserted into the second cavity;

[0010] The valve core is adapted to slide between a first position and a second position, control oil flows in the control channel, the control oil is used to push the valve core to slide to the first position and close the oil inlet channel and the oil outlet channel through the first core body, and pressure oil is arranged in the oil inlet channel, the pressure oil is used to push the valve core to slide to the second position and open the oil inlet channel and the oil outlet channel.

[0011] Further, a first step surface is formed at the joint of the first cavity and the second cavity, and a second step surface is formed at the joint of the first core body and the second core body, when the valve core is located at the first position, the second step surface abuts against the first step surface.

[0012] Further, the diameter of the first core body is equal to the inner diameter of the first cavity, and the diameter of the second core body is equal to the inner diameter of the second cavity.

[0013] In some embodiments, the first cavity and the oil inlet channel are formed with a third step surface, when the valve core is located at the first position, the end surface of the first core body abuts against the third step surface.

[0014] Further, the end surface of the first core body is provided with an outer chamfer along the circumference, and the third step surface is provided with an inner chamfer along the circumference, when the valve core is located at the first position, the outer chamfer abuts against the inner chamfer.

[0015] In some embodiments, the valve sleeve is further provided with an internal leakage channel communicated to the valve cavity, and the internal leakage channel is communicated to the second cavity.

[0016] Further, a valve cover is further included, the valve cover is connected to the valve sleeve and used to close the second cavity.

[0017] In some embodiments, a spring is further included, the spring is sleeved on the valve core, and two ends of the spring are fixedly connected with the valve cover and the valve core respectively, and the spring is used to reset the valve core.

[0018] In the second aspect, the application provides a hydraulic system, and the hydraulic system comprises the unloading valve in the above-mentioned embodiments.

[0019] In some embodiments, the hydraulic system further comprises an oil motor, an electromagnetic valve for controlling the oil pressure of the control oil in the control channel, and a servo valve for controlling the oil pressure of the pressure oil in the oil inlet channel, the oil outlet channel is connected to the oil cylinder of the oil motor, and the internal leakage channel is connected with an oil return pipeline.

[0020] The unloading valve and the hydraulic system provided by the application have at least the following beneficial effects:

[0021] When the system pressure suddenly rises, the valve core of the application is divided into a first core body and a second core body with different radii, the stability of the valve core when the valve of the electromagnetic valve is opened is improved by increasing the end surface area on one side of the control oil channel, and since the diameter of the second core body of the valve core in the unloading valve is greater than the diameter of the first core body, even if the system pressure suddenly rises, the force on the first core body is difficult to exceed the force on the second core body, greatly reducing the risk of abnormal conduction of the oil inlet channel and the oil outlet channel, and further improving the stability of the unloading valve state. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative effort.

[0023] Figure 1 A structural schematic view of the unloading valve in a closed state according to an embodiment of the application is shown in the figure.

[0024] Figure 2 A structural schematic view of the unloading valve in an open state according to an embodiment of the application is shown in the figure.

[0025] Figure 3 A structural schematic view of the valve sleeve according to an embodiment of the application is shown in the figure.

[0026] Figure 4 A structural schematic view of the valve core according to an embodiment of the application is shown in the figure.

[0027] Figure 5 A structural schematic view of the hydraulic system according to an embodiment of the application is shown in the figure.

[0028] In the figure, various reference signs represent:

[0029] 1, valve sleeve; 11, oil inlet channel; 12, oil outlet channel; 13, control channel; 14, valve cavity; 15, first cavity; 16, second cavity;

[0030] 2, valve core; 21, first core body; 22, second core body;

[0031] 3, first step surface;

[0032] 4, second step surface;

[0033] 5, third step surface;

[0034] 6, outer chamfer;

[0035] 7, inner chamfer;

[0036] 8, inner leakage passage;

[0037] 9, valve cover; 91, spring;

[0038] 100, oil motor; 101, electromagnetic valve; 102, servo valve. DETAILED DESCRIPTION

[0039] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0040] It should be noted that when a component is referred to as "fixed to" or "disposed on" another component, it can be directly or indirectly on the other component. When a component is referred to as "connected to" another component, it can be directly or indirectly connected to the other component. The terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or position based on the orientation or position shown in the drawings, and are only for the convenience of description, and cannot be understood as a limitation on the technical solutions. The terms "first", "second" are only for the convenience of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0041] The first aspect of the embodiment of the present application provides a unloading valve. The unloading valve of the embodiment of the present application will be described below in combination with the drawings.

[0042] Please refer to Figure 1 and Figure 2 , Figure 1 and Figure 2 show the structural schematic diagram of the unloading valve of the present application, which comprises a valve sleeve 1 and a valve core 2 installed in cooperation with each other.

[0043] Specifically, continue to refer to Figures 1-4The valve sleeve 1 is provided with an oil inlet channel 11, an oil outlet channel 12 and a control channel 13, and the valve sleeve 1 is internally provided with a valve cavity 14, which comprises a first cavity 15 and a second cavity 16 coaxially arranged, the inner diameter of the second cavity 16 is greater than that of the first cavity 15; the control channel 13 is communicated to the second cavity 16, and the oil inlet channel 11 and the oil outlet channel 12 are communicated to the first cavity 15, and the inner diameter of the oil inlet channel 11 is smaller than that of the first cavity 15.

[0044] The valve core 2 comprises a first core body 21 and a second core body 22 coaxially arranged, the diameter of the second core body 22 is greater than that of the first core body 21, the first core body 21 is inserted into the first cavity 15, and the second core body 22 is inserted into the second core body 22. Understandably, the first core body 21 and the second core body 22 are cylindrical cores with different diameters, and the first core body 21 and the second core body 22 are integrally formed into the valve core 2.

[0045] Among them, the valve core 2 is adapted to slide between the first position and the second position, the control channel 13 flows with control oil, the control oil is used to push the valve core 2 to slide to the first position and close the oil inlet channel 11 and the oil outlet channel 12 through the first core body 21; the oil inlet channel 11 is provided with pressure oil, the pressure oil is used to push the valve core 2 to slide to the second position and open the oil inlet channel 11 and the oil outlet channel 12.

[0046] Further, the unloading valve closes or opens the oil inlet channel 11 and the oil outlet channel 12 through the movement of the valve core 2 in the valve sleeve 1, and the valve core 2 is used to control the flow of hydraulic oil, when the system pressure exceeds the preset value, the valve core 2 will move to open the channel, and the hydraulic oil flows back to the oil tank.

[0047] The valve sleeve 1 is the main part of the unloading valve, used to be sleeved outside the valve core 2, which provides guidance and support for the valve core 2 to move on the correct track. The valve sleeve 1 is a metal shell with multiple holes and channels for connecting the oil inlet, oil outlet and control port, i.e. the oil inlet channel 11, the oil outlet channel 12 and the control channel 13 in the embodiment, wherein the control channel 13 is used to connect the electromagnetic valve 101, and the electromagnetic valve 101 controls the on-off according to the set pressure.

[0048] The working principle of the unloading valve is as follows:

[0049] When the system pressure is lower than the set pressure of the control channel 13, the valve of the electromagnetic valve 101 is closed, the control oil does not enter the control oil channel, at this time the oil pressure on the first end face of the valve core 2 is less than the oil pressure on the second end face of the valve core 2, the pressure oil pushes the valve core 2 to slide to the second position, the oil inlet channel 11 and the oil outlet channel 12 are connected, the pressure oil enters the system through the oil inlet channel 11; when the system pressure reaches or exceeds the set pressure of the control channel 13, the valve of the electromagnetic valve 101 is opened, the control oil enters the control oil channel and generates a control pressure on the valve core 2, the control pressure acting on the rear of the valve core 2 pushes the valve core 2 to move to the first position, closes the oil inlet channel 11 and the oil outlet channel 12, and the pressure oil no longer enters the system, and the system pressure decreases.

[0050] It can be understood that the movement of the valve core 2 depends on the pressure difference on both ends of the valve core 2, the end face of the valve core 2 close to the oil inlet channel 11 is defined as the first end face, the end face of the valve core 2 close to the control channel 13 is defined as the second end face, the area of the first end face is S1, the area of the second end face is S, the cross-sectional area of the oil inlet channel 11 is S2, since the diameter of the second core body 22 is greater than the diameter of the first core body 21, the inner diameter of the oil inlet channel 11 is smaller than the inner diameter of the first cavity 15, so S>S1>S2, and when the first core body 21 closes the oil inlet channel 11, the first core body 21 will form a circular stepped face at the joint of the oil inlet channel 11, and the area of the stepped face is (S1-S2).

[0051] When the valve of the electromagnetic valve 101 is closed, the second end face is no longer subjected to the control oil, at this time the first end face of the valve core 2 is subjected to a force F2=P*S1, and the second end face of the valve core 2 is subjected to a force F2=0. The valve core 2 will move to the second position under the action of the pressure oil, and the oil inlet channel 11 and the oil outlet channel 12 are connected.

[0052] When the valve of the electromagnetic valve 101 is opened, the control oil acts on the second end face, the oil pressure of the pressure oil on the side of the first end face is P, and the oil pressure of the control oil on the side of the second end face is P1. It should be noted that the oil pressure of the control oil is not less than that of the pressure oil, that is, in normal use, P≤P1. The pressure oil acts on the first end face in the area of the oil inlet channel 11, that is, the pressure oil acts on the area S2. Of course, the oil outlet channel 12 also has an oil pressure P2 acting on the first end face, P2 mainly acts on the stepped face (S1-S2), and the area of S2 is much larger than (S1-S2). It should be noted that according to the statistics of use, the size of P2 is basically the same as that of P, and P2 will not exceed 1.5 times of P. At this time, the first end face of the valve core 2 is subjected to a force F1=P*S2+P2*(S1-S2), and the second end face of the valve core 2 is subjected to a force F2=P1*S. By judging the size of F1 and F2, the moving direction of the valve core 2 can be determined. Specifically, when F1 is greater than F2, the valve core 2 moves to the second position, and when F1 is less than F2, the valve core 2 moves to the first position.

[0053] When judging the size of F1 and F2, two cases need to be considered, one case is that the system pressure is stable, and the other case is that the system pressure is unstable, that is, the system pressure will suddenly rise.

[0054] When the system pressure is stable, the size of P2 is basically the same as the size of P, the force F1 on the first end face of the valve core 2 is P*S2+P2*(S1-S2), which is approximately equal to P*S1, and the force F2 on the second end face of the valve core 2 is P1*S. It can be found that P≤P1, and even when P=P1, since the area S of the second end face is larger than the area S1 of the first end face, the force F2 on the second end face is always greater than the force F1 on the first end face, so the valve core 2 can be kept in the first position and block the oil inlet channel 11 and the oil outlet channel 12.

[0055] When the system pressure is unstable, that is, P2 suddenly rises, that is, P2=1.5P, the force F1 on the first end face of the valve core 2 is P*S2+1.5P*(S1-S2)=1.5P*S1-0.5P*S2, at this time the force on the first end face of the valve core 2 is greater than P*S1, so when P=P1, if the area S of the second end face is equal to the area S1 of the first end face, the force F2 on the second end face may be less than the force F1 on the first end face, at this time the valve core 2 will be pushed to the second position, causing the oil inlet channel 11 and the oil outlet channel 12 to be abnormally conducted, so the unloading valve state at this time is extremely unstable and has the possibility of opening, which will interfere with the stable state of the system.

[0056] But the area S of the second end face in the embodiment is larger than the area S1 of the first end face, so even if the system pressure suddenly rises, the force F1 on the first end face (the first core body 21) is difficult to exceed the force F2 on the second end face (the second core body 22), greatly reducing the risk of abnormal conduction of the oil inlet channel 11 and the oil outlet channel 12, improving the stability of the unloading valve state, and further being able to better maintain the system stable.

[0057] It should be noted that the valve core 2 of the conventional unloading valve is provided in a cylindrical shape, that is, the area S of the second end face is equal to the area S1 of the first end face, so when the system pressure suddenly rises, the valve core 2 is likely to be pushed to the second position by high pressure, that is, the risk of abnormal conduction of the unloading valve will be greatly increased. The embodiment is to reduce the risk of abnormal conduction of the unloading valve, so the valve core 2 is divided into the first core body 21 and the second core body 22 with different radii, and the area of the end face on the control oil channel side is increased to improve the stability of the valve core 2 when the valve of the electromagnetic valve 101 is opened.

[0058] In some embodiments, refer to Figures 1-4, the abutting portion of the first cavity 15 and the second cavity 16 is formed with a first step surface 3, and the abutting portion of the first core 21 and the second core 22 is formed with a second step surface 4, when the valve core 2 is in the first position, the second step surface 4 abuts against the first step surface 3.

[0059] When the valve core 2 is in the first position, the first to ensure that the first end surface abuts in the first cavity 15, at this time the valve core 2 is subjected to stress concentration in the first end surface, resulting in the first end surface is subjected to stress will be very large, prone to cause the valve core 2 damage. In order to share the stress of the first end surface, when the valve core 2 is in the first position, the second step surface 4 abuts against the first step surface 3, so that the stress of the valve core 2 will be divided to the first step surface 3 and the second step surface 4, so that the stress of the valve core 2 is more dispersed, reduce the risk of damage of the valve core 2.

[0060] Further, the diameter of the first core 21 is equal to the inner diameter of the first cavity 15, and the diameter of the second core 22 is equal to the inner diameter of the second cavity 16.

[0061] In other words, the valve core 2 and the valve cavity 14 are closely fitted, so as to ensure that the fluid does not leak from the gap between the two. If there is a large gap between the valve core 2 and the valve cavity 14 of the valve sleeve 1, the fluid will generate vortex and impact when passing at high speed, resulting in rapid wear of the valve core 2 and the valve cavity 14. Close fitting can reduce such wear, prolong the service life of the unloading valve, and improve the safety of the system.

[0062] In some embodiments, in order to further improve the close fitting of the valve core 2 and the valve cavity 14, the first cavity 15 and the oil inlet channel 11 are formed with a third step surface 5, and when the valve core 2 is in the first position, the end surface of the first core 21 abuts against the third step surface 5.

[0063] In some embodiments, referring to Figures 1-4 , the end surface of the first core 21 is provided with an outer chamfer 6 along the circumference, and the third step surface 5 is provided with an inner chamfer 7 along the circumference, and when the valve core 2 is in the first position, the outer chamfer 6 abuts on the inner chamfer 7.

[0064] The inner chamfer 7 refers to the chamfering treatment on the third step surface 5, which can reduce the risk of stress concentration caused by sharp inner corners, and can ensure that the outer chamfer 6 of the first core 21 can be smoothly matched and abutted on the third step surface 5, while reducing the wear in the assembly process.

[0065] The outer chamfer 6 refers to the chamfering treatment on the outer edge of the first core 21, which can make the cooperation between the first core 21 and the third step surface 5 more smooth, reduce the assembly difficulty, and the design of the outer chamfer 6 can disperse the stress between the first core 21 and the third step surface 5, prolong the service life of the unloading valve and the valve core 2.

[0066] Further, the outer chamfer 6 can be achieved by turning, milling or grinding, etc., and the inner chamfer 7 can be achieved by using a special-shaped drill, reamer or lathe to complete the machining of the inner chamfer 7.

[0067] In some embodiments, referring to Figures 1-3 , the valve sleeve 1 is further provided with an internal leakage passage 8 communicating with the valve cavity 14, and the internal leakage passage 8 communicates with the second cavity 16.

[0068] Further, the internal leakage passage 8 is connected to an oil tank or a bypass passage for discharging excess fluid (pressure oil and control oil) between the valve core 2 and the inner wall of the valve cavity 14.

[0069] When the system pressure exceeds the set value, the internal leakage passage 8 will open to discharge the excess fluid back to the oil tank or bypass, thereby reducing the system pressure and protecting the equipment from overpressure damage. In some cases, sudden pressure changes can cause hydraulic shock, and the internal leakage passage 8 can quickly respond and release the pressure to reduce the impact of hydraulic shock on the system.

[0070] Further, referring to Figures 1-2 , the unloading valve further comprises a valve cover 9 connected to the valve sleeve 1 and used to close the second cavity 16. The valve cover 9 is used to close the top of the valve sleeve 1, fix the valve core 2 and ensure the sealing of the entire valve cavity 14.

[0071] Further, the valve cover 9 is a metal cover with threads or flanges, which is fixed on the valve sleeve 1 by bolts or threads. The valve cover 9 uses the same material as the valve sleeve 1 to ensure matching and sealing.

[0072] Further, referring to Figures 1-2 , the unloading valve further comprises a spring 91 sleeved on the valve core 2, and the two ends of the spring 91 are fixedly connected with the valve cover 9 and the valve core 2 respectively, and the spring 91 is used to reset the valve core 2.

[0073] The spring 91 is used to set the opening and closing pressure of the unloading valve. When the pressure of the pressure oil exceeds the pre-set pressure of the spring, the spring will be compressed, causing the valve core 2 to move and open the passage. When the pressure of the pressure oil drops to the recovery pressure, the spring pushes the valve core 2 back to the original position to close the passage. The spring is a helical metal spring installed between the valve core 2 and the valve cover 9. The spring uses high-strength spring steel to ensure elasticity and durability.

[0074] In a second aspect of the embodiments of the present application, a hydraulic system is provided, referring to Figure 5 , comprising the unloading valve in the above embodiments.

[0075] Further, referring to Figure 5The hydraulic system further comprises an oil motor 100, a solenoid valve 101 and a servo valve 102, the solenoid valve 101 is used for controlling the oil pressure of the control oil in the control channel 13, and the servo valve 102 is used for controlling the oil pressure of the pressure oil in the oil inlet channel 11; the oil outlet channel 12 is connected to a cylinder of the oil motor 100, and the inner leakage channel 8 is connected with an oil return pipeline.

[0076] When the pressure of the hydraulic system is unstable, the force F1 received by the first core body 21 is difficult to exceed the force F2 received by the second core body 22 due to the area S of the second end face being larger than the area S1 of the first end face, the risk of abnormal conduction of the oil inlet channel 11 and the oil outlet channel 12 is greatly reduced, the stability of the unloading valve state is improved, and the stability of the hydraulic system can be better maintained.

[0077] The above merely describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An unloading valve, characterized in that, include: A valve sleeve is provided with an oil inlet channel, an oil outlet channel, and a control channel. The valve sleeve has an internal valve cavity comprising a first cavity and a second cavity coaxially arranged, the inner diameter of the second cavity being larger than the inner diameter of the first cavity. The control channel connects to the second cavity, and the oil inlet channel and the oil outlet channel connect to the first cavity, the inner diameter of the oil inlet channel being smaller than the inner diameter of the first cavity. The valve sleeve also has an internal leakage channel connecting to the valve cavity, and the internal leakage channel connects to the second cavity. The valve core includes a first core and a second core arranged coaxially, the diameter of the second core is larger than the diameter of the first core, the first core is inserted into the first cavity, and the second core is inserted into the second cavity; The valve core is adapted to slide between a first position and a second position. Control oil flows in the control channel. The control oil is used to push the valve core to slide towards the first position and close the oil inlet channel and the oil outlet channel through the first core body. Pressure oil is provided in the oil inlet channel. The pressure oil is used to push the valve core to slide towards the second position and open the oil inlet channel and the oil outlet channel. The end face of the valve core near the oil inlet channel is the first end face, and the end face of the valve core near the control channel is the second end face. The area of ​​the first end face is S1, the area of ​​the second end face is S, and the cross-sectional area of ​​the oil inlet channel is S2, where S > S1 > S2.

2. The unloading valve according to claim 1, characterized in that, A first stepped surface is formed at the junction of the first cavity and the second cavity, and a second stepped surface is formed at the junction of the first core and the second core. When the valve core is in the first position, the second stepped surface abuts against the first stepped surface.

3. The unloading valve according to claim 1, characterized in that, The diameter of the first core is equal to the inner diameter of the first cavity, and the diameter of the second core is equal to the inner diameter of the second cavity.

4. The unloading valve according to claim 1, characterized in that, The first cavity and the oil inlet channel are formed with a third stepped surface. When the valve core is in the first position, the end face of the first core abuts against the third stepped surface.

5. The unloading valve according to claim 4, characterized in that, The end face of the first core has an outer chamfer along the circumference, and the third step surface has an inner chamfer along the circumference. When the valve core is in the first position, the outer chamfer abuts against the inner chamfer.

6. The unloading valve according to claim 1, characterized in that, It also includes a valve cover, which is attached to the valve sleeve and used to close the second cavity.

7. The unloading valve according to claim 6, characterized in that, It also includes a spring sleeved on the valve core, with both ends of the spring fixedly connected to the valve cover and the valve core, respectively, for resetting the valve core.

8. A hydraulic system, characterized in that, Includes the unloading valve as described in any one of claims 1-7.

9. The hydraulic system according to claim 8, characterized in that, The hydraulic system also includes a hydraulic actuator, a solenoid valve, and a servo valve. The solenoid valve is used to control the oil pressure of the control oil in the control channel, the servo valve is used to control the oil pressure of the pressure oil in the inlet channel, the outlet channel is connected to the cylinder of the hydraulic actuator, and the internal leakage channel is connected to a return oil pipeline.

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