A pilot-operated relief valve

Abstract

This application relates to the field of hydraulic technology and discloses a pilot-operated relief valve, including a housing, a valve seat, a valve sleeve, and a spool. The housing has a housing cavity and an oil outlet, which communicate with the housing cavity. The housing cavity extends through the housing to form an oil inlet and a mounting port at both ends of the housing, with the oil outlet located at the end of the housing facing the oil inlet. The valve seat is sealed and installed at the mounting port. The valve sleeve is installed in the housing cavity, and a valve sleeve cavity is formed within the valve sleeve, extending through the valve sleeve along the axial direction of the housing. The spool is installed in the valve sleeve cavity, and a throttling channel is formed within the spool, with both ends of the throttling channel communicating with the valve sleeve cavity and the oil inlet, respectively. By installing a single spool within the valve sleeve, the number of spools in the pilot-operated relief valve is reduced, thereby lowering the precision requirements for the fit between the valve sleeve and the spool, and reducing the production cost of the pilot-operated relief valve. Simultaneously, the connection of a single spool to the valve sleeve reduces the risk of internal leakage in the pilot-operated relief valve and improves its operational stability.

Description

Technical Field

[0001] This application relates to the field of hydraulic technology, and more particularly to a pilot-operated relief valve. Background Technology

[0002] In the travel and steering hydraulic circuit of an excavator, a pilot-operated relief valve is usually required to provide overload protection and replenish hydraulic fluid.

[0003] Currently, pilot-operated relief valves on the market have a large number of spools, which leads to high precision requirements for the fitting of pilot-operated relief valves, making them more difficult to manufacture. Furthermore, during use, pilot-operated relief valves have a greater risk of internal leakage (leakage between the interlocking spools), affecting the stability of their operation. Utility Model Content

[0004] This application provides a pilot-operated relief valve to improve the stability of pilot-operated relief valve operation.

[0005] To achieve the above objectives, the main technical solutions adopted in this application include:

[0006] This application provides a pilot-operated relief valve, including a housing, a valve seat, a valve sleeve, and a spool valve core. The housing has a housing cavity and an oil outlet, the oil outlet communicating with the housing cavity. Along the axial direction of the housing, the housing cavity extends through the housing to form an oil inlet and a mounting port at both ends of the housing. The oil outlet is located at the end of the housing facing the oil inlet. The valve seat is sealed and installed at the mounting port, extending at least partially into the housing cavity. The valve sleeve is installed in the housing cavity, and a valve sleeve cavity is formed within the valve sleeve, extending through the valve sleeve along the axial direction of the housing. The spool valve core is installed on the valve... The valve sleeve cavity, along the axial direction of the outer shell, has a throttling channel formed inside the spool valve core. The two ends of the throttling channel are connected to the valve sleeve cavity and the oil inlet, respectively. Along the axial direction of the outer shell, the valve sleeve has a degree of freedom of movement relative to the valve seat, so that the valve sleeve has a pressure relief state for relieving pressure on the oil inlet and a closed state for closing the oil inlet. When the valve sleeve is in the pressure relief state, the valve sleeve connects the oil inlet and the oil outlet. When the valve sleeve is in the closed state, the valve sleeve disconnects the oil inlet and the oil outlet, and the oil in the oil inlet flows to the valve sleeve cavity through the throttling channel.

[0007] Furthermore, along the axial direction of the outer casing, the spool valve core has a degree of freedom of movement relative to the valve sleeve, so that the spool valve core has an oil-passing state that connects the oil inlet and the valve sleeve cavity and a shut-off state that disconnects the oil inlet and the valve sleeve cavity.

[0008] Furthermore, the spool valve core has a throttling slope, which is located at the end of the spool valve core facing the oil inlet, and a throttling cavity is formed between the throttling slope and the inner wall of the valve sleeve cavity.

[0009] Furthermore, the spool valve core is formed with a throttling orifice, and the two ends of the throttling orifice are respectively connected to the throttling slope and the end of the spool valve core facing the valve seat.

[0010] Furthermore, along the axial direction of the outer casing, the spool valve core includes a first limiting section, a second limiting section, and a connecting section. The first limiting section and the second limiting section are respectively connected to the two ends of the connecting section, thereby limiting the amount of movement of the spool valve core relative to the valve sleeve.

[0011] Furthermore, the pilot-operated relief valve also includes an inner spring, which is located inside the valve sleeve cavity, and the two ends of the inner spring abut against the valve seat and the spool respectively, so as to apply a first force toward the oil inlet to the spool.

[0012] Furthermore, the pilot-operated relief valve also includes an external spring, which is located inside the valve sleeve cavity, and its two ends abut against the valve seat and the valve sleeve respectively, so as to apply a second force toward the oil inlet to the valve sleeve.

[0013] Furthermore, a first sealing surface is formed inside the housing, and the first sealing surface is located between the oil inlet and the oil outlet; when the valve sleeve is in the closed state, the end face of the valve sleeve facing the oil inlet at least partially abuts against the first sealing surface.

[0014] Furthermore, a valve seat cavity is formed within the valve seat, the valve seat cavity including a pressure relief hole and a drain hole, the pressure relief hole communicating with the valve sleeve cavity, and the drain hole communicating with the oil outlet; the pilot-operated relief valve also includes a pressure relief assembly, the pressure relief assembly being installed within the valve seat cavity, and the pressure relief assembly abutting against the pressure relief hole.

[0015] Furthermore, the pressure relief assembly includes a cone valve core and a pressure relief spring. The two ends of the pressure relief spring are connected to the cone valve core and the valve seat, respectively. The pressure relief spring applies a third force toward the pressure relief hole to the cone valve core.

[0016] By installing a single spool valve inside the valve sleeve, the number of spool valves in the pilot-operated relief valve is reduced, thereby lowering the fitting accuracy requirements between the valve sleeve and the spool valve and reducing the production cost of the pilot-operated relief valve. At the same time, the connection between a single spool valve and the valve sleeve can reduce the risk of internal leakage in the pilot-operated relief valve and improve the operational stability of the pilot-operated relief valve. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the pilot-operated relief valve provided in this application.

[0019] Figure 2 yes Figure 1The figure shows a cross-sectional view of a pilot-operated relief valve.

[0020] Figure 3 yes Figure 1 The diagram shows the structural structure of the valve sleeve of the pilot-operated relief valve.

[0021] Figure 4 yes Figure 1 The diagram shows the structure of the spool of the pilot-operated relief valve.

[0022] Explanation of reference numerals in the attached drawings: outer casing 1, outer casing cavity 101, oil outlet 102, oil inlet 103, mounting port 104, first sealing surface 105, valve seat 2, valve seat cavity 201, pressure relief hole 2011, drain hole 2012, valve sleeve 3, valve sleeve cavity 301, support bar 302, second sealing surface 303, spool valve core 4, throttling channel 401, throttling slope 402, throttling cavity 403, throttling orifice 404, first limiting section 405, second limiting section 406, connecting section 407, inner spring 5, outer spring 6, pressure relief assembly 7, cone valve core 701, pressure relief spring 702. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] like Figure 1 and Figure 2 As shown, as one implementation, this application provides a pilot-operated relief valve, including a housing 1, a valve seat 2, a valve sleeve 3, and a spool 4. The valve seat 2 is installed at the end of the housing 1, the valve sleeve 3 is installed inside the housing 1 and slidably connected to the valve seat 2, and the spool 4 is installed inside the valve sleeve 3. By installing a single spool 4 inside the valve sleeve 3, the number of spool 4 in the pilot-operated relief valve is reduced, thereby reducing the fitting accuracy requirements of the valve sleeve 3 and the spool 4 and reducing the production cost of the pilot-operated relief valve. At the same time, the connection between a single spool 4 and the valve sleeve 3 can reduce the risk of internal leakage of the pilot-operated relief valve and improve the operational stability of the pilot-operated relief valve.

[0025] To facilitate a clear explanation of the technical solution of this application, the following definitions are provided: Figure 1 The left and right directions are shown. The axial direction of outer shell 1 is... Figure 1 The left and right directions in the middle.

[0026] Specifically, the outer casing 1 has an outer casing cavity 101 and an oil outlet 102. The oil outlet 102 is located on the side wall of the outer casing 1 and communicates with the outer casing cavity 101. Along the axial direction of the outer casing 1, the outer casing cavity 101 penetrates the outer casing 1 to form an oil inlet 103 and an installation port 104 at both ends of the outer casing 1. The oil outlet 102 is located at the end of the outer casing 1 facing the oil inlet 103.

[0027] The valve seat 2 is installed in the mounting port 104 and extends at least partially into the housing cavity 101, thereby sealing the mounting port 104.

[0028] The valve sleeve 3 is installed in the outer shell cavity 101, and a valve sleeve cavity 301 is formed inside the valve sleeve 3. The valve sleeve cavity 301 penetrates the valve sleeve 3 along the axial direction of the outer shell 1.

[0029] The spool valve core 4 is installed in the valve sleeve cavity 301. Along the axial direction of the outer shell 1, a throttling channel 401 is formed inside the spool valve core 4. The two ends of the throttling channel 401 are connected to the valve sleeve cavity 301 and the oil inlet 103, respectively. The oil at the oil inlet 103 can flow into the valve sleeve cavity 301 through the throttling channel 401 to facilitate pressure relief at the oil inlet 103.

[0030] The spool 4 is used to throttle and depressurize the oil in the inlet 103, so that there is basically no sealing requirement between the spool 4 and the valve sleeve 3. This makes the risk of internal leakage between the spool 4 and the valve sleeve 3 of the pilot-operated relief valve basically zero, improving the stability of the pilot-operated relief valve. At the same time, it can reduce the processing requirements of the spool 4 and the valve sleeve 3, and reduce the production cost of the pilot-operated relief valve.

[0031] The valve seat 2 extends at least partially into the valve sleeve cavity 301, and seals the opening of the valve sleeve cavity 301 toward the valve seat 2. Correspondingly, a pressure relief hole 2011 is formed on the valve seat 2, so that the oil at the oil inlet 103 flows sequentially through the throttling channel 401 and the valve sleeve cavity 301 before flowing into the valve seat 2.

[0032] Along the axial direction of the housing 1, the valve sleeve 3 has a degree of freedom of movement relative to the valve seat 2, such that the valve sleeve 3 has a depressurization state for depressurizing the oil inlet 103 and a closed state for closing the oil inlet 103.

[0033] When the valve sleeve 3 is in the depressurization state, the valve sleeve 3 connects the oil inlet 103 and the oil outlet 102, causing the oil pressure at the oil inlet 103 to drop rapidly.

[0034] When the valve sleeve 3 is in the closed state, the valve sleeve 3 disconnects the oil inlet 103 and the oil outlet 102, and the oil in the oil inlet 103 flows to the valve sleeve cavity 301 through the throttling channel 401.

[0035] The pressure relief function of the pilot-operated relief valve is realized by the movement of the valve sleeve 3 relative to the valve seat 2, thereby protecting the components in the oil circuit.

[0036] like Figure 2 As shown, in one implementation, a valve seat cavity 201 is formed in the valve seat 2. The valve seat cavity 201 includes a pressure relief hole 2011 and a drain hole 2012. The pressure relief hole 2011 extends into the valve sleeve cavity 301 and communicates with the valve sleeve cavity 301, so that the pressure relief oil in the valve sleeve cavity 301 can flow into the valve seat cavity 201 through the pressure relief hole 2011. The drain hole 2012 communicates with the oil outlet 102, so that the oil in the valve seat cavity 201 can be discharged to the outside of this pilot-operated relief valve through the oil outlet 103.

[0037] To maintain the oil pressure at the inlet 103, the pilot-operated relief valve also includes a pressure relief assembly 7. The pressure relief assembly 7 is installed in the valve seat cavity 201 and abuts against the pressure relief hole 2011. When the oil pressure in the valve sleeve cavity 301 is greater than the set pressure value of the pressure relief assembly 7, the pressure relief assembly 7 opens, allowing the oil to be discharged into the valve seat cavity 201 through the pressure relief hole 2011.

[0038] As one implementation, the pressure relief assembly 7 includes a cone valve core 701 and a pressure relief spring 702. The two ends of the pressure relief spring 702 abut against the cone valve core 701 and the valve seat 2, respectively, and apply a third force toward the pressure relief hole 2011 to the cone valve core 701 through the pressure relief spring 702.

[0039] When the oil pressure in the valve sleeve cavity 301 is greater than the third force, the pressure relief spring 702 is compressed, the cone valve core 701 separates from the pressure relief hole 2011, so that the oil can flow through the pressure relief hole 2011 into the valve seat cavity 201.

[0040] Specifically, the end of the cone valve core 701 facing the pressure relief hole 2011 is tapered, and at least part of the end of the cone valve core 701 facing the pressure relief hole 2011 extends into the pressure relief hole 2011, so that the cone valve core 701 and the pressure relief hole 2011 form a linear seal.

[0041] like Figure 2 and Figure 3 As shown, as one implementation, multiple support bars 302 are formed on the outer circumferential wall of the valve sleeve 3 along the circumference of the valve sleeve 3. The outer wall of the support bar 302 is connected to the inner wall of the outer shell 1 by a clearance fit or a transition fit. There is a certain gap between adjacent support bars 302, so that a flow channel is formed between the valve sleeve 3 and the outer shell 1, and the flow channel is connected to the oil outlet 102.

[0042] The liquid flowing out of the drain hole 2012 flows through the flow channel to the oil outlet 102, so that the oil at the oil inlet 103 can flow through the throttling channel 401, the valve sleeve cavity 301, the valve seat cavity 201, and the flow channel to the oil outlet 102 in sequence, thereby realizing the pressure relief of the oil inlet 103.

[0043] As one implementation, along the axial direction of the outer casing 1, the spool valve 4 has a degree of freedom of movement relative to the valve sleeve 3, so that the spool valve 4 has an oil-passing state that connects the oil inlet 103 and the valve sleeve cavity 301 and a cut-off state that disconnects the oil inlet 103 and the valve sleeve cavity 301.

[0044] When the spool valve core 4 is in the oil-passing state, the throttling channel 401 connects the oil inlet 103 and the valve sleeve cavity 301 respectively, so that the oil in the oil inlet 103 can flow into the valve sleeve cavity 301. At the same time, in this state, the cone valve core 701 is separated from the pressure relief hole 2011, so that the oil can flow into the valve seat cavity 201 through the pressure relief hole 2011.

[0045] When the spool 4 is in the closed state, the spool 4 moves toward the valve seat 2, which closes the opening of the throttling channel 401 toward the oil inlet 103, further increasing the pressure on the valve sleeve 3 toward the oil inlet 103, causing the valve sleeve 3 to move toward the valve seat 2, and connecting the oil inlet 103 with the oil outlet 102, thus realizing the overload protection function of the pilot-operated relief valve.

[0046] It should be noted that when the cone valve core 701 abuts against the pressure relief hole 2011 and seals the pressure relief hole 2011, although the throttling channel 401 is connected to the oil inlet 103 and the valve sleeve cavity 301 respectively, the oil at the oil inlet 103 cannot flow through the spool valve core 4. In this state, the spool valve core 4 is also in the closed state.

[0047] like Figure 2 and Figure 4 As shown, in one implementation, the spool valve core 4 is formed with a throttling slope 402. The throttling slope 402 is located on the circumferential sidewall of the spool valve core 4. A throttling cavity 403 is formed between the throttling slope 402 and the inner wall of the valve sleeve cavity 301. The throttling slope 402 is located at the end of the spool valve core 4 facing the oil inlet 103.

[0048] When the spool valve core 4 is in the oil-passing state, the throttling chamber 403 is connected to the oil inlet 103 so that the oil at the oil inlet 103 can flow into the throttling chamber 403.

[0049] As one implementation, the spool valve core 4 is formed with a throttling orifice 404, which is connected to the throttling cavity 403 to form a throttling channel 401. The two ends of the throttling orifice 404 are respectively connected to the throttling slope 402 and the end of the spool valve core 4 facing the valve seat 2, so as to transport the oil in the throttling cavity 403 to the valve sleeve cavity 301 near the valve seat 2 through the throttling orifice 404.

[0050] As one implementation, along the axial direction of the housing 1, the spool valve 4 includes a first limiting section 405, a second limiting section 406, and a connecting section 407. The first limiting section 405 and the second limiting section 406 are respectively connected to the two ends of the connecting section 407, and the movement of the spool valve 4 relative to the valve sleeve 3 is limited by the first limiting section 405 and the second limiting section 406.

[0051] Specifically, the diameters of the first limiting segment 405 and the second limiting segment 406 are larger than the diameter of the connecting segment 407, so as to limit the movement of the spool valve core 4 by means of the first limiting segment 405 and the second limiting segment 406.

[0052] Furthermore, the throttling slope 402 is located at the end of the connecting section 407 near the first limiting section 405, and the throttling hole 404 completely penetrates the second limiting section 406 and at least partially penetrates the connecting section 407.

[0053] As one implementation, the pilot-operated relief valve also includes an inner spring 5, which is located inside the valve sleeve cavity 301, and the two ends of the inner spring 5 abut against the valve seat 2 and the spool 4 respectively, so as to apply a first force toward the oil inlet 103 to the spool 4.

[0054] With the inner spring 5 in place, under normal conditions, the two ends of the throttling channel 401 are connected to the valve sleeve cavity 301 and the oil inlet 103 respectively, so as to relieve pressure on the oil inlet 103 through the throttling channel 401.

[0055] When the oil pressure at the inlet 103 is too high, the throttling effect of the throttling channel 401 causes the spool valve 4 to move toward the valve seat 2, and the inner spring 5 is compressed until the first limit section 405 of the spool valve 4 abuts against the valve sleeve 3, causing the throttling channel 401 to close. As the oil pressure at the inlet 103 continues to increase, the valve sleeve 3 moves toward the valve seat 2, so that the inlet 103 is connected to the outlet 102, thereby realizing the overload protection function of the pilot-operated relief valve.

[0056] As one implementation, the pilot-operated relief valve also includes an outer spring 6, which is located inside the valve sleeve cavity 301, and the two ends of the outer spring 6 abut against the valve seat 2 and the valve sleeve 3 respectively, so as to apply a second force toward the oil inlet 103 to the valve sleeve 3.

[0057] With the external spring 6 in place, the valve sleeve 3 abuts against the outer shell 1 under normal conditions, so that the oil inlet 103 and the oil outlet 102 are closed. When the valve sleeve 3 moves toward the valve seat 2, the oil inlet 103 and the oil outlet 102 are connected, thus realizing the overload protection function of the pilot-operated relief valve.

[0058] As one implementation, a first sealing surface 105 is formed inside the housing 1, and the first sealing surface 105 is located between the oil inlet 103 and the oil outlet 102; when the valve sleeve 3 is in the closed state, the end face of the valve sleeve 3 facing the oil inlet 103 at least partially abuts against the first sealing surface 105.

[0059] The end of the valve sleeve 3 facing the oil inlet 103 has a second sealing surface 303. When the valve sleeve 3 is in the closed state, the second sealing surface 303 at least partially abuts against the first sealing surface 105.

[0060] Furthermore, the first sealing surface 105 is inclined relative to the axial direction of the outer casing 1, and similarly, the second sealing surface 303 is inclined relative to the axial direction of the outer casing 1.

[0061] The inclination angle of the first sealing surface 105 relative to the axis of the outer casing 1 is greater than or less than the inclination angle of the second sealing surface 303 relative to the axis of the outer casing 1, so as to achieve linear sealing between the first sealing surface 105 and the second sealing surface 303.

[0062] The overload protection principle of this pilot relief valve is as follows:

[0063] When the oil pressure at the inlet 103 is too high, the spool 4 moves toward the valve seat 2 until the first limit section 405 of the spool 4 abuts against the valve sleeve 3, and the throttling channel 401 is closed. As the oil pressure at the inlet 103 continues to increase, the valve sleeve 3 moves toward the valve seat 2, so that the inlet 103 is connected to the outlet 102, thereby relieving the pressure at the inlet 103.

[0064] The oil replenishment principle of this pilot relief valve is as follows:

[0065] The oil inlet 103 is under negative pressure, and the oil flows into the flow channel between the valve sleeve 3 and the outer shell 1 at the oil outlet 102. The oil provides a force to the valve sleeve 3 toward the valve seat 2, causing the valve sleeve 3 to move toward the valve seat 2. The oil inlet 103 and the oil outlet 102 are connected to achieve oil replenishment.

[0066] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

[0067] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A pilot operated spill valve characterized by, include: The outer casing (1) has an outer casing cavity (101) and an oil outlet (102) formed inside it. The oil outlet (102) communicates with the outer casing cavity (101). Along the axial direction of the outer casing (1), the outer casing cavity (101) penetrates the outer casing (1) to form an oil inlet (103) and an installation port (104) at both ends of the outer casing (1). The oil outlet (102) is located at the end of the outer casing (1) facing the oil inlet (103). Valve seat (2), which is sealed and installed in the mounting port (104), and the valve seat (2) extends at least partially into the housing cavity (101); A valve sleeve (3) is installed in the outer shell cavity (101). A valve sleeve cavity (301) is formed inside the valve sleeve (3). Along the axial direction of the outer shell (1), the valve sleeve cavity (301) penetrates the valve sleeve (3). A spool valve (4) is installed in the valve sleeve cavity (301) along the axial direction of the outer shell (1). A throttling channel (401) is formed inside the spool valve (4). The two ends of the throttling channel (401) are respectively connected to the valve sleeve cavity (301) and the oil inlet (103). Wherein, along the axial direction of the outer shell (1), the valve sleeve (3) has a degree of freedom of movement relative to the valve seat (2), such that the valve sleeve (3) has a depressurization state for depressurizing the oil inlet (103) and a closed state for closing the oil inlet (103); When the valve sleeve (3) is in a depressurized state, the valve sleeve (3) connects the oil inlet (103) and the oil outlet (102); When the valve sleeve (3) is in the closed state, the valve sleeve (3) disconnects the oil inlet (103) and the oil outlet (102), and the oil in the oil inlet (103) flows to the valve sleeve cavity (301) through the throttling channel (401).

2. The pilot-operated relief valve according to claim 1, characterized in that, Along the axial direction of the outer casing (1), the spool valve (4) has a degree of freedom of movement relative to the valve sleeve (3), such that the spool valve (4) has an oil-passing state connecting the oil inlet (103) and the valve sleeve cavity (301) and a shut-off state disconnecting the oil inlet (103) and the valve sleeve cavity (301).

3. A pilot-operated relief valve according to claim 1, characterized in that, The spool valve core (4) has a throttling slope (402) located at the end of the spool valve core (4) facing the oil inlet (103), and a throttling cavity (403) is formed between the throttling slope (402) and the inner wall of the valve sleeve cavity (301).

4. A pilot-operated relief valve according to claim 3, characterized in that, The slide valve core (4) has a throttling orifice (404), and the two ends of the throttling orifice (404) are respectively connected to the throttling slope (402) and the end of the slide valve core (4) facing the valve seat (2).

5. A pilot-operated relief valve according to claim 1, characterized in that, Along the axial direction of the outer casing (1), the spool valve (4) includes a first limiting section (405), a second limiting section (406), and a connecting section (407). The first limiting section (405) and the second limiting section (406) are respectively connected to the two ends of the connecting section (407). The first limiting section (405) and the second limiting section (406) limit the amount of movement of the spool valve (4) relative to the valve sleeve (3).

6. A pilot-operated relief valve according to claim 1 or 2, characterized in that, The pilot-operated relief valve also includes an inner spring (5), which is located in the valve sleeve cavity (301), and the two ends of the inner spring (5) abut against the valve seat (2) and the spool valve core (4) respectively, so as to apply a first force toward the oil inlet (103) to the spool valve core (4).

7. A pilot-operated relief valve according to claim 1, characterized in that, The pilot-operated relief valve also includes an outer spring (6), which is located inside the valve sleeve cavity (301). The two ends of the outer spring (6) abut against the valve seat (2) and the valve sleeve (3) respectively, so as to apply a second force toward the oil inlet (103) to the valve sleeve (3).

8. A pilot-operated relief valve according to claim 1, characterized in that, A first sealing surface (105) is formed inside the outer casing (1), and the first sealing surface (105) is located between the oil inlet (103) and the oil outlet (102); When the valve sleeve (3) is in the closed state, the end face of the valve sleeve (3) facing the oil inlet (103) at least partially abuts against the first sealing surface (105).

9. A pilot-operated relief valve according to claim 1, characterized in that, A valve seat cavity (201) is formed inside the valve seat (2). The valve seat cavity (201) includes a pressure relief hole (2011) and a drain hole (2012). The pressure relief hole (2011) is connected to the valve sleeve cavity (301), and the drain hole (2012) is connected to the oil outlet. The pilot-operated relief valve also includes a pressure relief assembly (7), which is installed in the valve seat cavity (201) and abuts against the pressure relief hole (2011).

10. A pilot-operated relief valve according to claim 9, characterized in that, The pressure relief assembly (7) includes a cone valve core (701) and a pressure relief spring (702). The two ends of the pressure relief spring (702) are connected to the cone valve core (701) and the valve seat (2) respectively. The pressure relief spring (702) applies a third force toward the pressure relief hole (2011) to the cone valve core (701).

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