Automatic unloading valve with filter

Abstract

The utility model discloses an automatic unloading valve with a filter. The automatic unloading valve comprises a main valve assembly, a pilot control valve assembly and a filter assembly which are sequentially connected, the control liquid path in the main valve assembly is communicated with the control liquid path in the pilot control valve assembly, and the control liquid path in the pilot control valve assembly is communicated with the flow channel in the filter assembly. According to the automatic unloading valve with the filter, the filter assembly is installed on the automatic unloading valve, the filter effect on emulsion is achieved, and the phenomenon that a hole channel in the unloading valve is blocked by particulate matter or metal impurities in the emulsion is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of emulsion pumps, in particular to an automatic unloading valve with a filter. Background Art

[0002] The automatic unloading valve is an important pressure control component of the emulsion pump. Under the actual working conditions of coal mines, the emulsion is easily polluted by the underground environment and is likely to be mixed with particulate matters such as coal powder. The existing unloading valves do not have a filtering function. After the polluted emulsion enters the unloading valve, the particulate matters or metal impurities in the emulsion are likely to block some small channels inside the unloading valve, resulting in the inaction of hydraulic components such as the pilot valve rod and the thrust piston inside the unloading valve, causing the pump to operate under overpressure, which is very dangerous, has serious potential safety hazards, and will damage the pipelines and hydraulic equipment used in the liquid supply process.

[0003] In summary, it is necessary to invent an automatic unloading valve with a filter to solve the above technical problems. Summary of the Invention

[0004] The technical problem to be solved by the utility model is to provide an automatic unloading valve with a filter for the deficiencies of the above-mentioned existing technologies. The automatic unloading valve with a filter is equipped with a filter assembly, which has a filtering effect on the emulsion and reduces the phenomenon that the particulate matters or metal impurities in the emulsion block the internal channels of the unloading valve.

[0005] To achieve the above technical purposes, the technical solution adopted by the utility model is as follows:

[0006] An automatic unloading valve with a filter, comprising a main valve assembly, a pilot control valve assembly and a filter assembly connected in sequence;

[0007] The control liquid path inside the main valve assembly is communicated with the control liquid path inside the pilot control valve assembly, and the control liquid path inside the pilot control valve assembly is communicated with the flow channel inside the filter assembly.

[0008] As a further improved technical solution of the utility model, it further comprises a transition plate or a pilot solenoid valve connected to the filter assembly, and the flow channel inside the filter assembly is communicated with the channel inside the transition plate or the channel inside the pilot solenoid valve.

[0009] As a further improved technical solution of the present utility model, the filter assembly includes a filter base and a filter cartridge. A filter element is installed in the filter cartridge. The filter cartridge is fixedly connected to the filter base. The inlet of the liquid inlet channel in the filter base is the liquid inlet of the filter assembly. The liquid inlet channel in the filter base is communicated with the inlet of the filter cartridge. The outlet of the filter cartridge is communicated with the transition channel in the filter base. The transition channel in the filter base is communicated with the liquid outlet channel in the filter base through the pore channel in the transition plate or the pore channel in the pilot solenoid valve. The outlet of the liquid outlet channel in the filter base is the liquid outlet of the filter assembly;

[0010] The liquid inlet and outlet of the filter assembly are communicated with the control liquid circuit in the pilot control valve assembly.

[0011] As a further improved technical solution of the present utility model, the main valve assembly includes a main valve body. A high-pressure liquid inlet is provided in the middle of the main valve body, a unloading return liquid port is provided at the lower part, and a high-pressure liquid supply port is provided at the upper part;

[0012] A main valve seat, a support sleeve, a main valve guide sleeve, a main valve core, a thrust piston and a main valve spring are arranged at the lower part inside the main valve body. The bottom of the main valve body is connected with a main valve plug for locking the main valve seat, the support sleeve and the main valve guide sleeve on the inner wall of the lower part of the main valve body. The bottom of the main valve core is connected to the top of the thrust piston. A main valve spring is connected between the thrust piston and the main valve plug. The thrust piston is located inside the main valve guide sleeve and the thrust piston can slide inside the main valve guide sleeve. Under the action of the main valve spring, the top of the main valve core is pressed against the main valve seat; A hole is provided on the support sleeve for communicating the D cavity where the bottom of the main valve core is located with the unloading return liquid port;

[0013] A check valve seat, a check valve core and a check valve spring are arranged at the upper part inside the main valve body. The top of the main valve body is connected with a check valve plug for locking the check valve seat on the inner wall of the upper part of the main valve body. A check valve spring is connected between the top of the check valve core and the check valve plug. The check valve plug presses the bottom of the check valve core against the check valve seat through the check valve spring; A hole is provided on the check valve plug for communicating the B cavity where the top of the check valve core is located with the high-pressure liquid supply port.

[0014] As a further improved technical solution of the present utility model, four control liquid circuits are arranged in the main valve assembly, and a first control liquid circuit, a second control liquid circuit, a third control liquid circuit and a fourth control liquid circuit are formed on the end face of the main valve body; The first control liquid circuit is communicated with the high-pressure liquid inlet, the second control liquid circuit is communicated with the high-pressure liquid supply port, the third control liquid circuit is communicated with the unloading return liquid port, and the fourth control liquid circuit is communicated with the C cavity between the thrust piston and the main valve plug through the pore channel on the main valve guide sleeve and the pore channel on the thrust piston.

[0015] As a further improved technical solution of the utility model, the pilot control valve assembly includes a pilot valve body; a pilot valve plug is connected to the bottom of the pilot valve body, and a pilot valve seat, an intermediate sleeve and a pilot valve guide sleeve are sequentially connected inside the pilot valve body from bottom to top. A sliding sleeve is slidably connected inside the pilot valve guide sleeve, and the sliding sleeve is locked on the pilot valve rod through a locking nut. The pilot valve rod can slide inside the intermediate sleeve. A core rod is connected to the top of the pilot valve rod, a disc spring is sleeved on the core rod, the core rod is arranged inside a valve barrel fixedly connected to the top of the pilot valve body, a nut is connected to the top of the valve barrel and the nut is used to compress the disc spring. After the nut is threadedly connected to the top of the valve barrel, the nut compresses the disc spring, and the disc spring presses the bottom of the pilot valve rod against the top of the pilot valve seat through the core rod.

[0016] As a further improved technical solution of the utility model, four control liquid paths are arranged inside the pilot control valve assembly, and a fifth control liquid path, a sixth control liquid path, a seventh control liquid path and an eighth control liquid path are formed on the end face of the pilot valve body; wherein, one end of the fifth control liquid path is hermetically connected to the second control liquid path inside the main valve body and a throttle screw is connected to this end. The fifth control liquid path is communicated with the pore passage on the pilot valve guide sleeve, so that the liquid in the fifth control liquid path can act on the lower part of the sliding sleeve; one end of the sixth control liquid path is hermetically connected to the first control liquid path inside the main valve body and a throttle screw is connected to this end. The sixth control liquid path is hermetically connected to the liquid inlet of the filter assembly; one end of the seventh control liquid path is hermetically connected to the fourth control liquid path inside the main valve body and a throttle screw is connected to this end. The seventh control liquid path is communicated with the pore passage on the intermediate sleeve, so that the liquid in the seventh control liquid path can act on the lower part of the pilot valve rod pressed on the pilot valve seat. The seventh control liquid path is hermetically connected to the liquid outlet of the filter assembly; one end of the eighth control liquid path is hermetically connected to the third control liquid path inside the main valve body, and the eighth control liquid path is communicated with the cavity between the bottom of the pilot valve rod inside the pilot valve body and the pilot valve plug.

[0017] The beneficial effects of the utility model are as follows:

[0018] Because some pore passages in the automatic unloading valve are small, such as the pore passages on the main valve guide sleeve, the pore passages on the thrust piston, the pore passages on the intermediate sleeve, the flow channels inside the pilot solenoid valve, etc., they are easily blocked by particulate matters or metal impurities in the liquid, resulting in inaction of hydraulic components such as the pilot valve rod and the thrust piston, causing the pump to work under overpressure, which is very dangerous and will damage the liquid supply pipeline and the liquid-using equipment; or the pressure cannot be established all the time and the liquid cannot be supplied to the working face. The automatic unloading valve with a filter of the utility model completely solves the above problems. The filter assembly has a filtering effect on the emulsion liquid, reducing the phenomenon that the particulate matters or metal impurities in the emulsion liquid block the unloading valve. Description of the Drawings

[0019] Figure 1This is a side sectional view of the main valve assembly in the automatic unloading valve with a filter according to the present utility model.

[0020] Figure 2 This is a structural sectional view of the automatic unloading valve with a filter according to the present utility model. Specific embodiments

[0021] The following further describes the specific embodiments of the present utility model with reference to the accompanying drawings:

[0022] As Figure 1-2 shown, this embodiment provides an automatic unloading valve with a filter, which includes a main valve assembly A, a pilot control valve assembly B, a filter assembly C, and a transition piece D that are fixedly connected in sequence;

[0023] The control liquid path in the main valve assembly A is communicated with the control liquid path in the pilot control valve assembly B, the control liquid path in the pilot control valve assembly B is communicated with the flow path in the filter assembly C, and the flow path in the filter assembly C is communicated with the flow path of the transition piece D.

[0024] The transition piece D is a transition plate or a pilot solenoid valve, and the flow path in the filter assembly C is communicated with the pore channel in the transition plate or the pore channel in the pilot solenoid valve. When the transition piece D is a transition plate, the automatic unloading valve in this embodiment belongs to a mechanical automatic unloading valve; when the transition piece D is a pilot solenoid valve, the automatic unloading valve in this embodiment belongs to an electromagnetic automatic unloading valve.

[0025] As Figure 2 shown, the filter assembly C includes a filter base C1 and a filter cartridge C2. A filter element C3 is installed in the filter cartridge C2. The filter cartridge C2 is threadedly and hermetically connected to the filter base C1. The inlet of the liquid inlet flow path c1 in the filter base C1 is the liquid inlet of the filter assembly C. The liquid inlet flow path c1 in the filter base C1 is communicated with the inlet of the filter cartridge C2. The outlet of the filter cartridge C2 is communicated with the transition flow path c2 in the filter base C1. The transition flow path c2 in the filter base C1 is communicated with the liquid outlet flow path c3 in the filter base C1 through the pore channel in the transition plate or the pore channel in the pilot solenoid valve. The outlet of the liquid outlet flow path c3 in the filter base C1 is the liquid outlet of the filter assembly C. The liquid inlet and liquid outlet of the filter assembly C are communicated with the control liquid path in the pilot control valve assembly B. When the filter element C3 needs to be replaced, as long as the filter cartridge C2 is unscrewed from the filter base C1, the filter element C3 in the filter cartridge C2 can be replaced.

[0026] As Figure 1-2 shown, the main valve assembly A includes a main valve body A4. A high-pressure liquid inlet A1 is provided in the middle of the main valve body A4, a unloading return liquid port A3 is provided at the lower part, and a high-pressure liquid supply port A2 is provided at the upper part.

[0027] As Figure 2As shown in the figure, a main valve seat A12, a support sleeve A14, a main valve guide sleeve A16, a main valve core A11, a thrust piston A15 and a main valve spring A18 are arranged at the lower part inside the main valve body A4. A main valve plug A19 for locking the main valve seat A12, the support sleeve A14 and the main valve guide sleeve A16 on the inner wall of the lower part of the main valve body A4 is connected to the bottom of the main valve body A4. The bottom of the main valve core A11 is connected to the top of the thrust piston A15. A main valve spring A18 is connected between the thrust piston A15 and the main valve plug A19. The thrust piston A15 is located inside the main valve guide sleeve A16 and the thrust piston A15 can slide inside the main valve guide sleeve A16. Under the action of the main valve spring A18, the top of the main valve core A11 is pressed tightly on the main valve seat A12. A hole for communicating the D chamber A13 where the bottom of the main valve core A11 is located with the unloading return port A3 is provided on the support sleeve A14.

[0028] As Figure 2 shown in the figure, a check valve seat A9, a check valve core A8 and a check valve spring A6 are arranged at the upper part inside the main valve body A4. A check valve plug A7 for locking the check valve seat A9 on the inner wall of the upper part of the main valve body A4 is connected to the top of the main valve body A4. A check valve spring A6 is connected between the top of the check valve core A8 and the check valve plug A7. The check valve plug A7 presses the bottom of the check valve core A8 tightly on the check valve seat A9 through the check valve spring A6. A hole for communicating the B chamber A5 where the top of the check valve core A8 is located with the high-pressure liquid supply port A2 is provided on the check valve plug A7.

[0029] As Figure 2 shown in the figure, four control liquid paths are arranged inside the main valve assembly A, and a first control liquid path a1, a second control liquid path a2, a third control liquid path a3 and a fourth control liquid path a4 are formed on the end face of the main valve body A4. The first control liquid path a1 is communicated with the high-pressure liquid inlet A1, the second control liquid path a2 is communicated with the high-pressure liquid supply port A2, the third control liquid path a3 is communicated with the unloading return port A3, and the fourth control liquid path a4 is communicated with the C chamber A17 between the thrust piston A15 and the main valve plug A19 through the hole channels on the main valve guide sleeve A16 and the thrust piston A15.

[0030] As Figure 2As shown in the figure, the pilot control valve assembly B includes a pilot valve body B12; a pilot valve plug B10 is connected to the bottom of the pilot valve body B12, and a pilot valve seat B9, an intermediate sleeve B11, and a pilot valve guide sleeve B8 are sequentially connected inside the pilot valve body B12 from bottom to top. The locking sleeve is threadedly connected to the inner wall of the pilot valve body B12 to lock the pilot valve guide sleeve B8, the intermediate sleeve B11, and the pilot valve seat B9 on the inner wall of the pilot valve body B12. A sliding sleeve B7 is slidably connected inside the pilot valve guide sleeve B8, and the sliding sleeve B7 is locked on the pilot valve rod B6 through a locking nut B5. The pilot valve rod B6 can slide inside the intermediate sleeve B11, and a core rod B3 is connected to the top of the pilot valve rod B6. A disc spring B4 is sleeved on the core rod B3. The core rod B3 is arranged inside a valve barrel B2 fixedly connected to the top of the pilot valve body B12, and a nut B1 is connected to the top of the valve barrel B2, and the nut B1 is used to compress the disc spring B4. After the nut B1 is threadedly connected to the top of the valve barrel B2, the nut B1 compresses the disc spring B4, and the disc spring B4 presses the bottom of the pilot valve rod B6 against the top of the pilot valve seat B9 through the core rod B3.

[0031] As Figure 2 shown, four control liquid paths are provided inside the pilot control valve assembly B, and a fifth control liquid path b1, a sixth control liquid path b2, a seventh control liquid path b3, and an eighth control liquid path b4 are formed on the end face of the pilot valve body B12; among them, one end of the fifth control liquid path b1 is hermetically connected to the second control liquid path a2 inside the main valve body A4 through a sealing ring and a throttle screw is connected to this end. The fifth control liquid path b1 is communicated with the hole on the pilot valve guide sleeve B8, so that the liquid in the fifth control liquid path b1 can act on the lower part of the sliding sleeve B7; one end of the sixth control liquid path b2 is hermetically connected to the first control liquid path a1 inside the main valve body A4 through a sealing ring and a throttle screw is connected to this end. The other end of the sixth control liquid path b2 is hermetically connected to the liquid inlet of the filter assembly C; one end of the seventh control liquid path b3 is hermetically connected to the fourth control liquid path a4 inside the main valve body A4 through a sealing ring and a throttle screw is connected to this end. The seventh control liquid path b3 is communicated with the hole on the intermediate sleeve B11, so that the liquid in the seventh control liquid path b3 can act on the lower part of the pilot valve rod B6 pressed on the pilot valve seat B9. The seventh control liquid path b3 is hermetically connected to the liquid outlet of the filter assembly C; one end of the eighth control liquid path b4 is hermetically connected to the third control liquid path a3 inside the main valve body A4, and the eighth control liquid path b4 is communicated with the cavity between the bottom of the pilot valve rod B6 and the pilot valve plug B10 inside the pilot valve body B12.

[0032] Working principle:

[0033] By adjusting the nut B1 on the pilot control valve assembly B to change the compression amount of the disc spring B4, the working pressure of the automatic unloading valve can be set.

[0034] When high-pressure liquid enters chamber A10 through high-pressure liquid inlet A1, it will be divided into three paths simultaneously. The first path of liquid passes through a series of control liquid paths and filtration, and then reaches chamber A17 in chamber C, where it acts on the back of thrust piston A15 together with main valve spring A18. The second path of liquid acts on main valve core A11, and the third path of liquid enters chamber A5 in chamber B through one-way valve core A8.

[0035] Specifically, the first path of liquid passes through the first control liquid path a1, the sixth control liquid path b2, and the liquid inlet flow channel c1 in filter base C1 to reach the filter element C3 inside the filter. After filtration, it enters the liquid outlet flow channel c3 in filter base C1 through the pore channels in transition piece D, and then acts on the lower part of pilot valve rod B6 pressed against pilot valve seat B9 through the seventh control liquid path b3 and the pore channels on intermediate sleeve B11. After passing through the seventh control liquid path b3, the fourth control liquid path a4, the pore channels on main valve guide sleeve A16, and the pore channels on thrust piston A15, it enters chamber A17 in chamber C and acts on the bottom of thrust piston A15, causing pilot valve rod B6 and thrust piston A15 to be subjected to liquid pressure. First, due to the pre-tightening force set by the disc spring, pilot valve rod B6 is tightly pressed against pilot valve seat B9, and pilot valve rod B6 is in a closed state. Secondly, because the diameter of thrust piston A15 is larger than that of main valve core A11, even if the first path of liquid and the second path of liquid form a counterflush under the same pressure, main valve core A11 will also be in a closed state.

[0036] After the third path of liquid enters chamber A5 in chamber B, in addition to supplying liquid to the working face through high-pressure liquid supply port A2, it also acts on the lower part of sliding sleeve B7 through the second control liquid path a2, the fifth control liquid path b1, and the pore channels on pilot valve guide sleeve B8. If the pressure at high-pressure liquid inlet A1 of the automatic unloading valve increases, that is, the pump outlet pressure increases, the pressure in chamber A5 in chamber B will also increase simultaneously. When the force acting on sliding sleeve B7 exceeds the pre-tightening force of the disc spring, that is, when the pump pressure is greater than the set pressure of the automatic unloading valve, sliding sleeve B7 drives pilot valve rod B6 to lift from pilot valve seat B9. At this time, the first path of liquid coming out of filter assembly C will directly enter the eighth control liquid path b4 through the gap between pilot valve rod B6 and pilot valve seat B9, and then enter chamber A13 in chamber D through the third control liquid path a3, and flow back to the emulsion tank through unloading return liquid port A3. In this way, the fourth control liquid path a4 and the back of thrust piston A15 will lose pressure, and main valve core A11 will be opened, that is, it will leave main valve seat A12. The second path of liquid acting on main valve core A11 will also directly flow back to the emulsion tank through unloading return liquid port A3. At the same time, one-way valve core A8 will be closed downward under the action of the liquid pressure in chamber A5 in chamber B. In this way, the high-pressure liquid behind chamber A5 in chamber B will not flow back, and the working face is in a pressure-holding state.

[0037] If the hydraulic pressure in chamber B A5 drops, the force acting on the sliding sleeve B7 will become smaller. When it becomes smaller than the pre-tightening force of the disc spring B4, the pilot valve stem B6 will move downward, causing the pilot valve stem B6 to press onto the pilot valve seat B9 again. Then, the hydraulic pressure is restored in the first control hydraulic circuit a1, the sixth control hydraulic circuit b2, the flow passage in the filter assembly C, the seventh control hydraulic circuit b3, the fourth control hydraulic circuit a4, and the passage in the main valve guide sleeve A16. After the thrust piston A15 is stressed, it moves upward to close the main valve core A11, and the liquid once again opens the one-way valve core A8 to supply liquid to the working face.

[0038] Since some of the passages in the automatic unloading valve are very small, such as the passages in the main valve guide sleeve A16, the passages in the thrust piston A15, the passages in the intermediate sleeve B11, the flow passages in the pilot solenoid valve, etc., they are easily blocked by particulate matter or metal impurities in the liquid, resulting in the inaction of hydraulic components such as the pilot valve stem B6 and the thrust piston A15, causing the pump to operate under overpressure, which is very dangerous and will damage the liquid supply pipeline and the liquid-using equipment; or the pressure cannot be established all the time, and the liquid cannot be supplied to the working face. This automatic unloading valve with a filter completely solves the above problems, enabling the valve to continuously cycle at a rate of 4 - 6 times per minute of pressure increase → unloading → pressure increase during normal operation.

[0039] The protection scope of the present utility model includes but is not limited to the above embodiments. The protection scope of the present utility model shall be subject to the claims, and any substitutions, deformations, and improvements that are easily conceivable by those skilled in the art to this technology shall fall within the protection scope of the present utility model.

Claims

1. An automatic unloading valve with a filter, characterized in that: It includes a main valve assembly (A), a pilot control valve assembly (B), and a filter assembly (C) connected in sequence; The control liquid path in the main valve assembly (A) is communicated with the control liquid path in the pilot control valve assembly (B), and the control liquid path in the pilot control valve assembly (B) is communicated with the flow channel in the filter assembly (C).

2. The automatic unloading valve with a filter according to claim 1, characterized in that, It further includes a transition plate or a pilot solenoid valve connected to the filter assembly (C), and the flow channel in the filter assembly (C) is communicated with the pore channel in the transition plate or the pore channel in the pilot solenoid valve.

3. The automatic unloading valve with a filter according to claim 2, characterized in that, The filter assembly (C) includes a filter base (C1) and a filter cartridge (C2). A filter element (C3) is installed in the filter cartridge (C2). The filter cartridge (C2) is fixedly connected to the filter base (C1). The inlet of the liquid inlet flow channel (c1) in the filter base (C1) is the liquid inlet of the filter assembly (C). The liquid inlet flow channel (c1) in the filter base (C1) is communicated with the inlet of the filter cartridge (C2). The outlet of the filter cartridge (C2) is communicated with the transition flow channel (c2) in the filter base (C1). The transition flow channel (c2) in the filter base (C1) is communicated with the liquid outlet flow channel (c3) in the filter base (C1) through the pore channel in the transition plate or the pore channel in the pilot solenoid valve. The outlet of the liquid outlet flow channel (c3) in the filter base (C1) is the liquid outlet of the filter assembly (C); The liquid inlet and the liquid outlet of the filter assembly (C) are communicated with the control liquid path in the pilot control valve assembly (B).

4. The automatic unloading valve with a filter according to claim 1, characterized in that, The main valve assembly (A) includes a main valve body (A4). A high-pressure liquid inlet (A1) is provided in the middle of the main valve body (A4), a unloading return liquid port (A3) is provided at the lower part, and a high-pressure liquid supply port (A2) is provided at the upper part; At the lower part inside the main valve body (A4), there are provided a main valve seat (A12), a support sleeve (A14), a main valve guide sleeve (A16), a main valve core (A11), a thrust piston (A15), and a main valve spring (A18). The bottom of the main valve body (A4) is connected with a main valve plug (A19) for locking the main valve seat (A12), the support sleeve (A14), and the main valve guide sleeve (A16) on the inner wall of the lower part of the main valve body (A4). The bottom of the main valve core (A11) is connected to the top of the thrust piston (A15). A main valve spring (A18) is connected between the thrust piston (A15) and the main valve plug (A19). The thrust piston (A15) is located inside the main valve guide sleeve (A16) and the thrust piston (A15) can slide inside the main valve guide sleeve (A16). Under the action of the main valve spring (A18), the top of the main valve core (A11) is pressed against the main valve seat (A12); A hole is provided on the support sleeve (A14) for communicating the D chamber (A13) where the bottom of the main valve core (A11) is located with the unloading return liquid port (A3); A one-way valve seat (A9), a one-way valve core (A8) and a one-way valve spring (A6) are provided on the upper inner side of the main valve body (A4); a one-way valve plug (A7) for locking the one-way valve seat (A9) on the upper inner wall of the main valve body (A4) is connected to the top of the main valve body (A4); a one-way valve spring (A6) is connected between the top of the one-way valve core (A8) and the one-way valve plug (A7); the one-way valve plug (A7) presses the bottom of the one-way valve core (A8) against the one-way valve seat (A9) through the one-way valve spring (A6); and a hole is provided on the one-way valve plug (A7) for connecting the B cavity (A5) where the top of the one-way valve core (A8) is located with the high-pressure liquid supply port (A2).

5. The automatic unloading valve with a filter according to claim 4, characterized in that, Four control liquid circuits are provided in the main valve assembly (A), and a first control liquid circuit (a1), a second control liquid circuit (a2), a third control liquid circuit (a3) and a fourth control liquid circuit (a4) are formed on the end face of the main valve body (A4); the first control liquid circuit (a1) is connected to the high-pressure liquid inlet (A1), the second control liquid circuit (a2) is connected to the high-pressure liquid supply port (A2), the third control liquid circuit (a3) is connected to the unloading return liquid port (A3), and the fourth control liquid circuit (a4) is connected to the C cavity (A17) between the thrust piston (A15) and the main valve screw plug (A19) through the hole on the main valve guide sleeve (A16), the hole on the thrust piston (A15), and the C cavity (A17) between the thrust piston (A15) and the main valve screw plug (A19).

6. The automatic unloading valve with a filter according to claim 1, characterized in that: The pilot control valve assembly (B) includes a pilot valve body (B12); the bottom of the pilot valve body (B12) is connected to a pilot valve plug (B10); the interior of the pilot valve body (B12) is sequentially connected to a pilot valve seat (B9), an intermediate sleeve (B11) and a pilot valve guide sleeve (B8) from bottom to top; the interior of the pilot valve guide sleeve (B8) is slidably connected to a sliding sleeve (B7); the sliding sleeve (B7) is locked on the pilot valve stem (B6) by a locking nut (B5); the pilot valve stem (B6) can slide in the intermediate sleeve (B11); the pilot valve stem (B6) The top of the pilot valve body (B12) is connected to a core rod (B3), and a butterfly spring (B4) is sleeved on the core rod (B3). The core rod (B3) is set in a valve cylinder (B2) fixedly connected to the top of the pilot valve body (B12). The top of the valve cylinder (B2) is connected to a nut (B1), and the nut (B1) is used to compress the butterfly spring (B4). When the top of the valve cylinder (B2) is threadedly connected to the nut (B1), the nut (B1) compresses the butterfly spring (B4), and the butterfly spring (B4) presses the bottom of the pilot valve stem (B6) against the top of the pilot valve seat (B9) through the core rod (B3).

7. The automatic unloading valve with a filter according to claim 6, characterized in that, There are four control liquid paths provided inside the pilot control valve assembly (B), and a fifth control liquid path (b1), a sixth control liquid path (b2), a seventh control liquid path (b3), and an eighth control liquid path (b4) are formed on the end face of the pilot valve body (B12); among them, one end of the fifth control liquid path (b1) is hermetically connected to the second control liquid path (a2) inside the main valve body (A4) and a throttle screw is connected to this end, and the fifth control liquid path (b1) is communicated with the pore passage on the pilot valve guide sleeve (B8), so that the liquid in the fifth control liquid path (b1) can act on the lower part of the sliding sleeve (B7); one end of the sixth control liquid path (b2) is hermetically connected to the first control liquid path (a1) inside the main valve body (A4) and a throttle screw is connected to this end, and the sixth control liquid path (b2) is hermetically connected to the liquid inlet of the filter assembly (C); one end of the seventh control liquid path (b3) is hermetically connected to the fourth control liquid path (a4) inside the main valve body (A4) and a throttle screw is connected to this end, and the seventh control liquid path (b3) is communicated with the pore passage on the intermediate sleeve (B11), so that the liquid in the seventh control liquid path (b3) can act on the lower part of the pilot valve stem (B6) pressed on the pilot valve seat (B9), and the seventh control liquid path (b3) is hermetically connected to the liquid outlet of the filter assembly (C); one end of the eighth control liquid path (b4) is hermetically connected to the third control liquid path (a3) inside the main valve body (A4), and the eighth control liquid path (b4) is communicated with the cavity between the bottom of the pilot valve stem (B6) and the pilot valve plug (B10) inside the pilot valve body (B12).

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