Pilot-operated pressure reducing valve test tool and test method

Abstract

The invention provides a pilot-operated type pressure reducing valve testing tool and a testing method, and relates to a hydraulic valve testing equipment structure, and the pilot-operated type pressure reducing valve testing tool comprises a pilot-operated type pressure reducing valve, a variable throttling valve, a fixed throttling opening, a variable throttling valve, a pressure gauge, a testing valve block and a flow meter, the oil inlet is connected with the hydraulic table high-pressure oil supply pilot-operated pressure reducing valve and the variable throttle valve; the variable throttling valve and the fixed throttling screw plug are combined to control the pilot pressure of the pilot pressure reducing valve, and pilot oil is discharged through an oil drainage port of the test valve block; the pressure gauges are arranged at an oil inlet, an oil outlet and a pilot port of the test valve block respectively, and an oil return port of the test valve block is communicated with a flowmeter arranged in the hydraulic table. According to the test device, the leakage rate, the pressure reduction characteristic and the minimum starting pressure of the pilot-operated type pressure reducing valve are tested by controlling hydraulic oil, so that whether the pilot-operated type pressure reducing valve is qualified or not is judged; the testing device has the advantages of being capable of simultaneously meeting testing requirements of different functions of the pilot-operated type pressure reducing valve, safe in testing and high in efficiency.

Description

Technical Field

[0001] The present invention relates to a structure of a hydraulic valve testing device, in particular to a testing tooling and testing method for a pilot-operated pressure reducing valve. Background Art

[0002] A pilot-operated pressure reducing valve is a spool valve composed of a valve sleeve, a valve core and a spring. The output pressure is controlled by controlling the opening degree between the valve sleeve and the valve core. It is commonly used in the oil distribution station of a hydraulic system and can supply oil to multiple actuators simultaneously;

[0003] The pilot-operated pressure reducing valve can be installed in the oil distribution station of the hydraulic system, and can control the pressure boosting process of the hydraulic system, making its oil supply pressure slowly rise from zero pressure to a lower working pressure, and then slowly rise to the normal test pressure. The whole pressure boosting process is slow, stable, with extremely small pressure shock, and can achieve rapid unloading without pressure shock. Therefore, the matching precision requirements of the valve sleeve and the valve core of the pilot-operated pressure reducing valve are extremely high. To ensure its qualified precision, it is necessary to test its leakage amount, pressure reducing characteristics and minimum starting pressure;

[0004] In order to test the pilot-operated pressure reducing valve batchwise, quickly and safely, the present invention provides a testing tooling and testing method for the pilot-operated pressure reducing valve. Summary of the Invention

[0005] The present invention provides the following technical solutions:

[0006] A testing tooling for a pilot-operated pressure reducing valve, including a testing valve block installed on a hydraulic table, the pilot-operated pressure reducing valve is detachably connected in the testing valve block. The testing valve block also has an internal oil passage for forming a circulating flow between the hydraulic table and the pilot-operated pressure reducing valve. The internal oil passage includes an inlet oil passage for feeding high-pressure oil from the hydraulic table to the pilot-operated pressure reducing valve and an outlet oil passage for discharging oil from the pilot-operated pressure reducing valve to the hydraulic table.

[0007] A set of return branches are also branched and connected on the inlet oil passage. A variable throttle valve one, a fixed throttle orifice and a variable throttle valve two are sequentially connected in conduction on the return branch. The variable throttle valve one, the variable throttle valve two and the fixed throttle orifice jointly control the pilot pressure of the pilot-operated pressure reducing valve, and the pilot oil is discharged into the hydraulic table through the valve block oil drain port at the end of the return branch. A first pressure gauge is arranged at the valve block inlet port of the testing valve block where the inlet oil passage is connected, a second pressure gauge is arranged at the valve block outlet port of the testing valve block where the outlet oil passage is connected, a third pressure gauge is arranged at the valve block pilot port of the testing valve block where the return branch is connected, and a flowmeter is also arranged in the hydraulic table to measure the oil flow of the testing valve block returning oil to the hydraulic table on the outlet oil passage. The valve block return oil port of the testing valve block is connected to the flowmeter arranged in the hydraulic table;

[0008] So far, during the test, the test valve block is installed on the hydraulic bench, and the pilot-operated pressure reducing valve is detachably connected to the test valve block to ensure the convenience of the test. Through the combination of the first variable throttle valve, the fixed throttle orifice, and the second variable throttle valve, the pilot pressure of the pilot-operated pressure reducing valve to be tested is controlled to ensure that different test requirements are met. The pressure change of the pilot-operated pressure reducing valve to be tested is detected by a pressure gauge, and the leakage volume change of the pilot-operated pressure reducing valve to be tested is detected by a flowmeter to assist in judging whether the product is qualified. In summary, the leakage volume, pressure reducing characteristics, and minimum starting pressure of the pilot-operated pressure reducing valve are tested by controlling the hydraulic oil, so as to judge whether the pilot-operated pressure reducing valve is qualified. It has the advantages of being able to meet the requirements of different function tests of the pilot-operated pressure reducing valve at the same time, and the test is safe and efficient;

[0009] Among the above, the first variable throttle valve is arranged in the test valve block and communicates with the internal oil passage of the test valve block; the fixed throttle orifice is arranged in the test valve block and connected after the first variable throttle valve; the second variable throttle valve is arranged in the test valve block and connected after the fixed throttle orifice; the first variable throttle valve, the fixed throttle orifice, and the second variable throttle valve can be combined to control the pilot pressure to drive the opening of the pilot-operated pressure reducing valve;

[0010] The first pressure gauge, the second pressure gauge, and the third pressure gauge are respectively arranged on the test valve block; the test valve block is arranged on the hydraulic bench and communicates with the hydraulic bench. The test valve block has a valve block inlet oil port, a valve block outlet oil port, a valve block return oil port, a valve block pilot port, and a valve block drain port; the valve block inlet oil port communicates with the hydraulic bench, the first variable throttle valve, the pilot-operated pressure reducing valve, and the first pressure gauge; the valve block outlet oil port communicates with the pilot-operated pressure reducing valve and the second pressure gauge; the valve block return oil port communicates with the pilot-operated pressure reducing valve and the flowmeter arranged in the hydraulic bench; the valve block pilot port communicates with the pilot-operated pressure reducing valve, the fixed throttle orifice, and the second variable throttle valve; the valve block drain port communicates with the hydraulic bench; the flowmeter is arranged in the hydraulic bench and can detect the leakage volume of the pilot-operated pressure reducing valve.

[0011] Preferably, the pilot-operated pressure reducing valve includes:

[0012] A valve sleeve, the valve sleeve has a valve sleeve inlet oil port, a valve sleeve outlet oil port, a valve sleeve return oil port, and a valve sleeve pilot port that communicate with the test valve block; the valve sleeve inlet oil port communicates with the first variable throttle valve and the valve block inlet oil port; the valve sleeve outlet oil port communicates with the valve block outlet oil port; the valve sleeve return oil port communicates with the valve block return oil port, and a pilot control cavity is arranged on one side of the valve sleeve close to the valve sleeve pilot port;

[0013] A valve core, the valve core is arranged in the valve sleeve, and under the action of the pilot pressure in the pilot control cavity, the valve core can slide in the inner cavity of the valve sleeve; the valve core has a spring cavity, and a through hole is opened in the spring cavity so that when the spring is compressed, the oil in the spring cavity can be discharged from the through hole;

[0014] A spring, with two ends of the spring respectively abutted against the valve sleeve and the valve core, so that when there is no pilot pressure acting, the valve core always moves in the direction of closing the oil inlet of the valve sleeve.

[0015] Preferably, the test valve block is detachably connected to the hydraulic bench.

[0016] A method for testing a pilot-operated pressure reducing valve, based on the above-mentioned pilot-operated pressure reducing valve test tooling, includes the following steps:

[0017] S1. By starting the hydraulic bench, the pilot-operated pressure reducing valve is connected to the hydraulic bench through the valve block oil inlet, the valve block oil return port, and the valve block oil drain port. High-pressure oil is input into the valve block oil inlet and adjusted to the test pressure.

[0018] S2. By adjusting the first variable throttle valve, the pilot-operated pressure reducing valve is disconnected from the valve block oil inlet, and the value of the first pressure gauge is the test pressure; by adjusting the second variable throttle valve, the value of the third pressure gauge is 0 MPa, and the value of the second pressure gauge is approximately 0 MPa; observe the reading of the flowmeter to judge whether the leakage amount between the oil inlet and the oil outlet of the valve sleeve of the pilot-operated pressure reducing valve is qualified.

[0019] S3. By adjusting the first variable throttle valve, the pilot-operated pressure reducing valve is connected to the valve block oil inlet, and the value of the first pressure gauge is the test pressure; by adjusting the second variable throttle valve, the values of both the third pressure gauge and the second pressure gauge are the test pressure. Observe the reading of the flowmeter to judge whether the leakage amount between the oil outlet and the oil return port of the valve sleeve of the pilot-operated pressure reducing valve is qualified.

[0020] S4. By adjusting the first variable throttle valve, the pilot-operated pressure reducing valve is connected to the valve block oil inlet, and the value of the first pressure gauge is the test pressure; by adjusting the second variable throttle valve, the value of the third pressure gauge slowly decreases from the test pressure; observe the value of the second pressure gauge decreasing as the value of the third pressure gauge decreases to judge whether the pressure reducing characteristic of the pilot-operated pressure reducing valve is qualified.

[0021] S5. By adjusting the first variable throttle valve, the pilot-operated pressure reducing valve is connected to the valve block oil inlet, and the value of the first pressure gauge is the test pressure; by adjusting the second variable throttle valve, the value of the third pressure gauge slowly rises from 0 MPa to the minimum start-up pressure of the pilot-operated pressure reducing valve. Observe the value of the second pressure gauge starting to change from 0 MPa after the value of the third pressure gauge rises to the minimum start-up pressure to judge whether the minimum start-up pressure of the pilot-operated pressure reducing valve is qualified.

[0022] Preferably, the test pressure is greater than or equal to 21 MPa, and the minimum starting pressure is greater than 0.6 MPa.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The pilot-operated pressure reducing valve test tooling includes a test valve block, a pilot-operated pressure reducing valve, variable throttle valves (collectively referred to as variable throttle valves including variable throttle valve one and variable throttle valve two), fixed throttle orifices, and pressure gauges. The hydraulic bench is connected through the test valve block, and high-pressure oil is input to ensure a stable test pressure. The pilot input of the pilot-operated pressure reducing valve is controlled by the combination of the variable throttle valves and fixed throttle orifices installed on the test valve block to ensure a specified pilot pressure. The pressure changes of each oil port of the pilot-operated pressure reducing valve during the process are detected by the pressure gauges installed on the test valve block, and the leakage amount of the pilot-operated pressure reducing valve during the process is detected by the flowmeter provided on the hydraulic bench. Multiple tests can be completed through the pilot-operated pressure reducing valve test tooling, greatly reducing the cost and difficulty of the test;

[0025] 2. The test method for the pilot-operated pressure reducing valve is completed by using the above-mentioned pilot-operated pressure reducing valve test tooling. The test method for the pilot-operated pressure reducing valve is simple to operate, safe and reliable, with high-precision test data and good repeatability. It can perform batch tests before the pilot-operated pressure reducing valve is warehoused and used, reducing the defective rate of the final product and improving work efficiency;

[0026] 3. The test method for the pilot-operated pressure reducing valve provides tests for the leakage amount, pressure reducing characteristics, and minimum starting pressure of the pilot-operated pressure reducing valve, covering all functional test requirements of the pilot-operated pressure reducing valve and can meet the tests of similar products. Description of the Drawings

[0027] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0028] Figure 1 is the hydraulic schematic diagram of the pilot-operated pressure reducing valve test tooling according to the embodiment of the present application.

[0029] Figure 2 is the structural schematic diagram of the pilot-operated pressure reducing valve test tooling according to the embodiment of the present application.

[0030] Figure 3 is the partial oil passage cross-sectional view of the pilot-operated pressure reducing valve test tooling according to the embodiment of the present application.

[0031] Figure 4 is Figure 3 the cross-sectional view of the A-A section in

[0032] Figure 5It is a cross-sectional view of the pilot-operated pressure reducing valve according to an embodiment of the present application.

[0033] Figure 6 It is a schematic flow chart of the test method for the pilot-operated pressure reducing valve according to an embodiment of the present application.

[0034] Description of reference numerals:

[0035] 1. Pilot-operated pressure reducing valve; 2. First variable throttle valve; 3. Fixed throttle orifice; 4. Second variable throttle valve; 5. Third pressure gauge; 6. Second pressure gauge; 7. First pressure gauge; 8. Test valve block; 801. Inlet port of the valve block; 802. Outlet port of the valve block; 803. Return port of the valve block; 804. Pilot port of the valve block; 805. Drain port of the valve block; 9. Flow meter; 10. Hydraulic bench; 200. Valve sleeve; 201. Inlet port of the valve sleeve; 202. Outlet port of the valve sleeve; 203. Return port of the valve sleeve; 204. Pilot port of the valve sleeve; 205. Pilot control chamber; 300. Spool; 301. Spring chamber; 302. Through hole; 400. Spring. Detailed implementation manners

[0036] Embodiment 1

[0037] As Figure 1 shown, a test tool for a pilot-operated pressure reducing valve, in this embodiment, includes a test valve block detachably installed on a hydraulic bench, the pilot-operated pressure reducing valve is detachably connected inside the test valve block, and the test valve block further has an internal oil passage for forming a circulating flow between the hydraulic bench 10 and the pilot-operated pressure reducing valve 1. The internal oil passage includes a liquid inlet oil passage for feeding high-pressure oil from the hydraulic bench 10 to the pilot-operated pressure reducing valve 1 and a liquid outlet oil passage for discharging oil from the pilot-operated pressure reducing valve 1 to the hydraulic bench 10.

[0038] A set of return branches are branched and connected to the liquid inlet oil passage. The return branches are sequentially connected with a first variable throttle valve 2, a fixed throttle orifice 3, and a second variable throttle valve 4. The first variable throttle valve 2, the second variable throttle valve 4, and the fixed throttle orifice 3 jointly control the pilot pressure of the pilot-operated pressure reducing valve, and the pilot oil is discharged to the inside of the hydraulic bench through the drain port of the test valve block at the end of the return branch. A first pressure gauge 7 is arranged at the inlet port of the test valve block where the liquid inlet oil passage is connected, a second pressure gauge 6 is arranged at the outlet port of the test valve block where the liquid outlet oil passage is connected, a third pressure gauge 5 is arranged at the pilot port of the test valve block where the return branch is connected, and a flow meter is further arranged inside the hydraulic bench to measure the oil flow rate of the test valve block returning oil to the hydraulic bench on the liquid outlet oil passage. The return port of the test valve block is connected to the flow meter 9 arranged inside the hydraulic bench;

[0039] So far, during the test, the test valve block is installed on the hydraulic bench, and the pilot-operated pressure reducing valve is detachably connected to the test valve block to ensure the convenience of the test. Through the combination of the first variable throttle valve, the fixed throttle orifice, and the second variable throttle valve, the pilot pressure of the tested pilot-operated pressure reducing valve is controlled to ensure that different test requirements are met. The pressure change of the tested pilot-operated pressure reducing valve is detected by a pressure gauge, and the leakage rate change of the tested pilot-operated pressure reducing valve is detected by a flowmeter to assist in judging whether the product is qualified. In summary, the leakage rate, pressure reducing characteristics, and minimum starting pressure of the pilot-operated pressure reducing valve are tested by controlling the hydraulic oil, so as to judge whether the pilot-operated pressure reducing valve is qualified. It has the advantages of being able to meet the requirements of different function tests of the pilot-operated pressure reducing valve at the same time, and having safe and efficient tests;

[0040] Among the above, the first variable throttle valve 2 is arranged in the test valve block 8 and communicates with the internal oil passage of the test valve block 8; the fixed throttle orifice 3 is arranged in the test valve block 8 and connected after the first variable throttle valve 2; the second variable throttle valve 4 is arranged in the test valve block 8 and connected after the fixed throttle orifice 3; the first variable throttle valve 2, the fixed throttle orifice 3, and the second variable throttle valve 4 can be combined to control the pilot pressure to drive the opening of the pilot-operated pressure reducing valve 1;

[0041] The first pressure gauge 7, the second pressure gauge 6, and the third pressure gauge 5 are respectively arranged on the test valve block 8; the test valve block 8 is arranged on the hydraulic bench 10 and communicates with the hydraulic bench 10. The test valve block 8 has a valve block oil inlet 801, a valve block oil outlet 802, a valve block oil return port 803, a valve block pilot port 804, and a valve block oil drain port 805; the valve block oil inlet 801 communicates with the hydraulic bench 10, the first variable throttle valve 2, the pilot-operated pressure reducing valve 1, and the first pressure gauge 7; the valve block oil outlet 802 communicates with the pilot-operated pressure reducing valve 1 and the second pressure gauge 6; the valve block oil return port 803 communicates with the pilot-operated pressure reducing valve 1 and the flowmeter 9 arranged in the hydraulic bench 10; the valve block pilot port 804 communicates with the pilot-operated pressure reducing valve 1, the fixed throttle orifice 3, and the second variable throttle valve 4; the valve block oil drain port 805 communicates with the hydraulic bench 10; the flowmeter 9 is arranged in the hydraulic bench 10 and can detect the leakage rate of the pilot-operated pressure reducing valve 1.

[0042] The pilot-operated pressure reducing valve 1 includes:

[0043] A valve sleeve 200, the valve sleeve 200 has a valve sleeve oil inlet 201, a valve sleeve oil outlet 202, a valve sleeve oil return port 203, and a valve sleeve pilot port 204 that communicate with the test valve block 8; the valve sleeve oil inlet 201 communicates with the first variable throttle valve 2 and the valve block oil inlet 801; the valve sleeve oil outlet 202 communicates with the valve block oil outlet 802; the valve sleeve oil return port 203 communicates with the valve block oil return port 803, and a pilot control cavity 205 is arranged on one side of the valve sleeve 200 close to the valve sleeve pilot port 204;

[0044] A spool 300 is provided in a valve sleeve 200, and the spool 300 can slide in the inner cavity of the valve sleeve 200 under the action of a pilot pressure in a pilot control cavity 205; the spool 300 has a spring cavity 301, and a through hole 302 is provided in the spring cavity 301 so that when the spring is compressed, the oil in the spring cavity 301 can be discharged from the through hole 302;

[0045] A spring 400, with both ends of the spring 400 abutted against the valve sleeve 200 and the spool 300 respectively, so that when there is no pilot pressure, the spool 300 always moves in the direction of closing the oil inlet 201 of the valve sleeve.

[0046] Embodiment 2

[0047] A method for testing a pilot-operated pressure reducing valve, based on a testing tool for a pilot-operated pressure reducing valve in Embodiment 1, includes the following steps:

[0048] S1. By starting the hydraulic bench 10, the pilot-operated pressure reducing valve 1 is connected to the hydraulic bench 10 through the valve block oil inlet 801, the valve block oil return port 803, and the valve block oil drain port 805. High-pressure oil is input through the valve block oil inlet 801 and adjusted to the test pressure;

[0049] By adopting the above technical solution, a stable test pressure of 21 MPa is provided for the testing tool of the pilot-operated pressure reducing valve;

[0050] S2. By tightening the variable throttle valve 1, the pilot-operated pressure reducing valve 1 is disconnected from the valve block oil inlet 801, and the value of the first pressure gauge 7 is the test pressure; by loosening the variable throttle valve 2, the value of the third pressure gauge 5 is 0 MPa, and the value of the second pressure gauge 6 is approximately 0 MPa; observe the reading of the flowmeter 9 to judge whether the leakage between the oil inlet 201 and the oil outlet 202 of the valve sleeve of the pilot-operated pressure reducing valve 1 is qualified;

[0051] By adopting the above technical solution, the pilot pressure of the pilot-operated pressure reducing valve is adjusted to judge whether the leakage between the oil inlet and the oil outlet of the pilot-operated pressure reducing valve is qualified when the pilot pressure is 0 MPa;

[0052] S3. By loosening the variable throttle valve 1, the pilot-operated pressure reducing valve 1 is connected to the valve block oil inlet 801, and the value of the first pressure gauge 7 is the test pressure. By tightening the variable throttle valve 2, the values of the third pressure gauge 5 and the second pressure gauge 6 are both the test pressure. Observe the reading of the flowmeter 9 to judge whether the leakage between the oil outlet 202 and the oil return port 203 of the valve sleeve of the pilot-operated pressure reducing valve 1 is qualified;

[0053] By adopting the above technical solution, the pilot pressure of the pilot-operated pressure reducing valve is set to determine whether the leakage amount between the oil outlet and the oil return port of the pilot-operated pressure reducing valve is qualified when the pilot pressure is the test pressure;

[0054] S4. By loosening the variable throttle valve 1-2, the pilot-operated pressure reducing valve 1 is communicated with the oil inlet 801 of the valve block, and the value of the first pressure gauge 7 is the test pressure. By loosening the variable throttle valve 2-4, the value of the third pressure gauge 5 slowly decreases from the test pressure; observe the value of the second pressure gauge 6 decreasing as the value of the third pressure gauge 5 decreases to determine whether the pressure reducing characteristic of the pilot-operated pressure reducing valve 1 is qualified;

[0055] By adopting the above technical solution, the pilot pressure of the pilot-operated pressure reducing valve is set to determine whether the oil outlet pressure of the pilot-operated pressure reducing valve slowly decreases as the pilot pressure slowly decreases from the test pressure to 0 MPa;

[0056] S5. By loosening the variable throttle valve 1-2, the pilot-operated pressure reducing valve 1 is communicated with the oil inlet 801 of the valve block, and the value of the first pressure gauge 7 is the test pressure. By tightening the variable throttle valve 2-4, the value of the third pressure gauge 5 slowly rises from 0 MPa to the minimum starting pressure of the pilot-operated pressure reducing valve 1. Observe that the value of the second pressure gauge 6 starts to change from 0 MPa after the value of the third pressure gauge 5 rises to the minimum starting pressure to determine whether the minimum starting pressure of the pilot-operated pressure reducing valve 1 is qualified;

[0057] By adopting the above technical solution, the pilot pressure of the pilot-operated pressure reducing valve is set to determine whether the oil outlet pressure of the pilot-operated pressure reducing valve changes when the pilot pressure slowly rises from 0 MPa to greater than 0.6 MPa.

[0058] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A pilot pressure reducing valve test tool, characterized in that: It includes a test valve block installed on the hydraulic platform, the pilot pressure reducing valve is detachably connected in the test valve block, and the test valve block also has an internal oil passage for forming a circulation between the hydraulic platform and the pilot pressure reducing valve, and the internal oil passage includes an inlet oil passage for high-pressure oil from the hydraulic platform to the pilot pressure reducing valve and an outlet oil passage for oil from the pilot pressure reducing valve to the hydraulic platform; The inlet oil circuit is also branched with a group of return branches, and the return branch is provided with a variable throttle valve 1, a fixed throttle port and a variable throttle valve 2 which are connected in sequence. The variable throttle valve 1, the variable throttle valve 2 and the fixed throttle port combine to control the pilot pressure of the pilot pressure reducing valve, and discharge the pilot oil into the hydraulic platform through the valve block oil drain port of the test valve block at the tail end of the return branch. A first pressure gauge is arranged on the valve block oil inlet port of the inlet oil circuit connected to the test valve block, a second pressure gauge is arranged on the valve block oil outlet port of the test valve block connected to the outlet oil circuit, a third pressure gauge is arranged at the valve block pilot port of the return branch connected to the test valve block, and a flow meter is also arranged in the hydraulic platform to measure the oil flow rate of the test valve block returning to the hydraulic platform from the test valve block on the outlet oil circuit, and the valve block oil return port of the test valve block is connected to the flow meter arranged in the hydraulic platform.

2. A pilot-operated pressure reducing valve testing tool according to claim 1, characterized in that: The pilot-operated pressure reducing valve comprises: A valve sleeve, wherein the valve sleeve has a valve sleeve oil inlet, a valve sleeve oil outlet, a valve sleeve oil return port and a valve sleeve pilot port which are connected to the test valve block, the valve sleeve oil inlet is connected to the variable throttle valve 1 and the valve block oil inlet, the valve sleeve oil outlet is connected to the valve block oil outlet, the valve sleeve oil return port is connected to the valve block oil return port, and a pilot control chamber is provided on one side of the valve sleeve close to the valve sleeve pilot port; A valve core, the valve core is arranged in the valve sleeve, the valve core can slide in the inner cavity of the valve sleeve under the action of the pilot pressure in the pilot control cavity, the valve core has a spring cavity, and a through hole is opened on the spring cavity so that when the spring is pressurized, the oil in the spring cavity can be discharged from the through hole; A spring, two ends of which are respectively in contact with the valve sleeve and the valve core, so that when there is no pilot pressure, the valve core always moves in the direction of closing the oil inlet of the valve sleeve.

3. A pilot-operated pressure reducing valve testing tool according to claim 1, characterized in that: The test valve block is detachably connected to the hydraulic platform.

4. A method for testing a pilot pressure reducing valve, based on a pilot pressure reducing valve testing tool as claimed in any one of claims 1 to 3, characterized in that: The steps include: S1, by starting the hydraulic platform, so that the pilot pressure reducing valve is connected with the hydraulic platform through the oil inlet of the valve block, the oil return port of the valve block, and the oil drain port of the valve block, and high-pressure oil is input into the oil inlet of the valve block and adjusted to the test pressure; S2. By adjusting the variable throttle valve 1, the pilot pressure reducing valve is disconnected from the oil inlet of the valve block, and the first pressure gauge value is the test pressure; by adjusting the variable throttle valve 2, the third pressure gauge value is 0 MPa, and the second pressure gauge value is approximately 0 MPa; observing the indication of the flow meter to determine whether the leakage amount between the valve sleeve oil inlet and the valve sleeve oil outlet of the pilot pressure reducing valve is qualified; S3, by adjusting the variable throttle valve 1, so that the pilot pressure reducing valve is connected to the oil inlet of the valve block, the value of the first pressure gauge is the test pressure, by adjusting the variable throttle valve 2, so that the values ​​of the third pressure gauge and the second pressure gauge are both the test pressure, observing the reading of the flow meter, to determine whether the leakage between the valve sleeve oil outlet and the valve sleeve oil return port of the pilot pressure reducing valve is qualified; S4, by adjusting the variable throttle valve 1, so that the pilot pressure reducing valve is connected to the oil inlet of the valve block, the first pressure gauge value is the test pressure, and by adjusting the variable throttle valve 2, the third pressure gauge value is slowly reduced from the test pressure; Observe that the second pressure gauge value decreases as the third pressure gauge value decreases, so as to determine whether the pressure reducing characteristic of the pilot-operated pressure reducing valve is qualified; S5. The pilot pressure reducing valve is connected to the oil inlet of the valve block by adjusting the variable throttle valve 1, and the first pressure gauge value is the test pressure. The variable throttle valve 2 is adjusted to make the third pressure gauge value slowly rise from 0 MPa to the minimum starting pressure of the pilot pressure reducing valve. The second pressure gauge value is observed to change from 0 MPa as the third pressure gauge value rises to the minimum starting pressure, so as to determine whether the minimum starting pressure of the pilot pressure reducing valve is qualified.

5. A pilot-operated pressure reducing valve testing method according to claim 4, characterized in that: The test pressure is greater than or equal to 21 MPa, and the minimum starting pressure is greater than 0.6 MPa.

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