A main valve core flow, displacement, and hydraulic force testing system and testing method

Abstract

The application discloses a kind of main valve core flow, displacement, hydraulic force test system and test method, comprising: two displacement sensors, the balanced valve to be measured, hydraulic test component;The main valve core of the balanced valve to be measured and the pilot valve core are coaxially arranged oppositely;Two displacement sensors are respectively fixed with main valve core, control piston coaxially;Hydraulic test component detects the pressure of return oil outlet A, load oil port B, feedback spring cavity pressure measuring port Pc, pilot oil inlet X by each pressure sensor;And by main load, pilot control, three oil circuits of return oil back pressure, load pressure, pilot pressure and return oil back pressure are controlled respectively, while return oil flow is measured by flowmeter simultaneously.The application can synchronously dynamically measure the flow, displacement and hydraulic force of main valve core under different working conditions.

Description

Technical Field

[0001] This invention relates to the field of hydraulic testing, and more particularly to a main valve core flow rate, displacement, and hydraulic dynamics testing system and method. Background Technology

[0002] Balance valves are primarily used in hydraulic systems with overload conditions to control the lowering speed of actuators. The stability of the main valve spool directly affects the safety of the actuator's lowering. When testing the performance of balance valves, the flow rate and displacement at the main valve port are key test parameters. To ensure the pressure-holding performance of the balance valve, the main valve spool often adopts a cone spool structure. When the loaded oil flows through the main valve spool, it generates significant hydraulic force, affecting the stability of the main valve spool. Current technology lacks a system and method for conducting full-condition testing of the hydraulic force of the main valve spool of a balance valve. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a testing system and method for testing the flow rate, displacement, and hydraulic dynamics of the main valve core.

[0004] The specific technical solution is as follows:

[0005] A main valve core flow, displacement, and hydraulic force testing system includes: a first displacement sensor, a tested balance valve, a second displacement sensor, and a hydraulic testing assembly; the tested balance valve includes a main valve body, a pilot valve body, and an end cap, which are sequentially fixed from front to back, as well as a main valve core and a pilot valve core arranged coaxially opposite to each other; the first displacement sensor is coaxially fixed to the front end of the main valve core, and the second displacement sensor is coaxially fixed to the disc of the control piston of the tested balance valve;

[0006] The main valve body of the tested balance valve is provided with a return oil port A, a load oil port B, and a feedback spring cavity pressure measuring port Pc. The pilot valve body is provided with a pilot drain port L, and the end cover is provided with a pilot inlet port X. The pilot drain port L is connected to the oil tank return oil.

[0007] The hydraulic testing assembly includes: a main load oil circuit, a pilot control oil circuit, a return oil back pressure oil circuit, and pressure sensors; the pressure sensors are used to detect the pressure at ports A, B, Pc, and X, respectively.

[0008] In the main load oil circuit, the inlet of the hydraulic power source is connected to the oil tank, and the outlet is connected to both the inlet and port B of the load pressure regulating unit via the main oil supply circuit; the outlet of the load pressure regulating unit returns to the oil tank.

[0009] In the pilot control oil circuit, the inlet of the pilot hydraulic power source is connected to the oil tank, and the outlet is connected to both the inlet of the pilot pressure regulating unit and the inlet of the pilot safety unit via the pilot oil supply circuit; the outlet of the pilot pressure regulating unit is connected to port X, and the outlet of the pilot safety unit returns to the oil tank.

[0010] In the back pressure oil circuit, the inlet of the back pressure regulating unit is connected to port A, and the outlet returns to the oil tank via the return oil flow detection unit.

[0011] Furthermore, in the tested balance valve, a cavity is opened in the main valve body, and a stepped through hole is axially opened in the pilot valve body. The stepped through hole includes a first cylindrical hole, a second cylindrical hole, a third cylindrical hole, and a fourth cylindrical hole from front to back. The main valve sleeve and the pilot valve sleeve are coaxially and tightly arranged in the internal cavity of the main valve body and the pilot valve body, forming axial and radial limits. The rear end portion of the pilot valve sleeve is located in the first cylindrical hole.

[0012] The main valve core is coaxially slidably arranged in the cavity inside the main valve sleeve, with its front end extending out of the main valve sleeve; the pilot valve core is coaxially slidably arranged in the cavity inside the pilot valve sleeve, and is coaxially opposite to the pilot valve core; the small diameter end of the pilot valve core extends rearward out of the pilot valve sleeve and is located in the second cylindrical hole.

[0013] The main valve core adopts a conical slide valve structure, and its front end forms a main valve port with the main valve sleeve; the connection between the large-diameter end and the small-diameter end of the pilot valve core forms a pilot valve port with the pilot valve sleeve; one end of the feedback spring abuts against the rear end of the main valve core, and the other end abuts against the large-diameter end of the pilot valve core; in the initial state, the preload of the feedback spring ensures that the main valve port and the pilot valve port are closed.

[0014] The control piston is arranged in the third and fourth cylindrical holes of the pilot valve body, forming a sliding fit with the pilot valve body; the disc part of the control piston is located on the rear side and is in contact with the end cover, and the shaft part is located at the front end, and is coaxially mounted with the small diameter end of the pilot valve core; one end of the pilot spring abuts against the disc part of the control piston, and the other end abuts against the pilot valve body. In the initial state, the preload of the pilot spring ensures that the control piston is in the closed state.

[0015] Furthermore, an annular groove is formed on the inner wall of the main valve body at a position corresponding to the middle of the main valve sleeve to form a load chamber, and the load oil port B on the main valve body is connected to the load chamber.

[0016] The cavity between the front end of the main valve core and the main valve body is a back pressure cavity, and the main valve return port A opened on the main valve body is connected to the back pressure cavity.

[0017] The cavity where the feedback spring is located is called the feedback spring cavity, and the feedback spring cavity pressure measuring port Pc opened on the main valve body is connected to the feedback spring cavity.

[0018] The pilot drain port L on the pilot valve body is connected to the cavity where the pilot spring is located.

[0019] A pilot control chamber is formed between the end cap and the control piston, and the pilot oil inlet X on the end cap is connected to the pilot control chamber.

[0020] Furthermore, the housing of the first displacement sensor is mounted on the main valve body, and the interior of the housing can withstand the hydraulic oil pressure. The movable iron core of the sensor passes through the main valve body and is fixed to the front end of the main valve core through a threaded connection, and the movable iron core of the sensor is coaxial with the main valve core.

[0021] Furthermore, the housing of the second displacement sensor is mounted on the end cover, and the interior of the housing can withstand hydraulic oil pressure. The movable iron core of the sensor passes through the end cover and is fixed to the disc of the control piston through a threaded connection, and the movable iron core of the sensor is coaxial with the control piston.

[0022] Furthermore, in the main load oil circuit, the hydraulic power source is a variable pump, and the load pressure regulating unit is a load proportional relief valve.

[0023] In the pilot control oil circuit, the pilot hydraulic power source is a gear pump, the pilot safety unit is a manual relief valve, and the pilot pressure regulating unit is a proportional pressure reducing valve.

[0024] In the back pressure oil circuit, the back pressure regulating unit is a back pressure proportional relief valve, and the back oil flow detection unit is a flow meter.

[0025] A method for testing the flow rate, displacement, and hydraulic dynamics of a main valve core, based on the aforementioned main valve core flow rate, displacement, and hydraulic dynamics testing system, includes the following steps:

[0026] S1: Arrange the main valve core flow, displacement, and hydraulic force testing system;

[0027] S2: Linearly select the back pressure value at the return port A of the measured balance valve to construct a preset back pressure value set N;

[0028] S3: Test the flow rate, displacement, and hydraulic force during a process where the load pressure remains constant and the pilot pressure changes;

[0029] S4: Test the flow rate, displacement, and hydraulic force during the process of constant pilot pressure and changing load pressure;

[0030] S5: Determine whether the test of all preset back pressure values ​​in set N has been completed. If not, adjust the return oil back pressure to a specific non-zero back pressure value in set N through the back pressure adjustment unit, and then repeat S2 and S3. If yes, output the flow rate, displacement and hydraulic force data of the main valve core under different return oil back pressure conditions.

[0031] Furthermore, the flow rate of the main valve core is detected by the return oil flow detection unit, and the displacement of the main valve core is detected by the first displacement sensor; the hydraulic force is the sum of the force exerted forward by the oil in the feedback spring chamber on the main valve core and the force exerted forward by the feedback spring on the main valve core, minus the force exerted backward by the oil in the load port on the main valve core and the force exerted backward by the oil in the return port on the main valve core; if the hydraulic force is greater than zero, the hydraulic force of the main valve core is forward; if the hydraulic force is less than zero, the hydraulic force of the main valve core is backward.

[0032] Furthermore, the force exerted by the oil in the feedback spring cavity on the main valve core is the product of the pressure at the Pc port and the area of ​​its action on the main valve core.

[0033] The force exerted by the oil at the load port on the main valve core is the product of the pressure at port B and the area of ​​its action on the main valve core.

[0034] The force exerted by the oil at the return port on the main valve core is the product of the pressure at port A and the area of ​​its action on the main valve core.

[0035] The force exerted by the feedback spring on the main valve core is the sum of the displacement of the main valve core and the displacement of the pilot valve core, multiplied by the spring stiffness of the feedback spring.

[0036] The beneficial effects of this invention are:

[0037] (1) The test system of the present invention can simultaneously measure the flow rate, displacement and hydraulic force of the main valve core.

[0038] (2) The present invention can dynamically test the changes in hydraulic force during the movement of the main valve core under different working conditions. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the main valve core flow, displacement, and hydraulic dynamics testing system in an embodiment of the present invention.

[0040] Figure 2 This is a flowchart of the main valve core flow rate, displacement, and hydraulic force testing method in an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the force on the main valve core in an embodiment of the present invention.

[0042] In the figure, the components are: first displacement sensor 1, tested balance valve 2, main valve core 2-1, pilot valve core 2-2, control piston 2-3, main valve body 2-4, pilot valve body 2-5, end cap 2-6, feedback spring 2-7; second displacement sensor 3, hydraulic test assembly 4, variable pump 4-1, load proportional relief valve 4-2, back pressure proportional relief valve 4-3, flow meter 4-4, gear pump 4-5, manual relief valve 4-6, proportional pressure reducing valve 4-7, first pressure sensor 4-8, second pressure sensor 4-9, third pressure sensor 4-10, and fourth pressure sensor 4-11. Detailed Implementation

[0043] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The objectives and effects of the present invention will become clearer as a result. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0044] like Figure 1 As shown, a main valve core flow, displacement, and hydraulic force testing system includes: a first displacement sensor 1, a tested balance valve 2, a second displacement sensor 3, and a hydraulic testing assembly 4. The tested balance valve 2 must satisfy the following requirement: the main valve core 2-1 and the pilot valve core 2-2 are arranged coaxially.

[0045] In this embodiment, the tested balance valve 2 includes: a main valve core 2-1, a pilot valve core 2-2, a control piston 2-3, a main valve body 2-4, a pilot valve body 2-5, an end cap 2-6, and a feedback spring 2-7. The main valve body 2-4, pilot valve body 2-5, and end cap 2-6 are coaxially fixed and sealed from front to back. The main valve body 2-4 and pilot valve body 2-5 constitute a total valve body. Both the main valve body 2-4 and pilot valve body 2-5 have cavities that are interconnected, forming a total valve cavity. The pilot valve body 2-5 has a stepped through-hole axially formed inside, which, from front to back, includes a first cylindrical hole, a second cylindrical hole, a third cylindrical hole, and a fourth cylindrical hole.

[0046] The main valve sleeve and pilot valve sleeve are coaxially arranged in the main valve cavity from front to back, forming axial and radial limits between them and between them and the main valve body. An annular groove is formed on the inner wall of the main valve body 2-4 at a position corresponding to the middle of the main valve sleeve, forming a load cavity between them. Several radial through holes are formed circumferentially in the middle of the main valve sleeve, connecting the load cavity to the internal cavity of the main valve sleeve. The front end of the pilot valve sleeve is located inside the main valve body 2-4, and the rear end is arranged in the first cylindrical hole of the pilot valve body 2-5. The main valve core 2-1 is coaxially slidably arranged in the internal cavity of the main valve sleeve, with its front end extending out of the main valve sleeve; the cavity between this part and the main valve body 2-4 is a back pressure cavity. The pilot valve core 2-2 is coaxially slidably arranged in the internal cavity of the pilot valve sleeve, with its small-diameter end extending rearward from the pilot valve sleeve and located in the second cylindrical hole. The main valve core 2-1 and the pilot valve core 2-2 are coaxially opposite each other.

[0047] The main valve core 2-1 adopts a conical slide valve structure, and the front end of the main valve core 2-1 forms the main valve port between itself and the main valve sleeve; the connection between the large-diameter end and the small-diameter end of the pilot valve core 2-2 (referred to as the middle section) forms the pilot valve port between itself and the pilot valve sleeve. One end of the feedback spring 2-7 abuts against the rear end of the main valve core 2-1, and the other end abuts against the large-diameter end of the pilot valve core 2-2. It has a certain preload in the initial state to ensure that both the main valve port and the pilot valve port are in a tightly closed state without leakage, and to realize mechanical feedback between the main valve core 2-1 and the pilot valve core 2-2, so that the two influence each other; the cavity where the feedback spring 2-7 is located is referred to as the feedback spring cavity.

[0048] The control piston 2-3 is arranged in the third and fourth cylindrical holes of the pilot valve body 2-5, forming a sliding fit with the pilot valve body 2-5. The disc portion of the control piston 2-4 is located on the rear side and abuts against the end cover 2-6, while the shaft portion is located at the front end and is coaxially mounted with the small-diameter end of the pilot valve core 2-2. A pilot control chamber is formed between the end cover 2-6 and the control piston 2-3. In the initial state, there is a clearance distance between the shaft portion of the control piston 2-4 and the small-diameter end of the pilot valve core 2-2 to ensure that the initial position of the pilot valve core 2-2 is not affected by the control piston 2-4. One end of the pilot spring abuts against the disc portion of the control piston 2-4, and the other end abuts against the pilot valve body 2-5 (i.e., the front end face of the third cylindrical hole). In the initial state, the pilot spring has a certain preload to ensure that the control piston 2-3 is in the closed state.

[0049] The main valve body 2-4 has a main valve return port A connected to the back pressure chamber, and a load port B connected to the load chamber via external load oil. The main valve body 2-4 and the main valve sleeve have corresponding through holes connected to the feedback spring chamber, forming the feedback spring chamber pressure measuring port Pc. The pilot valve body 2-5 has a pilot drain port L connected to the cavity where the pilot spring is located, and the end cover 2-6 has a pilot inlet port X connected to the pilot control pressure source via external pilot control chamber.

[0050] The housing of the first displacement sensor 1 is installed on the main valve body 2-4 of the balance valve being tested. The inside of the sensor housing can withstand the hydraulic oil pressure. The movable iron core of the sensor passes through the main valve body 2-4 and is fixed to the front end of the main valve core 2-1 of the balance valve through a threaded connection. The movable iron core of the sensor is coaxial with the main valve core 2-1. The housing of the second displacement sensor 3 is installed on the end cover 2-6 on the right end of the balance valve being tested. The inside of the sensor housing can withstand the hydraulic oil pressure. The movable iron core of the sensor passes through the end cover 2-6 and is fixed to the disc of the control piston 2-3 through a threaded connection. The movable iron core of the sensor is coaxial with the control piston 2-3.

[0051] The hydraulic testing system component 4 includes: a hydraulic source (variable pump 4-1 in this embodiment), a load pressure regulating unit (load proportional relief valve 4-2), a back pressure regulating unit (back pressure proportional relief valve 4-3), a return oil flow detection unit (flow meter 4-4), a pilot hydraulic source (gear pump 4-5), a pilot safety unit (manual relief valve 4-6), a pilot pressure regulating unit (proportional pressure reducing valve 4-7), a first pressure sensor 4-8, a second pressure sensor 4-9, a third pressure sensor 4-10, and a fourth pressure sensor 4-11.

[0052] The A port of the balanced valve under test is connected to the inlet of the back pressure proportional relief valve 4-3 through a pipeline. A first pressure sensor 4-8 is installed on this section of the pipeline to detect the pressure at the A port in real time. The outlet of the back pressure proportional relief valve 4-3 is connected to the oil tank through a pipeline, and a flow meter 4-4 is installed on this section of the pipeline.

[0053] The inlet of the variable pump 4-1 is connected to the oil tank, and its outlet is connected to the first main pipeline. The first main pipeline is divided into a first branch pipeline and a second branch pipeline. The first branch pipeline is connected to the load port B of the balanced valve under test. The second pressure sensor 4-9 is installed on the first branch pipeline to detect the pressure at port B in real time. The second branch pipeline is connected to the inlet of the load proportional relief valve 4-2, and the outlet of the load proportional relief valve 4-2 is also connected to the oil tank.

[0054] The Pc port of the balanced valve under test is connected to the fourth pressure sensor 4-11 for real-time detection of the Pc port pressure; the L port is connected to the oil return from the oil tank.

[0055] The inlet of gear pump 4-5 is connected to the oil tank, and its outlet is connected to the second main pipeline. The second main pipeline is divided into a third branch pipeline and a fourth branch pipeline. The third branch pipeline is connected to the inlet of proportional pressure reducing valve 4-7. The outlet of proportional pressure reducing valve 4-7 is connected to the pilot inlet X port of the measured balance valve through a pipeline. The third pressure sensor 4-10 is installed in this pipeline passage to detect the pressure at port X in real time. The fourth branch pipeline is connected to the inlet of manual relief valve 4-6. The outlet of manual relief valve 4-6 is also connected to the oil tank.

[0056] The pressure at port B can be controlled by adjusting the current of the load proportional relief valve 4-2, the back pressure of the return oil at port A can be changed by adjusting the back pressure proportional relief valve 4-3, and the pressure at port X can be controlled by adjusting the proportional pressure reducing valve 4-7. The first pressure sensor 4-8 measures the pressure at port A, the second pressure sensor 4-9 measures the pressure at port B, the third pressure sensor 4-10 measures the pressure at port X, and the fourth pressure sensor 4-11 measures the pressure at port Pc.

[0057] like Figure 2 As shown, based on the above-mentioned main valve core flow, displacement, and hydraulic dynamics testing system, this embodiment also proposes a main valve core flow, displacement, and hydraulic dynamics testing method, including the following steps:

[0058] S1: Set up the above-mentioned main valve core flow, displacement, and hydraulic force test system.

[0059] S2: Linearly select the back pressure value of the main valve return port A of the tested balance valve to construct a preset back pressure value set N.

[0060] S3: Flow rate, displacement, and hydraulic dynamics test during pilot pressure change with constant load pressure: Adjust the load proportional relief valve 4-2 to maintain the pressure at port B at a fixed value, set the back pressure proportional relief valve 4-3 to zero pressure, and adjust the current of the three-way proportional pressure reducing valve 4-7 to linearly load the pressure at port X from 0 to 2MPa at a certain slope (i.e., linearly load from 0 to 2MPa at a certain slope), and then linearly reduce the pressure from 2MPa to 0MPa. During the pilot pressure change, the test system records the displacement of the main valve core 2-1, the displacement of the pilot valve core 2-2, and the pressure at port A (P) in real time through two sets of displacement sensors (first displacement sensor 1 and second displacement sensor 3), four sets of pressure sensors (first pressure sensor 4-8, second pressure sensor 4-9, third pressure sensor 4-10, and fourth pressure sensor 4-11), and the flow meter 4-4. A ), B-port pressure (P) B ), Pc chamber pressure (P C The pressure at port X and the return oil flow rate are used to test the flow rate and displacement of the main valve core 2-1 under this operating condition, and the hydraulic force is calculated in real time based on these data. The above test process can be repeated by changing the pressure value at port B.

[0061] S4: Flow rate, displacement, and hydraulic force test during load pressure variation with constant pilot pressure: Adjust proportional pressure reducing valve 4-7 to maintain the pressure at port X at a fixed value, which must be greater than the pilot pressure that the main valve core 2-1 can open. Set the back pressure proportional relief valve 4-3 to zero pressure. Adjust the current of the load proportional relief valve 4-2 to linearly load the pressure at port B from 0-30MPa at a certain slope, and then linearly reduce it from 30MPa-0MPa. The test system records the displacement of the main valve core 2-1, the displacement of the pilot valve core 2-2, and the pressure at port A (P) in real time through two sets of displacement sensors, four sets of pressure sensors, and a flow meter. A ), B-port pressure (P) B The system measures the pressure in the Pc chamber, the pressure at the X port, and the return oil flow rate to test the flow rate and displacement of the main valve core 2-1 under this operating condition, and calculates the hydraulic force in real time based on these data. The test process can be repeated by changing the pressure value at the X port.

[0062] S5: Determine whether the test of all preset back pressure values ​​in set N has been completed. If not, perform flow rate, displacement and hydraulic force tests under different return oil back pressures. That is, by adjusting the pressure of back pressure relief valve 4-3, change the return oil back pressure of the tested balance valve to a specific non-zero back pressure value in set N, and repeat the test process of S2 and S3. If yes, output the complete performance data of main valve core 2-1 under different return oil back pressure conditions (including flow rate, displacement and hydraulic force).

[0063] During the S3-S5 process, the flow rate and displacement (X) of the main valve core 2-1 under different operating conditions. m The displacement can be directly read by the first displacement sensor 1 and the flow meter 4-4. After the main valve core 2-1 is opened, the pilot valve core 2-2 of the measured balance valve is pressed against the control piston 2-3, and the displacement of the pilot valve core (X) is measured. p The displacement can be read by the second displacement sensor 3; however, the hydraulic force of the main valve core 2-1 cannot be directly detected, such as... Figure 3 As shown, this embodiment proposes a method for calculating the hydraulic force Y of the main valve core 2-1 based on the pressures at ports A, B, and Pc. The expression is as follows:

[0064] ;

[0065] ;

[0066] In the formula, A2 is the area of ​​the main valve return port pressure acting on the main valve core 2-1, (A1-A2) is the area of ​​the load pressure acting on the main valve core 2-1, and A3 is the area of ​​the feedback spring chamber pressure acting on the main valve core 2-1; P A The pressure at port A (i.e., the pressure at the main valve return port) is P. B For the pressure at port B (i.e., the load pressure), P CFor the Pc port pressure (i.e., the feedback spring chamber pressure), F k The force exerted by the feedback spring 2-7 on the main valve core 2-1; k f To provide feedback on the spring stiffness of springs 2-7, X m Main valve core 2-1 displacement, X p For the displacement of pilot valve core 2-2.

[0067] When the calculated hydraulic force Y value is greater than 0, the hydraulic force direction of the main valve core 2-1 is forward (i.e., on the left side of the figure); when the Y value is less than 0, the hydraulic force direction of the main valve core 2-1 is backward (i.e., on the right side of the figure).

[0068] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A main valve core flow rate, displacement, and hydraulic dynamics testing system, characterized in that, include: The test components include a first displacement sensor, a balanced valve under test, a second displacement sensor, and a hydraulic testing assembly. The balanced valve under test comprises a main valve body, a pilot valve body, and an end cap, which are sequentially fixed from front to back, as well as a main valve core and a pilot valve core arranged coaxially opposite to each other. The first displacement sensor is coaxially fixed to the front end of the main valve core, and the second displacement sensor is coaxially fixed to the disc of the control piston of the balanced valve under test. The main valve body of the tested balance valve is provided with a return oil port A, a load oil port B, and a feedback spring cavity pressure measuring port Pc. The pilot valve body is provided with a pilot drain port L, and the end cover is provided with a pilot inlet port X. The pilot drain port L is connected to the oil tank return oil. The hydraulic testing assembly includes: a main load oil circuit, a pilot control oil circuit, a return oil back pressure oil circuit, and pressure sensors; the pressure sensors are used to detect the pressure at ports A, B, Pc, and X, respectively. In the main load oil circuit, the inlet of the hydraulic power source is connected to the oil tank, and the outlet is connected to both the inlet and port B of the load pressure regulating unit via the main oil supply circuit; the outlet of the load pressure regulating unit returns to the oil tank. In the pilot control oil circuit, the inlet of the pilot hydraulic power source is connected to the oil tank, and the outlet is connected to both the inlet of the pilot pressure regulating unit and the inlet of the pilot safety unit via the pilot oil supply circuit; the outlet of the pilot pressure regulating unit is connected to port X, and the outlet of the pilot safety unit returns to the oil tank. In the back pressure oil circuit, the inlet of the back pressure regulating unit is connected to port A, and the outlet returns to the oil tank via the return oil flow detection unit.

2. The main valve core flow rate, displacement, and hydraulic dynamics testing system according to claim 1, characterized in that, In the tested balance valve, the main valve body has a cavity, and the pilot valve body has a stepped through hole axially arranged inside. The stepped through hole includes a first cylindrical hole, a second cylindrical hole, a third cylindrical hole, and a fourth cylindrical hole from front to back. The main valve sleeve and the pilot valve sleeve are coaxially and tightly arranged in the internal cavity of the main valve body and the pilot valve body, forming axial and radial limits. The rear end of the pilot valve sleeve is located in the first cylindrical hole. The main valve core is coaxially slidably arranged in the cavity inside the main valve sleeve, with its front end extending out of the main valve sleeve; the pilot valve core is coaxially slidably arranged in the cavity inside the pilot valve sleeve, and is coaxially opposite to the main valve core; the small diameter end of the pilot valve core extends rearward out of the pilot valve sleeve and is located in the second cylindrical hole. The main valve core adopts a conical slide valve structure, and its front end forms a main valve port with the main valve sleeve; the connection between the large-diameter end and the small-diameter end of the pilot valve core forms a pilot valve port with the pilot valve sleeve; one end of the feedback spring abuts against the rear end of the main valve core, and the other end abuts against the large-diameter end of the pilot valve core; in the initial state, the preload of the feedback spring ensures that the main valve port and the pilot valve port are closed. The control piston is arranged in the third and fourth cylindrical holes of the pilot valve body, forming a sliding fit with the pilot valve body; the disc part of the control piston is located on the rear side and is in contact with the end cover, and the shaft part is located at the front end, and is coaxially mounted with the small diameter end of the pilot valve core; one end of the pilot spring abuts against the disc part of the control piston, and the other end abuts against the pilot valve body. In the initial state, the preload of the pilot spring ensures that the control piston is in the closed state.

3. The main valve core flow rate, displacement, and hydraulic dynamics testing system according to claim 2, characterized in that, An annular groove is formed on the inner wall of the main valve body at a position corresponding to the middle of the main valve sleeve, forming a load chamber. The load oil port B on the main valve body is connected to the load chamber. The cavity between the front end of the main valve core and the main valve body is a back pressure cavity, and the main valve return port A opened on the main valve body is connected to the back pressure cavity. The cavity where the feedback spring is located is called the feedback spring cavity, and the feedback spring cavity pressure measuring port Pc opened on the main valve body is connected to the feedback spring cavity. The pilot drain port L on the pilot valve body is connected to the cavity where the pilot spring is located. A pilot control chamber is formed between the end cap and the control piston, and the pilot oil inlet X on the end cap is connected to the pilot control chamber.

4. The main valve core flow rate, displacement, and hydraulic dynamics testing system according to claim 1, characterized in that, The housing of the first displacement sensor is mounted on the main valve body. The housing can withstand the hydraulic oil pressure. The movable iron core of the sensor passes through the main valve body and is fixed to the front end of the main valve core through a threaded connection. The movable iron core of the sensor is coaxial with the main valve core.

5. The main valve core flow rate, displacement, and hydraulic dynamics testing system according to claim 1, characterized in that, The housing of the second displacement sensor is mounted on the end cover. The housing can withstand hydraulic oil pressure. The movable iron core of the sensor passes through the end cover and is fixed to the disc of the control piston by a threaded connection. The movable iron core of the sensor is coaxial with the control piston.

6. The main valve core flow rate, displacement, and hydraulic dynamics testing system according to claim 1, characterized in that, In the main load oil circuit, the hydraulic power source is a variable pump, and the load pressure regulating unit is a load proportional relief valve. In the pilot control oil circuit, the pilot hydraulic power source is a gear pump, the pilot safety unit is a manual relief valve, and the pilot pressure regulating unit is a proportional pressure reducing valve. In the back pressure oil circuit, the back pressure regulating unit is a back pressure proportional relief valve, and the back oil flow detection unit is a flow meter.

7. A method for testing the flow rate, displacement, and hydraulic dynamics of a main valve core, implemented based on the main valve core flow rate, displacement, and hydraulic dynamics testing system according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Arrange the main valve core flow, displacement, and hydraulic force testing system; S2: Linearly select the back pressure value at the return port A of the measured balance valve to construct a preset back pressure value set N; S3: Test the flow rate, displacement, and hydraulic force during a process where the load pressure remains constant and the pilot pressure changes; S4: Test the flow rate, displacement, and hydraulic force during the process of constant pilot pressure and changing load pressure; S5: Determine whether the test of all preset back pressure values ​​in set N has been completed. If not, adjust the return oil back pressure to a specific non-zero back pressure value in set N through the back pressure adjustment unit, and then repeat S2 and S3. If yes, output the flow rate, displacement and hydraulic force data of the main valve core under different return oil back pressure conditions. The flow rate of the main valve core is detected by the return oil flow detection unit, and the displacement of the main valve core is detected by the first displacement sensor; the hydraulic force is the sum of the force of the oil in the feedback spring chamber acting forward on the main valve core and the force of the feedback spring acting forward on the main valve core, minus the force of the oil in the load port acting backward on the main valve core and the force of the oil in the return port acting backward on the main valve core. If the hydraulic force is greater than zero, the hydraulic force of the main valve core is directed forward. If the hydraulic force is less than zero, the hydraulic force of the main valve core will be directed backward.

8. The method for testing the flow rate, displacement, and hydraulic dynamics of the main valve core according to claim 7, characterized in that, The force exerted by the oil in the feedback spring cavity on the main valve core is the product of the pressure at the Pc port and the area of ​​its action on the main valve core. The force exerted by the oil at the load port on the main valve core is the product of the pressure at port B and the area of ​​its action on the main valve core. The force exerted by the oil at the return port on the main valve core is the product of the pressure at port A and the area of ​​its action on the main valve core. The force exerted by the feedback spring on the main valve core is the sum of the displacement of the main valve core and the displacement of the pilot valve core, multiplied by the spring stiffness of the feedback spring.

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