A hydraulic cylinder testing device and testing method

Abstract

This invention relates to a testing apparatus and method for a hydraulic cylinder. The hydraulic cylinder testing apparatus includes: an oil tank; a rod-side port with a first pressure gauge installed at the rod-side port; a rodless-side port with a second pressure gauge installed at the rodless-side port; a directional valve assembly for adjusting the opening and closing of the connecting oil circuits of the rod-side and rodless-side ports; a hydraulic pump connected to the oil tank and connected to both the rod-side and rodless-side ports via the directional valve assembly, with a third pressure gauge installed at the pump's outlet; and a throttle valve connected to the oil tank and connected to both the rod-side and rodless-side ports via the directional valve assembly, with a fourth pressure gauge installed at the throttle valve's inlet. The testing apparatus of this invention can achieve a single connection with the hydraulic cylinder, conveniently completing hydraulic cylinder venting, trial operation, and full unloading after testing, and can test the performance of the hydraulic cylinder under pressure resistance, external leakage, internal leakage, and starting pressure conditions.

Description

Technical Field

[0001] This invention relates to the field of hydraulic testing technology, specifically to a hydraulic cylinder testing device and testing method. Background Technology

[0002] Single-rod double-acting hydraulic cylinders are the most widely used type of hydraulic cylinder in hydraulic systems. The performance of single-rod double-acting hydraulic cylinders affects the operation and efficiency of hydraulic systems, so testing the various performance characteristics of this type of hydraulic cylinder is particularly important.

[0003] The testing methods for single-rod double-acting hydraulic cylinders are divided into two types: single-cylinder and double-cylinder drag (or top) tests. Double-cylinder tests place higher demands on the test bench, requiring it to withstand higher loading forces and accommodate test specimens with different installation types, installation distances, and strokes. The test specimens are typically difficult to disassemble and assemble. In single-cylinder tests, the oil port has multiple connection states, requiring frequent changes to the port state during the test, resulting in cumbersome operation and low efficiency. Summary of the Invention

[0004] In view of this, the present invention provides a hydraulic cylinder testing device and testing method, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems existing in the prior art.

[0005] To achieve the aforementioned objective, a first aspect of the present invention provides a hydraulic cylinder testing apparatus, wherein the hydraulic cylinder testing apparatus comprises:

[0006] Oil tank, the oil tank being used for supplying and recovering oil;

[0007] A rod chamber interface is provided for connecting to the rod chamber of the hydraulic cylinder under test. The rod chamber interface is used for introducing and discharging oil, and a first pressure gauge is provided at the rod chamber interface for measuring the pressure at the rod chamber interface.

[0008] A rodless cavity interface is provided for connecting to the rodless cavity of the hydraulic cylinder under test. The rodless cavity interface introduces and discharges oil, and a second pressure gauge is provided at the rodless cavity interface for measuring the pressure at the rodless cavity interface.

[0009] The reversing valve assembly is used to adjust the opening and closing of the connecting oil circuit of the rod chamber interface and the rodless chamber interface. The reversing valve assembly is used to adjust the test device to make it suitable for performance testing of the hydraulic cylinder under exhaust, trial operation, unloading, pressure resistance and external leakage, internal leakage and starting pressure conditions.

[0010] A hydraulic pump, the oil inlet of which is connected to the oil tank, the oil outlet of which is guided to the oil circuit and connected to the rod chamber interface and the rodless chamber interface respectively through the reversing valve group, and a third pressure gauge is provided at the oil outlet of the hydraulic pump;

[0011] A throttle valve is provided, with its outlet connected to the oil tank and its inlet connected to the oil circuit via the directional valve assembly, which in turn connects to the rod-side port and the rodless-side port respectively. A fourth pressure gauge is also provided at the inlet of the throttle valve.

[0012] In the test apparatus described above, optionally, the reversing valve assembly includes:

[0013] The first and second positions normally closed reversing valve is connected to the rodless chamber interface and the oil tank.

[0014] The second two-position two-normally closed reversing valve is connected to the rodless chamber interface and the throttle valve.

[0015] The third two-position two-normally closed reversing valve is connected to the rod chamber interface and the throttle valve;

[0016] The fourth two-position two-normally closed reversing valve is connected to the rod chamber interface and the oil tank;

[0017] The first and second normally open directional control valves are connected to the rodless chamber interface and, via a three-position four-way directional control valve, to the hydraulic pump and the oil tank; and

[0018] The second two-position two-way normally open directional valve is connected to the rod chamber interface and, through the three-position four-way directional valve, to the hydraulic pump and the oil tank.

[0019] In the test apparatus described above, optionally, the oil circuit connecting the first two-position two-normally closed directional valve to the rodless cavity interface, the oil circuit connecting the second two-position two-normally closed directional valve to the rodless cavity interface, and the oil circuit connecting the first two-position two-normally open directional valve to the rodless cavity interface are connected in pairs.

[0020] The oil circuit connecting the third two-position two normally closed directional valve to the rod chamber interface, the oil circuit connecting the fourth two-position two normally closed directional valve to the rod chamber interface, and the oil circuit connecting the second two-position two normally open directional valve to the rod chamber interface are connected in pairs.

[0021] The oil circuit connecting the second two-position two-normally closed directional valve and the throttle valve is connected to the oil circuit connecting the third two-position two-normally closed directional valve and the throttle valve.

[0022] The connecting oil circuit of the rodless cavity interface is symmetrically arranged with respect to the connecting oil circuit of the rod cavity interface.

[0023] In the test apparatus described above, optionally, the oil tank includes a first oil tank connected to the hydraulic pump and the three-position four-way directional valve, a second oil tank connected to the throttle valve, a third oil tank connected to the first two-position two-normally closed directional valve, and a fourth oil tank connected to the fourth two-position two-normally closed directional valve.

[0024] In the test apparatus described above, optionally, the throttle valve is connected to a first relief valve leading to the oil tank; and the hydraulic pump is connected to a second relief valve leading to the oil tank.

[0025] To achieve the aforementioned objective, a second aspect of the present invention provides a method for testing a hydraulic cylinder using the testing apparatus described in the first aspect of the present invention, wherein the rod chamber of the hydraulic cylinder under test is connected to the rod chamber interface, and the rodless chamber of the hydraulic cylinder under test is connected to the rodless chamber interface.

[0026] In the test method described above, optionally, during the exhaust test:

[0027] Adjust the throttle valve to open a small opening, energize the third two-position two normally closed directional valve, and fill the rod chamber of the hydraulic cylinder under test with oil until the oil output from the throttle valve outlet is stable, and de-energize the third two-position two normally closed directional valve.

[0028] The second normally closed directional valve is energized to supply oil to the rodless chamber of the hydraulic cylinder under test until the oil output from the outlet of the throttle valve is stable, and the second normally closed directional valve is de-energized.

[0029] The second normally closed directional valve is de-energized, and oil is introduced into the rod chamber of the hydraulic cylinder under test until the piston rod is fully retracted.

[0030] In the test method described above, optionally, during the trial operation test: the three-position four-way directional valve controls the piston rod of the hydraulic cylinder under test to reciprocate throughout its full stroke, and the pressure curves of the first pressure gauge and the second pressure gauge are recorded and observed during the reciprocating motion. The processing and assembly quality of the hydraulic cylinder under test is judged based on the flatness of the pressure curves.

[0031] In the test method described above, optionally, when performing the pressure resistance and external leakage condition tests:

[0032] Extend the piston rod of the hydraulic cylinder under test to its full extent, adjust the pressure resistance test pressure of the rodless chamber of the hydraulic cylinder under test, energize the first and second normally open directional valves, close the rodless chamber of the hydraulic cylinder under test, stop the oil supply to the rodless chamber, and record and observe the pressure of the second pressure gauge.

[0033] The piston rod of the hydraulic cylinder under test is fully retracted. The pressure resistance test pressure of the rod chamber of the hydraulic cylinder under test is adjusted. The second normally open directional valve is energized, the rod chamber of the hydraulic cylinder under test is closed, the oil supply to the rod chamber is stopped, and the pressure of the first pressure gauge is recorded and observed.

[0034] Based on the pressure drop of the second and first pressure gauges, determine whether there is an external leak.

[0035] In the test method described above, optionally, when performing the internal leakage condition test:

[0036] During the piston rod retraction process of the hydraulic cylinder under test, several test points are selected so that the first two-position normally open directional valve is energized, the rodless chamber of the hydraulic cylinder under test is closed, and oil is supplied to the rod chamber of the hydraulic cylinder under test to the rated pressure. The piston rod is observed to see if it extends. The pressure ratio between the rodless chamber and the rod chamber and the closeness of the pressure ratio to the piston area ratio between the rodless chamber and the rod chamber are observed by the second pressure gauge and the first pressure gauge, and the presence of internal leakage is determined accordingly.

[0037] In the test method described above, optionally, the starting pressure state test includes a starting pressure test of the rod chamber and a starting pressure test of the rodless chamber, wherein:

[0038] During the starting pressure test of the rod chamber, the first two-position two-normally open directional valve, the first two-position two-normally closed directional valve, and the third two-position two-normally closed directional valve are energized, oil enters the rod chamber, and the rodless chamber is opened through the first two-position two-normally closed directional valve. By adjusting the opening of the throttle valve or the oil flow rate, the pressure of the rod chamber is adjusted to the point where the piston rod of the hydraulic cylinder under test moves. The pressure change of the rod chamber throughout the process is recorded using the fourth pressure gauge.

[0039] During the starting pressure test of the rodless chamber, the second normally open directional valve, the second normally closed directional valve, and the fourth normally closed directional valve are energized, oil enters the rodless chamber, and the rod chamber is opened through the fourth normally closed directional valve. By adjusting the opening of the throttle valve or the oil flow rate, the pressure of the rodless chamber is adjusted to the point that the piston rod of the hydraulic cylinder under test moves. The pressure change of the rodless chamber throughout the entire process is recorded using the fourth pressure gauge.

[0040] In the test method described above, optionally, after the test is completed, the first two-position two-normally closed reversing valve and the fourth two-position two-normally closed reversing valve are energized, the rodless chamber is fully unloaded by opening the first two-position two-normally closed reversing valve, and the rod chamber is fully unloaded by opening the fourth two-position two-normally closed reversing valve.

[0041] The hydraulic cylinder testing device of the present invention has a simple structure. The test circuit of the hydraulic cylinder testing device is composed of various reversing valves, so as to realize the hydraulic cylinder and the testing device in one connection. The venting and test operation of the hydraulic cylinder can be completed, and the hydraulic cylinder can be tested for pressure resistance, external leakage, internal leakage and starting pressure. Attached Figure Description

[0042] The disclosure of this invention will become more apparent from the accompanying drawings. It should be understood that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings:

[0043] Figure 1 This is a schematic diagram of one embodiment of the hydraulic cylinder testing device of the present invention;

[0044] Figure 2 for Figure 1 A schematic diagram illustrating the principle of connecting the hydraulic cylinder to be tested in an embodiment of the hydraulic cylinder testing apparatus.

[0045] Reference numerals in the attached diagram: 1-Rod chamber interface; 2-Rodless chamber interface; 3-Hydraulic pump; 4-Throttle valve; 5-First pressure gauge; 6-Second pressure gauge; 7-Third pressure gauge; 8-Fourth pressure gauge; 11-First two-position two-normally closed directional control valve; 12-Second two-position two-normally closed directional control valve; 13-Third two-position two-normally closed directional control valve; 14-Fourth two-position two-normally closed directional control valve; 15-First two-position two-normally open directional control valve; 16-Second two-position two-normally open directional control valve; 17-Three-position four-way directional control valve; 18-First relief valve; 19-Second relief valve; 20-Hydraulic cylinder under test; 21-Rod chamber; 22-Rodless chamber; 23-First oil tank; 24-Second oil tank; 25-Third oil tank; 26-Fourth oil tank; 27-Piston; 28-Piston rod. Detailed Implementation

[0046] Referring to the accompanying drawings and specific embodiments, the structure, composition, features, and advantages of the hydraulic cylinder testing apparatus and testing method of the present invention will be described below by way of example. However, all descriptions should not be construed as limiting the present invention in any way.

[0047] Furthermore, for any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature shown or implied in the various figures, the present invention still allows for any combination or deletion of these technical features (or their equivalents) without any technical obstacle, and thus these further embodiments according to the present invention should also be considered within the scope of this description.

[0048] It should also be noted that the terms "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship of the hydraulic cylinder test device shown in the accompanying drawings. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0049] Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," "third," or "fourth" may explicitly or implicitly include at least one of those features.

[0050] Figure 1 This is a schematic diagram of one embodiment of the hydraulic cylinder testing device of the present invention.

[0051] The hydraulic cylinder testing device of the present invention can perform exhaust test, trial run test, pressure resistance and external leakage test, internal leakage test and starting pressure test on the hydraulic cylinder under test, and unload after the test is completed.

[0052] To conduct the above experiments, from Figure 1 As can be seen from the embodiments, the hydraulic cylinder testing device is provided with a rod chamber interface 1 that connects to the rod chamber of the hydraulic cylinder under test and a rodless chamber interface 2 that connects to the rodless chamber of the hydraulic cylinder under test. The hydraulic cylinder testing device forms the inlet and outlet oil passages, exhaust oil passages and open oil passages for the rod chamber and the rodless chamber respectively through the combination of oil tank, reversing valve group, hydraulic pump 3 and throttle valve 4, thereby forming the test circuit for various tests.

[0053] In such Figure 1 In one embodiment, a first pressure gauge 5 for measuring the oil pressure at the rod-side interface 1 is provided at the rod-side interface 1, and a second pressure gauge 6 for measuring the pressure at the rodless interface 2 is provided at the rodless interface 2. The performance of the hydraulic cylinder under test can be evaluated under various tests by measuring the curves of the first pressure gauge 5 and the second pressure gauge 6.

[0054] A third pressure gauge 7 is provided at the oil outlet of the hydraulic pump 3 to measure the hydraulic pressure at the oil outlet of the hydraulic pump 3. The third pressure gauge 7 measures the pressure at the oil outlet of the hydraulic pump 3. In an optional embodiment, the hydraulic pump 3 is connected to a second relief valve 19 leading to the oil tank. The second relief valve 19 can both adjust the pressure at the oil outlet of the hydraulic pump 3 to meet the test requirements and ensure that the hydraulic pump 3 operates normally under reasonable oil pressure without being damaged.

[0055] A fourth pressure gauge 8 is provided at the oil inlet of the throttle valve 4. The opening of the throttle valve 4 can be adjusted to the pressure value required for the test based on the measurement value of the fourth pressure gauge 8. Furthermore, the fourth pressure gauge 8 is connected to a first relief valve 18 that leads to the oil tank. The first relief valve 18 ensures that the fourth pressure gauge 8 operates normally and is not damaged under reasonable oil pressure.

[0056] according to Figure 1 In one embodiment, the oil tank includes a first oil tank 23, a second oil tank 24, a third oil tank 25, and a fourth oil tank 26; the reversing valve assembly includes a first two-position two-way normally closed reversing valve 11, a second two-position two-way normally closed reversing valve 12, a third two-position two-way normally closed reversing valve 13, a fourth two-position two-way normally closed reversing valve 14, a first two-position two-way normally open reversing valve 15, a second two-position two-way normally open reversing valve 16, and a three-position four-way reversing valve 17. In an optional embodiment, the first oil tank 23, the second oil tank 24, the third oil tank 25, and the fourth oil tank 26 can be the same oil tank.

[0057] The oil inlet and outlet circuits of the rod chamber are as follows: A second two-position two-way normally open directional valve 16 and a three-position four-way directional valve 17 are sequentially connected from the rod chamber interface 1. The three-position four-way directional valve 17 allows selective connection to one of two paths: one path connects to the first oil tank 23 to discharge oil from the oil circuit; the other path connects to the first oil tank 23 via a hydraulic pump 3, allowing oil from the first oil tank 23 to be drawn into the oil circuit. The second two-position two-way normally open directional valve 16 can open or close the oil inlet and outlet circuits of the rod chamber according to test requirements.

[0058] During the test, when oil enters the rod chamber, the oil is drawn from the first oil tank 23 by the hydraulic pump 3 and flows sequentially through the three-position four-way directional valve 17 and the second two-position two-normally open directional valve 16 to the rod chamber interface 1 and is introduced into the rod chamber of the hydraulic cylinder. Adjusting the second relief valve 19 can make the oil pressure at the rod chamber interface 1 reach the test requirements. When oil exits the rod chamber, the oil flows from the rod chamber interface 1 sequentially through the second two-position two-normally open directional valve 16 and the three-position four-way directional valve 17 back to the first oil tank 23.

[0059] The exhaust oil passage of the rod chamber interface 1 is as follows: A third two-position two-normally closed directional valve 13 and a throttle valve 4 are sequentially connected from the rod chamber interface 1 to the second oil tank 24. The third two-position two-normally closed directional valve 13 can be opened or closed according to various test requirements. During the test, when the rod chamber is vented, oil and gas are discharged from the rod chamber interface 1, passing sequentially through the third two-position two-normally closed directional valve 13 and the throttle valve 4 to the second oil tank 24. Adjusting the opening of the throttle valve 4 can bring the oil pressure of the rod chamber interface 1 to the test requirements.

[0060] The open oil passage of the rod chamber is connected sequentially from the rod chamber interface 1 to a fourth two-position two-normally closed directional valve 14, which connects to the fourth oil tank 26. This fourth two-position two-normally closed directional valve 14 can open or close the open oil passage of the rod chamber according to various test requirements. During the test, when the rod chamber is open, oil flows from the rod chamber interface 1 through the fourth two-position two-normally closed directional valve 14 to the fourth oil tank 26.

[0061] It should be noted that the third two-position two-normally closed directional valve 13, the fourth two-position two-normally closed directional valve 14, and the second two-position two-normally open directional valve 16 can completely close the rod chamber interface 1 according to the test requirements, thereby closing the rod chamber of the hydraulic cylinder under test.

[0062] exist Figure 1 In one embodiment, the oil circuit connecting the third two-position two-normally closed directional valve 13 to the rod chamber interface 1, the oil circuit connecting the fourth two-position two-normally closed directional valve 14 to the rod chamber interface 1, and the oil circuit connecting the second two-position two-normally open directional valve 16 to the rod chamber interface 1 are connected in pairs to simplify the rod chamber connection oil circuit, thereby facilitating the closure of the rod chamber interface 1 by the third two-position two-normally closed directional valve 13, the fourth two-position two-normally closed directional valve 14, and the second two-position two-normally open directional valve 16. In an optional embodiment, the third two-position two-normally closed directional valve 13, the fourth two-position two-normally closed directional valve 14, and the second two-position two-normally open directional valve 16 can also each form their own connection oil circuit with the rod chamber interface 1, as long as the rod chamber interface 1 can be closed.

[0063] from Figure 1 As can also be seen from the embodiments, on the left side of the illustrated embodiment, the oil tank includes a third oil tank 25, and the reversing valve group further includes a first two-position two normally closed reversing valve 11, a second two-position two normally closed reversing valve 12, and a first two-position two normally open reversing valve 15.

[0064] The oil inlet and outlet circuits of the rodless cavity are as follows: A first two-position two-way normally open directional valve 15 and a three-position four-way directional valve 17 are sequentially connected from the rodless cavity interface 2. The three-position four-way directional valve 17 allows selective connection to one of two paths: one path connects to the first oil tank 23 to discharge oil from the oil circuit; the other path connects to the first oil tank 23 via a hydraulic pump 3, allowing oil from the first oil tank 23 to be drawn into the oil circuit. The first two-position two-way normally open directional valve 15 can open or close the oil inlet and outlet circuits of the rodless cavity according to test requirements.

[0065] During the test, when oil enters the rodless chamber, the oil is drawn from the first oil tank 23 by the hydraulic pump 3 and flows through the three-position four-way directional valve 17 and the first two-position two-normally open directional valve 15 to the rodless chamber interface 2 and is introduced into the rodless chamber. Adjusting the second relief valve 19 can make the oil pressure of the rodless chamber interface 2 meet the test requirements. When oil exits the rodless chamber, the oil flows from the rodless chamber interface 2 through the second two-position two-normally open directional valve 16 and the three-position four-way directional valve 17 back to the first oil tank 23.

[0066] The venting oil passage of the rodless chamber is as follows: A second two-position two-normally closed directional valve 12 and a throttle valve 4 are sequentially connected from the rodless chamber interface 2 to the second oil tank 24. The second two-position two-normally closed directional valve 12 can be opened or closed according to various test requirements. During the test, when the rodless chamber vents, the oil flows from the rodless chamber interface 2 through the second two-position two-normally closed directional valve 12 and the throttle valve 4 to the second oil tank 24. Adjusting the opening of the throttle valve 4 can bring the oil pressure at the rodless chamber interface 2 up to the test requirements.

[0067] The open oil passage of the rodless chamber is connected sequentially from the rodless chamber interface 2 to a first two-position two-normally closed directional valve 11, which connects to a third oil tank 25. The first two-position two-normally closed directional valve 11 can open or close the open oil passage of the rodless chamber according to various test requirements. During the test, when the rodless chamber is open, oil flows from the rodless chamber interface 2 through the first two-position two-normally closed directional valve 11 to the third oil tank 25.

[0068] It should be noted that the first two-position normally closed directional valve 11, the second two-position normally closed directional valve 12, and the first two-position normally open directional valve 15 can completely close the rodless chamber interface 2 according to the test requirements, thereby closing the rodless chamber of the hydraulic cylinder under test.

[0069] exist Figure 1In one embodiment, the oil circuit connecting the first two-position two-normally closed directional valve 11 to the rodless cavity interface 2, the oil circuit connecting the second two-position two-normally closed directional valve 12 to the rodless cavity interface 2, and the oil circuit connecting the first two-position two-normally open directional valve 15 to the rodless cavity interface 2 are connected in pairs to simplify the connection oil circuit of the rodless cavity, thereby facilitating the closure of the rodless cavity interface 1 by the first two-position two-normally closed directional valve 11, the second two-position two-normally closed directional valve 12, and the first two-position two-normally open directional valve 15. In an optional embodiment, the first two-position two-normally closed directional valve 11, the second two-position two-normally closed directional valve 12, and the first two-position two-normally open directional valve 15 can also each form their own connection oil circuit with the rodless cavity interface 2, as long as the rodless cavity interface 2 can be closed.

[0070] according to Figure 1 In one embodiment, the oil connection circuit of the rodless chamber interface 2 is symmetrically arranged with the oil connection circuit of the rod chamber interface 1. The oil connection circuit of the second two-position two-normally closed directional valve 12 and the throttle valve 4 is connected with the oil connection circuit of the third two-position two-normally closed directional valve 13 and the throttle valve 4. The inlet and outlet oil circuits of the rod chamber and the inlet and outlet oil circuits of the rodless chamber share a hydraulic pump 3. The oil outlet of the hydraulic pump 3 guides the connecting oil circuit to selectively connect to the rod chamber interface 1 and the rodless chamber interface 2 respectively by switching the three-position four-way directional valve 17. This symmetrical arrangement simplifies the connecting oil circuit of the test device, and the connecting oil circuits for flowing to or out of the rod chamber interface 1 or the rodless chamber interface 2 are equal, thereby facilitating and accurately testing the hydraulic cylinder under test. In an optional embodiment, the connecting oil circuit can also be asymmetrically arranged, as long as it is convenient to open or close the rod chamber interface 1 and the rodless chamber interface 2 according to the test requirements.

[0071] It should be noted that the first two-position two-way normally closed directional control valve 11, the second two-position two-way normally closed directional control valve 12, the third two-position two-way normally closed directional control valve 13, the fourth two-position two-way normally closed directional control valve 14, the first two-position two-way normally open directional control valve 15, the second two-position two-way normally open directional control valve 16, and the three-position four-way directional control valve 17 can be solenoid valves. In other embodiments, these directional control valves can also be operated manually.

[0072] Figure 2 for Figure 1 A schematic diagram illustrating the principle of connecting the hydraulic cylinder under test in an embodiment of the hydraulic cylinder testing apparatus. When testing the hydraulic cylinder 20 under test, as follows... Figure 2 As shown, the rod chamber 21 of the hydraulic cylinder under test 20 is connected to the rod chamber interface 1, and the rodless chamber 22 of the hydraulic cylinder under test is connected to the rodless chamber interface 2. The test methods for each state of the hydraulic cylinder under test are described below with reference to this diagram.

[0073] Exhaust test:

[0074] Step A: Expel the gas from the inlet and outlet oil passages of the rod chamber interface 1. The third-position two-way normally closed directional valve 13 is energized to open the venting oil passage of the rod chamber interface 1; the throttle valve 4 is opened and adjusted to a small opening to control the oil pressure at the rod chamber interface 1; the three-position four-way directional valve 17 is switched to... Figure 2 The right position in the middle is used to open the oil inlet and outlet passage of the rod chamber.

[0075] Hydraulic pump 3 starts, and oil is drawn from the first oil tank 23 through the inlet and outlet oil passages of the rod chamber. The oil passes sequentially through the three-position four-way directional valve 17, the second two-position two-normally open directional valve 16, and then through the outlet oil passage of the rod chamber interface 1, through the third two-position two-normally closed directional valve 13, and the throttle valve 4. This process discharges the gas in the inlet and outlet oil passages of the rod chamber 21 along with the oil to the second oil tank 24, until only oil is discharged from the outlet of the throttle valve 4, and the oil flow is stable, indicating that the gas in the inlet and outlet oil passages of the rod chamber has been completely discharged. The third two-position two-normally closed directional valve 13 is de-energized to close the inlet and outlet oil passages of the rod chamber. Hydraulic pump 3 continues to pump oil into the rod chamber 21, ensuring that the rod chamber 21 contains oil, thereby providing lubrication for the movement of piston 27 and piston rod 28, and preventing dry friction that could cause wear on piston 27, piston rod 28, and the internal components of the hydraulic cylinder 20 under test.

[0076] Step B: Expel the gas from the inlet and outlet oil passages and the exhaust oil passage of the rodless chamber interface 2. The second normally closed directional valve 12 is energized to open the exhaust oil passage of the rodless chamber 22; switch the three-position four-way directional valve 17 to... Figure 2 The left position is used to open the oil inlet and outlet passage of the rodless cavity 22.

[0077] The hydraulic fluid is drawn from the first oil tank 23 by the hydraulic pump 3 through the inlet and outlet oil passages of the rodless chamber 22. It passes sequentially through the three-position four-way directional valve 17 and the first two-position normally open directional valve 15, and then through the second two-position normally closed directional valve 12 and the throttle valve 4. This process discharges the gas in the inlet and outlet oil passages of the rodless chamber 22 along with the hydraulic fluid to the second oil tank 24, until only hydraulic fluid is discharged from the outlet of the throttle valve 4, and the oil flow is stable. This indicates that the gas in the inlet and outlet oil passages of the rod chamber has been completely discharged. The second two-position normally closed directional valve 12 is de-energized to close the exhaust oil passage of the rodless chamber.

[0078] Step C: Expel the gas from the rod chamber 21. The third-position normally closed directional valve 13 is energized to open the venting oil passage of the rod chamber 21. The hydraulic pump 3 continues to supply oil to the rodless chamber 22 through its inlet and outlet oil passages. The oil in the rodless chamber 22 compresses and pushes out the piston 27, causing the piston 27 to push the gas in the rod chamber 21, which is then discharged through the venting oil passage of the rod chamber 21 to the second oil tank 24, until the piston rod 28 is fully extended. The third-position normally closed directional valve 13 is de-energized to close the venting oil passage of the rod chamber 21.

[0079] Step D: Expel the gas from the rodless chamber 22. The second normally closed directional valve 12 is energized to open the exhaust oil path of the rodless chamber 22; switch the three-position four-way directional valve 17 to... Figure 2 The right position opens the oil inlet / outlet passage of the rod chamber 21. Oil enters the rod chamber 21 through the oil inlet / outlet passage, compressing and pushing the piston 27 back. This piston 27 then pushes the gas in the rodless chamber 22, causing it to exit through the rodless chamber interface 2 and through the exhaust oil passage to the second oil tank 24, until the piston rod 28 is fully retracted. The second position normally closed reversing valve 12 is de-energized to close the exhaust oil passage of the rodless chamber 22.

[0080] Step E: Repeat steps C and D, observing the mixing of oil and gas discharged into the second oil tank 24, until only oil is discharged, indicating that the gas in the rod chamber and rodless chamber has been completely discharged. Stop the test apparatus.

[0081] In an optional embodiment, only steps A to B, namely, venting the gas in the inlet and outlet oil passages of the rod chamber interface 1 and venting the gas in the inlet, outlet, and exhaust oil passages of the rodless chamber interface 2, can be performed without performing steps C to E.

[0082] It should be noted that, for ease of transport, the initial state of the hydraulic pump under test is typically with the piston rod 28 fully retracted. At this point, only the rod chamber 21 of the hydraulic cylinder 20 contains gas. The venting test primarily vents the gas in the rod chamber 21; for the rodless chamber 22, only the air in the connecting oil line needs to be vented. In an optional embodiment, the piston rod 28 of the hydraulic pump under test can be in any position initially, and the venting test requires venting the gas from both the rodless chamber 22 and the rod chamber 21.

[0083] Trial run test:

[0084] Repeatedly switch the three-position four-way directional valve 17 to... Figure 2 The right and left positions of the gauges are used to repeatedly open and close the oil inlet and outlet passages of the rod chamber 21 and the rodless chamber 22 of the hydraulic cylinder under test, thereby controlling the full-stroke reciprocating motion of the piston 27 of the hydraulic cylinder under test. During the trial operation, oil is repeatedly introduced into the rod chamber 21 and the rodless chamber 22. This oil provides thrust and lubrication in the hydraulic cylinder under test, driving the reciprocating motion of the piston 27 and reducing the friction damage rate between the piston 27 and the inner wall of the hydraulic cylinder 20. The pressure curves of the first pressure gauge 5 and the second pressure gauge 6 are recorded and observed during this reciprocating motion. If the pressure curve is stable, it indicates that the gas in the rod chamber 21 and the rodless chamber 22 has been completely discharged; if the pressure curve fluctuates violently or fluctuates regularly, it indicates that the resistance is changing, indicating that the machining and assembly quality of the hydraulic cylinder 20 is low, and the seals of the hydraulic cylinder 20 may be damaged.

[0085] After the exhaust test and trial operation test are completed, the following tests can be carried out.

[0086] The pressure resistance and external leakage condition tests are as follows:

[0087] Pressure resistance and external leakage test of rodless chamber 22: Three-position four-way directional valve 17 is energized and switched to the position as follows: Figure 2 The left position is used to open the inlet and outlet oil passages of the rodless chamber 22 of the hydraulic cylinder 20 under test. The hydraulic pump 3 is turned on, and oil enters the rodless chamber 22 through the inlet and outlet oil passages. The oil in the rodless chamber 22 pushes the piston 27, thereby pushing the oil in the rod chamber 21 to be discharged from the inlet and outlet oil passages of the rod chamber 21 and flow back to the first oil tank 23 through the three-position four-way reversing valve 17 until the piston rod 28 is fully extended.

[0088] Hydraulic pump 3 continues to supply oil to rodless chamber 22, and by adjusting the opening of the second relief valve 19, the oil pressure in the oil inlet and outlet circuit from the outlet of hydraulic pump 3 to rodless chamber 22 is adjusted so that the pressure value of the second pressure gauge 6 reaches the test requirement value, thereby adjusting the oil pressure in rodless chamber 22 to reach the test requirement value. The first two-position normally open directional valve 15 is energized to close rodless chamber 22, and hydraulic pump 3 stops supplying oil to rodless chamber 22 to save wear and tear on hydraulic pump 3.

[0089] Observe the pressure measurement curve of the second pressure gauge 6. When the pressure measurement value drops rapidly, it indicates that there is external leakage in the rodless chamber 22 of the hydraulic cylinder under test. When the measurement value drops within a reasonable range, it indicates that there is no external leakage in the rodless chamber 22 of the hydraulic cylinder and that the pressure resistance is good.

[0090] Pressure resistance and external leakage test of rod chamber 21: Three-position four-way directional valve 17 is energized and switched to the following position. Figure 2 The right position is used to open the oil inlet and outlet passages of the rod chamber 21 of the hydraulic cylinder 20 under test. The hydraulic pump 3 is turned on, and oil enters the rod chamber 21 through the oil inlet and outlet passages. The oil in the rod chamber 21 pushes the piston 27, thereby pushing the oil in the rodless chamber 22 to be discharged from the oil inlet and outlet passages of the rodless chamber 22 and flow back to the first oil tank 23 through the three-position four-way reversing valve 17 until the piston rod 28 is fully retracted.

[0091] Hydraulic pump 3 continues to supply oil to the rod chamber 21, and adjusts the oil pressure in the oil inlet and outlet circuit from the outlet of hydraulic pump 3 to the rod chamber 21 by adjusting the opening of the second relief valve 19, so that the first pressure gauge 5 reaches the test requirement value, thereby adjusting the oil pressure in the rod chamber 21 to reach the test requirement value. The second normally open directional valve 16 is energized to close the rod chamber 21, and hydraulic pump 3 stops supplying oil to the rod chamber 21 to save hydraulic pump wear.

[0092] Observe the pressure measurement curve of the first pressure gauge 5. When the pressure measurement value drops rapidly, it indicates that there is external leakage in the rod chamber 21 of the hydraulic cylinder under test. When the measurement value drops within a reasonable range, it indicates that there is no external leakage in the rod chamber 21 of the hydraulic cylinder and that the pressure resistance is good.

[0093] Internal leakage condition test:

[0094] Select several test points during the retraction of the piston rod 28 of the hydraulic cylinder 20 under test. Switch the three-position four-way directional valve 17 to... Figure 2 The right position is activated to open the inlet and outlet oil passages of the rod chamber 21. The hydraulic pump 3 is turned on, and oil enters the rod chamber 21 through the inlet and outlet oil passages. The oil in the rod chamber 21 pushes the piston 27 to retract. When the piston 27 retracts to the selected test point, the first two-position normally open directional valve 15 is energized to close the rodless chamber 22. The hydraulic pump 3 continues to supply oil to the rod chamber 21 to the rated pressure. Observe whether the piston rod 28 extends. If the piston rod 28 extends, it indicates that there is internal leakage at the selected test point; otherwise, it indicates that there is no internal leakage at the selected test point.

[0095] Next, the pressure ratio between the rodless chamber 22 and the rod chamber 21 is observed using the second pressure gauge 6 and the first pressure gauge 5. This pressure ratio is then compared with the piston area ratio of the rodless chamber 22 and the rod chamber 21. If they match, it indicates that there is no internal leakage at the selected test point; otherwise, it indicates that there is internal leakage at the selected test point. This process is repeated for each selected test point to identify the internal leakage point of the hydraulic cylinder under test.

[0096] Due to the manufacturing process of hydraulic cylinders, the middle part of the hydraulic cylinder may often become bulged, deformed, or roughened. In this case, internal leakage will occur in the middle part. Therefore, several test points during the retraction process of the piston rod 28 can be selected from the middle part of the hydraulic cylinder 20 under test, so as to more directly and accurately determine the location of internal leakage of the hydraulic cylinder, which is convenient for the maintenance and performance evaluation of the hydraulic cylinder 20 under test.

[0097] Starting pressure test:

[0098] Starting pressure test of rod chamber 21: The first two-position normally open directional valve 15 is energized to close the inlet and outlet oil passages of rodless chamber 22; the first two-position normally closed directional valve 11 is energized to open the open oil passage of rodless chamber 22, so that no pressure is generated in the oil in rodless chamber 22, thereby better testing the starting pressure of rod chamber 21. The third two-position normally closed directional valve 13 is energized to open the vent oil passage of rod chamber 21, and the oil pressure of rod chamber 21 is adjusted by the throttle valve 4 in the vent oil passage; switch the three-position four-way directional valve 17 to... Figure 2 The right position is used to open the oil inlet and outlet passage of the rod chamber 21.

[0099] At the start of the test, hydraulic pump 3 is turned on, and oil flows into rod chamber 21 through the inlet and outlet oil passages. The opening of throttle valve 4 is finely adjusted from maximum to minimum to regulate the oil pressure in rod chamber 21 until the oil in rod chamber 21 pushes piston 27 to move into rodless chamber 22. The oil in rodless chamber 22 flows to the third oil tank 25 through the open oil passage of rodless chamber 22. The entire process is recorded using fourth pressure gauge 8, resulting in a curve of pressure change in rod chamber 21. After piston 27 transitions from static friction to dynamic friction, the frictional force decreases, and thus the oil pressure also decreases. This is shown as overshoot in the curve, which is the starting pressure value of rod chamber 21.

[0100] In an optional embodiment, the oil pressure in the rod chamber 21 can be adjusted by regulating the flow rate at the outlet of the hydraulic pump 3, thereby controlling the oil flow rate into the rod chamber 21 and thus achieving the purpose of regulating the oil pressure in the rod chamber 21. In other embodiments, the oil pressure in the rod chamber 21 is adjusted upward from 0 bar, with an adjustment range of up to 0.01 bar, thereby achieving fine adjustment at low pressure and allowing for more accurate measurement of the starting pressure of the rod chamber 21.

[0101] Starting pressure test of rodless chamber 22: The second normally open directional valve 16 is energized to close the oil inlet passage of rod chamber 21; the fourth normally closed directional valve 14 is energized to open the open oil passage of rod chamber 21, so that no pressure is generated in the oil in rod chamber 21, thereby better testing the starting pressure of rodless chamber 22. The second normally closed directional valve 12 is energized to open the vent oil passage of rodless chamber 22, and the oil pressure of rodless chamber 22 is adjusted by the throttle valve 4 in the vent oil passage; switching the three-position four-way directional valve 17 as follows... Figure 2 The left position is used to open the oil inlet and outlet passage of the rodless cavity 22.

[0102] At the start of the test, hydraulic pump 3 is turned on, and oil flows into rodless chamber 22 through the inlet and outlet oil passages. The opening of throttle valve 4 is finely adjusted from maximum to minimum to regulate the oil pressure in rodless chamber 22 until the oil in rodless chamber 22 pushes piston 27 to move into rod chamber 21. The oil in rod chamber 21 flows to the fourth oil tank 26 through the open oil passage of rod chamber 21. The entire process is recorded using the fourth pressure gauge 8, resulting in a pressure change curve of rodless chamber 22. After piston 27 transitions from static friction to dynamic friction, the frictional force decreases, and thus the oil pressure also decreases. This is shown as overshoot in the curve, which is the starting pressure value of rodless chamber 22.

[0103] In an optional embodiment, the oil flow rate into the rodless chamber 22 can be controlled by adjusting the flow rate at the outlet of the hydraulic pump 3, thereby achieving the purpose of adjusting the oil pressure in the rodless chamber 22. In other embodiments, the oil pressure in the rodless chamber 22 is adjusted upward from 0 bar, with an adjustment range of up to 0.01 bar, thereby achieving low-pressure fine adjustment and allowing for more accurate measurement of the starting pressure of the rodless chamber 22.

[0104] It should be noted that in the above tests, pressure gauge 8 is a small-range pressure gauge, and the first relief valve 18 is a low-pressure relief valve to ensure that the fourth pressure gauge 8 is not damaged due to excessive oil pressure; the second relief valve 19 can keep the hydraulic pump 3 within a reasonable range to ensure that the hydraulic pump 3 is not damaged due to excessive oil pressure.

[0105] The hydraulic cylinder testing device of the present invention symmetrically arranges various reversing valves at the rod-side interface 1 and the rodless interface 2, integrating various test circuits and venting functions into one testing device. The hydraulic cylinder under test is connected to the testing device once, and by switching the various reversing valves, venting, trial operation, external leakage, internal leakage, and starting pressure tests can be achieved, thus improving testing efficiency.

[0106] For example, the system can completely purge the gas from the hydraulic cylinder before testing, preventing dry friction between the piston rod and the cylinder wall during movement. This avoids damage to the friction pair and seals of the cylinder wall and piston rod, and prevents further impact on other test results. Additionally, the system eliminates the need for a continuous high-pressure oil supply from the hydraulic pump during pressure testing, reducing pump wear. For hydraulic cylinders with very low starting pressure, the testing apparatus does not require additional piping for adjustment, simplifying the test structure. For internal leakage testing, the apparatus can test internal leakage during full extension and retraction of the piston rod, and also comprehensively monitor the overall condition of the hydraulic cylinder. With increasingly sophisticated hydraulic cylinder sealing technology, the testing apparatus can measure external leakage even when the leakage is extremely small.

[0107] After the test, the first two-position normally closed directional valve 11 is energized to open the open oil circuit of the rodless chamber 22. The oil in the rodless chamber 22 flows to the third oil tank 25 through the first two-position normally closed directional valve 11, so that the rodless chamber 21 is fully unloaded and the oil pressure in the rodless chamber 21 is fully released, avoiding oil spraying caused by residual internal pressure when the pipeline is removed.

[0108] Similarly, the fourth two-position two-normally closed directional valve 14 is energized to open the open oil passage of the rod chamber 21. The oil in the rod chamber 21 flows to the fourth oil tank 26 through the fourth two-position two-normally closed directional valve 14, so that the rod chamber 21 is fully unloaded and the oil pressure in the rod chamber is fully released, avoiding oil spraying caused by residual internal pressure when the pipeline is removed.

[0109] During various tests, the test apparatus of the present invention can save the wear and tear on the hydraulic pump, allow the piston rod to remain at any position inside the hydraulic cylinder by switching the directional valve, and adjust the pressure of the rod chamber or rodless chamber by adjusting the opening of the throttle valve, thereby making it more convenient and effective to measure the performance of the hydraulic cylinder under test in various states.

[0110] This invention integrates various test circuits and venting functions for single-cylinder hydraulic cylinder testing into a single functional module. The test piece can complete all test items with a single connection to this module, improving testing efficiency. Venting is treated as a separate test step. The bypass throttle valve serves both to regulate minute oil supply pressure and to facilitate venting. During trial operation, the processing quality is assessed by observing the pressure throughout the piston rod's stroke. In the internal leakage test, the internal leakage situation throughout the stroke is determined by comparing the pressures in the two chambers. In the pressure resistance and external leakage tests, the test chamber is sealed after reaching the set pressure, replacing the continuous oil supply method of the hydraulic pump and allowing for assessment of external leakage by observing the pressure drop in the test chamber.

[0111] The technical scope of this invention is not limited to the contents of the above specification. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the scope of this invention.

Claims

1. A hydraulic cylinder testing device, characterized in that, The hydraulic cylinder testing device includes: Oil tank, the oil tank being used for supplying and recovering oil; A rod chamber interface (1) is used to connect the rod chamber (21) of the hydraulic cylinder (20) to be tested. The rod chamber interface (1) is used to introduce and discharge oil, and a first pressure gauge (5) is provided at the rod chamber interface (1) to measure the pressure at the rod chamber interface (1). The rodless cavity interface (2) is used to connect the rodless cavity (22) of the hydraulic cylinder (20) to be tested. The rodless cavity interface (2) introduces and discharges oil, and a second pressure gauge (6) is provided at the rodless cavity interface (2) to measure the pressure at the rodless cavity interface (2). The reversing valve group is used to adjust the opening and closing of the connecting oil circuit of the rod chamber interface (1) and the rodless chamber interface (2). The reversing valve group is used to adjust the test device to make it suitable for the performance test of the hydraulic cylinder (20) in the exhaust state, trial operation state, unloading state, pressure resistance state, external leakage state, internal leakage state, and starting pressure state. A hydraulic pump (3) is provided. The oil inlet of the hydraulic pump (3) is connected to the oil tank. The oil outlet of the hydraulic pump (3) is connected to the oil circuit through the reversing valve group to the rod chamber interface (1) and the rodless chamber interface (2) respectively. A third pressure gauge (7) is provided at the oil outlet of the hydraulic pump (3). Throttling valve (4), the outlet of the throttle valve (4) is connected to the oil tank, the inlet of the throttle valve (4) is connected to the oil circuit through the reversing valve group to the rod chamber interface (1) and the rodless chamber interface (2) respectively, and a fourth pressure gauge (8) is provided at the inlet of the throttle valve (4). The reversing valve assembly includes: The first two-position normally closed directional valve (11) is connected to the rodless chamber interface (2) and the oil tank. The second two-position two-normally closed reversing valve (12) is connected to the rodless chamber interface (2) and the throttle valve (4). The third two-position two-normally closed reversing valve (13) is connected to the rod chamber interface (1) and the throttle valve (4). The fourth two-position two-normally closed directional valve (14) is connected to the rod chamber interface (1) and the oil tank. The first two-position two-way normally open reversing valve (15) is connected to the rodless chamber interface and connected to the hydraulic pump (3) and the oil tank through the three-position four-way reversing valve (17). The second two-position two-way normally open directional valve (16) is connected to the rod chamber interface and connected to the hydraulic pump (3) and the oil tank through the three-position four-way directional valve (17).

2. The test apparatus as described in claim 1, characterized in that, The oil circuit connecting the first two-position two-normally closed reversing valve (11) to the rodless cavity interface (2), the oil circuit connecting the second two-position two-normally closed reversing valve (12) to the rodless cavity interface (2), and the oil circuit connecting the first two-position two-normally open reversing valve (15) to the rodless cavity interface (2) are connected in pairs. The oil circuit connecting the third two-position two normally closed reversing valve (13) to the rod chamber interface (1), the oil circuit connecting the fourth two-position two normally closed reversing valve (14) to the rod chamber interface (1), and the oil circuit connecting the second two-position two normally open reversing valve (16) to the rod chamber interface (1) are connected in pairs. The oil circuit connecting the second two-position two-normally closed reversing valve (12) and the throttle valve (4) is connected to the oil circuit connecting the third two-position two-normally closed reversing valve (13) and the throttle valve (4). The connecting oil circuit of the rodless cavity interface (2) is symmetrically arranged with the connecting oil circuit of the rod cavity interface (1).

3. The test apparatus as described in claim 1, characterized in that, The oil tank includes a first oil tank (23) connecting the hydraulic pump (3) and the three-position four-way directional valve (17), a second oil tank (24) connecting the throttle valve (4), a third oil tank (25) connecting the first two-position two-way normally closed directional valve (11), and a fourth oil tank (26) connecting the fourth two-position two-way normally closed directional valve (14).

4. The test apparatus as described in any one of claims 1 to 3, characterized in that, The throttle valve (4) is connected to a first relief valve (18) leading to the oil tank; the hydraulic pump (3) is connected to a second relief valve (19) leading to the oil tank.

5. A method for testing a hydraulic cylinder using the testing apparatus as described in claim 2 or 3, characterized in that, Connect the rod chamber (21) of the hydraulic cylinder under test (20) to the rod chamber interface (1), and connect the rodless chamber (22) of the hydraulic cylinder under test to the rodless chamber interface (2).

6. The test method as described in claim 5, characterized in that, During the test of the aforementioned exhaust condition: Adjust the throttle valve (4) to open a small opening, so that the third two-position two normally closed reversing valve (13) is energized, and oil is supplied to the rod chamber (21) of the hydraulic cylinder under test (20) until the oil output from the outlet of the throttle valve (4) is stable, and the third two-position two normally closed reversing valve (13) is de-energized. The second normally closed directional valve (12) is energized to supply oil to the rodless chamber (22) of the hydraulic cylinder under test (20) until the oil output from the outlet of the throttle valve (4) is stable, and the second normally closed directional valve (12) is de-energized; the second normally closed directional valve (12) is de-energized to supply oil to the rod chamber (21) of the hydraulic cylinder under test (20) until the piston rod (28) of the hydraulic cylinder under test (20) is fully retracted.

7. The test method as described in claim 5, characterized in that, During the test of the trial operation state: the three-position four-way reversing valve (17) controls the piston rod (28) of the hydraulic cylinder under test (20) to reciprocate throughout the entire stroke, and records and observes the pressure curves of the first pressure gauge (5) and the second pressure gauge (6) during the reciprocating motion, and judges the processing and assembly quality of the hydraulic cylinder under test based on the flatness of the pressure curve.

8. The test method as described in claim 5, characterized in that, During the tests for pressure resistance and external leakage: Extend the piston rod (28) of the hydraulic cylinder (20) under test to its full extent, adjust the pressure resistance test pressure of the rodless chamber (22) of the hydraulic cylinder under test, energize the first two-position two-normally open reversing valve (15), close the rodless chamber (22) of the hydraulic cylinder (20) under test, stop the oil supply to the rodless chamber (22), and record and observe the pressure of the second pressure gauge (6); The piston rod (28) of the hydraulic cylinder under test (20) is fully retracted. The pressure resistance test pressure of the rod chamber (21) of the hydraulic cylinder under test (20) is adjusted. The second normally open reversing valve (16) is energized. The rod chamber (21) of the hydraulic cylinder under test (20) is closed. The oil supply to the rod chamber (21) is stopped. The pressure of the first pressure gauge (5) is recorded and observed. Based on the pressure drop of the second pressure gauge (6) and the first pressure gauge (5), determine whether there is an external leak.

9. The test method as described in claim 5, characterized in that, When conducting the test for the aforementioned internal leakage condition: During the retraction of the piston rod (28) of the hydraulic cylinder under test (20), several test points are selected so that the first two-position two-normally open reversing valve (15) is energized, the rodless chamber (22) of the hydraulic cylinder under test (20) is closed, and oil is supplied to the rod chamber (21) of the hydraulic cylinder under test (20) to the rated pressure. The piston rod (28) is observed to see if it extends. The pressure ratio of the rodless chamber (22) and the rod chamber (21) and the closeness of the pressure ratio to the piston area ratio of the rodless chamber (22) and the rod chamber (21) are observed by the second pressure gauge (6) and the first pressure gauge (5), and the presence or absence of internal leakage is determined accordingly.

10. The test method as described in claim 5, characterized in that, The starting pressure test includes a starting pressure test of the rod chamber (21) and a starting pressure test of the rodless chamber (22), wherein: During the starting pressure test of the rod chamber (21), the first two-position two-normally open reversing valve (15), the first two-position two-normally closed reversing valve (11) and the third two-position two-normally closed reversing valve (13) are energized, oil enters the rod chamber (21), and the rodless chamber (22) is opened through the first two-position two-normally closed reversing valve (11). By adjusting the opening of the throttle valve (4) or the oil flow rate, the pressure of the rod chamber (21) is adjusted to the movement of the piston rod (28) of the hydraulic cylinder (20) under test. The pressure change of the rod chamber (21) throughout the process is recorded by the fourth pressure gauge (8). During the start-up pressure test of the rodless chamber (22), the second two-position two-normally open reversing valve (16), the second two-position two-normally closed reversing valve (12), and the fourth two-position two-normally closed reversing valve (14) are energized, oil enters the rodless chamber (22), and the rod chamber (21) is opened through the fourth two-position two-normally closed reversing valve (14). By adjusting the opening of the throttle valve (4) or the oil flow rate, the pressure of the rodless chamber (22) is adjusted to the movement of the piston rod (28) of the hydraulic cylinder (20) under test. The pressure change of the rodless chamber (22) throughout the process is recorded using the fourth pressure gauge (8).

11. The test method as described in claim 5, characterized in that, After the test is completed, the first two-position two-normally closed reversing valve (11) and the fourth two-position two-normally closed reversing valve (14) are energized. The rodless chamber (22) is fully unloaded by opening the first two-position two-normally closed reversing valve (11), and the rod chamber (21) is fully unloaded by opening the fourth two-position two-normally closed reversing valve (14).

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