A hydraulic motor durability test system under simulated seawater medium external pressure environment

Abstract

This invention relates to a durability testing system for hydraulic motors under simulated seawater external pressure conditions, comprising: a seawater pressurization system for providing a simulated seawater external pressure environment to the tested hydraulic motor; and an actuator testing system for driving and controlling the operation of the tested hydraulic motor. The actuator testing system transmits oil medium pressure to the seawater pressurization system via an accumulator bladder to simulate the internal pressure environment of a pressure tank, and regulates the transmitted pressure via a pressure reducing valve. This invention organically integrates the two systems, reducing test construction and maintenance costs while simultaneously enabling durability testing of actuators such as hydraulic motors under seawater external pressure conditions.

Description

Technical Field

[0001] This invention belongs to the field of reliability testing technology for electromechanical products, specifically relating to a hydraulic motor durability testing system under simulated seawater medium external pressure environment. Background Technology

[0002] In traditional industry, most hydraulic motors operate in an air-medium environment. The output shaft seal typically only withstands the leakage oil pressure within the motor housing, which is usually very low (generally not exceeding 0.5 MPa). Since the external environment of the output shaft is air, the influence of external pressure on the output shaft is largely negligible. Durability tests for traditional electromechanical products (such as hydraulic motors and hydraulic cylinders) are generally conducted in an air environment to verify changes in their performance indicators under long-term operating conditions.

[0003] However, in deep-sea equipment, actuators such as hydraulic motors are typically exposed to seawater. When deep-sea equipment operates at depths exceeding 100 meters, the motor output shaft faces seawater pressure of 1 MPa. Furthermore, as the operating depth increases, the seawater pressure on actuators such as hydraulic motors further increases, drastically altering the working environment of sealed components like the output shaft. Therefore, traditional durability tests conducted in air cannot fully simulate the actual working environment of actuators such as hydraulic motors.

[0004] To simulate the actual working environment of actuators such as hydraulic motors under external pressure, current technology typically places these actuators in a pressure tank, pressurizing them to simulate a deep-sea environment. Durability tests are then conducted by connecting the hydraulic motors via through-tank oil pipes. However, the water medium used in the pressure tank during testing is primarily fresh water, which differs from seawater. If seawater were used instead, a dedicated seawater pressurization system would be required, and the corresponding hydraulic pumps, valves, and piping would all need to meet the reliability requirements for long-term operation in a seawater environment, significantly increasing construction and maintenance costs. Furthermore, since the working medium for hydraulic motors and actuators is oil, an additional oil-based testing system would be needed, further increasing testing costs.

[0005] Therefore, how to achieve durability testing of actuators such as hydraulic motors in real deep-sea external pressure environments with low construction and maintenance costs is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide a durability testing system for hydraulic motors under simulated seawater external pressure. This system addresses the high equipment costs and maintenance difficulties inherent in existing technologies that require separate construction of seawater pressurization and oil-based testing systems. This invention organically integrates the two systems, reducing construction and maintenance costs while simultaneously enabling durability testing of actuators such as hydraulic motors under seawater external pressure.

[0007] The technical solution of this invention is to provide a hydraulic motor durability testing system under simulated seawater medium external pressure environment, comprising:

[0008] A seawater pressurization system is used to provide a simulated external seawater pressure environment for the tested hydraulic motor;

[0009] An actuator testing system for driving and controlling the operation of a hydraulic motor under test;

[0010] The actuator test system transmits the oil medium pressure to the seawater pressurization system through the bladder of the accumulator to simulate the internal pressure environment of the water pressure tank, and regulates the transmitted pressure through the pressure reducing valve.

[0011] Preferably, the actuator testing system includes a hydraulic tank, a hydraulic pump, a motor, a flow meter, a proportional directional valve, a two-way throttle valve, a pressure sensor, a pressure gauge, a check valve, a relief valve, a pressure reducing valve, an accumulator, a hydraulic motor under test, a hydraulic motor to be tested, a coupling, a shut-off valve, a pressure chamber, and an isolation valve.

[0012] The hydraulic oil tank outlet is connected to the hydraulic pump inlet, the motor is connected to the hydraulic pump drive, and the hydraulic pump outlet is connected to the test hydraulic motor inlet via the flow meter, proportional directional valve, and bidirectional throttle valve in sequence.

[0013] The oil outlet of the hydraulic motor under test is connected to the oil inlet of the hydraulic motor under test via the proportional directional valve and the check valve, and the oil outlet of the hydraulic motor under test is connected to the return port of the hydraulic oil tank via the relief valve.

[0014] The oil outlet of the hydraulic pump is connected in sequence to the inner cavity of the accumulator's bladder via the isolation valve and the pressure reducing valve. The outer cavity of the accumulator's bladder is connected to the inner cavity of the pressure tank. The pressure tank is equipped with a shut-off valve for injecting seawater medium.

[0015] The pressure sensor and pressure gauge are respectively installed on the inlet and outlet oil pipes of the hydraulic motor under test and the hydraulic motor being tested.

[0016] Preferably, the accumulator is a bladder-type accumulator, with its inner cavity connected to the oil outlet of the pressure reducing valve via a pipeline. The outside of the bladder is in direct contact with the seawater medium inside the pressure tank. The oil pressure and seawater pressure are balanced and transmitted through the elastic deformation of the bladder. By adjusting the output pressure of the pressure reducing valve, the oil pressure inside the accumulator bladder is controlled, thereby regulating the seawater pressure inside the pressure tank.

[0017] Preferably, the hydraulic motor under test and the hydraulic motor under test are coaxially connected via the coupling, and the proportional directional valve and the bidirectional throttle valve are used to control the speed and direction of the hydraulic motor under test; the return oil from the hydraulic motor under test is supplied to the hydraulic motor under test via the check valve, and the hydraulic motor under test establishes load pressure through the relief valve.

[0018] Preferably, when the hydraulic motor under test rotates forward, the first electromagnet of the proportional directional valve is energized, and the hydraulic oil passes through the flow meter, the proportional directional valve, and the two-way throttle valve, and enters the first working port of the hydraulic motor under test through the pipeline. The return oil from the second working port of the hydraulic motor under test enters the third working port of the hydraulic motor under test through the proportional directional valve, the second check valve, and the pipeline. The oil then flows back to the hydraulic oil tank through the fourth working port of the hydraulic motor under test, through the pipeline, and the first relief valve.

[0019] Preferably, when the tested hydraulic motor reverses, the second electromagnet of the proportional directional valve is energized, and the hydraulic oil passes through the flow meter, the proportional directional valve, and the two-way throttle valve, and enters the second working port of the tested hydraulic motor through the pipeline. The return oil from the first working port of the tested hydraulic motor enters the fourth working port of the tested hydraulic motor through the proportional directional valve, the first check valve, and the pipeline. The oil then flows back to the hydraulic oil tank through the third working port of the tested hydraulic motor, the pipeline, and the second relief valve.

[0020] Preferably, the pressure chamber is equipped with two shut-off valves, namely a first shut-off valve and a second shut-off valve. The first shut-off valve is connected to an external seawater injection pipeline for injecting seawater into the pressure chamber. The second shut-off valve is connected to an exhaust pipeline for venting air from the pressure chamber during the water injection process. When the second shut-off valve vents seawater, the first and second shut-off valves are closed, and the internal cavity of the pressure chamber is filled with seawater, changing the external environment of the tested hydraulic motor from air to seawater.

[0021] Preferably, after the pressure tank is filled with seawater, the isolation valve is opened, and the oil pressure output by the hydraulic pump enters the bladder of the accumulator through the isolation valve and the pressure reducing valve. Since the bladder is an elastic body, the pressure inside and outside the bladder of the accumulator is the same, that is, the seawater pressure inside the pressure tank is the same as the oil pressure inside the bladder of the accumulator. By adjusting the pressure reducing valve and observing the fifth pressure gauge, the current seawater pressure can be viewed and set.

[0022] Preferably, the relief valve includes a first relief valve and a second relief valve, and the check valve includes a first check valve and a second check valve; wherein:

[0023] The inlet of the first relief valve is connected to the fourth working port of the hydraulic motor being tested, and the outlet of the first relief valve is connected to the hydraulic oil tank.

[0024] The oil inlet of the second relief valve is connected to the third working oil port of the hydraulic motor being tested, and the oil outlet of the second relief valve is connected to the hydraulic oil tank.

[0025] The first check valve is located between the proportional directional valve and the fourth working port of the test hydraulic motor, with its inlet connected to the proportional directional valve and its outlet connected to the fourth working port of the test hydraulic motor.

[0026] The second check valve is located between the proportional directional valve and the third working port of the test hydraulic motor. Its inlet is connected to the proportional directional valve, and its outlet is connected to the third working port of the test hydraulic motor.

[0027] Preferably, the system further includes a third relief valve, the oil inlet of which is connected to the oil outlet of the hydraulic pump, and the oil outlet of which is connected to the hydraulic oil tank, for setting the maximum working pressure of the system and providing overload protection for the system.

[0028] The pressure sensor includes a first pressure sensor, a second pressure sensor, a third pressure sensor, and a fourth pressure sensor;

[0029] The pressure gauges include a first pressure gauge, a second pressure gauge, a third pressure gauge, a fourth pressure gauge, and a fifth pressure gauge;

[0030] The fifth pressure gauge is installed on the oil outlet pipe of the pressure reducing valve to display the oil pressure inside the accumulator bladder.

[0031] The proportional directional valve includes a first electromagnet and a second electromagnet, which are used to control the proportional directional valve to switch to the forward operating position and the reverse operating position, respectively.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] This invention transmits the pressure of the actuator testing system (oil medium) to the seawater pressurization system via an accumulator bladder. This eliminates the need for a separate, corrosion-resistant high-pressure seawater system; only a pressure chamber and simple piping are required to simulate the external pressure environment of seawater, significantly reducing equipment construction and maintenance costs. Using a bladder-type accumulator as the pressure transmission element, the elastic deformation of the bladder achieves a balanced transmission of oil and seawater pressure, eliminating mechanical friction and leakage risks, resulting in stable and highly accurate pressure transmission. Simultaneously, by setting the oil pressure within the accumulator bladder using a pressure-reducing valve, the seawater pressure within the pressure tank can be precisely controlled, simulating deep-sea environments at different depths (pressure levels), thus broadening its applicability. Furthermore, this system is not only suitable for seawater media but can also be replaced with fresh water or other media as needed to achieve durability testing of hydraulic motors under different external pressure environments, demonstrating excellent versatility. Moreover, through the coordination of components such as proportional directional valves, two-way throttle valves, and relief valves, this system can simulate the working state of the tested hydraulic motor under different speeds, directions, and loads, meeting diverse durability testing requirements. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a hydraulic motor durability testing system under simulated seawater medium external pressure environment, as described in this invention.

[0035] In the picture:

[0036] 1. Hydraulic oil tank;

[0037] 2. Hydraulic pump;

[0038] 3. Motor;

[0039] 4. Flow meter;

[0040] 5. Proportional directional valve;

[0041] 6. Two-way throttle valve;

[0042] 7.1 First pressure sensor; 7.2 Second pressure sensor; 7.3 Third pressure sensor; 7.4 Fourth pressure sensor;

[0043] 8.1 First pressure gauge; 8.2 Second pressure gauge; 8.3 Third pressure gauge; 8.4 Fourth pressure gauge; 8.5 Fifth pressure gauge;

[0044] 9.1 First check valve; 9.2 Second check valve;

[0045] 10.1 First relief valve; 10.2 Second relief valve; 10.3 Third relief valve;

[0046] 11. Pressure reducing valve;

[0047] 12. Accumulator;

[0048] 13.1 The hydraulic motor under test; 13.2 The hydraulic motor to be tested;

[0049] 14. Couplings;

[0050] 15.1 First shut-off valve; 15.2 Second shut-off valve;

[0051] 16. Pressure chamber;

[0052] 17. Isolation valve;

[0053] a. The first electromagnet;

[0054] b. The second electromagnet;

[0055] A. The first working oil port of the hydraulic motor under test;

[0056] B. The second working oil port of the tested hydraulic motor;

[0057] C. Test the third working oil port of the hydraulic motor;

[0058] D. Test the fourth working oil port of the hydraulic motor;

[0059] A1, First pipeline;

[0060] B1, Second Pipeline;

[0061] C1, Third pipeline;

[0062] D1, Fourth Pipeline. Detailed Implementation

[0063] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0064] Example 1

[0065] This embodiment discloses a hydraulic motor durability test system under simulated seawater medium external pressure environment.

[0066] Reference Appendix Figure 1It mainly consists of 1-hydraulic oil tank, 2-hydraulic pump, 3-motor, 4-flow meter, 5-proportional directional valve, 6-two-way throttle valve, 7.1-first pressure sensor, 7.2-second pressure sensor, 7.3-third pressure sensor, 7.4-fourth pressure sensor, 8.1-first pressure gauge, 8.2-second pressure gauge, 8.3-third pressure gauge, 8.4-fourth pressure gauge, 8.5-fifth pressure gauge, 9.1-first check valve, 9.2-second check valve, 10.1-first relief valve, 10.2-second relief valve, 10.3-third relief valve, 11-pressure reducing valve, 12-accumulator, 13.1-tested hydraulic motor, 13.2-matched hydraulic motor, 14-coupling, 15.1-first shut-off valve, 15.2-second shut-off valve, 16-pressure chamber, 17-isolation valve, etc.

[0067] Hydraulic oil tank 1 supplies hydraulic oil to the test system; hydraulic pump 2 and motor 3 provide power to the system; flow meter 4 records the actual flow rate used by the test motor; proportional directional valve 5 is used for program control of the hydraulic motor speed and direction; two-way throttle valve 6 is used for manual adjustment of the hydraulic motor speed; first pressure sensor 7.1, second pressure sensor 7.2, first pressure gauge 8.1, and second pressure gauge 8.2 record the actual working pressure of the two chambers of the tested hydraulic motor 13.1; third pressure sensor 7.3, fourth pressure sensor 7.4, third pressure gauge 8.3, and fourth pressure gauge 8.4 record the actual working pressure of the two chambers of the tested hydraulic motor 13.2; coupling 14 is used to connect the tested hydraulic motor... Motor 13.1 and test hydraulic motor 13.2, first check valve 9.1 and second check valve 9.2 are used to replenish oil to test hydraulic motor 13.2, first relief valve 10.1 and second relief valve 10.2 are used to adjust the load pressure of test hydraulic motor 13.2, third relief valve 10.3 is used to protect the system and set the maximum working pressure of the system, pressure reducing valve 11 is used to adjust the pressure acting on the air chamber of bladder accumulator 12, bladder accumulator 12 transmits the air chamber oil pressure to the seawater pressure inside pressure tank 16, first shut-off valve 15.1 and second shut-off valve 15.2 are used to inject seawater and vent air into pressure tank 16, and isolation valve 17 is used to cut off the pressure connection between the two systems.

[0068] When the tested hydraulic motor 13.1 rotates forward, the system works as follows: the first electromagnet a of the proportional directional valve 5 is energized. At this time, the hydraulic oil passes through the flow meter 4, the proportional directional valve 5 and the two-way throttle valve 6, and enters the first working port A of the tested hydraulic motor 13.1 through the first pipeline A1. At this time, the tested hydraulic motor 13.1 is defined as rotating forward. The return oil from the second working port B of the tested hydraulic motor 13.1 passes through the proportional directional valve 5, through the second check valve 9.2, and through the fourth pipeline D1 into the third working port C of the tested hydraulic motor 13.2. The oil then passes through the fourth working port D of the tested hydraulic motor 13.2, through the third pipeline C1 and through the first relief valve 10.1 back to the hydraulic oil tank 1.

[0069] When the tested hydraulic motor 13.1 rotates forward, flow control is achieved by adjusting the valve opening of the proportional directional valve 5. The actual speed of the tested hydraulic motor 13.1 is calculated in real time by the flow meter 4. By adjusting the first relief valve 10.1, pressure is established in the cavity where the fourth working port D of the tested hydraulic motor 13.2 is located, thereby loading the motor load. At this time, the actual working pressure of the two cavities of the tested hydraulic motor 13.1 can be displayed by the first pressure gauge 8.1, the second pressure gauge 8.2, the first pressure sensor 7.1, and the second pressure sensor 7.2. The actual working pressure of the two cavities of the tested hydraulic motor 13.2 can be displayed by the third pressure gauge 8.3, the fourth pressure gauge 8.4, the third pressure sensor 7.3, and the fourth pressure sensor 7.4. The current load of the motor can be calculated.

[0070] When the tested hydraulic motor 13.1 reverses, the system works as follows: the second electromagnet b of the proportional directional valve 5 is energized. At this time, the hydraulic oil passes through the flow meter 4, the proportional directional valve 5 and the two-way throttle valve 6, and enters the second working port B of the tested hydraulic motor 13.1 through the second pipeline B1. At this time, the tested hydraulic motor 13.1 is defined as reversing. The return oil from the first working port A of the tested hydraulic motor 13.1 passes through the proportional directional valve 5, through the first check valve 9.1, and through the third pipeline C1 into the fourth working port D of the tested hydraulic motor 13.2. The oil then flows back to the hydraulic oil tank 1 through the third working port C of the tested hydraulic motor 13.2, through the fourth pipeline D1 and through the second relief valve 10.2.

[0071] When the tested hydraulic motor 13.1 reverses, flow control is achieved by adjusting the opening of the proportional directional valve 5. The actual speed of the tested hydraulic motor 13.1 is calculated in real time by the flow meter 4. By adjusting the second relief valve 10.2, pressure is established in the cavity where the third working oil port C of the tested hydraulic motor 13.2 is located, thereby loading the motor load. At this time, the actual working pressure of the two cavities of the tested hydraulic motor 13.1 can be displayed by the first pressure gauge 8.1, the second pressure gauge 8.2, the first pressure sensor 7.1, and the second pressure sensor 7.2. Similarly, the actual working pressure of the two cavities of the tested hydraulic motor 13.2 can be displayed by the third pressure gauge 8.3, the fourth pressure gauge 8.4, the third pressure sensor 7.3, and the fourth pressure sensor 7.4, allowing the calculation of the current motor load.

[0072] The pressure in the pressure chamber 16 is established as follows: the first shut-off valve 15.1 and the second shut-off valve 15.2 are opened, and seawater is manually injected through the first shut-off valve 15.1. The air inside the pressure chamber 16 is discharged through the second shut-off valve 15.2. When the second shut-off valve 15.2 discharges seawater, it proves that the internal cavity of the pressure chamber 16 is filled with seawater. The first shut-off valve 15.1 and the second shut-off valve 15.2 are closed. At this time, the external environment of the tested hydraulic motor 13.1 changes from air to seawater.

[0073] After the pressure tank 16 is filled with seawater, the isolation valve 17 is opened. The oil pressure output by the hydraulic pump 2 enters the bladder of the accumulator 12 through the isolation valve 17 and the pressure reducing valve 11. Since the bladder is an elastic body, the pressure inside and outside the bladder of the accumulator 12 is the same at this time. That is, the seawater pressure inside the pressure tank 16 is the same as the oil pressure inside the bladder of the accumulator 12. At the same time, the pressure reducing valve 11 is adjusted. By observing the fifth pressure gauge 8.5, the current seawater pressure can be viewed and set.

[0074] Example 2

[0075] This embodiment is basically the same as Embodiment 1, except that, depending on the experimental requirements, the seawater medium in the pressure chamber 16 can be replaced with fresh water to simulate the external pressure conditions under a fresh water environment. Other operating procedures are the same as in Embodiment 1 and will not be repeated here.

[0076] This invention connects two independent systems (seawater and oil) by using an accumulator bladder to transmit pressure. At the same time, this solution can be used to simulate external environments with different media. Simply changing the medium in the pressure tank (seawater, freshwater, or oil) is sufficient to simulate the external pressure environment, greatly reducing the cost of equipment construction and maintenance.

[0077] The above description only illustrates preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. Any equivalent procedural modifications made using this specification are included within the patent protection scope of this invention.

Claims

1. A durability testing system for a hydraulic motor under simulated seawater medium external pressure environment, characterized in that: include A seawater pressurization system is used to provide a simulated external pressure environment of seawater for the tested hydraulic motor; An actuator testing system for driving and controlling the operation of a hydraulic motor under test; The actuator test system transmits the oil medium pressure to the seawater pressurization system through the bladder of the accumulator (12) to simulate the internal pressure environment of the water pressure tank, and adjusts the transmitted pressure through the pressure reducing valve (11).

2. The hydraulic motor durability test system under simulated seawater medium external pressure environment according to claim 1, characterized in that: The actuator test system includes a hydraulic tank (1), a hydraulic pump (2), a motor (3), a flow meter (4), a proportional directional valve (5), a two-way throttle valve (6), a pressure sensor (7), a pressure gauge (8), a check valve (9), a relief valve (10), a pressure reducing valve (11), an accumulator (12), a hydraulic motor under test (13.1), a hydraulic motor under test (13.2), a coupling (14), a shut-off valve (15), a pressure chamber (16), and an isolation valve (17). The outlet of the hydraulic oil tank (1) is connected to the inlet of the hydraulic pump (2), the motor (3) is connected to the hydraulic pump (2) in a transmission, and the outlet of the hydraulic pump (2) is connected to the inlet of the hydraulic motor (13.1) under test via the flow meter (4), the proportional directional valve (5), and the two-way throttle valve (6) in sequence. The oil outlet of the tested hydraulic motor (13.1) is connected to the oil inlet of the tested hydraulic motor (13.2) via the proportional directional valve (5) and the check valve (9), and the oil outlet of the tested hydraulic motor (13.2) is connected to the return port of the hydraulic oil tank (1) via the overflow valve (10). The oil outlet of the hydraulic pump (2) is connected in sequence to the inner cavity of the bladder of the accumulator (12) via the isolation valve (17) and the pressure reducing valve (11). The outer cavity of the bladder of the accumulator (12) is connected to the inner cavity of the pressure tank (16). The pressure tank (16) is equipped with a shut-off valve (15) for injecting seawater medium. The pressure sensor (7) and pressure gauge (8) are respectively installed on the inlet and outlet oil pipes of the hydraulic motor under test (13.1) and the hydraulic motor under test (13.2).

3. The hydraulic motor durability testing system under simulated seawater medium external pressure environment according to claim 2, characterized in that: The accumulator (12) is a bladder-type accumulator. Its inner cavity is connected to the oil outlet of the pressure reducing valve (11) through a pipeline. The outside of the bladder is in direct contact with the seawater medium in the pressure tank (16). The oil pressure and seawater pressure are balanced and transmitted through the elastic deformation of the bladder. By adjusting the output pressure of the pressure reducing valve (11), the oil pressure in the bladder of the accumulator (12) is controlled, thereby adjusting the seawater pressure in the pressure tank (16).

4. The hydraulic motor durability testing system under simulated seawater medium external pressure environment according to claim 2, characterized in that: The test hydraulic motor (13.1) and the matching hydraulic motor (13.2) are coaxially connected through the coupling (14). The proportional directional valve (5) and the two-way throttle valve (6) are used to control the speed and direction of the test hydraulic motor (13.1). The return oil of the test hydraulic motor (13.1) is supplied to the matching hydraulic motor (13.2) through the check valve (9). The matching hydraulic motor (13.2) establishes load pressure through the relief valve (10).

5. The hydraulic motor durability testing system under simulated seawater medium external pressure environment according to claim 4, characterized in that: When the tested hydraulic motor (13.1) rotates forward, the first electromagnet (a) of the proportional directional valve (5) is energized, and the hydraulic oil passes through the flow meter (4), the proportional directional valve (5) and the two-way throttle valve (6), and enters the first working port of the tested hydraulic motor (13.1) through the pipeline. The return oil from the second working port of the tested hydraulic motor (13.1) enters the third working port of the tested hydraulic motor (13.2) through the proportional directional valve (5), the second check valve (9.2) and the pipeline. The oil then flows back to the hydraulic oil tank (1) through the fourth working port of the tested hydraulic motor (13.2) through the pipeline and the first relief valve (10.1).

6. The hydraulic motor durability testing system under simulated seawater medium external pressure environment according to claim 4, characterized in that: When the tested hydraulic motor (13.1) reverses, the second electromagnet (b) of the proportional directional valve (5) is energized, and the hydraulic oil passes through the flow meter (4), the proportional directional valve (5) and the two-way throttle valve (6), and enters the second working port of the tested hydraulic motor (13.1) through the pipeline. The return oil from the first working port of the tested hydraulic motor (13.1) enters the fourth working port of the matched hydraulic motor (13.2) through the proportional directional valve (5), the first check valve (9.1) and the pipeline. The oil then flows back to the hydraulic oil tank (1) through the third working port of the matched hydraulic motor (13.2) through the pipeline and the second relief valve (10.2).

7. The hydraulic motor durability testing system under simulated seawater medium external pressure environment according to claim 2, characterized in that: The pressure chamber (16) is equipped with two shut-off valves, namely a first shut-off valve (15.1) and a second shut-off valve (15.2). The first shut-off valve (15.1) is connected to an external seawater injection pipeline for injecting seawater into the pressure chamber (16). The second shut-off valve (15.2) is connected to an exhaust pipeline for venting air from the pressure chamber (16) during the water injection process. When the second shut-off valve (15.2) vents seawater, the first shut-off valve (15.1) and the second shut-off valve (15.2) are closed, and the internal cavity of the pressure chamber (16) is filled with seawater. The external environment of the tested hydraulic motor (13.1) changes from air to seawater.

8. The hydraulic motor durability testing system under simulated seawater medium external pressure environment according to claim 7, characterized in that: After the pressure tank (16) is filled with seawater, the isolation valve (17) is opened. The oil pressure output by the hydraulic pump (2) enters the bladder of the accumulator (12) through the isolation valve (17) and the pressure reducing valve (11). Since the bladder is an elastic body, the pressure inside and outside the bladder of the accumulator (12) is the same, that is, the seawater pressure inside the pressure tank (16) is the same as the oil pressure inside the bladder of the accumulator (12). By adjusting the pressure reducing valve (11) and observing the fifth pressure gauge (8.5), the current seawater pressure can be viewed and set.

9. The hydraulic motor durability test system under simulated seawater medium external pressure environment according to claim 2, characterized in that: The relief valve (10) includes a first relief valve (10.1) and a second relief valve (10.2), and the check valve (9) includes a first check valve (9.1) and a second check valve (9.2); wherein: The inlet of the first relief valve (10.1) is connected to the fourth working port of the test hydraulic motor (13.2), and the outlet of the first relief valve (10.1) is connected to the hydraulic oil tank (1). The oil inlet of the second relief valve (10.2) is connected to the third working oil port of the hydraulic motor (13.2) being tested, and the oil outlet of the second relief valve (10.2) is connected to the hydraulic oil tank (1). The first check valve (9.1) is located between the proportional directional valve (5) and the fourth working port of the test hydraulic motor (13.2), with its inlet connected to the proportional directional valve (5) and its outlet connected to the fourth working port of the test hydraulic motor (13.2). The second check valve (9.2) is located between the proportional directional valve (5) and the third working port of the test hydraulic motor (13.2). Its inlet is connected to the proportional directional valve (5), and its outlet is connected to the third working port of the test hydraulic motor (13.2).

10. The hydraulic motor durability testing system under simulated seawater medium external pressure environment according to claim 2, characterized in that: The system also includes a third relief valve (10.3), the oil inlet of which is connected to the oil outlet of the hydraulic pump (2), and its oil outlet is connected to the hydraulic oil tank (1), which is used to set the maximum working pressure of the system and to provide overload protection for the system. The pressure sensor (7) includes a first pressure sensor (7.1), a second pressure sensor (7.2), a third pressure sensor (7.3), and a fourth pressure sensor (7.4). The pressure gauge (8) includes a first pressure gauge (8.1), a second pressure gauge (8.2), a third pressure gauge (8.3), a fourth pressure gauge (8.4), and a fifth pressure gauge (8.5). The fifth pressure gauge (8.5) is installed on the oil outlet pipe of the pressure reducing valve (11) to display the oil pressure in the accumulator (12) bladder; The proportional directional valve (5) includes a first electromagnet (a) and a second electromagnet (b), which are used to control the proportional directional valve (5) to switch to the forward working position and the reverse working position, respectively.

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