A hydraulic pump-motor testing system and testing method

Abstract

The present invention discloses a hydraulic pump and motor test system and a test method. The test system includes: a variable pump, a hydraulic motor, a hydraulic pump, a relief valve, and a fuel tank; wherein, the oil outlet of the variable pump is connected to the oil outlet of the hydraulic pump; wherein, the oil outlet of the hydraulic pump serves as a hydraulic oil source when the hydraulic pump is operating, outputting hydraulic oil; the pipeline connecting the oil outlet of the variable pump and the oil outlet of the hydraulic pump is also respectively connected to the oil inlet of the hydraulic motor and the oil inlet of the relief valve; the fuel tank is respectively connected to the oil inlet of the variable pump, the oil inlet of the hydraulic pump, the oil outlet of the hydraulic motor, and the oil outlet of the relief valve. By adopting the embodiment of the present invention, the oil outlet of the hydraulic pump can be used as a high-pressure oil source, and the hydraulic potential energy can be input into the hydraulic motor through the hydraulic oil to realize energy recovery, avoiding the energy waste caused by using the relief valve for loading.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic pump and motor performance testing, and particularly to a hydraulic pump and motor testing system and a testing method. Background Art

[0002] During the testing process of a hydraulic test bench, electrical energy from the power grid is converted into mechanical energy by a motor, which then drives a hydraulic pump to convert the electrical energy into hydraulic potential energy, and relevant parameters of the hydraulic circuit are detected in accordance with national testing standards. However, a large amount of hydraulic potential energy is converted into heat and consumed during the testing of such a hydraulic test bench. In the prior art, a power recovery type hydraulic test bench is used to test hydraulic components to solve this problem. However, this type of test bench generally uses an overflow valve for test loading, which will cause the hydraulic potential energy to be converted into heat and consumed, resulting in an energy waste problem. Summary of the Invention

[0003] The present invention provides a hydraulic pump and motor testing system and a testing method to solve the technical problem of energy waste caused by using an overflow valve for test loading in a power recovery type test bench.

[0004] To solve the above technical problem, an embodiment of the present invention provides a hydraulic pump and motor testing system, including: a variable pump, a hydraulic motor, a hydraulic pump, an overflow valve, and a fuel tank;

[0005] Wherein, the oil outlet of the variable pump is connected to the oil outlet of the hydraulic pump; wherein, the oil outlet of the hydraulic pump is a hydraulic oil source when the hydraulic pump is running, and outputs hydraulic oil;

[0006] The pipeline connecting the oil outlet of the variable pump and the oil outlet of the hydraulic pump is also respectively connected to the oil inlet of the hydraulic motor and the oil inlet of the overflow valve;

[0007] The hydraulic motor is connected to the hydraulic pump through a coupling;

[0008] The fuel tank is respectively connected to the oil inlet of the variable pump, the oil inlet of the hydraulic pump, the oil outlet of the hydraulic motor, and the oil outlet of the overflow valve.

[0009] In the present invention, the hydraulic motor and the hydraulic pump are coaxially connected to ensure the same rotational speed of the two and start the testing system; the oil outlet of the hydraulic pump is connected to the oil outlet of the variable pump and the oil inlet of the overflow valve, and then connected to the oil inlet of the hydraulic motor; the high-pressure oil source at the oil outlet of the hydraulic pump, which is generally wasted in different forms, together with the high-pressure oil source at the oil outlet of the variable pump, drives the hydraulic motor together to realize the recovery of the hydraulic potential energy of the hydraulic pump, avoiding the energy waste caused by using an overflow valve for loading.

[0010] Furthermore, the hydraulic pump and motor testing system further includes a power motor;

[0011] Among them, the power motor is connected to the variable pump through a coupling.

[0012] Furthermore, the hydraulic pump-motor test system further includes a reversing valve;

[0013] The pressure oil ports of the reversing valve are respectively connected to the oil outlet of the variable pump, the oil outlet of the hydraulic pump, and the oil inlet of the overflow valve;

[0014] The oil outlet of the reversing valve is connected to the oil inlet of the hydraulic motor;

[0015] The oil inlet of the reversing valve is connected to the oil return port of the hydraulic motor;

[0016] The oil return port of the reversing valve is respectively connected to the oil outlet of the overflow valve and the fuel tank.

[0017] Furthermore, the hydraulic pump-motor test system further includes a first pressure sensor and a second pressure sensor;

[0018] Among them, the first pressure sensor is installed on the branch path from the connection between the oil outlet of the variable pump and the oil outlet of the hydraulic pump to the oil inlet of the overflow valve;

[0019] The second pressure sensor is installed at the oil outlet of the overflow valve.

[0020] In the present invention, the power motor is coaxially connected to the variable pump. By adjusting the speed of the power motor, the displacement of the variable pump can be controlled, and further the speed of the hydraulic motor can be adjusted; the reversing valve in the present invention is connected to the oil inlet of the hydraulic motor, the oil outlet of the variable pump, and the oil outlet of the hydraulic pump to control the rotation direction of the hydraulic motor; the first pressure sensor installed on the common branch path of the oil outlet of the variable pump and the oil outlet of the hydraulic pump can measure the oil outlet pressure, and the second pressure sensor installed at the oil outlet of the overflow valve can measure the oil return pressure to obtain relevant data required for testing.

[0021] Furthermore, the hydraulic pump-motor test system further includes: an air filter, a fuel tank magnet, a heater, and an oil drain ball valve;

[0022] Among them, the air filter is installed at the air inlet of the fuel tank;

[0023] The fuel tank magnet is installed at the bottom inside the return side of the fuel tank;

[0024] The heater is installed inside the fuel tank;

[0025] The oil drain ball valve is installed at the bottom of the fuel tank.

[0026] The air filter installed at the air inlet of the fuel tank filters the air entering the fuel tank to ensure the dryness and cleanliness of the air; the fuel tank magnet installed at the bottom inside the return side is used to filter out iron filings through the return oil filter; the heater installed inside the fuel tank heats the hydraulic oil in the fuel tank; the drain ball valve installed at the bottom of the fuel tank enables the discharge of the hydraulic oil; the above devices together enable the fuel tank to work in a stable state, thereby ensuring the stable operation of the test system.

[0027] Further, the hydraulic pump motor test system further includes: a temperature sensor, a liquid level sensor, and a liquid level sight glass;

[0028] Wherein, the temperature sensor is installed at the top of the fuel tank;

[0029] The liquid level sensor is installed inside the fuel tank;

[0030] The liquid level sight glass is installed on the side of the fuel tank.

[0031] In the present invention, the temperature sensor installed at the top of the fuel tank, the liquid level sensor inside the fuel tank, and the liquid level sight glass on the side of the fuel tank are respectively used to monitor or collect the temperature of the fuel tank, the hydraulic oil volume in the fuel tank, and the hydraulic oil level, ensuring that the staff continuously monitors the working state of the fuel tank to maintain the test system working in a normal state.

[0032] On the other hand, the present invention also provides a hydraulic pump motor test method, which is applied to the hydraulic pump motor test system described in the embodiments of the present invention. The hydraulic pump motor test method includes:

[0033] Adjust the speed of the hydraulic motor to make the speed stable at the rated speed;

[0034] After the hydraulic motor works at the rated speed, adjust the hydraulic motor to make the hydraulic motor work at the rated pressure, and record the outlet pressure and the return port pressure;

[0035] Calculate the energy recovery rate according to the outlet pressure and the return port pressure.

[0036] Further, the adjusting the speed of the hydraulic motor to make the speed stable at the rated speed is specifically:

[0037] Adjust the speed of the power motor and the displacement of the variable pump to make the hydraulic motor work at the rated speed.

[0038] Further, the after the hydraulic motor works at the rated speed, adjusting the hydraulic motor to make the hydraulic motor work at the rated pressure, and recording the outlet pressure and the return port pressure is specifically:

[0039] After the hydraulic motor operates at the rated speed, adjust the relief valve so that the outlet pressure of the variable pump gradually increases, thereby stabilizing the inlet pressure of the hydraulic motor at the rated pressure;

[0040] When the inlet pressure of the hydraulic motor is stabilized at the rated pressure, record the outlet pressure on the branch line from the connection between the outlet of the variable pump and the outlet of the hydraulic pump to the inlet of the relief valve, and the return oil pressure at the outlet of the relief valve.

[0041] Furthermore, the calculation expression of the energy recovery rate is:

[0042]

[0043] Among them, η Mm is the mechanical efficiency of the motor, η Mv is the volumetric efficiency of the motor, η bv is the volumetric efficiency of the variable pump, η bm is the mechanical efficiency of the variable pump, η b is the total efficiency of the variable pump, η p is the total efficiency of the loading pump, η M is the total efficiency of the motor, p m is the pressure difference between the outlet and inlet of the hydraulic motor, p b is the pressure difference between the outlet and inlet of the variable pump, p1 is the return oil pressure, and p2 is the outlet pressure of the variable pump.

[0044] The present invention adjusts the power motor, variable pump, etc., so that the hydraulic motor operates at the rated state, then measures the outlet pressure and return oil pressure, and calculates the energy recovery rate of the hydraulic pump-motor test system. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic connection diagram of an embodiment of the hydraulic pump-motor test system provided by the present invention;

[0046] Figure 2 is a schematic connection diagram of another embodiment of the hydraulic pump-motor test system provided by the present invention;

[0047] Figure 3 is a schematic flow chart of an embodiment of the hydraulic pump-motor test method provided by the present invention;

[0048] Among them, the reference numerals in the drawings of the specification are as follows: 1 variable pump, 2 hydraulic motor, 3 hydraulic pump, 4 relief valve, 5 power motor, 6 power pipeline, 7 reversing valve, 8 temperature sensor, 9 liquid level window, 10 air filter, 11 tank magnet, 12 heater, 13 liquid level sensor, 14 drain ball valve, 15 tank, 16-1 first pressure sensor, 16-2 second pressure sensor. Specific Embodiment

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] Embodiment 1

[0051] Please refer to Figure 1 , which is a schematic connection diagram of an embodiment of the hydraulic pump and motor test system provided by the embodiments of the present invention. The hydraulic pump and motor test system includes: a variable pump 1, a hydraulic motor 2, a hydraulic pump 3, a relief valve 4, and a fuel tank 15.

[0052] Wherein, the oil outlet of the variable pump 1 is connected to the oil outlet of the hydraulic pump 3; wherein, the oil outlet of the hydraulic pump 3 is a hydraulic oil source during the operation of the hydraulic pump, and outputs hydraulic oil.

[0053] The pipeline connecting the oil outlet of the variable pump 1 and the oil outlet of the hydraulic pump 3 is also respectively connected to the oil inlet of the hydraulic motor 2 and the oil inlet of the relief valve 4.

[0054] The hydraulic motor 2 is connected to the hydraulic pump 3 through a coupling.

[0055] The fuel tank 15 is respectively connected to the oil inlet of the variable pump 1, the oil inlet of the hydraulic pump 3, the oil outlet of the hydraulic motor 2, and the oil outlet of the relief valve 4.

[0056] In this embodiment, by connecting the oil outlet of the hydraulic pump 3 to the oil outlet of the variable pump 1 with a pipeline, and the pipeline is also connected to the relief valve, the oil inlet and the oil inlet of the hydraulic motor 2, the hydraulic potential energy generated by the hydraulic pump 3 can be transmitted to the oil inlet of the hydraulic motor 2 through the oil outlet of the hydraulic pump 3 as the high-pressure port, and then return to the fuel tank through the oil outlet of the hydraulic motor 2. The relief valve 4 can adjust the flow rate of the hydraulic oil flowing through the relief valve 4, thereby adjusting the pressure at the oil outlet of the variable pump 1 and the pressure at the oil inlet of the hydraulic motor 2. In addition, the hydraulic motor 2 is coaxially connected to the hydraulic pump 3, and the two maintain the same rotational speed; the output torque feedback of the hydraulic motor 2 drives the hydraulic pump 3, and the hydraulic pump 3 inputs high-pressure hydraulic oil into the hydraulic motor 2 to stabilize the system pressure of the hydraulic motor 2 at a preset value.

[0057] The oil outlet of the hydraulic pump of the present invention is connected to the oil outlet of the variable pump and the oil inlet of the overflow valve, and then connected to the oil inlet of the hydraulic motor; the high-pressure oil source at the oil outlet of the hydraulic pump, which is generally wasted in different forms, together with the high-pressure oil source at the oil outlet of the variable pump, jointly drives the hydraulic motor, realizing the recovery of the hydraulic potential energy of the hydraulic pump and avoiding the energy waste caused by using the overflow valve for loading.

[0058] Please refer to Figure 2 , which is a schematic connection diagram of another embodiment of the hydraulic pump-motor test system provided by the embodiment of the present invention. The hydraulic pump-motor test system further includes: a power motor 5.

[0059] Wherein, the power motor 5 is connected to the variable pump 1 through a coupling.

[0060] Furthermore, the hydraulic pump-motor test system further includes a reversing valve 7;

[0061] The pressure oil ports of the reversing valve 7 are respectively connected to the oil outlet of the variable pump 1, the oil outlet of the hydraulic pump 3, and the oil inlet of the overflow valve 4;

[0062] The oil outlet of the reversing valve 7 is connected to the oil inlet of the hydraulic motor 2;

[0063] The oil inlet of the reversing valve 7 is connected to the oil return port of the hydraulic motor 2;

[0064] The oil return port of the reversing valve 7 is respectively connected to the oil outlet of the overflow valve 4 and the fuel tank 15.

[0065] Furthermore, the hydraulic pump-motor test system further includes a first pressure sensor 16-1 and a second pressure sensor 16-2;

[0066] Wherein, the first pressure sensor 16-1 is installed on the branch line from the connection point of the oil outlet of the variable pump 1 and the oil outlet of the hydraulic pump 3 to the oil inlet of the overflow valve 4;

[0067] The second pressure sensor 16-2 is installed on the oil outlet of the overflow valve 4.

[0068] In this embodiment, the power motor 5 is coaxially connected to the variable pump 1. By adjusting the rotational speed of the power motor 5, the displacement of the variable pump 1 can be controlled, thereby achieving the adjustment of the rotational speed of the hydraulic motor 2. The reversing valve 7 in the present invention is connected to the oil inlet of the hydraulic motor 2, the oil outlet of the variable pump 1, and the oil outlet of the hydraulic pump 3 to control the rotational direction of the hydraulic motor 2. The first pressure sensor 16-1 installed on the common branch of the oil outlet of the variable pump 1 and the oil outlet of the hydraulic pump 3 can measure the oil outlet pressure, and the second pressure sensor 16-2 installed on the oil outlet of the overflow valve can measure the oil return port pressure to obtain the relevant data required for testing.

[0069] Furthermore, the hydraulic pump and motor test system further includes: an air filter 10, a tank magnet 11, a heater 12, and an oil drain ball valve 14;

[0070] Wherein, the air filter 10 is installed at the air inlet of the fuel tank 15;

[0071] The tank magnet 11 is installed at the bottom inside the return side of the fuel tank 15;

[0072] The heater 12 is installed inside the fuel tank 15;

[0073] The oil drain ball valve 14 is installed at the bottom of the fuel tank 15.

[0074] In this embodiment, the air filter 10 installed at the air inlet of the fuel tank 15 filters the air entering the fuel tank 15 to ensure the dryness and cleanliness of the air. The tank magnet 11 installed at the bottom inside the return side of the fuel tank 15 is used to filter the iron filings passing through the oil return filter. The heater 12 installed inside the fuel tank 15 heats the hydraulic oil in the fuel tank 15. The oil drain ball valve 14 installed at the bottom of the fuel tank 15 can achieve the discharge of the hydraulic oil. The above devices together enable the fuel tank 15 to work in a stable state, thereby ensuring the stable operation of the test system.

[0075] Furthermore, the hydraulic pump and motor test system further includes: a temperature sensor 8, a liquid level sensor 13, and a liquid level sight glass 9;

[0076] Wherein, the temperature sensor 8 is installed at the top of the fuel tank 15;

[0077] The liquid level sensor 13 is installed inside the fuel tank 15;

[0078] The liquid level sight glass 9 is installed on the side of the fuel tank 15.

[0079] In this embodiment, the temperature sensor 8 installed on the top of the fuel tank 15, the liquid level sensor 13 inside the fuel tank 15, and the liquid level sight glass 9 on the side of the fuel tank 15 are respectively used to monitor or collect the temperature of the fuel tank 15, the hydraulic oil volume of the fuel tank 15, and the hydraulic oil level, ensuring that the staff continuously monitors the working state of the fuel tank 15 to maintain the test system working in a normal state.

[0080] In this embodiment, the pipeline connecting the variable pump 1 with the hydraulic motor 2, the hydraulic pump 3, the overflow valve 4, and the reversing valve 7 is the power pipeline 6, and the fuel tank is also connected to the variable pump 1, the hydraulic motor 2, the hydraulic pump 3, the overflow valve 4, and the reversing valve 7 respectively through the power pipeline 6. In the hydraulic pump - motor test system of the present invention, the element to be measured can be the hydraulic motor 2 or the hydraulic pump 3.

[0081] Please refer to Figure 3 , which is a schematic flow diagram of an embodiment of the hydraulic pump - motor test method provided by the embodiment of the present invention. It mainly includes steps 101 to 103, and the specific content is as follows:

[0082] Step 101: Adjust the speed of the hydraulic motor to make the speed stable at the rated speed.

[0083] In this embodiment, the adjusting the speed of the hydraulic motor to make the speed stable at the rated speed is specifically: adjusting the speed of the power motor and the displacement of the variable pump so that the hydraulic motor operates at the rated speed.

[0084] Step 102: After the hydraulic motor operates at the rated speed, adjust the hydraulic motor so that the hydraulic motor operates at the rated pressure, and record the outlet pressure and the return - oil port pressure.

[0085] In this embodiment, the after the hydraulic motor operates at the rated speed, adjusting the hydraulic motor so that the hydraulic motor operates at the rated pressure, and recording the outlet pressure and the return - oil port pressure is specifically: after the hydraulic motor operates at the rated speed, adjust the overflow valve so that the outlet pressure of the variable pump gradually increases, and then make the inlet - oil port pressure of the hydraulic motor stable at the rated pressure; when the inlet - oil port pressure of the hydraulic motor is stable at the rated pressure, record the outlet pressure on the branch pipeline from the connection of the outlet of the variable pump and the outlet of the hydraulic pump to the inlet of the overflow valve, and the return - oil port pressure of the outlet of the overflow valve.

[0086] Step 103: Calculate the energy recovery rate according to the outlet pressure and the return - oil port pressure.

[0087] In this embodiment, the calculation expression of the energy recovery rate is:

[0088]

[0089] where η Mm is the mechanical efficiency of the motor, η Mv is the volumetric efficiency of the motor, η bv is the volumetric efficiency of the variable pump, η bm is the mechanical efficiency of the variable pump, η b is the overall efficiency of the variable pump, η p is the overall efficiency of the loading pump, η M is the overall efficiency of the motor, p m is the pressure difference between the outlet and inlet ports of the hydraulic motor, p b is the pressure difference between the outlet and inlet ports of the variable pump, p1 is the return port pressure, and p2 is the outlet port pressure of the variable pump.

[0090] In this embodiment, the volumetric efficiency of the variable pump ≥ 95%, and the overall efficiency of the variable pump ≥ 85%; the volumetric efficiency of the motor ≥ 95%, and the overall efficiency of the motor ≥ 83%; when the return port pressure is 0, the energy recovery rate of the hydraulic pump - motor test system is 74%, and generally the energy recovery efficiency is between 40% and 70%.

[0091] The present invention adjusts the power motor, variable pump, etc., enables the hydraulic motor to work under the rated condition, then measures the outlet port pressure and return port pressure, and calculates the energy recovery rate of the hydraulic pump - motor test system.

[0092] In the present invention, the hydraulic motor and the hydraulic pump are coaxially connected to ensure the same rotational speed of the two and start the test system; the outlet port of the hydraulic pump is connected to the outlet port of the variable pump and the inlet port of the relief valve, and then connected to the inlet port of the hydraulic motor; the high - pressure oil source at the outlet port of the hydraulic pump, which is generally wasted in different forms, and the high - pressure oil source at the outlet port of the variable pump jointly drive the hydraulic motor, realizing the recovery of the hydraulic potential energy of the hydraulic pump and avoiding the problem of energy waste caused by using the relief valve for loading.

[0093] The above - described specific embodiments further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above - described are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. In particular, for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hydraulic pump motor test system, characterized in that, Comprising: Variable pump, hydraulic motor, hydraulic pump, relief valve, power motor, reversing valve and oil tank; Wherein, the oil outlet of the variable pump is connected to the oil outlet of the hydraulic pump; wherein, the oil outlet of the hydraulic pump is a hydraulic oil source when the hydraulic pump operates, outputting hydraulic oil; The pipeline connecting the oil outlet of the variable pump and the oil outlet of the hydraulic pump is also respectively connected to the oil inlet of the hydraulic motor and the oil inlet of the relief valve; The hydraulic motor is connected to the hydraulic pump through a coupling; The oil tank is respectively connected to the oil inlet of the variable pump, the oil inlet of the hydraulic pump, the oil outlet of the hydraulic motor and the oil outlet of the relief valve; The power motor is connected to the variable pump through a coupling; The pressure oil ports of the reversing valve are respectively connected to the oil outlet of the variable pump, the oil outlet of the hydraulic pump and the oil inlet of the relief valve; The oil outlet of the reversing valve is connected to the oil inlet of the hydraulic motor; The oil inlet of the reversing valve is connected to the oil return port of the hydraulic motor; The oil return port of the reversing valve is respectively connected to the oil outlet of the relief valve and the oil tank.

2. The hydraulic pump motor test system according to claim 1, wherein Also comprising a first pressure sensor and a second pressure sensor; Wherein, the first pressure sensor is installed on the branch from the connection of the oil outlet of the variable pump and the oil outlet of the hydraulic pump to the oil inlet of the relief valve; The second pressure sensor is installed on the oil outlet of the relief valve.

3. The hydraulic pump and motor test system according to any one of claims 1-2, characterized in that, Also comprising: Air filter, oil tank magnet, heater and drain ball valve; Wherein, the air filter is installed at the air inlet of the oil tank; The oil tank magnet is installed at the bottom inside the return side of the oil tank; The heater is installed inside the oil tank; The drain ball valve is installed at the bottom of the oil tank.

4. The hydraulic pump motor test system according to claim 3, characterized in that, Also comprising: Temperature sensor, liquid level sensor and liquid level sight glass; Wherein, the temperature sensor is installed at the top of the oil tank; The liquid level sensor is installed inside the oil tank; The liquid level sight glass is installed on the side of the oil tank.

5. A hydraulic pump motor testing method, characterized in that, Applied to the hydraulic pump motor test system according to any one of claims 1 - 3, the hydraulic pump motor test method comprises: Adjust the speed of the hydraulic motor to make the speed stable at the rated speed; After the hydraulic motor operates at the rated speed, adjust the hydraulic motor to make the hydraulic motor operate at the rated pressure, and record the oil outlet pressure and the oil return port pressure; Calculate the energy recovery rate according to the oil outlet pressure and the oil return port pressure.

6. The hydraulic pump motor testing method according to claim 5, wherein The adjusting the speed of the hydraulic motor to make the speed stable at the rated speed is specifically: Adjust the speed of the power motor and the displacement of the variable pump to make the hydraulic motor operate at the rated speed.

7. The hydraulic pump motor testing method according to claim 5, characterized in that The after the hydraulic motor operates at the rated speed, adjusting the hydraulic motor to make the hydraulic motor operate at the rated pressure, and recording the oil outlet pressure and the oil return port pressure is specifically: After the hydraulic motor operates at the rated speed, adjust the relief valve to gradually increase the oil outlet pressure of the variable pump, so that the oil inlet pressure of the hydraulic motor is stabilized at the rated pressure; When the inlet pressure of the hydraulic motor is stabilized at the rated pressure, record the outlet pressure of the branch line from the connection between the outlet of the variable pump and the outlet of the hydraulic pump to the inlet of the overflow valve, and the return oil pressure at the outlet of the overflow valve.

8. The hydraulic pump motor testing method according to claim 5, characterized in that, The calculation expression of the energy recovery rate is as follows: Among them, η Mm is the mechanical efficiency of the motor, η Mv is the volumetric efficiency of the motor, η bv is the volumetric efficiency of the variable pump, η bm is the mechanical efficiency of the variable pump, η b is the overall efficiency of the variable pump, η p is the overall efficiency of the loading pump, η M is the overall efficiency of the motor, p m is the pressure difference between the oil outlet and the oil inlet of the hydraulic motor, p b is the pressure difference between the oil outlet and the oil inlet of the pressure variable pump, p1 is the return oil port pressure, and p2 is the oil outlet pressure of the variable pump.

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