A low-temperature cold start multi-parameter test system for a hydraulic motor

Abstract

The present application belongs to the technical field of polar cold region equipment test, and relates to a low-temperature cold start multi-parameter test system for hydraulic motor, which is used for evaluating the cold start performance of the hydraulic motor under an extremely low-temperature environment. The system comprises a low-temperature test area arranged in a low-temperature environment test box, and a room-temperature energy supply area and a room-temperature measurement and loading area arranged outside the low-temperature environment test box. The system arranges the energy supply, test, measurement and loading units according to the temperature sensitivity, so that the test hydraulic motor and necessary in-box connecting and measuring components are in the low-temperature environment, while the energy supply, torque and rotating speed measurement and loading components are in the room-temperature environment. The system realizes the low-temperature cold start test under the zero rotating speed preloading condition through a through-wall shafting, an openable and closable sealing device and multi-parameter synchronous acquisition.

Description

Technical Field

[0001] This invention belongs to the field of polar cold-region equipment testing technology, and relates to a multi-parameter testing system for low-temperature cold start of hydraulic motors, used to evaluate the performance of hydraulic motors under load and cold start in extremely low-temperature environments. Background Technology

[0002] Hydraulic transmission systems are commonly used in polar vessels, offshore platform deck machinery, and engineering equipment in high-altitude and cold regions. Whether these systems can successfully start under load in low-temperature environments directly determines the availability and operational safety of the equipment.

[0003] At low temperatures, the viscosity of hydraulic oil increases dramatically, significantly increasing the viscous shear resistance in the various clearances within the hydraulic motor. Simultaneously, thermal contraction of metal components alters the actual dimensions of the distribution end face clearance, tooth tip clearance, and bearing clearance. These two factors combined result in difficulty starting the motor, slow pressure build-up, or even failure to start. Accurately evaluating the low-temperature, load-bearing cold-start performance of hydraulic motors is fundamental to selecting hydraulic equipment and developing cold-start strategies for cold-region applications.

[0004] In existing high and low temperature testing systems for hydraulic pumps / motors, there are arrangements where the test specimen is placed inside the high and low temperature test chamber, while the torque and speed measurement unit is placed outside the chamber. These systems often employ hydraulic loading circuits that rely on rotational flow to establish loading pressure. This makes it difficult to stably apply a calibrable pre-set braking torque at zero speed, thus making them more suitable for steady-state performance testing and less suitable for directly evaluating the ability to start under load and break static friction. In low-temperature conditions, the oil is typically supplied directly from a high and low temperature oil tank after temperature adjustment, and the operating temperature is characterized by the air temperature inside the chamber or the oil temperature in the tank, thus limiting the lower limit of the test temperature. The shaft section passing through the chamber often has supports, which introduce additional frictional torque that varies with temperature at low temperatures. The problems of cold leakage and frost formation in the shaft holes of the chamber wall are usually not addressed. Furthermore, the oil port pressure, oil port temperature, and surface temperature of the test specimen are generally not measured, making it impossible to obtain cold start characterization parameters such as the inlet and outlet pressure difference.

[0005] The fundamental difficulty in low-temperature cold start testing of hydraulic motors lies in the fact that the test system requires the tested hydraulic motor, its connected shaft system, and nearby temperature and pressure measurement components to be in a low-temperature state. However, once the oil supply, torque and speed measurement, and loading components are all in a low-temperature environment, their own characteristics will change with temperature, causing the changes in the tested hydraulic motor to be confused with changes in the equipment itself. Existing testing methods have the following problems: Firstly, the overall cooling method makes the oil supply capacity uncontrollable. If the hydraulic pump station and the motor under test are placed in a low-temperature environment, the pump's volumetric efficiency, the set pressure of the relief valve, and the pipeline resistance all change significantly with the temperature. The flow rate and pressure supplied to the motor under test are no longer constant known inputs, making it impossible to determine whether the difficulty in starting the motor is caused by increased resistance or decreased oil supply capacity.

[0006] Secondly, the loading device being placed in a low-temperature environment makes the loading amounts incomparable. The core of cold start evaluation is whether the motor can overcome static friction and start under load, thus requiring a defined load to be applied when the motor speed is zero. Eddy current dynamometers and inertia disks cannot provide a preset braking torque at zero speed, and common hydraulic loading circuits that rely on rotational flow to establish pressure are also difficult to stably apply a calibrated load at zero speed; magnetic powder brakes, however, can provide a set braking torque at zero speed. If a magnetic powder brake is placed in a low-temperature chamber, the state of its magnetic powder and the resistance of its excitation coil may change with temperature, causing the braking torque corresponding to the same excitation current to drift; its operating heat will also interfere with the temperature field inside the chamber.

[0007] Third, placing the torque measurement unit in a low-temperature environment causes measurement reference drift. Strain gauge or magnetoelectric torque sensors experience zero-point drift and sensitivity changes at extremely low temperatures, rendering their calibration relationships invalid. If the measurement is changed to first cooling in a low-temperature chamber and then removing it to room temperature, the oil temperature will rise rapidly during the transfer process, and the measured results will not reflect the true state at the target temperature.

[0008] Fourth, using the temperature of the air inside the chamber as a substitute for the operating temperature introduces deviations. The temperature of the air inside the cryogenic chamber is not consistent with the actual temperature of the oil inside the motor under test. The oil is gradually cooled as it enters the cryogenic chamber from the room temperature pump station through the pipeline. The actual temperature when it reaches the motor oil port depends on the pipeline length, flow rate, and insulation conditions. If the temperature of the air inside the chamber is used as the operating temperature for calibration, it will introduce an unpredictable system deviation.

[0009] Fifth, after the measurement and loading unit is removed from the low-temperature chamber, the drive shaft must pass through the chamber wall. The through hole on the chamber wall becomes a continuous cold leakage channel. External humid air enters the chamber through this hole, which on the one hand makes it difficult to reach and maintain the set low temperature and the temperature field is unstable. On the other hand, frost and ice layers condense at the hole and on the adjacent shaft section, which may interfere with the operation of the shaft. If the through hole is completely sealed, it will hinder the normal rotation of the shaft. The two are contradictory.

[0010] Sixth, if a support bearing is installed in the shaft section to stabilize the shaft system, the grease in the bearing will thicken at low temperature, generating an additional frictional torque that varies with temperature. This torque is measured by the torque sensor, and its increasing trend with temperature is in the same direction as the increasing trend of the low-temperature resistance of the tested motor itself, making it impossible to separate from the measurement results.

[0011] Seventh, the loading and measurement ranges are mismatched with the cold start conditions. The critical process of cold start occurs at extremely low speeds and in the range of output torque far below the rated value. However, conventional test benches are configured with loading units and torque sensors according to the rated motor conditions, and the measurement range is on the order of the rated torque. Within this range, the resolution and dynamic response are insufficient, and it is impossible to capture the starting transient.

[0012] Eighth, conventional test benches typically only monitor oil temperature, making it difficult to distinguish between the effects of increased oil viscosity and thermal shrinkage of metal parts from the test results; moreover, the process of cooling, holding, testing, and reheating at each temperature point is time-consuming, the thermal state of the device is discontinuous between each temperature point, and the data comparability is poor.

[0013] In response to the above situation, it is necessary to develop a test system specifically suitable for evaluating the cold start of hydraulic motors under load at extremely low temperatures. Summary of the Invention

[0014] To address the problems existing in the prior art, this invention provides a multi-parameter testing system for low-temperature cold start of hydraulic motors. The system arranges the power supply, test, measurement, and loading units according to temperature sensitivity zones, placing the hydraulic motor under test and necessary internal connections and measurement components in a low-temperature environment, while the power supply, torque and speed measurement, and loading components are kept at room temperature. Low-temperature cold start testing under zero-speed pre-loading conditions is achieved through a through-wall shaft system, an openable and closable sealing device, and synchronous acquisition of multiple parameters.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A multi-parameter testing system for low-temperature cold start of a hydraulic motor includes a low-temperature test area set inside a low-temperature environment test chamber 1, and a room-temperature power supply area and a room-temperature measurement loading area set outside the low-temperature environment test chamber 1.

[0016] The low-temperature test area includes a test hydraulic motor 2, a sensor for detecting the status of the motor oil port and the body temperature, and a through-wall drive shaft 30 passing through the wall of the low-temperature environment test chamber 1; the test hydraulic motor 2 is connected to the room temperature measurement loading area through the through-wall drive shaft 30.

[0017] The sensors include an integrated inlet pressure and temperature sensor 15 and an integrated outlet pressure and temperature sensor 16, a motor body surface temperature sensor 17, and an internal air temperature sensor 18. The integrated inlet pressure and temperature sensor 15 and the integrated outlet pressure and temperature sensor 16 are respectively installed at the two oil ports of the hydraulic motor under test 2. The motor body surface temperature sensor 17 is installed on the surface of the housing of the hydraulic motor under test 2. The internal air temperature sensor 18 is installed inside the low temperature environment test chamber 1.

[0018] The room temperature measurement loading area includes a torque speed sensor 12 and a magnetic powder brake 13 connected in sequence. The torque speed sensor 12 is connected to the tested hydraulic motor 2 through a through-wall transmission shaft 30.

[0019] The magnetic powder brake 13 is controlled by the brake excitation controller 14 to apply a set load before the tested hydraulic motor 2 is started.

[0020] The room temperature power supply area includes a hydraulic pump station located outside the low temperature environment test chamber 1. The hydraulic pump station is connected to the hydraulic motor 2 under test through an oil inlet pipe 19 and an oil return pipe 20 passing through the chamber wall.

[0021] The tested hydraulic motor 2 is fixed inside the low-temperature environment test chamber 1 by the tooling bracket 3 inside the chamber; several height adjustment shims 29 are stacked between the base of the tooling bracket 3 inside the chamber and the motor mounting surface, and the shaft alignment between the tested hydraulic motor 2 and the external measuring loading chain is corrected by adding or removing the height adjustment shims 29.

[0022] The motor output shaft 4 of the tested hydraulic motor 2 is connected to the through-wall transmission shaft 30 via a first coupling 11a; one end of the torque and speed sensor 12 is connected to the outer end of the through-wall transmission shaft 30 via a second coupling 11b, and the other end of the torque and speed sensor 12 is connected to the output shaft of the magnetic powder brake 13 via a third coupling 11c.

[0023] The rated torque range of the torque-speed sensor 12 is less than the rated output torque of the hydraulic motor 2 under test, and the rated torque of the magnetic powder brake 13 is less than the rated output torque of the hydraulic motor 2 under test.

[0024] The hydraulic pump station includes a hydraulic pump 21, a drive motor 22, an electromagnetic relief valve 23, a flow meter 24, a three-position four-way directional valve 25, an oil tank 26, a throttle valve 33, a filter 34, and a pressure gauge 35. The hydraulic pump 21 is driven by the drive motor 22. Its suction port is connected to the oil tank 26 via the filter 34, and its outlet is connected to the inlet of the three-position four-way directional valve 25 via the throttle valve 33 and the flow meter 24. The pressure gauge 35 is connected to the oil line between the flow meter 24 and the three-position four-way directional valve 25. The two working ports of the four-way directional valve 25 pass through the wall of the low-temperature environment test chamber 1 via the inlet oil line 19 and the return oil line 20, respectively, and are connected to the two oil ports of the hydraulic motor under test 2. The return oil port of the three-position four-way directional valve 25 is connected to the oil tank 26. The electromagnetic relief valve 23 is connected in parallel to the outlet of the hydraulic pump 21 and is used to set the system safety pressure and achieve rapid unloading at the end of the test. The three-position four-way directional valve 25 is used to switch the inlet and return oil directions of the two oil ports of the hydraulic motor under test 2 to achieve bidirectional cold start test.

[0025] The system also includes an openable and closable sealing device 6 installed at the through-shaft hole 5 on the wall of the low temperature environment test chamber (1). The openable and closable sealing device 6 includes a fixed sealing component 7, a detachable sealing component 8 and a flexible brush ring 9. During the non-testing stage, the fixed sealing component 7 and the detachable sealing component 8 cooperate to seal the annular gap between the through-shaft hole 5 and the through-wall drive shaft 30. During the testing stage, the detachable sealing component 8 is removed and the flexible brush ring 9 lightly touches the through-wall drive shaft 30.

[0026] The system also includes a data acquisition and control system 27, which is used to acquire flow rate, pressure and temperature of the two oil ports of the motor, surface temperature of the motor body, air temperature inside the housing, torque, speed and load status, and output control signals to the start control circuit of the drive motor 22 and the brake excitation controller 14.

[0027] The system also includes a low-temperature chamber temperature control unit 28, which together with the low-temperature environment test chamber 1 forms a temperature control loop and provides the temperature status to the data acquisition and control system 27.

[0028] The beneficial effects of the testing system provided by this invention are as follows: (1) The temperature influence boundary is clear. The room temperature power supply area and the room temperature measurement loading area are located outside the low temperature environment test chamber 1; the low temperature test area includes the test hydraulic motor 2 and its integrated motor output shaft 4, the tooling bracket 3 inside the chamber, the integrated inlet pressure and temperature sensor 15, the integrated outlet pressure and temperature sensor 16, the motor body surface temperature sensor 17, the air temperature sensor inside the chamber 18, the first coupling 11a, and the section of the through-wall drive shaft 30 inside the chamber. This reduces the influence of the temperature changes of the pump station, torque and speed sensor 12, and magnetic powder brake 13 on the test results.

[0029] (2) Zero-speed load start evaluation can be achieved. The magnetic powder brake 13 can apply a set load when the hydraulic motor under test 2 has not yet rotated, thus enabling the evaluation of the motor's ability to start under load conditions by overcoming static friction.

[0030] (3) The operating temperature is taken from the actual value measured at the motor oil port. After the oil enters the low temperature box from the room temperature pump station, it is gradually cooled. The actual temperature when it reaches the motor is measured by the pressure and temperature integrated sensor close to the current oil inlet. Using this measured oil temperature as the operating temperature can reduce the deviation introduced by substituting the air temperature or oil temperature in the tank for the operating temperature.

[0031] (4) Balancing through-wall sealing and shaft rotation. The openable and closable sealing device 6 acts on the annular gap between the through-shaft hole 5 and the through-wall drive shaft 30. During the non-testing stage, the through-wall drive shaft 30 does not rotate, and the gap is completely sealed by the fixed sealing part 7 and the detachable sealing part 8. During the testing stage, the detachable sealing part 8 is removed without opening the box, and the flexible brush ring 9 lightly touches the through-wall drive shaft 30, thereby reducing cold leakage and humid air intrusion without hindering rotation.

[0032] (5) It can reduce the additional friction caused by temperature. The length of the through-wall drive shaft 30 is adapted to the thickness of the box wall, the support span is short, the supports at both ends meet the requirements of shaft system stiffness and alignment, and no intermediate support is set in the through-shaft hole 5, thereby reducing the additional friction introduced by the change of the lubrication state of the support bearing at low temperature.

[0033] (6) It can assist in the analysis of two types of low-temperature effects and improve the testing efficiency. The oil port temperature and the motor body surface temperature are measured simultaneously. Combined with comparative tests under different thermal conditions, it can assist in the analysis of the relative influence of oil viscosity changes and thermal shrinkage of metal parts on cold start response. With continuous cooling temperature trigger test and unified feature quantity extraction, the comparability between various temperature points can be improved.

[0034] In summary, this invention reduces the interference of temperature changes at the oil supply end, measurement end, and loading end on the results by arranging the power supply, test, measurement, and loading units according to temperature-sensitive zones, and by designing supporting systems for cross-zone oil circuits, through-wall shaft systems, orifice sealing, and signal acquisition. This enables multi-parameter synchronous testing of the low-temperature load cold start process of hydraulic motors. Attached Figure Description

[0035] Figure 1 This is the overall schematic diagram of a multi-parameter testing system for low-temperature cold start of hydraulic motors.

[0036] Figure 2 This is a schematic diagram showing the arrangement of the test motor and measuring points inside the low-temperature environment test chamber.

[0037] Figure 3 This is a schematic diagram of the through-shaft hole openable sealing device in a non-test state, where (a) is a sectional view and (b) is a right view.

[0038] Figure 4 This is a schematic diagram of the through-shaft hole openable sealing device in test state, where (a) is a sectional view and (b) is a right view.

[0039] Figure 5 This is a schematic diagram of the arrangement of the through-wall axis system and the external measurement loading chain.

[0040] Figure 6 The diagram shows the tooling support and height adjustment structure inside the box, where (a) is an overall schematic diagram and (b) is a magnified view of a part.

[0041] Figure 7 This is a flowchart for a continuous cooling temperature-triggered test.

[0042] Figure 8 This is a schematic diagram of the time-domain curve of cold start pressure difference and feature quantity extraction.

[0043] Figure 9 This is a block diagram of the measurement and control system.

[0044] In the diagram: 1. Low-temperature environment test chamber; 2. Hydraulic motor under test; 3. Tooling bracket inside the chamber; 4. Motor output shaft; 5. Through-shaft hole; 6. Openable and closable sealing device; 7. Fixed sealing component; 8. Removable sealing component; 9. Flexible brush ring; 10. Magnetic powder brake bracket; 11a. First coupling; 11b. Second coupling; 11c. Third coupling; 12. Torque and speed sensor; 13. Magnetic powder brake; 14. Brake excitation controller; 15. Inlet pressure and temperature integrated sensor; 16. Outlet pressure and temperature integrated sensor. Sensors; 17 Motor body surface temperature sensor; 18 Internal air temperature sensor; 19 Oil inlet line; 20 Oil return line; 21 Hydraulic pump; 22 Drive motor; 23 Electromagnetic relief valve; 24 Flow meter; 25 Three-position four-way directional valve; 26 Oil tank; 27 Data acquisition and control system; 28 Low temperature chamber temperature control unit; 29 Height adjustment shim; 30 Through-wall drive shaft; 31 Torque and speed sensor bracket; 32 External bottom plate of the chamber; 33 Throttle valve; 34 Filter; 35 Pressure gauge. Detailed Implementation

[0045] The invention will now be further described with reference to the accompanying drawings.

[0046] like Figure 1 As shown, the present invention discloses a low-temperature cold start multi-parameter testing system for a hydraulic motor, comprising a low-temperature environment test chamber 1, a hydraulic motor under test 2, a tooling bracket inside the chamber 3, a motor output shaft 4, a through-shaft hole 5, an openable and closable sealing device 6, a fixed sealing component 7, a detachable sealing component 8, a flexible brush ring 9, a magnetic powder brake bracket 10, a first coupling 11a, a second coupling 11b, a third coupling 11c, a torque and speed sensor 12, a magnetic powder brake 13, a brake excitation controller 14, an integrated inlet pressure and temperature sensor 15, an integrated outlet pressure and temperature sensor 16, and a motor body surface temperature sensor 17. The chamber includes an air temperature sensor 18, an oil inlet pipe 19, an oil return pipe 20, a hydraulic pump 21, a drive motor 22, an electromagnetic overflow valve 23, a flow meter 24, a three-position four-way directional valve 25, an oil tank 26, a data acquisition and control system 27, a low-temperature chamber temperature control unit 28, a height adjustment shim 29, a through-wall drive shaft 30, a torque and speed sensor bracket 31, an outer bottom plate 32, a throttle valve 33, a filter 34, and a pressure gauge 35. The through-wall drive shaft 30, the oil inlet pipe 19, and the oil return pipe 20 span the walls of the low-temperature environment test chamber 1, and the signal lines of each sensor are connected to the data acquisition and control system 27. The specific design is as follows: (I) Room Temperature Power Supply Zone. The hydraulic pump 21, drive motor 22, electromagnetic relief valve 23, flow meter 24, three-position four-way directional valve 25, oil tank 26, throttle valve 33, filter 34, and pressure gauge 35 constitute a hydraulic pump station, which is arranged as a whole in the room temperature environment outside the low temperature environment test chamber 1. Before the test, the same oil condition, pump speed, relief valve setting, and throttle valve opening are used, and the actual oil supply boundary is recorded by the flow meter 24 and pressure gauge 35 to reduce the influence of oil supply unit temperature changes on the comparison results of each temperature point.

[0047] (II) Low-Temperature Test Area. The hydraulic motor under test 2 is fixed by the tooling bracket 3 inside the chamber. The integrated inlet pressure and temperature sensor 15 and the integrated outlet pressure and temperature sensor 16 are installed near the two oil ports. The motor body surface temperature sensor 17 maintains reliable thermal contact with the housing. The air temperature sensor 18 inside the chamber is kept away from the air outlet and local heat sources. The sensor leads are led out through a sealed interface, and a low-temperature shrinkage allowance is reserved to avoid tension acting on the probe.

[0048] (III) Room Temperature Measurement Loading Area. The torque-speed sensor 12 is fixed to the outer base plate 32 of the chamber via the torque-speed sensor bracket 31, and the magnetic powder brake 13 is fixed to the magnetic powder brake bracket 10. Both are located in a room temperature environment. Before the formal test, the torque-speed sensor 12 is preheated, zeroed, and its range is verified. The relationship between the excitation current and braking torque of the magnetic powder brake 13 is verified at room temperature. The magnetic powder brake 13 can apply a set load when the speed of the tested hydraulic motor 2 is zero.

[0049] (iv) Oil circuit interface. The oil inlet pipe 19 and the oil return pipe 20 pass through the wall of the low-temperature environment test chamber 1. The sections inside the chamber should have similar lengths, directions, and insulation conditions as much as possible, and avoid direct scouring from the air outlet of the low-temperature chamber. Before the test, air should be purged from the circuit and the joint seals should be checked. During the test, the actual oil temperature and pressure measured by the sensor near the motor oil port should always be used as the operating condition data.

[0050] (V) Shaft System Interface. The shaft system, along the power transmission direction, consists of the tested hydraulic motor 2, motor output shaft 4, first coupling 11a, through-wall drive shaft 30, second coupling 11b, torque and speed sensor 12, third coupling 11c, and magnetic powder brake 13. The diameter and length of the through-wall drive shaft 30 are selected according to the transmitted torque, support span, and allowable deflection. No bearings, bushings, radial supports, or contact seals are installed in the through-shaft hole 5. The three couplings are used to connect adjacent shaft ends and compensate for assembly deviations within the allowable range.

[0051] (vi) A through-shaft hole openable and closable sealing device 6, comprising a fixed sealing component 7, a detachable sealing component 8, and a flexible brush ring 9, used to seal the annular gap between the through-shaft hole 5 and the through-wall drive shaft 30; the detachable sealing component 8 is a two-half structure split along the axial direction, which is assembled with the fixed sealing component 7 by fasteners, so that it can still be removed as a whole even when both ends of the through-wall drive shaft 30 are connected to couplings. Both the fixed sealing component 7 and the detachable sealing component 8 adopt a heat-insulating structure to reduce heat exchange. During the non-testing stage, the through-wall drive shaft 30 does not rotate, and the fixed sealing component 7 and the detachable sealing component 8 are closed to seal the annular gap; during the testing stage, the detachable sealing component 8 is removed without opening the low-temperature environment test chamber 1, the fixed sealing component 7 is left at the hole opening, and the flexible brush ring 9 lightly contacts the through-wall drive shaft 30, allowing the through-wall drive shaft 30 to rotate while restricting airflow at the annular gap.

[0052] (vii) Shaft alignment and thermal deformation compensation. First, perform rough alignment at room temperature, and then check the center height and coupling deviation during the low-temperature calibration process before the formal test, and complete the correction by adding or removing the height adjustment shims 29. After completing the low-temperature calibration, close the low-temperature environment test chamber 1 and fix the shim assembly; during the formal continuous cooling test, only check the alignment status, and do not open the chamber to adjust the shims.

[0053] (viii) Range and protection. The torque range of the torque speed sensor 12 and the loading range of the magnetic powder brake 13 are selected according to the expected peak value and set load of the tested hydraulic motor 2 during the cold start stage, and a transient overload margin is reserved; the data acquisition and control system 27 is set with maximum allowable pressure, maximum allowable torque and start-up timeout conditions, and stops the drive motor 22 and unloads the oil circuit when any protection condition is triggered.

[0054] (ix) Signals and Control. Pressure, temperature, flow rate, torque, speed, and excitation status channels use a unified clock to record the drive motor 22 start command, excitation setting, commutation status, and cryogenic chamber temperature status. The sampling frequency of each channel is determined based on the sensor bandwidth and the duration of the cold start transient, and zero-point and communication status checks are performed before each test.

[0055] This invention achieves comparable testing of the cold start performance of hydraulic motors under load at extremely low temperatures by dividing the system into three zones based on temperature sensitivity and processing the oil circuits, shaft systems, and signal interfaces between the three zones separately.

[0056] The structural layout of each part of the hydraulic motor low-temperature cold start multi-parameter testing system is as follows: The low-temperature environment test chamber 1 should cover the predetermined test temperature range. Before testing, check the chamber seal, through-wall piping and signal interfaces, verify the readings of the low-temperature chamber temperature control unit 28 and the internal air temperature sensor 18, and confirm the temperature control capability within the target temperature range by running the chamber with an empty chamber or equivalent load.

[0057] The hydraulic pump 21 is driven by the drive motor 22. Its suction port is connected to the oil tank 26 via the filter 34. Its outlet is connected to the inlet of the three-position four-way directional valve 25 via the throttle valve 33 and the flow meter 24. The pressure gauge 35 is connected to the oil line between the flow meter 24 and the three-position four-way directional valve 25. The two working oil ports of the three-position four-way directional valve 25 pass through the wall of the low-temperature environment test chamber 1 via the inlet oil line 19 and the return oil line 20, respectively, and are connected to the two oil ports of the hydraulic motor 2 under test. The return oil port of the three-position four-way directional valve 25 is connected to the oil tank 26. The electromagnetic relief valve 23 is connected in parallel to the outlet of the hydraulic pump 21 and is used to set the system safety pressure and achieve rapid unloading at the end of the test.

[0058] The shaft system, along the power transmission direction, consists of the tested hydraulic motor 2, motor output shaft 4, first coupling 11a, through-wall drive shaft 30, second coupling 11b, torque and speed sensor 12, third coupling 11c, and magnetic powder brake 13. The motor output shaft 4 is integrated with the tested hydraulic motor 2 body and does not penetrate the wall; the first coupling 11a is located inside the housing; the through-wall drive shaft 30 passes through the wall via a through-shaft hole 5; an openable and closable sealing device 6 seals the annular gap between the through-shaft hole 5 and the through-wall drive shaft 30; and a flexible brush ring 9 lightly contacts the through-wall drive shaft 30 during the test.

[0059] The torque and speed sensor 12 is fixed by the torque and speed sensor bracket 31, and the magnetic powder brake 13 is fixed by the magnetic powder brake bracket 10. The two are installed together on the outer bottom plate 32 of the box and are kept coaxial.

[0060] Furthermore, the data acquisition and control system 27 includes a temperature trigger control module and a cold start feature quantity extraction module.

[0061] The temperature trigger control module is configured to: complete shaft alignment calibration before formal testing, and preset test temperature points, temperature allowable range, stabilization time, load value, steady-state criteria, and safety limits; during cooling, keep the openable sealing device 6 in a non-test state, continuously monitor the motor inlet oil temperature, motor body surface temperature, and air temperature inside the chamber; when the inlet oil temperature enters the target temperature allowable range and reaches the preset stabilization time, only verify the shaft status and switch the openable sealing device 6 to the test state, then start the acquisition and drive motor 22 according to the predetermined sequence. After completing the test at one temperature point, stop the machine, unload, reinstall the detachable sealing component 8, and continue cooling to the next temperature point.

[0062] The cold start feature extraction module is used to perform steering mapping, inlet and outlet pressure difference calculation, steady-state range determination and feature extraction on valid test data, and output the peak pressure difference at start-up, pressure build-up time and steady-state pressure difference; the specific criteria for each feature are consistent in the same set of comparative tests.

[0063] Furthermore, the fixed sealing component 7 and the detachable sealing component 8 adopt a heat-insulating structure that can reduce heat exchange and adapt to the target low-temperature environment. The two are connected in a detachable manner, so that the openable sealing device 6 can switch between the test state and the non-test state.

[0064] Furthermore, the motor body surface temperature sensor 17 is disposed at one or more locations on the housing of the tested hydraulic motor 2 that can reflect changes in structural temperature, for recording the surface temperature of the motor body.

[0065] Furthermore, the three-position four-way directional valve 25 is used to switch the rotation direction of the tested hydraulic motor 2 to achieve bidirectional load cold start performance testing.

[0066] Furthermore, the wall-penetrating sections of the oil inlet pipe 19 and the oil return pipe 20 can be insulated as needed for the test; the operating temperature is based on the measured oil temperature near the motor oil port to reduce the impact of heat exchange differences in the wall-penetrating sections on the test results.

[0067] Reference Figure 1 The low-temperature environment test chamber 1 is equipped with a device capable of covering the predetermined test temperature, continuously cooling down according to a preset temperature control program, and maintaining the target low-temperature environment. The test system is divided into a room temperature power supply zone, a low-temperature test zone, and a room temperature measurement loading zone according to temperature sensitivity. The low-temperature test zone includes the test hydraulic motor 2 and its integrated motor output shaft 4, the tooling bracket 3 inside the chamber, the integrated inlet pressure and temperature sensor 15, the integrated outlet pressure and temperature sensor 16, the motor body surface temperature sensor 17, the air temperature sensor inside the chamber 18, the first coupling 11a, and the section of the through-wall drive shaft 30 inside the chamber. The room temperature measurement loading zone includes the torque and speed sensor 12, the magnetic powder brake 13 and its brackets 31 and 10, and the bottom plate 32 outside the chamber. The remaining oil supply components are located in the room temperature power supply zone.

[0068] In this embodiment, the room temperature power supply zone includes a hydraulic pump 21, a drive motor 22, an electromagnetic relief valve 23, a flow meter 24, a three-position four-way directional valve 25, an oil tank 26, a throttle valve 33, a filter 34, and a pressure gauge 35. The drive motor 22 drives the hydraulic pump 21 to supply oil to the tested hydraulic motor 2; the electromagnetic relief valve 23 is used to regulate or limit the system pressure, the flow meter 24 is used to measure the oil supply flow rate, and the three-position four-way directional valve 25 is used to control the oil flow and direction. The operating range of the above components is selected according to the test pressure, flow rate, and direction requirements of the tested hydraulic motor 2, and all are arranged in a room temperature environment. The suction port of hydraulic pump 21 is connected to oil tank 26 via filter 34. Its outlet is connected to the inlet of three-position four-way directional valve 25 via throttle valve 33 and flow meter 24. Pressure gauge 35 is connected to the oil line between flow meter 24 and three-position four-way directional valve 25. Electromagnetic relief valve 23 is connected in parallel to the outlet of hydraulic pump 21. Throttle valve 33 is used to regulate oil supply flow, filter 34 is used to ensure oil cleanliness, and pressure gauge 35 is used to display oil supply pressure locally. The two oil ports of the tested hydraulic motor 2 pass through inlet oil line 19 and return oil line 20 respectively to exit the low temperature environment test chamber 1 and are connected to the two working oil ports of three-position four-way directional valve 25 respectively. The return oil port of three-position four-way directional valve 25 is connected to oil tank 26. Each end of the three-position four-way directional valve 25 is equipped with an electromagnet, which is controlled by an interlock button so that only one is energized at any given time. Switching the energized side changes the rotation direction of the hydraulic motor 2 under test. When the hydraulic motor 2 under test rotates forward, the inlet line 19 is for oil inlet and the return line 20 is for oil return; when it rotates in reverse, their functions are interchanged. The hydraulic oil used for the test is selected according to the applicable medium of the hydraulic motor 2 under test and the viscosity-temperature characteristics at the target low temperature, and the oil state is kept consistent before each test. The flow meter 24 has a range that covers the test oil supply flow range, and its measurement accuracy meets the comparison requirements between different temperature conditions.

[0069] Reference Figure 2 The tested hydraulic motor 2 is fixed inside the low-temperature environment test chamber 1 by the tooling bracket 3. An integrated inlet pressure and temperature sensor 15 is installed on the inlet oil line 19 near one motor port, and an integrated outlet pressure and temperature sensor 16 is installed on the return oil line 20 near the other motor port. During forward rotation testing, they serve as the inlet and outlet measuring points respectively; during reverse rotation testing, the data acquisition and control system 27 switches their inlet and outlet roles. The pressure and temperature ranges of the two sensors cover the test conditions of the corresponding oil circuits. The motor body surface temperature sensor 17 is fixed in a manner that maintains good thermal contact without affecting motor operation, and the chamber air temperature sensor 18 is positioned to reflect the chamber ambient temperature while avoiding local heat sources.

[0070] In this embodiment, the operating temperature is based on the oil temperature measured by the pressure-temperature integrated sensor near the current oil inlet, rather than the air temperature inside the tank. During shutdown and cooling, the oil in the pipeline near the motor cools down with the tank environment; after startup, the oil from the room temperature power supply zone may cause changes in the inlet oil temperature. Therefore, the data acquisition and control system 27 continuously records the inlet oil temperature, and only uses cold start data where the inlet oil temperature is within the target allowable range for the characteristic quantity calculation of the corresponding temperature point. The data from the tank air temperature sensor 18 is used to monitor the environmental conditions and determine whether the temperature field is abnormal.

[0071] In this embodiment, the body temperature response and oil temperature response of the tested hydraulic motor 2 are not completely synchronized. By simultaneously recording the port temperature and the motor body surface temperature, and comparing the cold start characteristic quantities under different thermal states under the same other oil supply, loading, and installation conditions, the correlation between the two types of temperature states and the change in cold start resistance can be analyzed. This comparison is used to help determine the relative influence of oil viscosity changes and structural thermal shrinkage, and does not directly equate the readings of the two temperature sensors with a complete separation of the two mechanisms.

[0072] Reference Figure 3 and Figure 4 The through-shaft hole 5 is located on the wall of the low-temperature environment test chamber 1, and its diameter is larger than that of the through-wall drive shaft 30. An openable and closable sealing device 6 is located in the hole area and consists of a fixed sealing component 7, a removable sealing component 8, and a flexible brush ring 9. Only the through-wall drive shaft 30 passes through the through-shaft hole 5; no bearings, bushings, radial supports, or sealing rings are installed. The fixed sealing component 7 and the removable sealing component 8 adopt an insulation structure that reduces heat exchange and adapts to the target low-temperature environment. The removable sealing component 8 is a two-half structure split along the axial direction, which is assembled with the fixed sealing component 7 using fasteners. It can be removed or reinstalled as a whole without disassembling the shaft system or opening the low-temperature environment test chamber 1, allowing switching between test and non-test states.

[0073] Reference Figure 3 During non-testing phases such as cooling and heat preservation, the tested hydraulic motor 2 is not supplied with oil, the through-wall drive shaft 30 does not rotate, and the fixed sealing component 7 and the detachable sealing component 8 are closed to seal the annular gap between the through-shaft hole 5 and the through-wall drive shaft 30. The cooling and heat preservation process of the low-temperature environment test chamber 1 often lasts for several hours. If the through-shaft hole 5 is open during this period, cold air will continue to leak through the hole, and external humid air may also enter and condense frost at the hole opening and adjacent shaft sections. This will not only make it difficult to reach the set temperature inside the chamber and cause an unstable temperature field, but may also form ice layers that affect the operation of the rotating shaft. Sealing the annular gap can reduce the above risks.

[0074] Reference Figure 4During the testing phase, the removable sealing component 8 is removed while the fixed sealing component 7 remains. The flexible brush ring 9 is positioned in the central area of ​​the fixed sealing component 7 and lightly contacts the through-wall drive shaft 30, allowing the through-wall drive shaft 30 to rotate while restricting airflow at the annular gap. The flexible brush ring 9 uses a bristle material that maintains flexibility and wear resistance at the target low temperature. Its bristle length, circumferential uniformity, and preload are designed to prevent significant leakage and ensure that the additional rotational resistance does not exceed the allowable error. After assembly, a low-speed rotation is used to check for any jamming or excessive tightness in certain areas.

[0075] Reference Figure 5 The shaft system, along the power transmission direction, consists of the tested hydraulic motor 2, motor output shaft 4, first coupling 11a, through-wall drive shaft 30, second coupling 11b, torque and speed sensor 12, third coupling 11c, and magnetic powder brake 13. The motor output shaft 4 is the output shaft of the tested hydraulic motor 2, integrated with the main body, and does not pass through the chamber wall; the first coupling 11a is located inside the low-temperature environment test chamber 1; the through-wall drive shaft 30 passes through the through-shaft hole 5. The tested hydraulic motor 2 is fixed by the tooling bracket 3 inside the chamber, the torque and speed sensor 12 is fixed by the torque and speed sensor bracket 31, and the magnetic powder brake 13 is fixed by the magnetic powder brake bracket 10. Both brackets 31 and 10 are mounted on the outer bottom plate 32 of the chamber. The connection specifications of the three couplings 11a, 11b, and 11c are matched to the adjacent shaft ends, ensuring the entire shaft system remains aligned.

[0076] As can be seen from the above connection relationships, the components inside the low-temperature environment test chamber 1 include the tested hydraulic motor 2 and its integrated motor output shaft 4, the internal tooling bracket 3, the integrated inlet pressure and temperature sensor 15, the integrated outlet pressure and temperature sensor 16, the motor body surface temperature sensor 17, the internal air temperature sensor 18, the first coupling 11a, and the internal section of the through-wall drive shaft 30. The physical components spanning the chamber wall are only the through-wall drive shaft 30, the oil inlet pipe 19, and the oil return pipe 20. Additionally, sensor signal lines are connected to the data acquisition and control system 27.

[0077] In this embodiment, the through-wall drive shaft 30 passes through the through-shaft hole 5, and no bearings, bushings, radial supports, or contact seals are installed inside the through-shaft hole 5. The diameter of the through-shaft hole 5 is larger than the diameter of the through-wall drive shaft 30. The axial length and diameter of the through-wall drive shaft 30 are determined based on the housing wall structure, transmitted torque, support span, critical speed, and allowable deflection, and the free rotation of the shaft system and coupling deviation are verified under room temperature and low temperature calibration conditions.

[0078] If a support bearing is installed in the low-temperature region, its lubrication state may change with temperature, generating additional frictional torque. This torque, along with the low-temperature resistance of the tested hydraulic motor 2, will be reflected in the measurement results. In this embodiment, by matching the length, diameter, support span, and allowable deflection of the through-wall drive shaft 30, intermediate supports are not required within the through-shaft hole 5, thereby reducing this type of temperature-related additional friction and improving the interpretability of the torque measurement results.

[0079] In this embodiment, the range of the torque-speed sensor 12 covers the expected peak cold-start torque and speed, while retaining transient overload margin; the loading range of the magnetic powder brake 13 covers the predetermined cold-start load. The range selection simultaneously considers low-torque resolution, sampling bandwidth, and overload capacity, avoiding exceeding the sensor's allowable range during abnormal starts in pursuit of a smaller range.

[0080] Both the magnetic powder brake 13 and the brake excitation controller 14 are located at room temperature. Before testing, the correspondence between the excitation current and the braking torque is verified under specified preheating conditions, and the zero speed set value is recorded. Before each start of the hydraulic pump 21, the brake excitation controller 14 first reaches the set excitation state, and the data acquisition and control system 27 confirms that the feedback value is within the allowable range before proceeding to the start-up step.

[0081] The data acquisition and control system 27 receives signals from the flow meter 24, the inlet pressure and temperature integrated sensor 15, the outlet pressure and temperature integrated sensor 16, the motor body surface temperature sensor 17, the chamber air temperature sensor 18, the torque and speed sensor 12, and the brake excitation controller 14, and outputs commands to the start control circuit of the drive motor 22 and the brake excitation controller 14; the low temperature chamber temperature control unit 28 and the low temperature environment test chamber 1 form a temperature control circuit, and provide the chamber temperature status to the data acquisition and control system 27.

[0082] Reference Figure 6 A height adjustment shim 29 is installed between the motor mounting surface and the base of the tooling bracket 3 inside the chamber. During installation, the coaxiality of the hydraulic motor 2 under test, the through-wall drive shaft 30, the torque and speed sensor 12, and the magnetic powder brake 13 are first adjusted at room temperature. Then, a low-temperature calibration is performed before the formal test to ensure that the system reaches a representative low temperature and is fully thermally stable. The center height and coupling deviation are checked, and the height adjustment shim 29 is added or removed if necessary. After the shim combination is determined, the chamber is resealed and preparations for rewarming or recooling are completed. No further adjustments are made during the formal continuous cooling test. Figure 7 The “Check Alignment Status” shown is only used to confirm that the pre-calibration status is not abnormal; if vibration, jamming or misalignment is found during the test, the temperature sequence will be terminated and recalibrated.

[0083] Reference Figure 7This embodiment employs a control method of "low-speed monitoring during the cooling phase and high-speed synchronous acquisition during the cold start phase." The continuous cooling cold start test is completed within a single temperature sequence from high to low temperature, with no retemperature resetting between test temperature points. Short-term stabilization conditions can be set at each test temperature point to ensure consistent triggering conditions. The specific process is as follows: Before the formal test in step (1), complete the hydraulic circuit venting and leakage check, zeroing of each measurement channel, loading calibration of the magnetic powder brake 13, and low-temperature shaft alignment calibration; preset the test temperature point, temperature allowable range, stabilization time, load value, start-up threshold, steady-state criterion, maximum allowable pressure, maximum allowable torque, sampling frequency, start-up timeout, and maximum test time. At this time, only the load value setting is completed, and the magnetic powder brake 13 has not yet been loaded.

[0084] Step (2) Cooling and standby stage: Drive motor 22 stops, openable and closable sealing device 6 is in non-test state, and fixed sealing part 7 and detachable sealing part 8 cooperate to seal the annular gap. Low temperature environment test chamber 1 continuously cools down, and data acquisition and control system 27 monitors motor inlet oil temperature, motor body surface temperature and air temperature inside the chamber at low speed; when the inlet oil temperature enters the current target allowable range and continues to reach the preset stable time, the centering mark is checked to confirm that there is no frost or jamming on the exposed shaft section and no abnormality at the zero point of the measurement channel, and then the detachable sealing part 8 is removed from outside the chamber.

[0085] After temperature triggering in step (3), high-speed synchronous acquisition is started first to record the baseline, and then the brake excitation controller 14 applies the set load; after the load feedback enters the allowable range, the data acquisition and control system 27 sends a command to the start control circuit of the drive motor 22 to make the hydraulic pump 21 supply oil. During the test, the pressure and temperature of the two oil ports, the oil supply flow rate, the output torque, the speed, the surface temperature of the motor body, the air temperature inside the box, and the excitation status are recorded synchronously.

[0086] Step (4) When the rotational speed and inlet / outlet pressure difference meet the preset steady-state criteria, or when the maximum allowable test time is reached, stop the drive motor 22 and unload the oil circuit to end the high-speed acquisition of the temperature point. Then release the load, reinstall the removable sealing part 8 and confirm that the through-shaft hole 5 is resealed; if there are still uncompleted test temperature points, continue to cool down without reheating and repeat steps (2) to (4).

[0087] After step (5) is started, the data acquisition and control system 27 continuously records the actual inlet oil temperature; if the inlet oil temperature within the characteristic calculation time window exceeds the target allowable range, the original data is retained and the corresponding characteristic is marked as invalid. If the system pressure or torque exceeds the safety limit, shaft jamming, communication abnormality or start-up timeout occurs during the start-up process, the machine is immediately stopped and unloaded, and the temperature point is recorded as abnormal or start-up failed; before the cause is identified, the machine is not repeatedly started at the same temperature point to avoid the heat generated by the previous start-up changing the thermal state of the tested hydraulic motor 2.

[0088] Reference Figure 8 The data acquisition and control system 27 determines the current inlet and outlet sides based on the actual rotation of the tested hydraulic motor 2: when rotating forward, it reads the roles set by the inlet pipeline 19 and the return pipeline 20; when rotating in reverse, it exchanges the inlet and outlet roles of the integrated inlet pressure and temperature sensor 15 and the integrated outlet pressure and temperature sensor 16. The inlet and outlet pressure difference is calculated as Δp = p_in - p_out and saved along with the rotation status.

[0089] Firstly, the peak pressure difference at startup is used to characterize the driving pressure difference required to overcome static friction under a set load. The data acquisition and control system 27 records the start command time of the drive motor 22 as t0, and the moment when the absolute value of the rotational speed first exceeds the preset startup threshold and continues to reach the confirmation time as t1. Within a time window of a preset duration from t0 to t1, the maximum value of the inlet and outlet pressure difference Δp is searched and taken as the peak pressure difference at startup; the threshold and time window are kept consistent in the same set of comparative tests.

[0090] Secondly, the pressure build-up time is the time elapsed from t0 until the inlet-outlet pressure difference Δp first reaches the set proportion of the steady-state pressure difference. In this embodiment, 90% of the steady-state pressure difference can be used as the judgment proportion; if a steady-state interval that meets the steady-state criteria is not formed within the maximum allowable test time, the test is marked as unsuccessful pressure build-up, and the pressure build-up time is not forcibly calculated.

[0091] Third, the steady-state pressure difference is the average value of the inlet and outlet pressure differences within a preset statistical time window after both the rotational speed and the inlet / outlet pressure difference simultaneously meet the steady-state criterion. The steady-state criterion can be determined by the range of rotational speed fluctuation, the range of pressure difference fluctuation, and the duration. The same criterion is used for the same set of comparative tests, and the standard deviation or fluctuation range within the statistical time window is saved at the same time to determine the validity of the steady-state value.

[0092] Reference Figure 9All pressure, temperature, flow, torque, and speed channels use a unified time reference. For each test, the target temperature, actual inlet oil temperature, motor body surface temperature, internal air temperature, commutation status, excitation settings and feedback, oil supply settings, protection thresholds, raw timing data, and characteristic quantity results are saved. The sampling frequency is not lower than the frequency required to capture cold start transients and is matched with the effective bandwidth of each sensor. If the pressure or torque exceeds the safety limit, communication is interrupted, or the start-up timeout occurs, the data acquisition and control system 27 immediately stops the drive motor 22 and unloads the oil circuit, while simultaneously recording the cause of the abnormality.

[0093] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A multi-parameter testing system for low-temperature cold start of a hydraulic motor, characterized in that, The hydraulic motor low-temperature cold start multi-parameter test system includes a low-temperature test area set inside the low-temperature environment test chamber (1), and a room temperature power supply area and a room temperature measurement loading area set outside the low-temperature environment test chamber (1). The low-temperature test area includes a test hydraulic motor (2), a sensor for detecting the status of the motor oil port and the body temperature, and a through-wall drive shaft (30) that passes through the wall of the low-temperature environment test chamber (1); the test hydraulic motor (2) is connected to the room temperature measurement loading area through the through-wall drive shaft (30); The sensors include an integrated inlet pressure and temperature sensor (15) and an integrated outlet pressure and temperature sensor (16), a motor body surface temperature sensor (17), and an air temperature sensor inside the chamber (18). The integrated inlet pressure and temperature sensor (15) and the integrated outlet pressure and temperature sensor (16) are respectively installed at the two oil ports of the hydraulic motor under test (2). The motor body surface temperature sensor (17) is installed on the surface of the housing of the hydraulic motor under test (2). The air temperature sensor inside the chamber (18) is installed inside the low temperature environment test chamber (1). The room temperature measurement loading area includes a torque speed sensor (12) and a magnetic powder brake (13) connected in sequence. The torque speed sensor (12) is connected to the tested hydraulic motor (2) through a through-wall drive shaft (30). The room temperature power supply area includes a hydraulic pump station located outside the low temperature environment test chamber (1). The hydraulic pump station is connected to the hydraulic motor under test (2) through an oil inlet pipe (19) and an oil return pipe (20) passing through the chamber wall.

2. The low-temperature cold start multi-parameter testing system for hydraulic motors according to claim 1, characterized in that, The tested hydraulic motor (2) is fixed inside the low-temperature environment test chamber (1) by the tooling bracket (3) inside the chamber; several height adjustment shims (29) are stacked between the base of the tooling bracket (3) inside the chamber and the motor mounting surface. The shaft alignment between the tested hydraulic motor (2) and the external measuring loading chain is corrected by adding or removing the height adjustment shims (29).

3. The low-temperature cold start multi-parameter testing system for hydraulic motors according to claim 1, characterized in that, The motor output shaft (4) of the test hydraulic motor (2) is connected to the through-wall transmission shaft (30) via the first coupling (11a); one end of the torque speed sensor (12) is connected to the outer end of the through-wall transmission shaft (30) via the second coupling (11b), and the other end of the torque speed sensor (12) is connected to the output shaft of the magnetic powder brake (13) via the third coupling (11c).

4. The low-temperature cold start multi-parameter testing system for hydraulic motors according to claim 1, characterized in that, The magnetic powder brake (13) is controlled by a brake excitation controller (14) to apply a set load before the hydraulic motor (2) under test is started.

5. The low-temperature cold start multi-parameter testing system for hydraulic motors according to claim 1, characterized in that, The rated torque range of the torque-speed sensor (12) is less than the rated output torque of the hydraulic motor (2) under test, and the rated torque of the magnetic powder brake (13) is less than the rated output torque of the hydraulic motor (2) under test.

6. The low-temperature cold start multi-parameter testing system for hydraulic motors according to claim 1, characterized in that, The hydraulic pump station includes a hydraulic pump (21), a drive motor (22), an electromagnetic relief valve (23), a flow meter (24), a three-position four-way directional valve (25), an oil tank (26), a throttle valve (33), a filter (34), and a pressure gauge (35). The hydraulic pump (21) is driven by the drive motor (22), and its suction port is connected to the oil tank (26) via the filter (34). Its outlet is connected to the inlet of the three-position four-way directional valve (25) via the throttle valve (33) and the flow meter (24). The pressure gauge (35) is connected between the flow meter (24) and the three-position four-way directional valve (25). The two working ports of the three-position four-way directional valve (25) pass through the wall of the low-temperature environment test chamber (1) via the inlet oil line (19) and the return oil line (20) respectively, and are connected to the two oil ports of the hydraulic motor (2) under test. The return oil port of the three-position four-way directional valve (25) is connected to the oil tank (26). The electromagnetic relief valve (23) is connected in parallel to the outlet of the hydraulic pump (21) to set the system safety pressure and achieve rapid unloading at the end of the test. The three-position four-way directional valve (25) is used to switch the inlet and return oil directions of the two oil ports of the hydraulic motor (2) under test to achieve bidirectional cold start test.

7. The low-temperature cold start multi-parameter testing system for hydraulic motors according to claim 1, characterized in that, The system also includes an openable and closable sealing device (6) installed at the through-shaft hole (5) on the wall of the low temperature environment test chamber (1). The openable and closable sealing device (6) includes a fixed sealing component (7), a detachable sealing component (8), and a flexible brush ring (9). During the non-testing stage, the fixed sealing component (7) and the detachable sealing component (8) work together to seal the annular gap between the through-shaft hole (5) and the through-wall drive shaft (30). During the testing stage, the detachable sealing component (8) is removed and the flexible brush ring (9) lightly touches the through-wall drive shaft (30).

8. A multi-parameter testing system for low-temperature cold start of a hydraulic motor according to claim 1, characterized in that, The system also includes a data acquisition and control system (27), which is used to acquire flow rate, pressure and temperature of the two oil ports of the motor, surface temperature of the motor body, air temperature inside the box, torque, speed and loading status, and output control signals to the start control circuit of the drive motor (22) and the excitation controller of the brake (14).

9. A multi-parameter testing system for low-temperature cold start of a hydraulic motor according to claim 1, characterized in that, The system also includes a low-temperature chamber temperature control unit (28), which together with the low-temperature environment test chamber (1) forms a temperature control loop and provides the temperature status to the data acquisition and control system (27).

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