Automatic gearbox wading test method

Abstract

The invention discloses an automatic gearbox wading test method, which relates to the technical field of automobile testing and comprises the following steps of: injecting water into a standard wading test site to enable the water level of the standard wading test site to reach a set height H1; preheating the to-be-tested vehicle to enable the oil temperature in the gearbox to reach the set temperature T; the vehicle to be tested is subjected to a first wading test, and gearbox oil is sampled and marked as A1; carrying out a second wading test on the to-be-tested vehicle, sampling gearbox oil, and marking as A2; sending all gearbox oil samples to a laboratory for standardized analysis to obtain the moisture content in the samples, and comparing the moisture content with a standard value so as to judge whether a to-be-detected vehicle is qualified or not; therefore, the wading capability of the automatic gearbox is verified, and the situation that the performance of the gearbox is reduced due to the water inflow risk under the cross-country wading working condition is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile testing technology, in particular to a water test method for automatic transmission. BACKGROUND

[0002] With the increasing demand of consumers for driving convenience and comfort, the market demand for automatic transmission continues to grow. Especially in the environment of urban traffic congestion, automatic transmission can greatly reduce the operating burden of the driver. At the same time, with the advancement of technology and the reduction of cost, automatic transmission is gradually popularized to more vehicle models and sub-markets.

[0003] Automatic transmission has obvious advantages compared with manual transmission. New automatic transmission such as 8-speed, 9-speed or even 10-speed transmission is becoming a trend. They make the engine always in the best working condition through denser gear ratio design, reduce fuel consumption and power loss. Modern automatic transmission is closely integrated with the electronic system of the vehicle to realize intelligent control. Through the learning and analysis of driving behavior by the on-board computer, the automatic transmission can gradually adapt to the driving habits of the driver, automatically select the most appropriate shift timing, and provide a more comfortable driving experience.

[0004] However, the internal components of automatic transmission are precise, and there is a risk of water entering under off-road water conditions. After water enters, it will contaminate the transmission oil, damage the lubricating performance and heat dissipation effect of the oil, and cause the performance of the transmission to decline. Therefore, automatic transmission needs to have reliable water-proof design.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a water test method for automatic transmission to verify the water crossing ability of automatic transmission and ensure that there is no risk of water entering under off-road water conditions, resulting in a decline in the performance of the transmission.

[0007] The above-mentioned optimized structure of the present application is realized by the following technical scheme: a water test method for automatic transmission, comprising the following steps: Step S1: water is injected into the standard water test site to make the water level reach a set height H1; Step S2: the vehicle to be tested is preheated to make the oil temperature in the transmission reach a set temperature T; Step S3: the vehicle to be tested is subjected to a first water test, and the transmission oil is sampled and labeled as A1; Step S4: the vehicle to be tested is subjected to a second water test, and the transmission oil is sampled and labeled as A2; Step S5: send all gearbox oil samples to the laboratory for standardized analysis to obtain the water content in the sample, and compare it with the standard value to determine whether the vehicle to be tested is qualified.

[0008] In some embodiments, the step S3 comprises the following steps: Step S31: the vehicle to be tested enters the water channel of the standard water test site at a set speed V1, continues to drive for a set length S1 after leaving the water channel, and returns to the inspection area; Step S32: 125ml of post-test gearbox oil is taken and added to a 250ml measuring cup, and then 125ml of fresh gearbox oil is added, sealed and labeled A1.

[0009] In some embodiments, the step S4 comprises the following steps: Step S41: the vehicle to be tested is started again to make the oil temperature in the gearbox reach a set temperature; Step S42: the vehicle to be tested enters the water channel of the standard water test site at a set speed V2, continues to drive for a set length S1 after leaving the water channel, and returns to the inspection area; Step S43: 125ml of post-test gearbox oil is taken and added to a 250ml measuring cup, and then 125ml of fresh gearbox oil is added, sealed and labeled A2.

[0010] In some embodiments, in the step S31 and the step S42, the vehicle to be tested should be shifted to each gear during driving for the set length S1.

[0011] In some embodiments, in the step S42, the vehicle to be tested needs to manually shift from 2nd gear to 1st gear during driving in the water channel of the standard water test site.

[0012] In some embodiments, before sampling the gearbox oil in the step S3 and the step S4, the gearbox oil needs to be cooled to room temperature.

[0013] In some embodiments, the following step is further included: step S6: between the step S4 and the step S5, the vehicle to be tested is subjected to a third water test, and the gearbox oil is sampled and labeled as A3.

[0014] In some embodiments, the step S6 comprises the following steps: Step S61: water is added to the standard water test site to make the water level reach the maximum height H2.

[0015] Step S62: the vehicle to be tested is preheated to make the oil temperature in the gearbox reach a set temperature; Step S63: after the test vehicle drives in the water channel of the standard wading test site at a set speed V3 for a set length S2, the parking brake is set, the gearbox oil is heated, and the vehicle is idled for a set time; Step S64: 125ml of the test gearbox oil is extracted and added to a 250ml measuring cup, 125ml of fresh gearbox oil is added, and it is sealed and labeled A4.

[0016] In some embodiments, in step S63, the test vehicle is equipped with an exhaust pipe to direct exhaust away from the water surface to prevent stalling.

[0017] The one or more technical solutions described above in the embodiments of the present application have at least the following technical effects or advantages: (1) The present application covers three typical wading scenarios, including instantaneous scouring in shallow water, continuous penetration in off-road deep water, and static oil pressure and continuous water pressure during parking in deep water, through two basic tests in shallow water and a supplementary test in deep water, thereby achieving full coverage of wading scenarios and improving the accuracy of wading performance testing of the test vehicle.

[0018] (2) The test gearbox oil is naturally cooled to room temperature before sampling, which can avoid the escape of gaseous water at high temperature, resulting in lower test values, and further ensure the accuracy of the test results.

[0019] (3) In the present application, all gears are switched in a set order during the driving of the test vehicle. Since the internal oil pressure and force state of the sealing components are different in different gears, full switching of gears can cover various sealing conditions in the actual use of the gearbox, avoiding the situation that weak points of waterproofing are not discovered due to missing gears. Moreover, the vehicle speed is matched with the gear during gear switching, which can avoid abnormal gearbox caused by gear shifting impact. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 The flowchart of the present application. DETAILED DESCRIPTION

[0022] Embodiments of the present application are described below in detail with reference to the accompanying drawings, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0023] In the description of the present application, it should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0024] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly specified and limited.

[0025] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] Reference Figure 1 A method for automatic transmission water test, through a closed loop process of scene simulation, parameter control, sample collection and result determination, the precise evaluation of the waterproof performance of the transmission is realized, which specifically comprises the following steps: Step S1: water is injected into the waterway area of the standard water test site, the water level can be monitored in real time through the water level scale line on the inner wall of the site, until the water level is stable and reaches the set height H1, H1 can be the simulation of the water depth of the urban shallow water area, usually set to 150mm, keep the water flow smooth during the water injection process, avoid the uneven load caused by water level fluctuation in subsequent test; Step S2: The vehicle to be tested is parked in the preheating area, the vehicle is started and kept idling, the oil temperature is monitored in real time through the transmission oil temperature sensor (accuracy ±1℃), the oil temperature in the transmission is made to reach the set temperature T, T is usually set to 82℃, to ensure that the transmission sealing assembly (such as fluorine rubber oil seal) is in the elastic state during actual work, to avoid the sealing performance evaluation distortion caused by the oil temperature deviation; Step S3: The vehicle to be tested enters the first water test link, and the transmission oil is scientifically sampled after the water driving is completed, which is marked as A1, to capture the water risk after the first shallow water area driving; Step S4: After the vehicle to be tested is adjusted, it enters the second water test link, to further verify the sealing performance through the intensified working conditions, and the sampling is taken after the test, which is marked as A2, to form a comparison with A1, to evaluate the influence of dynamic working conditions on the waterproof performance; Step S5: All the transmission oil samples collected during the test, including A1, A2 and optional A3, are sent to the laboratory together with the fresh oil sample blank control A4, the Karl Fischer water content determination method can be used for standardized analysis, the water content of each sample is calculated respectively, then the water content of each test sample is subtracted from the background water content of A4, to exclude the interference caused by the water brought by the new oil, to obtain the actual water content increment caused by the actual water, and finally compared with the standard value (0.05%), if the increment of all samples is lower than the standard value, and there is no leakage, abnormal sound and other problems during the test, the vehicle to be tested is determined to be qualified; otherwise, it is determined to be unqualified.

[0027] In some embodiments, step S3 includes the following steps: Step S31: The vehicle to be tested drives from the preheating area to the transition driving area at the entrance of the waterway area, which can be a 20m asphalt pavement, accelerates to the set speed V1, usually set to 35km / h, to simulate the actual driving speed in the urban shallow water area, then enters the waterway area at a constant speed, continues to drive for a set length S1 after completely passing through the waterway, usually 5km, to cover the common short distance driving distance on the urban road, returns to the inspection area after driving, parks and turns off the engine, and prepares for subsequent sampling; Step S32: After the transmission oil is naturally cooled to room temperature, to avoid the detection value being low due to the gaseous water escaping at high temperature, a special sampling tube can be used to avoid oil sample pollution, 125ml of the test oil is extracted from the sampling port of the transmission oil sump, slowly injected into a clean 250ml glass measuring cup, 125ml of fresh transmission oil of the same type is added, and a glass rod is used to stir gently for 30 seconds, to ensure that the new and old oils are fully mixed, to simulate the actual scene of supplementing new oil after the user finds that the oil is slightly emulsified, then the measuring cup is sealed with a sealing gasket, the sample number A1, test date, transmission type and test parameters (V1, H1) are marked on the cup body, to prevent sample confusion or pollution.

[0028] In some embodiments, step S4 comprises the following steps: Step S41: re-start the vehicle for secondary preheating, and monitor in real time through the oil temperature sensor to ensure that the gearbox oil temperature is re-stabilized to reach the set temperature T, consistent with step S2, to avoid changes in the sealing assembly state due to a decrease in oil temperature after the first test, affecting the comparability of the test results; Step S42: the vehicle to be tested drives from the inspection area to the transition driving area, accelerates to the set speed V1, and enters the water channel area at a constant speed, during which the vehicle is completely immersed in water at the middle position of the water channel to ensure that the vehicle is subjected to stable water pressure, and the gearbox is manually shifted from 2nd gear to 1st gear, and the vehicle is driven away from the water channel while maintaining 1st gear, thereby simulating the gear shifting condition during downhill wading, during which the main oil pressure of the gearbox increases from 1.2 MPa to 3.0 MPa to strengthen the dynamic pressure load of the sealing assembly, and the vehicle continues to drive for a set length S1 after leaving the water channel, consistent with step S31, and during the driving process, the shift lever is sequentially switched to P, R, N, D, and each forward gear in manual mode, and each gear is maintained for ≥30 seconds to ensure that the sealing performance under each gear is verified, and finally returns to the inspection area and stops; Step S43: After the gearbox oil is cooled to room temperature, follow the same operation procedure as step S32 to extract 125 ml of test oil, add 125 ml of fresh oil, mix and seal, and label the sample number A2 and test parameters (V1, gear shifting operation) on the cup body to ensure that A2 and A1 have the same sample processing conditions to ensure the comparability of the test results.

[0029] In some embodiments, in steps S31 and S42, during the driving process of the vehicle to be tested on the set length S1 (5 km), all gears need to be completely switched in the order of D gear-1st gear-2nd gear-...-highest gear-R gear-P gear-N gear-D gear, and each gear is maintained for ≥30 seconds, and the vehicle speed is matched with the gear during gear shifting to avoid gearbox abnormalities caused by gear shifting impact. The internal oil pressure of the gearbox and the stress state of the sealing assembly are different under different gears, such as 1.2 MPa of parking oil pressure under P gear and 0.8-2.5 MPa of driving oil pressure under D gear. Complete gear switching can cover various sealing conditions in the actual use of the gearbox to avoid missing weak points of waterproofing that are not discovered.

[0030] In some embodiments, in step S42, during the driving process of the vehicle to be tested in the water channel of the standard wading test site, after entering the middle position of the water channel, the vehicle is completely immersed in water, the water pressure is stable, 2nd gear is manually shifted to 1st gear, the throttle opening is kept stable during gear shifting to avoid sudden speed reduction, and 1st gear is maintained after gear shifting to leave the water channel.

[0031] When the 2nd gear is down 1 gear, the synchronizer inside the gearbox and the gear meshing state are switched quickly, the main oil pressure will suddenly rise from 1.2 MPa to 3.0 MPa within 0.5 seconds, and the input shaft oil seal and other sealing components will be slightly deformed under the impact of oil pressure. If there is a large sealing gap or material defects, the risk of water ingress will significantly increase at this time. Through this enhanced working condition, the dynamic sealing weaknesses can be accurately exposed.

[0032] In some embodiments, before sampling the gearbox oil in steps S3 and S4, the vehicle to be tested needs to be parked in a ventilated and shady place after being turned off. The oil temperature is monitored in real time through the gearbox oil temperature sensor, and sampling is performed after the oil temperature drops to the normal temperature range. Direct sunlight or wind blowing to accelerate cooling is avoided to prevent uneven local oil temperature.

[0033] The solubility of water in gearbox oil decreases with increasing temperature. Sampling at high temperature can cause gaseous water in the oil to escape, resulting in a low detection result. Cooling to normal temperature before sampling can ensure that the water is completely dissolved in the oil, and the detection result truly reflects the actual water ingress situation.

[0034] In some embodiments, for vehicle models that need to cope with off-road deep water area conditions, such as SUVs and off-road vehicles, the test method further includes step S6, which is between steps S4 and S5. The vehicle to be tested enters the third water test phase to simulate extreme deep water area scenarios. After the test, the gearbox oil is sampled and labeled as A3. The waterproof performance under extreme conditions is evaluated through this sample to further improve the judgment basis.

[0035] In some embodiments, step S6 includes the following steps: Step S61: After step S4 is completed, slowly refill the water, monitor the water level through the water level scale until the water level stabilizes at the maximum height H2. H2 is the simulated off-road deep water area water depth, usually set to 600 mm; Step S62: Park the vehicle to be tested in the preheating area and start the vehicle for preheating. Monitor in real time through the oil temperature sensor to ensure that the gearbox oil temperature reaches the set temperature T. Consistent with step S2, if it is a DHT gearbox, the motor preheating needs to be started at the same time, so that the motor stator temperature reaches 40-50℃ to simulate the actual use of the motor heat state; Step S63: Then the vehicle drives to the transition driving area, accelerates to the set speed V2, usually 30 km / h, to simulate the slow driving speed in the off-road deep water area, and drives at a constant speed in the waterway area for a set length S2, usually 15 m, to ensure that the vehicle is always in deep water. After driving, set the parking brake in the waterway area to ensure that the gearbox parking locking mechanism is fully engaged, start the gearbox oil heating device through the on-board diagnostic system (OBD) to maintain the oil temperature within the set temperature T ± 3℃ range, and keep the engine idling for a set time, usually 8 minutes, to simulate the typical time of parking and waiting in the off-road scene; Step S64: After idling, drive the vehicle out of the waterway area and back to the inspection area, turn off the engine and wait for the gearbox oil to cool to room temperature. According to the operation process of step S32, draw 125 ml of test oil sample, add 125 ml of fresh oil, mix and seal. Label the sample number A3 and test parameters (H2, V2, idling time) on the cup body.

[0036] In some embodiments, in step S63, a retractable stainless steel exhaust pipe is installed at the end of the exhaust pipe of the vehicle to be tested, with the same diameter as the original vehicle and the length adjusted to be 50 ± 10 mm higher than the water surface to prevent water from flowing back into the engine and causing the engine to stall when driving in the deep water area. The exhaust pipe can be made of 304 stainless steel, and the exhaust pipe is fixed on the vehicle chassis by a special bracket, and a rubber shock pad is used at the connection between the bracket and the chassis to reduce vibration. A rainproof cap is installed at the outlet end of the exhaust pipe to prevent rainwater from splashing in during driving.

[0037] When the water level in the deep water area is H2 = 600 mm, the original exhaust pipe will be completely submerged, causing the engine exhaust back pressure to rise from 2 kPa to more than 20 kPa, which will cause the engine to stall within 30 seconds and prevent the subsequent parking idling test from being completed. After the retractable exhaust pipe is raised above the water surface, the exhaust back pressure can be maintained within 2 kPa, ensuring normal idling of the engine and ensuring smooth completion of the deep water area test.

[0038] The specific working process is as follows: Slowly fill the waterway area with water, and observe the water level in real time through the water level scale until the water level stabilizes at the set height H1 = 150 mm. After the water is filled, wait for 5 minutes to confirm that the water level does not decrease significantly before proceeding to the subsequent test.

[0039] Start the vehicle to be tested and keep it idling, and monitor the gearbox oil temperature in real time through the oil temperature sensor. When the oil temperature stabilizes at the set temperature T = 82℃, maintain the temperature for 3 minutes to avoid sudden oil temperature drop.

[0040] The vehicle drives from the preheating area to the transition driving area, slowly accelerates to the set speed V1 = 35 km / h, enters the waterway area at a constant speed of 35 km / h, and continues to drive on the ordinary road for a set distance S1 = 5 km after completely passing through the waterway; during the driving process, all gears can be completely switched in the order of D gear-1 gear-2 gear-...-highest gear-R gear-P gear-N gear-D gear, each gear is maintained for driving ≥ 30 seconds, and the vehicle speed is matched with the gear during switching; after completing the 5 km driving, the vehicle returns to the inspection area, is turned off and the engine is turned off, and is prepared for sampling.

[0041] After the vehicle is turned off, it is parked in a ventilated and cool place, and is monitored in real time through the oil temperature sensor until the transmission oil is cooled to room temperature; 125 ml of test oil is extracted from the sampling port of the transmission oil pan using a special sampling pipe, and is slowly injected into a clean measuring cup; 125 ml of fresh transmission oil is added to the measuring cup, and is gently stirred along the wall of the cup with a glass rod for 30 seconds to ensure that the old and new oils are fully mixed; the cover with a sealing gasket is covered and tightly sealed; the sample number A1, the test date, the transmission type, and the test parameters (V1 = 35 km / h, H1 = 150 mm) are marked on the cup body, and the sample is stored in a cool and dry place.

[0042] The vehicle is started again, and the idle preheating mode is entered again, and the oil temperature is monitored through the oil temperature sensor to ensure that the transmission oil temperature is stabilized again to T = 82°C, and is maintained for 3 minutes; if the oil temperature drops too quickly, the idle speed can be appropriately increased to raise the oil temperature, but the speed should not be too high to cause the oil temperature to exceed the temperature.

[0043] The vehicle drives to the transition driving area, accelerates to V1 = 35 km / h and maintains a stable speed; enters the waterway area at a constant speed, drives to the middle of the waterway, ensures that the vehicle is completely immersed in the water, the water pressure is stable, manually reduces the transmission from 2 gear to 1 gear, maintains the throttle opening during the gear shifting process, and drives to the exit of the waterway; after driving out of the waterway, continue to drive S1 = 5 km, and completely switch all gears in the order of D gear-1 gear-2 gear-...-highest gear-R gear-P gear-N gear-D gear during the driving process, each gear is maintained for driving ≥ 30 seconds, and the vehicle speed is matched with the gear during switching; after completing the driving, the vehicle returns to the inspection area, is turned off and the engine is turned off.

[0044] After the transmission oil is cooled to room temperature, the same operation process as step S32 is performed: 125 ml of test oil is extracted, 125 ml of fresh oil is added, and is mixed and sealed; the sample number A2 and the test parameters (V1 = 35 km / h, 2 gear to 1 gear operation) are marked on the cup body, and are stored together with the A1 sample to ensure consistent storage conditions.

[0045] For vehicles such as off-road vehicles that require water, a deep water area extreme test needs to be added After the completion of the shallow water area test, re-inject slowly; through the water level scale monitoring, until the water level is stable to H2=600mm; after injection, stand for 10 minutes, confirm the water level is stable, check the waterway area without leakage.

[0046] Park the vehicle to the preheating area, start and idle, make the transmission oil temperature stable to T=82℃; install a telescopic stainless steel exhaust pipe at the end of the vehicle exhaust pipe, adjust the length to make the outlet 50±10mm above the water surface, fix it firmly with a support, check the sealing of the connection; drive the vehicle to the transition driving area, accelerate to the set speed V2=30km / h, keep the speed stable and enter the waterway area at a uniform speed; drive at 30km / h for a set distance S2=15m in the waterway area, set the parking brake in the waterway area after driving; start the transmission oil heating device through the OBD system, keep the engine idling for 8 minutes; during idling, arrange observers to listen for abnormal noise of the transmission and check the sealing components for leakage.

[0047] After idling, release the parking brake, drive out of the waterway area at 30km / h, return to the inspection area and turn off the engine; after the transmission oil cools to room temperature, follow the operation procedure S32: extract 125ml of test oil, add 125ml of fresh oil, mix and seal; mark the sample number A3 and test parameters (H2=600mm, V2=30km / h, idling for 8 minutes) on the cup body, store it together with A1 and A2.

[0048] Collect 250ml of fresh transmission oil, seal and mark as blank control sample A4; send A1, A2, A3 (optional), and A4 samples together to the laboratory for standardized analysis using Karl Fischer moisture determination method to obtain the water content data of each sample.

[0049] Calculate the actual water content increment of each test sample: increment = test sample water content - A4 sample water content, excluding the background moisture interference of new oil; Comparison and determination: if the increment of all test samples is <0.05% (standard value), and there is no leakage of sealing components, abnormal noise of the transmission, etc. during the test, the vehicle under test is determined to be qualified; If the increment of any sample is ≥0.05%, or there is leakage or abnormal noise during the test, the vehicle under test is determined to be unqualified, and the unqualified reasons are recorded.

[0050] After the qualification determination is completed, drain the water in the waterway area, clean the test site; maintain the vehicle under test: replace the transmission oil, remove the exhaust pipe (for vehicles tested in deep water area), check the status of each part of the transmission, and ensure that the vehicle returns to normal use state; organize the test data and records (including sample test report and process observation record), form a complete test file.

[0051] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for testing the wading depth of an automatic transmission, characterized in that: Includes the following steps: Step S1: Fill the standard wading test site with water until the water level reaches the set height H1; Step S2: Preheat the vehicle under test to bring the transmission oil temperature to the set temperature T; Step S3: The vehicle under test undergoes its first wading test, and a sample of the transmission fluid is taken and labeled A1; Step S4: The vehicle under test undergoes a second wading test, and a sample of the transmission fluid is taken and labeled A2; Step S5: Send all transmission fluid samples to the laboratory for standardized analysis to obtain the water content in the samples. Compare the water content with the standard value to determine whether the vehicle under test is qualified.

2. The water wading test method for an automatic transmission according to claim 1, characterized in that: Step S3 includes the following steps: Step S31: The vehicle under test enters the waterway of the standard wading test site at a set speed V1, continues to travel a set distance S1 after leaving the waterway, and returns to the inspection area. Step S32: Extract 125ml of the test transmission fluid and add it to a 250ml measuring cup, then add 125ml of fresh transmission fluid, seal and label it A1.

3. The water wading test method for an automatic transmission according to claim 2, characterized in that: Step S4 includes the following steps: Step S41: The vehicle under test is restarted to allow the transmission oil temperature to reach the set temperature; Step S42: The vehicle under test enters the waterway of the standard wading test site at a set speed V2, continues to travel a set distance S1 after leaving the waterway, and returns to the inspection area. Step S43: Extract 125ml of the test transmission fluid and add it to a 250ml measuring cup, then add 125ml of fresh transmission fluid, seal and label it A2.

4. The water wading test method for an automatic transmission according to claim 3, characterized in that: In steps S31 and S42, the vehicle under test should shift to different gears while traveling a set distance S1.

5. The water wading test method for an automatic transmission according to claim 3, characterized in that: In step S42, the vehicle under test needs to be manually downshifted from 2nd gear to 1st gear while driving in the waterway of the standard wading test site.

6. The water wading test method for an automatic transmission according to claim 1, characterized in that: Before sampling the transmission fluid in steps S3 and S4, the transmission fluid must be allowed to cool to room temperature.

7. The water wading test method for an automatic transmission according to claim 1, characterized in that: It also includes the following steps: Step S6: Between step S4 and step S5, the vehicle under test undergoes a third wading test, and a sample of the transmission fluid is taken and labeled A3.

8. The water wading test method for an automatic transmission according to claim 7, characterized in that: Step S6 includes the following steps: Step S61: Fill the standard wading test site with water until the water level reaches the maximum height H2; Step S62: Preheat the vehicle under test to bring the transmission oil temperature to the set temperature; Step S63: After the vehicle under test travels a set distance S2 in the waterway of the standard wading test site at a set speed V3, the parking brake is set and the transmission fluid is heated, and the vehicle is idled for a set time. Step S64: Extract 125ml of the test transmission fluid and add it to a 250ml measuring cup, then add 125ml of fresh transmission fluid, seal and label it A4.

9. The water wading test method for an automatic transmission according to claim 8, characterized in that: In step S63, the vehicle under test is equipped with an exhaust pipe to direct exhaust gas to the water surface to prevent the engine from stalling.

10. The water wading test method for an automatic transmission according to claim 1, characterized in that: In step S5, the fresh transmission fluid is sealed and labeled A4, and sent to the laboratory for standardized analysis to obtain the water content in the fresh transmission fluid.

Images