As one of the important components of the bogie system, the gearbox is used to transmit the torque generated by the electric motor through the coupling and drive the wheels, transmitting the traction of subway vehicles. The gearbox, due to its unique function and structure, is a component with a high failure rate Z in the bogie, and its performance directly determines the operational performance of the bogie.
The phenomenon of oil leakage in subway gearbox is one of the common gearbox failure modes, mainly caused by the following reasons: oil leakage from the sealing surface of the gearbox, oil leakage from the bearing seal, oil leakage from the exhaust hole of the end cover, oil leakage from the oil filling and drainage ports, etc. The oil leakage and seepage of various components in the gearbox not only affects the surface working condition of each component, but also reduces the lubrication ability of other small parts inside the gearbox, exacerbating the temperature rise and causing serious wear of internal parts. After Z, it leads to damage to other related components of the gearbox. So it is of great practical significance to analyze the causes of subway gearbox oil leakage and take some relevant measures to solve this problem.
1 Principle and composition of gearbox
There are two types of subway vehicles, namely high-speed trains and trailers. The vehicles without power are trailers, while the vehicles with power transfer energy are high-speed trains. There are traction motors and gearboxes suspended on the high-speed trains. The high-speed trains drive the traction motors to rotate by receiving the energy transmitted by the pantograph, mainly through electric transmission to achieve the transformation and transmission of kinetic energy. As a variable speed mechanism, the gearbox converts the higher speed of the traction motor into an appropriate wheelset speed, thereby driving subway vehicles forward. The drive gearbox for subway vehicles is located at the bottom of the power car body, with one end suspended on the axle and the other end suspended on the frame. During high-speed operation, the impact of the track directly affects the gearbox.
2 Gearbox lubrication method
When subway vehicles operate on the main line, due to the complex working conditions of the line, the bogie is frequently subjected to vibration and impact from the track. In order to improve the performance of the gearbox and ensure the lifespan of each component inside the gearbox, reliable lubrication and sealing measures must be taken during the design process. The lubrication method of the bearings and gears in the gearbox is precisely through the rotation of the gears, which drives the flow of lubricating oil inside the gearbox, generating splashing oil mist for lubrication. This "splashing lubrication method" acts on the meshing surface between the gears and other parts of the gearbox to achieve cooling and lubrication. There is an oil mark on the lower box of the gearbox, with two horizontal lines above it, representing the Z high oil level and Z low oil level. Under normal operating conditions, the oil level must be maintained between the two lines indicated by the Z high oil level and the Z low oil level.
3 Common faults and solutions of gearbox
(1) Labyrinth seal failure
Labyrinth seal failure may be caused by the following reasons: during the design and manufacturing process of the gearbox, due to poor design or assembly quality of the labyrinth seal, the assembly tolerance of the labyrinth seal and other parts of the gearbox is too large, and oil and gas are easy to seep out at the labyrinth seal; Adding too much lubricating oil to the gearbox can cause the oil level to exceed the upper mark, and a high oil level can cause oil and gas to escape from the maze. The specific solution measures include: draining an appropriate amount of gearbox lubricating oil, adjusting the oil level to near the middle scale line, cleaning the outer surface of the gearbox contaminated by oil and gas, regularly observing the gearbox oil level. If the oil level drops significantly or there is obvious dripping phenomenon, the gearbox output end cover must be removed for internal inspection, using specialized equipment to detect dimensions and fit tolerances, and replacing the sealing structure and O-ring.
(2) Box surface fault
The failure of the joint surface may be caused by the following reasons: improper assembly of the joint surface of the box (improper assembly of sealant or O-ring), improper application of sealant, and failure to cover the entire joint surface area, which may cause lubricating oil to seep out from the gap; During the assembly of the gearbox, before adjusting the clearance of the intermediate stage bearing, sealant is applied to the joint surface of the gearbox. However, the bolts on the joint surface are not fully tightened. After the clearance adjustment is completed, some of the sealant may have started to harden. When tightening all the bolts on the joint surface, the sealant cannot be squeezed evenly, resulting in gaps or missing points in some areas, which can lead to lubricating oil leakage. The specific solutions are as follows: clean and assemble in strict accordance with the maintenance specifications; after applying sealant to the box closing surface, ensure that all bolts are tightened as required when adjusting the bearing clearance, and select the sealant model and apply it in a standardized manner according to the relevant requirements.
(3) Oil pointer position fault
The position failure of the oil pointer may be caused by the following reasons: seal failure or poor installation; Cracks in the glass plate caused by foreign objects hitting or mistakenly spraying cleaning agent on the glass cover plate. The specific solutions include: regular observation when the oil level does not decrease; When there is no obvious oil leakage, replace it during normal maintenance operations; When the oil level drops significantly or there is obvious oil leakage, replace it immediately.
(4) Oil blackening fault
Oil blackening may be caused by the following reasons: a new bearing may cause oil blackening after a period of running in; The oxide skin on the replaced new bearing ball that has not been removed may be washed off by the oil during operation, resulting in blackening of the oil; During the maintenance process of the gearbox, the oil used for running in and testing was not replaced in a timely manner. Mixing the testing oil with new oil (with a brighter color) will cause the oil to turn black.
The specific solution measures include: first observe whether the blackened oil precipitate in the gearbox is in the form of powder or metal fragments. The powdery foreign matter should be caused by poor cleanliness inside the gearbox. If there are metal fragments, the cause should be identified, and the gearbox should be flushed with oil and refueled before proceeding? During the running in test, after the test is completed, it is necessary to raise one end of the high-speed shaft of the gearbox while it is hot and drain as much oil as possible from the magnetic plug side of the gearbox. Regularly replace the running and testing oil during the maintenance process to ensure the cleanliness of the oil.
(5) Oil seepage and leakage fault
Due to the use of a non-contact labyrinth seal structure, oil mist will overflow outward along the labyrinth seal gap. During the overflow process, the majority of the oil mist condenses and flows back to the box, while a small portion of the oil mist continues to spread outward. The oil mist that spreads outward will condense on the outer surface of the bearing seat and sealing ring when encountering cold air, and combine with the dust in the environment? Accumulation forms wet ash stains that are adsorbed on the surface of the box: another part condenses in the annular groove of the water outlet, and after cooling, it is discharged from the water outlet together with the external cooling water vapor, forming liquid sagging marks near the water outlet, which may cause the sagging marks to diffuse during vehicle operation. In addition, an excessive amount of lubricating oil in the gearbox can exacerbate the above phenomenon. The specific solution measures include: for areas where the putty has dried, please clean the putty thoroughly and use a cleaning agent to clean it. Apply a layer of silicone seal to the sealing connection and surrounding areas. After adding new lubricating oil to the gearbox, it is necessary to ensure that the amount of lubricating oil leakage within one oil change cycle does not cause the gearbox lubricating oil level to decrease from the medium level to below the Z low level. If the lubricating oil level gradually decreases, it cannot meet the normal oil change cycle of gearbox maintenance. In combination with maintenance, appropriate time should be selected for leakage prevention measures. Before the gearbox oil level drops below the Z low level, it is necessary to add lubricating oil again.
(6) Oil emulsification failure
The emulsification failure of gearbox oil may be caused by the following reasons: the main reason is that external dust, dust, water vapor, etc. are sucked into the interior of the gearbox from the gearbox breather or seal, especially when subway vehicles pass through tunnels, forming negative pressure at the gearbox breather. Polluting small particles such as dust, dust, water vapor, etc. are easily poured into the gearbox interior with the airflow, causing lubricating oil emulsification or blackening. The specific solution is to first discharge the old oil, then add 5% of the normal refueling amount of working oil for flushing, and then discharge it. Add the normal amount of working oil to the standard oil level. Under normal circumstances, operate for 1-3 hours, and the oil temperature can reach 40 ℃. After the gearbox is shut down, drain all lubricating oil while it is hot within 30 minutes, and then add the working oil again to the standard oil level according to maintenance requirements. During normal operation for 1-3 months, monitor the lubricating oil of the gearbox and randomly sample for physical and chemical tests to ensure that the lubricating oil performance meets the usage requirements.
4 A General Fault Diagnosis Method for Gearboxes
If a gearbox malfunctions, it needs to be diagnosed in a timely manner and can be quickly located and judged through efficient and scientific diagnostic methods. The common methods for diagnosing gearbox faults are:
Spectrum analysis method, when a gearbox malfunctions, the fault information contained in its vibration signal usually appears in the form of modulation. By demodulating the fault information, the source of the fault problem can be determined.
Signal analysis method: Dynamic signals such as noise, vibration, and temperature rise generated by the gearbox during operation are collected using professional equipment. Based on the signal analysis method, faults are analyzed and diagnosed.
Wear analysis method: according to the metal wear theory, through collecting the samples in the gearbox lubricating fluid, the kinematic viscosity test, water content test, metal wear analysis in the lubricating fluid, and the wear metal parts per million in the lubricating fluid to determine the source of materials, so as to determine the state of the lubricating fluid, and conduct a comprehensive evaluation of the oil performance.
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2023-06-09