Abstract: Oil seals are important sealing components in agricultural machinery. Oil seal leakage not only wastes engine oil and pollutes the environment, but also accelerates component wear and affects the service life of the machinery. Therefore, the reasons for oil leakage in agricultural machinery oil seals were analyzed and preventive measures were proposed.
Keywords: agricultural machinery; Oil seal; Oil leakage; preventive measure
Oil seals are used to seal shaft parts and achieve liquid lubrication. They ensure that the liquid lubricating oil does not leak through the extremely narrow sealing contact surface of their lips and the rotating shaft at a certain pressure. Oil seals, as mechanical components for sealing, are widely used in agricultural machinery. Agricultural machinery such as combine harvesters and tractors are equipped with various oil seals, which can effectively prevent the leakage of lubricating oil and hydraulic oil, and prevent dust and dirt from entering the interior of the machine. The most common failure of oil seals is oil leakage, which leads to a decrease in the amount of lubricating oil and directly affects the reliability of various agricultural machinery and equipment. This article mainly analyzes the causes and preventive measures of oil leakage in oil seals.
1. Reasons for oil leakage from oil seals
(1) Improper installation of oil seals. The oil seal is pressed or deformed during installation; Oil encapsulation reverse; When the oil seal is installed on the shaft through the shaft head thread spline, the lip is scratched or the spring falls off; Arbitrarily shortening the length of the spiral self tightening spring can lead to oil seal leakage or early leakage.
(2) The shaft itself has defects. After long-term use, crankshaft, rear axle shaft and other shaft parts undergo bending fatigue deformation, and the radial and end face runout tolerances exceed the specified standards (the radial runout tolerance of the rear axle shaft is not more than 0.04mm. The end face runout tolerance of the rear axle shaft and the radial runout tolerance of the journal surface of the installed large conical gear are not more than 0.05mm, and the straightness tolerance is not more than 0.1mm). When the tractor is running, the shaft produces significant radial and end face runout, and the viscoelastic "following" performance of the oil seal blade on the surface of the journal is reduced, leading to leakage.
(3) At the contact between the surface of the journal and the oil seal blade, there are defects such as circular grooves, ripples, and oxide skin on the surface, which cause the two to fit and even create gaps. In addition, shaft parts are not polished or replaced during major repairs, so during the trial operation stage, the oil seal blade will fail early due to rapid wear and tear. According to data and usage, more than 50% of the cases where the rotating shaft seal is damaged are caused by surface wear at the contact between the journal and the oil seal lip, resulting in leakage.
(4) Improper installation of the oil deflector (taking the rear axle oil deflector as an example) The oil baffle is installed upside down. When replacing the rear axle shaft oil deflector, place the open end of the oil deflector towards the small end of the inner ring of the tapered roller bearing, which prevents gear oil from flowing into the annular oil chamber (after the oil seal is installed into the inner hole of the tapered roller bearing seat, it forms a 13mm wide annular oil chamber together with the rear axle journal and tapered roller bearing) or the annular oil chamber has too little gear oil, causing dry friction between the rear axle journal and the oil seal lip, which burns out the oil seal blade. Therefore, when installing the oil deflector on the shaft, be sure to face the open end of the oil seal towards the open end (with spring end) The oil baffle is loose or not installed in place. After the oil seal is installed into the inner hole of the tapered roller bearing seat, the end face of the open end of the oil seal should be flush with the inner end face of the tapered roller bearing seat. After the oil baffle is installed on the rear axle shaft journal, there should be a gap of 2-2.4mm between the end face of the open end of the oil baffle and the end face of the open end of the oil seal. However, due to the loose fit (or axial sliding) or not being installed in place between the oil baffle and the rear axle shaft journal, the end face of the open end of the oil baffle blocks the end face of the open end of the oil seal, making it difficult for gear oil to enter the contact area between the rear axle shaft journal and the oil seal lip, causing dry friction between the rear axle shaft journal and the oil seal lip, causing the oil seal lip to overheat, harden, or burn out. Therefore, when installing the oil baffle onto the rear axle shaft, it is necessary to ensure an interference of 0.147~0.377mm.
(5) Not following the tractor technical maintenance procedures Excessive or insufficient filling of gear oil can cause oil seal leakage. The gear oil of the central transmission and gearbox is connected and shared, and its oil level can be checked by unscrewing the oil filler plug (along with the dipstick). The oil level should reach the upper line of the dipstick, and if it is insufficient, it can be added. If it is excessive, it can be discharged by the small inspection plug on the left side of the oil filler. ② Regularly replace the lubricating oil and the gear oil in the gearbox and central transmission gear compartment. Some operators believe that completely changing the lubricating oil is a waste, only adding new oil and rarely changing the gear oil in the central transmission and gearbox. In this way, the accumulation of impurities in the lubricating oil will cause abrasive wear of the shaft, bearing parts, and oil seal, accelerating the early failure of the oil seal. Change the gear oil according to the season, otherwise using winter gear oil in summer or summer gear oil in winter will cause oil seal leakage.
(6) The gear oil is not clean. ① Some transmission boxes and rear axle shells of agricultural machinery are cast parts, and there will still be molding sand, sticky sand, residue or metal chips left inside after sand cleaning. It is difficult to clean these impurities during repair, and these impurities will enter the gear oil, causing oil seal wear When the tractor is undergoing major repairs, parts such as gears, shafts, and bearings may not be cleaned thoroughly, resulting in unclean gear oil Improper storage, transportation, storage, and use of lubricating oil can also lead to the invasion of impurities.
(7) Poor oil seal quality. Poor manufacturing quality of oil seals, or improper transportation or storage, resulting in aging of the oil seal lip, loss of surface luster, and decreased elasticity; Oil seal deformation or lip cracking; Insufficient elasticity of the coil spring or rust or damage to the spring can promote early failure of the oil seal. Therefore, when installing the oil seal, it is necessary to carefully inspect the appearance quality and specifications. The oil seal is a vulnerable component that needs to be replaced regularly. It is recommended to replace it during tractor overhaul and the use of used oil seals is prohibited.
2. Preventive measures
Oil leakage from oil seals is a common fault, and preventive measures should be taken.
(1) For abnormal heating components, timely troubleshooting should be carried out to avoid overspeed and overload operation, and to prevent the temperature rise of the oil seal lip from causing rubber aging and rapid wear.
(2) Regularly check the oil level and quality of the lubricating oil. If the oil level is too low or there are too many impurities, it is necessary to completely replace the new oil. The brand and quality of the replaced oil should meet the requirements of the season.
(3) During the running-in period and early stages of factory use after major tractor repairs, it is necessary to regularly check the oil seal for oil leakage. If the rear axle shaft oil seal is used, unscrew the left and right screw plugs at the "grease filled inside" position on the rear wall of the rear axle box, and carefully observe with the help of light, work lights, or flashlights to see if there is gear oil leakage from the oil seal lip along the tapered roller bearing seat towards the outside. During normal work, attention should be paid not to allow the gear oil in the central transmission bevel gear chamber and the final transmission device housing to leak into the steering clutch and brake chamber. To check if this phenomenon occurs, it is necessary to unscrew the oil drain plug under the rear axle compartment (between the partition and the steering clutch chamber) and tighten any bolt of the brake band limiter to drain the accumulated oil.
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2023-09-28