With the rapid development of China's automobile industry, Gearbox infrastructure design matures, not only the main function of the Gearbox to improve the requirements of the Gearbox of secondary functions, auxiliary functions and even appearance also has a higher demand. Oil spill failure is one of the major failures of the domestic Gearbox products, the failure rate is high, become the focus of customer complaints. In this paper, a number of improvement measures are put forward for the oil leakage fault of the rear bearing.
Output shaft The rear bearing supports the output shaft and is fixed in the rear bearing bore of the Gearbox housing. After the output shaft, the bearing housing is bolted to the rear end of the Gearbox case to realize the axial positioning of the bearing after the output shaft. The flange assembly is spline-connected to the output shaft to transfer the rotational speed and torque of the output shaft to the drive shaft connected to the flange. Output shaft after the bearing and flange assembly between the use of the output shaft seal, the output shaft seal and flange assembly between the relative rotation, are dynamic seal, so here is the easy point of oil spill failure.
The output shaft oil seal consists of metal skeleton, sealing oil main lips and dustproof vice lip. The outer diameter of the oil seal and the hole of the shell are fitted with the interference fit. After the oil seal is installed, the oil seal and the rotating shaft form a layer of oil film (about 0.002 5mm) with fluid lubrication characteristic controlled by the oil seal edge, Liquid surface tension, the oil film just to make the oil film and air contact with the formation of a new moon, to prevent the leakage of lubricants, in order to achieve sealing. Oil seal at the mouth of the processing line, the direction of rotation and the opposite direction. The return line facilitates the formation of a stable oil film on the contact surface, imparts the heat generated by the friction to reduce power consumption and creates a suction force that urges the outside air inward.
And the oil seal with the shaft surface roughness should not be too low, it should not be too high, generally recommended to choose Ra0.8 ~ Ra3.2. Shaft surface is too rough, oil seal lip wear too fast, easy to cause leakage; shaft surface is too smooth, the oil is easy to squeeze out from the sealing surface, the film will become thinner or even disappear, resulting in lips fever or burning. In the actual application of the oil seal process, many designers tend to easily into the design errors, that the shaft surface the more smooth the better, it is not true, the axis of the design process, should be a reasonable choice of oil seal surface roughness. The surface is too smooth not only can not play the effect of sealing oil, processing costs will increase dramatically.
The sealing function of the oil seal is mainly achieved by sealing the main lip. The main lip is a rubber material, in the production site, it is easy to be sharp metal scratches, and small wounds are not easy to be found by the operator, caused by the Gearbox factory oil spill failure, causing customer dissatisfaction. In response to this failure mode, the following measures are often taken:
(1) Design: To make the oil seal easy to install and avoid the installation of damage, need to chamfer on the shaft 15 ° ~ 30 °.
(2) on-site material storage and transportation: in order to protect the oil seal, in the storage and material transport process should be kept reasonable packaging, the scene when the use of demolition of packaging; oil seal should be placed in a clean material box.
(3) field assembly: with the oil seal with the parts in the transport process should avoid bumps, should be cleaned before assembly; oil seal assembly should be used special tooling, and tooling work surface should be protected to ensure that the assembly process does not damage the oil seal , While ensuring the coaxial degree of oil seal and fittings; oil seal pressure process in the shaft surface oil.