Study Of Sealing Performance And Wear Mechanism Of Oil Seal Used In Engine

Along with the development of internal combustion engine industry,all kinds of engine components develop toward high pressure, high temperature and high velocity. So the engine components have an increasing requirement. The rotation axis oil seal, must bear the working conditions such as high/low temperature, high linear velocity, heavy load and so on. And they must have the features of small frictional resistance, abrasion resisting, long service life and reliable sealing. This research is aimed at improving the seal structure and the sintering technology of filled PTFE, eventually manufacturing sealing products with high performance and decreasing the dependence of imported products.According to the research results of relative papers at home and abroad, the main contents and research methods in this paper are listed as follow:(1) Analyze mechanical properties and wear mechanism of oil seal materials. Compare friction coefficient and wear resistance of PTFE filled with different fillers in room temperature and high temperature. Study influence to friction coefficient and wear rate of the material considered load, velocity and friction styles on it simultaneously. Moreover, wear mechanism of friction pairs is detected. Therefore PTFE filled with carbon fiber is selected as oil seal material which is suitable for conditions of automobile crankshaft.(2) Establish nonlinear finite element model of oil seal structure. Analyze compressive stress distribution and deformation conditions of interference fit between oil seal and axis which have different structure. Optimal selection of oil seal structure is based on leakage formula of sealing clearance. Analysis of oil seal finite element has geometric nonlinearity, material nonlinearity and contact nonlinearity. Two analysis steps are created in finite element calculation. Translation amount and rotational motions are set in Y axis of rigid reference point to simulate force situation of oil seal after it is installed on immobile and running crankshaft. Leakage rate is calculated in accordance with the maximum gradient of pressure increased segment and the decreased one of contact compressive stress. In addition, shape of seal interval is derived by Reynolds equation. Results show that PTFE oil seal which is designed reasonably must has a small disparity between the maximum gradient of pressure increased segment and the decreased one and has flatter contact stress distribution.(3) Deduce seal coefficient of spiral groove PTFE oil seal and optimize structure parameters of oil seal. Suppose the pumpage and leakage of lubricating oil inside spiral groove is the clearance flow between two surfaces. According to flow equilibrium principle of spiral reflux groove oil seal, seal capacity of oil seal can become the mathematical model based on the design variables of spiral groove relative width, relative groove depth and helix angle. Spiral groove extends in turning to the inner edge of the seal. Adjust oil pressure, and measure critical rotational speed to verify formula of seal coefficient.(4) Study on stress relaxation, tensile and compression of carbon fiber filled PTFE composite materials through different sintering processes. Improve elasticity of oil seal and sealing performance. And it is verified by bench test. Results show that sintering process directly effects on the sealing performance such as oil seal radial force, recoverability, following behaviors and so on. The following behaviors of oil seal and axis which is used water cooling process at the temperature of 340℃is better than those which are used wind cooling process at the same temperature and general sintering process. It has inferior mechanical properties to the one made by general sintering process, but can increase following behaviors and decrease leakage rate.(5) Inspect assembly quality and durability of oil seal in automobile engine. Refer to reliability test method of automobile engine, the engine must be on full-load power test at the rotational speed of 3000r/min and 6000r/min. During the period of experiment, leakage of PTFE oil seal doesn't appear and wear degree is within the allowable range. It's proved that PTFE oil seal can meet the requirement of engine strengthen experiment.