Sealing Performance Of Automotive Steering Gear Oil Seal Material And The Study Of Friction And Wear

With the development of science and technology,the application of many high technology makes the maximum driving speed of the car becoming higher and higher,and the shaft’s speed turns to faster and faster.But this also give new requirements for the reliability of the seal.Steering gear oil seal is one of the key parts of the automobile steering device,and the main function is to prevent the steering gear lubricating oil from leaking out and the external dust,sand,powder and other impurities and pollutants going into the body.It can protect bearings,gears and other parts of the normal work.Its quality not only affects the car steering system seal performance and service life but also the safety of car driving.Therefore,the property of oil seal material itself and the structural parameters of it play crucial roles in the sealing performance.In this paper,by comparing the traditional oil seal materials,PTFE was selected as the matrix,and graphite（Gr）,glass fiber（GF）,calcium carbonate（Ca CO₃）,Nano-Diamond were selected as the filler to modify it.The mechanical properties of the material and the influence of the structural parameters of the oil seal on the sealing properties are studies as following:（1）Pure PTFE was modified by filling four materials with different contents,and their friction coefficient,wear amount,tensile strength and modulus,compressive strength and modulus were investigated and analyzed.Under the dry friction testing,the graphite shows good performance under 200N and 300N loading,and the lowest friction coefficient of 0.178 and 0.16 is obtained,which is 11%and18%lower than that of pure PTFE,respectively.At the same time,the wear rate is also greatly reduced by 77%and 83%under same conditions.Furthermore,the tensile properties and compressive properties of the composites with filler are also greatly improved.Under the tensile and compression test,GF showed good tensile properties when the content was 2wt%and when the content was increased to 8wt%,the tensile strength reached 30.2MPa,while pure PTFE was only 24MPa,an increase of 24%.The compressive modulus and compressive strength of graphite are better than other materials.The compressive strength is up to 58MPa and the modulus is up to 1.1GPa,which is far superior to the pure PTFE material.PTFE composites modified with different fillers also have better friction properties.（2）Finite element simulation software ABAQUS was used to simulate and analyze the three-dimensional model of oil seal,and the influence of different structural parameters of oil seal on the sealing performance was studied.At the same time,through the orthogonal test method,using the orthogonal table of three levels and four factors,the stress and lip deformation under the influence of three different factors were obtained.The optimal parameter combination among many combinations was determined and combined with the finite element simulation analysis,the maximum lip contact stress was 1.063MPa,and the minimum value of all combinations was obtained.On the one hand,it can ensure the static sealing performance of the oil seal.On the other hand,it will not cause serious lip wear due to uneven stress distribution and excessive stress,so as to ensure the normal operation of the oil seal to a large extent.（3）Through the principle of pump suction effect and the calculation formula of pump suction rate and the method of control variables,influence of changing a parameter on pump suction rate is investigated under the condition that other parameters is remained.The results show that pump absorption decreases with the increase of contact width b.When contact width b is too large,pump absorption tends to 0.Under the premise of guaranteeing pumping effect,the pump absorption rate increases with the increase of oil side lip Angleα,and decreases with the increase of air side lip Angleβ.The increase of oil film thickness h and contact load F also greatly increases the pump absorption rate.（4）Sealing coefficient K is an important index to measure the sealing performance of oil seal.Relative slot width K₁,relative slot depth K₂and helix Angleαhave important relationship with sealing ability.The sealing ability can be optimized by optimizing these three parameters.The relationship curves of relative groove width K₁,relative groove depth K₂,helix Angleαand sealing coefficient K were studied by using Matlab software and the method of control variables.Additionally,the influence curves of return oil groove parameters on sealing coefficient were analyzed,and the influences of different return oil structural parameters on sealing coefficient K were obtained.According to the analysis,when the relative groove width K₁is 0.6,helix Angleαis 0.35,and relative groove depth K₂is 3.4,the maximum sealing coefficient K of 0.5589 is obtained.