Modification Design And Experimental Research Of Automobile Transmisson Gears

As a key part of automobile power system, the transmission plays aremarkable role in the automobile power performance, economy and comfort.Gears as indispensable parts of automotive transmission, because of theirmachining quality and assembly quality, there exist meshing impact and partialload in gear meshing, which result in the increasing of the vibration noise andreducing the bearing capacity. Gear modification can effectively solve theabove problems, and modification parameters need to be determined accordingto the conditions of transmission gears. The difference of effects caused bydifferent modification parameters is very big. If the modification parametersare selected improperly, it will not improve the gear meshing performance, andit will affect the normal engagement, so the gear modification research hasimportant theoretical significance and practical value.The initial modification design of transmission gears was completed inthis paper, based on the established mathematical model and simulationanalysis. Then the dynamic characteristics test and bending fatigue strengthtest before and after initial modification were carried out to verify the feasibility of the initial modification scheme. Based on this, the initialmodification parameters were optimized by the objective of the meshingdynamic characteristics such as gear transmission error. This paper put forwarda new modification design verified feasibly through the simulation analysis toobtain the optimal modification scheme.The initial modification design of the tooth profile with addendummodification and the tooth lead with drum modification was done at first. Amathematical model of initial modification was established to determine theoriginal modification parameters, then combined the simulation results ofdifferent modification parameters to determine the suitable parameters.Completing the initial modification design, the dynamic characteristicstest and bending fatigue strength test on gear modification were performed.The test results show that, the gear noise before the initial modification is81.56dB, the noise is82.55dB after the modification, increased by1%; TheRMS value as vibration performance indicator before the initial modification is3.59mm/s2, the RMS value is4.17mm/s2after the modification, increased by16%; the bending fatigue strength before the initial modification is781MPa, itis946MPa after the modification, increased by21.12%. After the initialmodification, the gear dynamic characteristics became worse, bending fatiguestrength enhanced. But the bending fatigue test of gears was limited by the testcondition, and the method of staggering teeth meshing was adopted, sobending fatigue test results only has a certain reference. Through comprehensive analysis, the optimal modification was needed.In the optimal modification design, tooth lead adopted tooth end reliefsuited for the condition of smaller meshing skewness; tooth profile stilladopted addendum modification. Establishing a mathematical model ofoptimal modification and analysing the effects of different parameters on gearmodification were to determine the appropriate parameters. Through theoptimal modification, the transmission error was reduced, gears ran smoothlycompared to initial modification, then vibration and noise were reduced in geartransmission. And the optimal modification also made the load distributionmore even than initial modification, greatly improved the bearing capacity andservice life of gears.