| The transmission is a very important part in automotive powertrainsystem. Vibration and noise of the transmission will directly affect theperformance of the whole vehicle. Automotive transmission noises can bebroken down into four groups according to their causes: squealing, rattling,engagement noise and bearing noise, among which rattle noise plays animportant role. Gear rattle is an impulsive phenomenon that occurs onunloaded gears which do not transmit any power. These unloaded gears,free in rotation, can knock each other under some operation conditions andthus cause rattle nosie.This dissertation aims at the rattle problem of a manual transmission.Based on the SJTU-GM joint powertrain test bench, the vibration andnoise experiment was carried to fully investigate characteristics of the gearrattle phenomenon. And find out which idler gears were rattling underdifferent operation conditions and how the parameters influence thestrength of gear rattle. Also finally in the end, it gives some recommendedadvice in engineering design to eliminate or reduce gear rattle.The noise and vibration test bench is introduced firstly, also with thesensors used in the test. And then the structure of the manual transmissionis analyzed and the possibility of each idler gear under different operationconditions is got by the analysis. According to the analysis, theexperimental method and processes are determined. After the experiment, the data is analyzed based on the angle domain resampling and envelopedemodulation and then get the conclusion.This article finds out that gear rattle is mainly affected by thefluctuation of engine speed, which is caused by ignition torque pulses ofthe engine. And the amplitude of the2ndharmonic of engine speed canshow the strength of gear rattle. In1stgear position, the2ndidler gear israttling. In2ndgear position, the gear rattle strength decrease as:4thidlergear,3rdidler gear,5thidler gear and1stidler gear. In3rdgear position, the5thidler gear is rattleing. |
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