| The transmission is an important part of automotive drive line. Vibration and noise of the transmission will affect the working performance of a vehicle directly. Automotive transmission noises can be broken down into four groups according to their causes: squealing, rattling, engagement noise and bearing noise, among which rattle noise plays an important role. Due to its intrusive characteristics, rattle noise serves as a challenge to vehicle compartment comfort.This dissertation aims at the rattle problem of a manual transmission. Using a drive line test bench, vibration and noise experiments were carried out to investigate characteristics of the rattling phenomena. Causes and frequencies of low speed gears were identified. The influence of various working conditions on rattle noise was also studied.The platform of transmission test is a clutch and transmission dyno established by Shanghai Jiao Tong University and General Motors Inc. (China). The mechanism of rattle phenomenon is introduced first, followed by the description of test stand structure and general test procedure. After that, details of dyno experiments are presented, showing how rattle noise is reproduced by varying exciting frequencies and how characteristic frequency of rattle is identified. At last, effects of different working parameters to the transmission are studied.The article point out that noise level will increase by 2dB when rattling phenomenon appears and the rattling frequencies of 1st, 2nd, 3rd and reverse gear are 1700Hz ~ 1860Hz, 2250Hz ~ 2350Hz, 1030Hz ~1200Hz, and 1520Hz ~ 1640Hz, respectively. Rattle phenomenon will easier to recur in the speed range of 1200rpm to 2000rpm with proper load torque (387N·m) and high oil temperature. The rattling possibility in different gear position from easy to difficult is: Reverse gear, 2nd gear, 3rd gear, 1st gear. |
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