真空泵裝載於車之改良隔震設計

Improved Vibration Isolation Design of Vehicle Vacuum Pump Mountings

黎宣敏(Hsuan-Ming Li)

指導教授 ： 鐘添東

國立臺灣大學/工學院/機械工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.10091

摘要

本文利用有限元素分析研究煞車輔助真空泵裝載於車的改良隔震設計。為了能夠以有限元素模型進行較準確的動態行為預測,橡膠隔震襯墊的動態特性量測就成了重要的課題之一。本研究中提出了一可重構式的量測載具,於是橡膠隔震襯墊的軸向及徑向的動態特性皆可利用敲擊測驗量測得知。橡膠動態特性的量測設備包含了衝擊錘、加速規、力規及頻譜分析儀。將所量得的入力、反力、軸向及徑向的加速度訊號輸入頻譜分析儀,橡膠隔震襯墊的動態特性即可求得。本研究中也執行了結構動態量測以瞭解真空泵裝載的振動特性,諸如自然頻率、振形及傳輸比。結構動態量測所得的結構振動特性會與模態分析比較以驗證有限元素模型的正確性。驗證有限元素模型後,以橡膠隔震襯墊所裝載的位置以及方向做為設計參數,提出了改良的隔震設計。最後，將此改良設計的初型製作出並進行結構動態量測。量測結果顯示結構在真空泵運作頻率的傳輸比確實有顯著的下降,驗證了此改良設計的可行性。

關鍵字

振動隔離 ； 橡膠動態特性量測 ； 結構動態量測 ； 有限元素模型

並列摘要

This thesis studies the improved vibration isolation design of the brake-assist-vacuum-pump mounting on the vehicle using FEM analysis. One of the critical factors in achieving accurate dynamic predictions is the dynamic characterization of the rubber vibration isolators. In this study, fixtures are proposed to use the impact test for measuring both the axial and radial dynamic behavior of rubber vibration isolators. The test instruments include an impact hammer, an accelerometer, a spectrum analyzer and a force sensor. The input force, blocked force, axial and radial acceleration are then analyzed using the NI 9234 spectrum analyzer. Therefore, the dynamic characteristics of rubber vibration isolators can be obtained. Structural dynamics measurements have also been employed to determine the vibration characteristics such as natural frequencies, mode shapes and transmissibility of the vibration isolation system. Using the NI 9234 spectrum analyzer and Star modal analysis software, the modal parameters are acquired and compared with the simulated results, where the simulation is done based on the rubber dynamic characterization results. Most of the simulated natural frequencies achieve good consistence with the measured natural frequencies. As a result, the FEM model was validated and used in the improved vibration isolation design afterward. Adopting the mounting inclination angle and mounting position of vibration isolators as design parameters, improved vibration isolation design was then carried out. The prototype of improved vibration isolation design was manufactured, and the structural dynamic measurement was employed. It can be observed in the structural dynamic measurement that the transmissibility at pump excitation frequency of the new design has an obvious declination. This validates the feasibility of the improved vibration isolation design.

並列關鍵字

Vibration isolation ； Dynamic characterization of rubber ； Structural dynamics measurement ； Finite element model

參考文獻

[2] Y. Yu, N. G. Naganathan and R.V. Dukkipati, 2001, “A literature review of automotive vehicle engine mounting system,” Mechanism and Machine Theory, vol.36, pp. 123-142.

[3] M. Afzal, 2009, “Flexible mounting system design theory and practice,” Master of Science Thesis, Marcus Wallenberg Laboratory for sound and Vibration, Stockholm.

[4] M. Horovitz, 1957, “Suspension of internal-combustion engines in vehicles,” Proceeding Institution Mechanical Engineers, vol.1957, pp.17-51.

[5] J.H. Kim and J.M. Lee, 2000, “Elastic foundation effects on the dynamic response of engine mount system,” Proceeding Institution Mechanical Engineers, part D, Vol.214, pp.45-53.

[7] L.R. Wang, Z.H. Lu and I. Hagiwara, 2002, ”Finite element simulation of the static characteristics of a vehicle rubber mount,” Proceeding Institution Mechanical Engineers, part D, Vol.216, pp.965-973.