機車駐車架振動異音診斷與減振設計

The Diagnosis and Improvement of the Noise and Vibration Problems for the Parking Stand of Motorcycles

宋繼開(Chi-Kai Sung)

指導教授 ： 陳永樹

元智大學/工程學院/機械工程學系/碩士(2006年)

摘要

機車之駐車架，主要為供停車時架起機車用。但是行進時，又必須收起。因此，與車體間保持一定之穩固性與彈性，若設計稍有不妥，異音因而產生。本研究以某一型駐車架產生振動異音之機車為案例，就相關問題作診斷與改善。
研究首先觀察駐車架振動異音發生時之條件與異音產生根源在何處。為了解決此振動現象，首先探討駐車架異音的發生是否為共振現象或是一般性振動？透過有限元素模態分析及模態測試找出駐車架的自然頻率，並以實車動態實驗方法，應用階次分析之技術，瞭解引擎的使用轉速內，是否有激發駐車架的自然頻率？
由試驗結果之瀑布圖(Waterfall)顯示，異音發生的瞬間係在引擎轉速達6,500rpm時。且由組成頻率的振幅值中，可發現108Hz(1倍轉速頻率)振幅是最大的，2倍轉速頻率開始的振動能量都不大。而駐車架的自然頻率在203Hz或305Hz附近，所以駐車架本身並沒有明顯的共振現象。隨後卸下駐車架，將加速度規直接貼附在引擎側上，發現6,500rpm時異音已無，但在108Hz之屬引擎振動峰值仍存在，可見振動來源為引擎之1倍轉速所引起。
駐車架雖然沒有共振，但引擎的振動能量導致駐車架左右搖擺，造成在其鎖付結構之相互拍打產生異音。所以要消除異音，本研究所選定之改善方案，即在引擎支架末端之拍打部位變更為貼附一橡膠材料，進行實車測試後，已證實可達成消除異音之效果。

關鍵字

機車，駐車架，振動、噪音診斷，自然頻率，共振

並列摘要

The parking stand of the motorcycle is mainly used for erecting the motorcycle while parking and also has to bounce back while driving. Therefore, it has to be kept under the vehicle’s chassis with certain stability and elasticity. However, the irritating noise or vibration is sometimes accompanied with the riding speed if the design is improper. The study will then focuses on how to diagnose and improve the vibration noise of a parking stand of a certain type of motorcycle.
Firstly, the condition for the occurrence of the vibration noise of parking stand is identified and the vibration source is investigated. For examining whether the vibration comes from resonance or just the general vibration, both the finite element analysis and modal test are conducted so as to obtain the natural frequencies of the parking stand. A real vehicle is tested on a dynamometer with accelerometers attached both on the engine and the parking stand to acquire the corresponding signals simultaneously within the whole engine speed range.
Based on the test results, it is observed that the noise was generated when the engine speed is at 6,500 rpm approximately which corresponds to 108Hz in the frequency domain. However, the first two natural frequencies of the parking stand are around 203Hz and 305Hz respectively. It is then obvious that the parking stand itself does not have resonance when noise occurs. For double checking the results, the parking stand is removed afterwards with an accelerometer attached directly on the engine side. Under this situation, there is no noise at 6,500rpm but a peak acceleration of the engine vibration still exists at 108Hz. It is then concluded that the vibration has been caused by rotating frequency of the engine.
Although the parking stand does not have resonance, the engine vibration makes it hit against the body frame that generates the noise. It is then improved with a design change by adding a rubber pad at area near the end of the stand so as to reduce the impact. The real vehicle is tested again and found that the noise is no longer exists after this design improvement.

並列關鍵字

parking stand, motorcycle, natural frequency, noise, vibration, resonance

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