DVD主軸馬達3D不平衡磁路模擬分析之研究

Analytical study on 3D unbalance magnetic-circuit simulation for DVD spindle motor

林源峰(Yuan Feng Lin)

指導教授 ： 劉宗平 ； 林琮焜

元智大學/工程學院/電機工程學系/碩士(2003年)

摘要

直流無刷主軸馬達因其具有小體積、高轉速，以及高準確度等特性，它已成為DVD播放系統中穩定承載碟片旋轉的關鍵性組件。由於永磁轉子與定子間不對稱的磁交鍊作用，使得馬達產生顯著的頓轉轉矩(cogging torque)。這嚴重地影響直流無刷馬達的操控性，以及DVD系統讀寫的品質。
為了降低頓轉轉矩，但不能損及馬達的高效率，於傳統電機的設計理念中，先對定子槽齒和充磁座進行修弧的磁性設計與分析，以便減低其磁耦合效應。然而，轉矩常數也會因磁阻之增加而減少，使得高轉速馬達的整體效能變差。隨著碟片容量密度與馬達轉速規格的提高，致使馬達本體的機械結構與組裝，以及充磁電流耦合所造成的不平衡效應等，衍生出所不希望出現的振動，它將成為光學讀取頭的振動源，嚴重地影響高轉速光碟機系統的整體效能。
在此論文中，我們運用有限元素法為基礎的磁路分析軟體，針對三相九槽十二極徑向繞線型主軸馬達，進行研究與分析。首先建立馬達的3D磁路模型，然後分別改變馬達轉子與定子間的相對高度、磁石高度，以及轉軸與轉子間的偏心等參數，探討它們對頓轉轉矩的影響，並且分析頓轉轉矩與軸向振動之關係。另外，我們還利用馬達轉子的轉軸位置和永久磁石的高度等參數，探討機電磁耦合的動態磁不平衡力，以期提昇高轉速主軸馬達的動態性能，有效地降低高倍速光碟機的振動量。

關鍵字

主軸馬達 ； 磁路

並列摘要

DC brushless spindle motor is assigned to load a disc with steady rotation in DVD player and plays as an important role in the system. A spindle motor can exist the cogging torque, which induced from unbalance electromagnetic coupling effect between the rotor and the stator, will damage the operation of motor and the accessing speed in the DVD system.
From the traditional electromechanical design concept, the cogging torque, which induced from electromagnetic coupling effect, will be designed to decrease by arcing the salient poles of the stator and the magnetization fixture. Due to the increasing capacity density in disc and the requirements of high-speed DVD spindle motor in its player, the magnitude of vibration induced from unbalanced magnetic forces by mechanical construction and excited current will induce the significant source of exciting shock to affect the performance of the pick-up head. These phenomena will degrade the tracking rate and prolong the retry period of a data storage process in the DVD player.
In this thesis, a 3D magnetic-circuit model was first built for a low cogging torque three phases 12P/9S DC brushless DVD spindle motor. Then, we had excited the simulations to calculate the cogging torque by changing the relative height between the rotor and the stator, the height of the permanent magnet, and shifting the axle center of the rotor. We had analyzed the relation between the cogging torque and the vibration, and the dynamic unbalanced force. By using the proposed model, a high performance DVD spindle motor, which possess high efficiency and low vibration, can be obtained.

並列關鍵字

spindle motor ； magnetic-circuit

參考文獻

[2] 葉春敏，”21 世紀記錄媒體主角DVD”，工業材料，131 期，第71-76頁(1997)。

[11] Hanselman, D. C., “Minimum Torque Ripple, Maximum Efficiency Excitation of Brushless Permanent Magnet Motors”, IEEE Trans. On Industry Electronics, Vol. 41, No.3, pp.292-300 (1994).

[15] Hwang, C.-C., John, S.-B., and Bor, S.-S., ”The Analysis of a NdFeB Permanent-Magnet Motor for CD-ROM Drive”, The 17th Symposium on Electrical Power Engineering, pp.817-820 (1996).

[17] Hwang, C.-C., John, S.-B., and Wu, S.-S., ”Reduction of CoggingTorque in Spindle Motor for CD-ROM Drive”, IEEE Trans. On Magnetics, Vol.34, No.2, pp.468-470 (1998).

[18] Howe, D. and Zhu, Z. Q., “The Influence of Finite Element Discretion on the Prediction of Cogging Torque in Permanent Magnet Excited Motors”, IEEE Trans. On Magnetics, Vol. 28, No.2, pp.1080-1083 (1992).