牙醫手機之磁黏滯式煞車動力量測平台設計開發與性能探討

Abstract

高速牙醫手持鑽機(Dental handpieces，簡稱高速牙醫手機)擁有極佳的散熱性能，以及可控制的切削速度與切削力量等優勢，在口腔醫療產業中被廣泛的應用。在開發高性能、低噪音與低震動等性能優異的牙醫手機時，如何針對牙醫手機進行性能檢測亦是牙醫手機發展過程的一大關鍵。 本論文之目標為設計開發一套牙醫手機性能量測系統，及時擷取其動態扭力矩與轉速等資訊。量測系統以磁流變液體之液體黏滯力為煞車原理，藉由控制磁通量密度改變液體黏滯性，改變作用於牙醫手機主軸上之煞車力矩，延長煞停時間。磁流變液體透過磁場控制即可達成不同黏滯係數，形成較簡易的煞車力控制，同時避免了摩擦式煞車所產生的滯滑現象與剛性接觸振動。 系統之量測目標為現有牙醫手機筒匣。從磁流變液體煞車理論開始進行分析，並使用有限元素法模擬，找出影響煞車性能的關鍵。並藉由磁場分析模擬，找出磁通量密度與磁流變液體之關係，設計出適當的可調整磁場範圍。藉由這些分析，逐步找出適當的設計參數，完成實體化設計。 本論文開發之牙醫手機動力量測平台，可實際完成筒匣之動力性能量測。煞車力矩量測單元使用像散式讀取頭，實現量測微小扭力矩之目標。本平台之量測範圍為0.1~1.5 Nmm，敏感度為4.4 Nmm/V，線性誤差為2.4%。

Dental handpieces are widely used in dental industry because of their operational advantages such as controllable cutting speed and cutting force. To achieve more stable operation and higher performance of dental handpieces, the development of performance measuring technology of high-speed dental handpieces is essential. In this thesis, the design and development of a dental handpiece measuring system of which can acquire its dynamic torque and its rotational speed, has been accomplished. With the principle of adaptable contact viscosity of magnetorheological fluid, the viscous force can be acted on the tested dental handpiece spindle as the breaking torque, and easily controlled by varying different magnet field intensity applied on the magnetorheological fluid. Due to the characteristic of magnetorheological fluid, the stick-slip phenomenon and vibration can be avoided compared to the traditional friction-brake type measurement system. To measure the performance of the dental handpieces, the research starts from deriving the viscous background theory of magnetorheological fluid. FEA (finite element analysis) and CFD (computational fluid dynamics) simulation have been approached to figure out the relationship between the design parameter and measuring system performances. Appropriated working range of applied magnet field intensity has also been studied by magnetic-electric field simulation software ANSYS Maxwell. Several experiments were implemented to verify the system performance. With the integrated DVD pickup head, the micro braking-torque measuring can be realized. The newly developed measuring platform of dental handpieces has its operational measurement range from 0.1 to 1.5 Nmm, the sensitivity of 4.4 Nmm/V, and linear error of 2.4%.