奈米顆粒流體對汽車煞車總幫之密封圈(PTFE)摩擦力影響研究

Nanoparticles Fluid Effects on the Friction Force of PTFE Seal for Vehicle Brake Tandem Master Cylinder

高木榮(Mu-Jung Kao)

指導教授 ： 林鴻明 ； 鍾清枝

國立臺北科技大學/機電學院/機電科技研究所/博士(2008年)

摘要

本研究在於汽車煞車總幫之密封圈(PTFE)靜態摩擦力特性研究，用煞車油和本實驗室研製不同尺寸奈米顆粒潛於煞車油中來測試汽車煞車總幫之密封圈靜態摩擦力特性，PTFE 密封圈在煞車之圓形鋁缸內摩擦作動黏滑(stick-slip) 是系統必然伴隨之物理現象，其內桿推力作用後其密封圈會隨推力及速度變化產生靜摩擦力和動摩擦力間交替變化黏滑現象，黏滑對煞車力傳遞有反應時間影響及油封壽命之影響，如何克服黏滑或降低此現象是多數學者專家探討議題。
本研究發展出一種具有圓形顆粒奈米氧化鋁潛佈於煞車油中，作動於PTFE 密封圈和煞車作動鋁缸間，圓形顆粒奈米氧化鋁之圓形特性提供滾動特性，因滾動而降低密封圈和煞車作動鋁缸間之摩擦力，如此對煞車力傳遞有反應時間及黏滑有降低之現象，並降低PTFE 密封圈破裂使油封壽命延長之優點，其最主要影響之摩潤因素包括速度、黏度、停滯時間及鋁缸粗糙度都會對鋁缸內摩擦力變化不同產生不同黏滑現象，擬應用本實驗開發之奈米氧化鋁及奈米氧化銅顆粒潛佈於煞車油來測試其PTFE 密封圈之圓形鋁缸內摩擦力變化及作動特性分析。
實驗結果顯示本實驗室製備電漿電弧放電奈米氧化鋁之煞車油具有均勻分配之圓形顆粒分佈於煞車油中，圓形具有滾動摩擦力低之特性，此特性提供兩滑動機件在初始摩擦期間奈米氧化鋁提供真圓度高之滾動摩擦低之特性，降低密封圈和煞車幫鋁缸間之摩擦係數，再者50 nm大小也對其摩擦特性有關，鋁缸粗糙度約在中心線粗糙度130 nm，分別予以50 nm及 100 nm奈米氧化鋁之煞車油測試都具有對鋁缸內摩擦力降低效果，又以50 nm摩擦力降低效果較佳，因此小的奈米氧化鋁顆粒更能降低摩擦力，其對煞車力傳遞會降低系統反應時間及黏滑(stick-slip)之現象，其影響因素包括速度、黏度、停滯時間及鋁缸粗糙度都會對鋁缸內摩擦力變化不同及第產生不同黏滑現象，降低煞車傳遞力反應時間及黏滑(stick-slip)現象，可同時降低煞車系統之振動與噪音，增進油封及煞車系統壽命延長，確保煞車性能。

關鍵字

煞車總幫 ； 黏滑 ； 奈米煞車油 ； 奈米顆粒 ； 摩擦係數

並列摘要

In this study, the friction force of polytetrafluroethylene (PTFE) seal for vehicle brake tandem master cylinder is evaluated through experimental tests, using the proposed testing system.
The friction force of seal between exterior aluminum wall and interior piston is typically a combination of several friction regions and the contact friction can be divided into solid friction, boundary lubrication and hydrodynamic lubrication. The static friction force and stick-slip effect is considered as a crucial step to form vibration and predict the life time of the V-shaped seal. The behavior of an elastomeric seal for vehicle Tandem master cylinder is measured and analyzed in velocity by using three types of nanoparticles brake fluids made by our laboratory. Working conditions are simulated for different piston rod velocity and cylinder supply pressure.
The results show that nanoaluminum oxide brakefluid with its ball shape can highly reduce friction force to avoid seal excessive wear and reduce slick slip in brake applications. The solid friction force can be reduced by the assistance of the rollingof nanoparticles. Besides, the generalized Sommerfield number in lubrication theory, S0, is increased by the nanoparticles added and increased viscosity. The solid friction is lower due to nanoparticles rolling during the movement start. The nanoparticles provide function of rolling, mend surface and increasing viscous in order to being good lubricants. Accordingly, the friction force is about 3% lower than that without adding nanoparticles in brake system. The frequency and the magnitude of stick-slip are lower than that without adding nanoparticles in brake system. The outstanding physical properties in the operation of vehicle brake master cylinder will lead to reduce the seal excessive wear and reduce stick slip in brake applications.

並列關鍵字

Tandem master cylinder ； Stick slip ； Brake nanofluid ； Friction coefficient ； Solid friction

參考文獻

[1]. C. GAO AND D. Kuhlmann-Wilsdorf, “On stick–slip and the velocity dependence of friction at low speeds, ”J. Tribol. 112 (1990), pp. 354–360.

[2]. C. Gao, D. Kuhlmann-Wilsdorf and D. Makel, “ Fundamentals of stick–slip, " Wear 162–164 (1993) 1139–1149.

[3]. C. Gao, D. Kuhlmann-Wilsdorf and D. Makel,“The dynamic analysis of stick–slip motion,” Wear 173 (1994), pp. 1–12.

[4]. A. H. Brian, “ Stick slip and control in low-speed motion, ” IEEE Transations on Automatic control, vol. 38, No.10, (1993), pp. 1483–1496.

[6]. F. V. De Velde and P. De Baets, “The friction force during stick–slip with velocity reversal,” Wear 216 (1998), pp. 138–149.