• 대한전기학회논문지:시스템및제어부문D
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• 제51권10호
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• pp.477-482
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• 2002

One of the key technologic requirements for rotary blood pumps is the sealing of the motor shaft. A mechanical seal, a journal bearing, magnetic coupling, and magnetic suspension have been developed, but they have drawbacks such as wear, thrombus formation, and power consumption. A magnetic fluid seal is durable, simple, and non power consumptive. Long-term experiments confirmed these advantages. The seal body was composed of a Nd-Fe-B magnet and two pole pieces; the seal was formed by injecting magnetic fluid into the gap (50${\mu}m$) between the pole pieces and the motor shaft. To contain the ferro-fluid in the seal and to minimize the possibility of magnetic fluid making contact with blood, a shield with a small cavity was attached to the pole piece. While submerged in blood, the sealing pressure of the seal was measured and found to be 31kPa with magnetic fluid LS-40 (saturated magnetization, 24.3 KA/m) at a motor speed of 10,000 rpm and 53kPa under static conditions(0mmHg). The specially designed magnetic fluid seal for keeping liquids out is useful for axial flow blood pumps. The magnetic fluid seal was incorporated into an intra-cardiac axial flow blood pump.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.373-374
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• 2002

Magnetic fluid seals are used in a wide variety of gas and dust sealing applications. However, it is difficult to seal for liquid because of its characteristic. This study will be a basic guide for a magnetic fluid seal for liquid, especially for blood to be practically used in medical instruments such as rotary blood pumps by clarifying its seal properties. Sealing pressure test, durability test, and hemolysis test have been conducted for this seal. In this study, magnetic fluid, sealing fluid, eccentricity ratio, revolution speed were selected as parameters. As results of the tests, it has been found that the properties of magnetic fluid seal depend on the solvent and the saturation magnetization of magnetic fluid. Therefore, the selection of magnetic fluid is important for this seal. It also has been found that eccentricity ratio of the shaft caused harmful effect for seal properties. In conclusion, it has been showed that magnetic fluid seals could be possibly used in medical instruments such as blood pumps when blood come in contact with magnetic fluids.

• 한국기계가공학회지
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• 제10권2호
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• pp.79-83
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• 2011

Magnetic seal uses a magnetic fluid to seal a gap between a rotating shaft and housing. It is distinguished from other kinds of seals from the fact that solid contact does not occur in the seal. This implies that it is free from solid rubbing thus dustless and provides a clean circumstance. That is the reason why the magnetic seal is used exclusively for most of vacuum chambers in semiconductor process where dustless clean circumstance is critical. A magnetic seal has been developed of which design parameters are determined based on published data, and an air pressure test has been done to examine its sealing capability. Effects of some design parameters have been studied through FEM analysis. The results show some notable aspects of design parameters and provide suggestions for developing the seals. Regarding the sealing capacity of the magnetic seal the factor to match the theoretical value with the actual one was found to be 0.4~0.7, which means still there is some discrepancy between theory and actual.

• 한국재료학회지
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• 제12권4호
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• pp.264-268
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• 2002

Magnetic fluid is a very stable colloid that is attracted by magnetic force as wholly. The magnetic fluids is composed with 10 nm magnetic materials such as magnetite, iron etc., which is dispersed homogeneously in solvent by coating surfactant on their surface. Also this colloid is not separated into magnetic particles and solvent even under magnetic field, centrifugal force, gravity. Due to these properties, the magnetic fluids is used in high vacuum seal, exclusion seal, damper, etc. I would like to introduce the specific properties and applications of the magnetic fluids.

• Tribology and Lubricants
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• 제14권3호
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• pp.32-38
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• 1998

This paper presents the magnetic flux distributions of a ferrofluid seal at the sealing gap between the pole pieces and the rotating shaft. The optimized shape of pole pieces has been determined by using the computer simulations. The computed results indicate that the sloped pole piece of 27$^{\circ}$ shows good flux distributions compared with that of the conventional flat pole pieces and may reduce frictional heats due to a reduced surface contact areas of magnetic fluids.

• Journal of Magnetics
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• 제22권2호
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• pp.299-305
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• 2017

Magnetic fluid, a new type of magnetic material, is a colloidal liquid constituted of nano-scale ferromagnetic particles suspended in carrier fluid. Magnetic fluid sealing is one of the most successful applications of magnetic fluid. As a new type of seal offering the advantages of no leakage, long life and high reliability, the magnetic fluid seal has been widely utilized under vacuum- and low-pressure-differential conditions. In practical applications, for improved pressure capacity, a multistage sealing structure is always used. However, in engineering applications, a uniform distribution of magnetic fluid under each tooth often cannot be achieved, which problem weakens the overall pressure capacity of the seals. In order to improve the pressure capacity of magnetic fluid seals and broaden their applications, the present study theoretically and experimentally analyzed the degree of non-uniform distribution of multistage magnetic fluid seals. A mathematical model reflecting the relationship between the pressure capacity and the distribution of magnetic fluid under a single tooth was constructed, and a formula showing the relationship between the volume of magnetic fluid and its contact width with the shaft was derived. Furthermore, the relationship of magnetic fluid volume to capacity was analyzed. Thereby, the causes of non-uniform distribution could be verified: injection of magnetic fluid; the assembly of magnetic fluid seals; the change of magnetic fluid silhouette under pressure loading; the magnetic fluid sealing mechanism of pressure transmission, and seal failure. In consideration of these causes, methods to improve the pressure capacity of magnetic fluid seals was devised (and is herein proposed).

• 한국생산제조학회지
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• 제19권3호
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• pp.365-369
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• 2010

Magnetic fluid seal is characterized by its simple design, low friction and being dustless. Those advantages are deduced from the fact that the sealing element is not a solid such as rubber or plastic but it is a fluid. Those are critical for application to a rotating shaft which is inserted into a vacuum chamber where high level of vacuum and cleanness are required. For the reason the magnetic fluid seal has become a standard for vacuum chambers for semiconductor and LCD processing. It should be noted that its sealing performance is sensitive to temperature. If necessary, water cooling should be considered. Thus anticipation of the temperature distribution of the magnetic fluid seal is important before applying it. In this paper an FEM analysis of the heat transfer has been executed and compared with experimental results. An overall convective heat transfer coefficient has been adopted for the analysis, which results in satisfactory consistency of the theoretical and experimental results.

• 한국자기학회지
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• 제4권4호
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• pp.326-334
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• 1994

친수성-고점도 자성유체를 Nd-영구자석과 병용하여 기름밀봉 장치로의 개발을 목표로 실험 검토하였다. etylene glycol 액상중에 $Fe_{3}O_{4}$를 분산시킨 자성유체는 매질의 비등점이 다른 액상보다 높고 점성이 높아서 기름밀봉 성능을 향상시킬 수 있을 뿐만 아니라 본 장치의 부품중 대부분 을 이루고 있는 철강재를 부식시키지 않았다. 본 자성유체중 $Fe_{3}O_{4}$ 농도가 증가할수록 점도 와 자성율이 증가하여 기름밀봉 성능을 향상시킬 수 있었다. 본 장치는 대기압하에서 기름밀봉 성능이 매우 우수하였다.

• 한국자기학회지
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• 제9권2호
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• pp.121-126
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• 1999

친수성 철계 자성유체의 제조와 이 자성유체를 Nd-영구자석과 병용하여 기름 밀봉 장치의 개발을 목적으로 실험검토한 결과 다음과 같은 결론을 얻었다. 1)평균 입경 100$\AA$, 자화값 125.5emu/g, 대기중 15$0^{\circ}C$까지 산화 변질성이 없는 실리카 피착 철 초미립자의 표면에 오레인산 이온, D.B.S. 이온 및 T.M.A. 이온을 흡착한 후 ethylene glycol 용액중에 분산시켜 친수성 철 분말 자성유체를 제조할 수 있었다. 2)이상의 친수성 철 분말 자성유체[70%(g/ )Fe]를 영구자석(3200 Gauss)과 병용하여 기름 밀봉 장치에 응용한 결과 영구자석의 설치 개수를 영구자석 6단 그리고 구동축과 밀봉 장치 사이 간격 0.2mm의 조건에서 압력 7400g/$\textrm{cm}^2$까지 견딜 수 있는 우수한 내압 특성을 얻었다.

• 대한기계학회논문집A
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• 제21권1호
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• pp.53-61
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• 1997

The performance characteristics of magnetic fluid seals are studied numerically as a function of working gap, pole width, angle of pole sharpening, and shaft speed. The temperature distribution of a magnetic fluid seal with multiple tooth is investigated as a function of the contact fraction of magnetic fluids at the periphery of pole tooth using a finite element method. The most significant design parameter of a magnetic fluid seal is the working gap between the pole pieces and the rotating shaft. The result shows that with increasing the working gap, the friction torque decreases radically. The practical working gap for the pole pieces with triangular tooth zone profile is 0.2-0.4mm. The FEM results indicate that the optimal filling of a magnetic fluid between the pole pieces and the shaft is very important due to the accumulations of nonuniform friction heating within the pole pieces, which may interfere the magnetic circuit flow.