Sealing techniques of magnetic fluid take advantage of response of Magnetic fluids. When a Magnetic fluid is placed into a gap between the surfaces of rotating and stationary elements in the presence of magnetic fluid, it assumes the shape of a"Liquid O-ring" to comple电话y fill the gap.
The magnetic fluid vacuum rotary feed through is a device that transmits rotary motion into a vacuum chamber. The basic components are permanent magnet, two pole pieces, a magnetically permeable shaft and Magnetic fluid. The shaft (of pole pieces)
contains a multistage structure, completed bye the pole pieces and the shaft, concentrating magnetic flux in the radial gap under each stage. In the ideal situation, all flux lines are confined under each stage, and none are in interstate region. The magnetic fluid is trapped and held in each-stage, forming a series of " Liquid Oring" with intervening regions that are filled with air. Each stage can typically sustain a pressure differential of 0.15-0.2 atmospheres. All stages act in series to provide a total pressure capability for the seal. For vacuum applications Magnetic fluid seals are normally designed to sustain a pressure differential of greater than two atmospheres, thus allowing a safety margin.
Hermetic sealing: The Magnetic fluid surrounding the shaft provides a hermetic seal against gas, vapor, mist and other contaminants.
长寿命特性："液体O型密封圈"由一个稳定的磁性流体构成，其装置可长期使用10年无需维修。
Long life: A(Liquid O-ring) seal is formed by using an inert, stable, low vapor pressure Magnetic fluid. Units have been in operation for over ten years with no maintenance.
High Reliability: The seal contains a simple, permanent magnetic structure and a non-wearing Magnetic fluid. The only parts subject to mechanical wear are self-contained ball bearings.
Non-contaminating: Since there is no seal wear, there are no particles produced to degrade the system. In addition, low vapor pressure Magnetic fluid maintains seal integrity even in hard vacuums to better than 10-8Torr.
最佳的力矩传输特性：力矩可100%的输送，保证一个无阻碍的单向运行。
Optimum Torque Transmission: Through-shaft construction permits 100 percent torque transmission and provides in-phase rotation without backlash.
Low Viscous Drag and High-Speed Capability: The low viscous drag of the Magnetic fluid, and non-contacting seal configuration of the Magnetic fluid feed through assure its extremely smooth operation and its high-speed capabilities.
磁性流体密封装置的轴承疲劳寿命按照以下的方法来计算
To determine Ball bearing Rating Fatigue Life of Ferro fluid sealed spindles, please use this table and the basic equation below.
L0：壳体端面到负载的距离
Distance fro housing end to load point
L1：真空侧轴承到壳体端面的距离
Distance from load side ball bearing to housing end
L2：轴承间距
Ball bearing span
Cr：轴承基本额定支负载
Dynamic load rating of ball bearing
L3：长度
Total length of shaft
Fa：压差产生的轴向负载
Axial exerted by atmospheric pressure
Cor：轴承基本额定静负载
Static load rating of ball bearing
Fr：径向负载
Radial load
n：转速
Rotation speed
fw：负载系统
Load factor
P：轴承当量动负载
Equivalent load
Lh：额定寿命
Rating fatigue life
●这些负荷能力特指使用SUJ2材料的轴承，如果使用SUS材料的轴承，则使用参数的80%。
This load capacity is for SUJ2 bearings. If bearing are used. Please apply an 80% darting factor.
For a vacuum application, to obtain the fatigue life factor, Lh, of Model Number SFL202NN, when it is
used under a radial load Fr=50kgf at the shaft end and the rotation speed is n=200rpm.
由于轴承头部承受有Fr=50kgf，以下方法求出轴承6005上的Fr1，Fr2。
Radial load Fr=50kgf is applied at the shaft end, and the radial load on #6005 ball bearing should be distributed to Fr1 and Fr2. The can be obtained from the equation following:
由上述的负载分配求出额定寿命。（由于真空侧轴承不承受的负载比较高，仅计算真空侧轴承的寿命。此外，本计算由于真空压差产生的轴向负载Fa=3.14kgf很小，所以只计算了长向负载。当轴向负载很大时，必须考虑它的影响。）
From the distributed radial load Fr above, the rated fatigue Life Lh is obtained as follows:
(In this case, the Fr of the load side bearing is greater than at the second bearing. Calculate the Radial load at the load side only. For a vacuum application, the Axial load exerted by the atmospheric pressure difference, Fa=3.14kgf, is small enough to disregard. Therefore, only the Radial load is calculated. If the value of Fa is large, please include it in the calculation.)
