磁头气膜浮动块浮动特性的影响因素

近年来，随着创新性技术的不断应用，硬盘驱动器的气膜浮动块（以下简称浮动块）也有了较大改进，例如浮动块表面的设计越来越精巧，而性能却更加稳定。因此很好的理解哪些因素是影响气膜浮动块浮动特性的主要原因显得尤为重要。分析这些因素对浮动块的影响结果，有利于我们改进浮动块的特性并对其发展前景做出预测，本文对这些影响因素做了概括总结。     

轻负荷磁头的气动特性

本文采用数值方法求解修正雷诺方程,给出轻负荷、小间隙浮动块的气膜压强分布,飞升曲线以及浮动块几何尺寸、负荷、重心位置的误差对磁头气动特性的影响等结果。     

浮动磁头浮动特性分析

1.前言本文以小型磁盘装置JK-811的圆形浮动块为例,用数值计算方法,对浮动块的静态特性进行了分析。分析中,假定空气是可压缩流体,空气的惯性力可以忽略不计,以及空气膜厚度具有弯曲的表面和有限的宽度。影响浮动状态的各因素有:浮动块的外形、浮动块支撑机构、浮动块负荷机构、浮动块表面状态、盘表面的振动以及使用环境。设计浮动块时须注意:1)加强浮动块和磁盘之间流动的气垫的刚性,以提高固有的振动频率;2)提高空气     

TRC磁头浮动块公差敏感性问题研究

采用数值法研究了ＴＰＣ磁头浮动块的公差敏感性问题。首先给出数值模拟公式，然后对一种ＴＰＣ磁头浮动块进行数值优化，研究此浮动块对加工工艺公差的敏感性。加工工艺公差主要包括台阶偏心公差、刻蚀深度公差、球冠面的Ｃｒｏｗｎ和Ｃａｍｂｅｒ。给出了影响浮动特性诸多参数的公差表，并对综合影响作了研究。     

用模块化方法(BBA)分析飞行磁头浮动块机构的亚微米浮动间隙的动态特性

本文用模块化方法(BBA)来叙述由悬挂万向支架弹簧机构、驱动臂机构及空气轴承浮动块组成的总的飞行磁头浮动块机构的亚微米浮动间隙的动态特性。基于模态综合方法及有限元方法基础上的BBA适用于由流体润滑膜系统及结构机构系统组成的系统。悬挂万向支架弹簧及驱动臂作为一个三维分布质量系统影响到浮动块的动态特性,以及除了空气膜谐振外,由悬挂万向支架弹簧机构与驱动臂机构引起的谐振或非谐振存在于浮动块的频率响应中。对于上述这些现象已成为清楚的了。而且,从浮动块动态特性的观点来比较温彻斯特(Winchester)机构及惠特尼(Whitney)机构,并获得这两种悬挂机构的允许的介质加速度值,进行了理论值与实验结果的比较。比较结果表明:两者很好地吻合,而且,BBA计算机模拟被证实是对整套飞行磁头机构进行动态特性分析的正确的及高效的方法。     

磁头浮动块在浮动过程中的磨损

温式磁盘驱动器中的三轨式铁氧体磁头浮动块是以接触启停方式浮动的。本文分析了该磁头浮动块在其整个浮动过程——边界润滑浮动、混合润滑浮动和完全动压润滑浮动中的磨损情况,并且对嵌入磁盘内的浮动块磨损微粒进行了数量分析。结果表明,当磁盘速度大于20m/s时,完全动压浮动中的磁头浮动块的磨损大大减少并趋于零;正常设计的磁头浮动块在以接触启停浮动方式的整个浮动过程中磨损微小,对正常工作无影响。     

磁头浮动特性研究——动态分析

本文对流体润滑方程和浮动块动力学方程进行了耦合时域动态求解。结合实际磁盘机中的一种两轨式磁头浮动块,对浮动块的各项动态性能作了分析。仿真了磁头浮动块飞越各种盘片障碍物时的飞行姿态和浮动块对盘片波动的响应。通过对冲击响应进行FFT变换求取了空气支撑的频率结构。     

用离子刻蚀法制作的浮动薄膜磁头

有报告报道了制作浮动薄膜磁头的新方法以及它们的特性。人们曾经通过使用不需要玻璃粘接技术的工艺过程和使用离子刻蚀法来组成浮动表面(空气支撑表面,这种表面可形成负压浮动块)这种方法企图找到浮动薄膜磁头的简单公式。整个工艺过程包括:在一个厚度与浮动块长度相等的铁氧体或陶瓷基体上制作薄膜4 4圈的换能器,然后进行切割、研磨、离子刻蚀浮动块表面以形成一个负压的浮动块,最后切成单个核。已获得的结果表明,比起以前的浮动薄膜磁头制作方法,现在的要简单得多。而且。试验结果还证明:磁头的浮动特性也比以前的浮动薄膜磁头的好得多。现在的磁头的读/写特性也可与原来的浮动薄膜磁头的相媲美。     

磁头浮动特性研究——静态分析

本文研究了磁头浮动块在5 1/4英寸磁盘机中的静态浮动性能。对流体润滑方程进行了隐式有限差分求解。分析了直进式和摆臂式两种磁头驱动方式对浮动块浮动性能的影响,即考虑了偏斜角(skew angle)的影响,同时分析了小盘效应(small disk effect)。     

磁记录浮动块动态参数仿真

建立了考虑浮动系统动态特性综合分析的近似模型;在磁记录浮动块动态性能方面,给出了浮动系统动力参数(刚度、阻尼、固有频率)及其变化特性的仿真测试方法与结果。     

The effect of air bearing contour design on thermal pole-tip protrusion

Thermal flying height control has recently been implemented in magnetic recording disk drives to reduce the flying height at the read/write element of magnetic recording sliders. This paper investigates the effect of air bearing contour design on thermal pole-tip protrusion and flying characteristics of magnetic recording sliders. A number of air bearing surface designs are examined to study the relationship between air bearing surface design and efficiency of thermal pole-tip protrusion.     

Simulation of the head disk interface for discrete track media

This paper investigates the effect of discrete tracks on the steady state flying behavior of sub ambient proximity sliders. A finite element based air bearing simulator is used to simulate the flying characteristics of sliders over a grooved disk surface. Sliders flying over discrete track disks “see” a disk surface that consists of ridges and grooves. The air bearing pressure build-up for sliders flying over discrete track disks is different from that for sliders flying over plane disks. Low air bearing pressure can be expected for those regions of the slider that are positioned over grooves, while high air bearing pressure exists over ridges. The air bearing characteristics are determined for several pico and femto-type air bearing sliders flying over discrete track disks. An empirical equation is obtained describing the loss of flying height of a slider flying over discrete track disks.     

Effects of environmental temperature and humidity on thermal flying height adjustment

Thermal actuated sliders are being widely used in today’s hard disk drive industry for its advantages of easier control of flying height (FH) and less risk of contacts with the disk. This article uses a coupled-field analysis method, which includes an air bearing model, a heat transfer model and a thermal-structural finite element model to investigate the FH changes of thermal actuated sliders at various environmental conditions. The mechanism of water vapour’s contribution to air bearing pressure loss is explained and a new humidity model is proposed to calculate this pressure loss. The temperature effects are also considered in the simulation models. It is observed that the environmental temperature and humidity have significant effects on slider’s FH changes, but their effects on the thermal protrusion height are limited. A humidity sensitivity study is also made and the results are discussed. It is found that the slider with thermal protrusion on its trailing pad will be more sensitive to the humidity. Besides air bearing stiffness, some other factors such as peak pressure, protrusion shape and air bearing surface (ABS) design will also contribute to the slider’s humidity sensitivity.     

Dynamic response of 1-in. form factor disk drives to external shock and vibration loads

The dynamic response of the head disk interface is investigated numerically for two different designs of 1-in. hard disk drive enclosures, the so-called “thin” enclosure and the “thick” enclosure. First, the in-plane and out-of-plane vibration response is determined. Then, the effects of linear shock and head slap are studied. Simulation results show that the thinner enclosure has better performance with respect to forced vibrations in terms of reduced amplitude of slider vibrations. In addition, the effect of operational shock on the dynamic characteristics of textured and untextured sliders is studied. A finite element formulation of the time-dependent Reynolds equation (with Boltzmann slip flow correction) was used to obtain the air bearing response. The results show that the dynamic flying characteristics of textured sliders are improved compared to that of untextured sliders.     

Dynamic instability of thermal-flying-height-control sliders at touchdown

With the wide application of thermal flying-height control (TFC) technology in the hard disk drive industry, the head-disk clearance can be controlled to as low as ~1?nm. At this ultra-low clearance, the air bearing slider is subject to relatively large interfacial forces, and it experiences more complicated dynamics, compared with the flying case. In this study we conduct a numerical analysis to investigate the dynamics of TFC sliders during touchdown. The general trend of the slider’s motion predicted by the numerical simulation qualitatively agrees with experimental findings. The touchdown process begins with a slight intermittent contact between the slider’s trailing edge and the disk, followed by a partial slider-disk contact at the trailing edge accompanied by a large pitch motion at the 1st air bearing mode; this pitch motion gets suppressed and the slider comes into stable sliding on the disk as the protrusion is further increased.     

Interactions between nano-spacing flying head sliders and ultra-thin liquid lubricant films with non-uniform distribution in hard disk drives

This paper describes the effect of ultra-thin liquid lubricant films on air bearing dynamics and flyability of less than 10 nm spacing flying head sliders in hard disk drives. In particular, the effect of non-uniform lubricant film distributions on head/disk interface dynamics are studied. The disks with lubricant on one half of disk surface thicker than the other half were used in this study. The dynamics of sliders is monitored using acoustic emission (AE) and the interactions between the slider and disk are investigated experimentally. The disks were also examined with a scanning micro-ellipsometer before and after each test. Complicated slider responses were observed and clarified. In addition, it was found that the periodic lubricant film thickness modulations or non-uniformity caused by the slider-disk contact interactions could be observed. It is suggested that this lubricant film thickness non-uniformity will be one of the technical issues in order to achieve ultra-low head/disk contact interface of less than 10 nm.     

Dynamics of air bearing sliders flying on partially planarized bit patterned media in hard disk drives

Bit patterned media (BPM) recording is one of the promising techniques for future disk drives in order to increase the areal density above 1?Tbit/in². However, the BPM can change the topography of the disk surface and thus have an effect on the flying characteristics of the air bearing sliders. So achieving a stable flying attitude at the hard disk interface (HDI) becomes one of the main considerations for BPM. In this paper, we apply three methods (complete homogenization, Taylor expansion homogenization and averaging) to solve this BPM problem and finally choose the Taylor expansion homogenization method to investigate the slider??s flying attitude on partially planarized patterned media as well as at transitions over different pattern types such as might occur at boundaries between data and servo sections.     

Thermal protrusion induced air bearing frequency variations

The thermal flying height control sliders are widely used in hard disk drives. This paper studies the relationship between the air bearing frequencies and the thermal protrusion values of a thermal flying height control slider by simulation. Simulation results show that the second pitch mode of the slider increases significantly as the thermal protrusion increases. This feature could be used to in situ monitor the thermal protrusion values and the flying heights of the slider. Discussions on all the air bearing frequency modes are given, and the reasons of the frequency variations due to thermal protrusion are explained in details.     

Active-head sliders using piezoelectric thin films for flying height control

This paper describes design and fabrication of a MEMS-based active-head slider using a PZT thin film for flying height control in hard disk drives. A piezoelectric cantilever integrated in the air bearing slider is used to adjust the flying height individually. An air bearing surface (ABS) geometry that minimizes the aerodynamic lift force generated beneath the head has been designed based on the molecular gas film lubrication (MGL) theory. The sliders with PZT actuators were fabricated monolithically by silicon micromachining process. Performance of the actuator was tested by using an optical surface profiler. Furthermore, the fabricated slider was mounted on a suspension and the flying height of the slider above a spinning disk has been measured by multiple wavelength interferometry. Change in the head-disk spacing has been successfully confirmed by applying voltage to the actuator.     

Fabrication and experimental study of Al2O3-TiC sliders with piezoelectric nanoactuators for flying height control

A gap flying height (FH) of less than 5 nm between the read/write element and the surface of the disk is required for ultrahigh density recording. A stable and constant FH must also be sustained in the presence of altitude and temperature changes and manufacturing tolerance. A FH adjustment or controlled slider that is capable of adjusting its gap FH has been proposed previously. In this paper we demonstrate an inexpensive and low-temperature approach for integrating piezoelectric materials in the fabrication of current small form-factor Al₂O₃-TiC sliders. A bulk PZT sheet is bonded onto the back of row-bars and the sliders are separated by a standard dicing process. It requires no deep reactive-ion etching (DRIE) or high temperature processes and is suitable for mass production. A conventional design and a new special air bearing surface (ABS) design have been fabricated and tested by an optical profiler and a FH tester. A nonflying actuation stroke of 0.6–0.8 nm/V has been observed. The FH measurements showed that the ABS plays a key role in increasing the actuation efficiency, which also agrees well with the numerical analysis.