Air Bearing Dynamics of Sub-Ambient Pressure Sliders During Dynamic Unload

Abstract

The increasing effort to use sub-ambient pressure air bearing sliders for dynamic load/unload applications in magnetic hard disk drives requires desirable air bearing characteristics during the dynamic unload event. This paper establishes air bearing design criteria for achieving a smooth head unload performance, through a correlation study between the modeled unloading air bearing dynamics of two 30 percent proximity recording sub-ambient pressure sliders and motion sequence of the same sliders by a high-speed video camera. It is shown that the air bearing lifting force quickly responds to changes in fly height and pitch, while the suction force is relatively resistant to changes in fly height, but somewhat more sensitive to changes in pitch. This unique distinction results in different decreasing rates between the air bearing lifting and suction forces during the unload process, creating a strong dependence of the unloading characteristics on the location of the suction cavities. Both the modeled unloading air bearing dynamics and experimentally recorded motion sequence illustrate that a toward-trailing-edge located suction force acts to pitch the slider up, while the moment produced by a toward-leading-edge located suction force induces a negative pitch motion, resulting in an excessive flexure deformation and dimple separation. Therefore, placing the suction cavities towards the trailing edge offers a reliable unloading performance for the sub-ambient pressure air bearing sliders.

An Alternative Simulation Method for Calculation of Microgas Flows under Flying Head Sliders

“…From the flow rate expressions (11) and (12) for Poiseuille and Couette flows in the slip flow case one can conclude that in the slip flow regime the following Reynolds equation is obtained in place of (10):…”

“…By using Fukui-Kaneko's generalized Reynolds equations some useful results of the slider design were obtained: Hu et al [10] investigated partial contact air bearing characteristics of tripad sliders. Hu et al [11] investigated the air bearing dynamics of two configurations of authentic sized sub-ambient pressure sliders and found the way to ensure the reliability of the unloading performance of the types of sliders considered. Tagawa et al [12] computed the slider's responses to nanotextured disc surfaces.…”

“…The equation modified to include slip and transitional effects is still called Reynolds equation. It is essentially a mass conservation relation applied to the cross sections of the squeezed air flow and is obtained from the continuity equation by integrating it over the vertical direction with the employment of the momentum equation, and now the generalized Reynolds equation is in routine use to calculate the air bearing parameters in sliders with complicated air bearing surfaces (see e.g., [3,[10][11][12][13]). The direct simulation Monte-Carlo (DSMC) method [14] is appropriate for simulation of thin film flows in sliders.…”

Optimal dimple point of SFF HDD suspension for improving the unloading performance

“…In addition, it allows for lower power consumption because of no stiction and prevents the head-slap between slider and disk for non-operating conditions. Also suspension plays a very important role in L/UL mechanism and is one of the most dominant components among other components which affect the L/UL system (Bogy and Zeng 2000;Albrecht and Sai 1999;Peng 1999;Hu et al 1999;Zeng and Bogy 1999a, b;Zeng et al 1999;Zeng and Bogy 2000a, b). During the unloading process suspension stiffness is changed by each step.…”

Experimental study on head-disk interaction in ramp loading process

“…Researchers in the field [1]- [6] have done a lot of works in the simulation of dynamic load/unload process and have achieved good results. Experimental studies have employed high-speed CCD camera [3], [5] and strain gauge [2] to measure lift-off force and flying attitude change in the unloading process. The Laser Doppler Vibrometer (LDV) [6] was successfully used to study the slider-disk contact based on the measurement of loading velocity of the slider.…”