Noriaki Hishida

Hydrodynamic bearing with non-uniform spiral grooves for high-speed HDD spindle

A novel hydrodynamic bearing with non-uniform spiral grooves was proposed for high-speed HDD spindle in this paper. Theoretical approach indicated that the non-uniform grooved bearing expanded the critical bearing number about 123% larger than the classic bearing with uniform grooves. The utility of the proposed bearing for high-speed spindle was experimentally confirmed.

Optimization of Groove Dimensions in Spiral-Grooved Journal Bearings for RRO or NRRO Characteristics

Spiral-grooved bearings have recently attracted large attention for spindles of precision equipment. In this paper, optimizing the groove dimensions of spiral-grooved journal bearings for RRO or NRRO characteristics is discussed. Evaluation indexes for operating bearings concerning the static displacement of the rotor and RRO and NRRO amplitudes are firstly proposed. The appropriate groove designs (groove width, angle, and depth) for minimizing the proposed evaluation indexes are given, and it is also shown that the design can improve bearing run-out performances much more than the currently recommended design. In addition, by separating the optimum groove designs for the two groups, guidelines for designing of the groove configuration for good RRO and NRRO characteristics are comprehensively indicated.Copyright

Optimization of Groove Dimensions in Spiral-Grooved Journal Bearings for Spindles of Precision Equipments

Spiral-grooved bearings have lately attracted considerable attentions as better substitutions for current ball bearings, especially in motor spindles of precision equipments such as hard disk drive systems. Their high stiffnesses and high damping abilities can realize good run-out characteristics even for such small-sized equipments. Regarding the groove dimensions of the spiral-grooved journal bearings, it seems that we usually design them according blindly to a traditional standard aiming for maximizing the direct bearing stiffness. It is also the fact that the bearings designed according to this standard can realize comparatively good bearing performances. On the other hand, there have been considerably few discussions on optimum designs of the groove dimensions specialized for a reduction of amplitude of the operating run-out, which is a major characteristic for applications to precision equipments. The optimization of groove dimensions of the spiral-grooved journal bearings is, then, discussed in this paper. The subjects for optimizations are: 1) reduction of rotor displacement against a static load, 2) reduction of amplitude of the operating repeatable run-out (RRO) due to an unbalanced rotor mass, and 3) reduction of amplitude of the operating non-repeatable run-out (NRRO) against an external impulse load.Copyright

Evaluation of Performances of Small-Sized Journal Bearing with MoS2-Shot Surface Coating (1st Report, Evaluation through Observation of Surface Property and Experimental Stribeck Diagram)

MoS2-shot coating technology is recently focused as one of potential methods of surface modification to realize a low friction state. In this paper, performances of a small-sized journal bearing with MoS2-shot coating, which is aimed to be applied to a spindle of precision equipment such as magnetic recording storage system, are experimentally investigated through the observation of surface property and Stribeck diagram. Scanning electron microscope (SEM) images and reflection electron microscope (REM) images of SUS surface with MoS2-shot coating show that original MoS2 particles are broken into smaller pieces at bumping against SUS surface by jet flows of highly pressurized air, and are forcibly embedded into the surface with forming micro-dimples. Results of coefficient-of-friction characteristics of shaft-sleeve interface of the journal bearing, i.e., Stribeck diagram, show MoS2-shot bearing can realize a low friction performance at a low rotational speed and reduce the magnitude of stick-slip much compared with the case of no-coating bearing.