Tribology in hard-disk drive (HDD) has been key technology for increasing recording density. It is a quite long history of 69 years since HDD with particulate recording media, composed of γ-Fe₂O₃ particles and resins matrix had commercialized in 1956. Nano-tribology has been key issue since the thin film disk had developed because head-disk spacing, lubricant film, overcoat, and medium roughness are small in atomic level. Unfortunately, the R&D history is going to be lost for the last several decades. Purpose of this report is to memorize tribology in HDD.

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Journal bearings have been used to support increasingly large-sized and high-speed rotating machinery for industrial use and must be designed so that the maximum pad surface temperature during operation is below an allowable limit. To this end, thermohydrodynamic lubrication (THL) models are employed. The models, however, are sometimes difficult to obtain numerically converged solutions. This paper presents a new THL model that incorporates an arbitrary Lagrangian-Eulerian (ALE) method into the conventional laminar THL model and also includes the low Reynolds number type k-ɛ model, which is applicable to the turbulent oil film situation, and predicts the performance of tilting pad journal bearings. The new model proposed is found to give the predictions more robustly that are in reasonable agreement with the experimental results ranging from laminar to turbulent oil films, that is, the measured pad surface temperature and its maximum value, journal surface temperature, minimum oil film thickness, and frictional power loss that are presented in the open literature.

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The present study describes effects of additional treatment on the stability performance of mechanical tensioner for timing chain system to synchronize camshafts and crankshaft for automotive engines. Effectiveness of surface texturing consisting of the aligned bumps to the coil spring surface for the stability performance was found on the previous study. To obtain further improvement of the stability performance, the additional treatment, a micro shot peening and a defocused laser radiation was applied to the coil spring surface after the texturing. The stability performance was evaluated with a developed apparatus possible to simulate a service condition of the mechanical tensioner. As results, the application of the additional treatment to the counter spring surface is effective means to improve the stability performance accompanying with small wear. In the shot peening process, compressive residual stress which was an important factor to the reliability of the spring strength, was applied to the coil spring surface. Therefore, the application of the shot peening to the counter surface was recommended.

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[in Japanese]

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