[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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The Technical Committee on Molded Plastic Gears, a subordinate organization of the Japan Society for Precision Engineering (JSPE), is engaged in activities to solve technical issues spanning various specialized fields―such as materials, strength, vibration, precision evaluation, molding processing, and monitoring technologies―related to plastic gears, whose applications are increasingly expanding in recent years. This report explains the latest trends in the technological development of plastic gears, focusing primarily on the efforts of this committee.

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With the electrification of automobiles, lightweight and self-lubricating plastic materials are widely used in sliding parts. This article reviews the friction and wear characteristics of fiber-reinforced PA66 and steel, which exhibit excellent creep resistance, based on fundamental tests conducted under grease lubrication. It further discusses the influence of material composition―such as molecular weight, fiber diameter, and fiber type―as well as grease additives, on tribological performance. Optimizing the molecular weight and GF diameter of GF-reinforced PA66 improves interfacial adhesion, which is effective in reducing wear and plastic creep, and using grease containing carboxylate form a highly lubricious tribofilm on the steel surface, resulting in reduced friction and improved wear resistance. Furthermore, applying these findings to plastic gears under high load conditions can decrease change in tooth thickness and extend failure life.

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Plastic spur gears are widely used in automotive, consumer, and office equipment due to their light weight, low noise, and design flexibility. However, their lifetime prediction remains challenging because plastics exhibit more complex material behavior than metals. This article reviews recent advances in durability prediction, focusing on three major failure modes - static fracture, tooth root fatigue, and abrasive wear - using PA (polyamide) 46 as a representative material, which, owing to its high crystallinity, maintains stable mechanical properties over a wide temperature range and exhibits superior wear and heat resistance. Predictive methods have been refined by incorporating hydrostatic pressure-dependent yielding, anisotropic material properties, crack growth models with temperature-adjusted parameters, and Archard’s law extended with pressure-dependent wear coefficients. These developments, supported by experiments, finite element analysis, and machine learning, improve accuracy in estimating gear performance.

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This paper provides an overview of resin cages used in rolling bearings, focusing on their material properties and recent technology trends. Compared to metal cages, resin cages offer advantages such as light weight, low friction, low noise, and superior corrosion resistance. Various materials such as phenolic resin, polyamide resin, and super engineering plastics are selected based on the operating environment. In addition, the cage shape is designed to meet performance objectives for rolling bearings, such as achieving higher speed and reducing friction, and various analytical methods are employed to optimize the design. As a result, these cages can satisfy the demand for high performance under stringent operating conditions.

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This article summarizes a Japan-Germany collaborative research project on hydrogen-compatible polymer and rubber seal materials. Over three years, the teams developed and evaluated sustainable materials using advanced tribological testing and life cycle assessment. The project fostered mutual understanding, integrated diverse research approaches, and produced results that contribute to both technical progress and future international cooperation.

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Compared with metals, polymeric materials have advantages such as lightweight, reduced noise and self-lubricating properties which make their use in many tribological applications highly desirable. Lubrication has the potential to further improve their tribological performance. However, lubrication does not always improve friction and wear in polymeric material. This review discusses both positive and negative effects of lubrication, focusing on interfacial mechanisms, with particular emphasis on PEEK and its composites.

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Automotive ball joints are used in the connection parts of steering and suspension systems, and are one of the important safety components. Ball joints are required to have high stability, load-bearing capacity, and high rigidity, and products have been developed to meet these requirements. As with other automotive parts, performance requirements for ball joints are becoming increasingly stringent. To meet these requirements, it is necessary to clarify phenomena from the perspective of tribology, which is a key technology in ball joints, and basic research is required to achieve this. This paper provides an overview of automotive ball joints and discusses future requirements. It also introduces the results of research conducted to address tribological issues in ball joints.

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[in Japanese]

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