Firstly, the current situation surrounding a motorcycle market in the world and the category of motorcycles are outlined. After overviewing the major characteristics of motorcycle engines, for example, an engine revolution, a lightweight design, a cooling system and an engine oil, then picking up major components of the motorcycle engine, component technologies and its tribological issues are described. As actual components, a Ti made valve lifter, a monolithic Al cylinder, a connecting rod and a crank pin are covered. The function required for the each components and the tribological issues occurring on a contacting and/or sliding surfaces to be solved are explained. Then materials and surface treatments which is applied for the components are introduced.

Recent passenger car engine characteristics and their tribological issues are explained. Hybrid engine is characterized by its frequent stop and start and low temperature operating condition, and downsizing turbo engine is characterized by direct fuel injection and frequent boosted operating condition. Recent friction reduction technologies are also explained considering their trade-offs such as wear, noise and oil consumption, in terms of piston, piston rings, cylinder, crankshaft, bearings and oil.

Recently, many technologies of commercial vehicle engine are making rapid progress on turbocharging, fuel injection and diesel combustion, exhaust gas after treatment etc. These engines have high BMEP (brake mean effective pressure) and realize “downsizing and downspeeding engine.” This paper describes the tribological issue which are occurred by high cylinder pressure and thermal load of these engines.

Improvement of fuel efficiency of the vehicle engine is a serious issue to solve the energy problem. Friction reduction of piston is so useful way of contribution to improve fuel efficiency. In this paper, now and the future tendency of piston design for reducing friction loss and latest friction reduction technology by improving piston skirt surface property are introduced.

To reduce friction loss between piston rings and cylinder liner is important for achievement of high efficient engine. In this report,the ways of reduction friction of piston rings and cylinder liner are introduced. Effects of shape, coatings and texturing of peripheral of piston rings, surface characteristics of cylinder liner, and engine oil on friction are described. When friction of piston rings and cylinder liner is reduced, lubricating oil consumption is needed to be unchanged or decrease. Therefore in order to design of piston rings, both low friction and low lubricating oil consumption are needed to be taken into consideration.

In development of the automotive engine, the improvement of the fuel economy is one of the most important demands. Furthermore, effective utilization of the numerical simulation is focused with improvement of processing computer capability for efficiency improvement of engine development. In this paper, trends in numerical simulation for engine bearing and details of the friction prediction model are introduced. Fluid friction and asperity contact friction are included in this model. The fluid friction is calculated using the piezo-viscous effect and the non-Newtonian lubricant properties. On the other hands, the asperity contact friction is calculated using theory of Greenwood & Tripp. Verification of friction prediction accuracy was compared with experimental value. As a result, predicted friction shows a good agreement with experimental value.

The development of new tribo-materials will accelerate the progress of tribological performance, and thus it is very important to clarify the mechanical characteristics of tribo-materials and determine the positioning of the mechanical properties. Here, the positioning of the mechanical properties of the various materials means a ranking of intrinsic material properties such as Young’s modulus, hardness, fracture toughness and so on. From this background, researches have been conducted on “Micro Slurry-jet Erosion; MSE” method, focusing on the accumulation of data regarding the mechanical characteristics of material surfaces for thin films, ceramics, resins and so on. Material positioning in the MSE maps obtained by the erosion rates of the MSE tests for various materials are demonstrated and discussed.

Diamond-like-carbon (DLC) is widely used as a hard protective layer with a relatively low surface energy. In the head/disk interface in magnetic disk storages, however, monolayer perfluoro-polyether lubricant with a high bond ratio is coated on DLC to avoid DLC‒DLC contact to secure head/disk wear reliability. This paper theoretically analyzes the effect of lubricant thickness and bond ratio on the adhesion force between head and disk surfaces in a sub-nanometer thickness regime. It was found that although the adhesion force can be reduced by increasing bond ratio to one, the adhesion force has the lowest sensitivity to lubricant thickness variations at 0.85 bond ratio. In addition, the maximum adhesion force can be minimized when lubricant thickness is ～0.6nm. This suggests that the current lubricant thickness of 1.0-1.2nm can be reduced to 0.6nm accompanying with a slight decrease in the adhesion force and a slight increase in allowance to lubricant thickness variation. This tribo-surface design concept can be applied to other fields such as micro/nano electrical-mechanical systems.