In the tribology of mechanical elements using lubricating oil, verification of the dynamic surface pressure distribution during sliding operation is necessary in order to elucidate the sliding condition. The same also applies to the piston rings which are the sliding part of compression reciprocating device. Although some verification case in static condition or limited sliding area has been studied, there are many unknown aspects in this field. The thin-film sensor, since it has small influence on the shape of the sliding surface, is widely used as a measurement method of the sliding surface pressure between two different surfaces, however this method has never been applied to the piston ring in the past. In this study, various film deposition methods on the piston ring of the thin-film sensor were examined, and the thin-film pressure sensor with a total thickness of 4.6 μm was successfully formed on the sliding surface by sputtering. The surface pressure distribution of the sliding part was measured using the reciprocating sliding tester by this thin-film pressure sensor, and the measurement values were in good agreement with the mixed lubrication model between the piston ring and the cylinder liner.

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<div class="section abstract"><div class="htmlview paragraph">Reducing of lubricant oil consumption (LOC) remains a major issue for internal-combustion engines. Especially in recent years, in order to comply with Particular Number (PN) regulations and lower oil viscosity to reduce friction loss, need to reduce the LOC has increased. Controlling the upward oil flow, that passes the piston and piston rings, is effective in reducing the LOC. In addition, oil control ring (OCR) has significant effect on upward oil flow. Therefore, development of a high-precision prediction method of oil behavior around the OCR is important for prediction of LOC. So, the model of Three-piece type oil control ring (3POCR) motion within the OCR groove and the model of oil behavior around the 3POCR were developed using the computer aided engineering (CAE) method in this paper. These models calculate in detail the upward oil outflow to the 3rd land from the OCR groove, which is based on the relation between the OCR motion and the gas pressure as well as the inertial force of oil. Since factors that greatly affect the prediction accuracy are the gas pressure around the OCR and the OCR motion, these were measured and verified in the actual engine. Furthermore, oil behavior observation using in-cylinder visualization engine, and oil film thickness measurement using optical fiber were conducted for experimental verification of the oil behavior model around the 3POCR. As a result, qualitative tendency of calculated results and measured results showed good agreement. Also, comparison in two different OCR specification, the similarly tendency was obtained. Therefore, the effectiveness of the developed prediction model was confirmed.</div></div>