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A monolithic type aluminum (Al) cylinder made of hypereutectic Aluminum-Silicon alloy has been widely used for motorcycle applications. It has a lightweight structure and a superior cooling ability owing to its material property and surface finishing. Usually the cylinder bore surface of the monolithic type Al cylinder is finished by an etching process or a honing process in order to expose silicon (Si) particles from aluminum (Al) matrix for the improvement of the tribological properties. The morphology of the cylinder bore surface including the exposure of Si particles is supposed to make an important effect on its tribological properties, especially on the anti-scuffing property. In this research, the anti-scuffing property of three kinds of cylinder bore finishing, an etched surface, a Si exposure honed surface and a conventional plateau honed surface is evaluated with using a reciprocated type wear tester. The experimental results are analyzed by using Weibull analysis.

The improvement of fuel consumption is the most important issue for engine manufactures from the viewpoint of energy and environment conservation. A piston-cylinder system plays an important role for the reduction of an engine friction. For the improvement of the frictional behavior of the piston-cylinder system, it is beneficial to observe and analyze the frictional waveforms during an engine operation. To meet the above-mentioned demand, frictional waveforms were measured with using the renewed floating liner device. In the newly developed floating liner device, an actual cylinder block itself was used as a test specimen. The measured single cylinder was an aluminum monolithic type made of hypereutectic Al-17%Si alloy using a high pressure die casting process. The combined piston was a light weight forged piston and a DLC coated piston ring was used. For the measurement, 110cc air cooled single cylinder engine was used.

This study focuses on improving durability of the resin coated piston developed especially for the monolithic cylinder made of a hypereutectic Al-Si alloy, so-called DiASil®. The newly developed resin was designed to be cured at a relatively low temperature considering over-aging of a piston and confirmed that it exhibited a lower friction coefficient compared to an existing resin coating. Furthermore, pistons of which skirts had various depth and pitch of grooves filled with the resin coating were offered to evaluate wear and seizure characteristics. The results showed deeper grooves on piston skirts were remarkably effective to delay a seizure. All the seizures were triggered when the ratio of Al substrate exposed to the sliding surface reached up to 60-80%, which implied it can be the empirical criteria for a seizure. Therefore, it can be considered the seizure does not occur as long as adequate resin coating remained in the grooves.

A monolithic cylinder block using a hyper-eutectic Al-Si alloy provides superior cooling performance and light weight. Through the mechanical recessing process a soft honing stone polishes the aluminum matrix away and exposes the primary-Si crystal. This is a good way to obtain superior tribological properties at the bore surface. To reveal the basic mechanism of the mechanical recessing process, this research used experimental recess testing and a boundary element method calculation simulating the actual honing process. A pin-on-disk type recess test using an elastic polyurethane pin and an A390-alloy disk was carried out. An increased number of rubbings exposed the primary Si crystals from the aluminum matrix. The exposure height of the Si particle initially increased but stayed constant to a critical exposure height above the increased rubbing number of 500. The mathematical simulation revealed that the provided pressure on the Si particle determined the critical exposure height.