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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.

An ultra lightweight valve lifter made from titanium alloy was developed for high performance motorcycles. A beta titanium alloy that was fulfilling not only higher strength but also cold forgeability was selected among several types of titanium alloys. A solution treatment and aging combined with the cold forging made a refinement of the grain size of beta phase. As a result, a tensile strength and an elongation of the alloy were reached to 1170MPa and 10.3% respectively. During the solution treatment, oxygen diffusion (OD) treatment was also performed on the beta titanium alloy. The surface hardness of OD layer was increased up to as high as 600 HV. Subsequently, a diamond like carbon (DLC) layer having a hardness value of around 2500HV was formed on the titanium substrate in order to provide a superior tribological property. In between the DLC layer and the substrate, a sputtered Ti layer was formed as an intermediate adhesive layer.

A monolithic aluminum block using a newly developed Al-20%Si alloy was made by a vacuum die-casting process. The bore surface design was a sleeveless type with uniformly dispersed primary-Si crystals around 20μm. The die-casting technology consists of a highly airtight die with two series of evacuation systems. The vacuum level in the die cavity was determined to be as low as 5kPa. The gas content of the block was found to be as low as 5cc/100g Al, which has enabled T6 heat treatment. The die cavity temperature was carefully controlled to generate a fine dispersion of primary-Si crystals. The engine testing has proved that the bore wall temperature is 30 K lower than that of the aluminum block enclosing a press-fitted cast iron liner. The superior cooling performance has decreased the oil consumption value to one half that of the aluminum block enclosing a cast iron liner.

Hard anodic oxide coating (hard anodizing) technology giving hardness values above HV300 was developed for a piston alloy containing a high Cu concentration (Al-12%Si-4Cu-0.5Mg). This technology was developed to improve the result that the anodic oxide coating in a sulfuric acid bath on the alloy can give hardness values as low as HV200. The combination of mixed acid electrolytes (40gL-1 oxalic acid and sulfuric acid less than 150gL-1) and periodic reverse electrolyzing enables the piston-ring groove to form a hard anodic oxide coating film having hardness values above HV300, coating thickness of 20 μm, and surface roughness of Ra 2.0μm. This mixed acid electrolyzing was found to prevent the electrochemical dissolution of Cu. The periodic reverse waveform cools the piston-ring groove to prevent burning.

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.

The role of design in merchantability has become increasingly important in recent years. In this context, there is a need to establish a design-oriented design method for structural components. Topology optimization is a method that can create shapes beyond human knowledge, and its applicability as a design feature is expected. However, the objective function cannot be set freely at present, and optimization of strength requirements is a particular challenge. In this paper, a case study is conducted on a steering wheel bridge to apply topology-optimized geometry, which has design potential, to a structural member by conducting two-step optimization of topology and geometry.

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.

Laser powder bed fusion is one of the metal additive manufacturing technologies, so-called 3D printing. It has attracted great attentions due to high geometrical flexibility and remarkable metallurgical characteristics. An oil catch tank has been widely used in automotive industries for filtering oil vapors or carbon sludge from blow-by gas as a conventional usage. A pneumatic valve system mainly adopted to high-performance engines is also a potential application of it because undesirable oil infiltrates into air springs during engine operation, resulting in an excess spring pressure. This work focused on developing a lightweight oil catch tank which can be applied to a pneumatic valve system by taking advantage of additive manufacturing techniques. Al-Mg-Sc alloy powder with high tensile strength as well as high ductility were used under the consideration of specific strength, printability and availability.

A carburizing is widely applied for many kinds of engine components for motorcycles. On the other hand, a delayed fracture phenomenon of strengthened steel materials occurred under actual usage is a serious concern. The delayed fracture characteristics of surface modified steels such as a carburized steels followed by a tempering have a difficulty being evaluated by only measuring a partial characteristic of the hardened portion due to the existence of an inhomogeneity of a microstructure and a gradient of strength. Therefore, the studies on the characteristics of the delayed fracture of the surface modified steels are not so many. In this paper, the authors evaluated the delayed fracture characteristics of carburized and tempered actual components by comparing hydrogen desorption curves acquired with a thermal desorption spectroscopy using hydrogen-charged specimens with changing tempering conditions.