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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.

In recent years, efforts to reduce CO2 emissions (carbon neutrality) have accelerated worldwide. In the aluminum manufacturing industry, CO2 emissions can be reduced by switching the raw materials of choice; from virgin ingots to recycled ingots. However, the possible characteristic change accompanying the usage of impurity-ridden recycled ingots severely limits its applications, which also limits its potential contribution to carbon neutrality. Determining how impurity elements present in recycled ingots can affect the function of manufactured components is a necessary first step towards expanding the usage of recycled ingots. In this study, we aimed to apply recycled ingots to the monolithic cylinder made of hypereutectic Al-Si alloy and investigated how impurity elements in recycled ingots affect properties (especially seizure characteristic). Die-cast cylinders using virgin and recycled ingots were manufactured and their properties were investigated.

Carburized and quenched materials with high fatigue strength are often used for motorcycle engine parts. Nitrided materials exhibit less deformation during heat treatment than carburized and quenched materials, so if the same or higher fatigue strength can be achieved with nitrided materials as with carburized and quenched materials, the geometric precision of parts can be increased and we can reduce engine noise as well as power loss. When the fatigue strengths of a nitrided material with its compound layer surface put into γ’ phase through nitriding potential control (hereafter, G), and a nitrided material put into ε phase (hereafter, E) were measured, the results showed the fatigue strength of the G to be about 11% higher than that of carburized and quenched materials. It was inferred that the strength of the compound layer determines fatigue strength.

Reduction in the cycle-to-cycle variation (CCV) of combustion in internal combustion engines is required to reduce fuel consumption, exhaust emissions, and improve drivability. CCV increases at low load operations and lean/dilute burn conditions. Specifically, the factors that cause CCV of combustion are the cyclic variations of in-cylinder flow, in-cylinder distributions of fuel concentration, temperature and residual gas, and ignition energy. However, it is difficult to measure and analyze these factors in a production engine. This study used an optically accessible single-cylinder engine in which combustion and optical measurements were performed for 45 consecutive cycles. CCVs of the combustion and in-cylinder phenomena were investigated for the same cycle. Using this optically accessible engine, the volume inside the combustion chamber, including the pent-roof region can be observed through a quartz cylinder.

A connecting rod made of titanium alloy is effective for lower fuel consumption and higher power output comparing to a steel one because the titanium connecting rod enables to reduce the weight of both of reciprocating and rotating parts in an entire engine substantially. But up to now, it has been adopted only to expensive and small-lot production models because a material cost is high, a processing is difficult and a wear on a sliding area should be prevented. In order to adopt the titanium connecting rods into a more types of motorcycles, appropriate materials, processing methods and surface treatment were considered. Hot forging process was applied not only to reduce a machining volume but also to enhance a material strength and stiffness. And the fracture-splitting (FS) method for the big-end of the titanium connecting rod was put into a practical use.

This paper proposes a novel engine starter system composed of a small-power electric motor and a simple mechanical valve train. The system makes it possible to design more efficient starters than conventional systems, and it is especially effective to restart engines equipped with idling stop systems. Recently, several idling stop systems, having intelligent start-up functions and highly-efficient generate capabilities have been proposed for motorcycles. One of challenges of the idling stop systems is the downsizing of electric motors for starting-up. However, there are many limitations to downsize the electric motors in the conventional idling stop systems, since the systems utilize the forward-rotational torque of the electric motors to compress the air-fuel mixture gas in the cylinders. Our studies exceeded the limitations of downsizing the electric motors by mainly using the engine combustion energy instead of the electric energy to go over the first compression top dead center.

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.

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 two-stroke engines were in the main stream of the outboard motors, but they have been replaced with the four-stroke counterparts reflecting the environmental protection movement in recent years. However, the replacement with four-stroke engines involves increased number of components and additional displacement, and the outboard motors tend to be larger and heavier. This represents an issue, since the maneuverability of the boat is degraded due to the inappropriate weight distribution on the boat. Yamaha outboard motors F300B and VF250A, of which the production started in the year 2009, are equipped with four-stroke engines, and yet achieved the light weight equivalent to their two-stroke counterparts. The production volume of these models reached 20,000 units.

This paper reports visualization of behavior of spray, wall film, and initial flame propagation in an SI engine with port fuel injection system for motorcycle in order to directly investigate their influences on combustion and relations among them. Borescopes were used to visualize the flame propagation in the combustion chamber and wall film in the intake port. Various injection systems and injection parameters were tested: injection direction, timing, and size of droplets to investigate the effect of mixture formation. It is concluded that combustion stability under low load condition is greatly influenced by mixture inhomogeneity in the combustion chamber whose evidence is the luminous emission. It is caused by direct induction of considerable amount of liquid fuel with large size of droplets into combustion chamber or too inhomogeneous mixture in the intake port.

Mixture formation is one of the most important factors for the combustion in the spark ignition engine with port fuel injection. The relation between combustion and mixture quality, however, is not quantitatively well established. In this study, the connection of combustion and mixture formation was explored with various measurement techniques. Borescopes were used in order to investigate the flame propagation in the combustion chamber and behavior of spray and fuel film on the wall in the intake port. For the purpose of investigation on the effect of mixture formation, various port fuel injection systems and parameters were tested and compared: direction, timing, and size of droplet. An SI engine for small vehicle was used under condition of 4 000 rpm. The investigation by images obtained has shown that inhomogeneity of mixture causes low combustion stability, especially due to direct introduction of fuel droplets into the combustion chamber.

A construction of the technology concerning fuel consumption improvement is an important problem not only for the four-wheeled vehicle but also for the motorcycle in recent years when petroleum resources are depleted rapidly. Yamaha originally developed a new fuel injection system (YMJET-FI) and applied the system to a single cylinder, water-cooled and small-displacement engine. In this paper, we would introduce the results of improving the fuel economy with keeping high performance. Improvements were noted in three matters, namely, in the lower load range, 1.Strengthening of in-cylinder flow, 2.Atomization of fuel spray, and 3.Reduction of wall film quantity.

Regarding S.I. gasoline engine, it is one of the most important matters to eliminate cyclic variation of combustion. Especially with high compression ratio and high boosted engine, the difficulties increase more. This paper describes the analysis of combustion process precisely by using many ion-current probes and CFD with the unique approaches. The number of used ion-current probes is 80 and they are mounted on whole combustion chamber wall especially including moving intake and exhaust valve faces. Thus cyclic variations of flame propagation can be measured precisely under high compression ratio and high boosted conditions in a multi-cylinder engine. In addition, CFD combustion simulation is conducted through full four strokes of continuous nine cycles. Moreover air motion and pressure vibration in intake and exhaust manifolds in whole cycles are considered. These unique approaches have made CFD result correspond to the measurement result of cyclic variations of actual combustion.

The fracture splitting (FS) method for case hardened connecting rods has been developed to improve engine performance while decreasing production costs. The FS method is widely used for automotive connecting rods because it effectively improves their productivity. Normalized forging steels, microalloyed forging steels and powder metals have generally been used as the material in the FS method as they are easily split due to their brittleness. On the other hand, the materials to be used for high performance motorcycles are case hardened low carbon steels because they allow the connecting rods to be lightweight due to their high fatigue strengths. These materials, which have a hardened area of approx. 0.5mm in depth from the surface, have a ductile texture inside. This texture obstructs the crack propagation and makes the split force too high to split without deforming the bearing area.

A high-quality die-casting technology has been developed for lightweight aluminum frame structures that produces high-strength aluminum parts that are also weldable. This new technology has been used in casting frames for motorcycles and snowmobiles and has enabled improved frame designs with far fewer component parts than was possible before. This die-casting technology also results in a significant reduction in energy consumption during the manufacturing process.

A control system for auto driving of motorcycle using anthropomorphic robot has been developed to efficiently evaluate a motorcycle with high accuracy, the performance of which is becoming higher. For magnetostriction-type load sensor, which is absolutely necessary for this system, the strain gauge type load cell has been used conventionally. However, the detection sensitivity, strength, and responsibility have not been satisfied completely under engine vibration conditions. To solve this problem, a magnetostriction-type load sensor has been newly developed. As a result of the tests with actual machines, it is found that this magnetostriction-type load sensor satisfies the conditions necessary for the motorcycle drive control system and measurement system.

The in-cylinder flow, mixture distribution, combustion and exhaust emissions in a research, five-valve purpose-built gasoline engine are discussed on the basis of measurements obtained using laser Doppler velocimetry (LDV), fast spark-plug hydrocarbon sampling, flame imaging and NOx/HC emissions using fast chemiluminescent and flame ionisation detectors/analysers. These measurements have been complemented by steady flow testing of various cylinder head configurations, involving single- and three-valve operation, in terms of flow capacity and in-cylinder tumble strength.

The Bonded Valve Seat System is the latest technology to realize drastic reduction in valve temperature in SI engines characterized by the good thermal conductivity of extremely thin valve seats bonded directly on the aluminum cylinder head. A unique and highly rationalized resistance bonding technique was developed to maintain adequate bonding strength and positioning precision in a short bonding period of around one second. Engineering data on optimization of bonding-section geometry, valve seat material and the surface treatment and bonding parameters were presented and discussed regarding the mechanism. The geometry of the bonding section of the cylinder head was optimized by FEM analysis so that the aluminum material should deform to embed the valve seat ring with the action of expelling the surface contamination and the oxide film. The bonding facility was modified so that the electrode axis should move flexibly according to distortion of the cylinder head during bonding.

Measurement using a three-dimensional anemometric-tester was made for the gas flow inside the cylinder of a two-stroke engine while the shape of the transfer port was modified. The relationship between port shape and engine performance was investigated for various factors that characterize the flow in cylinder. In this paper, we focused mainly on two engine running conditions: the maximum output at 11750 rpm and the output at 10000 rpm. As a result, we found that the maximum output is most related to the tangential inclination angles of the main transfer port, and the inner vent radius of the main transfer duct.

Connecting rod design factors, such as geometric shape, capscrew torque and materials can significantly affect bore distortion and assembly stress. In this paper, experiments using different materials were conducted on several connecting rod big-ends with various shapes, bosses and bolts. The results show that the distortion of the big-end bore and the bolt stress are influenced considerably by the big-end shape, the bolt axial tension and the material under inertia force. It was also observed that the bolt bending stress and the load separating the big-end joint surface could be calculated with high accuracy using three-dimensional FEM in the initial connecting rod design.