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Technical Paper

Study of bonded valve-seat system (BVS)

2000-06-12
2000-05-0144
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.
Journal Article

Development of Fracture-Split Connecting Rods Made of Titanium Alloy for Use on Supersport Motorcycles

2015-11-17
2015-32-0830
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.
Technical Paper

Development of Fracture Splitting Method for Case Hardened Connecting Rods

2004-09-27
2004-32-0064
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.
Journal Article

Application of Vacuum Assisted Carbide Dispersion Carbonitriding to Connecting Rods

2013-10-15
2013-32-9082
In four-cycle single-cylinder motorcycle engines, high Hertzian stress is generated on and beneath the big-end surface of the connecting rod. If the surface strength would be improved, the diameter of the big-end could be made smaller, making the entire engine smaller and lighter. Therefore, application of carbide dispersion carbonitriding using a vacuum furnace (hereinafter referred to as “vacuum CD carbonitriding”) on the big-end surface was investigated. Vacuum CD carbonitriding was carried out by three processes. The first was a CD carburizing process. This process is done to obtain granular cementite, but in order to avoid decreasing the strength, it is necessary to prevent the formation of coarsened cementite at the grain boundary. The second process was a refining process. This process is done for the purpose of refining the prior austenite grain size. The third process was a carbonitriding process.
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