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When measuring the stress generated on connecting rods during operation with a strain gauge there are technical problems in taking the signal wires outside of the engine. As a means to solve this problem, we have developed a wire take-out method which consists of a steel wire to hold the signal wire and a tensioner to give tension to the steel wire. The adoption of this technique made it possible to measure the stress on connecting rods at a high speed range exceeding 10,000rpm, which has been impossible before. The results of analysis obtained by the wire take-out method revealed that speed ranges exceeding 10,000rpm generated a high frequency fluctuation due to the bending vibration of the connecting rod.

The authors developed, for use in diesel engines, ceramic tappets cast in aluminum alloy that drastically improved wear resistance and valve train dynamics. The ceramic tappets consist of two parts: a ceramic head, which contacts the cam and push rod, and a tappet body made of aluminum alloy. Concerning the ceramic, silicon nitride was the best material of the three ceramics evaluated in the tests and the sliding surface, in contact with the cam and push rod, was left unground. As for the aluminum alloy, hyper-eutectic aluminum-silicon alloy with a controlled pro-eutectic silicon size was selected. A reliability analysis using the finite-element method (FEM) was also made on the structure of the ceramic tappet for enhanced durability and reliability. The combination of this tappet and a cam made of hardened ductile cast iron, hardened steel, or chilled cast iron, respectively exhibits excellent wear resistance.

Silicon nitride (SN) valves promise significant reductions in weight and inertial force for valve trains because they are only two-fifths the weight of equivalent metal versions. This study evaluates how the higher engine speeds and lower valve spring loads that they permit contribute to higher engine output and greater fuel economy. It also evaluates their reliability in the presence of valve bounce and other adverse conditions that ceramic valves normally fail to withstand. For this purpose, material studies, actual engine tests and finite element method (FEM) analysis were conducted. Long-term durability tests revealed that SN valves are capable of providing the necessary resistance to breakage.