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The fluctuation of the crankshaft rotational speed of a turbo supercharged direct-injection diesel (hereafter called i-CTDi) engine is large, causing the timing chain load and the valve train driving torque to increase. To overcome this, a simulation method that enables the timing chain load and the valve train driving torque to be predicted while taking account of the fluctuation of the crankshaft rotational speed was established. In this simulation, all of the moving parts centered about the crankshaft were coupled, and an engine in a working condition was faithfully constructed in the computer. In the construction of the model, the issue of the conflicting topics of securing accuracy and reducing computing time was solved by looking at the frequency response of each part and adopting a simple model. As a result, it was possible to predict both the timing chain load and the valve train driving torque with high accuracy and in a short time.

The mechanism of noise production in engine accessory drive belts was discussed. Applying geometric considerations to the transversal vibration of the belt, which is one cause of belt noise, the research showed that vibration of the belt is affected by fluctuations in the rotational speed of the crankshaft, and that the amplitude of the vibrations fluctuates cyclically. The cycle of this amplitude fluctuation is synchronous with engine speed, and for a 3-cylinder gasoline engine, its frequency is the (1.5*n)th engine rotation order. The spectrum pattern of belt vibration therefore shows components of the natural frequency±(1.5*n)th orders. The research demonstrated that at engine speeds at which the natural frequency±(1.5*n)th orders and the (1.5*n)th order frequencies, the engine excitation orders, are identical, multiple engine orders excite resonance in the belt, producing a high degree of belt vibration.