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In an attempt to decrease the amount of CO2 emitted by engines and yet improve engine output power, various approaches to the development of variable valve-lift mechanisms and the application of direct fuel injection and supercharger mechanisms are rapidly gaining popularity. In the case of the swing motion which takes place in variable valve-lift mechanisms, the relative speed between the two components reaches zero at the location where the load is high and the oil film tends to break, thereby leading to wear. Furthermore, the use of a supercharger and a direct injection device generates soot, which promotes further wear. Therefore establishing a reliable method for estimating wear has become a pressing issue. Wear problems caused by the swing motion occur during boundary lubrication, and we have devised a solution for them.

To develop ideal oil circuits, it was necessary to establish technology that would accurately predict lubrication oil pressure and flow rates. Therefore, the oil flow rate was predicted by applying load fluctuations, calculated using multi body dynamics, to an oil film model. In addition, the pressure loss of complex oil passages was obtained using 3-dimensional computational fluid dynamics (hereafter, “3D-CFD”). Furthermore, the pressure loss of the oil pressure switching valves and other parts that are difficult to predict using 3D-CFD were measured as single parts, and these results were linked with one-dimensional internal flow analysis to develop a prediction method for lubrication oil pressure and flow rate distributions. Verification tests were ultimately performed using a completed engine, and the results confirmed that this simulation method accurately reproduces the oil pressure and oil flow rate in each part.

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.

Simulation technology that enables the holding limit of a tensioner to be predicted in advance was developed, and the effect of the tensioner on the chain clarified. The simulation model was constructed using multi-body dynamics. For the analysis, a link-by-link method was used, and a hybrid model of the tensioner consisting of multiple masses and oil was created. In comparing the tensioners, the main viewpoint was the difference between the spring type and hydraulic tensioners. The effect of each tensioner on the chain load and the chain behavior was clarified through this analysis, and as a result it was possible to predict the optimum chain system design by simulation.

An increasing number of chain systems have used low cost blade tensioners. However, its functional mechanism had not been logically figured out. One reason for this is that a blade tensioner generates large transversal vibration. Consequently, in the case of the longitudinal model, the load prediction accuracy was inadequate. Accordingly, a link-by-link model was created, allowing transversal vibration to be taken into account. As a result, the features of a chain system using a blade tensioner were clarified, thus enabling the chain load and behavior to be predicted with a higher degree of accuracy than before.

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.