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The development of environmental improvement technologies in the automobile industry is underway. These technologies are also developed for internal combustion engines, which remain the mainstream power source for most vehicles. Nissan Motor Company has developed a multi-locking hydraulic VTC (Valve Timing Control) system and adopted it on the newly developed QR25DER engine of the Pathfinder and Infiniti JX hybrid vehicles. The implementation of the developed system allows for an optimized variable valve timing at both, cold engine start, and idle stop re-start from EV mode. This paper describes an outline, the principle, and effects of the multi locking hydraulic VTC system.

Recently, it has been expected that titanium alloy valves will be adopted at extremely high rate to motorcycle engines where higher engine performance is required than in automobiles. However, there were difficulties with respect to reliability required for motorcycle engines. The reason for this is that engine valves of motorcycle engines are not only smaller in stem diameter, but also used at a higher maximum engine speed than those of automobile engines. This study is about a development of titanium alloy engine valves that meet reliability requirements in motorcycle engines.

To achieve a clean atmospheric environment and a stable fuel supply, considerations are being given to the use of methanol fuel as one of the fuel used by alternative fuel vehicles. This report describes the development and studies of a brushless motor-driven fuel pump to be employed for a methanol electronic fuel injection system. Several problems remained to be solved for the fuel pumps used with methanol fuel, and hence considerations were given to the following items: (1) A control unit was developed that can be used in high-pressure fuel. This unit has been downsized substantially due to the adoption of a system in which it is subjected to forced cooling with the fuel.

The relation between the dynamic control range and the valve behavior has been studied. The results show that reduction of valve bounce and short valve closing time are important to the expansion of the dynamic control range. Non-linearity of fuel flow at short pulse widths is caused by the valve bounce and inertia force. Therefore, lessening valve weight is very effective to obtain good linearity. Our valve is composed of a steel ball, a pipe and an armature welded together by laser, and the weight is reduced to half of a conventional pintle needle. The valve is closed only by spring force. While satisfying minimum operating voltage; 6 V, dimensional factors were optimized to obtain higher spring preset load. This made it possible to reduce the valve closing time. Consequently this injector exhibits a greater dynamic control range.