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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.

This paper describes a newly developed hydraulic variable valve timing control (VTC) system, targeting the internal combustion gasoline engine, with an optimum angular position locking mechanism to reduce tailpipe emissions (TPE). In general, emission control catalysts are used as one measure to reduce TPE. However, there is the issue that catalysts cannot remove pollutants before reaching its light-off temperature at cold engine start. To address this issue, we have been using a method of increasing the valve overlap period between intake valve opening (IVO) and exhaust valve closing (EVC) by operating a VTC system at engine start. This brings engine-out emissions (EOE) back to the combustion chamber to be burned, thereby reducing EOE levels. However, this method requires about 3 seconds for the sufficient hydraulic pressure to start VTC operations.

Various technologies for improving the environmental performance of vehicles have been vigorously developed in the automotive industry in recent years. In this regard, the core technologies for improving vehicle fuel economy are still mostly aimed at internal combustion engines. This paper presents a new variable displacement oil pump (VDOP) that was adopted for enhancing the fuel economy of a newly developed 1.2-liter three-cylinder supercharged gasoline direct injection engine. It describes the purpose, benefits, performance and variable displacement principle of the VDOP. Published papers concerning the development of the new engine, the friction reduction technologies it embodies and additional details of the mechanisms incorporated in the new oil pump are cited in the references for the further information of the reader.