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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.

Exhaust emission regulation has become stricter year by year because of the global movements of environment protection. In consequence, turbocharger application to diesel engines became indispensable. Especially a variable geometry turbocharger (VGT) is perceived as the essential item. Of late years, the diesel engine has a trend of higher exhaust temperature to increase specific output. At the same time, needs of the turbocharger application to the gasoline engine has been rising again in order to reduce the size. In spite of this trend of the emission temperature increment, VGT of the variable nozzle vane type which is commonly available in the current market has problems of high temperature resistance due to its complex structure. AISIN SEIKI has developed a variable flow turbocharger (VFT), which is able to resolve those problems.

With the world-wide trend to protect the environment, emission legislation is becoming increasingly stringent. The role of cars is being reviewed from the point of the view of preserving the global environment and it has led to the development of vehicles that are environment-friendly. At same time, vehicles are also required with more comfort and better driveability than ever before. To meet these requirements, usage of turbocharged diesel engines are being increased and recently the variable geometry turbocharger (VGT) such as VNT has received a lot of attention within the automotive industry, as it has the significant benefit of being able to increase engine torque in the low speed region without compromising performance in the high speed region. Aisin Seiki has now succeeded in developing a novel type of variable turbocharger, called Variable Flow Turbocharger (VFT),which has a very simple structure that overcomes the disadvantages of commercially available VGTs.