The New L4 Gasoline Engines with VALVEMATIC System

Authors

J. Harada, T. Yamada, K.Watanabe, Toyota Motor Corporation, Aichi

Year

2008

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 672

Summary

Reduction of CO2 emissions is one of the major responsibilities of car manufacturers. It is an especially urgent task to develop new technologies with a simple, compact and widely applicable mechanism which can be used for middle class engines of mass volume production category. Toyota has developed a continuously variable valve timing and lift control system called ”VALVEMATIC”. By implementing this system fuel consumption can be improved by using smaller valve lift during low and middle engine loads (reduction of pumping loss by closing the intake valve earlier).


The system consists of a special rocker arm which realizes continuously variable valve timing and lift. It is located between a conventional roller-rocker arm and the camshaft. An electrically actuated motor is used to control the lift and valve opening duration, while a hydraulically controlled variable valve timing mechanism (VVT-i) is also applied on both intake and exhaust cam shafts. The newly developed actuator contains Toyota’s original planetary roller screw unit translating rotary movement of the motor into linear actuation. Thanks to the alignment of rocking center and actuator drive direction, a compact design has been achieved.


In 2007, VALVEMATIC has been introduced into the Japanese market on a 2.0L engine (3ZR-FAE), which has the largest displacement of the ZR series. The engine employs a cam housing structure with valve train system separated from the cylinder head. The structure realized a high ratio of part commonization with the conventional engine, and an easy mounting of the VALVEMATIC-system by changing only the cam housing assembly.


The engine achieved 5-10% fuel consumption improvement and good drivability by using a newly developed cooperative control of VALVEMATIC, VVT-i and the throttle valve. Maximum power also improved by approximately 11kW thanks to the maximized volumetric efficiency using VALVEMATIC. Furthermore, exhaust emissions were improved due to increased induction flow rate into the cylinders at smaller valve lift operating conditions.

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