Bota, J., Kumagai, T., Kuboyama, T., and Hatamura, K., "Development of Continuously Variable Phase and Lift/Duration Mechanism for Widely Available Automobile Engines," SAE Int. J. Engines 6(1):327-335, 2013, doi:10.4271/2013-01-0591.
The variable valve lift and duration (in the following: VVLD) devices, some have been mass-produced already in the world, are necessary to be assembled with the variable cam phaser (in the following: VCP) to optimize open and close valve timing. On the other hand, with the variable valve phase and lift (in the following: VVPL) mechanism, the valve event is advanced with decreasing the valve lift and duration. Hence, no additional VCP is required when using the VVPL for throttle-less operation.A new VVPL has been developed as a mechanical, swing-cam actuation mechanism. The mechanisms of the conventional production VVLD devices are investigated and the functional analysis of the possible mechanisms is carried out to identify and design a simple mechanism for the new VVPL. The designed VVPL system is capable of continuously varying the valve lift from 0 mm to 10 mm, with the higher valve lift for any of the given duration.CAE oriented study, conducted before the production of the prototype, predicted the unexpected problems of the system at the design stage. By the multi-body dynamic simulation, predicting the dynamic behavior of the system, the requirement for the design to obtain the stable operation in the entire operation range was clarified.The trial manufactured VVPL was tested on the 4-cylinder test bench after the single cylinder test, and successfully operated up to 7000rpm of engine speed. The accuracy of the multi-body dynamic simulation was evaluated with the measured dynamic behavior. It was found that the high speed limitation of the system was sufficiently predicted by the multi-body simulation.Following the functional test, the newly designed VVPL system was installed into the 4-cylider gasoline engine and its effect on fuel efficiency was evaluated on the firing test bench. As a result, a large improvement in fuel efficiency was obtained with the developed VVPL system, as expected.