Application of a Variable Valve Event and Timing System to Automotive Engines 2000-01-1224
This paper describes a new variable valve system that enables continuous control of valve events, i.e. time periods when the valve is open. In this system, valve events are controlled by varying the camshaft angular speed by means of an offset between the center of the camshaft and that of the medium member that transfers crankshaft torque to the camshaft. The medium member, a rotating disk, has a drive pin to enable the transfer of torque. The system has a mechanism that produces an offset between the center of the rotating disk and that of the camshaft as well as an actuator that drives the mechanism. This makes it possible to develop a compact system that can be installed in existing DOHC direct-acting valve train engines without making any major cylinder head modifications. Test results verified that valve events could be broadly controlled through the use of an electronically controlled hydraulic actuator, and that control could be achieved up to the low speed region with the use of engine oil pressure.
The system was applied to a 4-cylinder, 1.6L engine, and test results showed that torque improved from 10 to 15% and by 10% at maximum power. We also confirmed that both fuel economy and exhaust emissions at part-load were substantially improved when using the system.