Continuous Variable Valve Timing (CVVT) system advances or
retards the valve timing of the intake and exhaust valve in accordance
with the ECM control signal which is calculated by the engine speed and
load.
By controlling CVVT, the valve over-lap or under-lap occurs,
which makes better fuel economy and reduces exhaust gases (NOx, HC) and
improves engine performance through reduction of pumping loss, internal
EGR effect, improvement of combustion stability, improvement of
volumetric efficiency, and increase of expansion work.
This system consists of
- the CVVT Oil Control Valve (OCV) which supplies the engine
oil to the cam phaser or spills the engine oil from the cam phaser in
accordance with the ECM PWM (Pulse With Modulation) control signal,
- the CVVT Oil Temperature Sensor (OTS) which measures the engine oil temperature,
- and the Cam Phaser which varies the cam phase by using the hydraulic force of the engine oil.
The engine oil which is supplied through the CVVT oil control
valve varies the cam phase in the direction (Intake Advance/Exhaust
Retard) or opposite direction (Intake Retard/Exhaust Advance) of the
engine rotation by rotating the rotor connected with the camshaft inside
the cam phaser.