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).
CVVT improves engine performance through reduction of pump loss,
internal EGR effect, improvement of combustion stability, improvement of
volumetric efficiency, and increase of expansion work.
This system consist of
–
the CVVT Oil Control Valve (OCV) which supplies the engine
oil to the cam phaser or runs out 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 released out of 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.
Operation Principle
The CVVT has the mechanism rotating the rotor vane with
hydraulic force generated by the engine oil supplied to the advance or
retard chamber in accordance with the CVVT oil control valve control.
[CVVT System Mode]
(1) Low Speed / Low Load
(2) Part Load
(3) Low Speed / High Load
(4) High Speed / High Load
Driving Condition
Exhaust Valve
Intake Valve
Valve Timing
Effect
Valve Timing
Effect
(1) Low Speed /Low Load
Completely Advance
* Valve Under-lap * Improvement of combustion stability
Completely Retard
* Valve Under-lap * Improvement of combustion stability
(2) Part Load
Retard
* Increase of expansion work * Reduction of pumping loss * Reduction of HC
Retard
* Reduction of pumping loss
(3) Low Speed /High Load
Retard
* Increase of expansion work
Advance
* Prevention of intake back flow (Improvement of volumetric efficiency)
Special Service Tools
Tool (Number and Name)IllustrationApplicationRKE Battery Checker(09954-2P100)Measuring the RKE batteryvoltageCorrection jig of LDWS(09890-3N100)Correction of LDWS (Lane Departure Warning System)
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