The Working Process of VVT system
In order to better explain the working process of the VVT system, the following takes the intake VVT as an example to summarize the three most basic working processes:
1. Reference position: The duty cycle of the PWM signal input to the OCV is usually 0%, and the spool does not move. The oil pressure in the oil chamber on the right side of the phaser is greater than the oil pressure in the oil chamber on the left side and the left side of the blade abuts against the stator shoulder, so that there is no relative rotation between the rotor and the stator, and the camshaft is not adjusted relative to the crankshaft timing. Usually, the intake VVT reference position is the intake valve phase lag position, that is, the intake valve lag opens and closes.
2. Working position: The duty ratio of the PWM signal input to the OCV is gradually increased, the spool moves to the farthest position, and the pressure of the left oil chamber in the phaser is gradually increased. After unlocking, when the pressure in the left oil chamber is greater than the pressure in the right oil chamber and overcomes the friction torque of the camshaft as well as the internal friction torque of the phaser, the rotor rotates clockwise relative to the stator, and the cam axial timing advances direction adjustment, that is, the intake valve will open and close in advance.
3. Stable position, also called control position: After the rotor rotates clockwise relative to the stator, the duty cycle of the input OCV PWM signal is about 50%. The oil chamber on both the left and right sides of the phaser is simultaneously supplied with oil, and the rotor and stator will remain in this relative position. Usually, after VVT intervention adjustment, most of the time works at a dynamic stable position at a certain angle.
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