Variable Valve Timing Solenoid: Description and Operation

GF05.20-P-2100V Component Description For A Camshaft Solenoid







Location
The solenoids are located in front of the respective camshaft.

Task
The solenoids actuate the control plunger on the vane-cell adjuster according to the performance map related duty cycle. Depending on their position, more or less pressure oil flows from the hollow camshaft into the oil galleries of the vane-type adjuster.

Design
The solenoids for camshaft adjustment are designed as proportional magnets, i.e. the direction of the armature and thus the position of the control plunger in the vane-type adjuster are dependent on the intensity of the current in the coil.







Function
The solenoids before the camshafts are actuated by the ME control unit at the ground end by means of a PWM signal (150 Hz). The voltage supply for the solenoid takes place from circuit 87. The vane-cell adjuster are actuated according to the performance map related duty cycle.

The maximum current (duty cycle 100 %) is emitted for a short time (about 0.5 seconds) for rapid adjusting of the anchor. A hold-in winding voltage with a small duty cycle is then set afterwards. The coil resistance at room temperature is approx. 7.5 ohms.

Depending on their position, the oil volume in the vane-type adjusters is controlled. This takes place through differently arranged holes in the control plunger as well as through oil ducts in the vane-cell adjusters. The adjusting range of the camshaft is limited by the forming of the vane-cell adjuster mechanically. If the solenoids are no longer actuated then resetting takes place against the direction of rotation.

The following positions are possible:
- Filling the oil gallery
Pressure oil flows out of the hollow camshafts into the vane- cell adjuster. The camshafts adjust themselves to the respective direction of rotation. The inlet camshafts adjust to "advanced". The exhaust camshafts adjust themselves due to their reversed direction of rotation to "retarded".
- Oil gallery closed
Each camshaft position is detected by a camshaft Hall sensor. Once the requested adjustment has been achieved then the respective solenoid will be actuated in such a way that oil galleries in the vane-cell adjusters are closed.
- Emptying the oil gallery
The camshafts adjust themselves against their direction of rotation.