Crankshaft: (page 2 of 2)

When the quantity of air taken in by the engine is lower than a pre-set value, the solenoid (1) is deactivated and the valve box (2) pushed by the counter-spring (3) is lifted up allowing the passage of oil from the channeling (A) to reach the variator. In this case the timing of the intake valves is not changed.

If the quantity of intake air exceeds the pre-set value, the solenoid (1) is activated and pushes the valve box (2) downwards. In this position the oil arriving from the channeling (A) enters the piston chamber (B) and passes through a hole into the internal channel (C) in the piston. The oil can only exit this channel through the upper hole (leading to the oil-to-variator delivery duct (D)) as the lower hole no longer opens onto the exhaust duct (E) as the valve box (2) is lowered. The oil passes through the channeling (D) and (F) and reaches the chamber (G) moving the piston (4) axially towards the engine.

The piston is externally equipped with helical teeth and as a result of the axial movement is forced to rotate clockwise (as seen from the timing side). This rotation is transmitted to the pinion through a straight toothed grooved profile. The pinion (5) which is rotated by the threaded tug of the camshaft (6) transmits the rotation to the shaft, and in this way the timing of the intake valves is varied by 30°.

When the solenoid is deactivated, the valve box (2) returns to the initial position, interrupting the flow of pressurized oil to the piston (4) but permitting the return of the oil to the outlet due to the thrust from the counter spring (7).

The channeling (L) enables the camshaft journal to be lubricated under the various operating conditions.

The oil which leaks into the solenoid chamber (H) is discharged through the drainage hole (E).

1. solenoid
2. valve box
3. counter-spring
4. piston
5. pinion
6. camshaft
7. counter spring