3360125 - 1036C OVERHEAD CAMSHAFTS (2) IN CYLINDER HEAD (1)
DESCRIPTION OF COMPONENTS
Camshafts
Specifications
TypeMade from ductile cast iron they each rotate on six supports and are controlled directly by the toothed belt.The camshaft oil seal function is performed at the front by oil seals.
Phase transformer
Specifications
System detailsA variable valve timing system with electronic control and hydraulic acutation has been adopted for the timing side camshaft.This device makes it possible to alter the timing diagram (inlet stage) depending on the load required by the engine; this parameter is processed by the control unit depending on the signals received by the air flow meter and by the rpm sensor and sent as a command to the phase transformer electromagnet.Composition
StructureThe device is composed of a main assembly fittedon the inlet side camshaft and is designed to alter the angular position of the actual shaft in relation to the drive pulley.There is also an actuator valve, controlled by an electromagnet, both on the intake manifold and connected hydraulically to the main assembly by means of appropriate ducts.Operation
Operation in closed stage (fc)When the closed phase is required (idling and maximum power zone), the solenoid (1) is de-energized therefore the valve body (2) remains raised thrust by the opposing spring (3) preventing fluid from channel (A) from reaching the variable valve timing system.In this case, intake valve timing remains unchanged (closed).Operation in open stage (fa)When the open stage is requested (average speeds at high torque) the solenoid (1) is energized thereby pushing the valve body (2) downwards.In this position, fluid from channel (A) enters chamber (B) of the piston and then flows on through a hole into channel (C) inside the piston.The oil can only leave the above duct via the top port (in contact with the the oil supply duct (D) to radiator) because as the valve body (2) is lowered the bottom port is not in contact with the drainage duct (E).The oil flows through channels (D) and (F) into chamber (G), which moves the piston (4) axially toward the engine. Because the piston is fitted with external helical teeth, it is forced to turn clockwise.Its rotation is transmittted via a splined curb toothed section to piston (5) which is tightened onto the threaded shank of camshaft (6) and transmits rotation to the shaft, thus altering intake valve timing by 25°.When the solenoid is de-energized, the valve body (2) returns to its original position cutting off the flow of pressurised fluid to the piston (4) but allowing fluid to return to the exhaust thanks to the effect of the opposing spring (7).Channel (L) allows the camshaft journal to be lubricated under different operating conditions.The fluid that leaks into electromagnet chamber (H) drains out through drainage port (E).
Tappets
Specifications
TypeThe hydraulic tappets automatically take up valve clearance during engine service. This offers the advantage of reducing:
- maintenance operations
- engine noise.
Operation
Operation in open stageWhen the camshaft cam acts on the tappet (1) and consequently on the piston (2), as a result of the closure of the ball valve (4), the oil in the chamber (6) transmits the movement of the piston (2) directly to the hose (3) and, as a result, to the valve.At this stage, due to the high pressure acting on the oil, some of the oil in the chamber (6) leaks through the tiny gap between the piston (2) and the hose (3).
