Mazda 2006 MX-5 - Variable Valve Timing Mechanism Construction;Operation; Component and Function

MECHANICAL
01–10–18
VARIABLE VALVE TIMING MECHANISM CONSTRUCTION/OPERATION [LF]
E5U011012111N05
Component and Function
Operation outline
• The variable valve timing actuator has two hydraulic chambers: a valve timing advance chamber and a valve
timing retard chamber. They are located between the integrated housing of the camshaft sprocket and the
camshaft integrated rotor. The oil pump supplies engine oil. to each chamber. Hydraulic pressure applied to
each chamber is controlled by the oil control valve (OCV) and the relative phases of the camshaft sprocket and
the camshaft are modified to obtain optimum valve timing according to engine operation conditions.
At engine start
• When the stopper pin in the variable valve timing actuator engages with the rotor, which is at the position of
maximum valve timing retard due to spring force, the camshaft sprocket and the camshaft rotate as one unit.
When the oil pump pressure rises and the stopper pin is disengaged, it becomes possible to modify the relative
angles of the camshaft sprocket and the camshaft.
Advancing valve timing
• When the spool valve in the oil control valve (OCV) moves to the left according to the PCM signal, hydraulic
pressure, from the oil pump, feeds into the valve timing advance passage and finally to the valve timing
advance chamber in the variable valve timing actuator. Then, the rotor integrated with the camshaft rotates in
the valve timing advance direction, against the housing driven by the crankshaft, and the valve timing is
advanced.
Variable valve timing actuator • Continuously modifies the phases of the intake camshaft and crankshaft at the forward
end of the intake camshaft using hydraulic pressure from the oil control valve (OCV).
Oil control valve (OCV) • Operated by current (duty signal) from the PCM. Switches the hydraulic oil passages
to the variable valve timing actuator.
CKP sensor • Inputs engine revolution signal to the PCM.
CMP sensor • Inputs cylinder identification signal to the PCM.
PCM • Controls the oil control valve (OCV) so that optimum valve timing is obtained according
to engine operation conditions.
PCM
OIL CONTROL VALVE (OCV)
SPOOL VALVE
OIL PUMP
CAMSHAFT
VARIABLE VALVE TIMING ACTUATOR
ROTOR
HOUSING
OIL PAN
TO VALVE TIMING
ADVANCE CHAMBER
VALVE TIMING
ADVANCE
CHAMBER
FROM VALVE TIMING
RETARD CHAMBER
HYDRAULIC PRESSURE FLOW
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