Mazda 6 Training Manual page 39

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
maimum 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.
.
1 PCM
2 Oil control valve (OCV)
3 Spool valve
4 Oil pump
5 Camshaft
6 Variable valve timing actuator
7 Rotor
Retarding valve timing
• When the spool valve in the oil control valve (OCV) moves to the right according to the PCM signal, hydraulic
pressure, from the oil pump, feeds into the valve timing retard passage and finally to the valve timing retard
chamber in the variable valve timing actuator. Then, the rotor integrated with the camshaft rotates in the valve
timing retard direction, against the housing driven by the crankshaft, and valve timing is retarded.
VALVE MECHANISM
8 Housing
9 Oil pan
10 To valve timing advance chamber
11 Valve timing advance chamber
12 From valve timing retard chamber
13 Hydraulic pressure flow
B
AME2211N017
B–31