VARIABLE VALVE TIMING MECHANISM CONSTRUCTION/OPERATION [LF, L3]

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Component and function

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.

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.

•  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.

•  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.

am3zzn00001490

1	PCM
2	Oil control valve (OCV)
3	Spool valve
4	Oil pump
5	Camshaft
6	Variable valve timing actuator
7	Rotor
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

•  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.

am3zzn00001491

1	PCM
2	Oil control valve (OCV)
3	Spool valve
4	Oil pump
5	Camshaft
6	Variable valve timing actuator
7	Rotor
8	Housing
9	Oil pan
10	To valve timing retard chamber
11	Valve timing retard chamber
12	From valve timing advance chamber
13	Hydraulic pressure flow

•  The spool valve in the oil control valve (OCV) is located near the middle of the valve timing advance and retard positions. Because of this, hydraulic pressures are maintained in both valve timing advance and retard chambers of the variable valve timing actuator. At the same time, relative angles of the rotor and the housing are fixed and maintained, resulting in fixed valve timing.

am3zzn00001492

1	PCM
2	Oil control valve (OCV)
3	Oil pump
4	To valve timing advance chamber
5	To valve timing retard chamber
6	Hydraulic pressure flow