VARIABLE VALVE TIMING MECHANISM [SKYACTIV-G 1.3, SKYACTIV-G 1.5 (WITH 4-1 EXHAUST SYSTEM)]

id0110q30020q4


Outline

•  The variable valve timing mechanism changes the valve timing.
•  By optimizing the change in the valve timing, the internal EGR amount and effective compression ratio are controlled, pumping loss is reduced, and the combustion is controlled optimally.
•  A hydraulic pressure type variable valve timing mechanism has been adopted on the intake side.

Structural View

am2zzn00003065

Structure

Part name
Function
Hydraulic variable valve timing actuator
(See HYDRAULIC VARIABLE VALVE TIMING ACTUATOR [SKYACTIV-G 1.3, SKYACTIV-G 1.5 (WITH 4-1 EXHAUST SYSTEM)].)
OCV
(See OIL CONTROL VALVE (OCV) [SKYACTIV-G 1.3, SKYACTIV-G 1.5 (WITH 4-1 EXHAUST SYSTEM)].)
Intake camshaft position sensor
(See CAMSHAFT POSITION (CMP) SENSOR [SKYACTIV-G 1.3, SKYACTIV-G 1.5].)
Crankshaft position sensor
(See CRANKSHAFT POSITION (CKP) SENSOR [SKYACTIV-G 1.3, SKYACTIV-G 1.5].)


Operation

•  The variable valve timing mechanism has the following four modes:
•  The four modes are determined by the operation of the OCV and hydraulic variable valve timing actuator.

Mode

OCV operation

(spool valve)

Hydraulic pressure

Hydraulic variable valve timing

actuator operation

Valve timing

Stopper pin

Rotor
Fixed mode
Maximum retard position
To retard chamber
×
Maximum retard position
Maximum retard
Advance mode
To advance side
To advance chamber
—
Move to advance side
Advance
Retard mode
To retard side
To retard chamber
—
Move to retard side
Retard
Hold mode
Middle point
To advance/retard chamber
—
Hold at optimum position
Hold at optimum position

×  :Engages with rotor depression
—  :Disengages from rotor depression

Fixed mode

•  The rotor depression at the maximum retard position and the stopper pin in the hydraulic variable valve timing actuator are engaged by the spring force. Due to this, the housing (intake camshaft sprocket) and the rotor (intake camshaft) rotate as a single unit.
am2zzn00003066


Advance mode

•  The spool valve in the OCV moves to the advance side and hydraulic pressure is applied to the advance chamber in the hydraulic variable valve timing actuator by a signal from the PCM. Due to this, the rotor (intake camshaft) rotates in the advance direction relative to the housing (intake camshaft sprocket), and the valve timing is advanced.
am2zzn00003067


Retard mode

•  The spool valve in the OCV moves to the retard side and hydraulic pressure from the oil pump is applied to the retard chamber by a signal from the PCM. Due to this, the rotor (intake camshaft) rotates in the retard direction relative to the housing (intake camshaft sprocket), and the valve timing is retarded.
am2zzn00003068


Hold mode

•  The spool valve in the OCV is positioned the area around the middle point at advance and retard by a signal from the PCM. At this time, hydraulic pressure is applied to both of the advance and retard chambers in the variable valve timing actuator. Due to this, there is no change in the relative angle of the rotor (intake camshaft) and the housing (intake camshaft sprocket) and the current valve timing is held.
am2zzn00003069

Note
•  To switch to the fixed mode (lock-pin in hydraulic variable valve timing actuator engaged with rotor depression) when the ignition is switched OFF (LOCK), the engine stop condition is extended (within approx. 0.5 s) under the following conditions: Due to this, engine re-startability has been improved. (ATX)
―  During or right after fast idle increase (during control of catalytic converter earlier activation)
―  Right after operating to D/R/M position while the vehicle is parked at high-altitude, or operating from D/R/M position to P/N position