Toyota Variable Valve Timing. VVT-iE (gen.II)

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Eugenio,77
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Jul 2018

Toyota Variable Valve Timing. Evolution

Type VVT-iE (gen.2) - timing drive by chain, electrical variable valve timing mechanism for intake and traditional hydraulic VVT for exhaust. Applied for engines: Dynamic Force (A25A, M20A, V35A), NR series (-FKE).


VVT-iE system (Variable Valve Timing - intelligent Electric) allows to smoothly change the valve timing according to engine operating conditions. This is achieved by rotating the intake camshaft relative to the drive sprocket in the range of 70° (A25A) или 85° (V35A) (crankshaft rotation angle). The electric motor is used for adjustment, which allows to operate effectively at low temperatures or at low engine speeds with low oil pressure. The drive operates directly from power on moment, so it can provide the most optimal timing at starting.

VVT-i system (Variable Valve Timing - intelligent) allows to smoothly change the valve timing according to engine operating conditions. This is achieved by rotating the exhaust camshaft relative to the drive sprocket in the range of 41-44° (crankshaft rotation angle)*.

At inline-4 engines both camshaft are driven by single timing chain. At V6 engines the main timing chain drives the intake camshaft and than by short connecting chain the exhaust camshaft is driven.

VVT-iE actuator

The actuator consists of motor with EDU and 2-stage cycloidal reductor.

1 - control motor with EDU, 2 - sprocket gear, 3 - bearing, 4 - eccentric shaft, 5 - planetary gear, 6 - camshaft gear, 7 - sprocket, 8 - intake camshaft.

The VVT-iE motor consists of brushless DC motor (mounted in the timing chain cover), EDU control unit and a Hall-effect rotation sensor. EDU serves as an intermediary between the engine control unit and the drive motor, controlling the direction and frequency of its rotation. The EDU constantly transmits to the engine control unit current data on the speed of the electric motor, the direction of rotation and the state of the control signals.


The cycloidal gearbox includes sprocket gear, eccentric shaft, planetary gear and camshaft gear. The eccentric shaft drives the planetary gear. The sprocket gear has 1 tooth more than the large planetary gear, and the camshaft gear has 1 tooth more than the small planetary gear. When the eccentric shaft rotates, the planetary gear moves and simultaneously rotates, being engaged to the gears of the sprocket and camshaft. For each revolution of the eccentric shaft driven by the electric motor, the planetary gear moves 1 tooth relative to the sprocket gear and camshaft gear.

1 - sprocket gear, 2 - eccentric shaft, 3 - planetary gear (large), 4 - camshaft gear, 5 - planetary gear (small). eccentric shaft rotates: a - 120°, b - 240°, c - 360°, d - by 1 tooth of planetary gear


Advance. By ECM signal the motor rotates faster than camshaft. Driven via reduction unit the camshaft gear rotates clockwise and the camshaft connected to it is moved in the advance direction.

1 - control motor with EDU, 2 - sprocket gear, 3 - eccentric shaft, 4 - planetary gear, 5 - camshaft gear, 6 - sprocket. a - sprocket speed, b - camshaft speed, c - advance.

Retard. By ECM signal the motor rotates slower than camshaft. Driven via reduction unit the camshaft gear rotates counter-clockwise and the camshaft connected to it is moved in the retard direction.

1 - control motor with EDU, 2 - sprocket gear, 3 - eccentric shaft, 4 - planetary gear, 5 - camshaft gear, 6 - sprocket. a - sprocket speed, b - camshaft speed, c - retard.

Hold. After reaching the target timing, motor rotates at the same speed as the camshaft.


VVT-i actuator

New type actuator is used for Dynamic Force engines - with the oil control valve integrated to the central bolt.

A25A: 1 - oil control solenoid, 2 - solenoid coil, 3 - plunger, 4 - shaft.

V35A: 1 - oil control solenoid, 2 - solenoid coil, 3 - plunger, 4 - shaft.

VVT-i actuator with a bladed rotor is installed to the exhaust camshaft. When the engine stopped the lock pin holds the rotor at maximum advance position for normal starting.

A25A: 1 - control valve, 2 - housing, 3 - vane, 4 - lock pin, 5 - sprocket, 6 - camshaft. a - stop, b - operation.

ECM controls the oil flow to advance and retard chambers by solenoid, based on the signals of the camshaft position sensors. When engine stopped the valve spool is moved by spring to ensure maximum advance angle.

1 - control valve. a - to advance chamber, b - to retard chamber, c - oil pressure, d - drain

Advance. ECM switches solenoid to an advance position and shifts the spool of the control valve. Engine oil under pressure is supplied to the rotor in advance chamber, turning it together with the camshaft in the advance direction.

1 - vane, 2 - from ECM, 3 - control solenoid. a - rotation direction, b - retard chamber, c - advance chamber, d - to advance chamber, e - from retard chamber, f - drain

Retard. ECM switches solenoid to an retard position and shifts the spool of the control valve. Engine oil under pressure is supplied to the rotor in retard chamber, turning it together with the camshaft in the retard direction.

1 - vane, 2 - from ECM, 3 - control solenoid. a - rotation direction, b - retard chamber, c - advance chamber, d - from advance chamber, e - to retard chamber, f - drain

Hold. ECM calculates the target angle according to the driving conditions, and after the set position achieved it switches the control valve to the neutral position until the next change of external conditions.


Valve timing (A25A-FKS)


Valve timing (V35A-FTS)


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