Lexus RX300 (MCU15). Manual — part 44

EG

ENGINE — 1MZ-FE ENGINE

Lock Pin

Exhaust Camshaft

157EG24

Housing
(Fixed on driven gear)

Vane Seal

Vane Side

Driven Gear

Intake Camshaft

Exhaust Camshaft

VVT-i Controllers

Hydraulic
Pressure

170EG05

Vane
Portion

Fixed on
Intake
Camshaft

Housing
Side

170EG06

To VVT-i Controller
(Advance Side) (Retard Side)

Sleeve

Spool Valve

Connector

Spring

Drain

Oil Pressure

Drain

Coil

Plunger

49

Construction

1) VVT-i Controller

This controller consists of the housing driven from the exhaust camshaft and the vane coupled with
the intake camshaft.
The oil pressure sent from the advance or retard side path at the intake camshaft causes rotation in the
VVT-i controller vane circumferential direction to vary the intake valve timing continuously. Also, when
the engine is stopped, in order to improve startability, intake camshaft will become the most retarded
state because of the external force such as the valve spring force. At this time, a lock pin fixes the
housing and the vane in the VVT-i controller. After the engine starts, the lock pin is released by the
hydraulic pressure.

2) Camshaft Timing Oil Control Valve

The camshaft timing oil control valve controls
the spool valve position in accordance with
the duty control from of the engine ECU thus
allocating the hydraulic pressure that is ap-
plied to the VVT-i controller to the advance
and the retard side. When the engine is
stopped, the camshaft timing oil control valve
is in the most retarded state.

ENGINE — 1MZ-FE ENGINE

50

Operation

The camshaft timing oil control valve selects the path to the VVT-i controller according to the advance,
retard or hold signal from the engine ECU. The VVT-i controller rotates the intake camshaft in the timing
advance or retard position or holds it according to the position where the oil pressure is applied.

1) Advance

When the camshaft timing oil control valve is positioned as illustrated below by the advance signal
from the engine ECU, the resultant oil pressure is applied to the timing advance side vane chamber to
rotate the camshaft in the timing advance direction.

VVT-i Controller Housing

Rotating
Direction

Vane (Fixed on intake camshaft)

Oil Pressure

Engine ECU

187EG35

2) Retard

When the camshaft timing oil control valve is positioned as illustrated below by the retard signal from
the engine ECU, the resultant oil pressure is applied to the timing retard side vane chamber to rotate
the camshaft in the timing retard direction.

Rotating Direction

Oil Pressure

Engine ECU

187EG36

EG

ENGINE — 1MZ-FE ENGINE

51

3) Hold

The engine ECU calculates the target timing angle according to the traveling state to perform control
as described in the previous page. After setting at the target timing, the valve timing is held by keeping
the camshaft timing oil control valve in the neutral position unless the traveling state changes.
This adjusts the valve timing at the desired target position and prevents the engine oil from running
out when it is unnecessary.

Oil Pressure

Engine ECU

187EG37

ENGINE — 1MZ-FE ENGINE

EX

IN

EX

EX

IN

IN

TDC

BDC

Latest timing

187EG39

178EG19

178EG20

To retard side

To advance side

52

In proportion to the engine speed, intake air volume, throttle position and coolant temperature, the Engine
ECU calculates an optimal valve timing under each driving condition and control the camshaft timing oil
control valve. In addition, Engine ECU uses signal from the VVT sensors and the crankshaft position
sensor to detect the actual valve timing, thus performing feedback control to achieve the target valve timing.

" Operation During Various Driving Condition (Conceptual Diagram) A

162EG46

Engine
Load

Range 4

Engine Speed

Range 1, 2

Range 3

Range 5

Full Load Perfomance

Operation State

Range

Valve Timing

Objective

Effect

During Idling

1

Eliminating overlap to reduce
blow back to the intake side

Stabilized
idling rpm
Better fuel
economy

At Light Load

2

Decreasing overlap to elimi-
nate blow back to the intake
side

Ensured en-
gine stability

At Medium
Load

3

Increasing overlap to increase
internal EGR for pumping loss
elimination

Better fuel
economy
Improved
emission
control