Lexus RX300 (MCU15). Service 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
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