Engine
Fuel system
Marea-Marea Weekend^
1998 range
10.
ENGINE IDLE SPEED ACTUATOR
(step motor) (IB02)
1.
Bearing 5. Screw
2. Lead screw 6. Anti-rotation
3. Coils grooves
4. Magnets 7. Plunger
The actuator is fitted to the throttle body and consists
of:
- An electric step motor with two windings in the stator
and a rotor that contains a certain number of perma-
nent magnet pairs.
- A worm and screw reduction unit that converts rota-
tory motion into linear motion.
In order to idle, i.e. with throttle (4) fully closed, the
engine needs a certain amount of air (Qo) and fuel to
overcome internal friction and maintain rpm levels.
To the quantity of air Qo that leaks through the closed
throttle valve (4) during idling, an additional quantity of
air Q must be added to allow the engine to maintain
rpm levels constant, particularly during warm up and
when electrical users or external loads are activated (air
conditioner, automatic transmission, etc).
To achieve this result, the system uses a step motor (1)
fastened to butterfly valve case (5) controlled by ECU
(6) which moves a rod fitted with a plunger (3) during
operation. This alters the cross-section of by-pass duct
(2) and thus the amount of air (Qo + Q) taken in by the
engine.
In order to govern this type of action, the ECU uses
angular engine speed and coolant temperature input
from the relevant sensors.
+ 12V
o-
n
Q. Air flow regulated by plunger (va-
riable)
| | | | | | | | | Qo. Air flow leaking through throttle
(constant)
21
®
C
20
L,D A
6
40 \
© i
L, B
36
Publication no. 506.763/09
Содержание 1998 Marea Weekend
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