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D
E
4
AILY
URO
ACTUATORS
The injection system comprises three classes of actuators
interlocked with the electronic control unit:
- electro-injectors (see relevant heading);
- regulators (see relevant headings) requiring PWM control
(Pulse Width Modulation):
• for pressure
• EGR (if mounted)
• turbocharger with variable geometry (if mounted);
- actuators with continuous ON/OFF signal to:
• engage electromagnetic coupling for radiator cooling
fan;
• turn on/off air-conditioner compressor (if mounted);
• Cruise Control;
• starter heater control;
• fuel filter heating;
• electric supply pump.
NOTE
All the power controls are made with relays located
in the cab.
PWM (Pulse Width Modulation) controls
A PWM control has an active and an inactive state that
alternate within a constant set length of time. During the active
state the actuator control circuit is closed, which is thus
powered with the control voltage; whereas, during the
inactive state the circuit is open.
The duration of the two states may be varied with the
condition that the sum of the two times is equal to the length
of the modulation delivery.
The duration of the active state determines the duty-cycle,
which is normally expressed as a percentage of the total time.
Therefore, if the duration of the two active and passive states
are the same, the duty-cycle is equal to 50%.
For reasons of diagnostics, the duty-cycle is limited between
1% and 99%; the control resolution is equal to 0.005%
(1/20000 of the time).
The time length has been chosen taking account of the
dynamic actuator response specifications.
Too low a carrier frequency could cause oscillations in the
actuator, while too high a frequency would decrease control
resolution.
The control of the E.G.R. (if fitted) and the turbocharger with
variable geometry (if fitted) occurs through the idle
modulating valve.
Print 603.93.651
311
F1C ENGINE
Base - March 2006
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