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2) Collecting PM of DPF
There is a filter installed in the DPF and the PM filtered by this filter is burned (regeneration) when
the temperature of exhaust gas is increased due to post-injection. The filter has a honeycomb-
like structure to capture the particulate matter and the inlet and outlet of each channel are closed
alternatively. Once the exhaust gas enters to the inlet of a channel, it is released from the outlet of
the adjacent channel through the porous wall because of the closed outlet of the first channel,
and the PM is collected in the first channel.
[Collecting PM of CDPF]
Normally, when the driving distance becomes approx. 600 to 1,200 km, enough amount of
soot to be burned is filtered and accumulated in the CDPF. The ECU increases the amount of
fuel post-injection to increase the temperature of the exhaust gas up to 600°C, so that the
soot is burned. The soot is burned for 15 to 20 minutes (may differ by conditions).
15-150000-00
A fourth correction is made according to the pressure error.
This correction is used to reduce the injection timing advance when the pressure in the rail is
higher than the pressure demand.
A fifth correction is made according to the rate of EGR.
This correction is used to correct the injection timing advance as a function of the rate of
exhaust gas recirculation. -
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When the EGR rate increases, the injection timing advance must in fact be increased in order to
compensate for the fall in termperature in the cylinder.
A. Main Flow Control
The main flow represents the amount of fuel injected into the cylinder during the main injection.
The pilot flow represents the amount of fuel injected during the pilot injection.
The total fuel injected during 1 cycle (main flow + pilot flow) is determined in the following manner.
When the driver depress the pedal, it is his demand which is taken into account by the system
in order to determine the fuel injected.
When the driver release the pedal, the idle speed controller takes over to determine the
minimum fuel which must be injected into the cylinder to prevent the enigne from stalling. -
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It is therefore the greater of these 2 values which is retained by the system. This value is then
compared with the lower flow limit determined by the ESP system.
As soon as the injected fuel becomes lower than the flow limit determined by the ESP system, the
antagonistic torque (engine brake) transmitted to the drive wheels exceeds the adherence
capacity of the vehicle and there is therefore a risk of the drive wheels locking.
The system thus chooses the greater of these 2 values (main flow & pilot flow) in order to prevent
any loss of control of the vehicle during a sharp deceleration.
As soon as the injected fuel becomes higher than the fuel limit determined by the ASR trajectory
control system, the engine torque transmitted to the wheels exceeds the adhesion capacity of the
vehicle and there is a risk of the drive wheels skidding. The system therefore chooses the smaller
of the two values in order to avoid any loss of control of the vehicle during accelerations.
The anti-oscillation strategy makes it possible to compensate for fluctuations in engine speed
during transient conditions. This strategy leads to a fuel correction which is added to the total fuel
of each cylinder.
A switch makes it possible to change over from the supercharge fuel to the total fuel according to
the state of the engine.
Until the stating phase has finished, the system uses the supercharged fuel.
Once the engine changes to normal operation, the system uses the total fuel. -
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(5) Fuel Control
The main fuel is obtained by subtracting the pilot injection fuel from the total fuel.
A mapping determines the minimum fuel which can control an injector as a function of the rail
pressure. As soon as the main fuel falls below this value, the fuel demand changes to 0 because
in any case the injector is not capable of injecting the quantity demand.
