DIESEL PARTICULATE FILTER (DPF) SYSTEM <4HN>

ANTICIPATING METHOD OF PM ACCUMLATION

Anticipation by odometer

The engine-ECU calculates the travel distance using the vehicle speed signal. When the vehicle travels the specified distance from the last DPF regeneration, the engine-ECU anticipates the PM accumulated.
The engine-ECU classifies the operation into 5 types according to the vehicle speed and the engine torque: running at excessive low speeds, general speeds and high speeds as well as running on urban and suburb streets. The engine-ECU sets or updates the travel distance to the next regeneration for each type according to the travel distance.

Anticipation by difference in pressure

The engine-ECU assumes the PM accumulated in the DPF using the following information: the amount of exhaust gas calculated by the intake air mass sensor and the exhaust gas temperature sensor; the pressure difference, between the upstream of DPF and the atmosphere, detected by the exhaust differential pressure sensor.

WARNING ABOUT CLOGGED DPF

When the assumed PM accumulation reaches the specified level, the engine-ECU automatically carries out the DPF regeneration and always keeps the DPF optimal state. When the DPF regeneration is not sufficiently carried out due to the short travel distance or the running at low speeds, or when the accumulated PM is beyond the specified level due to the other reasons, the engine-ECU carries out the DPF regeneration according to the level, stores the diagnosis code and warns the driver. The DPF regeneration carried out by the engine-ECU according to the level of accumulated PM is as follows:

<Step 1 - Level without damage>

When the PM accumulation judged by the pressure difference at the exhaust differential pressure sensor is beyond the normal level, the engine-ECU carries out the DPF regeneration and stores the diagnosis code P1490. At this level, the engine-ECU does not warn the driver.

<Step 2 - Slightly excessive level of accumulated PM>

When the PM accumulation is beyond the level of Step 1, the engine-ECU continuously carries out the DPF regeneration, storing the diagnosis code P0420. The engine-ECU does not warn the driver.

<Step 3 - Abnormal level of accumulated PM>

When the level of PM accumulation might damage the engine, the engine-ECU illuminates the engine warning lamp and stores the diagnosis code P1447. At that time, the engine-ECU considerably decreases the output for the safety. This vehicle state needs the forcible regeneration of the DPF to be carried out using the M.U.T.-III. There are 2 methods for the forcible regeneration using the M.U.T.-III: in the running state and in the stopped state.

DPF MAINTENANCE

The DPF periodical check is not necessary. The DPF must be replaced every 180,000 km. This replace prevents the engine performance from deteriorating due to the earlier clogged DPF and keeps the DPF optimal state. The PM accumlated in the DPF is burnt, but neither the cerium in the fuel additive Eolys 176 or the ash is burnt. When the DPF is replaced, the monitor function of DPF regeneration and the amount of additive accumulated in the DPF must be initialised using the special function of M.U.T.-III.

DPF REGENERATION CONTROL

The DPF regeneration has the forcible regeneration by M.U.T.-III and the automatic regeneration automatically performed while the vehicle is running. The automatic regeneration is performed under the following conditions:

Engine coolant temperature: 60°C or more
Vehicle speed: 60 km/h or more
The rate of accumulation PM exceeds the specified value.
When the total travel accumulated on the vehicle reaches the updated value according to the operation conditions
Operating the rear window defogger, fan and glow plug increases the electrical load and the engine load.

Performing the optimum engine control for the DPF regeneration, the engine-ECU increases the temperature up to the point at which the DPF regeneration can be carried out, and then keeps the temperature to burn the PM.

REGENERATION CONTROL

The engine-ECU increases the temperature in the DPF to approximately 450°C within the short time for the DPF regeneration by carrying out the following control:

Contents for control of regeneration

Fully close the EGR valve to increase the combustion temperature.
Carry out the additional fuel injection after the main injection ATDC 20° - ATDC 120° to increase the exhaust gas temperature.
Adjust the throttle valve opening degree to regulate the intake air amount.
Adjust the boost pressure with the variable geometry control motor.

The engine-ECU carries out the feedback control to keep the temperature of exhaust gas entering the DPF at approximately 450°C, using the exhaust gas temperature sensor after starting the DPF regeneration. The temperature of exhaust gas entering the DPF is adjusted by controlling the additional injection amount after the main injection and intake air amount.

When the vehicle is not driven under the required driving conditions during the DPF regeneration, the engine-ECU stops the DPF regeneration control once. When the vehicle is driven again under the required driving conditions for the regeneration within the specified time period, the engine-ECU restarts the DPF regeneration control.

EXHAUST DIFFERENTIAL PRESSURE SENSOR

The exhaust differential pressure sensor is installed to the right side of engine compartment bulkhead, the back of heat insulation material. The exhaust differential pressure sensor detects the pressure difference between the upstream of DPF and the atmosphere, and outputs the voltage to the engine-ECU according to the pressure difference.

EXHAUST GAS TEMPERATURE SENSOR

The exhaust gas temperature sensor is mounted to the upstream side of the DPF. This detects the exhaust temperature using the thermistor and outputs the voltage to the engine-ECU according to the temperature. This sensor has the characteristic that the resistance value decreases as the temperature increases. The engine-ECU uses this output voltage to control the DPF regeneration and monitors the exhaust gas temperature to protect the DPF.