Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1986-10-08
1988-05-31
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
Methods
60285, F01N 302
Patent
active
047472642
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the automatic regeneration of a soot filter in an exhaust gas line of a diesel-internal combustion engine (diesel engine) in a passanger vehicle, using a throttle valve, operable by means of a control device, in the intake line in order to achieve an exhaust temperature corresponding to the ignition temperature of the soot accumulated in the soot filter in dependence on measured variables forming input signals for the control device, namely at least the speed of the diesel engine, the back-pressure of the soot filter and the exhaust temperature.
In a known system for regenerating a soot filter (U.S. Pat. No. 4,211,075), a throttle valve in the intake air line is controlled in such a manner that in certain operating conditions, as a result of closing the throttle valve and the resulting reduction in the air supply, the exhaust temperature rises, with the result that in a soot filter provided in the exhaust line the ignition temperature of the soot deposited there is achieved. By maintaining this condition for some minutes, it is possible to regenerate the soot filter in that the soot which has accumulated there is completely burned up.
It is a prerequisite in this system that during the regenerating process the engine is driven in the upper part-load range, which in a vehicle drive means either at a high speed or when overcoming a gradient. In the lower part-load range on the other hand, the exhaust temperatures required for igniting the soot accumulated in the filter are not normally achieved; in order in this case also to permit a periodic regeneration, additional heating devices are provided. In the known system, the throttle valve position is controlled by a microcomputer, the input signals of which correspond to the following measured variables: accelerator pedal position, engine speed, exhaust temperature upstream of the soot filter, temperature inside the soot filter. The regenerating process may be initiated automatically or by hand. A variable control of the throttle valve taking into account the measured variables mentioned, is intended to ensure that, for the protection of the soot filter, the filter temperature does not exceed a specific maximum value, and that there is a lower excess of oxygen in the exhaust gas for the suppression of smoke while the soot which has accumulated in the soot filter is burnt off.
In a purely temperature-dependent control of the regenerating process, there is a risk that at full load or, if excluded by a protective function, at operating states in the upper part-load range, uncontrolled regenerations will commence, which moreover are not dependent on the actual contamination of the filter. Frequent regeneration processes mean, however, a higher fuel consumption and greater contamination of the soot filter. In addition, when the engine is in overrun operation with the throttle valve open, high filter temperatures may occur even when the filter is empty, and thereby initiate unnecessary and unwanted regenerating processes.
In contrast, in a process of the type mentioned in the introduction, the present invention is based on the problem of achieving a controlled, automatic regeneration of the soot filter dependent on defined operating conditions of the car, a specific discharged state of the soot filter being achieved once a regeneration process has ended.
This problem is solved in accordance with the invention by the following system logic:
1. The speed n of the diesel engine, the back pressure PVF measured upstream of the soot filter and the exhaust temperature are each compared with present lower limit values ng, PGU, TGU.
2. The back pressure PVF is additionally compared with a preset upper pressure limit PGO.
3. When all measured variables lie above the limit values mentioned, the control device generates a signal "close throttle valve".
4. The two limit values for the pressure, PGU and PGO, are shifted with the speed (n) in accordance with their respective alteration.
By fixing lower limit values for the speed, the back pres
REFERENCES:
patent: 4211075 (1980-07-01), Ludecke
patent: 4450682 (1984-05-01), Sato
patent: 4462208 (1984-07-01), Hicks
patent: 4492079 (1985-01-01), Takagi
patent: 4509327 (1985-04-01), Enga
patent: 4522027 (1985-06-01), Hasegawa
patent: 4566271 (1986-01-01), French
Kugland Peter
Santiago Enrique
Ullmer Alois
Hart Douglas
Zeuna-Srarker GmbH & Co. KG
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