Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1997-01-22
1998-10-27
Denion, Thomas E.
Power plants
Internal combustion engine with treatment or handling of...
Methods
60284, 60285, 60295, F01N 300
Patent
active
058264256
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of automatically initiating regeneration of a particulate filter of a diesel engine with a rail injection system.
BACKGROUND ART
As is known, to safeguard the environment, increasing effort is being made, and in many countries tighter restrictions are being imposed, to control the exhaust of internal combustion engines.
As regards diesel engines in particular, the main problems are due to the presence in the exhaust gas of nitric oxides (NO.sub.x) and particulates, as opposed to a very low content of carbon monoxide (CO) and hydrocarbons (HC).
To minimize the particulate content of exhaust gas, some systems feature, along the exhaust line, a filter for retaining the unburned particles of which the particulate is composed, and which must therefore be cleaned ("regenerated") periodically by burning off the trapped particulate.
Since combustion of the particulate is naturally initiated automatically at high temperature--around 500.degree.-550.degree. C.--which is only reached in particular circumstances, some filters are fitted with heating elements which are activated periodically to heat the filter to the temperature at which combustion of the trapped particulate is initiated automatically. Other systems present a catalyst for reducing the initiating temperature to roughly 350.degree. C., which solution, however, is only effective under medium engine load conditions. In the case of prolonged low-load operation of the engine (e.g. town driving) and/or in the presence of low external temperatures (in winter), the temperature of the exhaust gas is lower than the combustion initiating temperature, so that the particulate gradually builds up on the filter, thus resulting in increased counterpressure, impaired performance, increased fuel consumption and possibly even stalling of the engine.
Moreover, in certain driving conditions, a high buildup of particulate may result in "critical" regeneration phenomena, in turn resulting in sudden, uncontrolled combustion of the particulate, heating inside the ceramic matrix of the filter, and damage to the filter itself.
A method for regenerating a particulate filter of a diesel engine according to the preamble of claim 1 is disclosed in EP-A-0 070 619, wherein a post-injection phase is carried out directly in the cylinders in the exhaust stroke so as to supply unburnt fuel to the filter. Regeneration of the filter is effected without causing a rise in the exhaust gas temperature.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a method of automatically initiating combustion of the particulate trapped in the filter, even under engine load conditions in which the exhaust gas temperature is not guaranteed equal to or above the initiating temperature of known systems.
According to the present invention, there is provided a method of automatically initiating regeneration of a particulate filter of a diesel engine comprising a main injection phase and an auxiliary post-injection phase including injection of fuel into the engine cylinders during the expansion stroke of the engine, characterized in that the injection is carried out through a rail injection system so as to generate post-injected fuel combusts causing a rise in the exhaust gas temperature of the engine.
BRIEF DESCRIPTION OF DRAWINGS
A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 shows a block diagram of a known diesel engine injection system;
FIG. 2 shows a graph of pressure and injection, in relation to the engine strokes, according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows schematically a diesel engine rail injection system 1 of the type to which the present invention relates. Of system 1, only the parts pertinent to the present invention are shown, the fuel conduits being indicated by continuous lines, and the dotted lines indicating the electric lines supplying the c
REFERENCES:
patent: 4452040 (1984-06-01), Kobashi
patent: 4509327 (1985-04-01), Enga
patent: 4565065 (1986-01-01), Kimura
patent: 4709547 (1987-12-01), Pischinger
patent: 5207058 (1993-05-01), Sasaki
patent: 5479775 (1996-01-01), Kraemer
Patent Abstract of Japan, vol. 17, No. 558 (M-1493), 7 Oct. 1993 for JP 05-156993.
Canale Silvio
Rossi Sebastiano Giovanni Maria
C.R.F. Societa Consortile per Azioni
Denion Thomas E.
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