Exhaust emission control

Details Exhaust emission control Exhaust emission control

1992-08-13

1993-11-30

Cross, E. Rollins

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

60300, 1231425R, 123 4108, F01N 300, F02N 1702, F01P 714

Patent

active

052654184

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the controlling of the operation of internal combustion engines, in order to improve the control of the level of emissions in the exhaust gases, particularly during engine warm-ups.
It is recognised that it is generally more difficult to control the level of exhaust emissions and to achieve stable operation of an engine in the low load range, as compared with the higher ranges of engine load. It is also recognised that these difficulties increase when the engine is at a low operating temperature, such as may exist after an initial start up of the engine.
Further, in regard to engines operating with catalytic converters in the exhaust system, these catalysts do not become effective until they have reached an effective operating temperature generally referred to as "light off" temperature of the catalyst. This light off of the catalyst is generally dependent upon the heat input to the catalyst by the exhaust gases and this is dependent upon the exhaust gases being of a sufficiently high temperature to rapidly effect heating of the catalyst to light off temperature.
It is therefore the object of the present invention to provide a method and means for operating an internal combustion engine which will contribute to overcoming or reducing the above problems and to the achievement of improved control of the exhaust emissions.
With this object in view, there is provided according to the present invention, a method of operating an internal combustion engine, characterised by, at least when the engine is operating under idle and/or low load conditions at a temperature below a predetermined value, applying a parasitic load to the engine to increase engine fuel demand, and increasing fueling rate to the engine in response to said engine fuel demand to thereby raise the temperature of the exhaust gases.
By raising the temperature of the exhaust gases, the rate of rise of the operating temperature of the engine and of the temperature of the catalyst is increased, thus the engine reaches stable operating conditions more quickly and the period of time required to light off the catalyst is reduced, thus reducing the period of engine operation without effective treatment of the exhaust gases by the catalyst.
It will be appreciated that the use of the parasitic load is not always necessary at all engine start ups; as where the engine has previously been operating, the operating temperature of the engine and the temperature of the exhaust gases may be sufficiently high to achieve quickly effective operation of the engine and light off of the catalyst. Accordingly, in order to obtain improved fuel efficiency, the parasitic load is only applied to the engine when start up occurs while the temperature of the engine is below a predetermined value, that value being selected for the particular engine to be a temperature at which the engine will operate at an acceptable level of stability and light off of the catalyst will be achieved within a relatively short acceptable time interval from engine start up.
It has been found that the present invention is particularly relevant to the operation of two stroke cycle engines as such engines have less built in running loads and generally lower exhaust temperatures than four stroke cycle engines that incorporate valve mechanisms which apply a significant load to the engine. However, it is to be understood that the present invention does have application to engines operating on the four stroke cycle and will, in such engines, contribute to improvement in the stability of the engine operation and the effectiveness of the catalyst system.
The method of the present invention may be further characterised by raising the temperature of the air being inducted into the engine or directly heating the catalyst in the exhaust system. It is to be appreciated that the raising of the temperature of the inducted air will further contribute to increasing the rate of rise of the operating temperature of the engine, and raising the temperature of the exhaust gases, each of which wil

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