Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1993-11-29
1995-09-12
Lazarus, Ira S.
Power plants
Internal combustion engine with treatment or handling of...
Methods
60276, 60289, F01N 320
Patent
active
054488850
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a test method for a device for injection of air into the exhaust gases of an internal combustion engine and, more particularly, to such a method permitting verification of the good mechanical condition of this device and the precision of regulation of the quantity of air injected, obtained with the aid of this device.
Ever more severe antipollution standards oblige the quantities of harmful gases ejected into the atmosphere by internal combustion engines to be reduced. To this end, vehicles are currently equipped these days with a "catalytic" converter arranged in the outlet line of the exhaust gases of the engine in order to oxidise or to reduce the said harmful gases, uncombusted hydrocarbons, carbon oxides, nitrogen oxides, etc. The correct operation of such a catalytic converter requires, as is well known, the presence of means of regulation of the air/fuel mixture supplying the engine. It is necessary, moreover, that the catalyst contained in the chamber is brought to a certain operating temperature, around 350.degree. C., for example.
On starting the engine from cold, however, the temperature of the latter and of the catalytic converter is substantially equal to ambient temperature and thus very far below the correct operating temperature of the catalytic chamber. Furthermore, during such starting, the air/fuel mixture supplying the engine is traditionally highly enriched in fuel. The result of this is that the exhaust gases of the engine then contain quantities of harmful gases, especially uncombusted hydrocarbons and carbon oxides, considered as excessive by certain antipollution standards.
In order to reduce these quantities of harmful gases which cannot then be processed by the catalyst, it has been thought to inject an oxidising gas, air for example, into the exhaust gases of the engine in order to oxidise the harmful products contained in these gases. In FIG. 1 of the attached drawing is represented a device for injection of air into the outlet line 1 of the exhaust gases of an internal combustion engine M. The device comprises a duct 2 connected to a filter 3 placed at the air intake of the inlet piping 4 of the engine M, an air pump 5 and a duct 6 connecting, through a regulating valve 7, the output from the air pump to the outlet line 1 for the exhaust gases of the engine, upstream from a chamber 8 containing an oxidising catalyst for the harmful gases contained in the exhaust gases.
The air is injected during starting of the engine in order to make up for the temporary inefficiency of the catalytic chamber 8 by bringing about, thanks to the oxygen contained in the air, oxidation of the hydrocarbons and the carbon oxides which is suitable for transforming at least a part of the latter into less harmful types (carbon dioxide, water, etc.). The quantity of air injected has to be regulated precisely. In fact, a lack of injected air would bring about incomplete oxidation reactions while an excess of air would bring about too great a cooling of exhaust gases, preventing any chemical reaction in the latter.
In order to do this, the valve 7 is driven by a computer 9 which is normally associated with the engine for controlling the fuel richness of the air/fuel mixture which supplies the engine, this richness being regulated by adjustment of opening time t.sub.i of at least one fuel injector 10 placed in the inlet piping 4. Conventionally also, an oxygen probe 11 is placed in the outlet line 1 of the exhaust gases in order to deliver a signal representing the oxygen richness of these exhaust gases to the computer 9.
The computer is duly programmed in order to, on the one hand, control, in closed loop, the fuel richness of the air/fuel mixture supplying the engine, with the aid of the signal delivered by the oxygen probe 11 and of an appropriate regulation of the opening time t.sub.i of the injectors 10 and, on the other hand, to control the rate of opening of the valve 7 of the device for injection of air into the exhaust of the engine, in the engine start phase. Conv
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Greenberg Laurence A.
Lazarus Ira S.
Lerner Herbert L.
O'Connor Daniel J.
Siemens Automotive S.A.
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