Internal combustion engine exhaust system equipped with pollution reduction systems

Abstract

Exhaust system for an internal combustion engine ( 1 ) of a motor vehicle which is equipped with a first oxidation catalytic converter or precatalytic converter ( 4 ) positioned near the outlet of gas from the engine, and with a particulate filter ( 9 ) associated with a second oxidation catalytic converter ( 8 ) these being positioned downstream of the precatalytic converter. It comprises first means for generating an increase in the temperature of the gases leaving the engine ( 1 ), second means for generating an exothermal reaction in the precatalytic converter ( 4 ) and third means ( 5 ) for generating an exothermal reaction in the catalytic converter ( 8 ) so as to split the burden of generating the increase in exhaust gas temperature required for regenerating the particulate filter ( 9 ) between the engine, the precatalytic converter and the catalytic converter.

1 . Exhaust gas line for a motor vehicle internal combustion engine, equipped with a first oxidation catalyst, or pre-catalyst, placed near the engine exhaust exit, and a particulate filter associated with a second oxidation catalyst placed downstream of the pre-catalyst,
 which comprises first means capable of producing a degradation in combustion efficiency in order to raise the temperature of the gas exiting the engine, second means for generating an exothermic reaction in the pre-catalyst, and third means for generating an exothermic reaction in the catalyst, so as to distribute the task of raising the exhaust gas temperature, required for regenerating the particulate filter, between the engine, the pre-catalyst and the catalyst.   
   
   
       2 . Exhaust line according to  claim 1 ,
 wherein the degradation in combustion efficiency is achieved by retarding the main fuel injection, i.e., with an injection that is later relative to the top dead center (TDC) of the cycle.   
   
   
       3 . Exhaust line according to  claim 2 ,
 wherein the main injection is retarded by 2 to 20° crank angle relative to a normal injection.   
   
   
       4 . Exhaust line according to  claim 1 ,
 wherein the degradation in combustion efficiency is achieved by reducing the quantity of air taken into the engine.   
   
   
       5 . Exhaust line according to any of the preceding claims,
 wherein the means for raising the temperature of the gas exiting the engine make it possible to obtain gas temperatures between 200 and 650° C. upstream of the pre-catalyst.   
   
   
       6 . Exhaust line according to any of the preceding claims,
 wherein the means for generating an exothermic reaction in the pre-catalyst are capable of initiating a fuel post-injection phase in the engine. angle.   
   
   
       7 . Exhaust line according to  claim 6 ,
 wherein the post-injection is late and is between 90 and 240° crank   
   
   
       8 . Exhaust line according to  claim 1 ,
 wherein the temperature of the exothermic reaction in the pre-catalyst is between 20 and 200° C.   
   
   
       9 . Exhaust line according to  claim 1 ,
 wherein the means for generating an exothermic reaction in the catalyst is a fuel introduction device located between the pre-catalyst and the catalyst.   
   
   
       10 . Exhaust line according to  claim 1 ,
 wherein the temperature of the exothermic reaction in the catalyst is between 20 and 300° C.   
   
   
       11 . Exhaust line according to  claim 1 ,
 wherein the three means for heating the exhaust gas are activated successively according to the difference between the temperature of the gas at the engine exit and the temperature needed at the upstream end of the particulate filter in order to carry out the regeneration thereof.   
   
   
       12 . Exhaust line according to  claim 1 ,
 wherein at least two of the means for heating the exhaust gas are activated simultaneously.   
   
   
       13 . Exhaust line according to  claim 12 ,
 wherein the two exothermic reactions are produced simultaneously and controlled so as to achieve the best compromise between HC treatment and fuel consumption.   
   
   
       14 . Exhaust line according to  claim 1 ,
 wherein, at high engine speeds and medium and high loads, the means for raising the temperature of the gas exiting the engine are given precedence over the other two means for heating the gas.   
   
   
       15 . Exhaust line according to  claim 1 ,
 wherein control of the heating means is preset by mapping.   
   
   
       16 . Exhaust line according to  claim 1 ,
 wherein control of the heating means is by closed-loop regulation.   
   
   
       17 . Exhaust line according to  claim 16 ,
 wherein regulation uses one or more temperatures recorded by sensors at various points in the exhaust line.   
   
   
       18 . Exhaust line according to  claim 16 ,
 wherein regulation of the means that generate the exothermic reactions takes the exhaust gas flow rate into account.   
   
   
       19 . Exhaust line according to  claim 16 , characterized in that when the means for raising the temperature of the gas exiting the engine operate by retarding the main injection, regulation acts on the retard angle thereof 
   
   
       20 . Exhaust line according to  claim 16 ,
 wherein, in order to regulate the exothermic reaction on the pre-catalyst, the quantity and timing of the post-injection is adjusted.   
   
   
       21 . Exhaust line according to  claim 9 ,
 wherein, in order to regulate the exothermic reaction on the catalyst ( 8 ), the average flow rate of the fuel injected into the exhaust is controlled.   
   
   
       22 . Exhaust line according to  claim 1 ,
 wherein, in order to control the strategy for raising the gas temperature, the preset mapped and closed-loop regulation control modes are combined.   
   
   
       23 . Exhaust line according to  claim 22 ,
 wherein mapped regulation of engine heating is coupled with regulation by sensor for the exothermic reactions in the pre-catalyst and catalyst.   
   
   
       24 . Exhaust line according to  claim 1 ,
 wherein, during the regeneration phase, the means for heating the exhaust gas are used continuously.   
   
   
       25 . Exhaust line according to  claim 1 ,
 wherein, during the regeneration phase, the means for heating the exhaust gas are used intermittently.   
   
   
       26 . Exhaust line according to  claim 1 ,
 wherein, during the regeneration phase, the means for heating the exhaust gas are used in continuously variable quantities.   
   
   
       27 . Exhaust line according to  claim 1 ,
 wherein the catalyst is located upstream of the particulate filter.   
   
   
       28 . Exhaust line according to  claim 1 ,
 wherein the catalyst and the particulate filter are integrated onto the same support.   
   
   
       29 . Exhaust line according to  claim 1 ,
 wherein the fuel has an additive to promote particulate filter regeneration.