FR2768176A1 - INTERNAL COMBUSTION ENGINE, ESPECIALLY FOR A MOTOR VEHICLE - Google Patents

Abstract

Internal combustion engine (1), in particular for a motor vehicle engine comprising means for burning an air / fuel mixture in a combustion chamber (4) with a catalyst (12) for treating the combustion gases. The catalyst (12) includes an accumulator catalyst (13) and an oxidation catalyst (14). Air supply means are provided upstream of the oxidation catalyst (14).

Description

State of the art

  The invention relates to a method for implementing an internal combustion engine, in particular a vehicle,

  in which a fuel / air mixture is burnt in a combustion chamber and the exhaust gases from the combustion are treated with a catalyst, the catalyst (12)

  used to reduce nitrogen oxides and to oxidize hydrocarbons and / or carbon monoxide. The invention also relates to a motor with com-

  internal bustion in particular for a motor vehicle, comprising means for combustion of a fuel / air mixture

  in a combustion chamber and a catalyst for treating the exhaust gases released by combustion, the catalyst comprising a catalyst-accumulator and an oxidation catalyst.

  Such a method and such an internal combustion engine

  dull are known according to document DE 195 06 980 C2. In this document, the exhaust gases from combustion are supplied to a catalyst intended, among other things, to reduce nitrogen oxides. On the one hand, such a catalyst functions as an oxidation catalyst, which means that in the event of a lack of oxygen, it takes oxygen from the nitrogen oxides and oxidizes the hydrocarbons from combustion as well as the possible

  carbon monoxide. The excess oxygen would allow the ca-

  oxidation catalyst also reduce nitrogen oxides.

  Due to excess oxygen, this reaction does not occur.

  not, however, and the oxidation catalyst used

  excess oxygen. Furthermore, the catalyst mentioned above

  above works as a catalyst-accumulator. That means

  fie that in case of excess oxygen the catalyst absorbs nitrogen oxides resulting from combustion and in case of lack

  of oxygen, it restores the absorbed nitrogen oxides.

  The use of the oxidation catalyst and the ca-

  talyseur-accumulator in the catalyst mentioned above makes it possible to take nitrogen oxides which cannot be used by the oxidation catalyst in the event of an excess of oxygen, in the catalyst-accumulator and to temporarily ensure their

  storage. In case of lack of oxygen, the catalyst-

  accumulator can restore nitrogen oxides to replenish them

  poured by the oxidation catalyst. The catalyst-accumulator can receive only a limited mass of nitrogen oxides. As a result, the catalyst-accumulator must be discharged again after a certain charging time during which it takes oxy-

  nitrogen. This discharge takes place in the event of a lack of oxygen. This is why, the internal combustion engine is controlled and / or adjusted so as to have a rich fuel / air mixture. Under these conditions, the catalyst-accumulator resti-

  kills the nitrogen oxides that will be used in the oxidation catalyst to oxidize hydrocarbons and / or carbon monoxide. As reaction products we get nitrogen,

water and carbon dioxide.

  It has been found that such a discharge of the cataly-

  seur-accumulator, frequently gives an excess of hydrocarbon and carbon monoxide. This excess cannot be oxidized by the oxygen released from the nitrogen oxides, so that the hydrocarbons and / or carbon monoxide are discharged into the environment when they are pollutants. The object of the present invention is to develop a method and an internal combustion engine corresponding to the

  type defined above, allowing in all cases an oxy-

  complete information on carbohydrates and / or monoxides

bone.

  This problem is solved by a process of the type

  finish above, characterized in that air is supplied to the catalyst. The air supply oxidizes the hydrocarbons and carbon monoxide which separate from the nitrogen oxides and are oxidized by the oxygen contained in the supply air. An excess of hydrocarbons and carbon monoxide can thus be eliminated by an air supply. This converts all of the hydrogen and carbon monoxide in the water and the carbon dioxide. Under these conditions, the harmful components of hydrocarbons and / or carbon monoxide are no longer simply released to the outside. The method according to the invention can be used on internal combustion engines with injection of fuel into the suction pipe and preferably in mo-

  torers which operate with a lean fuel / air mixture.

  Furthermore, the method according to the invention can be applied to an internal combustion engine in which the fuel is

  injected directly into the injection chamber.

  It is particularly advantageous to supply air during the operating phase during which

  the internal combustion engine has a lack of oxygen.

  This is precisely the operating phase in which the excess of hydrocarbons or carbon monoxide occurs most strongly. The air supply in the operating phase guarantees complete oxidation

  hydrocarbons and carbon monoxide.

  According to an advantageous development of the invention, a pump provides the air supply. This guarantees the air supply even if a vacuum prevails in the

  catalyst due to the passage of exhaust gases. In or-

  tre, the pump can be controlled by a control device according to the respective operating phase, that is to say

  that it can be started or cut.

  According to an advantageous development of the invention, a valve controlled in particular by the control device is mounted upstream of the oxidation catalyst. It allows very precise control and / or regulation

  the air supply to the oxidation catalyst.

  It is particularly advantageous that a non-return valve is provided upstream of the oxidation catalyst. It safely prevents exhaust gases from escaping from the catalyst before they are oxidized and / or

  that exhaust gases do not reach the pump.

  The present invention will be described below in more detail with the aid of the single appended figure which shows a block diagram of an exemplary embodiment of an internal combustion engine of a motor vehicle according to the invention. The figure shows an internal combustion engine 1

  with a reciprocating piston 2 movable in a cylinder 3. The cy-

  lindre 3 comprises a combustion chamber 4 to which a suction pipe 6 and an exhaust pipe 5 are connected by valves 5. The combustion chamber 4 is also equipped with an injector 8 and a spark plug

ignition 9.

  In a first mode of operation, that is to say

  say the stratified operating mode of the combustion engine

  internal tion 1, the fuel is injected by the injector 8

  in the combustion chamber 4 during the compression phase

  sion generated by piston 2 and this locally in

  the direct environment of the spark plug 9 and timing-

  gically, directly before the piston 2 reaches its top dead center. Then, the spark plug 9 ignites the fuel so that in the next phase, the piston 2 is driven by the

expansion of the ignited fuel.

  In a second mode of operation, that is to say

  say the homogeneous mode of the internal combustion engine 1, the fuel is injected by the injector 8 into the combustion chamber 4 during the suction phase produced by the piston 2. The air sucked in at the same time creates turbulence in the injected fuel which is evenly distributed in

  the combustion chamber 4. Then, we compress the car-

  burant / air during the compression phase and the

  spark plug 9. Expansion of the ignited fuel

drags piston 2.

  ) In stratified mode, as in homogeneous mode, the driven piston turns a crankshaft 10 which finally

drives the vehicle wheels.

  In stratified mode and in homogeneous mode, the mass of fuel injected by the injector 8 into the combustion chamber 4 is controlled and / or regulated by the

  command 11, in particular to minimize consumption

  tion of fuel and / or exhaust gases. For this, the control device 11 comprises a microprocessor whose memory, in particular a ROM memory (read-only memory) contains

  a program for executing the command and / or regulation. The exhaust pipe 7 is connected to a cat-

  lyser 12 comprising a catalyst-accumulator 13 for storing nitrogen oxides and an oxidation catalyst 14 for ensuring oxidation, in particular of hydrocarbons and carbon monoxide. The accumulator catalyst 13 is located upstream of the oxidation catalyst 14 in the direction of passage

exhaust gases.

  Depending on the ratio of fuel / air mixture set by the control unit 11, there are in the

  combustion 4 of engine 1, i.e. an excess of oxygen,

  that is to say a lean mixture, i.e. a lack of oxygen, that is to say

  say a rich mixture or the stoichiometric ratio

  between fuel and air. The rich mixture can be adjusted in particular

  homogeneous mode for engine 1 while adjusting the lean mixture to reduce consumption, in particular by

laminate mode.

  In case of excess oxygen, the oxidation catalyst 14 could reduce the nitrogen oxides sent to the

  catalyst 12 and thereby extract oxygen from the nitrogen oxides.

  Due to the excess oxygen, the oxidation catalyst 14 does not take up the excess oxygen. The nitrogen oxides not used by the oxidation catalyst 14 are then taken up by

  the catalyst-accumulator 13 to be stored. This constitutes

  kills the loading phase of the catalyst-accumulator 13;

  in this phase the nitrogen oxides arrive on the cataly-

sister 12.

  In case of lack of oxygen, the catalyst-

  accumulator 13 restores the accumulated nitrogen oxides. That

  corresponds to a catalyst discharge operation-

  accumulator 13 for which the nitrogen oxides leave the case

  talyseur 12. Due to the lack of oxygen, it was not sufficient

  enough oxygen so that the oxidation catalyst 14

  takes oxygen from nitrogen oxides to oxidize hydrocarbons

  bures and carbon monoxide resulting from combustion.

  The catalyst-accumulator 13 cannot store limited quantities of nitrogen oxides. For this reason, it

  the loading operation must be limited in time. Then, the catalyst-accumulator 13 must again be emptied. These 5 loading and unloading operations are controlled and / or regulated by the control device 11 by a power supply.

  appropriate oxygen intake. The oxygen supply is made by the operation of the motor 1 in homogeneous mode or in stratified mode. In particular, to influence the oxygen supply, a throttle valve is used.

  fitted to the suction pipe 6.

  Means are provided between the catalyst-

  accumulator 13 and oxidation catalyst 14 to provide

air to catalyst 12.

  In the exemplary embodiment shown in FIG.

  gure, the means consist of a tube 16 connecting the cataly-

  12 to a controlled pump 17. In addition, the tube 16 has an integrated valve 18. The pump 17 can be started or cut for example by the control device 11. The valve 18 can also be opened or closed by

the control unit 11.

  Alternatively, instead of the controlled valve 18, it is also possible to have a non-return valve or the like and / or to make the pump 17 not controlled,

  that is to say to make it work permanently.

  In the exemplary embodiment shown in FIG.

  gure, when the catalyst-accumulator 13 is discharged, that is to say in the event of a lack of oxygen, the pump 17 is connected and the valve 18 is opened. Air and thus oxygen

  additional arrive on the oxidation catalyst 14.

  As in the event of an oxygen fault, i.e. for a

  lange fuel / rich air, we have more hydrocarbons and / or carbon monoxide, which are oxidized on the one hand by the oxygen taken on nitrogen oxides and on the other hand by oxygen

additional air extract.

  To charge the catalyst-accumulator 13, the valve 18 is closed. The pump 17 can continue to run or

to be arrested.

  Alternatively, even when the catalyst is charged-

  accumulator 13, i.e. in case of excess oxygen and

  thus for a leaner fuel / air mixture, it is pos-

  open the valve 18 and let the pump 17 run.

  In this case, the valve 18 can be replaced by a non-return valve already mentioned, which in particular prevents the gases

  do not reach the pump 17.

Claims (3)

R E V E N D I C A T I ON S   1) Method for using an internal combustion engine (1), in particular a vehicle, according to which a fuel / air mixture is burned in a combustion chamber (4) and treated with a catalyst (12 ) the exhaust gases from combustion, - the catalyst (12) serving to reduce nitrogen oxides and to oxidize hydrocarbons and / or carbon monoxide, characterized in that   air is supplied to the catalyst (12).   ) Method according to claim 1, characterized in that the air is supplied during an operating phase when the internal combustion engine (1)   works with a lack of oxygen.   3) Internal combustion engine in particular for a motor vehicle comprising means for combustion of a mixture   fuel / air in a combustion chamber (4) and a   talyser (12) for treating the exhaust gases released by combustion, - the catalyst (12) comprising a catalyst-accumulator (13) and an oxidation catalyst (14), characterized in that means are provided upstream oxidation catalyst   (14) to ensure an air supply.   4) Internal combustion engine according to claim 3, characterized by a pump (17) for supplying air.    ) Internal combustion engine according to one of Claims 3 or 4, characterized by   a valve (18) controlled, in particular by a control device   valve (11), this valve being mounted upstream of the catalyst oxidation (14).   ) Internal combustion engine according to one of the claims   tions 3 or 5, characterized by a non-return valve mounted upstream of the catalyst oxidation (14).