FR2742808A1 - METHOD AND DEVICE FOR CONTROLLING AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Method and device for controlling an internal combustion engine with first means for measuring the fuel supplied to the engine. Second means carry out a treatment at the outlet of the exhaust gases by dosing additional fuel which reacts with the exhaust gases. A signal corresponding to the quantity of additional fuel is predetermined from a signal (MNOX) which corresponds to the quantity of nitrogen oxides to be reduced, and a coefficient (X).

Description

STATE OF THE ART The invention relates to a method and a device for

  controlling an internal combustion engine, according to which first means of the engine measure the fuel burned in the engine and second means carry out a treatment at the outlet of the exhaust gases and according to which additional fuel is metered which reacts with the treatment means exhaust gases. Such a method and such a device for controlling an internal combustion engine are already known according to document EP-A 0 621 400. This document describes a method and a device

  to control an internal combustion engine consisting of

  fuel burnt by the engine. In addition, a catalyst is provided. The fuel is dosed for the engine so that part of the fuel is released unburnt through the exhaust gas lines, into the catalyst to react with the

nitrogen oxides (NOX).

  This quantity of additional metered fuel must be defined very precisely because if the quantity is too small, the reaction is insufficient and, if the quantity is too large, unburnt hydrocarbons (HC) are expelled with

the exhaust gas.

  OBJECT OF THE PRESENT INVENTION The aim of the present invention is to develop the method and the device for controlling an internal combustion engine corresponding to the type defined above, so that the

  quantity of fuel is dosed in order to minimize emissions-

  exhaust gases and in particular components

NOX and HC.

Advantages of the invention

  The invention relates to a method of the type defined above.

  above, characterized in that a signal which corresponds to the quantity of additional fuel, predetermined from

  of a signal, corresponds to the quantity of nitrogen oxides to be

  duire, and is predetermined by a coefficient.

  The invention also relates to a device for

the implementation of this process.

  The means of the invention make it possible to minimize

NOX and HC emissions.

  According to other advantageous characteristics of the invention: - the signal corresponding to the quantity of nitrogen oxides to be reduced, is predetermined according to the different

  operating parameters; - the signal which corresponds to the quantity of fuel

  additional rant, is reduced by a value corresponding to the gross emission of hydrocarbons;

  - the amount of additional fuel is limited

  tée at the maximum authorized value;

  - the amount of additional fuel is addi-

  until it reaches a predetermined value; - as operating parameters, we take

  account of the rotation speed of the internal combustion engine

  dull, the amount of fuel injected, and a temperature signal;

  - the additional fuel is metered if the temperature

  erasure of the second means is within a range of pre-

determined;

  - the temperature of the second means is simulated by-

  shooting at least the speed of rotation and the amount of

fuel injected.

  The invention also relates to a device for

  the implementation of this process, this device being characteristic

  se in that means which predetermine a corresponding signal

  to the quantity of additional fuel, starting from a signal which corresponds to the quantity of nitrogen oxides to be reduced,

and a coefficient.

  Drawings The invention will be described below using a

  embodiment shown in the drawing, the only figure of which

  gure is a block diagram of the invention.

  Description of the exemplary embodiment

  The reference 100 designates an adjustment element fixing the quantity of hydrogen or of hydrocarbons. This control element receives an MHC signal corresponding to the quantity of hydrocarbons to be dosed. This MHC signal is supplied by a combination point 105. This combination point receives the MHCS output signal from a summation point 110 and the output signal

TF of a filter 120.

  Summation point 110 receives an MHCK signal which

  is the output signal from combination point 125. The first

  first input of the combination point 125 receives the output signal from a minimum selector 130 the first input of which receives an MHCW signal corresponding to the output signal of a

  combination point 132. The first entry of the combination point

  naison 132 receives the MHCT signal with an algebraic signal po-

  sitive; this signal corresponds to the output signal of a combination point 134. The first input of the combination point 134 receives an MNOX signal corresponding to the output signal of a

  combination point 136. The first entry of the combination point

  naison 136 receives the output signal from a junction point

  138 whose first input receives a NOXG signal.

  This NOXG signal is provided by a character field.

  NOX 140 attributes. Characteristic field 140 is requested

  cited by a speed signal N supplied by a speed sensor 142 and a fuel control

  144 which defines the quantity of QK fuel to be injected. The se-

  as input to combination point 138 receives a NOXT signal

  from a field of mo warming characteristics

  145. The reheating characteristics field receives the temperature TW of the cooling water which has been determined using a temperature sensor 147. The combination of the

  combination point 138 is preferably done by multiplica-

tion.

  The second entry of combination point 136 re-

  receives the NOXE output signal from an exhaust gas reinjection control 150. This regulation 150 processes the output signal from a combination point 152. The first input from the combination point 152 receives the signal ES of positive sign which comes from the exhaust gas reinjection characteristics field 154. In this characteristics field, the signal ES is recorded independently of the rotation speed N and of the quantity of fuel QK. The second input of the combination point 152 receives the signal EI preceded by a negative sign coming from the training circuit of average value 156. The combination at the combination point 136 is preferably carried out

by addition.

  The second input of the combination point 134 receives an output signal X from a coefficient characteristic field 160. The coefficient characteristic field also receives the speed of rotation N and the quantity of fuel to be injected QK. The combination at the combination point

  134 is preferably done by multiplication.

  The second entry of combination point 132 re-

  receives a mechanical signal MHCR with a negative algebraic signal

  tif; this signal corresponds to the output signal of a point of

  combination 162. The combination in point 132 is preferably

reference by addition.

  Combination point 162 receives an HCG output signal from an HC characteristic field, 165, as well as a

  HCT output signal of a temperature characteristic field

  ture 170. The HC characteristic field means that this large

  HCG depends on the rotation speed N and the quantity

  of fuel to inject QK. The HCT value of the character field

  Temperature characteristics 170 depends on the temperature of the TW cooling water. The combination at the combination point

  162 is preferably done by multiplication.

  The second input of the minimum selector 130 re-

  receives an MHCM signal of a limiting characteristic field

  tion 175 receiving as input variable, the speed of

  rotation N and the quantity of QK fuel to be injected.

  The second input of the combination point 125 which combines the two signals preferably by addition, receives the output signal DHC from a dynamic correction means 182

  processing in turn the output signal of a DT1 180 filter

  cevant the amount of QK fuel to inject.

  The second entry of combination point 105 re-

  receives the output signal TS from a temperature-dependent filter 120. The filter 120 works a temperature signal T supplied to a combination point 190. The first input of the

  combination point 190 receives a signal from a combination point

  naison 191. The first entry of the combination point 191 re-

  receives a temperature signal TK supplied by a time sensor

  temperature mounted downstream of the catalyst. The second input of the combination point 191 receives a signal T4 already supplied by a combination point 192. The first input of the combination point

  naison 192 receives an output signal from a character field

  tick 196 which deals with the speed of rotation and the quantity of fuel. The second entry of the combination point 192 receives

  the output signal from a temperature characteristic field

  ture 194 which treats the temperature of the cooling water TW. Combination point 192 combines the two sizes of

  preferably by multiplication. Combination point 191

  bin the two input signals preferably by addition. The second input of the combination point 190 receives the signal

  exit from a circuit predetermining a coefficient 198. The com-

  pairing at the combination point 190 is preferably done by multiplication. The installation described above operates as follows: Starting from at least the speed of rotation N and the quantity of fuel QK to be injected, the quantity NOXG is recorded in the characteristic field NOX 140. It

  this is the amount of nitrogen oxides NOX also contained

  naked in the exhaust gases. This NOXG value thus obtained is multiplied at the combination point 138 by a NOXT comparison coefficient which comes from the field of heating characteristics. This field of characteristics takes into account the influence of the engine temperature or the temperature

  cooling water for NOX emission.

  Correspondingly, the reinjection coefficient

  tion of the exhaust gases is recorded in the field of

  exhaust gas reinjection characteristics 154 as a function of the same input quantities. Based on the deviation from the regulation of the exhaust gas reinjection applied

  at the exit from the combination point 152, the reinforcement regulation

  exhaust gas junction 150 provides the quantity NOXE by which the quantity NOXG is corrected. This correction is done

  at combination point 136 preferably by addition.

  The NOXE quantity takes into account the correction of the deviation post-injection compared to standard conditions. For example, for a lower atmospheric pressure or a higher air temperature, by comparison of the air mass of the field of basic characteristics 154, the exhaust gas reinjection is adjusted according to the

  quantity of fresh air, measured, EI. Thus, for post-injection, there is no need to take into account once again the influence of atmospheric pressure and the temperature10 of the aspirated air.

  At the output of the combination point 136, there is the signal MNOX which corresponds to the amount of NOX to be reduced.

  This signal which gives a measure of the quantity of nitrogen oxides to be reduced, is predetermined according to different parameters of

  operation such as the rotation speed N of the internal combustion engine, the quantity of fuel QK at in-

  eject, as well as the temperature signal TW. The relationship between the quantity of NOX to be reduced and the quantity of HC hydrocarbons required results from the following equation: HC = X * NOX. The coefficient X depends on the coating of the catalyst; if necessary, other quantities can also be taken into account. This coefficient X is provided in the field of characteristics 160, independently of the speed of rotation and the quantity of fuel QK. In point 134, the calculated quantity MNOX of nitrogen oxides NOX emitted is multiplied by the

  coefficient X. At the exit from the combination point 134, we have

  installation of an MHCT signal indicating the quantity of fuel

additional, necessary.

  At the exit from the combination point 134, there are

  of the MHCT signal which corresponds to the quantity of hydrocarbons ne-

  necessary to oxidize the quantity MNOX of nitrogen oxides NOX.

  This quantity MHCT is defined on the basis of the quantity of NOX to be reduced and the coefficient X predetermined according to the parameters

Operating.

  In the field of characteristics 165 is recorded the gross emission of HCG hydrocarbons generated by combustion as a function of the rotation speed N and the quantity of

  QK fuel. This gross HC emission, released by the combustion-

  tion, does not have to be dosed because it is already contained in the exhaust gas. This HCG value of the gross emission

  of hydrocarbons is corrected using a character field

  HCT ticks as a function of temperature in point 162. The quantity

  required amount of oil is reduced to the point of

  combination 132 of this corrected MHCR value.

  An extremely reliable MHCM value for the additional quantity of fuel to be dosed is entered in the field.

  limit 175. The minimum selection 130 limits the quantity of additional fuel to be metered MHCW, to the maximum authorized value MHCM. This means that the smaller of the two values is used. At combination point 125, the value is corrected

  limited by a DHC correction coefficient containing a cor-

dynamic rection.

  At summation point 110, the quantity of additional fuel to be metered MHCK is added until the minimum quantity which is injected by the metering system used is reached. When the threshold value is exceeded, we

  dose the minimum amount at the next injection.

  The conversion of NOX in the reduction catalyst

  tion mainly depends on the temperature T in the cataly-

  sister. The temperature T of the catalyst is not measured directly. The temperature T4 upstream of the catalyst is simulated using the characteristic field 196, as a function of the quantity QK and of the rotation speed N. In addition, there is

  temperature compensation made using the cor-

  temperature rection 194 at the combination point 192. The temperature

  T4 temperature thus obtained upstream of the catalyst is added,

  at combination point 191, at the temperature downstream of the cat-

  TK lyser, captured by a sensor. Then at the combination point

  , we form the average value of the two values.

  The filter 120 takes into account that the catalyst only works satisfactorily in a certain temperature range. Therefore, it is expected that at

  temperatures below or above the temperature range

  tures, the value of the output signal TF of the filter 120 is set to the value 0 and that, in the temperature range in which the catalyst works satisfactorily, the signal of

  The output takes the value 1. The output signal from the combination point 105 is applied to the adjustment element 100. This adjustment element

  on the amount of additional fuel. For a first embodiment, provision is made for the adjustment element 100 to be

  tee in the exhaust gas line, and the additional fuel is injected directly into the exhaust gas. For another embodiment, provision is made for the adjusting element 100 to be an element which doses the fuel necessary for the combustion chambers for normal combustion.

  male. In this case, the adjusting element is controlled so that the unburned fuel arrives in the exhaust gas line. For this, after the injection proper, we dose to burn at the bottom dead center, that is to say at the time of gas exchange.

Claims (8)

CLAIMS R E V E N D I C A T I O N S   1) Method for controlling an internal combustion engine, according to which of the first means of the engine meters the fuel   burnt in the engine and second means carry out a treatment at the outlet of the exhaust gases, according to which additional fuel is metered which reacts with the means of treatment   exhaust gas, characterized in that a signal (MHCT) which corresponds to the quantity of additional fuel, predetermined from a signal (MNOX), corresponds to the quantity of oxides of nitrogen to be reduced, and is   predetermined by a coefficient (X).   2) Method according to claim 1, characterized in that the signal (MNOX) corresponding to the amount of nitrogen oxides to   reduce, is predetermined according to the different operating parameters.   3) Method according to one of the preceding claims, characterized in that   the signal (MHCT) which corresponds to the quantity of fuel   is reduced by a value (MHCR) corresponding to the gross emission of hydrocarbons.   4) Method according to one of the preceding claims,   characterized in that the amount of additional fuel is limited to the value maximum allowed (MHCM).    ) Method according to one of the preceding claims,   characterized in that the amount of additional fuel is added up to   reach a predetermined value.   6) Method according to any one of claims 1 to 5, characterized in that   as operating parameters, account is taken of the vi-   rotation size (N) of the internal combustion engine,   amount of fuel injected (QK), and a temperature signal ture (TW).   7) Method according to claim 1, characterized in that the additional fuel is metered if the temperature of the second   mean is within a predetermined range of values.   8) Process according to any one of the preceding claims.   tes, characterized in that the temperature of the second means is simulated from at least   the rotation speed (N) and the quantity of fuel in- thrown (QK).   9) Control device for an internal combustion engine   which of the first means of the engine measures the fuel burned in the internal combustion engine and of the second means   perform a treatment at the outlet of the exhaust gases,   positive which doses additional fuel reacting with the exhaust gas treatment means, according to one   any of claims 1 to 8,   characterized by means which predetermine a signal (MHCT) corresponding to the quantity of additional fuel, starting from a signal (MNOX) which corresponds to the quantity of nitrogen oxides to be reduced, and a coefficient (X).