FR2731469A1 - METHOD AND DEVICE FOR DETERMINING THE QUANTITY OF FUEL TO BE INJECTED WHEN RE-OPERATING A CYLINDER WHICH HAD BEEN FREE OF INJECTION - Google Patents

Abstract

a) Method and device for determining the quantity of fuel to be injected during the return to service of a cylinder which had been deprived of injection in an internal combustion engine, in which a base quantity of fuel to be injected is modified by an additional amount to inject. b) Method and device characterized in that the additional quantity to be injected for the first combustion is determined, after putting the cylinder back into service, as a function of the residual gases in the cylinder.

Description

"Method and device for determining the quantity of car-

  to be injected when a cy-

  lindre who had been deprived of injection "

State of the art

  The present invention relates to a method and a

  device for determining the amount of fuel

  injecting when returning to service a cylinder which had been deprived of injection in an internal combustion engine, in which a quantity of fuel base to be injected

  is modified with an additional amount of injection.

  For regulation of the traction control system (ASR) or in forced inertia operation mode, or

  for the limitation of the speed of rotation or the limitation

  the speed of the vehicle, temporarily

  injection different cylinders. When returning to

  vice of the cylinders which had been deprived of injection, the initial dosage of the fuel is decisive for the comfort of

  of the vehicle and for the emission of exhaust gas

  is lying. In the case of a selective injection system for cylinders, known from DE-43 28 835 A1, the excess fuel injected during the return to service of a cylinder which had been deprived of injection is determined according to the number of injection cycles that had

been deprived of injection.

Advantages of the invention

  Good values, in terms of

  of the vehicle and the emission of exhaust gas

  are obtained by virtue of the fact that the additional quantity to be injected for the first combustion is determined, after the return to service of the cylinder, in

  function of the residual gases in the cylinder.

  According to other features of the invention

  tion: - an additive superposition of a correction value, a function of the residual gases, and the value

  of the motor, a load value corrected at

  shot from which is determined by dividing by a factor

  predefined air volume, the quantity to be injected

  this setting air factor.

  - the quantity of fuel to be injected necessary for the adjustment

  the set air factor is modified by a quantity

  correction mark which is suitable for the compensation of a

amount of wall film.

  - the amount of correction is based on the difference

  number of wall films determined for

  two consecutive injection cycles.

  the quantity of correction is modified by an amount to be injected which comes from the superposition by addition

  a basic quantity to be injected and a value of cor-

  divided by a pre-set reference air factor

nor, function of the residual gases.

  - when the cylinder is connected, a correction value is formed which depends on the residual gas charge and

  the number of injection cycles that have been removed.

  - when connecting and disconnecting the cycle cyclically

  lighter with respectively a single injection

  Between two injection cycles, a correction value (dfgas) is generated which depends on the charge and the residual gases. The invention also relates to a device for implementing the above method, for determining the quantity of fuel to be injected at the time of restarting.

  vice of a cylinder which has been deprived of injection in a

  internal combustion engine, wherein said device modifies a base injection amount by an additional amount of injection, characterized in that

  means are provided for determining the additional quantity

  injection chamber according to the residual gases in the cylinder before it is put back into service, and

  what these means do not provide this additional quantity

  to inject only for the first combustion after the

commissioning of the cylinder.

  Drawings. The present invention will be described hereinafter in more detail with the aid of an embodiment shown in the accompanying drawings in which:

  FIG. 1 shows the block diagram of a system

  to determine a surplus of fuel to be injected after the re-commissioning of a cylinder and - Figure 2 shows a variant of a fragment of the diagram

in blocks according to Figure 1.

  Description of the exemplary embodiments.

  When returning to service a cylinder that had previously been deprived of injection, there is some residual gas mass. In particular in the case of a

  long injection of the cylinder, the gases

  Other products consist almost exclusively of fresh air. To ensure that in the cylinder the air factor X is equal to 1, a surplus fuel is injected once in the cylinder.

  each private injection cylinder at the time of

  vice, in addition to the compensation of the film effect of pa-

  king, surplus which preferably forms a stoichiometric relationship

metric with the residual gases.

  FIG. 1 shows the block diagram of a system which determines the injected fuel surplus necessary for the compensation of the wall film and the complete combustion of the residual gases during the first cycle of the return to service. of a cylinder. According to the present exemplary embodiment, it is determined, in block 100, from a characteristic field which depends on the angle of intersection of the camshaft wnwue and the speed of rotation n, the mass of the residual gases. dtlrgO in the case of a determined ambient pressure and a determined exhaust gas temperature, in thrust mode.

  Taking into account the actual pressure

  the ambient temperature and the actual exhaust gas temperature in the thrust mode, the

  actual residual mass dtlrg by means of

  tiplicatives fdkh and tab, the size fdkh indicating the

  ratio of the effective pressure of the atmosphere to

  and the predetermined pressure of the atmosphere

  astonishing, and the size tab indicating a function of the

  engine temperature and the temperature of the intake air.

  In the exemplary embodiment shown, the multiplicative quantity which is a function of the temperature of the exhaust gas tab is calculated for simplicity by means of a

  characteristic curve present in block 101, in function

  temperature of the motor tmot. When the angle of in-

  tersection of the camshaft wnwue is only a function of the speed of rotation n, the residual mass of the gases

  dtlrgO can be calculated also by means of a characteristic curve

  feature that depends on the speed of rotation.

  A correction value dtlrgs, which corresponds to the residual mass of the gases dtlrg, is then connected by means of a switch 102 to a summing point 103, when the first combustion cycle takes place during the

  commissioning of a cylinder which had been deprived of

  Eject. The switch 102 is controlled by a decommissioning signal B which, when the cylinder is deprived of injection, takes the value 1, and goes to zero when the cylinder is to be put back into service. The timing circuit 104 and the point of difference 105

  form the control signal itself for the communication

  102, so that the latter closes when the injection deprivation signal B passes from 1 to 0. During all the other cycles outside the first combustion cycle after the restarting, the switch 102

stays at zero.

  The correction value dtlrgs is superimposed on the charge value t1 by addition to the summation point 103, from which a quantity is outputted. Starting from the division of this quantity by a predefined air factor lCons in a block, one obtains the quantity of fuel to be injected necessary th in the first combustion cycle

  after restarting the cylinder.

  The quantity of fuel to be injected

  previously, does not arrive directly in the cylinder.

  dre, because of the effect of film on the walls. For this reason, we add to this quantity of injection

  additional fuel dtewf through

  The final result of this is the actual amount of injection ti which contains a surplus of fuel to be injected as a function of the residual gaseous mass in the cylinder to compensate for the film.

on the walls.

  The determination of the fuel supplement to be injected, which is necessary to compensate for the film on the walls, is also apparent from FIG.

  characteristic curve in block 108 and a

  in block 109, the constant quantity of the wfo wall film (value to be achieved) is calculated, when

  X = 1, depending on the value of the charge tl, of the

  rotation speed n and motor temperature tmot. The value to be reached of the quantity corresponding to the wall film wfo, is multiplied by a factor fwfrg which results

  of the division of the correction value dtlrgs correspon-

  the residual mass of gas, by the value of the

  load tl, and summation then with a value 1.

  To arrive at the actual value to be achieved

  of the wflam wall film, the block 111 is

  produces two quantities wfo and fwfrg by the pre-

defined Xcons-

  The value to reach wflam for quantity

  corresponding to the wall film is then only

  by means of a switch 112 to reprocess the

  fuel injection to inject dtewf, when the signal of

  deprivation of injection B indicates the return to service of the cy-

  lindre. Otherwise, the switch 12 is set to zero. By means of a memory (PT1) 113 the quantity corresponding to the wall film as a function of time wflamt is reproduced. The time constant zfw of this memory 113 may be predefined by two characteristic fields in blocks 114 and 115, depending on the value of

  tl load and tmot motor temperature. A switch

  The timer 116 controlled by the injection deprivation signal B branches the time constant zfw either from the characteristic field of the block 114 for normal operation, or from the characteristic field of the block 115 for the push mode connection. For each cylinder the quantity corresponding to the wflamt wall film is calculated

  once per cycle, in offset time. The supplement of car-

  The amount of fuel required to compensate for the wall film results from the difference between the quantity of fuel corresponding to the wall film, calculated from the

  current cycle, and the quantity corresponding to the film

  kings of the previous cycle. A timer 117 and a summation point 118 produce this difference. The injection fuel supplement dtewf, determined in the manner described, is superimposed on the summing point 107 to the amount to be injected additively. This provides the amount of fuel ti placed in the cylinder. The switch 119, controlled by the injection deprivation signal B, is at the value 0 when the cylinder must be disconnected, and the switch is closed.

  when the cylinder is put back into service.

  FIG. 2 shows another variant for calculating the quantity of fuel to be injected ti during the

  commissioning of a cylinder which has been deprived of

  tion. The value of the correction dtlrgs, calculated according to FIG. 1, is divided in the block 200 by a predefined air factor cons, and the new correction value

  dtergs, which results, is added to a point of

  201 to a basic amount to be injected

  food. The amount to be injected corrected, which results from this, is fed in the manner that has already been described above, by the additional amount to

  inject, and is transmitted in the value ti.

  For the case where the stop of the injection in a

  cylinder takes place more than once or twice after

  it is possible to start from the fact that the residual gases in the cylinder consist for the most part of fresh air

and not in exhaust.

  In order to determine the quantity to be injected, it is then possible to make the correction value equal to the residual mass of the gases determined in FIG. But when the stop of the injection into a cylinder only takes place

  once or twice behind one another, the exhaust gases

  are not yet completely replaced by fresh air. Especially in the case of a cylinder that

  "box", which is a disconnection and a cy-

  In the case of ASR-EZ, for example, in the case of an automatic adjustment of the slipping, it is not possible to use the correction value described above which is based on the fact that the residual gases consist essentially of fresh air. In block 119 of FIG. 1, a correction value dfgas is determined which deviates from the correction value dtlrg, using the following method: The fraction of residual exhaust gas in the cylinder is reduced when the number of cylinders put out of service increases. After a commissioning, we

  obtains the mass of AbAgas exhaust fumes

  following formula: AAbgas (i) = Abtl (gas () + dtli - 1) * dtlrg (i) (1) tl (i) + dtlrg (i - i) in which tl (i) is the supply e when of the cycle and dtlrg (i) reproduces the mass of gases

  residuals that remain in the cylinder after i cy-

  injection key. The fresh air released in the residual gases is obtained after decommissioning by the following formula: dfgas (i) = dtlr (i) AAbgas (i) (2) When a cylinder "box" is obtained the

  amount of fresh air dfgas found in the gases

  from equation 1 and equation 2, by the following equation: dfgas (i) = dtlrgi t (i) 1) (3) tl (i) + dtlrg (i)

  Assuming that the mass of residual gases is

  In a short cycle, equation 3 can be simplified as follows: dfgas = (4) 1 / tl + 1 / dtlrg Depending on whether the cylinder is out of service for a longer period of time or the "box" cylinder, one can connect either the value dtlrg or the value dfgas, by means of a switch 120, as correction value dtlrgs. The control signal for this switch comes from FIG. 1 of the injection deprivation signal B. A block 121 detects the number of injection

  cylinder before commissioning. If the number of

  cylinder injection is 1 and the Injection B signal at the same time indicates a

  service, an AND gate 122 then delivers a signal of

  tation 120, so that it switches to the dfgas value. In all other cases it is the value dtlrg which is connected as the correction value dtlrgs. In the case of the embodiments described above, the additional amount of

  fuel to be injected according to the mass of gas

  duels in the private injection cylinder. But we can also

  if, to determine an additional quantity to be injected, use other criteria, for example quantity,

  density or composition of residual gases.

R E V E N D I CATIONS

  1- Method for determining the amount of car-

  to be injected when a cylinder is put back into service

  which had been deprived of injection into an internal combustion engine, in which a base quantity of

  fuel to be injected is modified by an additional quantity

  injection method, characterized in that the quantity

  additional quantity to be injected for the first combustion is determined, after the restarting of the cylinder,

  function of the residual gases in the cylinder.

  2. Process according to claim 1, characterized

  se in that one forms by an additive superposition

  a correction value (dtlrgs), a function of the residual gases

  dual, and the load value (tl) of the engine, a value

  corrected charge (tlsum) from which

  mine by dividing by a predefined set air factor (Ions), the quantity to be injected (tes) necessary to the setting

of this set air factor.

  3. Process according to claim 2, characterized

  in that the amount of fuel to inject required

  setting of the set air factor (XCons) is changed

  a correction amount (dtewf) that is suitable for

  the compensation of a quantity of wall film (wflam).

  4. Process according to claim 3, characterized

  in that the amount of correction (dtewf) is established from the difference of the amounts of wall film

  determined for two consecutive injection cycles.

  Method according to one of the preceding claims

  cedentes, characterized in that the amount of correction (dtewf) is modified by an amount to be injected (tes) which comes from the superposition by addition of a quantity of

  base to be injected and a correction value (dtlrg) divided

  set by a predefined set air factor (XCons),

residual gas function.

he

  6. Process according to claim 2, characterized

  in that a correction value (dfgas) is formed when the cylinder is connected, which depends on the residual gas charge and the number of injection cycles that have been eliminated.

  7- Process according to claim 2, characterized

  in that when connecting and disconnecting cyclically

  of the cylinder with injection deprivation only between two injection cycles, a correction value (dfgas) is formed which depends on the

charge and residual gases.

  8- Device for implementing the method se-

  any one of claims 1 to 7 for determining

  destroying the quantity of fuel to be injected during the return to service of a cylinder which has been deprived of injection in an internal combustion engine, in which this device modifies a quantity of injection base by an additional quantity of injection, characterized in that

  means are provided for determining the additional quantity

  injection chamber according to the residual gases in the cylinder before it is put back into service, and

  what these means do not provide this additional quantity

  to inject only for the first combustion after the

commissioning of the cylinder.