FR2851012A1 - Air/fuel mixture regulating method for internal combustion engine, involves determining amount of fuel effectively injected, to correct injection duration, based on fuel correction value - Google Patents

Abstract

The method involves determining an amount of fuel effectively injected in an intake manifold (10) or in a combustion chamber (35), and correcting injection duration based on a fuel correction value. The amount of fuel injected is determined as a function of number of fuel injections for a combustion phase in a cylinder (5) of an internal combustion engine (1).

Description

Field of the invention

  The present invention relates to a method of regulating an air / fuel mixture of an internal combustion engine according to which the injection time is corrected for the adaptation of an air / fuel mixture ratio.

  STATE OF THE ART In current internal combustion engines with electronic fuel injection control, lambda regulation and adaptation of the mixture ensure correct prior control of the air / fuel mixture port ratio k .. For this, we correct the relative fuel mass injected rk as follows: rk = r1p + rka * fr * fra (1) lamsbg in this formula: rlp = expected relative air charge fr = regulation coefficient of lambda regulation fra = multiplicative correction value for fuel mass 20 rka = additive correction value for fuel mass and lamsbg = set value for the air / fuel mixture ratio X which must be adjusted by lambda regulation.

  The fuel mass, relative, injected, rk, thus serves as an input quantity to determine the required injection time ti. The adaptation of the mixture thus finally corresponds to an adaptation of the injection time.

  For the correction of the relative fuel mass rk according to equation (1), only one injection of fuel per combustion phase is taken into account. For multiple injections per combustion phase, the correction of the relative fuel mass rk according to equation (1) does not give a correct result.

  Disclosure and advantages of the invention The present invention relates to a method of regulation of the type defined above, characterized in that, as a function of a regulation factor, the mass of fuel actually injected is determined, and starting from this mass of fuel actually injected, the injection time is corrected as a function of at least one correction value.

  In this way, it is avoided that for example fouling or other deterioration such as for example the wear of an injector does not result in the adaptation of a mass of fuel injected which would be different from the mass of fuel actually injected for ultimately correct the required injection time and compensate for the deterioration of the injector. If the injection time is corrected by relying on the mass of fuel actually injected, then this mass of fuel actually injected will also be available for other functions of the internal combustion engine. Since a mass of injected fuel is used as the input to a large number of fields of characteristics of the engine control, it is advantageous to use the mass of fuel actually determined.

  It is particularly advantageous that, starting from the mass of fuel actually injected, a suitable mass of fuel 15 is determined, using at least one fuel correction value, and that the duration of injection is determined as a function the appropriate mass of fuel injected. This makes it possible to deduce the mass of fuel injected adapted from the mass of fuel actually injected so that the mass of fuel actually injected can also be used for other calculations in which it is necessary to use the mass of fuel actually injected.

  It is also particularly advantageous for the mass of fuel injected adapted to be determined as a function of a mass of fuel coming from the ventilation of the tank. Thus, in determining the required injection time, account is taken of the ventilation of the reservoir and the adaptation of the injection time is all the more precise.

  According to another advantageous characteristic, the suitable mass of injected fuel is determined as a function of a number of fuel injections for a combustion phase in a cylinder 30 of the internal combustion engine. This gives a correct adaptation of the injection time even in the case of multiple injections per combustion phase.

  It is also advantageous to start from the mass of fuel actually injected in order to determine the injection duration and to correct this injection duration thus obtained using at least one injection duration correction value. This also makes it possible to give up the determination of an injected, adaptive fuel mass. In the case of multiple injections, for better combustion, it is also possible to adapt the injection duration required for each injection separately.

  According to another advantageous characteristic, the mass of fuel actually injected is determined as a function of a mass of fuel necessary for compensating for transient operation. Under these conditions, the determination of the mass of fuel actually injected will be more precise.

  It is particularly advantageous if, in determining the mass of fuel actually injected, account is taken of an upstream control coefficient, in particular for starting. This avoids strong regulatory deviations.

  Drawings The present invention will be described below in more detail with the aid of exemplary embodiments represented in the appended drawings in which: - Figure 1 is a block diagram of an internal combustion engine, - the Figure 2 is a functional diagram for determining the relative fuel mass actually injected as well as a suitable relative fuel mass, injected, - Figure 3 is a functional diagram for determining the injection time from the relative fuel mass adapted, injected, FIG. 4 is a functional diagram for determining the duration of injection from the relative mass of fuel actually injected.

  Description of embodiments According to FIG. 1, the reference 1 designates an internal combustion engine with a heat engine. The heat engine or internal combustion engine can be a gasoline engine or a diesel engine. In the following, it will be assumed by way of example that the thermal engine 30 is a petrol engine. The internal combustion engine 1 comprises at least one cylinder 5 with a piston 4 and a combustion chamber 35. The combustion chamber 35 receives fresh air via an air supply 10; this supply is also called the suction tube below. The mass of air supplied is controlled by the position of a throttle flap 15 fitted to the suction pipe 10.

  In addition, the combustion chamber 35 is connected to the suction pipe 10 by an intake valve 25 which can open or close.

  According to Figure 1, the suction pipe 10 comprises an injector 20 which injects fuel into this suction pipe 10 to form the air / fuel supply mixture; this mixture arrives in the combustion chamber 35 through the intake valve 25 in the open position. The air / fuel mixture is ignited there by a spark plug 5 which starts the combustion of the air / fuel mixture driving the piston 40. The burnt exhaust gases can be evacuated through the exhaust valve 45 in the manifold. exhaust 50 of the internal combustion engine 1. The exhaust manifold 50 includes an oxygen sensor 55 also called a lambda probe which determines the ratio 10 of the air / fuel mixture in the exhaust gas line 50. The device described in Figure 1 thus constitutes an internal combustion engine or heat engine equipped with an injection into the intake manifold. Alternatively, the fuel can also be injected directly into the combustion chamber 35. It does not matter for the process of the invention whether the fuel is injected, as shown in FIG. 1, into the intake manifold 10 or directly in the combustion chamber 35. By relating the mass of air supplied through the throttle valve 15 to the maximum volume of the combustion chamber 35 and to normal conditions, such as for example a predetermined temperature 20 and an air pressure predetermined, the relative air mass M is obtained. By referring to the mass of fuel injected by the injector 20 relative to the maximum volume of the combustion chamber 35 and by entering the normal operating conditions, the mass is determined. relative fuel rk. In addition, the internal combustion engine 1 also comprises a control unit 60 also called engine control. The engine control 60 thus controls or manages the opening angle of the throttle flap 15 as well as the injection time of the injection valve 20. This allows the engine control 60 to adjust the mass of relative air rl and mass of fuel re30 lative rk. The inlet valve 25 and the exhaust valve 45 can also be controlled to open and close the combustion chamber 35 to the suction pipe 10 or to the exhaust pipe or pipe 50, also from motor control 60. This situation is called fully variable valve control. Alternatively, one can also open the intake valve 25 and the exhaust valve 45 by the camshafts and close them under the same conditions; these camshafts are driven by the crankshaft itself driven by the piston 40. The method of the invention can be carried out for the two types of control of the intake valve 25 and of the exhaust valve 45, these two types being known to the specialist and not being shown for this reason in Figure 1, so as not to complicate the figure. The engine control 60 further controls the spark plugs 30 in a manner known to those skilled in the art; the candle control has also not been shown in Figure 1 for the sake of simplification. This makes it possible to adjust the instant of ignition by the engine control 60. To detect the engine rotation speed (engine speed) of the internal combustion engine 1, it is possible to have a rotation speed sensor 60 which measures the rotations of the crankshaft and transmits the information to the engine control 60. The ratio of the air / fuel mixture measured by the lambda probe 55 is also supplied to the engine control 60 to be used.

  For different operating modes of the internal combustion engine 1, it is possible to predefine, in the engine control 60, different set values lamsbg of the air / fuel mixture ratio. Thus, for example for the homogeneous mode of the internal combustion engine 1, it is possible to have a set value lamsbg = 1; for the lean operating mode or lean speed of the internal combustion engine 1, it is possible to have a set value lamsbg for example = 2. Thus, in homogeneous mode, the relative air mass rl corresponds to the relative fuel mass rk whereas for example in the lean mode as described, the relative air mass rl is twice the relative mass of fuel rk. In general, there is a combustion operation consisting in burning the air / fuel mixture which is in the combustion chamber 35 and there will be a single injection of fuel for a determined period regardless of whether the injection takes place. done in the intake manifold 10 or directly in the combustion chamber 35 of the cylinder 5 insofar as for injection into the suction manifold, it is ensured that the fuel injected arrives essentially essentially entirely into the combustion chamber 35 through the intake valve 25. For this case, there will be a fuel injection by combustion operation.

  The mass of fuel, relative, rk, injected, is corrected according to equation (1) to carry out the described pre-control of the air / fuel mixture ratio. The correction of the relative fuel mass to be injected rk is especially necessary because the injector 20 becomes charged with coke over time and wears out and this is why the quantity of fuel, relative, injected rk, decreases over time for same injection duration. The additive correction value rka of the fuel mass and the multiplicative correction value fra of the fuel mass can take account of the coke charge on the injection valve 20 s by controlling the air / fuel mixture. The fuel mass, relative, rka thus corrected, can then be supplied by the engine control 60 for an extended injection time. In this way, it is also possible to compensate for the error of the relative fuel mass rk caused by the deposition of coke or the wear of the injector 20. The coking of the injector 20 is only one example of a cause of a defective relative mass of fuel rk which can be compensated for by the correction values rka, fra. The correction values rka and fra of the fuel mass also make it possible very generally to correct a relative, defective fuel mass, rk, according to equation (1) by relying on a faulty behavior of the injector 20.

  For the correction of the relative fuel mass rk according to equation (1) one can use the predictable relative air charge rlp which is determined from one or more previous combustion cycles. In the simplest case, the mass corresponding to the preceding combustion is simply measured, for example using a mass air flow meter not shown in FIG. 1 such as a mass air meter with hot film. and reference is made to the maximum volume of the combustion chamber 35 as well as to the normal conditions described for the relative air mass. Alternatively, the average value of three previous combustions can also be used with the relative air mass as the forecast relative air mass rlp each time. The lambda lamsbg value for the air / fuel mixture ratio is the value that we want to obtain for this ratio in the combustion chamber 35. In rich mode or for X = 1, the lambda regulation in the engine control 60 30 can directly determine the set value lamsbg with the effective air / fuel mixture ratio provided by the lambda sensor 55. By the regulation factor fr, the engine control 60 determines the relative fuel mass rk according to equation (1) , so that the air / fuel mixture ratio measured using the lambda probe 55 is slaved to 35 the set point lamsbg taking into account the conversion described da combustion chamber 35 to the exhaust pipe 50 The corrections rka and fra thus correct the behavior of the injectors 20.

  Provision may also be made to take account, for the correction of the relative fuel mass rk, of a transition compensation or of wall film, also necessary rkukg. For the correction of the relative fuel mass rk, account may also be taken of the possibly existing tank ventilation 1000 and shown in FIG. 1, which results in the effective relative fuel mass rkte in the intake manifold 10. In in addition, to regulate the air / fuel mixture ratio, account can be taken of a pre-control coefficient fvst to avoid relatively large regulatory deviations, in particular at the time of starting. Thus, from equation (1) for the correction of the fuel mass, relative, injected, rk, we will have the following formula: rk [[rlP Is * fr + rkukgJ * fra-rkte (2) Llamsbg La relative fuel mass rk, corrected according to equation (1) or equation (2), injected, can be used as input quantity for the calculation of the required injection time ti. The relative fuel mass rkO actually injected is however not known. According to the invention, it is only intended to determine the relative fuel mass 20 rkO actually injected and to cut from a relative, suitable fuel mass, rkti, the latter serving to determine the duration of injection ti.

  If the internal combustion engine is operating at a point of constant engine speed, relative air mass rA and setpoint lamsbg of the constant air / fuel mixture ratio, then the behavior of the injector 20 as a function time will be adapted for example because of wear, fouling or coking. Bine that the relative air mass rI remains constant, the regulation coefficient fr will change slowly, which will be adapted by adapting the mixture by the multiplicative correction coefficient fra for the fuel mass and / or the correction value adaptive fuel mass rka. It follows that the relative fuel mass, injected, corrected by calculation according to equation (1) or equation (2) will not correspond to the relative fuel mass rkO actually injected. For a constant operating point with a constant relative air mass rl and a constant setpoint lamsbg for the air / fuel mixture ratio, the relative fuel mass actually injected rkO will not change. This is why the invention provides for correctly calculating the relative fuel mass rkO actually injected. In the case of the constant operating point, the relative fuel mass rkO actually injected must also remain constant if the injection time 5 ti is continuously adapted. On the other hand, it must be ensured that starting from the relative, suitable fuel mass rkti, the injection time ti is correctly adapted.

  This distinction between the relative fuel mass actually injected rkO and the relative, adapted fuel mass, rkti can be achieved by applying the following calculation formulas: rkO = lip * fvst * fr + rkukg (3) lamsbg rkti = [( rkO- rkte) (rka * anze)] * fra (4) in these formulas anze represents the number of injections for combustion in cylinder 5.

  FIG. 2 shows the determination of the relative fuel mass rkO actually injected and the adapted relative fuel mass 20 rkti according to a functional diagram. Starting from the predictable relative air mass rlp, this mass is multiplied by an upstream control coefficient fvst in a first multiplier 70. The result of the multiplication is applied to a limiter 75 and will be limited by it, if applicable appropriate up or down. Next, the product of the multiplication, if necessary limited, is divided in a divider 85 by the set value lamsbg of the air / fuel mixture ratio. The quotient obtained is multiplied in a second multiplier 80 by the regulation coefficient fr. The result of the multiplication is added in a first adder 90 to the fuel mass, relative, injected, rkukg, if necessary necessary for the transition compensation or of the wall film. The sum thus obtained corresponds to the relative fuel mass rkO actually injected according to equation (3). This mass is thus available in the functional diagram of FIG. 2 as an output quantity for further processing. This quantity is also applied to a subtractor 95 which reduces it by the relative mass of rkte fuel coming from the tank ventilation 1000, insofar as this exists as in FIG. 1. The result of the subtraction is applied to a second adder 105. The latter additionally receives the product formed in a third multiplier 100 from the additive correction value rka of the fuel mass and the anze number of injections for combustion in the cylinder 5. This product is then added in a second adder 105 to the result of the subtraction provided by the subtractor 95. The result of the addition is multiplied in a fourth multiplier 110 with the multiplicative correction value fra of the fuel mass. The product formed is the mass of fuel rkti, relative, adapted, according to equation (4) as another output quantity of the functional diagram of FIG. 2.

  The value thus obtained of the suitable relative fuel mass rkti is then applied according to the functional diagram of FIG. 3 to a function 115 to calculate the duration of injection ti. The function 115 thus determines, in a manner known to the specialist, the duration of injection ti of the injector 20, necessary for the injection of the mass of car15 burant relatively suitable rkti.

  The engine control 60 can then control the injector 20 with this value for the injection time ti.

  As the adaptation of the mixture ultimately results in the correction of the injection time ti, it is provided as a variant according to a se20 cond embodiment of the invention, to directly calculate the necessary injection time ti from the value calculated according to equation (3) and the functional diagram of FIG. 2 for the relative fuel mass rkO actually injected; then this injection duration ti is corrected using an injection duration correction value, adaptive, tiofa 25 and / or a multiplicative correction value of the injection duration tifa.

  In this way, each injection can be adapted separately for a combustion phase in the cylinder 5. In this case, it is no longer necessary to know the number of anze injections for combustion in the cylinder 5.

  Figure 4 shows the adaptation of the injection time ti according to a second embodiment using a functional diagram.

  In this case, the value of the relative fuel mass rkO actually injected is applied, obtained according to equation (3) and the functional diagram of FIG. 2, after subtraction of the relative fuel mass 35 rkte coming from the tank ventilation. 1000 in a subtractor 200, again at function 115 to calculate the corresponding injection time ti 'then the corresponding injection time ti' in a third adder 120 is added to the adaptive injection time correction value tiofa . The sum is applied to a fifth multiplier 125 which multiplies with the multiplication injection correction value tifa. The result is the adapted injection time ti supplied to control the injector 20 according to the functional diagram in FIG. 4.

  In the first embodiment according to FIG. 2, both the additive correction value rka and the multiplicative correction value fra are used for the fuel mass.

  As a variant, it is also possible to use only the additive correction value rka or only the multiplication correction value fra for the fuel mass. In an idle operating state, the additive correction value rka has a stronger influence on the fuel mass and the same is true for the multiplicative correction value fra in an operating state with a relatively high load. If we only use the additive correction value is rka, then in the functional diagram of Figure 2 we can delete the fourth multiplier 110. If we only use the multiplicative correction value fra, we can delete the second adder 105 in the functional diagram of FIG. 2.

  In the second embodiment according to FIG. 4, we use both the additive correction value tiofa and the multiplicative correction value tifa for the duration of injection.

  As a variant, it is also possible to use only the additive correction value tiofa or only the multiplicative correction value tifa for the duration of injection. In an operating state of ra25 lenti characterized by a short injection time, the additive correction value tiofa intervenes more strongly in the injection time whereas for an operating state with a comparatively high load characterized by operating times. large injections, the multiplication correction value tifa will have a greater impact on the duration of injection. If we use the additive correction value tiofa, then in the functional diagram of FIG. 4 we can delete the third adder 120. If we only use the multiplicative correction value tifa, then in the functional diagram of the FIG. 4, the fifth multiplier 125 can also be deleted.

  In the second embodiment, it is not necessary to determine the suitable relative fuel mass rkti according to equation 4. Thus, for the prior control or adaptation of the air / fuel mixture ratio in the combustion chamber 35 it is possible to have a mass of fuel injected for a single or multiple injection of fuel with several injection phases for a single combustion phase, by carrying out the correction of the injection duration for these injection operations. Thus, in the case of single or multiple injection, 5 for each combustion phase, the relative mass of fuel actually injected will be correctly corrected using the adapted injection time ti.

  To adapt the injection time ti it is for example provided for a constant operating point of the internal combustion engine to keep the regulation coefficient fr as constant as possible with respect to a predetermined value, for example the unit value.

  The additive correction value rka and / or the multiplicative correction value fra of the fuel mass according to the first embodiment will then be chosen so that the regulation coefficient fr is kept essentially constant with respect to a predetermined value.

  Correspondingly, for the second embodiment, the additive correction value tiofa and / or the multiplicative correction value tifa will be chosen for the injection duration so that the regulation coefficient fr will be essentially maintained at a predefined value 20 completed for the operating point of the internal combustion engine 1.

  For the adaptation of the relative fuel mass rk according to the method described, it is not necessary that for the combustion phases with multiple injections, each injection operation corresponds to the injection of the same fuel mass.

  It is nevertheless necessary to avoid that the instant of injection of an injection operation is too close to the minimum duration of injection.

Claims (7)

  10) Method for regulating an air / fuel mixture of an internal combustion engine (1) according to which the injection time is corrected for the adaptation of an air / fuel mixture ratio, characterized in that as a function of a regulatory factor, the mass of fuel actually injected is determined, and starting from this mass of fuel actually injected, the injection time is corrected as a function of at least one correction value. 2) Method according to claim 1, characterized in that starting from the mass of fuel actually injected, a suitable mass of fuel is determined, by at least one fuel correction value and the duration of injection is determined as a function the appropriate mass of fuel injected.   30) Method according to claim 2, characterized in that as at least one fuel correction value, an additive or multiplicative correction value is chosen.   40) Method according to claim 2 or claim 3, characterized in that one determines the mass of fuel injected adapted, according to a mass of fuel from a tank ventilation (1000).   50) Method according to claims 2, 3 or 4,   characterized in that the suitable injected fuel mass is determined as a function of a number of fuel injections for a combustion phase in a cylinder (5) of the internal combustion engine (1).   60) Method according to claim 1, 35 characterized in that starting from the mass of fuel actually injected, the injection duration is determined and this injection duration thus obtained is corrected using at least one value of injection correction.   70) Method according to claim 6, characterized in that, as at least one injection duration correction value, an additive or multiplicative injection duration correction value is chosen.   80) Method according to claim 1, characterized in that the effective injected fuel mass is determined as a function of a fuel mass necessary for transition compensation. 90) Method according to claim 1, characterized in that an upstream control factor is taken into account to determine the mass of fuel actually injected. 15