Method for dynamic gas partial pressure correction of an internal combustion engine with external mixture formation

Abstract

A method for dynamic gas partial pressure correction of an internal combustion engine with external mixture formation. A mixture formation is carried out in an intake manifold upstream of the cylinder of the internal combustion engine, and in which in addition to the gas partial pressure of the fresh air flowing continuously into the intake manifold, the gas partial pressure of the fuel, fed discontinuously into the intake manifold, is also taken into account. The gas partial pressure of the fuel, fed into the intake manifold, said pressure which is assumed to be stationary as a function of determined parameters, is dynamically adjusted for each of the cylinder-individual, temporally successive injections, discharged into the intake manifold, by means of a correction factor and a fresh air correction filling value.

Claims

1. A method for operating an internal combustion engine, in which a mixture of fresh air and fuel is carried out in an intake manifold upstream of cylinders of the internal combustion engine, and in which in addition to a gas partial pressure of the fresh air flowing continuously into the intake manifold, a stationary gas partial pressure of the fuel fed discontinuously into the intake manifold is also taken into account, the stationary gas partial pressure being calculated using predetermined parameters, the method comprising: calculating a correction factor in an intake manifold-side balancing time grid from a ratio of a stationary fresh air filling value and a fresh air correction value determined in the balancing time grid; and dynamically adjusting, via the correction value, the stationary gas partial pressure of the fuel fed into the intake manifold for each of temporally successive injections of the cylinders, such that for each of the temporally successive injections of the cylinders, a dynamic gas partial pressure is determined, the dynamic gas partial pressure being a characteristic variable for the calculation of respective cylinder injection quantities into the intake manifold.

2. The method according to claim 1, wherein the intake manifold is assigned a balance zone, in which a mass flow of the fresh air via a throttle valve and a mass flow of the fuel via an injection nozzle, and a mass flow of the mixture of the fresh air and the fuel via an intake valve are balanced.

3. The method according to claim 2, wherein a time difference between an end of feeding a fuel injection element at the time when the fuel injection element closes and a time when the respective intake valve of the cylinders closes is continuously determined individually for each cylinder in the balancing time grid.

4. The method according to claim 3, wherein the stationary fresh air filling value in the balancing time grid is calculated on the basis of a mass flow characteristic curve of the fresh air in the balancing time grid.

5. The method according to claim 3, wherein a gradient characteristic curve is used to determine a gradient of the mass flow of the fresh air, flowing in continuously via the throttle valve, and to integrate the gradient of the mass flow into the balancing time grid, and thus a dynamic correction filling value of the fresh air in the balancing time grid is calculated.

6. The method according to claim 5, wherein a total amount of fresh air, from the dynamic correction filling value and the stationary filling value, is set in relation to a total amount of the stationary filling value of the fresh air, as a result of which the correction factor is formed.

7. The method according to claim 1, wherein the stationary gas partial pressure is multiplied by the correction factor, which results in a correction value which corresponds to the dynamic gas partial pressure which is taken into account in each of the temporally successive injections of the cylinders discharged into the intake manifold.

8. The method according to claim 7, wherein the correction value with consideration that the injection quantity, which has already been discharged in an injection time period before the balancing time grid with respect to one of the cylinders is taken into account in a next injection into the intake manifold, which takes place with respect to a subsequent one of the cylinders.

9. A system architecture for operating an internal combustion engine, in which a mixture of fresh air and fuel is carried out in an intake manifold upstream of cylinders of the internal combustion engine, and in which in addition to a gas partial pressure of the fresh air flowing continuously into the intake manifold, a stationary gas partial pressure of the fuel fed discontinuously into the intake manifold is also taken into account, the system architecture comprising: a component in which the stationary gas partial pressure is calculated using predetermined parameters, the component being assigned further components from which a correction factor results, the correction factor being multiplied in one of the further components by the stationary gas partial pressure, which results in a correction value as an output variable of the component, the correction value corresponding to a dynamic gas partial pressure, which is taken into account in each of temporally successive injections of the cylinders discharged in the intake manifold and the dynamic gas partial pressure being a characteristic variable for the calculation of respective cylinder injection quantities into the intake manifold, wherein the correction factor is calculated in an intake manifold-side balancing time grid from a ratio of a stationary fresh air filling value and a fresh air correction value determined in the balancing time grid.

10. The system architecture according to claim 9, wherein the predetermined parameters, including at least one of an intake manifold temperature, a split factor, a target lambda value, a fuel/gas rail temperature or characteristic values of the quality of the fuel, are supplied on the input side of the component, as a result of which the calculated stationary gas partial pressure is output as the output variable on the output side of the component.

11. The system architecture according to claim 9, wherein a crankshaft angle of a crankshaft at a first time and the crankshaft angle at a second time, as a function of the intake camshaft closing the intake valve, are determined as input variables in the one of the further components, and the crankshaft angles are converted into a time difference as the output variable of the one of the further components by subtraction in a subtraction component and by multiplication with a conversion factor in a multiplication component.

12. The system architecture according to claim 11, wherein a mass flow via a throttle valve is fed on the input side of another one of the further components, wherein in a gradient calculation component, a gradient calculation of the gradient of the throttle valve mass flow takes place in the balancing time grid, which is subsequently limited upwards and downwards and smoothed in a gradient limiting component and a low-pass filter component before the gradient is fed as an output variable to a multiplication component.

13. The system architecture according to claim 12, wherein the time difference as the output variable of the one of the further components and the gradient of the throttle valve mass flow are fed to an input side of the multiplication component, wherein after the multiplication, the dynamic correction filling value is present, which is added to the stationary fresh air filling value in an addition component and is set in relation to the stationary fresh air filling value in a ratio component after which the correction factor arises as the output variable.

14. The system architecture according to claim 9, wherein the correction factor is the input variable for the component, wherein the correction factor in the component is multiplied by the stationary gas partial pressure as the output variable from the component with the correction factor, which results in the correction value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows a structural design of the components of an internal combustion engine;

(3) FIG. 2 shows a diagram to illustrate a cylinder-individual qualitative system behavior in the case of a positive load change selected in the exemplary embodiment; and

(4) FIGS. 3 and 4 show the associated components of the system architecture.

DETAILED DESCRIPTION

(5) As shown in FIG. 1, a gaseous fuel, for example, gasoline or natural gas, is supplied to intake manifold 100.4.

(6) FIG. 1 shows a structural design of the components of an internal combustion engine 100.

(7) In addition, a so-called balance zone is shown in FIG. 1, the importance of which will be explained in more detail.

(8) Internal combustion engine 100 comprises, as components essential to the invention, a throttle valve 100.1, an injection nozzle 100.2 (hereinafter referred to as an injector), an intake valve 100.3 as an interface between intake manifold 100.4 and cylinder 100.5 of internal combustion engine 100, which in a known manner forms combustion chamber 100.5A for the mixture. Throttle valve 100.1 and injector 100.2 are assigned to intake manifold 100.4.

(9) The mass flows via throttle valve 100.1, injector 100.2, and intake valve 100.3 within balance zone B are illustrated using arrows P100.1, P100.2, and P100.3 shown in FIG. 1, said flows which can be balanced in balance zone B.

(10) FIG. 2, associated with FIG. 1, shows a diagram to illustrate a cylinder-individual qualitative system behavior in the case of a positive load change selected in the exemplary embodiment.

(11) Different mass flows over time t, according to the X axis, are shown on the Y axis of the diagram in FIG. 2. On the Y axis of the diagram in FIG. 2, on the one hand, the real mixture mass flow P100.4 is shown over time t in intake manifold 100.4 in characteristic curve K4. On the other hand, on the Y axis of the diagram in FIG. 2, the mass flow P100.1 is shown in addition over time t of the continuously inflowing fresh air via throttle valve 100.1 in characteristic curve K1.

(12) It becomes clear (compare characteristic curve K1) that the continuously inflowing fresh air via throttle valve 100.1 is assumed to be stationary in the phases I, II, III shown.

(13) Within the crank angle intervals of phases I, II, III, IV, the stationary fresh air mass flow is usually calculated by means of averaging according to characteristic curve K1 using a crank angle-synchronous computational grid.

(14) As a result, fresh air fillings per intake (compare intake phase II in the respective cylinders 100.5-n) can be expected over time with a stationary mass flow.

(15) According to the invention, a time-defined crank angle interval is used as the balancing time grid Δt13 as the basis for the following method, as will be explained in more detail below.

(16) In addition, the Y axis of the diagram in FIG. 2 shows the mass flow gradient 50 of throttle valve 100.1 according to the characteristic curve K′, which can be assigned chronologically to the balancing time grid in time interval Δt13.

(17) On the X time axis of the diagram in FIG. 2, the times tEB, t1, t2, and t3, which are essential to the invention, are defined individually for each cylinder in phases I, II, III (work phase IV not shown) of a work cycle of one of multiple cylinders 100.5-n.

(18) The exhaust phase of a preceding cylinder 100.5-4 is marked with I, the intake phase of a first cylinder 100.5-1 is marked with II, and the compression phase of the first cylinder 100.5-1 is marked with III.

(19) In the exhaust phase I of the preceding cylinder 100.5-4, the fuel is already supplied in intake manifold 100.4 via injector 100.2 (compare mass flow arrow P100.2 in FIG. 1) with respect to first cylinder 100.5-2.

(20) The time tEB in FIG. 2 defines the start t1 of feeding the fuel into intake manifold 100.4 with respect to first cylinder 100.5-1, whereas the time t1 defines the end of feeding the fuel to intake manifold 100.4 with respect to first cylinder 100.5-1 within exhaust phase I of the preceding cylinder 100.5-4.

(21) The time t2 defines the time at which intake valve 100.3 opens during intake phase II of piston 100.5B of first cylinder 100.5-2.

(22) The time t3 defines the time at which intake valve 100.3 closes during the compression phase III of piston 100.5B of first cylinder 100.5-1.

(23) The time t3 is the prediction time within the method; i.e., intake valve 100.3 of first cylinder 100.5-1 closes.

(24) Taking into account the dynamic correction filling value F.sub.dyn in the balancing time grid 40, Δt13, the injection quantity in the injection period (tEB to t1) of the next injection into intake manifold 100.4 is dynamically corrected with respect to second cylinder 100.5-2 following the first cylinder, so that a dynamic correction of the gas partial pressure is determined in balancing time grid Δt13 via the ratio of the stationary filling quantity F.sub.stat of the absolute fresh air mass deviation, determined using mass flow gradient 50.

(25) The system architecture of the solution of the invention is explained hereafter on the basis of FIGS. 1 and 2 and the following FIGS. 3 and 4.

(26) FIGS. 3 and 4 show the associated components of the system architecture.

(27) So far (compare FIG. 3), a stationary gas partial pressure calculation of the fuel has already been carried out in a first component 300 in the existing system architecture, but no dynamic corrections have been taken into account.

(28) An intake manifold temperature 300.1, a split factor between gasoline and gas 300.2, a target lambda (A) value 300.3, a fuel/gas rail temperature 300.4, and quality characteristic values 300.5 are used as input variables in the calculation of the stationary gas partial pressure of the fuel. The stationary gas partial pressure 30 of the fuel in intake manifold 100.4 is thus available as the output variable of component 300.

(29) According to the invention, it is now taken into account that the gas partial pressure in the dynamics is not stationary but changeably “dynamic.”

(30) According to the invention, the time difference Δt13 is first determined in the balancing time grid between the end of the supplying tEB of the fuel last supplied at time t1 into intake manifold 100.4 in exhaust phase I (compare FIG. 2) of preceding cylinder 100.5-4 and the time t3 in compression phase III of subsequent cylinder 100.5-1, in which intake valve 100.3 of cylinder 100.5 closes.

(31) It is understood that the time difference Δt13 varies depending on the output of the internal combustion engine.

(32) In this time difference Δt13, more fresh air (possibly too lean mixture) can flow via throttle valve 100.1 in the dynamics in the positive load change, described by way of example, and less fresh air (possibly too rich mixture) in the event of a negative load change. In the case of a previously fixedly discharged amount of fuel, which is introduced into intake manifold 100.4 in FIG. 2 between the start of feeding the fuel at time tEB and the end of feeding at time t1, the mixture situation in intake manifold 100.4 changes dynamically until the intake valve of cylinder 100.5-1 closes.

(33) According to the invention, the mass flow gradient 50 via throttle valve 100.1 is included in the correction method in accordance with the characteristic curve K1′ in FIG. 2 for the fresh air determination in the balancing time grid Δt13.

(34) Via the fresh air mass flow gradient 50 according to the characteristic curve K1′, the dynamic correction filling value F.sub.dyn is calculated in time steps within the balancing time grid Δt13 via the previously determined time difference Δt13 between time t1 and time t3.

(35) The dynamic correction filling value F.sub.dyn is added to the filling value F.sub.stat which is stationary in balancing time grid Δt13 according to mass flow P100.1 via throttle valve 100.1 according to the characteristic curve K1 in FIG. 2 and is related to the absolute filling value F.sub.stat present in the balancing time grid.

(36) According to the invention, this results in a percentage change in the filling in intake manifold 100.4 in the balancing time grid Δt13, which is used according to the invention as correction factor 60 for the dynamic filling correction of the fresh air filling.

(37) This correction factor 60 of the so-called dynamic filling correction of the fresh air filling in intake manifold 100.4 is multiplied by the stationary gas partial pressure p.sub.stat, and the dynamic gas partial pressure p.sub.dyn, determined thereby, is taken into account as the “dynamically corrected” partial pressure p.sub.dyn as output variable 70 in the calculation of the fuel injection quantity in the next injection event (tEB to t1) in intake manifold 100.4 with respect to the next cylinder 100.5-2.

(38) This means that the “dynamically corrected” gas partial pressure p.sub.dyn is always corrected before each new injection into intake manifold 100.4 by the dynamic filling correction of the fillings (stationary filling value F.sub.stat and dynamic correction filling value F.sub.dyn) by means of correction value 70 determined in the previous work cycle.

(39) A second component 400, a third component 500, as well as a fourth component 600 and a fifth component 700 are used to determine the correction value 70 according to FIG. 3 within the system architecture.

(40) In the second component 400 (compare FIG. 3), crankshaft angle 400.1 of the crankshaft at time t1 and crankshaft angle 400.2 as a function of the intake camshaft closing intake valve 100.3 are determined as input variables, and in component 400 (compare FIG. 4) by subtraction of crankshaft angles 400.1 and 400.2 in a subtraction component 400A and by multiplication with a conversion factor in the multiplication component 400B are converted into the time difference Δt13, so that it is present as output variable 40 of second component 400, which corresponds to the time difference Δt13 and therefore the balancing time grid.

(41) In third component 500 (compare FIG. 3), mass flow P100.1, over time t, of the continuously inflowing fresh air via throttle valve 100.1 according to the characteristic curve K1, is determined as the input variable, from which the gradient of the throttle valve mass flow of throttle valve 100.1 is calculated as output variable 50 according to characteristic curve K1′ according to FIG. 2.

(42) The gradient calculation takes place in a gradient calculation component 500A (compare FIG. 4), wherein the gradient of the throttle valve mass flow in the balancing time grid Δt13, according to component 400, is limited upwards and downwards and smoothed in a gradient limiting component 500B (compare FIG. 4) and a low-pass filter component 500C (compare FIG. 4) before it is fed to a multiplication component 600A in component 600.

(43) After multiplication, the dynamic correction filling value F.sub.dyn is present in multiplication component 600A. In an addition module 600B, the dynamic filling is added to the stationary filling and in a ratio component 600C related to filling value F.sub.stat which results in the correction factor 60 as an output variable.

(44) Correction factor 60 represents the input variable for the fifth component 700, in which correction factor 60 is multiplied in the so-called multiplication component 700 by the stationary gas partial pressure p.sub.stat as the output variable from the first component 300 with correction factor 60; this results in the calculated correction value 70, which corresponds to the dynamic gas partial pressure p.sub.dyn which is taken into account in the next injection event into intake manifold 100.4 for calculating the injection quantity.

(45) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.