EP1527267B1 - Method for improving the true running of an internal combustion engine - Google Patents

Abstract

Disclosed is a method for improving the true running of internal combustion engines, especially internal combustion engines with jet-guided petrol direct injection, wherein the true running is substantially improved by means of a variation of the lift of the injection valves.

Description

State of the art

The invention relates to a method for compensating torque differences of the cylinders of an internal combustion engine, wherein the fuel injection system of the internal combustion engine for each cylinder has a variable displacement injector.

Due to the unavoidable manufacturing tolerances of components of the fuel injection system and the internal combustion engine give the individual cylinders of the internal combustion engine, despite the same control of the injectors a different performance, or a different moment from. This manifests itself in a non-circular running of the internal combustion engine, in particular in the partial load range and at idle.

From the DE 33 36 028 A1 is a device for influencing control variables of an internal combustion engine known, with the help of which the votes of the individual cylinders services are individually controlled and approximated to each other. This results in the desired round run of the internal combustion engine. The power control of the individual cylinders of the internal combustion engine takes place by the variation of the injection duration.

From the DE 196 42 653 C1 a method for improving the smoothness of an internal combustion engine is known in which once detected irregularities in the torque output of individual cylinders are corrected by changes in the map of the internal combustion engine. As a result, this method is relatively static and can not adequately take account of short-term changes in smoothness.

In modern engine concepts, especially in internal combustion engines with spray-guided gasoline direct injection, a variation of the injection duration is not readily possible because the injection duration has an influence on the mixture formation. As a result, the mixture formation can be adversely affected by a change in the injection duration and the ignition of the mixture formed in the combustion chamber can not take place at the correct time.

Advantages of the invention

The inventive method for compensation of torque differences of the cylinder of an internal combustion engine according to claim 1, initially allows an improvement of the concentricity of the internal combustion engine, without changing the injection duration. Since the injection duration remains unchanged, the mixture formation in the combustion chambers of the internal combustion engine does not change, so that no deterioration in the mixture formation and the ignition of the mixture occurs.

By restricting the cylinder equalization factor to a maximum value and a minimum value, the changes of the valve lift of the injectors are limited to a range within which the valve lift can be controlled with sufficient precision.

With the help of the method according to the invention, a good concentricity of the internal combustion engine can also be achieved if the tolerances of the internal combustion engine or the injection valves are relatively large. First, the concentricity is improved by changing the stroke of the injectors. When this possibility has been exhausted, the small remaining correction range, which is outside the maximum value and the minimum value of the cylinder equalization factor, is covered by a change in the injection duration. This change in the duration of injection is relatively low and does not adversely affect the mixture formation and the operating behavior of the internal combustion engine.

Since injection valves with a variable stroke are already used today in mass production, the method according to the invention can be implemented without additional costs, apart from the costs for programming the control unit.

It has proved to be particularly advantageous if electrically controlled injection valves, in particular piezo valves with outwardly opening injection nozzles, are used as injection valves, since in these the injection quantity per unit time can be effected by a correction of the stroke of the injection valve as a function of a cylinder equalization factor. The correction of the stroke can be done by a correction of the drive voltage or the charge with which the piezo actuator is acted upon. In the following, only a correction of the drive voltage will be discussed in connection with the invention. This always means a correction of the load.

The conversion of the correction factor into a drive voltage, or a charge can also be done indirectly by z. B. a desired flow rate or a desired needle stroke or a desired Aktorhub is corrected and this target value is then converted into a drive voltage, or a charge.

The correction of the drive voltage is particularly simple if the drive voltage is corrected by multiplying by the cylinder equalization factor. Even with these embodiments of the method according to the invention, no changes to the injection system are required, with the exception of a reprogramming of the control unit.

It has proved to be advantageous if the required injection quantity of the cylinder is multiplied by the correction factor and then converted into a cylinder-specific injection time.

The desired improvement in the smoothness of the internal combustion engine can also be achieved by a computer program or a control device for an internal combustion engine, which operate according to one of the previously described methods.

Further advantages and advantageous embodiments of the invention are the following drawings, the description and the claims removable.

drawing

Fig. 1:

ein Blockschaltbild eines ersten Ausführungsbeispiels;

Fig. 2:

ein Blockschaltbild eines zweiten Ausführungsbeispiels;

Fig. 3:

ein Blockschaltbild der Aufteilung des Zylindergleichstellungsfaktors in eine Änderung der Ladung, bzw. Spannung und eine Änderung der Einspritzdauer;

Fig. 4:

ein Blockschaltbild der Änderung der Einspritzdauer des erfindungsgemäßen Verfahrens; und

Fig. 5:

ein Beispiel eines mit einer mittels Piezoaktor betätigten Hochdruckeinspritzventils mit variablem Hub.

In the drawing show:

Fig. 1:

a block diagram of a first embodiment;

Fig. 2:

a block diagram of a second embodiment;

3:

a block diagram of the division of the cylinder equalization factor in a change in the charge or voltage and a change in the Injection duration;

4:

a block diagram of the change in the injection duration of the method according to the invention; and

Fig. 5:

an example of a variable-stroke high pressure injector actuated by a piezoactuator.

Description of the embodiments

Fig. 1 shows a block diagram, based on which a first embodiment of the method according to the invention will be described below.

Depending on the load requirements of the internal combustion engine, not shown, an electrically actuated injection valve (not shown) with a drive voltage U _{drive, i} , or a charge Q _{i is} controlled. The index 'i' stands for the number of a cylinder. It is i = 1 to n, if 'n' is the number of cylinders of the internal combustion engine This is to be expressed that the drive voltage U _drive , or the charge Q _i as a function of other parameters, in connection with the Invention should not be addressed, for each cylinder Z _i can be set individually.

During operation of the internal combustion engine, partial torques M _i emitted by the cylinders of the internal combustion engine, which add up to the total output of the internal combustion engine, are detected. In this case, the detection of the partial moments M _i does not necessarily include a direct measurement, but it may, for example Also, the observation and measurement of the rotational speed of the crankshaft and a correlation of this rotational speed with the ignition timing of the cylinder of the internal combustion engine done. When the partial torques M _{i of} the cylinders Z _i differ from each other within an engine operating stroke, cylinder equalization factor is then formed for each cylinder, so that the smooth running of the engine is improved in consideration of the cylinder equalization factor.

In Fig. 1 the cylinder _{equalization factor} is designated by F _{ZGST, i} . Also, this cylinder _{equalization factor} F _{ZGST, i} will usually be different for each cylinder Z _i .

In order to arrive at a corrected drive voltage U _{drive, i} , or a charge Q _{i of} the injection valve of the cylinder Zi, not shown, and consequently to a corrected stroke of the injection valve, the drive voltage U is _{driving, i} , or the charge Q _i with the Cylinder _equalization factor F _{ZGST, i} multiplied. The product of drive _voltage U _{drive, i} and cylinder _{equalization factor} F _{ZGST, i} is the corrected drive _voltage or the corrected charge.

In Fig. 2 a further embodiment of the method according to the invention is shown as a block diagram. The essential difference from the embodiment according to Fig. 1 is that the cylinder _{equalization factor} F _{ZGST, i is limited} by a maximum value F _{ZGST, Max} and a minimum value F _{ZGST, Min} in a limiter 1.

The limiter 1 has the in the Fig. 2 illustrated Characteristic, that is, when the cylinder _{equalization factor is} smaller than the minimum value F _{ZGST, Min} , the cylinder _{equalization factor} F _ZGST , _{i is set} equal to the minimum value F _{ZGST, Min} , and if the cylinder _{equalization factor} F _{ZGST, i is} greater than the maximum value F _{ZGST, Max} , the Cylinder _{equalization factor} F _{ZGST, i} equal to the maximum value F _{ZGST, Max} replaced. Otherwise, the cylinder _{equalization factor} F _{ZGST i} remains unchanged. With the by the limiter 1 optionally modified cylinder _{equalization factor} F _{ZGST i} , in the same way as based on the Fig. 1 explains, the drive voltage U _{drive, i} , or the charge Q _{i of} the injection valve (not shown) in a corrected drive voltage, or a corrected charge (not shown) converted.

In Fig. 3 A description will be given of the method used when the cylinder _{equalization factor} F _ZGST , _{i is} greater than the maximum value F _{ZGST, Max} or less than the minimum value F _{ZGST, Min} . The basic idea with this supplement to the method is that the difference of the power of the cylinders Z _{i, which} can not be compensated by the stroke of the injection _valve, occurs as a result of a change in the cylinder- _specific injection _duration F _{T_injection i} .

For this purpose, it is checked whether the cylinder _{equalization factor} F _ZGST , greater than the maximum value F _ZGST , _Max . If this check is negative, a correction factor F _{T injection, i is} set equal to 1.0 for the duration of the injection. If the test is positive, the correction factor F _{T_injection, i} , is formed by forming a quotient of the cylinder _{equalization factor} F _{ZGST, i} and the maximum value F _{ZGST, Max} .

By this measure, the part of the cylinder equalization factor, not by a Changing the stroke of the injector can be considered, taken by increasing the injection duration. The correction factor F _{T_einspritz, i} is greater than 1.0 in the case described last.

In parallel, it is checked whether the cylinder _{equalization factor} F _{ZGST, i is} smaller than the minimum value F _{ZGST, Min} . If this test fails, the correction factor F _{T injection, i} is set equal to 1.0. If this test is positive, the correction factor F _{T_injection, i is formed} from the quotient of cylinder _{equalization factor} F _{ZGST, i} and the minimum value F _ZGST , _Min . In the case described last, the correction value F _{T_insprit, i} now has a value less than 1.0.

In Fig. 4 is shown how the injection time in response to the correction factor F _{T_einspritz, i is} corrected.

It is assumed that due to the load requirements of the internal combustion engine and other operating parameters, a certain required amount of fuel is calculated by the control unit of the internal combustion engine. This required fuel quantity is multiplied by the correction factor F _{T_injection, i} , and then an injection time for the cylinder Z _{i concerned is} calculated from this multiplied required fuel quantity. Thus, even with cylinders whose operating behavior by manufacturing tolerances has great differences, a very smooth running can be achieved by namely a part of the differences is compensated by a cylinder-individual variation of the valve lift of the injectors and the remaining part by a cylinder-individual variation of the injection duration of the injectors.

In Fig. 5 an injection valve 3 is shown schematically, which is suitable for carrying out the method according to the invention. However, the invention is not limited to this type of injectors 3. The injection valve 3 consists of a nozzle body 5 in which a nozzle needle 7 is guided. At a projecting into the combustion chamber of an internal combustion engine, not shown, end 9 of the injection valve 3 is a sealing seat (not shown) formed in the nozzle body 5, which cooperates with the nozzle needle 7, that when the nozzle needle 7 is opened, ie in the illustrated position of the injection valve 3 is moved to the left, the nozzle needle 7 lifts off from the sealing seat, not shown. By a coil spring 11 which is supported at one end on the nozzle body 5 and the other end to the nozzle needle 7, the nozzle needle 7 (not shown) in its sealing seat is moved when the injection valve 3 is de-energized.

Actuates the nozzle needle 7 and thus the injection valve 3 by a piezoelectric actuator 13. Between the piezoelectric actuator 13 and the nozzle needle 7, an intermediate piston 15 is arranged, which is performed as the nozzle needle 7 in the nozzle body 5. The indicated by the dashed circle 5 area 17 of the nozzle body 5 in which both the nozzle needle 7 and the intermediate piston 15 are guided, also serves as a hydraulic coupler between the piston 15 and the nozzle needle 7. The space between the piston 15 and the nozzle needle 7 is filled with fuel and transmits the fast control movements, which are transmitted from the piezoelectric actuator 13 to the intermediate piston 15, directly to the nozzle needle. 7

When the distance between the nozzle needle 7 and Intermediate piston 15 changes slowly, enters a certain leakage of fuel between the nozzle needle 7 and intermediate piston 15 on the one hand and nozzle body 5 in the region 17, so that the changes in the distance between the nozzle needle 7 and intermediate piston 15 are compensated. Cause of changes in length of the injection valve 3 and consequently the distance between the nozzle needle 7 and intermediate piston 15 may be temperature changes of the injection valve 3.

A second coil spring 19 presses the piston 15 against the piezoelectric actuator 13, so that these two components are always connected to each other without play.

Via a fuel supply 21, the injection valve 3 is supplied with fuel.

Claims (8)

1. Method for compensating for differences in torque between the cylinders (Z_i, where i = l to m) of an internal combustion engine, wherein the fuel injection system of the internal combustion engine has an injection valve (3) with a variable stroke for each cylinder (Z_i), characterized by the following method steps:

   - sensing of the partial torques (M_i) which are output by the cylinders (Z_i) of the internal combustion engine,

   - formation of a cylinder equalization factor (F_ZGST,i) for each cylinder (Z_i), wherein the cylinder equalization factor (F_ZGST,i) is limited to a maximum value (F_ZGST,max) in the upward direction and to a minimum value (F_ZGST,Min) in the downward direction,

   - correction of the stroke of the injection valve (3) assigned to the cylinder (Z_i), as a function of the cylinder equalization factor (F_ZGST,i) and

   - determination of a correction factor (F_{T_einspritz,i}) for the injection period,

   wherein the correction factor (F_{T_einspritz,i}) is equal to 1.0 if the cylinder equalization factor (F_ZGST,i) is smaller than the maximum value (F_ZGST,Max) and larger than the minimum value (F_ZGST,Min),
   wherein the correction factor (F_{T_einspritz,i}) is equal to the quotient of the cylinder equalization factor (F_ZGST,i) and the maximum value (F_ZGST,Max) when the cylinder equalization factor (F_ZGST,i) is larger than the maximum value (F_ZGST,Max), and
   wherein the correction factor (F_{T_einspritz,i}) is equal to the quotient of the cylinder equalization factor (F_ZGST,i) and the minimum value (F_ZGST,Min) when the cylinder equalization factor (F_ZGST,i) is smaller than the minimum value (F_ZGST,Min).
2. Method according to Claim 1, characterized in that the stroke of the injection valve (3) is corrected by correcting an actuation voltage (U_{Ansteuer, i}) or an electrical charge of the injection valve (3) as a function of the cylinder equalization factor (F_ZGST,i).
3. Method according to Claim 2, characterized in that the actuation voltage (U_Ansteuer,i) or the electrical charge is corrected by multiplication by the cylinder equalization factor (F_ZGST,i).
4. Method according to one of the preceding claims, characterized in that the required injection quantity of the cylinder (Z_i) is multiplied by the correction factor (F_{T_einspritz,i}) and is subsequently converted into a cylinder-specific injection time (T_Einspritz,i).
5. Method according to one of the preceding claims, characterized in that it is provided for use in internal combustion engines with petrol direct injection, in particular with jet-controlled petrol direct injection.
6. Computer program, characterized in that it operates according to one of the preceding methods.
7. Computer program according to Claim 6, characterized in that it can be stored on a storage medium.
8. Control unit for an internal combustion engine, characterized in that it operates according to one of the methods according to one of Claims 1 to 5.

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