DE10317684B4 - Method and control device for operating an internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine, wherein a control of at least one injection valve of the internal combustion engine takes place in accordance with the individual behavior of the injector used representing flow to charge quantity characteristic during operation, characterized in that for calculating the flow to charge quantity characteristic curve a slope characteristic curve for the individual injection valve (i) is determined by varying a charge with which the individual injection valve (i) is actuated with respect to a reference charge (Qref) by a predetermined amount (ΔQ) and changing the charge ( ΔQ) is detected in the internal combustion engine, and the slope of the characteristic curve for the individual injection valve (i) is calculated from the change in the charge (ΔQ) and the change in the lambda value (Δλ).

Description

The invention relates to a method for operating an internal combustion engine and in particular for controlling the injection valves thereof. The invention further relates to a control device for operating the internal combustion engine and a computer program for such a control device.

State of the art

In the prior art methods for quantity error compensation of injection valves of internal combustion engines are basically known, for example from the DE 100 11 690 C2 or the DE 100 12 025 A1 , The methods known from these publications relate in particular to the adaptation of quantity tolerances in fuel high-pressure injection valves in stratified operation (λ> 1) of the internal combustion engine; they are universal, that is applicable to fuel injection valves of different design and operation.

The WO 01/11228 A1 shows a method for metering fuel with a fuel injector for a direct injection internal combustion engine, in which by varying a control signal for the injection valve, a valve lift is varied, resulting in a fixed valve lift after a short time, a static fuel flow. In a series of measurements with different valve strokes, ie with different control signals, a function of an amount of fuel to the corresponding control signal is then determined. According to this function, the injection valve is operated in active mode.

The DE 101 63 894 A1 shows a method for metering an amount of fuel for a direct-injection internal combustion engine having a plurality of combustion chambers, wherein at an operating point of the internal combustion engine, an injected into a respective combustion chamber fuel amount is determined as an actual fuel amount. From the actual fuel quantities of the individual combustion chambers, an average value is formed, wherein a difference value between the determined mean value is determined to a desired fuel quantity. In active mode, the current injection in each combustion chamber is adjusted by the difference value to the desired fuel quantity.

The WO 2003/006 810 A1 shows a method for operating a direct-injection internal combustion engine, in which the lambda values of the exhaust gas to the corresponding injection quantities of each combustion chamber is determined in an internal series of experiments. In this case, correction values for the injection quantities of each combustion chamber are determined, which are then used to adjust the injection quantities.

The JP 2002-039000 A shows a control device with lambda control, in which a fuel injection amount is controlled in response to a signal generated by a lambda probe. The JP 2002-021 620 A (equivalent to EP 1 139 448 A1 ) shows a method and apparatus for injecting fuel using an injector having a piezoelectric element.

With regard to future internal combustion engines with optimized jet guidance, high-pressure fuel injection valves have been developed in which the flow or the amount of fuel to be injected into the combustion chamber of the internal combustion engine is controlled via the injection time ti and / or via the needle stroke NH of the injection valve i. A desired needle lift NH is set in these high-pressure injectors for a desired injection time ti by applying a corresponding required amount of charge thereto. The amount of charge required for a desired activation is calculated in the individual case on the basis of a reference characteristic stored in a control unit for controlling the injection valves. In this reference characteristic, the flow D is plotted against the charge Q to be applied.

Such a D (Q) reference characteristic NH _Ref is in 2 shown. This stored reference characteristic represents either the behavior of a selected reference valve or the average behavior of a plurality of produced high-pressure injection valves of the same type. It may therefore differ from the behavior of individual injection valves of the same type produced and used. Such deviating characteristics are in 2 represented by the reference NH1 or NH2. The methods described in the introductory publications for adapting quantity tolerances in high-pressure injection valves disregard the described differences between the average and the individual behavior of high-pressure injection valves, which may also be the cause of inaccuracies in the metering of fuel.

Based on this prior art, it is the object of the invention to provide a method, a control unit and a computer program for operating an internal combustion engine in such a way that with them increased accuracy in the metering of fuel by high-pressure injection valves in internal combustion engines can be realized.

The object is solved by the features of the independent claims. Advantageous developments of the invention are described in the subclaims. Accordingly, the invention provides that during operation of the internal combustion engine, a control of at least one injection valve of the internal combustion engine is carried out in accordance with by a the individual behavior of the injection valve representing flow / charge quantity characteristic.

Advantages of the invention

By taking into account this individual characteristic curve, a substantial improvement in the accuracy in the metering of fuel can be realized in comparison with the prior art, where only a characteristic curve representing the average behavior of injection valves of the same type was used. This increased metering accuracy also allows the future planned use of spray-guided combustion method for the operation of the internal combustion engine, which are characterized by a reduced exhaust emission and reduced consumption compared to conventional methods.

Advantageous embodiments of this method are the subject of the dependent claims.

The above object is further achieved by a control device for controlling an internal combustion engine and by a computer program for such a control device. The advantages of the control device and computer program according to the invention correspond to the advantages mentioned above with reference to the method according to the invention.

drawings

The description is attached to three figures, wherein

1 the inventive method;

2 different flow to charge quantity characteristics for a high-pressure injection valve; and

3 a control unit for operating an internal combustion engine.
shows.

Description of the embodiments

The invention will now be described in detail in the form of various embodiments with reference to the figures.

More specifically, in 1 a method for calculating the slope of a flow to charge quantity characteristic for an individually used high-pressure injection valve of an internal combustion engine shown. In this case, the slope k _{i describes} the ratio of flow to the charge to be applied to the injection valve in order to achieve the desired needle stroke NH or flow. For the determination of this gradient, the internal combustion engine is initially operated in the so-called homogeneous operation, that is, for example, at λ = 1 (method step a)).

Then, in a subsequent step b), a so-called adaptation range is defined, within which a reference operating point can be suitably selected. As long as this adaptation range has not been established, the method according to the invention will not be continued further and instead there will always be a return to method step a).

After successful approach of the adaptation range, the reference operating point is set within this adaptation range. The reference operating point is characterized in particular by the fact that the speed of the internal combustion engine and the respective relative air mass supplied to it are quasi-stationary. Further, for example, λ = 1 and there are belonging to this reference operating point injection time ti and the associated _Ref be applied to the injector charge Q _Ref actuated (process step c)).

As soon as this reference operating point is set, it is checked whether an individual cylinder lambda measurement is active in the internal combustion engine (method step d)). As long as this is not the case, the method according to the invention enters a waiting loop, which is realized by a return to method step c). However, if the single-cylinder lambda measurement is active, the charge to be applied to the injector will be offset from the charge Q _{Ref applied} for adjustment of the reference operating point by a predetermined amount ΔQ. This calibration of the charge by ΔQ initially results in a change of lambda by the amount Δλ. The reference operating point remains essentially unchanged, since the torque build-up in homogeneous operation is only weakly influenced by the combustion lambda.

Under the conditions described here, namely that both the relative air mass r1 and the injection duration ti each remain quasi-stationary, this detected change in lambda corresponds to a specific change in the fuel quantity ΔD flowing through the injection valve. From the two quantities Δλ and ΔQ or ΔD and ΔQ, the individual gradient of the injection valve i used can then be calculated according to the following formula: k _i = Δλ / ΔQ = ΔD / ΔQ. (1)

With the help of this individual slope k _i , a correction factor f _Korr can be calculated which represents the deviation of the individual slope k _i from the slope of a predetermined reference characteristic which represents the average behavior of a multiplicity of produced injection valves of the same type. The calculation of the correction factor f _Korr is performed according to the following formula: f _cor = k _i / k _ref . (2)

The recognition of the change in the size λ resulting from the dimming of the charge and the calculation of the correction factor take place in 1 in step f). If the calculation of the correction factor has not been successful, the method according to the invention provides for a return to the beginning of step d).

If, on the other hand, however, the calculation of the correction factor has been successful, then this is used to calculate an individual D _i / Q _{i characteristic} curve in step g) for the injection valve i used. As already indicated above, the present invention calculated correction factor f _corr serves only to the slope of the D (Q) characteristic of the actual behavior of the injection valve to adjust. A possible offset error is not taken into account by the method according to the invention.

A use of the calculated according to the invention adapted D _i (Q _i ) characteristic in a later operation of the internal combustion engine, as shown in 1 is indicated by a return of step g) to step a), preferably takes place only if any offset errors are negligible compared to the inventively compensated errors in the slope of the characteristic of the injector used with respect to the reference characteristic or also be corrected by suitable methods.

3 shows a control unit 100 for controlling injection valves of an internal combustion engine according to the described method.

The inventive method can be at least partially realized as a computer program, which preferably on a the control unit 100 associated computing device 110 ( 3 ), for example a microprocessor, expires. As such, it can be stored together with other computer programs for controlling and / or regulating the internal combustion engine on a computer-readable data carrier. The data carrier may be, for example, a floppy disk, a compact disc or a so-called flash memory. The computer program stored on the data carrier can be sold as a product to a customer. In the case of a software implementation, it is also possible to transfer the computer program together with other computer programs for controlling and / or regulating the internal combustion engine - without the aid of an electrical data carrier - via an electronic communication network, in particular the Internet, as a product to a customer and to sell in this way.

Claims (8)

Method for operating an internal combustion engine, wherein a control of at least one injection valve of the internal combustion engine takes place in accordance with the individual behavior of the injector used representing flow to charge quantity characteristic during operation, characterized in that for calculating the flow to charge quantity characteristic curve a slope characteristic curve for the individual injection valve (i) is determined by varying a charge with which the individual injection valve (i) is actuated with respect to a reference charge (Qref) by a predetermined amount (ΔQ) and changing the charge ( ΔQ) is detected in the internal combustion engine, and the slope of the characteristic curve for the individual injection valve (i) is calculated from the change in the charge (ΔQ) and the change in the lambda value (Δλ). A method according to claim 1, characterized in that the flow is calculated to charge quantity characteristic curve for the individual injection valve by correcting a predetermined reference characteristic with the aid of a correction factor f _Korr . Method according to claim 2, characterized in that the correction factor f _{Korr is} calculated according to the following formula: f _cor = k _i / k _ref ; where k _{i is} the slope of the characteristic curve for the individual injection valve; and k _{ref represents} the slope of the reference characteristic. A method according to claim 3, characterized in that for the calculation of the slope k _i the flow (D) to charge quantity (Q) characteristic for an individual injection valve (i) of an internal combustion engine, the following steps are performed: - Operating the internal combustion engine in the homogeneous operation with preferably λ = 1; - Setting a reference operating point in the internal combustion engine by driving the Injector (i) with a reference charge (Q _Ref ) for each reference injection periods (t _Ref ); - Changing the charge with which the injection valve (i) is controlled, with respect to the reference charge (Q _Ref ) by a predetermined amount (ΔQ); Detecting a change in the lambda value (Δλ) resulting from the change in the charge (ΔQ) in the internal combustion engine; and - calculating the slope k _i, which is individual for the injection valve, according to the following formula: k _i = Δλ / ΔQ = ΔD / ΔQ (1) where Δλ = ΔD is valid only on condition that both the relative air mass (rl) and the duration of injection (ti) remain constant. A method according to claim 4, characterized in that the adjustment of the reference operating point takes place only within a predefined adaptation operating range of the internal combustion engine. A method according to claim 5, characterized in that the change in the amount of charge (ΔQ) with the aim of detecting a resulting change in the lambda value (Δλ) takes place only when a single-cylinder lambda measurement is active. Control unit ( 100 ) for operating an internal combustion engine, in particular in a vehicle, characterized in that the control unit ( 100 ) is configured to perform the control of the internal combustion engine according to the method of one of claims 1 to 6. Computer program for a control unit ( 100 ) of an internal combustion engine, characterized by program code, which is set up for carrying out a method according to one of claims 1 to 6, when it is mounted on a control unit ( 100 ) associated computing device ( 110 ), in particular a microprocessor.

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