DE102009002096A1 - Internal-combustion engine e.g. petrol-driven internal-combustion engine, operating method, involves evaluating influence of variation in difference of irregular variations of cylinders, and determining fuel composition - Google Patents

Abstract

The method involves executing cylinder-individual variation of fuel amount supplied to a cylinder to an unlubricated or lubricated air-/fuel-mixture in an afterstart phase of an internal combustion engine e.g. petrol-driven internal-combustion engine. A variation to the air-/fuel-mixture is executed at another cylinder. A difference of irregular operations of the cylinders is evaluated in association with the air-/fuel-mixture. The influence of the variation in the difference of the irregular variations is evaluated. A fuel composition is determined from the evaluation of the influence. The fuel mixture comprises petrol/ethanol fuel mixture, petrol/methanol fuel mixture and/or petrol/ethanol/methanol fuel mixture and/or diesel/biodiesel fuel mixture. An independent claim is also included for a device for operating an internal-combustion engine.

Description

State of the art

The The invention relates to a method and an apparatus for operating an internal combustion engine with at least two cylinders, which with stored in a tank fuel in different fuel quality and / or stored fuel mixtures from a first and at least a second fuel in different mixing ratios can be operated and where different fuel qualities and / or fuel mixtures of different composition different Air / fuel ratios to achieve a stable Require combustion and / or a different evaporation behavior exhibit.

The The invention further relates to a corresponding device for Implementation of the procedure.

at the start of internal combustion engines based on gasoline engines plays the metering of the fuel quantity to be injected is a decisive factor Role for the ignitability of the air / fuel mixture as well as for the exhaust gas composition. The needed Fuel quantity depends heavily on the fuel properties, in particular, the vaporization properties of the fuel, from.

With A start amount adaptation can be done via the evaluation of the Speed of the internal combustion engine, for example, too lean air / fuel ratio be recognized. With a Nachstartadaption the rough running becomes evaluated the internal combustion engine. With a subsequent Mixture greasing can be a bad evaporation behavior of the fuel be compensated.

Internal combustion engines On the basis of gasoline engines are generally fueled Hydrocarbons derived from fossil fuels based on refined Operated oil. To this fuel is increasingly off renewable raw materials (plants) produced alcohol, for example Ethanol or methanol, in different mixing ratios added. In the US and Europe is often a mix of 75-85% Ethanol and 15-25% gasoline used under the brand name E85. The internal combustion engines are designed so that they are both pure Gasoline can also be operated with mixtures up to E85; this is called "flex-fuel operation".

By Any mixture of gasoline and alcohol results in a wide Variability of the fuel properties, in particular the stoichiometry and the evaporation behavior.

From the DE 41 17 440 C2 a method for adaptively adjusting a fuel / air mixture for taking into account fuel properties in the operation of an internal combustion engine is known which comprises a lambda controller which outputs a control factor RF, and having an adaptation integrator which outputs a variable adaptation speed adaptation factor AF, in addition to the control factor FR affects the setting of the fuel / air mixture. It is provided that it is checked whether the lambda control deviation amplitude exceeds a first threshold, and, if so, the adaptation speed is set to an increased value until a predetermined condition is satisfied, after which switches back to a low adaptation speed becomes.

The method makes it possible to operate internal combustion engines, which can be operated with different fuels, trouble-free. For example, when switching from a fuel gasoline to a fuel mixture of 85% ethanol and 15% gasoline, the injection time must be increased by more than 20% in order to obtain the same lambda values in the exhaust gas. After in the scriptures DE 41 17 440 C2 described method is carried out a corresponding adaptation intervention. Since a fuel change in comparison to the compensation of aging influences or manufacturing influences very strong correction of the injection times and thus the adaptation intervention must be made, the adaptation rate is significantly increased in a pre-proposed process when a fuel change detected.

On The basis of the adjusted adaptation value can be the fuel mixture ratio be determined. Despite the increased speed of adaptation the process requires a sufficiently long settling time. Does a refueling process cause a large change in the fuel mixture ratio This can lead to starting difficulties and misfiring resulting in increased exhaust emissions leads.

In addition to a change in the fuel mixing ratio of an internal combustion engine operated in flex-fuel operation, a variation of the fuel quality, for example even in the case of pure gasoline operation, can lead to starting problems. The fuel quality is particularly a factor in the evaporation properties of the fuel. If the proportion of alcohol is unknown, a distinction between the two causes is difficult. An enrichment of the air / fuel mixture in response to a poor starting behavior of the internal combustion engine is therefore not always suitable in a flex-fuel application, as is the case of pure Ben is known zinbetrieb ago.

From another application of the applicant with the file number DE 10 2007 035 317 a method is known for operating an internal combustion engine having at least two cylinders, which can be operated with fuel stored in a tank in different fuel quality and / or stored fuel mixtures of a first and at least a second fuel in different mixing ratios and wherein different fuel qualities and / or fuel mixtures different composition require different air / fuel ratios to achieve stable combustion and / or have a different evaporation behavior. It is provided that a cylinder-specific variation of the amount of fuel supplied to the cylinder is performed on at least one cylinder to a lean and / or a rich air / fuel mixture that the influence of the variation on the starting characteristics and / or the smoothness of Cylinder and / or the internal combustion engine is evaluated and that with an achieved improvement in the starting characteristics and / or the smoothness of a fuel adaptation for all cylinders is performed.

The method enables the rapid detection and avoidance of start-up problems with a change in the fuel quality or the fuel composition with effect on the ignitability of the fuel:
In the application of the method shows, however, that in an evaluation of the uneven running problems can occur in practice, which can lead to a faulty interpretation of running smoothness. On the one hand, very stable boundary conditions with regard to, for example, rotational speed, load and / or temperature are required, which can not always be guaranteed in practice. On the other hand, variations due to manufacturing tolerances and / or aging of the components may distort the evaluation.

It It is therefore an object of the invention to provide a method for providing an optimal air / fuel mixture in particular for to provide the restart phase of an internal combustion engine, in which ensures a reliable evaluation of the uneven running is.

It is still an object of the invention, a device for carrying out of the method.

Disclosure of the invention

The The object concerning the method is solved by that in a Nachstartphase the internal combustion engine at least a cylinder a cylinder individual variation of the Cylinder supplied fuel amount to a lean or to a rich air / fuel mixture and at least one second cylinder a corresponding variation to a fat or lean air / fuel mixture carried out and subsequently it evaluated a difference in the rough running of both cylinders becomes, whereby the influence of the variation on the difference of the Laufunruhe both cylinders is evaluated and from a fuel adaptation for all cylinders performed or the fuel composition is determined.

The The object relating to the device is solved by that the internal combustion engine has a control / evaluation unit, with a cylinder-specific variation of the cylinders supplied Amount of fuel to a lean or a rich air / fuel mixture specifiable and a difference of the rough running of the mixture variation involved cylinder is evaluable.

With the method and the device according to the invention to carry out the method can be found in particular in the Post-start an optimal air / fuel mixture given Be sure to have a trusted feedback before at this stage the lambda probe is available, being reliable and it can be accurately recognized if the mixture is too lean or too rich is. This applies to both gasoline-powered internal combustion engines as well as for flex-fuel applications, as previously described. According to the invention, it is provided that differences of rough running or running noise values between at least two Cylinders are used and not absolute Laufunruhewerte. In order to can the o. g. Disadvantages in terms of unstable Boundary conditions or scattering are largely eliminated. One Another advantage arises from the fact that in the evaluation the difference of the rough running or smooth running of only two cylinders a clearer and above all earlier feedback to derive the mixture; than this in an evaluation the total running unrest would be possible.

In a preferred variant of the method is provided that the cylinder-individual Variation of the air / fuel mixture of the first cylinder and of the second cylinder at one for both cylinders together taken constant target lambda value is performed. The target lambda value can be time-dependent, depending on the load and operating phase be.

The variation of the air / fuel mixture of the first cylinder and the second cylinder can be carried out continuously or periodically, typically a variation until about 10% to the average of the air / fuel mixture of the first cylinder and the second cylinder is precontrolled. In addition, the variation of the air / fuel mixture between the two cylinders can be exchanged, whereby the previously fat-operated cylinder for lean-operated cylinder and the previously lean-operated cylinder to rich-operated cylinder. This has the advantage that cylinder individual differences (inequality) can be filtered out.

In a further variant of the method can be provided that the Individual cylinder variation of the air / fuel mixture of the first cylinder symmetrical to the cylinder individual variation of the Air / fuel mixture of the second cylinder performed becomes. On the one hand, this offers the advantage that overall through the Variation of the lambda value for the entire internal combustion engine remains constant. On the other hand, the variation of the air / fuel mixture Control technology simply by sign change for both cylinders involved are specified.

In an alternative process variant can while maintaining the Principles of evaluation of the difference of the running unrest provided be that the cylinder-specific variation of the air / fuel mixture of the first cylinder by means of a cylinder-specific variation the air / fuel mixture of several other cylinders of the internal combustion engine performed is taken, taking together for all cylinders involved a constant target lambda value is set.

As well It is also conceivable that the cylinder - specific variation of the Air / fuel mixture performed on several pairs of cylinders is, where for all involved cylinder pairs together a constant target lambda value is set. Also Here is the retention of the evaluation principle in terms of Difference of the uneven running of each pair of cylinders involved provided.

at the implementation of the process variants has proved to be advantageous when the target lambda value is λ = 1 is set. This is derived from the course of the Laufunruhe depending on the lambda value. The curve is similar a "bathtub" and has a pronounced Rise at a value from λ = 1. The rough running decreases for Values λ> 1 rapidly too. Ideally, therefore, the cylinders are by a value λ = 1 operated, with one cylinder at a value λ> 1 and the other involved Cylinder at λ <1 is operated, which is very easy to implement and also relatively Insensitive to disturbances for the smoothness is.

The Evaluation method also provides that the difference of the rough running with a predetermined threshold or with a setpoint for the difference of the rough running is compared and dependent from the result of the comparison, the entire mixture is emaciated or greased What makes a simple and robust adaptation of the mixture preparation can be realized. For this purpose, a corresponding control loop, for example, in the form of a PI controller, provided accordingly in the device circuit technology or by means of a corresponding Software is realized.

there can be provided that from the value for the rough running of the lean operated cylinder / lean cylinder operated a value for the rough running of the grease operated cylinder / the grease operated cylinder is subtracted and compared with the threshold, and, if this threshold is exceeded, the total mixture is greased, and, if the negated threshold falls below is, the entire mixture is emaciated. This evaluation can be done without large hardware and / or software effort in a short time be realized within the control / evaluation unit. One does to take advantage of that due to the course of the rough running in Dependence of the lambda value and the previously determined Difference in the rough running of the cylinder a forecast over the current lambda value is possible and accordingly Merging can be performed. Be the threshold not exceeded and the negated threshold not falls short, it can be assumed that the current Lambda value close to the target lambda value, usually λ = 1, lies.

The Functionality of the method with those previously described Process variants can in the control / evaluation or in a superordinate engine control unit of the internal combustion engine be implemented as hardware and / or as software. A software implementation has the advantage that in the presence of new findings, the parameters are very can be changed quickly by a software update.

A preferred application of the method as described above is to adapt the operating parameters of an internal combustion engine to the composition of a gasoline / ethanol fuel mixture and / or a gasoline / methanol fuel mixture and / or a gasoline / ethanol / methanol fuel mixture and / or or a diesel / biodiesel fuel mixture. Especially in flex-fuel applications, this method can be used to determine the ethanol content in gasoline. Likewise advantageously, the method can also be used to check the plausibility of an ethanol sensor. This method can also be used in a system without a sensor, in which, for example, an ethanol content determination by means of a start / warm-up adaptation takes place. Here it is made use of, that the rough running, especially in the post-start phase due to the specific Ver evaporation properties is very much dependent on the ethanol content or the methanol content in the fuel mixture. This makes it possible, among other things, to separate the ethanol content error from the usual multiplicative fuel errors.

A likewise preferred application of the method provides for the adaptation of the Operating parameters of the internal combustion engine to a present gasoline quality in front.

The Invention will be described below with reference to one shown in the figures Embodiment explained in more detail. Show it:

1 a schematic diagram of a flowchart of the method and

2 a schematic diagram of the rough running as a function of a lambda value or an ethanol content.

1 shows a flowchart 1 for the inventive method. After a start 10 the procedure is first in a query 20 for the switch-on condition checks whether all switch-on conditions are met. This can be, for example, certain waiting times between periodically performed interventions or operating parameters which indicate a trouble-free running of the internal combustion engine. If the query condition is not met, it repeats until all conditions are met. It can also be provided that the method is initially stopped.

If all conditions are met, the system performs a lean / rich function block 30 a targeted leaning of the air / fuel mixture for a first cylinder of the internal combustion engine. At the same time, in the example assumed, a greased air / fuel mixture is offered to a second cylinder, wherein the leaning and the enrichment of the air / fuel mixture for both cylinders of the internal combustion engine is to be performed symmetrically in the assumed method example. Preferably, a value of λ = 1 is maintained over all cylinders.

Subsequently, in a run evaluation block 40 determined a difference of the rough running of both involved in the process cylinder. In this case, the difference of the rough running is formed by a value of the uneven running of the cylinder operated with greased air / fuel mixture cylinder is subtracted from a value of the uneven running of the cylinder operated with lean air / fuel mixture. This thus formed difference of rough running (ΔL) is in a query block 50 initially compared with a threshold (S). If the threshold (S) is exceeded, what with a query 51 is checked, the total mixture is enriched (Gemischanfettung 60 ). If the negated threshold (-S) is exceeded, what with a query 52 is checked, the total mixture is emaciated (Gemischabmagerung 70 ). Will the threshold (S) in the query 51 not exceeded and the negated threshold (-S) in the query 52 not fallen below, it can be assumed that a lambda value 112 near λ = 1 is present. In this case, there is no total blend or total blend lean, with a return to the beginning of the process and the steps from the query 20 be repeated or the process is stopped, for example, if a timeout has been detected.

In another query 80 can be provided that is checked by means of this query, if a period end is reached. This query is required in particular in a periodic application of the method. If this is not the case, the difference of smoothness in the chute evaluation block continues 40 determined and according to the comparison with the threshold value (query block 50 ) the entire mixture greased or emaciated (Gemischanfettung 60 or mixture leaning 70 ). When the period end is reached, another query is made 90 a check whether the end condition has been reached. This may be the case, for example, if the lambda control is active in the after-start phase of the internal combustion engine or reliable values of the lambda sensor are supplied in full. If this is the case, the process is stopped (End 100 ). If this is not the case, the system learns a re-run of the method steps starting with the query 20 ,

In 2 is in a diagram 110 the course of a value for the rough running 111 depending on a lambda value 112 shown. The "trough-like" curve has a strong increase at a value λ = 1. At low lambda values 112 well below λ = 1 decreases the running noise 111 also very strong too. Ideally, the difference is smoothness 116 at a target lambda value 113 (Here λ = 1) is relatively low, because in this section of the curve, the rough running of the operated by the procedure lean cylinder 117 and the corresponding fat-operated cylinder 118 only slightly different. A total lambda value 119 of the two cylinders involved in the mixture variation corresponds to the target lambda value 113 (here λ = 1).

Will a large differential smoothness when too lean mixture 114 detected, there is a procedure Gemischanfettung 120 , Will a large differential smoothness when too rich mixture 115 detected an intermittent mixture takes place 130 ,

In a flex-fuel application, for example, it can also be provided that the uneven running 111 depending on an ethanol content 140 instead of the lambda value 112 is evaluated.

With the method and the device for carrying out the Method provides an optimal mixture in the post-start phase being, being a reliable and opposite Disturbances robust evaluation of the rough running is applied.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4117440 C2 [0007, 0008]
• - DE 102007035317 [0011]

Claims (12)

Method for operating an internal combustion engine having at least two cylinders, which can be operated with a different fuel quality and / or stored fuel mixtures from a first and at least a second fuel in different mixing ratios and wherein different fuel qualities and / or fuel mixtures of different composition different Require air / fuel ratios to achieve stable combustion and / or have a different evaporation behavior, characterized in that in a Nachstartphase the internal combustion engine at least a first cylinder, a cylinder-specific variation of the cylinder fuel amount supplied to a lean or a rich air - / Fuel mixture and performed on at least one second cylinder, a corresponding variation to a rich or lean air / fuel mixture and subsequently evaluating a difference in the rough running of both cylinders, the influence of the. Variation is evaluated on the difference of the rough running of both cylinders and from this a fuel adaptation is performed for all cylinders or the fuel composition is determined. A method according to claim 1, characterized in that the cylinder-specific variation of the air / fuel mixture of the first cylinder and the second cylinder at a combined for both cylinders constant target lambda value ( 113 ) is carried out. Method according to claim 1 or 2, characterized that the cylinder-specific variation of the air / fuel mixture of the first cylinder symmetrical to the cylinder-individual variation the air / fuel mixture of the second cylinder performed becomes. A method according to claim 1 or 2, characterized in that the cylinder-specific variation of the air / fuel mixture of the first cylinder is carried out by means of a cylinder-specific variation of the air / fuel mixture of a plurality of other cylinders of the internal combustion engine, wherein taken together for all cylinders involved constant target lambda value ( 113 ) is set. A method according to claim 1 or 2, characterized in that the cylinder-individual variation of the air / fuel mixture is carried out on a plurality of cylinder pairs, wherein taken together for all participating cylinder pairs a constant target lambda value ( 113 ) is set. Method according to one of claims 1 to 5, characterized in that as a target lambda value ( 113 ) the value λ = 1 is set. Method according to one of claims 1 to 6, characterized in that the difference of the rough running with a predetermined threshold is compared and dependent from the result of the comparison, the entire mixture is emaciated or greased becomes. Method according to claim 7, characterized in that that from the value of the rough running of the lean cylinder / the lean cylinder operated a value for the rough running of the Bold operated cylinder / the fat operated cylinder and deducted is compared with the threshold, and if that threshold is exceeded is, the total mixture is greased, and, if the negated Threshold is exceeded, the entire mixture is emaciated. Application of the method according to one of the claims 1 to 8 for the adaptation of the operating parameters of an internal combustion engine to the composition of a gasoline / ethanol fuel mixture and / or a gasoline / methanol fuel mixture and / or a gasoline / ethanol / methanol fuel mixture and / or a diesel / biodiesel fuel mixture. Application of the method according to one of the claims 1 to 8 for the adaptation of the operating parameters of the internal combustion engine to a given gasoline quality. Device for operating an internal combustion engine with at least two cylinders stored in a tank Fuel of different fuel quality and / or stockpiled fuel mixtures from a first and at least a second fuel in different mixing ratios can be operated and where different fuel qualities and / or fuel mixtures of different composition different Air / fuel ratios to achieve a stable Require combustion and / or a different evaporation behavior have, characterized in that the internal combustion engine a Control / evaluation has, with a cylinder-individual Variation of the amount of fuel supplied to the cylinders to a lean or to a rich air / fuel mixture specifiable and a difference in the turbulence of those involved in the mixture variation Cylinder is evaluable. Apparatus according to claim 11, characterized in that the functionality of the method according to claims 1 to 8 in the control / evaluation unit or in a higher-level motor control unit of the internal combustion engine is implemented.