DE102018009102A1 - Method for correcting a fuel quantity to be introduced into at least one combustion chamber of an internal combustion engine for a motor vehicle - Google Patents

Abstract

The invention relates to a method for correcting an amount of fuel to be introduced into at least one combustion chamber of an internal combustion engine for a motor vehicle by means of a fuel injection, comprising the steps: during a reference state, during which the amount to be corrected is not introduced: determining reference values, which are at least one Characterize speed increase (n_incr_s1) and at least one quantity of fuel introduced into the internal combustion engine during the reference state (step S1); during a test state during which the quantity to be corrected is introduced into the combustion chamber: determining test values which characterize at least one speed increase (n_incr_s2) and at least one quantity of fuel introduced into the internal combustion engine during the test state (step S2); Comparing the reference values with the test values (step S3); and correcting the amount depending on the comparison (step S4).

Description

The invention relates to a method for correcting a quantity of fuel to be introduced into at least one combustion chamber of an internal combustion engine for a motor vehicle by means of a fuel injection.

The DE 10 2010 051 035 A1 discloses a method for correcting an air path error of a cylinder of an internal combustion engine of a motor vehicle, in which an injection quantity of the cylinder is corrected.

In addition, the DE 10 2008 051 820 A1 a method for the individual correction of injection quantities or duration, in particular for a ballistic area of a fuel injector.

Furthermore, the DE 10 2004 053 418 A1 a method for controlling an injection system of an internal combustion engine as known.

It is an object of the present invention to provide a method so that operation of an internal combustion engine for a motor vehicle with particularly low fuel consumption can be ensured.

This object is achieved by a method having the features of patent claim 1. Advantageous refinements with expedient developments of the invention are specified in the remaining claims.

The method according to the invention for correcting a quantity of a preferably liquid fuel to be introduced into at least one combustion chamber of an internal combustion engine for a motor vehicle by means of a fuel injection comprises a first step in which reference values are determined during a reference state during which the quantity to be corrected is not introduced into the combustion chamber which characterize at least one or more speed increases over a characteristic crank angle range and at least one or more fuel quantities introduced into the internal combustion engine during the reference state. In other words, the reference values characterize at least one or more, at least one or more burns occurring during the reference state in the internal combustion engine, in particular in the combustion chamber, on an output shaft of the internal combustion engine designed as a crankshaft, or applied and exerted torques of the internal combustion engine occurring during the reference state .

Furthermore, the reference values characterize at least one or more fuel quantities which are introduced into the internal combustion engine, in particular at least into the combustion chamber, during the reference state. For this purpose, for example, at least one or more reference signals are recorded, in particular recorded, during the reference state, the at least one reference signal or the reference signals characterizing or characterizing the reference values. In other words, for example, the respective reference signal is formed by the reference values or the reference signal comprises the reference values.

In a second step of the method, during a test state during which the amount to be corrected is introduced into the combustion chamber, test values are determined which show at least one or more speed increases over a characteristic crank angle range, and at least one or more amounts of fuel introduced into the internal combustion engine during the Characterize the test state. In other words, the test values characterize combustion air ratios of the internal combustion engine that occur during the test state. Furthermore, the test values characterize at least one or more torques of the internal combustion engine that are introduced or exerted on the crankshaft via at least one or more burns occurring during the test state in the internal combustion engine, in particular in the combustion chamber. Furthermore, the test values characterize at least one or more fuel quantities that are introduced into the internal combustion engine, in particular at least into the combustion chamber, during the test state.

In a third step of the method, the reference values are compared with the test values, with the amount being corrected as a function of the comparison in a fourth step of the method. For example, in particular in the second step, at least one target value of the quantity to be corrected is specified. Depending on the condition, in particular the aging condition, of the internal combustion engine, in particular an injector of the internal combustion engine, an actual value of the quantity to be corrected results from the predetermined target value, the actual value or the quantity to be corrected actually having the actual value in the Combustion chamber is introduced. For example, the quantity to be corrected is introduced into the combustion chamber by means of the injector, in particular injected directly into the combustion chamber. In particular with increasing lifespan or with As the age of the internal combustion engine, in particular the injector, increases, the actual value can deviate from the target value. The target value thus characterizes a target quantity of the quantity to be corrected, and the actual value characterizes an actual quantity of the quantity to be corrected.

It has proven to be particularly advantageous if the actual value or the actual quantity is determined indirectly, in particular on the basis of the test values. The ascertained actual value of the speed increase or the ascertained actual quantity is compared with the nominal value or with the nominal quantity, the quantity being corrected on the basis of the comparison. The target quantity is predetermined, for example, by actuation, in particular by electrical actuation, of the injector. If it is determined on the basis of the comparison that the actual value deviates excessively from the target value, the quantity to be corrected is corrected in such a way that the control of the injector is corrected, that is to say adapted to the deviation. The quantity or the control is corrected in such a way that a difference between the actual value and the target value is at least reduced or eliminated.

The method according to the invention is thus a method for correcting the quantity also referred to as the injection quantity on the basis of at least one additional test injection and quantity detection via a difference in the speed increase or the speed increase. The aforementioned test injection means the introduction, in particular the injection, of the amount to be corrected during the test state. The invention is based in particular on the following knowledge: In today's engine applications, there are ever increasing demands on the injection quantity accuracy of injectors with regard to emission stability. Furthermore, it is becoming more and more important in this context to keep the injection quantities at least essentially constant or stable over their service life. Small injection quantities for so-called pilot or pre-injections and / or for so-called post or post-injections play an important role here. Previous quantity corrections for the correction of such quantities, also referred to as very small quantities, are usually carried out during overrun operation. In today's applications, there are hardly any overrun phases due to roll or sail functions. This means that an overrun phase would have to be actively requested, but this would lead to an increase in fuel consumption. In addition, the post-injection cannot be corrected during the overrun operation, that is to say during the overrun, so that the conditions are completely different due to the lack of main injection. The aforementioned problems and disadvantages can be avoided by means of the method according to the invention, since both the reference state and the test state are preferably carried out during a fired operation of the internal combustion engine or is a fired operation of the internal combustion engine. During the fired operation, the internal combustion engine, in particular at least the combustion chamber, is supplied with fuel and air, so that combustion processes take place in the internal combustion engine, in particular in the combustion chamber. Both the reference state and the test state preferably each comprise several successive work cycles of the internal combustion engine.

The reference state is a state of the internal combustion engine without the amount to be introduced, in particular injection, of the correcting quantity, so that the reference state is, for example, an operation with a pre-injection and a subsequent main injection within the respective work cycle. The combustion air conditions, the air masses and the injected fuel quantities are recorded for an applicable number of work cycles. Thereupon at least or exactly one additional test injection is carried out during the reference state, in particular within the respective working cycle of the reference state, in the course of which the quantity to be corrected is introduced into the combustion chamber, in particular injected directly. The test injection is activated or carried out, for example, with a desired injection quantity that is important for the application for an applicable number of work cycles. In addition, the above-mentioned signals, that is to say the combustion air conditions, the air masses and the injected fuel quantities, are recorded or recorded during the test state. A quantity correction requirement is determined via a relative comparison of the signals during the test state and during the reference state.

With the aid of the method according to the invention, important injection quantity ranges of the injector can be corrected and at least essentially kept constant or stable over its service life. Post-injection with completely different conditions can also be corrected and kept stable. There are no longer any overrun phases, although the process is not restricted to very small quantities.

Further advantages, features and details of the invention result from the following description of a preferred exemplary embodiment and from the drawing. The features and combinations of features mentioned above in the description and the following in The features and combinations of features mentioned in the description of the figures and / or shown alone in the figures can be used not only in the combination specified in each case, but also in other combinations or on their own without departing from the scope of the invention.

• 1 ein Flussdiagramm zum Veranschaulichen eines erfindungsgemäßen Verfahrens;
• 2 Diagramme zum weiteren Veranschaulichen des Verfahrens;
• 3 ein Diagramm zum weiteren Veranschaulichen des Verfahrens;
• 4 ein weiteres Diagramm zum weiteren Veranschaulichen des Verfahrens; und
• 5 ein weiteres Diagramm zum weiteren Veranschaulichen des Verfahrens;

The drawing shows in:

• 1 a flowchart to illustrate a method according to the invention;
• 2nd Diagrams to further illustrate the method;
• 3rd a diagram to further illustrate the method;
• 4th another diagram to further illustrate the method; and
• 5 another diagram to further illustrate the method;

In the figures, identical or functionally identical elements are provided with the same reference symbols.

1 shows a flowchart to illustrate a method for correcting a quantity of a fuel, in particular a liquid fuel, to be introduced into at least one combustion chamber, preferably a cylinder, of an internal combustion engine for a motor vehicle, in particular for a motor vehicle, by means of a fuel injection, in particular by means of direct fuel injection. The internal combustion engine can be operated in a fired mode by means of the fuel. In a first step S1 During a reference state during which the quantity to be corrected is not introduced into the combustion chamber, reference values are determined which characterize at least or exactly an increase in speed over a defined angular range and fuel quantities introduced into the internal combustion engine during the reference state. Thus, for example, respective signals are recorded, in particular recorded, during the reference state. A first of the signals characterizes the speed increase that occurs during the reference state. A second of the signals characterizes the amounts of fuel that are introduced, in particular directly injected, into the internal combustion engine and thus at least into the combustion chamber during the reference state. The signals include the reference values or are formed by the reference values. Since the internal combustion engine is supplied with the fuel and air during the reference state, the internal combustion engine is operated in the fired mode during the reference state. In the fired mode, combustion processes take place in the internal combustion engine, in particular at least in the combustion chamber.

With one preferably the first step S1 subsequent second step S2 During a test state during which the quantity to be corrected is introduced into the combustion chamber, in particular directly injected, test values are determined which characterize at least or exactly an increase in speed over a defined angular range and fuel quantities introduced into the internal combustion engine during the test state. For example, the aforementioned signals are recorded, in particular recorded, during the test state, the signals then characterizing or encompassing the test values. In a third step S3 In the method, for example, the reference values are compared with the test values, so that, for example, in a fourth step S4 the amount of the method is corrected depending on the comparison. In particular, it is provided that, for example, in a second step S2 or a third step S3 the quantity to be corrected is determined, in particular calculated, on the basis of the test values or on the basis of the signals. The quantity is introduced, in particular injected, by activation, in particular electrical activation, of at least one injector, by means of which the quantity is introduced into the combustion chamber, in particular injected directly into the combustion chamber.

From this activation of the injector, the quantity results as an actual quantity, which is determined, in particular calculated, on the basis of the signals or on the basis of the test values. The control is based on a target quantity, which is specified. In other words, it is desired that the actual quantity results from the control of the injector in such a way that the actual quantity corresponds to the nominal quantity or deviates only slightly from the nominal quantity. For example, the actual quantity is compared with the target quantity. If the actual quantity deviates excessively from the nominal quantity, it can be concluded from this deviation that the control of the injector did not lead to the introduction of the desired nominal quantity. As a result, the control of the injector and thus the actual quantity can be corrected so that the actual quantity corresponds to the target quantity, which is also referred to as the target quantity. For example, the actual quantity is compared with the target quantity by means of a map and / or a transfer function. On the basis of the comparison or on the basis of the deviation, for example, a correction value is determined, by which the control or the quantity is corrected, so that the actual quantity corresponds to the target quantity. This correction value is stored in a memory device, for example an electronic computing device for controlling and / or regulating the internal combustion engine. In particular, the correction is carried out by correcting a control period of the injector.

2nd shows diagrams 10th and 12 to further illustrate the process. On the ordinate 14 of the diagram 10th for example, the quantity or its value is plotted, the quantity being introduced into the combustion chamber, in particular directly injected, for example as part of an additional injection. On the ordinate 16 of the diagram 12 is a ratio of lambda to air mass, and on the respective abscissa 18th of the diagrams 10th and 12 work cycles of the internal combustion engine are plotted. At the first step S1 or during the reference state, for example, the signals are averaged in order to thus realize respective values for the air masses, the combustion air conditions and the fuel quantities. At one step S5 For example, an additional injection, in particular an additional pilot injection, is activated on at least or exactly one combustion chamber, which results in a difference D results in the levels of the signals. The difference correlates with the amount realized by the additional injection, which is to be corrected, for example, or is being corrected.

Due to hydraulic pressure wave effects in a fuel distribution element, also referred to as a rail, the injection quantity introduced by the additional test injection can systematically vary depending on the operating point. For this reason, a transfer function or a map for the operation-independent target speed increase difference may be necessary, the map in 4th is shown. This in 4th The map shown is a map with an increase in the target speed as a transfer function for a specific desired quantity of the additional injection, also referred to as test injection, and is dependent on the operating point, in particular for injectors that are in good working order. On the abscissa 20th the speed of the internal combustion engine is plotted, and on the ordinate 22 the load or the torque of the internal combustion engine is plotted, for example. According to the map 4th a detected target speed increase difference is entered for a specifiable rail pressure.

• Dehzahlanstieg S1: n_incr_s1 = (seg_n_max_s1 - seg_n_min_s1)
• Dehzahlanstieg S2: n_incr_s2 = (seg_n_max_s2 - seg_n_min_s2)
• Differenz Drehzahlanstieg: Diff_n_incr_s2-s1 = (n_incr_s2 - n_incr_s1)

The speed increase difference is according to 5 determined as follows:

• Rise number increase S1 : n_incr_s1 = (seg_n_max_s1 - seg_n_min_s1)
• Rise number increase S2 : n_incr_s2 = (seg_n_max_s2 - seg_n_min_s2)
• Difference in speed increase: Diff_n_incr_s2-s1 = (n_incr_s2 - n_incr_s1)

In one embodiment, the angle ranges can be defined differently depending on the operating point. It is with OT denotes the top dead center.

The value of the difference in the speed increase lies between S1 and S2 (Diff_n_incr_s2-s1) within a tolerance band to be determined around the target speed increase difference expected for this operating point, no correction is made. Is that S2 - S1 Difference in speed increase above a threshold of the map target value, the control duration of the injector is gradually decremented.
Is that S2 - S1 Difference in speed increase below a threshold of the map target value, the control duration of the injector is incremented incrementally.

Furthermore shows 3rd a diagram on the abscissa 24th the control duration of the injector is plotted. On the ordinate 26 the amount of fuel resulting from the control duration of the injector is applied, which is introduced into the combustion chamber, in particular injected directly. Important pre- and post-injection quantity points for different rail pressures are in 3rd With P designated. Furthermore, with K denotes that the method is a correction function by means of which the quantity of fuel to be introduced into the combustion chamber by means of the test or additional injection can be kept stable or at least essentially constant.

Reference symbol list

10th

diagram

12

diagram

14

abscissa

16

abscissa

18th

ordinate

20th

abscissa

22

ordinate

24th

abscissa

26

ordinate

D

difference

K

Correction function

n_incr_s1

Speed increase

n_incr_s2

Speed increase

Diff_n_incr_s2-s1

Difference in speed increase

OT

Top Dead Center

P

Point

S1

first step

S2

second step

S3

Third step

S4

fourth step

S5

step

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102010051035 A1 [0002]
• DE 102008051820 A1 [0003]
• DE 102004053418 A1 [0004]

Claims (4)

Method for correcting a quantity of fuel to be introduced into at least one combustion chamber of an internal combustion engine for a motor vehicle by means of a fuel injection, comprising the steps: during a reference state during which the quantity to be corrected is not introduced: determining reference values which characterize at least one speed increase (n_incr_s1) and at least one quantity of fuel introduced into the internal combustion engine during the reference state (step S1); during a test state during which the quantity to be corrected is introduced into the combustion chamber: determining test values which characterize at least one speed increase (n_incr_s2) and at least one quantity of fuel introduced into the internal combustion engine during the test state (step S2); Comparing the reference values with the test values (step S3); and Correction of the amount depending on the comparison (step S4). Procedure according to Claim 1 , characterized in that the reference state and the test state each extend over several successive work cycles of the internal combustion engine. Procedure according to Claim 2 , characterized in that the amount to be corrected is introduced into the combustion chamber in each working cycle of the internal combustion engine during the test state. Method according to one of the preceding claims, characterized in that the amount is injected directly into the combustion chamber.

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