WO2016134943A1

WO2016134943A1 - Method and device for operating an internal combustion engine

Info

Publication number: WO2016134943A1
Application number: PCT/EP2016/052399
Authority: WO
Inventors: Hong Zhang; Gerhard Eser
Original assignee: Continental Automotive Gmbh
Priority date: 2015-02-26
Filing date: 2016-02-04
Publication date: 2016-09-01
Also published as: DE102015203458B3

Abstract

Disclosed is an internal combustion engine having several cylinders, each of the cylinders being associated with a respective fuel injection valve and being associated with a common exhaust gas probe which is arranged in or upsteam of a catalytic converter in a exhaust gas tract and which provides a measurement signal (MS_A). Furthermore, a crankshaft angle sensor is associated with the internal combustion engine, the measurement signal (MS_N) of which sensor is representative of a plot of a crankshaft angle of a crankshaft. In order to operate the internal combustion engine, a noise characteristic (RM) is determined on the basis of a plot of the measurement signal (MS_A) of each exhaust gas probe, which noise characteristic is representative of a measure of a noise of the measurement signal (MS_A) of the respective exhaust gas probe. On the basis of a plot of the measurement signal (MS_N) of the crankshaft angle sensor, an uneven running characteristic (LU) associated with each cylinder is determined. On the basis of the uneven running characteristic (LU) associated with each respective cylinder and the noise characteristic (RM), corresponding control signals (SG_INJ) for controlling the corresponding fuel injection valves are adapted for the purpose of adjusting an air/fuel ratio in the individual cylinders.

Description

description

Method and device for operating an internal combustion engine A contribution pollutant emissions in an operation of a

To keep the engine as small as possible, can be provided through the ge ^¬ Suppressing of emissions arising in the respective cylinders during combustion of the air / fuel mixture. On the other hand are in

Internal combustion engines exhaust aftertreatment systems in use, which convert the pollutant emissions generated during the combustion process of the air / fuel mixture in the respective cylinder into harmless substances. For this purpose, catalytic converters are used, the

Convert carbon monoxide, hydrocarbons and possibly nitrogen oxides into harmless substances.

Targeting the generation of pollutant emissions during combustion as well as converting the pollutant components to high efficiency by an exhaust catalyst requires a very precisely adjusted air / fuel ratio in the respective cylinder. From DE 10 2005 009 101 B3 a cylinder-specific lambda control is known, wherein a cylinder-individual

Air / fuel ratio deviation is determined, which is then fed to a controller whose output is a regulator value for influencing the air / fuel ratio in the respective cylinder. The controller comprises an integral component.

From DE 10 2006 026 390 AI an electronic control ^¬ device for controlling the internal combustion engine in a motor vehicle is known with a Laufunruheermittlungseinheit and with an injection quantity correction unit, wherein a defined group of cylinders is associated with a lambda probe. The injection quantity correction unit is such out ^¬ staltet that the injection quantity of a to be examined ZY Linders of the group defined by a one Laufunruhedif- reference value associated differential adjustment is lean adjustable in the direction and the amount of injection of at least one of the remaining cylinders is made rich adjusted accordingly in direction, so that a total of a predetermined lambda value is achieved. It is furthermore designed such that a cylin ^¬ derindividueller Differenzverstellwert for each cylinder is adjustable and that cylinder-individual correction values can be determined by the cylinder-individual Differenzverstellwerte be set in relation to each other.

From DE 102012223129 B3 a method for operating an injection device for an internal combustion engine is described, in which a profile of a value of a rotational speed of a crankshaft within a predetermined period of time for each combustion chamber of the plurality of combustion chambers is determined. Furthermore, the respective courses are compared with a predetermined comparison course in order to determine a deviation between the respective power output of the combustion chambers from a predetermined power output. Furthermore, in each case a differential is determined and / or an integral of the profile is determined within the predetermined time period. In addition, the respective differentials determined are compared with a differential of the predefined comparison profile and / or of the respectively determined integral with an integral of the predefined comparison profile.

From DE 10 2009 027 822 AI a method for determining a trim of at least one cylinder of an internal combustion engine is known, wherein the at least one cylinder is operated in succession in at least one lean phase and at least one rich phase in order to provide exhaust gas neutrality on the average, wherein a running noise signal is evaluated in a lean phase in order to obtain a cylinder-specific characteristic regarding the trim.

DE 10 2005 047 829 B3 describes a method for controlling the uneven running of reciprocating engines. A Fourier series is used with Zl summands a _n , b _n ..., where n = 2, 3, ... to Z, where Z is the number of cylinders of the engine, as a series representation of mean engine speed values , The order n is chosen so that at least an odd multiple of half the camshaft frequency is taken into account in the series representation for generating a control deviation e _n . An individual contribution to the control deviation for each addend of the series representation is calculated by means of a predetermined value k = k (n), k (n) originating from a preliminary investigation and being the value at which the maximum expression of the effect of the last ignition of the cylinder, which will ignite next, is measured. An overall deviation% is formed from the individual contributions.

The object underlying the invention is to provide a method and a device for operating an internal combustion engine with a plurality of cylinders, which or in a simple and reliable manner contributes to a

Low pollutant operation.

The object is solved by the features of the independent claims. Advantageous embodiments are characterized in the subclaims. An embodiment of the invention is characterized by a method and a corresponding apparatus for operating an internal combustion engine having a plurality of cylinders, each associated with an injection valve and each associated with a common exhaust probe disposed in an exhaust tract in or upstream of an exhaust catalyst is. The exhaust gas probe provides a measurement signal. Furthermore, a crankshaft angle sensor is provided, whose measurement signal is representative of a curve of a crankshaft angle of a crankshaft.

Depending on a profile of the measurement signal of the respective exhaust gas probe, a noise characteristic value is determined, which is representative of a measure of a noise of the measurement signal of the respective exhaust gas probe. Depending on a course of the measurement signal of the crankshaft angle sensor, an uneven running characteristic associated with the respective cylinder is determined. Depending on the the respective cylinder associated rough running characteristic and the noise characteristic value, respective control signals for driving the respective injection valves adapted in terms of equalizing an air / fuel ratio in the individual cylin ^¬ countries.

In this way, the knowledge is used that the

Noise characteristic is characteristic of an uneven

Metering of fuel to the individual cylinders. By additionally taking into account the respective unevenness characteristic value, which is representative of a similarity measure of segment times of the respective cylinder compared to segment times of the other cylinders, an assignment to the individual cylinders is then possible in a suitable manner and thus a simple and reliable matching of the air - / Fuel ratio in the individual cylinders possible. _n

5

Thus, an exact ^¬ He knowledgeable a phase position or a point in time of the decisive for the respective cylinder measurement signal of the exhaust probe is in this procedure is not mandatory, which would otherwise be determined empirically and can be corrected by a subsequent adaptation. This adaptation is especially in special exhaust ^¬ configurations, such as a turbocharger, with greatly varying times of the measurement signal of the exhaust probe is a particular challenge.

According to an advantageous embodiment, the determination of the noise characteristic value comprises a Fourier transformation. In particular, this may include a fast Fourier transform. This enables a particularly efficient calculation.

According to a further advantageous embodiment, the respective uneven running parameter is indicative of a direction of a similarity measure of segment times of the respective cylinder in comparison to the segment times of the other cylinders. The direction is in particular represented by a sign.

In accordance with a further advantageous refinement, the respective uneven running parameter characterizes a relevance of adapting the respective actuating signal to trigger the respective injection valve. The relevance has in particular either a relevance value, for example a Neut ^¬ ralwert, such as 1, or a Irrelevanzwert, such as a fade value, such as 0. In this connection it is particularly advantageous if the irregular running characteristic value is determined such that within a predetermined range of the degree of similarity of segment time ^¬ time of the respective cylinder in comparison to segment time durations of the other cylinders its relevance irrelevance having. In this way, the control signal for a respective cylinder can simply not be adapted within the suitably predetermined range, which can be determined for example by appropriate tests or simulations can be determined, while it is correspondingly adapted when the relevance value is present.

According to a further advantageous embodiment, the noise characteristic value is fed on the input side to a PI controller. By providing the PI controller, a particularly efficient and effective adaptation of the respective actuating signal can take place.

In this context, it is advantageous if a degree of taking into account a control actuating signal of the PI controller for adjusting the respective actuating signal for driving the respective injection valve is determined, depending on the rough running characteristic value taking into account the similarity measure of segment time periods of the respective cylinder compared to segment time periods of the other Cylinder. In this way, a particularly effective adjustment in the sense of equalizing the air / fuel ratios in the individual cylinders can he follow ^¬.

Segment time durations here designate durations of a respective cylinder segment, wherein a cylinder segment results from the crankshaft angle of a working cycle divided by the number of cylinders of the internal combustion engine. For example, in a four-stroke internal combustion engine with four cylinders, a crankshaft angle of 720 ° results: 4, ie 180 °.

Embodiments of the invention are explained in more detail below with reference to the schematic drawings. Show it:

1 shows an internal combustion engine with a control device, FIG. 2 shows a block diagram of the control device,

FIGS. 3A and 3B show first signal curves,

FIG. 3C shows a frequency spectrum associated with the first signal progressions;

Figures 4A and 4B second waveforms and

FIG. 4C shows an associated to the second waveforms

Frequency spectrum.

Elements of the same construction or function are identified across the figures with the same reference numerals.

An internal combustion engine (FIG. 1) comprises an intake tract 1, an engine block 2, a cylinder head 3 and an exhaust tract 4. The intake tract 1 preferably comprises a throttle valve 11, furthermore a collector 12 and an intake manifold 13 which leads to a cylinder ZI via an intake passage is guided in the engine block 2. The engine block 2 further includes a crankshaft 21, which is coupled via a connecting rod 25 with the piston 24 of the cylinder ZI. The cylinder head 3 includes a valve gear with a gas ^¬ inlet valve 30, a gas outlet 31, and valve actuators 32, 33. The cylinder head 3 further comprises an injection valve 34 and a spark plug 35. Alternatively, the injector 34 may be arranged in the intake tract. 1

The exhaust tract 4 comprises an exhaust gas catalyst 40, which is preferably designed as a three-way catalyst. ₀

O

A control device 6 is provided, which is assigned to sensors which detect different measured variables and determine the measured values of the measured variable. Operating variables include not only the measured variables but also derived from these variables. The control device 6 controls depending on at least one of the operating variables, the actuators associated with the internal combustion engine, and to which respective actuators are associated, by generating actuating signals for the actuators.

The control device 6 may also be referred to as a device for operating the internal combustion engine.

The sensors are a pedal position sensor 71, which detects the position of an accelerator pedal 7, an air mass meter 14, which air mass flow upstream of the throttle valve 11 detected, a temperature sensor 15 which detects an intake air ^¬ temperature, a pressure sensor 16 which detects the intake manifold pressure, a crankshaft angle sensor 22, which detects a crankshaft angle, to which a rotational speed is then assigned to ^¬ , a torque sensor 23 which detects a torque of the crankshaft 21, a camshaft angle sensor 36a, which detects a camshaft angle and an exhaust probe 41, which detects a residual oxygen content of the exhaust gas and the measurement signal MS_A is characteristic of the air / fuel ratio in the cylinder ZI when burning the engine

Air / fuel mixture. The exhaust gas sensor 41 is formed for example as a ^¬ lambda probe, in particular as a linear lambda probe, and generates, if it is formed as a linear lambda probe from ^¬, over a wide range of relevant

Air / fuel ratio to a proportional to this measurement signal.

The measurement signal MS_N of the crankshaft angle sensor 22 is thus representative of a profile of the crankshaft angle of the crankshaft 21. Preferably, a donor gear with teeth on the Crankshaft 21 arranged and associated with the crankshaft angle sensor 22, so that depending on the measurement signal of the crankshaft angle sensor 22 tooth times can be determined. Depending on the configuration, any subset of ge ^the cited sensors can be present or additional sensors may also be present.

The actuators are, for example, the throttle valve 11, the gas inlet and gas outlet valves 30, 31, the injection valve 34 or the spark plug 35.

In addition to the cylinder ZI, further cylinders Z2 to Z4 are also provided, to which corresponding actuators are then assigned. Preferably, each exhaust bank on cylinders, which can also be referred to as a cylinder bank, is assigned in each case an exhaust gas line of the exhaust gas tract 4 and the respective exhaust gas line is assigned an exhaust gas probe 41 correspondingly. The control device 6 preferably comprises a computing unit and a memory for storing data and programs. For operating the internal combustion engine, a program for operating the internal combustion engine is stored in the control device 6, which can be executed during operation in the arithmetic unit. The software implemented by the program, the block diagram described below with reference to FIG 2. The program for operating the internal combustion engine is in particular started promptly to an engine start of the internal combustion engine. A block Bl (Figure 2), the measurement signal MS_A the exhaust gas probe is supplied on the input side. Depending on the profile of the measurement signal ^¬ MS_A the exhaust gas sensor 41 is a noise characteristic value RM is determined in the block Bl, which is representative of a measure of noise of the measurement signal of the respective exhaust-gas probe MS_A 41st In a particularly simple manner, the noise characteristic value can be determined of the exhaust gas sensor 41 via a respective predetermined period at ^¬ game in consideration of a summation of jumps of the measurement signal MS_A.

Especially good, the noise characteristic value can RM by means of a Fou ^¬ rier transformation are determined, preferably using a fast Fourier transform, also abbreviated to FFT, is used. In this context, a filter is preferably used, which is formed, for example in the form of a bandpass ^¬ . The filter is preferably designed such that it includes a frequency which correlates to the respective current rotational speed, in particular a frequency which correlates to a current frequency, in particular approximately in the middle segment of the period. In particular, it includes the associated one of the respective central ^¬ Seg ment time period fundamental frequency.

The noise characteristic value is thus determined taking into account the frequency spectrum of the measurement signal MS_A of the exhaust gas probe 41.

In this context, in particular the knowledge is used that an amplitude in the range of the above-mentioned basic frequency of the Fourier-transformed in the case of unequal air / fuel ratios in the respective cylinders ZI to Z4 exceeds a predetermined threshold value. Thus, the amplitude in the range of the fundamental frequency, for example,, decisively into ^¬ particular, be used to determine the noise characteristic value RM.

The noise characteristic RM is in turn fed to the input side of a block B3, in which a controller, in particular a PI controller, is formed. The controller in the block B3 is also supplied in particular also a desired value, the suitable advance is predetermined. In particular, a control difference is determined from the difference of the setpoint value and the noise characteristic value RM and then supplied to the controller, in particular to the PI controller. On the output side, the controller generates in block B3

Regulator set signal R_SG, which is fed to a block B5, which comprises in particular a multiplier.

The measurement signal MS_N of the crankshaft angle sensor 22 is fed to the input side of a block B7.

The block B7 is designed to determine, depending on a progression of the measurement signal MS_N of the crankshaft angle sensor 22, an uneven running characteristic LU assigned to the respective cylinder ZI to Z4. The rough-running characteristic value LU is in particular representative of a similarity measure of segment time durations that is the respective cylinder in comparison to segment time periods of the other cylinders. In this context, for example, so-called tooth times can be analyzed or a speed gradient can also be analyzed.

For example, the rough running characteristic value LU is determined in such a way that is indicative of a direction of a similarity measure of segment time periods of the respective cylinder ZI to Z4 compared to segment time periods of the other cylinders ZI to Z4. The direction is here represented in particular by a sign, ie plus or minus.

In addition, the rough running characteristic value LU is determined, for example, in such a way that it is indicative of a relevance of adapting the respective actuating signal SG_INJ for driving the respective injection valve. In particular, the relevance has either a relevance value, for example a neutral value, such as 1, or an irrelevance value, for example a blanking value, such as 0. In addition, the rough-running value is determined, for example, in such a way that its relevance has an irrelevance value within a predetermined range of the degree of similarity of segment time durations of the respective cylinder ZI to Z4 in comparison to segment duration of the other cylinders ZI to Z4.

For example, the smooth running characteristic may have the discrete values +1, 0 and -1. According to a further embodiment, a degree of taking into account a regulator control signal of the PI controller for adjusting the respective control signal SG_INJ for driving the respective injection valve 34 is determined depending on the rough running value LU taking into account the similarity measure of segment time periods of the respective cylinder ZI to Z4 in FIG

Comparison to segment time durations of the other cylinders. In this case, the rough running value potentially has further values apart from the above-mentioned values +1, 0 and -1. The controller output signal R_SG with the uneven running characteristic value LU is in the block B5 then ^¬ multi plied by the multiplier, and depending on this product is carried out a ent ^¬ speaking adjusting the respective adjusting signal SG_INJ of the respective injection valve. The respective actuating signal is determined, for example, primarily as a function of an air mass flow and a rotational speed value, for example with the aid of a characteristic map which was determined in advance.

In another embodiment, the rough running value LU and the noise characteristic RM are linked, for example

multiplicatively, and then linked on the input side to the block B3 supplied, in particular as an actual value. In this case, it may be possible to multiply the control loop signal R_SG in the block B5 be dispensed with the rough running characteristic LU and thus the rough running characteristic LU may not be supplied to the block B5.

FIGS. 3A and 3B show profiles of the measurement signal MS_A, wherein FIG. 3B illustrates a first window area F1 of the signal according to FIG. 3A in a more precisely timed manner. The signal curves in FIGS. 3A and 3B are plotted over the time t. The ordinate in FIGS. 3A and 3B is a voltage, respectively.

FIG. 3C shows a frequency spectrum of the first window area F1, wherein the abscissa is the frequency and the ordinate is in particular a voltage or may be a signal power. The ordinate may also represent a current.

In the first pane Fl no relevant difference in the distribution of the air / fuel mixture is present in the Zy ^¬ alleviate. The basic oscillation corresponding to the current segment time duration is in this case in the range of approximately 15 Hz and the amplitude of the frequency spectrum in this range is, for example, 12 × 10 -4 v.

FIG. 4A again shows the course of the measurement signal MS_A of the exhaust gas probe 41, and FIG. 4B shows the signal curve temporally higher in a second window area F2 (see also FIG. 4A).

FIG. 4C plots the frequency spectrum in relation to the second window area F2 of the measurement signal MS_A of the exhaust gas probe 41 in accordance with FIG. 3C. In this example too, the fundamental frequency which corresponds to the respective current segment time duration is in the range of 15 Hz. However, in the region of the second window region, a coercion of the Injection occurs, so that an unequal distribution of the air / fuel ratio in the individual cylinders is present. The fundamental frequency also corresponds in each case to the ignition frequency.

It is clearly apparent that the amplitude of the Fre ^¬ spec- trum in the range of the fundamental frequency in the case of the figure is significantly higher 4C namely by approximately a factor of 50 compared to Figure 3C, in which case, for example, an unequal distribution of 10% between the cylinders has been adjusted. Thus, for example, one cylinder is adjusted by -10% and the other by +10% with respect to its

Air / fuel ratio. In a particularly simple embodiment, the noise characteristic value RM is determined, for example, as a function of the amplitude of the frequency spectrum in the region of the fundamental frequency.

It has been found that in particular in internal combustion engines, which are operated with gasoline and in particular in a

Homogeneous operation, ie in particular with an air / fuel ratio, are operated in the vicinity of the value λ = 1, by the combination of the consideration of the control signal R_SG and the uneven running characteristic LU a particularly precise adjustment of the control signal SG_INJ for the injection into the respective cylinder ZI to Z4 can be achieved, especially as in an internal combustion engine operated with gasoline and operated in the vicinity of the stoichiometric air / fuel ratio, the relationship between fuel mass and torque in the vicinity of the stoichiometric air / fuel ratio ^¬ nisses is not particularly pronounced. In addition, when using a linear lambda probe as the exhaust gas probe 41 no jump behavior around the stoichiometric air / fuel ratio is present around and thus is a signal difference the measurement signal MS_A at an unequal distribution of the

Air / fuel ratio is not very pronounced.

By the above procedure, it is possible to use the measurement signal MS_A of the exhaust gas probe 41 for the determination of the unequal distribution of the air / fuel ratio, without having to determine the exact assignment to cylinder injection or cylinder filling exactly. Thus, if necessary, an active adjustment such as in the so-called Cybl_Hom method, which is described for example in DE 10 2006 026 390 Al, or an adaptation of the phase shift can be dispensed with. Further, as is also a cylinder-specific lambda control in unfavorable exhaust ^¬ configurations, such as with an exhaust gas turbocharger, very precise possible.

Reference sign list

1 intake tract

11 throttle

12 collectors

13 intake manifold

14 air mass sensor

15 temperature sensor

16 intake manifold pressure sensor

2 engine block

21 crankshaft

22 crankshaft angle sensor

23 torque sensor

24 pistons

25 connecting rod

3 cylinder head

30 gas inlet valve

31 gas outlet valve

32, 33 valve drive

34 injection valve

35 spark plug

36 camshaft

36a camshaft angle sensor

4 exhaust tract

40 catalytic converter

41 exhaust gas probe

6 control device

7 accelerator pedal

71 pedal position transmitter

Z1-Z4 cylinder

KW crankshaft angle

SG INJ Control signal for controlling the respective injection valve

MS A measuring signal of the exhaust gas probe MS_N Measuring signal of the crankshaft angle sensor

RM noise characteristic

LU running noise characteristic

Bl - B7 block

R_SG control signal

Fl first window area

F2 second window area

t time

f frequency

Claims

Method for operating an internal combustion engine having a plurality of cylinders (ZI, Z2, Z3, Z4), each associated with an injection valve (34) and each associated with a common exhaust probe (41) in or upstream of a catalytic converter (40) in a Ab ^¬ gastrakt (4) is arranged and a measurement signal (MS_A) provides, and with a crankshaft angle sensor (22) whose measurement signal (MS_N) is representative of a curve of a crankshaft angle of a crankshaft (21), wherein

a noise characteristic value (RM) which is representative of a measure of a noise of the measurement signal (MS_A) of the respective exhaust gas probe (41) is determined as a function of a course of the measurement signal (MS_A) of the respective exhaust gas probe,

depending on a progression of the measurement signal (MS_N) of the crankshaft angle sensor (22), an uneven running characteristic value (LU) assigned to the respective cylinder (ZI, Z2, Z3, Z4) is determined,

- Depending on the respective cylinder (ZI, Z2, Z3, Z4) associated with uneven running characteristic (LU) and the noise ^{¬ characteristic} value (RM) j eweilige control signals (SG_INJ) for controlling the respective injectors (34) are adapted in the sense of an adjustment of an air - / Fuel Ver ^¬ ratio in the individual cylinders (ZI, Z2, Z3, Z4).

Method according to claim 1,

in which the determination of the noise characteristic value (RM) comprises a Fourier transformation.

Method according to one of the preceding claims,

in which the respective uneven running characteristic value (LU) is indicative of a direction of a similarity measure of Segments mentZeitdauern the respective cylinder (ZI, Z2, Z3, Z4) compared to segment time periods of the other cylinders (ZI, Z2, Z3, Z4).

4. The method according to any one of the preceding claims,

in which the respective uneven running characteristic value (LU) is indicative of a relevance of adapting the respective actuating signal (SG_INJ) for controlling the respective injection valve (34).

5. The method according to claim 4,

in which the rough running characteristic value (LU) is determined such that within a predetermined range of similar ^¬ keitsmaßes of segment durations of the respective cylinder (ZI, Z2, Z3, Z4) in comparison to segment times of the other cylinder (ZI, Z2, Z3, Z4) its relevance one

Has irrelevance value.

6. The method according to any one of the preceding claims,

in which the noise characteristic value (RM) is fed on the input side to a PI controller.

7. The method according to claim 6,

where a degree of consideration of a

Regulating control signal of the PI controller for adjusting the ^¬ respective control signal (SG_INJ) for controlling the j eweiligen injector (34) is determined depending on the rough running characteristic (LU) taking into account the

Similarity measure of segment time periods of the respective cylinder (ZI, Z2, Z3, Z4) compared to segment time periods of the other cylinders (ZI, Z2, Z3, Z4).

8. An apparatus for carrying out a method according to any one of the preceding claims.