DE102016222709A1 - Method for determining combustion misfires in a spark-ignited internal combustion engine - Google Patents

Abstract

A method for determining misfiring in a spark-ignited internal combustion engine (10), comprising the steps of time-measuring a speed of an exhaust gas turbocharger (26) and determining based on the measured time-dependent speed whether a misfire is present in the internal combustion engine (10) ,

Description

Technical area

The invention relates to a method and an electronic control unit for determining combustion misfires in a spark-ignited internal combustion engine, a computer program and a machine-readable storage medium.

State of the art

From practice, it is known that spark ignited internal combustion engines, i. Gasoline engines, which have at least one spark plug as electronically controlled ignition system in order to ignite a fuel-air mixture in a combustion chamber of at least one of the spark plug associated cylinder of the internal combustion engine, may have misfires. In such combustion misfires, the ignition of the fuel-air mixture in the combustion chamber of the cylinder is insufficient or fails completely. To detect such misfires, onboard diagnostic methods for detecting misfires during operation of the internal combustion engine are performed.

Example describes DE 196 27 540 A1 a method for detecting misfires, in which a rotational nonuniformity of a crankshaft rotational movement of a crankshaft, which is connected to the cylinder (s) of the internal combustion engine is analyzed. It is also known to draw conclusions about the presence of combustion misfires of the internal combustion engine via an evaluation of a signal of a lambda probe, which is arranged in an exhaust gas discharge system of the internal combustion engine. It is also possible, in another method for detecting misfires, to detect either an electrical voltage (a so-called combustion voltage) at the spark plug (s) or an ion current at the spark plug (s).

There is a need to accurately detect combustion misfires in spark-ignited internal combustion engines, in particular over wide operating ranges, in a simple and efficient manner, in particular without errors.

Disclosure of the invention

A method and electronic control apparatus for determining misfiring in a spark-ignition internal combustion engine, a computer program, and a machine-readable storage medium are provided in accordance with the independent claims.

According to a first aspect, there is provided a method for determining combustion misfires in a spark-ignited internal combustion engine, comprising the steps of time-measuring a speed of an exhaust gas turbocharger and determining based on the measured time-dependent speed whether a combustion misfire is present in the internal combustion engine.

In the method according to the invention, which may be part of an onboard diagnosis for a spark ignition internal combustion engine, a speed of an exhaust gas turbocharger of the internal combustion engine is used to draw conclusions about combustion misfires during operation of the internal combustion engine. The exhaust-gas turbocharger of the internal combustion engine can typically have a turbine wheel with exhaust gas relative to the cylinder or the cylinder and a compressor wheel which is connected to the cylinder or the cylinder on the air intake side and which are connected to one another via a rotor shaft. The compressor wheel, the turbine wheel and the rotor shaft together can form the so-called "power tool". Hot exhaust gas discharged from the cylinders drives the turbine wheel, which in turn drives the compressor wheel connected via the rotor shaft, which is used for improved suction of cold air into the combustion cylinders, as the air is thereby compressed. Depending on an operating cycle of the internal combustion engine, the exhaust gas emission and thus the rotational movement of the exhaust gas turbocharger undergo a uniform pulse-like movement during normal operation, and a deviation from this normal behavior may allow a conclusion to a combustion misfire in the cylinders. In particular, a sporadic, missing or inadequate combustion of the fuel-air mixture in the cylinders can be expressed for example by a lower speed of the respective exhaust pulse or the absence of such a speed, since exhaust with at least partially unburned fuel-air mixture a has significantly lower enthalpy than exhaust gas from fully combusted fuel-air mixture.

Since the exhaust gas turbocharger from the internal combustion engine, including the crankshaft, as well as the entire other powertrain, including transmission, mechanically decoupled, and thus no feedbacks to the road conditions such as bumps are given in the road, determined via the speed of the exhaust gas turbocharger combustion misfires, in particular in contrast to the determined from the rotational movement of the crankshaft combustion misfire, be better recognized.

The detection of combustion misfires by means of the rotational speed of the exhaust gas turbocharger is Especially in the range of low engine speeds and engine loads advantageous in which, for example, methods for detecting misfires based on a rotational irregularity of the crankshaft rotational movement would react particularly sensitive to bumps in the road. In internal combustion engines equipped with a dual mass flywheel between the internal combustion engine and the transmission, robust detection of sporadic combustion misfires via a signal indicative of crankshaft rotation may be particularly difficult. The method can therefore be used in particular in such a design of the drive train, since the exhaust gas turbocharger from the engine, the transmission and the drive train is mechanically decoupled.

The internal combustion engine may have one or more cylinders, that is, be designed as a single-cylinder or multi-cylinder.

In one embodiment, the rotational speed of a compressor wheel of the exhaust gas turbocharger can be measured. In this case, for example, a sensor for measuring the rotational speed of the compressor wheel, for example, a speed sensor with the name RS-T1 sensor from Robert Bosch GmbH can be used. The arrangement of the sensor on the compressor wheel can cause a great longevity of the sensor component used, since the air intake side of the exhaust gas turbocharger is colder than the exhaust gas side of the exhaust gas turbocharger. The accuracy of the speed measurement is not affected because the turbine wheel is connected to the compressor wheel via a rotor shaft and thus has the same rotational movement.

Additionally or alternatively, the rotational speed of the turbine wheel of the exhaust gas turbocharger can be measured. Additionally or alternatively, the rotational speed of the rotor shaft of the exhaust gas turbocharger can be measured. For this purpose, corresponding sensors for measuring the rotational speed of the turbine wheel or the rotor shaft can be provided, which can be configured as an RS-T1 sensor.

In one embodiment, the misfire may be determined by comparing a maximum amplitude of a speed swing of the measured time-dependent speed with a reference amplitude value, wherein the misfire may be present when the maximum amplitude of the speed swing of the measured time-dependent speed is less than the reference amplitude value. This measure can enable a high-resolution, precise detection of the misfire by the individual exhaust pulses is analyzed due to the effluent, hot and enthalpy-containing exhaust gas combustion process such that per exhaust pulse, a maximum amplitude of the speed increase is determined in a Drehzahlhub. If, for example, the combustion stops, this manifests itself directly by a significantly lower maximum rotational speed amplitude of the respective exhaust pulse, so that a smaller rotational speed stroke is present or such a rotational speed stroke does not occur. A comparison with a reference amplitude value thus makes it possible in a simple and accurate way to determine whether a misfire is present or not.

The maximum amplitude of the Drehzahlhubs can be determined such that a quantitative difference between an amplitude maximum of the Drehzahlhubs and a reference reference level can be determined. The reference reference level may correspond to a rotational speed of zero or a substantially constant rotational speed of the exhaust gas turbocharger or a linearly rising or falling rotational speed of the exhaust gas turbocharger, on the basis of which an increase in rotational speed in the rotational speed stroke can be determined. Such a constant speed can occur, for example, in that the exhaust gas turbocharger has reached a rotational speed not equal to zero during operation of the internal combustion engine. A linearly rising or falling speed can occur, for example, in that the exhaust gas turbocharger accelerates or decelerates uniformly during operation of the internal combustion engine. In order to determine the maximum amplitude, it is possible in particular to use an evaluation unit which corresponds to a phase of a working cycle of a cylinder, i. a time for compressing the fuel-gas mixture, for expanding the fuel-gas mixture, for expelling the combusted fuel-gas mixture in the form of exhaust gas or for drawing in air when using a direct fuel injection or a fuel gas Mixture when using a port injection, corresponds. In other words, the evaluation unit which can correspond to an interval of 720 degrees crankshaft / number of cylinders can be determined as a function of the number of cylinders. In each of the evaluation units then a speed increase is expected, the maximum amplitude can be determined.

In one embodiment, the reference amplitude value may correspond to a fraction of an average value or an average value of maximum amplitudes of rotational speed hubs of the measured time-dependent rotational speed in an operation without combustion misfires. This allows a dynamic determination of the reference amplitude value as a function of the operating point of the internal combustion engine, that is, at different engine speeds and / or load ranges. Alternatively, the reference amplitude value may be fixed.

Additionally or alternatively, a misfire may be determined by determining a half-width of the measured time-dependent speed during the exhaust pulse and comparing it to a corresponding reference half-value value, the misfire being present when the half-width of the speed-hump of the time-dependent speed is less than the reference half-value value. The half-width of the Drehzahlhubs can be determined in the evaluation unit such that the speed is adjusted, for example, with a curve whose curve half-width corresponds to the half-width. Similar to the reference amplitude value, the reference half-value width value may correspond to a fraction of an average value or an average value of half-widths of speed hubs of the measured time-dependent speed in non-misfire mode or may be a fixed value. This measure may also allow a simple, efficient and accurate detection of misfiring during operation of the internal combustion engine.

In one embodiment, a wastegate for closing a bypass line for passing an exhaust gas to a turbine of the exhaust gas turbocharger may be electrically controlled such that the measured time-dependent speed is sufficiently large to determine the misfire based on the measured time-dependent speed. The wastegate may also be known by the term "wastegate valve". This measure may allow that at very low engine speeds and engine loads or even at very high engine speeds and engine loads flowing out of the cylinders exhaust gas is not completely bypassed via the bypass line on the turbocharger, but that the wastegate is slightly opened, so that exhaust gas turbine drive and thus the speed of the exhaust gas turbocharger can be measured time-dependent. Thus, the method can accurately and reliably detect misfiring over wide operating ranges.

In one embodiment, variably adjustable guide vanes of the turbine wheel of the exhaust gas turbocharger may be electrically controlled such that the measured time-dependent speed is sufficiently large to determine the misfire based on the measured time-dependent speed. This measure may alternatively be performed to regulate the exhaust gas flow via the wastegate. The corresponding variably adjustable turbine geometries of the turbine wheel, in which a design of the guide vanes of the turbine wheel can be changed by adjusting the vanes by means of electrical control, can cause a sufficiently large exhaust mass is available, which can be passed through the turbine. Thus, the process can accurately and reliably detect combustion misfires over wide operating ranges and turbine geometries.

In one embodiment, the method further comprises determining rotational nonuniformity of rotational motion of a crankshaft of the internal combustion engine and determining based on the determined rotational nonuniformity whether a combustion misfire is present in the internal combustion engine. This measure can for example be used selectively for certain operating ranges of the internal combustion engine, in which combustion misfires can be detected with insufficient accuracy based on the measured time-dependent speed of the exhaust gas turbocharger. This makes it possible to ensure accurate detection of combustion misfires over wide operating ranges of the internal combustion engine. Alternatively, it is also possible for both methods to be used simultaneously to determine if the detected misfires are plausible by comparing the results of both detection techniques. Overall, the accuracy of the method can be increased.

The determination of the rotational irregularity can be carried out, for example, by means of time-dependent measurement of a rotational speed of the crankshaft. In this case, it can be determined that the combustion misfire exists when the speed drops short time. Alternatively or additionally, the determination of the rotational nonuniformity can be accomplished by, as in DE 196 27 540 A1 described, a time is measured, which elapses until the crankshaft continues to rotate by a defined rotation angle. In this case, it can be determined that the combustion misfire is present when the measured time duration or a quantity derived therefrom increases briefly.

In one embodiment, the combustion misfire may be present in the internal combustion engine when the misfire is determined based on the measured time-dependent speed and rotational nonuniformity. Thus, errors in determining the misfires can be avoided by one of the two techniques.

If a combustion misfire is detected, the internal combustion engine can be suitably controlled to initiate appropriate countermeasures, by means of which combustion in the cylinders is improved. Such countermeasures can be, for example, the limitation of the representable load of the internal combustion engine and / or have the limitation or reduction of the valve overlap of the intake and exhaust valves of the cylinder, ie the time can be minimized or set to zero, in which the intake valve and the exhaust valve of the respective cylinder are both open simultaneously, so that the residual gas remaining in the cylinder limited and so the combustion can be improved.

According to a second aspect, there is provided an electronic control unit for detecting combustion misfires in a spark-ignited internal combustion engine arranged to perform steps of a method according to the first aspect. In this case, the electronic control unit can be designed, for example, as a conventional processor on which runs a special computer program which controls the method according to the first aspect. Alternatively or additionally, the electronic control unit may have corresponding units that can perform one or more method steps. In this case, the electronic control unit or the units can be realized for example by means of corresponding circuits.

According to a third aspect, there is provided a computer program configured to perform steps of a method according to the first aspect.

According to a fourth aspect, a machine-readable storage medium is provided, on which a computer program according to the third aspect is stored. The machine-readable storage medium can be designed, for example, as an external memory, as an internal memory, as a hard disk or as a USB memory device.

list of figures

• 1 eine schematische Ansicht eines Verbrennungsmotors und ein elektronisches Steuergerät gemäß einem Ausführungsbeispiel;
• 2 ein Verfahren zum Ermitteln von Verbrennungsaussetzern bei dem Verbrennungsmotor in 1 gemäß einem Ausführungsbeispiel; und
• 3 ein schematisches Diagramm, das eine zeitabhängige Drehzahl eines Abgasturboladers des Verbrennungsmotors in 1 zeigt.

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

• 1 a schematic view of an internal combustion engine and an electronic control unit according to an embodiment;
• 2 a method for determining combustion misfires in the internal combustion engine in 1 according to an embodiment; and
• 3 a schematic diagram showing a time-dependent speed of an exhaust gas turbocharger of the internal combustion engine in 1 shows.

Description of embodiments

An in 1 shown, designed as a gasoline engine combustion engine 10 a drive train 11 has four cylinders 12a - 12d on top of that with an air delivery system 14 and an exhaust removal system 16 are connected. In each of the cylinders 12a - 12d is a piston 18a - 18d arranged, via a corresponding lifting rod with a crankshaft 20 of the internal combustion engine 10 connected is. A spark plug 22a - 22d is on each of the four cylinders 12a - 12d provided and allows combustion of a via the air supply system 14 Feedable fuel-air mixture in a combustion chamber 24a - 24d of the associated cylinder 12a - 12d , The cylinders 12a - 12d are set to work in a four-stroke operation, where the internal free volume in the combustion chamber 24a - 24d the cylinder 12a - 12d by means of the pistons 18a - 18d is reducible or enlargeable to the crankshaft 20 drive.

Pulsed exhaust gas is exhausted via the exhaust system 16 an exhaust gas turbocharger 26 of the internal combustion engine 10 can be fed, that is a turbine wheel 28 and a compressor wheel 30 that has a rotor shaft 32 connected to each other. The turbine wheel 28 In one embodiment, variable, electrically adjustable vanes 33 exhibit. In an alternative embodiment, the turbocharger 26 one in the exhaust removal system 16 built-in, electronically controlled wastegate 34 exhibit. For better understanding, both the variable-shape vanes 33 as well as the wastegate 34 in 1 shown.

Through the wastegate 34 can the turbine wheel 28 Gas are supplied when the wastegate 34 in an open position (drawn drawn) is located. In a closed position (dashed line) is the wastegate 34 set up to prevent the exhaust gas from the combustion chamber 24a - 24d the exhaust gas turbocharger 26 is fed, or the wastegate 34 is adapted to the exhaust gas of a bypass line 36 feed the exhaust gas to the turbine wheel 28 leads past.

A speed sensor 38 for measuring a rotational speed of the compressor wheel 30 is on the compressor wheel 30 arranged. Alternatively, the speed sensor 38 at the turbine wheel 28 or at the rotor shaft 32 be arranged. Furthermore, another speed sensor 40 for measuring the rotational speed of the crankshaft 20 on the crankshaft 20 arranged. Measuring signals of the speed sensors 38 . 40 become an electronic control unit 42 which may be part of an electronic engine control unit (ECU) and is adapted to misfire the combustion engine 10 during operation and to determine the internal combustion engine 10 Appropriate to initiate countermeasures. Such countermeasures can be for example Limiting the maximum permissible load of the internal combustion engine 10 include. Alternatively or additionally, as a countermeasure, the maximum valve overlap of the intake and exhaust valves of the cylinder 12a - 12d be limited, so that less residual gas remains in the respective cylinders, whereby the combustion is improved.

The electronic control unit 42 has a first unit 44 for determining the speed based on that of the sensors 38 . 40 measured speeds and one unit 46 which is adapted to the combustion misfires of the internal combustion engine 10 based on an output signal of the unit 44 to investigate.

During operation of the internal combustion engine 10 is the method described below for determining combustion misfires of the internal combustion engine 10 carried out. As 2 is shown in a first method step S2, by the sensor 38 is executed, a speed of the compressor wheel 30 the exhaust gas turbocharger 26 time-dependent measured in given time intervals. Alternatively, in this method step S2, the rotational speed of the turbine wheel 28 or the rotor shaft 32 measured. In a further method step S4, that of the unit 44 of the electronic control unit 42 is executed, it is determined whether the measured, time-dependent speed of the compressor wheel 30 is sufficiently large in size to misfire in the internal combustion engine 10 to recognize. For this purpose, it is determined, for example, whether the measured rotational speeds amount in terms of an exhaust pulse from the combustion chamber 24a - 24d seen exhaust gas, which represents an evaluation unit, are sufficiently large and / or have a sufficiently large half-width.

If this is the case, in a step S6, the unit 46 of the electronic control unit 42 is executed, determines whether the maximum amplitude of a Drehzahlhubs the measured time-dependent speed in the evaluation time unit of the output pulse is less than a predetermined reference amplitude value. Alternatively or additionally, it can be determined in step S6 whether the half-value width of the rotational speed of the measured time-dependent rotational speed in the time unit of the output pulse is smaller than a predetermined reference half-value width value.

If at least one of the determinations of step S6 is affirmative, in a method step S8, which is also performed by the unit 46 of the electronic control unit 42 is executed determines that a misfire in the internal combustion engine 10 is present.

If, however, it is determined in method step S4 that the measured rotational speed is not sufficiently high in order to reliably detect combustion misfires, in a method step S10 which is determined by the unit 46 of the electronic control unit 42 is executed, if any, the wastegate 34 controlled such that the wastegate 34 slightly opens or further opens to the exhaust gas flow through the turbine wheel 28 to initiate or increase. Alternatively, the vanes 33 of the turbine wheel 28 be made such that the exhaust gas mass via the turbine wheel 28 is enlarged. Following this, the method step S2, S4 is carried out again.

If it is determined in method step S6 that the maximum amplitude is greater than or equal to the reference amplitude value and / or the half-value width is greater than or equal to the reference half-value width value, it is determined in a method step S12 that no combustion misfire, ie normal operation of the internal combustion engine 10 without dropouts, is present.

Optionally, in a method step S14 performed by the sensor 40 is executed, a time-dependent speed of the crankshaft 20 be measured. In an optional method step S16 performed by the unit 44 of the electronic control unit 42 is executed, a rotational nonuniformity of the crankshaft 20 based on the measured speed of the crankshaft 20 determined. In an optional method step S18 performed by the unit 46 of the electronic control unit 42 is performed, is based on the rotational nonuniformity, especially the measured speed of the crankshaft 20 , determines whether a combustion misfire of the internal combustion engine 10 is present.

If this is the case, in an optional method step S20, the unit 46 of the electronic control unit 42 is executed, it is determined whether it has been determined in the two steps S6 and S18 that there is a combustion misfire. If so, step S8 is executed. If this is not the case, it is determined in the method step S12 that a normal operation of the internal combustion engine 12 is present.

If the determination in step S18 is negative, it is also determined in a step S12 that the normal operation exists without combustion misfire. In this case, the process may be executed without the step S20.

The steps S14, S16, S18 may be executed in parallel to the steps S2, S4, S6. It is also possible that step S20 is not present in the method, and steps S2-S6 alternatively to the steps S14, S16, S18 in response to a load range and an engine speed of the internal combustion engine 10 be executed.

In an optional step S22 following the step S8 of the unit 46 of the electronic control unit 42 can be executed, the above-described countermeasure is initiated and output appropriate control signals.

In 3 is the time-dependent measured in step S2 speed of the exhaust gas turbocharger 26 over an engine cycle of the four-cylinder internal combustion engine 10 in 1 shown. In this case, 50 designates a crankshaft angle in degrees associated with a measuring time, 51 an amplitude of the exhaust gas in arbitrary units, 52 a rotational speed of the compressor wheel 30 in revolutions per minute and 54 the measured speed curve. The speed 54 whose amplitude is in 3 is about 500 revolutions per minute, is measured when the hot exhaust gas when flowing out of the combustion chamber 24a - 24d on the turbine wheel 28 the exhaust gas turbocharger 26 and drives it, which in turn is the compressor wheel 30 drives. The measured speed 54 can therefore be regarded as a measure of the energy contained in the exhaust gas or the energy converted by the combustion process or enthalpy. A firing interval of the cylinders 12a - 12d is in the example shown 180 ° crankshaft, so that, as in 3 shown, four combustions take place within two crankshaft revolutions and in one stroke, in the per cylinder 12a - 12d The phases of compression, expansion, expulsion and suction occur, four exhaust pulses, so one exhaust pulse per cylinder 12a - 12d , to be measured, each as a revolving speed 54a - 54d can be seen. Be the individual speed strokes 54a - 54d , So the speed amplitudes evaluated, it can from the misfiring, resulting in a much lower stroke 54a - 54d or absence of the speed 54a - 54d express, be determined.

For evaluation is a speed 54a - 54d , which corresponds to a period of 720 degrees crankshaft / number of cylinders (here 4), ie 180 degrees crankshaft, a time window 56 whose length corresponds to the evaluation time unit or a time length of one of the working clock phases. A maximum amplitude 58 in this time window 56 is the difference between a minimum value 60 , which represents a reference level value, and a maximum value 62 the speed 54 within the time window 56 , A half-width 64 the speed stroke 54a - 54d For example, it can be determined by adjusting the speed of the lift with a Gaussian curve. The maximum amplitude 58 or the half-width 64 may be compared with the reference amplitude value and the reference half-value width value, respectively, in step S6.

In a misfire, for example, for the Drehzahlhub 54d is shown, the maximum amplitude is less than the reference amplitude value. The half-width is also less than the reference half-value width. The reference amplitude value and / or the reference half-value width value may be in the electronic control unit 42 be stored depending on the engine speed and the engine load or over several speed strokes 54a - 54d in an operation of the internal combustion engine without combustion misfire as a fraction of an average value or as the average value are calculated.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• DE 19627540 A1 [0003, 0020]

Claims (11)

Method for determining combustion misfires in a spark-ignited internal combustion engine (10), comprising the steps of: - Time-dependent measuring (S2) a speed of an exhaust gas turbocharger (26) and Determining (S6) based on the measured time-dependent speed (54) whether a combustion misfire is present in the internal combustion engine (10). Method according to Claim 1 , wherein the rotational speed of a compressor wheel (30) of the exhaust gas turbocharger (10) is measured. A method according to any one of the preceding claims, wherein the misfire is determined by comparing a maximum amplitude (58) of a speed (54a-54d) of the measured time-dependent speed (54) with a reference amplitude value, the misfire being present when the maximum amplitude ( 58) of the rotational speed (54a-54d) of the measured time-dependent rotational speed (54) is smaller than the reference amplitude value. Method according to Claim 3 wherein the reference amplitude value corresponds to a fraction of an average value or an average value of maximum amplitudes (58) of rotational speeds (54a-54c) of the measured time-dependent rotational speed (54) during operation of the internal combustion engine (10) without combustion misfires. Method according to one of the preceding claims, wherein a wastegate (34) for closing a bypass line (36) for passing an exhaust gas on a turbine wheel (28) of the exhaust gas turbocharger (26) is electrically controlled such that the measured time-dependent speed (54) sufficiently large is to determine the misfire based on the measured time-dependent speed (54). Method according to one of Claims 1 to 4 wherein variably adjustable vanes (33) of the turbine wheel (28) of the exhaust gas turbocharger (26) are electrically driven so that the measured time dependent speed (54) is sufficiently large to determine the combustion misfire based on the measured time dependent speed (54). Method according to one of the preceding claims, comprising the steps: - Determining (S16) a rotational nonuniformity of a rotational movement of a crankshaft (20) of the internal combustion engine (10), and Determining (S18) based on the determined rotational nonuniformity whether a combustion misfire is present in the internal combustion engine (10). Method according to Claim 7 wherein the combustion misfire is present in the internal combustion engine (10) when the misfire is determined based on the measured time-dependent speed (54) and the rotational nonuniformity. An electronic control unit (42) for determining combustion misfires in a spark ignition internal combustion engine (10) adapted to perform steps of a method according to any one of Claims 1 to 8th perform. Computer program adapted to perform steps of a method according to one of Claims 1 to 8th perform. Machine-readable storage medium on which a computer program is based Claim 10 is stored.

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