GB2531298A

GB2531298A - Determination of the effective fuel-air ratio of a supercharged internal combustion engine with scavenging air component

Info

Publication number: GB2531298A
Application number: GB1418249.7A
Authority: GB
Inventors: Stefan Horst
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2014-10-15
Filing date: 2014-10-15
Publication date: 2016-04-20
Also published as: GB201418249D0

Abstract

The invention relates to the adjustment of the cylinder 21, 22, 23, 24 air/ fuel ratio for the optimisation of combustion in an internal combustion engine of a motor vehicle. It involves measurement of a crank angle on a crankshaft 3 to determine the point in the combustion cycle at which to take or select scanned lambda probe 8 measurements of the combustion products. These are combined with global lambda values in a computer model such as an exhaust gas pressure or exhaust gas back pressure model to calculate an effective combustion lambda. The crank angle detection may take place or be selected when no scavenging air flow is visible in the exhaust gas flow. The scavenging air flow may also be calculated. The effective combustion lambda may be compared to a set point value and a correction value calculated when a deviation occurs. The scanned lambda probe signal may be filtered and statistically evaluated. The computer may send signals to a control unit to adjust the cylinder air-gas mixture. Lambda probe 8 measurements may be taken for each cylinder 21, 22, 23, 24 and an effective combustion lambda may be calculated for each individual cylinder.

Description

s Determination of the effective fuel-air ratio of a supercharged internal combustion engine with scavenging air component The invention relates to a method and a device for the fuel reduction andlor power increase of an internal combustion engine in particular of a motor vehicle. An effective combustion lambda in a cylinder can be calculated with the method.

Because of the continuously changing legal stipulations for the emission of pollutants of motor vehicle combustion engines, the industry attempts to optimize the fuel consumption of motor vehicles as one of numerous measures. This means attempts are made among others to optimize the fuel consumption based on the power of the combustion engine.

There is therefore a need for a method and a drive system for a motor vehicle, with which the fuel of an internal combustion engine can be reduced and/or a power increase of the internal combustion engine achieved.

This object is solved through the features of the Patent Claims 1 and 9. Further configurations of the invention are in each case subject of the subclaims. These can be combined with one another in a technologically practical manner. The description, in particular in connection with the drawings, additionally characterizes and specifies the invention.

According to an aspect, the invention relates to a method for the fuel consumption reduction and/or power increase of an internal combustion engine comprising the steps: a) detecting a crank angle, at which out of a cylinder the exhaust gases of a cylinder combustion can be representatively measured on a lambda probe, b) continuous measuring of an exhaust gas flow on the lambda probe, c) scanning a signal of the lambda probe at the time of the detection of the crank angle d) sending the detected and/or scanned value to a computer, e) correcting the scanned value with the help of an exhaust gas pressure or exhaust gas back pressure model stored in the computer, and U calculating an effective combustion lambda of the cylinder based on the sent values and a global lambda value stored in the computer The crank angle is the angular position of the crankshaft at a certain time. The time in the described method is the time at which out of the combustion engine the exhaust gas of a single cylinder combustion can be representatively measured on the lambda probe by means of a scanner, for example an integrated circuit (IC) or a voltage transducer, wherein the exhaust gas is the combustion product of an air-fuel mixture combusted in the cylinder respectively in a combustion chamber of the cylinder.

In other words, the method commences when the crankshaft has reached the preset known angular position. At that moment, the exhaust gas flow of the cylinder combustion is measured on the lambda probe, respectively a signal of the lambda probe in particular of a pre-turbine probe, is canned.

Alternatively, the method can also be realized with a post-turbine probe.

In the following, the method is described with the help of a device with a pre-turbine probe, without the use of a post-turbine probe being excluded because of this. The restriction to a pre-turbine probe in the description merely serves for better readability.

The global lambda value stored in the computer can be represented by an exhaust gas pressure or exhaust gas back pressure model.

The signal of the pre-turbine probe shows the dynamic characteristic of individual cylinder exhaust gas with minor deviation from the actual value, since only a minor mixing-through with the exhaust gas of other cylinders occurs. At the time of the scan, the measured amplitude therefore is near the actual combustion lambda value of the combustion.

The combustion lambda is measured through the sequential scan but has a systematic error which can be depicted by a comparison with the model values stored in the computer.

From the data that is detected, scanned and corrected with the help of the model the computer, following optional filtering of the data, can calculate an effective scavenging air component in the exhaust gas flow, since at the moment, at which the exhaust gas flow is detected on the lambda probe sensor, no or at least almost no scavenging air component is visible in the detected exhaust gas flow.

The exhaust gas pressure or exhaust gas back pressure model in the case of which the exhaust gas back pressure is an input quantity in the model, comprises a corrective for the lambda probe signal.

The computer can compare the calculated effective combustion lambda of the cylinder with a combustion lambda preset in the model for the detected exhaust gas mass flow and/or the tapped-off pre-turbine probe value. A likewise present systematic deviation of the combustion lambda is applied into the mentioned model, against which the one with the measurement value is compared. In other words, the exhaust gas pressure or exhaust gas back pressure model can have a correction value for the scanned probe signal, wherein in particular the exhaust gas back pressure can form an input quantity in the model.

If in the process a deviation between the calculated and the modelled combustion lambda is determined, the computer can calculate a correction value in order to bring the calculated effective combustion lambda up to the modelled combustion lambda or render it in accordance with the latter.

This means, a correction of the measured cylinder-specific lambda value can be carried out with the help of the values of the model stored in the computer.

Following this, the scavenging air component can be calculated from the current lambda value tapped off on the pre-turbine probe and the global lambda stored in the computer. Following the calculation of the model-based correction and optional filtering the calculation of the actual absolute set point values can take place. Here, individual cylinder deviations are primarily corrected, while secondarily the effective combustion lambda is globally adjusted quantitatively correctly by adapting the injection quantity.

In an embodiment, the scavenging air component can also be corrected instead of the injection quantity in order to correct the measured lambda value, for example through a correction of the crankshaft position.

The model can include at least the following input parameters: * exhaust gas back pressure (model value via crank angle. engine load) * probe ageing coefficient, * ethanol component.

The model with these parameters can be constructed via an extemal, generic model calculation (GD power) and stored in the computer as a characteristic diagram calculation operation.

Downstream of this, a calibration factor is included in the calculation which is obtained from a rotational speed load-dependent correction characteristic diagram. This calibration factor is applied during engine setup.

For the quantity of the deviation, a limit value can be preset in the computer which has to be reached or exceeded before the computer calculates a correction value.

As a function of the calculated correction value, the computer can generate signals and send these to a control unit.

Because of this, the quantity of a fuel and/or combustion air supply to the cylinder can for example be adapted via the computer in order to achieve a reduction of the fuel consumption and/or a power increase of the internal combustion engine. Or the component of the scavenging air in the exhaust gas can be increased in order to for example have sufficient oxygen component for re-treatment, for example a re-combustion of the exhaust gas for example ii the catalytic converter, which leads to a reduction of pollutants in the exhaust gas discharged into the environment.

In addition to or instead of the quantity of the combustion air supply, its temperature and/or oxygen content can be changed for example. In the case of the fuel, a fineness of the atomization through an injection system can be regulated instead or additionally to the quantity.

The described method can be carried out one after the other for each of the cylinders respectively for the cylinders jointly igniting in a cycle. Thus, the effective combustion lambda of each individual cylinder or jointly igniting cylinder can be calculated so that upon a complete revolution of the crankshaft the values of all cylinders of the internal combustion engine are detected and for example synchronized. Because of this, optimization of the combustion of all cylinders of the internal combustion engine can be achieved, which can lead to a reduction of the fuel consumption and/or a power increase of the internal combustion engine in the exhaust gas after the catalytic converter and an improvement of the smooth operation of the engine.

The signals of at least the detector and of the scanner can be transmitted to the computer via cable connections, such as for example as electrical signals via electrical cables or as optical signals via light-conductive cables, or wirelessly via a local radio network. In the computer unit, at least the signal of the pre-turbine probe scanned by the scanner can be corrected first and thereafter optionally filtered and statistically evaluated.

A further aspect of the invention relates to a drive system for a motor vehicle. The drive system comprises a) an intemal combustion engine with a turbocharger, b) a camshaft for controlling valves for at least one cylinder of the internal combustion engine, c) a detector, which detects an angle 3f rotation of a crankshaft of the internal combustion engine, d) a lambda probe sensor, which continuously detects an exhaust gas flow flowing out of the at least one cylinder on a lambda probe, e) a scanner, which at any time scans current values of the lambda probe sensor, f) and a computer, which can be signal-connected to at least the detector and the scanner, g) wherein the computer comprises a memory in which the global lambda values for the internal combustion engine are stored, h) and the computer calculates an effective combustion lambda of the at least one cylinder and/or a scavenging air component in the exhaust gas flow after the at least one cylinder from a detected angle of rotation of the crankshaft and/or a scanned lambda probe signal and the global and/or sequential lambda values.

Here, the detector can detect the angle of rotation of the crankshaft at which the exhaust gas flow of a single combustion flows out of the cylinder.

The scanner evaluates the continuous signal of the lambda probe that can be scanned at any time. In particular1 the signal is evaluated exactly at the time at which the exhaust gas of a single cylinder combustion is present on the lambda probe or pre-turbine probe. The scavenging air, which normally reaches the exhaust tract through a positive gradient during a valve overlap, is at least not substantially present at this time.

The crank angle for the scan is determined by measurement and applied. If the drive system has an internal combustion engine with more than one cylinder, the detector can individually detect and scan one after the other the angle of rotation of the crankshaft and the scanner the lambda probe value for each individual cylinder of the internal combustion engine.

From the detected and scanned values, the computer can calculate an effective combustion lambda and/or in particular globally the scavenging air component or a Is scavenging air component for each individual cylinder. Here, the calculated values of the combustion lambda can first be compared with the values of an exhaust gas pressure or exhaust gas back pressure model which can be stored in the computer and corrected and filtered when necessary. With these corrected values of the combustion lambda, the actual scavenging air component can then be determined.

With the drive system, a fuel consumption of the internal combustion engine can be reduced and/or a power of the internal combustion engine increased and/or the emission of pollutants by the vehicle simultaneously reduced. In addition, the smooth operation of the internal combustion engine can thereby be improved.

Existing drive systems can be converted in order to achieve the mentioned advantages. For this purpose, any missing detectors or scanners have to be retrofitted and a computer program with the appropriate models and the necessary algorithms uploaded on an existing computer. Here, the scanner for quick sequential scanning of the lambda probe values can be formed for example by an integrated circuit (IC), which is integrated in a control unit for the drive system.

A further aspect relate to a computer program for carrying out the method described above.

The computer can comprise a digital microprocessor unit (CPU) which is data connected to a storage system and a BUS system, a working memory (RAM) and a storage means. The CPU is designed to execute commands which are embodied as a program stored in a storage system, to detect input signals from the data BUS and emit output signals to the data BUS. The storage system can have various storage media such as optical, magnetic, solid and other non-volatile media, on which a S corresponding computer program for carrying out the method and the advantageous configurations is stored. The program can be of such a nature that it is capable of embodying or carrying out the methods described here, so that the CPU can carry out the steps of such methods.

Suitable for carrying out a method is a computer program, which comprises program code means in order to carry out all steps of the method when the program is executed on a computer.

The computer program can be read into already existing control units and used with IS simple means in order to control a method for the fuel consumption reduction and/power increase of an internal combustion engine of the motor vehicle.

The computer program product can also be integrated in control units as a retrofit option.

A further aspect relates to a computer program product which is also described as a computer or machine-readable medium, and which is to be understood as a computer program code on a carrier. Here, the carrier can be of a volatile or non-volatile type with the consequence that this also be referred to as a volatile or non-volatile nature of the computer program product.

An example for a volatile computer program product is a signal, for example an electromagnetic signal like an optical signal, which is a carrier for the computer program code. The carrying of the computer program code can be achieved by modulating the signal with a conventional modulation method such as QPSK for digital data, so that binary data which represent the computer program code are impressed on the volatile electromagnetic signal. Such signals are utilized for example when a computer program product is transmitted to a laptop without cable via a Wi-Fi connection.

In the case of a non-volatile computer program product, a computer program code is embodied in a substrate-bound storage medium. Then, the storage medium is the abovementioned non-volatile carrier, so that the computer program code is permanently or non-permanently stored in or on the storage medium. The storage medium can be of a conventional type such as is known in the field of computer technology, for example a flash memory, an ASIC, a CD and the like.

Throughout the description and the claims the expression "a" is utilized as indefinite article not restricting the number of parts to a single one. Should "a" have the meaning of only one", such is to be understood from the context to the person skilled in the art or is unambiguously disclosed by the use of suitable expressions such as for example "a single".

In the following, an exemplary embodiment is explained in more detail with the help of the drawings. It shows: Fig. 1: schematically a drive system for a motor vehicle with an internal combustion engine having a turbocharger, Fig. 2: schematically a method sequence.

A drive system 1 for a motor vehicle is schematically shown in Figure 1.

The drive system 1 comprises an internal combustion engine 2 within the exemplary embodiment four cylinders 21, 22, 23, 24. Each of the cylinders 21, 22, 23, 24 has valves 5, which can be opened and closed by a camshaft which is not shown.

The internal combustion engine 2 comprises a turbocharger 4 with a compressor 12 and a turbine 13. The compressor 12 supplies the internal combustion engine 2 with compressed air for combustion, the exhaust gas flowing out of the cylinders 21, 22, 23, 24 is conducted through the turbine 13 and drives the compressor 12.

On the crankshaft 3, a detector 6 is arranged, which can detect an angle of rotation of the crankshaft 3 and pass it on to a computer 9. With the detector 6, an angle of rotation of the crankshaft 3 and of a crankshaft trigger for controlling the valves 5 for each of the cylinders 21, 22, 23, 24 can be detected for example.

Having left the cylinders 21 22, 23, 24, an exhaust gas flow of a single combustion in one of the cylinders 21, 22, 23, 24 can be measured on a lambda probe 8.

In a line 11, which connects the internal combustion engine 2 to the turbine 13 of the turbocharger 4, a lambda probe 8 is arranged. For rapid sequential scanning of the lambda probe value on the lambda probe 8 at a preset time, a scanner 7 in the form of an integrated circuit is arranged in the computer 9 in the shown exemplary embodiment.

The computer 9 comprises a memory 10, in which for example global lambda values for the internal combustion engine 2 and/or an exhaust gas pressure or exhaust gas back pressure model of the internal combustion engine 2 are stored.

The detector 6, the lambda probe 8 and the scanner 7 are signal-connected to the computer 9.

The computer 8 can process the received data of the detector 6 and of the scanner 7 and from this data calculate an effective combustion lambda for each of the cylinders 21, 22,23,24.

In addition, the detector 6 detects an angle of rotation of the crankshaft 3 at which out of only one of the cylinders 21, 22, 23, 24 the exhaust gas flows after the combustion.

On the lambda probe 8, the exhaust gas flow is continuously measured and at the moment, at which the detector has detected the corresponding crank angle, the scanner 7 scans the current value on the lambda probe 8.

Since the exhaust gas mass flow at the time of the measurement on the lambda probe 8 is at least substantially free of scavenging air, the computer can with a stored algorithm calculate the effective combustion lambda and/or a scavenging air component in the exhaust gas mass flow for the cylinder 21, 22, 23, 24 from at least one of the values of the detector 6 andlor of the scanner 7 and the global lambda value for the internal combustion engine 2 stored in the memory 10, the exhaust gas mass flow of which has just been measured on the lambda probe 8.

Figure 2 shows a schematic method sequence for a method with which a fuel consumption of an internal combustion engine of a motor vehicle can be reduced and/or a power increase of the internal combustion engine can be achieved.

-10 -The method comprises the steps: detecting a crank angle A at which out of a cylinder the exhaust gases of a cylinder combustion are present on a lambda probe, measuring the exhaust gas flow B of the cylinder at the time of the detection of the crank angle and scanning of a signal C of a pre-turbine probe at the time of the detection of the crank angle.

Calculating an effective combustion lambda of a cylinder combustion out of the scanned value and a correction value of a default model.

The calculated effective combustion lambda can be compared with a modelled combustion lambda, respectively a set point value of an exhaust gas pressure or exhaust gas backpressure model stored in the computer. If the computer does not determine any deviations of the values or deviations of the values in a permissible limit value range, the method ends and can recommence.

In the case of deviations, the computer can calculate correction values and send control inputs to a control, which can then carry out adjustments E on individual parameters of the drive system.

The effectiveness of these adjustments can be verified during the next measurement for the same cylinder.

Although in the preceding description some possible embodiments of the invention were disclosed it should be understood that numerous versions of embodiments exist through combination possibilities of all features and embodiments that were mentioned and furthermore of all technical features and embodiments that are obvious to the person skilled in the art. It is to be understood, furthermore, that the exemplary embodiments are to be understood merely as examples which do not in any way restrict the scope of protection, the applicability and the configuration. The preceding description is rather intended to show the person skilled in the art a suitable way of realizing at least one exemplary embodiment. It is to be understood that with an exemplary embodiment numerous changes with regard to function and arrangement of the elements can be carried out without leaving the scope of protection disclosed in the claims and its equivalent.

-11 -List of reference characters 1 Drive system 2 Internal combustion engine 21 Cylinder 22 Cylinder 23 Cylinder 24 Cylinder 3 Crankshaft 4 Turbocharger Valve 6 Detector 7 Scanner 8 Lambda probe 9 Computer Memory 11 Line 12 Compressor 13 Turbine A Detecting B Measuring C Scanning D Calculatinglcomparing/correcting E Adjusting

Claims

CLAIMS1. A method for the fuel consumption reduction and/or power increase of an internal combustion engine (2) of a motor vehicle, comprising the steps: a) detecting (A) a crank angle of a crankshaft (3) at which out of a cylinder (21, 22, 23, 24) the exhaust gases of a cylinder combustion can be representatively measured on a lambda probe (8), b) measuring (B) the exhaust gas flow on the lambda probe (8), c) scanning (C) a signal of the lambda probe (8) at the time of the detection of the crank angle d) sending the detected and/or scanned value to a computer (9), e) correcting (D) the scanned value with the help of an exhaust gas pressure or exhaust gas back pressure model stored in the computer (9), and 0 calculating (D) an effective combustion lambda of the cylinder (21, 22, 23, 24) on the basis of the sent values and of a global lambda value stored in the computer (9).
2. The method according to Claim 1, wherein at the moment of the detection of the crank angle no scavenging air flow is visible in the measured exhaust gas flow.
3. The method according to any one of the preceding claims, wherein the calculated combustion lambda is compared with a set point value of the combustion lambda of the model.
4. The method according to the preceding claim, wherein in the case of a deviation of the effective combustion lambda a correction value is calculated from the set point value.
5. The method according to Claim 1, wherein at the moment of the scanning of the angle of the crankshaft (3) no scavenging air flow is visible in the scanned signal and the scavenging air flow is calculated by the computer (9) together with the effective combustion lambda out of the measured air mass flow, the global lambda and the scanned lambda probe value.

-13 -
6. The method according to any one of the preceding claims, wherein the scanned signal is filtered and statistically evaluated in the computer (9).
7. The method according to any one of the preceding claims, wherein the computer (9) on the basis of the calculated effective combustion lambda and/or the calculated scavenging air flow serds a signal to a control unit which adjusts an air-gas mixture for the cylinders (21, 22, 23, 24) in order to bring about a fuel consumption reduction and/or a power increase of the internal combustion engine (2).
8. The method according to any one of the preceding claims, wherein the crank angle is detected by the detector (6) and the lambda probe value for each cylinder (21, 22, 23, 24) of the internal combustion engine (2) is scanned by the scanner (7), and from these values the effective combustion lambda for each individual cylinder (21, 22, 23, 24) is calculated by the computer (9).
9. A drive system (1) for a motor vehicle, the drive system (1) comprising: a) an internal combustion engine (2) with a turbocharger (4), b) a camshaft for controlling valves (5) for at least one cylinder (21, 22, 23, 24) of the internal combustion engine (2), c) a detector (6), which detects an angle of rotation of a crankshaft (3) of the internal combustion engine (2), d) a lambda probe sensor, whict' continuously detects an exhaust gas flow flowing out of the at least one cylinder (21, 22, 23, 24) on a lambda probe (8), e) a scanner (7), which scans current values of the lambda probe sensor at any time, and a computer (9), which can be signal-connected at least to the detector (6) and the scanner (7), g) wherein the computer (9) comprises at least one memory (10), in which global lambda values for the internal combustion engine (2) are stored, h) and the computer (9) from the detected angle of rotation of the crankshaft (3) and/or a scanned lambda probe signal and the global lambda values calculates an effective combustion lambda of the at least one cylinder (21, 22, 23, 24) and/or a scavenging air component in the exhaust gas flow after the at least one cylinder (21, 22, 23, 24).

-14 -
10. The drive system according to Claim 9, wherein the detector (6) detects the angle of rotation of the crankshaft (3), at which out of the at least one cylinder (21, 22, 23, 24) the exhaust gas flow of a single combustion is present on the lambda probe (8).
11. The drive system according to any one of the Claims 9 to 10, wherein the scanner (7) scans the lambda probe value at the time of the detection of the angle of rotation of the crankshaft (3).lo 12 The drive system according to any one of the Claims 9 to 11, wherein the detector (6) detects the angle of rotation of the crankshaft (3) and the scanner (7) individually scans the lambda probe value for each cylinder (21, 22, 23, 24) of the internal combustion engine (2), and the computer (9) calculates an effective combustion lambda and/or a scavenging air component for each of the cylinders (21, 22, 23, 24).13. A computer program for carrying out a method according to any one of the Claims ito 8.14. The computer program product comprising program code means which are stored on a computer-readable data carrier in order to carry out the method according to any one of the Claims 1 to 6 when the program code means are executed on a computer.