WO2012079935A1

WO2012079935A1 - Method for controlling and adapting an air/fuel mixture in an internal combustion engine

Info

Publication number: WO2012079935A1
Application number: PCT/EP2011/070789
Authority: WO
Inventors: Frank Lehn
Original assignee: Robert Bosch Gmbh
Priority date: 2010-12-15
Filing date: 2011-11-23
Publication date: 2012-06-21
Also published as: EP2652298A1; CN103249933A; DE102010063119A1

Abstract

The method relates to a method for controlling and adapting an air/fuel ratio of an air/fuel mixture in an internal combustion engine (2), in particular in a spark ignition engine; having the following steps: - providing an actual lambda value (Lambda_Act), which specifies a current air/fuel ratio value, and a setpoint lambda value (Lambda_Setp), which specifies a desired air/fuel ratio value; - determining as a function of the actual lambda value (Lambda_Act) a correction value for controlling and adapting the actual lambda value (Lambda_Act) to the setpoint lambda value (Lambda_Setp), wherein the correction value corresponds, as a function of the deviation of the actual lambda value (Lambda_Act) from the setpoint lambda value (Lambda_Setp), to a charge correction value (C_Corr2) for applying a variable which influences the air charge of the internal combustion engine (2) or a fuel correction value (F_Corr) for applying a variable which influences the fuel quantity to be injected in the internal combustion engine (2).

Description

description

title

Method for regulating and adapting an air / fuel mixture

in an internal combustion engine

Technical area

The invention relates to internal combustion engines, in particular to methods for regulating and adapting an air / fuel mixture, which is supplied to a cylinder of the internal combustion engine. The invention relates in particular to methods for regulating and adapting an air / fuel mixture during operation of the internal combustion engine.

State of the art

Gasoline engines are operated in conventional operation with an air / fuel mixture that is close to a stoichiometric balance, i. H. one

Lambda value of the air / fuel mixture is about 1. Such internal combustion engines are today almost exclusively represented by so-called EGAS systems. EGAS systems provide electronic control of a throttle device with a throttle and lambda control for regulating and adapting the air / fuel ratio. The control or adaptation can be carried out by means of sensors for detecting the air present in the combustion chamber, such as by means of an air mass meter, or intake manifold pressure sensors and sensors for detecting the exhaust gas composition, such as with the aid of lambda probes.

In the operation of conventional gasoline engines, controlled by the throttle valve, the cylinders of the engine supplied an amount of air and a stoichiometric amount of this amount of fuel into the combustion chamber or injected into the suction pipe located in front of the inlet valve. With the aid of the mixture control, it is attempted to set the air / fuel mixture at least approximately to the stoichiometric equilibrium. The adjustment of the air supplied to the cylinders, the so-called air filling, is predetermined by a driver of a motor vehicle operated by the internal combustion engine. The driver controls the torque, in particular by an electronically connected to the control unit accelerator pedal, the accelerator pedal position is interpreted as a rule, as a corresponding driver's desired torque and thus converted into a corresponding desired filling. The desired filling corresponds to the amount of air in the torque-generating cylinders, which is needed to provide the driver's desired torque. The desired filling corresponds to a position of the throttle valve, so that the control unit sets the throttle valve accordingly.

Apart from dynamic effects, the actual filling follows

Target filling, whereby the actual filling is permanently detected by models or sensors by the control unit. The amount of fuel associated with the actual charge is calculated accordingly and fed to the cylinders. Because of due

Aging effects, component tolerances and the like deviations between the actual filling or the actually injected fuel quantity and the desired air charge or the desired injected

Fuel quantity occur in the control unit control and

Realized adaptation method. In a charge adaptation, within a charge control for calculating the target position of the throttle flap, the air charge is corrected on the basis of the desired charge specified by the driver request torque by comparing the target charge with a measured actual charge. If the setpoint and actual filling deviate from one another, it is assumed that the throttle valve model used does not map the reality accurately enough, and the model is adapted with correction factors until the setpoint and actual filling coincide again. Thus, for example, soiling or drift effects of the throttle during vehicle life can be corrected and adapted.

Furthermore, a mixture adaptation and control is provided in order to achieve the desired stoichiometric mixture with lambda equal to or approximately 1, even with respect to tolerances of components, soiling or drift effects to ensure that can be done by the downstream catalyst optimal exhaust gas purification. For this purpose, the signal provided by the lambda probe is continuously detected and the mixture is regulated and adapted by a corresponding correction value - depending on the design of the engine system - either by adjusting the amount of fuel injected or by adjusting the air charge by correcting the throttle position.

As long as no errors in the calculations or errors of the sensors or actuators or their connections to the control unit occur within the control unit, the adaptations can use the correction of the fuel quantity to be injected or the correction of the air charge to be supplied to the component changes due to aging, drift and the like to correct. However, it is possible that erroneous calculations within the controller or faulty sensor or actuator functions occur and so cause adaptation or correction variables, which lead to an increase in the torque of the controlled by the control unit internal combustion engine, without this being desired by the driver. Based on this, there may be an unwanted acceleration of the vehicle, which may endanger the driver or other persons.

It is therefore an object of the present invention to provide a method and a device for carrying out an adaptation which acts on the adjustment of the air / fuel ratio, with which an undesired increase in torque due to a faulty calculation in the control unit is avoided can.

Disclosure of the invention

This object is achieved by the method for adapting an engine system according to claim 1 and by the device, the motor system and the computer program product according to the independent claims.

Further advantageous embodiments of the present invention are specified in the dependent claims. According to a first aspect, a method is provided for regulating and adapting an air / fuel ratio of an air / fuel mixture in an internal combustion engine, in particular in a gasoline engine. The procedure comprises the following steps:

Providing an actual lambda value indicative of a current air / fuel ratio indication and a desired lambda value indicative of a desired air / fuel ratio indication;

Indicates fuel ratio;

dependent on the actual lambda value, determining a correction variable for regulating the actual lambda value to the desired lambda value,

wherein the correction quantity depends on the deviation of the actual lambda value from the desired lambda value corresponds to a filling correction value for applying a size influencing the air charge of the internal combustion engine or a fuel correction value for acting on a size influencing the fuel quantity of the internal combustion engine to be injected.

One idea of the above method for performing a control and adaptation in an engine system is to adapt the adaptation by the Korrekturbzw. Adaption size to perform so that under no circumstances can increase the torque provided by the engine occurs. This is achieved by the fact that the control and adaptation intervention can be carried out both with regard to the quantity of fuel to be injected and with regard to the air charge to be set. In order to avoid torque increases due to a faulty calculation or another error, it is ensured that the adaptation intervention neither increases the quantity of fuel to be injected nor increases the air charge in the cylinder. The mixture control and adaptation can then be carried out by either reducing the amount of fuel to be injected or the air charge to be supplied to the cylinders. Furthermore, as the correction variable, the filling correction value for applying the quantity influencing the air filling of the internal combustion engine can be used if the actual lambda value is greater than the desired lambda value.

Alternatively or additionally, the fuel correction value for applying a quantity of fuel to be injected to the combustion can be used as the correction variable. If the actual lambda value is smaller than the desired lambda value, this variable can be used.

Furthermore, the correction quantity can be chosen such that only a reduction of the fuel quantity or the air charge due to the correction quantity is permitted.

According to a further aspect, an apparatus for adapting an air / fuel ratio of an air / fuel mixture in an internal combustion engine, in particular in a gasoline engine, is provided. The device is designed to:

an actual lambda value indicative of a current air / fuel ratio indication and a desired lambda value indicative of a desired air / fuel ratio indication;

depending on the actual lambda value, a correction variable for regulating the

Actual lambd value to determine the desired lambda value, wherein the correction variable depending on the deviation of the actual lambda value of the target lambda value corresponds to a filling correction value for acting on the size of the air filling of the internal combustion engine influencing variable or a fuel correction value for acting on an influencing the fuel quantity of the internal combustion engine.

In another aspect, an engine system is provided. The engine system includes:

an internal combustion engine;

a positioner for adjusting an air charge in the internal combustion engine;

- An encoder for setting an amount of fuel to be injected;

- a controller to:

provide an actual lambda value indicative of a current air / fuel ratio indication and a desired lambda value indicative of a desired air / fuel ratio indication;

dependent on the actual lambda value to determine a correction variable for controlling the actual lambda value to the desired lambda value, wherein the correction variable depends on the deviation of the actual lambda value from the desired lambda value a filling correction value for acting on a size influencing the air filling of the internal combustion engine Corresponds to the fuel correction value for applying a size influencing the amount of fuel to be injected of the internal combustion engine.

In another aspect, a computer program product is provided that includes program code that, when executed on a computing device, performs the above method.

Brief description of the drawings

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

Figure 1 is a schematic representation of an engine system with an internal combustion engine with intake manifold injection; and

FIG. 2 shows a block diagram for illustrating the functions implemented in the control unit of the engine system for adjusting the air charge in the cylinders, determining the quantity of fuel to be injected and the corresponding adaptation methods.

Description of embodiments

Figure 1 shows a schematic representation of an engine system 1 with an internal combustion engine 2. The internal combustion engine 2 is a gasoline engine with, in this embodiment, four cylinders 3. The internal combustion engine 2 and the cylinders 3, air is supplied via an air supply system 4. In the air supply system 4, an air mass sensor 5 is arranged on the input side, which may be formed as a hot film air mass sensor to detect an amount of air flowing into the internal combustion engine 2.

Downstream of the air mass sensor 5, a throttle valve actuator with a throttle valve 6 is arranged, which can control the air flow into the internal combustion engine 2 and thus the present in the cylinders 3 air filling by adjusting a throttle valve 6. The air charge is defined as the amount of air that is available in a cylinder 3 in a combustion, and is specified as the air mass flow, which indicates the air charge in proportion to the speed.

Between the throttle valve 6 and the intake valves (not shown) of the cylinders 3, an injection valve 7 is arranged to inject fuel of a predetermined amount of fuel into the so-called suction pipe section of the air supply system 4. Alternatively or additionally, it is also possible to arrange injection valves 7 directly on the cylinders 3 in order to allow a direct injection of fuel.

Combustion exhaust gases from the cylinders 3 are discharged via an exhaust gas discharge section 8. A lambda probe 9, which measures the oxygen content of the combustion exhaust gas and makes available a corresponding lambda signal, is arranged in the exhaust gas removal section 8. The lambda signal makes it possible to determine whether the air / fuel mixture provided in the cylinders 3 for combustion was in a stoichiometric equilibrium, or if there was too much or too little fuel or too much or too little air filling during the combustion.

If more air is present in the combustion chamber of the cylinder 3 at the time of combustion than is required for a stoichiometric air / fuel ratio, then this is an excessively lean mixture. The lambda value which corresponds to 1 at a stoichiometric air / fuel ratio is then greater than 1. If more fuel is present in the combustion chamber of the cylinders 3 than is needed for a stoichiometric air / fuel ratio at the time of combustion, this is the case too rich a mixture, which is indicated by a lambda value of less than 1.

The engine system 1 is operated by a control unit 10. The control unit 10 detects system state variables via various sensors and controls corresponding actuators for operating the internal combustion engine 2. Thus, the control unit 10 receives, for example, an indication of the amount of air flowing into the cylinder 3, d. H. via the air charge, and an indication of the current lambda value, which indicates whether the air / fuel mixture was too rich or too lean during combustion in the cylinder 3 or a stoichiometric

Air / fuel ratio of 1 had. Depending on the system state variables of the engine system 1 and depending on a driver-predetermined torque FWM specified externally, the control unit 10 then presets a control for the throttle valve actuator and a control for the injection valve 7. For controlling the throttle valve actuator, a voltage corresponding to a certain adjustment angle of the throttle valve 6 is correspondingly specified.

The injection valves 7 are correspondingly driven with an opening period, wherein the opening period is essentially attributable to an amount of fuel to be injected.

In detail, Figure 2 shows the realized in the control unit 10 functions. The functional blocks are implemented either as software and / or as hardware in the controller 10. In a filling control block 21, the desired position Dsoii of the throttle valve 6 is determined in accordance with a driver's desired torque FWM or another setpoint torque input specified by the driver by actuation of an accelerator pedal. The driver's desired torque FWM, which the driver prescribes via a corresponding position of the accelerator pedal, in gasoline engines essentially corresponds to a nominal charge F _So n which is directly converted into the desired position D _So n of the throttle valve 6 in the charge control block 21.

A charge detection block 22 determines the actual actual charge F | _St via an evaluation of the flowing through the air supply system 4 air amount LM, which can be determined by means of the air mass sensor 5. The provided actual filling F | _St serves as the basis of a mixture calculation in a mixture calculation block 23, in which the actual filling F | _St corresponding So II fuel quantity Ksoii is determined. An indication of the target fuel amount K _So nwill supplied to an injection calculation block 24, which determines, depending on the target fuel amount Ks _o ii opening time of the injectors 7 and the injection valves 7 drives accordingly.

In a filling adaptation block 25, the desired filling F _SO II with the actual filling F | _St compared and at a deviation between the desired filling F _SO II and the actual charge Fist a corresponding filling correction value F _K0 rri is determined in a known manner and the filling control block 21 provided to effect a corresponding correction of the control of the throttle valve 6. Is the Actual filling F | _St smaller than the target filling F _So n, the throttle valve 6 is opened. Is the actual filling F | _St greater than the target filling F _So n, the throttle valve 6 is closed further. By means of a mixture control block 26, a regulation of the air / fuel mixture is realized. The control can provide a proportional component and a differential component. The regulation of the air / fuel mixture is based on an actual lambda value Lambda _st supplied by the lambda probe 9 and serves to regulate the air / fuel ratio to an air / fuel ratio predetermined by a desired lambda value Lambda _S0 ii.

The mixture control block 26 further comprises an adaptation, which can be realized for example in the form of an integral part of the control or separately from the control. The mixture control block 26 provides a further charge correction value FK _OIT 2 for the charge control block 21 and a fuel amount correction value K _Kor r for the mixture calculation block 23.

While the implementation of the mixture control a filling manipulated variable S _F üiiung either provided to the stuff control 21 or a fuel control value S to the mixture _Kr aftstoff calculation block 23 to the current

Istlambdawert Lambdai _st corresponding to the desired lambda value Lambda _S0 ii regulate, long-term changes in the engine system 1 are detected by the integral component of the mixture control. The mixture control block 26 is therefore designed such that the integral component of the mixture control is forwarded to the charge control block 21 and to the mixture calculation block 23 separately from the remaining components, such as proportional and differential components.

The mixture control block 26 is configured so that it can provide both the filling control block 21 with the further filling correction value F _Kor r2 and the mixture calculating block 23 with a fuel correction value K _Kor r.

If it is determined via the integral component of the mixture control that the air / fuel mixture tends to be too rich (lambda <1), the corresponding integration variable is output as fuel correction value K _Korr to the mixture calculation block 23. However, the fuel correction _value K _Kor r has a sign, which is a reduction in the amount of fuel to be injected, ie the target fuel quantity, indicates. It is provided in the mixture control block 26 that the fuel correction value K _Kor r is output so that only reductions in the amount of fuel to be injected in the mixture calculation block 23 are permitted.

If, in the other case, it is determined via the integration value that the air / fuel mixture tends to be too lean (lambda> 1), then the fuel correction value K _Kor r, which increases the setpoint fuel quantity, is not predetermined as in previous adaptation methods, but the further charge correction becomes value F _Kor r2 is provided to the charge control block 21 so as to effect a throttle position correction in the closing direction. This can be done by selecting a suitable sign of the further filling correction value F _Kor r2. In this way, the mixture adaptation based on the integral component of the mixture control can only lead to a reduction of the provided torque.

The exclusive permitting of torque-reducing adaptation interventions prevents that an adaptation can also lead to an increase in torque. As a result, an additional security against an increase in torque due to incorrect calculations is ensured in the control unit 10.

When the actual charge F |. Calculated in the charge detection block 22 _St due to a fault (eg calculation error in the control unit, fault of a sensor or actuator function or in their supply lines) is smaller than that actually in the

Air supply system 4 flowing air mass, so the use of the Fülungsungs adaption block 25 causes the throttle valve 6 is opened further. As a result, a larger air charge actually reaches the cylinders 3 of the internal combustion engine 2. Since the fuel calculation is based on the incorrectly too small actual charge Fist, initially too little fuel is output. This leads to a lean air / fuel mixture, which is detected by the lambda probe 9 in the form of a lambda value greater than 1. Unlike the methods of the prior art, the mixture control block 26 is not readjusted to compensate for the insufficient fuel amount of fuel, which would lead to an increase in torque, but an intervention in the filling control is performed by the further filling correction value F _Kor r2 is adjusted, which causes the throttle valve adjuster closes the throttle valve 6 accordingly.

During this process, the fuel correction value K _Kor r remains constant and thus an increase in torque is prevented by an increased Kraftstoffbeimessung. The mixture control and the mixture adaptation based on the integration values thus counteract the charge adaptation of the charge adaptation block 25 and compensates for their response to the actual charge Fist determined to be too small. Since neither the real air charge increases nor has it led to an increase in the amount of fuel to be injected, in contrast to previous methods, there is no increased torque output compared to the driver desired torque FWM desired by the driver.

If, due to an error, such as a calculation error in the control unit 10, an error of the function of an actuator (eg injector) or a sensor or an error in their supply lines, within the mixture calculation block 23, an increase in the amount of fuel, the amount of fuel is greater as the one who is the real actual filling F | _St would be appropriate in order to achieve a corresponding to the desired lambda value air / fuel ratio, the air / fuel mixture is too rich, because in relation to the air charge too much fuel is injected. The stuffing controller 21 does not respond to this error. However, the mixture control block 26 does not now increase the quantity of air supplied to the internal combustion engine 2 with the aid of the further fueling correction value FK _OIT 2, but acts with the fuel correction value K _Kor r on the fuel quantity to be injected. The further filling correction value F _Kor r2 is not changed by this method. As a result, the mixture control block 26 can directly counteract and compensate for the excessive amount of fuel injected due to the fuel metering error. Since in this case neither the actual air charge has increased nor too high an amount of fuel has been injected, in contrast to previous methods, there is no increased torque compared to the driver desired torque FWM desired by the driver.

Claims

claims

A method for controlling and adapting an air / fuel ratio of an air / fuel mixture in an internal combustion engine (2), in particular in a gasoline engine; with the following steps:

Providing an actual lambda value (Lambda _st ) indicative of a current air / fuel ratio indication and a desired lambda value (lambda soii) indicative of a desired air / fuel ratio indication;

- depending on the Istlambdawert (Lambdai _st), determining a correction variable for controlling and adapting the Istlambdawert (Lambdai _st) to the nominal lambda value (lambda _S0 ii),

characterized in that

the correction quantity depends on the deviation of the actual lambda value (lambda _st ) from the set lambda value (lambda _S0 ii) a filling correction value (F _Kor r2) for applying a quantity influencing the air charge of the internal combustion engine (2) or a fuel correction value (K _Kor r) for charging a corresponds to the amount of fuel to be injected of the internal combustion engine (2) influencing size.

2. The method of claim 1, wherein as the correction value of the filling correction value (F _Kor r2) for acting on the air filling of the internal combustion engine (2) influencing variable is used when the actual lambda value (Lambdaist) is greater than the desired lambda value (lambda _S0 ii) -

3. The method of claim 1 or 2, wherein as the correction value of the fuel correction value (K _K0 rr) for acting on the fuel quantity of the internal combustion engine (2) influencing variable is used when the Istlambda (Lambdai _st ) is smaller than the Solllambda (Lambdasoii ).

4. The method according to any one of claims 1 to 3, wherein the correction amount is selected so that only a reduction of the fuel amount or the air filling is allowed due to the correction amount.

Device for regulating and adapting an air / fuel ratio of an air / fuel mixture in an internal combustion engine (2), in particular in a gasoline engine; the device being designed to:

an actual lambda value (Lambda _st ) indicating a current air / fuel ratio indication and a desired lambda value (lambda _S0 ii) indicative of a desired air / fuel ratio indication;

depending on the actual lambda value (lambda _st ), determining a correction quantity for regulating and adapting the actual lambda value (lambda _st ) to the desired lambda value (lambda _s oii), the correction quantity being dependent on the deviation of the actual lambda value from the desired lambda value (lambda) during a fill correction value Applying a magnitude influencing the air charge of the internal combustion engine (2) or a fuel correction value for charging a variable influencing the fuel quantity of the internal combustion engine (2) to be injected.

Motor system (1) comprising:

an internal combustion engine (2);

- An encoder (6) for adjusting an air charge in the internal combustion engine;

- An encoder (7) for setting an amount of fuel to be injected;

a controller (10) to:

an actual lambda value (Lambda _st ) indicative of a current air / fuel ratio indication and a desired lambda value (lambda _S0 ii) indicative of a desired air / fuel ratio indication;

dependent on the actual lambda value (Lambdai _st ) to determine a correction variable for regulating and adapting the actual lambda value (lambda _st ) to the desired lambda value (lambda _S oii), wherein the correction quantity depends on the deviation of the actual lambda value (lambda _st ) from the desired lambda value (lambda _S0 ii) a filling correction value (F _Kor r2) for acting on the air filling of the internal combustion engine (2) influencing variable or a fuel correction value (K _Kor r) for acting on the fuel quantity of the internal combustion engine (2) influencing variable corresponds.

A computer program product containing program code which, when executed on a data processing unit, performs the method of any one of claims 1 to 4.