EP1315894A1

EP1315894A1 - Mixture adaptation method for internal combustion engines with direct gasoline injection

Info

Publication number: EP1315894A1
Application number: EP01962668A
Authority: EP
Inventors: Gholamabas Esteghlal
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-09-01
Filing date: 2001-08-23
Publication date: 2003-06-04
Anticipated expiration: 2021-08-23
Also published as: US6725826B2; DE50108335D1; KR20020068333A; DE10043093A1; EP1315894B1; WO2002018767A1; RU2002113751A; US20030106522A1; CN1388858A; JP2004507656A

Abstract

The invention relates to a method for compensating mis-adaptation in the pre-control system of a fuel metering system for an internal combustion engine that is operated in at least the two different operating modes homogenous mode and shift mode. The homogenous mode comprises mixture control and adaptation of the mixture control. A changeover between the operating modes takes place in accordance with a desired operating mode, which is determined based on a plurality of operating mode requirements. The operating mode requirements are each prioritised and the desired operating mode is determined according to the priority of the operating mode requirements. The method momentarily switches over to homogenous mode with activation of the adaptation process even outside the normal conditions in which the adaptation process is activated. A deviation of the adaptation variable from its neutral value during the momentary activation is evaluated as a suspected error and if there is a suspected error, the engine control programme increases the adaptation priority under normal activation circumstances.

Description

Mixture adaptation method for internal combustion engines with gasoline direct injection

State of the art

It is already known to superimpose a pilot control with a control when regulating the fuel / air ratio for internal combustion engines. It is also known to derive further correction variables from the behavior of the control manipulated variable in order to compensate for mismatches in the precontrol to changed operating conditions. This compensation is also referred to as adaptation. US Pat. No. 4,584,982 describes, for example, an adaptation with different adaptation variables in different areas of the load / speed spectrum of an internal combustion engine (area adaptation). The different adaption sizes are aimed at the compensation of different errors. Three types of errors can be distinguished according to cause and effect: Errors in a hot film air mass meter have a multiplicative effect on the fuel metering. Leakage air influences have an additive effect per unit of time and errors in the compensation of the retarding of the injection valves have an additive effect per injection. According to legal regulations, emissions-related errors should be recognized with on-board means and, if necessary, an error lamp should be activated. The mixture adaptation is also used for fault diagnosis. If, for example, the corrective action of the adaptation is too great, this indicates an error.

The measured lambda value deviates from the physically available lambda value in engines with gasoline direct injection mainly in stratified operation over the service life, the sample distribution and in the case of non-regulated probe heating.

Since the mixture adaptation takes the measured lambda into account for learning the error, the adaptation in shift operation is not expedient. For the adaptation, therefore, a switch is made to homogeneous operation and the mixture adaptation is activated.

From DE 1 98 50 586 an engine control program is known which controls the switchover between shift operation and homogeneous operation.

In shift operation, the engine is operated with a strongly stratified cylinder charge and a large excess of air in order to achieve the lowest possible fuel consumption. The stratified charge is achieved by means of a late fuel injection, which ideally leads to the combustion chamber being divided into two zones: the first zone contains a combustible air-fuel mixture cloud on the spark plug. It is surrounded by the second zone, which consists of an insulating layer of air and residual gas. The potential for optimizing consumption results from the possibility of avoiding the engine To operate charge exchange losses largely unthrottled. Shift operation is preferred at a comparatively low load.

At higher loads, when the focus is on performance optimization, the engine is operated with a homogeneous cylinder charge. The homogeneous cylinder filling results from early fuel injection during the intake process. As a result, there is more time available for mixture formation until combustion. The potential of this operating mode for performance optimization results, for example, from the use of the entire combustion chamber volume for filling with a combustible mixture.

With regard to the known adaptation, there are several switch-on conditions:

For example, the engine temperature must have reached the switch-on temperature threshold and the lambda sensor must be ready for operation. Furthermore, the current values of load and speed must lie in certain areas in which learning takes place. This is known for example from US 4,584,982. Homogeneous operation must also exist. According to the known program, the switchover from shift operation to homogeneous operation does not depend on whether there is an error in the system.

The invention aims to increase the period in which the engine can be operated in a shift-optimal manner. Switching to homogeneous operation for diagnosis reduces the consumption advantage of direct petrol injection, since homogeneous operation is less fuel-efficient than shift operation. Switching to homogeneous operation increases the Fuel consumption is therefore unnecessary if there is no fault. It should be avoided as far as possible without worsening the discovery of emissions-related errors.

This effect is achieved with the features of claim 1.

In particular, a method for compensating for mismatches in the precontrol of a fuel metering (adaptation) for an internal combustion engine is disclosed, which is operated in the at least two different operating modes homogeneous operation and stratified operation

- in which a mixture control and an adaptation of the mixture control take place in homogeneous operation

- And in which a switch is made between the operating modes as a function of a desired operating mode, which is determined from a plurality of operating mode requests, each of the operating mode requests being assigned a priority

and in which the determination of the target operating mode is carried out as a function of the priorities of the operating mode requirements,

- With a brief switchover to homogeneous operation with activation of a temperature-dependent adaptation, even outside the normal switch-on conditions of an area-dependent adaptation

- and in which a deviation of the adaptation size from its neutral value during the brief activation of the temperature-dependent adaptation is rated as a suspected fault and in which the engine control program increases the priority of the range-dependent adaptation under normal switch-on conditions if a suspected fault is present. One embodiment provides that the short-term mixture adaptation below the minimum temperature of the area-dependent adaptation is activated.

Another embodiment provides that the minimum temperature of the area-dependent adaptation is greater than or equal to 70 ° Celsius.

Another embodiment provides that the short-term mixture adaptation is activated for a time in the range of approximately 10 to 20 seconds.

A further embodiment provides that the physical urgency is withdrawn when the error in the normal range-dependent mixture adaptation has been learned, so that the range-dependent mixture adaptation is released by the engine control program under normal urgency.

A further embodiment provides that the value of the temperature-dependent short-term adaptation is maintained when the car is parked and is reset during the initialization phase after the next start by the value learned in the context of the normal range-dependent mixture adaptation.

Another embodiment provides that the operating parameter-dependent (range-dependent) mixture adaptation has a multiplicative and / or additive effect on the fuel metering.

Another embodiment provides that the value or values of the area-dependent adaptation above a Temperature threshold to be renewed and on the

Act on fuel metering regardless of temperature.

Another embodiment provides that the deviation of the current temperature-dependent adaptation factor from a long-term adaptation factor is formed to form the suspected error.

The invention is also directed to an electronic control device for carrying out at least one of the methods and embodiments specified above.

An essential part of the invention is a short-term mixture adaptation, which also outside the normal switch-on conditions of the adaptation, in particular below the minimum temperature of the region-dependent adaptation. According to the invention, the short-term mixture adaptation is only activated for a very short time in the range of approximately 10 to 20 seconds. If there is an error, the correction value of the short-term temperature-dependent adaptation will deviate from its neutral value.

According to the invention, the deviation increases the urgency of the normal mixture adaptation as part of the operating mode control program. If their running conditions are then fulfilled, the normal mixture adaptation is started comparatively quickly.

If the error in the normal range-dependent mixture adaptation has been learned, the physical urgency is withdrawn and the range-dependent mixture adaptation only runs when it is released by the engine control program under normal urgency. Since the temperature-dependent short-term adaptation retains its value when the car is parked and is incorrect again in the adapted state the next time it is started, it is reset during the initialization phase after the next start by the value learned as part of the normal area-dependent GemiSchad adaption.

This has the advantage that the physical urgency of the normal adaptation increases immediately in the non-adapted state.

Since the temperature-dependent adaptation should only provide a 3 to 4% correction in the normal state, the maximum of the integrator is corrected downwards or upwards depending on the learned error, so that, for example, only 5% correction is allowed for a 20% learned error ,

The invention provides the following advantages:

In the error-free state, the switchover to homogeneous operation takes place only at long intervals. In the faulty state when the engine is cold, very short and then long time intervals are run first. The short time intervals are repeated if the error is not learned after the start. When the error has been learned, homogeneous operation is again carried out at long intervals. In the method according to the invention, the switchover to homogeneous operation, which is less favorable in terms of consumption, is activated only very briefly and the temperature-dependent mixture adaptation is immediately activated if a fault is suspected. If there is no fault in the system, the mixture adaptation is activated less frequently, so that the period in which the engine can be operated in shift mode is optimized. In the following an embodiment of the invention is explained with reference to the drawing.

Fig. 1 shows the technical environment of the invention. FIG. 2 illustrates the formation of a fuel metering signal on the basis of the signals from FIG. 1 and FIG. 3 discloses the formation of a temperature-dependent adaptation variable as used in the invention and FIG. 4 represents an embodiment of the invention in the form of functional blocks.

1 in FIG. 1 represents an internal combustion engine with an intake manifold 2, an exhaust pipe 3, a fuel metering device 4, sensors 5-8 for operating parameters of the engine and a control unit 9. The fuel metering device 4 can, for example, consist of an arrangement of injection valves for direct injection of There is fuel in the combustion chambers of the internal combustion engine.

The sensor 5 supplies the control unit with a signal about the air mass ml sucked in by the engine. Sensor 6 provides an engine speed signal n. Sensor 7 provides the engine temperature T and sensor 8 provides a signal Us about the exhaust gas composition of the engine. From these and possibly other signals via further operating parameters of the engine, the control unit forms, in addition to further manipulated variables, the fuel metering signals ti for controlling the fuel metering means 4 such that a desired behavior of the engine, in particular a desired exhaust gas composition, is established.

FIG. 2 shows the formation of the fuel metering signal. Block 2.1 represents a map, which is determined by the speed n and the relative air charge rl is addressed and the pilot control values rk for the formation of the fuel metering signals are stored. The relative air filling rl is related to a maximum filling of the combustion chamber with air and thus to a certain extent indicates the fraction of the maximum combustion chamber or cylinder filling. It is essentially formed from the signal ml, rk corresponds to the fuel quantity assigned to the air quantity rl.

Block 2.2 shows the known multiplicative lambda control intervention. A mismatch in the amount of fuel to the amount of air is shown in the signal Us of the exhaust gas probe. From this, a controller 2.3 forms the control manipulated variable fr, which reduces the mismatch via the intervention 2.2.

The metering signal, for example a trigger pulse width for the injection valves, can already be formed from the signal corrected in this way in block 2.4. Block 2.4 thus represents the conversion of the relative and corrected fuel quantity into a real control signal taking into account fuel pressure, injector geometry, etc.

Blocks 2.5 to 2.9 represent the known operating parameter-dependent (area-dependent) mixture adaptation, which can have a multiplicative and / or additive effect. The circle 2.9 should represent these 3 possibilities. The switch 2.5 is opened or closed by the means 2.6, wherein the means 2.6 are supplied with operating parameters of the internal combustion engine, such as temperature T, air mass ml and speed n. Means 2.6 in connection with the switch 2.5 thus enables an activation of the three mentioned adaptation options depending on the operating parameter range. The formation of the Adaptation intervention fra on the fuel metering signal formation is illustrated by blocks 2.7 and 2.8. With switch 2.5 closed, block 2.7 forms the mean value frm of the control variable fr. Deviations of the mean value frm from the neutral value 1 are transferred from block 2.8 to the adaptation intervention variable fra. For example, the control manipulated variable fr initially approaches 1.05 due to a mismatch in the precontrol. The deviation 0.05 from the value 1 is transferred from block 2.8 to the value fra of the adaptation intervention. In a multiplicative fra intervention, fra then goes to 1.05, with the result that fr goes back to 1. The adaptation ensures that mismatches in the pilot control do not have to be corrected every time the operating point changes. This adaptation of the adaptation variable fra is carried out at high temperatures of the internal combustion engine, for example above a cooling water temperature of 70 ° Celsius with switch 2.5 then closed; Once adjusted, fra also affects the formation of the fuel metering signal when switch 2.5 is open.

This known adaptation is supplemented by the further correction frat within the scope of the invention, which becomes effective in link 2.10.

An embodiment of the frat formation is shown in FIG. 3. Block 3.1 supplies the deviation of the mean control manipulated variable frm from the value 1 to an integrator block 3.2. Block 3.3 activates the integrator for comparatively low engine temperatures T from an interval TMN <T <TMX. TMN as the lower interval limit can be, for example, 20 ° Celsuis; TMX as the upper interval limit can correspond, for example, to the temperature at which the conventional adaptation by closing the switch 2.5 is activated. A typical value for this temperature is 70 ° Celsius.

The output value of the integrator, with the value frak, provides a measure of the mismatch when the engine is comparatively cold.

This value is used when the engine is cold

Fuel metering signal formation is taken into account without there being any differences at high temperatures from the known adaptation when the engine is warm.

This is achieved, for example, by blocks 3.4 to 3.6 and 2.10.

In this context, it is essential to link the integrator output frak with a temperature-dependent variable ftk. In the example, ftk represents a multiplicative correction that varies between zero and one. The value zero results when the engine is warm, that is, when T> TMX. Then the minimum selection in block 3.7 returns the value TMX. In block 3.8, the difference between TMX and TMX is zero, which is fed to the quotient formation in block 3.9 as a counter. Block 3.8 accordingly delivers the value zero for the size of the temperature-dependent size ftk. The value 1 is added to this value ftk = zero in block 3.6. The sum frat therefore has the value 1 and does not change the fuel metering signal formation when the engine is warm when the multiplicative link in block 2.10. In other words, when the engine is warm, ftk has a maximum weakening effect on frak. In the case of a cold engine with, for example, T = zero "Celsius, the minimum selection delivers the value zero and the subsequent quotient formation gives the value 1. ftk is then neutral and effective minimally weakening or not weakening to frak. To compensate for the addition of 1 in block 3.6 for this case, a subtraction of 1 takes place in block 3.4. With a cold engine (T = zero), frak therefore acts as (frak-1) * l + l = frak unchanged and therefore not weakened to the fuel metering signal formation. In other words: the further adaptive (temperature-dependent) correction only works when the engine is cold. The correction varies continuously between the extreme values shown.

The map 3.10 provides values K for the

Integration speed in integrator 3.2 depends on values for drl and n. For example, K becomes smaller the larger drl. drl is the change in the intake air mass, which is particularly large, for example, in transitional operating states. In this way, mismatches have an effect

Transitional operating states only in a weakened form based on the adaptation.

Since the motor temperature changes and the value frak learned in the integrator should be independent of the temperature, the frm deviation from one is multiplied by the factor ftk.

4 represents an embodiment of the invention in the form of functional blocks.

Block 4.1 stands for the formation of the sizes frat and frak shown in FIG. 3. To form the suspected error, a long-term adaptation factor fratia is first formed in the area of the temperature-dependent mixture adaptation (block 4.2). To a certain extent, this is the proportion of the cold adaptation factor frak that is always with the engine cold occurs. If there is always a similar value, e.g. a value of 2.5%, for the temperature-dependent adaptation in the error-free state, this value does not indicate an error in any case. This always occurring value is saved in the control unit.

Furthermore, the deviation of the current temperature-dependent adaptation factor frak from the long-term adaptation factor fratia is formed to form the suspected error:

dfrat = amount (frak - fratia)

The difference formation and the amount formation are represented by blocks 4.3 and 4.4. Then a comparison of dfrat with an error suspicion threshold FVLRAS (block 4.5) takes place. If this is exceeded, the condition B-fvlra is set in block 4.6 via a flip-flop. The suspected error corresponds to a high urgency for the normal adaptation that takes place when the engine is warm. Due to the high urgency that resulted from the setting of the suspected error in the context of the short-term temperature-dependent adaptation, as soon as the other switch-on conditions for the normal mixture adaptation exist, the system switches to homogeneous operation and the normal mixture adaptation is activated (block 4.7).

Claims

Expectations

1. Method for compensating for mismatches in the pre-control of fuel metering for an internal combustion engine that is operated in the at least two different operating modes: homogeneous operation and shift operation,

- whereby mixture control and an adaptation of the mixture control take place in homogeneous operation

- and switching between the operating modes depending on a target operating mode, which is determined from a plurality of operating mode requests, with each of the operating mode requests being assigned a priority

- and the determination of the target operating mode is carried out depending on the priorities of the operating mode requirements,

- whereby a switch is made to homogeneous operation with activation of a temperature-dependent adaptation for a short time even outside the normal switch-on conditions of an area-dependent adaptation

- and a deviation of the temperature-dependent adaptation variable from its neutral value during the short-term activation is considered a suspected error and whereby the engine control program increases the priority of the adaptation under normal switch-on conditions if there is a suspicion of an error.

2. The method according to claim 1, characterized in that the short-term mixture adaptation is activated below the minimum temperature of the area-dependent adaptation.

3. The method according to claim 2, characterized in that the minimum temperature of the area-dependent adaptation is greater than or equal to 70° Celsius,

4. Method according to claim 1 or 2, characterized in that the short-term mixture adaptation is activated for a time in the range of approximately 10 to 20 seconds.

)

5. The method according to claim 1, characterized in that the physical urgency is withdrawn when the error in the normal range-dependent mixture adaptation has been learned, so that the range-dependent mixture adaptation is released by the engine control program with normal urgency.

6. The method according to claim 1, characterized in that the value of the temperature-dependent short-term adaptation is maintained when the car is switched off and is reset during the initialization phase after the next start by the value learned as part of the normal area-dependent mixture adaptation.

1 . Method according to one of the preceding claims, characterized in that the operating parameter-dependent (area-dependent) mixture adaptation has a multiplicative and/or additive effect on the fuel metering.

8. The method according to any one of the preceding claims, characterized in that the value or values of the area-dependent adaptation are renewed above a temperature threshold and act on the fuel metering independently of the temperature.

9. The method according to one of the preceding claims, characterized in that to form the suspected error, the deviation of the current temperature-dependent adaptation factor from a long-term adaptation factor is formed.

10. Electronic control device for carrying out at least one of the methods according to claims 1 - 9.