DE19728926C1 - Method of lambda-controlled after-start delay in an internal combustion engine with lambda control - Google Patents

Abstract

A presettable adjustment in the controller output (FR) for the 1 settings is made by way of a presettable time lapse ( DELTA t), causing a thin or rich shift in the mixture strength of the injected fuel-air mixture through its valve (60). The cut-off time of the internal combustion engine (10) is recorded through a time metre, relying on the cut-off time and motor temperature to select the adjustment time lapse ( DELTA t) for the controller output. Its selection also depends on values for the air mass time integral and/or for a control probe (70), fitted behind a catalytic convertor.

Description

State of the art

The invention relates to a method for post-start shift of the λ control in an internal combustion engine with a λ control.

In an internal combustion engine with λ control depending on the air ratio λ detected by a λ probe by a control device from the internal combustion engine seem to be burned air-fuel mixture poses.

Both in the cold start and post start phase when cold Engine as well as in the post-start phase when the engine is hot it can happen that the λ-probe is switched on area, d. H. at a low probe temperature regulates a setpoint for a mixture that is too lean. This effect can be caused by oxygen enrichment, which, for example, partially in overrun Probe can occur partially in the catalyst, ver be strengthened. This allows after the shutdown phase  the internal combustion engine high nitrogen oxide (NOx) values arise.

From DE 195 45 418 A1 is an electronic Control device for the fuel metering of a Internal combustion engine known during start, after start or warm-up the fuel-air mixture is enriched, the extent of enrichment depending on Integral of the air mass supplied to the internal combustion engine is withdrawn.

DE 43 08 813 shows a control system for the Fuel metering of an internal combustion engine, in which the Switchover from control to regular operation after a Predefinable period of time after the start of the internal combustion engine is made, the period of time depending on the temperature of the Internal combustion engine is dependent on the start. As an alternative to Specifying a time period depends on the Starting temperature of the internal combustion engine is a threshold for specified an operating parameter, if exceeded is switched from control to regulation during operation.

For this reason, it is known that the setpoint of the λ- To design the control depending on the temperature that when the engine is cold, an engine-dependent fat shift of the air-fuel mixture and an approximate compensation of the un Desired nitrogen oxide levels in the exhaust gas is achieved.

DE 25 22 283 C3 describes a device for starting and / or post-start shift of the λ control of one Internal combustion engine supplied, by means of an elec tric fuel injection system formed force Known substance-air mixture, in particular for Achieve a good runout after the start or in the post-start phase by a relatively agile circuit one from the operating state of the burning Engine, in particular on the speed and the Load condition and depending on the engine temperature Post-start shift of the λ control is made.

Such a circuit as well as corresponding underlying methods cannot easily be used in existing injection systems can be integrated. About that is also known from DE 25 22 283 C3 Circuit does not take into account a λ regulation.

The invention is therefore based on the object Method and an electronic control device for post-start shifting the λ control an internal combustion engine with λ control in this way form that in the simplest possible way a reduction tion of the harmful nitrogen oxides in the post-start  phase in internal combustion engines with λ control enabled becomes.

This task is done in a post-start procedure shift of the λ control in an internal combustion engine solved with λ control in that a predetermined Time span a predeterminable change in the manipulated variable of the λ control is carried out independently of the control process is such that a lean or fat shift of the Air / fuel mixture results.

The fact that over a predetermined period of time Predeterminable change in the manipulated variable of the λ control for Achieve a lean or fat shift of the Air-fuel mixture is made on particularly advantageous way by engaging in the already existing λ control of the internal combustion engine a significant reduction in nitrogen oxides with optimal Operation of the internal combustion engine, d. H. in operation at an optimal air ratio.

With regard to optimal fat shift is provided in an advantageous embodiment, that the shutdown time of the internal combustion engine, d. H. the Time in which the internal combustion engine is switched off, recorded by a time counter and the size and duration the change in the manipulated variable depends on the shutdown time is chosen (claim 2). In this way, the fat ver shifting the air-fuel mixture very precisely can be adapted to the probe temperature without  to be detected by a sensor or the like needs.

The assignment of the change in the manipulated variable to the time can, for example, by prior application in be recorded in a map.

Within the scope of the invention and its further development according to claim 2, that the change in the manipulated variable with the Switching on the λ control is ended. As for a λ Regulation an operational probe is required can the time until the λ controller is switched on, i.e. H. the time it takes for the probe to be ready, evaluated as an indirect measure of the probe temperature become. It is assumed that a operational λ-probe the post-start phase ended is.

In a further embodiment it is provided that the size and duration of the change in the manipulated variable in Dependence on the engine temperature and / or the Probe temperature is selected (claim 3).

In addition, in another embodiment be provided that the change in the manipulated variable then is aborted if the air mass time integral and / or that of a guide probe behind the Output catalyst a predetermined value Threshold value exceeds (see claim 4).

In this case, the can advantageously recorded air mass to determine the post-start phase be used.  

In principle, the λ control can be different che way be trained.

For example, it can be provided that the λ- Control is designed as a continuous PID controller. In in this case it is advantageously provided that a given value over a given period of time is added to the setpoint of the manipulated variable (see claim 5).

In another embodiment in which the λ- Regulation is designed as a two-point controller advantageously provided that the integral part extended over a predetermined period of time or is kept constant and / or that to the Proporio a predetermined value is added (see claim 6).

In terms of the device, the object of the invention solved by the features of claim 7. The electronic according to the invention Control device is then by the subject matter of claims 8 and 9 further developed, comparatively to those previously in claims 5 and 6 specified procedures and their explanation in the introduction to the description is referred.

The following description of exemplary embodiments and their drawings representation is intended to further explain the invention.

The drawing shows:

Fig. 1 shows schematically the manipulated variable of the λ control in a two-point controller over time with and without post-start shifting the λ control of the fuel-air mixture and

Fig. 2 shows schematically the λ control circuit of an internal combustion engine.

An internal combustion engine with λ control is shown schematically in FIG. 2. As is apparent from Fig. 2, the internal combustion engine 10 includes an intake manifold 20 and an exhaust line 30. In the intake manifold 20 , a Luftmas senmesser 40 is arranged, which detects the air mass flow ms and passes on to a control circuit 50 . The speed n of the internal combustion engine 10 is detected by a tachometer on the engine 10 and also passed on to the control circuit 50 , which from the Luftmas senstrom ms and the speed n and possibly other detected and not shown in Fig. 2 input variables such. B. determines the engine temperature and the like. An injection time ti, the injection valves 60 is supplied.

In the exhaust pipe 30 , a λ-probe 70 is arranged which detects the air ratio of the internal combustion engine 10 in front of a catalytic converter (not shown). The air ratio λ detected by the λ probe 70 is fed to a controller 80 , which outputs a manipulated variable FR, which is included in the injection time ti in a manner known per se.

In Fig. 2, a λ control loop is shown as an example. The control circuit or the λ controller 50 can be designed as a two-point controller, continuous PI controller or PID controller.

The manipulated variable FR of the λ control is shown schematically for a two-point controller over time t in FIG. 1.

The course of the manipulated variable labeled I corresponds a fat shift known per se, which at for example, depending on the speed and load, takes one Shift the scheme to a slightly bold Achieve value at which the catalyst converted well.

The λ probe 70 essentially detects changes in the air ratio λ by λ = 1, ie a λ jump from λ <1 to λ <1 and vice versa (shown in FIG. 1 in the lower part using the probe voltage).

Such a λ jump, ie a jump of the control variable, initially leads to a strongly rising or falling edge 100 of the manipulated variable FR, which corresponds to the proportional component of the two-point controller. This is followed by the integral component 110 in a manner known per se.

The injected air-fuel ratio influenced by this manipulated variable FR leads to a value λ = 1 in the exhaust pipe 30 .

The change in the manipulated variable FR is based on the change with II designated curve explained.

In order to achieve a grease shift of the air-fuel mixture, the increasing integral component 110 signaling a change in the air ratio from rich to lean in the two-point controller 80 is extended by a predetermined time interval Δt. As a result, the manipulated variable FR changes such that a fat shift results in the injected air-fuel ratio.

Instead of the constant shift, a further increase in the rising flank of the integral component 110 by the predetermined time period Δt is also possible (shown in dashed lines in FIG. 1).

In addition, the proportional and inte Grail share also a predetermined proportional value added or subtracted or the proportional part run asymmetrically so that the entire Manipulated variable takes on a larger value on average.

The size and duration of the change in the manipulated variable FR can be selected as a function of the shutdown time of the combustion engine 10 , which is detected by a timer. The longer the internal combustion engine 10 is switched off, the greater the grease shift selected in the sense given above.

The additional post-start shift described above can also be used with λ control, which takes place when the probe is warm, ends become.

It is also possible that the post-start shift in Depends on the engine temperature at each Engine control is detected anyway, and / or the Probe temperature can be selected.

In addition, the duration of the change of the Stell size depending on whether that  Time integral of the air mass flow and / or of a guide probe behind the catalytic converter is arranged (not shown), output value exceeds a threshold.

Through the above decision criteria ensured that a fat shift of the sprayed air-fuel mixture, i. H. an after Start shift of the λ control only in the night start phase is made.

Claims (9)

1. The method for post-shifting the λ control in an internal combustion engine with a λ control, characterized in that a predeterminable change in the manipulated variable (FR) of the λ control is carried out over a predeterminable time period (Δt) such that a lean or Fat shift of the mixture composition of the injected fuel-air mixture results. 2. The method according to claim 1, characterized in that the shutdown time of the internal combustion engine ( 10 ) is detected by a time counter and the size and duration (Δt) of the change in the manipulated variable (FR) is selected as a function of the shutdown time. 3. The method according to claim 1, characterized in that the size and duration (Δt) of the change in  Manipulated variable (FR) depending on the motor temperature temperature and / or probe temperature is selected. 4. The method according to claim 1, characterized in that the duration (Δt) of the change in the manipulated variable (FR) depending on the determined value of the Air mass time integral and / or from the issued Worth a guide probe behind a Kataly sator is arranged, is selected. 5. The method according to any one of claims 1 to 4, characterized in that when the λ- Controller as a continuous PID controller via a front given time period (Δt) to a predeterminable value is added to the setpoint of the manipulated variable (FR). 6. The method according to any one of claims 1 to 4, characterized in that when the λ controller is designed as a two-point controller, the increasing integral component ( 110 ) is extended by a predetermined period of time (Δt) or is kept constant over a period of time and / or a predetermined value is added to the proportional and integral part. 7. Electronic control device ( 50 ) with a lambda controller ( 80 ) for the fuel metering of an internal combustion engine for carrying out the method according to claim 1, characterized in that the control device makes a predeterminable change in the manipulated variable FR of the lambda control over a predeterminable period of time delta such that a post-start, lean or rich shift of the composition of the fuel-air mixture supplied to the internal combustion engine is effected. 8. Electronic control device ( 50 ) with a lambda controller ( 80 ) for the fuel metering of an internal combustion engine according to claim 7, characterized in that, in the case of a continuous PID controller, the change in the manipulated variable is brought about by adding a predeterminable value to the desired value of the manipulated variable. 9. Electronic control device ( 50 ) with a lambda controller ( 80 ) for the fuel metering of an internal combustion engine according to claim 7, characterized in that in a two-point controller, the increasing integral component ( 110 ) is extended by a predetermined period of time λt or is kept constant over a period of time and / or a predetermined value is added to the proportional and integral part.