DE10043106A1 - Control method of direct fuel injection type internal combustion engine, involves adjusting ignition angle, if moving speed of accelerator exceeds threshold - Google Patents

Abstract

The adjustment (B-drlkrdy) for the ignition angle, is performed after each operation cycle of the engine, if moving speed (dwped-w) of accelerator exceeds threshold (dyespv). Independent claims are also included for the following: (a) Computer program stored in a flash memory for engine control; (b) Control unit for internal combustion engine

Description

State of the art

The present invention relates to a method for Control of an internal combustion engine with a combustion chamber and with an accelerator pedal, with the fuel in the combustion chamber is injected directly and the ignition angle Knock prevention can be adjusted late.

A method of the type mentioned at the outset is based on the market known. With him, the fuel is directly via an Combustion chamber arranged injection valve in this injected. This can reduce throttle losses be avoided what fuel consumption one such internal combustion engine lowers. In particular Such an internal combustion engine can cause operating situations a so-called "knocking" tendency. Below this is an early one and uncontrolled combustion of fuel in the combustion chamber understood which occurs especially when the Internal combustion engine is very hot. In such cases fuel already injected into the combustion chamber  the actual ignition on the hot walls of the Ignite the combustion chamber and lead to pre-combustion. This is e.g. B. avoided by the ignition angle after is adjusted late.

However, retarding the ignition angle should only occur in those situations where there is a knocking Combustion in the combustion chamber is to be expected. This is e.g. B. then the case when the internal combustion engine is highly dynamic is operated when it suddenly has a higher one Load is required.

The object of the present invention is a method of the type mentioned in the introduction so that a knocking combustion in the combustion chamber of the internal combustion engine safe even in such highly dynamic situations can be avoided.

This task is carried out in the process mentioned at the beginning solved in that in an operating state Internal combustion engine after an adjustment of the ignition angle late when the movement speed of the Accelerator pedal exceeds a limit.

The method according to the invention assumes that a there is a sudden increase in load when that Accelerator pedal by the user at very high speed is pushed through. It is express at this point noted that the term "accelerator pedal" of course is not to be understood in the narrow sense. Instead be this includes all facilities with which the User controlling his performance requirement Announces internal combustion engine, this can be a Accelerator pedal, a throttle or z. B. a throttle grip  act.

A sudden depression of the accelerator pedal is according to the invention then when the accelerator pedal movement speed exceeds a limit. The limit is like this chosen that when the same is exceeded by the Internal combustion engine performed more or less like that abruptly increases that with a high probability Knock on combustion in the combustion chamber of the Internal combustion engine occurs. Now if the Accelerator pedal movement speed greater than that Limit is, the ignition angle is already retarded, is reliably prevented if the Internal combustion engine on the suddenly changed Power request due to a sudden Performance change reacts, it actually becomes a knocking combustion in the combustion chamber of the internal combustion engine comes.

Advantageous developments of the invention are in Subclaims specified.

So z. B. proposed that the accelerator pedal-based adjustment of the ignition angle is carried out late only in a fuel-operated operating state of the internal combustion engine. The background to this is as follows:
There are essentially two options for changing the torque of an internal combustion engine: In the so-called “air-guided” system, a throttle valve is opened to increase the torque of the internal combustion engine. This increases the air filling in the combustion chamber of the internal combustion engine. The increased air charge is again measured by a sensor (HFM sensor) arranged in the intake pipe, and an amount of fuel corresponding to the air charge is then injected into the combustion chamber.

The second option is to change the Torque of the internal combustion engine over one fuel-guided system. With this is the Throttle valve mostly fully open. An increase of the torque of the internal combustion engine is determined by a Increased amount of fuel injected. The Air filling is almost with this fuel-guided system always maximum. This in turn means that the fuel Air mixture in the combustion chamber in the fuel-guided system mostly not essentially stoichiometric, but is lean.

During a performance change in the air-guided system because of the long controlled system (accelerator pedal - throttle valve - HFM sensor - injection) with a certain time delay done, it is in the fuel-guided system because of the relatively short controlled system (accelerator pedal - injection) pretty spontaneous. In addition, the air is filled with fuel-guided system roughly constant, so they is not suitable for the detection of changes in performance.

Therefore, it offers itself in the fuel-operated operating state the internal combustion engine according to the invention Accelerator-based adjustment of the ignition angle late especially because here regardless of the filling of the Combustion chamber a change in the torque of the Internal combustion engine immediately recognized and the corresponding Measures to avoid knocking are initiated can.

In a further development of this variant of the invention  suggested that the accelerator pedal dependent displacement of the Ignition angle essentially only in one Operating state of the internal combustion engine takes place in which the Fuel-air mixture in the combustion chamber is not essentially is stoichiometric (i.e. lambda <1) and especially in such an operating state of the internal combustion engine takes place in which the fuel-air mixture in the combustion chamber stratified.

Under a stratified air-fuel mixture understood that only in the area of the spark plug ignitable fuel-air mixture is present in the from Areas of the combustion chamber remote from the spark plug, however a relatively lean mixture to pure air is available.

A homogeneously lean fuel-air mixture with a lambda up to approx. 1.5 can be done by an injection in the intake stroke be effected. Even leaner heterogeneous mixtures can u. a. also provided by a double injection : Here is a small amount of fuel injected into the combustion chamber that they are in this Distributed essentially homogeneously. Later another one Amount of fuel injected into the combustion chamber, which however stratified essentially in the area of the spark plug remains. In both cases there will be a torque change the engine at generally complete open throttle valve and approximately constant air filling by changing the amount of fuel injected causes so that here the accelerator pedal-based adjustment the ignition angle to avoid knocking is also particularly good suitable.

According to the invention, an adjustment of the  Ignition angle is late when the speed a change in the air charge in the combustion chamber exceeds. As has already been stated above, a change in the torque of the internal combustion engine also by changing the air filling in the combustion chamber, so by changing the throttle valve angle become. This means the said "air-guided" System.

Since usually internal combustion engines in different Operating modes can be operated, d. H. air guided and fuel-guided, this enables the invention Training an optimal detection depending on the operating mode a change in torque and thus allows in all relevant operating modes to avoid knocking combustion to take necessary measures. Basically, depending on the operating mode (fuel or air-guided) between pedal or air filling-based Ignition angle adjustment switched.

In a further development of this variant of the invention suggested that the air filling dependent shift of the ignition angle only occurs when the fuel Air mixture in the combustion chamber is essentially stoichiometric is present. Such a stoichiometric fuel Air mixture generally lies in the air-guided Operating mode of the internal combustion engine before.

According to the shift of the Ignition angle after a certain number of Crankshaft revolutions reversed. This Measure takes account of the fact that in Dynamic operation only the risk of knocking combustion occurs during a sudden torque change. The  Shifting the ignition angle can therefore mostly on this be restricted to a very short period of time, no more than takes a few crankshaft revolutions.

In a further development of the method according to the invention the accelerator pedal speed limit, from which the Ignition angle is retarded from the speed of the Crankshaft of the internal combustion engine and / or the temperature the internal combustion engine. This is due to the fact that the tendency of the fuel to knock Combustion on the one hand from the speed of the crankshaft and on the other hand, the temperature of the internal combustion engine depends. At high speed and / or at low The temperature of the internal combustion engine is that Lower likelihood of dangerous knocking that the corresponding limit can be higher.

That further development of the inventive method in which two limit values are provided, which are offset by an offset Differentiate achieving hysteresis. It is particularly favorable if the offset from the speed is dependent.

The invention also relates to a computer program which is suitable for performing the above method if it is running on a computer. Particularly preferred is there when the computer program on a memory, is stored in particular on a flash memory.

Finally, the invention relates to a control and / or control device for operating a Internal combustion engine, which for control and / or regulation of the above method is suitable.  

The following is an embodiment of the invention with reference to the accompanying drawing in detail explained. The drawing shows:

Fig. 1 is a block diagram of an internal combustion engine; and

FIG. 2 shows a flowchart of a method for operating the internal combustion engine from FIG. 1.

In Fig. 1, an internal combustion engine is identified overall by reference numeral 10. It comprises a combustion chamber 12 , to which fuel is fed directly via an injection valve 14 . The fuel is ignited by a spark plug 16 , which is fed by an ignition system 18 .

Air is supplied to the combustion chamber 12 from an intake pipe 20 via an intake valve (not shown). In the intake pipe 20 there is a chamber in which a throttle valve 22 is arranged. The throttle valve 22 is adjusted by a servomotor 24 . The internal combustion engine 10 further includes a crankshaft 26 .

Furthermore, a control and regulating device 28 is provided, which receives signals from several sensors: First of all, this includes a speed sensor 30 which taps the speed of the crankshaft 26 and emits corresponding signals to the control and regulating device 28 . A position transmitter 32 is also provided, which detects the position of the throttle valve 22 . The air mass flowing through the intake pipe 20 into the combustion chamber 12 is recorded via a hot film air flow meter 34 (HFM sensor).

In the control and regulating device 28 , the air filling in the combustion chamber 12 is determined from the corresponding signal. Finally, the angular position of an accelerator pedal 36 is detected by an angle sensor 38 , which is also connected on the input side to the control and regulating device 28 . On the output side, the control and regulating device 28 outputs control signals to the servomotor 24 , the injection valve 14 and the ignition system 18 .

A memory 40 is present in the control and regulating device 28 , preferably a flash memory, in which a computer program is stored. This computer program realizes a method for operating internal combustion engine 10 , which is explained below with reference to FIG. 2:
First, it is explained how knocking is avoided in the air-guided operation of the internal combustion engine 10 : on the one hand, the signals from the HFM sensor 34 and the position transmitter 32 of the throttle valve 22 become an actual one in the control and regulating device 28 in a manner not shown here Air filling rl (block 42 ) in the combustion chamber 12 is determined. On the other hand, in conjunction with a timer (not shown), an actual load gradient drl_w and a predicted load gradient drlp_w are determined (blocks 44 and 46 ). These load gradients are therefore the change in the air filling per unit of time in the combustion chamber 12 , that is to say the speed of the change in the air filling rl in the combustion chamber 12 . A code word CWKR is used in block 50 to switch between the actual filling gradient drl_w and the predicted filling gradient drlp_w in block 48 .

A speed reference point distribution SNM16KRUB is determined in block 54 from the speed nmot (block 52 ) provided by the speed sensor 30 . In the same way, a reference point distribution SRL04DYUB for the relative filling is determined from the air filling r1 determined in block 52 in block 56 . These reference point distributions are in turn fed into blocks 58 and 60 in characteristic maps KFDYES and KFDYESOF.

On the output side, a limit value dyesv (block 62 ) is determined in the map KFDYES in block 58 and an offset dyesofv (block 64 ) is determined in the map KFDYESOF (block 60 ). In block 66 , the offset dyesofv is added to the limit value dyesv. In blocks 68 and 70 , the limit value dyesv or dyesv + dyesofv is compared with a filling gradient drlkrmx (block 72 ), which is determined as follows.

As a background, it is initially pointed out that the determination of the filling gradient drl_w or the predicted filling gradient drlp_w takes place synchronously with the rotational speed nmot, whereas the comparison in blocks 68 and 70 takes place in a certain cycle, e.g. B. at intervals of 10 ms. At low speed, at which only one value for the filling gradient is determined per cycle, the corresponding filling gradient drl_w or drlp_w is used directly as the value drlkrmx for the comparison in blocks 68 and 70 . At high speed, on the other hand, the maximum value drlkrmx that occurred during the last cycle in block 74 from several filling gradients is used for the comparison in blocks 68 and 70 via bit B_drknv (block 73 ).

If the result of the comparison in block 68 is "true", ie if the filling gradient drlkrmx is greater than the limit value dyesv, a corresponding signal is fed into the switch 76 . If the internal combustion engine 10 is in the “homogeneous” operating mode 10 , the fuel is injected into the combustion chamber 12 through the injection valve 14 in such a way that it is distributed uniformly in the combustion chamber 12 and a stoichiometric air-fuel ratio or lambda of less than or equal to 1 is set is indicated by a bit B_hom (block 78 ) and the switch 76 is set such that a bit B_drlkrdy (block 80 ) is set (provided the result in block 68 is "true".

This bit indicates to the control system that the ignition angle should be retarded to avoid knocking. If the answer in block 70 is also "true", ie if the limit value increased by the offset dyesofv is exceeded, a bit B_drlkrdyof is set in switch 81 , analogous to what has been said above. This indicates that the adaptation of the ignition angle adjustment is released early.

As described above, the method described above is used when the internal combustion engine 10 is operating in homogeneous mode. In this operation, the torque of the internal combustion engine 10 is controlled by the position of the throttle valve 22 , which in turn results in a corresponding change in the air charge rl in the combustion chamber 12 .

Depending on the air filling rl in the combustion chamber 12 , such an amount of fuel is injected into the combustion chamber 12 through the injection valve 14 that a stoichiometric fuel-air mixture 12 is present. Such an operating mode is also referred to as "air-guided". By the described method, when the air filling in the combustion chamber 12 changes suddenly, that is, when. B. the throttle valve 22 is suddenly opened, a corresponding bit B_drlkrdy or B_drlkrdyof (blocks 80 and 82 ) is set, as a result of which the ignition angle is retarded and this prevents knocking.

However, the internal combustion engine 10 shown in FIG. 1 can also work in a fuel-operated operating state, preferably in shift operation. In this, the throttle valve 22 is essentially completely open, the combustion chamber 12 of the internal combustion engine 10 is therefore always filled to the maximum with air. In this case, a change in the torque of the internal combustion engine 10 is brought about by the fact that a corresponding amount of fuel is injected into the combustion chamber 12 through the injection valve 14 . Since the air filling in the combustion chamber 12 is essentially always constant, it cannot be used to detect a change in performance in which knocking combustion can occur. If the internal combustion engine 10 is in such an operating state, the procedure is therefore as follows:
The movement speed dwped_w of the accelerator pedal 36 is determined in block 84 via the signal provided by the angle sensor 38 . A limit value dyespv (block 88 ) for the speed of movement of the accelerator pedal 36 is determined from the speed-dependent interpolation point distribution SNM16KRUB (block 54 ) in a characteristic curve KRDYESP (block 86 ). On the one hand, this is again fed directly to a comparison block 90 and, on the other hand, added with the offset dyesofv in block 92 and fed to a further comparison block 94.

If the result of the comparison in block 90 is "true", the movement speed dwped_w of the accelerator pedal 36 is greater than the limit value dyespv (block 88 ) and the internal combustion engine 10 is not in the homogeneous operating mode, which is indicated by the fact that the bit B-hom (block 78 ) is not set and the switch 76 is set accordingly, then the bit B_drlkrdy is set in block 80 and the ignition angle is thereby retarded to avoid knocking combustion. The same applies to bit B_drlkrdyof in block 82 .

In this way, even in an operating mode of the internal combustion engine 10 in which an increase in the output of the internal combustion engine 10 is brought about directly by the amount of fuel injected into the combustion chamber 12 of the internal combustion engine 10 through the injection valve 14 , reliable prevention against knocking combustion is achieved guaranteed in the event of a sudden increase in performance. Depending on the operating mode (fuel-guided or air-guided), a switch is made between a pedal-based and an air-filling-based ignition angle adjustment.

It should be pointed out here that in principle the knock prevention could also be carried out based on the accelerator pedal in the air-guided operating mode of the internal combustion engine 10 with a preferably stoichiometric mixture. Since in this operating mode the actual increase in the power of the internal combustion engine 10 takes place only after a time delay for the movement of the accelerator pedal 36 , since an opening of the throttle valve 22 does not immediately result in a changed filling in the combustion chamber 12 due to the compressibility of the air and the frictional flow in the intake pipe 20 such an accelerator-based knock prevention would lead to an early adjustment of the ignition angle in the air-guided operation of the internal combustion engine 10 .

The method described above therefore ensures that in each operating mode of the internal combustion engine 10 , whether fuel-guided or air-guided, the ignition angle is adjusted at exactly the right time. A speed-dependent adjustment of the ignition angle to the rear is made possible via the speed-dependent interpolation point distribution SNM16KRUB (block 54 ). Alternatively or additionally, the temperature of the internal combustion engine 10 can also be used to determine the limit value dyesv. The same applies to the offset dyesofv.

Claims (13)

1. A method for controlling an internal combustion engine ( 10 ) with at least one combustion chamber ( 12 ) and with an accelerator pedal ( 36 ) in which fuel is injected directly into the combustion chamber ( 12 ) and the ignition angle can be adjusted late to avoid knocking, characterized that, at least in one operating state of the internal combustion engine ( 10 ), the ignition angle is adjusted (B_drlkrdy) late when the movement speed (dwped_w) of the accelerator pedal ( 36 ) exceeds a limit value (dyespv). 2. The method according to claim 1, characterized in that the accelerator pedal-dependent displacement (B_drlkrdy) of the ignition angle takes place only in a fuel-operated operating state of the internal combustion engine ( 10 ). 3. The method according to any one of claims 1 or 2, characterized in that the accelerator pedal-based adjustment (B_drlkrdy) of the ignition angle takes place essentially only in such an operating state of the internal combustion engine ( 10 ) in which the fuel-air mixture in the combustion chamber ( 12 ) is not essentially stoichiometric, and takes place in particular in such an operating state of the internal combustion engine in which the fuel-air mixture ( 10 ) is present in layers in the combustion chamber ( 12 ). 4. The method according to any one of the preceding claims, characterized in that at least in an operating state of the internal combustion engine ( 10 ), an adjustment (B_drlkrdy) of the ignition angle is carried out late when the speed (drl_w) of the change in the air charge (rl) in the combustion chamber ( 12 ) exceeds a limit (dyesy). 5. The method according to claim 4, characterized in that the air filling-dependent shift (B_drlkrdy) of the ignition angle takes place only in an air-guided operating state of the internal combustion engine ( 10 ). 6. The method according to any one of claims 4 or 5, characterized in that the air filling-dependent shift (B_drlkrdy) of the ignition angle takes place only in such an operating state of the internal combustion engine ( 10 ) in which the fuel-air mixture in the combustion chamber ( 12 ) is essentially stoichiometric , 7. The method according to any one of the preceding claims, characterized in that the displacement of the Ignition angle after a certain number of Crankshaft revolutions is reversed again. 8. The method according to any one of the preceding claims, characterized in that the limit value (dyespv) of the accelerator pedal speed (dwped_w), from which the ignition angle is retarded, depends on the speed (nmot) of the crankshaft ( 26 ) of the internal combustion engine ( 10 ) , 9. The method according to any one of the preceding claims,  characterized in that two limit values are provided which are offset by an offset (dyesofv) Differentiate achieving hysteresis. 10. The method according to claim 9, characterized in that the offset (dyesofv) depends on the speed (nmot) is. 11. Computer program, characterized in that it is used for Implementation of the method according to one of claims 1 to 10 is suitable when running on a computer becomes. 12. Computer program according to claim 10, characterized in that it is stored on a memory, in particular on a flash memory ( 40 ). 13. Control and / or regulating device for operating an internal combustion engine ( 10 ), characterized in that it is suitable for controlling and / or regulating the method according to one of claims 1 to 10.