DE102012211754A1 - Method for operating combustion engine, involves injecting fuel into chamber using injector, where difference between nominal- and actual lambda values enables determining fuel quantity injected by injector during control duration - Google Patents

Abstract

The method involves injecting fuel into a combustion chamber (14) within an operating period using a first fuel injector (20a) and a second fuel injector (20b), where the first fuel injector injects greater amount of fuel than the second fuel injector in an adaptation mode. Control duration for the second injector is gradually increased from zero or decreased toward zero. Difference between nominal lambda value and actual lambda value determined in the adaptation mode enables determining fuel quantity that is injected by the second injector during the control duration. Independent claims are also included for the following: (1) a computer program comprising a set of instructions to perform a method for operating a combustion engine (2) a control and/or regulating device.

Description

State of the art

The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1.

From the market, it is known to determine or evaluate the actual movement of the valve element and its stroke in the case of electromagnetically actuated injection valves via suitable feedback variables, for example a coil current or a coil voltage. The aim is to uniformly adjust the movement of the valve element and its stroke by means of suitable algorithms from stroke to stroke of an injection valve and over several injection valves. Particularly important here is the so-called small amount range, in which only a very minimal amount of fuel is injected into the combustion chamber through the injection valve or through the injector. Such a small amount range is, for example, then, when the internal combustion engine is operated at idle, when reinstating a fuel injection after a fuel cut, at idle with simultaneously operated tank ventilation, etc ..

Furthermore, internal combustion engines are known from the market, in which the fuel passes through an injector, but divided into several injections into the combustion chamber, and internal combustion engines in which each combustion chamber are assigned a plurality of injectors. Thus, there are internal combustion engines in which an injector injects the fuel directly into a combustion chamber, whereas another injector injects fuel into an intake pipe, which leads to this combustion chamber. Internal combustion engines are also known in which an injector injects the fuel into the intake manifold in the intake manifold, in each case in front of one of two intake valves of a combustion chamber.

The DE 10 2010 038 625 A1 describes an internal combustion engine with an injector, which injects the fuel directly into the combustion chamber, and an injector, which injects the fuel into a suction pipe leading to this combustion chamber. To calibrate the injector, which injects the fuel into the intake manifold, that injector is used, which injects the fuel directly into the combustion chamber.

Disclosure of the invention

Object of the present invention is to make the fuel metering even more precise especially in the smallest amount.

This object is achieved by a method having the features of claim 1. Advantageous developments are specified in subclaims. In addition, find important features for the invention in the following description and in the drawing.

The inventive method has the advantage that it can be performed not only in idle, but in many different, almost any operating points of the internal combustion engine. Phases in which the internal combustion engine is operated at idle, can therefore be used for other important diagnoses as well as, for example. For carrying out a tank ventilation, or the engine can be switched off for the full utilization of consumption potentials. The method according to the invention can therefore be carried out relatively frequently, so that, for example, a temperature and / or wear-related change in the property of an injector can be promptly detected and corrected. In this case, the inventive method is extremely inexpensive and simple, since it can be dispensed with a detection of a coil current through a resistor.

The basis of the method is to let fuel pass through a first injection and by means of a second injection within a working cycle in a combustion chamber of the internal combustion engine. It should be noted at this point that the concept of the "first" injection and the "second" injection should express no time order but only the presence of two separate injection events. It is therefore entirely possible within the scope of the present invention for the second injection to take place before the first injection in terms of time. It is also possible for certain internal combustion engines, that the first injection and the second injection take place at the same time.

The method according to the invention is based on the fact that the injector characteristic curve, that is to say the relationship between actuation signal or actuation duration and injected fuel quantity, is known almost exactly at comparatively long actuation durations and corresponding comparatively large quantities of injected fuel. A corresponding desired lambda value can therefore be set very precisely by means of such a comparatively long injection. If a very small amount of fuel is now injected into the combustion chamber through the second injection with a drive duration of close to zero, this leads to a change in the actual lambda value. The changed lambda value or the extent of the change, ie the difference between the desired lambda value and the actual lambda value, can therefore be assigned to the second smallest quantity injection or the deviation of the characteristic curve in the smallest amount range from a linear characteristic curve. The one with this second injection Injected fuel quantity can therefore be determined very accurately and assigned to the activation duration for the second injection. Thus, it is possible with the method according to the invention to determine the activation duration at which the injector opens in the first place, and it is possible to create a characteristic curve for the injector in the smallest amount range which effects the second injection.

In a first development, it is proposed that the second injection takes place in a suction pipe of the internal combustion engine. The determination of a characteristic curve for an injector that injects into the intake manifold, in the normal operation of an internal combustion engine has been particularly difficult, since there is usually no direct relationship between the injected fuel quantity and the torque generated during combustion in a port injection. With the method according to the invention, the determination of a characteristic in the smallest amount range is now also possible for such an injector. Therefore, it is also proposed that the first injection takes place in a suction pipe of the internal combustion engine.

In a further development, it is proposed that the first injection be effected by means of a first injector and the second injection by means of a second injector. This is known from the market as a so-called "twin injection". In such a case, the internal combustion engine has at least two intake valves per combustion chamber, with each intake valve being assigned its own intake passage. In each inlet channel, an injector is arranged in each case, which injects the fuel in front of the inlet valve. With the method according to the invention, both injectors can be examined with regard to their minimum quantity injection quality and their control adapted for consumption and emission-optimized operation.

The quality of the adaptation of the control of these two injectors is further improved if a wall film dynamics in the combustion chamber is taken into account in the determination of the amount of fuel injected by the second injection at a certain actuation period. This takes into account the fact that when a relatively large amount of fuel passes through the one intake valve into the combustion chamber, whereas no or only a very small amount of fuel passes through the other intake valve into the combustion chamber, the wall films in the combustion chamber compared to an operating state, in which an equal amount of fuel passes through both intake valves into the combustion chamber, change with time, which leads to instationary effects that can falsify the detected lambda value.

It is also possible that the method according to the invention is carried out by the first injection takes place directly into the combustion chamber, whereas the second injection takes place in a suction pipe. The fuel quantity injected by the first injector by means of the first injection can be determined quite accurately on the basis of the mostly direct relationship between injected fuel quantity and torque generated during combustion, so that this region of the characteristic line of an injector can also be checked and, if necessary, adapted.

It is also proposed that in the adaptation mode, the entire amount of fuel to be injected for a desired operating point is injected by means of the first injection, and that the driving duration for the second injection is gradually increased from approximately zero. As soon as the minimum activation period for the second injection is reached, fuel additionally enters the combustion chamber, so that the mixture present in the combustion chamber is richer than the desired mixture. With this type of procedure, the minimum activation duration thus approaches "from below". This method makes it possible to evaluate relatively quickly the absolute smallest amount range and the minimum drive time, the emission behavior of the internal combustion engine is disturbed only comparatively short.

Alternatively, in the adaptation mode, it is possible to design the controls for the two injections so that the total amount of fuel to be injected for a desired operating point is divided between the two injections and the second injection drive duration is gradually reduced to approximately zero. For example, it is possible to divide the amount of fuel to be injected in half (50:50) between the two injections. To the same extent as the actuation duration for the second injection is lowered, the actuation duration for the first injection is increased, so that-assuming a predetermined injector curve, which is generally linear in this range-a total of the same amount of fuel is always injected. However, the closer the activation duration for the second injection is to the zero value, the more non-linear the relationship between activation duration and actually injected fuel quantity becomes. This leads to a poorer or richer mixture, which in turn can be detected via the lambda value or the difference between the actual lambda value and the desired lambda value. In this case, one thus approaches "from above" the minimum activation duration. In this way, a relatively complete course of the injector characteristic curve is obtained, and the above-mentioned wall-film dynamics play only a minor role here. In this context, it should be noted that the starting point for this type of Method, a half split the amount of fuel to be injected on the first injection and the second injection is conceivable. In order to shorten the process duration, however, as a starting point, for example, 75% of the fuel quantity to be injected can be injected by means of the first injection, 25% by the second injection.

In particular with intake manifold injection, it is advantageous to take the value 1 as the desired lambda value at which a comparatively favorable emission behavior is present.

The method according to the invention can be used in a large number of application scenarios. Mention has already been made of the "twin injection". It should also be noted, however, that the method according to the invention is not restricted to a specific type of fuel, but can be used, for example, in the case of gasoline, ethanol or a mixture of these fuels. The use is also useful, as also already mentioned, in internal combustion engines in which the fuel is injected both directly into the combustion chamber and into an intake pipe of the combustion chamber. However, the present method is also applicable to a so-called "bi-fuel system" with different injectors for different types of fuel. Applicable, the present method is also in internal combustion engines, which have only a single injector per combustion chamber, regardless of whether this is arranged in the intake manifold or injects the fuel directly into the combustion chamber.

Hereinafter, embodiments of the invention will be explained with reference to the accompanying drawings. In the drawing show:

1 a schematic representation of an internal combustion engine with intake manifold Twininjektor;

2 a flowchart of a method for operating the internal combustion engine of 1 and

3 a flowchart of an alternative method for operating the internal combustion engine of 1 ,

An internal combustion engine carries in 1 Overall, the reference number 10 , It includes four cylinders 12a to 12d , These are identical. Below are therefore only the elements of the cylinder 12a explained in detail.

The cylinder 12a includes a combustion chamber 14 , the intake side two intake valves 16a and 16b having. In each of these open a Saugrohrabschnitt 18a respectively. 18b , in each of which an injector 20a respectively. 20b is arranged, which the fuel in the Saugrohrabschnitt 18a respectively. 18b before the respective inlet valve 16a and 16b injects. The other components of a fuel system to which the injectors 20a and 20b are connected, such as fuel pump, fuel lines, tank, etc. are in 1 not shown.

From the combustion chamber 14 lead two exhaust valves 22a and 22b to an exhaust pipe 24 , In operation of the internal combustion engine 10 is a only schematically indicated crankshaft 26 set in rotation, whose position and rotational speed of a crankshaft sensor 28 is detected. In the exhaust pipe 24 is a lambda sensor 30 arranged, which allows the composition of the combustion chamber 14 existing fuel-air mixture and from this - in knowledge of the amount of air supplied - again to detect the amount of injected fuel. To the internal combustion engine 10 also includes a control and regulating device 32 , the signals, among others, from the crankshaft sensor 28 and from the lambda sensor 30 receives. To be controlled by the control and regulating device 32 including the injectors 20a and 20b , For operation of the internal combustion engine 10 has the control and regulating device 32 via a memory on which computer programs for carrying out various methods are stored. Variants of such methods will now be described with reference to FIGS 2 and 3 explains:

The procedure starts in a block 34 , In a branching block 36 is queried whether the characteristics, ie the relationship between the driving times and the injected fuel quantities, the injectors 20a and 20b be determined or adapted in the smallest amount range. Is the answer in the block 36 negative, the internal combustion engine 10 in the block 38 operated in a normal operating mode in which they each inject an equal amount of fuel. From there, the program ends in a block 40 ,

Is the result of the query in the block 36 however positive, will be in the block 42 set that the two injectors 20a and 20b no longer, as in normal operation, within each cycle inject an equal amount of fuel based on a same drive. Instead, after a common single-cylinder lambda adaptation, the mixture in all the combustion chambers 14 the cylinder 12a to 12d to a lambda value of 1, the second injector 20b shut off and the first injector 20a with twice the drive time compared to the normal operating mode 38 driven. Or, in other words, the total amount of fuel required to achieve a lambda value of 1 will now be from the first injector 20a by means of an injected by him first injection into the suction pipe section 18a from where he injected into the combustion chamber 14 arrives.

Now the previously switched off injector 20b in the block 44 gradually, so for example from working game to work cycle, with a rising duty cycle (the injectors are driven with pulse width modulation) driven. In 46 it checks if the lambda sensor 30 a deviation of the actual lambda value from the desired lambda value (here = 1) is detected. As long as this is not the case, it will be in front of the block 44 jumps back. Is the answer in the block 46 If the difference between the actual lambda value and the setpoint lambda value is detected, the corresponding activation time is displayed in the block 48 stored. This is the minimum actuation time, which is also referred to as the "actuation time" of the second injector 20b referred to as. This is the minimum drive required to move the injector 22b to open at all. The corresponding quantity of fuel injected in such an activation is the smallest possible amount of fuel which is produced by the injector during a driving process 20b can be injected. This is also in the block 48 stored.

In the block 50 Now continues the drive duration for the second injection by the second injector 20b increased from working game to working game. As a result, the difference between the actual lambda value and the desired lambda value continues to increase. From the difference can turn on the through the second injector 20b in the combustion chamber 14 closing amount of fuel to be closed. There are now continuously pairs of values for the control duration and the corresponding into the combustion chamber 14 through the injector 20b stored amount of fuel stored, and thereby in the block 52 established a characteristic that determines the relationship between the driving time and injected fuel quantity through the injector 20b produced at the second injections. After a certain control period, or when a sufficient linearity of the characteristic curve is detected, the method in block 40 completed.

This procedure is then used with the injector 20b repeatedly, in this case, the first injection is thus carried out by the injector 20b whereas the injector 20a performs the second injection. These two methods will then turn for the remaining cylinders 12b . 12c and 12d repeated. At the end are the characteristics for the smallest quantity injection for all injectors of the internal combustion engine 10 stored.

Not shown, but it is possible in the determination of the fuel injected by the second injection, the unsteady wall film dynamics in the combustion chamber 14 to take into account. Namely, if an injector is completely switched off at the beginning of the process and then passes through the other injector a correspondingly double amount of fuel into the combustion chamber, with time results in a correspondingly asymmetric distribution of the fuel film on the walls of the combustion chamber 14 , It evaporates fuel in one area, whereas in another area, additional fuel adheres. This can be taken into account by a correspondingly slow implementation of the present method or by corresponding factors.

An alternative to that in 2 shows shown method 3 : Again after a start in 54 is in 56 Checked if the injector 20b to be investigated with regard to its micro quantity injection behavior. Is the answer in the block 56 negative, the internal combustion engine 10 in the block 58 in a normal operating mode with a constant half split of the fuel quantity to be injected by the two injectors 20a and 20b operated.

Is the answer in the block 56 on the other hand, positive, starting from an initially half split of the fuel quantity to be injected by the two injectors 20a and 20b and a lambda value of 1 for all cylinders 12a to 12d the activation time for the injector 20b from working cycle to working game lowered, whereas the driving time for the injector 20a is increased to the same extent. In this way, at least in the area of the "normal quantity injection" of the characteristics of the two injectors 20a and 20b Furthermore, the same desired amount of fuel injected in total for each cycle. In this phase is in the block 62 the actual lambda value is monitored for a difference to the desired lambda value. As soon as such occurs, this is considered a deviation of the second injection by the second injector 20b injected small amount of fuel from the assumed amount of fuel. From the difference of the actual lambda value from the desired lambda value, the corresponding insufficient or too much injected fuel quantity is determined and the corresponding activation duration of the second injector 20b assigned. This all happens in the block 64 , There, therefore, successive value pairs are created, which have a characteristic curve of the injector 20b form. Once by means of the lambda sensor 30 is detected that the difference between the actual lambda value and the target lambda value changes abruptly, it is assumed that the driving time is now so short that the second injector 20b no longer opens at all, so a second injection does not take place at all. The associated drive time is also in the block as the minimum drive time 64 stored. In the block 66 it is checked whether the minimum activation duration has already been reached. If not, it will be in front of the block 60 jumps back. Otherwise the procedure ends in 59 ,

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010038625 A1 [0004]

Claims (12)

Method for operating an internal combustion engine ( 10 ), in which the fuel within a working cycle by means of a first injection and by means of a second injection into a combustion chamber ( 14 ), characterized in that in an adaptation mode at least at times the first injection injects a significantly larger amount of fuel than the second injection, and the drive duration for the second injection gradually increases from approximately zero or is gradually reduced to approximately zero, and is closed in the adaptation mode from a determined during a certain actuation time difference of a desired lambda value to an actual lambda value on the fuel injected at this drive time by means of the second injection amount of fuel. A method according to claim 1, characterized in that the second injection into a suction pipe ( 18b ) of the internal combustion engine ( 10 ) he follows. A method according to claim 2, characterized in that the first injection into a suction pipe ( 18a ) of the internal combustion engine ( 10 ) he follows. A method according to claim 3, characterized in that the first injection by means of a first injector ( 20a ) and the second injection by means of a second injector ( 20b ) respectively. A method according to claim 4, characterized in that in the determination of the injected at a certain actuation period by means of the second injection amount of fuel a wall film dynamics in the combustion chamber ( 14 ) is taken into account. A method according to claim 2, characterized in that the first injection directly into the combustion chamber ( 14 ) he follows. Method according to one of the preceding claims, characterized in that in the adaptation mode, the entire amount of fuel to be injected for a desired operating point is injected by means of the first injection, and that the driving time for the second injection is gradually increased from approximately zero. Method according to one of claims 1 to 6, characterized in that in the adaptation mode, the controls for the two injections are designed so that the total amount of fuel to be injected for a desired operating point is divided between the two injections, and the driving time for the second injection gradually is lowered to about zero. Method according to one of the preceding claims, characterized in that the desired lambda value = 1. Method according to one of the preceding claims, characterized in that by means of the first injection, a different fuel is injected than by means of the second injection. Computer program, characterized in that it is programmed to carry out a method according to one of claims 1 to 10. Control and / or regulating device ( 32 ) for an internal combustion engine ( 10 ), characterized in that it comprises a memory on which a computer program according to claim 11 is stored.

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