DE102015223283A1 - Method for transition compensation in an internal combustion engine - Google Patents

Abstract

The invention relates to a method for transition compensation in an internal combustion engine (100) with intake manifold injection and direct injection, wherein an increase in a load request to the internal combustion engine (100) a proportion of a direct injection into a combustion chamber of the internal combustion engine to be introduced in a total amount of fuel to be introduced into the combustion chamber fuel amount is increased.

Description

The present invention relates to a method for transition compensation in an internal combustion engine with intake manifold injection and direct injection and a computing unit and a computer program for its implementation.

State of the art

One possible method of fuel injection in gasoline engines is the intake manifold injection, which is increasingly being replaced by direct fuel injection. The latter method leads to significantly better fuel distribution in the combustion chambers and thus to better power output with lower fuel consumption.

Furthermore, there are also gasoline engines with a combination of intake manifold injection and direct injection, a so-called dual system. This is particularly advantageous in the light of ever stricter emission requirements or emission limit values, since intake manifold injection, for example, results in better emission values at medium load ranges than direct injection. In the full load range, however, the direct injection allows, for example, a reduction in the so-called knocking.

However, a deviation in the fuel-air mixture, for example due to incorrect fuel metering in a dynamic transition with a change in the load requirement, usually results in both a deterioration of the exhaust emission values and possibly noticeable performance losses for the driver.

From the DE 11 2011 105 782 T5 and the DE 11 2011 105 773 T5 For example, methods are known in which in a dual system, when a target amount can not be achieved with desired injection times, additional fuel amounts are deducted by intake manifold or direct injection. A quantity of fuel which has been removed by means of direct injection is intended to be injected during an intake phase, since the required fuel quantity can no longer be introduced in a compression phase.

From the DE 10 2008 041 689 A1 For example, a method is known in which, in a dual system, an adaptation of a model which describes an accumulation of fuel in a wall film in the intake manifold is undertaken. For this purpose, several times between intake manifold and direct injection back and forth and thereby exploited that only in the intake manifold injection fuel is stored in the wall film.

Disclosure of the invention

According to the invention, a method for transition compensation as well as a computing unit and a computer program for its implementation with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

Advantages of the invention

An inventive method is used for the transition compensation in an internal combustion engine with intake manifold injection and direct injection. In this case, when an increase in a load request to the internal combustion engine, a proportion of a fuel quantity to be introduced by means of direct injection into a combustion chamber of the internal combustion engine is increased at a total amount of fuel to be introduced into the combustion chamber.

In this case, a transition compensation is to be understood as meaning that for an injection system, a greater or lesser amount of fuel is determined and applied in comparison with the fuel quantity actually required by a current operating point. The reason for this is that, for example, an increase in the load requirement requires an increased demand for fuel and air to be supplied. A portion of the injected into a suction pipe of the internal combustion engine amount of fuel settles on the walls of the suction pipe and forms a wall film there. In the case of changed conditions in the intake manifold, for example, the fuel quantity necessary for the wall film becomes larger. In addition to the amount of fuel required to provide the desired torque, therefore, an additional amount of additional charge should be taken into account for the wall film.

Accurate determination of the required additional amount of fuel for the wall film is often not possible, so that a so-called. Overcompensation can take place, i. More fuel is injected into the intake manifold than necessary for the wall film. It is accepted that fuel is unnecessarily consumed by a too rich air-fuel mixture and emission levels are deteriorated because too lean a mixture would lead to an impairment of performance or smoothness of the internal combustion engine. Another reason for overcompensation may be, for example, different geometric dimensions and thus different wall films in the individual intake manifolds.

In the proposed method is now achieved by increasing the proportion of introduced by direct injection into the combustion chamber amount of fuel to be introduced into the total amount of fuel in the combustion chamber, that the Increasing the amount of fuel to be introduced into the intake manifold by means of intake manifold injection can be reduced. Since this also less fuel for the formation of the wall film is necessary, the overcompensation can be reduced. The result is lower fuel consumption and better emissions.

Preferably, an amount of fuel required to maintain and / or build up a wall film of fuel in an intake manifold of the internal combustion engine is covered by the intake manifold injection. In this way, the necessary wall film can continue to be obtained as usual, but by utilizing the dual system and the associated possibilities of fuel consumption and emission levels can be improved.

Advantageously, an additional amount of fuel required due to the increase in the load requirement is covered by the direct injection. As a result, there is no need to increase the increase in load caused by the intake manifold injection into the intake manifold due to the increase in load. This leads to a very small amount due to a wall film structure, which can be built up so slowly.

It is advantageous if the total amount of fuel to be introduced into the combustion chamber due to the increased load requirement is covered by the direct injection, and wherein by means of the intake manifold injection only one for receiving and / or building a wall film of fuel in an intake manifold of the internal combustion engine fuel quantity in the Suction tube is introduced. The additional amount of fuel required for the desired load request can thus be completely covered by the direct injection, which means that the deviations occurring between the inlet pipe injection and the amount of fuel introduced into the combustion chamber and reduced by the wall film formation are reduced.

Preferably, after the increase in the load request, the proportion of the fuel quantity to be introduced into the combustion chamber by means of direct injection is set to a desired value. The optimal split for the load demand achieved between the two types of intake manifold and direct injection injection can be restored after the transition.

Advantageously, the desired value is set after a predetermined period of time and / or a predetermined number of revolutions of the internal combustion engine after the increase in the load request. This time period can be chosen, for example, so that it can be assumed that a steady state in which, in particular, the wall film no longer changes. This allows a simple calculation when the desired setpoint is reset.

Alternatively, it is preferable that the target value is set after a wall film of fuel in a suction pipe of the internal combustion engine no longer changes after the load demand is increased. In this way, the desired setpoint can be reset as soon as possible.

Expediently, for this purpose, a point in time at which the wall film of fuel no longer changes is determined by means of a model and / or by means of a lambda value in an exhaust pipe of the internal combustion engine. For example, in the model, what amount of fuel may be taken into account for building the wall film under the respective conditions of the internal combustion engine, i. In particular load request before and after the increase, is necessary and when this will be achieved in the current injection conditions. About the lambda value can be seen when an introduced into the intake manifold excess fuel is no longer in the wall film structure, since then the air-fuel mixture is richer.

Advantageously, the setpoint is set abruptly or by continuous changes. Depending on the amount of the share to be changed and taking into account the best possible driving comfort, a faster or not noticeable transition to the desired value can be found.

An arithmetic unit according to the invention, e.g. a control unit, in particular an engine control unit, of a motor vehicle is, in particular programmatically, configured to perform a method according to the invention.

Also, the implementation of the method in the form of a computer program is advantageous because this causes very low costs, especially if an executive controller is still used for other tasks and therefore already exists. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical memories, such as e.g. Hard drives, flash memory, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below with reference to the drawings.

Brief description of the drawings

1a and 1b schematically show two internal combustion engines, which can be used for a method according to the invention.

2 schematically shows a cylinder of an internal combustion engine, which can be used for a method according to the invention.

3 shows a charge history, correction amounts and lambda values during an increase of the load request in a method not according to the invention.

4 schematically shows a sequence of a method according to the invention in a preferred embodiment.

Embodiment (s) of the invention

In 1a is schematic and simplifies an internal combustion engine 100 which can be used for a method according to the invention. By way of example, the internal combustion engine 100 four combustion chambers 103 on, with each combustion chamber a suction tube 106 is assigned, of which for clarity, only one is provided with a reference numeral. All suction tubes point here in a common initial section (in the figure above left).

Every suction pipe 106 indicates for each associated combustion chamber 103 a fuel injector 107 on, which is located in the suction pipe just before the combustion chamber. The fuel injectors 107 thus serve a port injection. Furthermore, each combustion chamber 103 a fuel injector 111 for a direct injection on.

In 1b is schematic and simplifies another internal combustion engine 200 which can be used for a method according to the invention. By way of example, the internal combustion engine 100 four combustion chambers 103 on, which in each case a suction tube 206 is assigned.

The suction pipes 206 have in a common initial section (in the figure above left) for all combustion chambers 103 a common fuel injector 207 on, which is arranged in the initial section, for example, shortly after a throttle, not shown here. The fuel injector 207 thus serves a port injection. Furthermore, each combustion chamber 103 a fuel injector 111 for a direct injection on.

At the suction pipes 206 is clearly visible that they differ in their geometric dimensions. Significant differences in length result, for example, in so-called V-engines, in which, for example, in one half of the combustion chambers, the intake manifold from the initial section must be significantly longer than in the other half of the combustion chambers, which are closer to the initial section. Furthermore, it should be noted that the intake manifolds may, depending on the exact geometry of the internal combustion engine, have further deviations from one another than can be seen only schematically here.

Both shown internal combustion engines 100 and 200 thus have a so-called dual system, ie via intake manifold injection and direct injection. The difference is only in the type of intake manifold injection. While, for example, the in 1a shown intake manifold injection allows a more accurate fuel metering for each combustion chamber, as can be used, for example, for higher quality internal combustion engines, which is in 1b shown intake manifold injection easier in their design and their control. The two internal combustion engines shown may in particular be gasoline engines.

In 2 is a cylinder 102 the internal combustion engine 100 schematic and simplified, but more detailed than in 1a shown. The cylinder 102 has a combustion chamber 103 by moving a piston 104 is increased or decreased. The present internal combustion engine may in particular be a gasoline engine.

The cylinder 102 has an inlet valve 105 on to air or a fuel-air mixture in the combustion chamber 103 involved. The air gets over the suction pipe 106 supplied as part of an air supply, at which the fuel injector 107 located. Sucked air is via the inlet valve 105 in the combustion chamber 103 of the cylinder 102 admitted. A throttle 112 in the air supply system is used to set the required air mass flow into the cylinder 102 ,

The internal combustion engine can be operated in the course of a port injection. With the help of the fuel injector 107 In the course of this intake manifold injection fuel is in the intake manifold 106 injected so that there forms an air-fuel mixture, via the inlet valve 105 in the combustion chamber 103 of the cylinder 102 is admitted.

The internal combustion engine can also be operated in the course of a direct injection. For this purpose, the fuel injector 111 on the cylinder 102 attached to fuel directly into the combustion chamber 103 inject. In this direct injection, the air required for combustion is Fuel mixture directly in the combustion chamber 103 of the cylinder 102 educated. The cylinder 102 is still with an ignition device 110 provided to start combustion in the combustion chamber 103 to create a spark.

Combustion gases are removed from the cylinder after combustion 102 over an exhaust pipe 108 pushed out. The ejection is dependent on the opening of an exhaust valve 109 also on the cylinder 102 is arranged. Inlet and outlet valves 105 . 109 are opened and closed to a four-stroke operation of the internal combustion engine 100 perform in a known manner. By means of a lambda probe 123 can be a lambda value of the exhaust gas in the exhaust pipe 108 be determined.

The internal combustion engine 100 can be operated with direct injection, with intake manifold injection or in mixed operation. This allows the choice of the optimal operating mode for operating the internal combustion engine 100 depending on the current operating point. So can the internal combustion engine 100 for example, in a port injection operation when operated at a low speed and a low load, and may be operated in a direct injection mode when operated at a high speed and a high load. However, over a wide operating range it makes sense to use the internal combustion engine 100 operate in a mixed operation in which the combustion chamber 103 supplied amount of fuel is supplied proportionately through intake manifold injection and direct injection.

Furthermore, one is as a control unit 115 trained computing unit for controlling the internal combustion engine 100 intended. The control unit 115 can the internal combustion engine 100 in the direct injection, the intake manifold injection or the mixed operation operate. Furthermore, the control unit 115 also values of the lambda probe 123 to capture.

In relation to 2 explained in more detail operation of the internal combustion engine 100 can also be applied to the internal combustion engine 200 according to 1b transferred, only with the difference that only one common fuel injector is provided for all combustion chambers or cylinders. In the case of intake manifold injection or in a mixed operation, therefore, the single fuel injector is actuated.

In 3 are a filling curve F, a correction amount K and a lambda λ during an increase in the load request in a method not according to the invention in each case over the time t shown.

For the filling curve F, curves of a nominal value F _soll and an associated actual value F _{ist are} shown. As can be seen on the course of the setpoint value F _soll , which is predetermined, for example, by a driver request, the amount of fuel to be introduced into the combustion chamber increases when the load request to the internal combustion engine is increased at time t ₁ . The actual value F _is the setpoint value F _soll with a certain delay, which is caused, for example, by the reaction times in the control of the fuel injectors. With a reduction of the load request at time t ₂ , the amount of fuel to be introduced into the combustion chamber decreases again.

Furthermore, with the reference numerals 301 . 302 and 303 Fuel amounts stored in the wall film, shown. It can be seen that, prior to the increase in the load request, two units of fuel (fuel quantity 301 ) are stored in the wall film. After the load requirement has increased, four units of fuel (amount of fuel) can now be exemplified in the wall film due to the changed conditions in the intake manifold and the overall increased amount of fuel 302 ) are stored in the wall film. After a reduction in the load request, only two units of fuel (fuel quantity 303 ) are stored in the wall film.

To build the wall film accordingly, two units of fuel (fuel quantity 311 ) necessary, which must be deducted in addition to an already increased due to the increased load requirement amount of fuel by means of the intake manifold injection and therefore can be taken into account in a correction amount.

In addition, two further units of fuel (fuel quantity 321 ) is taken into account in the correction quantity. These additional units of fuel are overcompensating for the present case, since they are not necessary for the construction of the wall film. One reason why these additional units are discontinued fuel can be, for example, that an accurate determination of the required excess amount of fuel for the wall film is not possible or that different geometric dimensions of the individual intake manifolds use the correction value of that intake manifold, in which he is highest, surrendered. The aim here is to avoid a fuel-vapor-poor, ie lean mixture as far as possible, since this would lead to engine jerking.

In the course of the correction amount K, from the time t _{1 of} the increase of the load request, the two units of fuel quantity 311 as well as the additional two units of fuel quantity 321 to recognize, which are discontinued by means of the intake manifold injection. Because the fuel amount 321 only as Overcompensation is present and is not needed for the construction of the wall film or for combustion in the combustion chamber, the amount of fuel 321 an unused and thus unnecessarily offset amount of fuel.

In the course of the lambda value λ it can be seen that from the time t ₁ to a short peak 330 due to an update error, the lambda value in the direction of less than 1, ie in the direction of rich air-fuel mixture in the combustion chamber goes. This shows that the fuel quantity 321 not necessary for the combustion. The update error occurs when the filling of the combustion chamber changes between the calculation of the injection and the time of the actual injection. This can be counteracted, for example, by increasing the amount of correction.

In order to degrade the wall film from time t ₂ , the two units of fuel (fuel quantity 312 ), which now no longer remain stored in the wall film, in addition to an already reduced due to the reduced load requirement amount of fuel that must be discontinued by the intake manifold injection, be taken into account in a correction amount. The fuel to be degraded from the wall film thus leads to a negative correction amount, since less fuel must be introduced into the intake manifold by means of the intake manifold injection, since the fuel to be degraded from the wall film also enters the combustion chamber.

To account for these two units of fuel from the wall film (fuel quantity 312 ) will now be exemplified a negative correction amount of one and a half units of fuel (fuel quantity 322 ) used. Half the unit fuel (fuel quantity 323 ), which could actually also be taken into account in the correction quantity, is not taken into account here in the context of a so-called undercompensation. One reason why half the unit of fuel is not taken into account may be, for example, that with a different combustion chamber and the associated intake manifold, a smaller amount of fuel is available from the wall film degradation.

Since no distinction is made between the individual combustion chambers or intake manifolds, for each combustion chamber that correction amount can be used which results in that combustion chamber in which the smallest amount of fuel from the wall film degradation is available. It is accepted that fuel is unnecessarily consumed by a too rich air-fuel mixture and emission levels are deteriorated because too lean a mixture would lead to an impairment of performance or smoothness of the internal combustion engine.

In the course of the correction amount K from the time t _{2 of} the reduction of the load request, the one and a half units of fuel quantity 322 to recognize, which are deposited by means of the intake manifold injection less. Furthermore, half the unit of fuel quantity 323 in the context of undercompensation. Because the fuel amount 323 is present as undercompensation from the degradation of the wall film, but is not needed for combustion in the combustion chamber, the amount of fuel 323 an unused amount of fuel.

In the course of the lambda value λ is to see that from the time t _2, the lambda value in the direction of less than 1, ie in the direction of rich air-fuel mixture in the combustion chamber goes. This shows that the fuel quantity 323 not necessary for the combustion.

In 4 schematically a flow of a method according to the invention is shown in a preferred embodiment. First of all, fuel quantities K _S and K _{D can be used} for intake manifold or direct injection, which correspond to a desired distribution of the total fuel quantity, ie K _S + K _D, to the two types of injection.

Now, an increase L of a load request to the internal combustion engine can be required. It can then be determined due to the increase L more amount K of fuel, which is required due to the increased torque requirement determined.

The additional quantity K can now be taken into account, for example, in the fuel quantity K _D for the direct injection, that is to say K ' _D = K + K _D , where K' _{D designates} the fuel quantity of the direct injection to be finally disposed.

The via the suction tube, i. via the intake manifold injection itself and the wall film, introduced into the combustion chamber fuel amount is kept constant despite load changes. Ie. Excessive or reduced quantities from the wall film are corrected by correcting the intake manifold injection quantity.

It is also conceivable that the amount of fuel K ' _S deposited by means of the intake manifold injection is reduced and specified up to the amount of fuel required for wall film support and accordingly the amount of fuel K' _D deposited by the direct injection is K _S - K ' _{s in} addition to the additional quantity K K _w comprises, ie K ' _D = K + K _D + K _S - K' _s - K _w . K _w is the proportion of fuel that is released from the wall film storage during load changes, thus contributing to the total amount of fuel entering the combustion chamber.

It is also conceivable that only part of the additional quantity K is covered by the direct injection and the other part of the additional quantity K is still covered by the intake manifold injection.

In all of the examples listed, however, the proportion of the amount of fuel to be introduced into the combustion chamber by means of direct injection is increased at the total amount of fuel to be introduced into the combustion chamber. In this way, the overcompensation can be reduced or even avoided.

After the wall film has been built up, it is possible, for example after a predetermined period of time or after it has been established that the wall film has been built up, to set a desired value A for a proportion of the amount of fuel to be introduced into the combustion chamber by means of direct injection. Accordingly, a setpoint value A '= 1 - A results as a proportion for the intake manifold injection.

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 112011105782 T5 [0005]
• DE 112011105773 T5 [0005]
• DE 102008041689 A1 [0006]

Claims (12)

Method for transition compensation in an internal combustion engine ( 100 . 200 ) with intake manifold injection and direct injection, wherein at an increase (L) of a load request to the internal combustion engine ( 100 . 200 ) a proportion of a direct injection into a combustion chamber of the internal combustion engine to be introduced amount of fuel (K _D ) is increased at a total amount to be introduced into the combustion chamber fuel quantity. Method according to claim 1, wherein one for obtaining and / or constructing a wall film of fuel in a suction pipe ( 106 . 206 ) of the internal combustion engine ( 100 . 200 ) required amount of fuel is covered by the intake manifold injection. The method of claim 1 or 2, wherein a due to the increase (L) of the load request required amount (K) of fuel is covered by the direct injection. Method according to one of the preceding claims, wherein the total due to the increased load requirement in the combustion chamber ( 103 ) is covered by the direct injection, and wherein by means of the intake manifold injection only one for a maintenance and / or construction of a wall film of fuel in a suction pipe ( 103 ) of the internal combustion engine ( 100 . 200 ) required amount of fuel in the intake manifold ( 106 . 206 ) is introduced. Method according to one of the preceding claims, wherein after the increase (L) of the load request, the proportion of the amount of fuel to be introduced into the combustion chamber by means of direct injection is set to a desired value (A). A method according to claim 5, wherein the target value (A) is set after a predetermined period of time and / or a predetermined number of revolutions of the internal combustion engine after the increase (L) of the load request. The method of claim 5, wherein the set point (A) is adjusted after a wall film of fuel in a suction pipe ( 106 . 206 ) of the internal combustion engine ( 100 . 200 ) after the increase (L) of the load request no longer changes. A method according to claim 7, wherein a time at which the wall film of fuel no longer changes, by means of a model and / or by means of a lambda value in an exhaust pipe ( 108 ) of the internal combustion engine ( 100 . 200 ) is determined. Method according to one of claims 6 to 8, wherein the desired value (A) is set abruptly or by continuous changes. Arithmetic unit ( 115 ), which is adapted to perform a method according to any one of the preceding claims. Computer program comprising a computing unit ( 115 ) to perform a method according to any one of claims 1 to 9, when it on the computing unit ( 115 ) is performed. Machine-readable storage medium with a computer program stored thereon according to claim 11.

Images