DE102015217730A1 - Method for operating an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine (100) with intake manifold injection and direct injection, wherein an amount of fuel is detected which evaporates in a suction pipe (106) leading to a combustion chamber (103) of the internal combustion engine (100, 200) an inlet valve (105) of the combustion chamber (103) is closed, and wherein at least one operating parameter for a filling of the combustion chamber (103) is determined taking into account the determined amount of fuel.

Description

The present invention relates to a method for operating 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.

From the US 2012/024069 A1 For example, a method is known to associate a detected deviation in the ratio of fuel to air in the individual combustion chambers with each other of the type of injection in an internal combustion engine with dual system.

In order to improve a response of a turbocharger, within the scope of a so-called "scavenging" an intake and an exhaust valve of a combustion chamber can be opened simultaneously in order to obtain higher flow values in the exhaust pipe and thus in the turbocharger. In order to avoid that fuel enters the exhaust pipe, for example, in a dual system, the proportion of intake manifold injection can be reduced.

Disclosure of the invention

According to the invention, a method for operating an internal combustion engine as well as a computing unit and a computer program for carrying it out 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 to operate an internal combustion engine with intake manifold injection and direct injection. In this case, an amount of fuel is determined which evaporates in an intake manifold leading to a combustion chamber of the internal combustion engine, while an intake valve of the combustion chamber is closed, and at least one operating parameter for a filling of the combustion chamber is determined taking into account the determined fuel quantity and expediently so used or given. That is, the determined operating parameter is used as a setpoint for the operation of the internal combustion engine. This allows one or more predetermined operating parameters for the filling of the combustion chamber to be corrected, for example, on the basis of a specific load request, taking into account the determined fuel quantity. Thus, for example, a predetermined amount of fuel to be introduced can be reduced taking into account already evaporated fuel in the intake manifold.

In a change in the load request to the internal combustion engine, for example. When accelerating or decelerating a motor vehicle, a change in the amount of fuel to be added via the intake manifold injection is usually necessary. Now, in the context of a so-called transition compensation, it is possible to take into account that, due to the changed fuel quantity, a wall film of fuel must build up on the inside of the intake manifold and correct the fuel quantity accordingly. However, this does not take into account that fuel, for example. From the wall film, vaporized in the intake manifold with the injection valve closed and flows into the combustion chamber with opening of the injector.

If the inlet valve and the outlet valve are open at the same time, as can be done, for example, in the context of the so-called "scavenging" to improve the response of a turbocharger, this additional, evaporated fuel quantity can be flushed through the combustion chamber and thus into the exhaust tract , This is also referred to as so-called over-rinsing and may, for example, result in overheating of the catalyst and / or poor emission levels.

However, if, as proposed, the fuel quantity vaporized in the intake manifold when the intake valve is closed is determined and taken into account when specifying at least one operating parameter for filling the combustion chamber, the overflow of fuel can be avoided. In this way, on the one hand, for example, components such as the catalyst can be protected and, on the other hand, a low-emission and low-fuel operation of the internal combustion engine can be made possible. In addition, it is particularly advantageous that the best possible "scavenging", ie an improved response of the turbocharger by increasing the Exhaust gas flow, when air can flow directly from the intake pipe into the exhaust pipe, is possible.

It is advantageous if the at least one operating parameter comprises at least one actuation parameter of the inlet valve and / or the outlet valve of the combustion chamber. In particular, the at least one activation parameter of the intake valve and / or of the exhaust valve may each comprise an adjustment of a valve lift and / or an opening time and / or a closing time. This is possible in particular when using an internal combustion engine with a variable valve train, by means of which the opening and closing times and the valve strokes of the valves can be set individually. As a variable valve train here come, for example, electric or electro-mechanical valve trains or hydraulic valve trains in question, which are known per se. In this way, the valves can now be selectively controlled so that no fuel enters the exhaust pipe. For example, the exhaust valve may be closed earlier while the valve lift is increased. Thus, although a high exhaust gas flow to drive the turbocharger can be achieved, however, the exhaust valve can also be closed early, so that fuel can not get into the exhaust pipe.

The at least one operating parameter preferably comprises an amount of fuel to be introduced into the intake manifold by means of intake manifold injection, an injection period and / or an injection start. Thus, for example, the vaporized fuel quantity can be credited to the fuel quantity to be metered on the basis of the current load request. Likewise, for example, the start of injection can be adjusted to take into account the additionally present, evaporated fuel quantity. In this way, a particularly simple avoidance of over-rinsing can take place.

In the case of the amount of fuel to be introduced into the intake manifold by means of intake manifold injection, it is advantageous to consider a build-up or dismantling of a wall film of fuel in the intake manifold. For an even more accurate adjustment of the amount of fuel to be metered is possible. In addition, it can also be prevented in this way that still unburned fuel is flushed through the combustion chamber.

Preferably, if it is determined during the determination of the at least one operating parameter that a required fuel quantity to be introduced into the combustion chamber by means of intake manifold injection can not be completely introduced into the combustion chamber by means of intake manifold injection, the at least one operating parameter comprises an amount of fuel to be introduced into the combustion chamber by means of direct injection does not cover the portion which can be introduced into the combustion chamber by means of intake manifold injection. If, for example, due to a large change in the load requirement, a very large amount of fuel quantity to be metered by intake manifold injection would be required, but due to a long valve opening duration, this would result in valve over-flushing of fuel, so part of the fuel quantity to be metered by intake manifold injection may be be introduced by means of intake manifold injection by direct injection into the combustion chamber. It is also conceivable that not only a part but the entire amount of fuel to be metered by means of intake manifold injection is transferred to the direct injection. This is due to the flexibility in a dual system very easy, so that on the one hand, the necessary amount of fuel is introduced into the combustion chamber and on the other hand, a rinse is avoided.

Advantageously, the determination of the amount of fuel that evaporates in the intake manifold, a formation of a vaporization model for an evaporation of fuel in the intake manifold. This is a particularly easy way to determine the amount of evaporated fuel. Such a model can be stored, for example, for the relevant internal combustion engine in an exporting control unit.

Expediently, the evaporation model comprises at least one of the following variables as an input variable: a wall film amount of fuel in the intake manifold, a temperature in the intake manifold, a temperature of intake air, a temperature of the internal combustion engine, a temperature of an oil in the internal combustion engine (the temperatures can be particularly in transient temperature cycling such For example, a warm-up and / or a start of the internal combustion engine are taken into account), a boost pressure, an intake manifold pressure, a flow velocity of air and / or a fuel-air mixture in the intake manifold (the flow rate can, for example. By a signal of an air mass meter, from a Speed and / or based on an air mass flow), a composition of an air and / or a fuel-air mixture in the intake manifold, a humidity of a sucked air in the intake manifold, an air pressure outside of the intake manifold, an exhaust gas recirculation rate (eg. internal or external) and a fuel quality (eg. on an ethanol content and / or a distinction between winter and summer fuel). By using these parameters, it is possible to use the model to determine the quantity of evaporated fuel very accurately, thus avoiding over-flushing.

It is advantageous if, furthermore, an exhaust gas recirculation rate, in particular an internal exhaust gas recirculation rate, taking into account the determined Fuel quantity regulated and / or adjusted. By opening the exhaust valve during an open intake valve and thus during an intake of air or fuel-air mixture in this case also exhaust gas can be sucked into the combustion chamber. While in internal combustion engines with pure intake manifold injection or pure direct injection, a desired exhaust gas recirculation rate can be set very easily, is problematic in a dual system especially in mixed operation that possibly fuel that is introduced in the course of the intake manifold injection into the intake manifold, not completely enters the combustion chamber and then, for example, evaporated in the intake manifold. In a subsequent cycle of the intake of air and exhaust gas, the fuel remaining in the intake manifold and vaporized can then be pushed through the combustion chamber into the exhaust pipe. This can lead to bad emission levels. By taking into account the evaporated fuel, however, better emission levels can now be achieved.

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 drawing.

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 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 and a suction tube 106 on which to each of the combustion chambers 103 connected.

The suction tube 106 points for each combustion chamber 103 a fuel injector 107 on, which is located in the respective section of 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 and a suction tube 206 on which to each of the combustion chambers 103 connected.

The suction tube 206 points for all combustion chambers 103 a common fuel injector 207 on, for example, is arranged in the intake manifold shortly after a throttle valve, not shown here. The first fuel injector 207 thus serves a port injection. Furthermore, each combustion chamber 103 a fuel injector 111 for a direct injection on.

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 a fuel metering allowed individually 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 to an air supply system, 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-fuel mixture required for combustion is 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.

For the inlet valve 105 is an intake valve drive 105 ' provided and for the exhaust valve 109 is an exhaust valve drive 109 ' intended. These valve trains provide a variable valvetrain, allowing both the opening and closing times and the valve strokes of the valves to be individually adjusted. The valve trains can be formed, for example, electro-mechanically or hydraulically. The adjustment of both the times and the valve lift can be done, for example, continuously or in stages. It is understood that the valves of the other combustion chambers or cylinders, for example, in the 1 and 2 are shown, also have such valve trains.

Furthermore, an intake manifold pressure sensor 120 and a combustion chamber pressure sensor 125 provided, bringing a pressure in the intake manifold 106 or a pressure in the combustion chamber 103 can be determined.

There is also a turbocharger 130 provided in the out of the exhaust pipe 108 branched exhaust gas is supplied to drive there, for example, a turbine. In the turbocharger 130 In turn, another turbine is driven via this turbine, which compresses the intake fresh air and, for example, via a charge air cooler 131 to the intake manifold 107 leads. In this way, an increased pressure in the intake manifold can be provided.

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 the valve trains 105 ' and 109 ' and values from the intake manifold pressure sensor 120 and the combustion chamber pressure sensor 125 to capture. Likewise, the control unit 115 For example, the turbocharger 120 drive.

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 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 in the intake manifold is permanently activated.

In 3 schematically a flow of a method according to the invention is shown in a preferred embodiment. First, different quantities can be determined, which are used as input variables for calculating the evaporated fuel quantity by means of an evaporation model.

By way of example, an amount of fuel M _W present in a wall film in the intake manifold is shown here. This fuel quantity M _W can be determined, for example, by means of a model for forming a wall film, if appropriate also taking into account further variables such as pressure and temperature in the intake manifold.

Furthermore, a temperature T _{S of} the intake manifold and a temperature T _{B are shown} in the combustion chamber of the internal combustion engine. These temperatures can be determined, for example, by means of suitable temperature sensors or by means of a model.

Furthermore, an intake manifold pressure P _S in the intake manifold and a boost pressure P _{B are} shown in the combustion chamber. These pressures can, for example. By means of in 2 shown sensors, intake manifold pressure sensor 120 and boost pressure or combustion chamber pressure sensor 125 , be determined. Again, if necessary, a suitable model can be used.

The named quantities or the associated values are now fed to an evaporation model V as input variables. It is understood that even more or other of the above variables can be used as input variables for the evaporation model. The number or type of variables used may, for example, depend on the desired accuracy and / or the available sizes.

From the evaporation model V now a fuel quantity M _{V is} determined, which evaporates in the intake manifold, while the inlet valve is closed. The vaporized amount of fuel corresponds to the injected amount of fuel less the amount of fuel stored in the wall film. The mass of the fuel stored in the wall film is proportional to the intake manifold pressure or the amount of air. Furthermore, there is a strong temperature dependence, which means that at low temperature more fuel is stored in the wall film, as well as a dependence on the fuel used. Further corrections are dependent on the valve timing of the intake and exhaust valves, and the speed of the internal combustion engine. An empirical wall film model for a dynamic correction is usually present in the control unit. The necessary relationships can then be mapped, for example, in the form of characteristic curves and / or characteristic diagrams and / or by means of numerical models.

Taking into account the evaporated fuel quantity M, for example, a total amount of fuel M _{K to} be metered in by means of intake manifold injection can be determined as the operating parameter (desired value). It is also conceivable that for this purpose a required amount of fuel to be metered is corrected on the basis of the evaporated fuel quantity. In addition, suitable values for a valve lift h _E , an opening time t _{o, E} and a closing time t _{S, E of} the intake valve and a valve lift h _A , an opening time t _{o, A} and a closing time t _{S, A of} the exhaust valve as operating parameters (setpoint ) be determined. Thus, for example, by means of the opening time t _{O, E} and the closing time t _{S, E,} the opening duration of the intake valve can be adjusted or adjusted. The same applies to the opening duration of the exhaust valve.

It is understood that not necessarily all the valve sizes mentioned for the valves compared to a conventional procedure for filling, in which the vaporized fuel amount is not taken into account, be changed or must be.

Furthermore, if, for example, it is detected that the determined fuel quantity M _K , which would be metered in by means of intake manifold injection, can not be achieved with the mentioned variables of the valve control, without overflowing fuel, the fuel quantity M _{K is} reduced and instead a quantity of fuel to be metered in by means of direct injection accordingly be increased to avoid over-rinsing.

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

• US 2012/024069 A1 [0004]

Claims (12)

Method for operating an internal combustion engine ( 100 . 200 ) with intake manifold injection and direct injection, whereby an amount of fuel (M _V ) is determined in a suction pipe ( 106 . 206 ) leading to a combustion chamber ( 103 ) of the internal combustion engine ( 100 . 200 ) evaporates while an inlet valve ( 105 ) of the combustion chamber ( 103 ) is closed, and wherein at least one operating parameter for a filling of the combustion chamber ( 103 ) is determined taking into account the determined amount of fuel (M _V ). The method according to claim 1, wherein the at least one operating parameter comprises at least one activation parameter of the inlet valve. 105 ) and / or an exhaust valve ( 109 ) of the combustion chamber ( 103 ). Method according to claim 2, wherein the at least one activation parameter of the inlet valve ( 105 ) and / or the exhaust valve ( 109 ) each comprise an adjustment of a valve lift (h _E , h _A ) and / or an opening time (t _{O, E} , t _{O, A} ) and / or a closing time (t _{S, E} , t _{S, A} ). Method according to one of the preceding claims, wherein the at least one operating parameter a by means of intake manifold injection into the intake manifold ( 106 . 206 ) amount of fuel to be introduced (M _K ), an injection period and / or an injection start comprises. Method according to claim 4, wherein in the intake manifold injection into the intake manifold ( 106 . 206 ) amount of fuel to be introduced (M _K ) a build or dismantling of a wall film of fuel in the intake manifold ( 106 . 206 ) is taken into account. Method according to one of the preceding claims, wherein, when determining the at least one operating parameter, it is determined that a required injection into the combustion chamber by means of intake manifold injection ( 103 ) to be introduced amount of fuel is not completely by means of intake manifold injection into the combustion chamber ( 103 ) can be introduced, the at least one operating parameters by means of a direct injection into the combustion chamber ( 103 ) amount of fuel to be introduced, at least not by means of intake manifold injection into the combustion chamber ( 103 ) covers the recoverable amount. Method according to one of the preceding claims, wherein the determination of the amount of fuel (M _V ) in the intake manifold ( 106 . 206 ) evaporates, a formation of an evaporation model (V) for evaporation of fuel in the intake manifold ( 106 . 206 ). The method of claim 7, wherein the evaporation model (V) comprises at least one of the following quantities as an input quantity: a wall film amount (M _W ) of fuel in the intake manifold, a temperature (T _S ) in the intake manifold, a temperature of intake air, a temperature (T _B ) of the internal combustion engine, a temperature of an oil in the internal combustion engine, a boost pressure (P _B ), an intake manifold pressure (P _S ), a flow rate of an air and / or a fuel-air mixture in the intake manifold, a composition of an air and / or a Fuel-air mixture in the intake manifold, a humidity of air sucked into the intake manifold, an air pressure outside the intake manifold, an exhaust gas recirculation rate and a fuel quality. Method according to one of the preceding claims, wherein furthermore an exhaust gas recirculation rate is controlled and / or adjusted taking into account the determined amount of fuel (M _V ). 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.

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