DE102013221326A1 - Method for controlling a boost pressure of an internal combustion engine - Google Patents

Abstract

The present invention relates to a method for regulating a boost pressure (12) of an internal combustion engine (1), wherein the internal combustion engine (1) burns a mixture of air and fuel and comprises an exhaust gas turbocharger (2), wherein the exhaust gas turbocharger (2) comprises a turbine (3 ), which is driven by an exhaust gas mass flow (4) of the internal combustion engine (1), characterized in that the regulation of the boost pressure (12) in a first region (16), in which the rotational speed of the internal combustion engine (1) a first rotational speed ( 13), but remains below a second speed (14), by increasing the proportion of air in the mixture and in a second area (17) in which the speed of the internal combustion engine exceeds the second speed (14) by an additional one Opening a bypass (5) of the turbine (3) of the exhaust gas turbocharger (2) is achieved.

Description

The present invention relates to a method for controlling a boost pressure of an internal combustion engine. Furthermore, the invention relates to a control device on which such a method is executable.

In internal combustion engines with turbocharger, as they are often used in motor vehicles, a boost pressure control is needed. Since the exhaust gas turbocharger generates the boost pressure as a function of the exhaust gas mass flow, the boost pressure increases with increasing exhaust gas mass flow. To prevent the boost pressure exceeding a permissible limit, this is limited by the boost pressure control.

The boost pressure control is usually carried out in such a way that a bypass valve of the turbocharger is opened. Thus, a portion of the exhaust gas mass flow is conducted past the exhaust gas turbocharger, so that the volume flow to drive the exhaust gas turbocharger decreases. This method is for example from the DE 103 10 221 A1 known. Another approach is from the US 4,873,961 A known. This document discloses that cylinder pressure loads resulting from boost pressure can be reduced such that the mixture of the internal combustion engine to be burned is emaciated. However, the prior art has not yet been able to provide a method of boost pressure control that efficiently operates an internal combustion engine.

It is an object of the invention to provide a method for controlling a boost pressure of an internal combustion engine that enables safe and low-consumption operation of the internal combustion engine with ease of execution.

The object is achieved by a method for regulating a boost pressure of an internal combustion engine with the features of the independent claim. The internal combustion engine burns a mixture of air and fuel and includes an exhaust gas turbocharger, which supplies the air to the internal combustion engine. By the exhaust gas turbocharger, the air of the mixture is advantageously compressible, so that the air is supplied to the engine under a charge pressure generated by the exhaust gas turbocharger. For this purpose, the exhaust gas turbocharger comprises a turbine which is driven by an exhaust gas mass flow of the internal combustion engine. Furthermore, the exhaust gas turbocharger preferably comprises a compressor, with which the boost pressure can be generated. According to the invention, at least two speed ranges are present in which the regulation of the boost pressure according to the invention takes place differently. Thus, a first region is present in which the rotational speed of the internal combustion engine exceeds a first rotational speed but remains below a second rotational speed. In the first region, the boost pressure is preferably not limited, but still preferably a load on the engine is reduced. This is inventively achieved in that the proportion of air in the mixture is increased. Likewise, a second region is present in which the rotational speed of the internal combustion engine exceeds the second rotational speed. In this area, a charge pressure limitation takes place according to the invention, wherein this is preferably done in addition to the regulation from the first area. According to the invention, a bypass of the turbine of the exhaust gas turbocharger is opened for this purpose.

The second region is preferably limited by a third rotational speed. Thus, there is a third range in which the rotational speed of the internal combustion engine exceeds the third rotational speed. In this area preferably takes place a regulation of the boost pressure such that only the bypass is opened. Thus, especially the additional control from the first area, i. H. increasing the proportion of the air of the mixture, as opposed to the second area, does not take place in the third area.

Particularly preferably, the proportion of air in the mixture is reduced in the third range. In this way, the mixture for the speed within the third range can be optimized, so that the internal combustion engine is very efficient operable.

Likewise, it is particularly preferred that the boost pressure in the third area is lowered. Since rotational speeds are present in the third range through which the load limits of the internal combustion engine can be exceeded, the charge pressure in this region is preferably lowered so as not to overload the internal combustion engine. Thus, the control according to the invention according to this embodiment ensures safe and reliable operation of the internal combustion engine.

Finally, it is particularly preferably provided that in the third region, a pressure in an exhaust gas pipe leading to the exhaust gas mass flow does not exceed a predetermined maximum value between the internal combustion engine and the turbine. Since high speeds of the internal combustion engine prevail in the third region, a high exhaust gas mass flow is also present. Since too high exhaust gas mass flow can damage the exhaust gas turbocharger due to excessive turbocharger speed, it is preferably provided that the pressure in the exhaust gas line is limited by the inventive method in an advantageous embodiment. So a safe and reliable operation of the exhaust gas turbocharger is possible.

In an advantageous embodiment of the invention, the control is carried out such that in the second region, a predetermined maximum proportion of air in the mixture is not exceeded. Thus, in particular a reliable operation of the internal combustion engine is ensured. Alternatively or additionally, it is provided that in the second region, a predetermined maximum rotational speed of the turbine is not exceeded. In this way, an overload of the turbine is advantageously prevented.

Preferably, the control is performed such that in the first region, an increase of the boost pressure takes place up to a predetermined maximum value. Alternatively or additionally, it is provided that the control in the second area comprises holding the boost pressure at the maximum value. Thus, the performance of the internal combustion engine in the first region and / or in the second region is not limited, yet it is ensured that the internal combustion engine is operated within the load limits.

Advantageously, the control of the boost pressure is performed exclusively when at a current speed, a maximum boost pressure can be achieved. The boost pressure is therefore not unnecessarily limited, so that the performance of the internal combustion engine is not unnecessarily reduced by the control according to the invention.

The determination that a maximum charge pressure is achievable is particularly preferably carried out on the basis of a characteristic map or on the basis of a characteristic curve. The map or the characteristic is determined individually, in particular for the internal combustion engine.

In particular, the method according to the invention is carried out in a vehicle with an internal combustion engine. Here, the control of the boost pressure is preferably carried out exclusively at a maximum possible accelerator opening. At maximum accelerator opening, the combustion engine is required to achieve the highest possible output. Therefore, it is advantageously ensured by the control according to the invention that the internal combustion engine on the one hand is not overloaded, on the other hand, is operated as energy efficient as possible.

The internal combustion engine is preferably a gasoline engine. For such engines, the prior art is only a few efficient exhaust gas turbocharger for selection. This is particularly problematic that the prior art requires a small exhaust gas turbocharger, which generates a high boost pressure even at a low exhaust gas mass flow. In this way, the occurrence of a "turbo lag", i. H. A response of the exhaust gas turbocharger only at higher speeds can be avoided. However, a restriction of the rotational speed of the exhaust-gas turbocharger is carried out by such small exhaust gas turbochargers at high engine speeds and thus at a high exhaust-gas mass flow, so that an inefficient limitation of the boost pressure arises. Thus, the inventive method advantageously represents a solution for gasoline engines, which are thus efficient and reliable operable.

Furthermore, the invention relates to a control device that can be used in particular in a vehicle. The control unit is preferably set up such that it carries out the method described above.

The invention will now be described by way of example with reference to the accompanying drawings. In the drawings is

1 a schematic illustration of an internal combustion engine with turbocharger wherein the boost pressure of the internal combustion engine with the method according to an embodiment of the invention is adjustable, and

2 a schematic view of a boost pressure curve, when the method is applied according to the embodiment.

1 shows an internal combustion engine 1 with an exhaust gas turbocharger 2 , The turbocharger 2 includes a turbine 3 that of an exhaust mass flow 4 is driven and a compressor 8th which is powered by the turbine. The exhaust gas mass flow 4 is due to the operation of the internal combustion engine 1 generated. About a bypass 5 can the exhaust gas mass flow 4 the turbine 3 bypass and go directly to an exhaust system 6 be directed. Thus, a speed of the turbine 3 and thus the speed of the exhaust gas turbocharger 2 over the bypass 5 adjustable.

Furthermore, the internal combustion engine comprises 1 an air supply 7 , The air supply 7 gets air from the compressor 8th the exhaust gas turbocharger 2 supplied under a boost pressure. The compressor 8th sucks air through an intake system 10 at. Advantageously, that of the compressor 8th compressed air before transfer to the air supply 7 through a charge air cooler 9 cooled.

Thus shows 1 an internal combustion engine 1 , the exhaust gas turbocharger powered by exhaust gases 2 used to increase performance. The internal combustion engine 1 is advantageously a drive motor of a vehicle and is preferably controlled by an accelerator pedal. The turbocharger 2 is preferably designed such that this at low speeds of the internal combustion engine 1 already one high boost pressure generated. However, this has the disadvantage that the increasing with increasing speed boost pressure at high speeds existing load limits of the engine 1 exceeds. Therefore, a control unit 11 according to an embodiment of the invention, which executes a method for controlling the boost pressure according to an embodiment of the invention. This is the control unit 11 with the bypass 5 , the internal combustion engine 1 and the air supply 7 connected to one-way or two-sided transmission of signals.

2 shows a schematic course of a boost pressure of the internal combustion engine 1 when the method according to the invention is used according to an embodiment. By doing 2 underlying coordinate system, the abscissa denotes a speed of the internal combustion engine 1 and the ordinate the boost pressure. The procedure is only carried out when a maximum opening of the accelerator pedal is reached. At low and medium accelerator opening, the engine can 1 and the bypass 5 be driven in particular with methods of the prior art.

At the maximum opening of the accelerator pedal is based on the speed of the internal combustion engine 1 and a current boost pressure 12 checks whether a maximum value predefined in a map or a characteristic curve 19 the boost pressure 12 is reachable.

When determining the boost pressure 12 is preferably the ambient pressure taken into account, which is measured in a conventional engine control of a drive motor of a vehicle. If the boost pressure is within a maximum range, then the following control takes place, depending on the rotational speed of the internal combustion engine. In this case, a composition of a mixture of fuel and air is changed according to the invention, the internal combustion engine 1 is fed for combustion. The ratio of air to fuel is described by the index lambda.

Starting from an idling speed of the internal combustion engine 1 Initially, an operation of the internal combustion engine 1 , in particular with lambda 1 . 4 , with a maximum torque of the internal combustion engine 1 as well as completely closed bypass 5 , So will from the turbine 3 the exhaust gas turbocharger 2 one for the current speed of the internal combustion engine 1 highest possible boost pressure 12 generated.

From a first speed 13 the engine load must be limited to damage the internal combustion engine 1 to avoid. In particular, the speed in a first range, with the first speed 13 starts and from a second speed 14 is limited, a maximum value of the cylinder pressure can be achieved. In the case of processes from the prior art, the boost pressure is already here 12 even limited, so that an alternative boost pressure curve 20 would result. The control according to the invention according to the embodiment instead provides that in the first area 16 an emaciation of the mixture, ie an increase in the proportion of air in the mixture takes place, so that lambda is increased. Therefore, how is out 2 it can be seen, a further increase in the boost pressure 12 possible without the load limits of the internal combustion engine 1 be reached or exceeded.

By leaning, the burning speed of the mixture within the internal combustion engine is reduced 1 , Thus, the intensity of combustion decreases, reducing the pressure within the cylinders of the internal combustion engine 1 decreases or at least does not increase any further.

From the second speed 14 the boost pressure must be limited to the internal combustion engine 1 not to overload. At the second speed 14 begins a second area 17 that by a third speed 15 is limited. In the second area 17 It is no longer possible, the load limits of the internal combustion engine 1 by further leaning the mixture. Thus, for example, a maximum lambda can be achieved, so that upon further emaciation an ignitability of the internal combustion engine 1 no longer exists. In particular, lambda must not exceed 1.65. Alternatively or additionally, for example, further leaning no longer prevent an increase in the cylinder pressure. In addition, in the second area there is a risk that the turbine 3 the exhaust gas turbocharger 2 due to excessive speeds caused by the high exhaust gas mass flow 4 of the internal combustion engine 1 is caused at high speeds is damaged.

Therefore, in the second area 17 initially carried out the same rule as in the first area 16 , This means that the mixture is emaciated, if this is still possible. In addition, in the second area 17 the bypass 5 open, with the opening of the bypass 5 only as small as to limit the boost pressure 12 is necessary. The boost pressure 12 it remains preferably constant in the second area. In particular, the boost pressure 12 at the maximum value 19 held.

In a third area 18 that with the third speed 15 starts, the boost pressure needs 12 finally lowered to the internal combustion engine 1 not to overload. This will be the bypass 5 opened, wherein the opening is larger than in the second Area 17 , In this way, the cylinder pressure and the pressure in the exhaust pipe between the engine 1 and turbine 3 the exhaust gas turbocharger 2 limited. In addition, the mixture is preferably enriched, ie, the proportion of air is reduced, so that lambda decreases. In this way, the internal combustion engine 1 operated as energy efficient as possible.

Are preferred during a development of the internal combustion engine 1 a maximum value for lambda, ie an ignition limit of the internal combustion engine 1 , a maximum value for the pressure in the exhaust pipe between the internal combustion engine 1 and turbine 3 , a maximum value for the speed of the turbine 3 , a maximum value for the cylinder pressure of the internal combustion engine 1 , as well as other load limits of the internal combustion engine 1 established. The maps or characteristic curves for controlling the bypass are thereby 5 as well as for the determination of the maximum value described above 19 the boost pressure 12 determined. These are then in the control unit 11 storable. Method for controlling the bypass 5 are known from the prior art and will not be explained further here.

The inventive method is independent of a size of the internal combustion engine 1 applicable. Therefore, the said lambda values are to be assigned only to a specific exemplary embodiment, since the lambda ranges are different engine parameters and operating parameters of the internal combustion engine 1 depend. These are in particular the compression ratio, the boost pressure, the displacement, the bore diameter and flow conditions in the combustion chamber or the ignition timing of the internal combustion engine 1 ,

LIST OF REFERENCE NUMBERS

1

internal combustion engine

2

turbocharger

3

turbine

4

Exhaust gas mass flow

5

bypass

6

exhaust system

7

air supply

8th

compressor

9

Intercooler

10

exhaust system

11

control unit

12

Boost pressure (progress message)

13

first speed

14

second speed

15

third speed

16

first (speed) range

17

second (speed) range

18

third (speed) range

19

maximum value of the boost pressure

20

alternative boost pressure curve

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 10310221 A1 [0003]
• US 4873961 A [0003]

Claims (12)

Method for controlling a boost pressure ( 12 ) of an internal combustion engine ( 1 ), wherein the internal combustion engine ( 1 ) burns a mixture of air and fuel and an exhaust gas turbocharger ( 2 ), wherein the exhaust gas turbocharger ( 2 ) a turbine ( 3 ), which by an exhaust gas mass flow ( 4 ) of the internal combustion engine ( 1 ), characterized in that the regulation of the boost pressure ( 12 ) in a first area ( 16 ), in which the speed of the internal combustion engine ( 1 ) a first speed ( 13 ), but below a second speed ( 14 ) by increasing the proportion of air in the mixture and in a second region ( 17 ), in which the speed of the internal combustion engine, the second speed ( 14 ), by additionally opening a bypass ( 5 ) of the turbine ( 3 ) of the exhaust gas turbocharger ( 2 ) is achieved. Method according to claim 1, characterized in that the second area ( 17 ) by a third speed ( 15 ), the control of the boost pressure ( 12 ) in a third area ( 18 ), in which the speed of the internal combustion engine ( 1 ) the third speed ( 15 ), by opening the bypass only ( 5 ) is achieved. Method according to claim 2, characterized in that in the third area ( 18 ) the proportion of air in the mixture is lowered. Method according to one of claims 2 or 3, characterized in that the boost pressure ( 12 ) in the third area ( 18 ) is lowered. Method according to one of claims 2 to 4, characterized in that in the third area ( 18 ) a pressure in a the exhaust gas mass flow ( 4 ) leading exhaust pipe between internal combustion engine ( 1 ) and turbine ( 3 ) does not exceed a predetermined maximum value. Method according to one of the preceding claims, characterized in that in the second area ( 17 ) a predetermined maximum proportion of air in the mixture is not exceeded and / or in the second range ( 17 ) a predetermined maximum speed of the turbine ( 3 ) is not exceeded. Method according to one of the preceding claims, characterized in that the control of the boost pressure ( 12 ) in the first area ( 16 ) increasing the boost pressure ( 12 ) to a predetermined maximum value ( 19 ) and / or in the second area ( 17 ) holding the boost pressure ( 12 ) at the maximum value (19). Method according to one of the preceding claims, characterized in that the control of the boost pressure ( 12 ) is executed only when, in a current operating state of the internal combustion engine ( 1 ) a predetermined maximum value of the boost pressure ( 19 ) is reachable. A method according to claim 8, characterized in that based on a map of the internal combustion engine ( 1 ) determines whether the maximum value (19) of the boost pressure ( 12 ) is achieved without regulation. Method according to one of the preceding claims, characterized in that the control of the boost pressure ( 12 ) is executed only at a maximum possible accelerator opening. Method according to one of the preceding claims, characterized in that the internal combustion engine ( 1 ) is a gasoline engine. Control unit ( 11 ), in particular for a vehicle, characterized in that the control device is set up to carry out a method according to one of the preceding claims.

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