DE102008044269A1 - Method for adjusting exhaust gas recirculation rate of internal combustion engine, involves detecting exhaust residual percentage in fresh-gas mixture in intake manifold - Google Patents

Abstract

The method involves detecting exhaust residual percentage in fresh-gas mixture (F-man) in intake manifold (6). The exhaust residual percentage algorithm of fresh-gas mixture is detected by an algorithm. The exhaust residual percentage of fresh-gas mixture is controlled in intake manifold in a closed-loop. An independent claim is also included for an internal combustion engine.

Description

The The invention relates to a method for adjusting the exhaust gas recirculation rate of a Internal combustion engine, an internal combustion engine and a vehicle with as stated in the preambles of the respective independent claims Features.

It is known that the regulations for the exhaust emissions of internal combustion engines with increasing number of vehicles are constantly tightening, such as EURO 6 standard in Europe or Tier 2 or Bin 5 in USA. Some manufacturers prefer to use different firing strategies like HCCI (Homogeneous Charge Compression Ignition) or active aftertreatment devices such as NOx (nitrogen oxide) or SCR (Selective Catalytic Reduction) catalysts. however These technologies require a considerable amount of material and development efforts that increase the complexity of the systems and for the consumer high consequential costs such as higher fuel consumption and technological sustainability costs mean.

A the known strategies, the emissions of an internal combustion engine To lower, it is the exhaust gas purification through an exhaust gas recirculation to improve. The exhaust gases still contain a relatively large amount of oxygen and will so partially mixed with the fresh air, creating less fresh air from the atmosphere must be removed. For this purpose, the exhaust gases are taken either directly after the exhaust manifold or first by a catalyst or particle filter containing Purified emission control system and then partly over a designated for this purpose Taken from supply line and the fresh air supply admixed to the intake manifold.

To Known methods, the air preparation structure is carried out such that a compression pressure, exhaust gas recirculation and air mass flow determined become. Exhaust gas recirculation usually becomes either in a percentage of recirculated exhaust gases or the residual gases in the intake manifold.

The Known controls the exhaust systems of an internal combustion engine use with exhaust gas recirculation an air mass sensor or so-called MAF sensor (Mass Air Flow) for determining the Air mass flow, the residual gas content of recirculated exhaust gases from model calculations estimated becomes. This does not make it possible the residual gas content of recirculated exhaust gases controlled in the fresh air-exhaust gas mixture to control, for. In a closed loop. An exact regulation of the residual gas content is of the utmost importance, though a stable combustion operation of the internal combustion engine when preserved low NOx emissions shall be. Such a regulation of the residual gas content of recirculated exhaust gases in the fresh air-exhaust gas mixture in the closed loop is through An additional Residual gas component sensor feasible, However, which increases the effort and thus the production costs. As a residual gas content sensor here can be a NOx sensor, an oxygen concentration sensor or a COx sensor can be used.

Of the Invention is based on the object, the controlled setting the exhaust gas recirculation rate of a To improve internal combustion engine such that the accuracy and reliability the preparation of the fresh air-exhaust gas mixture increased and the production costs the internal combustion engine are lowered simultaneously.

The inventive tasks are obtained by a method according to claim 1, by an internal combustion engine according to claim 9 and a vehicle according to claim 15.

• – wenigstens ein Restgasanteil im Frischluft-Abgasgemisch im Einlaßkrümmer erfaßt wird,
• – aus dem erfaßten Restgasanteil der Frischluftmassenfluß nach einem Algorithmus ermittelt wird, und
• – der Restgasanteil des Frischluft-Abgasgemischs im Einlaßkrümmer in einem geschlossenen Regelkreis gesteuert wird.

A method according to the invention for adjusting the exhaust gas recirculation rate of an internal combustion engine having at least one intake manifold connected to a fresh air supply line and an exhaust gas recirculation and at least one exhaust manifold connected to an exhaust system, comprising a control system for setting an exhaust gas recirculation rate, comprises the following method steps which ensure that

• - At least one residual gas content in the fresh air-exhaust gas mixture is detected in the intake manifold,
• - From the detected residual gas content of the fresh air mass flow is determined by an algorithm, and
• - The residual gas content of the fresh air-exhaust gas mixture in the intake manifold is controlled in a closed loop.

The exhaust gas recirculation rate is in this case the ratio of the mass flow of the fresh air to the mass flow of recirculated exhaust gases, in which a residual gas content is present. The residual gas content, however, represents the proportion of a residual gas such as NOx, COx or oxygen O ₂ in the entire gas flow at the respective relevant position in the system.

It is of another benefit when capturing the residual gas content the fresh air-exhaust gas mixture in the intake manifold by means of at least one NOx sensor, oxygen concentration sensor or COx concentration sensor running becomes.

According to a further preferred embodiment of the method according to the invention, the means for detecting the residual gas content of the fresh air-exhaust gas mixture comprise at least one temperature sensor for detecting the temperature in Inlet manifold and / or is provided in the fresh air supply line and / or exhaust gas recirculation.

Further The means for detecting the residual gas content of the fresh air / exhaust gas mixture preferably comprise at least one pressure sensor provided for detecting the pressure in the intake manifold is.

Especially far-reaching advantages are read by embodiments according to the invention achieve, if to control the fresh air supply a controllable Fresh air throttle and / or for controlling the exhaust gas recirculation rate a controllable residual throttle is used.

Of the inventive algorithm for determining the fresh air mass flow from the detected residual gas content the fresh air-exhaust gas mixture in the intake manifold considered in further preferred Embodiments at least one parameter of a motor control model the internal combustion engine. It can For example, calculated temperature values or volumes of components the fresh air and exhaust strands be.

Additionally or Alternatively, the algorithm for determining the fresh air mass flow from the recorded Residual gas content of the fresh air-exhaust gas mixture in the intake manifold at least take into account a parameter of an auxiliary sensor of the internal combustion engine.

woraus folgt:

wobei die Abkürzungen wie folgt aufzuschlüsseln sind:

F_MAN

Restgasanteil im Einlaßkrümmer

F_EGR

Restgasanteil im Abgasrückführungssystem

F_FXH

Restgasanteil im Abgasstrang vor oder nach Abgasreinigungsmaßnahmen

P

Druck

R

Gaskonstante

T

Temperatur

T

mittlere Temperatur

^TEGR

Temperatur in der Abgasrückführung

^TMAN

Temperatur im Einlaßkrümmer

T_IS

Temperatur im Einlaßsystem

V

Gesamtvolumen

V_EGR

Volumen der Abgasrückführung

V_IS

Volumen des Frischluftzufuhrstranges

^VMAN

Volumen des Einlaßkrümmers

W_AIR

Frischluftmassenfluß

W_AP

Massenfluß der Frischluft-Abgasmischung

W_EGR

Abgasmassenfluß

und das Gesamtvolumen sich zusammensetzt aus: V = VEGR + VIS + VMAN. The determination of the fresh air mass flow from the detected residual gas content is preferably carried out according to the following mathematical relationship:

From which follows:

where the abbreviations are to be broken down as follows:

F _MAN

Residual gas content in the intake manifold

F _EGR

Residual gas content in the exhaust gas recirculation system

F _FXH

Residual gas content in the exhaust system before or after emission control measures

P

print

R

gas constant

T

temperature

T

medium temperature

^T EGR

Temperature in the exhaust gas recirculation

^T MAN

Temperature in the intake manifold

T _IS

Temperature in the intake system

V

total volume

V _EGR

Volume of exhaust gas recirculation

V _IS

Volume of fresh air supply line

^V MAN

Volume of intake manifold

W _AIR

Frischluftmassenfluß

W _AP

Mass flow of fresh air exhaust gas mixture

W _EGR

Abgasmassenfluß

and the total volume is composed of: V = V EGR + V IS + V MAN ,

To In a second aspect, the objects of the invention are achieved by an internal combustion engine with a connected to a fresh air supply line and exhaust gas recirculation Intake manifold and an exhaust manifold connected to an exhaust system, comprising a control system for setting an exhaust gas recirculation rate, solved by that means to run of the method described above according to one of the preferred embodiments are provided.

there have the means to perform of the method means for detecting the residual gas content of the fresh air-exhaust gas mixture in the intake manifold and for determining the fresh air mass flow from the detected residual gas content on.

Preferably have the means for detecting at least one residual gas portion of the Fresh air exhaust gas mixture at least one NOx sensor, oxygen concentration sensor or COx concentration sensor.

In a further preferred embodiment of the internal combustion engine according to the invention have the means for detecting the residual gas content of the fresh air-exhaust gas mixture at least one temperature sensor for detecting the temperature in the intake manifold and / or is provided in the fresh air supply line and / or exhaust gas recirculation.

The Means for detecting a residual gas content of the fresh air-exhaust gas mixture comprise according to a Another preferred embodiment of the present invention, at least a pressure sensor provided for detecting the pressure in the intake manifold is. The captured Pressure is used to calculate and / or determine the residual gas content used.

For controlling the fresh air supply is preferably at least one controllable fresh air throttle and / or for controlling the exhaust gas recirculation rate at least one controllable residual throttle intended. The respective throttles are arranged in the respective supply lines.

The inventive tasks become after another aspect also by a vehicle with a Internal combustion engine according to one of the previously described preferred Embodiments solved.

The Invention is suitable for use in exhaust gas recirculation systems with a so-called High pressure exhaust gas recirculation as well in systems with low pressure exhaust gas recirculation. Of course you can the invention also in exhaust gas recirculation systems use find that both equipped with a high-pressure exhaust gas recirculation and with a low-pressure exhaust gas recirculation are.

Further preferred embodiments of the invention will become apparent from the others, in the subclaims mentioned features. Furthermore arise further features of the invention, properties and advantages from the following description of the embodiments with reference to the attached Characters.

The Invention will be described below in embodiments with reference to FIG associated Drawings explained. Show it:

1 a schematic representation of the internal combustion engine according to the invention with exhaust gas recirculation,

2 a flowchart of the inventive method for adjusting the exhaust gas recirculation rate, and

3 a schematic representation of a logic circuit for controlling the internal combustion engine according to the invention with exhaust gas recirculation.

1 shows a schematic representation of the internal combustion engine according to the invention with exhaust gas recirculation 9 ,

A fresh air strand 3 has a compressor 1 , a fresh air supply 2 and a fresh air system 4 on, with the fresh air system 4 For example, symbolizes a volume V _{IS of} the intake system, in which there is a temperature T _{IS of} the fresh air in the intake system. The fresh air line 3 is with the intake manifold 6 connected. According to the invention, the fresh air supply line is missing 3 an air mass sensor for detecting the fresh air mass flow W _AIR .

Via an exhaust gas recirculation supply line 10 is the exhaust gas recirculation 9 as well with the intake manifold 6 connected, so that the fresh air and the recirculated exhaust gases are mixed together. The mixing of the fresh air with the recirculated exhaust gases is performed, for example via a respective controllable throttle valve (not shown) by a controller and set an exhaust gas recirculation rate r _MAN as a function of control parameters.

The exhaust gas recirculation 9 has an EGR system or exhaust gas recirculation system 8th and an exhaust gas recirculation supply line 10 on. The EGR system 8th is analogous to the fresh air system 4 considered with a symbolizing volume V _EGR the exhaust gas recirculation system in which there is a temperature T _{EGR of} the exhaust gases in the exhaust gas recirculation system. Further symbolically is a turbine 7 shown in the exhaust system, which is the compressor 1 via a shaft (not shown) by outflowing exhaust gases drives.

In the intake manifold 6 According to the invention, a FMAN sensor or a residual gas sensor 5 arranged, with which the residual gas content F _MAN is detected in the intake manifold. It can be detected with this sensor, the oxygen content, the NOx or COx content or a combination thereof. Also the intake manifold 6 is assigned a volume V _MAN , in which a temperature T _MAN exists. The detected residual gas F _MAN in the intake manifold is used as the authoritative parameter size for the determination of all variables required for control.

The respective temperatures T _MAN , T _IS and T _EGR are either detected by a respective temperature sensor (not shown) and / or determined in part from a motor control model. For the calculation, for example, an average temperature T is formed from the three above temperature values. According to the invention, this mean temperature is assigned to the total volume V: V = V EGR + V IS + V MAN ,

That in the intake manifold 6 formed fresh air exhaust gas mixture flows with a mass flow of fresh air exhaust gas mixture W _AP in the cylinder of the internal combustion engine. The exhaust gases emitted by the internal combustion engine pass through the exhaust gas cleaning measures of the exhaust system (not shown) or are already tapped before and into the exhaust gas recirculation system 8th initiated with an exhaust gas mass flow W _EGR and a residual gas _content in the exhaust line F _EXH .

woraus für den gesuchten Frischluftmassenfluß folgt:

wodurch dieser ohne einen Luftmassensensor im Frischluftstrang ermittelt worden ist und außerdem die Steuerung des Restgasanteils im Einlaßkrümmer F_MAN in einem geschlossenen Regelkreis ausgeführt wird.A controller, not shown, controls the throttle valves of the fresh air line and the exhaust gas recirculation line in response to the detected residual gas F _MAN in the intake manifold and possibly detected temperature in at least one of the participating volumes. A preferred calculation method uses the following mathematical relationship relations

what follows for the sought fresh air mass flow:

whereby it has been determined without an air mass sensor in the fresh air line and also the control of the residual gas content in the intake manifold F _{MAN is performed} in a closed loop.

2 shows a flowchart of the inventive method for adjusting an exhaust gas recirculation rate r _MAN in a preferred embodiment.

In method step S1, the engine state parameters are detected and used in S2, for example, for online calibration of the FMAN sensor. In step S3, the detection of the residual gas F _MAN and in S5, for example, a pressure detection in the intake manifold. In step S4, the detected variables are processed and transferred to further process steps.

In method step S6, the residual gas _component F _EXH in the exhaust gas system is determined. In parallel, a differentiation of the F _MAN sensor signal takes place in step S7, the result of which is used in step S10.

in the Step S9 takes into account a delay in the EGR system due to the propagation of the exhaust gases along the exhaust gas recirculation line occurs and also this result is used in step S10.

Parallel For this purpose, the detected in step S5 pressure in the intake manifold is the Supplied to step S8, where that seized Pressure signal is subjected to differentiation. The result This differentiation is also supplied to the method step S10 as previously the signals described above.

Finally, in method step S10, a calculation of the fresh air mass flow W _{AIR takes place} . This can, for example, as under 1 specified to be executed.

3 shows a schematic representation of a logic circuit 16 for controlling the internal combustion engine according to the invention with exhaust gas recirculation. This circuit is a typical generated by the well-known program tool SIMULINK Fa. The MathWorks function circuit and has a structure of defined logical building blocks whose function is sufficiently known from the documentation for SIMULINK program tool and therefore need not be explained in detail.

The logical block 11 is used to determine the residual gas _content F _EXH in the exhaust system before or after the exhaust gas cleaning _measures and the temperature T _{EXH of} the exhaust gases after leaving the cylinder.

In the logical block 12 will the under 2 Differentiation of the FMAN sensor signal described in step S7.

In the logical block 13 will the under 2 performed in step S8 differentiation of the pressure sensor signal.

block 14 represents a time delay and block 15 determines the flow delay in the EGR system, as described in 2 shown in step S9.

At the exit 17 is the signal sought to the determined fresh air mass flow W _AIR .

1

compressor

2

Fresh air supply

3

Fresh air train

4

Fresh air system

5

FMan sensor, Residual gas sensor

6

intake manifold

7

turbine

8th

EGR system, Exhaust gas recirculation system

9

Exhaust gas recirculation

10

Exhaust gas recirculation supply line

11..15

logically block

16

logical circuit

17

output

S1..S10

steps

EGR

recirculated exhaust gases

F _MAN

Residual gas in the intake manifold

F _EGR

Residual gas in the exhaust gas recirculation system

F _EXH

Residual gas in the exhaust system before or after emission control measures

MAF sensor

Air mass sensor

FMan sensor

Residual gas sensor

P

print

R

gas constant

_MAN

Exhaust gas recirculation rate

T

temperature

T

middle temperature

T _EGR

temperature in the exhaust gas recirculation system

T _MAN

temperature in the intake manifold

T _IS

temperature in the intake system

T _EXH

temperature the exhaust gases to the outlet the cylinder

V

volume

V _EGR

volume the exhaust gas recirculation system

V _IS

volume of the intake system

V _MAN

volume the intake manifold

W _AIR

Frischluftmassenfluß

W _AP

Mass flow of fresh air exhaust gas mixture

W _EGR

Abgasmassenfluß

Claims (15)

Method for setting the exhaust gas recirculation rate (r _MAN ) of an internal combustion engine with at least one with a fresh air supply line ( 3 ) and an exhaust gas recirculation ( 9 ) and at least one exhaust manifold connected to an exhaust manifold, comprising a control system for setting an exhaust gas recirculation rate (r _MAN ), characterized in that at least one residual gas component (F _MAN ) is detected in the fresh air exhaust gas mixture in the intake manifold, from the detected residual gas component (F _MAN ) of the fresh air mass flow (W _AIR ) is determined according to an algorithm, and the residual gas content (F _MAN ) of the fresh air-exhaust gas mixture in the intake manifold is controlled in a closed loop. A method according to claim 1, characterized in that the detection of the residual gas content (F _MAN ) of the fresh air-exhaust gas mixture in the intake manifold using at least one of a NOx sensor, oxygen concentration sensor or COx concentration sensor is performed. Method according to one of the preceding claims, characterized in that the means for detecting the residual gas content (F _MAN ) of the fresh air-exhaust gas mixture comprise at least one temperature sensor which is provided for detecting the temperature in the intake manifold and / or in the fresh air supply line and / or the exhaust gas recirculation. Method according to one of the preceding claims, characterized in that the means for detecting the residual gas content (F _MAN ) of the fresh air-exhaust gas mixture comprise at least one pressure sensor which is provided for detecting the pressure in the intake manifold. Method according to one of the preceding claims, characterized characterized in that for controlling the fresh air supply a controllable fresh air throttle and / or for controlling the exhaust gas recirculation rate controllable residual throttle is used. Method according to one of the preceding claims, characterized in that the algorithm for determining the fresh air mass flow (W _AIR ) from the detected residual gas content (F _MAN ) of the fresh air exhaust gas mixture in the intake manifold takes into account at least one parameter of an engine control model of the internal combustion engine. Method according to one of the preceding claims, characterized in that the algorithm for determining the fresh air mass flow (W _AIR ) from the detected residual gas component (F _MAN ) of the fresh air-exhaust gas mixture in the intake manifold takes into account at least one parameter of an auxiliary sensor of the internal combustion engine. Method according to one of the preceding claims, characterized in that the determination of the fresh air mass flow (W _AIR ) from the detected residual gas fraction (F _MAN ) is carried out according to the following mathematical relationship:

From which follows:

where the abbreviations are to be broken down as follows: F _MAN residual gas content in the inlet manifold F _EGR residual gas _content in the exhaust gas recirculation system F _EXH residual gas _content in the exhaust gas line before or after the _{emission control measures} P pressure R gas constant T temperature T mean temperature T _EGR temperature in exhaust gas recirculation T _MAN temperature in intake manifold T _IS temperature in intake system V total volume ^V EGR volume of exhaust gas recirculation V _IS volume of fresh air supply line V _MAN volume of intake manifold W _AIR fresh air mass flow W _AP mass flow of fresh air exhaust mixture W _EGR exhaust mass flow, and the total volume is composed of: V = V EGR + V IS + V MAN Internal combustion engine with one with a fresh air supply line ( 3 ) and an exhaust gas recirculation ( 9 ) connected intake manifold ( 6 ) and an exhaust manifold connected to an exhaust system, comprising a control system for adjusting the exhaust gas recirculation rate (r _MAN ), characterized in that means are provided for carrying out the method according to one of the preceding claims. Internal combustion engine according to claim 9, characterized in that the means for carrying out the method comprise means for detecting the residual gas fraction (F _MAN ) of the fresh air exhaust gas mixture in the intake manifold and for determining the fresh air mass flow (W _AIR ) from the detected residual gas fraction (F _MAN ). Internal combustion engine according to claim 10, characterized in that the means for detecting the residual gas content (F _MAN ) of the fresh air-exhaust gas mixture comprise at least one NOx sensor, oxygen concentration sensor or COx concentration sensor. Internal combustion engine according to claim 10 or 11, characterized in that the means for detecting the residual gas content (F _MAN ) of the fresh air-exhaust gas mixture comprise at least one pressure sensor which is provided for detecting the pressure in the intake manifold. Internal combustion engine according to one of the preceding claims, characterized in that the means for detecting the residual gas content (F _MAN ) of the fresh air-exhaust mixture comprise at least one temperature sensor for detecting the temperature in the intake manifold (T _MAN ) and / or fresh air supply line (T _IS ) and / or exhaust gas recirculation (T _EGR ) is provided. Internal combustion engine according to one of the preceding claims, characterized in that at least one controllable residual throttle is provided for controlling the fresh air supply at least one controllable fresh air throttle and / or for controlling the exhaust gas recirculation rate (r _MAN ). Vehicle with an internal combustion engine after a of the preceding claims.