DE102010038326A1 - Increasing the exhaust gas recirculation flow or the exhaust gas recirculation rate with the exhaust gas recirculation valve already open - Google Patents

Abstract

One aspect of the invention relates to an engine control method for an internal combustion engine with an exhaust gas turbocharger, boost pressure regulator, throttle and exhaust gas recirculation with exhaust gas recirculation valve. To increase the exhaust gas recirculation flow or the exhaust gas recirculation rate when the exhaust gas recirculation valve is already essentially open, the charge pressure regulator is activated in such a way that the exhaust gas-side pressure is increased upstream of the turbine. According to the method, the degree of opening of the throttle is also reduced, so that an increase in the fresh air flow or the pressure on the intake tract downstream of the throttle associated with the actuation of the boost pressure actuator is at least partially compensated for or prevented.

Description

The invention relates to an engine control method for an internal combustion engine with exhaust gas turbocharger and exhaust gas recirculation. In particular, the invention relates to increasing the exhaust gas recirculation flow (or exhaust gas recirculation rate) while the exhaust gas recirculation valve is already substantially open.

Internal combustion engines are known from the prior art, which include an exhaust gas turbocharger with turbine and compressor and an external exhaust gas recirculation with exhaust gas recirculation valve. An exemplary internal combustion engine for this is in the textbook "Diesel Engine Management", Robert Bosch GmbH, 4th edition, Vieweg-Verlag, pages 330-332 described. The statements made there for exhaust gas recirculation are hereby incorporated by reference into the disclosure content of the application.

In an internal combustion engine with an exhaust gas turbocharger and exhaust gas recirculation, an unstable regulation can occur when specifying the cylinder charge (fresh air flow and exhaust gas recirculation flow), in particular in the case when the exhaust gas recirculation flow is only achieved by throttling the air flow.

The amount of the recirculated exhaust gas depends on the opening degree of the exhaust gas recirculation valve. In addition, the amount of returned. Exhaust gas influenced by the pressure difference between the exhaust gas pressure upstream of the turbine (also referred to as exhaust back pressure) and the intake manifold pressure.

In order to increase the exhaust gas recirculation flow (or the exhaust gas recirculation rate) with the EGR valve substantially open, the pressure on the intake side may be reduced by decreasing the opening degree of the throttle valve, since reducing the opening degree throttles the fresh air and thus reducing the pressure downstream of the throttle, whereby the exhaust gas recirculation flow increases. This increase in the exhaust gas recirculation flow via the adjustment of the throttle valve has a high dynamic, d. H. When reducing the opening degree of the throttle, the exhaust gas recirculation flow increases in a short time. The reduction of the fresh air flow and the pressure downstream of the throttle associated with the reduction in the degree of opening of the throttle can be adjusted only slowly if desired by the charge pressure controller, which influences the power consumption of the turbine. Namely, the charge pressure regulator notices the reduction of the boost pressure and controls the charge pressure plate accordingly to compensate; However, the compensation of this reduction in the intake-side fresh air flow and the intake-side boost pressure takes longer because the boost pressure regulator must intervene on the exhaust gas side and the turbocharger must be accelerated; by controlling the boost pressure plate at the same time increases the exhaust gas pressure upstream of the turbine and causes a rapid increase of the exhaust gas recirculation flow; Due to the rapid reaction of the exhaust gas recirculation flow to the throttle valve and the boost pressure plate, the system tends to oscillate when coupled via the boost pressure control (suction pressure).

From the publication DE 103 34 809 A1 For example, a control unit for an exhaust gas recirculation internal combustion engine and turbocharger with variable turbine geometry is known which increases the degree of restriction of the turbine to increase the amount of exhaust gas recirculation with the EGR valve fully open so that the exhaust gas pressure in the exhaust passage upstream of the turbine is increased.

It is an object of the invention to provide an engine control method for an internal combustion engine with exhaust gas turbocharger and exhaust system, wherein when increasing the exhaust gas recirculation flow or the exhaust gas recirculation rate at already substantially open exhaust gas recirculation valve, the slow boost pressure plate has no or only a slight tendency to oscillate. In addition, it is an object of the invention to provide a corresponding engine control unit.

The object is solved by the features of the independent claims.

A first aspect of the invention relates to an engine control method for an internal combustion engine. The internal combustion engine has an exhaust gas turbocharger with a turbine and a compressor. This is, for example, an exhaust gas turbocharger with variable turbine geometry. This exhaust gas turbocharger type is also referred to as VTG (variable turbine geometry - VTG) or variable nozzle turbocharger (VNT) loaders. Alternatively, it is also possible to use another exhaust gas turbocharger, for example a so-called wastegate loader.

Further, there is a boost pressure plate which adjusts the boost pressure thereby by affecting the power consumption by the turbine. In other words, the charge pressure controller influences the drive of the turbine. By influencing the drive of the turbine, a certain exhaust side pressure is established upstream of the turbine. The charge pressure regulator can be, for example, the charge pressure regulator of a VGT supercharger or the charge pressure regulator of a wastegate supercharger.

Furthermore, a throttle with adjustable opening degree is present; this is preferably downstream in the intake tract of the internal combustion engine arranged the compressor. The internal combustion engine has exhaust gas recirculation with an exhaust gas recirculation valve, which branches off exhaust gas upstream of the turbine and returns downstream of the throttle into the intake tract.

In order to increase the exhaust gas recirculation flow (in particular the mass of the exhaust gas recirculation flow) or the exhaust gas recirculation rate with an already substantially open exhaust gas recirculation valve, the following steps are carried out according to the method:
The boost pressure plate is controlled such that the exhaust gas pressure upstream of the turbine is increased. By increasing the exhaust backpressure, the exhaust gas recirculation flow and the exhaust gas recirculation rate increase. This increase in the exhaust backpressure and the exhaust gas recirculation flow has a high dynamic, ie with control of the boost pressure plate, which initially engages the exhaust side, the exhaust gas pressure is increased quickly and thus also quickly increases the exhaust gas recirculation flow.

According to the method, moreover, the opening degree of the throttle is reduced, so that an increase of the fresh air flow or the intake tract side boost pressure associated with the driving of the boost pressure plate is at least partially compensated or prevented downstream of the throttle. The slow dynamic increase in the fresh air flow can therefore be regulated by the fast-acting throttle.

The above-described problem of increased oscillation tendency of the system does not occur here so. The turbocharger in this case causes a slow increase of intake manifold side boost pressure upstream of the throttle; the charge pressure downstream of the throttle can be kept almost constant with the throttle and the reaction to the exhaust gas recirculation flow is low. Also, the throttle is not affected by an increased tendency to oscillate, as this can quickly compensate for the increase in the fresh air flow described above.

In the method, it can be provided that the boost pressure plate increases the fresh air flow or the intake air side pressure, and only then does the throttle at least partially compensate for the increase. Preferably, the throttle reacts quickly, so that even a slight increase is detected and is at least partially compensated by the throttle. Alternatively, it could also be provided that a possible increase is already prevented in advance by the throttle simultaneously with the boost pressure, shortly thereafter activated or even shortly before driven, so that no increase occurs (which is otherwise detected and then by the throttle would have to be compensated).

In the method, preferably the exhaust gas recirculation (in particular the mass of the exhaust gas recirculation stream or the exhaust gas recirculation rate) and the boost pressure with an EGR controller (EGR - exhaust gas recirculation) or a boost pressure regulator regulated. According to the invention, the boost pressure plate is used to increase the exhaust gas recirculation in the case of a substantially open EGR valve; Therefore, the invention preferably provides a coupling of EGR controller and boost pressure regulator in the case of too small exhaust gas recirculation amount at substantially open EGR valve.

It should be noted that a substantially open exhaust gas recirculation valve does not necessarily have to be completely open; it is sufficient if the exhaust gas recirculation amount would not rise at all or only negligibly due to any further opening of the exhaust gas recirculation valve.

Preferably, the internal combustion engine is a diesel engine, although the method may also be used with a gasoline engine.

Preferably, a VTG turbocharger with variable turbine geometry is used. Diesel engines typically use a VTG charger rather than a wastegate charger due to the lower thermal load compared to gasoline engines. In the case of a VTG loader, the flow cross section through which the exhaust gas flows onto the turbine can be varied by means of adjustable guide vanes. The boost pressure plate is preferably controlled to increase the exhaust gas pressure upstream of the turbine such that the flow cross section is reduced by adjusting the guide vanes. In the case of a VTG supercharger, the charge pressure controller comprises, for example, an adjusting box with adjusting lever or adjusting linkage, which influences the position of the guide vanes via an adjusting ring.

Alternatively, a so-called wastegate loader can be used. Here, a variable proportion of the exhaust gas is passed via a bypass valve past the turbine into the exhaust system. This allows adjustment of the boost pressure.

In both cases (VTG loader or wastegate loader), the boost pressure is thus adjusted by influencing the power consumption of the turbine.

• – der Frischluftstrom oder der Ladedruck sowie
• – der Abgasrückführstrom (insbesondere die Masse des Abgasrückführstroms) oder die Abgasrückführrate

geregelt. Hierdurch wird die Zylinderfüllung (Frischluftstrom und Abgasrückführstrom) vorgegeben. Die Regelung des Abgasrückführstroms bzw. der Abgasrückführrate erfolgt vorzugsweise über die Messung der Luftmasse und einer Modellierung der Zylinderfüllung.In the engine control method, it is preferable

• - The fresh air flow or the boost pressure and
• - The exhaust gas recirculation flow (in particular the mass of the exhaust gas recirculation flow) or the exhaust gas recirculation rate

regulated. As a result, the cylinder filling (fresh air flow and exhaust gas recirculation flow) is specified. The regulation of the exhaust gas recirculation flow or the exhaust gas recirculation rate is preferably carried out via the measurement of the air mass and a modeling of the cylinder filling.

A second aspect of the invention relates to an engine control unit for an internal combustion engine as described above. The engine control unit is configured to carry out the following steps to increase the exhaust gas recirculation flow or the exhaust gas recirculation rate while the exhaust gas recirculation valve is already substantially open. The boost pressure regulator is controlled in such a way that the exhaust gas pressure upstream of the turbine is increased. In addition, the opening degree of the throttle is reduced, so that a slow increase in the fresh air flow or the intake tract side pressure downstream of the throttle associated with the driving of the boost pressure plate is at least partially compensated for or prevented.

The above statements on the method according to the invention according to the first aspect of the invention also apply correspondingly to the control device according to the invention according to the second aspect of the invention.

A third aspect of the invention relates to a motor vehicle having an internal combustion engine as described above and an engine control unit according to the second aspect of the invention.

The invention will be described below with reference to the accompanying drawings with reference to an embodiment.

The drawing shows an example of an internal combustion engine with turbocharger and exhaust gas recirculation. The control of the internal combustion engine via an electronic engine control unit 10 , The internal combustion engine comprises an exhaust gas turbocharger with compressor 1 and turbine 2 , Downstream of the compressor 1 is a charge air cooler 3 provided that cools the fresh air to a certain temperature. Downstream of the intercooler 3 there is a throttle 4 with adjustable degree of opening, the amount of fresh air on the opening degree of the throttle 4 is set. Exhaust gas is via an exhaust gas recirculation 5 upstream of the turbine 2 branched off and downstream of the throttle 4 recycled. The amount of recirculated exhaust gas depends on the degree of opening of an exhaust gas recirculation valve 6 from. In addition, the amount of the recirculated exhaust gas by the pressure difference between the exhaust gas pressure P ₂ upstream of the turbine 2 (also referred to as exhaust back pressure) and the intake manifold pressure P ₁ influenced. The exhaust gas recirculation 5 can optionally have two parallel paths: a path with a cooler 7 and a bypass path without a cooler. The division of the exhaust gas on the two paths can be via a valve 8th be set.

Preferably, a VTG loader is used, which is a turbine 2 having variable turbine geometry; Alternatively, a wastegate loader could be used. In the case of a VTG loader, the flow cross section through which the exhaust gas flows onto the turbine can be varied by means of adjustable guide vanes. An electrically controlled charge pressure regulator 11 shifts, for example, via an adjusting lever or an adjusting linkage (not shown) an adjusting ring (not shown), which in turn affects the position of the vanes.

The engine control unit 10 Among other things, it serves to control the boost pressure plate 11 via a signal 12 , the activation of the actuator (not shown) of the throttle 4 via a signal 13 and the control of the actuator (not shown) of the exhaust gas recirculation valve 6 via a signal 14 , For controlling / regulating engine parameters are provided by the engine control unit 10 Sensor signals received, for example, a sensor signal of an air mass meter (not shown).

The engine control unit 10 is used to control the cylinder filling (fresh air content and proportion of recirculated exhaust gas). The engine control unit regulates this 10 the mass of exhaust gas recirculation flow (EGR mass) or the EGR rate (eg, the ratio of the EGR mass to the total charge). For this rule, the engine control unit includes 10 an EGR controller. Furthermore, the engine control unit regulates 10 the boost pressure, for example the pressure P ₁ ; this includes the engine control unit 10 a boost pressure regulator. To control the boost pressure of the pressure P ₁ downstream of the throttle 4 measured; but the boost pressure could also be upstream of the throttle 4 be measured. Alternatively, instead of the boost pressure, the fresh air flow can also be regulated as a controlled variable.

As stated above, the amount of recirculated exhaust gas depends on both the degree of opening of an exhaust gas recirculation valve 6 as well as the pressure difference between the exhaust gas pressure P ₂ upstream of the turbine 2 and the intake manifold pressure P ₁ .

To increase the exhaust gas recirculation flow or the exhaust gas recirculation rate with already substantially open exhaust gas recirculation valve controls the engine control unit 10 the boost pressure plate 11 via a signal 12 such that the exhaust gas pressure P _{2 is} upstream of the turbine 2 is increased. The boost pressure plate 11 causes an adjustment of the vanes of the turbine 2 such that the flow cross section is reduced. The VTG loader and the adjustment of the vanes towards a smaller flow area are in the textbook "Diesel Engine Management", Robert Bosch GmbH, 4th edition, Vieweg-Verlag on pages 54-55 described. The statements made there are hereby incorporated by reference into the disclosure of the application.

By increasing the exhaust back pressure P ₂ , the exhaust gas recirculation flow and the exhaust gas recirculation rate increase. This increase in the exhaust back pressure and the exhaust gas recirculation flow has a high dynamic, ie with control of the boost pressure plate 11 , which engages on the exhaust side, the exhaust gas pressure P _{2 is} increased rapidly and thus also quickly increases the exhaust gas recirculation flow.

Although the coupling between the turbine and the compressor also leads to an increase in the fresh air flow (before the supply of the exhaust gas, ie upstream of the throttle 4 or right after the throttle 4 ) and the suction-side pressure P ₁ . However, this increase takes place only slowly after a certain dead time, so that at first the fresh air flow and the pressure P ₁ remain almost constant.

The engine control unit 10 controls the throttle actuator 4 via a signal 13 such that the opening degree of the throttle valve 4 is reduced, so that one with the driving of the boost pressure plate 11 otherwise resulting slow increase of the fresh air flow (before the supply of the exhaust gas, ie before the throttle 4 or right after the throttle 4 ) or the intake-side pressure P ₁ is corrected immediately. The fresh air flow is ambient air that passes through the compressor 1 comes. The slow increase in the fresh air flow or the intake tract-side pressure P ₁ is thus on the fast-acting throttle 4 corrected.

Thus, the invention allows a coupling of EGR controller and boost pressure regulator in the case of too small exhaust gas recirculation amount at substantially open EGR valve. Because the boost pressure plate 11 in a short time can increase the pressure P ₂ on the exhaust side and over the throttle 4 a concomitant slow increase in airflow quickly from the throttle 4 can be corrected, no oscillation of the system occurs.

Thus, the invention enables a high Einregelqualität of air and exhaust gas and thus a good and stable setting, in particular control, a desired filling (air and exhaust gas). This results in lower emissions and drivability benefits.

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 10334809 A1 [0006]

Cited non-patent literature

• "Diesel Engine Management", Robert Bosch GmbH, 4th edition, Vieweg-Verlag, pages 330-332 [0002]
• "Diesel Engine Management", Robert Bosch GmbH, 4th Edition, Vieweg-Verlag on pages 54-55 [0032]

Claims (7)

Engine control method for an internal combustion engine comprising - an exhaust gas turbocharger with a turbine ( 2 ) and a compressor ( 1 ), - a boost pressure plate ( 11 ), which adjusts the boost pressure by the power consumption by the turbine ( 2 ), whereby a certain exhaust gas pressure (P ₂ ) upstream of the turbine ( 2 ), - a throttle ( 4 ) with adjustable opening degree and - an exhaust gas recirculation ( 5 ) with exhaust gas recirculation valve ( 6 ), which exhaust gas upstream of the turbine ( 2 ) branches off and downstream of the throttle ( 4 ) into the intake tract, wherein, in order to increase the exhaust gas recirculation flow or the exhaust gas recirculation rate in the case of an already substantially open exhaust gas recirculation valve (FIG. 6 ) the following steps are performed: - controlling the boost pressure plate ( 11 ) such that the exhaust gas pressure (P ₂ ) upstream of the turbine ( 2 ), and - reducing the opening degree of the throttle ( 4 ), so that one with the driving of the boost pressure plate ( 11 ) associated increase - the fresh air flow or - the intake manifold side pressure (P ₁ ) downstream of the throttle at least partially - compensated or - prevented. Engine control method according to claim 1, wherein the turbine ( 2 ) is a turbine with variable turbine geometry and the flow cross section through which the exhaust gas flows to the turbine is variable by adjustable guide vanes and the boost pressure plate ( 11 ) is controlled such that the flow cross-section is reduced. Motor control method according to one of the preceding claims, wherein - the fresh air flow or the boost pressure ( 4 ) and - the exhaust gas recirculation flow or the exhaust gas recirculation rate are regulated. A motor control method according to any one of the preceding claims, which is a motor control method for a diesel engine. Engine control method according to one of the preceding claims, wherein the throttle ( 4 ) in the intake tract of the internal combustion engine downstream of the compressor ( 1 ) is arranged. Engine control unit ( 10 ) for an internal combustion engine which - an exhaust gas turbocharger with a turbine ( 2 ) and a compressor ( 1 ), - a boost pressure plate ( 11 ), which adjusts the boost pressure by the power consumption by the turbine ( 2 ), whereby a certain exhaust gas pressure (P ₂ ) upstream of the turbine ( 2 ), - a throttle ( 4 ) with adjustable opening degree and - an exhaust gas recirculation with exhaust gas recirculation valve ( 6 ), which exhaust gas upstream of the turbine ( 2 ) branches off and downstream of the throttle ( 4 ) into the intake tract, wherein the engine control unit ( 10 ) is set up to increase the exhaust gas recirculation flow or the exhaust gas recirculation rate when the exhaust gas recirculation valve is already substantially open ( 6 ) carry out the following steps: - controlling the boost pressure plate ( 11 ) such that the exhaust gas pressure upstream of the turbine ( 2 ), and - reducing the opening degree of the throttle ( 4 ), so that an increase associated with the control of the boost pressure controller - the fresh air flow or - the intake-tract-side pressure (P ₁ ) downstream of the throttle at least partially - compensated or - prevented. Motor vehicle - with an internal combustion engine which - an exhaust gas turbocharger with a turbine ( 2 ) and a compressor ( 1 ), - a boost pressure plate ( 11 ), which adjusts the boost pressure by the power consumption by the turbine ( 2 ), whereby a certain exhaust gas pressure (P ₂ ) upstream of the turbine ( 2 ), - a throttle ( 4 ) with adjustable opening degree, and - an exhaust gas recirculation ( 5 ) with exhaust gas recirculation valve ( 6 ), which exhaust gas upstream of the turbine ( 2 ) branches off and downstream of the throttle ( 4 ) into the intake tract, comprises, and - an engine control unit ( 10 ) according to claim 6.

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