WO2013068140A1

WO2013068140A1 - Method for controlling the exhaust-gas temperature of a direct-injection internal combustion engine

Info

Publication number: WO2013068140A1
Application number: PCT/EP2012/066148
Authority: WO
Inventors: Thorsten Schnorbus; Christian FRENKEN
Original assignee: Fev Gmbh
Priority date: 2011-11-11
Filing date: 2012-08-17
Publication date: 2013-05-16
Also published as: CN103930664A; DE102011055273A1

Abstract

Method for controlling the exhaust-gas temperature of a direct-injection internal combustion engine 2, in which method the combustion fuel injection is divided into a plurality of individual injections, and in which method the temperature T3 of the exhaust gas which exits the internal combustion engine 2 is determined predictively by means of at least one model 11, 12 at a predefined load by setting of the position aQ50 of the centre of area of the heat release and of the injection quantity minj of the entire combustion fuel injection.

Description

Method for controlling the exhaust gas temperature of a direct-injection internal combustion engine

description

The invention relates to a method for controlling the exhaust gas temperature of a direct-injection internal combustion engine and a direct-injection internal combustion engine with such a control.

The temperature of the exiting from an internal combustion engine exhaust gas is of particular importance for the subsequent in the exhaust system and equipment. In particular, exhaust aftertreatment devices sometimes require minimum temperatures for efficient exhaust gas purification. In addition, at least minimum temperatures are required for the regeneration of exhaust aftertreatment, which are to be achieved as efficiently as possible. On the other hand, certain temperature limits must not be exceeded in order not to thermally overload components such as the turbine of a turbocharger.

The temperature of the exiting from a direct-injection internal combustion engine exhaust gas corresponds to the temperature after the exhaust valve or, if a turbocharger of the internal combustion engine is directly downstream, the temperature before turbine of the turbocharger. This temperature is usually regulated by already known control methods. However, there are delays in the control of the control variable in each control loop, since these must first be determined or measured, in order then to be fed back to the controller in the feedback. In order to counteract this problem, WO 2009/1 12056 A1 proposes to provide a temperature model of a gas in a combustion chamber of a cylinder in order to predictively determine the temperature of an exhaust gas emerging from the combustion chamber of the cylinder and to supply it to a regulator. At the In addition, an internal combustion engine is provided with an HC emission model for determining the HC emission of an exhaust gas leaving the combustion chamber. This is used to control the regeneration of an emission control system, in particular a particulate filter.

The object of the present invention is to predictively determine the temperature of the exhaust gas emerging from the internal combustion engine at a given load and to set it in real terms. The engine should be operated in such a way that a predetermined temperature of the exhaust gas emerging from the internal combustion engine is established.

The object is achieved by a method for controlling the exhaust gas temperature of a direct-injection internal combustion engine, in which the burning fuel injection is divided into several individual injections and

wherein the temperature of the exhaust gas exiting the internal combustion engine at a given load is predictively determined by adjusting the position of the centroid of the heat release and the injection amount of the total combustion fuel injection by means of at least one model. Furthermore, the object is achieved by a direct-injection internal combustion engine having a control unit for controlling the temperature of an exhaust gas emerging from the internal combustion engine according to the aforementioned method.

The advantage of this method is that the temperature of the exhaust gas leaving the internal combustion engine is predictively determined, ie controlled. Thus, the temperature can be set much faster, so that it comes even with superimposed control loop only to extremely low over or undershoot the temperature to be set. By combustion fuel injections is meant all torque-forming fuel injections. Not included are post injections that are no longer combustible and serve only to provide HC emissions for subsequent exhaust aftertreatment devices. The predetermined load is dependent on the requested medium pressure of the internal combustion engine. The location of the area focal point of the heat release is based on the crank angle of the internal combustion engine. The course of the injection has a certain course of implementation, that is, the combustion result. It follows, with respect to the situation at least approximately identical, a course of heat release whose area has a center of gravity, the position of which can be determined based on the crank angle on the basis of the integral of the heat release.

The invention is based on the fact that there are basically several combinations of the quantity distribution to the individual injections for a requested mean pressure, that is to say for a given load, for several combusting injections. Depending on the distribution of quantities to the individual injections, the position of the center of gravity of the heat release and thus also the temperature of the exhaust gas emerging from the internal combustion engine shifts. When the position of the centroid of the heat release in the direction of "early", i.e. at a crank angle shortly after top dead center, is shifted, the exhaust gas temperature decreases. to a larger crank angle after top dead center, the exhaust gas temperature increases. If now the desired temperature of the exhaust gas leaving the internal combustion engine is determined, then only a possible quantity distribution and thus a position of the centroid of the heat release remain. This is used to predictively determine the optimum injection quantities for the individual injections.

In this case, a heat release model is used to set the position of the center of gravity of the heat release and the injection quantity, by means of which the heat release of the respective injections can be predicted.

Furthermore, a temperature model is used, by means of which the temperature of the exhaust gas emerging from the internal combustion engine can be predictively predicted on the basis of the position of the area center of gravity of the heat release.

To increase the accuracy of a control loop can be superimposed. The individual layers of the predictively determined injections can be adjusted by means of this regulator, for example a combustion position regulator. For a combustion position controller combustion chamber pressure sensors are provided, by means of which the combustion chamber pressure can be measured. Preferably, the fuel injection is split into a main injection and a post-injection. In principle, however, several post-injections and / or one or more pre-injections are conceivable.

If a turbocharger is provided, the temperature in front of the turbine of the turbocharger is controlled by controlling the temperature of the exhaust gas leaving the internal combustion engine.

In particular, in exhaust aftertreatment devices, such as particulate filters, the temperature of the exiting from the engine exhaust gas is controlled so that a regeneration of the exhaust gas aftertreatment device can be performed as efficiently as possible. As efficient as possible means that the lowest possible fuel requirement for regeneration occurs.

The proposed control of the exhaust gas temperature may refer to a single combustion chamber of the internal combustion engine or to a group of combustion chambers or cylinders.

Preferred embodiments are explained in more detail below with reference to the drawings. Show here

1 shows a schematic representation of an internal combustion engine with exhaust system,

FIG. 2 shows a schematic representation of a method sequence,

FIG. 3 is a diagram showing the relationship between the temperature of the

Shows exhaust gas via injection quantity and heat release center of gravity Figure 4 is a diagram showing the relationship between the mean pressure on injection quantity and heat release center of gravity and

FIG. 5 shows a diagram which shows the injection quantity via the heat release center position as a function of a predetermined exhaust gas temperature and a predetermined mean pressure.

1 shows schematically the structure of an internal combustion engine with an exhaust system. 1 A diesel internal combustion engine 2 is connected to a first exhaust pipe 3, which leads to a turbine 4 of a turbocharger. The first exhaust pipe 3 may include one or more exhaust manifolds in which the exhaust gas streams are merged into different combustion chambers or cylinders of the diesel engine 2. Here, further components, such as EGR valves and branches may also be provided.

The turbine 4 is connected via a second exhaust pipe 5 to an exhaust gas aftertreatment device in the form of an oxidation catalytic converter 6 and a particle filter 7. This is followed by a third exhaust pipe 8 connects. Both in the second exhaust pipe 5 and in the third exhaust pipe 8 further components may be provided.

In order to control the temperature of the exhaust gas leaving the diesel engine 2 upstream of the turbine 4, which is usually designated T ₃ , in the first exhaust pipe 3, a method based on the method sequence shown in FIG. 2 is provided. According to FIG. 2, in method step 10 by means of a heat release model 11 and by means of a temperature model 12 from a predetermined indicated mean pressure PMI, a predetermined temperature T ₃ of the exhaust gas leaving the internal combustion engine, the current temperature T _Sa ug of the intake air and the air mass m i _zy in the one or more cylinder (s) the position of AQ50 of the centroid of heat release and the entire Einspritzmen- ge QINJ determined.

In method step 9, the difference temperature T _De ita, which must be reached from the inlet valve to the outlet valve, is previously calculated from the predetermined temperature T _{3 of} the exhaust gas and the temperature T _S au _{g of} the intake air. In method step 13, the injection quantities q _M i and qp ₀ i of the individual injections are then determined from position aQ50 of the centroid of the heat release and the total injection quantity q _in j and the positions phi _M i and phipoi of the individual injection starts.

As a basis for the method, as shown in Figure 3, the resulting relationships of the exhaust gas temperature T ₃ over the entire injection quantity q _in j and the heat release center of gravity aQ50 serve. It can be seen that with increasing injection q _in j, the exhaust gas temperature T ₃ increases. Further, the temperature T ₃ continuously increases when the injection amount q _in j is constant and the heat release center of gravity aQ50 is shifted toward "late".

FIG. 4 shows the relationship between the mean pressure PMI over the entire injection quantity q _in j and the heat release center of gravity aQ50. It can be seen here that with increasing injection quantity q _in j the mean pressure PMI increases. Furthermore, the mean pressure PMI falls at a constant injection quantity q 1 when the heat release center position aQ50 is adjusted to "late." The dependencies of the total injection quantity q _in j on the heat release center of gravity aQ50 according to FIG 3, the dependence of the total injection quantity q _in j on the heat release center of gravity aQ50 at constant exhaust gas temperature T _3. From the context according to Figure 4, the dependence of the total injection quantity q ^ on the heat release center of gravity aQ50 at constant mean pressure This results in the diagram shown in Figure 5, according to which at a given temperature T ₃ and a given mean pressure PMI only one injection quantity qinj results at a certain heat release center of gravity aQ50 Dependence of the heat release center of gravity aQ50 divided among the individual injections. LIST OF REFERENCE NUMBERS

1 internal combustion engine with exhaust system

2 diesel engine

3 first exhaust pipe

4 turbine

5 second exhaust pipe

6 oxidation catalyst

7 particle filter

8 third exhaust pipe

9 process step

10 process step

1 1 Heat release model

12 temperature model

13 Process step aQ50 Heat release center of gravity

m _zy i mass of the intake air

phi _M i Injection start of the main injection

phipoi start of injection injection

PMI indexed medium pressure

Qinj total injection quantity

CjMI injection quantity of the main injection

CjPol injection quantity of the post-injection

T ₃ temperature of the exiting the internal combustion engine exhaust gas

Tüelta differential temperature via internal combustion engine

Tsaug temperature of the intake air

Claims

Method for controlling the exhaust gas temperature of a direct-injection internal combustion engine Claims

1 . Method for controlling the exhaust gas temperature of a direct-injection internal combustion engine (2),

wherein the burning fuel injection is divided into a plurality of individual injections and

wherein the temperature (T ₃ ) of the exhaust gas exiting the engine (2) at a given load (PMI) is adjusted by adjusting the location (aQ50) of the area of heat release and the amount of injection (q _in j) of the total fuel injection by at least one model (1 1, 12) is determined predictively.

2. The method according to claim 1, characterized in that for adjusting the position (aQ50) of the center of gravity of the heat release and the injection quantity (qinj) a heat release model (1 1) is used, by means of which the heat release of the respective injections is predictable.

3. The method according to claim 2, characterized in that for adjusting the temperature (T ₃ ), a temperature model (12) is used, by means of which the temperature (T ₃ ) of the from the internal combustion engine (2) exiting exhaust gas based on the position (aQ50 ) of the center of gravity of the heat release is predictable.

4. The method according to any one of the preceding claims, characterized in that the positions of the individual predictive injections by means of of a layered combustion controller.

5. The method according to claim 4, characterized in that Brennraumdruck- sensors are provided, by means of which the combustion chamber pressure for the regulation of the combustion position is measured.

6. The method according to any one of the preceding claims, characterized in that the combustion fuel injection is divided into a main injection and a post-injection.

7. The method according to any one of the preceding claims, characterized in that a turbocharger is provided and the temperature in front of the turbine (4) of the turbocharger by controlling the temperature (T ₃ ) of the from the internal combustion engine (2) exiting exhaust gas is controlled.

8. The method according to any one of the preceding claims, characterized in that an exhaust gas aftertreatment device, in particular a Partikelfil- ter (7) is provided, wherein the temperature (T ₃ ) of the exiting the internal combustion engine exhaust gas is controlled such that a regeneration of the exhaust aftertreatment device as efficiently as possible.

9. Direct injection internal combustion engine (2) with a control unit for the control of the temperature (T ₃ ) of an internal combustion engine (2) exiting exhaust gas according to one of the preceding claims.

10. direct injection internal combustion engine according to claim 9, characterized in that a turbocharger is provided and the temperature (T ₃ ) of the exhaust gas upstream of the turbine (4) of the turbocharger is controllable.

1 1. Direct injection internal combustion engine according to claim 10, characterized in that an exhaust aftertreatment device, in particular a particle filter (7), is provided, wherein by controlling the temperature of the Ab- is adjustable before the turbine so that an efficient regeneration of the exhaust gas aftertreatment device can be performed.

12. direct injection internal combustion engine according to one of claims 9 to 1 1, characterized in that at least one combustion chamber pressure sensor is provided for a combustion position control.

13. Direct injection internal combustion engine according to one of claims 9 to 12, characterized in that a temperature sensor for determining the temperature (T ₃ ) of the exhaust gas emerging from the internal combustion engine is provided.