WO2000071879A1 - Method and device for controlling an internal combustion engine - Google Patents

Abstract

Means for influencing the exhaust gas of said internal combustion engine are provided. When certain conditions are present, a special operating mode in which the exhaust gas preferably has a higher energy content, is initiated. In said special operating mode, a key part of the combustion process is influenced in such a way that the temperature of the exhaust gas is raised.

Description

Method and device for controlling an internal combustion engine

State of the art

The invention relates to a method and a device for controlling an internal combustion engine.

A method and a device for controlling an internal combustion engine are known from the unpublished DE 199 06 287. In the system described there, a particle filter is used that filters out particles contained in the exhaust gas. In certain operating conditions, the particle filter is regenerated by suitable measures. The exhaust gas temperature must be increased for regeneration. Operating conditions with increased exhaust gas temperatures generally result in increased fuel consumption.

Furthermore, methods and a device for controlling an internal combustion engine are known. In which a charger uses the energy contained in the exhaust gas to compress the air that is fed to the internal combustion engine. Such chargers have a delayed response in certain operating states, for example at low speeds.

Object of the invention The invention is based on the object of providing a method and a device for controlling an internal combustion engine with an exhaust gas aftertreatment system, with which the particle filter can be regenerated in a fuel-efficient manner and / or the behavior of a charger can be improved.

This object is achieved by the features characterized in the independent claims.

Advantages of the invention

With the procedure according to the invention, an advantageous regeneration of the particle filter and / or an improvement in the behavior of a charger is possible. This is achieved by influencing the center of combustion in such a way that the exhaust gas temperature and / or the energy content of the exhaust gas increases.

It is particularly advantageous if the center of combustion is shifted in the late direction. The negative effects on combustion are avoided by having at least two pre-injections before the injection.

Further particularly advantageous configurations are characterized in the subclaims.

drawing

The invention is explained below with reference to the embodiments shown in the drawing. FIG. 1 shows a block diagram of the device according to the invention, FIG. 2 shows a time course of the control signal AD for the Fuel metering, Figure 3 block diagram of part of the device according to the invention and Figure 4 is a flow diagram of the method according to the invention.

Description of exemplary embodiments

The device according to the invention is illustrated below using the example of a self-igniting internal combustion engine in which the fuel metering is controlled by means of a so-called common rail system. The invention

The procedure is not limited to these systems. It can also be used in other internal combustion engines.

100 denotes an internal combustion engine which receives fresh air via an intake line 102 and emits exhaust gases via an exhaust line 104. An exhaust gas aftertreatment means 110 is arranged in the exhaust gas line 104, from which the cleaned exhaust gases reach the surroundings via the line 106. The exhaust gas aftertreatment means 110 essentially comprises a so-called pre-catalyst 112 and a filter 114 downstream. A temperature sensor 124, which provides a temperature signal T, is preferably arranged between the pre-catalyst 112 and the filter 114. Sensors 120a and 120b are provided in front of the pre-catalytic converter 112 and after the filter 114. These sensors act as differential pressure sensor 120 and provide a differential pressure signal DP that characterizes the differential pressure between the inlet and outlet of the exhaust gas aftertreatment agent.

A turbine 162 is arranged in the exhaust line 104, which drives a compressor arranged in the intake line 102 via a shaft 164. The internal combustion engine 100 is metered fuel via a fuel metering unit 140. This measures fuel via injectors 141, 142, 143 and 144 to the individual cylinders of internal combustion engine 100. The fuel metering unit is preferably a so-called common rail system. A high pressure fuel pump delivers fuel to a pressure accumulator. The fuel reaches the internal combustion engine via the injectors.

Various sensors 151 are arranged on the fuel metering unit 140, which provide signals that characterize the state of the fuel metering unit. A common rail system is, for example, the pressure P in the pressure accumulator. Sensors 152, which characterize the state of the internal combustion engine, are arranged on the internal combustion engine 100. This is preferably a speed sensor that provides a speed signal N and other sensors that are not shown.

The output signals of these sensors go to a controller 130, which is shown as a first sub-controller 132 and a second sub-controller 134. The two partial controls preferably form a structural unit. The first sub-control 132 preferably controls the fuel metering unit 140 with control signals AD that influence the fuel metering. For this purpose, the first partial control 132 includes a fuel quantity control 136. This supplies a signal ME, which characterizes the quantity to be injected, to the second partial control 134.

The internal combustion engine is equipped with means that influence the exhaust gas. In the illustrated embodiments, this is a charger and / or a particle filter. In addition to these, other means can be seen that affect the exhaust gas. Such means for exhaust gas treatment are, for example, catalysts.

The second partial control 134 preferably controls the exhaust gas aftertreatment system and detects the corresponding sensor signals for this purpose. Furthermore, the second sub-controller 134 exchanges signals, in particular via the injected fuel quantity ME, with the first sub-controller 132. Preferably, the two controls mutually use the sensor signals and the internal signals.

The first sub-control, which is also referred to as engine control 132, controls depending on various signals that characterize the operating state of internal combustion engine 100, the state of fuel metering unit 140 and the environmental condition, as well as a signal that indicates the power and / or desired by the internal combustion engine Characterized torque, the control signal AD for controlling the fuel metering unit 140. Such devices are known and used in a variety of ways.

In diesel internal combustion engines in particular, particle emissions can occur in the exhaust gas. For this purpose, it is provided that the exhaust gas aftertreatment means 110 filter them out of the exhaust gas. Through this filtering process, 114 particles collect in the filter. These particles are then burned in certain operating states and / or after certain times to clean the filter. For this purpose, it is usually provided that the temperature in the exhaust gas aftertreatment means 110 is increased so that the particles burn in order to regenerate the filter 114.

In internal combustion engines, catalysts are often used as exhaust gas aftertreatment agents. So-called DENOX catalysts, in particular, have to be regenerated at certain intervals become. This means that deposits, in particular sulfur and / or sulfur compounds, are removed by an increased exhaust gas temperature.

In the case of particle filters, the pre-catalyst 112 is provided for increasing the temperature. The temperature is increased, for example, by increasing the proportion of unburned hydrocarbons in the exhaust gas. These unburned hydrocarbons then react in the pre-catalytic converter 112 and thereby increase its temperature and thus also the temperature of the exhaust gas that enters the filter 114.

This temperature increase of the pre-catalytic converter and the exhaust gas temperature requires an increased fuel consumption and should therefore only be carried out when this is necessary, i.e. the filter 114 is loaded with a certain proportion of particles. One possibility of recognizing the loading condition is to detect the differential pressure DP between the inlet and outlet of the exhaust gas aftertreatment agent and to determine the loading condition on the basis of this. This requires a differential pressure sensor 120.

The size B, which determines the loading state of the filter 114, is determined by means of various sensors. The size B for the load condition is then used to control the exhaust aftertreatment system, i.e. depending on the load state, a special operating state is initiated, which is also referred to as regeneration in the following.

FIG. 1 shows the device with a charger and an exhaust gas aftertreatment means 100 which comprises a particle filter 114. The procedure according to the invention can also be used in systems which are only equipped with a charger or only with an exhaust gas aftertreatment agent. According to the invention, the regeneration is initiated and / or supported by increasing the exhaust gas temperature. In order to increase the exhaust gas temperature, the center of combustion is shifted towards late. This means that a substantial part of the injection takes place after top dead center TDC. A late injection usually results in worsened exhaust emissions. This is counteracted by the fact that at least two pre-injections take place before the actual main injection.

According to the invention, there is an increase in the exhaust gas temperature in an internal combustion engine equipped with a supercharger in the presence of special operating states. The following problem can occur in internal combustion engines with a supercharger. If acceleration of the internal combustion engine is desired at small loads, that is to say small injection quantities, and / or at low speeds, the charger only reacts with a certain time delay, since in this operating state it has only little energy available for compression. It is provided according to the invention that such operating states are regarded as a special operating state in which measures to increase the exhaust gas temperature are initiated.

FIG. 2 shows the courses of the control signal A for one of the injectors 141 to 144 over time. The conditions in normal operation are plotted in sub-figure 2a. The main injection HE, in which the substantial proportion of fuel of the internal combustion engine is metered, takes place in the area of the top dead center OT. A first pre-injection VE1 takes place before the main injection HE. This is used to condition the combustion chamber. Pre-injection can reduce emissions, especially sound missions are significantly reduced. To further improve the combustion, a second pilot injection VE2 can be provided, which is shown in dashed lines. The two pre-injections occur well before top dead center.

The sub-figure 2b shows the conditions when the special operating state is present. The main injection HE, in which the substantial proportion of fuel is metered into the internal combustion engine, has been significantly shifted in the late direction. It occurs after top dead center OT. A first pre-injection VE1 takes place before the main injection HE. This is used to condition the combustion chamber before the main injection. A second pre-injection VE2 is provided for conditioning the combustion chamber before the first pre-injection VE1. The first pre-injections take place immediately before or in the area of top dead center. Furthermore, an increased amount of fuel is metered in the first pilot injection VE1 compared to normal operation.

FIG. 3 shows the device according to the invention as a block diagram. Elements already described in FIG. 1 are identified by corresponding reference symbols.

The second partial control 134 supplies a variable to a correction value determination 300, which indicates whether a special operating state is present. An internal combustion engine with a particle filter is a size B that characterizes the loading state of the filter 114. The correction value determination 300 applies a correction 310 with correction values DFB and DME. The first partial control acts on the correction with signals FB and ME. The correction then supplies the signal AD to the fuel metering unit. On the basis of various signals, the first partial control calculates signals that determine the start of injection FB and the injection duration ME. This calculation is carried out both for the main injection and for the pre-injections. If the correction value determination 300 detects that a special operating state is present, it delivers the correction values DFB and DME to the correction 310 Signal DME corrected the duration of the injection. The correction value DFB is selected such that the injection is shifted towards the late as shown in FIG. 2. The correction value DME is selected so that the torque given off by the internal combustion engine remains constant. Furthermore, the correction value DME, in particular during the pre-injection, is selected so that the emissions are reduced.

FIG. 4 shows a flow diagram to illustrate the procedure according to the invention. In a first step, different sizes are recorded. For example, the loading state B of the filter 114 is determined. The subsequent query 410 checks whether there is a special operating state. This is the case, for example, when the loading state B exceeds a threshold value. If there is no special operating state, step 400 follows again. If there is a special operating state, then in

Step 420 initiated the measures described above.

In an internal combustion engine with a supercharger, various variables, such as the speed and / or a load variable, are recorded in a first step. The subsequent query 410 checks whether there is a special operating state. This is the case, for example, when the speed N is lower and / or the load is greater than a threshold value. If there is no special operating state, step 400 follows again. If there is a special operating state, the measures described above are initiated in step 420.

It is particularly advantageous that the turbocharger output of the supercharger can be increased significantly with the same exhaust gas emission by shifting the center of combustion towards late.

The increase in fuel consumption is minimized by the fact that the measure is used only when the special operating state is present, such as when accelerating from low speeds and / or for regenerating the particle filter.

With the second pilot injection, the main injection can be shifted very late, without major emissions occurring.

Claims

Expectations 1. A method for controlling an internal combustion engine, which comprises means which influence the exhaust gas of the internal combustion engine, a special operating state being initiated in the presence of certain conditions, in which an increased energy content of the exhaust gas is desired, wherein in the special operating state a center of combustion is influenced such that the exhaust gas temperature increases. 2. The method according to claim 1, characterized in that the center of combustion is shifted towards late. 3. The method according to claim characterized in that in the special operating state at least a first and a second pre-injection takes place before a main injection. 4. The method according to any one of the preceding claims, characterized in that the means which influence the exhaust gas is a charger, a particle filter and / or a catalyst. 5. The method according to any one of the preceding claims, characterized in that the special operating state is initiated when a variable which characterizes the loading state of the particle filter exceeds a threshold value. 6. The method according to any one of the preceding claims, characterized in that a special operating state is initiated when an increase in the power of the loader is desired. 7. An apparatus for controlling an internal combustion engine, which comprises means which influence the exhaust gas of the internal combustion engine, a special operating state being initiated in the presence of certain conditions, in which an increased energy content of the exhaust gas is desired, with means which in the special operating state influence a center of combustion in such a way that the exhaust gas temperature increases.