DE102018004145A1 - Method for operating an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine, in particular 4-stroke internal combustion engine, in a Katalysatorheizbetrieb in which at least one cylinder interior of the internal combustion engine via at least one intake passage of the internal combustion engine supplied air together with an amount of fuel in the at least one cylinder interior to form exhaust gas and the exhaust gas is supplied via at least one exhaust passage of the internal combustion engine at least one exhaust gas catalyst of the internal combustion engine to heat the at least one exhaust gas catalyst to a predetermined operating temperature. A first subset (10) of the amount of fuel is introduced via the at least one intake passage into the cylinder interior and a second subset (20) of the amount of fuel directly into the cylinder interior.

Description

The invention relates to a method for operating an internal combustion engine, in particular four-stroke internal combustion engine, in a Katalysatorheizbetrieb, wherein at least one cylinder interior of the internal combustion engine via at least one intake tract of the internal combustion engine supplied air together with an amount of fuel in the at least one cylinder chamber to form exhaust gas and the exhaust gas is supplied via at least one exhaust passage of the internal combustion engine at least one exhaust gas catalyst of the internal combustion engine to heat the at least one exhaust gas catalyst to a predetermined operating temperature.

After a cold start, ie in cold cylinder interiors, which can also be referred to as combustion chambers, internal combustion engines emit particularly large amounts of pollutants, such as hydrocarbons (HC) and carbon monoxide (CO). In order to comply with respective prescribed by the legislature emission limits, an operation of the internal combustion engine is sought, in which an exhaust gas catalyst is heated as soon as possible after the cold start to a temperature at which a sufficient conversion of pollutants is possible. This temperature is also referred to as so-called light-off temperature.

In order to achieve the fastest possible heating of the catalytic converter to the light-off temperature, internal combustion engines are often operated in air deficiency, ie in a so-called substoichiometric combustion of a fuel-air mixture to ensure, for example, a reliable ignition of the fuel-air mixture. As a further measure for accelerating the heating of the catalytic converter, a so-called secondary air injection is known, by which a post-oxidation of the exhaust gas generated as a result of the combustion of the fuel-air mixture in the exhaust duct or in the catalytic converter can be effected. A disadvantage of the known measures, however, is an increased fuel consumption due to the substoichiometric (rich) fuel-air mixture and various complex design measures in connection with the secondary air injection.

To avoid such disadvantages, proposes the DE 10 2004 017 988 A1 a method for operating a spark-ignition internal combustion engine with direct fuel injection after the cold start. There is a pre-injection of a first amount of fuel in an intake stroke of the internal combustion engine, by which a homogeneous, lean fuel-air mixture is formed. Subsequently, a main injection of a second amount of fuel takes place in a working stroke of the internal combustion engine immediately before the ignition in the combustion chamber, with which in the region of a spark plug a stratified, rich fuel-air mixture is formed, the main injection as a multiple injection with multiple layer injections in short time sequence is carried out.

Moreover, in direct injection internal combustion engines during a catalyst heating operation, it is known to split into early injection of the fuel during a suction stroke and additionally or alternatively a compression stroke of a piston of the internal combustion engine and a late injection just before or during ignition (spark ignition).

Combustion engines used with hybrid drives, which are used, for example, in so-called plug-in hybrid motor vehicles, often operate at significantly lower operating temperatures, in particular lower average operating temperatures, compared to operation in a conventional, purely internal combustion engine drive due to a principle reduced operating time. This results in worse conditions for mixture formation, ie for the preparation of the fuel-air mixture, which can result in increased pollutant emissions and a dilution of an engine oil by fuel as a result. Of the dilution of the engine oil, which can also be referred to as Schmierölverdünnung, especially internal combustion engines are affected in the cylinder interiors (combustion chambers) fuel is injected directly. Such internal combustion engines are also referred to as direct-injection internal combustion engines.

To improve the mixture formation is from the DE 10 2015 219 042 A1 a method for operating an internal combustion engine is known in which a direct injection of fuel via a first injection valve and a port injection of fuel via a second injection valve. After a cold start of the internal combustion engine is doing a hundred percent intake manifold injection to meet all requirements for mixture formation and the exhaust gas.

Object of the present invention is to provide a method of the type mentioned, by which even at a frequently interrupted operation of an internal combustion engine, a rapid heating of a catalytic converter can be achieved on the operating temperature.

This object is achieved by a method having the features of claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

The invention is based on a method for operating an internal combustion engine, in particular a four-cycle internal combustion engine, in a catalyst heating operation in which at least one cylinder interior of the internal combustion engine is supplied with air via at least one intake duct of the internal combustion engine together with an amount of fuel in the at least one cylinder interior is converted by exhaust gas and the exhaust gas is supplied via at least one exhaust passage of the internal combustion engine at least one exhaust gas catalyst of the internal combustion engine to heat the at least one exhaust gas catalyst to a predetermined operating temperature. The cylinder interior can generally also be referred to as a combustion chamber, in which a mixture of the air and the amount of fuel is converted, that is burned in other words. The operating temperature can also be referred to as the light-off temperature.

In order to achieve a rapid heating of the catalytic converter to its operating temperature even with a frequently interrupted operation of the internal combustion engine, it is provided according to the invention that a first subset of the amount of fuel via the at least one intake into the cylinder interior and a second subset of the amount of fuel introduced directly into the cylinder interior becomes. This is advantageous since, as a result, the introduction of the first subset into the intake passage, which may be a suction pipe of the internal combustion engine, a good homogenization of a mixture of the air and the first subset can be achieved, with an entry of fuel in an engine oil amount of the internal combustion engine can be kept particularly low. The second subset of the amount of fuel is introduced directly into the cylinder chamber, whereby particularly good conditions for the implementation, in other words a fire of the mixture of the second subset and the air and thus provided for the ignition of the (total) amount of fuel and the air is. By direct introduction of the second subset in the cylinder interior can be generated in this increased turbulence, which can lead to a faster and more complete combustion of the mixture of the amount of fuel and air and, consequently, to a faster heating of the catalytic converter to its predetermined operating temperature.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing (s). The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or alone in the single figure can be used not only in the respectively indicated combination but also in other combinations or alone, without the frame to leave the invention.

The single FIGURE shows a diagram which shows respective injection intervals of a first subset of a fuel quantity and a second subset of a fuel quantity in a method for operating an internal combustion engine in a Katalysatorheizbetrieb over a crank angle curve.

The single figure shows a diagram in which an exhaust valve lift course AH a gas exchange valve designed as an outlet valve and an inlet valve lift course EH one, designed as an inlet valve gas exchange valve of a not further illustrated here, designed as a four-stroke internal combustion engine internal combustion engine over a crank angle curve [° KW] shows. In addition, a cylinder pressure curve pz , which is qualitatively adjusted in the present operation of the internal combustion engine in a Katalysatorheizbetrieb applied. In the catalytic converter heating operation, at least one cylinder interior of the internal combustion engine is supplied with at least one intake passage of the internal combustion engine together with an amount of fuel in the at least one cylinder interior to form exhaust gas and the exhaust gas is supplied via at least one exhaust passage of the internal combustion engine at least one exhaust gas catalyst of the internal combustion engine to the at least to heat a catalytic converter to a predetermined operating temperature (light-off temperature). This will be a first subset 10 the amount of fuel through the at least one intake passage into the cylinder interior and a second subset 20 the amount of fuel introduced directly into the cylinder interior.

The first subset 10 is timed before a compression stroke 40 and before the second subset 20 initiated, whereby a particularly favorable homogenization of a fuel-air mixture from the first subset and the air can be achieved already in the intake. In addition to the compression stroke 40 are in the diagram also an intake stroke 30 , an expansion stroke 50 and a Ausschiebetakt 60 So with others Words all work cycles of the internal combustion engine specified qualitatively.

The second subset 20 is introduced in the present case as an ignition injection into the cylinder interior. In other words, the introduction of the second subset takes place 20 in the cylinder interior as ignition injection. By means of the ignition injection can at a spark plug of the internal combustion engine at the time of ignition 70 (Ignition) particularly good conditions for a fire of the fuel-air mixture are provided.

The ignition 70 the amount of fuel is during the second subset 20 is introduced into the cylinder interior. As a result, a particularly rapid ignition of the fuel-air mixture still during the introduction of the second subset 20 be achieved in the cylinder interior. As a result, the method can also be used at higher rotational speeds of a crankshaft of the internal combustion engine in order to bring about the heating of the exhaust gas catalytic converter to the operating temperature.

The second subset 20 is present after an upper ignition dead center ZOT a cylinder interior at least partially limiting, not shown here piston of the internal combustion engine introduced into the cylinder interior and the fuel quantity after the upper ignition dead center ZOT as a result of ignition 70 is inflamed. This results in spite of the Katalysatorheizbetriebs a comparatively favorable focus of combustion. Next to the upper ignition dead center ZOT of the piston are respective bottom dead centers in the diagram UT of the piston and an upper charge exchange dead center LW-OT applied to the piston.

The first subset is preferred 10 introduced through a first electromagnetically actuated multi-hole valve via the at least one intake passage into the cylinder interior. This allows a particularly appropriate dosage of the first subset 10 , The first subset 10 is injected in the present case with a first fuel pressure between 5 bar and 10 bar in the at least one intake passage, whereby a particularly favorable homogenization of the mixture from the first subset 10 and the air in the intake passage is achieved.

The second subset 20 is introduced in the present case by a second electromagnetically actuated multi-hole valve or alternatively by a piezoelectrically operable, outwardly opening annular gap valve in the cylinder interior. This allows a particularly appropriate dosage of the second subset 20 , The expression "opening outwards" means that the annular gap valve is designed to open in the direction of an environment of the annular gap valve.

The second subset 20 may preferably be injected into the cylinder interior with a second fuel pressure which is greater than 200 bar. This allows a particularly favorable jet break one of the second subset 20 formed fuel jet.

In the method, the second subset 20 be injected by the second electromagnetically actuated multi-hole valve or alternatively by the piezoelectrically actuated annular gap valve centrally in the cylinder interior, whereby, for example, a wetting of the piston or a wetting of the cylinder interior bounding cylinder walls and thus a Schmierölverdünnung (entry of fuel into the engine oil ) can be avoided.

Overall, in the method, a direct injection of the second subset 20 with an injection of the first subset 10 in the intake passage, which may be a suction pipe of the internal combustion engine combined. In Katalysatorheizbetrieb is the total, from the first subset 10 and the second subset 20 existing fuel quantity thus divided into the injection into the intake port and in the direct injection. The injection of the first subset 10 , which can also be referred to as the first injection, takes place in the method before the compression stroke 40 , which can also be referred to as the compression phase. The injection of the second subset 20 , which can also be referred to as the second injection, takes place directly in the cylinder interior (combustion chamber) shortly before or during ignition 70 , which in this case after the top ignition dead center ZOT takes place (ignition injection).

LIST OF REFERENCE NUMBERS

10

first subset

20

second subset

30

intake

40

compression stroke

50

expansion stroke

60

exhaust stroke

70

ignition

AH

Auslassventilhubverlauf

EH

Einlassventilhubverlauf

LW-OT

Upper landing change dead center

pz

Cylinder pressure curve

UT

bottom dead center

ZOT

upper ignition dead center

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 102004017988 A1 [0004]
• DE 102015219042 A1 [0007]

Claims (8)

Method for operating an internal combustion engine, in particular 4-stroke internal combustion engine, in a Katalysatorheizbetrieb, wherein at least one cylinder interior of the internal combustion engine via at least one intake passage of the internal combustion engine supplied air is reacted together with an amount of fuel in the at least one cylinder interior to form exhaust gas and the exhaust gas is supplied to at least one exhaust gas catalyst of the internal combustion engine via at least one exhaust passage of the internal combustion engine to heat the at least one catalytic converter to a predetermined operating temperature, characterized in that a first subset (10) of the amount of fuel via the at least one intake passage into the cylinder interior and a second subset ( 20) of the amount of fuel is introduced directly into the cylinder interior. Method according to Claim 1 , characterized in that the first subset (10) is introduced in time before a compression stroke (40) and before the second subset (20). Method according to Claim 1 or 2 , characterized in that the second subset (20) is initiated as an ignition injection in the cylinder interior. Method according to one of the preceding claims, characterized in that an ignition (70) of the amount of fuel takes place while the second subset (20) is introduced into the cylinder interior. Method according to Claim 4 , characterized in that the second subset (20) initiated after an upper ignition dead center (ZOT) in the cylinder interior and the fuel quantity after the upper ignition dead center (ZOT) due to the ignition (70) is inflamed. Method according to one of the preceding claims, characterized in that the first subset (10) is introduced via a first electromagnetically actuable multi-hole valve via the at least one intake passage into the cylinder interior. Method according to one of the preceding claims, characterized in that the second subset (20) by a second electromagnetically actuated multi-hole valve or by a piezoelectrically actuated, outwardly opening annular gap valve is introduced into the cylinder interior. Method according to Claim 7 , characterized in that the second subset (20) is injected centrally into the cylinder interior by the second electromagnetically operable multi-hole valve or by the piezoelectrically operable annular gap valve.

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