DE19963930A1 - Method for operating an internal combustion engine, in particular a motor vehicle - Google Patents

Abstract

An internal combustion engine (1), in particular, for a motor vehicle, is disclosed, in which fuel is injected during an inlet phase in a first operating mode, or, in a second operating mode, the fuel may be injected into a combustion chamber (4), during a compression phase and whereby a catalyst (12) may be fed with exhaust gases. An additional post-combustion injection may be carried out at an operating point with a low exhaust gas temperature, by means of a controller (18).

Description

State of the art

The invention relates to a method for operating a Internal combustion engine, in particular of a motor vehicle, at the fuel in a first mode during a Suction phase or in a second operating mode during a Compression phase in a combustion chamber of the internal combustion engine is injected, and in which a catalyst with exhaust gases is applied. The invention also relates to a Control device for an internal combustion engine, in particular one Motor vehicle and an internal combustion engine in particular for a motor vehicle.

Such a method, such a control device and such an internal combustion engine are, for example, at a so-called gasoline direct injection known. There is the fuel in a homogeneous operation during the Intake phase or in a shift operation during the Compression phase in the combustion chamber of the internal combustion engine injected. The homogeneous operation is preferably for the Full load operation of the internal combustion engine is provided during shift operation for idle and part-load operation suitable is. For example, depending on the requested torque is at such  direct injection internal combustion engine between the mentioned operating modes.

For the conversion of exhaust gases in the catalytic converter It is the internal combustion engine described above required that the catalyst have a predetermined Operating temperature.

The internal combustion engine described can be in one Operating point operated at a low Exhaust gas temperature is present. Such an operating point lies z. B. in idle mode, in which the Internal combustion engine at a low idling speed is operated.

In such an idle mode, little is achieved Fuel injected into the internal combustion engine. This can have the consequence that the catalyst due to the low, resulting exhaust gas temperature cools down. So that is a conversion and thus cleaning of the exhaust gases Internal combustion engine no longer guaranteed.

Object and advantages of the invention

The object of the invention is a method for operating to create an internal combustion engine with which also Operating points with a low exhaust gas temperature sufficient cleaning of the exhaust gases is guaranteed.

This task is initiated in a procedure mentioned type according to the invention solved in that Operating point with a low exhaust gas temperature at least an additional injection after combustion is carried out. With one control unit and one Internal combustion engine of the type mentioned in the introduction the task solved accordingly.  

The additional injection makes it flammable Mixture generated in the region of the catalyst. By the still hot catalyst, this mixture is ignited and burned. The heat generated in this way is prevented cooling of the catalyst. The convertibility the catalyst remains and a cleaning of the Exhaust gas is therefore also in operating points with a guaranteed low exhaust gas temperature.

In an advantageous development of the invention the number and / or the times of the additional Injections chosen such that an operating temperature the catalyst is not undercut. That number and / or the times can be determined in advance. Alternatively or additionally, it is possible to determine the number and / or the times depending on the current one To control and / or regulate the temperature of the catalyst.

In a further advantageous development of the Invention will be the number and / or the times of additional injections chosen so that none Overheating of the catalyst takes place. Here too the number and / or the times are determined in advance and / or are currently influenced.

In an advantageous embodiment of the invention the temperature of the catalyst is measured, and the additional injections only performed when one Limit temperature is undershot. So that can Saving fuel and avoiding pollutant emissions become.

The application of the invention is particularly advantageous in Idle and / or in the second mode of operation Internal combustion engine. The idle represents an operating point at which a low exhaust gas temperature can occur.  

The idle is usually at a direct-injection internal combustion engine in shift operation carried out. The method according to the invention therefore comes preferably in shift operation and idle Internal combustion engine for use.

The realization of the inventive method in the form of a Control that for a control unit one Internal combustion engine, in particular a motor vehicle, is provided. Here is on the control Program stored on a computing device, in particular on a microprocessor, executable and for Execution of the method according to the invention is suitable. In this case, the invention is based on a Control stored program realized so that this control provided with the program in the same The invention represents how the method for its Execution the program is suitable. As a control can in particular be an electrical storage medium for Use, for example, a read-only memory or a flash memory.

Other features, applications and advantages of the Invention result from the following description of embodiments of the invention, which in the Drawing are shown. Thereby form all described or illustrated features for themselves or in any Combination the subject of the invention, regardless of their summary in the claims or their Relationship and regardless of their wording or Representation in the description or in the drawing.

Embodiments of the invention

The only figure in the drawing shows a schematic  Representation of an embodiment of a Internal combustion engine according to the invention.

The figure shows an internal combustion engine 1 of a motor vehicle, in which a piston 2 can be moved back and forth in a cylinder 3 . The cylinder 3 is provided with a combustion chamber 4 which is delimited inter alia by the piston 2 , an inlet valve 5 and an outlet valve 6 . An intake pipe 7 is coupled to the inlet valve 5 and an exhaust pipe 8 is coupled to the exhaust valve 6 .

In the area of the intake valve 5 and the exhaust valve 6, an injection valve 9 and a spark plug 10 protrude into the combustion chamber 4 . Fuel can be injected into the combustion chamber 4 via the injection valve 9 . The fuel in the combustion chamber 4 can be ignited with the spark plug 10 .

The internal combustion engine 1 has several such cylinders 3 with associated combustion chambers 4 , pistons 2 , intake valves 5 and exhaust valves 6 . Each of the cylinders 3 is also assigned an injection valve 9 and a spark plug 10 .

In the intake pipe 7 , a rotatable throttle valve 11 is accommodated, via which air can be fed to the intake pipe 7 . The amount of air supplied is dependent on the angular position of the throttle valve 11 . A catalytic converter 12 is accommodated in the exhaust pipe 8 and serves to clean the exhaust gases resulting from the combustion of the fuel.

The catalyst 12 is a storage catalytic converter 12 'which is coupled to a three-way catalyst 12 ". The catalyst 12 is thus provided, among other things, nitrogen oxides (NOx) to buffer and convert this as well as hydrocarbons (HC). For the conversion it is necessary for the catalytic converter 12 to have an operating temperature of at least about 350 degrees C. Below this operating temperature there is no or only an incomplete conversion.

A control device 18 is acted upon by input signals 19 , which represent operating variables of the internal combustion engine 1 measured by sensors. The control unit 18 generates output signals 20 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. Among other things, the control unit 18 is provided to control and / or regulate the operating variables of the internal combustion engine 1 . For this purpose, the control unit 18 is provided with a microprocessor, which has stored a program in a storage medium, in particular in a flash memory, which is suitable for carrying out the control and / or regulation mentioned.

In a first operating mode, a so-called homogeneous operation of the internal combustion engine 1 , the throttle valve 11 is partially opened or closed depending on the desired torque. The fuel is injected into the combustion chamber 4 by the injection valve 9 during an induction phase caused by the piston 2 . The injected fuel is swirled by the air simultaneously sucked in via the throttle valve 11 and is thus distributed substantially uniformly in the combustion chamber 4 . The fuel / air mixture is then compressed during the compression phase in order to then be ignited by the spark plug 10 . The piston 2 is driven by the expansion of the ignited fuel. The resulting torque depends, among other things, on the position of the throttle valve 11 in homogeneous operation. In view of a low pollutant development, the fuel / air mixture is set to lambda equal to one if possible.

In a second operating mode, a so-called stratified operation of the internal combustion engine 1 , the throttle valve 11 is opened wide. The fuel is injected from the injection valve 9 into the combustion chamber 4 during a compression phase caused by the piston 2 , specifically locally in the immediate vicinity of the spark plug 10 and at a suitable time before the ignition point. Then the fuel is ignited with the aid of the spark plug 10 , so that the piston 2 is driven in the now following working phase by the expansion of the ignited fuel. The resulting torque largely depends on the injected fuel mass in shift operation. The stratified operation is essentially provided for the idle operation and the partial load operation of the internal combustion engine 1 .

When the internal combustion engine 1 is operating, in which fuel is burned in the combustion chambers 4 in homogeneous mode or in stratified mode, exhaust gases are produced which act on the catalytic converter 12 . The resulting conversion of the exhaust gases represents an exothermic reaction, which leads to heating of the catalytic converter 12 . As a result of this heating, the catalytic converter 12 maintains its operating temperature required for a conversion.

When the internal combustion engine 1 is controlled and / or regulated by the control device 18, there are operating points in homogeneous operation and in particular in shift operation, in which only a low exhaust gas temperature is generated by the internal combustion engine 1 . This low exhaust gas temperature can have the result that the operating temperature of the catalytic converter 12 required for the conversion is not reached or fallen below. This would lead to a deterioration in exhaust gas purification.

To avoid such a cooling of the catalytic converter 12 , at least one additional injection is carried out after combustion in an operating point with a low exhaust gas temperature in stratified operation of the internal combustion engine. This additional injection, which can also be referred to as double injection, reaches the exhaust pipe 8 and to the catalytic converter 12 without being burned. There, the additionally injected fuel is burned on the hot exhaust pipe 8 and / or on the still hot catalytic converter 12 . This combustion generates heat which prevents the catalytic converter 12 from cooling down.

The number and / or the timing of such duplicate injections can be selected by the control unit 18 so that on the one hand the time required for a conversion operating temperature of the catalyst does not fall below 12, but on the other hand, no overheating of the catalyst takes place 12th

As a further measure, it can be provided that a temperature sensor 13 is assigned to the catalytic converter 12 , which measures the current temperature of the catalytic converter 12 and forwards it to the control unit 18 . In contrast to the above method, in which the double injection is carried out during the entire period in which the internal combustion engine 1 is in an operating point with a low exhaust gas temperature, the double injection by the control unit 18 can only be limited to the period in which an operating point with a low exhaust gas temperature the current temperature of the catalytic converter 12 falls below a limit value. The limit value can be, for example, approximately 400 degrees Celsius and can be stored in the control unit 18 .

The idling of the internal combustion engine 1 represents an operating point with a low exhaust gas temperature. The above-described method is therefore carried out by the control unit 18 in particular when the internal combustion engine 1 is idling. In the case of the described direct-injection internal combustion engine, idling is preferably carried out in shift operation.

If necessary, for example during the warming up of the Internal combustion engine, but can also idle in Homogeneous operation. In this case it can described procedures are applied accordingly.

Claims (9)

1. Method for operating an internal combustion engine ( 1 ), in particular a motor vehicle, in which fuel is injected into a combustion chamber ( 4 ) of the internal combustion engine ( 1 ) in a first operating mode during an induction phase or in a second operating mode, and in which a Exhaust gases are applied to the catalytic converter ( 12 ), characterized in that at an operating point with a low exhaust gas temperature, at least one additional injection is carried out after combustion. 2. The method according to claim 1, characterized in that the number and / or the times of the additional injections are chosen such that an operating temperature of the catalyst ( 12 ) is not fallen below. 3. The method according to any one of claims 1 or 2, characterized in that the number and / or the times of the additional injections are chosen such that no overheating of the catalyst ( 12 ) takes place. 4. The method according to any one of claims 1 to 3, characterized in that the temperature of the catalyst ( 12 ) is measured, and that the additional injections are only carried out when the temperature falls below a limit. 5. The method according to any one of claims 1 to 4, characterized by the application when the internal combustion engine is idling ( 1 ). 6. The method according to any one of claims 1 to 5, characterized by the application in the second operating mode of the internal combustion engine ( 1 ). 7. Control element, in particular flash memory, for a control device ( 18 ) of an internal combustion engine ( 1 ), in particular a motor vehicle, on which a program is stored which can be run on a computing device, in particular on a microprocessor, and for executing a method according to one of the Claims 1 to 6 is suitable. 8. Control unit ( 18 ) for an internal combustion engine ( 1 ), in particular of a motor vehicle, wherein in the internal combustion engine ( 1 ) fuel can be injected into a combustion chamber ( 4 ) in a first operating mode during an intake phase or in a second operating mode during a compression phase, and a catalyst ( 12 ) can be acted upon with exhaust gases, characterized in that at least one additional injection after combustion can be carried out by the control device ( 18 ) at an operating point with a low exhaust gas temperature. 9. Internal combustion engine ( 1 ), in particular for a motor vehicle, in which fuel can be injected into a combustion chamber ( 4 ) in a first operating mode during an intake phase or in a second operating mode during a compression phase, in which exhaust gas can be applied to a catalytic converter ( 12 ), and with a control unit ( 18 ), characterized in that at least one additional injection can be carried out after combustion by the control unit ( 18 ) at an operating point with a low exhaust gas temperature.