DE19930086A1 - Method for operating an internal combustion engine - Google Patents

Abstract

The invention relates to an internal combustion engine (1), especially for a motor vehicle, which is provided with a combustion chamber (4). Fuel can be directly injected into said combustion chamber by means of an injection valve (9) during an induction phase in a first mode of operation or during a compression phase in a second mode of operation and can be ignited by a spark plug (10) . Additional delayed fuel injection into said combustion chamber (4) is carried out in order to purify the storage catalyst.

Description

State of the art

The invention relates to a method for operating a Internal combustion engine, in particular a motor vehicle, at the fuel in a first mode during a Suction phase or in a second operating mode during a Compression phase injected directly into a combustion chamber and ignited. 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. Possibly. are also other operating modes intended. For example, depending on the requested torque is at such  direct injection internal combustion engine between the mentioned operating modes.

It is particularly useful for performing shift operation requires that a storage catalytic converter is present, with which nitrogen oxides are temporarily stored can to them during a subsequent homogeneous operation to reduce in a three-way catalyst. This Storage catalytic converter is in shift operation with the Load nitrogen oxides and unload them in homogeneous operation. The sulfur content of the fuel leads to a Poisoning of the storage catalytic converter with sulfur. It must therefore a so-called sulfur detoxification again and again of the storage catalytic converter. This is a suitable fuel / air mixture and a temperature of the exhaust gas supplied to the storage catalytic converter required in the normal operation of the Internal combustion engine not or only under a high load is achieved.

The object of the invention is a method for operating to create an internal combustion engine with which also an operation of the internal combustion engine with low loads sulfur detoxification of the storage catalytic converter is possible is.

This task is initiated in a procedure mentioned type according to the invention solved in that Purpose of detoxifying a storage catalyst additional late fuel injection into the Combustion chamber is carried out. With a control unit and an internal combustion engine of the type mentioned the task is solved accordingly.

There is therefore a double injection. In addition to the injection taking place in the  Shift operation or in homogeneous operation is also an later injection of fuel into the combustion chamber carried out. This additional fuel leads to one increased combustion, which in turn leads to an increase the temperature of the exhaust gas leads. This hotter exhaust then arrives at the storage catalytic converter and has one there Sulfur detoxification results.

The method according to the invention can be carried out at any time become. In homogeneous operation, as well as in shift operation the additional late injection will be added. This makes it possible even in normal operation of the Internal combustion engine detoxifies the sulfur Storage catalytic converter to carry out without much effort.

In an advantageous development of the invention the additional injection during the expansion phase or during the ejection phase from the injector carried out. This ensures that the additional injection occurs later than the normal one Injection in shift operation or in homogeneous operation.

It is particularly advantageous if the additional injected fuel is ignited by the spark plug. This ensures that the additional fuel is burned in any case and not unburned to the Environment is released.

In an advantageous development of the invention the additional fuel over a given period of time is injected continuously. This ensures that a complete sulfur detoxification of the Storage catalyst is performed. The period can depend on the operating parameters of the internal combustion engine and can also be applicable.  

It when the temperature of the Exhaust gas is increased to about 650 degrees or more and when the detoxification of the storage catalytic converter is repeated. In this way it becomes a permanent one Storage capacity of the storage catalytic converter reached.

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 program stored 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, 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.

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 , at least one inlet valve 5 and at least one 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 .

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 catalytic converter 12 is a three-way catalytic converter which is combined with a storage catalytic converter or a combination of a storage catalytic converter and a three-way catalytic converter. The catalytic converter 12 is thus intended, inter alia, to temporarily store nitrogen oxides (NO _x ).

The combustion of the fuel in the combustion chamber 4 causes the piston 2 to move back and forth, which is transmitted to a crankshaft (not shown) and exerts a torque thereon.

A control device 18 is acted upon by input signals 19 , which represent operating variables of the internal combustion engine 1 measured by sensors. For example, the control unit 18 is connected to an air mass sensor, a lambda sensor, a speed sensor and the like. Furthermore, the control unit 18 is connected to an accelerator pedal sensor, which generates a signal that indicates the position of an accelerator pedal that can be actuated by a driver and thus the requested torque. 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. For example, the control unit 18 is connected to the injection valve 9 , the spark plug 10 , the throttle valve 11 and the like and generates the signals required to control them.

Among other things, the control unit 18 is provided to control and / or regulate the operating variables of the internal combustion engine 1 . For example, the fuel mass injected into the combustion chamber 4 by the injection valve 9 is controlled and / or regulated by the control unit 18, in particular with regard to low fuel consumption and / or low pollutant development. 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 sucked in simultaneously 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 as close to one as possible around lambda.

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 .

The storage catalytic converter of the catalytic converter 12 is loaded with nitrogen oxides during the shift operation. In a subsequent homogeneous operation, the storage catalytic converter is discharged again and the nitrogen oxides are reduced by the three-way catalytic converter. The storage catalytic converter absorbs sulfur over time. This leads to a limitation of the storage capacity of the storage catalytic converter. For this reason, a so-called sulfur detoxification must take place again and again.

In order to carry out the sulfur detoxification, it is necessary to supply the catalytic converter 12 with exhaust gas which is hotter than usual and which therefore exceeds a predetermined temperature. This temperature can be, for example, 650 degrees. This exhaust gas must also be mixed at least temporarily under-stoichiometrically.

For this purpose, the internal combustion engine 1 is operated in an operating mode which corresponds to the so-called cat heating. This operating mode is used per se to quickly heat the catalyst 12 to its operating temperature in the warm-up phase of the internal combustion engine 1 , provided that it has not yet reached it.

In the catalytic converter heating mode, a second late fuel injection is carried out after the compression phase in addition to the fuel injection that takes place during the intake phase or during the compression phase. Kat heating is therefore a double injection in which additional fuel is injected directly into combustion chamber 4 of internal combustion engine 1 during the expansion phase or during the exhaust phase.

This additional fuel is ignited and burned in the combustion chamber 4 or in the exhaust pipe 8 or in the area of the exhaust. This can be done either directly with the help of the spark plug 10 . It is also possible for the additional fuel to ignite and burn automatically without the spark plug 10 having to be operated, due to the combustion already taking place.

The late fuel injected increases the temperature of the exhaust gas. The temperature reaches values of around 650 degrees and higher. As stated, this increase in temperature per se is used to quickly heat the catalyst 12 up to its operating temperature.

In the present case, however, the catalytic converter heating is used to detoxify the storage catalytic converter due to the increased temperature of the exhaust gas. The Kat heating is therefore carried out for the specified period of time required for the sulfur detoxification. This leads to an increased temperature of the exhaust gas, which - as has been explained - leads to detoxification of the storage catalytic converter of the catalytic converter 12 .

This sulfur detoxification of the storage catalyst an additional late fuel injection then repeated over and over again Criteria performed again so the Storage capacity of the storage catalytic converter is retained.

Claims (9)

1. Method for operating an internal combustion engine ( 1 ), in particular a motor vehicle, in which fuel is injected directly from an injection valve ( 9 ) into a combustion chamber ( 4 ) and from a spark plug in the fuel in a first operating mode during an intake phase or in a second operating mode during a compression phase ( 10 ) is ignited, characterized in that an additional late injection of fuel into the combustion chamber ( 4 ) is carried out for the purpose of detoxifying a storage catalytic converter. 2. The method according to claim 1, characterized in that the additional injection is carried out during the expansion phase or during the exhaust phase of the injection valve ( 9 ). 3. The method according to any one of claims 1 or 2, characterized in that the additionally injected fuel is ignited by the spark plug ( 10 ). 4. The method according to any one of claims 1 to 3, characterized characterized that the additional fuel over a predetermined period is injected continuously. 5. The method according to any one of claims 1 to 4, characterized characterized that the temperature of the exhaust gas to about 650 degrees or more is increased.   6. The method according to any one of claims 1 to 5, characterized characterized that the detoxification of the Storage catalyst is repeated. 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 device ( 18 ) for an internal combustion engine ( 1 ), in particular of a motor vehicle, the internal combustion engine ( 1 ) having a combustion chamber ( 4 ), in the fuel in a first operating mode during an intake phase or in a second operating mode during a compression phase directly from one Injection valve ( 9 ) can be injected and ignited by a spark plug ( 10 ), characterized in that the control unit ( 18 ) can be used to detoxify an additional late injection of fuel into the combustion chamber ( 4 ) for the purpose of detoxifying a storage catalytic converter. 9. Internal combustion engine ( 1 ), in particular for a motor vehicle with a combustion chamber ( 4 ), into which fuel can be injected directly from an injection valve ( 9 ) and from a spark plug ( 10 ) in a first operating mode during an intake phase or in a second operating mode during a compression phase is flammable, and with a control device ( 18 ), characterized in that the control device ( 18 ) can be used to detoxify a storage catalytic converter to perform an additional late injection of fuel into the combustion chamber ( 4 ).