DE19963925A1 - Method for operating a storage catalytic converter of an internal combustion engine - Google Patents

Abstract

The invention relates to an internal combustion engine (1), in particular for a motor vehicle, which is provided with a storage catalyst (12'). Said storage catalyst can be fed with and can discharge nitrous oxides. A temperature sensor (13, 14) is provided for measuring the temperature of the exhaust gas that flows through the storage catalyst (12') and/or for measuring the temperature of the storage catalyst (12'). The measured temperature is compared with a threshold value, using a control device (18).

Description

State of the art

The invention relates to a method for operating a Storage catalyst of an internal combustion engine in particular a motor vehicle in which the storage catalytic converter with Nitrogen oxides is loaded and unloaded. Also concerns the Invention a control device for an internal combustion engine in particular a motor vehicle and a 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.  

It is particularly useful for performing shift operation required that a storage catalytic converter is available, with which nitrogen oxides are temporarily stored can to them during a subsequent homogeneous operation to reduce. This storage catalyst is in the Load shift operation with the nitrogen oxides and in Unload homogeneous operation. This loading and unloading, thermal stress and poisoning leads to a Storage catalytic converter aging.

Object and advantages of the invention

The object of the invention is a method for operating of a storage catalytic converter of an internal combustion engine create with which the aging of the storage catalytic converter can be recognized.

This task is initiated in a procedure mentioned type according to the invention solved in that the Temperature of the flowing through the storage catalytic converter Exhaust gas and / or the temperature of the storage catalytic converter is measured and compared with a threshold value. At a control unit and an internal combustion engine each the type mentioned at the beginning will be the task accordingly solved.

Discharging the storage catalytic converter is exothermic Reaction that gives off heat. This leads to a Temperature increase of the exhaust gases or the storage catalytic converter even during the release of nitrogen oxides. The aging of the Storage catalytic converter leads to a lower one Storage capacity of nitrogen oxides in the same. This is synonymous with a lower temperature increase when discharging the storage catalytic converter, because less Nitrogen oxides are to be discharged. This reduction in Temperature rise is therefore a measure of the aging of the  Storage catalytic converter.

By measuring the temperature of the Exhaust gas or the storage catalyst can thus by Control unit on the age-related condition of the Storage catalyst are closed. In particular, can from the control unit when a threshold value is reached aging is no longer acceptable, at the z. B. no longer sufficient exhaust gas cleaning is guaranteed.

It is thus a simple and by the invention inexpensive detection of the aging of the Storage catalytic converter possible. The procedure after Invention is stable and independent of others Influences. In particular, the invention is broad regardless of changes in the sensors involved.

In an advantageous development of the invention measured a temperature increase and with a Temperature increase compared to that of a new one Storage catalytic converter has been measured and it becomes the Difference compared to an upper limit. Alternatively or in addition, an increase in temperature is measured and compared with a modeled temperature increase, and it becomes the difference with an upper limit compared. An alternative or additional will be one Temperature increase measured and with a Temperature increase compared to that at a Limit catalyst has been measured and it becomes the Difference compared to a lower limit. All three Possibilities allow a simple and effective Detection of the aging condition of the storage catalytic converter.

In a further advantageous development of the Invention a maximum temperature is measured and with  compared to a lower threshold. This enables one even more simplified detection of the state of aging of the storage catalytic converter.

It is particularly advantageous if the temperature in and / or measured immediately after the storage catalytic converter becomes. By combining the two temperature measurements the accuracy of the entire process can be increased.

In an advantageous embodiment of the invention the inventive method for diagnosing Storage capacity of the storage catalytic converter used.

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 .

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 combined with a three-way catalytic converter 12 ". The catalyst 12 is thus provided, among other things, nitrogen oxides (NOx) cache. In the catalyst 12, a temperature sensor 13 is provided. Alternatively, or In addition, a temperature sensor 14 is provided in the exhaust pipe immediately after the catalytic converter 12 .

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 .

The storage catalytic converter 12 ′ of the catalytic converter 12 is loaded with nitrogen oxides during the shift operation. In a subsequent homogeneous operation, the storage catalytic converter 12 ′ is discharged again and the nitrogen oxides are reduced by the three-way catalytic converter 12 ″.

The storage catalytic converter 12 'absorbs sulfur over time during its continuous loading and unloading with nitrogen oxides. This leads to a limitation of the storage capacity of the storage catalytic converter 12 ′, which is referred to below as aging.

The discharge of the storage catalytic converter 12 ′ represents an exothermic reaction in which heat is generated. This results in an increase in the temperature of the exhaust gases flowing through the storage catalytic converter 12 '. This temperature increase is measured by the temperature sensor 13 and / or by the temperature sensor 14 . At the same time, the exothermic reaction also increases the temperature of the storage catalytic converter 12 ′ itself, which is measured alternatively or additionally by the temperature sensor 13 and possibly also by the temperature sensor 14 .

Due to the aging of the storage catalytic converter 12 ', the ability to store nitrogen oxides in the storage catalytic converter 12 ' decreases. At the same time, this leads to a reduction in the discharge process due to the lower storage of nitrogen oxides. The temperature rise due to the exothermic reaction resulting from the discharge is thus also lower. This lower temperature increase is in turn measured by the temperature sensor 13 and / or by the temperature sensor 14 .

The currently measured temperature increase during operation of the internal combustion engine 1 is monitored by the control unit 18 . This can be done in that the instantaneous temperature increase is compared with an increase in temperature that has been measured at a new storage catalyst 12 'and a new catalyst 12th Alternatively or additionally, this can be done by comparing the current temperature increase with a modeled temperature increase. Alternatively or additionally, a comparison can also be made with an increase in temperature of a so-called limit catalyst. The limit catalytic converter is a catalytic converter that is just still operational or has just become defective.

When comparing with a new storage catalytic converter, the difference between the currently measured temperature increase and the temperature increase of the new storage catalytic converter becomes ever greater. If the difference between the current increase in temperature to the temperature increase of the new storage catalyst an upper threshold, it is concluded by the control device 18 that the storage catalytic converter 12 'of the catalyst 12 has now reached the aging, which is no longer acceptable in terms of a sufficient exhaust gas purification . The control unit 18 then generates z. For example, a signal that can be recognized by the driver or by a workshop, and the necessary replacement of the storage catalytic converter 12 'or the entire catalyst 12 indicates.

When using the modeled temperature increase, the difference to the current temperature increase is also becoming ever larger, so that the difference is compared with an associated upper threshold value, upon reaching which the storage catalytic converter 12 'must be replaced.

When using a limit catalytic converter, the difference to the current temperature increase becomes smaller and smaller, so that the difference is compared with an associated lower threshold value, upon reaching which the storage catalytic converter 12 'must be replaced.

Alternatively or additionally, the comparison absolute temperatures.

The temperature increase due to the exothermic reaction during the discharge of the storage catalytic converter 12 ′ is synonymous with a maximum temperature that is measured by the temperature sensor 13 and / or the temperature sensor 14 . This maximum temperature becomes lower over time due to the aging of the storage catalytic converter 12 '. If the maximum temperature falls below a lower threshold value, the storage catalytic converter 12 'must be replaced.

The above method can be used continuously during the operation of the internal combustion engine 1 . Alternatively or additionally, it is possible to use the method specifically for diagnosing the storage capacity of the storage catalytic converter 12 '.

Claims (10)

1. A method for operating a storage catalytic converter ( 12 ') of an internal combustion engine ( 1 ), in particular a motor vehicle, in which the storage catalytic converter ( 12 ') is loaded and unloaded with nitrogen oxides, characterized in that the temperature of the storage catalytic converter ( 12 ') flowing exhaust gas and / or the temperature of the storage catalytic converter ( 12 ') is measured and compared with a threshold value. 2. The method according to claim 1, characterized in that a temperature increase is measured and compared with a temperature increase which has been measured in a new storage catalytic converter ( 12 '), and in that the difference is compared with an upper limit value. 3. The method according to any one of claims 1 or 2, characterized characterized in that a temperature increase is measured and is compared with a modeled temperature increase, and that the difference is compared to an upper limit becomes. 4. The method according to any one of claims 1 to 3, characterized characterized in that a temperature increase is measured and is compared with a temperature increase that occurs at a Limit catalyst has been measured and that the difference is compared with a lower limit.   5. The method according to any one of claims 1 to 4, characterized characterized in that a maximum temperature is measured and with a lower threshold value is compared. 6. The method according to any one of claims 1 to 5, characterized in that the temperature in and / or immediately after the storage catalyst ( 12 ') is measured. 7. The method according to any one of claims 1 to 6, characterized by the use for diagnosing the storage capacity of the storage catalytic converter ( 12 '). 8. Control element, in particular flash memory, for a control unit ( 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 7 is suitable. 9. Control device ( 18 ) for an internal combustion engine ( 1 ), in particular of a motor vehicle, the internal combustion engine ( 1 ) having a storage catalytic converter ( 12 ') which can be loaded and unloaded with nitrogen oxides, characterized in that a temperature sensor ( 13 , 14 ) for measuring the temperature of the exhaust gas flowing through the storage catalytic converter ( 12 ') and / or the temperature of the storage catalytic converter ( 12 ') is provided, and that the measured temperature is comparable to a threshold value by the control device ( 18 ). 10. Internal combustion engine ( 1 ), in particular for a motor vehicle, with a storage catalytic converter ( 12 ') which can be loaded and unloaded with nitrogen oxides, and with a control unit ( 18 ), characterized in that a temperature sensor ( 13 , 14 ) for measuring the Temperature of the exhaust gas flowing through the storage catalytic converter ( 12 ') and / or the temperature of the storage catalytic converter ( 12 ') is provided, and that the measured temperature is comparable to a threshold value by the control device ( 18 ).