Method of monitoring the operation of a catalytic converter

• US 5,610,844 A
• Filed: 02/17/1995
• Issued: 03/11/1997
• Est. Priority Date: 08/17/1992
• Status: Expired due to Term

• Current Assignee: Emitec Gesellschaft für Emissionstechnologie mbH (Continental AG)
• Original Assignee: Emitec Gesellschaft für Emissionstechnologie mbH (Continental AG)
• Inventors: Maus, Wolfgang, Bruck, Rolf, Swars, Helmut
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): Stamber, Eric W.
• Application Number:
  US08/390,676
• Time in Patent Office: 753 Days
• Field of Search: 364/557, 364/496, 364/431.05, 364/431.06, 364/431.08, 60/274, 60/277, 60/285, 60/286, 60/287, 73/118.1
• US Class Current: 700/274
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 13/008 Mounting or arrangement of exhaust sensors in or on exhaust apparatus sensor arrangements for engine control F02D41/1439
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F02B 2075/027 four
• CPC Class Codes: F02D 41/0235 in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for analyzing a condition of at least one partial volume of a catalytic converter through which a gas mixture flows, includes measuring a temperature with a sensor at least at one location or in a region within a partial volume during a change of chemical and/or physical properties of the gas mixture. The location or the region and a configuration of the sensor are selected in such a way that a reaction of the measured temperature to a change of the properties of the gas mixture is at least approximately representative of a reaction of the temperature in the partial volume of the catalytic converter. Set point values are determined for the respective change in the properties of the gas mixture on the basis of a thermodynamic model while taking physical boundary conditions and properties of the partial volume into account. The reaction of the measured temperature is determined and compared with the set point values.

Claims

1. A method for analyzing a condition of at least one partial volume of a catalytic converter through which a gas mixture flows, which comprises:

triggering a change of at east one of chemical and physical properties of a gas mixture flowing through a catalytic converter at least twice in defined intervals for creating a particular change pattern differing from all other conceivable operational conditions in an internal combustion engine and being recognizable when observing a reaction of a measured temperature;

measuring a temperature with a sensor at least at one location or in a region within a partial volume of the catalytic converter during the change of the at least one of chemical and physical properties;

selecting the location or the region and a configuration of the sensor in such a manner that a reaction of the measured temperature resulting in the change of properties of the gas mixture is at least approximately representative of a reaction of the temperature in the partial volume;

determining set point values for the respective change in the properties of the gas mixture on the basis of a thermodynamic model while taking physical boundary conditions and properties of the partial volume into account; and

determining and comparing the measured temperature reaction with the set point values.

2. The method according to claim 1, which comprises:

observing a derivative of the measured temperature with respect to time as the reaction;

selecting the location or the region and the configuration of the sensor for at least approximately representing a chronological change of the temperature in the partial volume of the catalytic converter with the derivative of the measured temperature with respect to time;

determining set point values for the respective change of the properties of the gas mixture; and

determining and comparing the derivative of the measured temperature with respect to time with the set point values.

3. The method according to claim 2, which comprises determining a maximum of the derivative of the temperature with respect to time during the duration of the change.

4. The method according to claim 3, which comprises comparing the maximum determined in the course of the duration of a change with set point values or maxima previously measured during similar changes.

5. The method according to claim 2, which comprises comparing the derivative of the temperature with respect to time in the partial volume with at least one of previously determined values for identical condition changes of the gas mixture, values determined in another catalytic converter, and set point values determined on the basis of model calculations, in an electronic evaluation device.

6. The method according to claim 2, which comprises registering and analyzing different changes of the derivatives of the temperature with respect to time during different types of changes of the properties of the gas mixture, for obtaining statements regarding the condition of the partial volume with respect to various functions, including converting ability and cold-starting behavior.

7. The method according to claim 2, which comprises purposely disrupting a predetermined, exactly defined condition of an internal combustion engine, and comparing the reaction of the derivatives with respect to time regarding the disruption with predetermined set point value ranges.

8. The method according to claim 7, which comprises disrupting the condition of the internal combustion engine after a prolonged phase of constant output during a phase of load reduction by briefly injecting fuel into at least one combustion chamber while ignition is turned off.

9. The method according to claim 2, which comprises observing effects of a defined transient process of an engine, including a cold-starting phase and an acceleration phase, on the derivatives with respect to time.

10. The method according to claim 1, which comprises observing as an observation signal an integral of the temperature with respect to time over the duration of the respective change as the reaction, and if necessary optionally delaying the observation signal by a reaction delay time occurring in the catalytic converter.

11. The method according to claim 1, which comprises creating the change pattern as a periodic change, preferably having a frequency of 0.1 to 10 Hz and in particular 0.5 to 2 Hz.

12. The method according to claim 1, which comprises creating the change pattern as an aperiodic change preferably being formed of at least three changes.

13. The method according to claim 1, which comprises creating changes with different strengths.

14. The method according to claim 1, which comprises selecting the change of the properties of the gas mixture as a sudden and brief increase in a content of chemical energy in the gas mixture.

15. The method according to claim 14, which comprises creating the increase in the chemical energy in a phase of otherwise constant or exactly known operational conditions of the catalytic converter, by additionally supplying catalytically convertible components, in particular hydrocarbons.

16. The method according to claim 15, which comprises briefly increasing the chemical energy content of the gas mixture for setting the amount of fuel as well as the ratio of fuel and air with respect to the entire gas mass flow in the catalytic converter to an optimum conversion ability in the volume of the catalytic converter during the duration of the change, in particular for completely converting the amount of fuel over the duration of the change and over the length of the catalytic converter.

17. The method according to claim 1, which comprises placing the catalytic converter downstream of an internal combustion engine having an electronic control in order to clean exhaust gases, wherein the change in the properties of the gas mixture takes place because of an operational change of an internal combustion engine.

18. The method according to claim 17, which comprises briefly increasing the chemical energy content of the gas mixture for setting the amount of fuel as well as the ratio of fuel and air with respect to the entire gas mass flow in the catalytic converter to an optimum conversion ability in the volume of the catalytic converter during the duration of the change, in particular for completely converting the amount of fuel over the duration of the change and over the length of the catalytic converter.

19. The method according to claim 17, which comprises causing a sudden change of the temperature of the gas mixture with the operational change.

20. The method according to claim 17, which comprises suddenly changing the mass flow of the gas mixture as the operational change.

21. The method according to claim 17, which comprises determining set point value ranges with a model function disclosing functional connections of the temperatures in different partial volumes of the catalytic converter with each other and with data of an electronic control of the internal combustion engine for at least one of a respective condition and a respective condition change of the internal combustion engine.

22. The method according to claim 21, which comprises considering tolerances which may result from at least one of inaccuracies of transistors, production tolerances in the catalytic converters and deviations in a mixture preparation of the internal combustion engine, in setting a value of the set point value range.

23. The method according to claim 21, which comprises:

a) determining a derivative of the temperature with respect to time to be expected for a first partial volume with a model function by calculating an exhaust gas temperature and energy released in the catalytic converter from data available from the engine control, including rpm, mass throughput, supplied amount of fuel and engine temperature;

b) comparing at least one of the temperature measured in the first partial volume and its derivative with respect to time with the calculated temperature and its derivative with respect to time, while registering deviations outside of a set point value range;

c) calculating a derivative with respect to time to be expected in a subsequent partial volume with a model function, while taking into consideration data available from the engine control and derivatives with respect to time being measured in the previous partial volumes;

d) comparing a derivative with respect to time being measured in the subsequent partial volume with the calculated derivative with respect to time, while registering deviations outside of a set point value range; and

e) determining whether and to what extent the catalytic converter as a whole still provides its functions and which partial volumes are possibly damaged and to what extent, from the registered deviations.

24. The method according to claim 1, which comprises selecting an analyzed partial volume of the catalytic converter to be in a region of an outflow end.

25. The method according to claim 1, which comprises analyzing conditions of at least two partial volumes with a corresponding number of temperature measurements.

26. The method according to claim 25, which comprises:

observing a total volume of the catalytic converter, being formed of several partial volumes;

detecting the condition of each partial volume by determining approximately representative derivatives of the temperature as simultaneously as possible during the changes in the properties of the gas mixture; and

combining the individual detected conditions into a total picture of a total condition of the catalytic converter.

27. The method according to claim 1, which comprises measuring temperature at a catalytically active layer with each temperature sensor.

28. The method according to claim 27, which comprises placing each temperature sensor in intimate heat contact with a support structure of the catalytic converter, and selectively integrating each temperature sensor into walls of the support structure.

29. The method according to claim 27, which comprises placing each temperature sensor in the flow of the gas mixture for permitting a good heat transfer from the support structure through the gas mixture to the temperature sensor.

30. The method according to claim 1, which comprises selecting a first partial volume to be located in a precatalyst, and selecting second and subsequent partial volumes to be located in different cross-sectional regions or partial bodies of a main catalyst.

31. The method according to claim 1, which comprises carrying out the temperature measurements with punctiform temperature sensors or temperature sensors measuring representatively over a partial volume of the catalytic converter.

32. The method according to claim 1, which comprises turning off a lambda control of the catalytic converter during monitoring.