DE102007011487A1 - Method for monitoring the functionality of a particulate filter, and corresponding exhaust system - Google Patents

Abstract

The method according to the invention for monitoring the functionality of a particle filter (1) through which exhaust gas flows is characterized in that the temperature (9) of the exhaust gas (3) is detected after the particle filter (1) flows through, and then when the temperature (9) is greater or equal to a predeterminable limit temperature (13), an error signal is provided. The inventive method allows advantageously simple way to monitor the functionality of a particulate filter (1). The limit temperature (13) is chosen in particular such that there is a high probability of malfunction or failure of the particulate filter in their presence. The limit temperature (13) is preferably selected to be significantly higher, for example by about 200 ° C. (Celsius), than an operating temperature of the particulate filter (1), in particular during continuous regeneration. Alternatively, the limit temperature (13) can also be selected in the region of a disintegration temperature at which irreversible damage to the particle filter (1) occurs until it is destroyed.

Description

object The present invention is a method for monitoring the functionality of an exhaust gas flowed through Particulate filter, and a corresponding exhaust system. The invention can advantageously in exhaust systems, in particular of internal combustion engine be used. The invention relates to the so-called "On board" diagnosis (OBD) of elements in the exhaust system of internal combustion engine, especially in automobiles.

far far In many countries exhaust emission limits are set by law, which are complied with by the exhaust gas from internal combustion engines have to. Many legal requirements also require the monitoring of the functionality of the used Systems for exhaust gas treatment, the so-called "on-board" diagnosis (OBD).

to Reduction of the proportion of particles in the exhaust gas become particle filters used, for example, honeycomb bodies with alternately consist of closed channels. In particulate filters is the on-board diagnosis usually about the pressure drop over determines the particle filter. If the pressure drops too much is concluded that a malfunction of the particulate filter. For the determination of the pressure drop must be two pressure values that must be recorded.

Of these, The invention is based on the object, a method for monitoring a particulate filter and a corresponding Propose exhaust system, in which a simpler detection and Evaluation of measured values can be done.

These Task is solved by the independent claims. The dependent claims are advantageous Training courses addressed.

The Inventive method for monitoring the functionality of an exhaust gas flowed through Particulate filter, based on the temperature of the exhaust gas is detected after flowing through the particulate filter and then if the temperature is greater than or equal to one specifiable limit temperature, an error signal is provided becomes.

The provision of an error signal is understood in particular to be recognizable to the user or monitor of the internal combustion engine in whose exhaust system the particle filter is formed, for example in the form of an optical and / or acoustic signal. A particulate filter is understood to mean a closed filter which has mutually sealed channels which force the exhaust gas flow through the walls between channels, but in particular also a so-called bypass filter (also called an open filter) in which the entire exhaust gas flow is not forced through the walls but only a side stream of the exhaust gas can flow through the walls. The basics of such filters are for example from the WO-A-01/80978 , of the WO-A-02/00326 and the WO-A-2004/015251 to which reference is made in full with regard to the design and construction of the filter and the disclosure of which is included in so far in this application. Furthermore, the formation of the particulate filter as a ceramic monolith is possible and according to the invention.

Under the detection of the temperature of the exhaust gas after flowing through the particulate filter is understood in particular a measurement. However, the temperature can not only be downstream of the particulate filter, but also measured within the particulate filter and then accordingly on the temperature of the exhaust gas after flowing through the particulate filter getting closed.

• a) ein Bauteil, insbesondere ein Heiß- oder Kaltleiter, dessen elektrischer Widerstand sich abhängig von der Temperatur ändert;
• b) ein Halbleiter-Temperatursensoren;
• c) ein Wärmefühler mit Schwingquarz als Messelement, dessen Resonanzfrequenz sich abhängig von der Temperatur ändert;
• d) ein Thermoelement;
• e) ein pyroelektrisches Messelement;
• f) ein Bimetallstreifen;
• g) ein Curie-Effekt-Temperatursensor; und
• h) ein Temperatursensor, der auf dem Raman-Effekt basiert, beispielsweise verteilte faseroptische Temperatursensoren.

The detection of the temperature represents in particular a measurement, preferably with at least one of the following sensors:

• a) a component, in particular a hot or cold conductor whose electrical resistance changes depending on the temperature;
• b) a semiconductor temperature sensors;
• c) a quartz crystal thermal sensor as a measuring element, the resonant frequency of which changes as a function of the temperature;
• d) a thermocouple;
• e) a pyroelectric measuring element;
• f) a bimetal strip;
• g) a Curie effect temperature sensor; and
• h) a temperature sensor based on the Raman effect, for example distributed fiber optic temperature sensors.

The Measurement takes place in the rear region of the particle filter, preferably in the last 15%, more preferably in the last 10%, or also the last 5% of the length of the particulate filter or just behind this, for example less than 5 cm (centimeters) behind the particulate filter, more preferably less than 3 cm behind this. The limit temperature is preferably 900 ° C (Celsius), 1000 ° C, 1100 ° C or even 1200 ° C. Particularly preferred here is a limit temperature of 900 ° C. The limit temperature is a gas temperature, often below the Material temperature of the particulate filter is. Thus already can at gas temperatures of 900 ° C damage of the particulate filter, if the temperatures are higher here lie.

In particular, the provision of the error signal may also depend on the length of time take place, in which the temperature is above the limit temperature. Here, a weighting with the temperature difference between temperature and limit temperature is advantageous, in which an error signal occurs as a function of the integral of the temperature profile above the limit temperature. Thus, an error signal is provided at small temperature differences (ie a slight overshoot of the limit temperature) after a first time and at large temperature differences after a second time, wherein the first time is longer than the second time.

The method according to the invention advantageously allows simple monitoring of the functionality of a particle filter based on a single measured value. Particularly in the case of particle filters which are continuously regenerated by nitrogen dioxide (NO ₂ ), ie which are operated according to the so-called CRT (continuously regenerating trap) process, the process according to the invention has proved to be particularly advantageous, since these particle filters usually have a specific temperature window , namely 200 to 500 ° C (Celsius), in particular 300 to 400 ° C are operated and any significant upward deviation gives an indication of a faulty or faulty operating condition.

One another possibility lies in the regeneration over Oxygen, in which a Rußabbrand the soot-containing particles takes place in the particle filter via an oxidation with oxygen. The average operating temperature is 430 to 600 ° C in the case of a corresponding catalytically active coating of the Particulate filter or at 600 to 700 ° C without such Coating.

According to one advantageous embodiment of the invention Method is the particulate filter at least partially made of metal built up.

For example the particle filter can be made of at least one metallic layer or at least one at least partially structured and one in the be constructed substantially smooth. The metallic ones are preferred Layers connected to each other, in particular cohesively such as by brazing.

Prefers is an embodiment of the method in which the limit temperature at least 200 ° C above an average operating temperature the particulate filter is located.

Especially in the CRT-operated particle filters has such significant increase in operating temperature as a signal for a faulty operating condition of the particulate filter proven.

According to one further advantageous embodiment of the invention Process corresponds to the limit temperature of a disintegration temperature of the particulate filter.

Under the temperature of disintegration becomes, in particular, a temperature understood in which an irreversible damage to the particulate filter he follows. This is preferred in soldered particulate filters in Essentially the soldering temperature. Thus can reach at the limit temperature of a serious injury to the Particulate filter, in particular the at least partial destruction of the particulate filter are assumed. Here possible a corresponding error signal a quick replacement of a damaged Particulate filter.

According to one further advantageous embodiment of the invention Method is the temperature with a measuring signal emitting electromagnetic Temperature sensor detected.

Under Such a temperature sensor is in particular a thermocouple, a thermoresistor, a thermistor, a thermistor, a Semiconductor thermosensor, a quartz thermocouple, a pyroelectric measuring element and / or Curie effect temperature sensor Understood. Preference is given to the installation of a thermoresistor, a thermocouple and / or a PTC material (positive temperature coefficient, positive temperature coefficient). Preference is given to a measurement signal understood an electrical voltage.

According to one further advantageous embodiment of the invention Method, the error signal is provided when the measurement signal is missing.

this includes is understood in particular that the temperature sensor no measurement signal outputs, has an infinite electrical resistance or the like. This is an indication that the temperature sensor is also irreversible damaged, for example, was destroyed.

According to one further advantageous embodiment of the invention Method, at least the occurrence of an error signal is stored readable.

This allows advantageously at a later Maintenance the reading of the output error signals, preferably with Date and time, as well as the length of the occurrence of the error signal. Further data on the occurrence of the error signal can be stored.

In addition, an exhaust system for carrying out the method according to the invention is proposed, the at least one particulate filter and ei NEN downstream of the particulate filter formed temperature sensor for monitoring the temperature of the particulate filter comprises.

The disclosed for the inventive method Details and advantages can be in the same way to the inventive Apply and transfer the exhaust system and vice versa. Hereinafter The invention will be more apparent from the accompanying drawings explained, without reference to the details and embodiments shown there to be limited. They show schematically:

1 a first embodiment of an exhaust system according to the invention;

2 A second embodiment of an exhaust system according to the invention; and

3 for example, a temperature profile of the temperature of the exhaust gas downstream of the particulate filter.

1 shows a particle filter 1 in an exhaust system 2 , In operation become exhaust system 2 and particle filters 1 of exhaust 3 flows through an internal combustion engine. Behind the particle filter 1 is a temperature sensor 4 for monitoring the temperature of the particulate filter 1 educated. The temperature sensor 4 detects the temperature of the exhaust gas 3 after flowing through the particle filter 1 , The measured values of the temperature sensor 4 be via a first signal line 5 to a controller 6 transfer. In the control 6 An evaluation of the measured values takes place. According to the invention, the measured temperature of the exhaust gas after flowing through the particulate filter 1 vergli Chen with a predetermined limit temperature and then, if the temperature is greater than or equal to the limit temperature, provided an error signal. This is done, for example, by transmitting a corresponding error signal via a second signal line 7 to an interface 8th , About the interface 8th For example, the notification of a user or of monitoring personnel may take place, for example by displaying an optical and / or output of an acoustic warning signal.

2 shows a further embodiment of an exhaust system according to the invention 2 , In contrast to the first embodiment, here is the temperature sensor 4 within the particulate filter 1 formed, in particular within the last 10% of the length of the particulate filter 1 in the flow direction of the exhaust gas 3 , preferably within the last 5% of the length.

3 schematically shows a through the temperature sensor 4 recorded temperature profile 9 , Shown is the temperature (T) versus time (t), each in arbitrary units. In a first 10 , a second one 11 and a third temperature peak 12 lies the temperature profile 9 above a predefinable limit temperature 13 , In these time ranges, a corresponding error signal is provided.

The method according to the invention advantageously makes it easy to monitor the functionality of a particulate filter 1 , The limit temperature 13 is particularly chosen so that there is a high probability of malfunction or failure of the particulate filter in their present. The limit temperature is preferred 13 significantly higher, for example by about 200 ° C (Celsius), than an operating temperature of the particulate filter 1 , especially chosen during a continuous regeneration. Alternatively, the limit temperature 13 also in the region of a disintegration temperature, in which there are irreversible damage to the particulate filter 1 until the destruction comes, be chosen.

1

particulate Filter

2

exhaust system

3

exhaust

4

temperature sensor

5

first signal line

6

control

7

second signal line

8th

interface

9

temperature curve

10

first temperature peak

11

second temperature peak

12

third temperature peak

13

limit temperature

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 01/80978 A [0007]
• WO 02/00326 A [0007]
• WO 2004/015251 A [0007]

Claims (10)

Method for monitoring the functionality of a particle filter through which exhaust gas flows ( 1 ), where the temperature ( 9 ) of the exhaust gas ( 3 ) after flowing through the particle filter ( 1 ) and then when the temperature ( 9 ) greater than or equal to a predefinable limit temperature ( 13 ), an error signal is provided. Method according to Claim 1, in which the particle filter ( 1 ) is a bypass filter. Method according to one of the preceding claims, in which the particle filter ( 1 ) is at least partially constructed of metal. Method according to Claim 3, in which the particle filter ( 1 ) has interconnected metallic layers. Method according to one of the preceding claims, in which the limit temperature ( 13 ) at least 200 ° C above an average operating temperature of the particulate filter ( 1 ) lies. Method according to one of the preceding claims, in which the limit temperature ( 13 ) a disintegration temperature of the particulate filter ( 1 ) corresponds. Method according to one of the preceding claims, in which the temperature ( 9 ) with a measuring signal emitting electro-magnetic temperature sensor ( 4 ) is detected. Method according to Claim 7, in which the error signal is provided when the measurement signal is absent. Method according to one of the preceding claims, in which at least the occurrence of an error signal is stored in readable form becomes. Exhaust system ( 2 ) for carrying out the method according to one of the preceding claims, comprising at least one particle filter ( 1 ) and one downstream of the particulate filter ( 1 ) trained temperature sensor ( 4 ) for monitoring the temperature ( 9 ) of the particulate filter ( 1 ).