DE102022103350B4 - Method for heating an exhaust system, an exhaust system and a motor vehicle - Google Patents

Abstract

Method for heating an exhaust system (10) of a motor vehicle with a catalytic converter (12), the exhaust system (10) comprising an electrically heatable heating disk (14) which is in the flow direction of a carrier mass flow (16) in front of the catalytic converter (12) in the exhaust system ( 10) is arranged, comprising the steps: - Determining values of one or more electrical parameters at, in particular, regular, time intervals during the heating of the electrically heatable heating disk (14); - Determining whether a sufficiently large carrier mass flow (16) is present by the determined values of the one or more electrical parameters of the electrically heatable heating disk (14) are evaluated, characterized in that evaluating the determined values of the one or more electrical parameters comprises: - Creating at least one time-dependent function (22) from the determined values of the at least one electrical parameter; -determining and evaluating at least one derivative function (24) of the time-dependent function (22) of the determined values of the at least one electrical parameter of the electrically heatable heating disk (14).

Description

The invention relates to a method for heating an exhaust system of a motor vehicle with a catalytic converter, the exhaust system comprising an electrically heatable heating disk which is arranged in the flow direction of a carrier mass flow in front of the catalytic converter in the exhaust system, comprising the steps: determining values of one or more electrical parameters at, in particular regular, time intervals during the heating of the electrically heatable heating pane; Determine whether there is a sufficiently large carrier mass flow by evaluating the determined values of the one or more electrical parameters of the electrically heatable heating disk. Furthermore, the invention relates to an exhaust system of a motor vehicle and a motor vehicle with such an exhaust system.

To ensure extremely low emissions, a heating disc can be used to preheat a motor vehicle's exhaust system. For this purpose, a carrier mass flow (e.g. air) flows around or through the electrically heated heating disk and the downstream catalytic converter is heated. If the carrier mass flow is not present or is insufficient, the heating disk can overheat and be damaged.

US 5740675 A discloses a system and a method for estimating a temperature of an exhaust system with an electrically heatable catalytic converter, the temperature of the exhaust system being estimated via the electrical parameters of the electrically heatable catalytic converter.

A generic method and an exhaust system that can be heated using this method are from the DE 10 2018 129 681 A1 known.

The disadvantage here is that a missing or insufficient carrier mass flow cannot be reliably detected and the heating disk cannot be protected from damage due to overheating.

It is the object of the invention to provide a method for heating an exhaust system of a motor vehicle, an exhaust system of a motor vehicle and a motor vehicle with such an exhaust system, whereby a missing or insufficient carrier mass flow can be reliably detected and damage to the heating disk due to overheating can be avoided.

The object is achieved by a method for heating an exhaust system of a motor vehicle according to claim 1, an exhaust system of a motor vehicle according to claim 7 and a motor vehicle according to claim 8.

• Erstellen mindestens einer zeitabhängigen Funktion aus den ermittelten Werten der mindestens einen elektrischen Kenngröße. Vorzugsweise wird aus den ermittelten Werten der Kenngröße(n) und den Zeitintervallen, in denen die Werte ermittelt worden sind, eine Kennlinie erstellt. Anders ausgedrückt, die ermittelten Werte der Kenngröße(n) werden in einem Diagramm über der Zeit aufgetragen, so dass eine Kennlinie entsteht.

The method according to the invention for heating an exhaust system of a motor vehicle with a catalytic converter, in particular for heating or preheating the catalytic converter, wherein the exhaust system comprises an electrically heatable heating disk which is arranged in the flow direction of a carrier mass flow (e.g. air) in front of the catalytic converter in the exhaust system , includes the steps:

• Creating at least one time-dependent function from the determined values of the at least one electrical parameter. A characteristic curve is preferably created from the determined values of the characteristic variable(s) and the time intervals in which the values were determined. In other words, the determined values of the parameter(s) are plotted in a diagram over time, so that a characteristic curve is created.

Determining and evaluating at least one derivative function (or a gradient) of the time-dependent function of the determined values of the at least one electrical parameter of the electrically heatable heating disk.

By a derivative function is meant the derivative function of the first degree. The derivative function corresponds in particular to the derivative in the mathematical sense, i.e. the slope of the time-dependent function from the determined (measured) values of the electrical parameter.

An insufficiently large carrier mass flow can be caused, for example, by a leak or a jamming of a valve in a line leading to the heating disk and the carrier mass flow. A carrier mass flow that is not sufficiently large can be a carrier mass flow that is missing and/or interrupted at time intervals. There may be an insufficiently large carrier mass flow if the carrier mass flow is (constantly) present, but not large enough (i.e. not sufficient to dissipate the heat energy from the heated heating disk, so that it can overheat).

By evaluating the determined values of the one or more electrical parameters, it can be reliably determined whether the carrier mass flow is present and whether it is sufficiently large to dissipate the thermal energy from the heated heating disk. If it is determined that the carrier mass flow is not sufficiently large, the heating disk can be switched off, for example and thus prevent the heating disc from overheating.

Preferably, the carrier mass flow in the exhaust system can be provided by a secondary air pump or an electric exhaust gas turbocharger.

Preferably, the one or more electrical parameters of the electrically heatable heating disk can be the electrical current, the electrical resistance, the electrical voltage and/or the electrical power of the electrically heatable heating disk.

The electrical power cannot be determined (measured) directly. However, it can, for example, be determined (determined) from the determined voltage and current, in particular mathematically.

• Vergleich des Verlaufs der Ableitungsfunktion (bzw. des Gradienten) mit einem Verlauf einer Idealableitungsfunktion, die aus einer Idealfunktion ermittelt wird, die aus idealen, vorbestimmten Idealwerten erstellt ist. Auch die Idealableitungsfunktion ist eine Ableitungsfunktion ersten Grades im mathematischen Sinne.

Preferably, evaluating the derivative function may include:

• Comparison of the course of the derivative function (or the gradient) with a course of an ideal derivative function, which is determined from an ideal function that is created from ideal, predetermined ideal values. The ideal derivative function is also a first degree derivative function in the mathematical sense.

In other words, a comparison of an actual gradient (the derivative function) can be made with an (ideal) target gradient (the ideal derivative function). It is also conceivable that the evaluation of the values is carried out by comparing the time-dependent function from the determined values with the ideal function or by comparing the individual values with the ideal values.

The ideal function can be created (determined) from ideal values that correspond to a carrier mass flow that is sufficiently large, i.e. OK. If a deviation is found in the comparison, it can be concluded that there is a missing and/or insufficient carrier mass flow.

This can preferably include evaluating the derivative function: comparing the starting value of the derivative function with the ideal starting value of the ideal derivative function.

In particular, the deviation of the values (i.e. the distance between the respective X value in the characteristic curve diagram) can be greatest here. For example, immediately at the start of the heating phase of the heating disk, a faulty carrier mass flow can be concluded and appropriate measures can be taken, such as: B. switching off the heating window and / or issuing an alarm signal (acoustic and / or visual) to the user or the driver of the motor vehicle.

• Ermitteln einer Zeitspanne, die zur Erreichung eines vorbestimmten Schwellwerts der Ableitungsfunktion benötigt wird.

Preferably, evaluating the derivative function may include:

• Determining a time period required to reach a predetermined threshold value of the derivative function.

Comparison of the determined time period with an ideal time period that is required to reach the predetermined threshold value of the ideal derivative function.

If there is a deviation between the determined time period and the ideal time period, it can be concluded that there is a missing and/or insufficient carrier mass flow.

According to the invention, an exhaust system of a motor vehicle comprising at least one catalytic converter and at least one electrically heatable heating disk is proposed, the exhaust system being set up in such a way that at least one value of an electrical parameter of the electrically heatable heating disk can be determined (measured).

The exhaust system can include a secondary air pump or an electric exhaust gas turbocharger.

Preferably, the exhaust system can be set up to be heated using a method according to the above statements. With regard to the advantages that can be achieved with this, reference is made to the relevant comments on the process. The measures described in connection with the method and/or the measures explained below can be used to further design the exhaust system.

In particular, the method can be used to heat the catalytic converter of the exhaust system.

According to the invention, a motor vehicle with an exhaust system according to the above statements is proposed. With regard to the advantages that can be achieved with this, reference is made to the relevant comments on the exhaust system. The measures described in connection with the exhaust system and/or the measures explained below can be used to further design the motor vehicle.

The motor vehicle can include a secondary air pump or an electric exhaust gas turbocharger.

• 1 schematisch eine Abgasanlage eines Kraftfahrzeugs;
• 2 ein Verhalten der Abgasanlage bei konstanter Spannung mit zeitabhängigen Funktionen der ermittelten Werte von Kenngrößen ( 2c, 2e, 2g) und deren Ableitungsfunktionen (2d, 2f, 2h);
• 3 eine vergrößerte Darstellung des Diagramms gemäß 2d;
• 4 ein Verhalten der Abgasanlage bei konstanter Leistung mit zeitabhängigen Funktionen der ermittelten Werte von Kenngrößen ( 4c, 4e, 4g) und deren Ableitungsfunktionen (4d, 4f, 4h); und
• 5 eine vergrößerte Darstellung des Diagramms gemäß 4h.

Further advantageous refinements result from the following description and the drawing. Shown in the drawing

• 1 schematically an exhaust system of a motor vehicle;
• 2 a behavior of the exhaust system at constant voltage with time-dependent functions of the determined values of parameters ( 2c , 2e , 2g) and their derivative functions ( 2d , 2f , 2h) ;
• 3 an enlarged view of the diagram according to 2d ;
• 4 a behavior of the exhaust system at constant power with time-dependent functions of the determined values of parameters ( 4c , 4e , 4g) and their derivative functions ( 4d , 4f , 4h) ; and
• 5 an enlarged view of the diagram according to 4h .

1 schematically shows an exhaust system 10 of a motor vehicle with a catalytic converter 12. The exhaust system includes an electrically heatable heating disk 14. In the present case, a carrier mass flow 16 is provided by a secondary air pump 18 or an electric turbocharger 20. The carrier mass flow 16 flows around or through the heating disk 14 and then reaches the catalytic converter 12. In other words, the heating disk 14 is arranged in front of the catalytic converter 12 in the exhaust system 10 in the flow direction of the carrier mass flow 16.

If the heating disk 14 is heated (indicated by an arrow), it heats up and heats the carrier mass flow 16, which flows around or through the heating disk 14. The carrier mass flow 16 heated in this way in turn heats the catalyst 12. If the carrier mass flow is missing or is not sufficiently present, the heat energy is not or only insufficiently removed by the heating disk 14, so that the heating disk 14 can overheat. This can be prevented by determining and evaluating characteristic values of at least one electrical parameter of the heating disk 14.

The 2a - 2h show the behavior of the exhaust system 10 at constant electrical voltage (U). In other words, the electrical voltage (U) remains constant over time (t) (cf. 2a) . 2 B illustrates the difference between an existing and sufficiently high carrier mass flow 16 (mSL) (solid line) and a non-existent carrier mass flow 16 (mSL) (dashed line) over time (t).

In the 2c , 2e , 2g a time-dependent function 22 of the determined values of parameters is plotted over time (t). The values of the time-dependent functions 22 were determined when the carrier mass flow 16 was not present. These time-dependent functions 22 are each shown by a dashed line. In addition, an ideal function 28 is shown over time (t) using a dashed line. The ideal functions 28 each correspond to the ideal values that would be measured with an existing carrier mass flow 16. The deviation of the respective values of the respective parameters is illustrated as a function of an existing or non-existent carrier mass flow 16.

In 2c The electrical current intensity (I) is plotted over time (t) as a parameter. In 2e The electrical resistance (R) is plotted over time (t) as a parameter. In 2g The electrical power (P) is plotted over time (t) as a parameter.

In the 2d , 2f , 2h The derivative functions 24 of the time-dependent functions 22 and the ideal derivative functions 26 of the ideal functions 28 are shown. That's how it is 2d the derivative of the electrical current intensity (I') is plotted over time (t). In 2f the derivative of the electrical resistance (R') is plotted over time (t). In 2h the derivative of the electrical power (P') is plotted over time (t).

In 3 is an enlarged view of the 2d shown. It can be seen that the starting value 30 of the derivative function 24 differs significantly from the ideal starting value 32 of the ideal derivative function 26. From the comparison of these two starting values 30, 32, it is possible to draw conclusions about an existing or non-existent carrier mass flow 16. In the present case, the starting value 30 is smaller than the ideal starting value 32.

In addition, the time required to reach a predetermined threshold value 36 can be determined from the respective derivative functions 24, 26. This threshold value 36 is reached in the derivative function 24 after a period of time 34. In the case of the ideal derivative function 26, this threshold value 36 is reached after an ideal time period 38. From the comparison of these two time periods 34, 38, conclusions can be drawn about an existing or non-existent carrier mass flow 16. In the present case, the time period 34 is shorter than the ideal time period 38.

The 4a - 4h show the behavior of the exhaust system 10 at constant electrical power (P). In other words, the electrical power (P) remains constant over time (t) (cf. 4a) . 4b illustrates the difference between an existing carrier mass flow 16 (mSL) (solid line) and a non-existent carrier mass flow 16 (mSL) (dashed line) over time (t).

In the 4c , 4e , 4g a time-dependent function 22 of the determined values of parameters is plotted over time (t). The values of the time-dependent functions 22 were determined when the carrier mass flow 16 was not present. These time-dependent functions 22 are each shown by a dashed line. In addition, an ideal function 28 is shown over time (t) using a dashed line. The ideal functions 28 each correspond to the ideal values that would be measured with an existing carrier mass flow 16. The deviation of the respective values of the respective parameters is illustrated as a function of an existing or non-existent carrier mass flow 16.

In 4c The electrical current intensity (I) is plotted over time (t) as a parameter. In 4e The electrical resistance (R) is plotted over time (t) as a parameter. In 4g The electrical voltage (U) is plotted over time (t) as a parameter.

In the 4d , 4f , 4h The derivative functions 24 of the time-dependent functions 22 and the ideal derivative functions 26 of the ideal functions 28 are shown. That's how it is 4d the derivative of the electrical current intensity (I') is plotted over time (t). In 4f the derivative of the electrical resistance (R') is plotted over time (t). In 4h the derivative of the electrical voltage (U') is plotted over time (t).

In 5 is an enlarged view of the 4h shown. It can be seen that the starting value 30 of the derivative function 24 differs significantly from the ideal starting value 32 of the ideal derivative function 26. From the comparison of these two starting values 30, 32, it is possible to draw conclusions about an existing or non-existent carrier mass flow 16. In the present case, the starting value 30 is greater than the ideal starting value 32.

In addition, the time required to reach a predetermined threshold value 36 can be determined from the respective derivative functions 24, 26. This threshold value 36 is reached in the derivative function 24 after a period of time 34. In the case of the ideal derivative function 26, this threshold value 36 is reached after an ideal time period 38. From the comparison of these two time periods 34, 38, conclusions can be drawn about an existing or non-existent carrier mass flow 16. In the present case, the time period 34 is longer than the ideal time period 38.

Reference symbol list

10

Exhaust system

12

catalyst

14

Heated heating disc

16

Carrier mass flow

18

Secondary air pump

20

turbocharger

22

Time dependent function

24

Derivative function

26

Ideal derivative function

28

Ideal function

30

Starting value

32

Ideal starting value

34

Period of time

36

Threshold

38

Ideal time span

t

Time

I

Current strength

R

Resistance

R'

Derivation of resistance

P

Electrical power

P'

Department of Electrical Management

U

Tension

Claims (8)

Method for heating an exhaust system (10) of a motor vehicle with a catalytic converter (12), the exhaust system (10) comprising an electrically heatable heating disk (14) which is in the flow direction of a carrier mass flow (16) in front of the catalytic converter (12) in the exhaust system ( 10) is arranged, comprising the steps: -determining values of one or more electrical parameters at, in particular regular, time intervals during the heating of the electrically heatable heating disk (14); -Determining whether a sufficiently large carrier mass flow (16) is present by evaluating the determined values of the one or more electrical parameters of the electrically heatable heating disk (14), characterized in that evaluating the determined values of the one or more electrical parameters comprises: -creating at least one time-dependent function (22) from the determined values of the at least one electrical parameter; -Determining and evaluating at least one derivative function (24) of the time-dependent function (22) of the determined values of the at least one electrical parameter of the electrically heatable heating disk (14). Procedure according to Claim 1 , characterized in that the carrier mass flow (16) in the exhaust system (10) is provided by a secondary air pump (18) or an electric exhaust gas turbocharger (20). Procedure according to Claim 1 or Claim 2 , characterized in that the one or more electrical parameters of the electrically heatable heating disk (14) are the electrical current, the electrical resistance, the electrical voltage and / or the electrical power of the electrically heatable heating disk (14). Procedure according to one of the Claims 1 - 3 , characterized in that evaluating the derivative function (24) includes: -comparing the course of the derivative function (24) with a course of an ideal derivative function (26), which is determined from an ideal function (28), which is created from ideal, predetermined ideal values . Method according to one of the preceding claims, characterized in that evaluating the derivative function (24) comprises: -comparing the starting value (30) of the derivative function (24) with the ideal starting value (32) of the ideal derivative function (26). Method according to one of the preceding claims, characterized in that evaluating the derivative function (24) comprises: -determining a time period (34) that is required to reach a predetermined threshold value (36) of the derivative function (24); -Comparison of the determined time period (34) with an ideal time period (38) that is required to reach the predetermined threshold value (36) of the ideal derivative function (26). Exhaust system (10) of a motor vehicle comprising at least one catalytic converter (12) and at least one electrically heatable heating disk (14), the exhaust system (10) being set up in such a way that at least one value of an electrical parameter of the electrically heatable heating disk (14) can be determined , characterized in that the exhaust system (10) is set up to use the method according to one of the Claims 1 until 6 to be heated up. Motor vehicle comprising an exhaust system (10). Claim 7 .

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