DE102018218029A1 - Procedure for evaluating the functionality of an exhaust gas catalytic converter - Google Patents

Abstract

A method for evaluating the functionality of an exhaust gas catalytic converter (2) connected downstream of an internal combustion engine (1) is made available. In the method, the internal combustion engine (1) is set into a sailing mode before determining an oxygen storage capacity of the exhaust gas catalytic converter (2), and the inertia of the moving parts of the internal combustion engine (1) set into sailing mode is used to carry the exhaust gas catalytic converter (2) Fill oxygen. After stopping the sailing operation, the oxygen storage capacity of the catalytic converter (2) filled with oxygen is checked. The functionality of the exhaust gas catalytic converter (2) is then assessed on the basis of the result of the check of the oxygen storage capacity of the exhaust gas catalytic converter (2).

Description

The present invention relates to a method for evaluating the functionality of an exhaust gas catalytic converter which is connected downstream of an internal combustion engine.

With regard to permissible pollutant emissions from motor vehicles with internal combustion engines, ever stricter legal regulations make it necessary to further reduce pollutant emissions from an internal combustion engine. It is therefore increasingly necessary to use the components of an exhaust system, e.g. a catalyst to monitor even while driving. This enables possible malfunctions to be identified at an early stage and appropriate countermeasures to be taken. However, the functional status monitoring enforced by the regulatory conditions must be reconciled with the demands of a consumer for high performance and a quick response to an actuation of the accelerator pedal that corresponds to the vehicle type. In recent years, vehicles have thus been equipped with a diagnostic function, so that functional condition monitoring of a catalytic converter connected downstream of an internal combustion engine is made possible while the motor vehicle is traveling, without noticeably influencing the driving behavior of the driver of the motor vehicle. Such functional status monitoring corresponds to the On Board Diagnostics (OBD) regulations.

It is known that the oxygen storage capacity of a catalytic converter can be determined by first reducing the oxygen in the catalytic converter and then feeding the internal combustion engine with a lean fuel / air mixture, whereby the catalytic converter is intentionally filled with oxygen. Starting with the switch from the rich to the lean fuel-air mixture, a time integral is calculated over the amount of oxygen introduced into the catalytic converter per unit of time.

On vehicles with conventional, non-hybrid powertrains, engine delays occur without delay when the engine is disconnected from the powertrain (overrun), and engine fuel cutoff during a delay is used to monitor the catalytic converter status for legally required on-board diagnostic systems. This so-called after-run mode leads to a storage of oxygen in the exhaust gas catalytic converter, which enables the monitoring of the oxygen storage capacity of the exhaust gas catalytic converter and thereby the state of health when refueling after the delay phase.

In hybrid electric vehicles, it is of great importance that, in order to reduce fuel consumption and carbon dioxide (CO ₂ ) emissions, the engine is disconnected directly from the powertrain when the engine is switched off (sailing operation) in order to maximize the electrical recuperation energy after the driver has expressed the wish has to stop driving the vehicle, e.g. at the beginning of a deceleration phase. If the engine were in overrun mode, ie if the engine was switched off, the engine would remain connected to the drive train, the energy recovered would be reduced by the engine towing energy, thereby reducing the CO ₂ advantage of the hybrid electrical system.

In order to meet the legal requirements, it is according to the US 2012/0222402 A1 As part of on-board diagnostics, it is necessary to subject the exhaust gas probes arranged in the exhaust line of an internal combustion engine to various tests while the engine is running. For this, the US 2012/0222402 A1 proposes a method in which a diagnosis of a catalytic converter located in an exhaust line is carried out during sailing. In the context of this method, the engine is operated in a first phase with a fuel-air mixture with a lambda value of 1 after the start of sailing, which leads to fuel consumption during sailing.

The US 2012/0053816 A1 discloses a method for determining the oxygen storage capacity of a catalyst during coasting.

The US 9,677,488 B2 discloses a self-diagnostic method for performing diagnosis of the exhaust gas sensor of an SCR (Selective Catalytic Reduction) system with multiple diagnostic sequences. In a second diagnostic sequence of the method, air is pumped into the exhaust system after an engine fuel shutdown at high engine speeds. The air pumped in results in a very low NOx content and a very high oxygen content within the exhaust system at the location of the exhaust gas sensor, which is used to measure the performance of the exhaust gas sensor with a view to measuring a low NOx content and a high oxygen content. The second diagnostic sequence ends when the engine has stopped after the engine fuel cut.

The US 7,937,995 B2 discloses a method of monitoring an exhaust gas purification component with gas storage capability for purifying exhaust gases from an internal combustion engine.

The US 2016/0319727 A1 discloses a method for on-board diagnosis of the oxidation catalytic converter of an exhaust system of an internal combustion engine of a vehicle with an engine control device and a temperature sensor in the exhaust system upstream of the oxidation catalytic converter. That in the US 2016/0319727 A1 The disclosed method includes operating the internal combustion engine in overrun mode and injecting an amount of fuel upstream of the oxidation catalyst. The change in temperature values over time is measured by the temperature sensor. The measurement data are then used to conclude whether the oxidation catalytic converter is working properly.

The US 7,499,792 B2 discloses a method for diagnosis of an exhaust gas catalytic converter. The diagnosis is carried out in the overrun mode of the motor vehicle, in which the fuel is switched off and the oxygen reservoir of the catalytic converter is completely loaded with oxygen.

The US 9,731,711 B2 discloses a system for controlling the diagnosis of an oxygen sensor in a hybrid electric vehicle (HEV). The diagnostic requirements should be met and a reduction in drive efficiency due to frequent diagnoses of the oxygen sensor should be avoided. If diagnosis of an oxygen sensor is required during the sailing mode of the hybrid vehicle, the engine controller may maintain the fuel cut and close the clutch between the engine and the engine shaft to perform the diagnosis.

The DE 10 2011 088 296 A1 discloses a method for dynamic monitoring of gas sensors of an internal combustion engine. Dynamic monitoring can be carried out on vehicles with sailing operation.

The US 8,831,818 B2 discloses a diagnostic method for an oxygen sensor of a hybrid vehicle.

The DE 10 2016 219 549 A1 discloses a method for monitoring a NOx storage catalytic converter, in particular an autonomously driving vehicle.

Opposite the US 2012/0222402 A1 It is the object of the present invention to provide a method for monitoring the function of a catalytic converter with which the fuel consumption can be reduced during the diagnosis.

The object is achieved by a method according to claim 1. The dependent claims contain advantageous refinements of the present invention.

The present invention provides a method for evaluating the functionality of an exhaust gas catalytic converter connected downstream of an internal combustion engine. In this method, the internal combustion engine is put into a sailing mode before the oxygen storage capacity of the exhaust gas catalytic converter is determined. Switching to sailing mode takes place by stopping the fuel supply to the internal combustion engine and decoupling the internal combustion engine from the drive train. According to the invention, the inertia of the moving parts of the internal combustion engine set to sailing is used to fill the exhaust gas catalytic converter with oxygen. In particular, the still high speed of the internal combustion engine after the start of the sailing operation is used to convey air through the internal combustion engine into the exhaust gas catalytic converter. The oxygen storage capacity of the exhaust gas catalytic converter filled with oxygen is then checked after the end of the sailing operation and the functionality of the exhaust gas catalytic converter is assessed on the basis of the result of the check of the oxygen storage capacity of the exhaust gas catalytic converter. This procedure reduces drag operation compared to conventional diagnostics of the internal combustion engine, so that braking energy recovery and fuel efficiency are increased.

An advantage of the present invention is that no fuel needs to be supplied to the engine during the entire sailing operation, since the functionality of the exhaust gas catalytic converter is only checked after the sailing operation has ended and in the sailing mode only the exhaust gas catalytic converter is filled with oxygen.

Another advantage of the present invention lies in the utilization of the moment of inertia of the rotating parts of the internal combustion engine when the engine is decoupled and without the supply of fuel. Due to the inertia of the parts of the internal combustion engine rotating at a high speed, typically 1500 revolutions per minute, an internal combustion engine typically takes several seconds to come to a standstill. This mostly converted into unused energy can be used effectively. According to the invention, the energy “released” until the internal combustion engine comes to a standstill is used to enrich the exhaust gas catalytic converter with oxygen. Another energy that arises during a braking process through conversion, the braking energy, is therefore no longer necessary to enrich the catalytic converter. The energy converted into electrical energy during a braking operation can thus be almost completely stored as recovery energy and can be made available to the motor vehicle again except for conversion losses.

With regard to fuel consumption and CO ₂ emissions in particular, it is of great importance for hybrid electric vehicles to release the coupling between the drive train and the internal combustion engine and to switch off the internal combustion engine as soon as the driver indicates that the vehicle should no longer be driven. This is the case, for example, at the start of a deceleration phase, if it can be foreseen that the driver will brake or only want the motor vehicle to roll out. In addition to closing the fuel supply to the fuel injection unit, it is also in the driver's interest to store the energy converted during a braking operation as recovery energy and to use it again later, for example, to drive the motor vehicle. However, if the engine remains connected to the powertrain in overrun, the recovery energy is reduced by the engine towing energy and reduces the CO ₂ advantage of the hybrid electrical system.

According to one embodiment of the method according to the invention, in order to check the oxygen storage capacity of the exhaust gas catalytic converter, the fuel is supplied to the internal combustion engine after the end of the sailing operation at a feed rate such that a fuel-rich exhaust gas mixture is produced. It is checked by means of a sensor connected downstream of the exhaust gas catalytic converter whether fuel-rich exhaust gas emerges from the exhaust gas catalytic converter before a predetermined amount of fuel has been injected into the internal combustion engine. The check whether fuel-rich exhaust gas emerges from the exhaust gas catalytic converter can be carried out in particular with the aid of a lambda probe. In this embodiment of the method, an insufficient oxygen storage capacity of the exhaust gas catalytic converter and thus an incompletely functional exhaust gas catalytic converter can be concluded if fuel-rich exhaust gas emerges from the exhaust gas catalytic converter before a predetermined amount of fuel has been injected into the internal combustion engine. In a further development of this embodiment, the amount of oxygen that is supplied by the exhaust gas catalytic converter during the sailing operation can be determined from the amount of fuel that has been fed to the internal combustion engine until the fuel-rich exhaust gas has left the exhaust gas catalytic converter and the selected air-fuel ratio when the fuel is supplied has been saved. As a result, the functionality of the exhaust gas catalytic converter can be assessed not only qualitatively but also quantitatively.

Operating the internal combustion engine in sailing operation results in the exhaust gas catalytic converter being filled with oxygen, but the amount of oxygen that can be supplied to the exhaust gas catalytic converter in sailing operation depends on the speed of the internal combustion engine at the start of sailing operation. Above a certain limit speed and above, a fully functional catalytic converter is completely filled with oxygen when the combustion engine comes to a standstill. At lower speeds at the start of sailing, i.e. at speeds below a limit, however, a fully functional catalytic converter is not completely filled with oxygen. If the speed at the start of the sailing operation is in the speed range below the limit speed, a full loading of the catalytic converter with oxygen is not possible. A fully functional catalytic converter that is not fully loaded with oxygen could falsify the result of the check of the oxygen storage capacity of the catalytic converter. In a development of the method according to the invention, the speed of the internal combustion engine is therefore determined at the start of the sailing operation, and the functionality of the exhaust gas catalytic converter is only assessed if the speed of the internal combustion engine at the start of the sailing operation is at a certain limit speed or above.

If the internal combustion engine is not disconnected from the drive train, the rotational speed of the components of the internal combustion engine is influenced by frictional forces. The reduction in the rotational speed of the components of the internal combustion engine as a function of the friction, which is predetermined by the road conditions and which acts on the internal combustion engine when the drive train is coupled in, is difficult to estimate in advance. In the case of an existing connection between the internal combustion engine and the drive train, the driving properties of the driver and the road surface properties can furthermore have a major influence on the rotational speed of the components of the internal combustion engine. The drive train is typically only separated shortly after the fuel supply has been closed, so that free rotation of the components of the internal combustion engine is only possible shortly after the fuel supply is closed. It is therefore advantageous if the time period between the closing of the fuel supply and the disconnection of the drive train is detected and only the speed at the end of this time period is compared with the limit speed. Failure to take into account the length of time between the closing of the fuel supply and the decoupling of the drive train for the sailing operation can lead to a fully functional catalytic converter not yet being fully loaded with oxygen when fuel is recirculated. A fully functional catalytic converter that is not fully loaded with oxygen leads to an early increase in the fuel content in the area of the sensor, so that the oxygen storage capacity of the catalytic converter is incorrectly determined to be too low. Since this case is not easily done by anyone fully functional exhaust gas catalytic converter, for example an exhaust gas catalytic converter whose oxygen storage capacity is reduced due to aging or damage, can increase the inaccuracy when evaluating the functionality of the exhaust gas catalytic converter. In an advantageous development of the invention, the time period between the closing of the fuel supply and the decoupling of the drive train therefore flows into the determination of the rotational speed of the internal combustion engine at the start of the sailing operation, as a result of which the inaccuracy in evaluating the functionality of the exhaust gas catalytic converter can be reduced. By reducing the time between the closing of the fuel supply and the decoupling of the drive train, it is also possible to further increase the accuracy in the determination of the time required for the full loading of a functional exhaust gas catalytic converter with oxygen.

According to one embodiment of the present invention, the internal combustion engine is controlled at a supply rate during the supply of fuel after the end of the sailing operation in such a way that a fuel-rich exhaust gas mixture is produced in such a way that overshoots are avoided.

According to one embodiment of the present invention, this is used on an internal combustion engine that is part of a hybrid drive. During the sailing operation of the internal combustion engine, the kinetic energy of the internal combustion engine is converted into electrical energy when the movement of the internal combustion engine is delayed.

• 1 zeigt ein Kraftfahrzeug, das für die Nutzung eines erfindungsgemäßen Verfahrens ausgelegt ist.
• 2 zeigt eine schematische Darstellung der einzelnen Verfahrensschritte des erfindungsgemäßen Verfahrens.

Further features, properties and advantages of the present invention result from the following exemplary embodiment with reference to the attached figures.

• 1 shows a motor vehicle which is designed for the use of a method according to the invention.
• 2nd shows a schematic representation of the individual process steps of the method according to the invention.

Below, with reference to the 1 and 2nd a method for monitoring the condition of a running internal combustion engine 1 downstream catalytic converter 2nd and a motor vehicle which is designed for the use of a method according to the invention.

In 1 A vehicle designed for the use of a method according to the invention is shown. In the exemplary embodiment shown, the vehicle is a motor vehicle 10th which is an internal combustion engine 1 , an electric motor 8th and an exhaust gas catalytic converter 2nd having. The catalytic converter 2nd is the combustion engine 1 downstream. Furthermore, the motor vehicle 10th a power injection unit to the internal combustion engine 1 is connected upstream. Furthermore, the motor vehicle 10th a lambda sensor 3rd on that the catalytic converter 2nd is connected downstream.

• Zu Beginn des Verfahrens wird der Verbrennungsmotor 1 in den Segelbetrieb versetzt, indem die Kraftstoffzufuhr der Kraftstoffeinspritzeinheit 4 geschlossen und der Verbrennungsmotor 1 vom Antriebsstrang 6 getrennt wird, wobei eine kurze Zeitdauer zwischen dem Schließen der Kraftstoffzufuhr und dem Trennen des Verbrennungsmotors 1 vom Antriebsstrang 6 vergehen kann, die jedoch möglichst kurz sein sollte (Schritt S1). Dabei wird im vorliegenden Ausführungsbeispiel geprüft, ob die Drehzahl des Verbrennungsmotors zu Beginn des Segelbetriebes hoch genug ist, um eine vollständige Beladung des Abgaskatalysators 2 mit Sauerstoff erreichen zu können. Hierbei wird angenommen, dass ein normaler Atmosphärendruck vorherrscht und der Sauerstoffgehalt bei 21 % liegt. Aus dem Abklingverhalten der rotierenden Komponenten des Verbrennungsmotors 1 bis zum Stillstand kann somit der Durchfluss der Sauerstoffmenge in den Abgaskatalysator 2 abgeschätzt werden. Für diese Abschätzung ist es jedoch notwendig, dass der Zeitpunkt, ab dem die rotierenden Komponenten des Verbrennungsmotors 1 sich frei bewegen, genau bestimmt werden kann. Hierzu ist es zum einen wichtig, den Zeitpunkt des Schließens der Kraftstoffzufuhr der Kraftstoffeinspritzeinheit 4 genau zu bestimmen. Zum anderen ist es wichtig, dass gleichzeitig zum Schließen der Kraftstoffzufuhr der Kraftstoffeinspritzeinheit 4 die Drehzahl des Verbrennungsmotors 1 gemessen wird. Die Drehzahl des Verbrennungsmotors 1 zu diesem Zeitpunkt kann nun als Ausgangspunkt für die Bestimmung der Sauerstoffmenge die dem Abgaskatalysator 2 zugeführt werden kann, herangezogen werden. Eine zu geringe Drehzahl der Komponenten des Verbrennungsmotors 1 kann nur eine geringe Menge an Sauerstoff in den Abgasstrang fördern, so dass der Abgaskatalysator 2, seine volle Funktionstüchtigkeit vorausgesetzt, nicht vollständig mit Sauerstoff befüllt werden kann. In diesem Fall muss bei der später folgenden Überprüfung der Sauerstoffspeicherkapazität des Abgaskatalysators 2 berücksichtigt werden, dass der Sauerstoffanteil im Abgaskatalysator 2 geringer als der maximal mögliche Sauerstoffanteil ist.
• Diese Vorgehensweise erhöht die Komplexität der Überprüfung der Sauerstoffspeicherkapazität des Abgaskatalysators 2 und damit einhergehend auch die Komplexität der Bewertung der Funktionsfähigkeit des Abgaskatalysators 2. Im vorliegenden Ausführungsbeispiel wird zur Vermeidung dieser erhöhten Komplexität das Bewerten der Funktionsfähigkeit des Abgaskatalysators 2 nur dann durchgeführt, wenn die Drehzahl mindestens einer vorgegebenen Grenzdrehzahl entspricht, die hoch genug ist,
• um eine vollständige Beladung des Abgaskatalysators 2 mit Sauerstoff erreichen zu können, wenn dieser voll funktionstüchtig ist. Die erläuterte Betrachtungsweise setzt jedoch voraus, dass sich die Komponenten des Verbrennungsmotors 1 tatsächlich frei bewegen. Dies setzt wiederum voraus,
• dass der Antriebsstrang 6 von dem Verbrennungsmotor 1 entkoppelt ist.
• Aufgrund dessen, dass die Entkopplung des Antriebsstranges 6 vom Verbrennungsmotor 1 nicht immer zeitgleich mit dem Schließen der Kraftstoffzufuhr der Kraftstoffeinspritzeinheit 4 erfolgt, ist es notwendig, die zeitliche Dauer zwischen dem Schließen der Kraftstoffzufuhr und der Entkopplung des Antriebsstranges 6 zu messen. Während der Kopplung zwischen dem Antriebsstrang 6 und den Komponenten des Verbrennungsmotors 1 beeinflussen der Fahrstil des Kraftfahrers, die Fahrbahneigenschaften, das Gelände und weitere Parameter das Abklingverhalten der rotierenden Komponenten des Verbrennungsmotors 1.
• Erst bei einer vollständigen Abkopplung des Antriebsstranges 6 von den rotierenden Komponenten des Verbrennungsmotors 1 kann das Abklingverhalten der Komponenten des Verbrennungsmotors 1 realistisch abgeschätzt werden. Hierdurch kann auch der Sauerstoffgehalt in den Abgaskatalysator 2 erst bei einer vollständigen Abkopplung des Antriebsstranges 6 von den rotierenden Komponenten des Verbrennungsmotors 1 realistisch abgeschätzt werden. Damit hat die Dauer zwischen dem Schließen der Kraftstoffzufuhr und der Entkopplung des Antriebsstranges 6 einen Einfluss auf die Überprüfung der Sauerstoffspeicherkapazität des Abgaskatalysators 2 und damit auf die Bewertung der Funktionsfähigkeit des Abgaskatalysators 2. Die Dauer zwischen dem Schließen der Kraftstoffzufuhr und der Entkopplung des Antriebsstranges 6 sollte daher so gering wie möglich gehalten werden. Alternativ besteht die Möglichkeit, diese Dauer zu erfassen und die Drehzahl des Verbrennungsmotors erst am Ende dieser Zeitdauer mit dem Drehzahlgrenzwert zu vergleichen.

An embodiment for evaluating the functionality of the internal combustion engine 1 downstream catalytic converter 2nd is described below with reference to 2nd described. In the in 2nd shown embodiment, the following steps are carried out:

• At the beginning of the process, the internal combustion engine 1 sailed by the fuel supply to the fuel injection unit 4th closed and the internal combustion engine 1 from the drive train 6 is separated, with a short period of time between the closing of the fuel supply and the disconnection of the internal combustion engine 1 from the drive train 6 can pass, which should however be as short as possible (step S1 ). In the present exemplary embodiment, it is checked whether the speed of the internal combustion engine at the beginning of the sailing operation is high enough to fully load the exhaust gas catalytic converter 2nd to be able to reach with oxygen. It is assumed that a normal atmospheric pressure prevails and the oxygen content is 21%. From the decay behavior of the rotating components of the internal combustion engine 1 The flow of the amount of oxygen into the catalytic converter can thus come to a standstill 2nd can be estimated. For this estimation, however, it is necessary that the time from which the rotating components of the internal combustion engine 1 move freely, can be precisely determined. For this, it is important, on the one hand, when the fuel supply to the fuel injection unit is closed 4th to determine exactly. Secondly, it is important that the fuel injection unit be closed at the same time as the fuel supply 4th the speed of the internal combustion engine 1 is measured. The speed of the internal combustion engine 1 At this point, the exhaust gas catalytic converter can now be used as the starting point for determining the amount of oxygen 2nd can be used. A too low speed of the components of the internal combustion engine 1 can only convey a small amount of oxygen into the exhaust system, so the catalytic converter 2nd , assuming its full functionality, cannot be completely filled with oxygen. In this case, the following check must be carried out the oxygen storage capacity of the catalytic converter 2nd be taken into account that the oxygen content in the catalytic converter 2nd is less than the maximum possible oxygen content.
• This procedure increases the complexity of checking the oxygen storage capacity of the catalytic converter 2nd and the complexity of the evaluation of the functionality of the catalytic converter 2nd . In the present exemplary embodiment, the functionality of the exhaust gas catalytic converter is assessed in order to avoid this increased complexity 2nd only carried out if the speed corresponds to at least a predetermined limit speed that is high enough,
• for a full load of the catalytic converter 2nd to be able to reach with oxygen if it is fully functional. However, the explained approach assumes that the components of the internal combustion engine 1 actually move freely. This in turn presupposes
• that the powertrain 6 from the internal combustion engine 1 is decoupled.
• Because of the decoupling of the drive train 6 from the internal combustion engine 1 not always at the same time as the fuel supply to the fuel injection unit is closed 4th takes place, it is necessary to determine the time between the closing of the fuel supply and the decoupling of the drive train 6 to eat. During the coupling between the drive train 6 and the components of the internal combustion engine 1 the driving style of the driver, the road characteristics, the terrain and other parameters influence the decay behavior of the rotating components of the internal combustion engine 1 .
• Only when the drive train is completely disconnected 6 of the rotating components of the internal combustion engine 1 can the decay behavior of the components of the internal combustion engine 1 can be realistically estimated. This can also result in the oxygen content in the catalytic converter 2nd only when the drive train is completely disconnected 6 of the rotating components of the internal combustion engine 1 can be realistically estimated. This means the time between closing the fuel supply and decoupling the drive train 6 an influence on the check of the oxygen storage capacity of the catalytic converter 2nd and thus on the evaluation of the functionality of the catalytic converter 2nd . The time between closing the fuel supply and decoupling the powertrain 6 should therefore be kept as low as possible. Alternatively, it is possible to record this duration and to compare the speed of the internal combustion engine with the speed limit value only at the end of this period.

In the context of the method according to the invention, the supply air is supplied to the internal combustion engine in sailing operation 1 not closed. The internal combustion engine 1 is therefore only operated with supply air. There is therefore no combustion in the combustion chamber of the internal combustion engine 1 instead of. That by the internal combustion engine 1 supplied air is therefore rich in oxygen. The exhaust gas catalytic converter fills up when the fuel supply is closed 2nd hence with oxygen, the inertia of the moving parts of the engine being sailed 1 for filling the catalytic converter 2nd is used (step S2 ).

The supply air is through the internal combustion engine 1 directed as long as the rotating components of the internal combustion engine 1 move. Only when the internal combustion engine 1 is completely switched off, i.e. when the rotating components of the internal combustion engine 1 are completely at rest, the oxygen supply to the catalytic converter 2nd completed. The third step S3 In the present exemplary embodiment, the method is therefore to wait until the internal combustion engine 1 is completely at rest. Once the internal combustion engine 1 is at rest or at a later time according to the invention in a fourth step S4 the sailing operation is stopped by the fuel supply of the fuel injection unit 4th opened again and the internal combustion engine 1 is started again. The time period varies from an immediate start as soon as the internal combustion engine 1 is completely at rest and waiting for the performance of the internal combustion engine 1 is needed again. Basically, in the context of evaluating the functionality of the exhaust gas catalytic converter 2nd the fuel supply to the fuel injection unit 4th opened again and the internal combustion engine 1 be started again before the internal combustion engine 1 is completely at rest, provided that until the fuel supply is restarted and the internal combustion engine is restarted 1 Elapsed time of sailing at the determined speed at the start of sailing was long enough to the exhaust gas catalytic converter 2nd completely filled with oxygen, if it should be fully functional.

As soon as the fuel supply is opened again, in a fifth step S5 the internal combustion engine 1 started again. The fuel-air ratio is set such that the internal combustion engine 1 is operated with a lambda value <1 (step S6 ). The internal combustion engine 1 is operated, so to speak, in the rich operating mode, the high proportion of fuel due to the im Catalytic converter 2nd stored oxygen is completely burned.

In the seventh step S7 According to the present invention, the time course of the fuel-air ratio in the exhaust gas after the fuel supply is reopened and the internal combustion engine is restarted 1 detected. The fuel-air ratio in the exhaust gas is measured by the exhaust gas catalytic converter 2nd downstream lambda probe 3rd . During the measurement of the time course of the proportion of fuel in the exhaust gas, that of the internal combustion engine 1 Fuel feed rate integrated to determine the amount of fuel supplied.

In step S8 the time course of the fuel-air ratio in the exhaust gas is evaluated. Due to the oxygen loading of the catalytic converter 2nd As already mentioned, the fuel is replaced by the one in the catalytic converter 2nd stored oxygen completely burned. As soon as in the catalytic converter 2nd stored oxygen is used up, this combustion no longer takes place, so that the fuel proportion in the exhaust gas rises sharply at this time. The fueling rate integrated up to the time of the increase indicates the amount of fuel supplied since the fueling was reopened. As part of the step S8 carried out evaluation of the in step S7 recorded time course of the fuel-air ratio in the exhaust gas, the time is determined at which the lambda sensor 3rd for the first time a high proportion of fuel in the exhaust gas is measured. The fuel feed rate integrated up to this point also becomes that of the internal combustion engine 1 amount of fuel supplied up to this point is determined. This amount of fuel is then compared to a predetermined threshold. If the fuel quantity does not reach this threshold value, the catalytic converter shows 2nd insufficient oxygen storage capacity and is assessed as not fully functional. On the other hand, if the threshold is reached or exceeded, the catalytic converter shows 2nd sufficient oxygen storage capacity and is considered to be fully functional. In addition, can optionally from the amount of fuel that the internal combustion engine 1 up to the point at which the lambda sensor 3rd for the first time a high proportion of fuel in the exhaust gas is measured, and the selected air-fuel ratio is the amount of oxygen emitted by the exhaust gas catalytic converter 2nd has been stored during the sailing operation, so that the functional state of the exhaust gas catalytic converter 2nd can be assessed not only qualitatively, but also quantitatively.

In the present embodiment, the engine can be started 1 by means of the rotating components of the drive train 6 of the motor vehicle 10th take place, provided the motor vehicle when restarting the internal combustion engine 1 still rolling. The powertrain 6 to the internal combustion engine 1 coupled. With a moving motor vehicle 10th the drive train components rotate 6 of the motor vehicle 10th and can therefore use the internal combustion engine 1 help to start. According to the legal regulations, it is required that the exhaust gas catalytic converter is functional 2nd is not only determined while standing, but also while driving.

In the present exemplary embodiment, the motor vehicle has 10th next to the internal combustion engine 1 an electric motor 8th on. The electric motor can 8th are used to start the internal combustion engine, for example when the kinetic energy of the motor vehicle is no longer sufficient to reliably start the internal combustion engine or the motor vehicle has come to a standstill during sailing. The energy stored by a braking process can thus be used to the internal combustion engine 1 to start. In this embodiment, the electric motor replaces 8th the function of a starter.

The present invention has been described in detail using an exemplary embodiment for explanatory purposes. However, a person skilled in the art recognizes that deviations from the exemplary embodiment are possible. The invention is therefore not intended to be limited to the exemplary embodiment, but only by the appended claims.

Reference list

1

Internal combustion engine

2nd

catalyst

3rd

Lambda sensor

4th

Fuel injection unit

6

Powertrain

8th

Electric motor

10th

Motor vehicle

S1

Closing the fuel supply to the fuel injection unit

S2

Filling the catalytic converter with oxygen

S3

Wait for the internal combustion engine to come to a complete standstill

S4

Open the fuel supply to the fuel injection unit

S5

Starting the internal combustion engine

S6

Operation of the internal combustion engine with lambda <1

S7

Measuring the time course of the fuel-air ratio in the exhaust gas after the fuel supply is reopened and the internal combustion engine is restarted

S8

Assess the functionality of the catalytic converter

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2012/0222402 A1 [0006, 0016]
• US 2012/0053816 A1 [0007]
• US 9677488 B2 [0008]
• US 7937995 B2 [0009]
• US 2016/0319727 A1 [0010]
• US 7499792 B2 [0011]
• US 9731711 B2 [0012]
• DE 102011088296 A1 [0013]
• US 8831818 B2 [0014]
• DE 102016219549 A1 [0015]

Claims (9)

Method for evaluating the functionality of an exhaust gas catalytic converter (2) connected downstream of an internal combustion engine (1), in which the internal combustion engine (1) is set into a sailing mode before determining an oxygen storage capacity of the exhaust gas catalytic converter (2), characterized in that the inertia of the moving parts of the combustion engine (1) set to sailing is used to fill the exhaust gas catalytic converter (2) with oxygen, the oxygen storage capacity of the exhaust gas catalytic converter (2) filled with oxygen is checked after the sailing operation has ended and the functionality of the exhaust gas catalytic converter (2) is checked the result of the check of the oxygen storage capacity of the catalytic converter (2) is evaluated. Procedure according to Claim 1 , characterized in that, in order to check the oxygen storage capacity of the exhaust gas catalytic converter (2), the fuel is supplied to the internal combustion engine (1) after the end of the sailing operation at such a feed rate that a fuel-rich exhaust gas mixture is produced, and by means of a sensor () connected downstream of the exhaust gas catalytic converter (2) 3) it is checked whether fuel-rich exhaust gas emerges from the exhaust gas catalytic converter (2) before a predetermined amount of fuel has been injected into the internal combustion engine (1). method Claim 2 , characterized in that from the amount of fuel which has been supplied to the internal combustion engine (1) until the fuel-rich exhaust gas emerges from the exhaust gas catalytic converter (2) and the selected fuel-air ratio when supplying the fuel, the amount of oxygen which is from the exhaust gas catalytic converter (2) has been stored during sailing operation. Procedure according to Claim 2 or Claim 3 , characterized in that the checking whether fuel-rich exhaust gas exits the exhaust gas catalytic converter (2) is carried out with the aid of a lambda probe (3) as a sensor. Procedure according to one of the Claims 1 to 4th , characterized in that the inertia of the moving parts of the internal combustion engine (1), which is set in sailing mode, is used to fill the exhaust gas catalytic converter (2) with oxygen, by the still high speed of the internal combustion engine (1) due to the inertia after the start of sailing mode. is used to convey air through the internal combustion engine (1) into the catalytic converter (2). Procedure according to one of the Claims 1 to 5 , characterized in that the speed of the internal combustion engine (1) is determined at the start of the sailing operation and the functioning of the exhaust gas catalytic converter (2) is only evaluated if the speed of the internal combustion engine (1) at the start of the sailing operation at a certain limit speed or above lies. Procedure according to one of the Claims 1 to 6 , characterized in that the time between the closing of the fuel supply and the decoupling of the drive train (6) is included in the determination of the speed of the internal combustion engine (1) at the start of the sailing operation. Procedure according to one of the Claims 1 to 7 , characterized in that the internal combustion engine (1) is controlled during the supply of the fuel at such a supply rate that a fuel-rich exhaust gas mixture is produced in such a way that overshoots are avoided. Procedure according to one of the Claims 1 to 8th , characterized in that it is used on an internal combustion engine (1), which is part of a hybrid drive, and during the sailing operation of the internal combustion engine (1) when the movement of the internal combustion engine (1) is delayed, its kinetic energy is converted into electrical energy.

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