DE102018200399B4 - Method for analyzing the oxygen storage capacity of a catalytic converter and drive for a motor vehicle - Google Patents

Abstract

Method for analyzing the oxygen storage capacity of a catalytic converter (6) arranged in an exhaust system (4) of an internal combustion engine (3), comprising: - decoupling the internal combustion engine (3) from a drive train (9), - driving the internal combustion engine (3) at a constant speed by means of an electric motor (10),- supplying a lean fuel-air mixture to the catalytic converter (6) until the catalytic converter (6) is completely loaded with oxygen,- supplying a rich fuel-air mixture to the catalytic converter (6),- determining of time profiles of combustion air ratios (λauf, λab) upstream and downstream of the catalytic converter (6) and determining the amount of oxygen that can be stored in the catalytic converter (6) from the determined time profiles of the combustion air ratios (λauf, λab), the rich fuel-air mixture is generated by injecting fuel into a combustion chamber of the internal combustion engine (3) and the electric motor (10) Störm moments due to the injection of fuel into the combustion chamber of the internal combustion engine (3) compensates.

Description

The present invention relates to a method for analyzing the oxygen storage capacity of a catalytic converter arranged in an exhaust system of an internal combustion engine and to a drive for a motor vehicle.

In motor vehicles, catalysts such. B. three-way catalysts are used to treat existing nitrogen oxides, hydrocarbons and / or carbon monoxide in the exhaust stream of an internal combustion engine and to reduce pollutant emissions. As the life of the catalytic converter increases, its effectiveness deteriorates due to the effects of high temperatures during use in the exhaust system. This loss of function is permanent, i. H. not regenerable, and increases the pollutant emissions of the vehicle increasingly and permanently.

Legislation therefore requires that the functionality of the catalytic converter be checked at specified minimum intervals. In addition, the so-called In-Use-Performance-Ratio (IUPR) is specified, which determines the relationship between the number of checks actually carried out in full in relation to the number of driving cycles that meet certain boundary conditions.

One of the reasons for the deterioration of the catalyst performance is the decrease in oxygen storage capacity. Therefore, the oxygen storage capacity is often determined and evaluated directly or indirectly for the function test of three-way catalytic converters. For example, a comparison with threshold values can be used to determine whether maintenance or repair of the catalytic converter is required.

A monitoring algorithm based on checking the oxygen storage capacity can, for example, be based on the phenomena described below. If the catalyst is supplied with a rich exhaust gas mixture, i. H. If the combustion air ratio λ upstream of the catalytic converter is less than 1, hydrocarbons and/or carbon monoxide contained in the exhaust gas flow and possibly nitrogen monoxide react with oxygen stored in the catalytic converter, so that the amount of oxygen stored decreases. Depending on the stored oxygen quantity, a combustion air ratio λ less than 1 is also detected downstream with a time delay. The originally stored amount of oxygen can also be inferred from the time delay.

Since the oxygen storage capacity decreases due to the aging of the catalyst, this is also reflected in the time delay, i. H. a combustion air ratio λ smaller than 1 is observed increasingly earlier downstream of the catalytic converter.

The analysis of the oxygen storage capacity can be carried out, for example, during a so-called overrun operating phase while the internal combustion engine is in overrun mode, i. H. in the case of an internal combustion engine coupled to the drive train, is operated without fuel supply. In other words, the internal combustion engine is dragged along. In this case, fresh air is pumped from the intake line via the combustion engine into the exhaust line, so that the combustion air ratio λ is initially greater than 1, i. H. a lean exhaust gas mixture is present. As a result, the catalyst is completely loaded with oxygen.

To analyze the oxygen storage capacity, such an overrun operating phase is now alternated with a further operating phase in which a rich exhaust gas mixture is generated by injecting fuel. The current state of the catalytic converter can be determined from the time delay described above between the detection of a combustion air ratio of less than 1 upstream and downstream of the catalytic converter.

In order to be able to carry out an analysis of the oxygen storage capacity reliably and accurately, the duration of the overrun operating phase must be long enough to ensure that the catalyst is fully loaded with oxygen. In addition, the accuracy of the analysis can be negatively influenced due to a continuously decreasing volume flow with varying engine speed.

If the motor vehicle is equipped with an electronically actuated clutch (e-clutch), however, the frequency and/or duration of the overrun operating phases usually decreases, since strategies are often used in connection with an electronically actuated clutch in which the engine is automatically switched off by the Wheels is decoupled, z. B. to save fuel. For example, the engine can be automatically decoupled from the wheels when the driver is not requesting engine power, e.g. B. the accelerator pedal is not actuated, and other conditions are met, e.g. no braking takes place. After decoupling, the engine speed drops very quickly. The engine can then continue to idle or be switched off.

The electronically actuated clutch thus enables the internal combustion engine to be automatically decoupled from the rest of the drive train, so that the internal combustion engine can be operated at idle or switched off. This avoids the combustion engine being dragged along and fuel consumption can be reduced. An analysis of the oxygen storage capacity is not possible or only possible to a limited extent, since the frequency and/or duration of the overrun operating phases is reduced.

The aspect described above with regard to an electronically actuated clutch is of great importance in particular in the case of hybrid electric vehicles. In a hybrid electric drive of a motor vehicle, the internal combustion engine can be switched off while the motor vehicle is coasting in order to reduce fuel consumption and pollutant emissions. To switch off the internal combustion engine, its fuel supply can be interrupted. With an electric motor used as a generator of the hybrid electric drive or a separate generator of the hybrid electric drive, energy can be recovered (recuperation), which improves the energy efficiency of the hybrid electric drive.

In order to increase the frequency and duration of overrun operating phases in a hybrid electric drive, the free rolling of the motor vehicle can be delayed, for example, by preventing the clutch from opening until the analysis of the oxygen storage capacity has been completed. In other words, after the accelerator pedal has been completely relieved, the internal combustion engine is still operated in an overrun operating phase for a predetermined period of time. However, this influences the handling of the motor vehicle, since the vehicle brakes faster when the clutch is closed. This can be disturbingly perceivable for a driver of the motor vehicle and possibly lead to customer dissatisfaction.

Alternatively, after the accelerator pedal has been completely relieved, a "free fall" of the internal combustion engine can be used when the internal combustion engine is decoupled from the drive train of the hybrid electric drive, during which an engine speed of the internal combustion engine drops from the last working speed to an idle speed of the internal combustion engine or to zero ( DE 10 2011 001 045 A1 ). However, the duration of such a free fall of the internal combustion engine is usually relatively short, so that it cannot be ensured that the catalytic converter is completely flushed with fresh air. Consequently, a robust analysis of the oxygen storage capacity cannot be reliably guaranteed.

From the DE 10 2017 201 643 A1 discloses a method for diagnosing a lambda probe, in which the fuel supply to the internal combustion engine is switched off during the diagnosis and the internal combustion engine, which is decoupled from the drive train, is driven by an electric motor for a predetermined period of time.

The present invention is based on the object of specifying a possibility with which a reliable analysis of the oxygen storage capacity of a catalytic converter in an exhaust system of a motor vehicle can be carried out.

This problem is solved by the subject matter of the independent claims. Advantageous developments of the invention are specified in the dependent claims.

The invention is based on the basic idea of carrying out an analysis of the oxygen storage capacity of a catalytic converter in the exhaust system of an internal combustion engine while the internal combustion engine is decoupled from the drive train, i. H. separate, and is driven by an electric motor. This advantageously enables a reliable and robust analysis of the oxygen storage capacity, with the driving behavior not being affected, or at most being slightly affected. In other words, the driver who has become accustomed to a decoupling strategy does not have to be confronted with an overrun phase in which the clutch unexpectedly remains closed and the vehicle slows down more quickly.

In addition, the analysis of the oxygen storage capacity can be carried out at a constant speed of the internal combustion engine and constant volume flows. This improves the reliability and accuracy of the analysis compared to the method known from the prior art, in which the analysis is carried out in an overrun operating phase with a continuously decreasing volume flow at varying engine speeds. A further improvement in accuracy can be achieved by specifying a specific target speed value for the combustion engine during the analysis, so that the scatter of the measured values can be reduced. The speed setpoint to be specified should not be too low in order to enable a quick analysis of the oxygen storage capacity.

The method according to the invention for analyzing the oxygen storage capacity of a catalyst arranged in an exhaust system of an internal combustion engine, e.g. B. a three-way catalytic converter, comprises decoupling the internal combustion engine from a drive train, driving the internal combustion engine by means of an electric motor, supplying a lean fuel-air mixture to the catalytic converter until the catalytic converter is completely loaded with oxygen, supplying a rich fuel-air mixture Mixture to the catalyst, a determination of time courses of combustion air conditions upstream and downstream of the catalytic converter and a determination of the amount of oxygen that can be stored in the catalytic converter from the determined time profiles of the combustion air ratios. The internal combustion engine can be designed, for example, to drive a motor vehicle, ie it can be the internal combustion engine of a motor vehicle.

The above features of the method can be performed in the order of explanation, but also in a different order or simultaneously as needed. For example, the time curves of the combustion air ratios are determined during the supply of the lean or rich fuel-air mixture.

The combustion air ratios over time can be measured using gas sensors, e.g. B. lambda probes are determined. The internal combustion engine can be decoupled from the rest of the drive train by releasing a clutch arranged in the drive train.

To analyze the oxygen storage capacity, the internal combustion engine is decoupled from the drive train and driven by an electric motor. The fuel supply to the internal combustion engine can preferably be interrupted, so that the internal combustion engine can be driven exclusively by the electric motor, at least at times. By driving the internal combustion engine by means of the electric motor, oxygen-containing fresh air continues to be conveyed through the intake line and the combustion chamber of the internal combustion engine into the exhaust line. If the fuel supply is low or interrupted, this can result in a lean fuel-air mixture, i. H. a fuel-air mixture with a combustion air ratio greater than 1, so that the catalytic converter is loaded with oxygen. An interruption of the fuel supply, e.g. B. the fuel injection, so that the catalyst only fresh air is supplied, as this is the fastest way to load the catalyst with oxygen and fuel can be saved.

It can be assumed that the catalytic converter is completely loaded with oxygen if the combustion air ratio downstream of the catalytic converter corresponds at least approximately to the combustion air ratio upstream of the catalytic converter.

After the catalyst has been completely loaded with oxygen, the catalyst is now supplied with a rich fuel-air mixture, i. H. a fuel-air mixture with a combustion air ratio of less than 1, supplied by fuel being supplied to the combustion chamber of the internal combustion engine. Additionally, fuel may be injected into the exhaust line upstream of the catalytic converter. The amount of oxygen stored in the catalytic converter and thus the amount of oxygen that can be stored in the catalytic converter can now be determined by evaluating the time curves of the combustion air ratio determined upstream and downstream of the catalytic converter. Based on the amount of oxygen that can be stored, a statement can be made about the condition of the catalytic converter and, if necessary, maintenance or repair measures can be initiated.

The point in time at which the method for analyzing the oxygen storage capacity is initiated can be selected as a function of detected operating parameters of the internal combustion engine, the drive train and/or the motor vehicle. Such an operating parameter can be, for example, a detected complete release of the accelerator pedal while the motor vehicle is being driven. Alternatively, an analysis of the oxygen storage capacity can be repeatedly initiated at predetermined time intervals or after predetermined operating cycles.

The analysis of the oxygen storage capacity can be carried out, for example, while the motor vehicle is coasting. The motor vehicle rolls freely when not being propelled by the internal combustion engine or the electric motor.

According to the invention, the internal combustion engine is driven at a constant speed by means of the electric motor. Optionally, a speed setpoint can be specified as a constant speed. The speed can preferably be selected in such a way that the time required for complete loading of the catalytic converter with oxygen is as short as possible in order to be able to carry out the analysis of the oxygen storage capacity quickly and thus to keep the energy consumption of the electric motor required to drive the internal combustion engine as low as possible.

According to the invention, when generating the rich fuel-air mixture by injecting fuel into a combustion chamber of the internal combustion engine, the electric motor compensates for disturbance (torque) torques that occur due to the injection of fuel into the combustion chamber of the internal combustion engine. When fuel is injected into the combustion chamber and ignited, the internal combustion engine is also driven by fuel combustion in addition to the electric motor, as a result of which additional torque is generated. By appropriately reducing the drive by means of the electric motor, such Disturbance moments compensated and z. B. the speed of the internal combustion engine can be kept constant. This can improve the reliability and accuracy of the oxygen storage capacity analysis.

According to various embodiment variants, the drive train can be designed as a hybrid electric drive train, for example as a hybrid electric drive train of a hybrid electric motor vehicle, and the electric motor can be an electric machine of the hybrid electric drive train. For example, an electric machine present to power the hybrid electric powertrain may be used to power the engine during the oxygen storage capacity analysis.

In a hybrid electric drive, the internal combustion engine can be driven by the electric motor. For this purpose, the electric motor can be drivingly connected to the internal combustion engine via a belt or a gear. Alternatively, the electric motor and the internal combustion engine can be arranged on the same axis. A clutch for separating the internal combustion engine from the electric motor can be provided as an option. In addition, in certain configurations of a hybrid electric drive, the internal combustion engine and the electric motor can be decoupled from the drive train of the hybrid electric drive. The invention makes use of these properties of a hybrid electric drive in order to drive the internal combustion engine, e.g. B. after a complete relief of an accelerator pedal of a hybrid electric vehicle, to be decoupled from the drive train of the hybrid electric drive during the analysis of the oxygen storage capacity and to be driven by at least one electric motor of the hybrid electric drive, e.g. B. over a predetermined period of time at a predetermined engine speed. As a result, the internal combustion engine is kept in a stable state without a supply of fuel and can pump fresh air into the exhaust line via the intake line.

For example, the hybrid electric powertrain may have a P0, P1, or P2 configuration. In other words, the electric machine can be provided at different positions of the hybrid drive train, e.g. B. at the PC position, z. B. as a so-called. Belt integrated starter generator, BISG, at the P1 position, z. B. as a so-called crank integrated starter generator, CISG or at the P2 position. In the case of a P2 configuration, two clutches, e.g. B. two electronically actuated clutches may be present. In this case, to analyze the oxygen storage capacity, the clutch between the electric machine and the transmission is opened, while the clutch between the electric machine and the combustion engine is closed or remains closed.

According to further embodiment variants, the internal combustion engine can be decoupled from the drive train by means of an electronically actuated clutch, a so-called e-clutch. An electronically actuated clutch enables the oxygen storage capacity analysis to be performed automatically without the need for manual intervention by the operator or driver. As a result, regular analyzes of the oxygen storage capacity can advantageously be carried out in a simplified manner.

According to further embodiment variants, a lean fuel-air mixture and a rich fuel-air mixture can be alternately supplied to the catalytic converter several times. Lean-rich cycles carried out several times can improve the accuracy of the analysis of the oxygen capacity, since mean values can be formed, for example, or other statistical evaluations can be carried out.

A drive according to the invention for a motor vehicle has an internal combustion engine with an exhaust line connected to the internal combustion engine for receiving an exhaust gas flow generated by the internal combustion engine, a catalytic converter arranged in the exhaust line, a sensor for determining the combustion air ratio arranged upstream of the catalytic converter in the exhaust line, a sensor downstream of the catalytic converter sensor arranged in the exhaust system for determining the air/fuel ratio, a clutch for connecting the internal combustion engine to a drive train, an electric motor which can be drivingly connected to the internal combustion engine and a control and/or regulating unit which is set up and designed for this purpose, control signals for decoupling the combustion -motors from the drive train, for driving the internal combustion engine at a constant speed by means of the electric motor, for supplying a lean fuel-air mixture to the catalyst, for generating e a rich fuel-air mixture by injecting fuel into a combustion chamber of the internal combustion engine, for supplying the rich fuel-air mixture to the catalytic converter and for compensating for disturbance torques due to the injection of fuel into the combustion chamber of the internal combustion engine by means of the electric motor.

The advantages mentioned above in relation to the method are correspondingly associated with the drive according to the invention. In particular, the drive for carrying out the method according to one of the aforementioned embodiment variants th or any combination of at least two of these variants can be used.

The internal combustion engine can be an Otto engine or a diesel engine. By means of the clutch, z. B. an electronically actuated clutch, the internal combustion engine can either be drivingly connected to the drive train of the drive or be detached from the drive train. The electric motor can be selectively connected to the internal combustion engine or decoupled from it, for example via a further clutch and via a section of the drive train. Alternatively, the electric motor can be selectively drivingly connected to the internal combustion engine or decoupled from it via a further clutch and a belt or a transmission. Alternatively, the electric motor may be continuously drivingly connected to the internal combustion engine.

The drive can be designed as a hybrid electric drive, with the electric motor being an electric machine of the hybrid electric drive. According to the above, the hybrid electric drive can have a P0, P1 or P2 configuration.

The sensors can be designed as lambda probes, for example. The catalytic converter can be designed, for example, as a three-way catalytic converter.

The control and/or regulation unit can be formed, for example, by vehicle electronics or engine electronics or separately from these vehicle components. The control and/or regulation unit can be connected in terms of signals to an injection system of the internal combustion engine in order to be able to interrupt or activate the supply of fuel to the internal combustion engine. The control and/or regulation unit can be connected in terms of signals to an actuator of the clutch in order to be able to release the clutch and keep it released during the analysis of the oxygen storage capacity. The control and/or regulation unit can optionally be connected to a further clutch in terms of signals in order to be able to drive the electric motor to the internal combustion engine and keep it connected. The control and/or regulation unit can be connected to the electric motor via signals in order to be able to control the electric motor for driving the internal combustion engine, e.g. B. at a constant speed.

According to various embodiment variants, the drive can have a processing unit that is set up and designed to determine the amount of oxygen that can be stored in the catalytic converter from time profiles of the determined combustion air ratios upstream and downstream of the catalytic converter. If it is the drive train of a motor vehicle, the processing unit can, for example, in the vehicle itself, z. B. as part of the engine control can be arranged. Alternatively, the processing unit can be arranged externally, with the time profiles of the determined combustion air ratios upstream and downstream of the catalytic converter being sent to the processing unit, e.g. B. be transmitted by a radio link.

• 1 eine schematische Darstellung eines Ausführungsbeispiels für einen erfindungsgemäßen Antrieb; und.
• 2 ein Diagramm zur Darstellung des Verlaufs einer Motordrehzahl eines Verbrennungsmotors eines Ausführungsbeispiels für einen Hybridelektroantrieb während der Analyse der Sauerstoffspeicherkapazität.

In the following, the invention is explained by way of example with reference to the attached figures using preferred embodiments, with the features presented below being able to represent an aspect of the invention both individually and in various combinations with one another. Show it:

• 1 a schematic representation of an embodiment of a drive according to the invention; and.
• 2 a diagram to show the course of an engine speed of an internal combustion engine of an embodiment for a hybrid electric drive during the analysis of the oxygen storage capacity.

1 shows a schematic representation of an embodiment of a drive 1 for a motor vehicle 2, wherein the drive 1 is designed as a hybrid electric drive.

The drive 1 has an internal combustion engine 3 with an exhaust line 4 connected to the internal combustion engine 3 for receiving an exhaust gas flow 5 generated by the internal combustion engine 3 . The internal combustion engine 3 is supplied with fresh air via the intake line 13. The internal combustion engine 3 can be connected to the drive train 9 or decoupled from the drive train 9 by means of the clutch 8b.

A catalytic converter 6 is arranged in the exhaust line 5 and is a three-way catalytic converter in the exemplary embodiment. Furthermore, in the exhaust line 5 upstream and downstream of the catalytic converter 6, lambda probes are arranged as sensors 7a, 7b for determining the combustion air ratios λ _up , λ _down upstream and downstream of the catalytic converter 6.

The drive 1 of the exemplary embodiment is designed as a P2 hybrid electric drive of a motor vehicle 2 , ie in addition to the internal combustion engine 3 it has an electric motor 10 for driving the motor vehicle 2 . The electric motor 10 is drivingly connected to the internal combustion engine 3 via the clutch 8a. Alternatively, the electric motor 10 also be directly connected to the internal combustion engine 3. Both clutches 8a, 8b are designed as electronically actuated clutches.

The drive 1 also has a control and/or regulation unit 11 which is set up and designed to transmit control signals for decoupling the internal combustion engine 3 from the drive train 9, for driving the internal combustion engine 3 at a constant speed by means of the electric motor 10, for supplying a lean Fuel-air mixture to the catalytic converter, to generate a rich fuel-air mixture by injecting fuel into a combustion chamber of the internal combustion engine 3, to supply the rich fuel-air mixture to the catalytic converter 6 and to compensate for disturbance torques due to the injection of the fuel output into the combustion chamber of the internal combustion engine 3 by means of the electric motor 10 . For this purpose, the control and/or regulation unit 11 is connected in terms of signals to an injection system (not shown) of the internal combustion engine 3, the electric motor 10 and the clutches 8a, 8b.

In addition, the drive 1 has a processing unit 12 which is set up and designed to determine the amount of oxygen that can be stored in the catalytic converter 6 from time profiles of the determined combustion air ratios λ _up , λ _down upstream and downstream of the catalytic converter 6 . For this purpose, the processing unit 12 is connected to the two sensors 7a, 7b in terms of signals.

2 shows a diagram showing the engine speed of the internal combustion engine 3 over time during the analysis of the oxygen storage capacity of the catalytic converter 6. The engine speed n is plotted over time t. The dependencies according to 2 can, for example, in the analysis of the oxygen capacity of the engine 1 according to 1 are observed, but are not on the in 1 Drive 1 shown limited.

At the beginning, the internal combustion engine 3 is operated at an instantaneous engine speed n _m . At time t ₁ an accelerator pedal of motor vehicle 2 is completely relieved and the fuel supply to internal combustion engine 3 is interrupted by a corresponding control signal being output to the injection system of internal combustion engine 3 by control and/or regulating unit 11 .

For comparison, the solid curve A represents an engine speed curve according to the prior art of an internal combustion engine operated in overrun mode of a conventional drive, which only has an internal combustion engine, or a micro-hybrid electric drive. The internal combustion engine is coupled to the drive train of the respective drive and is thereby dragged along . At time t ₅ the internal combustion engine is decoupled from the drive train of the respective drive by the driver. The engine speed then falls to a specified idle speed n _L and is maintained at idle speed n _L by means of an idle controller. If there is no further speed request, the combustion engine is switched off completely after a specified time, so that the engine speed drops to zero. For this purpose, the respective drive is equipped with an automatic start-stop system.

The dashed curve B represents an engine speed profile of an internal combustion engine with an electronic clutch and an overrun strategy. At time t ₁ , in comparison to the example described above, the internal combustion engine of the drive is additionally decoupled from the drive train of the drive. The internal combustion engine is then in a "free fall" in which the engine speed drops more rapidly. The engine speed can drop either to zero (time t ₄ , curve B1) or to the idling speed n _L (curve B2). The engine speed can then be regulated to the idle speed n _L by an idle controller or drop to zero as part of an automatic start-stop system (curve B2′).

The dot-dash curve C shows the engine speed profile during a method according to the invention for analyzing the oxygen capacity of the catalytic converter 6. After or at the same time as the fuel supply to the internal combustion engine 3 is interrupted, the internal combustion engine 3 is decoupled from the drive train 9 by releasing the clutch 8b and from time t ₃ by means of of the electric motor 10 driven at a predetermined engine speed n _v . In the exemplary embodiment, the internal combustion engine speed n _v is greater than the idle speed n _L . The fuel supply is interrupted by the output of a corresponding control signal from the control and/or regulation unit 11 to the injection system of the internal combustion engine 3 .

From time t ₅ onwards, the internal combustion engine 3 is no longer driven by the electric motor 10, so that the engine speed drops either to zero (curve C1) or to the idling speed n _L and can be maintained at the idling speed n _L by means of an idling controller (curve C2 ). The time period between times t ₂ and t ₅ is available for performing the oxygen storage capacity analysis. The analysis of the oxygen storage capacity is carried out while the motor vehicle 2 is coasting.

To analyze the oxygen storage capacity, the catalytic converter is supplied with a lean fuel-air mixture until the combustion air ratios λ _up , λ _down upstream and downstream of the catalytic converter 6 can be used to determine that the catalytic converter 6 is completely loaded with oxygen. A control signal is then output from the control and/or regulation unit 11 to the injection system of the internal combustion engine 3 in order to restore the fuel supply to the combustion chamber so that a rich fuel-air mixture is produced, which is supplied to the catalytic converter 6 as an exhaust gas flow 5 .

The combustion air ratios λ _up , λ _down upstream and downstream of the catalytic converter 6 are also determined by means of the sensors 7a, 7b and transmitted to the processing unit 12, which determines the amount of oxygen that can be stored in the catalytic converter 6 from the determined time profiles of the combustion air ratios λ _up λ _down . Optionally, several lean-rich cycles can be executed one after the other. Disturbing torques due to the injection of fuel into the combustion chamber of internal combustion engine 3 are compensated for by electric motor 10 .

Reference List

1

drive

2

motor vehicle

3

combustion engine

4

exhaust line

5

exhaust flow

6

catalyst

7a, 7b

sensor

8a, 8b

coupling

9

powertrain

10

electric motor

11

Control and/or regulation unit

12

processing unit

13

intake manifold

A

Speed curve (conventional; micro-hybrid)

B

Speed curve (mild or full hybrid)

C

Speed curve (according to the invention)

n

engine speed

nL

idle speed

nm

current engine speed

not applicable

specified engine speed

t

time

t1

Time (accelerator pedal relief; fuel cut-off)

t2

Time (start of specified period)

t3

Time (start of combustion engine drive by electric motor)

t4

Time (zero engine speed for mild or full hybrid)

t5

Time (end of combustion engine drive by electric motor)

λ

combustion air ratio

λon

Combustion air ratio upstream of the catalyst

λab

Combustion air ratio downstream of the catalyst

Claims (9)

Method for analyzing the oxygen storage capacity of a catalytic converter (6) arranged in an exhaust system (4) of an internal combustion engine (3), comprising: - decoupling the internal combustion engine (3) from a drive train (9), - driving the internal combustion engine (3) at a constant speed by means of an electric motor (10), - supplying a lean fuel-air mixture to the catalytic converter (6) until the catalytic converter (6) is completely loaded with oxygen, - supplying a rich fuel-air mixture to the catalytic converter (6), - determining of combustion air ratios over time (λ _up , λ _down ) upstream and downstream of the catalytic converter (6) and - determining the amount of oxygen that can be stored in the catalytic converter (6) from the determined combustion air ratios over time (λ _up , λ _down ), the rich fuel -Air mixture is generated by injecting fuel into a combustion chamber of the internal combustion engine (3) and wherein the electric motor gate (10) compensates for disturbance torques due to the injection of fuel into the combustion chamber of the internal combustion engine (3). procedure after claim 2 , wherein the drive train (9) is designed as a hybrid electric drive train and the electric motor (10) is an electric machine of the hybrid electric drive train. Method according to one of the preceding claims, wherein the internal combustion engine (3) with is decoupled from the drive train by means of an electronically actuated clutch (8b). Method according to one of the preceding claims, in which a lean fuel-air mixture and a rich fuel-air mixture are supplied to the catalytic converter (6) in alternation several times. Method according to one of the preceding claims, in which the lean fuel-air mixture is produced by cutting off the fuel supply to the internal combustion engine (3). Drive (1) for a motor vehicle (2), comprising: - an internal combustion engine (3) with an exhaust line (4) connected to the internal combustion engine (3) for receiving an exhaust gas stream (5) generated by the internal combustion engine (3), a catalytic converter (6) arranged in the exhaust system (4), - a sensor (7a) arranged upstream of the catalytic converter (6) in the exhaust system (4) for determining the air/fuel ratio (λ _auf ), - a sensor (7a) downstream of the catalytic converter (6) in the exhaust system ( 4) arranged sensor (7b) for determining the air/fuel ratio (λ _ab ), - a clutch (8a) for connecting the internal combustion engine (3) to a drive train (9), - an electric motor (10) which drives the internal combustion engine (3rd ) can be connected and - a control and/or regulation unit (11) which is set up and designed to transmit control signals for decoupling the internal combustion engine (3) from the drive train (9), for driving the internal combustion engine (3) with a constant Dr speed by means of the electric motor (10), for supplying a lean fuel-air mixture to the catalytic converter (6), for generating a rich fuel-air mixture by injecting fuel into a combustion chamber of the internal combustion engine (3), for supplying the rich fuel -Air mixture to the catalytic converter (6) and to compensate for disturbance torques due to the injection of fuel into the combustion chamber of the internal combustion engine (3) by means of the electric motor (10). Drive (1) after claim 6 , further comprising: - a processing unit (12) which is set up and designed to determine the amount of oxygen that can be stored in the catalytic converter (6) from the time profiles of the determined combustion air ratios (λ _up , A _down ) upstream and downstream of the catalytic converter (6). Drive (1) after claim 6 or 7 , wherein the catalyst (6) is designed as a three-way catalyst. Drive (1) according to one of Claims 6 until 8th , wherein the drive (1) is designed as a hybrid electric drive and the electric motor (10) is an electric machine of the hybrid electric drive.

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