DE102015216590A1 - Method and device for detecting an operation of an internal combustion engine with a sulfur-containing fuel - Google Patents

Abstract

The invention relates to a method for detecting an operation of an internal combustion engine (10) with a sulfur-containing fuel, wherein the internal combustion engine (10) has an exhaust gas channel (12) in which a three-way catalytic converter (14), upstream of the three-way Catalyst (14) a first lambda probe (16) and downstream of the three-way catalytic converter (14) a second lambda probe (18) is arranged, wherein the method comprises the steps of: - operating the internal combustion engine (10) with a superstoichiometric combustion air ratio and determining the oxygen storage capacity (OSC) of the three-way catalyst (14); - Operating the internal combustion engine (10) with a substoichiometric combustion air ratio and determining the oxygen discharge capacity (RSC) of the three-way catalyst (14); - Forming an OSC / RSC ratio (ORVIST) from the oxygen storage capacity (OSC) and the oxygen discharge capacity (RSC) of the three-way catalyst (14) - comparing the determined OSC / RSC ratio (ORVIST) with one in an operation of the Internal combustion engine (10) with a reference fuel determined and stored in a control unit (20) OSC / RSC ratio (ORVREF) and - detecting the presence of a sulfur-containing fuel when the determined OSC / RSC ratio (ORVIST) of the in the control unit (20 ) deviated OSC / RSC ratio (ORVREF). The invention further relates to a device for carrying out such a method.

Description

The invention relates to a method and a device for detecting an operation of an internal combustion engine with a sulfur-containing fuel. In motor vehicles with an internal combustion engine, in particular with a petrol engine, today three-way catalytic converters for exhaust aftertreatment standard. However, such three-way catalysts are subject to a certain aging, so that the performance of a three-way catalyst decreases over the lifetime or the term. In the operation of a motor vehicle, exhaust gas legislation may dictate on-board diagnostics of the three-way catalyst to ensure the operability of the three-way catalyst and to signal the need for replacement of the three-way catalyst in the absence of conversion rates. In previously used diagnostic methods, the Oxygen Storage Capacity (OSC) or the Removing Storage Capacity (RSC) of the three-way catalyst is determined and from these values on the performance of the three-way catalyst. By measuring the oxygen storage capacity and the oxygen discharge capability, the characteristic curve of a lambda probe arranged upstream of the three-way catalytic converter in the exhaust gas duct, in particular a leap lambda probe, can be corrected and thus an aging value of the three-way catalytic converter can be determined.

From the DE 10 2013 201 734 a method for operating a lambda sensor arrangement in an exhaust passage of an internal combustion engine is known, wherein a first lambda probe is arranged upstream of a three-way catalytic converter and a second lambda probe is arranged downstream of the three-way catalytic converter, wherein the second lambda sensor Probe is designed as a jump probe, wherein downstream of the three-way catalyst, a diagnosis of a map offset of the first lambda probe is performed and, if appropriate, an adaptation of a map offset error is performed. For this purpose, a value representing the oxygen storage capacity of the catalytic converter and another value representing the oxygen discharge capacity of the catalytic converter are recorded for the diagnosis during active lambda adjustment. From the ratio of oxygen discharge capacity and oxygen storage capacity, a characteristic offset of the first lambda probe is calculated.

However, sulfur-containing fuel falsifies the oxygen storage ability (OSC) and oxygen removal ability (RSC) of the three-way catalyst, so that when considering the oxygen storage ability and the oxygen discharge ability absolutely, a still sufficiently converting three-way catalyst is no longer "sufficiently converting". can be diagnosed. By the methods known hitherto it can not be distinguished whether a low oxygen storage capacity of the three-way catalyst is due to aging of the three-way catalyst or by using a sulfur-containing fuel. This means that the customer can get displayed a defective catalyst when using a sulfur-containing fuel, although this is still okay. Sulfur in the fuel can measure an oxygen storage capacity that is nearly 50% lower than when operating the same catalyst with a low sulfur reference fuel.

The invention is based on the object to recognize the operation of an internal combustion engine with a sulfur-containing fuel and thus to be able to perform a functionality analysis of the three-way catalyst regardless of the fuel quality.

• – Betreiben des Verbrennungsmotors mit einem überstöchiometrischen Verbrennungsluftverhältnis und Ermitteln der Sauerstoffspeicherfähigkeit (OSC) des Drei-Wege-Katalysators;
• – Betreiben des Verbrennungsmotors mit einem unterstöchiometrischen Verbrennungsluftverhältnis und Ermitteln der Sauerstoffaustragungsfähigkeit (RSC) des Drei-Wege-Katalysators;
• – Bilden eines OSC/RSC-Verhältnisses (ORV_IST) aus der Sauerstoffspeicherfähigkeit (OSC) und der Sauerstoffaustragungsfähigkeit (RSC) des Drei-Wege-Katalysators;
• – Vergleichen des ermittelten OSC/RSC-Verhältnisses (ORV_IST) mit einem bei einem Betrieb des Verbrennungsmotors mit einem Referenzkraftstoff ermittelten und in einem Steuergerät abgelegten OSC/RSC-Verhältnis (ORV_REF) und
• – Erkennen des Vorliegens eines schwefelhaltigen Kraftstoffs, wenn das ermittelte OSC/RSC-Verhältnis (ORV_IST) von dem im Steuergerät abgelegten OSC/RSC-Verhältnis (ORV_REF) abweicht.

According to the invention, a method for detecting an operation of an internal combustion engine with a sulfur-containing fuel is proposed, wherein the internal combustion engine has an exhaust gas passage, in which a three-way catalyst, in the flow direction of an exhaust gas of the internal combustion engine through the exhaust passage upstream of the three-way catalyst, a first Lambda probe and downstream of the three-way catalyst, a second lambda probe is arranged, wherein the method comprises the following steps:

• - Operating the internal combustion engine with a lean of stoichiometric combustion air ratio and determining the oxygen storage capacity (OSC) of the three-way catalyst;
• - Operating the internal combustion engine with a substoichiometric combustion air ratio and determining the oxygen discharge capacity (RSC) of the three-way catalyst;
• Forming an OSC / RSC ratio (ORV _IST ) from the oxygen storage _capacity (OSC) and the oxygen discharge _capacity (RSC) of the three-way catalyst;
• Comparing the ascertained OSC / RSC ratio (ORV _IST ) with an OSC / RSC ratio (ORV _REF ) determined during operation of the internal combustion engine with a reference fuel and stored in a control unit
• Detecting the presence of a sulfur-containing fuel when the determined OSC / RSC ratio (ORV _IST ) deviates from the OSC / RSC ratio (ORV _REF ) stored in the control unit.

In the study of oxygen storage capacity (OSC) and the Oxygen Scavenging Capacity (RSC) has highlighted contexts that make it possible to detect sulfur in the fuel. It can be seen that the OSC / RSC ratio increases to higher sulfur concentrations. Thus, a functional relationship between an expected OSC / RSC ratio and an actually determined OSC / RSC ratio can be formed. In the event that the oxygen storage capacity in a catalyst diagnosis drops below a threshold signaling a functional three-way catalyst, a reduced oxygen storage capacity due to a sulfur-containing fuel can be detected here and the oxygen storage capacity can be corrected to a value based on a model stored in the control unit which would be present when operating with a low sulfur reference fuel. Thus, the customer does not need to be unnecessarily replaced in a workshop and the three-way catalyst.

According to an advantageous embodiment of the method, it is provided that a catalyst age, a catalyst operating time and / or a mileage of the three-way catalyst is determined, wherein the determined OSC / RSC ratio (ORV _IST ) with one for the catalyst -Alter, the catalyst operating time and / or the mileage of the three-way catalyst according to a reference map expected OSC / RSC ratio (ORV _REF ) is compared and is concluded from a deviation on the presence of a sulfur-containing fuel. By including the catalyst age or the duration or duration of the adjustment can also be done in used three-way catalysts. In this case, a relationship is shown between the determined OSC / RSC ratio (ORV _IST ) and the sulfur content in the fuel and the determined OSC / RSC ratio (ORV _IST ) is compared with a reference value, which at a corresponding maturity, a corresponding age or a corresponding operating time of the three-way catalyst would be expected in an operation of the internal combustion engine with a low-sulfur reference fuel.

According to a further advantageous embodiment, it is provided that the OSC / RSC ratio (ORV _IST ) is determined at different load points of the internal combustion engine. As a result, a comparison with an expected OSC / RSC ratio (ORV _REF ) can be determined not only for individual reference points, but for a large part of the engine map. Thus, a more accurate and reliable comparison of the determined OSC / RSC ratio (ORV _IST ) with the OSC / RSC ratio (ORV _REF ) determined when operating with a low-sulfur reference _{fuel is} possible.

According to a further advantageous development, it is provided that the load points are determined at different rotational speeds and / or different exhaust gas mass flows. Thus, the engine map can be extended, and the adjustment is possible at different reference points, so that a faulty single measurement does not lead to a faulty overall result.

According to a further advantageous development, it is provided that the oxygen storage capacity (OSC) and the oxygen discharge capacity (RSC) are determined as oxygen breakdown or fat breakdown by the three-way catalyst at the second lambda probe. Due to the oxygen storage capacity or the oxygen discharge capacity, in the case of a substoichiometric, rich combustion air ratio or in the case of a superstoichiometric, lean combustion air ratio, a corresponding compensation takes place through the three-way catalytic converter, so that initially a stoichiometric exhaust gas is measured at the second lambda probe. Only when the oxygen storage capacity or the oxygen discharge capacity are exhausted, there is a breakdown by the three-way catalyst, so that at a stoichiometric combustion air ratio with a certain time delay at the second lambda probe, a rich exhaust gas is measured or delayed at a superstoichiometric combustion air ratio Oxygen breakdown is measured by the three-way catalyst. From this measurement, the oxygen storage capacity or the oxygen discharge capacity of the three-way catalyst can be determined in a simple manner.

According to a further development of the method, it is provided that a two-probe concept is used, wherein one of the lambda probes is designed as a jump probe and the respective other lambda probe as a broadband probe.

According to a further advantageous embodiment, it is provided that the OSC / RSC ratio in a Operation of the internal combustion engine with sulfur-containing fuel over an operation of the internal combustion engine is increased with low-sulfur reference fuel. Increasing the OSC / RSC ratio is easy to determine and thus well suited to detecting the presence of sulfur-containing fuel. It is particularly advantageous if the OSC / RSC ratio is greater than 1.2. The presence of a sulfur-containing fuel shifts the OSC / RSC ratio toward higher values. A threshold value of 1.2 seems to be particularly suitable, since an OSC / RSC ratio greater than 1.2 preferably occurs during operation of the combustion engine with sulfur-containing fuel.

According to a further improvement of the method, it is provided that a combustion air ratio λ _E determined by one of the lambda probes, preferably by a leap lambda probe, is corrected, in particular in the substoichiometric range, upon detection of a sulfur-containing fuel by means of a reference model stored in the control unit. Measurements have shown that in an operation of the internal combustion engine with sulfur-containing fuel, especially in jump lambda probes and there in particular in the stoichiometric region, with the same combustion air ratio λ _E , a shift of the probe voltage towards lower voltage values. As a result, the deviations in the OSC / RSC ratio compared to operation with low-sulfur reference fuel again significantly larger, so that the usually built in motor vehicle jump lambda probes even more likely by sulfur-containing fuel to a defective three-way catalyst , By correcting the measured voltage or the determined combustion air ratio, this effect can be reduced or eliminated.

According to the invention a device for detecting an operation of an internal combustion engine with a sulfur-containing fuel is proposed, wherein in an exhaust passage of the internal combustion engine, a three-way catalyst, in the flow direction of an exhaust gas of the internal combustion engine in the exhaust passage upstream of the three-way catalyst, a first lambda probe and wherein a second lambda probe is arranged downstream of the three-way catalytic converter, and wherein the first lambda probe and the second lambda probe are connected to a control unit of the internal combustion engine, the control unit containing a circuit or a program sequence which is set up to control a combustion air ratio λ _E supplied to the internal combustion engine so that in a first phase the internal combustion engine is operated with a superstoichiometric combustion air ratio, wherein the oxygen storage capacity of the three-way catalyst is determined, and the internal combustion engine in a second n phase is operated at a substoichiometric combustion air ratio, wherein the oxygen discharge capacity of the three-way catalyst is determined, and wherein the oxygen storage capacity and the oxygen discharge capacity of the three-way catalyst are set in an OSC / RSC ratio, characterized in that This determined OSC / RSC ratio is compared with a determined during operation with a reference fuel and stored in the control unit OSC / RSC ratio and a deviation of the actual OSC / RSC ratio from the OSC / RSC ratio stored in the controller present a sulfur-containing fuel signals. With such a device, an inventive method can be carried out without additional components, so that the presence of sulfur-containing fuel can be reliably detected.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 an internal combustion engine with an exhaust passage and a device according to the invention for detecting an operation of the combustion engine with sulfur-containing fuel,

2 a process diagram for the determination of the presence of sulfur-containing fuel and a correction option for the diagnosis of the three-way catalyst,

3 determined OSC / RSC ratios of a three-way catalytic converter when operating with different fuels at different load cuts measured with a broadband lambda probe,

4 the measurement deviations of a leap lambda probe due to sulfur-containing fuel at different sulfur concentrations,

5 determined OSC / RSC ratios of a three-way catalyst when operating with different fuels at different load cuts measured with a jump lambda probe.

1 shows an internal combustion engine 10 with an exhaust duct 12 as used in particular in a motor vehicle. In the exhaust duct 12 is a three-way catalyst 14 arranged, wherein in the flow direction of an exhaust gas of the internal combustion engine 10 through the exhaust duct 12 upstream of the three-way catalyst 14 a first lambda probe 16 and downstream of the three-way catalyst 18 a second lambda probe 18 are arranged. The first lambda probe 16 and the second lambda probe 18 are via signal lines 24 . 26 each with a control unit 20 for controlling the internal combustion engine 10 connected. The control unit 20 is also via another signal line 28 with fuel injectors 22 connected, with which in the combustion chambers of the internal combustion engine 10 injected fuel amount can be controlled. The first lambda probe 16 is preferably designed as a jumping probe. The second lambda probe 18 is preferably designed as a broadband probe.

In operation of the internal combustion engine 10 is via the control unit 20 a combustion air mixture λ _{E of} the internal combustion engine 10 adjusted so that the internal combustion engine 10 operated with a stoichiometric combustion air ratio, so that harmful exhaust gas components through the three-way catalyst 14 can be converted into harmless exhaust gas components.

In 2 is a flowchart for diagnosing the functionality of a three-way catalyst 14 shown. To determine the oxygen storage capacity (OSC) is the internal combustion engine 10 operated at a superstoichiometric combustion air ratio in a first phase, and measured, when this lean of stoichiometric combustion air ratio to a superstoichiometric exhaust gas at the second lambda probe downstream of the three-way catalyst 14 leads. To determine the oxygen removal capacity (RSC) of the three-way catalyst 14 becomes the internal combustion engine 10 operated in a second phase with a substoichiometric, rich combustion air ratio and measured when this substoichiometric combustion air ratio to a rich breakdown in the exhaust gas at the second lambda probe 18 downstream of the three-way catalyst 14 leads. The OSC and RSC values determined in this way are set to an OSC / RSC ratio (ORV). In the control unit 20 is stored a reference OSC / RSC ratio (ORV _REF ), which was determined, for example, by reference duration runs with a reference fuel with low sulfur content. The three-way catalyst 14 determined OSC / RSC ratio (ORV _IST ) is now compared in a subsequent step with the determined in the reference continuous run OSC / RSC ratio (ORV _REF ), wherein for the reference OSC / RSC ratio a characteristic over the catalyst age, the catalyst operating time and / or the duration of the three-way catalyst 14 is stored. Thus, an expected aging of the three-way catalyst 14 be taken into account when determining the OSC / RSC ratio or when determining the OSC value or the RSC value, respectively. On the basis of the ascertained OSC / RSC ratio, a detected factor for the determined OSC value can be determined during a recognized operation of the internal combustion engine with a sulfur-containing fuel, so that the actually determined OSC value can be corrected to an OSC value that is used during operation with a low-sulfur reference fuel. This corrected OSC value can now be used to recalculate an OSC / RSC ratio, be used for the diagnosis of a supposedly defective catalytic converter or stored in a memory of the controller. The currently measured OSC / RSC ratio can thus be improved by the correction to an improved diagnosis of the three-way catalyst 14 be used. Thus, the expected OSC / RSC ratio over the age, running time or operating time of the three-way catalyst 14 can be correctly determined, the corrected OSC value must be returned as a kind of control loop to the control unit. The expected OSC / RSC ratio over the runtime can be determined, for example, in the context of engine duration runs for exhaust gas measurement, or is already available as a by-product of such exhaust gas duration runs.

In 3 are measured OSC / RSC ratios of a three-way catalyst 14 at various load cuts and at different sulfur concentrations in the fuel, measured with a broadband lambda probe. In this case, the exhaust gas mass flow through the three-way catalyst is on the abscissa 14 in kg / h and on the ordinate of the OSC / RSC ratio at the corresponding exhaust gas mass flow. The different curves represent different fuel qualities, with the respective fuel quality a sulfur content in "parts per million" (ppm) is specified. It can be seen that with increasing sulfur content the OSC / RSC ratio drifts towards higher values. This behavior is particularly noticeable in the two diagrams on the left side of the picture. While operating with a low-sulfur reference fuel sets a largely constant over the exhaust gas mass flow OSC / RSC ratio, the OSC / RSC ratio increases at higher sulfur contents with the exhaust gas mass flow. At exhaust gas mass flows of 100 kg / h is thereby during operation of the internal combustion engine 10 with a low-sulfur reference fuel an OSC / RSC ratio of 1 or less 1, while in the presence of a sulfur-containing fuel OSC / RSC ratios greater than 1, in particular greater than 1.2 are determined. From this deviation can be concluded at the corresponding reference points of the map with high certainty on the presence of a sulfur-containing fuel.

In 4 is the probe voltage of a jump lambda probe as a function of the sulfur content of the fuel shown. It can be seen that even the jump lambda probe, in particular at substoichiometric combustion air ratio λ _E <1, is subject to a sulfur influence and the measured values drift at higher sulfur content at the same combustion air ratio λ _E in the direction of lower voltage values. at than the stoichiometric air-fuel ratio λ _E> 1, the deviation of the measurement result of the jump lambda sensor due to sulfur in the fuel is significantly less pronounced.

In 5 are measured OSC / RSC ratios of a three-way catalyst 14 at various load cuts and at different sulfur concentrations in the fuel, measured with a leap lambda probe shown. Compared to the in 3 shown measurements with a broadband lambda probe are the deviations from the measurement with low-sulfur reference fuel even more significant, so that the built-in usually in motorized jump lambda probes even more by sulfur-containing fuel on a defective three-way catalyst 14 as the laboratory measurement with a broadband lambda probe.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

exhaust duct

14

Three-way catalytic converter

16

first lambda probe

18

second lambda probe

20

control unit

22

Fuel injectors

24

signal line

26

signal line

28

signal line

λ _E

Combustion air ratio of the internal combustion engine

H

hour

kg

kilogram

ppm

part per million

OSC

Oxygen storage capability of the three-way catalyst

RSC

Oxygen removal capability of the three-way catalyst

ORV

Ratio of oxygen storage capacity and oxygen storage capacity

ORV _IS

actually determined relationship between OSC and RSC

ORV _REF

ratio between OSC and RSC determined according to a reference duration run with low-sulfur fuel

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• DE 102013201734 [0002]

Claims (10)

Method for detecting an operation of an internal combustion engine ( 10 ) with a sulfur-containing fuel, the internal combustion engine ( 10 ) an exhaust duct ( 12 ) and in the exhaust passage ( 12 ) a three-way catalyst ( 14 ), upstream of the three-way catalyst ( 14 ) a first lambda probe ( 16 ) and downstream of the three-way catalyst ( 14 ) a second lambda probe ( 18 ), the method comprising the following steps: - operating the internal combustion engine ( 10 ) with a superstoichiometric combustion air ratio and determining the oxygen storage capacity (OSC) of the three-way catalyst ( 14 ); - operating the internal combustion engine ( 10 ) with a substoichiometric combustion air ratio and determining the oxygen removal capacity (RSC) of the three-way catalyst ( 14 ); Forming an OSC / RSC ratio (ORV _IST ) from the oxygen storage _capacity (OSC) and the oxygen removal _capacity (RSC) of the three-way catalyst ( 14 ); Comparing the ascertained OSC / RSC ratio (ORV _IST ) with one during operation of the internal combustion engine ( 10 ) determined with a reference fuel and in a control unit ( 20 ) Stored OSC / RSC ratio (ORV _REF), and - detecting the presence of a sulfur-containing fuel when the determined OSC / RSC-ratio ((ORV _IST) of the control unit in the 20 ) deviated OSC / RSC ratio (ORV _REF ). A method according to claim 1, characterized in that a catalyst age, a catalyst service life or a mileage of the three-way catalyst ( 14 ), wherein the determined OSC / RSC ratio (ORV _IST ) with one for the catalyst age, the catalyst service life and / or the mileage of the three-way catalyst ( 14 ) is compared according to a reference characteristic expected OSC / RSC ratio (ORV _REF ) and is concluded from a deviation on the presence of a sulfur-containing fuel. A method according to claim 1 or claim 2, characterized in that the OSC / RSC ratio (ORV _IST ) at different load points of the internal combustion engine ( 10 ) is determined. A method according to claim 3, characterized in that the different load points are determined at different speeds and / or different exhaust gas mass flows. Method according to one of claims 1 to 4, characterized in that the oxygen storage capacity (OSC) and the oxygen discharge capacity (RSC) as oxygen breakdown or fat breakdown by the three-way catalyst ( 14 ) at the second lambda probe ( 18 ) be determined. Method according to one of claims 1 to 5, characterized in that for carrying out the method, a two-probe concept is used, wherein one of the lambda probes ( 16 . 18 ) as a jump probe and the other lambda probe ( 16 . 18 ) is designed as a broadband probe. Method according to one of claims 1 to 6, characterized in that the OSC / RSC ratio (ORV _IST ) during operation of the internal combustion engine ( 10 ) with sulfur-containing fuel compared to an operation of the internal combustion engine ( 10 ) is increased with a low-sulfur reference fuel. A method according to claim 7, characterized in that the OSC / RSC ratio (ORV _IST ) is greater than 1.2. Method according to one of claims 1 to 8, characterized in that a by one of the lambda probes ( 16 . 18 ), preferably in the sub-stoichiometric range, upon detection of a sulfur-containing fuel by means of a control unit in the control unit (preferably by a jump lambda probe, determined combustion air ratio λ _E) . 20 ) corrected reference model is corrected. Device for detecting an operation of an internal combustion engine ( 10 ) with a sulfur-containing fuel, wherein in an exhaust gas channel ( 12 ) of the internal combustion engine ( 10 ) a three-way catalyst ( 14 ), upstream of the three-way catalyst ( 14 ) a first lambda probe ( 16 ) and downstream of the three-way catalyst ( 14 ) a second lambda probe ( 18 ), and wherein the first lambda probe ( 16 ) and the second lambda probe ( 18 ) with a control device ( 20 ) of the internal combustion engine ( 10 ), the control unit ( 20 ) contains a circuit or a program sequence that is set up, an internal combustion engine ( 10 ) to control combustion air ratio λ _E so that in a first phase of the internal combustion engine ( 10 ) is operated at a superstoichiometric combustion air ratio, wherein the oxygen storage capacity (OSC) of the three-way catalyst ( 14 ) and is operated in a second phase with a substoichiometric combustion air ratio, wherein the oxygen removal capacity (RSC) of the three-way catalyst (RSC) ( 14 ), and wherein the oxygen storage capacity (OSC) and the oxygen removal capacity (RSC) of the three-way catalyst ( 14 ) are set in an OSC / RSC ratio (ORV), characterized in that the thus determined OSC / RSC ratio (ORV _IST ) with a during operation of the internal combustion engine ( 10 ) determined with a reference fuel and in the control unit ( 20 ) compared OSC / RSC ratio (ORV _REF ) and a deviation of the actual OSC / RSC ratio (ORV _IST ) from that in the control unit ( 20 ) stored OSC / RSC ratio (ORV _REF ) signals the presence of a sulfur-containing fuel.

Images