Method for diagnosing a carrier mass flow for an electrically heated catalyst and internal combustion engine

Abstract

The present invention relates to a method for diagnosing a carrier mass flow formed by a secondary air system (30) for an electrically heated catalyst (21) of an internal combustion engine (1), particularly in a vehicle, and to an internal combustion engine with a device for diagnosing a carrier mass flow. The method according to the invention comprises several steps. First, a target pressure value is calculated at at least one defined diagnostic position in an exhaust tract (20) of the internal combustion engine (1) upstream of the catalyst (21) and / or in the secondary air system (30). Subsequently, an actual pressure value is recorded at the defined diagnostic position by at least one pressure sensor (40) designed for this purpose. The actual pressure value and the target pressure value at the at least one defined diagnostic position are then compared.Subsequently, an error message is displayed if there is a defined deviation between the actual pressure value and the target pressure value.

Description

[0001] The present invention relates to a method for diagnosing a carrier mass flow for an electrically heated catalyst of an internal combustion engine, in particular in a vehicle, and an internal combustion engine with a device for diagnosing a carrier mass flow for an electrically heated catalyst.

[0002] Increasingly stringent regulations, such as the Euro 7 emissions standard, place ever greater demands on the reduction of emissions from internal combustion engines. Catalytic converters, which significantly reduce emissions from the exhaust gas mass flow during the operation of an internal combustion engine, are already known from current technology. However, these require a certain operating temperature to function effectively.

[0003] By providing a secondary air system that directs unburned fresh air from the intake tract directly into the exhaust tract, the start-up phase for such catalysts could be significantly reduced, allowing them to reach their operating temperature much earlier and thus reducing the emission of harmful emissions shortly after starting.

[0004] To further reduce emissions, electrically heated catalysts, so-called eCats, are used. These have a heating element, also known as a heating disc, which is located upstream of the catalyst and brings the catalyst up to operating temperature even faster.

[0005] The heating element is subjected to a heat transfer fluid flow, which is pumped through the exhaust system to transfer heat to the downstream catalytic converter. This heat transfer fluid serves as the medium for heat transfer and is introduced into the exhaust system via the secondary air system. The secondary air system typically includes a pump or an electric turbocharger, allowing the heat transfer fluid flow to be generated independently of the combustion process in the engine cylinders.

[0006] The carrier mass flow rate therefore has a direct influence on the temperature of the catalyst and thus on its conversion capacity and effectiveness during engine start-up. Since potential deviations in the carrier mass flow rate can therefore affect the engine's emissions, it is necessary to continuously monitor the carrier mass flow rate as part of the on-board diagnostics (OBD) system.

[0007] The prior art document DE 10 2022 103 350 A1 discloses a heatable catalyst through which a defined air mass flow is carried in order to transfer the heat generated by an electrically heated heating disc to the downstream catalyst, wherein the air mass flow is provided by a secondary air pump and the air mass flow is monitored by means of an analysis of one or more electrical parameters of the heating disc, in particular the electrical resistance.

[0008] Document DE 10 2023 109 889 B3 discloses a method for functional testing of the secondary air system of an internal combustion engine, wherein a pressure sensor is provided for detecting the pressure in the secondary air system.

[0009] German patent application DE 103 44 910 A1 discloses a diagnostic system for a secondary air injection system of a vehicle, which serves to reduce pollutant emissions after a cold start. The core concept of the method is that a control unit predicts a target pressure in the air supply line to the exhaust system and compares this value with an actual pressure measured by a pressure sensor. If the measured pressure deviates significantly from the predicted pressure, a system malfunction is diagnosed.

[0010] The German patent application DE 10 2021 205 533 A1 describes a method in which an electrically heated catalyst is heated before the engine starts by a two-stage secondary air injection: First, the heating element itself is heated with a small amount of air, then the heat is distributed over the entire catalyst with a strong airflow.

[0011] Document DE 10 2019 109 813 A1 discloses methods and systems for diagnosing a source of deterioration in a vehicle's exhaust system. In one example, a method may involve actuating an electric turbocharger to rotate in a first direction to assess the integrity of an exhaust pipe of the exhaust system, and rotating the turbocharger in a second direction to assess an exhaust manifold of the exhaust system after the vehicle's engine has been switched off. Pressures generated in the exhaust system are compared with threshold values ​​based on atmospheric pressure and / or turbocharger speed.

[0012] Document DE 10 2022 209 774 A1 relates to a method for operating a drive unit for a motor vehicle, which has an exhaust gas-generating drive unit and an exhaust aftertreatment system with a particulate filter for aftertreatment of the exhaust gas, wherein an actual pressure difference across the particulate filter is measured and a particle load and an ash load of the particulate filter are determined from it. It is provided that, using the particle load and the ash load, a separation efficiency of the particulate filter is determined based on a characteristic map and used to monitor emissions from the drive unit.

[0013] Document DE 10 2024 110 330 B3 concerns a procedure for the installation test of an exhaust aftertreatment component of an exhaust system and a secondary air system for an internal combustion engine, comprising the following steps.Activation of the secondary air system, wherein air is supplied to the exhaust system by a secondary air pump; installation test of the secondary air system, wherein an air pressure provided by the control of the secondary air pump is compared with an air pressure present in the flow direction downstream of the secondary air pump, wherein if the pressure difference between the two air pressures exceeds a first differential threshold, a faulty installation of the secondary air system is concluded; installation test of the exhaust aftertreatment component, wherein an air pressure upstream of the exhaust aftertreatment component and an air pressure downstream of the exhaust aftertreatment component are compared with each other, wherein if the pressure difference between the two air pressures exceeds a second differential threshold, a faulty installation of the exhaust aftertreatment component is concluded.

[0014] Against the background of the prior art described above, the object of the present invention is to provide an alternative method for diagnosing the carrier mass flow rate for an electrically heated catalyst and an internal combustion engine, including a diagnostic device. The method is intended to be a simple, reliable, and robust means of diagnosing the carrier mass flow rate. Diagnosis is defined here as verifying the intended configuration of the carrier mass flow rate. The decisive factor for this is the value of the actual mass flow rate or volumetric flow rate of the carrier mass flow rate.

[0015] This problem is solved by the subject matter of the dependent claims. Advantageous embodiments of the invention are contained in the sub-claims.

[0016] The inventive method for diagnosing a carrier mass flow rate for an electrically heated catalyst of an internal combustion engine with a secondary air system for generating the carrier mass flow rate comprises the following steps. First, the carrier mass flow rate is generated by the secondary air system independently of the combustion operation in the cylinders of the internal combustion engine and thus flows through the heating element of the downstream catalyst. Furthermore, a target pressure value is calculated at at least one defined diagnostic position in an exhaust system, in particular an exhaust system upstream of the catalyst, of the internal combustion engine and / or in the secondary air system. The exhaust system can be subdivided into an exhaust system upstream of the catalyst and an exhaust system downstream of the catalyst.A particulate filter can be located either upstream or downstream of the exhaust system. A pressure sensor, specifically located within the particulate filter, then measures the actual pressure at the defined diagnostic position. The diagnostic position is thus defined by the position of the pressure sensors. The actual pressure and the target pressure at the at least one defined diagnostic position are then compared. Unless otherwise specified, for the purposes of this registration, a comparison of two pressure values ​​refers to calculating the difference between them. An error message is then generated if a defined deviation exists between the actual and target pressure values.

[0017] A deviation is defined as the difference between the actual pressure value and the target pressure value and a defined threshold. If the calculated difference between the actual and target pressure values ​​exceeds a certain threshold, an error message is issued.

[0018] The display of an error message can encompass various scenarios and is a collective term for a multitude of actions. Firstly, an error message can cause the engine to stop starting, particularly if the process occurs before combustion begins in the engine's cylinders. Alternatively or additionally, an error message can also trigger an automated intervention in the control of other vehicle systems, such as automatically limiting throttle response, so that the engine can only operate in a specific mode at the start of a journey. Furthermore, it can simply mean issuing a warning to the driver without automatically intervening in any vehicle function.It is also possible that the driver may not see an error message at all, or only see it when instructed to visit a workshop. Therefore, the output of an error message may simply consist of storing the error information in a way that a workshop can read.

[0019] By supplying a carrier mass flow through the secondary air system, the measured pressure in the exhaust tract and the secondary air system increases due to the resulting back pressure, which is detected by the pressure sensor. The actual pressure value thus determined, when compared to the target pressure value, indicates whether the carrier mass flow is sufficient to heat the catalyst. If the carrier mass flow is too low, this suggests that the catalyst is not heating up as desired, because too little heat can be transferred from the heating element to the catalyst. As a result, the catalyst does not reach operating temperature and cannot perform its function as intended. Furthermore, an insufficient carrier mass flow can indicate faulty valves in the secondary air system, such as stuck valves, or leaks in the system.The inventive method thus enables uncomplicated, robust, and reliable diagnosis of the carrier mass flow due to the use of simple and known components. This, in turn, allows for the easy diagnosis of faults in the secondary air system or exhaust system. For this purpose, several diagnostic positions are preferably provided to simplify the localization of a fault.

[0020] According to the invention, at least one diagnostic position is defined between the merging of different exhaust streams from individual cylinders of the internal combustion engine and the catalyst. Alternatively or additionally, at least one diagnostic position is defined in the secondary air system upstream of a branch point in the secondary air system leading to different exhaust streams from individual cylinders of the internal combustion engine. The appropriately selected positions allow for the simplified detection of irregularities in the formation of the carrier mass flow.

[0021] In an advantageous embodiment of the method, the target pressure value is calculated as a function of external environmental conditions. These include, for example, the ambient temperature and ambient pressure. By taking the environmental conditions into account, the target pressure value can be determined precisely and adapted to the situation, thus reducing the risk of misdiagnosing the carrier mass flow.

[0022] A further advantageous embodiment of the method is one in which the recorded actual pressure value is additionally compared against an output pressure value, and an error message is also issued if the difference between the actual pressure value and the output pressure value does not exceed a defined amount. If this defined amount of the difference between the actual pressure value and the output pressure value is not exceeded, this indicates that a sufficiently large carrier mass flow could not be generated. The defined amount that must be exceeded between the actual pressure value and the output pressure value to avoid triggering an error message is preferably calculated in real time, taking the ambient conditions into account. The output pressure value is understood to be the pressure value of the at least one pressure sensor before or at the beginning of the start-up of the secondary air system.

[0023] Preferably, an actual pressure value is recorded at the defined diagnostic position and compared with the calculated target pressure value after the secondary air system has been started to establish the carrier mass flow and before combustion begins in the internal combustion engine. This allows combustion to be aborted or delayed if the carrier mass flow has not been established correctly and the catalyst has therefore not reached the desired operating temperature. Delaying the start is only useful if a carrier mass flow has been established, albeit not as desired. With a lower carrier mass flow, the catalyst heating will be delayed, but the operating temperature may still be reached within an acceptable timeframe, allowing combustion to begin.

[0024] The internal combustion engine according to the invention, comprising a device for diagnosing a carrier mass flow for an electrically heated catalyst, has a cylinder bank with at least one cylinder, an exhaust tract comprising a catalyst and designed to supply exhaust gas from the at least one cylinder to the environment, wherein the catalyst has a heating element, preferably in the form of a heating disc, and a secondary air system designed to introduce fresh air into the exhaust tract.Furthermore, at least one pressure sensor, located in the exhaust system and / or the secondary air system and designed to determine an actual pressure value, and an evaluation unit, designed to determine a target pressure value and compare it against the actual pressure value, are provided, so that the actual pressure value thus determined, by comparison with the target pressure value, provides information as to whether the carrier mass flow is sufficient to heat the catalyst or not, and also issues an error message in the event of a defined deviation between the actual pressure value and the target pressure value.

[0025] The device according to the invention can therefore be used to carry out the method according to the invention.

[0026] According to the invention, the internal combustion engine has several cylinders, the exhaust system has several exhaust streams designed to combine exhaust gas from the individual cylinders upstream of the catalyst, and the at least one pressure sensor is arranged between a merging of individual exhaust streams of the exhaust system and the heating element. This creates a corresponding diagnostic position at this point.

[0027] Alternatively or additionally, the internal combustion engine has multiple cylinders and the exhaust system has multiple exhaust streams, wherein the exhaust streams are designed to combine exhaust gas from the individual cylinders upstream of the catalytic converter, and the secondary air system is designed to introduce fresh air into the exhaust streams of the individual cylinders, wherein at least one pressure sensor is arranged upstream of a branch point of the secondary air system to the individual exhaust streams. This creates a corresponding diagnostic position at this point.

[0028] The invention is explained in more detail below with reference to the accompanying figure in one embodiment. Fig. Figure 1 shows a schematic representation of an embodiment of an internal combustion engine 1 according to the invention. This engine has a fresh air intake tract 10 and an exhaust gas intake tract 20. The fresh air intake tract 10 is equipped with an air filter 11, which filters out unwanted particles from the intake air that are unsuitable for combustion. The fresh air is supplied to cylinders 51 of a cylinder bank 50 for mixing with fuel and ultimately for combustion in the cylinders 51.

[0029] The exhaust system 20 has individual exhaust streams 22 that initially combine the exhaust gas, i.e., the combusted gas, from the individual cylinders 51. The combined exhaust gas is then directed into a catalyst 21. This catalyst has a heating element 23, which is designed in the form of a heating disc. The exhaust system 20 of the internal combustion engine 1 does not end at the catalyst 21, but also has a section downstream of the catalyst 21, which is not shown in the figure. Only the section of the exhaust system 20 upstream of the catalyst 21 is shown.

[0030] Furthermore, the internal combustion engine 1 has a secondary air system 30. This system draws fresh air from the fresh air intake tract 10 and introduces it directly into the exhaust streams 22 after the exhaust valves of the cylinders 51. This is done to induce a reaction in the exhaust gas, particularly at the beginning of combustion in the internal combustion engine 1, which reduces emissions during the cold start of the engine. For this purpose, the secondary air system 30 includes a secondary air pump 31 and one or more secondary air valves 32, which can selectively control the amount of fresh air required in the exhaust streams. This basic arrangement is already known from the prior art.

[0031] Furthermore, in the embodiment shown, according to Fig.1 Two pressure sensors 40 are provided, which measure the pressure in the exhaust system after the exhaust streams 22 merge and before the catalyst 21, or in the secondary air system 30 before the branching to the individual exhaust streams 22. The data recorded by the sensors are transmitted to an evaluation unit 60. It should be noted that embodiments of the invention are also conceivable which have only one pressure sensor 40.

[0032] To enable rapid heating of the catalyst 21, a carrier mass flow is supplied through the secondary air system 30 in the exhaust tract 20 during a cold start of the internal combustion engine 1. This flow absorbs the energy from the heating element 23 and transfers it directly to the condenser 21 to quickly bring it up to operating temperature. The correct size of the carrier mass flow is crucial.

[0033] The carrier mass flow creates back pressure in the exhaust system and the secondary air system. This back pressure is detected by the corresponding pressure sensors and compared to a target pressure value by the evaluation unit 60. The target pressure value is calculated based on the ambient conditions and represents the back pressure measurable at the diagnostic points, resulting from the carrier mass flow required to heat the catalyst. If a deviation between the actual and target pressure values ​​is too large—in other words, if the difference between the actual and target pressure values ​​exceeds a defined threshold—the evaluation unit issues a corresponding error message.This can lead to the combustion process in the internal combustion engine being prevented from starting, because it is assumed that the catalytic converter has not yet reached operating temperature due to an insufficient mass flow rate, or simply to the vehicle user receiving a notification to visit a workshop. Other types of error messages are also conceivable.

[0034] This method, through the use of the secondary air system, enables the diagnosis of the carrier mass flow before combustion begins in the cylinders. In summary, it provides a robust, straightforward, and reliable method for diagnosing the carrier mass flow, allowing for the detection of faulty catalyst heating even before combustion starts. This prevents the emission of impermissible pollutants. REFERENCE MARK LIST 1 Internal combustion engine 10 Fresh air tract 11 Air filters 20 Exhaust system 21 Catalyst 22 Exhaust system 23 Heating element 30 Secondary air system 31 Secondary air pump 32 Secondary valve 40 pressure sensor 50-cylinder bank 51 cylinders 60 evaluation units

Claims

[1] Method for diagnosing a carrier mass flow for an electrically heated catalyst (21) of an internal combustion engine (1) with a secondary air system (30) for generating the carrier mass flow, comprising the following steps: (A) Generating the carrier mass flow independently of combustion operation in cylinders of the internal combustion engine (1), (B) Flow of the carrier mass flow through a heating disk of the downstream catalyst (21), (C) Calculating a target pressure value at at least one defined diagnostic position in an exhaust system (20), in particular an exhaust system (20) upstream of the catalyst (21), the internal combustion engine (1) and / or in the secondary air system (30), (D) Recording of an actual pressure value at the defined diagnostic position by at least one pressure sensor designed for this purpose (40), (E) Comparison between the actual pressure value and the target pressure value at at least one defined diagnostic position, (F) Output of an error message if there is a defined deviation between actual pressure value and target pressure value, wherein at least one diagnostic position is defined between a merging of different exhaust streams (22) from individual cylinders (51) of the internal combustion engine (1) and the catalyst (21). [2] Method according to the preceding claim, wherein at least one diagnostic position is defined in the secondary air system (30) upstream of a branching of the secondary air system (30) to different exhaust streams (22) from individual cylinders (51) of the internal combustion engine (1). [3] Method according to one of the preceding claims, wherein the target pressure value is calculated as a function of external environmental conditions. [4] Method according to one of the preceding claims, wherein the recorded actual pressure value is compared against an output pressure value and an error message is issued if the difference between the actual pressure value and the output pressure value does not exceed a defined amount. [5] Method according to one of the preceding claims, wherein the recording of an actual pressure value at the defined diagnostic position and the comparison of the actual pressure value with the calculated target pressure value is carried out after the start of the secondary air system (30) to form the carrier mass flow and before the start of combustion in the internal combustion engine (1). [6] Internal combustion engine (1) comprising a device for diagnosing a carrier mass flow for an electrically heated catalyst (21), comprising a cylinder bank (50) with several cylinders (51), an exhaust system (20) with a catalyst (21) configured to supply exhaust gas from at least one cylinder (51) to the environment, wherein the catalyst (21) has a heating element (23) and the exhaust system (20) has several exhaust gas streams (22), wherein the exhaust gas streams (22) are configured to combine exhaust gas from the individual cylinders (51) upstream of the catalyst (21), a secondary air system (30) designed to introduce fresh air into the exhaust tract (20), at least one pressure sensor (40) which is arranged in the exhaust tract (20) between a merging of individual exhaust streams (22) of the exhaust tract (20) and the heating element (23) and is designed to determine an actual pressure value, and an evaluation unit (60) designed to determine a target pressure value and compare it against the actual pressure value, so that the actual pressure value thus determined, by comparison with the target pressure value, provides information as to whether the carrier mass flow is sufficient to heat the catalyst (21) or not, and to issue a message in the event of a defined deviation between the actual pressure value and the target pressure value. [7] Internal combustion engine according to the preceding claim, wherein the internal combustion engine (1) has several cylinders (51) and the exhaust system (20) has several exhaust streams (22), wherein the exhaust streams (22) are configured to combine exhaust gas from the individual cylinders (51) upstream of the catalyst (21), and the secondary air system (30) is configured to introduce fresh air into the exhaust streams (22) of the individual cylinders (51), wherein at least one pressure sensor (40) is arranged upstream of a branch of the secondary air system (30) to the individual exhaust streams (22).

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