DE102020215288A1 - Method and device for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust path of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust tract of an internal combustion engine, in which the effectiveness of the heating measures of the catalytic converter is estimated using the energy contained in the exhaust gas of the internal combustion engine. The energy contained in the exhaust gas of the internal combustion engine is determined by integrating the fuel mass flow or by integrating the air mass flow.

Description

The invention relates to a method and a device for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust path of an internal combustion engine.

In the exhaust path of internal combustion engines, components for exhaust gas cleaning are used, for example 3-way catalytic converters, SCR catalytic converters and particle filters. All of these components enable chemical reactions that lead to the conversion of pollutants contained in the exhaust gas into less dangerous substances. The pollutants mentioned are, for example, hydrocarbons, carbon monoxide and nitrogen oxides. The less hazardous substances mentioned are, for example, carbon dioxide, water and nitrogen dioxide. However, this conversion only works when the components provided for exhaust gas purification have reached their operating temperature. This is not yet the case in a cold start phase of the respective internal combustion engine.

In order to reduce the time it takes for the components used for exhaust gas cleaning to become functional, it is already known to take engine-related measures. One of these engine measures consists in supplying the exhaust system of the internal combustion engine with hot exhaust gas. For this purpose, the internal combustion engine is operated with parameters that cause poor efficiency of the internal combustion engine and thus lead to high exhaust gas temperatures, for example with an adjustment of the ignition angle and/or an increase in the idling speed.

Furthermore, in order to reduce the time it takes for the components used for exhaust gas purification to become functional, it is already known to blow heated secondary air into the exhaust gas path of the respective internal combustion engine downstream of the outlet valves of the cylinders.

Furthermore, it is already known to use an electrically heated catalytic converter in the exhaust path of an internal combustion engine.

From the DE 10 2017 222 235 A1 a method for heating components of an exhaust gas cleaning system arranged in an exhaust gas path of an internal combustion engine is already known, in which secondary air is blown into the exhaust gas path. Before being fed into the exhaust gas path, this secondary air is heated by means of an electrical secondary air heating device and, seen in the direction of flow of the exhaust gas, is introduced into the exhaust gas path upstream of a component to be heated.

In order to be able to reach the so-called light-off temperature of a catalytic converter as quickly as possible in the cold start phase of an internal combustion engine, it is already known to use sensors to monitor individual parameters of the internal combustion engine in this cold start phase and then when these parameters assume values at which impermissibly high pollutant emissions occur, in each case to take appropriate countermeasures.

Proceeding from the above-mentioned prior art, the object of the invention is to specify an improved diagnosis of the heating measures of a catalytic converter arranged in the exhaust gas path of an internal combustion engine.

This object is achieved by a method having the features specified in claim 1. Advantageous refinements and developments of the invention are specified in the dependent claims.

In the method according to the invention for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust gas path of an internal combustion engine, the effectiveness of the heating measures of the catalytic converter is estimated using the energy contained in the exhaust gas of the internal combustion engine. This method enables the effectiveness of the heating measures of the catalytic converter to be estimated without the need to diagnose individual parameters of the internal combustion engine and to monitor them with regard to exceeding predetermined threshold values, as is necessary with known methods. In contrast to this, the method according to the invention works at the system level and supplies information about whether the heating measures of the catalytic converter are working properly or whether this is not the case.

According to one embodiment of the invention, the energy contained in the exhaust gas of the internal combustion engine is determined by integrating the fuel mass flow or by integrating the air mass flow.

According to one embodiment of the invention, the determined fuel mass integral is compared with a target value for the fuel mass integral.

According to one embodiment of the invention, the comparison is made when a predetermined catalyst temperature is reached.

According to one embodiment of the invention, the specified setpoint is determined empirically and stored in a memory of the internal combustion engine.

According to one embodiment of the invention, the specified setpoint is stored in a setpoint fuel mass integral curve.

According to one embodiment of the invention, the specified setpoint is determined taking into account a catalytic converter temperature, a coolant temperature and a catalytic converter efficiency.

According to one embodiment of the invention, the specified setpoint is determined taking into account the charge of a battery of the internal combustion engine.

According to one embodiment of the invention, the specified desired value is determined taking into account the energy supplied to the catalytic converter by electrical heating.

According to one embodiment of the invention, an error signal is provided in the event that the difference between the determined fuel mass integral and the desired value for the fuel mass integral is greater than a predetermined threshold value.

According to one embodiment of the invention, the error signal is stored in an error memory or shown on a display.

According to one embodiment of the invention, the effectiveness of the heating measures is estimated in a cold start phase of the internal combustion engine.

According to one embodiment of the invention, a device for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust gas path of an internal combustion engine is provided, which has a control unit designed to control a method according to the invention.

• 1 eine Blockdarstellung einer Vorrichtung zur Abschätzung der Wirksamkeit der Heizmaßnahmen eines im Abgaspfad einer Brennkraftmaschine angeordneten Katalysators und
• 2 ein Diagramm zur Erläuterung der Erfindung.

The invention is explained below by way of example with reference to the figures. It shows

• 1 a block diagram of a device for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust gas path of an internal combustion engine and
• 2 a diagram to explain the invention.

the 1 shows a block diagram of a device for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust gas path of an internal combustion engine.

The one in the 1 The device shown has an internal combustion engine 1 which contains a plurality of cylinders 2 and an exhaust gas duct 4 . A catalytic converter 5 is arranged in the exhaust gas duct 4 and is provided for cleaning the exhaust gas introduced into the exhaust gas duct 4 . A temperature sensor 6 is arranged on or in the catalytic converter 5 and serves to detect the catalytic converter temperature. Catalyst temperature T detected by temperature sensor 6 is fed to a control unit 7 . As an alternative to this, the catalyst temperature can also be modeled in the control unit 7 . The catalytic converter temperature detected by the temperature sensor 6 or the modeled catalytic converter temperature is evaluated in the control unit, as will be explained below. The control unit 7 is intended, among other things, to provide injectors 3, by means of which fuel is injected into the cylinders 2 of the internal combustion engine 1, with control signals s1, s2, s3, which individually determine the start of injection and the injection duration of the respective injector.

The control unit 7 determines the control signals mentioned using a stored work program, taking into account sensor signals which are derived from sensors of components of the internal combustion engine that are not shown. These sensors include, among others, an accelerator pedal sensor, a speed sensor, a crankshaft sensor and a camshaft sensor. The control signals provided by the control unit 7 contain, in their entirety, information about the fuel mass currently required by the internal combustion engine and determined by the control unit 7, which is to be injected into the cylinders by means of the injectors 3.

In the present invention, the control unit 7 is also provided to determine a fuel mass integral, particularly in a cold start phase of the internal combustion engine, starting with the starting process, and to compare it with a specified setpoint value determined empirically in advance in order to obtain information about the effectiveness of the heating measures of the internal combustion engine Exhaust duct 4 of the internal combustion engine 1 arranged catalyst 5 to obtain.

The empirically specified setpoint is determined taking into account a catalyst temperature, a coolant temperature and a catalyst efficiency.

Since the catalytic converter temperature present at a starting time of the internal combustion engine depends, among other things, on the ambient temperature and the length of time for which the internal combustion engine was switched off before the starting process, a predetermined target value is determined for a large number of possible combinations of a starting temperature, an ambient temperature and a catalytic converter efficiency and the course of this target value is recorded during a normal heating-up process of the catalytic converter and stored in said memory. This course of the desired value corresponds to a fuel mass integral.

As an alternative to this, the charging of a battery of the internal combustion engine can also be taken into account when determining the setpoint values and the setpoint value curve.

A further alternative is that when determining the desired values and the course of the desired values, the energy supplied to the catalytic converter by electrical heating is also taken into account.

Yet another alternative consists in additionally taking into account the charging of a battery of the internal combustion engine and the energy supplied to the catalytic converter by electrical heating when determining the desired values and the course of the desired values.

Thus, after the described empirical determination of a large number of setpoint values or setpoint curves, a data field is available which corresponds to a large number of fuel mass integral curves. In the cold start phase of the internal combustion engine, the applicable fuel mass integral curve can be compared with a fuel mass integral curve determined by the control unit 7 in the cold start phase.

For this purpose, during the cold start phase of the internal combustion engine, when a specified catalytic converter temperature is reached, which is measured by temperature sensor 6 of the catalytic converter and is 400° C., for example, an associated setpoint value for the fuel mass integral is read from the stored data field and compared with the fuel mass integral determined by control unit 7 compared.

If the control unit 7 recognizes from the result of the comparison that the difference between the fuel mass integral calculated by the control unit and the stored desired value for the fuel mass integral is greater than a predetermined threshold value, then it recognizes that there is an error and generates an error signal. This error signal is stored in a memory and/or shown on a display. If, on the other hand, the control unit 7 recognizes from the result of the comparison that the difference between the fuel mass integral calculated by the control unit and the stored target value for the fuel mass integral is smaller than the specified threshold value, then it recognizes that there is no error and that the catalytic converter has its light-off temperature in the expected range time reached.

For example, the following relationship applies to the fuel mass integral: $$\text{MI}=\text{f}\left(\text{TST}\text{, TCST}\text{, EffK}\text{,}\mathrm{\Delta }\text{Q}\text{,}\mathrm{\Delta }\text{E}\right).$$

• MI das Kraftstoffmassenintegral,
• TST die Katalysatortemperatur zum Startzeitpunkt der Brennkraftmaschine,
• TCST die Kühlmitteltemperatur zum Startzeitpunkt der Brennkraftmaschine,
• EffK die Katalysatoreffizienz,
• ΔQ eine Batterieladungsänderung bei Hybridfahrzeugen und
• ΔE eine dem Katalysator durch elektrisches Heizen zugeführte Energie.

There are:

• MI is the fuel mass integral,
• TST is the catalyst temperature at the time the internal combustion engine is started,
• TCST is the coolant temperature at the time the engine is started,
• EffK the catalyst efficiency,
• ΔQ a battery charge change in hybrid vehicles and
• ΔE an energy supplied to the catalyst by electrical heating.

the 2 shows a diagram to explain the invention. In this diagram, the fuel mass integral MI is plotted at the top and the catalytic converter temperature T in °C is plotted at the right.

The curve K1 shows a target fuel mass integral curve that was determined empirically and stored in the memory of the control unit 7 . This setpoint fuel mass integral profile was determined in a cold start phase of the internal combustion engine, in which the ignition angle was adjusted and the idling speed was increased to accelerate heating of the catalytic converter.

Curve K2 shows a fuel mass integral curve that was also determined empirically. This fuel mass integral curve K2 was determined in a cold start phase of the internal combustion engine, in which the same starting conditions existed as when determining curve K1, but in which only an ignition angle adjustment was made to accelerate heating of the catalytic converter, but no increase in the idle speed.

The curve K3 shows a fuel mass integral profile that was also determined empirically. This fuel mass integral curve K3 was determined in a cold start phase of the internal combustion engine, in which the same starting conditions prevailed as when determining curves K1 and K2, but in which accelerated heating of the catalytic converter only increased the idle speed, but no ignition angle adjustment was made.

The curve K4 shows a fuel mass integral profile that was also determined empirically. This fuel mass integral profile K4 was determined in a cold start phase of the internal combustion engine, in which the same starting conditions prevailed as when determining curves K1, K2 and K3, but in which neither an ignition angle adjustment nor an increase in the idling speed was carried out to accelerate heating of the catalytic converter.

• Die Kurve K1 veranschaulicht, dass bei einer Katalysatortemperatur von 400°C das Kraftstoffmassenintegral MI einen Kraftstoffmassenintegralwert MI1 aufweist.
• Die Kurve K2 veranschaulicht, dass bei einer Katalysatortemperatur von 400°C das Kraftstoffmassenintegral MI einen Kraftstoffmassenintegralwert MI2 aufweist.
• Die Kurve K3 veranschaulicht, dass bei einer Katalysatortemperatur von 400°C das Kraftstoffmassenintegral MI einen Kraftstoffmassenintegralwert MI3 aufweist.
• Die Kurve K4 veranschaulicht, dass bei einer Katalysatortemperatur von 400°C das Kraftstoffmassenintegral MI einen Kraftstoffmassenintegralwert MI4 aufweist.

The following can be seen from a comparison of curves K1 to K4:

• The curve K1 illustrates that at a catalyst temperature of 400° C. the fuel mass integral MI has a fuel mass integral value MI1.
• The curve K2 illustrates that at a catalytic converter temperature of 400° C. the fuel mass integral MI has a fuel mass integral value MI2.
• The curve K3 illustrates that at a catalytic converter temperature of 400° C. the fuel mass integral MI has a fuel mass integral value MI3.
• The curve K4 illustrates that at a catalytic converter temperature of 400° C. the fuel mass integral MI has a fuel mass integral value MI4.

The following relationship applies: MI1<MI2<MI3<M14.

This means that the amount of fuel required to reach a catalytic converter temperature of 400°C in a cold start phase, on which curve K1 was based, is smaller than the amount of fuel required to reach the catalytic converter temperature of 400°C in the Determination of the curves K2, K3 and K4 were required.

From this it can be seen that the fuel mass integral, which is determined in the cold start phase of an internal combustion engine, provides information at the system level when a certain catalyst temperature is reached as to whether the heating process of the catalyst is proceeding as desired in the sense of curve K1, or whether the heating process is influenced by disturbances. Malfunctions are present if, at a specified catalytic converter temperature, the fuel mass integral value determined by the control unit deviates by more than a specified tolerance from an associated desired fuel mass integral value, which was determined empirically and stored non-volatile in a memory of the control unit. If such a fault is detected, associated information can be stored in a fault memory and/or a fault can be displayed on a display unit, so that the service personnel can initiate a remedy for the fault present.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was 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.

Patent Literature Cited

• DE 102017222235 A1 [0006]

Claims (13)

Method for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust tract of an internal combustion engine, characterized in that the assessment of the effectiveness of the heating measures of the catalytic converter is carried out on the basis of the energy contained in the exhaust gas of the internal combustion engine. procedure after claim 1 , characterized in that the energy contained in the exhaust gas of the internal combustion engine is determined by integrating the fuel mass flow or by integrating the air mass flow. procedure after claim 1 or 2 , characterized in that the determined fuel mass integral is compared with a target value for the fuel mass integral. procedure after claim 3 , characterized in that the comparison is made when a predetermined catalyst temperature is reached. procedure after claim 3 or 4 , characterized in that the predetermined setpoint is determined empirically and is stored in a memory of the internal combustion engine. procedure after claim 5 , characterized in that the specified desired value is stored in a desired fuel mass integral profile. procedure after claim 6 , characterized in that the predetermined target value is determined taking into account a catalyst temperature, a coolant temperature and a catalyst efficiency. procedure after claim 7 , characterized in that the predetermined setpoint is determined taking into account the charge of a battery of the internal combustion engine. procedure after claim 7 or 8th , characterized in that the predetermined desired value is determined taking into account the energy supplied to the catalytic converter by electrical heating. Procedure according to one of claims 3 - 9 , characterized in that in the event that the difference between the determined fuel mass integral and the target value for the fuel mass integral is greater than a predetermined threshold value, an error signal is provided. procedure after claim 9 , characterized in that the error signal is stored in an error memory or is shown on a display. Method according to one of the preceding claims, characterized in that the assessment of the effectiveness of the heating measures is carried out in a cold start phase of the internal combustion engine. Device for estimating the effectiveness of the heating measures of a catalytic converter arranged in the exhaust tract of an internal combustion engine, characterized in that it has a control unit (7) which is designed to control a method according to one of the preceding claims.

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