CN112292515A

CN112292515A - Method for checking a particulate filter, in particular for an internal combustion engine of a motor vehicle

Info

Publication number: CN112292515A
Application number: CN201980041833.3A
Authority: CN
Inventors: A·鲁里克; J·施瓦布
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2018-06-28
Filing date: 2019-06-24
Publication date: 2021-01-29
Anticipated expiration: 2039-06-24
Also published as: WO2020002182A1; CN112292515B; DE102018005111A1

Abstract

The invention relates to a method for testing a particle filter (18) of an internal combustion engine (10) having an exhaust gas system (16), a particle filter (18) arranged in the exhaust gas system (16), and at least one exhaust gas turbocharger (20), wherein the exhaust gas turbocharger (20) has: a turbine (22) which is arranged upstream of the particle filter (18) and has a turbine wheel (24) in an exhaust system (16) through which exhaust gas of the internal combustion engine (10) can flow; a bypass line (38) through which at least a portion of the exhaust gas bypasses the turbine wheel (22); and a bypass valve (40) which can be moved into a plurality of positions which differ from one another and which can regulate the amount of exhaust gas flowing through the bypass line (38), the method having the following steps: determining a position of the bypass valve (40); and checking the particulate filter (18) in dependence of the determined position of the bypass valve (40).

Description

Method for checking a particulate filter, in particular for an internal combustion engine of a motor vehicle

Technical Field

The invention relates to a method for checking a particulate filter, in particular for an internal combustion engine of a motor vehicle, according to the preamble of claim 1.

Background

Such a method for checking a particle filter of an internal combustion engine, in particular for a motor vehicle, having an exhaust system, a particle filter arranged in the exhaust system and at least one exhaust gas turbocharger, is known, for example, from DE 102008059697 a 1. In the method, the exhaust gas turbocharger has a turbine with a turbine wheel, which is arranged upstream of the particle filter in the exhaust gas system through which the exhaust gas of the internal combustion engine can flow. In addition, the exhaust-gas turbocharger has a bypass line, by means of which at least a portion of the exhaust gas can bypass the turbine wheel. That is, the exhaust gas flowing through the bypass line bypasses the turbine wheel and thus does not drive the turbine wheel. Furthermore, exhaust gas turbochargers have a bypass valve which can be moved into a plurality of positions which differ from one another, also referred to as wastegate or wastegate valve. By means of which the amount of exhaust gas flowing through the bypass line can be regulated, in particular depending on the position of the bypass valve.

Furthermore, DE 102015215373 a1 discloses an exhaust gas aftertreatment method for a supercharged, externally ignited internal combustion engine.

Disclosure of Invention

The object of the invention is to improve a method of the type mentioned in the introduction such that the particle filter can be inspected in a very simple manner.

This object is achieved by a method having the features of claim 1. Advantageous embodiments with suitable inventive developments are specified in the dependent claims.

In order to develop a method of the type described in the preamble of claim 1 such that a particle filter, for example, in the form of a diesel particle filter or an otto particle filter/fast-burn particle filter, can be checked, i.e., diagnosed, in a very simple manner, the invention provides that the respective, in particular current, position of the bypass valve is determined, in particular by means of an electronic computer. In addition, the particulate filter is checked in dependence on the determined bypass valve position.

The determined position is used, for example, as an actual position, which is compared with at least one ideal position. In this case, the particle filter is checked, for example, as a function of the comparison result.

The ideal position is retrieved, for example, from a characteristic curve stored in a memory means of the electronic computing device. In this case, it has proven to be particularly advantageous to set the desired position from the specific curve as a function of the current operating point of the internal combustion engine, in particular as a function of the current load.

The invention is based on the following recognition, among others: when using a particulate filter, for example for otto engines or gasoline engines or for diesel engines, the particulate filter should be diagnosable, i.e. checked, according to exhaust gas regulations. The inspection of the particulate filter includes, for example: it is checked whether the particulate filter is installed, i.e. installed in the exhaust equipment. Additionally, the checking may include: monitoring the filtration efficiency of the particulate filter and/or monitoring the degree of loading of the particulate filter. The degree of loading, also referred to as loading, characterizes the amount of particles contained in the particle filter, in particular soot particles which are filtered out of the exhaust gas by means of the particle filter and are deposited in the particle filter. The degree of loading is critical to assessing whether continued particulate containment is permitted. On the one hand, the filtration efficiency may decrease at high load levels. On the other hand, a significantly increased exhaust back pressure may lead to component damage.

In general, the detection of the particle filter and in particular its degree of loading is carried out by means of a Δ pressure sensor, also referred to as a differential pressure sensor, which by means of a pressure measurement upstream and downstream of the particle filter can determine a differential pressure, also referred to as a pressure Δ. The degree of load can be determined from the pressure delta. If the pressure Δ is below a predetermined threshold value, for example, it can be concluded that the particulate filter is not installed, damaged or removed, since even an unloaded particulate filter would cause a pressure change or a pressure Δ greater than zero. Another and/or alternative diagnostic possibility that does not require a delta pressure sensor is desirable. Such a further or alternative diagnostic option is advantageous if, for example, the signal provided by the Δ pressure sensor and characterizing the pressure Δ obtained with the Δ pressure sensor cannot be evaluated at least temporarily, if the Δ pressure sensor fails, or if such a Δ pressure sensor is to be rejected.

The method according to the invention forms an alternative diagnostic option, since the change in the position of the bypass valve, in particular of the bypass valve, is taken into account as a measure for the changing exhaust gas back pressure, which is usually caused by the particle filter or by its load and/or its damage, or for the change in the exhaust gas back pressure. In other words, the invention is based on the recognition that the particle filter influences the exhaust gas back pressure, so that, for example, a change in the exhaust gas back pressure occurs when the particle filter is previously installed and is then removed from the exhaust system and/or damaged or when the particle filter load increases. The exhaust gas back pressure or a change thereof leads to a change in the bypass valve position, so that the particle filter can be diagnosed from the bypass valve position, in particular from the change in the bypass valve position.

Since the pressure downstream of the turbine (p4) increases due to the particulate filter or its load, the pressure drop from pressure p3 (upstream of the turbine) to pressure p4 decreases. As a result, the bypass valve, also referred to as Wastegate (WG), must be further closed in dependence on the pressure drop change or in dependence on the change in pressure p4 in order to keep the exhaust-gas turbocharger rotational speed constant, for example, in order to prevent the intake pipe pressure from dropping. The closing of the waste gate in turn causes an increase in the exhaust back pressure p 3. The scavenging work is then increased, since the exhaust gases must be discharged from the combustion chamber against the higher pressure. Thereby resulting in a lower average effective pressure and thus a lower effective torque. The load detection of the engine control compensates this by means of the higher intake pipe pressure. This results in higher high pressure work, thereby compensating for higher ventilation work. In general, the same mean effective pressure can be adjusted despite the higher exhaust back pressure. Higher suction pipe pressure can be achieved by closing the waste gate more strongly. In the case of a drop in pressure p4, for example due to the removal of a particle filter, the above-mentioned effects are reversed, and the waste gate must be opened further and the required suction line pressure drops.

In summary, it is possible to deduce the degree of loading of the particle filter or whether the particle filter is installed at all, i.e. installed in the exhaust system, by changing the position of the bypass valve. To this end, the bypass valve position is compared to a reference position in the form of an ideal position, which may be generated, for example, when the vehicle initially begins to use a new unloaded particulate filter. The load amount can be back-calculated from the difference between the actual position and the reference position, or it can be diagnosed whether the particulate filter is detached or damaged.

Another subject of the invention is the use of the above-mentioned change in the suction line pressure caused by the particle filter or its loading as a diagnostic possibility, in particular as a diagnostic possibility for the calculation of the delta pressure. The reasons for possible inspiratory line pressure variations have been described above. In this case, for example, the pressure prevailing in the intake manifold is determined, in particular measured, and compared with a reference pressure. The reference pressure is, for example, the pressure that exists in the suction pipe in the case of an unloaded new particle filter. Depending on the deviation of the measured pressure from the reference pressure, it is possible to deduce the degree of loading of the particle filter or to diagnose whether the particle filter is damaged or not installed at all.

Since the particulate filter causes a significant back pressure, in particular in the case of large exhaust gas volumes, it is suitable to determine the pressure change as a function of the wastegate position or the intake manifold pressure change at higher rotational speeds, in particular in the high load range. Load ranges that do not require boost and thus wastegate control are not considered for diagnostics.

The diagnostic modality should be performed under similar environmental conditions that are also used to determine the reference values, as altitude and intake air temperature can affect bypass valve position and intake air duct pressure. The reference value may be determined at various or multiple engine operating points to improve diagnostic possibilities. The following advantages can be achieved in particular by means of the method according to the invention:

a significant cost saving when the delta pressure sensor is dispensed with,

can be used as an equivalent diagnosis,

compared to a pressure measurement by means of a delta pressure sensor, diagnostic results can be obtained at high exhaust gas volume flows and load ratios,

the diagnostic result can be determined more quickly from the cycle than from a pressure measurement with the delta pressure sensor, since, for example, it is also not necessary to wait for the dew point at the delta pressure sensor to end.

In general, it has been found that the detection of the Δ pressure via the particle filter can be recognized by a change in the wastegate position and/or a change in the intake manifold pressure, so that, for example, an identification of the removal of the particle filter, a determination of the degree of loading and a determination of the aging of the particle filter can be carried out.

Other advantages, features and details of the present invention will appear from the following description of preferred embodiments, taken in conjunction with the accompanying drawings. The features and feature combinations mentioned above in the description and the features and feature combinations mentioned below in the description of the figures and/or shown in the single figure can be used not only in the respectively specified combination but also in other combinations or individually without departing from the scope of the invention.

Drawings

The figures show a schematic representation of an internal combustion engine in the sole figure, which is designed to carry out the method according to the invention.

Detailed Description

The single figure shows the internal combustion engine 10 of a motor vehicle, which can preferably be designed as a motor vehicle and is designed here as a passenger car. The internal combustion engine 10 has a machine body 12 which forms at least one combustion chamber 14, which is configured, for example, as a cylinder. During the ignition operation of the internal combustion engine 10, a combustion process takes place in the combustion chamber 14, whereby exhaust gases of the internal combustion engine 10 are produced. The internal combustion engine 10 has an exhaust gas tract through which exhaust gas can flow, which is also referred to as an exhaust system 16. The exhaust system 16 has a particle filter 18 through which the exhaust gas can flow, by means of which particles, in particular soot particles, which may be contained in the exhaust gas can be at least partially filtered out of the exhaust gas. The internal combustion engine 10 is designed as a supercharged internal combustion engine and for this purpose comprises at least one or exactly one exhaust-gas turbocharger 20 having a turbine 22 with a turbine wheel 24. The turbine 22, and in particular the turbine wheel 24, is arranged within the exhaust gas device 16 such that the turbine 22 can be flowed through by at least a portion of the exhaust gas. The portion of the exhaust gas flowing through the turbine 22 may drive the turbine wheel 24.

The internal combustion engine 10 also has an intake duct 26, also referred to as an intake duct, through which air can flow. By means of the intake duct 26, the air flowing through the intake duct 26 is guided, in particular introduced, into the combustion chamber 14. In this case, an air filter 28 is provided in the intake duct 26 for filtering the air flowing through the intake duct 26. The exhaust-gas turbocharger 20 has a compressor 30, which is arranged in the intake tract 26 and comprises a compressor wheel 32. With the aid of the compressor wheel 32, the air flowing through the intake channel 26 can be compressed. For this purpose, the compressor wheel 32 is driven by the turbine wheel 24. The intake channel 26 comprises at least one line piece 34 through which air can flow, which is also referred to as an intake line. The pressure prevailing in the intake manifold during the ignition mode is also referred to as the intake manifold pressure.

As can be seen from the figure, the particulate filter 18 is arranged downstream of the turbine 22 and in particular downstream of the turbine wheel 24 in the flow direction of the exhaust gas flowing through the exhaust gas device 16.

The exhaust-gas turbocharger 20 has a bypass mechanism 36 which comprises at least one or exactly one bypass line 38. The bypass line 38 is in fluid communication with the exhaust gas system 16 at a branch point a and an opening point E. At the branch point a, the exhaust gas flowing through the exhaust gas system 16 can be at least partially diverted from the exhaust gas system 16 and introduced into the bypass line 38. Because the exhaust gas flowing through the bypass line 38 bypasses the turbine wheel 24, the turbine wheel 24 is not driven by the exhaust gas flowing through the bypass line 38, but is bypassed by the exhaust gas flowing through the bypass line 38. At the opening point E, the exhaust gas flowing through the bypass line 38 can flow out of the bypass line 38 and back into the exhaust gas system 16. The branching point a is arranged upstream of the turbine wheel 24, wherein the opening point E is arranged downstream of the turbine wheel 24 and upstream of the particle filter 18. Upstream of the turbine wheel 24, there is a first pressure of the exhaust gas, also denoted by p3, wherein the first pressure is also referred to as a first exhaust gas pressure. Downstream of the turbine wheel 24 and upstream of the particulate filter 18, a second exhaust gas pressure is present in the exhaust gas system 16, wherein the second pressure is also referred to as a second exhaust gas pressure. Since the exhaust gas is depressurized by means of the turbine wheel 24, the first exhaust gas pressure is generally lower than the second exhaust gas pressure, which is also denoted by p 4.

The bypass mechanism 36 also includes a bypass valve 40, also referred to as a wastegate or wastegate valve, which is disposed, for example, on the bypass line 38. By means of the bypass valve 40, the amount of exhaust gases flowing through the bypass line 38 can be regulated. As a result, the charging pressure of the exhaust gas turbocharger 20 can be regulated, in particular controlled.

The bypass valve 40 can be moved, in particular, by means of an actuator, not shown in the figures, into a plurality of different positions relative to one another. For example, each of the positions of the bypass valve 40 corresponds to exactly one amount of exhaust gas flowing through the bypass line 38.

In order to now be able to check and in particular diagnose the particle filter 18 in a very simple manner and without using a differential pressure sensor, for example, it is provided within the scope of the method for checking the particle filter 18 that the current position of the bypass valve 40 is determined. In addition, the particulate filter 18 is checked in accordance with the determined position of the bypass valve 40. For this purpose, the determined position is compared as an actual position with an ideal position, for example, in particular as a function of the current operating point of the internal combustion engine 10, in particular as a function of the current load. Alternatively or additionally, it is conceivable to determine, in particular measure, at least one pressure, also referred to as the intake manifold pressure, which is present in the intake manifold, in particular by means of a pressure sensor. In this case, it is conceivable to check the particle filter 18 as a function of the determined, in particular measured, intake manifold pressure. For this purpose, the measured intake manifold pressure is compared, for example, with a desired or reference pressure, in particular as a function of the current operating point or the current load of the internal combustion engine 10.

In particular, the degree of loading of the particle filter can be determined in the examination range of the particle filter 18. Alternatively or additionally, damage to the particulate filter 18 may be determined and/or a removal recognition may be performed, within which it is checked whether the particulate filter 18 is actually installed or not installed, for example, in the exhaust system 16.

List of reference numerals

10 internal combustion engine

12 machine body

14 combustion chamber

16 waste gas plant

18 particulate filter

20 exhaust gas turbocharger

22 turbine

24 turbine wheel

26 air inlet channel

28 air filter

30 compressor

32 compressor wheel

34 pipeline parts

36 bypass mechanism

38 bypass line

40 bypass valve

Branch point A

E point of access

Claims

1. A method for checking a particle filter (18) of an internal combustion engine (10) having an exhaust gas system (16), a particle filter (18) arranged in the exhaust gas system (16) and at least one exhaust gas turbocharger (20), wherein the exhaust gas turbocharger (20) has: a turbine (22) which is arranged upstream of the particle filter (18) and has a turbine wheel (24) in an exhaust system (16) through which exhaust gas of the internal combustion engine (10) can flow; a bypass line (38) via which at least a portion of the exhaust gas can bypass the turbine wheel (22); and a bypass valve (40) which can be moved to a plurality of positions different from each other and which can adjust the amount of exhaust gas flowing through the bypass line (38),

the method is characterized by comprising the following steps:

-determining the position of the bypass valve (40); and

-checking the particulate filter (18) in dependence of the determined position of the bypass valve (40).

2. Method according to claim 1, characterized in that the determined position is compared as an actual position with at least one ideal position, wherein the particle filter (18) is checked as a function of the comparison result.

3. The method of claim 2, wherein the ideal position is retrieved from a characteristic curve stored in a storage mechanism of an electronic computing device.

4. Method according to claim 3, characterized in that the ideal position is retrieved from the characteristic curve as a function of the current operating point of the internal combustion engine (10), in particular as a function of the current load.