DE102008001906A1 - Fuel-type detecting method for use in e.g. diesel internal combustion engine of vehicle, involves detecting conductivity of sensor during heating of sensor, and concluding fuel-type used for operating engine from changing conductivity - Google Patents

Abstract

The method involves detecting the loading of an exhaust gas flow of an internal combustion engine (10) with soot particles, and heating a particle sensor (16) to a predetermined temperature over a time interval, where the temperature lies below a soot combustion temperature. The conductivity of the particle sensor is detected during the heating of the sensor, and a fuel-type used for operating the internal combustion engine is concluded from the changing conductivity, where the sensor is arranged upstream of a particle filter (14) that is arranged in an exhaust gas pipe (12). Independent claims are also included for the following: (1) a computer program for executing a method for detecting a fuel type (2) a computer program product stored on a machine-readable medium for executing a method for detecting a fuel type.

Description

The The invention relates to a method for detecting the operation an internal combustion engine used type of fuel according to the species of independent claim 1.

object The present invention also relates to a computer program a computer program product with a program code written on a machine-readable carrier is stored to carry of the procedure.

State of the art

In vehicles with particulate filters, ie in particular in vehicles with diesel internal combustion engines, which have a diesel particulate filter in the exhaust system, a functional check of the diesel particulate filter in the course of on-board diagnostics (OBD) is required. Furthermore, a particle sensor for determining the amount of particles introduced into the filter is advantageous for detecting the filter loading state. The test for functionality of the diesel particulate filter and the loading prediction of the filter can be done for example by means of a resistive particle sensor, as for example from the DE 10 2004 036 388 A1 evident. In this sensor, particles from the exhaust gas are deposited on a ceramic sensor element. By measuring the electrical resistance between two interdigital electrodes deposited particles can be detected. The accuracy of the sensor in the constantly changing exhaust gas temperature of the internal combustion engine is achieved by a compensation of the temperature-dependent conductivity of the soot. In order to carry out a regeneration of the sensor, it is temporarily heated to a temperature at which soot particles accumulate on the particle filter. In the from the DE 10 2004 036 388 A1 As a result, the conductivity between the electrodes of the particulate sensor during heating is detected and used for evaluation of the state of the particulate sensor.

Diesel fuels can now with regard to their chemical composition, for example, the aromatics content, the sulfur content, the oxygen content and the like, as well as their physical properties such as density, viscosity, etc. regionally differ significantly. The fuel properties are also dependent how high the share of diesel fuel added Biodiesel or synthetic diesel is. With the fuel properties change also the combustion characteristics, for example the ignition delay, and thus also the exhaust and particle emissions.

task The invention is to provide a method which a Recognition of the fuel grade used in the internal combustion engine allows. The information obtained in this way the fuel grade can then be in an engine control unit used to set different application profiles be so as to the combustion process in terms of each Optimize fuel grade.

Disclosure of the invention

Advantages of the invention

These Task is by a method for recognizing the operation an internal combustion engine used fuel grade with the features of claim 1. The basic idea of the invention is the Detection of the fuel grade based on the emitted soot. For this purpose, the particle sensor over at least one time interval heated to at least a predetermined temperature and off the changing conductivity on the used fuel grade closed. The detection of the burnt Fuel grade is particularly important because of the composition of the fuel directly affects the aging of the diesel particulate filter and has downstream sensors, which by an ash load age constantly. In addition, some fuel additives also irreversibly poison oxidation catalysts. A fuel detection sensor represents a cost-effective monitoring measure the functionality of such exhaust aftertreatment systems In addition, the detection of the type of fuel allows also an adaptation of the combustion process to the fuel grade and such an improvement of the combustion processes and a concomitant reduction of harmful emissions. The Recognition of the fuel grade also allows customization the maintenance intervals to the type of fuel, for example Statements about the aging of seals, the oil consumption and the like possible, from fuel grade to fuel grade vary. Finally, an adaptation of a raw emission model for Soot particles and thus an improvement of the model-based Load forecast for a diesel particulate filter the detection of the fuel grade and thus an increased System security achievable.

By those listed in the dependent claims Measures are advantageous developments and improvements of the method specified in the independent claim possible. For example, an advantageous embodiment provides for the Particle sensor over a time interval to a predefinable Temperature to heat below the Rußabbrandtemperatur lies, and from the thereby adjusting temperature dependence to close the conductivity to the fuel grade.

Around also to determine the HC concentration in the exhaust and at the same time evaporation of HC molecules from the sensor surface to ensure looks another very beneficial Embodiment of the method according to the invention before, the particle sensor over a predeterminable time interval to heat to a predeterminable temperature, the boiling point the highest temperature boiling hydrocarbon component in the exhaust gas of the internal combustion engine corresponds, and from the itself adjusting temperature dependence of the conductivity to close the amount of hydrocarbons in the exhaust gas.

there is preferred from the temperature dependence of the conductivity during heating and during the Cooling of the sensor to the fuel grade or on the amount of hydrocarbon in the exhaust gas is closed.

The The object is further achieved by a method for detecting the type of fuel used to operate an internal combustion engine, in which the loading of an exhaust gas stream of the internal combustion engine with soot particles is detected by the conductivity between two electrodes of a particulate sensor exposed to the exhaust flow is detected, the particle sensor at least temporarily heated to a predeterminable temperature and the conductivity between the electrodes of the particle sensor at least during heating is detected. The method is characterized in that that the particle sensor is heated to a temperature which is greater than an assumed Rußabbrandtemperatur and that from the conductivity to the actual Rußabbrandtemperatur and from this to the fuel grade is closed. The basic idea of this invention Solution is from the burnup temperature to the fuel grade to close, here is exploited that different Fuel types different Rußabbrandtemperaturen exhibit.

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description explained in more detail.

It demonstrate:

1 a schematic representation of an internal combustion engine with a particle sensor;

2 schematically the course of an embodiment of the method according to the invention;

3 the temperature of the sensor over time and the particle conductivity over time to explain embodiments of the method according to the invention and

4 the relative conductivity over the temperature of the sensor to explain the method according to the invention.

Description of the embodiments

An internal combustion engine 10 represented in 1 has a particle filter 14 on that in an exhaust pipe 12 is arranged and has the task to filter harmful particles of the exhaust gas. Such a particulate filter may be for example a diesel particulate filter, which is provided for filtering harmful soot particles. Upstream of the particulate filter 14 is a particle sensor 16 arranged. This includes in the present embodiment, a resistive sensor 18 and a temperature sensor 20 , The output signals of the resistive sensor 18 and the temperature sensor 20 become a control device 24 , For example, an engine control unit supplied. The resistive sensor 18 comprises in known per se two interdigital electrodes, which are arranged on a ceramic carrier material (not shown). These electrodes are exposed to the exhaust gas flow. During normal operation, soot particles are deposited on the particle sensor 16 or the resistive sensor 18 at. As a result, the gap between the two electrodes is increasingly bridged, resulting in a change in impedance or when using DC, the electrical (ohmic) resistance. This change in the impedance or the ohmic resistance is a measure of the loading of the exhaust gas flow with soot particles. Like the impedance or resistance, the conductivity of the sensor also changes. The conductivity thus represents a measure of the loading of the exhaust gas flow with, for example, soot particles.

To the functioning of the particle sensor 16 over a longer period of time, this has a heating device 22 , in the 1 only indicated by dashed lines. With this heater 22 can the entire particle sensor 16 be heated to a temperature in the range between 550 ° C and 800 ° C. This sets at the on the particle sensor 16 deposited soot particles an exothermic reaction, oxidized by the deposited soot particles or burn off. At the end of this process called "regeneration" is the particle sensor 16 or the resisitive sensor 18 again at least substantially free of accumulated soot particles.

To determine the fuel grade, the particle sensor 16 specifically heated. During heating, the conductivity of the particle sensor 16 detected. From this conductivity can draw conclusions about the loading of the exhaust stream with Soot particles and thus obtained on the grade of fuel used, as will be explained in more detail below.

In 2 an embodiment of the method according to the invention for detecting the fuel grade used in an internal combustion engine is shown. First, in a block 201 a pulse-shaped heating of the particle sensor 16 , represented by rectangular temperature pulses 210 , Here, the self-adjusting current I is detected over the time t. This initially increases continuously because the particle sensor collects particles in the time interval considered which contribute to the current signal. He also shows peak-shaped peaks 220 due to the pulse-shaped heating of the sensor. This temperature-dependent change in conductivity is an intrinsic material property of the soot particles, soot particulate conductivity increases with temperature, comparable to a highly disordered semiconductor. Then the change of the current over the temperature dl / dT is determined. In a block 202 From the characteristic dl / dT from a database, the relative change in conductivity over the temperature is determined. In a first query block 203 is based on the database 202 checks whether there is a class 1 fuel, ie a standard fuel. If this is the case, in step 204 appropriate measures, in particular compensation measures, for example, the correction of the temperature dependence of the conductivity of carbon black for Class 1 fuel, but also a loading prognosis for the fuel class 1 and corresponding specifications for maintenance intervals of a class 1 fuel made.

If in block 203 it is determined that no class 1 fuel is present, in block 205 determines if a class 2 fuel is present. If this happens to be in block 206 appropriate measures for adjusting the combustion process, to determine the load forecast, the maintenance intervals and the like made for a class 2 fuel.

If no class 2 fuel is present in block 207 Determines if a class 3 fuel is present. If this is the case, be in block 208 appropriate measures have been initiated for a Class 3 fuel. This query may continue depending on the number of fuel classes used.

So, in summary, the particle sensor is spoken 16 over at least one, preferably a plurality of time intervals defined heated to a predeterminable temperature and detects the thereby adjusting conductivity change. From the conductivity change over time statements are made about the fuel grade.

An alternative embodiment of the method is in 3 shown. There, in the upper diagram a) the temperature T of the sensor over the time t and in the lower diagram b) the particle conductivity σ above the temperature T are shown. This embodiment not only allows the determination of the fuel grade but by acting on the sensor 16 with heating pulses of different "height" also a detection of the hydrocarbon concentration (HC concentration). For this purpose, first the sensor 16 with a heating pulse up to a temperature T ₁ applied. The warm-up hare is here on the basis of a straight line 301 and the cooling phase is based on a straight line 302 shown in the upper diagram. This results in the temperature profile of the conductivity σ shown in the lower graph b). This first increases starting at a temperature T ₀ up to the predetermined temperature T ₁ (line 301 in the lower graph) and does not change at the temperature T ₁ . The background to this behavior is that the temperature T ₁ is chosen to be greater than the boiling point temperature of the highest boiling component in the fuel. The temperature is preferably chosen to be 330 ° C. As a result, the conductivity σ increases irreversibly by evaporation of hydrocarbon molecules from the particle sensor 16 at. For this reason, the conductivity increases at temperature T ₁ . In the subsequent cooling phase, curve 302 , the conductivity decreases again. After the hydrocarbon molecules have evaporated in this way, another heating pulse, represented by the warm-up line, takes place 303 and the cooling line 304 in 3a ). In principle, these process steps can also be used to determine the HC concentration. The occurring conductivity σ is in 3b ). The conductivity first increases and then reversibly decreases again (curves 303 . 304 in 3b )). By recording the heating and cooling curves, it is possible to draw conclusions on both the HC concentration, as well as on the soot load and thus on the fuel grade.

The fuel diagnosis is performed by detecting the cooling behavior of the soot after heating up to a second temperature T ₂ , which is greater than the temperature T ₁ . As a result, the result of the fuel analysis can be carried out independently of gaseous components (HC components) in the exhaust gas.

Yet another solution according to the invention, shown in FIG 4 provides the sensor 16 to heat to a predetermined temperature which is greater than an assumed Rußabbrandtemperatur of the fuel used and in this case to measure the conductivity σ above the temperature and from the conductivity be the burnup temperature vote. This is done by determining a maximum of the conductivity over the temperature. In a fuel, for example of the type 1, illustrated by a line 410 in 4 This maximum sets earlier than with a Type 2 fuel represented by the line 420 in 4 , The temperature associated with the maximum conductivity is the burnup temperature T _Type1 of the type 1 fuel and the burnup temperature T _Type2 of the type 2 fuel. The basic idea of this solution is to determine the fuel composition via the soot burnup temperature. At the in 4 For example, type 1 fuel is a high ash content soot that catalyzes soot burnup.

The Determining the type of fuel can - as mentioned above explained - be used to appropriate Take measures that the exhaust aftertreatment system protect. For example, the combustion process fuel-specific adapted and thus reduced emissions become. In addition, statements about the maintenance intervals are taken as the aging of the seals, the oil consumption and the like also used by the Suspend the fuel grade. For example, at intensive use of biodiesel seals the essential more stressed than when using mineral Diesel.

About that In addition, a raw emission model for soot particles and thus an improvement of a model-based load forecast for a diesel particulate filter and herewith the system security can be increased.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102004036388 A1 [0003, 0003]

Claims (7)

Method for detecting the operation of an internal combustion engine ( 10 ) used, wherein the loading of an exhaust gas stream of the internal combustion engine ( 10 ) with soot particles is detected by the conductivity (σ) of a particle sensor exposed to the exhaust gas flow ( 16 ) is detected at least during the heating, characterized in that the particle sensor ( 16 ) is heated over at least one time interval to at least one predeterminable temperature (T ₁ , T ₂ ) and from the thereby changing conductivity (σ) is closed to the fuel grade used. Method according to claim 1, characterized in that the particle sensor ( 16 ) is heated over a time interval to a predeterminable temperature (T ₂ ), which is below the Rußabbrandtemperatur and that is concluded from the temperature dependence of the thereby determined conductivity (σ) on the fuel grade. Method according to claim 1 or 2, characterized in that the particle sensor ( 16 ) is heated over a time interval to a temperature (T ₁ ), which corresponds to the boiling point of the boiling point of the highest boiling hydrocarbon component in the exhaust gas of the internal combustion engine substantially and that from the thereby adjusting temperature dependence of the conductivity (σ) on the amount of hydrocarbon in the exhaust gas becomes. Method according to one of the preceding claims, characterized in that from the temperature dependence the conductivity (σ) during heating and while cooling down to the fuel grade and / or the amount of hydrocarbon in the exhaust gas is concluded. Method for detecting the operation of an internal combustion engine ( 10 ) used fuel type, in which the loading of an exhaust gas stream of the internal combustion engine ( 10 ) with soot particles is detected by the conductivity (σ) of a particle sensor exposed to the exhaust gas flow ( 16 ), the particle sensor ( 16 ) is heated temporarily to a predeterminable temperature and the conductivity (σ) of the particle sensor ( 16 ) is detected at least during the heating, characterized in that the particle sensor ( 16 ) is heated to a temperature which is greater than an assumed Rußabbrandtemperatur and that from the conductivity (σ) is concluded on the actual Rußabbrandtemperatur and from this to the fuel grade. Computer program that shows all the steps of a procedure according to one of claims 1 to 4 or 5, when it runs on a computing device. Computer program product with program code, which is stored on a machine-readable carrier, for carrying out the method according to one of claims 1 to 4 or 5, when the program is stored on a computer or a control device ( 24 ) is performed.