DE102016226044A1 - Method and device for monitoring the particle emission of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for monitoring the particle emission of an internal combustion engine equipped with a particle sensor with the following steps: - Check whether predetermined conditions for monitoring the particle emission are present, - Upon detection that the given conditions are present, calculation of the particle emission for the current operating point of the internal combustion engine , - Forming for a plurality of successive calculated particulate emissions each of the quotient of the calculated particulate emission and the associated maximum allowable emission taken from a map, - forming an average of the formed quotients and driving a fault lamp, if this average value is greater than 1.

Description

The invention relates to a method and a device for monitoring the particle emission of an internal combustion engine.

In addition to on-board monitoring of gaseous exhaust gas components, on-board particulate emissions monitoring of motor vehicles is also required in accordance with current exhaust gas legislation in the US and Europe. In this case, the motor vehicle may not exceed a specified particle emission in a driving cycle prescribed by law. If the particulate emission exceeds a predefined limit value by more than a threshold value specified by the legislator, then an error indication lamp of the motor vehicle is to be activated.

The said onboard monitoring of the particulate emissions must be carried out in the real operation of the motor vehicle. In the real operation of a motor vehicle, many particles are produced during engine warm-up. Even during a transient engine operation and high engine load, a lot of particles are produced. Likewise, uphill driving of the motor vehicle produces higher particulate emissions than traveling over level terrain.

Another problem with the above-mentioned on-board monitoring is that soot sensors arranged in the exhaust tract of the motor vehicle are only ready for operation when-similar to lambda sensors-the dew point in the exhaust gas is exceeded.

On the one hand, this means that said on-board monitoring can not be carried out during the entire driving cycle and, on the other hand, that the particle emissions are dependent on the motor vehicle dynamics and on the driving route of the respective motor vehicle.

From the DE 10 2007 059 523 B4 For example, a method and an apparatus for diagnosing a particulate filter are known. In these, a regeneration phase of the particulate filter is introduced, at least one fuel injection during the expansion phase of the internal combustion engine or in the Ausschiebephase to increase the temperature of the particulate filter carried out such that a burnup of the particles collected in the particulate filter is achieved, and there is also a measurement of HC emission in Exhaust line in the flow direction of the exhaust gas behind the particulate filter and diagnosing a defect of the particulate filter based on the measured HC emissions.

From the DE 10 2008 015 256 A1 are known a diagnostic method and a diagnostic system for a particulate filter of an internal combustion engine, in particular for a soot filter in a diesel motor vehicle. In this case, a particle concentration is detected by means of a particle sensor arranged downstream of the particle filter, and the combustion-relevant engine parameters are briefly changed by means of an engine control in such a way that an engine-side raw emission concentration increases significantly. A filter error message is output when the detected associated measured values of the particle concentration exceed a detection threshold value of the particle sensor, which is in particular significantly greater than a predetermined, preferably volume-related particle limit value.

From the DE 10 2009 007 126 A1 For example, a method and apparatus for measuring soot loading in exhaust systems of diesel engines is known. This measurement is carried out using a sensor downstream of a particle filter, a sensor element having a measure of the functionality of the particulate filter, wherein the soot loading of the sensor element by means of electrodes is measured resistively or capacitively and wherein the measuring voltage of the sensor element in dependence on at least one instantaneous operating parameters of Diesel engine is controlled.

From the DE 10 2010 054 671 A1 For example, a method of operating a soot sensor is known. This soot sensor has an interdigital electrode structure to which a measuring voltage is applied. Soot particles from an exhaust gas stream are deposited on the interdigital electrode structure. The measuring current flowing via the soot particles and the interdigital electrode structure is evaluated as a measure of the soot load of the soot sensor. The soot sensor has a heating element for burning the interdigital electrode structure. Depending on the operating state of the internal combustion engine, a time is determined for burnout of the soot sensor. Then, the burn-out of the interdigital electrode structure by heating the soot sensor with the heating element begins.

In the present invention takes place in the context of on-board monitoring of the particulate emission, a calculation of the particulate emission directly in the engine control. The calculated particulate emission is compared with a permissible particle flow dependent on the engine operating point.

For this calculation of the particulate emission, the speed, the engine torque and the coolant temperature must be within a permissible range.

$$\text{DMmin}<\text{DM}<\text{DMmax;}$$

$$\text{KMTmin}<\text{KMT}\text{.}$$

The following conditions for the rotational speed N, the engine torque DM and the coolant temperature KMT apply: $$\text{Nmin}<\text{N}<\text{N max;}$$

$$\text{DMmin}<\text{DM}<\text{DMmax;}$$

$$\text{KMTmin}<\text{KMT}\text{,}$$

• Nmin eine vorgegebene Minimaldrehzahl,
• N die Motordrehzahl
• Nmax eine vorgegebene Maximaldrehzahl,
• DMmin ein vorgegebenes Minimaldrehmoment,
• DM das Drehmoment und
• DMmax ein vorgegebenes Maximaldrehmoment, sowie
• KMT die Kühlmitteltemperatur und
• KMTmin eine vorgegebene Minimal-Kühlmitteltemperatur

Here are:

• Nmin a predetermined minimum speed,
• N is the engine speed
• Nmax a predetermined maximum speed,
• DMmin a predetermined minimum torque,
• DM the torque and
• DMmax a given maximum torque, as well
• KMT the coolant temperature and
• KMTmin a predetermined minimum coolant temperature

Furthermore, in order to perform the on-board monitoring of the particulate emission, it is necessary for the particulate sensor to be ready for operation. This is the case when, after a start, there is no more water in the exhaust gas. For this purpose, it is checked whether the exhaust gas temperature is greater than a predetermined minimum exhaust gas temperature: $$\text{AGT}>\text{AGTmin}$$

• AGT die Abgastemperatur und
• AGTmin die vorgegebene Minimal-Abgastemperatur.

Here are:

• AGT the exhaust gas temperature and
• AGTmin the predetermined minimum exhaust gas temperature.

Furthermore, in carrying out the onboard monitoring of the particle emission, the dead time of the particle sensor is important. This dead time depends on the gas mass flow and on the response time of the particle sensor: $$\text{TZ}\mathrm{=}\text{AZ}\mathrm{+}\text{AGV}•\text{FAK}\text{,}$$

• TZ die Totzeit des Partikelsensors,
• AZ die Ansprechzeit des Partikelsensors,
• AGV der Abgasvolumenstrom und
• FAK ein experimentell ermittelter Faktor.

Here are:

• TZ the dead time of the particle sensor,
• AZ the response time of the particle sensor,
• AGV the exhaust gas flow rate and
• FAK an experimentally determined factor.

The current particle mass flow PMSakt is - as will be explained in more detail below - determined and compared with a predetermined, maximum allowable particle mass flow PMSmax, which is dependent on the current operating point of the internal combustion engine and a stored map is taken. In this map, a maximum permissible particle mass flow PMSmax is stored in each case for a multiplicity of operating points. The various operating points are each assigned a momentary load, an instantaneous speed and a current coolant temperature. $$\text{PMSakt}=\text{PMSmes}/\text{Pm smax}\text{,}$$

• PMSakt der aktuelle Partikelmassenstromwertfaktor, welcher den Abstand zum zulässigen Wert charakterisiert,
• PMSmes der aus den Sensordaten abgeleitete und/oder von der Motorsteuerung ermittelte Partikelmassenstromwert und
• PMSmax der maximal zulässige Partikelmassenstrom.

It is

• PMSakt the current particle mass flow value factor, which characterizes the distance to the permissible value,
• PMSmes the derived from the sensor data and / or determined by the engine control particle mass flow value and
• PMSmax the maximum permissible particle mass flow.

In order to monitor the particle emission, the mean value is calculated from a number Z of successive actual particle mass flow value factors PMSakt: $$\text{PMSmit}=\text{PMSadd}/\text{Z}\text{,}$$

• PMSmit der berechnete Mittelwert,
• PMSadd die Summe von Z aufeinanderfolgenden aktuellen Partikelstrommassenwertfaktoren und
• Z die Anzahl der aufeinanderfolgenden aktuellen Partikelmassenstromwertfaktoren PMSakt, die zur Überwachung verwendet werden.

Where:

• PMSwith the calculated mean,
• PMSadd is the sum of Z consecutive actual mass flow mass factors and
• Z is the number of consecutive actual particulate mass flow value factors PMSakt used for monitoring.

Subsequently, a check is made as to whether the number of successive actual particle mass flow values is greater than a predefined minimum number of consecutive actual particle mass flow values: $$\text{Z}>\text{zmin}\text{,}$$

• Z die Anzahl der aufeinanderfolgenden Partikelmassenstrommesswerte und
• Zmin eine vorgegebene minimale Anzahl der aufeinanderfolgenden Partikelmassenstrommesswerte.

Where:

• Z is the number of consecutive particulate mass flow readings and
• Zmin is a predetermined minimum number of consecutive particulate mass flow readings.

If the comparison made shows that the quotient of the sum PMSadd and the number Z of the successive actual particle mass flow values PMSakt is greater than 1, then the engine control of the internal combustion engine detects the presence of an error and the engine control unit displays it on an error lamp and initializes an entry in a fault memory.

Possible causes of failure are, for example, in the presence of a vehicle with a particulate filter, a defect of the particulate filter and in the presence of a vehicle without particulate filter, an excessive oil emission.

The figure shows an apparatus which is designed to carry out the method described above. This device is provided for monitoring the particle emission using a particle sensor, which is a sensor for measuring the particle number or a sensor for measuring the particle mass flow.

The device shown in the figure has an electronic engine control 1 which is designed to control the method described above.

This engine control 1 works on a work program that resides in a workspace memory 5 is stored. Furthermore, the motor control input data are supplied. These input data include those of temperature sensors 2 provided sensor signals. These temperature sensors are a temperature sensor, which is provided for measuring the coolant temperature KMT, and a temperature sensor, which is provided for measuring the exhaust gas temperature AGT of the internal combustion engine. Furthermore, the engine control 1 Input data supplied by a speed sensor 3 come, which is provided for measuring the rotational speed N of the internal combustion engine. Further, the engine control 1 Input signals supplied by a load sensor 4 come. This load sensor may be a pressure sensor, an air mass sensor or a throttle sensor. By means of the air mass sensor, an air mass flow LMS is measured.

The engine control 1 evaluates these input data using their stored work program to determine a particle mass flow value PMSmes using the signals derived from the sensors. This determined particle mass flow value PMSmes is associated with a respective map memory 6 taken from the maximum permissible particle mass flow value PMSmax compared to detect whether the determined particle mass flow value is smaller than the maximum permitted particle flow value taken from the map or not. Preferably, the quotient of the determined particle mass flow value and the map memory 6 taken maximum permissible particle mass flow value formed. Subsequently, the said quotient is formed for further successive particle emissions, an average value is formed from the quotients formed and the control of an error lamp is carried out 7 then, if this mean is greater than 1. Furthermore, an entry in a fault memory 8 can be made. This measure informs the driver of the vehicle and also the workshop personnel about the inadmissibly high particle mass flow value so that suitable countermeasures can be taken.

The following will be explained with reference to an embodiment, as the engine control 1 determines the particle mass flow value PMSmes.

wobei

• AGM der Abgasmassenstrom,
• LM die beispielsweise unter Verwendung der Ausgangssignale des Lastsensors gemessene Luftmasse pro Zylinder,
• KM die beispielsweise von der Motorsteuerung 1 berechnete Kraftstoffmasse pro Zylinder,
• N die Motordrehzahl und
• ZZ die Zylinderzahl ist.

The exhaust gas mass flow AGM for a 4-cylinder engine is calculated from the intake air mass and the injected fuel mass as follows: $$\text{AGM}=\left(\text{LM}+\text{KM}\right)•\text{N}•\left(\text{ZZ}/\text{2}\right)/60$$

in which

• AGM the exhaust gas mass flow,
• LM is the air mass per cylinder measured, for example, using the output signals of the load sensor,
• KM the example of the engine control 1 calculated fuel mass per cylinder,
• N the engine speed and
• Currently the number of cylinders is.

The exhaust gas volume flow results with the density of exhaust gas according to http://www.schweizer-fn.de/stoff/abgas_stoff.php as follows: $$\text{AGV}=\text{AGM}/\text{AGD}\text{,}$$

• AGV der Abgasvolumenstrom,
• AGM der Abgasmassenstrom und
• AGD die Abgasdichte.

Where:

• AGV the exhaust gas volume flow,
• AGM the exhaust gas mass flow and
• AGD the exhaust gas density.

The exhaust gas density AGD is determined according to the following relationship: $$\text{AGD}=\left(\text{p}+\text{DG}\right)/\left(\left(273+\text{AGT}\right)•\text{R}\right)=\left(101325+\text{DG}\right)/\left(\left(273+\text{AGT}\right)•287\right)$$

• AGD die Abgasdichte,
• p der Luftdruck,
• GD der Abgasgegendruck,
• AGT die Abgastemperatur und
• R die Gaskonstante von Luft.

Here are:

• AGD the exhaust gas density,
• p the air pressure,
• GD exhaust back pressure,
• AGT the exhaust gas temperature and
• R is the gas constant of air.

Exhaust back pressure can be measured as well as calculated from a model.

wobei PMS der Sensorwert des Partikelsensors ist. The gas mass flow rate value PMSmes results as follows: $$\text{PMSmes}\left(\text{t}\right)=\text{AGV}\left(\text{t}-\text{TZ}\right)•\text{PMS}\text{.}$$

where PMS is the sensor value of the particulate sensor.

LIST OF REFERENCE NUMBERS

1

motor control

2

temperature sensors

3

Speed sensor

4

load sensor

5

Work Program Memory

6

Characteristics memory

7

error lamp

8th

error memory

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 102007059523 B4 [0006]
• DE 102008015256 A1 [0007]
• DE 102009007126 A1 [0008]
• DE 102010054671 A1 [0009]

Claims (10)

Method for monitoring the particle emission of an internal combustion engine equipped with a particle sensor, comprising the following steps: - check if given conditions for the monitoring of the particle emission are present, upon detection that the given conditions are present, calculation of the particle emission for the instantaneous operating point of the internal combustion engine, Forming for a plurality of consecutive calculated particulate emissions each of the quotient of the calculated particulate emission and the associated maximum allowable emission taken from a map, Forming an average of the formed quotients and - Driving a fault lamp when this average is greater than 1. Method according to Claim 1 , characterized in that it is checked whether the speed is between a predetermined minimum speed and a predetermined maximum speed. Method according to Claim 1 or 2 , characterized in that it is checked whether the torque is between a predetermined minimum torque and a predetermined maximum torque. Method according to one of the preceding claims, characterized in that it is checked whether the coolant temperature is greater than a predetermined minimum coolant temperature. Method according to one of the preceding claims, characterized in that it is checked whether the particle sensor is ready for operation. Method according to Claim 5 , characterized in that to check whether the particle sensor is ready, it is checked whether the exhaust gas temperature is greater than a predetermined minimum exhaust gas temperature. Method according to one of the preceding claims, characterized in that the calculation of the particle emission for the current operating point is carried out according to the following relationship: $$\text{PMSmes}\left(\text{t}\right)=\text{AGV}\left(\text{t}-\text{TZ}\right)•\text{PMS}\text{.}$$

where PMSmes (t) is the particulate emission for the current operating point, AGV is the exhaust gas volumetric flow, TZ is the dead time of the particulate sensor, and PMS is a particulate matter or particulate mass reading currently provided by the particulate sensor. Method according to Claim 7 , characterized in that the calculation of the exhaust gas volume flow is made according to the following relationship: $$\text{AGV}=\text{AGM}/\text{AGD}\text{.}$$

where AGV is the exhaust gas volume flow, AGM is the exhaust gas mass flow, and AGD is the exhaust gas density. Method according to Claim 8 , characterized in that the calculation of the exhaust gas mass flow is carried out according to the following relationship: $$\text{AGM}=\left(\text{LM}+\text{KM}\right)•\text{N}•\left(\text{ZZ}/2\right)/60$$

AGM being the exhaust gas mass flow, LM is the air mass per cylinder, KM is the fuel mass per cylinder, N is the speed and ZZ is the number of cylinders. Device for monitoring the particle emission of an internal combustion engine equipped with a particle sensor, characterized in that it comprises a motor control (1), which is designed to control a method according to one of the preceding claims.

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