DE102008040593A1 - Method for determining measure of water entry into exhaust duct of internal combustion engine, involves determining measure of water entry according to measure of supplied heat energy by heating element of exhaust sensor - Google Patents

Abstract

The method involves determining a measure of water entry (13) according to a measure of supplied heat energy by a heating element (15) of an exhaust sensor (14) arranged in an exhaust duct (12). The exhaust gas sensor is operated with an exhaust gas sensor diagnostic temperature set point, which lies above the evaporation temperature of water in the exhaust duct and below the risk temperature of the exhaust sensor. Independent claims are included for the following: (1) a device for determining a measure of water entry into an exhaust duct of an internal combustion engine; (2) a controller program; and (3) a controller program product.

Description

The The invention is based on a method for determining at least a measure of a water entry into the exhaust duct an internal combustion engine and a device for implementation the method according to the preamble of the independent claims.

object The present invention also includes a controller program and a controller program product.

State of the art

Exhaust gas sensors, In particular, ceramic exhaust gas sensors are used in exhaust gas purification devices of internal combustion engines for measuring the oxygen content of the exhaust gas and ultimately used to reduce emissions. For Exhaust gas cleaning is the fast operational readiness of the exhaust gas sensor important because much of the exhaust gases in the starting phase of Internal combustion engine accumulates. The ceramic sensor element of the exhaust gas sensor is at a temperature of, for example, 800 ° C operated and may be damaged by condensation drops during operation which can occur with cold exhaust gas. A cold one Exhaust gas is in particular in the starting phase of the internal combustion engine or for example after a fuel cut-off phase.

One another exhaust gas sensor is a particle sensor, which depends on may also be heated by its design. A sensor heater is especially in a collecting resistive particle sensor provided that the particle sensor in a regeneration process to particularly high temperatures for burning the Parti kelsensors of heats the accumulated particles, but also in continuous operation For example, to influence the particle accumulation and / or for example for evaporation of liquid precipitates on the sensor element can heat the particle sensor.

to Determination of at least one measure of the water input in the exhaust duct on the one hand Endoskopaufnahmen used with which, although it can be determined whether water droplets in the exhaust duct are present, but with which the water drop volume, the number the drop of water or the total amount of water only can be specified qualitatively. On the other hand, with the criterion end of dew point undershoot worked. The End of the dew point below corresponds to a temperature, from that no more water can occur in the exhaust system anymore. Therefore are in principle no statements about the second method a drop of water volume possible.

In the DE 199 03 439 A1 are described a method and an apparatus for operating an internal combustion engine, in whose exhaust passage an SCR catalyst (Selective Catalytic Reduction) is arranged, which reduces the nitrogen oxides contained in the exhaust gas of the internal combustion engine with a reagent to nitrogen. As a reagent, for example, the reducing agent ammonia is provided, which can be obtained from a urea-water solution or from a urea-formic acid-water solution as a precursor of the reagent. The dosage of the reagent or precursor must be carefully determined. Too low a dosage has the consequence that nitrogen oxides in the SCR catalyst can not be sufficiently reduced. Too high a dosage leads to a Reagenzmittelschlupfs, which can lead to an unnecessarily high reagent consumption on the one hand and on the other hand to an unpleasant odor nuisance.

In the DE 10 2004 056 412 A1 For example, a method and apparatus are described in which pressurized fuel is injected into the exhaust gas of an internal combustion engine downstream of an exhaust gas purification device including a catalyst and / or a particulate filter. The fuel used as a reagent should react exothermically on the catalytically active surface with the residual oxygen present in the exhaust gas of the internal combustion engine in order to heat the exhaust gas or the exhaust gas purification device.

In the DE 10 2005 041 661 A1 a method for operating a heating element of a ceramic sensor is described, which is arranged in the exhaust passage of an internal combustion engine. The heating element is only put into operation when the internal combustion engine is in an operating state in which no longer can be expected with the occurrence of a water entry into the exhaust duct. The presence of this operating condition is inferred when the heat flow, summed over a period of time, carried by the exhaust gas mass flow exceeds a heat flow threshold.

In the EP 635 148 B1 a device for operating a heating element of a ceramic sensor is described, which is also arranged in the exhaust passage of an internal combustion engine. Also in this case, the heating element is supplied only with heating energy when the internal combustion engine is in a certain operating condition. This operating state is when the coolant temperature of the internal combustion engine is above a coolant temperature threshold or when the temperature of the exhaust gas purification system is above a temperature threshold.

Of the Invention is based on the object, a simple method for Determining at least one measure for a water entry in the exhaust passage of an internal combustion engine and an apparatus for Indicate the implementation of the procedure.

Disclosure of the invention

The Inventive procedure for determining a measure of the water entry into the exhaust duct an internal combustion engine provides that the measure of the water input on the basis of at least one measure of a heating element of an exhaust gas arranged in the exhaust duct supplied heating energy is determined. While the measurement process, the exhaust gas sensor with an exhaust gas sensor diagnostic temperature setpoint operated above the evaporation temperature of water and is below the endangerment temperature of the exhaust gas sensor, from which damage to the exhaust gas sensor upon impact the water entry can occur on the exhaust gas sensor.

The inventive approach is particularly suitable for the application of, for example, a control device for the internal combustion engine. Based on the robustness of each Exhaust gas type compared to a water entry into the exhaust duct can be used to set an application-specific criterion, under which conditions the exhaust gas sensor to the exhaust gas sensor nominal temperature setpoint may be heated without damaging it Exhaust gas sensor comes.

The The procedure according to the invention is the same during continuous operation of the exhaust gas sensor in the exhaust passage applicable. In this application stands the protection of the exhaust gas sensor in the foreground.

The The inventive method can already described methods such as the endoscopy method or the method for determining the end of the dew point undershoot supplement or replace. In particular, allows the procedure of the invention is a quantitative Determination of the amount of water drawn into the exhaust duct, the Number of drops of water or water drop volume. So that can on the one hand indicated at least one of these parameters become. On the other hand, by comparing it with a threshold, preferably at least approximately zero be that there is no water entry or a previously occurred Water entry has stopped.

When heated exhaust gas sensors may be, for example, lambda sensors, NOx sensors, particle sensors, NH3 sensors, etc. may be provided.

advantageous Further developments and refinements of the invention Approach arise from dependent claims.

A Design provides that as a measure of the Water input is provided the amount of water by means of a Integration of at least one measure of the heating power can be determined.

A another embodiment provides that as a measure of the water entry the water drop volume is provided this also by means of an integration of at least one measure for the heating power is determined. A shortfall between individual drops of water and a stream of water can be based an assessment of the integration period.

A another embodiment provides that as a measure of the water input is provided the number of water drops, the counting of changes the heating power can be determined. In the sense of the present Invention is already counting changes the heating power as at least a measure of the considered heating energy supplied to the heating element of the exhaust gas sensor.

A Embodiment provides that a change in heating power is determined and that the integration with an increase in heating power started and ended with a waste. The change The heating power can be used in a differentiator by comparison with be rated at a gradient threshold.

According to one simple embodiment sees the integration of a measure for the heating power only the determination of time between an increase and a decrease in heating power.

According to one alternative embodiment is an integration of the entire heating power between the increase and the decrease of the heating power provided.

According to one advantageous development of this embodiment is in the integration takes into account and subtracts the heating energy that for normal heating of the exhaust gas sensor with the exhaust gas sensor measurement temperature setpoint needed to be an accurate measure of to get the water entry without offset. This is preferably done stored at the beginning of the integration heating power and considered as an offset during integration. Of the Offset is subtracted from the currently available heating power and integrated the result.

According to one Design is provided, the measure of the Water input only to be determined if a quasi-stationary State in the heating of the exhaust gas sensor is present, in which at least the exhaust gas sensor diagnostic temperature setpoint adjusted is and / or a quasi-stationary state in the exhaust duct is present, in which at least the exhaust gas temperature at least approximately is constant. This increases the accuracy of the invention How to determine the measure for the Water entry.

Of the Exhaust gas sensor diagnostic temperature set point is set to a value the above the evaporation temperature of water, ie above 100 ° C is located. The maximum exhaust gas sensor diagnostic temperature setpoint is set to a value below the hazard temperature the exhaust gas sensor is located, from which with damage to the Exhaust gas sensor must be expected. The hazard temperature is currently at maximum for ceramic exhaust gas sensors 200 ° C.

A Design provides that the measure of the Water entry in the exhaust gas region of the internal combustion engine based the heating energy is determined, which is a heating element of a lambda sensor and / or a particle sensor is supplied. such Exhaust gas sensors may include temperature sensors that directly a measure of the exhaust gas temperature sensor actual value provide. The provided by such exhaust gas sensors Measurement signals that do not specifically reflect temperature signals can continue to be assessed at least in certain operating phases be that at least an approximate measure of the temperature of the exhaust gas sensor can be obtained.

The inventive device for implementation of the method initially relates to a specially prepared Control device, the means of carrying out the process contains. As a means, for example, a temperature controller and an integrator provided. Optionally, continue to be a differentiator or a query, wherein the differentiator starts the integration and controls the integration result, and the query determines if a water entry is present, or if an occurred Water entry has now stopped.

The Control unit preferably contains at least one electrical memory, in which the process steps as a control unit program are stored.

The Control unit program according to the invention provides that all steps of the invention Procedure to be executed when it is in a control unit expires.

The Control unit program product according to the invention with a stored on a machine-readable carrier Program code carries the inventive Procedure when the program runs in a controller.

embodiments The invention are illustrated in the drawing and in the following description explained in more detail.

Brief description of the figure

The Figure shows a technical environment in which an inventive Procedure expires.

Detailed description the embodiments

The figure shows an internal combustion engine 10 , in their intake area 11 an air flow ms_L and in the exhaust duct 12 an exhaust gas flow ms_Abg occurs. The exhaust gas flow ms_Abg has an exhaust gas temperature te_Abg. The exhaust gas flow ms_Abg possibly introduces a water entry 13 with himself.

In the exhaust duct 12 is an exhaust gas sensor 14 arranged, which is at least partially exposed to the exhaust gas flow ms_Abg. The exhaust gas sensor 14 contains a heating element 15 that from a controller 20 can be acted upon by a heating power P_HZ. The exhaust gas sensor 14 puts the control unit 20 at least one exhaust gas sensor temperature actual value teS_IsW available.

The control unit 20 contains a temperature controller 21 in which the exhaust gas temperature te_Abg, the exhaust gas sensor temperature actual value teS_IsW, an exhaust gas sensor nominal temperature setpoint teS_Nen_SoW, an exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW and a first release signal FG1 are provided as input signals. The temperature controller 21 sets the heating power P_HZ for the heating element 15 and a second enable signal FG2 ready.

At least one measure of the heating power P_HZ becomes an integrator 22 , which is an offsets store 23 contains, as well as a differentiator 24 made available. The integrator 22 provides a water flow signal m_Fl and a first and second water droplet signal Vol_Tro, n_Tro. The water quantity signal m_Fl and the two water drop signals Vol_Tro, n_Tro become a signal evaluation 25 provided, which provides the first enable signal FG1, which next to the temperature controller 21 also the integrator 22 is made available.

The measuring principle for determining the water entry 13 in the exhaust duct 12 a combustion force machine 10 is based on the detection of at least one measure of the heating element 15 the exhaust gas sensor 14 from the heating controller 21 provided heating energy, wherein at least one measure m_Fl, Vol_Tro, n_Tro for the amount of water and / or the water drop volume and / or the number n of the water drops can be determined by the measure of the supplied heating energy. This takes into account a measure of the heating and evaporation of the water entry 13 needed energy from the heating element 15 the exhaust gas sensor 14 must be provided. The exhaust gas sensor 14 is for example a lambda sensor, a NOx sensor, a particle sensor, a NH3 sensor or another with a heating element 15 equipped exhaust gas sensor 14 ,

For determining at least one measure m_Fl, Vol_Tro, n_Tro for the water entry 13 becomes the exhaust gas sensor 14 not with the exhaust gas sensor nominal temperature setpoint teS_Nen_SoW, but with the exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW. The exhaust gas sensor nominal temperature setpoint teS_Nen_SoW is, for example, between 700 ° C and 850 ° C. In contrast, the exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW is significantly lower. The exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW must be set such that the water entry 13 from the surface of the exhaust gas sensor 14 can evaporate, so that the minimum exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW is about 100 ° C. The maximum exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW should be set to a value that ensures that the exhaust gas sensor is damaged 14 through the water entry 13 is avoided. The maximum exhaust gas sensor diagnostic temperature set point teS_Diag_SoW depends on the material as well as the design of at least the surface of the exhaust gas sensor 14 down in the exhaust duct 12 protrudes. Depending on the ceramic used, the maximum exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW, which is referred to below as the endangerment temperature of the exhaust gas sensor 14 is designated, for example, at 200 ° C.

Meets a water entry 13 on the surface of the exhaust gas sensor 14 , so withdraws the water entry 13 the exhaust gas sensor 14 due to its heat capacity thermal energy, resulting in a local cooling of the exhaust gas sensor 14 noticeable and which increases the required heating power P_HZ to maintain the exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW. During the measurement, the temperature controller tries 21 , the temperature of the exhaust gas sensor 14 constant to the specified exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW. The temperature controller 21 trying to get through the water entry 13 compensate for energy loss occurring and increases the heating power P_HZ. As the water entry 13 Under normal conditions no temperature can reach> 100 ° C, the setting of the exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW does not succeed as long as the water droplet on the exhaust gas duct 12 protruding surface of the exhaust gas sensor 14 is available.

The heating element 15 a certain amount of energy in the form of electrical energy must be the exhaust gas sensor 14 respectively. This amount of energy corresponds to taking into account the electrical and thermal losses of those heat energy used to heat the water entry 13 to about the boiling point and to complete evaporation of the water entry 13 necessary is.

These two energy components can be determined based on the mass, the specific heat capacity and the temperature of a water droplet, a number n of several drops of water or the amount of water in a given period of time in the exhaust duct 12 were registered. By determining at least one measure of this amount of energy can therefore be a measure of the water input 13 For example, the total amount of water that reflects the water quantity signal m_Fl or the water drop volume that reflects the waterdrop signal Vol_Tro may be provided. Moreover, the number n of water droplets which reflects the water droplet signal n_Tro can be determined only by counting the increases and decreases of the heating power.

The energy can be determined from the area under a power curve, which is for the heating of the exhaust gas sensor 14 required amount of energy without the occurrence of a water entry 13 to take into account. The energy in this case corresponds to the required or withdrawn heat energy for heating and vaporizing the water entry 13 , The extra heat energy can come from the heating element 15 electric power P_HZ multiplied by a period of time can be obtained. The electrical heating power P_HZ results from the product of voltage and current.

The integration of the heating power P_HZ takes place by means of the integrator 22 which starts the integration with the occurrence of a third enable signal FG3, which is the differentiator 24 provides. The third enable signal FG3 is provided when the heating power P_HZ initially has a predetermined positive change with respect to time and then a negative change with respect to time. The differentiator 24 determines the heating track gradient and compares the gradient with a positive or negative gradient threshold.

The two threshold crossings set the integration time of the integrator 22 firmly. Simultaneously with the first occurrence of the third enable signal FG3 at the beginning of the integration time, the last available heating power P_HZ is used as an offset for the following integration in the offset memory 23 deposited. During integration, the offset is subtracted from the current heating power P_HZ, so that the integrator 22 excluding those for heating and evaporating water 13 can determine the required energy.

A simpler embodiment provides that the integrator 22 integrated the entire heating power P_HZ, without the offset is taken into account. This also becomes a measure of the heating element 15 supplied energy.

An even simpler embodiment provides that the integrator 22 is realized only as a timer, which determines the lying between the increase of the heating power P_HZ and the rela tive drop in heating power P_HZ time, wherein the determined time also at least one measure of the heating element 15 the exhaust gas sensor 14 supplied energy reflects.

As already mentioned above, the counting of the rises or the waste of the heating power, wherein the counting process for determining the number n of water droplets can be used, as a determination of at least one measure for the heating element 15 the exhaust gas sensor 14 supplied heating energy considered within the meaning of the invention.

The differentiator 24 However, the third release signal FG3 preferably provides only when an at least quasi-stationary state in the heating of the exhaust gas sensor 14 and / or in the exhaust duct 12 the internal combustion engine 10 is present. The quasi-stationary state when heating the exhaust gas sensor 14 occurs when the exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW is stabilized. If this is the case, the temperature controller gives 21 the second enable signal FG2 to the differentiator 24 from.

Alternatively or preferably additionally, it is checked whether the exhaust gas temperature te_Abg is at least approximately constant. To verify this condition is the differentiator 24 Therefore, the exhaust gas temperature te_Abg continues to be provided.

The integrator 22 sets the measure m_Fl, Vol_Tro, n_Tro for the water entry 13 ready, where, for example, the amount of water m_Fl, the water drop volume Vol_Tro and / or the number n of water drops n_Tro can be output. A distinction between individual drops of water and a surge of water can in this case be made over the integration period, it being assumed that with an integration time of less than about 5 seconds individual drops of water are present and with longer integration times there is a rush of water. The number n of water drops can be calculated by counting the individual integration processes in the integrator 23 be determined.

The measure m_Fl, Vol_Tro, n_Tro for the water entry 13 in the exhaust duct 12 the internal combustion engine 10 For example, it can be used to check whether a water entry 13 in the exhaust duct 12 present or has ceased to exist. For a given water entry 13 there is a risk potential for particular ceramic exhaust gas sensors 14 when water drops or a splash of water impinge on the hot ceramic surface, the sensor temperature is above the hazard temperature at which cracks may occur or complete destruction of the ceramic can not be excluded.

The measure m_Fl, Vol_Tro, n_Tro for the water entry 13 in the exhaust duct 12 the internal combustion engine 10 can be used in the context of an application for determining whether the present combustion process a greater or lesser water input 13 caused.

Alternatively or additionally, the measure m_Fl, Vol_Tro, n_Tro for the water entry 13 in the exhaust duct 12 the internal combustion engine 10 be used for a decision whether the exhaust gas sensor 14 can be heated to the exhaust gas sensor nominal temperature setpoint teS_Nen_SoW. To do this, the query compares 25 the measure m_Fl, Vol_Tro, n_Tro for the water entry 13 with a threshold, which preferably corresponds to zero. If this is the case, the query represents 25 the first enable signal FG1 ready, the temperature controller 21 unlocks and the integrator 22 resets for a next measurement cycle. At the same time the offset memory becomes 23 deleted.

To increase the response time of the sensor, use a temperature control loop with a sampling rate> 10 Hz, for example 1 kHz. In addition, the use of a sensor material is recommended, which has a high thermal conductivity. Should also the damping of the water entry 13 reduced signal and increases the sensitivity for small drops of water should be, the heat capacity of the exhaust gas sensor 14 be as low as possible.

For installation locations near the internal combustion engine 10 a higher exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW is required. The exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW is then set from 100 ° C. to 200 ° C. to a higher exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW of, for example, 200 ° C. to, for example, 400 ° C., the material of the exhaust gas sensor 14 is to be selected such that the exhaust gas sensor 14 is insensitive to thermal shock voltages even at this exhaust gas sensor diagnostic temperature setpoint teS_Diag_SoW. For example, a metallic exhaust gas sensor is suitable 14 , which can be used in particular in the application.

In the practice could be with the invention Procedure waterdrop volume in the range of, for example Detect 1 to 15 μl with high accuracy.

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 19903439 A1 [0006]
• DE 102004056412 A1 [0007]
• DE 102005041661 A1 [0008]
• - EP 635148 B1 [0009]

Claims (14)

Method for determining a measure (m_Fl, Vol_Tro, n_Tro) for the water entry ( 13 ) in the exhaust duct ( 12 ) an internal combustion engine ( 10 ), characterized in that the measure (m_Fl, Vol_Tro, n_Tro) for the water entry ( 13 ) based on at least one measure of a heating element ( 15 ) one in the exhaust duct ( 12 ) arranged exhaust gas sensor ( 14 ) is determined, wherein the exhaust gas sensor ( 14 ) is operated with an exhaust gas sensor diagnostic temperature setpoint (teS_Diag_SoW), which is above the vaporization temperature of water in the exhaust gas channel ( 12 ) and below the endangerment temperature of the exhaust gas sensor ( 14 ), from which damage to the exhaust gas sensor ( 14 ) upon impact of the water entry ( 13 ) on the exhaust gas sensor ( 14 ) can occur. A method according to claim 1, characterized in that as a measure (m_Fl) for the water entry ( 13 ) the amount of water is provided, which is determined by integrating a measure of the heating power (P_HZ). A method according to claim 1, characterized in that as a measure (Vol_Tro) for the water entry ( 13 ) the water drop volume is provided, which is determined by means of an integration of a measure of the heating power (P_HZ). A method according to claim 1, characterized in that as a measure (n_Tro) for the water entry ( 13 ) the number (n) of water droplets is provided, which is determined by counting of changes in the measure of the heating power (P_HZ). Method according to claim 3 or 4, characterized that a change in the heating power (P_HZ) is determined and that the integration with an increase in heating power (P_HZ) started and ended when the heating power (P_HZ) falls. Method according to claim 5, characterized in that the dimension for the heating element ( 15 ) of the exhaust gas sensor ( 14 ) is determined by means of an integration, which provides for a determination of the duration between an increase and a decrease of the heating power (P_HZ). Method according to claim 6, characterized in that the dimension for the heating element ( 15 ) of the exhaust gas sensor ( 14 ) supplied heating energy based on an integration of the heating element ( 15 ) provided heating power (P_HZ) is determined. Method according to claim 7, characterized in that that the heating power present at the beginning of the integration (P_HZ) stored and during integration as an offset of the currently available heating power (P_HZ) is taken into account by subtraction. Method according to claim 1, characterized in that that the exhaust gas sensor diagnostic temperature setpoint (teS_Diag_SoW) in the range of greater than 100 ° C to 200 ° C lies. A method according to claim 1, characterized in that the measure (m_Fl, Vol_Tro, n_Tro) for the water entry ( 13 ) is determined when a quasi-stationary state in the heating of the exhaust gas sensor ( 14 ) is present, in which at least the exhaust gas sensor diagnosis target temperature (teS_Diag_SoW) is adjusted and / or a quasi-stationary state in the exhaust gas channel ( 12 ) is present, in which at least the exhaust gas temperature (te_Abg) is at least approximately constant. A method according to claim 1, characterized in that the measure (m_Fl, Vol_Tro, n_Tro) for the water entry ( 13 ) in the exhaust duct ( 12 ) of the internal combustion engine ( 10 ) is determined on the basis of the heating energy which is a heating element ( 15 ) is supplied to a lambda sensor and / or a particle sensor. Device for determining a measure (m_Fl, Vol_Tro, n_Tro) for the water entry ( 13 ) in the exhaust duct ( 12 ) an internal combustion engine ( 10 ), characterized in that at least one for performing the method according to one of claims 1 to 11 specially prepared control unit ( 20 ), the means ( 21 . 22 . 23 . 24 . 25 ) for carrying out the method. Control unit program, which carries out all the steps of a method according to one of claims 1 to 11, when the program is stored in a control unit ( 20 ) expires. A control program product having a program code stored on a machine-readable carrier for carrying out the method according to one of claims 1 to 11, when the program is stored in a control device ( 20 ) is performed.