Title of Invention	"METHOD AND DEVICE FOR OPERATING A MOTOR VEHICLE COMPRISING AN EXHAUST GAS HEATING DEVICE"
Abstract	Method and device for operating a motor vehicle (1) which has a drive (2) and an exhaust system (3) with at least one controllable heating device (4) which can be placed in contact with exhaust gas, comprising at least the following steps: (a) detecting at least one operating parameter (6) of the exhaust system (3), (b) determining at least one influential variable (7) of the heating device (4), (c) comparing the at least one influential variable (7) with a target parameter (8) of the exhaust system (3), (d) activating the heating device (4) such that the operating parameter (6) reaches the target parameter (8).

Title of Invention

"METHOD AND DEVICE FOR OPERATING A MOTOR VEHICLE COMPRISING AN EXHAUST GAS HEATING DEVICE"

Abstract

Method and device for operating a motor vehicle (1) which has a drive (2) and an exhaust system (3) with at least one controllable heating device (4) which can be placed in contact with exhaust gas, comprising at least the following steps: (a) detecting at least one operating parameter (6) of the exhaust system (3), (b) determining at least one influential variable (7) of the heating device (4), (c) comparing the at least one influential variable (7) with a target parameter (8) of the exhaust system (3), (d) activating the heating device (4) such that the operating parameter (6) reaches the target parameter (8).

Full Text	The present invention relates to a method for operating a motor vehicle which has a drive and an exhaust system with at least one controllable heating device which can be placed in contact with exhaust gas. It is considered to be known to place the exhaust gases generated by an engine of a motor vehicle in contact with a heating device in order to influence the temperature of the exhaust gas. Furthermore, it is also considered to be known that heating devices of said type are used, for example directly after a cold start or restart of an engine or of an exhaust system, to quickly bring the exhaust gases or the exhaust-gas purification components which are provided with a catalytically active coating up to the reaction temperature, in particular up to a temperature at which an interaction of the catalytic converter with the pollutants of the exhaust gas takes place. Heating devices which have already been proposed are in particular those which are heated as a result of ohmic resistance heating. The electrical conductor, which is traversed by current at desired times, is heated up on account of its resistance and can thereby heat the catalytically active material which is positioned thereon and/or the exhaust gas. There are various configurations of heating devices of said type; in particular, wire-mesh constructions, honeycomb bodies, plate constructions and the like have already been described. With regard to the operation in heating devices of said type, it is likewise considered to be known that said heating devices have been activated before or during the starting of the engine or if appropriate shortly after the starting of the engine in order to improve the cold-start behaviour for a limited time period, with it having been taken into consideration in particular that sufficient energy could be provided from the vehicle. Furthermore, it is also known to use heating devices of said type in combination with particle filters in order to permit a thermal regeneration of the trapped particles here. For this purpose, it is known to activate the heating devices when a predefined operating time period has elapsed or the particle loading in the filter has reached a predefined value. The known applications and/or strategies for use have however only partially led to the desired results. It was in particular found that the use of the heating device resulted in part in an undesirably high energy requirement and the activation cycles in part took up very long time periods. Proceeding from this, it is an object of the present invention to at least partially solve the problems highlighted with regard to the prior art. It is intended in particular to specify a method which permits the use of heating devices of said type in exhaust systems of mobile internal combustion engines in an energy-saving and effective manner. Said objects are achieved by means of a method as per the features of Patent Claim 1. Further advantageous embodiments and applications of the invention are specified in the dependent patent claims. It should be noted that the features listed individually in the patent claims can be combined with one another in any desired technologically expedient manner and highlight further embodiments of the invention. The invention is specified in more detail below, specifically in connection with the description and the figures, such that particularly preferred embodiment variants are also specified here. The method according to the invention for operating a motor vehicle, which has a drive and an exhaust system with at least one controllable heating device which can be placed in contact with exhaust gas, comprises at least the following steps: (a) . detecting at least one operating parameter of the exhaust system, (b) determining at least one influential variable of the heating device, (c) comparing the at least one influential variable with a target parameter of the exhaust system, (d) activating the heating device such that the operating parameter reaches the target parameter. The method according to the invention therefore relates in particular to the regulation of a heating device which is in contact with the exhaust gas of a motor vehicle engine, such that a desired target parameter of the exhaust system or a component therein is reliably reached. The "drive" can, in addition to known diesel or petrol engines, relate also to other comparable drives which ultimately generate a pollutant-laden exhaust gas or an exhaust gas which must be subjected to temperature treatment. The "exhaust system" is often formed by a tract (or a plurality of tracts), in particular in the manner of a tubular line. Said exhaust system, which conducts the exhaust gas in a preferred direction, now has provided in it at least one heating device which in particular at least partially spans the inner cross section of the exhaust system. Here, the heating device forms passages, ducts or the like through which the exhaust gas flows. The heating device can also have further functions in addition to its heating function, for example a catalytic conversion, accumulation or deflection of exhaust-gas constituents. According to step (a), at least one operating parameter of the exhaust system is firstly detected at a predefinable time (during the driving mode of the motor vehicle). The measurement of the operating parameter can take place by means of at least one measuring sensor, various sensors and/or a mathematical model. The temperatures of the exhaust gas at one or more positions of the exhaust system, the temperature of an exhaust-gas treatment component in the interior of the exhaust system, the composition of the exhaust gas, the mass flow of the exhaust gas and the like are considered in particular as operating parameters. Here, the measured or calculated value significant for the considered operating parameter is preferably registered or even stored. In step (b), which can fundamentally also take place before and/or at the same time as step (a), at least one influential variable of the heating device is determined. For this purpose, it is preferable firstly to resort to characteristic values of the heating device (for example thermal mass, geometric surface, current supply, electrical resistance and the like); however, the operating parameter measured in step (a) or one of the measured operating parameters is additionally taken into consideration. Here, use is made in particular of the knowledge that the influential variable of the heating device is dependent on at least one operating parameter of the exhaust system. In other words, this means, for example, that the heating device can bring about a temperature increase only to a certain extent for a given exhaust gas mass flow. Said temperature increase potential could be considered as an influential variable. In step (c), which is preferably carried out after steps (a) and (b), the at least one influential variable of the heating device is compared with a target parameter of the exhaust system. The target parameter is for example read out from a provided data store and/or has been calculated (if appropriate on an ongoing basis). Such a target parameter of the exhaust system can be a predefined value of one or more operating parameters of the exhaust system. It is fundamentally the case that the method according to the invention can be interrupted already if the measured operating parameter from step (a) is already in a preferred relationship with respect to the target parameter, that is to say additional measures need not be taken. A query of said type can be provided before and/or during or after step (a). If, however, it is determined that the measured operating parameter is not in a preferred relationship with respect to the target parameter, then on the basis of the comparison, it is determined to what extent the influential variable ensures with sufficient probability that the present operating parameter can be brought into the desired relationship with respect to the target parameter of the exhaust system when the heating device is actuated. In step (d), it is now proposed that an activation of the heating device should take place only when the operating parameter reaches the target parameter. For example, if the measured operating temperature of the exhaust system is so low that even an activation of the heating device will generate such a small temperature increase that the target temperature will not be reached, then the heating device is not activated. At this time, it can also be decided as to whether the method according to the invention is repeated directly until an activation of the heating device is expedient; it is however also possible to firstly implement other measures in order to finally start the use of the heating device in a favourable manner in terms of energy. It is thereby possible in particular for a permanent check of the possibility for use of a heating device to be realized. Here, an abort criterion is defined for situations in which the activation of the heating device is not expedient, before no other (additional, if appropriate simultaneous or preceding) measures promote the desired effect of the heating device. Particularly economical use, which is effective in terms of energy, of the heating device during operation of the motor vehicle is ensured in this way. According to one refinement, it is proposed that the method is carried out at least during a predominant time period between the activation and deactivation of the drive. It is very particularly preferable for the method to be started with the activation, carried out continuously and ended with the deactivation of the drive. In other words, this means in particular that the method, if appropriate in fixedly predefined and/or dynamic cycles, carries out a comparison of the at least one operating parameter of the exhaust system with the influential variable of the heating device, and an activation of the heating device takes place if required. Furthermore, it is also considered to be advantageous for step (a) to relate to at least one of the following parameters as operating parameters: exhaust-gas temperature, exhaust-gas mass flow. Furthermore, in particular the following parameters of the exhaust gas are also considered: exhaust-gas composition, concentration content of a predefined proportion of the exhaust gas, etc. Said operating parameters can be measured on an ongoing basis by means of (at least) one measuring sensor, a probe or a similar apparatus, though it is also possible to calculate the operating parameter for example from the operating date of the drive and further characteristic variables. With regard to step (b), it is preferable for the heating power of the heating device to be considered as an influential variable. The heating power relates in particular to the value which the heating device permits as a temperature increase for the given exhaust-gas mass flow. Consequently, a heating power (H) could for example be specified as a difference of the average temperature of the exhaust gas after contact with an active heating device (TII) to the average temperature of the exhaust gas before contact with the heating device (TI): H = TII - TI. In the case of honeycomb-shaped heating devices, in particular having at least partially structured sheet metal foils and a voltage source of 12 - 14 Volts, it is preferably possible to specify the following heating powers as (in particular lower) influential variables: H (Exhaust gas mass flow: 0.017 kg/s): 46 - 52 Kelvin; H (Exhaust gas mass flow: 0.023 kg/s): 40 - 44 Kelvin; H (Exhaust gas mass flow: 0.027 kg/s): 31-35 Kelvin; H (Exhaust gas mass flow: 0.030 kg/s): 24 - 28 Kelvin; H (Exhaust gas mass flow: 0.035 kg/s): 22 - 24 Kelvin; H (Exhaust gas mass flow: 0.040 kg/s): 18-22 Kelvin. The values stated above relate in particular to a heating device which comprises a sheet metal foil arrangement which has a multiplicity of ducts (300 to 600 cpsi) and which realizes the specified heating power over a 10 to 15 mm heating path (duct length in the flow direction of the exhaust gas). The ranges of fluctuation result for example from the sheet metal foil arrangement being heated during operation (heat capacity), the averaging of the dynamic temperature profiles and the like. According to one refinement of the method, the target parameter of the exhaust system in step (c) relates to at least one of the following parameters: exhaust-gas temperature, capacity for the reaction of particles contained in the exhaust gas, probability of catalytic reaction, capacity for the conversion of a state of aggregation of the exhaust gas or of an additive, etc. With regard to the capacity for the reaction of the particles contained in the exhaust gas, it should be noted that, with the heating device, it is for example possible to create an ambient condition in which a conversion of particles into gaseous constituents takes place. An increase in the probability of catalytic reaction can be obtained by virtue, for example, of ambient conditions being created at the heating device, and/or at exhaust-gas treatment components situated downstream thereof in the flow direction, in which a catalytically activated chemical reaction of exhaust-gas constituents is initiated. Furthermore, the target parameter can also relate to a capacity for the conversion of a state of aggregation of the exhaust gas and of an additive (reducing agent, water, etc.). Furthermore, a method is considered to be advantageous in which step (d) is carried out as a function of the target parameter over a predefined activation time period and the heating device is subsequently deactivated. It is very particularly preferable for the activation time period to be variable depending on the type of target parameter. For example, temperature increases of the exhaust gas can be realized over a shorter activation time period than a conversion of particles. Tests have shown that, for the following parameters and following boundary conditions, at the respectively described heating devices, the activation time periods listed below are advantageous: 1. At a catalytic converter which is connected downstream of the heating device and which has a catalytic coating for the oxidizing conversion of • carbon monoxide, an average temperature of the exhaust gas after contact with an active heating device (TII) should be present which ensures an exhaust-gas temperature of 150°C upon entry into the catalytic converter. 2. At a catalytic converter which is connected downstream of the heating device and which has a catalytic coating for the oxidizing conversion of hydrocarbons, an average temperature of the exhaust gas after contact with an active heating device (TII) should be present which ensures an exhaust-gas temperature of 170°C upon entry into the catalytic converter. 3. At a catalytic converter which is connected downstream of the heating device and which has a catalytic coating for the selective catalytic reduction of nitrogen oxides, an average temperature of the exhaust gas after contact with an active heating device (Tn) should be present which (a) ensures an exhaust-gas temperature of 200°C upon entry into the catalytic converter with a coating comprising vanadium, and (b) ensures an exhaust-gas temperature of 250°C to 600°C upon entry into the catalytic converter with a coating comprising iron zeolite (Fe-CSM system) (if appropriate varying as a function of the NOx composition of the exhaust gas flow). The deactivation of the heating element can be carried out in particular when an activation of the downstream catalytic converter or particle filter (for example with temperature difference monitoring across the catalytic converter or particle filter) has been detected. The method proposed here can then begin again with the monitoring. In order to ensure a particularly high level of effectiveness of the method, it is also proposed that step (d) is carried out by means of at least one electrically heatable honeycomb body. With a honeycomb body of said type, it is possible to realize relatively small ducts through which the exhaust gas is conducted. At the same time, the honeycomb body consequently provides a large contact area with the exhaust gas, so that intensive contact between the heat source and the exhaust gas can be realized here. It is consequently possible, with a compact arrangement of the honeycomb body, and by means of short activation cycles, for the desired target parameter to be effectively used in a multiplicity of measured operating states. For the construction of an electrically heatable honeycomb body of said type, reference is made to the patent publications of the applicant, in particular to the content of WO-A-96/10127, which can be taken into consideration here at all times for the explanation of the construction and the function of an electrically heatable honeycomb body of said type. Furthermore, it is also proposed that an external activation request of the heating device is denied if step (b) yields that the at least one influential variable of the heating device is not sufficient to meet the condition from step (d). This means in particular that the activation of the heating device could for example be demanded by other components of the motor vehicle; for example, probes could establish that the pressure drop across a particle trap is too great and that a regeneration would therefore be necessary. Likewise, the monitoring of the load operating point of the drive could also signal that the temperature of the exhaust gas is now too low. The engine management system could now want to activate the heating device. It was however found that, in precisely such situations, it is merely the case that additional energy for the heating device is required and consumed without ultimately definitely achieving the desired aim. It is therefore additionally proposed that said external activation takes place only if the condition from step (d) can be met. Furthermore, it should be noted that preferably at least one of the following variables is calculated: operating parameter of the exhaust system, influential variable of the heating device, target parameter of the exhaust system. The calculation of said variable(s) can take place on the basis of one or more of the other variables specified here. It is preferable for at least one of the variables to (also) be measured by means of measuring technology, in particular using at least one measuring sensor. The invention is particularly advantageously used in a motor vehicle comprising a drive and an exhaust system with at least one controllable heating device which can be placed in contact with exhaust gas, in which at least the heating device is connected to a control unit which is set up to carry out a method described here according to the invention. The invention and the technical field are explained in more detail on the basis of the figures. It should be noted that the figures show particularly preferred embodiment variants of the invention, to which the invention is however not restricted. In the figures, in each case schematically: Figure 1: shows a diagram with an illustration of one possible mode of operation of the method according to the invention, and Figure 2: shows a possible construction of an exhaust system for operating a motor vehicle according to the method explained here. Figure 1 illustrates a diagram in which an operating parameter of the exhaust system 6 (in this case the temperature 21) is plotted against the course of time 19. Proceeding from the left, it can be seen that the operating parameter 6 substantially adheres to a fixed value. At this time, it would for example be possible for step (a) to be carried out and for the present operating parameter 6 to be detected. Subsequently thereto, the influential variable 7 of the heating device is now determined (as per step (b)). Here, the influential variable 7 is illustrated by dashed lines, with it being detected during a comparison of the influential variable 7 with the target parameter 8 (illustrated here by dashed lines) that the influence is so great that the target parameter 8 can be reliably reached. For this reason, the heating device is now activated over an activation time period 17. In the case illustrated here, said activation time period 17 is sufficient to raise the operating parameter 6 over the target parameter 8, such that the desired result is reliably ensured. Further to the right in the diagram, that is to say at an (arbitrary) later time, a different situation is illustrated by way of example. Here, it is for example detected that, in a subsystem of the exhaust system, a temperature increase to the target parameter is now necessary. The engine management system would now start an activation request 18 at the illustrated time. Now, at the time of the activation request 18, the method according to the invention is carried out once again, with it being detected during the comparison of the influential variable 7 with the target parameter 8 that the target parameter 8 cannot be reached by means of an activation of the heating device. The heating device is therefore not activated here, but rather other measures (influence on the combustion processes in the drive, use of additives, etc.) are resorted to first. Figure 2 now schematically illustrates the construction of a motor vehicle 1 having a drive 2 and an exhaust system 3. The exhaust gas 9 generated in the drive 2 flows in the flow direction 20 through the exhaust system 3, with said exhaust gas flowing through a plurality of exhaust-gas purification components. The exhaust gas 9 can for example comprise particles 10. It is also possible for a supply 16 for an additive 11 (air, water, reducing agent, fuel, ... etc.) to be provided. The exhaust gas 9 now impinges on a heating device 4 which should in this case be embodied as an electrically heatable honeycomb body 12. Provided downstream of the controllable heating device 4 in the flow direction 20 is a catalytic converter 14 and an accumulator 15 (for example absorber, particle trap or the like). Here, by way of example for several other possible positions in the exhaust system 3, the converter 14 is provided with an internal measuring sensor 5. In order to carry out the method described here, the heating device 4 is also connected to a control unit 13 which is for example connected to the engine management and/or to the drive 2 and/or to the measuring sensor 5 and/or to the supply 16 for the additive 11. In order to carry out the method according to the invention, the control unit 13 can be provided with corresponding software and data processing means. List of reference symbols 1 Motor vehicle 2 Drive 3 Exhaust system 4 Heating device 5 Measuring sensor 6 Operating parameter of the exhaust system 7 Influential variable of the heating device 8 Target parameter of the exhaust system 9 Exhaust gas 10 Particle 11 Additive 12 Electrically heatable honeycomb body 13 Control unit 14 Converter 15 Accumulator 16 Supply 17 Activation time period 18 Activation request 19 Time 20 Flow direction 21 Temperature We Claim: 1. Method for operating a motor vehicle (1) which has a drive (2) and an exhaust system (3) with at least one controllable heating device (4) which can be placed in contact with exhaust gas, comprising at least the following steps: (a) detecting at least one operating parameter (6) of the exhaust system (3), (b) determining at least one influential variable (7) of the heating device (4), (c) comparing the at least one influential variable (7) with a target parameter (8) of the exhaust system (3), (d) activating the heating device (4) such that the operating parameter (6) reaches the target parameter (8). 2. Method according to Patent Claim 1, with said method being carried out at least during a predominant time period between the activation and deactivation of the drive (2). 3. Method according to Patent Claim 1 or 2, with step (a) relating to at least one of the following parameters as operating parameters (6): exhaust-gas temperature, exhaust-gas mass flow. 4. Method according to one of the preceding patent claims, with step (b) relating to the heating power of the heating device (4) as an influential variable (7). 5. Method according to one of the preceding patent claims, with the target parameter (8) of the exhaust system (3) in step (c) relating to at least one of the following parameters: exhaust-gas temperature, capacity for the reduction of particles (10) contained in the exhaust gas (9), probability of catalytic reaction, capacity for the conversion of a state of aggregation of the exhaust gas (9) or of an additive (11). 6. Method according to one of the preceding patent claims, with step (d) being carried out as a function of the target parameter (8) over a predefined activation time period (17) and with the heating device (4) subsequently being deactivated. 7. Method according to one of the preceding patent claims, with step (d) being carried out by means of at least one electrically heatable honeycomb body (12). 8. Method according to one of the preceding patent claims, with an external activation request (18) of the heating device (4) being denied if step (b) yields that the at least one influential variable (7) of the heating device (4) is not sufficient to meet the condition from step (d). 9. Method according to one of the preceding patent claims, with at least one of the following variables being calculated: operating parameter (6) of the exhaust system (3), influential variable (7) of the heating device (4), target parameter (8) of the exhaust system (3). 10. Motor vehicle (1) comprising a drive (2) and an exhaust system (3) with at least one controllable heating device (4) which can be placed in contact with exhaust gas (10), in which at least the heating device (4) is connected to a control unit (13) which is set up to carry out a method according to One of the preceding patent claims.

Full Text

The present invention relates to a method for operating a motor vehicle which has a drive and an exhaust system with at least one controllable heating device which can be placed in contact with exhaust gas.
It is considered to be known to place the exhaust gases generated by an engine of a motor vehicle in contact with a heating device in order to influence the temperature of the exhaust gas. Furthermore, it is also considered to be known that heating devices of said type are used, for example directly after a cold start or restart of an engine or of an exhaust system, to quickly bring the exhaust gases or the exhaust-gas purification components which are provided with a catalytically active coating up to the reaction temperature, in particular up to a temperature at which an interaction of the catalytic converter with the pollutants of the exhaust gas takes place.
Heating devices which have already been proposed are in particular those which are heated as a result of ohmic resistance heating. The electrical conductor, which is traversed by current at desired times, is heated up on account of its resistance and can thereby heat the catalytically active material which is positioned thereon and/or the exhaust gas. There are various configurations of heating devices of said type; in particular, wire-mesh constructions, honeycomb bodies, plate constructions and the like have already been described.
With regard to the operation in heating devices of said type, it is likewise considered to be known that said heating devices have been activated before or during the starting of the engine or if appropriate shortly after the starting of the engine in order to improve the cold-start behaviour for a limited time period, with it having been taken into consideration in particular that sufficient energy could be provided from the vehicle. Furthermore, it is also known to use heating devices of said type in combination with particle filters in order to permit a thermal
regeneration of the trapped particles here. For this purpose, it is known to activate the heating devices when a predefined operating time period has elapsed or the particle loading in the filter has reached a predefined value.
The known applications and/or strategies for use have however only partially led to the desired results. It was in particular found that the use of the heating device resulted in part in an undesirably high energy requirement and the activation cycles in part took up very long time periods.
Proceeding from this, it is an object of the present invention to at least partially solve the problems highlighted with regard to the prior art. It is intended in particular to specify a method which permits the use of heating devices of said type in exhaust systems of mobile internal combustion engines in an energy-saving and effective manner.
Said objects are achieved by means of a method as per the features of Patent Claim 1. Further advantageous embodiments and applications of the invention are specified in the dependent patent claims. It should be noted that the features listed individually in the patent claims can be combined with one another in any desired technologically expedient manner and highlight further embodiments of the invention. The invention is specified in more detail below, specifically in connection with the description and the figures, such that particularly preferred embodiment variants are also specified here.
The method according to the invention for operating a motor vehicle, which has a drive and an exhaust system with at least one controllable heating device which can be placed in contact with exhaust gas, comprises at least the following steps:
(a) . detecting at least one operating parameter of the exhaust system,
(b) determining at least one influential variable of the heating device,
(c) comparing the at least one influential variable with a target parameter of the exhaust system,
(d) activating the heating device such that the operating parameter reaches the target parameter.
The method according to the invention therefore relates in particular to the regulation of a heating device which is in contact with the exhaust gas of a motor vehicle engine, such that a desired target parameter of the exhaust system or a component therein is reliably reached.
The "drive" can, in addition to known diesel or petrol engines, relate also to other comparable drives which ultimately generate a pollutant-laden exhaust gas or an exhaust gas which must be subjected to temperature treatment. The "exhaust system" is often formed by a tract (or a plurality of tracts), in particular in the manner of a tubular line. Said exhaust system, which conducts the exhaust gas in a preferred direction, now has provided in it at least one heating device which in particular at least partially spans the inner cross section of the exhaust system. Here, the heating device forms passages, ducts or the like through which the exhaust gas flows. The heating device can also have further functions in addition to its heating function, for example a catalytic conversion, accumulation or deflection of exhaust-gas constituents.
According to step (a), at least one operating parameter of the exhaust system is firstly detected at a predefinable time (during the driving mode of the motor vehicle). The measurement of the operating parameter can take place by means of at least one measuring sensor, various sensors and/or a mathematical model. The temperatures of the exhaust gas at one or more positions of the exhaust system, the temperature of an exhaust-gas treatment component in the interior of the exhaust system, the composition of the exhaust gas, the mass flow of the exhaust gas and the like are considered in particular as operating parameters. Here, the measured or calculated value significant for the considered operating parameter is preferably registered or even stored.
In step (b), which can fundamentally also take place before and/or at the same time as step (a), at least one influential variable of the heating device is determined. For this purpose, it is preferable firstly to resort to characteristic values of the heating device (for example thermal mass, geometric surface, current supply, electrical resistance and the like); however, the operating parameter measured in step (a) or one of the measured operating parameters is additionally taken into consideration. Here, use is made in particular of the knowledge that the influential variable of the heating device is dependent on at least one operating parameter of the exhaust system. In other words, this means, for example, that the heating device can bring about a temperature increase only to a certain extent for a given exhaust gas mass flow. Said temperature increase potential could be considered as an influential variable.
In step (c), which is preferably carried out after steps (a) and (b), the at least one influential variable of the heating device is compared with a target parameter of the exhaust system. The target parameter is for example read out from a provided data store and/or has been calculated (if appropriate on an ongoing basis). Such a target parameter of the exhaust system can be a predefined value of one or more operating parameters of the exhaust system. It is fundamentally the case that the method according to the invention can be interrupted already if the measured operating parameter from step (a) is already in a preferred relationship with respect to the target parameter, that is to say additional measures need not be taken. A query of said type can be provided before and/or during or after step (a). If, however, it is determined that the measured operating parameter is not in a preferred relationship with respect to the target parameter, then on the basis of the comparison, it is determined to what extent the influential variable ensures with sufficient probability that the present operating parameter can be brought into the desired relationship with respect to the target parameter of the exhaust system when the heating device is actuated.
In step (d), it is now proposed that an activation of the heating device should take
place only when the operating parameter reaches the target parameter. For example, if the measured operating temperature of the exhaust system is so low that even an activation of the heating device will generate such a small temperature increase that the target temperature will not be reached, then the heating device is not activated. At this time, it can also be decided as to whether the method according to the invention is repeated directly until an activation of the heating device is expedient; it is however also possible to firstly implement other measures in order to finally start the use of the heating device in a favourable manner in terms of energy.
It is thereby possible in particular for a permanent check of the possibility for use of a heating device to be realized. Here, an abort criterion is defined for situations in which the activation of the heating device is not expedient, before no other (additional, if appropriate simultaneous or preceding) measures promote the desired effect of the heating device. Particularly economical use, which is effective in terms of energy, of the heating device during operation of the motor vehicle is ensured in this way.
According to one refinement, it is proposed that the method is carried out at least during a predominant time period between the activation and deactivation of the drive. It is very particularly preferable for the method to be started with the activation, carried out continuously and ended with the deactivation of the drive. In other words, this means in particular that the method, if appropriate in fixedly predefined and/or dynamic cycles, carries out a comparison of the at least one operating parameter of the exhaust system with the influential variable of the heating device, and an activation of the heating device takes place if required.
Furthermore, it is also considered to be advantageous for step (a) to relate to at least one of the following parameters as operating parameters: exhaust-gas temperature, exhaust-gas mass flow. Furthermore, in particular the following parameters of the exhaust gas are also considered: exhaust-gas composition,
concentration content of a predefined proportion of the exhaust gas, etc.
Said operating parameters can be measured on an ongoing basis by means of (at least) one measuring sensor, a probe or a similar apparatus, though it is also possible to calculate the operating parameter for example from the operating date of the drive and further characteristic variables.
With regard to step (b), it is preferable for the heating power of the heating device to be considered as an influential variable. The heating power relates in particular to the value which the heating device permits as a temperature increase for the given exhaust-gas mass flow. Consequently, a heating power (H) could for example be specified as a difference of the average temperature of the exhaust gas after contact with an active heating device (TII) to the average temperature of the exhaust gas before contact with the heating device (TI): H = TII - TI. In the case of honeycomb-shaped heating devices, in particular having at least partially structured sheet metal foils and a voltage source of 12 - 14 Volts, it is preferably possible to specify the following heating powers as (in particular lower) influential variables:
H (Exhaust gas mass flow: 0.017 kg/s): 46 - 52 Kelvin; H (Exhaust gas mass flow: 0.023 kg/s): 40 - 44 Kelvin; H (Exhaust gas mass flow: 0.027 kg/s): 31-35 Kelvin; H (Exhaust gas mass flow: 0.030 kg/s): 24 - 28 Kelvin; H (Exhaust gas mass flow: 0.035 kg/s): 22 - 24 Kelvin; H (Exhaust gas mass flow: 0.040 kg/s): 18-22 Kelvin.
The values stated above relate in particular to a heating device which comprises a sheet metal foil arrangement which has a multiplicity of ducts (300 to 600 cpsi) and which realizes the specified heating power over a 10 to 15 mm heating path (duct length in the flow direction of the exhaust gas). The ranges of fluctuation result for example from the sheet metal foil arrangement being heated during
operation (heat capacity), the averaging of the dynamic temperature profiles and the like.
According to one refinement of the method, the target parameter of the exhaust system in step (c) relates to at least one of the following parameters: exhaust-gas temperature, capacity for the reaction of particles contained in the exhaust gas, probability of catalytic reaction, capacity for the conversion of a state of aggregation of the exhaust gas or of an additive, etc. With regard to the capacity for the reaction of the particles contained in the exhaust gas, it should be noted that, with the heating device, it is for example possible to create an ambient condition in which a conversion of particles into gaseous constituents takes place. An increase in the probability of catalytic reaction can be obtained by virtue, for example, of ambient conditions being created at the heating device, and/or at exhaust-gas treatment components situated downstream thereof in the flow direction, in which a catalytically activated chemical reaction of exhaust-gas constituents is initiated. Furthermore, the target parameter can also relate to a capacity for the conversion of a state of aggregation of the exhaust gas and of an additive (reducing agent, water, etc.).
Furthermore, a method is considered to be advantageous in which step (d) is carried out as a function of the target parameter over a predefined activation time period and the heating device is subsequently deactivated. It is very particularly preferable for the activation time period to be variable depending on the type of target parameter. For example, temperature increases of the exhaust gas can be realized over a shorter activation time period than a conversion of particles. Tests have shown that, for the following parameters and following boundary conditions, at the respectively described heating devices, the activation time periods listed below are advantageous:
1. At a catalytic converter which is connected downstream of the heating device and which has a catalytic coating for the oxidizing conversion of
• carbon monoxide, an average temperature of the exhaust gas after contact with an active heating device (TII) should be present which ensures an exhaust-gas temperature of 150°C upon entry into the catalytic converter.
2. At a catalytic converter which is connected downstream of the heating device and which has a catalytic coating for the oxidizing conversion of hydrocarbons, an average temperature of the exhaust gas after contact with an active heating device (TII) should be present which ensures an exhaust-gas temperature of 170°C upon entry into the catalytic converter.
3. At a catalytic converter which is connected downstream of the heating device and which has a catalytic coating for the selective catalytic reduction of nitrogen oxides, an average temperature of the exhaust gas after contact with an active heating device (Tn) should be present which (a) ensures an exhaust-gas temperature of 200°C upon entry into the catalytic converter with a coating comprising vanadium, and (b) ensures an exhaust-gas temperature of 250°C to 600°C upon entry into the catalytic converter with a coating comprising iron zeolite (Fe-CSM system) (if appropriate varying as a function of the NOx composition of the exhaust gas flow).
The deactivation of the heating element can be carried out in particular when an activation of the downstream catalytic converter or particle filter (for example with temperature difference monitoring across the catalytic converter or particle filter) has been detected. The method proposed here can then begin again with the monitoring.
In order to ensure a particularly high level of effectiveness of the method, it is also proposed that step (d) is carried out by means of at least one electrically heatable honeycomb body. With a honeycomb body of said type, it is possible to realize relatively small ducts through which the exhaust gas is conducted. At the same
time, the honeycomb body consequently provides a large contact area with the exhaust gas, so that intensive contact between the heat source and the exhaust gas can be realized here. It is consequently possible, with a compact arrangement of the honeycomb body, and by means of short activation cycles, for the desired target parameter to be effectively used in a multiplicity of measured operating states. For the construction of an electrically heatable honeycomb body of said type, reference is made to the patent publications of the applicant, in particular to the content of WO-A-96/10127, which can be taken into consideration here at all times for the explanation of the construction and the function of an electrically heatable honeycomb body of said type.
Furthermore, it is also proposed that an external activation request of the heating device is denied if step (b) yields that the at least one influential variable of the heating device is not sufficient to meet the condition from step (d). This means in particular that the activation of the heating device could for example be demanded by other components of the motor vehicle; for example, probes could establish that the pressure drop across a particle trap is too great and that a regeneration would therefore be necessary. Likewise, the monitoring of the load operating point of the drive could also signal that the temperature of the exhaust gas is now too low. The engine management system could now want to activate the heating device. It was however found that, in precisely such situations, it is merely the case that additional energy for the heating device is required and consumed without ultimately definitely achieving the desired aim. It is therefore additionally proposed that said external activation takes place only if the condition from step (d) can be met.
Furthermore, it should be noted that preferably at least one of the following variables is calculated: operating parameter of the exhaust system, influential variable of the heating device, target parameter of the exhaust system. The calculation of said variable(s) can take place on the basis of one or more of the other variables specified here. It is preferable for at least one of the variables to
(also) be measured by means of measuring technology, in particular using at least one measuring sensor.
The invention is particularly advantageously used in a motor vehicle comprising a drive and an exhaust system with at least one controllable heating device which can be placed in contact with exhaust gas, in which at least the heating device is connected to a control unit which is set up to carry out a method described here according to the invention.
The invention and the technical field are explained in more detail on the basis of the figures. It should be noted that the figures show particularly preferred embodiment variants of the invention, to which the invention is however not restricted. In the figures, in each case schematically:
Figure 1: shows a diagram with an illustration of one possible mode of operation of the method according to the invention, and
Figure 2: shows a possible construction of an exhaust system for operating a motor vehicle according to the method explained here.
Figure 1 illustrates a diagram in which an operating parameter of the exhaust system 6 (in this case the temperature 21) is plotted against the course of time 19. Proceeding from the left, it can be seen that the operating parameter 6 substantially adheres to a fixed value. At this time, it would for example be possible for step (a) to be carried out and for the present operating parameter 6 to be detected. Subsequently thereto, the influential variable 7 of the heating device is now determined (as per step (b)). Here, the influential variable 7 is illustrated by dashed lines, with it being detected during a comparison of the influential variable 7 with the target parameter 8 (illustrated here by dashed lines) that the influence is so great that the target parameter 8 can be reliably reached. For this reason, the heating device is now activated over an activation time period 17. In
the case illustrated here, said activation time period 17 is sufficient to raise the operating parameter 6 over the target parameter 8, such that the desired result is reliably ensured.
Further to the right in the diagram, that is to say at an (arbitrary) later time, a different situation is illustrated by way of example. Here, it is for example detected that, in a subsystem of the exhaust system, a temperature increase to the target parameter is now necessary. The engine management system would now start an activation request 18 at the illustrated time. Now, at the time of the activation request 18, the method according to the invention is carried out once again, with it being detected during the comparison of the influential variable 7 with the target parameter 8 that the target parameter 8 cannot be reached by means of an activation of the heating device. The heating device is therefore not activated here, but rather other measures (influence on the combustion processes in the drive, use of additives, etc.) are resorted to first.
Figure 2 now schematically illustrates the construction of a motor vehicle 1 having a drive 2 and an exhaust system 3. The exhaust gas 9 generated in the drive 2 flows in the flow direction 20 through the exhaust system 3, with said exhaust gas flowing through a plurality of exhaust-gas purification components. The exhaust gas 9 can for example comprise particles 10. It is also possible for a supply 16 for an additive 11 (air, water, reducing agent, fuel, ... etc.) to be provided. The exhaust gas 9 now impinges on a heating device 4 which should in this case be embodied as an electrically heatable honeycomb body 12. Provided downstream of the controllable heating device 4 in the flow direction 20 is a catalytic converter 14 and an accumulator 15 (for example absorber, particle trap or the like). Here, by way of example for several other possible positions in the exhaust system 3, the converter 14 is provided with an internal measuring sensor 5.
In order to carry out the method described here, the heating device 4 is also
connected to a control unit 13 which is for example connected to the engine management and/or to the drive 2 and/or to the measuring sensor 5 and/or to the supply 16 for the additive 11. In order to carry out the method according to the invention, the control unit 13 can be provided with corresponding software and data processing means.
List of reference symbols
1 Motor vehicle
2 Drive
3 Exhaust system
4 Heating device
5 Measuring sensor
6 Operating parameter of the exhaust system
7 Influential variable of the heating device
8 Target parameter of the exhaust system
9 Exhaust gas
10 Particle
11 Additive
12 Electrically heatable honeycomb body
13 Control unit
14 Converter
15 Accumulator
16 Supply
17 Activation time period
18 Activation request
19 Time
20 Flow direction
21 Temperature

We Claim:
1. Method for operating a motor vehicle (1) which has a drive (2) and an exhaust system (3) with at least one controllable heating device (4) which can be placed in contact with exhaust gas, comprising at least the following steps:
(a) detecting at least one operating parameter (6) of the exhaust system (3),
(b) determining at least one influential variable (7) of the heating device (4),
(c) comparing the at least one influential variable (7) with a target parameter (8) of the exhaust system (3),
(d) activating the heating device (4) such that the operating parameter (6) reaches the target parameter (8).

2. Method according to Patent Claim 1, with said method being carried out at least during a predominant time period between the activation and deactivation of the drive (2).
3. Method according to Patent Claim 1 or 2, with step (a) relating to at least one of the following parameters as operating parameters (6): exhaust-gas temperature, exhaust-gas mass flow.
4. Method according to one of the preceding patent claims, with step (b) relating to the heating power of the heating device (4) as an influential variable (7).
5. Method according to one of the preceding patent claims, with the target parameter (8) of the exhaust system (3) in step (c) relating to at least one of the following parameters: exhaust-gas temperature, capacity for the
reduction of particles (10) contained in the exhaust gas (9), probability of catalytic reaction, capacity for the conversion of a state of aggregation of the exhaust gas (9) or of an additive (11).
6. Method according to one of the preceding patent claims, with step (d) being carried out as a function of the target parameter (8) over a predefined activation time period (17) and with the heating device (4) subsequently being deactivated.
7. Method according to one of the preceding patent claims, with step (d) being carried out by means of at least one electrically heatable honeycomb body (12).
8. Method according to one of the preceding patent claims, with an external activation request (18) of the heating device (4) being denied if step (b) yields that the at least one influential variable (7) of the heating device (4) is not sufficient to meet the condition from step (d).
9. Method according to one of the preceding patent claims, with at least one of the following variables being calculated: operating parameter (6) of the exhaust system (3), influential variable (7) of the heating device (4), target parameter (8) of the exhaust system (3).
10. Motor vehicle (1) comprising a drive (2) and an exhaust system (3) with at least one controllable heating device (4) which can be placed in contact with exhaust gas (10), in which at least the heating device (4) is connected to a control unit (13) which is set up to carry out a method according to
One of the preceding patent claims.

Documents:

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Patent Number

277271

Indian Patent Application Number

8450/DELNP/2009

PG Journal Number

48/2016

Publication Date

18-Nov-2016

Grant Date

16-Nov-2016

Date of Filing

23-Dec-2009

Name of Patentee

Emitec Gesellschaft für Emissionstechnologie mbH

Applicant Address

HAUPTSTRASSE 128, 53797 LOHMAR (DE)

Inventors:

#	Inventor's Name	Inventor's Address
1	BRÜCK, ROLF	FROBELSTRASSE 12, 51429 BERIGISCH GLADBACH (DE)
2	HODGSON, JAN	BLUMENHOF 23, 53840 TROISDORF (DE)
3	KONIECZNY, JÖRG-ROMAN	ELTERSBACH 7, 53804 MUCH (DE)

PCT International Classification Number

F01N 3/027

PCT International Application Number

PCT/EP2008/056179

PCT International Filing date

2008-05-20

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2007 025 419.0	2007-05-31	Germany