Abstract:
The invention relates to an arrangement ( 1 ) for operating an exhaust gas aftertreatment device, in particular of a motor vehicle, having a plurality of active sensors ( 3 - 8 ) and a control device ( 2 ) that comprises at least one voltage supply unit ( 9 ) to which the sensors ( 3 - 8 ) are operatively connected. According to the invention, the voltage supply unit ( 9 ) comprises at least two supply benches ( 13 - 15 ) that can be switched independently from each other. The sensors ( 3 - 8 ) are grouped according to the function thereof and are then associated with one of the supply benches ( 13 - 15 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an arrangement for operating an exhaust gas aftertreatment device, in particular of a motor vehicle, having a plurality of active sensors and a control module, which comprises at least one voltage supply unit, to which the sensors are operatively connected. 
     An exhaust gas aftertreatment device, which serves to reduce the pollutants present in the exhaust gas, is generally connected to the exhaust side of modern internal combustion engines. Such exhaust gas aftertreatment devices comprise a plurality of exhaust gas aftertreatment units such as, for example, catalytic converters, particle filters or the like. In order to ensure a long-term operating reliability, a number of sensors, which monitor/register the performance of the exhaust gas aftertreatment device or the various exhaust gas aftertreatment units, or their effect on the exhaust gas, are assigned to the exhaust gas aftertreatment device. For this purpose the sensors are operatively connected to a control module to which they deliver their signals. The signals are generally evaluated in the control module, and if necessary, for example, a warning display is activated for the driver of a motor vehicle. So-called “active sensors” are often used as sensors. These differ from the so-called “passive sensors” in that in order to fulfill their function they need electrical power, which is fed from outside. For this purpose the active sensors are connected to a voltage supply unit of the control module. The active sensors, also referred to as passive transducers, make it possible to determine static and virtually static measured variables. 
     SUMMARY OF THE INVENTION 
     According to the invention it is proposed that the voltage supply unit comprise at least two supply banks that can be switched independently of one another, and the sensors, grouped according to their function, each be assigned to one of the supply banks. In contrast to the state of the art, the active sensors are therefore connected to different supply banks that can be switched independently of one another, the sensors being divided between the supply bans according to their function. This means that active sensors (hereinafter simply referred to as sensors), which serve the same or a similar sub-function, are each assigned to a common supply bank. This has the advantage that if a malfunction should occur, only the sensors of one group, that is to say the group having the malfunction, are deactivated and the other sensors continue to operate. Thus it is possible for the exhaust gas aftertreatment device to continue operating even when sensors assigned to an exhaust gas aftertreatment unit are deactivated. Depending on the function of the particular group of sensors, the deactivation of the group is of greater or lesser significance for the exhaust gas aftertreatment device as a whole. Even if a particularly important group of sensors is deactivated, however, restricted operation of the exhaust gas aftertreatment device is still possible, thereby ensuring, in particular, that a driver can at least drive his motor vehicle to the next service workshop since, at least for a certain length of time, the restricted operation of the exhaust gas aftertreatment device serves to prevent lasting damage. 
     The arrangement preferably comprises a diagnostic circuit for detecting a malfunction of the sensors. The diagnostic circuit is preferably integrated into the control module. The diagnostic circuit monitors the functioning of the sensors and is operatively connected to the latter in such a way that it can attribute a detected malfunction to one of the sensors. 
     The diagnostic circuit is preferably designed in such a way that it deactivates one or more of the supply banks if a fault is detected in one of the sensors assigned to the corresponding supply bank. If the diagnostic circuit therefore diagnoses a malfunction and attributes it to a specific sensor, it deactivates the supply bank having the specific sensor, in order to prevent malfunctions in the exhaust gas aftertreatment device and any associated damage. Since the sensors are connected to the supply bank grouped according to their function, the deactivation of the other sensors connected to the same supply bank does not constitute a particularly intrusive restriction. 
     A first group of at least one sensor advantageously relates to particle filter regeneration. These sensors are preferably temperature sensors, or also pressure sensors, for example, which register the pressure of the exhaust gas upstream and downstream of a particle filter, in order to determine its charged state. 
     A second group of at least one sensor further relates to the metering of exhaust gas aftertreatment agent. The second sensors grouped according to their function therefore serve for the metering of exhaust gas aftertreatment agent. Such sensors are pressure sensors, for example, which register the pressure of the exhaust gas aftertreatment agent, or sensors which register the functional capability of an injection valve or its actuator, for example. These sensors may equally well be temperature sensors for registering the temperature of the exhaust gas aftertreatment agent. 
     A third group of at least one sensor is furthermore assigned to a feed module for the exhaust gas aftertreatment agent. The feed module, which is preferably embodied as a feed pump, serves for feeding and for the build-up of pressure for the preferably liquid exhaust gas aftertreatment agent. Sensors provided in this group, for example, register the speed of the feed module or the temperature and/or the pressure of the exhaust gas aftertreatment agent. The temperature sensor, for example, serves to monitor whether the temperature of the exhaust gas aftertreatment agent exceeds the freezing point of the exhaust gas aftertreatment agent, and therefore whether feeding of the exhaust gas aftertreatment agent is possible. Here, should the temperature sensor fail, for example, the third group or the corresponding supply bank is deactivated by the diagnostic circuit for safety reasons, so that the feed module is not operated and is not damaged due to frozen exhaust gas aftertreatment agent. The first group and the second group, as have been described above, can nevertheless continue to be operated, so that particle filter regeneration, for example, can be performed despite failure of the third group. This virtually ensures an emergency operation of the exhaust gas aftertreatment device, which allows the driver of a motor vehicle to drive to the nearest service workshop without components of the exhaust gas aftertreatment device being damaged in the process. 
     The distinguishing feature of inventive method for operating an exhaust gas aftertreatment device, particularly with an arrangement as described above, is that the sensors, grouped according to their function, are assigned to at least two supply banks of the voltage supply unit that can be switched independently of one another. Functionally circumscribed or functional groups of sensors are therefore formed, which are connected to different supply banks of the voltage supply unit, so that the groups can be switched off or deactivated independently of one another. 
     A supply bank is advantageously deactivated if a fault is detected or registered in a sensor assigned to the corresponding supply bank. Whilst the group or supply bank having the malfunction is deactivated, the other groups can continue to be operated and a restricted operation of the exhaust gas aftertreatment device can be ensured. This affords the advantages described above. 
     The invention will be explained in more detail below with reference to an exemplary embodiment. In the drawing: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic representation of an advantageous arrangement for operating an exhaust gas aftertreatment device, and 
         FIG. 2  shows an availability matrix representing the operating principle of the advantageous arrangement. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1 , in a schematic representation, shows an advantageous arrangement  1  for operating an exhaust gas aftertreatment device  16  of an internal combustion engine, in particular of a motor vehicle  17 . The arrangement  1  comprises a control module  2  and a plurality of active sensors  3  to  8 , which are connected to a voltage supply unit  9  of the control module  2 . The sensors  3  to  8  are assigned to different areas and/or elements of the exhaust gas aftertreatment device  16  and serve, among other things, for functional monitoring of various exhaust gas aftertreatment units, such as a particle filter, for example, or an injection valve for exhaust gas aftertreatment agent. 
     The sensors  3  to  8  are divided into three groups  10 ,  11  and  12 , being grouped according to their function. 
     The first group  10  comprises the sensors  3  to  5 , which relate to the regeneration of a particle filter  22  of the exhaust gas aftertreatment device  16 . Thus the sensors  3  and  4 , for example, serve for registering a pressure gradient over the particle filter  22 , on the basis of which the charged state of the particle filter can be determined. The sensor  5  serves, for example, for registering the temperature of the particle filter  22 , which must overwrite a specific threshold for the regeneration of the particle filter  22 . 
     The second group  11  comprises the sensor  6 , which is assigned to an injection valve  18  for exhaust gas aftertreatment agent. The injection valve  18  is suitably arranged on an exhaust pipe in such a way that exhaust gas aftertreatment agent fed to the injection valve  18  can be fed to the exhaust gas flowing through the exhaust pipe. The exhaust gas aftertreatment agent is preferably atomized by the injection process, so that it mixes particularly advantageously with the exhaust gas. The sensor  6  here serves, for example, for monitoring the functional capability of the injection valve  18  or of an actuator of the injection valve  18 . 
     The group  12  comprises the remaining sensors  7  and  8 , which are assigned to a feed system for the exhaust gas aftertreatment agent. Thus the sensor  7 , in particular, is assigned to a feed module  19 , preferably a feed pump  20 , and registers the functional capability of the feed pump  20 , for example, or the pressure of the delivered exhaust gas aftertreatment agent produced by the feed pump  20 . The sensor  8  is preferably embodied as a temperature sensor and registers the temperature of the exhaust gas aftertreatment agent to be fed. The sensor  8  therefore serves to ensure that the temperature of the exhaust gas aftertreatment agent lies above its freezing point. Should this not be the case, a heating unit of the exhaust gas aftertreatment device  16  or of the feed system for the exhaust gas aftertreatment agent is preferably activated, in order to thaw out the exhaust gas aftertreatment agent. Until the exhaust gas aftertreatment agent is thawed out, however, an activation of the feed pump  20  would damage it. 
     The sensors  3  to  8  grouped in this way are assigned to different supply banks  13 ,  14  and  15  that can be switched independently of one another. The groups  10 ,  11  and  12  can thereby be deactivated independently of one another. The voltage supply unit  9  preferably distributes the drive current equally to all sensor supply banks. For this purpose a voltage of 3.3V or 5V is preferably applied to all (sensor) supply banks. 
       FIG. 2  in a matrix shows the main advantage of the arrangement  1  and of the method described above. The groups  10 ,  11  and  12  are entered in the top line and the effect of a failure of the groups  10 ,  11  and  12  on the overall system and the other groups  10 ,  11  and  12  is entered in the lines below. 
     Should a diagnostic circuit  21  (not represented here) integrated into the control module  2  detect a malfunction in one of the groups  10 ,  11  or  12 , it deactivates the corresponding group  10 ,  11  or  12  having the malfunction, in order to safeguard it against damage. 
     Should the diagnostic circuit  21  detect a malfunction of the sensor  3  of the group  10 , it thus deactivates the entire group  10 . Owing to the advantageous grouping of the sensors  3  to  8 , however, this does not have any effect on the groups  11  and  12 . If the sensors  3 ,  4 ,  5  for the particle filter regeneration have failed, it is still possible to use the relevant sensors for the injection valve  18  or the feed system for the exhaust gas aftertreatment agent, as represented by a check in the corresponding box. 
     Should the diagnostic circuit  21  detect a malfunction of one of the sensors  7  or  8 , however, it deactivates the group  12 . As a result, only a limited injection of exhaust gas aftertreatment agent is still possible. This then depends on the remaining or vestigial pressure in the exhaust gas aftertreatment agent feed system, which can no longer be detected, however, owing to the failure of the group  12 . 
     The same correspondingly applies in the event of a failure of the group  11 , in which the group  10  still remains fully functional and particle filter regeneration thereby remains feasible, whilst the group  12  is only operationally useable to a limited extent, here represented by a check placed in brackets. 
     Overall, therefore, the advantageous arrangement  1  and the corresponding method allow continued operation of the exhaust gas aftertreatment device  16 , at least to a limited extent, in the event of a failure of one of the groups  10 ,  11  or  12 , so that a minimum pollutant reduction is still ensured and lasting damage is prevented.