FR2951777A1 - METHOD OF MONITORING THE HEATING SYSTEM OF A REDUCING AGENT RESERVOIR AND A DOSING FACILITY OF A SCR CATALYST SYSTEM - Google Patents

Abstract

A method of monitoring a heating system of a reducing agent tank and a metering system of a system comprising at least one tank heating means, at least one heating means of the pressure line and at least one heating means of the transfer module. According to the method, the operating parameters and the sensor values of the system are entered and within predefined tolerances (4, 5) are compared to reference values (1) to conclude that the heating system has failed behavior.

Description

FIELD OF THE INVENTION The present invention relates to a method for monitoring a heating system of a reducing agent tank and of a metering system of a system comprising at least one tank heating means, at least one heating means of the pressure line and at least one heating means of the transfer module. BACKGROUND OF THE INVENTION There are known methods and devices for managing a heat engine, especially for motor vehicles, the exhaust ducting of which is equipped with an SCR (selective reduction catalyst) catalyst to reduce NOx nitrogen oxides contained in the engine exhaust with a reducing agent to form nitrogen. This considerably reduces the nitrogen oxide content of the exhaust gas. For the course of the reaction, ammonia (NH3) is required which is mixed with the exhaust gas. As a reaction agent, ammonia NH 3 or NH 3 -relating reagents are thus used. In general, an aqueous solution of urea (aqueous urea solution) injected into the exhaust gas line upstream of the SCR catalyst is used for this purpose by means of a metering installation. This solution develops ammonia NH3 acting as a reducing agent. To store the aqueous solution of urea, a reducing agent reservoir or a reservoir of an aqueous solution of urea is used.

To transfer the aqueous urea solution from the reducing agent reservoir, a pump is generally used as part of a transfer module which transfers the solution through a conduit system. Thus, the aqueous solution of urea arrives via a pressure line and a metering valve such as an electromagnetic injector, under pressure, in the exhaust gas line. Standard aqueous solutions of urea, usually used, have the characteristic of freezing at a temperature of about -11 ° C. However, to ensure proper aftertreatment of exhaust gases even at low outside temperatures, it is necessary to heat at least the reducing agent reservoir. For that,

In general, a heating system consisting of tank heating, heating of the pressure line and heating of the transfer module as well as temperature sensors and appropriate heating control is used. The heating elements of the heating system usually comprise ohmic structure elements and PCT elements. PCT elements are cold conductive elements with electrically conductive materials that conduct better current at low temperatures than at high temperatures. The electrical resistance increases with the temperature so that the heat output decreases with the temperature thus ensuring a kind of self-regulation of the heating element which avoids overheating or a permanent power supply. The heating device of the reducing agent reservoir can be composed for example of two PTC elements connected in parallel, installed between two heating elements, ohmic, connected in series. The various elements of the heating system, in particular the PCT elements, are exposed to mechanical and electrical stresses. However, the damage of a component deteriorates its ability to operate, or even leads to complete failure of the system. In particular, if a PCT element is damaged, there will be a current passage too strong or too low in the heating means. As a properly functioning heating system with a proper aftertreatment condition of the exhaust gas, it is necessary to oversee the proper functioning of the heating system.

Document DE 102 34 561 A1 proposes a method and a device for controlling the operation of an electric heating installation equipped with a PCT element and according to which, after the connection of the heating installation, the intensity of the heating current flowing through the PCT element in a given period of time. It is determined whether, during the period, the intensity of the heating current has exceeded or at least reached a predefined threshold, which makes it possible, if necessary, to signal a fault. However, this method does not constitute a satisfactory solution if more than one heating element, in particular a combination of heating elements or a complex heating system, are to be checked because, in particular in the case

3 PCT elements connected in parallel, we can not have significant information on the nature and location of the disturbance. In addition, the intensity of the current in a heating installation undergoes significant variations so that this method easily provides erroneous information. OBJECT OF THE INVENTION The object of the present invention is to develop a means of monitoring a heating system of a reducing agent tank and of a dosing system of a system in order to guarantee safely a post- correct treatment of the exhaust gas, even at low outdoor temperatures, to have enough liquid solution of reducing agent. The invention thus proposes to safely detect faults, locate them and report or treat them.

DESCRIPTION AND ADVANTAGES OF THE INVENTION To this end, the invention relates to a method of monitoring a heating system of a reducing agent tank and a metering system of a system characterized in that the the operating parameters and the sensor values of the system are entered and within predefined tolerances they are compared to reference values to conclude that the heating system has failed. To monitor the heating system of a reducing agent tank and a dosing system of an SCR system with at least one tank heater, at least one pressure line heater and at least one transfer, the invention provides a method according to which the operating parameters and the values of the sensors of the catalyst system SCR are entered and these values are processed by comparing them with reference values in predefined tolerance ranges to deduce the case. a faulty behavior of the heating system. The method per- mits monitoring of the complex heating system of the reducing agent tank and the metering system of the SCR catalyst system to detect the multiple faults that may occur in the heating system. The method according to the invention makes it possible to locate any fault and to send a fault signal, which

4 makes it possible to remedy the defects. Due to the location of the fault, only part of the installation will be cut to prevent further damage. According to a particularly advantageous development, the method comprises as a program at least one UHC_Mon module, main for the main monitoring and the release of the various heating circuits and at least one UHC_MonCx module controlled to monitor the various heating circuits. The main monitoring and the release of the various heating circuits are preferably performed by a UHC_Mon module. For the different heating circuits or the different individual heaters, there are preferably separate subordinate (or controlled) UHC_MonCx modules. The organization of the method according to the invention in several modules allows targeted monitoring of the various components or combinations of components of the heating system and thus the location of a defect. The cutting into different modules also allows a targeted release of the various components of the heating system so that, for example, in the event of a fault in a part of the system, this part of the system can be cut in a targeted manner.

Particularly advantageously, the invention pre-sees four modules among which there is in particular the main module, UHC_Mon module, to monitor and release the various heating circuits. In addition, as a subordinate module or a controlled module, there is a UHC_MonC module 1 for monitoring a first tank heating circuit, a UHC_MonC2 module for monitoring the heating of the pressure line and the heating of the transfer module, which are united in one and the same. heating circuit and finally a UHC_MonC3 module for monitoring a second tank heating circuit.

Preferably, the subordinate modules include the UHC_MonC1 module, UHC_MonC2 module and / or UHC_MonC3 module to detect short circuits and / or line breaks in the heating system. The detection of short circuits and / or line breaks is mainly based on the detection of the PTC characteristic of the various heating elements. As indicated above, the PCT elements of the electrical heating components have a characteristic intensity curve as a function of temperature. The intensity increases continuously after connection in the case of a multi-element heating system 5 PCT. At the same time, the temperature increases under the effect of heating provided by the heating system. In the crystal of the PCT element, this clean heating increases its electrical resistance so that after reaching the maximum intensity, it will again be regulated in the decreasing direction. This characteristic curve of the intensity of the PCT element is used according to the invention to detect short circuits and / or line breaks in the heating system. According to the invention, the sensor values representing the total current or the current mirror passing through the respective heating elements are entered and this intensity is compared with predictable reference values for a correctly functioning heating installation. Preferably, the voltage applied to the respective heating installation is taken into account since it can have a considerable influence on the total current and thus on the maximum possible heating power. Preferably, the voltage of the battery is also used. The reference values are those pre-visible for proper operation of the heating element. In case of drift of the sensor values entered with respect to the reference values, it can be concluded that a fault has occurred and preferably emits a corresponding fault signal. To compare the measured value and the reference value, it is possible to use for example the maximum peak of the intensity of the total current of the respective unit. The use of the maximum current peak as a measurement value is particularly suitable because this value is determined in a very simple and faultless way. Thus, for example, after the moment of connection of the heating circuit, the total intensity can be read continuously. The value read will always be compared to the next read value. If the current value is larger than the previous value, it replaces the old value. This procedure is repeated until reaching the maximum intensity. The maximum intensity is reached if the previous value is larger than the current measured value. The maximum current peak thus detected will be used for comparison with a reference value. In other embodiments, intensity curves as a function of time can be used as a reference value and / or appropriate tolerance bands can be applied to the temperatures which reflect the characteristic, predictable current curve. According to a preferred embodiment, the method of the invention is characterized in that the UHC_Mon module comprises for the main monitoring and the release of the various heating circuits at least one of the following input parameters: heating circuits, 15 - the current intensity in the UHC_MonCx modules, and - preferably the temperature of the tank. The purpose of this module is to release the various heating circuits required as long as there is no fault and to calculate the total current required. This further allows to check if the tank temperature is too high. According to a preferred development of the method, the UHC_MonC 1 module for monitoring the first tank heating circuit comprises at least one of the following input parameters: battery voltage, duration since the last cut of the motor, temperature of the tank, - release of the SCR monitoring, - state of the heating control, - state of release until now of the UHC_MonC1 module, 30 - current measured in the first tank heating circuit and / or - state of the first stage of the tank heating power. These parameters, which are entered and processed in the form of sensor values and operating parameters, make it possible to detect short-circuit and idle faults by comparison with

7 the characteristic power curve of a system operating correctly. In order to determine the characteristic power curve or appropriate reference values, tolerance curves are preferably calculated from the battery voltage, the intensity, the reference curve and the tolerance coefficient. By entering and using the various parameters as described, the following parameters emitted by the UHC module MonC 1 can be seen: - the greatest electrical power at the heating level, - an indication that there has been a maximum power and / or - consideration of a warm start. For the comparison of the sensor values to the reference values, the maximum measured value (maximum power) is preferably compared with the maximum values modeled (min / max threshold). If the actual value exceeds the upper limit, it is recognized that there is a PTC short circuit. A short circuit can also be detected if a current is flowing while the heater is off. The modeled maximum values or the modeled intensity curves formed for example from the flow temperature and the heating time are thus compared with the real effective current signal and, in case of deviation exceeding predefined tolerances, it is concluded to a fault. According to another preferred development of the method, the UHC_MonC2 module for monitoring the heating of the pressure line and the transfer module comprises at least one of the following input parameters: battery voltage, duration since the last motor shutdown, - ambient temperature, - tank temperature, - SCR monitoring release, - heating control status, - UHC_MonC2 module release status, - current measured in the pipe heating circuit. pressure and / or

8 - state of the power stage of the heating of the pressure line. The input parameters of the UHC_MonC2 module are similar to the input parameters of the UHC_MonC1 module, except that in addition the ambient temperature is taken and in place of the UHC_MonC1 module's release state, the intensity measured in the UHC_MonC1 module. the first tank heating circuit and the state of the first tank heating power stage, the state of release of the UHC_MonC2 module is entered, the current measured in the heating circuit of the pressure line. and the state of the heating power stage of the pressure line. Similarly, for the input parameters of the UHC_MonC3 module monitoring the second tank heating circuit. In this case, it is preferable to enter at least one of the following input parameters: battery voltage, duration since the last cut of the motor, temperature of the tank, release of the SCR monitoring, state of the heating control, - hitherto released state of the UHC_MonC3 module, - current measured in the second tank heating circuit and / or 25 - state of the second tank heating power stage. Preferably, in the three subordinate modules described above, the short circuits and / or the line or line breaks in the various components of the heating system are detected in the manner described and they are located for transmission. corresponding fault messages or to intervene. In addition, input parameters, entered, can determine if there is a hot start. The modules of the method according to the invention for monitoring the different heating circuits or the different heatsings are not limited to the modules described. The realization of the different modules and

In particular, input parameters and output parameters can be adapted to the various embodiments of the components of the heating system to be monitored in each case. According to a particularly advantageous development of the method of the invention, at least one of the modules, in particular at least one or all of the subordinate modules, makes it possible to force a test mode in the case where the heating system or the heating circuit does not work. One can thus test the behavior of the module even if at this moment, the module is not implemented. This makes it possible to operate the various modules in test mode if the heating system or the various heating circuits no longer function, for example, for a prolonged period of time and that there is sufficient power available to execute a heating procedure at the same time. trial purposes. According to a preferred development of the method of the invention, the method is realized in the form of a circuit or a computer program executing all the steps of the method when the program is run on a computer or apparatus. control. Such a computer program or such an arrangement may be incorporated in the control apparatus of the heat engine which is also provided to control the heating. The realization in the form of a computer program has the advantage that the method can be installed in this form in existing vehicles without having to install particular circuits. The present invention will be described in more detail below with reference to an embodiment shown in the accompanying drawings in which: FIG. 1 shows the power versus time curve of an element PCT, for different cases of defects, - Figure 2 is a diagram of a main module forming part of a preferred embodiment of the method of the invention, - Figures 3-5 are diagrammatic representations of subordinate modules forming part of a preferred embodiment of the process of the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION The method according to the invention captures the operating parameters and sensor values of the SCR catalyst system to conclude by comparing these values or data with reference values, which the heating system has faulty behavior or not. The invention is interesting if the various heating elements of the heating system have a PTC type behavior. A characteristic PTC behavior typical of a PCT element is shown in Figure 1 which shows the heating / power time curve for a PCT element. The typical form of a normally functioning PCT element is shown as 1. The power curve 1 is in the power band 3 of the SCR catalyst system. After connection, the current increases continuously. Once a maximum of 2 is reached, the power drops again. This curve results from the fact that in the PCT element, as a cold conductor, the rise in temperature of the resistance element increases its electrical resistance so that when the intensity has reached the maximum, it decreases again. This characteristic curve 1 is used to detect deviations from this power curve within a predefined tolerance range for detecting incidents in the heating system. Using various operating and coefficient parameters, especially taking into account the battery voltage, the intensity, the reference curves and the tolerance coefficients, a higher tolerance curve 4 and a higher tolerance curve are calculated. lower tolerance curve 5. Tolerance curves 4, 5 define a tolerance band. Since the measured power curve does not move in the tolerance band, it is assumed that there is a fault. To compare the actual value or values with the reference values, it is possible to use, for example, the maximum intensity 2. If the measured maximum intensity of the current exceeds the maximum threshold 6 or is lower than the minimum threshold 7, this means that there is a fault. Figure 1 shows different cases of possible faults. If 35 before starting or connecting the PCT element or

11 heating, it detects a current or a power 8, this means that there is an external short circuit. If, when the PCT element is connected, the power increases sharply and exceeds the maximum threshold 6 as indicated by the trace 9, this means that there is a short circuit at the PCT element. If, after the PCT element is connected, power can not be measured, as indicated by the trace 10, this means that the PCT element is idling, that is to say that the electrical connection to the PCT element is cut off. The modules described hereinafter by way of example of the method according to the invention correspond to a UHC_Mon module main module as well as to three subordinate modules for monitoring different heating circuits; it is a module for monitoring a first tank heating circuit, the UHC_MonC1 module, a monitoring module for a second tank heating circuit, the UHC_MonC3 module and a monitoring module heating the pressure line and the transfer module, the UHC_MonC2 module, together in the same heating circuit. Figure 2 shows the input and output parameters of the main module, UHC_Mon module. The module 20 shown schematically has the function of releasing the various heating circuits required, (UHC_MonC1 modules, UHC_MonC2 module) UHC_MonC3 module), in the absence of defects and calculate the total current required (UHC_iTot). In addition, it is checked whether the temperature of the tank is too high. It is estimated that the tank is overheating if the measured tank temperature exceeds a predefined threshold. As an input parameter, the following values are used: - tank temperature (SCRCt1_tUTnk), - heating circuit demand (UHC_stCReq), - current intensity in the subordinate modules (UHtrPL_iSensDia, UHtrTnk2_iSensDia, UHtrTnk1_iSensDia). The reference PL denotes the heating means of the pressure line and the transfer module; Tnk1 and Tnk2 denote the two tank heating circuits. FIG. 3 shows the input and output parameters of the module controlled UHC_MonC module 1 for the monitoring of the

12 first tank heating circuit. The input parameters are as follows: - battery voltage (BattU_u), - time since the last motor shutdown (EngDa_tiEngOff), - tank temperature (SCRCt1_tUTnk), - release on the SCR monitoring side (SCRMon_stUHC), - state of the heating control (UHC_stCtl), - state of release until then of the UHC_MonC1 module, - intensity measured in the first tank heating circuit, (UHtrTnkl_iSensDia), - state of the first tank heating power stage (UHtrTnk1_stPs ). The output signals or parameters are as follows: - maximum electrical power encountered for heating (UHC_pwrTnkMaxVal), - indication that maximum power has occurred (UHC_stTnkPwrMaxEnd), - taken from a warm start (UHC_stTnkWrmStrt) . This module as well as the other subordinate modules have the function of detecting short-circuits and line breaks by means of the PCT characteristic of the heating circuits, that is to say for example in tank heaters. the heating of the pressure line and that of the transfer module. In addition, the subordinate modules may force a test mode in which the behavior of the module is tested while it is not required. In test mode, a heating scenario is described for performing the test if, for example, the heating system has not been operating for an extended period of time and if there is sufficient power to go through the test mode. For the comparison of the measured values and the reference values, the maximum measured value is preferably compared with the modeled values, in particular with the maximum modeled value 6 and the modeled minimum value 7. If the effective value exceeds the upper limit 6 , it is estimated that there is a short circuit PTC. If the value is lower

13 below the minimum value 7, it is estimated that there is a no-load run. In another measurement it is possible to check whether a current flows while the heating is off as shown in curve 8 in FIG. 1, which then makes it possible to conclude that there may be an external short circuit.

FIG. 4 shows the input and output parameters of the subordinate module 40, the UHC_MonC2 module serving to monitor the heating of the pressure line and of the heating of the transfer module, these two heating means being grouped together in a single circuit of heating. The different functions are similar to those of the parameters of the UHC_MonC 1 module. Here the input parameters are as follows: - battery voltage (BattU_u), - duration since the last cut of the motor (EngDa_tiEngOff), - ambient temperature (EnvT_t) ), - tank temperature (SCRCt1_tUTnk), - release on the SCR monitoring side (SCRMon_stUHC), - state of the heating control (UHC_stCtl), - release status until then of the UHC_MonC2 module (UHC_stMonC2), - measured intensity in the heating circuit of the pressure pipe (UHtrPL_iSensDia), - state of the power stage of the heating of the pressure pipe (UHtrPL_stPs). In addition to the short-circuit and no-load fault found in this module, as described above, a warm start (UHC_stPLWrmStrt) can be assumed. The subordinate module 50 UHC_MonC3 module shown in Figure 5 for monitoring the second tank heating circuit has the following input parameters: - battery voltage (BattU_u), - duration since the last shutdown of the engine (EngDa_tiEngOff), - tank temperature (SCRCt1_tUTnk), - release on the SCR monitoring side (SCRMon_stUHC), - state of the heating control (UHC_stCtl),

UHC_MonC3 (UHC_stMonC3) UHC_stMonC3 UHC_stMonC3 UHC_stMonC3 UHC_stMonC3 UHC_stMonC3 UHC_stMonC3 UHC_stMonC3 UHC_MonC3 Module UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MonC3 UHC_MONC3 In the case of a UHC-stTnkWrmStrt hot start, the calculation of the maximum value of the power curve as well as the modeling of the reference values and the associated tolerance bands are done in a comparable way for the UHC_MonCl, UHC_MonC2 and UHC_MonC3. 15

Claims (1)

CLAIMS 1 °) A method for monitoring a heating system of a reducing agent tank and a metering system of a system comprising at least one reservoir heating means, at least one means for heating the pressure line and at least one heating means of the transfer module, characterized in that the operating parameters and the sensor values of the system and within predefined tolerances (4, 5) are entered. It compares with reference values (1) to conclude that the heating system has failed. Method according to Claim 1, characterized in that it comprises, as a routine, at least one main UHC_Mon module (20) for the main monitoring and the release of the various heating circuits and at least one UHC_MonCx module ( 30, 40, 50) controlled to monitor the different heating circuits. 3) Method according to claim 2, characterized in that the controlled module is a UHC_MonC module 1 (30) for monitoring a first tank heating circuit, a UHC_MonC2 module (40) for monitoring the heating of the pressure line and a transfer module heater and / or UHC_MonC3 module (50) for monitoring a second tank heating circuit. 4) Method according to claim 2 or 3, characterized in that at least one of the controlled modules (30, 40, 50) equips the heating system to detect short circuits and / or breaks of conduct and the detection is based on the PTC characteristic (1) of the heating elements. 35 16 5 °) Method according to one of claims 2 to 4, characterized in that the UHC_Mon module comprises for the main monitoring and the release of the various heating circuits at least one of the following input parameters: - the demands heating circuits, - the current intensity in the UHC_MonCx modules, and - preferably the temperature of the tank. 6 °) Method according to one of claims 3 to 5, characterized in that the UHC_MonC module l (30) for monitoring the first tank heating circuit comprises at least one of the following input parameters: - voltage of battery, - time since the last engine shutdown, - tank temperature, - release of the SCR monitoring, - state of the heating control, - release status of the UHC_MonC 1 module, - current measured in the first circuit tank heating and / or - state of the first tank heating power stage. 7 °) Method according to one of claims 3 to 6, characterized in that to monitor the heating of the pressure line and the transfer module, the UHC_MonC2 module (40) has at least one of the input parameters following: - battery voltage, time since last motor shutdown, - ambient temperature, tank temperature, - SCR monitoring release, - heating control status, - UHC_MonC2 module release status, - current measured in the heating circuit of the pressure line and / or - state of the power stage of the heating of the pressure line. Method according to one of claims 3 to 7, characterized in that for monitoring the second tank heating circuit the UHC_MonC3 module (50) has at least one of the following input parameters: battery, - duration since the last engine shutdown, - tank temperature, - release of the SCR monitoring, 15 - state of the heating control, - state of release until now of the UHC_MonC3 module, - current measured in the second circuit tank heating and / or - state of the second tank heating power stage. Method according to one of Claims 2 to 8, characterized in that at least one of the UHC_MonCx modules (30, 40, 50) is controlled to force a test mode when the heating system is in operation. - 25 fage does not work. 10 °) computer program that performs all the steps of a method according to one of claims 1 to 9 when the program is executed by a computer or a control device. 30