FR2880064A1 - Discharge and dosing modules reciprocal adaptation method for motor vehicle, involves recording reference pressure value in control module based on pressure formed in exhaust gas duct during calibration cycle - Google Patents

Abstract

The method involves activating a dosing module (20) whereas a discharge module (10) is inactivated during starting of an exhaust gas cleaning system (1). A dosing valve (22) is opened and blowing air from a control valve (23) into a catalyst. A reference pressure value is recorded in a control module (40) based on pressure formed in an exhaust gas duct (30) during calibration cycle. An independent claim is also included for a device for reciprocal adaptation of a discharge module and a dosing module of an exhaust gas cleaning system.

Description

State of the art

  The present invention relates to a method of reciprocal adaptation of a delivery module and a metering module of an exhaust gas cleaning system comprising an exhaust gas duct and a control module, the module pump having a feed tank provided with a vent valve containing a uric acid solution supplied by a delivery pump a flow control valve and the dosing module compresses a stream of air with the aid of a pump for supplying a pressure accumulator and, through a control valve with the uric acid solution of the flow control valve to a metering valve and from there to a spraying unit installed in the gas line exhaust.

  The invention also relates to a device for reciprocating a delivery module and a dosing module for an exhaust gas cleaning system comprising an exhaust gas duct and a control module.

  In this context, given the future regulations concerning the emission of nitrogen oxides NoX from nitrogen oxides NoX of nitrogen oxides by motor vehicles, the exhaust gases must be treated appropriately. . To reduce the emissions of NOX nitrogen oxides from internal combustion engines, in particular diesel engines, the selective catalytic reduction process (SCR process) must be applied. For this, a defined amount of reducing agent consisting of urea or an aqueous solution of urea (HWL solution) is added to the exhaust gas.

  DE 10 139 142 A1 describes for example an exhaust gas cleaning system of an internal combustion engine using a SCR catalyst to reduce the emission of NOX nitrogen oxides. This catalyst reduces the nitrogen oxides contained in the exhaust gas using a reagent consisting of ammonia to arrive at nitrogen. Ammonia is provided by a hydrolysis catalyst installed upstream of the SCR catalyst from an aqueous solution of urea (HWL). The hydrolysis catalyst converts the urea contained in the HWL solution into ammonia and carbon dioxide. In a second step, ammonia reduces nitrogen oxides to nitrogen and generates water as a by-product. The precise mechanism of this reaction is described in sufficient detail in the literature and in particular in WEISSWELLER, pp. 441-449, 2000.

  Such an exhaust cleaning system usually has a modular structure; this system consists of a delivery module and a dosing module of the HWL solution. If necessary, for a production logic, it is possible to realize the delivery module and the dosing module at different locations. For example the discharge module can be built at the vehicle manufacturer and the dosing module at the engine manufacturer. This makes it difficult to compensate for manufacturing tolerances, which until now was possible only by recording an appropriate characteristic curve in the control unit. For logistical reasons, this solution requires for its implementation important means. In the current state of development, modules are provided on the ground in which the delivery module and the dosing module have been previously tuned to each other.

  OBJECTS OF THE INVENTION The object of the present invention is to develop a method for reciprocally adapting any dosing module and delivery module in a simple and economical manner.

  The invention also aims to develop a device of this type.

  DESCRIPTION AND ADVANTAGES OF THE INVENTION For this purpose, the invention relates to a method of the type defined above, characterized in that the control module contains the recording of a value of the reference pressure on the basis of the pressure developed in the exhaust pipe.

  The pressure recorded in the control module is independent of the air stream, the embodiment of the spray tube 35 and the various applications of the vehicle; it is a measure of the tolerance of the properties of the various modules, including control valves, metering valve and pressure control valve included. The deviations from the setpoint result in pressures different from the setpoint pressure for calculating an operating point for an optimal reduction of nitrogen oxides.

  When starting up the exhaust gas cleaning system, the dosing module is first activated while the discharge module is not yet activated. Thus, the pressure conditions and material flow rates depend solely on the properties of the metering module, the spray unit and the exhaust gas line without being influenced by the properties of the discharge module.

  As in another step, the metering valve is opened and the reference pressure is recorded in the control module after setting the fixed pressure conditions, this pressure also does not depend on the properties of the control module. discharge.

  To reduce the residual pressure in the feed tank which could interfere with the calibration, a variant of the method is provided in which the ventilation valve is opened during start-up and is closed again before opening the dosing valve. .

  In the further course of the operation of the exhaust gas cleaning system, it is preferably an embodiment in which the adaptation of the delivery module and the dosing module is made as appropriate and / or in intervals. defined in a cyclic manner. If necessary, a new calibration, if necessary, may be necessary if the part comprising the sensor with exhaust gas detection detects an increased content of nitrogen oxide. This ensures a long-lasting and safe reduction of the nitrogen oxides in the exhaust gas in the continuous operating mode. The aging of the components can thus be compensated to avoid any drift of the optimum operating point.

  A process variant provides for the reciprocal adaptation of a delivery module and a metering module of an exhaust gas cleaning system comprising a control module by forming a characteristic quantity or a respective characteristic curve for the discharge module and the dosing module and apply this magnitude or characteristic curve in the form of a machine-readable code on the respective module. The individual properties of the modules, for example those related to manufacturing tolerances, can be measured and the modules can be suitably characterized. During start-up, the method provides for the reading of the machine-readable code and its recording in the control module, for example in a non-volatile memory (EEPROM memory or similar memory). Using the code thus recorded, we can then calculate the best operating points for the various valves and valves.

  The invention also relates to a device for implementing such a method, this device being characterized in that a reference pressure resting on the basis of the pressure formed in the exhaust gas pipe during a Calibration cycle is saved in the control module. The device thus allows the calculation of the optimum operating point and thus ensures the optimal adaptation of the delivery module and the dosing module.

  The preferred embodiment of the device is characterized in that the control module executes the method in the form of a circuit and / or a program. The process flow can be integrated as a subroutine in a particularly simple manner in the control or management model or, in a variant, in a subordinate motor control program. The necessary modifications in the course of the process to further optimize the nitrogen oxide values contained in the exhaust gas can be achieved in a particularly fast manner.

  The present invention will be described below in more detail with the aid of an exemplary embodiment shown in the accompanying FIGURE which is a schematic view of an exhaust gas cleaning system. .

Description of the embodiment

  The single figure shows a delivery module 10 and a metering module 20 of an exhaust gas cleaning system according to the state of the art comprising an exhaust gas duct 30 and a control module 40.

  The delivery module 10 consists of a supply tank 11 provided with an air evacuation valve 11.1; the reservoir contains uric acid solution 12 (HWL solution). This solution is supplied to a metering valve 22 by a discharge pump 13. The flow control valve 14 connected to the discharge side of the discharge pump 13 opens while the system pressure is high and then returns the HWL solution. to the feed tank 11. The dosing module 20 compresses a stream of air 26 with a pump 25, a pressure accumulator 24 to send it through a regulating valve 23 with the d solution. Uric acid supplied by the discharge pump 13 to a metering valve 22. From there, the air / solution mixture HWL is introduced into the spraying unit 21 fitted to the exhaust gas line 30. Exhaust 30 receives an exhaust gas stream 31 in a first chamber of an oxidation catalyst 32. Next, the air / HWL solution mixture is sprayed into the exhaust gas stream 31 by the spraying unit. 21. The decomposition reaction of oxy Nitrogen then occurs in a second chamber constituted by the SCR catalyst 33. A pressure sensor 34 installed at the SCR catalyst measures the pressure and transmits the value to the control module 40.

  The reciprocal adaptation method of the delivery module 10 and the metering module 20 provides for recording in the control module 40 the value of a reference pressure based on the pressure that develops in the exhaust pipe. 30. For this purpose, when the exhaust gas cleaning system 1 is started up, the dosing module 20 is activated first by turning on the pump 25. The delivery pump 13 of the pump module 25 10 is not activated. This permits the establishment of a pressure in the pressure accumulator 24. The valve 13 sets predefined dosing and pressure conditions for the metering valve 22 downstream.

  In another step, the metering valve 22 is opened and the air of the regulating valve 23 is blown off by the spraying unit 21 into the SCR catalyst 33. The pressure in the SCR catalyst 33 is measured by the With the aid of the pressure sensor 34. After establishing fixed pressure conditions at the pressure sensor 34, the pressure is recorded as a reference pressure in the control module 40.

  After this calibration, the discharge module 10 is connected by activating the discharge pump 13 so that the exhaust gas cleaning system 1 goes into normal operating mode.

  A development variant provides for starting before the opening of the valve and its reclosing before the opening of the metering valve 22 so as to eliminate the residual pressure in the feed tank 11 before the calibration operation.

  For further operation of the exhaust gas cleaning system 1, the delivery module 10 and the dosing module 20 are adapted if necessary and / or in cyclically defined time intervals.

  A new calibration may, for example, become necessary if a sensor detects in the exhaust gas vein too high a nitrogen oxide content. This makes it possible to permanently and safely reduce the nitrogen oxides contained in the exhaust gas.

  The device provides for recording in the control module 40 the value of the reference pressure in a memory based on the pressure formed in the exhaust gas duct 30. The method as described above to adapt the delivery module 10 and the dosing module 20 is preferably made in the control module 40 in the form of a program and / or a circuit. Alternatively, the process flow can also be memorized in the usual manner in the motor control.

  A process variant provides for the reciprocal adaptation of the delivery module 10 and the metering module 20 of the exhaust gas cleaning system 1, to form a characteristic quantity or a respective characteristic curve for the delivery module 10 and the assay module 20 and apply them on each module in the form of a machine-readable code. The individual properties of the modules can, for example, measure manufacturing tolerances and suitably characterize the modules.

  During start-up, the method provides for the reading of machine-readable bar codes and their recording in the control module, for example consisting of a non-volatile memory (EEPROM memory or similar memory). With the help of the registered code, the optimum operating points of the various valves can be calculated.

  The method as described and the corresponding device allow reciprocal adaptation of any dosing and discharge modules in a simple and economical manner. This allows an optimal reduction of nitrogen oxides. It is furthermore advantageous that balancing is not carried out simply during the first start-up of the internal combustion engine but also after balancing, for example to compensate for the drift of aging.

Claims (1)

  1) Method for reciprocally adapting a delivery module (10) and a metering module (20) of an exhaust gas cleaning system (1) having an exhaust gas line (30) ) and a control module (40), the delivery module (10) having a supply tank (11) provided with a ventilation valve (11.1) containing a uric acid solution (12) provided by a pump a flow control valve (14) and the dosing module (20) compress an air stream (26) with a pump (25) to supply a pressure accumulator ( 24) and, through a control valve (23), a metering valve (22) together with the uric acid solution (12) through the flow control valve (14) and from there, the vein arrives at a spraying unit (21) installed in the exhaust gas line (30), characterized in that the control module (40) contains the recording of a value of the pressure reference point on the basis of the developed pressure in the exhaust pipe (30).   characterized in that, when the exhaust gas cleaning system (1) is started, the dosing module (20) is activated first, while the delivery module (10) is not activated yet. .   3) Method for mutual adaptation of a module according to claim 1, characterized in that in another step, the metering valve (22) is opened and the reference pressure is recorded after adjustment of the fixed pressure conditions in the control module (40).   4) Method of mutual adaptation of a module according to claim 1, 2) Method of reciprocal adaptation of a module according to claim 1 characterized in that one opens the ventilation valve (11.1) when start up and close it before opening the dosing valve (22).   5) Method of reciprocal adaptation of a module according to claim 1, characterized in that in the following operation of the exhaust gas cleaning system (1) where appropriate and / or cyclically, it adapts the discharge module (10) and the dosing module (20).   6) Device for reciprocating a delivery module (10) and a dosing module (20) in an exhaust gas cleaning system (1) having an exhaust gas line (30) and a control module (40) characterized in that a reference pressure on the basis of the pressure formed in the exhaust gas line (30) during a calibration cycle is recorded in the control module (40).   7) Reciprocal adaptation device of a module according to claim 6, characterized in that the program is developed in the control module (40) under the   form of a process according to claims 1 to 5.   8) A method of reciprocally adapting a delivery module (10) and a dosing module (20) in an exhaust gas cleaning system (1) comprising a control module (40) for setting implementation of the device according to any one of claims 6 and 7, characterized in that for the delivery module (10) and for the dosing module (20) a characteristic quantity or a characteristic curve is formed 9) Reciprocal adaptation method of a module according to claim 8, characterized in that during startup, the machine-readable code is read and stored in the control module (40).