Patent Application
20100050599
The invention relates to a method for the addition of a reducing agent in an exhaust gas line of an internal combustion engine of a motor vehicle.
It is generally known that in NOx storage catalysts, as service life increases, NOx regeneration capacity is reduced by the sulfur components that are contained in the fuel or motor oil and that are deposited in the NOx storage catalyst. To counteract such a sulfur contamination, various regeneration measures are already known for NOx storage catalysts. For example, such a desulfurization of an NOx storage catalyst can be achieved by traveling at high loads and high catalyst temperatures, which represents a so-called passive regeneration. Alternatively to this, a desulfurization can also, however, be actively carried out by an operating method of the internal combustion engine, by which the NOx storage catalyst temperature is increased in connection with an at least temporary exhaust gas enrichment, and reducing agent from the combustion engine is provided at the same time by the combustion under lean-air conditions. The currently common sulfur contents in the fuel of 10 to 50 ppm make it necessary to desulfurize the NOx storage catalyst in order to meet the applicable exhaust gas standard approximately every 500 to 5,000 km. All such known active desulfurization methods for NOx storage catalysts are based on providing elevated exhaust gas temperatures of over 550° C. in connection with a rich exhaust gas composition.
From DE 102 23 595 A1, moreover, a method is known for operating a motor vehicle with an NOx storage catalyst, in which in connection with an extensive availability of low-sulfur or sulfur-free fuels, the value of a state variable that characterizes a degree of sulfur contamination of the NOx storage catalyst is first determined. As a state variable, the NOx storage activity of the catalyst or the amount of NOx that can be stored in the catalyst during a lean phase can be selected here. In addition, as a state variable, the amount of sulfur that is stored in the catalyst during a preset time interval can also be selected. In addition, other variables can be the timing and duration of a release of a lean operating phase of the internal combustion engine that are determined based on the amount of NOx that can be stored in the catalyst during a lean phase, and the release period of the lean operating phase is selected as a state variable.
Based on the thus determined value of the state variable, an adjustment of the internal combustion engine in the operating phase is then carried out with a substoichiometric fuel-air ratio, the degree of efficiency of the internal combustion engine at any operating point between 50 km/h and 100 km/h being at most 3% worse than the same operating point without the generated state signal, in particular at an operating point that corresponds to steady, straight and level travel at an outside temperature of 20°.
In addition, a method for reactivating a nitrogen oxide storage catalyst, which has basic strontium or barium compounds on a carrier material that contains cerium oxide and, moreover, contains, with the carrier material, strontium and/or barium compounds that are formed by thermal aging, is known from DE 10 2005 034 344 A1. For regeneration, the compounds of strontium and/or barium are decomposed with the carrier material by treatment with a gas mixture that contains nitrogen dioxide, water vapor and optionally carbon dioxide at temperatures of between 300° and 500° C. An optimized regeneration of a nitrogen oxide storage catalyst is to be achieved therefrom.
The object of this invention is to make available a method and a device for the addition of a reducing agent in an exhaust gas line of an internal combustion engine of a motor vehicle, by means of which, in particular in connection with low-sulfur fuels, a reliable and fail-safe regeneration of an NOx storage catalyst of an exhaust gas line of an internal combustion engine that is optimized in the event of regeneration is possible.
According to the invention, a metering device is provided, by means of which at preset times, a preset amount of a reducing agent can be introduced into an exhaust gas line of an internal combustion engine of a motor vehicle, to create a stationary gas line connecting element that is made up of multiple parts at a defined position on the exhaust gas line and a connecting counter-element that can be connected in a detachable manner to this connecting element and that can be arranged independently of the exhaust gas line and motor vehicle and that can be arranged in particular removed from the motor vehicle. With such a multi-part design of the metering device, for service, the separate, connecting counter-element that is not carried along can preferably be connected to the exhaust gas line connecting element if the motor vehicle is parked and/or the internal combustion engine is idling, and then, for purposes of regeneration of at least one NOx storage catalyst for a preset time, a preset amount of reducing agent at a preset temperature can be introduced into the exhaust gas line. After completion of the regeneration, the connecting counter-element can again be detached from the exhaust gas line connecting element and secured at the site provided for this purpose.
This solution according to the invention is advantageous in particular in such internal combustion engines that are operated with a fuel whose sulfur content is less than or equal to 30 ppm, in particular less than or equal to 10 ppm. Also, the reducing agent is preferably a mixture of substances, with a sulfur content of less than or equal to 30 ppm, in particular less than or equal to 10 ppm.
With such a solution according to the invention, targeted desulfurization can be performed, namely independently of a street operation of a motor vehicle, in particular in connection with low-sulfur fuels during servicing of the motor vehicle at an auto repair shop or at a service facility. Thus, the often difficult and emergency servicing of engine electronics during the operation of a motor vehicle as well as other measures to be scheduled can be performed without the driver being aware of them and will therefore also not impair the driving comfort of the motor vehicle. Moreover, as a result, secondary emissions as well as changes in combustion noise can be reliably prevented.
According to another preferred configuration, the connecting counter-element can be a component of a stationary or mobile desulfurization device that is arranged at a service facility or auto repair shop. Thus, e.g., service sites can be set up at a service facility, by means of which the desulfurization and thus the regeneration of existing NOx storage catalysts can easily be performed during service.
The connecting counter-element and the exhaust gas line connecting element can especially preferably be connected by means of a quick-release fastener. This quick-release fastener can be designed especially simply to be sealed, in particular gas-tight and/or fluid-tight.
Moreover, the desulfurization device can preferably be designed with a reducing agent reservoir for a reducing agent, as well as also a control and regulating device for defined charging of the exhaust gas line with reducing agent. Thus, a reliable and fail-safe addition of reducing agent during service is possible.
According to another actual configuration, the desulfurization device has a line connection, in particular a hose line connection, between the reducing agent reservoir and the connecting counter-element, whereby the control and/or regulating device is then coupled or integrated indirectly or preferably directly into the hose line connection in the area between the connecting counter-element and the reducing agent reservoir.
The desulfurization device can also have a heating device, by means of which the reducing agent can be heated to a preset temperature. Thus, it is particularly easily ensured that the regeneration can also actually be performed effectively at the necessary temperatures.
According to an actual configuration, the exhaust gas line connecting element can be arranged in the exhaust gas line in the area between a diesel particle filter and an NOx storage catalyst, i.e., it can thus, according to a general idea, be arranged in front of at least one NOx storage catalyst in the direction of flow.
The
The single figure shows diagrammatically a design of an exhaust gas system of a motor vehicle with an internal combustion engine 1, to which an exhaust gas line 2 is connected, in which, seen in the flow direction of the exhaust gas stream, an oxidation catalyst 3, a diesel particle filter 4, an NOx storage catalyst 5, a locking catalyst 6 as well as a noise damper 7 are integrated. In this case, the catalysts or other components can have a conventional design and are not explained in more detail below.
In the area between the diesel particle filter 4 and the NOx storage catalyst 5, a connecting point 8 for reducing agents during service is provided here. At this connecting point 8, a metering device 9, which is made up of multiple parts from a stationary, gas line-side gas line connecting element 9a and a connecting counter-element 9b that can be connected detachably to the latter, is provided. As this is depicted only diagrammatically in
As is further indicated in the diagrammatic depiction of the single figure, the connecting counter-element 9b can be connected here to a reducing agent reservoir 12, which, e.g., is preferably a component of a stationary or mobile desulfurization device 13, which is indicated in broken lines in
As is further diagrammatically indicated in the single figure by the heating coil 14, the reducing agent of the desulfurization device 13 can also be preheated to be fed or added in the heated state to the exhaust gas line 2.
Moreover, a component of the desulfurization device 13 can also be a pumping device, by means of which it is ensured that the added reducing agent is added to the exhaust gas line at a specific pressure. In this connection, in particular in the area of the connecting element 9a, a nozzle device is preferably provided, by means of which a fine distribution of the added reducing agent into the exhaust gas line 2 is possible.
In principle, corresponding communication devices would also make it possible for this service point to communicate with the engine control of the respective motor vehicle during the regeneration; such communication would perform a “reset” subsequent to a successful regeneration.
In addition, sensor data, such as, for example, temperature and/or lambda values, from the engine control device could also be used for monitoring or regulating.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 045 594.6 | Sep 2008 | DE | national |
