Method for metering a reducing agent into an exhaust-gas treatment device, exhaust-gas treatment device and motor vehicle

摘要

A method for metering reducing agent to an exhaust gas treatment device having a feed point and an SCR catalytic converter converting nitrogen oxide compounds in the exhaust gas, includes at least: a) calculating the following target conversion rates indicating what fraction of the nitrogen oxide compounds in the exhaust gas can be converted by the catalytic converter: a first rate determined from the power output of an internal combustion engine; a second rate determined from the mass flow of nitrogen oxide compounds in purified exhaust gas; and a third rate determined from a ratio of quantities of nitrogen oxide compounds upstream and downstream of the catalytic converter; b) selecting the lowest rate; c) determining the dosing quantity of reducing agent for the selected rate; and d) dosing the determined dosing quantity into the exhaust gas treatment device. An exhaust-gas treatment device and a motor vehicle are also provided.

主权项

1. A method for metering a reducing agent into an exhaust-gas treatment device having a feed point and an SCR catalytic converter for the conversion of nitrogen oxide compounds in exhaust gas from a connected internal combustion engine, the method comprising the following steps:
a) calculating the following target conversion rates indicating what fraction of the nitrogen oxide compounds present in the exhaust gas can be converted by the SCR catalytic converter:
a.1) a first target conversion rate determined from a power output of the connected internal combustion engine;a.2) a second target conversion rate determined from a mass flow of nitrogen oxide compounds in purified exhaust gases; anda.3) a third target conversion rate determined from a ratio between a quantity of nitrogen oxide compounds upstream of the SCR catalytic converter and a quantity of nitrogen oxide compounds downstream of the SCR catalytic converter; b) selecting the lowest target conversion rate; c) determining a dosing quantity of reducing agent using the selected target conversion rate; and d) dosing the determined dosing quantity into the exhaust-gas treatment device.