METHOD FOR DETERMINING REDUCING AGENT SLIPPAGE AND MOTOR VEHICLE EMPLOYING THE METHOD

摘要

A method for determining reducing agent slippage from an exhaust-gas treatment device includes determining a difference between sensor signals of a second nitrogen oxide sensor and of a device for determining a nitrogen oxide compound quantity upstream of an SCR catalytic converter in an exhaust-gas flow direction; determining a controlling deviation from the difference and a target value of a controlling element; determining a gradient of an integral controlling component; and identifying reducing agent slippage if the controlling deviation exceeds a first threshold value and the gradient exceeds a second threshold value. The method and a corresponding device make it possible to reliably identify reducing agent slippage so that a very fast controlling element can be used.

主权项

1. A method for determining reducing agent slippage from an exhaust-gas treatment device, the method comprising the following steps:
providing the exhaust-gas treatment device with: an SCR catalytic converter; a reducing agent metering-in location disposed upstream of the SCR catalytic converter in an exhaust-gas flow direction; a device configured to determine a nitrogen oxide compound quantity upstream of the SCR catalytic converter in the exhaust-gas flow direction and configured to emit a sensor signal; and a second nitrogen oxide sensor disposed downstream of the SCR catalytic converter in the exhaust-gas flow direction and emitting a sensor signal; the device for determining a nitrogen oxide compound quantity and the second nitrogen oxide sensor not distinguishing between reducing agent and nitrogen oxide compounds; regulating a quantity of reducing agent metered into the exhaust-gas treatment device by using a controlling element having an integral controlling component and a target value; a) determining a difference between the sensor signals of the second nitrogen oxide sensor and the device for determining a nitrogen oxide compound quantity; b) determining a controlling deviation from the difference and the target value of the controlling element; c) determining a gradient of the integral controlling component; and d) identifying reducing agent slippage if the controlling deviation exceeds a first threshold value and the gradient exceeds a second threshold value.