Abstract: In an internal-combustion engine exhaust gas system, a storage tank stores the reducing agent, a supply pipe connects the storage tank to a metering unit which introduces the reducing agent into the exhaust gas system. A pump mechanism within the supply pipe conveys the reducing agent. A pressure sensor detects the pressure in the supply pipe downstream of the pump, and a pressure-releasing device has a return pipe connected to the storage tank and comes off the supply pipe. A first valve system is arranged in the supply pipe. A section of the return pipe is located at a higher level than the return pipe to form a storage volume for air present in the supply pipe. A second valve system is arranged in the supply pipe to create, when the second valve system is closed, a storage volume for pressurized reducing agent by way of this pipe branch.

Abstract: In a method for adapting the reducing agent feed in an exhaust gas aftertreatment system having an SCR catalyst for removing nitrogen oxides from the exhaust gas of an internal combustion engine and at least one reducing agent feed device, the minimum opening time of the reducing agent feed device is determined during operation and while suspending nitrogen emission, carrying out the following steps: a) the opening time of the reducing agent feed device is gradually prolonged until b) a reducing agent-sensitive sensor in the exhaust gas aftertreatment system detects a reducing agent signal. An exhaust gas aftertreatment system is designed accordingly for carrying out the method and a device is designed for controlling an exhaust gas aftertreatment system.

Abstract: A method for determining the state of a reducing agent in a reducing agent tank. The reducing agent is used for exhaust gas after-treatment of exhaust gas generated by an internal combustion engine. To inform the control unit of an internal combustion engine regarding the quality of the reducing agent in the reducing agent tank the method includes determining and recording the filling and extracting volumes of the reducing agent from the reducing agent tank by a fill level sensor, determining and recording the temperature of the reducing agent in the reducing agent tank by at least one temperature sensor over the entire service life of the exhaust gas after-treatment unit, determining and recording the distribution velocity of ultrasonic waves in the reducing agent by an ultrasonic transmitter and ultrasonic receiver, determining the state of a reducing agent from the parameters.

Abstract: A device (4) for introducing a liquid reducing agent (5) into an exhaust gas (6) of a combustion system (2) has a reservoir (20), a discharge element (23) for discharging the liquid reducing agent (5) into the exhaust gas (6), a feed line (22), interposed between the reservoir (20) and the discharge element (23), a delivery element (26) arranged in the feed line (22) for delivering the liquid reducing agent (5) in a direction of delivery (29) from the reservoir (20) to the discharge element (23). The feed line (22) is associated with a controllable venting element (34) upstream of the delivery element (26), the discharge element (23) is connected to the reservoir (20) via a return line (32) and a controllable shut-off element (36) is arranged in the return line (32).

Abstract: An apparatus for determining a tank fill level includes at least one cap, an extraction pipe which extends through the cap and at least partially has an electrically conductive material, a jacket pipe disposed around the extraction pipe and at least partially has an electrically conductive material, and a measuring unit forming a first electrode with the extraction pipe and a second electrode with the jacket pipe. A tank for a urea/water solution is also provided, in which the apparatus is used as a quality sensor and/or a fill level sensor. A motor vehicle having a tank is also provided.

Abstract: A method for operating a device for providing a liquid reactant to an exhaust gas system. The device includes at least one tank and an injection nozzle connected to one another by a line. The line has a pump for feeding the reactant. A controllable return line connected between the pump and the injection nozzle leads from the line to the tank. A controller controls operation of the injection nozzle, the pump and the return line, so that the reactant is only circulated intermittently through the controllable return line. A motor vehicle using the method is also provided.

Abstract: In an internal-combustion engine exhaust gas system, a storage tank stores the reducing agent, a supply pipe connects the storage tank to a metering unit which introduces the reducing agent into the exhaust gas system. A pump mechanism within the supply pipe conveys the reducing agent. A pressure sensor detects the pressure in the supply pipe downstream of the pump, and a pressure-releasing device has a return pipe connected to the storage tank and comes off the supply pipe. A first valve system is arranged in the supply pipe. A section of the return pipe is located at a higher level than the return pipe to form a storage volume for air present in the supply pipe. A second valve system is arranged in the supply pipe to create, when the second valve system is closed, a storage volume for pressurized reducing agent by way of this pipe branch.

Abstract: In a method for adapting the reducing agent feed in an exhaust gas aftertreatment system having an SCR catalyst for removing nitrogen oxides from the exhaust gas of an internal combustion engine and at least one reducing agent feed device, the minimum opening time of the reducing agent feed device is determined during operation and while suspending nitrogen emission, carrying out the following steps: a) the opening time of the reducing agent feed device is gradually prolonged until b) a reducing agent-sensitive sensor in the exhaust gas aftertreatment system detects a reducing agent signal. An exhaust gas aftertreatment system is designed accordingly for carrying out the method and a device is designed for controlling an exhaust gas aftertreatment system.

Abstract: A device (4) for introducing a liquid reducing agent (5) into an exhaust gas (6) of a combustion system (2) has a reservoir (20), a discharge element (23) for discharging the liquid reducing agent (5) into the exhaust gas (6), a feed line (22), interposed between the reservoir (20) and the discharge element (23), a delivery element (26) arranged in the feed line (22) for delivering the liquid reducing agent (5) in a direction of delivery (29) from the reservoir (20) to the discharge element (23). The feed line (22) is associated with a controllable venting element (34) upstream of the delivery element (26), the discharge element (23) is connected to the reservoir (20) via a return line (32) and a controllable shut-off element (36) is arranged in the return line (32).