System for storing an additive and for injecting it into engine exhaust gases

1. A system for storing an additive and for injecting the additive into exhaust gases of an internal combustion engine, the system comprising:

a tank to store the additive;

an injector and a pump to convey the additive from the tank to the injector via an injection line; and

a purge device configured to force a purge gas to flow through the entire injection line from the injector to the tank, the purge gas including engine exhaust gases.

2. The system according to claim 1 , wherein the purge device comprises:

a switch to reverse the flow of the pump.

3. The system as claimed in claim 1 , further comprising an additive return line including a pressure controller, and the pressure controller is located outside the tank when the pump is located outside the tank.

4. A method for storing an additive and for injecting the additive into an exhaust pipe of an internal combustion engine, the method comprising:

conveying an additive stored in a tank to an injector using a pump and via an injection line;

injecting the additive into the exhaust pipe using the injector; and

sporadically purging the injection line by flow of a purge gas through the entire injection line from the injector to the tank, the purge gas including engine exhaust gases.

5. The method according to claim 4 , wherein the additive is an aqueous urea solution.

6. The method according to claim 4 , wherein the engine exhaust gases are sucked into the injection line by opening the injector and by actuating a switch that has an effect of reversing a flow of the pump.

7. The method according to claim 4 , wherein the engine exhaust gases are sucked into the injection line by switching a 4/2-way valve that in a normal mode connects a point downstream of the pump to the injector, and in a purge mode, connects the injector to a point upstream of the pump.

8. The method according to claim 4 , wherein a temperature of the exhaust gases is controlled and/or regulated.

9. The method according to claim 4 , wherein, when the additive is frozen, the additive is melted before starting the pump and a temperature of the additive is maintained within a given range as long as the pump is running.

10. The system as claimed in claim 1 , further comprising an additive return line including a pressure controller, and the pressure controller is located inside the tank when the pump is located inside the tank.

11. The system according to claim 1 , wherein the purge device comprises:

a 4/2-way valve.