Method for operating a device for providing a liquid additive

1. A method for operating a device for providing a liquid additive, the method comprising the following steps:

providing a liquid additive feeding path having at least one first portion forming a heat conducting section from a heater of the device into a tank for the liquid additive and having at least one second portion with a component susceptible to freezing;

a) feeding the liquid additive along the feeding path of the device;

b) stopping the feeding of liquid additive; and

c) draining the feeding path until the at least one second portion is drained completely and stopping the draining with liquid additive maintained in the first portion.

2. The method according to claim 1 , which further comprises:

carrying out the feeding of the liquid additive along the feeding path in step a) in a feeding direction; and

carrying out the draining of the liquid additive in step c) at least predominantly counter to the feeding direction.

3. The method according to claim 2 , which further comprises feeding the liquid additive in a feeding direction of a pump and reversing the feeding direction for draining the feeding path according to step c).

4. The method according to claim 1 , which further comprises providing the at least one first portion with an enclosing area around the heater.

5. The method according to claim 1 , which further comprises providing a filter in the at least one first portion for filtering the liquid additive.

6. The method according to claim 1 , which further comprises operating a pump for a predetermined time interval for the partial draining of the feeding path in step c), and choosing the time interval to keep liquid additive in the at least one first portion.

7. The method according to claim 1 , which further comprises:

placing at least one sensor element at a point of the feeding path;

setting up the at least one sensor element for detecting if there is liquid additive at the point;

monitoring the partial draining of the feeding path in step c) by using the at least one sensor element; and

stopping the draining as soon as there is no longer any liquid additive at the point.

8. The method according to claim 7 , which further comprises providing the at least one sensor element as a pressure sensor measuring a pressure changing in dependence on a degree of filling of the feeding path.

9. The method according to claim 1 , which further comprises:

carrying out the partial draining of the feeding path in step c) by using a pump;

changing an operating parameter in dependence on a degree of filling of the feeding path with liquid additive; and

stopping the draining by the pump upon reaching a predetermined value of the operating parameter.

10. The method according to claim 9 , which further comprises:

setting the pump to a diagnostic mode at least at one predetermined point in time during the draining; and

determining the operating parameter, being dependent on the degree of filling of the feeding path, during the diagnostic mode.

11. The method according to claim 1 , which further comprises providing the feeding path with at least one siphon, and forming the at least one first portion in the siphon.

12. The method according to claim 1 , which further comprises:

providing a housing in the tank, the housing having the heater disposed therein, the housing together with the at least one first portion defining the heat conducting section.

13. The method according to claim 1 , which further comprises:

maintaining liquid additive in the first portion while the feeding of the liquid additive remains stopped during an operational stop.

14. A method for operating a device for providing a liquid additive, the method comprising the following steps:

providing a liquid additive feeding path having at least one first portion forming a heat conducting section from a heater of the device into a tank for the liquid additive and having at least one second portion with a component susceptible to freezing;

a) feeding the liquid additive along the feeding path of the device;

b) stopping the feeding of liquid additive;

c) partially draining the feeding path by maintaining the liquid additive in the at least one first portion while draining the at least one second portion; and

carrying out the partial draining of the feeding path in step c) by first draining the feeding path completely and subsequently partially filling the feeding path again with liquid additive, only until there is liquid additive in the at least one first portion and the second portion remains drained.

15. A device for providing a liquid additive, the device comprising:

a tank for the liquid additive;

a heater;

a feeding path for feeding the liquid additive along said feeding path, said feeding path having at least one first portion forming a heat conducting section from said heater into said tank, and said feeding path having at least one second portion;

a component susceptible to freezing being disposed in said at least one second portion; and

a controller being programmed to:

a) feed the liquid additive along said feeding path;

b) stop the feeding of liquid additive; and

c) drain said feeding path until said at least one second portion is drained completely and stop draining with liquid additive maintained in said first portion.

16. The device for providing a liquid additive, according to claim 15 , further comprising a housing disposed in said tank, said heater being disposed in said housing, said first portion together with said housing forming said heat conducting section from said heater into said tank.

17. The device for providing a liquid additive, according to claim 16 , further comprising a shroud surrounding said housing, said shroud and said housing defining said first portion.