Method for operating a dosing apparatus and motor vehicle having a dosing apparatus

Abstract

A method for operating a dosing apparatus for providing a liquid additive includes providing the dosing apparatus with at least one pump for pumping the additive from a tank into a pressure accumulator, a dosing valve for providing additive present in the pressure accumulator in a dosed manner, and a return valve through which additive present in the pressure accumulator can be led back into the tank. A dosing demand is established, subsequently the pump is activated to build up a pressure in the pressure accumulator, then the pressure in the pressure accumulator is set to a desired metering pressure, and thereafter the liquid additive is dispensed by the dosing valve. A motor vehicle having a dosing apparatus is also provided.

1 . A method for operating a dosing apparatus for providing a liquid additive, the method comprising the following steps:
 providing the dosing apparatus with at least one pump configured to deliver the additive from a tank into a pressure accumulator, a dosing valve configured to provide additive present in the pressure accumulator in a dosed manner, and a return valve configured to discharge the additive present in the pressure accumulator back into the tank;   a) identifying a dosing demand;   b) activating the at least one pump to build up a pressure in the pressure accumulator;   c) setting the pressure in the pressure accumulator to a dosing pressure; and   d) dispensing the additive through the dosing valve.   
     
     
         2 . The method according to  claim 1 , which further comprises performing steps a) to d) repeatedly in a loop during operation of the dosing apparatus. 
     
     
         3 . The method according to  claim 1 , which further comprises opening the return valve for setting the pressure in step c). 
     
     
         4 . The method according to  claim 1 , which further comprises performing at least steps c) and d) at least partially in parallel with one another. 
     
     
         5 . The method according to  claim 1 , which further comprises performing the following step after step d):
 e) lowering the pressure in the pressure accumulator.   
     
     
         6 . The method according to  claim 1 , which further comprises providing the return valve as a passively opening valve having an opening pressure corresponding to the dosing pressure. 
     
     
         7 . The method according to  claim 1 , which further comprises:
 providing the return valve as an actively opening valve having a valve drive;   providing a pressure sensor on the pressure accumulator; and   controlling the return valve using the valve drive and a controller to set the pressure in the pressure accumulator to the dosing pressure in step c).   
     
     
         8 . The method according to  claim 1 , which further comprises providing the pump with a pump chamber and at least one pump valve predefining a delivery direction. 
     
     
         9 . A motor vehicle, comprising:
 an internal combustion engine;   an exhaust-gas treatment apparatus configured to purify exhaust gases from said internal combustion engine;   a tank configured to store a liquid additive; and   a dosing apparatus configured to feed the additive from said tank to said exhaust-gas treatment apparatus;   said dosing apparatus including a pressure accumulator, at least one pump configured to deliver the additive from said tank into said pressure accumulator, a dosing valve configured to provide additive present in said pressure accumulator in a dosed manner, and a return valve configured to discharge the additive present in said pressure accumulator back into the tank; and   said dosing apparatus configured to:
 a) identify a dosing demand; 
 b) activate said at least one pump to build up a pressure in said pressure accumulator; 
 c) set the pressure in said pressure accumulator to a dosing pressure; and 
 d) dispense the additive through said dosing valve.