Delivery device for delivering a liquid additive out of a tank, method therefor and motor vehicle having a delivery device

Abstract

A delivery device for delivering a liquid additive out of a tank to an exhaust-gas treatment device includes a delivery duct with an overall volume and a pump disposed in the delivery duct. The delivery duct has a flexible wall portion, downstream of the pump in a delivery direction, with an outer side of the flexible wall portion situated opposite the delivery duct and bearing against a stop when a pressure in the delivery duct lies in a predefined operating pressure range. A spring element which is disposed on the outer side is constructed to deform the flexible wall portion in such a way that the overall volume is reduced in size when the pressure in the delivery duct is lower than a threshold pressure. A method for compensating a formation of ice in a delivery device and a motor vehicle having a delivery device are also provided.

1 . A delivery device for delivering a liquid additive out of a tank to an exhaust-gas treatment device, the delivery device comprising:
 a delivery duct having an overall volume;   a flexible wall portion with an outer side disposed opposite said delivery duct;   a stop against which said outer side bears when a pressure in said delivery duct lies in a predefined operating pressure range;   a pump disposed in said delivery duct upstream of said flexible wall portion in a liquid additive delivery direction; and   a spring element disposed on said outer side of said flexible wall portion and configured to deform said flexible wall portion to reduce a size of said overall volume of said delivery duct when a pressure in said delivery duct is lower than a threshold pressure.   
     
     
         2 . The delivery device according to  claim 1 , which further comprises a return line branching off from said delivery duct downstream of said pump in said delivery direction, and a return valve configured to close off said return line. 
     
     
         3 . The delivery device according to  claim 1 , which further comprises at least one force sensor disposed on said stop and configured to measure a force exerted on said stop by said flexible wall portion to determine a pressure in said delivery duct. 
     
     
         4 . The delivery device according to  claim 1 , wherein said pump has a pump outlet, said delivery duct has a chamber downstream of said pump outlet in said delivery direction, said pump outlet opens into said chamber, and said flexible wall portion is disposed on said chamber opposite said pump outlet. 
     
     
         5 . The delivery device according to  claim 1 , wherein said stop has a receptacle configured to accommodate said spring element when said flexible wall portion bears against said stop. 
     
     
         6 . The delivery device according to  claim 1 , wherein said flexible wall portion has a surface area, and said spring element exerts a spring force on said flexible wall portion corresponding to a pressure of 0.2 to 1.0 bar in relation to said surface area of said flexible wall portion when said flexible wall portion bears against said stop. 
     
     
         7 . A method for compensating a formation of ice in a delivery device having a delivery duct with an overall volume at least partially filled with liquid additive, the method comprising the following steps:
 providing a pump in the delivery device;   providing a return line with a return valve between the delivery duct and a tank for the liquid additive;   a) stopping operation of the pump;   b) opening the return valve of the return line producing a connection between the delivery duct and the tank;   c) actively reducing a size of the overall volume filled with the liquid additive;   d) discharging the liquid additive through the return valve into the tank; and   e) passively increasing the overall volume as the liquid additive in the delivery duct freezes.   
     
     
         8 . The method according to  claim 7 , which further comprises carrying out step c) by pressing a spring against a flexible wall portion into a chamber of the delivery duct. 
     
     
         9 . A motor vehicle, comprising:
 an internal combustion engine;   an exhaust-gas treatment device for purification of exhaust gases of said internal combustion engine;   a tank for a liquid additive; and   a delivery device according to  claim 1  configured to deliver liquid additive from said tank to said exhaust-gas treatment device.