Method of controlling operational venting of a plastics fuel tank and plastics fuel tank

Abstract

The invention relates to a method of controlling operational venting of a plastics fuel tank, in which the volume of the plastics fuel tank is kept within a predetermined differential pressure range relative to ambient pressure by means of at least one operational venting valve with pressure maintaining function, at least an upper limit of the differential pressure range defining a maximum admissible overpressure being varied as a function of the ambient temperature.

1 . Method of controlling operational venting of a plastics fuel tank, in which the volume of the plastics fuel tank is kept within a predetermined differential pressure range relative to ambient pressure by means of at least one operational venting valve with pressure maintaining function, at least an upper limit of the differential pressure range defining a maximum admissible overpressure being varied as a function of the ambient temperature. 
   
   
       2 . Method according to  claim 1 , characterized in that the upper limit of the differential pressure range is lowered if the ambient temperature exceeds at least a predetermined upper limit, and the upper limit of the differential pressure range is raised if the ambient temperature falls below at least a predetermined lower limit. 
   
   
       3 . Method according to  claim 1 , characterized by the use of at least one operational venting valve with a temperature-dependent opening and closing characteristic. 
   
   
       4 . Method according to  claim 1 , characterized in that the admissible differential pressure (AT) may amount to between 0 and 500 mbar. 
   
   
       5 . Method according to  claim 2 , characterized in that a temperature of 70° C. is selected as the predetermined upper limit for the ambient temperature. 
   
   
       6 . Plastics fuel tank for motor vehicles with means for inward and outward venting during fuel discharge (operational venting), having at least one operational venting valve between at least one operational venting point and a fuel vapor filter, the operational venting valve taking the form of a pressure maintaining valve, characterized in that the operational venting valve has an ambient temperature-dependent switching characteristic. 
   
   
       7 . Plastics fuel tank according to  claim 6 , characterized in that the operational venting valve takes the form of an automatically regulating valve operating without current. 
   
   
       8 . Plastics fuel tank according to  claim 6 , characterized in that the operational venting valve comprises at least one valve body held in a closed position under spring loading, at least one valve spring having a temperature-dependent spring constant. 
   
   
       9 . Plastics fuel tank according to  claim 6 , characterized in that the valve spring takes the form of a bimetallic spring. 
   
   
       10 . Plastics fuel tank according to  claim 6 , characterized in that the valve spring consists of a shape memory alloy. 
   
   
       11 . Plastics fuel tank for a hybrid motor vehicle according to  claim 1 .