Patent ID: 7393187

Claim:
A diaphragm pump for delivering liquid reducing agent to an exhaust-gas aftertreatment installation of an internal combustion engine, comprising: a pump casing having a base and defining an inlet passage and an outlet passage; a central support body disposed in said casing; a spring disposed in said casing and imparting a force against said central support body; a pump diaphragm disposed in said casing to define a reducing agent chamber thereabove with respect to said base and having: two limit positions; a first side secured to said pump casing; and a second side secured to said central support body; an electromagnet disposed at said base and operatively connected to said pump diaphragm to move said pump diaphragm to and fro with said central support body between said limit positions counter to said force of said spring upon actuation of said electromagnet; a non-return inlet valve fluidically connected to said inlet passage for supplying reducing agent to said reducing agent chamber; a non-return outlet valve fluidically connected to said outlet passage for discharging the reducing agent; and a pressure sensor connected to said pump casing and having a pressure sensor diaphragm, said pressure sensor diaphragm sensing a pressure of the reducing agent in said pump casing above said pump diaphragm and being disposed to have said pump diaphragm absorb an increase in volume of the reducing agent when the reducing agent freezes inside said reducing agent chamber by said pump diaphragm deviating counter to said force of said spring; said pressure sensor and said central support body defining a gap therebetween, said gap serving as a flow connection between said inlet passage and said outlet passage.