Diesel exhaust fluid control system

Abstract

An engine has an exhaust gas system and a reductant delivery system. The reductant delivery system includes a pump which pumps reductant from a tank an injector which injects reductant into the exhaust gas, and a heater for heating the reductant in the tank. A control system includes an ECU which controls the pump, the injector and the heater as a function of sensed temperatures. The control system includes an idle state, a defrost state, a recirculation state and a heating state.

We claim: 
     
         1 . In an engine having an exhaust gas system and a reductant delivery system, the reductant delivery system having a pump for supplying reductant from a reductant tank to an injector which injects the reductant into the exhaust gas and a heater for heating the reductant in the tank, a control system comprising:
 a reductant temperature sensor for sensing a temperature of the reductant; and   an electronic control unit (ECU) receiving signals the a reductant temperature sensor, the ECU controlling the pump, the injector and the heater as a function of the sensed reductant temperature.   
     
     
         2 . The control system of  claim 1 , wherein:
 the ECU turns on the heater to defrost the reductant if the sensed reductant temperature is below a first reductant temperature threshold.   
     
     
         3 . The control system of  claim 2 , wherein:
 the ECU turns off the heater if the sensed reductant temperature is above a second reductant defrost threshold.   
     
     
         4 . The control system of  claim 2 , wherein:
 the ECU maintains the injector in a disabled state if the sensed reductant temperature remains below a first reductant defrost threshold for at least a certain time period.   
     
     
         5 . The control system of  claim 4 , wherein:
 the ECU generates a tank insufficient heating flag if the sensed reductant temperature remains below a first reductant defrost threshold for at least a certain time period.   
     
     
         6 . The control system of  claim 1 , wherein:
 after the heater is turned on, the ECU unit keeps the heater  130  on until the reductant temperature stays above a threshold temperature for at least a certain time period.   
     
     
         7 . The control system of  claim 1 , wherein:
 the ECU receives an engine coolant temperature signal from an engine coolant temperature sensor; and   after the ECU determines that the reductant tank should be defrosted, the ECU turns on the heater only after the coolant temperature is higher than a threshold coolant temperature.   
     
     
         8 . The control system of  claim 1 , wherein:
 before turning off the heater, and while the injector is turned off, the ECU keeps the pump on for at least a certain duration to cause recirculation of the reductant.   
     
     
         9 . The control system of  claim 1 , further comprising:
 a coolant temperature sensor for sensing a temperature of engine coolant, the ECU receiving signals from the coolant temperature sensor, and the ECU turning the heater on only when the sensed coolant temperature exceeds a coolant temperature threshold.   
     
     
         10 . The control system of  claim 1 , wherein:
 the ECU controls turning on and off of the heater, and the ECU controls the pump to recirculate the reductant to enhance thawing of the tank.   
     
     
         11 . In an engine having an exhaust gas system and a reductant delivery system, the reductant delivery system having a pump for supplying reductant from a reductant tank to an injector which injects the reductant into the exhaust gas and a heater for heating the reductant in the tank, the heater being heated by engine coolant, a control system comprising:
 a reductant temperature sensor for sensing a temperature of the reductant; and   an electronic control unit (ECU) receiving signals from the reductant temperature sensor, the ECU controlling the pump, the injector and the heater as a function of the sensed reductant temperature.   
     
     
         12 . The control system of  claim 11 , wherein:
 a coolant temperature sensor senses a temperature of engine coolant; and   the ECU receives signals from the coolant temperature sensor, the ECU turning the heater on only when the sensed coolant temperature exceeds a coolant temperature threshold.   
     
     
         13 . The control system of  claim 11 , wherein:
 the ECU generates an excessive heating error flag if the sensed reductant temperature is above an upper reductant temperature threshold.   
     
     
         14 . The control system of  claim 11 , wherein:
 the ECU controls turning on and off of the heater, and the ECU controls the pump to recirculate the reductant to enhance thawing of the tank.   
     
     
         15 . The control system of  claim 1 , wherein:
 the ECU generates an excessive heating error flag if the sensed reductant temperature is above an upper reductant temperature threshold.