System and Method for Purging Reductant in a Reductant Dosing System

Abstract

A reductant supply system includes a pump having a suction side and a discharge side, and a tank that holds a reductant therein. A reductant supply passageway extends from the tank to the suction side of the pump so as to supply the reductant from the tank to the pump. Further, a reductant discharge passageway extends from the discharge side of the pump and is configured to supply the reductant to a reductant injection assembly that injects the reductant into an exhaust stream of an engine. The system further includes purge componentry that connects the reductant supply passageway to an ambient air source during a purging operation such that the reductant supply system draws air from the air source sequentially through the purge passageway, the reductant supply passageway, and the pump assembly to purge at least the reductant supply passageway and the pump assembly during the purging operation.

We claim: 
     
         1 . A reductant supply system, comprising:
 a tank defining a cavity, the cavity configured to hold a reductant;   a pump assembly having a suction side that is fluidly coupled to the tank, and having a suction side that is configured to fluidly couple to a reductant injection assembly, the reductant injection assembly configured to inject the reductant into an exhaust stream of an engine;   a reductant supply passageway that extends from the tank to the suction side of the pump assembly so as to fluidly couple the tank to the pump assembly; and   a purge passageway connected to the reductant supply passageway between an inlet of the reductant supply passageway and the pump assembly, the purge passageway configured to selectively couple the pump assembly to an ambient air source during a purging operation such that the pump assembly is configured to draw air from the ambient air source through both the reductant supply passageway and the pump assembly during the purging operation to purge the reductant from the reductant supply passageway and the pump assembly.   
     
     
         2 . The reductant supply system of  claim 1 , wherein the purge passageway includes a valve that selectively couples the reductant supply passageway to the ambient air source during the purging operation, wherein the ambient air source is an environment outside of the tank. 
     
     
         3 . The reductant supply system of  claim 1 , further comprising a reductant return passageway that is selectively configurable to return reductant from the suction side of the pump assembly back to the tank during the purge operation. 
     
     
         4 . The reductant supply system of  claim 3 , further comprising a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, wherein the reductant return passageway is selectively connectable to the reductant discharge passageway between the pump assembly and the reductant injection assembly. 
     
     
         5 . The reductant supply system of  claim 1 , comprising a cabinet that houses the tank, the pump assembly, the reductant supply passageway, and the purge passageway. 
     
     
         6 . The reductant supply system of  claim 5 , wherein the cabinet further houses a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, and the reductant discharge passageway includes a port that extends through a wall of the cabinet so as to removably couple the reductant discharge passageway to the reductant injection assembly. 
     
     
         7 . The reductant supply system of  claim 5 , further comprising a reductant replenishment passageway configured to removably couple the tank to a second tank that is spaced from the cabinet so as to replenish the reductant in the tank. 
     
     
         8 . The reductant supply system of  claim 1 , further comprising a compressed gas passageway configured to selectively connect a compressed gas source to the reductant injection assembly. 
     
     
         9 . A reductant supply system comprising a reductant dosing cabinet, the reductant dosing cabinet comprising:
 a tank that defines a cavity, the cavity configured to hold a reductant;   a pump assembly having a suction side that is fluidly coupled to the tank and a suction side that is configured to fluidly couple to a reductant injection assembly that injects the reductant into an exhaust stream of an engine;   a reductant replenishment passageway configured to fluidly couple the tank to a reductant replenishment assembly so as to replenish the reductant in the tank, wherein the reductant replenishment assembly is spaced from, and external to, the reductant dosing cabinet; and   a purge passageway configured to selectively couple the suction side of the pump assembly to the reductant replenishment assembly during a purge operation so as to return the reductant from both the tank and the pump assembly to the reductant replenishment assembly during the purge operation.   
     
     
         10 . The reductant supply system of  claim 9 , wherein the reductant dosing cabinet includes a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, and the reductant dosing cabinet includes at least one valve that is selectively configurable to supply the reductant to the reductant injection assembly during a dosing operation and divert the reductant to the purge passageway during the purge operation. 
     
     
         11 . The reductant supply system of  claim 9 , wherein the reductant replenishment passageway includes a port that extends through a wall of the cabinet so as to removably couple the reductant replenishment assembly to the tank. 
     
     
         12 . The reductant supply system of  claim 11 , wherein the reductant replenishment assembly includes a second tank, spaced from the reductant dosing cabinet, the second tank defining a second cavity that has a maximum volume configured to hold the reductant, wherein the maximum volume of the second tank is greater than a maximum volume of the tank. 
     
     
         13 . The reductant supply system of  claim 12 , wherein the reductant replenishment assembly includes a pump that is configured to flow the reductant from the second tank to the tank. 
     
     
         14 . The reductant supply system of  claim 9 , wherein the reductant dosing cabinet further comprises a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, and the reductant discharge passageway includes a port that extends through a wall of the reductant dosing cabinet so as to removably couple the reductant discharge passageway to the reductant injection assembly. 
     
     
         15 . The reductant supply system of  claim 9 , further comprising a compressed gas passageway configured to fluidly couple a compressed gas source to the reductant injection assembly. 
     
     
         16 . A method of purging reductant from a reductant dosing cabinet, the method comprising steps of:
 coupling the reductant dosing cabinet to a reductant injection assembly that injects the reductant into an exhaust stream of an engine and to a reductant replenishment assembly that is spaced from, and external to, the reductant dosing cabinet;   fluidly coupling a suction side of a pump assembly of the reductant dosing cabinet to the reductant replenishment assembly; and   operating the pump assembly so as purge the reductant in both a tank of the reductant dosing cabinet that is coupled to a suction side of the pump assembly and the pump assembly to the reductant replenishment assembly.   
     
     
         17 . The method of  claim 16 , wherein:
 coupling the reductant dosing cabinet includes coupling a reductant discharge passageway between the suction side of the pump assembly and the reductant injection assembly; and   fluidly coupling the suction side of the pump assembly includes selectively configuring at least one valve of the reductant dosing cabinet to divert the reductant away from the reductant injection assembly and to the purge passageway during the purge operation.   
     
     
         18 . The method of  claim 16 , wherein:
 coupling the reductant dosing cabinet includes coupling a reductant discharge passageway between the suction side of the pump assembly and the reductant injection assembly; and   the method further comprises steps of:
 fluidly coupling the reductant discharge passageway to a reductant return passageway between the pump assembly and the reductant injection assembly; and 
 flowing compressed gas from the reductant injection assembly through the reductant discharge passageway and the reductant return passageway so as to force reductant in the reductant discharge passageway and the reductant return passageway back to the tank. 
   
     
     
         19 . The method of  claim 16 , wherein operating the pump assembly includes flowing air in the tank through the pump assembly so as to force the reductant in the pump assembly to flow to the reductant replenishment assembly. 
     
     
         20 . The method of  claim 19 , comprising drawing air into a vent of the tank so as to fill a space in the cavity of the tank that was previously occupied by the reductant.