Venting of on-board vehicle emissions treatment system

Abstract

A system and method for controlling venting of an on-board vehicle emissions treatment substance storage and distribution system that selectively dispenses an emissions treatment substance from a storage tank on the vehicle to an exhaust system of the vehicle include selectively coupling the storage tank to the exhaust system when pressure in the storage tank exceeds a predetermined pressure associated with the exhaust system. The invention may also include selectively coupling the storage tank to atmosphere when a pressure differential between the storage tank and atmosphere exceeds a predetermined pressure differential.

1 . A method for controlling an on-board vehicle emissions treatment system that selectively dispenses an emissions treatment substance from a storage tank to an exhaust system of the vehicle, the method comprising: 
 selectively coupling the storage tank to the exhaust system in response to pressure in the storage tank exceeding a predetermined pressure associated with the exhaust system and decoupling the storage tank from the exhaust system otherwise to reduce or eliminate backflow of exhaust into the storage tank.    
   
   
       2 . The method of  claim 1  wherein the exhaust system includes a catalyst and wherein the step of selectively coupling comprises selectively coupling a portion of the storage tank above a maximum level of the emissions treatment substance to the exhaust system upstream of the catalyst to selectively deliver vapors from the storage tank to the exhaust system.  
   
   
       3 . The method of  claim 1  wherein the predetermined pressure associated with the exhaust system corresponds to a maximum anticipated exhaust pressure and wherein the step of selectively coupling comprises positioning a passive valve between the storage tank and the exhaust system that operates solely in response to a pressure differential across the valve to open when the pressure in the storage tank exceeds the predetermined pressure and to close when the pressure in the storage tank is less than the predetermined pressure.  
   
   
       4 . The method of  claim 1  wherein the step of selectively coupling comprises positioning a one-way valve between the storage tank and the exhaust system wherein the one-way valve opens when the pressure in the storage tank exceeds the predetermined pressure.  
   
   
       5 . The method of  claim 1  wherein the step of selectively coupling comprises controlling a solenoid valve disposed between the storage tank and the exhaust system such that the solenoid valve opens when the pressure in the storage tank exceeds the predetermined pressure associated with the exhaust system.  
   
   
       6 . The method of  claim 1  further comprising selectively coupling the storage tank to atmosphere when a pressure differential between the storage tank and atmosphere exceeds a predetermined pressure differential.  
   
   
       7 . The method of  claim 6  wherein the step of selectively coupling the storage tank to atmosphere comprises positioning a one-way valve between the storage tank and atmosphere, the one-way valve opening when the pressure differential between the storage tank and atmosphere exceeds the predetermined pressure differential to provide air from atmosphere to the storage tank, and closing when the pressure differential between the storage tank and atmosphere is less than the predetermined pressure differential to prevent vapor egress from the storage tank.  
   
   
       8 . The method of  claim 6  wherein the step of selectively coupling the storage tank to atmosphere comprises controlling a solenoid valve positioned between the storage tank and atmosphere to selectively provide air to the storage tank.  
   
   
       9 . An on-board vehicle emissions treatment system that selectively dispenses an emissions treatment substance from a storage tank on the vehicle to an exhaust system of the vehicle, the emissions treatment system comprising: 
 a venting valve disposed between the storage tank and the exhaust system, the venting valve selectively coupling the storage tank to the exhaust system when pressure in the storage tank exceeds a predetermined pressure associated with the exhaust system, and decoupling the storage tank from the exhaust system otherwise to reduce or eliminate exhaust backflow toward the storage tank.    
   
   
       10 . The emissions treatment system of  claim 9  further comprising: 
 a vacuum release valve disposed between the storage tank and atmosphere, the vacuum release valve selectively coupling atmosphere to the storage tank when a pressure differential between atmosphere and the storage tank exceeds a predetermined level and decoupling the storage tank from atmosphere otherwise.    
   
   
       11 . The emissions treatment system of  claim 10  wherein the vacuum release valve operates solely in response to the pressure differential between the storage tank and atmosphere.  
   
   
       12 . The emissions treatment system of  claim 9  wherein at least one of the venting valve and the vacuum release valve comprises a solenoid valve, the emissions treatment system further comprising: 
 a controller in communication with the at least one valve for selectively controlling the valve in response to current operating conditions.    
   
   
       13 . The emissions treatment system of  claim 9  wherein the venting valve operates solely in response to a pressure differential between the storage tank and the exhaust system.  
   
   
       14 . The emissions treatment system of  claim 9  further comprising: 
 a catalyst disposed downstream of an internal combustion engine, wherein the venting valve selectively couples the storage tank to the exhaust system upstream of the catalyst.    
   
   
       15 . The emissions treatment system of  claim 9  wherein the venting valve opens when the pressure in the storage tank exceeds a maximum exhaust pressure associated with operation of an internal combustion engine of the vehicle.  
   
   
       16 . A computer readable storage medium having stored data representing instructions executable by a computer to control an emissions treatment system of a vehicle, the emissions treatment system selectively dispensing an emissions treatment substance from a storage tank on the vehicle to an exhaust system of the vehicle, the emissions treatment system including a conduit with a controllable valve disposed between the storage tank and the exhaust system for selectively venting vapors from the storage tank to the exhaust system, the computer readable storage medium comprising: 
 instructions for controlling the valve to open in response to pressure in the storage tank exceeding exhaust system pressure to reduce or prevent backflow of exhaust into the storage tank.    
   
   
       17 . The computer readable storage medium of  claim 16  wherein the predetermined pressure corresponds to a maximum anticipated exhaust pressure to prevent exhaust from entering the storage tank when the valve is open.  
   
   
       18 . The computer readable storage medium of  claim 16  wherein the emissions treatment system includes a controllable vacuum release valve and wherein the computer readable storage medium comprises instructions for controlling the vacuum release valve in response to atmospheric pressure exceeding pressure of the storage tank by a predetermined amount.  
   
   
       19 . The computer readable storage medium of  claim 16  further comprising instructions for periodically opening the valve to deliver vapor from the storage tank to the exhaust system.  
   
   
       20 . The computer readable storage medium of  claim 16  further comprising instructions for opening the valve in response to temperature of at least one exhaust system component.