System and Method for Controlling Evaporative Emissions

Abstract

A system and method which implements a preferred embodiment of the present invention includes a pump control module for controlling evaporative emissions of engines. In one embodiment, fuel vapor is allowed to accumulate in an intake manifold for a first period of time after an engine is turned off. After the first period of time, the pump control module may open a vacant port and turn on a pump. The pump control module may run the pump for a second period of time. The second period of time may be determined based on the time needed to empty an estimated volume of accumulated fuel vapor from the intake manifold into one or more canisters, such as activated charcoal canisters. After the second period of time, the pump control module may decrease the running time and/or speed of the pump. When the engine is restarted, the vacant port may be closed, the pump may be turned off, and fuel vapor stored in the canisters may be controllably consumed via a purge valve mounted to the intake manifold. In one embodiment, a choke may be placed in between the vacant port and the canisters in order to reduce the number of canisters needed for a given pump size.

1 . A system for controlling evaporative engine emissions comprising:
 an intake manifold including a vacant port which connects to one or more canisters,   a pump which connects to said one or more canisters, and   a pump control module configured to run said pump after a first period of time.   
     
     
         2 . The system of  claim 1  wherein the length of said first period of time is approximately twenty minutes from the time that an ignition switch is turned off. 
     
     
         3 . The system of  claim 1  wherein the length of said first period of time is varied based on one or more of the following variables measured at said intake manifold: temperature, pressure and fuel vapor concentration. 
     
     
         4 . The system of  claim 1  wherein said pump control module is configured to run said pump for a second period of time after said first period of time. 
     
     
         5 . The system of  claim 1  wherein said pump control module is configured to run said pump for a second period of time after said first period of time and the length of said second period of time approximately two minutes. 
     
     
         6 . The system of  claim 1  wherein said pump control module is configured to run said pump for a second period of time after said first period of time and the length of said second period of time is varied based on one or more of the following variables measured at said intake manifold, said one or more canisters or a gas line connecting to said one or more canisters: temperature, pressure, and fuel vapor concentration. 
     
     
         7 . The system of  claim 1  wherein said pump control module is configured to run said pump for a second period of time after said first period of time and the length of said second period of time is determined based on one or more of the following factors: the size of said intake manifold, the size of said pump, the capacity of said one or more canisters, temperature, pressure, the capacity of a gas line, and the resistance to vapor flow of a gas line. 
     
     
         8 . The system of  claim 1  wherein said pump control module is configured to run said pump for a second period of time after said first period of time and configured to run said pump at a decreased rate after said second period of time. 
     
     
         9 . The system of  claim 1  wherein said pump control module is configured to run said pump for a second period of time after said first period of time and configured to modulate or cycle said pump after said second period of time. 
     
     
         10 . The system of  claim 1  wherein said pump control module is configured to run said pump for a second period of time after said first period of time and configured to run said pump at approximately a fifty percent duty cycle after said second period of time. 
     
     
         11 . The system of  claim 1  wherein, after an ignition switch is turned on, fuel vapor stored in said one or more canisters is consumed via a purge valve mounted to said intake manifold. 
     
     
         12 . The system of  claim 1  further comprising a choke between said vacant port and said one or more canisters. 
     
     
         13 . A method for controlling evaporative engine emissions comprising:
 after a first period of time, running a pump for a second period of time wherein said pump is connected to one or more canisters and said one or more canisters are connected to a vacant port of an intake manifold.   
     
     
         14 . The method of  claim 13 , wherein the length of said first period of time is approximately twenty minutes from the time that said ignition switch is turned off. 
     
     
         15 . The method of  claim 13  wherein the length of said first period of time is varied based on one or more of the following variables measured at said intake manifold: temperature, pressure and fuel vapor concentration. 
     
     
         16 . The method of  claim 13  wherein said pump is connected to a pump control module configured to start said pump. 
     
     
         17 . The method of  claim 13  wherein the length of said second period of time approximately two minutes. 
     
     
         18 . The method of  claim 13  wherein the length of said second period of time is varied based on one or more of the following variables measured at said intake manifold, said one or more canisters or a gas line connecting to said one or more canisters: temperature, pressure, and fuel vapor concentration. 
     
     
         19 . The method of  claim 13  further comprising running said pump at a decreased rate after said second period of time. 
     
     
         20 . The method of  claim 13  further comprising modulating or cycling said pump after said second period of time. 
     
     
         21 . The method of  claim 13  further comprising running said pump at approximately a fifty percent duty cycle after said second period of time. 
     
     
         22 . The method of  claim 13  wherein, after an ignition switch is turned on, fuel vapor stored in said one or more canisters is consumed via a purge valve mounted to said intake manifold. 
     
     
         23 . The method of  claim 13  wherein a choke is located between said vacant port and said one or more canisters. 
     
     
         24 . The method of  claim 13  further comprising determining the length of said second period of time based on one or more of the following factors: the size of said intake manifold, the size of said pump, the capacity of said one or more canisters, temperature, pressure, the capacity of a gas line, and the resistance to vapor flow of a gas line.