Controlling evaporative emissions in a fuel system

Abstract

Methods and fuel systems to reduce evaporative emissions of a volatile fuel. A fuel tank contains fuel, a carburetor mixes air with the fuel from the fuel tank, and a plurality of fluid paths route fuel amongst and/or between the fuel tank and the carburetor. A valve actuation device stops flow of fuel in one or more of the plurality of fluid paths and the carburetor is adapted to be drained of fuel during engine shutdown to reduce or prevent evaporative emissions from the fuel system. The carburetor is preferably designed so as to minimize a volume of fuel contained therein.

1. A method of controlling evaporative emissions of volatile fuel from a fuel system including a fuel tank and a carburetor with a fuel bowl, for use with an internal combustion engine, the method comprising the steps of:
 containing fuel within the fuel tank and within the carburetor; 
 permitting flow of fuel into the carburetor, at least when the internal combustion engine is operating; 
 preventing flow of fuel into the carburetor, at least when the internal combustion engine is not operating; and 
 withdrawing fuel out of the float bowl of the carburetor and into a receptacle of a plunger pump powered by manual actuation, substantially during shutdown of the internal combustion engine. 
 
     
     
       2. A method of controlling evaporative emissions of volatile fuel from a fuel system including a fuel tank and a carburetor with a fuel bowl, for use with an internal combustion engine with a crankshaft and a crankcase, the method comprising the steps of:
 containing fuel within the fuel tank and within the carburetor; 
 permitting flow of fuel into the carburetor, at least when the internal combustion engine is operating; 
 preventing flow of fuel into the carburetor, at least when the internal combustion engine is not operating; and 
 withdrawing fuel out of the float bowl of the carburetor and into a receptacle of a pneumatically-actuated diaphragm pump actuated by pressure pulses produced in the crankcase by the engine when the crankshaft is rotating, substantially during shutdown of the internal combustion engine. 
 
     
     
       3. The method of  claim 2  wherein the carburetor is elevated with respect to the fuel tank such that the step of permitting flow of fuel out is enabled by gravity flow of fuel. 
     
     
       4. The method of  claim 3  wherein the receptacle is the fuel tank. 
     
     
       5. The method of  claim 2  wherein the receptacle is separate from the fuel tank. 
     
     
       6. The method of  claim 5  further comprising permitting flow of fuel from the receptacle to at least one of the fuel tank, the carburetor, or a fluid path therebetween, substantially during startup of the engine. 
     
     
       7. The method of  claim 6  further comprising pumping fuel from the receptacle with the pneumatically-actuated diaphragm pump. 
     
     
       8. A method of controlling evaporative emissions of volatile fuel from a fuel system including a fuel tank and a carburetor with a fuel bowl, for use with an internal combustion engine, the method comprising the steps of:
 containing fuel within the fuel tank and within the carburetor; 
 permitting flow of fuel into the carburetor, at least when the internal combustion engine is operating; 
 preventing flow of fuel into the carburetor, at least when the internal combustion engine is not operating; and 
 withdrawing fuel out of the float bowl of the carburetor and into a receptacle of an electrically-actuated pump, substantially during shutdown of the internal combustion engine. 
 
     
     
       9. A method of controlling evaporative emissions of volatile fuel from a fuel system including a fuel tank and a carburetor for use with an internal combustion engine, the method comprising the steps of:
 containing fuel within the fuel tank and within the carburetor; 
 permitting flow of fuel into the carburetor, at least when the internal combustion engine is operating; 
 preventing flow of fuel into the carburetor, at least when the internal combustion engine is not operating; 
 permitting flow of fuel out of the carburetor and into a receptacle, substantially during shutdown of the internal combustion engine; 
 permitting flow of fuel vapor into the carburetor, at least when the internal combustion engine is operating; and 
 preventing flow of fuel vapor into the carburetor, at least when the internal combustion engine is not operating. 
 
     
     
       10. A method of reducing evaporative emissions from a carburetor for use with an internal combustion engine, which includes a fuel bowl, a fuel inlet passage in communication with the fuel bowl, an inlet valve for the inlet fuel passage, a float pivotable about a float pivot axis, and a fuel nozzle jet to communicate fuel within the fuel bowl to a fuel nozzle, the method comprising:
 minimizing at least one of the size of the inlet fuel passage or the lateral distance between the float pivot axis and at least one of the vertical axis of the inlet fuel passage or the inlet valve; and 
 maximizing at least one of the fuel contact surface area of the float or the lateral distance between the float pivot axis and a vertical axis of a fuel buoyancy force associated with the float; 
 wherein the volume of fuel within the fuel bowl is substantially minimized. 
 
     
     
       11. The method of  claim 10  wherein the step of minimizing includes minimizing both the size of the inlet fuel passage and the lateral distance between the float pivot axis and the axis of the inlet fuel passage. 
     
     
       12. The method of  claim 11  wherein the step of maximizing includes maximizing both the fuel contact surface area of the float and the lateral distance between the float pivot axis and the vertical axis of the fuel buoyancy force associated with the float. 
     
     
       13. The method of  claim 10  wherein the step of maximizing includes maximizing the fuel contact surface area of the float and the lateral distance between the float pivot axis and the fuel buoyancy force associated with the float. 
     
     
       14. The method of  claim 13  wherein the step of minimizing includes minimizing both the size of the inlet fuel passage and the lateral distance between the float pivot axis and the axis of the inlet fuel passage. 
     
     
       15. The method of  claim 10  further comprising:
 angling an inside bottom surface of the fuel bowl. 
 
     
     
       16. The method of  claim 15  further comprising:
 angling the inside bottom surface of the fuel bowl laterally and downwardly away from the float pivot axis. 
 
     
     
       17. The method of  claim 16  further comprising:
 angling the inside bottom surface of the fuel bowl toward a low-lying collection area of the fuel bowl.