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 fuel system for supplying fuel to an internal combustion engine with a crankshaft and a crankcase, the fuel system comprising:
 a fuel tank for containing fuel therein; 
 a carburetor having a fuel bowl in fluid communication with the fuel tank by at least one fluid path at least when the engine is operating; 
 a valve in fluid communication between the fuel tank and the fuel bowl of the carburetor constructed to prevent flow of fuel into the carburetor, at least when the internal combustion engine is not operating; 
 a pump in fluid communication with the fuel bowl of the carburetor to pump fuel out of the carburetor, substantially during shutdown of the internal combustion engine, and 
 the pump communicating with the crankcase of the engine and being actuated by pressure pulses produced in the crankcase by the engine when the crankshaft is rotating. 
 
     
     
       2. The fuel system of  claim 1  wherein the pump includes a fuel reservoir and the pump transfers fuel out of the fuel bowl of the carburetor and into the fuel reservoir, substantially during shutdown of the internal combustion engine and transfers fuel out of the reservoir to at least one of the fuel tank, the fuel bowl of the carburetor, or the at least one fluid path therebetween, substantially during startup of the internal combustion engine. 
     
     
       3. The fuel system of  claim 1  wherein the pump is a pneumatically-actuated diaphragm pump. 
     
     
       4. The fuel system of  claim 1  wherein the valve is also constructed to permit flow of fuel vapor from the fuel tank to the carburetor at least when the internal combustion engine is operating and to prevent flow of fuel vapor from the fuel tank to the carburetor at least when the internal combustion engine is not operating. 
     
     
       5. The fuel system of  claim 1  wherein the carburetor includes:
 a body for mixing air with fuel for delivery to the engine; 
 a float carried by the body and being movable about a pivot axis; and 
 a the fuel bowl carried by the body, wherein a fuel chamber is defined therebetween for containing fuel, the fuel bowl includes a closed end having an inside bottom surface sloped generally downwardly away from the pivot axis and further having a low-lying collection area and a fuel drain outlet disposed substantially at the low-lying collection area to enable substantially complete drainage of fuel out of the fuel bowl. 
 
     
     
       6. The fuel system of  claim 1  wherein the fuel bowl comprises
 an open end; 
 a wall portion extending from the open end; and 
 a closed end terminating the wall portion, the closed end including a low-lying collection area and a fuel drain outlet disposed substantially at the low-lying collection area. 
 
     
     
       7. The fuel system of  claim 1  wherein the pump and the valve are integrated into a pump and valve assembly. 
     
     
       8. The fuel system of  claim 7  wherein the carburetor and the pump and valve assembly are constructed for assembly as a single unit. 
     
     
       9. The fuel system of  claim 1  wherein the pump comprises:
 an interior; 
 a diaphragm disposed within the interior to divide the interior into a fuel reservoir on a reservoir side of the diaphragm and an oppositely disposed actuation chamber on an oppositely disposed actuation side of the diaphragm; 
 a biasing member to yieldably bias the diaphragm; 
 a fuel inlet in communication with the fuel reservoir; 
 an inlet check valve in communication with the fuel inlet; 
 a fuel outlet in communication with the fuel reservoir; and 
 an outlet check valve in communication with the fuel outlet. 
 
     
     
       10. A fuel system for supplying fuel to an internal combustion engine with an intake, a crankshaft and a crankcase, the fuel system comprising:
 a fuel tank for containing fuel therein; 
 a carburetor elevated with respect to the fuel tank and in fluid communication therebetween by at least one fluid path; 
 at least one valve in fluid communication between the fuel tank and the carburetor, the at least one valve constructed to prevent flow of fuel into the carburetor and permit flow of fuel away from the carburetor, at least when the internal combustion engine is not operating; 
 a pump in fluid communication with the carburetor to pump fuel to the carburetor substantially during startup and operation of the internal combustion engine, and 
 the pump communicating with one of the crankcase or intake of the engine and actuated by pressure pulses produced therein by the engine when the crankshaft is rotating and removing fuel from the carburetor when the engine is not operating. 
 
     
     
       11. A fuel system for supplying fuel to an internal combustion engine with an intake, a crankshaft and a crankcase, the fuel system comprising:
 a fuel tank for containing fuel therein; 
 a carburetor having a fuel bowl in fluid communication with the fuel tank by at least one fluid path at least when the engine is operating; 
 a valve in fluid communication between the fuel tank and the fuel bowl of the carburetor to prevent flow of fuel into the carburetor at least when the engine is not operating; 
 an accumulator pump in fluid communication with the fuel bowl of the carburetor to remove fuel from the fuel bowl carburetor substantially during shutdown of the engine; and 
 the accumulator pump communicating with one of the crankcase or the intake of the engine and actuated by pressure pulses produced therein by the engine when the crankshaft is rotating.