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 pump of a fuel system including a fuel tank and a carburetor adapted for use with an internal combustion engine, comprising:
 a carburetor having a mixing passage, a fuel bowl, a fuel nozzle communicating the mixing passage with the fuel bowl to supply fuel from the fuel bowl to the mixing passage when the engine is operating, and a float in the fuel bowl responsive to the level of liquid fuel in the fuel bowl to open and close a valve to supply fuel from the fuel tank to the fuel bowl; and 
 an accumulator pump comprising a diaphragm disposed within an interior of the fuel pump to divide the interior into a fuel reservoir on a reservoir side of the diaphragm and an oppositely disposed actuation chamber on an actuation side of the diaphragm; 
 a biasing member to yieldably bias the diaphragm; 
 a fuel inlet to the fuel reservoir and communicating with the fuel bowl; 
 an inlet check valve in communication with the fuel inlet; 
 a fuel outlet from the fuel reservoir and communicating with at least one of the fuel tank or fuel bowl; 
 an outlet check valve in communication with the fuel outlet; and 
 the biasing member moving the diaphragm to withdraw liquid fuel from the fuel bowl and into the fuel reservoir substantially during shutdown of the internal combustion engine. 
 
     
     
       2. The fuel pump of  claim 1  further comprising:
 a housing; and 
 a cover carried by the housing to define the interior therebetween, the diaphragm being sealingly engaged between the housing and the cover. 
 
     
     
       3. The fuel pump of  claim 2  further comprising a vacuum pump mounted to the cover and being adapted to convert vacuum pulses received from an external source into pressure pulses to pressurize the actuation chamber to move the diaphragm to discharge fuel from the fuel reservoir through the fuel outlet. 
     
     
       4. The fuel pump of  claim 3  wherein the vacuum pump comprises:
 a valve plate positioned against the cover; 
 a diaphragm plate positioned against the valve plate; 
 a valve diaphragm positioned between the valve plate and diaphragm plate and including an inlet valve and an outlet valve; 
 a cover positioned against the diaphragm plate; 
 a diaphragm positioned between the cover and the diaphragm plate; and 
 a biasing means positioned between the diaphragm and the cover. 
 
     
     
       5. The fuel pump of  claim 2  further comprising a plunger apparatus carried by the cover and being adapted to convert push-pull motion into displacement of the diaphragm. 
     
     
       6. The fuel pump of  claim 5  wherein the plunger apparatus comprises:
 a plunger including a plate portion positioned against the diaphragm and a stem portion extending from the plate portion through an aperture in the cover; and 
 a biasing member positioned between the plate portion of the plunger and the cover. 
 
     
     
       7. The fuel pump of  claim 2  further comprising a valve actuation device mounted to the housing and being in fluid communication between the fuel tank and the fuel chamber of the carburetor, wherein the valve actuation device permits flow of fuel from the fuel tank to the carburetor when the internal combustion engine is operating, and further wherein the valve actuation device prevents flow of fuel from the fuel tank to the carburetor when the internal combustion engine is not operating. 
     
     
       8. The fuel pump of  claim 7  wherein the valve actuation device comprises:
 a valve plate positioned against the housing; 
 a cover positioned against the valve plate; and 
 a rotatable valve positioned between the cover and the valve plate, the rotatable valve being rotatably biased to a valve closed position so as to automatically stop flow of fuel through at least one passage. 
 
     
     
       9. The fuel pump of  claim 2  wherein the cover includes a pressure port therein adapted to communicate pressurized air into and out of the actuation chamber. 
     
     
       10. The fuel pump of  claim 1  wherein the fuel bowl has a closed end including 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. 
     
     
       11. The fuel pump of  claim 10  wherein the closed end further includes an inside bottom surface that is sloped substantially toward the low-lying collection area. 
     
     
       12. The fuel pump of  claim 11  wherein the closed end further includes a drain channel provided in the inside bottom surface and in communication with the low-lying collection area. 
     
     
       13. A fuel system with a fuel tank for an internal combustion engine, comprising:
 a carburetor having a body with a mixing passage for supplying a fuel and air mixture to the engine when operating, a fuel bowl carried by the body, a nozzle communicating with the fuel bowl and the mixing passage to supply fuel from the fuel bowl to the mixing passage when the engine is operating, a valve constructed to control the flow of fuel from a fuel tank into the fuel bowl, and a float in the fuel bowl to open and close the valve in response to the level of liquid fuel in the bowl; and 
 an accumulator pump having a diaphragm providing in part a fuel reservoir on one side of the diaphragm and an actuation chamber on the other side of the diaphragm, a fuel inlet to the reservoir communicating with the fuel bowl adjacent the bottom of the fuel bowl when the carburetor and the engine are in a normal operating position, a fuel outlet from the fuel reservoir communicating with at least one of the fuel bowl or the fuel tank, a spring yieldably biasing the diaphragm to increase the volume of the fuel reservoir to withdraw liquid fuel from the fuel bowl and into the reservoir substantially during shutdown of the internal combustion engine, and while the engine is operating, the diaphragm is moved against the bias of the spring to decrease the volume of the fuel reservoir to discharge fuel from the reservoir through the fuel outlet and to at least one of the fuel tank or fuel bowl.