Fuel system with variable discharge pump

Abstract

The present invention relates generally to variable discharge pumps, and specifically pumps used in fuel injection systems. Typically, such pumps include a dedicated spill control valve for each pumping plunger, that also doubles as an avenue for refilling the pumping chambers. This double duty results in compromise in the design of the spill control valve to operate effectively in both spill and fill modes. The present invention addresses these issues by utilizing a shuttle valve member to allow the spill function and the fill function to be addressed in separate passageways while also allowing a pair of plungers to share a common spill control valve. The present invention find particular application in pumps used to supply high pressure fluid to common rails for fuel injection systems.

1 - 20 . (canceled)  
   
   
       21 . A fuel system for an engine comprising: 
 a high pressure pump having an inlet and an outlet;    a fuel rail fluidly connected to the outlet of the high pressure pump;    a plurality of fuel injectors fluidly connected to the fuel rail via respective branch passages;    an electronic control module in control communication with the high pressure pump via an electrical actuator;    the high pressure pump including a first plunger within a first pumping chamber and a second plunger within a second pumping chamber, the first pumping chamber and the second pumping chamber sharing a common spill valve, the spill valve being moveable in response to the electrical actuator; and    a shuttle valve being movable between a first position in which the first pumping chamber is in fluid communication with the spill valve and a second position in which the second pumping chamber is in fluid communication with the spill valve, the shuttle valve being configured to be moved to the first position when the first plunger is in a pumping stroke and to be moved to the second position when the second plunger is in a pumping stroke.    
   
   
       22 . The fuel system of  claim 21  including a fuel transfer pump with an outlet fluidly connected to the inlet of the high pressure pump.  
   
   
       23 . The fuel system of  claim 22  including a fuel tank fluidly connected to an inlet of the fuel transfer pump; and 
 a fuel injector return line fluidly connecting low pressure outlets of the plurality of fuel injectors to the tank.    
   
   
       24 . The fuel system of  claim 23  wherein the spill valve includes a latching valve member; 
 wherein the first and second plungers reciprocate within the first and second pumping chambers, respectively; and    wherein the latching valve member is moved toward a closed position by the electrical actuator, but is held in the closed position by fluid pressure in one of the first and second pumping chambers when one of the first and second plungers is in the pumping stroke.    
   
   
       25 . The fuel system of  claim 24  wherein the high pressure pump includes first and second intake valves associated with the first and second pumping chambers, respectively.  
   
   
       26 . The fuel system of  claim 25  wherein each of the first and second plungers are reciprocated via rotation of respective three lobed cams.  
   
   
       27 . The fuel system of  claim 26  wherein the plurality of fuel injectors includes three fuel injectors for each pumping plunger.  
   
   
       28 . A method of operating a fuel system, comprising the steps of: 
 supplying high pressure fuel to a common rail by reciprocating a first plunger within a first pumping chamber and a second plunger within a second pumping chamber;    controlling the high pressure fuel displaced from the first and second pumping chambers to the common rail with a shared spill valve;    closing the spill valve by energizing an electrical actuator coupled to the spill valve; and    moving a shuttle valve to a first position when the first plunger is in a pumping stroke and moving the shuttle valve to a second position when the second plunger is in a pumping stroke; and    supplying fuel to a plurality of fuel injectors from the common rail via individual branch passages.    
   
   
       29 . The method of  claim 28  further comprising the steps of de-energizing the electrical actuator after the spill valve closes and holding the spill valve closed for a remainder of a pumping stroke by the high pressure fuel displaced by one of the first plunger and the second plunger.  
   
   
       30 . The method of  claim 29  wherein the first and second plungers are parts of a high pressure pump; and 
 further comprising the step of supplying low pressure fuel to the high pressure pump via a fuel transfer pump.    
   
   
       31 . The method of  claim 28  further comprising the step of supplying fuel to the first and second pumping chambers via first and second intake valves, respectively.  
   
   
       32 . The method of  claim 31  wherein the first and second plungers are reciprocated by rotating first and second three lobed cams, respectively.