Fuel pump having plunger and fuel supply system using the same

Abstract

A delivery valve is connected to a discharge passage, through which fuel in a compression chamber is discharged. The delivery valve is screwed to a mount hole formed in the cylinder. A communication passage is formed in a body to extend through the sidewall between a screwed part, in which the mount hole and the body are screwed to each other, and a gasket. A small clearance is formed between an inner peripheral surface of the mount hole and an outer peripheral surface of the body. The communication passage provides communication between a fuel passage downstream of a valve seat member and the clearance. The clearance communicates with the suction chamber through a return passage formed in the cylinder.

1 . A fuel pump that supplies fuel to a delivery pipe, the fuel pump comprising: 
 a pump housing that has a compression chamber and at least one mount hole;    a plunger that is movable in the pump housing, the plunger being adapted to pressurizing fuel drawn into the compression chamber;    a delivery valve that communicates the compression chamber with the delivery pipe when fuel pressure in the compression chamber is equal to or greater than a threshold; and    at least one functional component that is provided to the at least one mount hole of the pump housing,    wherein the at least one functional component and the at least one mount hole define at least one clearance therebetween, and    fuel on a downstream side of the delivery valve returns into a low-pressure side thereof through the at least one clearance.    
     
     
         2 . The fuel pump according to  claim 1 , 
 wherein the at least one clearance includes a plurality of clearances, and    fuel on the downstream side of the delivery valve passes through the plurality of clearances to return into the low-pressure side.    
     
     
         3 . The fuel pump according to  claim 1 , wherein the delivery valve has an inlet of a return passage, through which fuel on the downstream side of the delivery valve returns to a low-pressure side thereof.  
     
     
         4 . The fuel pump according to  claim 1 , wherein the delivery valve is one of the at least one functional component.  
     
     
         5 . The fuel pump according to  claim 1 , 
 wherein the plunger is one of the at least one functional component, and    fuel on the downstream side of the delivery valve returns to a low-pressure side thereof through one of the at least one clearance defined in a sliding part, in which the plunger slides on the pump housing.    
     
     
         6 . The fuel pump according to  claim 1 , 
 wherein the at least one functional component includes at least one of a relief valve and a metering valve,    the relief valve restricts fuel pressure on the downstream side of the delivery valve from rising, and    the metering valve is arranged between the upstream of the compression chamber and the compression chamber, the metering valve being adapted to communicating and blocking the upstream of the compression chamber with the compression chamber.    
     
     
         7 . The fuel pump according to  claim 1 , wherein fuel passing through the at least one clearance returns into the pump housing.  
     
     
         8 . The fuel pump according to  claim 1 , 
 wherein the at least one mount hole has an inner peripheral surface, which is substantially circular in shape, and    the at least one functional component has an outer peripheral surface, which is substantially circular in shape.    
     
     
         9 . The fuel pump according to  claim 1 , wherein the at least one clearance communicates the downstream side of the delivery valve with an upstream side of the compression chamber at least in a condition where fuel pressure in the compression chamber is less than the threshold.  
     
     
         10 . A fuel supply system including a fuel pump comprising: 
 a pump housing that has a compression chamber and at least one mount hole;    a plunger that is movable in the pump housing, the plunger being adapted to pressurizing fuel in the compression chamber;    a delivery valve that communicates the compression chamber with a downstream of the delivery valve when pressure in the compression chamber is equal to or greater than a threshold; and    at least one fluid component that is adapted to communicating an upstream of the compression chamber with a downstream of the compression chamber,    wherein at least one of the plunger, the delivery valve, and the at least one of fluid component is provided to the at least one mount hole of the pump housing,    the at least one of the plunger, the delivery valve, and the at least one of fluid component defines at least one clearance with respect to the at least one mount hole, and    the at least one clearance communicates the downstream of the delivery valve with the upstream of the compression chamber at least in a condition where fuel pressure in the compression chamber is less than the threshold.    
     
     
         11 . The fuel supply system according to  claim 10 , 
 wherein the at least one fluid component includes at least one of a relief valve and a metering valve,    the relief valve is adapted to restricting pressure in the downstream of the delivery valve from rising, and    the metering valve is arranged between the upstream of the compression chamber and the compression chamber, the metering valve being adapted to communicating and blocking the upstream of the compression chamber with the compression chamber.    
     
     
         12 . The fuel supply system according to  claim 10 , 
 wherein the at least one clearance includes a plurality of clearances, and    the downstream of the delivery valve communicates with the upstream of the compression chamber through the plurality of clearances.    
     
     
         13 . The fuel supply system according to  claim 10 , wherein the delivery valve has an inlet of a return passage, through which the downstream of the delivery valve communicates with the upstream of the compression chamber.  
     
     
         14 . The fuel supply system according to  claim 10 , 
 wherein the plunger defines a sliding part, in which the plunger slides through one of the at least one mount hole of the pump housing, and    the plunger defines one of the at least one of the clearance with respect to the one of the at least one mount hole in the sliding part.    
     
     
         15 . The fuel supply system according to  claim 10 , wherein the at least one clearance communicates with an inside of the pump housing upstream of the compression chamber.  
     
     
         16 . The fuel supply system according to  claim 10 , 
 wherein the at least one mount hole has an inner peripheral surface, which is substantially circular in shape, and    the at least one functional component has an outer peripheral surface, which is substantially circular in shape.    
     
     
         17 . A fuel supply system including a fuel pump comprising: 
 a pump housing that has a compression chamber and a mount hole;    a plunger that is movable in the pump housing, the plunger being adapted to pressurizing fuel in the compression chamber;    a delivery valve that communicates the compression chamber with a downstream of the delivery valve when pressure in the compression chamber is equal to or greater than a threshold; and    wherein the delivery valve is provided to the mount hole of the pump housing,    the delivery valve defines a clearance with respect to the mount hole, and    the clearance communicates the downstream of the delivery valve with the upstream of the compression chamber at least in a condition where fuel pressure in the compression chamber is less than the threshold.    
     
     
         18 . A fuel supply system including a fuel pump comprising: 
 a pump housing that has a compression chamber;    a plunger that is movable in the pump housing to pressurize fuel in the compression chamber; and    a delivery valve that communicates the compression chamber with a downstream of the delivery valve when pressure in the compression chamber is equal to or greater than a threshold,    wherein the pump housing at least partially defines at least one clearance that communicates the downstream of the delivery valve with an upstream of the compression chamber at least in a condition where fuel pressure in the compression chamber is less than the threshold.