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 a part of fuel passage including a low pressure side through which fuel is supplied to the compression chamber and a high pressure side through which pressurized fuel from the compression chamber is supplied to the delivery pipe;   a plunger that is movable in the pump housing, the plunger being adapted to pressurizing fuel drawn from the low pressure side into the compression chamber; and   at least one functional component disposed in the fuel passage to control a fuel flow in the fuel passage, wherein   the functional component at least includes a delivery valve disposed in the high pressure side to allow a fuel flow from the compression chamber to the delivery pipe only when fuel pressure in the compression chamber is equal to or greater than a threshold,   the pump housing has a mount hole to which the functional component is mounted, the mount hole defining a small clearance between the pump housing and the functional component, and   the pump housing further has a return passage which regularly communicates between the low-pressure side and a downstream side of the delivery valve through the small clearance in order to regularly allow a return fuel flow from the high pressure side to the low pressure side.   
     
     
         2 . The fuel pump according to  claim 1 , wherein
 the mount hole has an inner peripheral surface, and   the functional component mounted to the mount hole has an outer peripheral surface, wherein   the mount hole defines the small clearance as an annular cylindrical clearance formed between the inner peripheral surface and the outer peripheral surface.   
     
     
         3 . The fuel pump according to  claim 2 , wherein
 the mount hole further has a screw on which the functional component is screwed, and   the functional component mounted to the mount hole has a screw engaged with the screw formed on the mount hole.   
     
     
         4 . The fuel pump according to  claim 3 , wherein
 the functional component has a body through which a communication passage is formed as a part of a passage between the low-pressure side and the downstream side of the delivery valve through the small clearance.   
     
     
         5 . The fuel pump according to  claim 1 , wherein
 the mount hole is a mount hole for the delivery valve, and defines the small clearance between the pump housing and the delivery valve, wherein   the delivery valve has a body defining a fuel passage on the downstream side of the delivery valve and having a communication passage formed on a side wall thereof to communicate the fuel passage therein and the small clearance.   
     
     
         6 . The fuel pump according to  claim 5 , wherein
 the mount hole has an inner peripheral surface and a bottom surface, and   the delivery valve has an outer peripheral surface and a distal end, wherein   the mount hole defines the small clearance as an annular cylindrical clearance formed between the inner peripheral surface and the outer peripheral surface, and defines an axial gap formed between the bottom surface and the distal end, and   the return passage is communicated with the small clearance via the axial gap.   
     
     
         7 . The fuel pump according to  claim 1 , wherein
 the mount hole further has a screw on which the functional component is screwed, and   the functional component mounted to the mount hole has a screw engaged with the screw formed on the mount hole, and   the small clearance includes a screwed part where the mount hole and the functional component are screwed each other.   
     
     
         8 . The fuel pump according to  claim 1 , wherein
 the mount hole is a mount hole for the delivery valve, and defines the small clearance between the pump housing and the delivery valve, and wherein   the functional component further includes another functional component other than the delivery valve,   the pump housing further has another mount hole to which the another functional component is mounted, the another mount hole defining another small clearance between the pump housing and the another functional component, and   the small clearance and the another small clearance are arranged in series between the low-pressure side and the downstream side of the delivery valve.   
     
     
         9 . The fuel pump according to  claim 8 , wherein
 the functional component has a member defining a fuel passage which is communicated with the downstream side of the delivery valve and has a passage formed on a side wall thereof to communicate the fuel passage therein and the small clearance.   
     
     
         10 . The fuel pump according to  claim 1 , wherein
 the mount hole has an inner peripheral surface and a screw on which the functional component is screwed, and   the functional component mounted to the mount hole has an outer peripheral surface and a screw engaged with the screw formed on the mounted hole, wherein   the mount hole defines the small clearance which includes:   an annular cylindrical clearance formed between the inner peripheral surface and the outer peripheral surface; and   a screwed part where the mount hole and the functional component are screwed each other, the return fuel flow from the high pressure side to the low pressure side is regularly allowed through both the annular cylindrical clearance and the screwed part.   
     
     
         11 . The fuel pump according to  claim 1 , wherein
 the pump housing and the functional component define a plurality of small clearances, and   fuel on the downstream side of the delivery valve passes through the plurality of small clearances to return into the low pressure side.   
     
     
         12 . The fuel pump according to  claim 1 , wherein
 the at least one functional component further includes   at least one of a relief valve and a metering valve, and wherein   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.   
     
     
         13 . The fuel pump according to  claim 1 , wherein the first clearance communicates with an inside of the pump housing. 
     
     
         14 . The fuel pump according to  claim 1 , wherein
 the mount hole has an inner peripheral surface, which is substantially circular in shape, and   the functional component has an outer peripheral surface, which is substantially circular in shape.