High pressure fuel pump for internal combustion engine

Abstract

A high pressure fuel pump for an internal combustion engine having a cylinder, a plunger slidably fitted in the cylinder and a seal mechanism for blocking fuel leakage from an end of a sliding portion between the cylinder and the plunger and also for preventing an lubricant for a driving mechanism of the plunger from entering into the cylinder from the end of the sliding portion of the cylinder and the plunger. A holder surrounding the end of the sliding portion of the cylinder and the plunger is provided. The seal mechanism comprises two mutually independent seal devices mounted with a specific spacing in a longitudinal direction from the end of the sliding portion of the cylinder and the plunger along a circumference of the plunger. The two seal devices are held on the circumference of the plunger by the holder surrounding the end of the sliding portion of the cylinder and the plunger while keeping the specific spacing.

What is claimed is:  
     
         1 . A high pressure fuel pump for an internal combustion engine having a cylinder, a plunger slidably fitted in the cylinder and a seal mechanism for blocking fuel leakage from an end of a sliding portion between said cylinder and said plunger and also for preventing an lubricant for a driving mechanism of said plunger from entering into said cylinder from said end of the sliding portion of said cylinder and said plunger, wherein: 
 a holder surrounding said end of the sliding portion of said cylinder and said plunger is provided;    said seal mechanism comprises two mutually independent seal devices mounted with a specific spacing in a longitudinal direction from said end of the sliding portion of said cylinder and said plunger along a circumference of said plunger; and    the two seal devices are held on the circumference of said plunger by said holder surrounding said end of the sliding portion of said cylinder and said plunger while keeping said specific spacing.    
     
     
         2 . A high pressure fuel pump according to  claim 1 , further comprising a spacer for regulating said specific spacing mounted between said two seal devices.  
     
     
         3 . A high pressure fuel pump according to  claim 1 , wherein the seal device on said cylinder side, of said two seal devices, has a fuel seal function, and the remaining seal device has a lubricant seal function.  
     
     
         4 . A high pressure fuel pump for an internal combustion engine having a cylinder, a plunger slidably fitted in the cylinder, a seal mechanism for blocking fuel leakage from an end of the sliding portion of said cylinder and plunger and also preventing a lubricant for a driving mechanism of said plunger from entering into said cylinder from said end of the sliding portion of said cylinder and said plunger, and a holder having a screw portion for threadedly engaging with a pump body, said cylinder being mounted in said holder and being fixed to the pump body by threadely engaging the holder with the pump body, wherein: 
 said holder has a cover portion for surrounding said sliding portion of the cylinder and plunger;    said seal mechanism comprises two mutually independent seal devices mounted with a specific spacing in a longitudinal direction from said end of the sliding portion of said cylinder and said plunger along a circumference of said plunger; and    the two seal devices are held on the circumference of said plunger by the cover portion of said holder while keeping the specific spacing.    
     
     
         5 . A high pressure fuel pump according to  claim 4 , further comprising a spacer for regulating said specific spacing mounted between said two seal devices.  
     
     
         6 . A high pressure fuel pump according to  claim 4 , wherein the seal device on said cylinder side, of said two seal devices, has a fuel seal function, and the remaining seal device has a lubricant seal function.  
     
     
         7 . A high pressure fuel pump for an internal combustion engine comprising a plunger for force-feeding fuel in a pressurization chamber, a suction valve provided at an inlet of the pressurization chamber, a discharge valve provided at an exit of the pressurization chamber, a low pressure chamber provided on an upstream side of the suction valve, a cylinder for slidably holding said plunger, and a seal structures for rendering an outer circumference of said plunger sealed fluid-tight located at two locations at an outside of said cylinder and in an axial direction of said plunger, 
 wherein an annular member made of a resin is used in the seal structure located on said pressurization chamber side, of said seal structures at two locations.    
     
     
         8 . A high pressure fuel pump according to  claim 7 , wherein the seal structure on the opposite side to the pressurization chamber, of said seal structures at two locations, is a rubber annular structure.  
     
     
         9 . A high pressure fuel pump for an internal combustion engine comprising a plunger for force-feeding the fuel in a pressurization chamber, a suction valve provided at an inlet of the pressurization chamber, a discharge valve provided at an exit of the pressurization chamber, a low pressure chamber provided on an upstream side of the suction valve, a cylinder for slidably holding said plunger, and seal structures for rendering an outer circumference of said plunger sealed fluid-tight located at two locations at an outside of said cylinder and in an axial direction of the plunger, 
 wherein there is provided in the cylinder a transverse hole by which the fuel leaked from the pressurization chamber to a fuel reservoir formed on a pressurization chamber side of the seal structures through a clearance between said cylinder and said plunger is returned to an inlet port.