Patent ID: 7478582

Claim:
A high pressure pump comprising a housing and a cylinder in said housing wherein a shaft-like plunger makes a reciprocating motion in a bore formed in said cylinder to compress a fluid fuel; said high pressure pump, wherein one end of said plunger is connected to a compression chamber for compressing the fluid fuel, while the other end is connected to a reciprocating motion drive source through a member; wherein a transverse aperture is connected with the bore through a cylindrical groove provided between axially opposite ends of the bore of said cylinder; and the clearance between said bore and said plunger depends on the axial location along said bore, wherein Ga≦Gb<Gc or Ga<Gb≦Gc and, wherein: Ga denotes a clearance between the bore on the portion from said compression chamber to said cylindrical groove and said plunger; Gb a clearance closer to the cylindrical groove, out of the clearances between the bore from said cylindrical groove to the drive source side and said plunger; and Gc a clearance closer to the drive source side, out of the clearances between the bore from said cylindrical groove to the drive source side and said plunger.