Gerotor pump

Abstract

A gerotor pump comprises a rotor chamber having a longitudinally extending central axis, an outer rotor rotatable in the rotor chamber with a radial clearance between an outer periphery of the outer rotor and the rotor chamber, an inner rotor rotatable in the outer rotor and cooperably engageable therewith to define a plurality of pumping chambers having respective volumes that vary when, in use, the inner rotor rotates relative to the outer rotor. The inner rotor is rotatable about an axis of rotation spaced from the central axis and contained in a first plane that contains the central axis and the rotor chamber is configured such that the radial clearance in at least one direction in the first plane is greater than at least one radial clearance in a second plane that extends perpendicular to the first plane and contains the central axis.

1 . A gerotor pump comprising:
 a rotor chamber having a longitudinally extending central axis,   an outer rotor rotatable in said rotor chamber with a radial clearance between an outer periphery of said outer rotor and said rotor chamber,   an inner rotor rotatable in said outer rotor and cooperably engageable therewith to define a plurality of pumping chambers having respective volumes that vary when, in use, the inner rotor rotates relative to the outer rotor,   said inner rotor being rotatable about an axis of rotation spaced from said central axis and contained in a first plane that contains said central axis, and   said rotor chamber being configured such that the said radial clearance in at least one direction in said first plane is greater than at least one radial clearance in a second plane that extends substantially perpendicular to said first plane and contains said central axis,   wherein said radial clearance has a minimum value and the, or each, said radial clearance in said second plane has said minimum value.   
     
     
         2 . A gerotor pump as claimed in  claim 1 , wherein said outer rotor has an axis of rotation at least substantially coincident with said central axis. 
     
     
         3 . A gerotor pump as claimed in  claim 1 , wherein said radial clearance has a maximum value and the, or each, said radial clearance in said first plane has said maximum value. 
     
     
         4 . A gerotor pump as claimed in  claim 1 , wherein between said first plane and said second plane, said radial clearance continuously decreases in size. 
     
     
         5 . A gerotor pump as claimed in  claim 1 , wherein said rotor chamber has a substantially elliptical cross-section. 
     
     
         6 . A gerotor pump comprising:
 a housing defining a rotor chamber,   an outer gear rotor received with radial clearance in said rotor chamber and rotatable in said rotor chamber,   an inner gear rotor rotatable in said outer gear rotor and having toothing cooperably engaging toothing of said outer gear rotor to form a plurality of variable volume pumping chambers,   said outer gear rotor being rotatable about an axis of rotation extending in a first plane,   said inner gear rotor being rotatable about an axis of rotation extending in a second plane spaced from said first plane and   said rotor chamber being configured such that at least one said radial clearance in said first plane is less than at least one radial clearance in a direction substantially perpendicular to said first plane,   wherein said radial clearance has a minimum value and the, or each, said radial clearance in said first plane has said minimum value.   
     
     
         7 . A gerotor pump as claimed in  claim 6 , wherein said radial clearance has a maximum value and the, or each, said radial clearance in said direction perpendicular to said first plane has said maximum value. 
     
     
         8 . A gerotor pump as claimed in  claim 7 , wherein said direction perpendicular to the first plane is the direction in which said second plane is spaced from said first plane. 
     
     
         9 . A gerotor pump as claimed in  claim 6 , wherein said rotor chamber has a generally elliptical cross section. 
     
     
         10 . A gerotor pump as claimed in  claim 6 , wherein said rotor chamber comprises a portion configured such that said radial clearance increases substantially continuously between said first plane and said direction perpendicular to said first plane. 
     
     
         11 . A fuel injection system comprising a gerotor pump as claimed in  claim 1 . 
     
     
         12 . A gerotor pump comprising:
 a rotor chamber having a longitudinally extending central axis,   an outer rotor rotatable in said rotor chamber with a radial clearance between an outer periphery of said outer rotor and said rotor chamber,   an inner rotor rotatable in said outer rotor and cooperably engageable therewith to define a plurality of pumping chambers having respective volumes that vary when, in use, the inner rotor rotates relative to the outer rotor,   said inner rotor being rotatable about a first axis of rotation, and   said outer rotor being rotatable about a second axis of rotation offset from said first axis of rotation in an offset direction,   wherein the radial clearance between the outer periphery of the outer rotor and the rotor chamber has a minimum value in a direction substantially perpendicular to the offset direction.   
     
     
         13 . A gerotor pump as claimed in  claim 12 , wherein said outer rotor has an axis of rotation at least substantially coincident with said central axis. 
     
     
         14 . A gerotor pump as claimed in  claim 12 , wherein said rotor chamber has a substantially elliptical cross-section. 
     
     
         15 . A gerotor pump comprising:
 a housing defining a rotor chamber,   an outer gear rotor received with radial clearance in said rotor chamber and rotatable in said rotor chamber,   an inner gear rotor rotatable in said outer gear rotor and having toothing cooperably engaging toothing of said outer gear rotor to form a plurality of variable volume pumping chambers,   said outer gear rotor being rotatable about an axis of rotation extending in a first plane,   said inner gear rotor being rotatable about an axis of rotation extending in a second plane spaced from said first plane in an offset direction, and   said rotor chamber being configured such that the radial clearance has a minimum value in a direction substantially perpendicular to the offset direction.   
     
     
         16 . A gerotor pump as claimed in  claim 15 , wherein said outer rotor has an axis of rotation at least substantially coincident with said central axis. 
     
     
         17 . A gerotor pump as claimed in  claim 15 , wherein said rotor chamber has a substantially elliptical cross-section.