High Pressure Pump

Abstract

A high pressure fuel pump unit includes a pump head, a cam-follower, a plunger extending along a longitudinal axis from a first extremity slidably arranged in a pumping bore of the pump head to a second extremity cooperating with the cam-follower lubricated by oil and, a spring compressed between the pump head and the cam-follower. The pump unit further includes an annular seal arranged around the plunger and fixed to the pump head in order to prevent mixing of fuel with oil.

1 . (canceled) 
     
     
         2 . A pump unit as set in  claim 6  wherein the seal is arranged within a seal retaining sleeve attached to the pump head. 
     
     
         3 . A pump unit as set in  claim 6  wherein the pumping bore opens out of the pump head in a cylindrical recess, the seal being arranged in said cylindrical recess. 
     
     
         4 . A pump unit as set in  claim 3  further comprising a bell shape member fixed to the pump head in a location surrounding said cylindrical recess, and axially extending to a distal end having an aperture through which the plunger extends. 
     
     
         5 . A pump unit as set in  claim 4  wherein the plunger is provided with an annular groove in a location that is permanently inside the bell shape member, said groove receiving an annular retaining clip which has an outer diameter that is larger than a diameter of the aperture so to prevent the plunger from accidently falling off the pumping bore during the assembly of the pump unit. 
     
     
         6 . A high pressure fuel pump unit comprising:
 a pump head;   a cam-follower for cooperating with a rotating cam;   a plunger extending along a longitudinal axis from a first extremity slidably arranged in a pumping bore of the pump head where fuel is pumped, to a second extremity cooperating with the cam-follower lubricated by oil;   a spring compressed between the pump head and the cam-follower for soliciting the cam-follower toward the cam; and   an annular seal arranged around the plunger and fixed to the pump head in order to prevent mixing of fuel with oil; the seal being a double lip seal, its two lips cooperating with the plunger;   wherein the seal solicits the plunger with a surrounding radial force inwardly oriented sufficient to prevent the plunger from accidentally falling off the pump head during the assembly of the pump unit   
     
     
         7 . A pump unit as set in  claim 2  wherein the pumping bore opens out of the pump head in a cylindrical recess, the seal being arranged in said cylindrical recess. 
     
     
         8 . A pump unit as set in  claim 7  further comprising a bell shape member fixed to the pump head in a location surrounding said cylindrical recess, and axially extending to a distal end having an aperture through which the plunger extends. 
     
     
         9 . A pump unit as set in  claim 8  wherein the plunger is provided with an annular groove in a location that is permanently inside the bell shape member, said groove receiving an annular retaining clip which has an outer diameter is larger than a diameter of the aperture so to prevent the plunger from accidently falling off the pumping bore during the assembly of the pump unit.