Fuel injection pump

Claim 1

In a fuel injection pump associated with an internal combustion engine including a housing within which a suction chamber is defined, a cylindrical bushing mounted within said housing, a bore defined within said bushing, a pump piston mounted within the bore for axial and rotary motion therein, a pump work chamber defined by the housing, the bushing and the piston, outlet pressure lines connecting said chamber with associated injection nozzles, a first relief channel connected to the pump work chamber, a second relief channel connected to the pump work chamber, and an annular slide serving as a fuel quantity regulating member adapted for changing the fuel quantity delivered by the fuel injection pump as a function of engine rpm by opening the first relief channel so as to permit the first relief channel to connect the work chamber to the suction chamber the improvement wherein: a. said second relief channel includes a first and second part; b. said first part of said second relief channel leads to said work chamber; c. said first relief channel and the second part of said second relief channel are formed within said pump piston; d. said first relief channel and said second part of said second relief channel include apertures which open into said suction chamber, with the relative position of said aperture being such that said annular slide opens the aperture of said second part of said second relief channel before it opens the aperture of said first relief channel; and e. said second part of said second relief channel includes a further aperture which communicates with the first part of said second relief channel when the pump piston is at its bottom dead center and which is displaced from said communiction when the pump piston has executed a predetermined part of its fuel delivery stroke.