Device for controlling preliminary injection

A device for controlling the preliminary injection by intermediate relief for internal combustion engines including an injection pump, an injection nozzle, a housing having a uniform inner bore and a control slide valve slidable within said uniform housing bore, said control slide valve including a central bore, and upper, middle, and lower shoulders thereon, said shoulders forming a narrow central annular groove and a wider lower annular groove, said central bore including an axially aligned throttle directly opposite said upper shoulder thereon;

• said housing including an upper annular groove and a lower annular groove;
• a feed line connecting with said uniform bore in said housing for feeding fuel between said injection pump and said uniform inner bore, a spring for urging said control slide valve into a rest position, said control slide valve being displaceable from said rest position against the force of said spring by the fuel fed from said injection pump via said feed line to said uniform housing bore, a delivery line connecting with said upper annular groove in said housing for feeding fuel between said upper housing bore and said injection nozzle, a working chamber disposed upstream of said control slide valve, a fuel reservoir, a relief line connecting with said lower annular groove in said housing for feeding fuel between said lower housing bore and said reservoir, said control slide valve including means for displacing, during a first portion of a sliding movement of said control slide valve from said rest position, a preliminary injection quantity of fuel from said working chamber through said central bore in said control slide valve into said delivery line, said lower annular groove on said control slide opening-up said relief line in order to terminate said preliminary injection, said upper shoulder on said control slide valve closing the passage between said working chamber and said delivery line, said control slide valve including means for connecting said feed line directly with said delivery line, during a second portion of said sliding movement of said control slide valve, for purposes of principal injection, characterized in that said middle shoulder on said control slide valve closes-off temporarily the passage between said relief line and said working chamber so that said control slide valve is isolated from reservoir pressure and is thereby braked until the passage between said relief line and said working chamber is re-established before again interrupting the direct passage between said delivery line and said feed line during the return movement of said control slide valve to said rest position.