Fuel injection rate shaping apparatus for a unit fuel injector

A fluid unit injector having a fluid pump cylinder, said pump cylinder including a discharge outlet associated with one end, a fluid receiving chamber external of the cylinder, a fluid port spaced from said outlet and interconnecting the interior of the cylinder with said receiving chamber, a plunger longitudinally reciprocable within said pump cylinder, said plunger and said cylinder defining a pumping chamber, the improvement comprising:

• means positioned within said fuel pump cylinder and being actuatable by movement of the plunger for shaping the rate at which force is exerted on liquid in the pumping chamber.

A mechanically-actuated fluid unit injector, said injector having a fluid pump cylinder having a discharge outlet associated with one end, a fluid receiving chamber externally of the cylinder, a fluid port spaced from said outlet and interconnecting the interior of the cylinder with said receiving chamber, a plunger longitudinally reciprocable within said pump cylinder, said plunger and said cylinder defining a pumping chamber, the improvement comprising:

• a plunger sleeve being movable in said pump cylinder and actuatable by movement of the plunger, said plunger sleeve including a longitudinal bore, said plunger being reciprocable in said bore, said plunger sleeve having an upper and a lower port connecting said bore to said receiving chamber, and;
• said plunger further including an internal passage connecting said pumping chamber to said bore, the passage being positioned such that during movement of the plunger in its pumping direction, said plunger blocks the plunger sleeve lower port to initiate a pre-injection and said plunger passage communicates with said lower port to terminate pre-injection, said plunger sleeve ports further being positioned such that during the movement of the plunger sleeve in its pumping direction, said lower port is closed to initiate main injection and said upper port is opened to terminated main injection.