Abstract:
Herein are disclosed methods of conditioning fluid, such as damping fluid, in an electronically-controlled unit injector (18) in order to facilitate quick starting of an engine (12). Fluid normally used to dampen the motion of an electrical actuator assembly (36) of the unit injector (18) can remain in the actuator assembly (36) after the engine (12) is stopped. If too much fluid remains and cools off in the actuator assembly (36), quick starting of a cold engine may be hindered. Each of the above methods expels and/or heats up at least a portion of the remaining fluid in the actuator assembly (36) while the engine (12) is at rest and thereby enables quicker response of the actuator assembly (36) when the engine (12) is started. Such quicker response improves the fuel injection delivery capability and timing accuracy of the unit injector (18) during engine startup.
Abstract:
A multipiece fuel pump plunger assembly for controlling the fuel injection rate and delivery during the initial injection portion of a fuel injection cycle for an internal combustion engine. The injector (2) includes a two piece plunger assembly including a plunger (60) and a plunger sleeve (58). The plunger (60) having a small predetermined diameter and being slidably positioned within a plunger sleeve (58) having a diameter greater than the diameter of the plunger (60). The multipiece plunger (60) is advantageous because it allows for shaping of the rate of fuel injected into the combustion process thereby reducing the excess fuel flow in the early portion of the injection cycle. Elimination of the excess fuel flow results in lower oxides of nitrogen and particulate exhaust emission levels and less engine noise.