Hydraulically actuated fuel injector with injection rate shaping

Abstract

Fuel injection rate shaping is integrated into the pressure intensification stage of a hydraulically actuated fuel injector having a pressure intensifier. In a first embodiment, the pressure intensification plunger is formed of two parts creating a damping chamber therebetween from which fluid is forced out through orifices in a lower one of the plunger parts during an initial phase of displacement of the upper part. Thus, injection will be performed initially at a lower pressure and rate, which increases once the plunger parts make contact. In a second embodiment, a throttled flow is set via a restrictor housing that telescopingly receives the upper plunger part, so that a lower injection rate occurs while fluid is bled off through a restricted flow path between the restrictor housing and the upper plunger part, and a higher injection rate is produced once a port in the upper plunger clears the restrictor housing. In a third embodiment, the two plunger parts of the intensifier have different areas relative to each other. In a fourth embodiment, flow to the intensifier plunger is varied by the intensifier plunger co-acting with a shaped inlet port increasing the effective area of the inlet port through which flow enters the intensifier as the intensifier plunger is displaced during its injection stroke. In a fifth embodiment, a throttling effect produced by a clearance between a protrusion on the intensifier plunger and a receiving bore in the intensifier body is used reduce the intensification effect during the initial phase of injection.