Fuel injector

A fuel injector as claimed in any one of the preceding claims, wherein the actuator comprises a fixed solenoid coil (3) and a return spring (11) for the movable plunger (2).

A fuel injector as claimed in any one of the preceding claims, wherein the monitoring means comprises position measurement circuitry the arrangement being such that in use the solenoid coil (3) provides motive force to the plunger (2) and to the piston means, and the solenoid coil (3) provides positional feedback information of the position of the plunger (2) to the position measurement circuitry of the monitoring means (10).

A fuel injector as claimed in any one of the preceding claims, wherein the solenoid coil (3) comprises a single winding with two external electrical connections.

A fuel injector as claimed in any one of the preceding claims, wherein the fuel injector (1) comprises fuel atomisation means, the arrangement being such that in use fuel is forced through the atomisation means by the movement of the actuator;

• the actuator generating sufficient force to pressurise the fuel to a level which will obtain satisfactory atomisation.

A fuel injector as claimed in any one of claims 21 to 24 wherein, in use, the fuel injector (1) delivers the fuel in two strokes of the plunger (2) and piston means (4), at least one of those strokes being over the full stroke distance of the plunger as dictated by the end stop (16), this enabling the positional feedback system calibration operation to be carried out more frequently.

A fuel injector as claimed in any one of the preceding claims, wherein the pump assembly comprises two pumps;

• a primary high pressure pump and a secondary low pressure pump, the arrangement being such that, in use, the primary high pressure pump transfers the metered fuel dose into an engine and the secondary low pressure pump generates positive pressure during an inlet stroke of the primary high pressure pump reducing the tendency for the formation of bubbles within the primary high pressure pump.

A method for detecting the position of a movable plunger (2) of a fuel injector (1) comprising an electrical actuator comprising a solenoid coil (3) and the movable plunger (2);

• a pump assembly comprising piston means being movable by the electrical actuator and monitoring means (10) for controlling the amount of fuel dispensed, the method comprising first moving the plunger (2) and the piston means using the solenoid coil, and characterised in that the method further comprises monitoring the change in the electrical properties of the solenoid coil (3) caused by the change in the position of the plunger (2) within the solenoid coil (3) to provide the position of the plunger (2).