Diesel Distributor Fuel-Injection Pumps VE - Gnarlodious

Diesel fuelinjectionsystems:An overview6Injection-pumpdesignsIn-line fuel-injection pumpsAll in-line fuel-injection pumps have aplunger-and-barrel assembly for eachcylinder. As the name implies, this comprisesthe pump barrel and the correspondingplunger. The pump camshaftintegrated in the pump and driven by theengine, forces the pump plunger inthe delivery direction. The plunger is returnedby its spring.The plunger-and-barrel assemblies arearranged in-line, and plunger lift cannotbe varied. In order to permit changes inthe delivery quantity, slots have beenmachined into the plunger, the diagonaledges of which are known as helixes.When the plunger is rotated by the movablecontrol rack, the helixes permit theselection of the required effective stroke.Depending upon the fuel-injection conditions,delivery valves are installed betweenthe pump’s pressure chamber andthe fuel-injection lines. These not onlyprecisely terminate the injection processand prevent secondary injection (dribble)at the nozzle, but also ensure a familyof uniform pump characteristic curves(pump map).PE standard in-line fuel-injection pumpStart of fuel delivery is defined by an inletport which is closed by the plunger’s topedge. The delivery quantity is determinedby the second inlet port being opened bythe helix which is diagonally machinedinto the plunger.The control rack’s setting is determinedby a mechanical (flyweight) governor orby an electric actuator (EDC).Control-sleeve in-line fuel-injectionpumpThe control-sleeve in-line fuel-injectionpump differs from a conventional in-lineinjection pump by having a “controlsleeve” which slides up and down thepump plunger. By way of an actuator shaft,this can vary the plunger lift to port closing,and with it the start of delivery and the startof injection. The control sleeve’s positionis varied as a function of a variety of differentinfluencing variables. Comparedto the standard PE in-line injection pumptherefore, the control-sleeve version featuresan additional degree of freedom.Distributor fuel-injectionpumpsDistributor pumps have a mechanical(flyweight) governor, or an electroniccontrol with integrated timing device. Thedistributor pump has only one plungerand-barrelasembly for all the engine’scylinders.Axial-piston distributor pumpIn the case of the axial-piston distributorpump, fuel is supplied by a vane-typepump. Pressure generation, and distributionto the individual engine cylinders, isthe job of a central piston which runs ona cam plate. For one revolution of thedriveshaft, the piston performs as manystrokes as there are engine cylinders.The rotating-reciprocating movement isimparted to the plunger by the cams onthe underside of the cam plate which rideon the rollers of the roller ring.On the conventional VE axial-piston distributorpump with mechanical (flyweight)governor, or electronically controlledactuator, a control collar defines theeffective stroke and with it the injectedfuel quantity. The pump’s start of deliverycan be adjusted by the roller ring (timingdevice). On the conventional solenoidvalve-controlledaxial-piston distributorpump, instead of a control collar anelectronically controlled high-pressuresolenoid valve controls the injected fuelquantity. The open and closed-loop controlsignals are processed in two ECU’s.Speed is controlled by appropriate triggeringof the actuator.Radial-piston distributor pumpIn the case of the radial-piston distributorpump, fuel is supplied by a vane-typepump. A radial-piston pump with cam ringand two to four radial pistons is responsible