Document 2R28OmgyDo7QVvjkevzyZBzb

653 tbi helix in relntion to port. In oted, changes clearance between tappet ernor-actuated control lever moves rcl determine, .mount ol fuel and valve stem. At full toad, clearance needle valve in or out to pass more or red, as will be seen later. Action is great and plunger moves a consider* leas fuel to pump chamber. located below the pump, lifts able distance before rocker opens spill After passing needle vatve, fuel flows Vl, tod spring action returns it. valve. At partial loads, clearance be* into the chamber as long es fuel-inlet hSi* ncloscs lh< pump barre1, comes less and effective pump stroke port is left open by plunger. In its low |ASi S pinion which engages a rack . decreases. est position, upper edge of plunger Ktusted 11x6 *overnor- With 11x19 Wobfcl-Plat Design. Another valve. opens inlet port approximately half P?#,gement, governor action can controlled1 constant-stroke pump is way. Fuel delivery commences when iSSiie angular position of plunger shown in Fig. 11. Individual pump cyl. upper edge of plunger, during upstroke, feSSut Interfering with its reciprocat- indera stand radially around a central closes inlet port Fuel injection termin ll'S'sction. A .transfer pump keeps In- rotary valve. Drive unit has a vertical ates when lower edge of plunger head SSon-pump suction line filled with takeoff for the governor and powers a reopens inlet port end cuts off delivery. |5jo port* *re alwBy| ubmerged. wobble plate which gives reciprocating Fuel displaced by plunger after cutoff *>dp*rf,n* Frlaelpto. As shown In Pig. motion to injcction-pump-plUnger push Is returned to inlet manifold through 7both inlet and bypau ports are rods. Central valve turns at wobble- drilled passage In plunger head. & when plunger is at bottom of its plate speed. Variable-Stroke Pvaps. Thus far all e. fuel fills space above plunger After passing through tranater pump, pumps pictured and discussed have Jji flaw* through vertical groove to strainer end filter, fuel flows to a recess operated with a constant stroke. fafbeilcal recess. Aa plunger starts up. formed by a spool-like reduction in Changes in pump discharge required to U closes porta and traps oil above. diameter of the rotary valve. Valve meet variations in losd can also be 0Pressure builds up in pump, spring* ends flt closely In the bore, preventing produced by altering length of pump discharge valve opens ond fuel any escape of fuel endwise. The middle stroke. In one design, for example, in* !&Ss to the nossle. When pressure at spool-like section of the valve has one dividual fuel pumps cluster around a Rattle reaches desired injection level, triangular section or /and, which has single cam drive. By extending or with &iti(tpriaf.loaded needle valve opens the aarrfe diameter as the spool ends. drawing the single driving cam, gov *& injection starts. It continues until Fuei flows from the valve recess to ernor changes pump stroke and omount (plunger has risen enough to cause up- the space ahead of the Injection-pump of fuel delivered. Fuel cam con be Bjet edge of helical recess to uncover the plunger, by way of a port, and excess moved to change injection timing. itijpan port, which releases pressure. fuel returns to the chamber in the some In another case, individual pump ?'Botb nosxle valve and pump delivery way. As the plunger moves in the dis cylinders mount above a camshaft that Bivalve snap shut and cycle repeats. charge direction, the central valve ro is really a shaft within a shaft; the &7* it can be seen that amount of fuel tates to a position where the triangular center being movable longitudinally. Onjected depends on how long It takes land starts to close the port Plunger This motion retracts or protrudes the ytw the helix to uncover the bypass motion then builds up pressure until cams to change pump stroke as needed report. ThU In turn depends on the plung- the delivery valve at the end of the tfo'i position in the barrel, which Is plunger space opens and fuel flows into UNIT INJECTORS. j'.'cDntroUed by the fuel ruck and gover* discharge tubing. Continued valve ro With the plunger turned far enough tation puts triangular land past port Unit injectors, a relatively recent de ^ttp^the right for the vertical groove to opening, relieving pressure in plunger velopment, combine the putpp fuel Srcfirter with the bypass, the pump chamber. Excess fuel returns to the valve and nossle in a single housing, SitxiUdi oo pressure because there is al* valve chamber through the port* thus eliminating discharge tubing. This is connection between the space Qeontlty Control. Control of amount permits extremely high injection pres Ifcve the plunger and the bypass port of fuel injected is effected by moving sures, up to about 20,000 psl In some Rmi U the atop position. As the con* rotary valve endwise, thus changing designs. ntrol rack turns plunger to left time* position of triangular land in relation The unit injector of Fig. 12 consists ^between closing of ports by plunger top to port When apex of triangle is oppo of a helix-grooved plunger in a barrel vud uncovering of bypass by helical site port, land closes port for a brief with ports: the plunger Is driven down Rfniove becomes longer, increasing ^u- interval only and fuel delivery Is short; by o cam-actuated rocker arm against Niitkm and omount of injection. Pumps when base of .triongle comes opposite the resistance of a spring; a governor- design are built os single units port, greater width of land closes port actuated control rack turns the plunger tue Pig. 7, or with a number of barrels for a much longer time, and delivery to position the helix with respect to the d plungers in a single housing. is increased proportionately. ports. Below is the delivery valve and |VALVB.CONTROUID pumps Jm Operating from the main drive unit, rotary valve turns at same speed, while wobble-plate action Is such that Indi- noule. Fig. 14 shows another unit-in jector design and Fig. 13 illustrates its operation. ^Constant-stroke pump of Pig. 9 oper* vldual injection plungers stand ot dif Ualt-1a|ectbr Operoilaa. As can be ffir* "spill-valve'* principle. Fuel ferent stroke positions ot any one time, seen in Fig. 13, the plunger has a helical cir***! suction chamber and flows and therefore in different relations to groove in its side, connected to the u&fnigh a suction valve Into the pump rotary valve. Wobble-plate action, ond space under the plunger by a passage. on the plunger downstroke. On &V$*' upstroke, pressure lifts the dis- fe^srge valve and fuel flows Into dis. its timing with rotation of valve, per* mits the single valve to serve each in* jector in turn. There are two porta on one side, an inlet port and a bypass port aboveT" With plunger in highest position, fuel vwge tubing until a spill valve opens Needla-Yolva Design. Fig. 10 shows enters Inlet port until lower edge of fcto^bypMj fvje] hack to suction eham* another valve-controlled constant- plunger dose* it and pressure rise be &&! <^9 reIea,e9 pressure end dis* stroke pump designed specifically for gins. When pressure reaches proper gjN**Valve *naP* shut. small engines. The plunger is cam oper level, oil discharges through the nozzle fneker and tappct'auembly for ated. Fuel enters the pump chamber valve. As downstroke begins, lower P'H valve is so arranged that the through an orifice whose area is regu edge of helix passes the bypass port, re gRjJttfol rod, which is governor-ectu- lated by a needle valve. Action of gov leasing pressure, and spring closes nos- Wu . April m* ptri II