CA1125605A

CA1125605A - Fuel injection systems

Info

Publication number: CA1125605A
Application number: CA340,607A
Authority: CA
Inventors: Boaz A. Jarrett; Dorian F. Mowbray
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1979-07-20
Filing date: 1979-11-26
Publication date: 1982-06-15
Also published as: AU5302179A; IT1125825B; DE2946576A1; ES486164A1; BR7907511A; PL219772A1; IT7927381A0; JPS5618061A; ZA796249B; FR2461827A1

Abstract

A B S T R A C T
A fuel injection system for an engine includes a plurality of pump/injectors each incorporating a pumping plunger actuated by movement of a respective armature forming part of an electromagnetic device. The extent of movement of the armature under the return motion of a spring determines the amount of fuel which will be supplied to the engine at the next stroke. This movement is det-ermined by an adjustable lever and the levers of the individual injectors are interconnected by a linkage to a single actuating device having associated with it a transducer to provide a signal indicative of the setting of the levers.

Description

~5 This invention ralates to a fuel injection system for supplying fuel to an internal combustion engine and of the kind comprising a plurality of individual injection pumps each including a reciprocable pumping plunger and means within the pump for actuating the associated plunger, each pump having associated therewith a fuel injection nozzle through which the fuel displaced by the associated plunger flows`in use, to a combustion space of the engine.

It is known to operate the plungers by hydraulic act-uating means which in turn is controlled by an electrically operated valve means. It has been suggested that the ylun-gers can be operated directly by an electrically powered device. The supply of electrical power to the valve means or the device is controlled by a control system which is supp-lied with signals representati~e of ~arious dssired and actual engine operating parameters and ~ith signals indicative of the position of the rotating parts of the engine, so that the delivery o~ fuel occurs at the correct time. The control of the fuel quantity presents a further problem and it has been proposed that the control can be achieved using trans-ducers a~sociated ~ith the pumps respectively to sense the position of the plungers and supply a signal to the control system which by partly energising the valves or the devices, is able to halt the movement of the plungers during their filling strokes. The pro~ision of the transducers and their connection to ths control system adds to the complexity of the fuel system and in addition the control system is made complex because it needs to be able to respond to the signals from each transducer and supply the necessary holding curr-ent to maintain the position of the associated plunger ~hilst at the same time being capable of supplying current to other of the fuel pumps. In addition the fuel quantity supplied to each injector can vary depending upon the rel-ative accuracy of the transducers.

The o~ject of the present invention is to provide a system of the kind specified in a simple and conveniant form.

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According to the invention in a fuel system of the kind specified each fuel pump includes ~n adjustable stop member operable to determine the position attained by the pump plunger during i~s filling stroke, linkage mean~
interconnecting the stop members, an actuating mQchanism for setting the position of said linkage means and a trans-ducer for providing a qignal indicative of thc setting of said stop members~ said signal in use being supplied to a control 3ystem which controls the operation of said actuat-ing mechanism.

In the accompanying drawings:-Figure 1 is a diagrammatic dr~wing of one e~ample ofa fuel sy3te~ in accordance with the in~ention9 and Figure 2 is a ~ectional side elevation showing part o~ the sy~tem seen in Figure 1, Referring to the drawings~ the fuel system comprises a plurality of pump/injector~ 9 equal in number to the number of cylinders of the associated engine. The pump injectors are illustrated in detail in Figure 2 and with reference to Figure 2, each pump injector comprise3 a housing 10 which is of general:Ly cylindrical form. Ths housing 10 is provided with a first boss portion 11 extend-ing axially from the housing and a ~econd boss portion 12 which extends laterall~ ~rom the hou~ing. Both boss portions are provided with screw threads.

The first boss portion is of hollow form and defin~s an internal step 13 against which is located the flange of a pump barrel 14. The pump barrel 14 extend~ with clearance within a cylindrical chamber 1~ defined within the hou3ing.
The flange of the pump barrel 14 is held in engagement with the step 13 by means of a sleeve 16 one end of which engages the flange, The othar end of the sleeve is of reducad diameter and engages with a flange 17 fo~ed on an injection nozzle assembly generally indicated at 18. The flange 17 of the no~zla asse~bly is engaged by a retaining nut 19 which is in screw t}~ead engagement with the boss portion 11. The ~.

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retaining nut defines a cylindrical aperture through w~ich part of the nozzle assembly extends and in use, the end face of this part of the no~zle assembly together with the end face of the retaining nut 19 are exposed within the coMbustion cha~ber of an engine. As shown~ a step on the retaining nut is located against a copper or like washer shown-in dotted outline at 20 and which is located against a step defined in a bore formed in the cylinder head of the engine.

The nozzle as3embly includes a valve member 21 one end of which dafines a head for co-operation with a seating.
The ~alve member is biased to the closed position by means of a coiled compression spring 220 As will be appreciated by those skilled in the art the nozzle assembly is of ths outwardly opening type which when fuel under pressure acts against the aforesaid valve head, the valve member is moved against the action of the spring to permit fuel to flow through an outlet.

Located within the bore defined in the p~p barrel is a pumping plunger 23. The pumping plunger extends from the end of the barrel and defines a flange between which and the end of the pump barrel is located a coiled compres-sion spring 24. The flanged end of the p~mping plunger is pro~ided with radially extending groov0s and the mo~ement of the pumping plunger under the action of the spring 24 is limitad b~ ~butment of the pumping plunger with a stop ring 25 which is located against a step defined in the housing. ~loreover~ the pumping plunger is provided with a recess which as shown, recei~es the end of a push-rod 26.

~ uel is supplied to the space defined within the housing in a mannerwhich will be explainsd, This fuel is ~der a small pressure and during outward mo~ement of the pumping plunger under the action of the spring 24~fuel is drawn into the cylinder defined by the pump barrel.
This fuel flows by way of a non-return valve qo that ~hen the plunger 23 is moved inwardly against the action of the spring 24 the non-return valve remains closed and the fuel displaced by the pumping plunger is supplied through the nozzle assembly.

The non-return ~al~e comprises a valve member 27 having a shank portion 28 which iq slidably supported within the bore in the pump barrel. The valve member also includes a ~alve head 29 which is of larger diameter than the ~hank portion and this in the closed position of the valve membery engages with an annular edge 30 defined at the end o~ an enlarged portion of the bore in the barre~. The valve membar is urged to the closed poYition by a compression ~pring 31 and extending through the valve member is a bore 320 In addition, the barrel 14 i9 provided djacent the flange, with a pair of radially extending ports 33.
At their outer ends the ports 33 communicate with the space defined between the oute~r periphery of the pump barrel and th0 ~all 15 of the chamber formed in the hou ing.
At the inner ends, the ports c:ommunicate with a circumferen-tial ~roove 34 formed in the periphery o~ the shank 28 of the valve member. Moreo~er, 1he shank 28 of the valve member is of a length such that towards the end of the strcke of the pumping plung~r, the latter will engage with the shank and lift the valve member against the ac~ion of the spring 31. When this occurs toward~ the end of the delivery of fuel by the pumping plunger, the pressurQ of fuel supplied to the nozzle iq lowered quickly to that obtain-ing in the chamber containing tha pump barrel. The reason for this i5 that when the valve member is lifted the groove 34 places the ports 33 in communication with the enlarged portion of the bore beneath the head of the valve me~ber.
As a re~ult of the rapid reduction in the fuel pres~ure, the head o~ the va]ve 21 can move quickly onto it~ seating and the risk of fuel being supplied through the nozzle assembl~
în an unatomised condition is minimised.

` ~%~ 5 Jhen the pumping plunger is returned under the action of the spring 24 the valve member 27 remains in a position such that the ports 33 are in communication with the bore and with the head 29 lifted from the edge 30. The reason for this i5 that fuel under pressure from the ~foresaid chamber acts on the valve head and flow o-f fuel occur~
into the bore occupied by the pumping p~unger. The flow of fuel into the bore continues until the moYem~nt of the plunger is halted ei-ther b~ the stop ring 25 or earlier as will be e~plained. ~s soon as movement o~ the plunger 23 is halted no further fuel can flow into tha bore and the fluid pressureq acting on the valve member 27 are equali_ed. As a result the valve member mo~es under the action of the spring 31 until the head engages the afore-said edge. The communication of the port~ 33 with the bore is therefore broken.

An electromagnetic device is provided for effecting movement of the piston 23. ~lis movement is achieved through the push rod 26 which Qxtends with clearance through a drilling34~formed in a core member 35 conveniently formed integrally with the housing 19. The core m0mber extends on the opposite side of the housing to the first boss portion 110 The core member is formed from magnetisable material and therefore in the present construction 50 i~
the h~using 10. It will be appreciated however that the core member and the housing may be formad as separate part~q.

The core member is of generally truncated conical configuration and it is provided with a plurality of circumferentially extending grooves 36. The grooves 36 define circumferentially extending ribs 37 and it will be noted that the further a particular rib is from the housing 10 the smal~er i~ its di~meter. ~oreover, this also applies to the depth of the grooves 36 and in general the width of the grooves increases as ths distance from the housing 10 increases.

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The outer surface of the ribs 37 are inclined to the axis of the core member a~d located within each groove i5 a winding 38. The ~indings con~eniently are connected in series in such a fashion that when electric current is passed through the winding~ the direction of current fl~w in adjac~nt windings is in th0 oppo~ite dir0ction. In thi 3 manner adjacent ribs 37 ~hen electric current is passed through the windings 9 will be magnetiQed to oppo~it~
magnetic polarity. Conveniently on~ end of the ~eries connected windings is connected to the oors member whilst the other end of the series connect~d windings is led out to a terminal which i~ carried by an electrically insulating block 4O which is sccured to the housing 10 as shown in Figure 3.

Surrounding the c~re member is an armature 41~ This is also formed from magnetisable material and ha9 a thin saction. The armature 41 can be regarded as a number of hoops of reducing diameter connected together by inclined portions such a.q shown at 4~ the internal fa~es o~ the inclined portion~ l~ing subst~.ntially parallel to the aforesaid faces of the ribs 37'. The armature is of cup-shaped form and the base wall is pro~ided with a pair of ~pertures 43 and a oentral aperture which receives a plug 44 in which is located the remote end of the push rod 26, In use) when the windings are Qupplied with electric current;
the armature will mo~e downwardl~ as shown in the drawing~
to reduca the reluctance of the air gaps betwesn the ribs and the inclined portions 42 of the armature, In so doing movement will be imparted to the pumping plunger 23.
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SurroundIng the armature is a hollow cup shap~d cover 45 which is formed from non-magnetic material conveniently as a die ca~ting from a ~.inc based alloy~ As will be seen frcm the dra~ing the cover has a stepped outer peripheral surface and the sides thereof taper to permit its tiith-drawal *rom the die cavity~ Th0 internal peripheral surface is also of stspped form and is shaped as will be described~
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to support the armature for axial mo~ement. Tha end portion of the co~er that i9 to say in g~neral that portion ~xtending between ths aforesaid external step which is refsrenced 46 and the housing 10, is formed with four internal rib~ 47 and defined between these ribs are rec2sses~
As explained in order to p~rmit the c~sting to ba removed from the die, the internal surfaces are tapered. Aft2r removal from the die cavity~ the ribs 47 are machined so as to define ~qurfaces which extend parallel to the axis o~ the core member. As a result four bearing surface~ 48 are formèd which are engaged by the arm~ture at it~ wider end~

The co~2r is provided with four further ribs 49 and again when manufactured these ar0 tapsred to permit removal of the ca~ting from the die. Subsequently the internal surfaces of the ribs 49 are machined to provide bearing surfaces 50 engaging with oomplementary surfaces of the armature nearer the narrow end thereof. rne space defined within the cover 35 is connected to a fuel inlet 52 formed in the boss 12 and in use~ fue:L can flow upwardly on the inside or the outqida of the a;~ature through the apertures 43 if it has flowed upwardly on the out~ide of the armature, and down the drilling 34-to the bore 1; in the housing. Thus-cooling of the windings i9 achieved by the fuel. The pump~
injector is retained in position witnin the bore in the cylinder head by means of a clamping ring 53 ~hich is in engagam~nt with the step 46 on the cover. ~ne clamping ring is provided with a pair of ears in which are loeated apertures through which extend in use~ threaded studs seoured within apertures formed in the cylinder head of the engi~e.
A pair of nuts 54 are engaged with the studs. One ~tud is shown in dotted outline in Figure 2.

The amount o~ fuel which i~ deli~ered through the nozæle depends upon ths position of the plunger 23 at the end of the filling strokeO This aq shown in Figure 1, is deter~in~d b~
means of an adjustable stop member in the form of a cam 54 ~L2~ 5 which i9 cRrried upon a shaft supported for angular moVQment within the cover 45~ The cam is engageable by the plug 44 of the armature 419 and connected to the shaft is a lever 55 whiGh is coupled to a linkage 56 which is also connected to the respective levers 55 of the remaining pump/injectors.

Ths linkage 56 is coupled to one end of a further pi~oted le~er 57 the other end of which is provided with a spherical end located between a piston 58 and an abutm~nt 59. The piqton and abutment are qlidable within a cylinder 60, the abutment being spring loaded by a coiled compression spring 61. The end of the cylinder containing the spring commun-icates with a drain whilst the other end of the cylinder communicates with the outlet of a pump61- which draws liquid conveniently fuel9 fxom a tank 62. In the example the tank contain~ fue an~ the outlet o~ the pump i~ connected to the fuel inlets 52 of the indi~idual pump/injectors. The output pressure of the pump is contro:Lled by a relief valve 63 and connected between the outlet of the pump and the c~linder 60 is a control valve 64, A point downstream of the valve 64 is connscted by way of a restrictor 65 to drain. The valve 64 i9 electrically controlled l~nd by reducing the degree of restriction offered by the valve so the pre~ure applied to the piston 58 is increased. A3 ths pres~ure applied to the piston 5~ increases the le~er 57, and the linkage 56 and the levsrs 55 move the cam 54 to allow the armature and plunger 23 to move further outwardly. In other words the effecti~e ~troke of the plungar at the next stroke i~ increased and so an increased quantity of fuel will be suppliad through the nozzle. Conver~ely, if the pressure applied to the piston 58 is reduced then the stroke of the plunger i5 reduced.

The valve 64 is controlled by a control system 66 which also acts as 2n engine governor, The system is supplied with a demand signal along a line 67 a~d with signals indicative of the position of the rotating ~rts of the engine along a line 68. Signals are supplied by the control systel~ to the windings of the pump/injectors to ensure that the latter are , ~, 2560.5 . o operated in timed relationship with the engine. The controL
system 66 is also provided with a signal indicative of the setting of the cams 54 by means of a transducer 69 which comprises a winding 70 ~ound upon a former surrounding the abutment 59. The latter varies the inductance of the winding 70, by its movement and the ~ignal supplied to the control system is used in the control system to ensure that the ~et-ting of the valve 64 i~ adjusted so that the correct quantity of fuel is supplied to the engine appropriate for the par-ticular desired and actual engine operating conditions.

Whilst a hydraulic actua~ing mechanism has been des-cribed for the purpose of adjusting the linkage and the cams it l~ill be appreciated that other forms of actuating mechanism could be used for example, an electrical motor or a pneumatic device.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fuel injection system for supplying fuel to an internal combustion engine and comprising a plurality of individual injection pumps each including a reciprocable pumping plunger, means within the pump for actuating the associated plunger, fuel injection nozzles associated with the pumps respectively and through which fuel displaced by the associated plungers flows, in use, to the combustion spaces of the engine, an adjustable stop member operable to determine the position attained by the pump plunger during its filling stroke, linkage means interconnecting the stop members, an actuating mechanism for setting the position of said linkage means and a transducer for providing a signal indicative of the setting of said stop members, said signal in use being supplied to a control system which controls the operation of said actuating mechanism.

2. A system according to claim 1 in which said stop member comprises an adjustable cam.

3. A system according to claim 2 in which said means for actuating the pumping plunger comprises an electromagnetic device including an armature operatively connected to the pumping plunger.

4. A system according to claim 3 in which said adjustable cam is mounted upon a cover surrounding the electromagnetic device.

5. A system according to claim 1 in which said actuating mechanism comprises a fluid pres-sure operable piston located within a cylinder, resilient means biasing the piston to a position in which a minimum amount of fuel will be supplied to the engine and valve means operable to vary the fluid pressure applied to said piston.

6. A system according to claim 5 including a pivotal lever, of end of which is connected to a link connected in turn with the lever respectively of the pumps, the other end of the lever being interposed between said piston and an abutment for said resilient means.

7. A system according to claim 6 in which said abutment forms one part of said transducer, the other part of said transducer being constituted by a winding surrounding said abutment and carried on a fixed member defining a cylinder for said piston and said abutment.

8. A system according to claim 5 including a supply pump for supplying fuel under pressure to said fuel pumps, said valve means including a valve connected between the outlet of the supply pump and a cylinder containing said piston and a restricted passage from a point downstream of said valvs whereby the pressure applied to said piston can be varied by adjustment of said valve.