GB2183370A - Fuel injection pumping apparatus - Google Patents

Abstract

A piston 35 movable in a cylinder 36 by fuel under pressure to vary the timing of fuel delivery. Following starting of the associated engine the piston is movable against the action of a first spring 50 to provide advance of the timing of fuel delivery up to a maximum amount as determined by a stop 58. When the engine rotates at a speed higher than its governed maximum speed, the piston can move an additional amount against the combined action of the spring 50 and an additional spring 56. <IMAGE>

Description

SPECIFICATION Fuel injection pumping apparatus This invention relates to a fuel injection pumping apparatusforsupplying fuel to an internal combustion engine, the apparatus being ofthe kind comprising an injection pump driven in timed relationship in use, with the associated engine, a feed pumpfor supplying fuel under pressure to the injection pump, a fuel control device for controlling the quantity of fuel supplied to the injection pump and thereby the quantity of fuel supplied to the engine at each injec- tion stroke of the injection pump, fuel pressure operable meansforcontrollingthetiming of delivery of fuel by the injection pumpandvalvemeansforcon- trolling the output pressure of the low pressure pump so that the pressure varies in accordance with the engine speed, the low pressure pump serving as the source offluid under pressure for said fluid pressure operable means.

In an apparatus ofthe aforesaid kindthefuelcontrol device which may for example be a simple throttle member, is operated by a governor mechanism responsive to the speed at which the apparatus is driven. The governor mechanism acts to control the maximum speed of the engine by reducing the rate offuel supply to the engine as a predetermined maximum speed is approached. The fluid pressure operable means acts to advance the timing offuel delivery as the speed of the associated engine increases and conventionally includes a stop whereby for normal full load operation oftheengine, there is a limit to the amount by which the timing can be advanced.Moreover, as the amount offuel which is supplied tothe engine is reducedthetiming offuel delivery automatically occurs later.

When under engine overrun conditions the engine speed exceeds the aforementioned predetermined maximum, it is found that misfire can occur ofthe very small quantities offuel which are supplied to the engine under such conditions and particularly this is the case when the fuel quality is poor. The misfire can be cured by advancing the timing offuel delivery. Various forms of fluid pressure operable means are known in which additional advancement of the timing of fuel delivery is obtained bythe use of a valve coupled to or associated with the throttle member. These however are effectivetocauseadv- anceofthetiming offuel deliverywhen the engine is operating belowthe predetermined maximum speed, a feature which may not be required.

The object ofthe present invention is to provide an apparatus ofthe kind specified in a simple and convenientform.

According to the invention in an apparatus of the kind specified said fuel pressure operable means comprises a cylinder, a piston movable in said cylinder and connected to a component of the injection pump, passage meansforadmitting fuel underpres surefromthe low pressure pump into one end ofthe cylinder to move the piston in the direction to advance the timing of fuel delivery, first resilient means acting to oppose the movement ofthe piston, a stop acting to limitthe movementofthe piston underthe action of fuel pressure and defining the normal maximum degree of advance upto a predetermined maximum engine speed, and second resilient means acting on said stop, said piston moving said stop against the action ofthe second resilient means in the event that the engine speed exceeds said predetermined maximum.

An example of a pumping apparatus in accordance with the invention will now be described with refer ence to the accompanying drawings in which:- Figure lisa sectional side elevation of a known form ofthe apparatus, and Figure2isasectional side elevation taken atright angles to the view of Figure 1 showing a partofthe apparatus not seen in Figure 1.

Referring to Figure 1 ofthe drawings, the apparatus comprises a two part housing 9, 10, the housing part 9 being provided with an open end in which is located the part 10 ofthe housing.

Formed within the part 10 ofthe housing is a bore in which is mounted a rotary cylindrical distributor member 11 which is coupled to an input shaft 12 journalled in the part9 ofthe housing. The shaft 12 is adapted to be driven in timed relationship with an engine with which the apparatus is associated.

Formed in the distributor member is a transverse bore 14in which is mounted a pairofreciprocable pumping plungers 15which are arranged to be moved inwardly as the distributor member rotates, through the intermediary of a pair of rollers 16 respectively by cam lobes not shown, formed on the internal peripheral surface of an annular cam ring 17 mounted within the part 9 ofthe housing.

Also formed in the distributor member is along- itudinallyextending passage 18which atone end is in communication with thetransverse bore 14 and at its other end is in communication with a radially disposed delivery passage 19. The delivery passage is arranged to register in turn with a plurality of equi angularly spaced delivery ports constituted as shown in the drawing, by passages 20. These are formed in the part 10 of the housing and in use are connected by pipe lines respectively to injection nozzles mounted on the associated engine.The registration ofthe passage 19 with one of the delivery portstakes placeduringthewholetimetheplungers 15 are being moved inwardly so thatfuel contained within the bore 11 will be displaced to a combustion space ofthe engine.

At another position the longitudinal passage 18 is in communication with a plurality of equi-angularly spaced and radially disposed inlet passages 22 which are arranged to register in turn with an inlet port 23 formed in the part 10 ofthe housing. The inlet port 23 is in communication with a control port 25 by way of a passage 24 and the control port is in communication with the outlet 26 of a low pressurefuel supply pump 27.

The effective size ofthe control port 25 can be varied byvarying the angularsetting of a throttle member 28 which has a groove formed therein and the arrangement is such that when an inlet passage 22 registers with the inlet port 23, fuel will flowfrom the outlet of the low pressure pump to the transverse bore to move the plungers 15 outwardly. The afore said registrationtakesplaceonlyduringthetime when the delivery passage 19 is out of register with a passage 20. By adjusting the angular setting ofthe throttle member 28, the rate at which fuel can fl ow to the bore 14 can be controlled and hence also the quantity offuel delivered to the engine at each injection stroke is controlled.

The low pressure pump 27 is provided with an inlet which communicates byway of a passage 29 with an inlet port 30 which is formed in a hollow part37 secured to the housing. The part 37 has mounted therein a tubularfilter element 32 and a reliefvalvewhich includes a spring loaded element 33. One end ofthe element 33 is exposed to the pressure offuel delivered bythe low pressure pump and itcontrolsthesize of spill port34throughwhichfuel can be returned to the inlet of the low pressure pump. The low pressure pump always pumps more fuel than is delivered to the engine with the result that the output pressure thereof is controlled in a manner which is dependent upon the speed of the engine and which increases therewith.

The cam ring 17 is mounted for angular adjustmentwithin the housing and this adjustment is effected by means of a fluid pressure operable means which includes a piston 35 mounted within a cylinder 36 formed in further partsecuredto the exterior of the housing part 9. The piston is connected to the cam ring by means of a peg 37, the peg locating within a transverse opening formed in the piston.

Fuel is supplied to oneend ofthe cylinder byway of a passage which includes a check valve 38, from the passage 26. The purpose of the check valve isto preventfuel passing from the cylinderto the outlet of the low pressure pump duetothe interaction ofthe roller 16 with the cam lobes.

The angular setting ofthethrottle member 28 is conveniently controlled by a mechanical governor which includes weights 39 accommodated in a cage driven by the shaft 12. The weights and cage are accommodated in the housing part 9 and the weights act upon an axially movableflanged collar40 mounted aboutthe drive shaft 12. The axial movement of the collar is resisted by a governor spring 41 which is mounted between one end of a pivotal lever 42 and an operator adjustable member 43.The other end of the lever42 bears upon the collar40 andthe oneend ofthe lever42 is connected by a tie rod 44to an arm mounted on the throttle member whereby as the speed of rotation ofthe engine increases, the collar 40 will be moved axially by the weights against the action ofthe spring and during this movement the throttle member 28 will be moved angularly toreduce the quantity of fuel delivered to the engine.

Turning now to Figure 2 ofthe drawings the one end of the cylinder 36 to which fuel under pressure is supplied from the outlet ofthe low pressure pump, Is closed by a plug 45 which defines a stop 46 which limitstheextentofmovementofthepiston underthe action of various springs as will be explained. The stop 46 therefore defines the maximum retarded position ofthe piston. The piston is loaded towards the stop by a light spring 47 which is interposed between the piston and a spring abutment plate 48. The abutment plate 48 defines a tubular spigot portion 49 which can be engaged bythe piston as is seen in Figure 2. The abutment plate is itself spring loaded by a first resilient means in the form of a coiled com pression spring 50, into engagement with a circlip 51 which is located within a recess formed in the cylin der36.The end ofthespring 50 remotefromthe abutment plate locates against an abutment surface defined by the end wall of a cylindrical recess52 formed in a closure cap 53 forthe end of the cylinder remotefrom the cap 45. The closure cap defines a further cylindrical recess 54 in which is mounted an axially movable member55, the member being urged towards the piston 35 by means of second re silientmeansintheform of a coiled compression spring 56,thespring 56 atone end engagingthe member 55 and at its opposite end engaging an end closure 57forthe recess 54.A bore extends between the recesses 52 and 54 and extending through the bore and intothe bore defined bythetubularspigot portion 49, is a stop member 58 which is provided with a flange 59 engageable by the axially movable member 55.

In operation, and assuming firstlythatthe associated engine is at rest, the piston 35 will be moved into contact with the stop 46 by means ofthe spring 47.

As previously stated, this position ofthe piston prov ides maximum retard ofthetiming of delivery of fuel.

This isforthe purpose of starting the associated engine. When the engine has started the piston will be acted upon by fuel under pressure and will move into engagement with the end of the spigot portion 49 as shown in the drawing and such movement will occur at a comparatively low engine speed. Asthe engine speed continues to increase the force due to the fuel under pressure applied to the piston will gradually increase and the preload of the spring 50 will be overcome, allowing the piston to move against the action ofthis spring to provide normal advancement of the timing of delivery of fuel throughout the range of engine speeds up to the predetermined maximum engine speed. The limit ofthe degree of advance provided by the piston in the normal working range of the engine is attained when the piston engages the stop member 58.This may occurslightly before the predetermined maximum engine speed but the actual speed at which this occurs can be varied by adjustment ofthe force exerted by the spring 50. The engagement ofthe piston with the stop member 58 does enable the dynamic timing of the apparatus to be checked on a test rig.

The predetermined maximum engine speed may be exceeded during overrun conditions and it is arranged that the outlet pressure ofthe low pressure pump will rise sufficiently to cause the piston to overcome the preload of the spring 56. The piston therefore moves against the combined action ofthe springs 50 and 56 to provide the additional advance ofthetiming offuel deliveryduring engine overrun conditions when the predetermined maximum engine speed has been exceeded. The amount of additional advance is limited either by the engagement of the axially movable member 55 with the end closure 57 or by the engagement of the abutment plate 48 with the end ofthe closure cap 53 which locates within the cylinder 36.

Claims (6)

1. Afuel injection pumping apparatusforsupplying fuel to an internal combustion engine, the apparatus comprising an injection pump driven in timed relationship in use, with the associated engine, a feed pump for supplying fuel under pressure to the injection pump, a fuel control device for controlling the quantity offuel supplied to the injection pump and thereby the quantity of fuel supplied to the engine at each injection stroke ofthe injection pump, fuel pressure operable meansforcontrolling thetiming of delivery offuel by the injection pump and valve meansforcontrolling the output pressure of the low pressure pump so that the pressure varies in accordance with the engine speed, the low pressure pump serving as the source offluid under pressure for said fluid pressure operable means, said fuel pressure operable means comprising a cylinder, a piston movable in said cylinder and connected two a component of the injection pump, passage means for admitting fuel under pressurefrom the low pressure pump into one end ofthe cylinderto movethe piston in the direction to advancethetiming offuel delivery, first resilient means acting to oppose the movement ofthe piston, a stop acting to limit the movement ofthe piston underthe action of fuel pres- sure and defining the normal maximum degree of advance up to a predetermined maximum engine speed, and second resilient means acting on said stop, said piston moving said stop against the action of the second resilient means in the event that the engine speed exceeds said predetermined maximum.

2. An apparatus according to Claim 1 in which said first resilient means comprises a coiled compression spring located intermediate an abutment plate engageable by the piston and an abutmentsurface defined by a closurecapforthe cylinder, said stop comprising a rod extending within said spring.

3. An apparatus according to Claim 2 in which said spring is a preloaded spring.

4. An apparatus according to Claim 2 in which said abutment plate carries a tubular spigot portion engageable by said piston, meansforlimitingthe movement of the abutment plate by the spring, and further resilient means acting between the abutment plate and the piston, said further resilient means acting to urge the piston against a further stop at said one end ofthe cylinderwhenthe associated engine is at rest.

5. An apparatus according to Claim 4 in which the meansforlimiting movement of the abutment plate comprises a circlip secured in the wall of said cylinder.

6. Afuel injection pumping apparatusforsupplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.