GB2133478A - Fuel injection pumps - Google Patents

Abstract

A reciprocable plunger fuel injection pump has a plunger 12 slidable in a bore 9 in which is formed a pair of spaced ports 15, 32 communicating with a fuel supply gallery. The plunger has a spill groove 17 having an inclined edge 17A. In normal operation the plunger is angularly movable to adjust the amount of fuel supplied by the pump by virtue of the edge 17A co-operating with the port 15. During starting the plunger is moved to an extreme angular position in which the port 15 is uncovered later and therefore an excess of fuel is supplied. The plunger also has a recess 34 which can co-operate with the port 32 to delay delivery of fuel when the plunger is set to provide an excess of fuel. <IMAGE>

Description

SPECIFICATION Fuel injection pumps This invention relates to fuel injection pumps for supplying fuel to an internal combustion engine of the compression ignition type and of the kind comprising a plunger reciprocably mounted within a bore, an outletfrom one end of the bore, a port formed in the wall ofthe bore, said port communicating with afuel inlet, meansformoving said plungertowards said one end ofthe bore, said plunger during such movement firstcovering saidportandthen displacing fuel through said outlet, meansforvaryingtheangular setting of said plunger and a spill groove on said plunger, said groove communicating with said one end ofthe bore and having an inclined control edge which during movementofthe plunger towards said one end ofthe bore and afterthe port has been covered by the plunger, uncovers the portto allow fuel to escape from the bore through the port, the angular setting ofthe plunger determining the amount of fuel which is displaced through the outlet.

In orderto provide for cold starting of a compression ignition engine, it is considered necessary to supply an amountoffuel in excessofthe normal maximum. This amount of fuel hasthe effect of increasing the compression ratio ofthe engine, due to accumulation offuelwithin the engine cylinders and it also acts to enhance the seal between the piston or pistons and the cylinder wall of walls. Increasing the compression ratio means that the temperature ofthe air at the end ofthe compression stroke will be higher and because the air is at its highesttemperature at the end ofthe compression stroke, it is desirable that the injection offuel shouldoccuratorjustbeforethetop dead centre position of the piston.This point of injection istoofarretardedfornormal operation of the associated engine.

Theobjectofthe invention isto provide an injection pump ofthe kind specified in a form capable of providing an excess offuelforstarting purposes and ata retardedtiming.

According to the invention an injection pump of the kind specified comprises a further port formed in the wall ofthe bore, said port being in communication with said fuel inlet and being positioned to be covered by said plunger during movementthereoftowards said one end of the bore, whereby when both ports are covered, fuel will be supplied through the outlet, said plunger defining a plane portion adjacent said inclined edge and positioned so that when the plunger is moved angularly to an excess fuel position, said plane portion will control said first mentioned port, so that it is uncovered later, du ring movement ofthe plunger towards said one end of the cylinder, said plunger further defining a recess at its end facing said one end ofthe cylinder, said recess, when the plunger is in said excess fuel position, delaying the covering of said further portsothatdelivervoffuel through said outlet starts later during movement of the plungertowards said one end of the bore.

Intheaccompanying drawings: Figure lisa sectional side elevation of one example ofthe pump; Figure 2 is a plan view of a part ofthe pump; and Figure 3 is a developed view ofthe upper portion of the pump plunger.

Referring to the drawings, the pump comprises a hollow body part lOin which is secured a pump barrel 11 having therein an axially extending cylindrical bore 9whichcontainsa plunger 12. Extending from the inner end of the bore 9 is an outlet 13 which contains a spring loaded non-return delivery valve 14. The outlet, in use, is connected to a fuel injection nozzle of a cylinder of an associated engine. Formed in the wall of the bore is a port 15 which communicates with an annularfuel supply gallery 16 defined between the barrel and the body, the gallery communicating with a fuel inlet.The port 15 is positioned in the bore so that during inward movement of the plunger itwill be covered, whereafterfurther inward movement of the plunger will displace fuel to the outlet 13 passed to deliveryvalve 14. When the plunger is moved outwardly as will be explained, fuel can flow into the bore through the port 15.

In the periphery of the plungerthere is formed a recess 17 which is more clearly seen in Figure 3 and the recess is bounded by an inclined control edge 1 7A which during inward movementofthe plunger and afterthe latter has covered the port 15, will uncover the port 15 to the recess 17. The recess communicates with the portion of the bore intermediate the plunger and the outlet, by way of an axial groove 17B and when the edge uncovers the port 15, further flow of fuel through the outlet ceases, the displaced fuel flowing, by way of the port 1 5,to the supply gallery 16.

The angular setting of the plunger 12 relative to the barrel 11 is adjustable by means to be described and because of the inclined nature ofthe control edge 17A .the angular position ofthe plungerdeterminesthe amountoffuel supplied through the outlet 13.

Surrounding the portion of the barrel remote from the outlet is a hollow sleeve 19 having a pair of longitudinal slots 20 extending inwardlyfrom the outer end. Located within the slots are a pair of radial lugs 21 which are formed on the plunger and the arrangement is such that longitudinal movement of the plungerwill not be transmitted to the sleeve whereas angular movement of the sleeve will be imparted to the plunger.

Formed on the outer periphery of the sleeve 19 is a plurality of teeth which engage with a toothed fuel control rod 22, m.ountedforaxial movementtrans- versely relative to the plunger axis, in the body part. At the outer end of the plunger is a spring abutment collar 24 between which, a washer 25 bearing on an internal shoulder in the body part, is a coiled compression spring 26 which urges the plunger outwardly. The collar 24 is located within a cam follower27 having a roller 28 adapted to co-actwith a cam 29 mounted on a shaft 31 driven bythe associated engine.

Turning nowto Figures 2 and 3, an additional port 32 informed in the wall ofthe barrel and extends into the bore, at substantially the same level as the port 15.

The port 32 also communicates with the fuel supply gallery and during inward movement ofthe plunger it is necessaryforboth ports to be covered by the plunger before fuel can flowthrough the outlet 13.

During normal operation, that is to say, when the engine has been started, the port32 isuncoveredto a circumferential groove 33, which communicates with the recess 17 and the groove 1 7B, after the port 15 has been uncovered by the control edge 17A. Ittherefore plays no part in terminating delivery offuel. The additional port 32 does however delay delivery of fuel when the plunger is setto an excess fuel position. In Figure 3the ports 15 and 32 are shown displaced angularly to positions 1 5A and 32A. This is forthe purpose ofillustration only and it will be appreciated thatwhat, in pratice, happens isthatthe plunger is displaced angularly relative to the ports.In the excess fuel position the port 15 is no longer uncovered bythe control edge 17A, but will be uncovered to the groove 33 at substantially the same time as the port 32, to terminate delivery of fuel. The quantity of fuel delivered is therefore substantially increased. However, in orderto delaythe initial deliveryoffuel a recess 34is provided in the end face of the plunger and the recess 34 is angularly aligned with the port32 when the plunger is in the excess fuel position. As a result when the plunger is in the excess fuel position, the port 32 will be covered laterduring the inward stroke ofthe plunger and thiswill cause a delay in the commencement offuel delivery, so that the delivery of fuel occurs at or just before the top dead centre position ofthe piston of the associated cylinder.The provision of the recess 34 does mean that the quantity of fuel is slightly reduced, but is nevertheless greater than the maximum quantity of fuel which can be delivered when the port 15 is controlled by the control edge 17A.

The recess 34 is open to the portion of the bore lying between the plungerand the outlet and as shown in Figure 2, it may extend to the axial groove 17B. The two ports are shown as being ofthe same diameter.

However, if desired the port 32 can be smaller than the port 15. As illustrated the ports are not diametrically disposed and the reason for this isto avoid any possibility ofthe groove 17B registering with the port 32 when the plunger is in the excess fuel position. It will be appreciated that the port diameters and the axial length of the recesstogetherwiththe distance between the end of the plunger and the groove 33 can be varied to suit a particular engine.

CLAIMS (Filed on 11 Oct 83) 1. Afuel injection pump for supplying fuelto an internal combustion engine ofthe compression igni tion type and ofthe kind comprising a plunger reciprocably mounted within a bore, an outlet from one end of the Sore, a portformed in the wall of the bore, said port communicating with a fuel inlet, means for moving said plungertowards said one end ofthe bore, said plunger during such movementfirst covering said port and then displacing fuel through said outlet, means for varying the angular setting of said plunger, a spill groove on said plunger, said groove communicating with said one end ofthe bore and having an inclined control edge which during movement ofthe plungertowards said one end ofthe bore and after the port has been covered by the plunger, uncovers the portto allowfuel to escape from the bore through the port, the angular setting ofthe plunger determining the amount of fuel which is displaced through the outlet, afurther port formed in the wall ofthe bore, said port being in communication with said fuel inlet and being positioned to be covered by said plungerduring movementthereoftowards said one end ofthe bore, whereby when both ports are covered, fuel will be supplied through the outlet, said plunger defining a plane portion adjacent said inclined edge and positioned so thatwhen the plunger is moved angularly to an excess fuel position, said plane portion will control said first mentioned port, so that it is uncovered later, during movementofthe plunger towards said one end ofthe cylinder, said plunger further defining a recess at its end facing said one end ofthe cylinder, said recess, when the plunger is in said excessfuel position, delaying the covering of said further portsothat delivery of fuel through said outlet starts later during movement ofthe plungertowards said one end of the bore.

2. A pump according to Claim 1 in which said spill groove communicates with said one end of the bore byway of an axial groove, said recess extending from said axial groove.

3. Afuel injection pump for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. follower27 having a roller 28 adapted to co-actwith a cam 29 mounted on a shaft 31 driven bythe associated engine. Turning nowto Figures 2 and 3, an additional port 32 informed in the wall ofthe barrel and extends into the bore, at substantially the same level as the port 15. The port 32 also communicates with the fuel supply gallery and during inward movement ofthe plunger it is necessaryforboth ports to be covered by the plunger before fuel can flowthrough the outlet 13. During normal operation, that is to say, when the engine has been started, the port32 isuncoveredto a circumferential groove 33, which communicates with the recess 17 and the groove 1 7B, after the port 15 has been uncovered by the control edge 17A. Ittherefore plays no part in terminating delivery offuel. The additional port 32 does however delay delivery of fuel when the plunger is setto an excess fuel position. In Figure 3the ports 15 and 32 are shown displaced angularly to positions 1 5A and 32A. This is forthe purpose ofillustration only and it will be appreciated thatwhat, in pratice, happens isthatthe plunger is displaced angularly relative to the ports.In the excess fuel position the port 15 is no longer uncovered bythe control edge 17A, but will be uncovered to the groove 33 at substantially the same time as the port 32, to terminate delivery of fuel. The quantity of fuel delivered is therefore substantially increased. However, in orderto delaythe initial deliveryoffuel a recess 34is provided in the end face of the plunger and the recess 34 is angularly aligned with the port32 when the plunger is in the excess fuel position. As a result when the plunger is in the excess fuel position, the port 32 will be covered laterduring the inward stroke ofthe plunger and thiswill cause a delay in the commencement offuel delivery, so that the delivery of fuel occurs at or just before the top dead centre position ofthe piston of the associated cylinder.The provision of the recess 34 does mean that the quantity of fuel is slightly reduced, but is nevertheless greater than the maximum quantity of fuel which can be delivered when the port 15 is controlled by the control edge 17A. The recess 34 is open to the portion of the bore lying between the plungerand the outlet and as shown in Figure 2, it may extend to the axial groove 17B. The two ports are shown as being ofthe same diameter. However, if desired the port 32 can be smaller than the port 15. As illustrated the ports are not diametrically disposed and the reason for this isto avoid any possibility ofthe groove 17B registering with the port 32 when the plunger is in the excess fuel position. It will be appreciated that the port diameters and the axial length of the recesstogetherwiththe distance between the end of the plunger and the groove 33 can be varied to suit a particular engine. CLAIMS (Filed on 11 Oct 83)

1. Afuel injection pump for supplying fuelto an internal combustion engine ofthe compression igni tion type and ofthe kind comprising a plunger reciprocably mounted within a bore, an outlet from one end of the Sore, a portformed in the wall of the bore, said port communicating with a fuel inlet, means for moving said plungertowards said one end ofthe bore, said plunger during such movementfirst covering said port and then displacing fuel through said outlet, means for varying the angular setting of said plunger, a spill groove on said plunger, said groove communicating with said one end ofthe bore and having an inclined control edge which during movement ofthe plungertowards said one end ofthe bore and after the port has been covered by the plunger, uncovers the portto allowfuel to escape from the bore through the port, the angular setting ofthe plunger determining the amount of fuel which is displaced through the outlet, afurther port formed in the wall ofthe bore, said port being in communication with said fuel inlet and being positioned to be covered by said plungerduring movementthereoftowards said one end ofthe bore, whereby when both ports are covered, fuel will be supplied through the outlet, said plunger defining a plane portion adjacent said inclined edge and positioned so thatwhen the plunger is moved angularly to an excess fuel position, said plane portion will control said first mentioned port, so that it is uncovered later, during movementofthe plunger towards said one end ofthe cylinder, said plunger further defining a recess at its end facing said one end ofthe cylinder, said recess, when the plunger is in said excessfuel position, delaying the covering of said further portsothat delivery of fuel through said outlet starts later during movement ofthe plungertowards said one end of the bore.

2. A pump according to Claim 1 in which said spill groove communicates with said one end of the bore byway of an axial groove, said recess extending from said axial groove.

3. Afuel injection pump for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.