GB2123492A

GB2123492A - Fuel injection pump

Info

Publication number: GB2123492A
Application number: GB08313902A
Authority: GB
Inventors: Christopher Martin Dona Little; Gerald Sydney Thomas
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1982-07-08
Filing date: 1983-05-19
Publication date: 1984-02-01
Also published as: GB8313902D0

Abstract

A fuel injection pump includes a plunger 15 reciprocable within a bore 12. A groove 17 is formed on the plunger and a groove 18 is formed in the wall of the bore. The groove 18 in use, is connected to a source of lubricating oil and the groove 17 can communicate with a port 21 extending from a wall of the bore to the interior of the pump. At the maximum outward position of the plunger the grooves are in communication and the groove 17 is in communication with the port 21 so that a flow of lubricating oil takes place through the grooves. This flow is halted when during inward movement of the plunger the groove 17 moves out of register with the port 21. <IMAGE>

Description

SPECIFICATION Fuel injection pump This invention relates to a fuel injection pump of the kind comprising a plunger reciprocably mounted in a bore, the plunger extending from one end of the bore, the plunger and the bore defining a pumping chamber, an outlet from the pumping chamber for connection in use to a fuel injection nozzle, means for feeding fuel to the pumping chamber and a groove defined on the plunger or in the bore, said groove acting to collect fuel leaking along the working clearance between the plunger and the wall of the bore.

It is known to supply lubricating oil under pressure to a further groove disposed between said first mentioned groove and said one end of the bore, in order to provide for lubrication of the plunger where the fuel itself does not provide adequate lubrication.

In some cases the pump is designed to pump what are known as residual fuels and these require to be heated to a high temperature before they can flow and be satisfactorily burnt in the combustion chamber of the engine. The high temperature of the fuel results in the wall of the bore and the plunger attaining a correspondingly high temperature and this may result in degradation of the lubricating oil and the formation of lacquer on the plunger and the bore.

The lacquer formation causes a reduction in the working clearance between the plunger and the wall of the bore and this impairs lubrication and may therefore result in seizure of the parts.

The object of the invention is to provide a pump of the kind specified in an improved form.

According to the invention in a pump of the kind specified a further groove is provided on the plunger and an additional groove is formed in the wall of the bore, said additional groove being disposed so that it communicates with said further groove at some period during the inward and outward movement of the plunger, an inlet to said additional groove for connection in use to a source of lubricating oil under pressure and means for allowing a flow of lubricating oil to take place from said additional groove at some time during the inward and outward movement of the plunger.

Examples of fuel pumps in accordance with the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a part sectional side elevation of a portion of the pump; and Figures 2 and 3 are less detailed sections of the pump showing modifications.

Referring to Figure 1 of the drawings, the pump comprises a body 10 in which is mounted a pump barrel 11 , the barrel having a stepped peripheral surface and locating against a step defined in the body 1 0. The barrel is retained in position by means of a delivery valve assembly (not shown), which extends to an outlet. Formed in the barrel is a bore 12 and surrounding a portion of the barrel is a fuel supply gallery 13 which in use is connected to a source of fuel under pressure. The barrel defines a spill port 14 which communicates with the aforesaid gallery.

Slidable within the bore is a pumping plunger 1 5. The plunger 1 5 extends from the lower portion of the bore and is connected to a tappet assembly (not shown). The tappet assembly in use, is engaged by a cam to impart inward or upward movement to the plunger against the action of a coiled compression spring 1 6 which when permitted by the cam, effects outward or downward movement of the plunger. In Figure 1 of the drawings the plunger is shown at its outermost position and it will be observed that the port 14 is uncovered. Fuel will therefore have filled the pumping chamber which is defined by the plunger and the bore 12 and during the inward movement of the plunger, fuel will be expelled through the port 14 until the port 14 is covered by the plunger.The fuel in the pumping chamber is then pressurised and when a sufficiently high pressure has been attained, the delivery valve will be opened to allow fuel flow to an injection nozzle of the associated engine through the outlet.

Formed in the bore 1 2 is a groove 1 5A which is connected to the fuel supply gallery 1 3. The groove 1 SA acts to collect fuel leaking from the bore along the working clearance defined between the plunger and the wall of the bore.

Formed in the plunger is a circumferential groove 1 7 and formed in the wall of the bore is a further circumferential groove 1 8. The groove 1 8 communicates with an inlet 19 in the body 10 and which in use is connected to a source of lubricating oil under pressure. This may be the lubrication system of the associated engine. It will be seen that in the lowermost position of the plunger the grooves 17 and 18 are in communication with each other and remain in communication with each other throughout the travel of the plunger, this travel being indicated by the arrow 20.

Formed in the wall of an extended portion of the barrel 11 is a port 21 and this communicates with a groove defined about the barrel which is in permanent communication by way of ports 22, with the interior of the body of the pump. The ports 22 are formed in an annular and angularly movable member which forms part of the fuel quantity control mechanism of the pump. The port 21 is positioned so that it communicates with the groove 1 7 towards the end of the outward movement of the plunger and when this communication is established a flow of lubricating oil can take place from the groove 1 8 to the groove 17, and through the ports 21 and 22. The oil contained in the grooves is therefore replenished with relatively cool oil from the lubrication system of the engine.Flushing the grooves of oil in this fashion minimises the risk of degradation of the lubricating oil particularly when the pump is used to supply residual fuel to the engine, the residual fuel being at a high temperature to ensure adequate fluidity. During the inward movement of the plunger the port 21 is covered so that the flow of lubricating oil ceases.

The working clearance between the wall of the bore and the plunger and which lies below the groove 17, is adequately lubricated by the oil which is contained in the groove 17. The movement of the plunger over which flow of lubricating oil takes place is indicated by the arrow X.

In Figure 2 the grooves 17, 1 8 in the plunger and the wall of the bore are allocated the same reference numerals, but in this case it will be noted that in the outermost position of the plunger as shown, the two grooves are not in communication with each other although the groove 17 is in communication with the port 21.

During inward movement of the plunger the groove 1 7 does register with the groove 18 to allow the flow of lubricating oil to take place.

However, after further inward movement of the plunger, the port 21 is covered so that the flow of lubricating oil is again halted. With this arrangement as compared with the arrangement shown in Figure 1, the period during which flow of lubricating oil can take place is reduced and this may have advantages where it is difficult to vent the interior of the body into which the lubricating oil flows. Figure 2 also shows a further modification and this is a restricted passage means defined by a flat 23 on the plunger. The flat communicates with the groove 1 7. In this modification the port 21 is omitted and flow of lubricating oil can therefore take place throughout most of the working cycle of the pump although at a restricted rate.

In the arrangement shown in Figure 3, the grooves 17 and 18 communicate only towards the end of the outward movement of the plunger, so that fresh oil can enter the groove 1 7. In order to effect replacement of the oil in the groove 18, the plunger is provided with a passage 24 which is brought into communication with the groove 1 8 during the inward movement of the plunger but during the time the groove 17 is out of communication therewith.

Claims

1. A fuel injection pump comprising a plunger reciprocably mounted in a bore, the plunger extending from one end of the bore, the plunger and the bore defining a pumping chamber, an outlet from the pumping chamber for connection in use to a fuel injection nozzle, means for feeding fuel to the pumping chamber and a groove defined on the plunger or in the bore, said groove acting to collect fuel leaking along the working clearance between the plunger and the wall of the bore, a further groove on the plunger and an additional groove formed in the wall of the bore, said additional groove being disposed so that it communicates with said further groove at some period during the inward and outward movement of the plunger, an inlet to said additional groove for connection in use to a source of lubricating oil under pressure and means for allowing a flow of lubricating oil to take place from said additional groove at some time during the inward and outward movement of the plunger.

2. A pump according to Claim 1 in which said means for allowing a flow of lubricating oil comprises passage means defined by the plunger.

3. A pump according to Claim 2 in which said passage means comprises a passage formed in the plunger, said passage at one end communicating with the interior of the pump and at its other end opening onto the periphery of the plunger at a position to register with said further groove during the inward movement of the plunger.

4. A pump according to Claim 2 in which said passage means is defined by a flat formed on the plunger, said flat communicating with said additional groove.

5. A pump according to Claim 1 in which said means for allowing a flow of lubricating oil comprises a port opening into said bore at a position to register with the further groove during the movement of the plunger.

6. A pump according to Claim 5 in which said further and additional grooves communicate with each other during the full range of movement of the plunger, said further groove being moved out of communication with said port after a predetermined inward movement of the plunger.

7. A pump according to Claim 5 in which said further and additional grooves are brought into communication with each other after a predetermined inward movement of the plunger, said further groove moving out of register with said port after a further predetermined inward movement of the plunger.

8. A fuel injection pump comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

9. A fuel injection pump comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 as modified by Figure 2 of the accompanying drawings.

1 0. A fuel injection pump comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 as modified by Figure 3 of the accompanying drawings.