US3857653A

US3857653A - Fuel injection pumping apparatus

Info

Publication number: US3857653A
Application number: US00381589A
Authority: US
Inventors: D Mowbray
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1972-07-21
Filing date: 1973-07-23
Publication date: 1974-12-31
Anticipated expiration: 1991-12-31
Also published as: DE2336907A1; FR2193932B1; IT989927B; GB1433125A; DE7326685U; ES417028A1; FR2193932A1; JPS4963829A; JPS5828421B2

Abstract

A fuel injection pumping apparatus includes a plunger on which is formed an inclined control groove which during inward movement of the plumger co-operates with a spill port to terminate injection of fuel. The plunger is provided with a barrier groove in which fuel leaking along the small clearance defined between the plunger and the wall of the cylinder in which it is mounted, collects. The accumulated fuel is ported to a low pressure source by means of an inclined groove which communicates with the circumferential groove and inclined groove registers during inward movement of the plunger with an additional spill port.

Description

United States Patent 1191 Mowbray Dec. 31, 1974 [54] FUEL INJECTION PUMPING APPARATUS 3,490,384 1/1970 Worby 417/494 X [75] Inventor: Dorian Farrar Mowbray, Burnham, FOREIGN PATENTS OR APPLICATIONS England 1,207,151 12/1965 Germany 417/494 [73] Assignee: C.A.V. Limited, Birmingham,

England Primary ExaminerCarlton R. Croyle Assistant Examiner-Richard E. Gluck [22] Filed: July 1973 Attorney, Agent, or FirmI-Iolman & Stern [21] Appl. No.: 381,589

[57] ABSTRACT 30 Foreign Application Priority Data A fuelinje ction pumping apparatus includes a plunger July 21 1972 Great Britain 34166/72 on wh1ch is formed an mclined control groove wh1ch during inward movement of the plunger co-operates [52] Cl 417/494 with 'a spill port to terminate injection of fuel. The [5 1] Int Cl 4b 39/10 plunger is provided with a barrier groove in which fuel [58] Fieid "417/494 5 499 leaking along the small clearance defined between the 123/l39 plunger and the wall of the cylinder in which it is mounted, collects. The accumulated fuel is ported to a [56] References Cited low pressure source by means of an inclined groove which communicates with the circumferential groove UNITED STATES PATENTS and inclined groove registers during inward movement aremsef of the plunger with an additional spill port.

eurer 3,368,491 2/1968 Shook et al 417/494 3 C a ms, 2 Drawing Figures FUEL INJECTION PUMPING APPARATUS This invention relates to fuel injection pumping apparatus of the kind comprising a plunger reciprocable within a bore, the bore and the inner end of the plunger defining a pumping chamber, an outlet from the pumping chamber, a spill port formed in the wall of the bore and groove means defining an inclined control edge on the plunger and which during inward movement of the plunger uncovers said spill port to allow fuel remaining in the pumping chamber to escape therethrough thereby to terminate flow of fuel through the outlet, the angular position of the plunger within the bore determining the quantity of fuel supplied through the outlet.

With such apparatus it is known to provide a circumferential barrier groove on the plunger and into which fuel at high pressure leaking past the plunger flows. It is also known to provide on the plunger at a diametrically opposed position to the groove means, a pressure balancing zone which communicates with the barrier groove and which acts to reduce the side thrust imposed upon the plunger during its inward movement. The zone may be formed by a flattened portion of the otherwise right cylindrical surface of the plunger and the zone and hence the barrier groove are vented to a low pressure at some point during the pumping cycle. Unfortunately the aforesaid zone acts as a trap to collect dirt and this dirt during reciprocation of the plunger may damage the surface of the bore and lead to early failure of the apparatus.

The object of the invention is to provide such an apparatus in a simple and convenient form.

According to the invention an apparatus of the kind specified comprises a circumferential barrier groove formed on the plunger at an axial position on the opposite side of the groove means to said end of the plunger, an inclined groove formed in the plunger substantially diametrically opposite said groove means and extending from said barrier groove towards said end of the plunger but terminating short thereof, and an additional port formed in the wall of the bore, said inclined groove communicating with said additional port during inward movement of the plunger to allow fuel which has collected in the barrier groove to escape through said port.

Preferably said inclined groove communicates with said additional port just before the control edge of said groove means uncovers said spill port.

One example of an apparatus in accordance with the invention will now be described with reference to the accompanying drawings in which:

HO. 1 is a sectional side elevation of the apparatus, and

FIG. 2 is a developed view of part of the apparatus of FIG. 1.

With reference to FIG. 1 of the drawings there is provided a hollow body part in which is secured a barrel 11 having therein an axial cylindrical bore containing a plunger 12.

At the inner end of the bore is an outlet 13 incorporating a spring loaded non-return delivery valve 14, the outlet being adapted for connection to an injection nozzle associated with an engine cylinder. Moreover, intermediate the ends of the bore is a spill port 15 which communicates with an annular recess 16 in the body part and to which fuel is fed by a feed pump or other convenient means. The port 15 is so positioned in the bore that it will be uncovered by the inner end of the plunger 12 when the latter is at the outward limit of its travel thus allowing fuel to enter the pumping chamber from the annular recess 16.

During the inward movement of the plunger the inlet port 15 will be covered and fuel will be delivered to the outlet 13 and hence to the engine cylinder by way of the delivery valve 14.

In the periphery of the plunger there is formed a helical groove 17. The groove communicates by way of a passage formed within the plunger, with the pumping chamber defined by the bore and the inner end of the plunger. As the plunger is moved inwardly the port 15 will first be covered by the end of the plunger and further movement of the plunger will effect displacement of fuel to the engine as described. At one axial position of the plunger the helical edge of the groove 17 will uncover the port 15 so that any fuel remaining in the pumping chamber and which is displaced by the plunger during its inward movement, will flow through the passage in the plunger, the groove and the port 15 and will not flow through the outlet. The angular setting of the plunger 12 relative to the barrel 11 is adjustable by means to be described and because of the helical shape of the edge of the groove, the angular setting of the plunger determines the instant at which the port 15 is uncovered.

Surrounding the portion of the barrel remote from the outlet is a hollow sleeve 19 having a pair of longitudinal slots 20 extending inwardly from 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 imparted to the plunger will not be transmitted to the sleeve whereas angular movement of the latter will be imparted to the plunger.

Formed on the outer periphery of the sleeve 19 are teeth which engage with a toothed fuel control rod 22 mounted for axial movement transversely relative to the plunger axis, in the body part. At the outer end of the plunger is a spring abutment collar 24 between which and 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 follower 27 having a roller 28 v adapted to co-act with a cam 29 rotatable by the engine with which the pump is associated. In order to prevent angular movement of the cam follower the latter is pro vided with flank portions 30 which extend downwardly beyond the roller 28 on opposite sides of the cam 29. The aforesaid flank portions of the follower co-operate with the side surfaces of the cam to prevent angular movement of the follower.

With reference now to FIG. 2, the plunger is provided with a circumferential barrier groove 32 which is positioned on the opposite side of the groove 17 from the end of the plunger. The barrier groove collects any fuel which leaks past the plunger during its inward movement. Furthermore, communicating with the barrier groove is an inclined groove 33 and this has the same hand as the groove 17 and extends towards but terminates short of the end of the plunger. The groove 33 starts at a position and has substantially the same angle as the groove 17 so that an appreciable portion thereof can be said to be diametrically opposite the groove 17.

The groove 33 since it communicates with the barrier groove 32 will be subject to the pressure of fuel within the barrier groove and this pressure will be intermediate the pressure within the pumping chamber and the pressure within the hollow chamber of the body part which contains the cam. The pressure within the groove will develop a side force on the plunger tending to balance the force acting on the plunger due to the pressure of fuel within the groove 17.

The fuel within the barrier groove 32 and the groove 33 is vented during the inward movement of the plunger and conveniently this is achieved by providing an extra spill port 34 shown in FIG. 2 and which is positioned to register with the groove 33. Conveniently the spill ports and 34 are at the same axial position but are diametrically disposed. Moreover, the groove 33 is so positioned that it communicates with the port 34 just before the port 15 is uncovered to the groove 17. Since the groove 33 is substantially parallel to groove 17 the time of communication as aforesaid takes place irrespective of the angular position of the plunger. The flow of fuel which occurs when the port 34 is uncovered serves to flush away any dirt which may have collected in the

grooves

32 and 33 so that the possibility of wear on the plunger and the surface of the bore is minimised.

I claim:

1. A fuel injection pump having a plunger located within a bore, a pumping chamber formed by said bore, an end of said plunger forming a wall of said chamber, a circumferential barrier groove formed on said plunger a first inclined groove formed in said plunger and axially spaced with respect to the end of said barrier groove, a second inclined groove formed in the plunger substantially diametrically opposite said first inclined groove and extending from said barrier groove towards said end of the plunger but terminating short thereof, said first inclined groove having a control edge, said first inclined groove communicating with a spill port located within a wall of said bore during inward movement of the plunger, and an additional port formed in the wall of said bore, said second inclined groove communicating with said additional port during inward movement of the plunger to allow fuel which has collected in the barrier groove to escape through said additional port.

2. An apparatus according to claim 1 in which said second inclined groove is positioned to communicate with said additional port just before the control edge of said first inclined groove uncovers said spill port.

3. An apparatus according to claim 2 in which the hand of said second inclined groove is the same as that of the first inclined groove.