GB2162906A

GB2162906A - Fuel injection pump

Info

Publication number: GB2162906A
Application number: GB08515288A
Authority: GB
Inventors: Arthur John Ellis
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1984-06-23
Filing date: 1985-06-17
Publication date: 1986-02-12
Also published as: IT8521249A0; GB8416064D0; GB2162906B; GB8515288D0; DE3521978A1; IT1184617B

Abstract

A fuel injection pump of the reciprocating plunger type has a spring 29 positioned between two abutments 26, 27. The abutment 26 engages the body of the pump and is held by a pin 30 against movement. It locates a flanged control sleeve 24 against axial movement. The abutment 27 is carried by the plunger 20 which has dogs 22 located in axial slots in the control sleeve. In use, the spring 29 acts to urge the plunger against an engine driven pump actuating component. Prior to assembling the pump to an engine the spring action urges the dogs 22 into engagement with a circlip 31 carried by the sleeve with the effect that the flange of the sleeve is urged into frictional engagement with the abutment 26 to prevent angular movement of the plunger and sleeve, thereby facilitating assembly. In an alternative arrangement the circlip 31 is replaced by a portion of the sleeve closing the outer end of one of the dog receiving slots. <IMAGE>

Description

SPECIFICATION Fuel injection pump This invention relates to a single cylinder fuel injection pump for supplying fuel to an internal combustion engine, the pump being of the kind comprising a body part, a pump barrel mounted in the body part, a pumping plunger slidable in the barrel and projecting therefrom, the pumping plunger and barrel defining a pumping chamber from which extends an outlet, a spill port formed in the wall of the barrel, an inclined spill control edge on the plunger whereby as the plunger is moved inwardly following covering of the spill port, fuel will be displaced through the outlet until said control edge uncovers said spill port, a control sleeve angularly movable about the barrel, the control sleeve having a portion extending beyond the barrel, interengaging means on the plunger and said sleeve portion whereby angular movement of the sleeve will impart angular movement to the plunger while allowing the plunger to partake of axial movement, an outer spring abutment carried by the plunger, an inner spring abutment abutting a portion of the body and a compression spring positioned between the abutments.

Following assembly of the aforesaid type of pump and calibration thereof, it is desired to be able to lock the plunger in a predetermined position so as to facilitate assembly of the pump to an associated engine, such assembly also involving the connection of a governor linkage which is also set at a predetermined position to the control sleeve. It is known to provide a locking screw for this purpose but once engine assembly has taken place the locking screw must be removed-to allow angular movement of the plunger during operation of the engine. The removal of the locking screw or disengagement of any other locking device, presents an additional operation in the assembly of the engine and this must be carried out for each pump fitted to the engine.

Moreover, it is not an easy operation to carry out if automated engine assembly methods are being employed.

The object of the present invention is to provide a pump of the kind specified in a form in which the locking of the plunger is released automatically upon assembly of the pump to an associated engine.

According to the invention in a pump of the kind specified the inner spring abutment is engageable by a flange on the control sleeve.

said inner spring abutment being located against axial movement in the body and the angular movement of the inner and/or the outer spring abutment being restrained by a connection with the body, and further means being provided on the control sleeve to limit the extent of relative movement of the plunger and sleeve under the action of the spring whereby prior to the assembly of the pump to an associated engine, the plunger will be held at a set angular position by frictional forces in the pump assembly.

Examples of fuel pump in accordance with the invention will now be described with reference to the accompanying drawings, Figure 1 illustrating one example and Figure 2 illustrating a further example.

Referring to Figure 1 of the drawings the pump comprises a body part 10 in which is formed an open ended cavity 11 in which is mounted a pump barrel 1 2 having a sleeve 1 3 extending from the cavity. The cavity is closed by a closure member 1 4 which defines a fuel outlet 1 5 for connection in use to an injection nozzle of the associated engine. The closure retains in position against the end surface of the barrel lying within the cavity, a delivery valve body 1 6 mounting a spring loaded delivery valve member 1 7 which is of conventional construction. Formed in the wall of the pump barrel is a spill and filling port 1 8 which communicates with the cavity.

Moreover, the cavity is connected to a fuel inlet 1 9 which in use is connected to a source of liquid fuel under pressure.

Mounted within the pump barrel is a pump plunger 20 having a portion which extends from the sleeve 1 3 of the pump barrel. The projecting end of the plunger defines a head 21 and on the projecting portion of the plunger is defined a pair of radially extending projections 22 which locate in axial slots 23 respectively formed in a control sleeve 24 which is angularly movable about the sleeve 1 3 of the pump barrel. The control sleeve has a flanged portion and mounts an outwardly extending control arm 25 which is connected in use, to a governor linkage. By moving the control sleeve 24 angularly, angular movement will be imparted to the plunger by way of the grooves 23 and projections 22. At the same time however relative axial movement of the plunger and sleeve can take place.The plunger in known manner, is provided with a helical control edge (not shown) whereby the amount of fuel displaced through the outlet during inward movement of the plunger, can be controlled.

Located against a step defined in the body is an inner spring abutment 26 and an outer spring abutment 27 locates against the head of the plunger. Located between the abutments is a coiled compression spring 29 which acts to bias the plunger outwardly, the plunger being moved inwardly by means of an engine driven component which engages the head 21. The inner spring abutment 26 is engaged by the flange on the control sleeve and this acts to locate the control sleeve against axial movement although of course it will be appreciated that clearance is provided to enable the sleeve to be moved angularly.

Moreover, a pin 30 is provided which locates the inner spring abutment against movement away from the step in the body and against angular movement relative to the body part.

The extent of relative axial movement of the control sleeve and the plunger under the action of the spring 29, is limited by means in the particular example, of a circlip 31 which is located within a groove formed in the internal peripheral surface of the control sleeve, the circlip being engageable by the projections 22 on the plunger. Alternatively the material forming the control sleeve can be deformed to close in the sides of the grooves 23 if so desired. Once assembly has been completed it will be noted that the control sleeve is captive to the body by reason of the pin 30 and the plunger is captive within the control sleeve by the action of the circlip 3-1. The circlip 31 is positioned such that the spring 29 is stressed when the projections are in engagement with the circlip.The practical effect therefore is that the flange 24 of the control sleeve is held in engagement with the inner spring abutment thereby producing substantial friction which acts to prevent angular movement of the plunger and control sleeve. Once assembly of the pump is complete therefore and following checking of the pump the plunger and control sleeve can be set in a predetermined position.

The frictional forces prevent movement of the plunger and control sleeve from this position.

During assembly of the pump to the engine the governor linkage also set to a predetermined position, is connected to the control arm 25 and in the final stages of assembly e.g. tightening of the mounting bolts of the pump, the engine component engages the plunger and lifts the projections 22 away from the circlip. In this situation the flange on the control sleeve is no longer held by the spring, in engagement with the inner spring abutment and the aforesaid frictional forces are removed thereby allowing the control sleeve and plunger to be moved angularly during normal operation of the engine. During operation of the engine it will be appreciated that the projections 22 do not engage the circlip, the outermost position of the plunger being determined by the engine driven component.

Turning now to Figure 2 a slightly different form of pump construction is illustrated. In this example the control sleeve 24 is provided with teeth on its periphery for engagement by a rack bar 32 which is movable tangentially by means of a peg 33 which in use is secured to the governor linkage. The inner spring abutment 26 can be secured, as with the example of Figure 1, by means of the pin 30.

In this case the mode of operation is the same as the example of Figure 1. However, Figure 2 is intended to show an alternative arrangement. The outer spring abutment 27 locates within a tappet assembly 34 which includes a roller 35 carried by means of a pin 36 in a tappet body 37. The tappet body 37 is provided with a slot 38A within which is located a guide pin 38 carried by the body, the action of the guide pin being to prevent relative angular movement of the tappet assembly and the body. Moreover, the outer spring abutment 27 is secured by a pin 39 to the tappet body. Following assembly of the pump and prior to its assembly within the associated engine, the spring 29 moves the outer spring abutment outwardly so that the projections 22 on the plunger engage with the circlip 31.

Moreover, since the lower spring abutment is secured to the tappet body and the latter is restrained against angular movement by the pin 38, frictional forces in the assembly, in particular between the foot of the plunger and the tappet body, will prevent angular movement of the control sleeve and plunger. Again it is emphasised that the outermost position of the plunger prior to assembly of the pump within the engine, is slightly greater than that which will normally be experienced by the plunger due, in the particular example, to engagement of the roller with the base circle of the engine driven cam.

In an alternative version of the example of Figure 2, the pin 39 and also the circlip 31 are omitted. One of the grooves only in the control sleeve 24 is partly closed and this has the effect of causing the control sleeve to tilt slightly. This through the inner spring abutment 28 and the spring 29, causes the outer spring abutment 27 to bind in the tappet body 37 thereby preventing angular movement of the control sleeve and plunger.

Claims

1. A single cylinder fuel injection pump for supplying fuel to an internal combustion engine comprising a body part, a pump barrel mounted in the body part, a pumping plunger slidable in the barrel and projecting therefrom, the pumping plunger and barrel defining a pumping chamber from which extends an outlet, a spill port formed in the wall of the barrel, an inclined spill control edge on the plunger whereby as the plunger is moved inwardly following covering of the spill port, fuel will be displaced through the outlet until said control edge uncovers said spill port, a control sleeve angularly movable about the barrel, the control sleeve having a portion extending beyond the barrel, interengaging means on the plunger and said sleeve portion whereby angular movement of the sleeve will impart angular movement to the plunger while allowing the plunger to partake of axial movement, an outer spring abutment carried by the plunger, an inner spring abutment abutting a portion of the body and a compression spring positioned between the abutments, said inner spring abutment being engageable by a flange on the control sleeve, said inner spring abutment being restrained by a connection with the body, and further means being provided on the control sleeve to limit the extent of relative movement of the plunger and sleeve under the action of the spring whereby prior to the assembly of the pump to an associated engine, the plunger will be held at a set angular position by frictional forces in the pump assembly. ~-

2.A single cylinder fuel injection pump according to Claim 1 including a pin acting to locate said inner spring abutment relative to the body to prevent axial and angular movement of the abutment, said further means on the control sleeve comprising a circlip carried by the sleeve for engagement by a part of the plunger the arrangement being such that the flange on the control sleeve is urged into frictional engagement with the inner spring abutment to resist angular movement of the control sleeve and plunger.

3. A single cylinder pump according to Claim 1 including a pin securing said outer spring abutment to a tappet assembly slidable within the body but restrained against angular movement therein, and said further means on the control sleeve comprising a circlip carried by the sleeve and engageable by a part of the plunger.

4. A single cylinder fuel injection pump for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

5. A single cylinder fuel injection pump for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.