GB2246399A - Fuel injection pump - Google Patents

Abstract

A fuel injection pump has a pumping plunger (13) slidable in a bore in a pump barrel (11). Surrounding a part of the barrel is an annular member (23) having a skirt portion in which is formed a slot (24) in which is slidable a projection (26) on the plunger. The angular setting of the plunger in the bore can be varied by moving the annular member angularly and in order to facilitate engagement of the projection within the slot the side walls at the entrance portion of the slot are flared. <IMAGE>

Description

FUEL . INJECTION PUMP This invention relates to a fuel injection pump of the kind comprising a pump barrel mounted in a pump body, a bore formed in the barrel, a pumping plunger slidable in the bore and projecting from one end thereof, a spring abutment coupled to the extending end of the plunger, a coiled compression spring located between the spring abutment and the body, the spring acting to urge the plunger outwardly of the bore, an annular member mounted for angular movement about the axis of the plunger, said annular member defining an axial open ended slot and a projection on the plunger which is engaged within said slot, whereby the angular setting of the plunger can be adjusted by adjusting the angular setting of the annular member whilst allowing relative axial movement of the plunger and the annular member.

It is the usual practice to provide the body of the pump with a hollow extension the interior surface of which provides a guide surface for a cylindrical part of the spring abutment. When assembling the pump the plunger is first coupled to the spring abutment and then the plunger is engaged in the bore. As the plunger is moved into the bore compress ion of the spring takes place and a position is reached at which the projection on the plunger should enter the open end of the slot. Even if it is possible to see the end of the slot it is not easy to engage the projection therein and often particularly where the end of the slot is not visible, several attempts may be necessary before the projection moves into the slot.Following engagement of the projection in the slot a locking device is engaged to retain the spring abutment in assembled relationship with the body.

The object of the present invention is to provide a pump of the kind set forth in a simple and convenient form whereby assembly of the pump is facilitated.

According to the invention the sides of the entrance portion of the slot are flared to assist movement of the projection into the slot.

An example of a pump in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of part of one example of a pump in accordance with the invention, Figure 2 is a view to an enlarged scale of part of the pump seen in Figure 1, and Figure 3 is a view taken at right angles to Figure 2.

Referring to the drawings the pump comprises a hollow body 10 in which there is located a pump barrel 11. Formed in the barrel is a bore 12 in which is mounted a reciprocable pumping plunger 13. The bore 12 together with the end of the pumping plunger and an end closure for the bore, define a pumping chamber 13 from which during inward movement of the plunger, fuel is expelled through an outlet once the end of the plunger covers a pair of filling ports 14 formed in the bore.

The ports in use are connected to a source of fuel under pressure.

The plunger extends from the end of the bore within the body and the extended portion of the plunger is provided with a mushroom shaped head 15. A portion of the body defines a hollow extension 16 within which is located a cylindrical portion 17 of a spring abutment 18.

The cylindrical portion 17 is shaped to define a fork 19 which is engaged with the head 15 of the plunger and surrounding the extension there is located a coiled compression spring 20 one end of which engages the abutment 18 and the other end of which is engaged with a further spring abutment 21 which bears against a step on the body. The spring abutment 18 defines a surface 22 which in use, is engaged by a cam or a rocker arm actuated by a cam, to impart inward movement to the plunger against the action of the spring, the spring acting to return the spring abutment and also the plunger as the abutment moves over the crest of the cam lobe.

Mounted about a reduced portion of the barrel 11 is an annular member 23 which has an integral skirt portion in which is formed a pair of diametrically disposed axially extending and open ended slots 24. In addition the portion of the annular member which is located about the pump barrel, is provided with peripheral teeth for engagement by a rack bar 25 slidable in the body 10. Moreover, engaged in the slots 24 are a pair of projections 26 integrally formed with the plunger whereby as the rack bar is moved axially, angular movement will be imparted to the plunger.

In known manner the plunger is provided with a helical slot 27 which during inward movement of the plunger is brought into register with one of the ports 14 to terminate the delivery of fuel from the pumping chamber 13 to the associated engine.

In assembling the pump the pump barrel is secured within the body and the head 15 of the plunger is located beneath the fork 19. With the spring 20 in place the plunger is located in the end of the bore and is moved inwardly, such movement causing compression of the spring 20. During such movement a position is reached where the projections 26 should pass into the slots 24. It will be understood however that with the extension 16 of the body it is impossible to see the slots and therefore to adjust the angular position of the annular member 23 so that the projections can pass into the slots. Several attempts are therefore necessary before the projections are engaged and further inward movement of the plunger can take place.Once the projections have been located in the slots, a pin 28 is engaged with the cylindrical portion 17 of the spring abutment, the pin passing through a slot 29 formed in the extension 16 of the body and having a closed end whereby the outermost position of the spring abutment and the plunger is determined.

In order to facilitate the engagement of the projections 26 in the slots 24 it is proposed as shown in Figures 2 and 3, to flare che entrance portions 29 of the slots. The remaining portions of the slots have parallel sides but the fact that the entrance portions are flared means that it is easier to secure engagement of the projections within the slots and the time taken to assemble the pump is reduced thereby resulting in a lower production cost. As shown in Figure 3, the flared surfaces 30 extend around the skirt position almost to the point of running into each other.

Claims (3)

1. A fuel injection pump of the kind comprising a pump barrel, a pumping plunger slidable in the bore and projecting from one end thereof, a spring abutment coupled to the extending end of the plunger, a coiled compression spring located between the spring abutment and the body, the spring acting to urge the plunger outwardly of the bore, an annular member mounted for angular movement about the axis of the plunger, said annular member defining an axial open ended slot and a projection on the plunger which is engaged within said slot whereby the angular setting of the plunger can be adjusted by angular movement of the annular member whilst allowing relative axial movement therebetween, and the sides of the entrance portion of the slot being flared to assist movement of the projection into the slot.

2. A pump according to Claim 1, in which the end portion of the annular member remote from the entrance portion of said slot is provided with peripheral teeth for engagement by a rack bar slidable in the pump body.

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