GB2125116A - Reciprocable plunger fuel injection pump - Google Patents

Abstract

A reciprocable plunger fuel injection pump has a plunger 14 extending from a bore in a pump barrel 10 mounted in a housing 11. The barrel extends slightly from the housing and has a first spring abutment 16 located about the extending portion. A hollow cylindrical extension 16A of the first spring abutment extends in spaced relationship about the plunger and guides the movement of a hollow cylindrical portion 15A of a second spring abutment 15. The second abutment has a recess the base wall of which is formed by the head of a member 23 the other end of which is engageable by the plunger. The head is engaged by a thrust member 22 which can slide at right angles to the axis of movement of the plunger and is itself engaged by an engine driven component. The transmission of side thrust to the plunger is minimised by the construction. <IMAGE>

Description

SPECIFICATION Reciprocable plunger fuel injection pump This invention relates to a reciprocable plunger fuel injection pump of the kind comprising a body, a plunger mounted in a bore in the body, said plunger extending from the body and having a spring abutment connected thereto, a coiled compression spring urging said abutment away from the body and a thrust member actuated in use by a component of an associated engine for imparting inward movement to the plunger against the action of said spring.

Such pumps are well known in the art and the plunger can be actuated through a rocker arm by means of a rotary cam. It is important to minimise so far as is possible, the application of side thrust to the plunger since this will cause wear of the plunger and the wall of the bore resulting in excessive leakage of fuel along the working clearance between the plunger and the wall of the bore.

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

According to the invention a fuel injection pump of the kind specified comprises a hollow cylindrical extension carried on the body and being located about the portion of the plunger extending from the body, said spring abutment having a hollow cylindrical portion slidable within said extension, a cylindrical member located in the bore in said hollow cylindrical portion, one end of said cylindrical member engaging the end of said plunger, the opposite end of said cylindrical member defining a flat head which forms the base wall of a recess in the spring abutment, a thrust member located in said recess, said thrust member being slidable on said surface and in use being engaged by said engine component, and means coupling said spring abutment to the plunger whereby said spring can impart outward movement to the plunger.

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 a socalled pump/injector embodying the invention, Figure 2 is a view to an enlarged scale of part of the pump seen in Figure 1 to show the assembly of parts of the pump, Figure 3 shows the mounting of the pump/injector to an engine cylinder head, and Figure 4 shows the shape of a washer forming part of the pump/injector.

Referring to Figure 1 of the drawings the pump comprises a pump body 10 which is often known in the art as a barrel. The barrel is located within a recess formed in a housing 11, by means of a retaining nut 12 which engages a flange on the barrel and urges one end face of the barrel into sealing engagement with the end face of the recess. Formed in the barrel is a bore 1 3 in which is slidable a plunger 14. The plunger extends from the end of the bore in the barrel. The skirt of the barrel extends from the housing and is surrounded by a spring abutment 1 6 which has a hollow cylindrical extension 1 6A which extends in spaced relationship about the plunger.

Slidable within the extension 1 6A is a hollow cylindrical portion 15A of a spring abutment 1 5 and extending between the abutments is a coiled compression spring 1 7 which acts as will be described, to effect outward movement of the plunger.

The bore 13 communicates with an outlet 1 8 and opening into the bore is a pair of ports 19 which communicate with a fuel supply gallery 20 defined in the recess. The gallery 20 communicates with a fuel inlet 21.

The abutment 1 5 is provided with a recess and located in the bore in the spring abutment 1 5 is a cylindrical member 23 which has a flat head forming the base wall of the recess. Located in the recess is a thrust member 22 which is slidable on the head of the member. The thrust member itself has a spherical recess in which in use is located the spherical end of an adjusting screw 33 carried by a rocker arm 34 (Figure 3) actuated by an engine driven cam. As the rocker arm moves the thrust member can slide on the surface of the head of the member 23 and the thrust member can pivot relative to the screw. The transmission of side thrust to the spring abutment is minimised.

In addition, the movement of the spring abutment 1 5 is guided by the extension 1 6A which is located about the body 10. Outward movement of the plunger is effected through a pin and slot connection between the plunger and spring abutment 1 5. The slot is slightly larger than the pin and acts to allow limited relative axial movement between the plunger and the abutment. The plunger is slightly smaller than the surrounding portion of the bore in the portion 1 5A again to prevent the transmission of side thrust to the plunger.

Referring now to Figure 2, the plunger 14 is provided with a step 24 and the barrel 10 is provided with a plurality of cylindrical apertures 25 in that portion thereof which extends beyond the housing and is surrounded by the spring abutment 1 6. Located in the apertures are stop pieces respectively in the form of balls 26. The diameters of the balls are larger than the axial lengths of the apertures 25 and in the fully assembled condition as shown in Figure 1 and in the right-hand portion of Figure 2, the balls 26 locate against the step 24 to limit the extent of outward movement of the plunger. Since the abutment 1 5 is retained relative to the plunger in the fully assembled position, the balls 26 also prevent the plunger and the abutment 1 5 together with the spring 17, becoming detached from the body 10.The left-hand portion of Figure 2 shows the assembly of the various components-and initially the plunger 14 is assembled with the spring abutment 15, the spring 17 and the abutment 1 6. The plunger is then partly assembled into the bore 1 3 and before the apertures 25 are covered by the spring abutment 16, the balls 26 are located in the apertures. The plunger is now moved further inwardly to the position shown in the left-hand portion of Figure 2. It will be noted that the spring abutment 1 6 has a flared end portion to its central bore and the effect of this flared portion is to impart a thrust to the balls in a direction transverse to the axis of movement of the plunger.As the plunger is moved inwardly the spring 1 7 will be compressed and as soon as the step 24 passes beyond the balls, the latter will be urged inwardly to the position shown in Figure 2. Furthermore, the spring abutment 16 can now slide axially to cover the apertures 25 in which the balls are located. It is arranged that the spring 17 is lightly stressed in the fully assembled state and this has the effect of maintaining the spring abutment 1 6 in position so as to prevent the balls 26 moving outwardly. The positions of the step 24 and of the apertures 25 are carefully chosen since the co-operation of the balls 26 with the step 24 determines the maximum outward movement of the plunger.Moreover, the plunger and the barrel 10 are accurately machined so that when the balls are located against the step 24 the plunger position assumes a known position in which it will be noted, the port 19 is substantially uncovered. Thus when the pump is assembled to the engine, the appropriate adjustment can be effected once the engine has been set to the correct position.

If at any time during the life of the pump/ injector, it is required to replace the plunger and also the barrel 10, due, for example, to wear, it is necessary to displace the spring abutment 1 6 to permit the balls to move outwardly within the apertures 25 and thereby permit further outward movement of the plunger. This can be effected by displacing the abutment 1 6 against the action of the spring.

Returning now to Figure 1 , the housing 11 mounts a fuel injection nozzle 27 and the outlet 1 8 is connected to the fuel inlet of the injection nozzle. The nozzle includes a spring loaded valve member, the spring being housed within a chamber 28 defined in the housing. This chamber is connected to a suitable drain port 29 opening onto the periphery of the housing and as shown in Figure 3, this drain port is open to a suitable passage 35 formed in the cylinder head 36 of the engine so that the fuel which flows through the port can be returned to the supply tank.

The pump/injector shown in Figure 1 is of the type in which the quantity of fuel supplied through the nozzle and also the timing of delivery of fuel, is controlled by a spill valve generally indicated at 30 and controlled by an electromagnetic actuator generally indicated at 31. The valve 30 controls the flow of fuel between the outlet 1 8 and the drain port 29 and when the valve is closed upon energisation of the actuator 31, the fuel flowing through the outlet 18 flows to the nozzle and the associated engine. If the valve 30 is opened while the plunger 14 is moving inwardly, the fuel which is displaced by the plunger will flow to the drain port.

The valve 30 includes a valve body 37 which is screwed into an extension 38 of the housing 11.

The body acts to retain against a step defined in a recess in the housing, a flanged sleeve 39. A washer 40 is interposed between the sleeve and the step, the washer having the outline shape shown in Figure 4. Opening onto the step is a port 41 connected to the pump outlet 1 8 and this port communicates with an enlargement in the bore in the sleeve, by way of a passage 42 in the sleeve.

The washer 40 is provided with an aperture 43 to permit fuel flow and in addition it has a locating slot 44 which engages with a dowel 45 carried by the extension 38 and extending into a locating slot in the sleeve 39. The narrower portion of the recess communicates with the port 29 and the bore in the sleeve mounts a slidable valve member 46 having a head 47 which can be urged into contact with a seating by energisation of the actuator 31 , to prevent spillage of fuel from the pump.

As shown in Figure 3 the lower portion of the housing together with the nozzle 27 are located within a generally complementary recess in the cylinder head of the engine. The end portion of the nozzle extends into the combustion chamber of the engine and a washer 48 prevents escape of gas from the combustion chamber into the bore.

The housing 11 on opposite sides of the port 29 mounts "0" ring seals which co-operate with the wall of the bore to prevent fuel escaping from the port leaking from the upper end of the bore and also leaking into a chamber 49 defined between a part of the bore and the housing. This chamber is connected to a source of fuel and the fuel inlet 21 is in communication with the chamber 49.

The extension portion 38 of the housing is located in a recess 50 defined in the cylinder head and the pump/injector is retained in position by a clamping ring 51.

Claims (2)

1. A reciprocable plunger fuel injection pump comprising a body, a plunger mounted in a bore in the body, said plunger extending from the body and having a spring abutment connected thereto, a coiled compression spring urging said abutment away from the body, a thrust member actuated in use by a component of an associated engine for imparting inward movement to the plunger against the action of said spring, a hollow cylindrical extension carried on the body and being located about the portion of the plunger extending from the body, said spring abutment having a hollow cylindrical portion slidable within said extension, a cylindrical member located in the bore in said hollow cylindrical portion, one end of said cylindrical member engaging the end of said plunger, the opposite end of said cylindrical member defining a flat head which forms the base wall of a recess in the spring abutment, a thrust member located in said recess, said thrust member being slidable on said surface and in use being engaged by said engine component, and means coupling said spring abutment to the plunger whereby said spring can impart outward movement to the plunger.

2. A pump according to Claim 1 in which said means comprises a pin and slot connection.