WO1993007385A1

WO1993007385A1 - Fuel pump

Info

Publication number: WO1993007385A1
Application number: PCT/GB1992/001708
Authority: WO
Inventors: Ronald Frederick Turner
Original assignee: Lucas Industries Public Limited Company
Priority date: 1991-09-28
Filing date: 1992-09-17
Publication date: 1993-04-15
Also published as: GB9120601D0

Abstract

A reciprocable plunger fuel injection pump has a spring abutment (19) slidably mounted on the pump body and is operatively coupled to the plunger (12) so that a spring (20) biases the plunger outwardly. The body defines a transverse opening (27) in which is located a ball (28) which engages with an inclined surface (14) on the plunger to limit the outward movement of the plunger. The ball is held in the opening by the spring abutment and the surface (29) of the spring abutment which is engaged by the ball is eccentrically disposed so that the transverse position of the ball and hence the outward limit position of the plunger can be adjusted.

Description

FUEL PUMP

This invention relates to a liquid fuel injection pump of the kind comprising a plunger reciprocable within a bore formed in a pump body, the plunger being movable inwardly to displace fuel from the bore, the displaced fuel flowing through an outlet when a port formed in the wall of the bore is covered by the plunger, a spring operable to move the plunger outwardly, a spring abutment mounted about the pump body and engaged with one end of the spring, a transverse opening formed in the pump body, a stop piece slidable in the opening, said stop piece being retained within the opening by its engagement with the internal surface of the spring abutment, the stop piece extending into the bore and an inclined shoulder formed on the plunger for engagement by the stop piece, the engagement of the stop piece with said shoulder acting to prevent the plunger falling out of the bore during transport and also acting to fix the plunger at a predetermined position in the bore.

One example of such a pump is seen in GB-A-2125115 in which the spring abutment is the one which is in engagement with a part of the pump body and therefore remains in the use of the pump, in engagement with the pump body. The spring abutment could however be

associated with the plunger and therefore in the use of the pump would move with the plunger. In the use of the pump the pump body is mounted on an engine and is driven by a component for example a cam on the engine camshaft.

When the pump is assembled to the engine and the engine component set at a predetermined position, it is possible to adjust the actuating linkage of the plunger for example a rocker, with the plunger set in its own predetermined position. In this manner the pump will start to deliver fuel to the engine at the correct instant. As stated delivery of fuel through the outlet takes place when during the inward movement of the plunger, the port is covered by the plunger. It is therefore necessary to fix accurately the aforesaid predetermined position of the plunger. A number of manufacturing dimensions influence the required axial movement of the plunger between these positions and these dimensions would have to be held to a very fine tolerance so as to achieve the required axial movement within the desired tolerance.

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

According to the invention in a pump of the kind specified the transverse position of said stop piece is adjustable so that said predetermined position of the plunger can be determined.

According to a further feature of the invention the surface of the spring abutment which is engaged by said stop piece is eccentrically disposed so that angular movement of the spring abutment will effect adjustment of said predetermined position.

An example of. a fuel injection pump in accordance with the invention will now be described with reference to the accompanying drawings in which:-

Figure 1 is a diagrammatic sectional side

elevation of the pump, the drawing illustrating two extremes of adjustment, and

Figure 2 is a sectional plan view along the line B-B of Figure 1. Referring to the drawings the pump comprises a pump body 10 in which is defined a bore 11. A pumping plunger 12 is slidably mounted within the bore and projects from one end thereof. The projecting end 13 of the plunger is of reduced diameter so that there is defined on the plunger an inclined shoulder 14.

Moreover, at the end of the projecting portion of the plunger there is defined a flange 15.

Formed in the wall of the bore is a pair of aligned ports 16 which in use are connected to a source of fuel under pressure. The ports are positioned to be covered by the head of the plunger during its inward movement and as soon as the ports are covered further inward movement of the plunger will displace fuel from the bore to an outlet which is not shown. The plunger is actuated through a fixed stroke and in order to control the quantity of fuel which is supplied through the outlet to an associated engine, an electro-magnetically operable spill control valve (not shown) is provided.

A portion of the bore 11 lies within a cylindrical extension 17 of the body and slidable axially about the extension 17 is the skirt portion 18 of a spring abutment 19. The spring abutment defines a flange which is engaged by one end of a coiled compression spring 20 the other end of which locates against a step defined on the body 10. The spring abutment is of hollow form and within the abutment there is located a flange 21 which is apertured to allow the flange 15 of the valve member to pass therethrough. A "C" clip 22 is located between the flanges so that the spring 20 will urge the plunger outwardly of the bore following its inward movement. The spring abutment also carries a thrust socket 23 which engages the end of the plunger and also defines a part spherical recess 24 in which in use, is located an adjusting member 25 which is mounted on a rocker arm 26 which forms part of the engine structure. The rocker arm is actuated by a cam and effects inward movement, of the plunger through a fixed stroke depending upon the lift of the cam and the lever ratio.

Formed in the wall of the cylindrical extension 17 adjacent its end remote from the main body 10 is a transverse opening 27 and located within the opening 27 is a stop piece in the form of a ball 28. Although the drawings show there to be two openings and two balls, in fact there is only one such opening and associated ball. The ball is retained within the opening by its engagement with the inner surface of the skirt 18 and it will be seen to engage with the inclined shoulder 14 to determine the maximum extent of movement of the plunger under the action of the spring 20 in other words, the aforesaid predetermined position of the plunger. The drawings show the full range of transverse movement of the bail 28, the left hand portion of the drawing illustrating the ball moved inwardly almost into contact with the surface of the portion 13 of the plunger and the right hand portion of the drawing shows the ball moved outwardly to its maximum extent. 3y virtue of the inclination of the shoulder 14 the axial position of the plunger varies depending upon the transverse position of the ball. The internal surface of the portion of the skirt 18 which is engaged by the ball when in contact with the shoulder, is eccentrically disposed and is indicated by the reference numeral 29. As the skirt 18 is moved angularly about the axis of movement of the plunger the ball will be moved inwardly or outwardly thus enabling the predetermined position of the plunger to be adjusted. If the surface of the shoulder 14 is inclined at 45° then the extent of axial adjustment of the plunger is equal to the degree of eccentricity of the surface 29.

With the arrangement described it is possible to determine accurately the predetermined position of the plunger by angular adjustment of the spring abutment. The degree of friction between the spring, the body 10 and the flange of the spring abutment will normally be sufficient to hold the spring abutment against angular movement during transport of the pump however, it is possible that angular movement will take place and therefore once the adjustment has been carried out, a mark is provided on the spring abutment which can be aligned with a suitable mark on the pump body once the pump has been assembled to the engine.

Following assembly of the pump to the engine and with the plunger set in the aforesaid predetermined position, the engine itself is moved to a predetermined position and the adjuster 25 associated with the rocker 26 is screwed outwardly to engage the spherical surface 24. Once engagement has been detected, the adjuster 25 is moved outwardly a predetermined number of turns to effect a further small inward movement of the plunger to set the plunger correctly so that fuel is delivered to the associated engine at the correct time. The ball 28 and the shoulder 14 therefore do not in the use of the pump form a stop to limit the extent of outward movement of the plunger.

In order to assemble the various components the plunger is located in the bore and then the ball is located in the aperture following which the skirt of the spring abutment is engaged over the extension and the spring compressed sufficiently to permit insertion of the "C" clip 22 between the flange 21 of the spring abutment and the flange 15 of the plunger.

It will be appreciated that the arrangement as described can be applied to the type of pump which is described in GB-A-2125115. In this case the spring abutment which retains the ball within the transverse opening is located against the pump body but it can be provided on its internal surface, with the eccentric surface as described, to allow adjustment of the predetermined position of the plunger.

Claims

1. A liquid fuel injection pump comprising a plunger (12) reciprocable within a bore (11) formed in a pump body, the plunger being movable inwardly to displace fuel from the bore, the displaced fuel flowing through an outlet when a port (16) formed in the wall of the bore is covered by the plunger, a spring (20) operable to move the plunger outwardly, a spring abutment (19) mounted about the pump body and engaged with one end of the spring, a transverse opening (27) formed in the pump body (17), a stop piece (28) slidable in said opening, said stop piece being retained within the opening by its engagement with the internal surface of the spring abutment, the stop piece extending into the bore and an inclined shoulder (14) formed on the plunger for

engagement by said stop piece in order to prevent the plunger falling out of the bore during transport and also acting to fix the plunger at a predetermined position in the bore, and means (29) operable to adjust the

transverse position of the stop piece (28) whereby said predetermined position of the plunger can be determined.

2. A pump according to Claim 1, in which said means comprises an eccentrically disposed surface defined on a skirt portion (18) of said spring abutment (19).

3. A pump according to Claim 2, in which said skirt portion (18) is slidable about an extension (17) of the pump body and the plunger is operatively connected to said spring abutment.