GB2124710A - Fuel pumping apparatus - Google Patents

Abstract

A fuel pumping apparatus for supplying fuel to an internal combustion engine includes an axially movable distributor member mounted in a body 27, plungers reciprocable in a bore in the distributor member and cam followers 44, 45 at the outer ends of the plungers for engagement with a cam ring 41. Stop plates 50 having inclined surfaces for engagement with complementary surfaces on the followers are carried on an annular plate 51 which is rotatably mounted about a spigot defined on the body 27. <IMAGE>

Description

SPECIFICATION Fuel pumping apparatus This invention relates to a fuel pumping apparatus for supplying fuel to a multi-cylinder internal combustion engine and of the kind comprising a rotary distributor member mounted within a body, a pair of pumping plungers mounted in a bore formed in the distributor member, a cam ring located in the body, the cam ring defining inwardly extending lobes to impart inward movement to the pumping plungers as the distributor member rotates, passage means in the distributor member and body whereby fuel can be supplied to the bore containing the plungers and further passage means through which the bore can be connected to outlet ports in turn during successive inward movements of the plungers, adjustable stop means for limiting the outward movement of the plungers, said distributor member being axially movable so as to vary the extent of outward movement of the plungers and a drive shaft carried by the body, said drive shaft being coupled to the distributor member.

An apparatus of the aforesaid kind is described in British Published Specification 2037365A. In the apparatus disclosed therein the drive shaft is provided with a cup-shaped enlargement which extends around the distributor member and is provided with slots in which are located cam followers. The cam followers are fixed axially relative to the distributor member and define inclined stop surfaces which co-operate with an inclined surface or surfaces formed on the interior of the aforesaid cup-shaped enlargement. The extent of allowed outward movement of the plungers therefore depends upon the axial position of the distributor member. The drive shaft is supported by a bearing in the body and the open end of the cup-shaped enlargement is located about a spigot defined in the body.Even with this support there is a tendency for the drive shaft and the enlargement to tilt when a lateral thrust is applied to the drive shaft as for example by the tension in a toothed drive belt. Tilting of the drive shaft can result in a variation in the amount of fuel delivered by the apparatus for a given axial position of the distributor member. Since the axial position of the distributor member within the body is used as an indication to an associated control system of the amount of fuel being supplied to the engine, such variation can lead to the incorrect amount of fuel being supplied to the associated engine.

The object of the present invention is to provide an apparatus of the kind specified in an improved form.

According to the invention an apparatus of the kind specified comprises a cup-shaped enlarged portion carried by the drive shaft, radial slots in said enlarged portion, cam followers located in the slots respectively, inclined surfaces defined on the cam followers, an annular plate mounted for rotation about a spigot defined by the body and a pair of axially extending stop plates carried by said annular plate, said stop plates defining inclined surfaces for co-operation with the inclined surfaces respectively on said cam followers.

An example of an apparatus 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 one example of the apparatus; Figure 2 is a section of a part of the apparatus seen in Figure 1 taken along a different radial plane; Figures 3 and 4 are sections through parts of the apparatus seen in Figures 1 and 2; Figure 5 is a sectional view to an enlarged scale of part of the apparatus seen in Figure 1 Figure 6 is an end view of part of the apparatus of Figure 5; and Figure 7 is a perspective view of part of the apparatus of Figure 1.

Referring to Figure 1 of the drawings, the apparatus comprises a body part generally indicated at 10 and which conveniently is formed by a generally cup-shaped portion 11, the open end of which is closed by a closure portion 12. The body portion 10 is provided with apertured lugs 13 whereby in use the apparatus can be secured to the engine with which it is associated.

The body portion 11 mounts a rotary drive shaft 14 which in use, is coupled to a drive member of the associated engine so that the drive shaft is rotated in synchronism with the engine. The drive shaft 14 extends into the generally cylindrical chamber 15 defined by the two body portions and has an enlarged cup-shaped portion 14a within the chamber. The enlarged portion is provided with a pair of diametrically disposed slots 16. The enlarged portion of the drive shaft is hollow and is provided with a counter bore 18. An oil seal 19 is provided at the outer end of the body portion 10 for engagement with the drive shaft 14 and a sleeve bearing 20 supports the shaft for rotation. An annular plate 21 surrounds the drive shaft and serves as an end closure for a low pressure fuel supply pump 22 and also serves to define a thrust face for the drive shaft.

The rotor 22a of the supply pump is carried by the drive shaft 14 and the rotor in turn carries vanes which co-operate with an eccentrically disposed surface on a stator ring 22b which is carried within a body portion 11. The low pressure pump has fuel inlet passage 23 connected to a fuel inlet 23a in a housing secured to the body portion 11 and a fuel outlet 24. Moreover, a relief valve 25 is provided to ensure that the output pressure of the pump remains within desired limits, the relief valve being connected between the inlet and the outlet.

Formed in the body portion 12 is a cylindrical bore 26 in which is fixed a sleeve 27. The sleeve 27 accommodates an angularly and axially movable distributor member 28 which projects into the chamber 15 and has an enlarged head portion lying within the chamber. Formed in the head portion of the distributor member is a transversely extending bore 29 in which is located a pair of pumping plungers 30. The bore 29 communicates with a blind passage 31 formed in the distributor member and which at its end within the head portion is sealed by means of a plug. As is more clearly shown in Figures 2,3 and 4 the passage 31 communicates with a pair of diametrically disposed longitudinal slots 32 formed in the periphery of the distributor member and communicating with the passage 31 by means of a single or a plurality of connecting passages.The passage 31 also communicates with a further longitudinal slot 33 formed in the periphery of the distributor member and this slot communicates in turn with a plurality of outlet ports 34 formed in the sleeve 27 and as seen in Figure 2, the outlet ports 34 communicate with outlets 35 respectively in the body portion 12. Each outlet incorporates a conventional form of delivery valve 36. The slots 32 register in turn with inlet ports 37 formed in the sleeve 27 and communicating with a circumferential groove 38 formed in the periphery of the sleeve. The groove 38 as shown in Figure 1, communicates with the outlet 24 of the low pressure pump 22 by way of an on/off valve 39 conveniently controlled by an electromagnetic device 40. If desired a single slot 32 may be provided with the number of inlet ports being equal to the number of outlets.

Surrounding the head portion of the distributor member 28 is an annular cam ring 41 on the internal peripheral surface of which are formed pairs of diametrically disposed cam lobes. In the particular example three pairs of lobes are provided since the apparatus is intended to supply fuel to a six cylinder engine. Moreover, the cam ring 41 is angularly movable about the axis of rotation of the distributor member by means of a fluid pressure operable device generally indicated at 42 and connected to the cam ring by way of a radially disposed peg 43. The device 42 conveniently includes a resiliently loaded piston housed within a cylinder to one end of which liquid under pressure can be supplied to act on the piston to urge the piston against the action of its resilient loading.

With reference now to Figures, 5,6 and 7, at the outer ends of the plungers are a pair of followers each of which comprises a roller 44 carried in a shoe 45. The followers are retained axially relative to the distributor member by a pair of side plates 46,47 which are secured to the side faces of the head portion of the distributor member. Conveniently the side plates are of annular form and have a pair of outwardly extending tongues 48, which locate in the slots 16 formed in the enlarged portion of the drive shaft. The plates act to transmit rotary motion to the distributor member from the drive shaft. The shoes 45 are also located within the aforesaid slots 16 and the rotary motion is transmitted to the shoes directly by the drive shaft.Moreover, one circumferential side face of each shoe is provided with a recess 49 which extends inwardly from the outer face of the shoe and has an inclined base wall. Conveniently as shown in Figure 6, it is the leading side face of the shoe which is recessed considered in terms of the direction of rotation.

Located within the recess 49 are stop plates 50 which project in an axial direction and which are mounted upon an annular plate 51. The plate 51 is located about a spigot defined by a portion of the sleeve 27 and is urged into engagement with a thrust surface defined by the body part 12 by means of coiled compression springs 52 which are in part housed within axial bores 53 defined in the cup shaped portion 14a. The ends of the springs which engage the plate locate in recesses respectively defined by apertures in support members fastened to the plate and formed integrally with the stop plates. The stop plates 50 and the plate 51 rotate with the distributor member and drive shaft and the springs act to urge the plate 21 into contact with the thrust surface.

The inner faces of the stop plates are inclined in a manner complementary to the base walls of the recesses 49.

In use, when fuel is supplied to the bore 29, upon registration of a groove 32 with an inlet passage 37, the plungers 30 are moved outwardly by the fuel pressure and in so doing impart outward movement to the shoes 45 and the rollers 44. The outward movement is limited by the abutment of the base walls of the recesses 49 with the surfaces of the stop plates 50 and by moving the distributor member axially the extent of outward movement can be varied. Thus the amount of fuel supplied to the bore 29 can be controlled and this in turn determines the amount of fuel delivered through an outlet when the plungers 30 are moved inwardly by a pair of cam lobes.

The axial position of the distributor member can be varied mechanically or hydraulically. In the arrangement described the variation is achieved by varying the pressure within a chamber 54 defined by the end of the bore 26 in the body portion 12. The end of the bore 26 is closed by a closure member and fuel under pressure is supplied to the chamber 54 by way of a restricted orifice 55 carried by the sleeve 27. The orifice 55 communicates with the outlet 24 of the pump 22. Fuel is allowed to escape from the chamber 54 so that the pressure in the chamber can be controlled, by way of an electromagnetically controlled valve 56. Moreover, the distributor member is biased by means of a coiled compression spring 57 which is housed within the blind bore 18 formed in the drive shaft 14.The spring 57 acts between the drive shaft and the distributor member and urges the distributor member against the action of fuel under pressure in the chamber 54 which acts on the distributor member.

By varying the pressure in the chamber 54 using the valve 56 so the axial position of the distributor member can be varied and therefore the amount of fuel delivered each time the plungers move inwardly can be varied.

For a given axial setting of the distributor member and ignoring leakage, the amount of fuel delivered by the plungers will remain the same through the speed range setting of the associated engine and an indication of the axial setting of the distributor member, is provided by a position transducer 58 which is carried on the end closure for the bore 26 and may be adjustably mounted thereon for the purpose of calibration. Conveniently the transducer has a part which is carried by the distributor member.

The signal provided by the position transducer can be utilised to provide a signal indicative of the speed of rotation of the distributor member and also a signal indicative of its axial position and therefore the amount of fuel being delivered by the apparatus.

In use, the signals will be supplied to an electronic control system which additionally is provided with signals representing various engine operating parameters and the desired engine speed. The control system controls the operation of the valve 56 to ensure that the correct amount of fuel is supplied to the associated engine.

With the arrangement as described tilting of the drive shaft due to side thrust applied to the shaft as by a driving belt for example, will have no effect upon the amount of fuel supplied by the apparatus.

This is because the position of the stop plates 50 is determined by the spigot defined by the sleeve 27 and the associated thrust surface defined by the adjacent part of the body part.

Claims (6)

1. Afuel pumping apparatusfor supplying fuel to a multi-cylinder internal combustion engine comprising a rotary distributor member mounted within a body, a pair of pumping plungers mounted in a bore formed in the distributor member, a cam ring located in the body, the cam ring defining inwardly extending lobes to impart inward movement to the pumping plungers as the distributor member rotates, passage means in the distributor member and body whereby fuel can be supplied to the bore containing the plungers and further passage means through the bore can be connected to outlet ports in turn during successive inward movements of the plungers, adjustable stop means for limiting the outward movement of the plungers, said distributor member being axially movable so as to vary the extent of outward movement of the plungers, a drive shaft carried by the body, said drive shaft being coupled to the distributor member, a cup-shaped enlarged portion carried by the drive shaft, radial slots in said enlarged portion, cam followers located in the slots respectively, inclined surfaces defined on the cam followers, an annular plate mounted for rotation about a spigot defined by the body and a pair of axially extending stop plates carried by said annular plate, said stop plates defining inclined surfaces for co-operation with the inclined surfaces respectively on said cam followers.

2. An apparatus according to Claim 1 including a thrust surface defined by said body, and resilient means acting on said annular plate to urge the plate into engagement with said surface.

3. An apparatus according to Claim 2 in which said plate is rotated by said stop plate.

4. An apparatus according to Claim 2 or 3 in which said resilient means comprises a plurality of coiled compression springs extending between said cup-shaped portion carried by the drive shaft and the annular plate.

5. An apparatus according to Claim 4 in which said springs are partly located within bores defined in said cup-shaped portion.

6. A fuel pumping apparatus for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as herein described with reference to the accompanying drawings.