GB2090341A - Fuel injection pumping apparatus - Google Patents

Abstract

A fuel injection pumping apparatus of the rotary distributor type includes two pairs of plungers 13, 37 which are moved inwardly by cam lobes on a cam ring 27. The plungers 13 alone are used at low engine speeds to supply fuel but under the control of a valve 38 both pairs of plungers are used to deliver fuel at higher engine speeds. The use of both pairs of plungers increases the rate of fuel supply by the apparatus. <IMAGE>

Description

SPECIFICATION Fuel injection pumping apparatus This invention relates to fuel injection pumping apparatus for supplying fuel to internal combustion engines and ofthe kind comprising a plunger reciprocable within a bore formed in a rotary distributor member, passage means for conveying fuel to and from said bore, and a cam having cam lobes for effecting inward movement of the plunger in the bore as the distributor or member rotates, thereby to display fuel from the bore to the associated engine.

Such pumps are well known in the art and supply fuel at a certain rate considered in terms of degrees of rotation of the distributor member, which is dependent upon the profile of the leading flanks of the cam lobes. In order to improve the efficiency of engine operation it is required to increase the rate of fuel delivery at higher engine speeds and the object of the present invention is to provide such an apparatus in a form in which this requirement is achieved.

According to the invention a pump of the kind specified comprises a further plunger mounted in a further bore, said further plunger being operated by said cam or a similar cam, and speed responsive valve means to connect said bores together so that both plungers are brought into operation to increase the rate of fuel delivery at the higher engine speeds.

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 the apparatus and Figure 2 is a diagrammatic illustration ofthe apparatus shown in Figure 1 showing additional components.

Referring to Figure 1 of the drawings the apparatus comprises a body part 10 in which is mounted a rotary cylindrical distributor member 11 which at one end is coupled to a drive shaft not shown adapted to be driven in timed relationship with an associated engine. Formed in the distributor member is a transverse bore 12 in which is mounted a pair of pumping plungers 13 and extending within the distributor member is a longitudinal passage 14.

Communicating with the passage 14 is a delivery passage 15 which extends to the periphery of the distributor member and which is arranged to register in turn with a plurality of outlet ports 16 which in use are connected to the injection nozzles respectively of the associated engine. The passage 14 also communicates with a plurality of radially disposed inlet passages 17 and these can communicate in turn with an inlet port 18 formed in the body.

The apparatus also includes a low pressure supply pump 19 which draws fuel through an inlet 20 and which has an outlet 21 which is in communication with a passage 22 formed in the body part. The output pressure of the low pressure pump is controlled by a relief valve 24 so that the pressure varies in accordance with the speed at which the apparatus is driven.

The passage 22 communicates with a circumferentially extending groove 23 formed in the periphery of the distributor member and this in turn communicates by way of a passage 25 with a fuel control device diagrammatically shown in 26. This may comprise an angularly adjustable throttle member the setting of which is determined by a governor mechanism not shown. The fuel control device controls the flow of fuel between the passage 25 and the port 18.

Surrounding the distributor member is a cam ring 27 on the internal peripheral surface of which is formed in the particular example, two pairs of inwardly extending cam lobes. The cam ring is angularly adjustable within the body part by a fluid pressure operable mechanism not shown which is responsive to the outlet pressure of the low pressure supply pump 19.

For engagement with the cam lobes there is provided a pair of cam followers each of which comprises a roller 28 which is carried by a shoe 29. These are slidable within radially disposed slots formed in a member 30 which surrounds the distributor member and which is directly coupled or integrally formed with the drive shaft. The shoes 29 are provided with lateral extensions 31 for engagement with stop rings 33 to limit the extent of outward movement of the followers and therefore the plungers 13.

In operation, the cam lobes are disposed so that when the port 18 is in communication with a passage 17, fuel is supplied to the bore 12 to effect outward movement of the plungers 13. The amount of fuel flowing to the bore is determined by the control device 26. As the distributor member continues to rotate the communication between the port 18 and a passage 17 is broken and the delivery passage 15 moves into register with an outlet port 16. Further rotation ofthe distributor member causes the cam lobes to impart inward movement to the followers and the plungers to displace fuel from the bore 12 to the particular outlet port and hence to an injection nozzle of the engine.During continued rotation of the distributor member the passage 15 is moved out of register with an outlet port16 and an inlet passage 17 moves into register with the inlet port 18 and the cycle as described is repeated so that fuel is supplied to the injection nozzles of the engine in turn.

The rate of fuel delivery considered relative to the rotation of the distributor member, is dependent upon the profile of the leading flanks of the cam lobes and the areas of the plungers. Neither of these can be altered once the apparatus has been manufactured.

As explained earlier it is desirable for the operation of some engines, that the rate of delivery of fuel should be increased at higher engine speeds.

In order to achieve the increased rate of fuel delivery a further bore 36 is provided together with a further pair of plungers 37. The cam followers are sufficiently long to engage the two pairs of plungers and the cam ring is also wide enough to cope with the increased length of the followers. If desired however separate followers may be provided for the two sets of plungers and the cam ring may also be divided.

Referring now to Figure 2, the bores 12 and 36 can be inter-connected by a speed responsive valve generally indica.ed at 38. This valve comprises a spring loaded spool 39 which is contained within a cylinder to one end of which can be admitted fuel underpres- sure from the passage 22. In operation therefore below a predetermined speed only the plungers 13 operate to deliver fuel to the associated engine however, when the spool 29 is moved against the action of its spring, the bores 12 and 36 are inter-connected so that both pairs of plungers operate to deliver fuel to the engine.When both pairs of plungers are brought into operation the movement of the plun- gers for the same quantity of fuel delivered to the engine, is reduced however, the rate of delivery of fuel is increased and if all the plungers have the same diameter, then the movement of the plungers is half the original movement of the plungers 13 and the rate of delivery twice the original rate. As shown, the plungers 37 are smaller in diameter than the plungers 13 and so the movement of the plungers when ail the plungers are in operation, is not quite half the original movement of the plungers 13. The fact that during the supply oifuel to the bores, the plungers move outwardly to a lesser extent, means that the timing of fuel delivery to the engine will be retarded. This can be compensated by appropriate adjustment of the cam ring 27.

Figure 2 shows an alternative way of controlling the application of pressure to the spool 39. The alternative method is to provide a valve 40 which includes a spring loaded valve member 41 actuated by a speed responsive mechanism such for example as a plurality of centrifugal weights 42. The valve member 41 controls the application of pressure to the spool 39 from a suitable source. It will be appreciated that the valve 38 can be made responsive to other engine operating parameters if so required.

Claims (4)

1. Afuel injection pumping apparatusforsupply- ing fuel to an internal combustion engine comprising a plunger reciprocable within a bore formed in a rotary distributor member, passage means for conveying fuel to and from said bore, a cam having cam lobes for effecting inward movement of the plunger in the bore as the distributor member rotates, thereby to displace fuel from the bore to the associated engine, a further plunger mounted in a further bore, said further plunger being operated by said cam or a similar cam, and speed responsive valve means to connect said bores together so that both plungers are brought into operation to increase the rate of fuel delivery at the higher engine speeds.

2. An apparatus according to Claim 1 in which said speed responsive valve means comprises a spring loaded spool valve operable to connect said bores together and a pump the output pressure of which varies in accordance with the speed at which the apparatus is driven, said spool valve being subject to the outlet pressure of said pump.

3. An apparatus according to Claim 1 in which said speed responsive valve means comprises a spring loaded spool valve operable to connect said bores together, a fluid pressure source and a valve for controlling the application of fluid under pressure from said source to said spool valve, and a speed responsive mechanism for operating said valve.

4. Afuel injection pumping apparatus comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.