GB2282191A - Fuel pumping apparatus - Google Patents

Abstract

A distributor type fuel pumping apparatus includes a rotary distributor member (13) mounting pumping plungers 15 and auxiliary plungers 34 which are utilised to effect operation of a shuttle valve member 44. The shuttle valve member in conjunction with an axially movable control rod 51 controls the operation of a spill valve member 40 which when operated during the inward movement of the pumping plungers (15) spills fuel to terminate delivery of fuel. The shuttle (44) is slidable in a cylinder (45) the axis of which is spaced from but parallel to the axis of rotation of the distributor member. The shuttle is prevented from rotating but the control rod 51 is rotatable within a bore (50) in the shuttle and is coupled to a centrifugal weight mechanism 60 through an axially movable member 57 which is spring biased against the action of the weight mechanism. <IMAGE>

Description

FUEL PUMPING APPARATUS This invention relates to a fuel pumping apparatus for supplying fuel to an internal combustion engine the apparatus being of the kind comprising a rotary distributor member in which is formed a bore, a pumping plunger slidable in the bore, a delivery passage formed in the distributor member, the delivery passage communicating with the bore and being positioned to register with a plurality of outlet ports in turn during successive inward movements of the pumping plunger, cam means for imparting inward movement to the pumping plunger as the distributor rotates, means for supplying fuel to the bore in the intervals between successive inward movements of the pumping plunger, a fluid pressure actuated spill valve operable during the inward movement of the pumping plunger to spill fuel from the bore thereby terminating the delivery of fuel through an outlet, a shuttle movable axially in a shuttle cylinder, an auxiliary plunger mounted in a further bore in the distributor member the auxiliary plunger being operable in synchronism with the pumping plunger, the further bore being connected to one end of the shuttle cylinder whereby as the auxiliary plunger is moved inwardly in the further bore the shuttle will be moved away from said one end of the cylinder, said shuttle at a predetermined position in its movement away from said one end of the cylinder acting to apply fluid under pressure to said spill valve to effect operation of the spill valve to terminate delivery of fuel, and means for adjusting said predetermined position whereby the amount of fuel delivered through the outlet ports can be varied.

An example of an apparatus of the aforesaid kind is described in EP-A0500231 in which the shuttle is mounted in a cylinder the axis of which is radially disposed relative to the axis of rotation of the distributor member. A return spring is provided to bias the shuttle towards the one end of the cylinder and in order to minimise friction since the shuttle is angularly movable by a governor mechanism, an hydraulic abutment is provided between the shuttle and the return spring. The hydraulic abutment essentially comprises two pistons housed in respective cylinders the inner ends of which are interconnected by a passage. One of the pistons is loaded by the spring towards the inner end of the cylinder in which it is located and the fluid pressure generated is applied to the other piston which in turn engages the shuttle.Although the two cylinders are located in side by side relationship the overall length of the shuttle together with said other piston and a housing which contains the cylinder housing that piston, adds considerably to the overall dimensions of the apparatus.

The object of the present invention is to provide such an apparatus in a more compact form.

According to the invention in an apparatus of the kind specified the axis of the shuttle cylinder is disposed generally parallel to but spaced from the axis of rotation of the distributor member and the apparatus further comprises a spring which biases the shuttle towards said one end of the cylinder, a blind bore formed in the shuttle, said blind bore extending inwardly from the end of the shuttle remote from said one end of the shuttle cylinder, a control rod slidable in said blind bore, said control rod extending from the bore and being coupled to an actuator member whereby the axial setting of the control rod can be adjusted, said control rod and said shuttle acting as a control valve to apply fluid under pressure to said spill valve when the shuttle has moved to a predetermined position away from said one end of the shuttle cylinder, said predetermined position being adjustable by axial movement of the control rod.

An example of an apparatus in accordance with the invention will now be described with reference to the accompanying drawing which is a sectional side elevation of the apparatus.

Referring to the drawing the apparatus comprises a housing which is formed in two parts 10, 11. The housing part 10 is provided with a sleeve 12 in which is mounted a rotary cylindrical distributor member 13. The distributor member extends from the sleeve and is provided with a transverse bore 14 in which is mounted a pair of pumping plungers 15. In the particular example a further bore is provided at right angles to the bore 14 and the further bore accommodates a further pair of pumping plungers. At their outer ends the plungers 15 engage cam followers 16 respectively each of which includes a roller which engages with the internal peripheral surface of an annular cam ring 1 7 which is angularly adjustable within the body part 10 by means of a fluid pressure operable piston 18.The inner ends of the plungers define a pumping chamber which is connected to an axial passage 19 formed in the distributor member and which communicates with a radially disposed delivery passage 20. The delivery passage is positioned to register with outlet ports 21 in turn, the outlet ports communicating with outlets 22 on the housing and which in use, are connected to the injection nozzles of the associated engine.

The distributor member is coupled to a drive shaft 23 which is journalled for rotation in the housing part 11. The drive shaft has an enlarged portion 24 which is of generally cup like form and which extends about the portion of the distributor member which extends from the sleeve 12.

This portion of the drive shaft is provided with slots in which the cam followers are located.

The passage 19 in the distributor member also communicates with a plurality of radially disposed inlet passages 25 and these are positioned to register in turn with one or a plurality of inlet ports 26 which are formed in the sleeve and which communicate with a circumferential groove 27 formed in the periphery of the sleeve and which communicates by way of a stop valve 28, with the outlet of a low pressure fuel supply pump generally indicated at 29. The pump 29 is of the vane type and has a rotor 30 which is coupled to the distributor member so as to rotate therewith. The pump 29 has associated with it a relief valve which is contained within a housing 31 which is secured to the housing part 10. The housing 31 defines a fuel inlet which is connected to a source of fuel.

Also formed in the extended portion of the distributor member are two further pairs of bores 32 which are blind and have their inner ends connected to a circumferential groove 33 formed on the periphery of the distributor member. Housed in the further bores are auxiliary plungers 34 respectively having their outer ends engaging the cam followers 16 respectively. The circumferential groove 33 is provided with longitudinal grooves 35 which are positioned about the axis of the distributor member for registration with an inlet port 36 which is in direct communication with the outlet of the low pressure pump 29.

In the end of the distributor member which projects from the sleeve there is formed a cylinder 37 and within the cylinder is slidable a piston 38. The piston is biased by a spring 39 towards the end wall of the cylinder and formed on the piston is a valve member 40 for engagement with a seating defined about a spill passage 41 which extends from the bore 14. A balance piston 42 is slidable within a drilling formed in the piston and the inner end of the drilling communicates with the spill passage 41 by way of a small passage. The diameter of the balance piston is slightly greater than the seat diameter of the valve member 40.

The inner end of the cylinder 37 communicates by way of passages, with a circumferential groove 42 formed on the periphery of the distributor member. The valve member 40 and the seating constitute a spill valve and the movement of the spill valve is triggered by the application of fluid under pressure supplied to the groove 42, the fluid pressure acting on the end surface of the piston 38.

In order to control the operation of the spill valve a control valve generally indicated at 43 is provided. The control valve comprises a shuttle 44 which is axially slidable in a shuttle cylinder 45, the shuttle cylinder being formed in the housing part 10. The inner end of the shuttle cylinder is in permanent communication with the circumferential groove 33 and the circumferential groove 42 is in permanent communication with a port 46 which opens into the shuttle cylinder at a position spaced from the inner end thereof. The shuttle is biased towards said one end of the shuttle cylinder by means of a spring 47 which is interposed between the shuttle and spring abutment 48 which is secured to the housing part 10.In addition, the shuttle is restrained against angular movement by means of a pin 49 which is located in a slot formed in a flange on the shuttle, the flange being engaged by the spring 47.

The shuttle is provided with a blind bore 50 and slidable in the bore and extending from the end thereof is a control rod 51. Formed on the periphery of the control rod is a circumferential groove 52 and for communication with this groove the shuttle is provided with a pair of ports 53, 54. The port 53 is in constant communication with the port 46 and the port 54 communicates with a circumferential groove formed in the outer peripheral surface of the shuttle and which communicates with a transfer port 55 which opens onto the periphery of the distributor member at a position to register in turn with the aforesaid inlet passages 25. The inner end of the bore in the shuttle communicates by way of a passage 56 in the control rod with the space within the housing.

The control rod passes with clearance through an opening in the spring abutment 48 and is non-rotatably and axially coupled to an actuator 57.

The actuator 57 is of stepped form and is mounted for rotation about a bearing rod 58 secured in the part 11 of the housing. Also mounted about the bearing rod is a cage 59 in which is located a plurality of governor weights 60. The cage is provided with teeth 61 on a portion of its peripheral surface and these teeth are engaged with complimentary teeth formed on the periphery of the drive shaft 23. The actuator is also provided with a step against which is located a bearing 62 which serves as an abutment for one end of a coiled compression spring 63 the other end of which engages an internal flange on a hollow cylindrical member 64, the member having an outwardly extending flange which is engaged by a forked member mounted upon an angularly adjustable shaft 65 which extends to the exterior of the housing and which in use, is coupled to the throttle control of the engine.

Consider now the operation of the apparatus. In the drawing the parts of the apparatus are shown in the position which they adopt following completion of the filling of the bores 14 and 32 with fuel. As will be observed the valve member 40 is in engagement with the seating and the balance piston 42 is in engagement with a fixed stop 67. During continued rotation of the distributor member the delivery passage 20 will move into register with an outlet port 21. Moreover, one of the inlet passages 25 will move into register with the transfer port 55. The inlet port or ports 26 are out of register with the inlet passages 25 and the filling port 36 is out of register with a groove 35. In addition, the shuttle is in engagement with an adjustable stop 66, it being held in this position by the action of the spring 47.The weights 60 of the governor are shown in their innermost position and in practice would with the engine in operation, have moved outwardly a small amount thereby effecting movement of the actuator 57 and also the control rod 51 to the right against the action of the spring 63.

As the distributor member further rotates the plungers 15 and 34 are moved inwardly by the action of cam lobes which are formed on the internal peripheral surface of the cam ring 17 and the inward movement of the pumping plungers 15 displaces fuel through the outlet 21 to an injection nozzle of the associated engine. Inward movement of the auxiliary plungers 34 also takes place and the fuel displaced by these plungers flows to the closed end of the shuttle cylinder 45. This fuel causes the shuttle 44 to be displaced against the action of the spring 47 and when the groove 52 communicates with the port 54 fuel at the high pressure developed during the inward movement of the pumping plungers, flows between the ports and is supplied to the inner end of the cylinder 37. This flow of fuel effects the initial movement of the piston 38 against the action of the spring 39.The effect of such movement is to lift the valve member 40 from the seating and the fuel displaced by the pumping plungers flows through the spill passage 41 into the cylinder 37. The piston is therefore displaced further against the action of the spring 39. The effect of spilling fuel through the passage 41 is to reduce the pressure of fuel supplied to the injection nozzle and this allows the valve member in the injection nozzle to close quickly and thereby produce rapid termination of the flow of fuel into the engine.

As the distributor member continues to rotate and the plungers 15 and 34 continue to move inwardly, further displacement of the piston 38 and the shuttle 44 takes place. When the rollers reach the crests of the cam lobes the delivery passage 20 starts to move out of register with the outlet port 21 and the passage 25 moves out of register with the transfer port 51. However, a passage 25 will start to move into register with an inlet port 26. In addition, when the rollers start to move down the trailing flanks of the cam lobes the piston 38 is returned by the action of the spring 39 and the fuel which was displaced into the cylinder 37 is returned to the bore 14.Additional fuel to make up for leakage and for the fuel supplied to the engine flows through the port 26 from the low pressure pump 29 and the pressure of fuel ensures that the balance piston is held in engagement with the stop 67. Furthermore, the spring 47 biases the shuttle towards the one end of the shuttle cylinder and the fuel displaced from the cylinder is returned to the bores 32 thereby moving the auxiliary plungers 34 outwardly. Any fuel which is lost due to leakage from the shuttle cylinder or the bores 32, is made up by fuel which flows to one of the longitudinal grooves 35 from the supply port 36. At the end of the filling stroke the parts of the apparatus assume the positions shown in the drawing and the cycle is repeated with fuel being supplied to the next outlet 22.

The axial position of the control rod 51 determines the instant during the movement of the shuttle 44 against the action of the spring 47 at which the ports 53 and 54 are placed in communication with each other. The axial setting of the control rod varies with the speed of the associated engine. As the speed increases for a given setting of the shaft 65, the weights move outwardly against the action of the spring 63 and the control rod is moved towards the right as seen in the drawing. The effect therefore is to reduce the amount of fuel which is supplied to the engine because the ports 53 and 54 will be brought into communication with each other earlier during the movement of the shuttle. Conversely if the speed falls the control rod 51 will move to the left and more fuel will be supplied to the associated engine. The actuator 57 is nonrotatably coupled to the control rod 51 so that the latter rotates and thereby frictional effects between the shuttle and the control rod are overcome.

The stop 66 is adjustable to determine the maximum amount of fuel which can be supplied to the associated engine it being appreciated that when the operator of the engine depresses the throttle pedal, the force exerted by the spring 63 will be increased and the governor weights will be moved inwardly to the position shown so that the maximum excursion of the shuttle is required before the ports 53 and 54 are brought into communication.

The stop valve 28 is electrically controlled and must be supplied with electrical power to permit fuel to flow from the outlet of the low pressure pump 29 to the bore 14. When the valve is de-energised it closes to prevent the supply of fuel so that further fuel flow to the associated engine ceases.

A further feature of the apparatus is the formation of the housing in the two portions 10, 11, the joint being in the region of the inner end of the drive shaft 23. This permits a tongue 67 which engages in a slot in the piston 18, to be manufactured as an integral part of the cam ring 17 and for the cylinder which accommodates the piston 18 to be integrally formed with the housing 10. The fuel under pressure which is applied to the piston is obtained from the outlet of the low pressure pump 29. The pressure of fuel supplied by the low pressure pump is arranged to vary in accordance with the speed at which the apparatus is driven and in this manner the timing of fuel delivery varies with engine speed.

Claims (4)

1. A fuel pumping apparatus for supplying fuel to an internal combustion engine comprising a rotary distributor member in which is formed a bore, a pumping plunger slidable in the bore, a delivery passage formed in the distributor member, the delivery passage communicating with the bore and being positioned to register with a plurality of outlet ports in turn during successive inward movements of the pumping plunger, cam means for imparting inward movement to the pumping plunger as the distributor rotates, means for supplying fuel to the bore in the intervals between successive inward movements of the pumping plunger, a fluid pressure actuated spill valve operable during the inward movement of the pumping plunger to spill fuel from the bore thereby terminating the delivery of fuel through an outlet, a shuttle movable axially in a shuttle cylinder, an auxiliary plunger mounted in a further bore in the distributor member the auxiliary plunger being operable in synchronism with the pumping plunger, the further bore being connected to one end of the shuttle cylinder whereby as the auxiliary plunger is moved inwardly in the further bore the shuttle will be moved away from said one end of the cylinder, said shuttle at a predetermined position in its movement away from said one end of the cylinder acting to apply fluid under pressure to said spill valve to effect operation of the spill valve to terminate delivery of fuel, means for adjusting said predetermined position whereby the amount of fuel delivered through the outlet ports can be varied, the axis of the shuttle cylinder being disposed generally parailel to but spaced from the axis of rotation of the distributor member and the apparatus further comprising a spring which biases the shuttle towards said one end of the cylinder, a blind bore formed in the shuttle, said blind bore extending inwardly from the end of the shuttle remote from said one end of the shuttle cylinder, and a control rod slidable in said blind bore, said control rod extending from the bore and being coupled to an actuator whereby the axial setting of the control rod can be adjusted, said control rod and said shuttle acting as a control valve to apply fluid under pressure to said spill valve when the shuttle has moved to a predetermined position away from said one end of the shuttle cylinder, said predetermined position being adjustable by axial movement of the control rod.

2. A fuel pumping apparatus according to Claim 1, in which said actuator comprises an axially movable member which is movable against the action of resilient means by a centrifugal weight mechanism, and means for adjusting the force exerted by said resilient means.

3. A fuel pumping apparatus according to Claim 2, in which said control rod and said axially movable member are rotatable with the weight mechanism, said resilient means comprising a coiled compression spring which acts against a step defined on said axially movable member, a bearing being disposed between said spring and said step.

4. A fuel pumping apparatus according to Claim 3, including an adjustable stop to limit the movement of the shuttle towards said one end of the cylinder.