GB2283540A - Fuel injection pumping apparatus - Google Patents

Abstract

A fuel injection pumping apparatus for supplying fuel to an engine is of the rotary distributor type having pumping plungers (14) actuated by cam lobes formed on an angularly adjustable cam ring (18). Adjustable means (34) is provided to control the quantity of fuel supplied by the apparatus and the setting of the means is effected by a control system (6). A pressure transducer (63) responsive to the fuel pressure developed during inward movement of the plungers, is provided and the signals provided by the transducer are processed to provide an engine speed signal for the control system (6). In an alternative arrangement the pressure transducer is located to respond to the pressure in a cylinder and piston device (19) used to adjust the cam ring (18) for varying the timing. <IMAGE>

Description

FUEL INJECTION PUMPING APPARATUS This invention relates to a fuel injection pumping apparatus for supplying fuel to an internal combustion engine, the apparatus being of the kind comprising a cam actuated pump which is coupled to a drive shaft, the drive shaft in use being driven in timed relationship with the associated engine, first means for distributing fuel displaced by the pump to a plurality of outlets in turn, second means for controlling the quantity of fuel supplied through said outlets and a control system responsive to at least one engine operating parameter and a desired operating parameter for controlling said second means.

One form of such an apparatus is shown in EP-A-0500231 and the apparatus comprises a rotary distributor member which is mounted in a surrounding body, the distributor member having a delivery passage which is positioned to register with outlet ports formed in the body and which connect with outlets on the exterior of the body. The distributor member also has a transverse bore in which is mounted a pair of pumping plungers which as the distributor member rotates, are driven inwardly by the action of cam lobes on the internal surface of an annular cam ring mounted in the body. The bore is connected to the delivery passage and the distributor member is driven by a drive shaft which in use is coupled to a rotary part of the engine.Fuel is supplied to the bore by way of an inlet port or ports in the body which cooperate with a passage or passages in the distributor member communicating with the bore. The amount of fuel which is supplied through the outlets is determined by a spill valve.

The spill valve in the example of the apparatus described above is in turn controlled by a control valve responsive to the operation of a governor.

The governor may be of the mechanical type but it is preferred that the governor should be constituted by an electronic control system which is responsive to various engine operating parameters and desired parameters in particular, the engine speed and the operator demand.

In addition the control system should determine the timing of fuel delivery to the engine by means of an electrically controlled actuating system which determines the angular setting of the aforesaid cam ring.

In order to carry out its control function various signals need to be supplied to the control system and in the past these signals have been provided by transducers mounted on the pumping apparatus. For example, associated with the drive shaft there has been a transducer for providing an engine speed signal and associated with the cam ring or its actuating mechanism, a further transducer for providing a signal indicative of the position of the cam ring. The provision of such transducers adds substantially to the cost of the apparatus and also its complexity.

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

According to the invention in an apparatus of the kind specified a single pressure transducer is provided which is responsive to the pressure of fuel in said bore, said pressure transducer providing an output signal which varies with the pressure and means being provided to process the output signals of said transducer to provide at least an engine speed signal.

In the accompanying drawings: Figure 1 is a diagrammatic part sectional view of the apparatus, and Figure 2 is a view in cross-section of part of the apparatus seen in Figure 1.

Referring to the drawings, the apparatus comprises a body 10 in which is mounted a fixed sleeve 11 defining a bore to receive a rotary cylindrical distributor member 12. The distributor member has an enlarged diameter portion projecting from the bore and in use is driven in timed relationship with an associated engine by means of a drive shaft 9.

Formed in the enlarged portion of the distributor member is a transverse bore 13 in which is mounted a pair of pumping plungers 14 the outer ends of which engage cam followers 15 each cam follower comprising a shoe 16 and a roller 17. The rollers engage the internal peripheral surface of an annular cam ring 18 which is mounted within the body 10.

The angular position of the cam ring is adjustable by means of a fluid pressure operable spring biased piston 19 which is coupled to the cam ring and is housed in a cylinder 8.

On the internal peripheral surface of the cam ring there is formed a plurality of pairs of cam lobes which extend from the base circle of the cam ring. As the distributor member rotates, the rollers engage with the leading flanks of the cam lobes to impart inward movement to the pumping plungers 14. The bore 13 is in communication with a longitudinal passage 20 which at one point communicates with a radially disposed delivery passage 21 positioned to register in turn with a plurality of outlet ports 22 formed in the sleeve and extending to outlets 23 respectively which are connected in use to the injection nozzles of the associated engine.

At another position the passage 20 is in communication with a plurality of radially disposed inlet passages 24 which are positioned to register in turn with inlet ports 25 formed in the sleeve 11 and communicating by way of an on/off valve 26, with the outlet of a low pressure fuel supply pump 27 having a fuel inlet 28. Although not shown, the inlet and outlet of the supply pump 27 are interconnected by way of a relief valve and the rotary part of the supply pump is coupled to the distributor member. By reason of the relief valve, the output pressure of the low pressure pump 27 varies in accordance with the speed at which the distributor member is driven and the aforesaid piston 19 is subjected to the outlet pressure of the low pressure pump under the control of a valve 7. The piston moves in opposition to the force exerted by its spring.

The passage 21 is arranged to register with an outlet port 22 during the whole time the plungers 14 are moved inwardly so that fuel displaced from the bore 13 can flow to the associated engine. As the distributor member rotates and as the rollers move over the crests of the cam lobes, the passage 21 moves out of register with an outlet port 22 and an inlet passage 24 moves into register with an inlet port 25. Fuel is therefore supplied to the bore 13 from the outlet of the low pressure pump and the plungers 14 are moved outwardly to their maximum extent so that the rollers engage the base circle of the cam ring. As described there is no method of controlling the quantity of fuel supplied through an outlet 23.In order to achieve the desired control, there is provided a further transverse bore 29 in the enlarged portion of the distributor member and located in the bore is a pair of further or auxiliary plungers 30 the outer ends of which engage the shoes 16 so that the auxiliary plungers are moved inwardly at the same time as the pumping plungers. The bore 29 is in constant communication with a circumferential groove 31 formed in the periphery of the distributor member and this groove is in constant communication with one end of a shuttle cylinder 32 which for convenience is defined by the bore of a sleeve 33 which is angularly adjustable within the body part 10 but is restrained from axial movement. Slidable within the shuttle cylinder 32 is a shuttle 34 which is spring biased towards the one end of the cylinder.

Formed in the sleeve 33 is a pair of axially spaced ports 36 and 37. The port 36 is in constant communication with a circumferential groove 38 formed on the distributor member whilst the port 37 is in constant communication with a port 39 which is formed in the sleeve and which opens onto the periphery of the distributor member at a position to register with the inlet passages 24. The registration of the port 39 with an inlet passage 24 is arranged to occur during the time the pumping plungers 14 are moved inwardly. The shuttle 34 is provided with a groove 40 which is in constant communication with the port 36 and extending from the groove 40 is an inclined groove 41 which as will be explained, is positioned to register with the port 37 after a predetermined movement of the shuttle. The shuttle is angularly adjustable and for this purpose is provided with an arm 42 which is coupled to an electromagnetically operable actuator 42A. By moving the shuttle 34 angularly the extent of movement of the shuttle away from said one end of the cylinder before the port 37 is brought into register with the groove 41, can be adjusted.

Also provided is a normally closed valve generally indicated at 43 and including a piston 44 which is housed within a cylinder 45 defined in an extension of the distributor member 12. The piston 44 is integral with a valve member 46 which co-operates with a seating defined in the end wall of the cylinder 45, the seating being located at one end of a passage 47 which communicates with the bore 13. The piston 44 is biased by a spring 48 so that the valve member 46 engages with the seating 48 and the spring is sufficiently strong to ensure that the valve member 46 is held in sealing engagement with the seating.

Operation starts with the items in the positions shown in Figure 1 which corresponds to the commencement of inward movement of the pumping plungers 14 and the auxiliary plungers 30. As the distributor member rotates the plungers 14 will displace fuel from the bore 13 and delivery of fuel to the associated engine will take place through an outlet 23. At the same time the plungers 30 are moved inwardly and fuel is displaced into the inner end of the cylinder 32 containing the shuttle 34. The shuttle therefore starts to move against the action of the biasing spring and this movement will continue so long as the plungers are moved inwardly.At some point during the movement of the shuttle the port 37 is brought into register with the groove 41 and fuel at the high pressure developed by the plungers 14 is supplied to the inner end of the cylinder 45 and this fuel acts upon the piston 44 to urge the piston against the action of the spring 48. As soon as the piston 44 starts to move, the valve member is lifted from its seating and the remaining fuel which is displaced by the plungers 14 can flow into the cylinder 45 through the passage 47 thereby displacing the piston 44 against the action of the spring 48. By varying the angular position of the shuttle 34 the extent of movement of the shuttle before the port 37 registers with the groove 41 can be controlled and therefore the position during the inward movement of the plungers 14 at which the valve 43 is opened.Thus by moving the shuttle angularly the quantity of fuel which can be supplied to the associated engine can be varied. As stated, the arm 42 is connected to the actuator 42A and the current flow in the actuator is determined by an electronic control system 6.

The sleeve 33 can also be moved angularly and two ways of achieving this are illustrated. In the first case a fluid pressure operable piston 59 is provided, the piston being spring biased against the action of the outlet pressure of the low pressure pump. By connecting the piston to the sleeve 33, so called torque control can be obtained. Another way of moving the sleeve is by means of an air pressure responsive diaphragm 60 which is responsive to the pressure of air delivered to the associated engine, the piston 59 and the diaphragm 60 can if desired, both be provided to control the position of the sleeve. However, if desired the sleeve 33 can be positioned by means of an actuator controlled by the control system.If movement of the sleeve 33 in the use of the apparatus is not required a setting screw may be provided whereby the position of the sleeve can be set during assembly of the apparatus.

When the plungers complete their inward movement and the rollers 17 move over the crests of the cam lobes, the plungers can move outwardly and fuel is returned from the one end of the cylinder 45 to the bore 13 by movement of the piston 44 by the spring 48. However, since fuel may have been supplied to the associated engine, fuel is supplied through one of the inlet passages 24 to the bore 13 to ensure that the plungers move outwardly their maximum extent. The shuttle 34 will also be urged towards the inner end of the cylinder 32 displacing fuel back to the bore 29. Any additional fuel which is required to make up for leakage, is supplied by means of auxiliary filling ports 61 connected to the outlet of the fuel supply pump and communicating at the appropriate time, with a passage 62 in the distributor member and which is in communication with the bore 29.The plungers 30 are moved outwardly to their maximum extent.

The timing of fuel delivery by the apparatus is varied by moving the cam ring 18 angularly within the body. If the pressure in the cylinder 8 is increased the piston 19 moves the cam ring in the opposite direction to the direction of rotation of the distributor member and the timing of fuel delivery to the engine is advanced. The operation of the valve 7 is controlled by the control system 6.

The control system 6 acts as a governor to control at least the idling speed and the maximum speed of the engine and in which case it is acting as a two speed governor and the fuel supply to the engine in the intermediate speed range is controlled by the operator. It may however control the engine speed over the whole speed range in response to a speed demand signal in which case it is acting as an all speed governor.

The control system also acts to ensure that other engine operating parameters are observed for example, it acts to ensure that no more than a certain level of fuel is supplied to the engine in order to minimise the level of smoke in the engine exhaust. The timing of the delivery of fuel to the engine must vary at least in accordance with the speed of the engine and preferably also in accordance with the amount of fuel which is being supplied to the engine.

The apparatus includes a pressure transducer 63 which is mounted on the body 10 and is responsive to the pressure in the passage which interconnects the ports 37 and 39. The port 39 during the inward movement of the plungers is connected to the bore 13 and therefore the fuel pressure in the passage connecting the ports is the same as that in the bore. The signal provided by the pressure transducer 63 is therefore representative of the pressure in the bore and will be of a pulsed nature during operation of the apparatus. It is possible therefore by counting the pulses which occur in a given time to determine the average engine speed in that time. A more accurate determination of the engine speed can be obtained by measuring the intervals between the pulses.This measurement can be carried out between the start of one pulse and the start of the next pulses or at a threshold value of pressure during each pulse. In addition, once the speed is known an indication of the degree of advance of the timing can be obtained by measuring the time interval between a known one of the pulses and an engine position signal. It is also possible to obtain by integrating with respect to time, the pressure pulses to determine the amount of fuel which is supplied to the engine.

The signals obtained can be utilized in the control system to enable it to control the settings of the various components of the apparatus.

Figure 2 shows an alternative position for the pressure transducer, the transducer being indicated at 64 and being located in the end cap 65 of the cylinder 8. The pressure transducer is responsive to the pressure of fuel in the end of the cylinder and this pressure varies as the rollers engage the leading flanks of the cam lobes, the pressure being of a pulsed nature similar to the pressure existing in the passage which connects the ports 37 and 39.

Claims (3)

1. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine comprising a cam actuated pump which is coupled to a drive shaft which is driven in use in timed relationship with the associated engine, first means for distributing fuel displaced by the pump to a plurality of outlet ports in turn, second means for controlling the quantity of fuel supplied through said outlets, a control system responsive to at least one engine operating parameter and a desired operating parameter and a single pressure transducer which provides a signal dependent upon the pressure of fuel developed by the cam actuated pump and means for processing the output signals of the transducer to provide an engine speed signal for the control system.

2. An apparatus according to Claim 1, in which said pressure transducer senses directly the fuel pressure developed by the pump.

3. An apparatus according to Claim 1, in which the pressure transducer is responsive to the pressure developed in a cylinder which contains a piston for positioning the cam.