GB2139383A

GB2139383A - Fuel injection pumping apparatus

Info

Publication number: GB2139383A
Application number: GB08412488A
Authority: GB
Inventors: Robert Thomas John Skinner
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1980-10-29
Filing date: 1981-09-04
Publication date: 1984-11-07
Also published as: GB2139383B; GB8412488D0

Abstract

A fuel injection pumping apparatus includes an electromagnetic valve 51 the flow of current in the solenoid of which is controlled by an electronic control system 55. The valve 51 controls the pressure applied to a surface on an axially movable distributor member 28 and hence controls the axial position of the distributor member to determine the amount of fuel supplied by the apparatus. In the event of failure a change- over valve 56 can be operated so that the pressure applied to the distributor member is determined by a further valve 57 which includes a spring loaded valve member the force acting upon which can be varied by a manually operable lever 58. <IMAGE>

Description

SPECIFICATION Fuel injection pumping apparatus This invention relates to a fuel injection pumping apparatus for supplying liquid fuel to internal combustion engines and of the kind comprising an injection pump operable to deliver fuel in timed relationship with an associated engine, a low pressure supply pump for supplying fuel to the injection pump, a component defining a surface against which fuel under pressure from the supply pump can act to control the amount of fuel supplied at each injection stroke of the injection pump, an electrically operated valve means for controlling said fuel pressure and an electronic control system responsive to various engine operating parameters for controlling the operation of said valve means.

It is conventional practice to arrange when the apparatus is at rest, for the parts of the apparatus to assume a position such that when an attempt is made to start the associated engine, the apparatus will immediately deliver the maximum amount of fuel. For this purpose the aforesaid component is biased by a resilient means and with an increase in the pressure of fuel the component is moved against the action of the resilient means to reduce the amount of fuel supplied. The advantage of this arrangement as opposed to an arrangement in which the component is biased to a minimum fuel position, is that there is no delay in the delivery of a substanial amount of fuel because there is no need for the fuel pressure to build up before delivery of fuel can start.

It is desirable and indeed regarded as essential by some engine manufacturers to provide a back-up system whereby the engine can be operated within safe limits, in the event of failure of the electronic control system. Such a back-up system should not result when it is in use, in an improved maximum performance which might cause the operator of the engine to operate on the back-up system in preference to the electronic control system. Moreover, the back-up system should be able to control the idling speed of the engine.

According to the invention in an apparatus of the kind specified said valve means includes a valve member having a surface subjected to the output pressure of said supply pump, said valve member with an increase in the pressure, being displaced to cause an increase in the pressure applied to said surface, resilient means biasing said valve member to oppose the movement of the valve member by said pressure and manually operable means for adjusting the force exerted by said resilient means.

Examples of fuel injection pumping apparatus in accordance with the invention and incorporating a back-up arrangement, will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of an apparatus which is shown in diagrammatic form in the remaining Figures and Figures 2, 3, 4 show the application of different back-up systems to the apparatus shown in Fig. 1.

Referring to Fig. 1 of the drawings, the apparatus comprises a housing 10 which is formed in two parts 11, 12, the part 11 being provided with apertured lugs 1 3 whereby it may be secured to the associated engine. The part 11 mounts a rotary drive shaft 14 which in use, is coupled to a drive member of the associated engine so that the shaft 14 rotates in synchronism with the engine. The drive shaft extends into a generally cylindrical chamber 1 5 and has an enlarged cup shaped portion 14a, within the chamber. The enlarged portion is provided with a pair of diametrically disposed slots 16 and it is also hollow. The open end of the enlarged portion is located about a spigot portion 1 7 defined by the part 1 2 of the body.The remainder of the interior surface of the enlarged portion tapers for a purpose which will be described.

The drive shaft is also provided with a counter bore 1 8 and an oil seal 1 9 is provided at the outer end of the body part 11 for engagement with the drive shaft. The latter is supported by a sleeve bearing 20. The shaft is located against axial movement by thrust surfaces which engage with the end surfaces of the enlarged portion of the shaft. In one case the thrust surface is defined directly by the part 1 2 of the body whilst in the other case, the thrust surface is defined by an annular plate 21 which surrounds the drive shaft and which additionally serves as an end closure for a low pressure fuel supply pump 22.The rotor 22a of the supply pump is carried by the drive shaft and it in turn carries vanes which co-operate with an eccentrically disposed surface on a stator ring 22b carried within the part 11 of the body. The low pressure pump has a fuel inlet 23 connected to a fuel inlet 23a in a housing secured to the body portion.

The low pressure pump also has an outlet 24 and a pressure relief valve 25 is provided to ensure that the output pressure of the low pressure pump remains within desired limits.

Formed in the part 1 2 of the body is a cylindrical bore 26 in which is fixed a sleeve 27. The sleeve 27 accommodates an angularly and axially moveable distributor member 28 which projects into the chamber 1 5 and has an enlarged head portion lying within the chamber. Formed in the head portion is a transversely extending bore 29 in which is located a pair of reciprocable 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. The passage communicates with a pair of diametrically disposed longitudinal slots 32 formed in the periphery of the distributor member and also with a single longitudinal slot 33 also formed in the periphery of the distributor member.The slot 33 can communicate in turn with a plurality of outlet ports 34 formed in the sleeve and which communicate with outlets 35 respectively which in use, are connected to the injection nozzles respectively of the associated engine. The slots 32 register in turn with inlet ports 37 formed in the sleeve and which extend inwardly from a circumferential groove 38 which communicates with the outlet 24 of the low pressure pump by way of an on/off valve 39 which is controlled by a solenoid device 40.

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 cam lobes are provided since the apparatus is intended to supply fuel to a six cylinder engine. The cam ring 41 is angularly moveable 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.

Positioned at the outer ends of the plungers are a pair of followers respectively 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. The side plates are of annular form and have outwardly extending portions which locate in the slots 1 6 formed in the drive shaft. The circumferential side faces of the shoes are provided with circumferentially extending projections 49 the radially outer surfaces of which are tapered to co-operate with the tapered surface formed on the internal surface of the enlarged portion of the drive shaft.

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 tapered surfaces on the shoes and shaft and by moving the distributor member axially the extent of outward movement of the plungers 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 35 when the plungers 30 are moved inwardly by a pair of the cam lobes.

The axial position of the distributor member is varied hydraulically and this is achieved by varying the pressure within a chamber 50 defined by the end of the bore 26 in the part 12 of the body. The end of the bore 26 is closed by a closure member and fuel under pressure is supplied to the chamber 50 by way of a valve seen at 51 in Fig. 2. Fuel can leave the chamber through a restricted orifice 52, the fuel flowing to the interior of the apparatus. The valve 51 is biased to the open position and can be closed by supplying an electric current to a solenoid associated with the valve. The supply of eiectric current to the solenoid is under the action of an electronic control system 55, the construction of which forms no part of the present invention but which for example may be of the kind described in British Patent Specification 1429293.The distributor member is biased by means of a coiled compression spring 53 located within the bore 18, the spring acting between the drive shaft and the distributor member and acting to urge the distributor member against the action of fuel under pressure in the chamber 50. A transducer 54 is located within the chamber 50 and it is utilized to provide an indication of the speed of rotation of the distributor member and also the axial setting of the distributor member, to the electronic control system 55.

Turning specifically to Fig. 2, fuel under pressure is supplied from the outlet of the supply pump 22 by way of a two-way valve indicated at 56 and in normal operation, fuel flows by way of the valve 56 to the chamber 50, the pressure in the chamber 50 being controlled by adjusting the effective size of the valve 51. As previously stated, this is under the control of the normal electronic control system 55. In the event of failure of the control system then the safe condition is for the valve to fail in the open position. The effect of this is that the pressure in the chamber 50 increases and the distributor member is moved the maximum extent against the action of the spring 53 to reduce the fuel flowing to the engine. This would probably cause the engine to stop. Another failure condition is where the valve 51 fails in the closed position and this will result in the pressure in the chamber 50 falling and an increase in the amount of fuel supplied to the engine. In this example, it is arranged that a failure of the electronic control system results in a warning to the operator of the engine and upon receipt of such warning, the operator manually operates the valve 56 to its aiternative position. In the alternative position the valve 51 is taken out of circuit and fuel is supplied to the chamber 50 by way of a manually operable valve 57. The valve is shown diagrammatically in Fig. 2 but it will be seen to comprise a ball which is loaded onto a seating by means of a spring. The force exerted by the spring can be varied.

Conveniently the abutment for the spring is connected to the throttle pedal of the engine by way of a pivotal lever indicated at 58. As the throttle pedal is depressed, the force exerted by the spring on the valve member increases thereby urging the valve member onto its seating to reduce the flow of fuel to the chamber 50. As a result the pressure in the chamber 50 will decrease and this will cause an increase in the amount of fuel supplied to the engine. As the engine speed increases however, the output pressure of the pump 22 will increase and this increase of pressure acting on the ball, will lift same from its seating to cause an increase of pressure in the chamber 50. As a result the distributor member will move against the action of the spring to reduce the amount of fuel supplied to the engine, a governing action is thus obtained.

Fig. 2 shows two graphs the upper being the plot of the output pressure of the pump 22 against the engine speed and the lower graph showing the governor characteristic.

The solid outline is the characteristic which is obtained with the electronic control system with the line 59 representing the idling characteristic and the line 60 representing the maximum fuel characteristic, this also including excess fuel. The dotted lines which appear between the lines 59 and 60 are the governor characteristics obtained using the valve 57 and it will be seen that they both lie within the boundaries of the equivalent lines attributable to the electronic control system. It will be seen therefore that the performance which can be obtained from the engine is inferior to that which can be obtained when the normal electronic control system is in operation.

Turning now to Fig. 3, the components are arranged differently on the paper and the only basic difference is the fact that the valve 56 has been replaced by an electromagnetically operable valve 61. Moreover, the construction of the valve 57 is slightly different. The valve 61 is still a two-way valve and it comprises a valve member 62 which is biased by means of a spring 63 to a position in which fuel is supplied to the chamber 50 by way of the valve 57. When the solenoid associated with the valve is energised, an armature 64 moves the valve member against the action of its spring to close off the passage connected to the valve 57. The fuel therefore flows to the chamber 50 by way of the valve 51 which is of course operated by the electronic control system.In the event of failure of the system the solenoid associated with the valve 61 is de-energised and the control of the engine using the valve 57 is effected automatically.

Turning now to Fig. 4, a slightly different arrangement is shown in which the roles of the valves 51, 61 and 57 shown in Fig. 3 are combined. The combined valve is shown at 65 and it includes a valve member 66 which can be urged onto a seating 67 to prevent the flow of fuel under pressure to the chamber 50. The valve member 66 is formed from magnetisable material and is contacted by a push rod 68 the other end of which is engaged by an armature 69 which is biased by a coiled compression spring 70, the force exerted by which can be varied by means of a lever 71 which in use, is connected to the throttle pedal of the associated engine. The spring 70 biases the valve member 66 into contact with the seating and ignoring for the moment the two solenoids which form part of the valve, the components of the valve thus far described perform the function of the valve 57 shown in Fig. 3.In other words, as the output pressure of the supply pump increases, the valve member 66 will be lifted from the seating to allow an increase of pressure within the chamber 50 thereby to move the distributor member 28 against the action of the spring to reduce the amount of fuel supplied to the engine.

Two solenoid windings 72, 73 are provided to exert magnetic force upon the valve member 66 and armature 69 respectively. The windings are connected to the electronic control system, the winding 72 being utilized to control the idling fuel characteristic whilst the winding 73 is utilized to control the maximum fuel characteristic. If the winding 73 and the associated portion of the normal electronic system is faulty then the idling characteristic will still be determined by the electronic control system. On the other hand if the winding 72 together with the associated portion of the normal electronic control system is faulty then the idling characteristic will be determined by the pressure acting on the valve member 66 and the opposing force exerted by the spring 70.

The valve 65 is constructed so that the risk of it becoming jammed is minimised. The push rod 68 is provided with adequate clearances but also a balancing passage is provided to ensure that the opposite ends of the push rod are subjected to the same fuel pressure so that there is little risk of particles of dirt within the fuel becoming trapped in the clearances provided.

Claims

1. A fuel injection pumping apparatus for supplying liquid fuel to an internal combustion engine comprising an injection pump operable to deliver fuel in timed relationship with an associated engine, a low pressure pump for supplying fuel to the injection pump, a component defining a surface against which fuel under pressure from the supply pump can act to control the amount of fuel supplied at each injection stroke of the injection pump, an electrically operated valve means for controlling said fuel pressure, an electronic control system responsive to various engine operating parameters for controlling the operation of said valve means, and said valve means including a valve member having a surface subjected to the output pressure of said supply pump, said valve member with an increase in the pressure, being displaced to cause an increase in the pressure applied to said surface, resilient means biasing said valve member to oppose the movement of the valve member by said pressure and manually operable means for adjusting the force exerted by said resilient means.

2. An apparatus according to Claim 1 in which said valve means includes a first valve including a solenoid the flow of current in which is controlled by said control system to determine said pressure, a second valve which includes said valve member, said resilient means and said manually operable means, said first and second valves being connected to a chamber in which said surface is located and a change over valve connected between the outlet of said supply pump and said first and swecond valves, said change-over valve being operable to determine which of said first and second valves controls said pressure.

3. An apparatus according to Claim 2 in which said change over valve is controlled by a further solenoid.

4. An apparatus according to Claim 1 including first and second solenoids the flow of current in which is controlled by said control system, one of said solenoids when energised acting to assist the action of said resilient means the other solenoid when energised acting to oppose the action of said resilient means.

5. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine and comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figs. 1 and 3 of the accompanying drawings.

5. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine and comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

6. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine and comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figs. 1 and 3 of the accompanying drawings.

7. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine and comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figs. 1 and 4 of the accompanying drawings.

1. A fuel injection pumping aparatus for supplying liquid fuel to an internal combustion engine comprising an injection pump operable to deliver fuel in timed relationship with an associated engine, a low pressure supply pump for supplying fuel under pressure to the injection pump, the output pressure of the supply pump varying in accordance with engine speed, a component defining a surface against which fuel pressure can act to control the amount of fuel supplied at each injection stroke of the injection pump, an electrically operated first valve for controlling the fuel pressure acting on said surface, an electronic control system responsive to various engine operating parameters for controlling the operation of said first valve, a second valve including a valve member, resilient means biasing the valve member towards a seating and manually operable means for adjusting the force exerted by the resilient means, and a change over operable to connect said first valve or said second valve in circuit with the outlet of the supply pump whereby the fuel pressure acting on said surface can be controlled either by said first valve and the electronic control system or by said second valve, the valve member of the second valve when the second valve is in circuit being subjected to the outlet pressure of the supply pump acting in opposition to the force exerted by said resilient means.

2. An apparatus according to Claim 1 in which said surface is located in a chamber to which the downstream ends of said first and second valves are connected, the apparatus including a restricted orifice through which fuel can leave said chamber.

3. An apparatus according to Claim 1 in which said change over valve is controlled by a solenoid.

4. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine and comprising the combination and arrangement ef parts substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.