Fuel injection pumping apparatus

Abstract

A fuel injection pumping apparatus for supplying fuel to an internal combustion engine includes a displacement piston which is contained in a cylinder. Fluid under pressure is supplied to one end of the cylinder from an accumulator to effect displacement of the piston to force fuel from the other end of the cylinder through an outlet. In addition, first and second valves are provided to control the application of fluid under pressure from the accumulator. The valves are operated by a stack of piezo-electric crystals.

Description

This invention relates to fuel injection pumping apparatus for supplying fuel to an internal combustion engine.

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

According to the invention, a fuel injection pumping apparatus for supplying fuel to an internal combustion engine comprises an accumulator in which fuel is stored at high pressure, a displacement piston contained within a cylinder, one end of said cylinder communicating with an outlet, valve means for controlling flow of fuel from a low pressure source to said one end of the cylinder, a first valve operable to allow fuel under pressure to act on one end of said displacement piston to displace fuel through said outlet, a second valve through which said one end of the cylinder can be connected to a drain, and means for actuating said valves whereby said piston can be moved to said one end of the cylinder to displace fuel through the outlet by opening the first valve and closing the second valve, said piston being moved away from said one end of the cylinder by closing the first valve and opening the second valve, the extent of movement of the displacement piston away from said one end of the cylinder being determined by reclosing said second valve.

In the accompanying drawings:

FIG. 1 shows one example of a fuel injection pumping apparatus in accordance with the invention,

FIG. 2 shows a further example.

FIG. 3 shows an alternative form of control valve, and

FIG. 4 shows a modification to the control valves shown in FIGS. 1 and 2.

Referring to FIG. 1 of the drawings, there is provided an accumulator 10 to which fuel is supplied under pressure by means of a pump 11. The fuel is stored in the accumulator at a pressure sufficient as will be explained, to displace fuel into the combustion space of an associated engine.

There is also provided a displacement member 12 which is slidable within a cylinder 13. One end of the cylinder is enlarged to form a chamber 14, and at this end of the cylinder there is provided a seating with which a shaped portion of the valve member 12 co-operates. In the closed position of the valve member fuel flow through spray orifices 15 into a combustion space of the associated engine is prevented.

The other end of the cylinder 13 communicates with a passage 16 which opens into a valve chamber 17. Located within the valve chamber are first and second valves. The first valve includes a valve element 18, which at one end is provided with a head 19 co-operating with a seating defined about the wall of the valve chamber 17. The valve member 18 is loaded by means of a coiled compression spring 20 into contact with the seating, and also the space surrounding the spring 20 communicates with the accumulator 10. In the open position of the first valve as shown, the accumulator is in communication with the passage 16 so that the displacement piston 12 is urged into contact with its seating. The valve member 18 is provided with a transverse drilling communicating with the passage 16 and the transverse drilling communicates with an axial drilling extending to the end of the valve member remote from the head 19. At this end of the valve member 18, the valve chamber 17 is enlarged, and the enlarged portion of the valve chamber communicates by way of a passage 21 with a drain.

A second valve is provided and this comprises a valve member 22 which is shaped to co-operate with the end of the valve member 18 out of which breaks the axial drilling. The valve member 22 when it is in contact with the valve member 18 prevents flow of fuel through the axial drilling and along the passage 21. The valve member 22 is urged into contact with the valve member 18 by means of an actuator piston 23, and the position of this piston is determined by a stack 24 of piezo-electric crystals. The stack of crystals is connected to the piston 23 by means of a lever 25.

The supply of electrical energy to the stack of crystals is by way of a control circuit 26a which receives a control signal from the associated engine, and also from a sensing coil 27 positioned at the end of the cylinder 13 remote from the chamber 14. In addition, the chamber 14 communicates by way of a non-return valve 28 with a source of fuel at a low pressure. In operation, and starting from the position in which the various parts are shown, it being appreciated that delivery of fuel to the associated engine has ceased, the stack of crystals is de-energised thereby allowing the head of the valve member 18 to move on to its seating under the action of the spring 20. Thus the first valve is closed and the connection between the accumulator 10 and a passage 16 is broken. In addition, the second valve is opened because the valve member 22 is allowed to move away from the valve member 18. When this occurs, fuel is supplied to the chamber 14 past the non-return valve 28 and the displacement piston 12 is moved by the pressure of fuel in the chamber 11 towards the other end of the cylinder 13. In so doing fuel is displaced through the axial drilling, and flows to drain by way of the passage 21. The extent of movement of the displacement piston is sensed by the sensing coil 27 and at a predetermined position, the control circuit 26a partially energises the stack of crystals 24. When this occurs, the valve member 22 is moved into engagement with the valve member 18 and the second valve is effectively closed. The movement of the displacement piston is therefore halted. At an appropriate time, a signal is supplied to the control circuit from the engine and the stack of crystals is fully energised thereby moving the valve member 18 to lift the head from the seating. Pressure from the accumulator therefore is applied to the end of the displacement piston and this is moved towards the seating. In so doing, fuel is displaced through the orifices 15 to the combustion space of the associated engine.

Referring now to FIG. 2, identical reference numerals are used wherever possible. In this arrangement the stack 24 of crystals acts against a piston 26 which is located within a cylinder in communication with a further cylinder containing a piston 27a which acts against a spring loaded plate 28 bearing against the valve member 22. Fuel is supplied via non-return valve 29 to keep the space between piston 26 and 27a full of fuel.

The displacement piston is indicated at 30, and as in the example of FIG. 1, one end of the cylinder containing the displacement piston communicates with a low pressure fuel supply passage 31 by way of a valve 32. In this case, however, the valve 32 is pressure actuated as will be explained. The other end of the cylinder containing the displacement piston communicates with the passage 16, and the sensing coil 27 is provided as in the previous example. In this example, fuel displaced from the one end of the cylinder containing the displacement piston passes by way of a passage 33 to an injection valve 34. This valve is of conventional form, that is to say it has a stepped external periphery, and the pressure of fuel supplied to the passage 33 acts against the step to lift the valve member 34 from a seating, thereby to allow flow of fuel through orifices 35 into the combustion space of the associated engine. Moreover, located intermediate the displacement piston and the valve member 34 is a push piece 36 and the end of the cylinder which contains the wider portion of the valve member 34 communicates with the passage 31. The valve 32 controls the flow of fuel from the passage 31 to said one end of the cylinder containing the displacement piston 30, and it is maintained in a closed position during delivery of fuel to the engine by the fact that accumulator pressure is applied to the wider end of the valve member constituting the valve 32. The mode of operation of the apparatus will now be described, bearing in mind that the parts of the apparatus are shown in the position in which they adopt at the end of the injection stroke. In this position, the first valve is open so that accumulator pressure acts on the displacement piston 30 and through the intermediary of the push piece 36 the valve member 34 is maintained in contact with the seating, and therefore no fuel flows through the orifices 35.

When the stack 24 of crystals is de-energised, the piston 27a is moved by the action of the spring loaded plate, and as a result, the valve members 22 and 18 move to their alternative positions. In this position of course, the first valve constituted by the valve member 18 is closed so that accumulator pressure is no longer applied to the valve member of the valve 32, and the displacement piston 30. In addition, the second valve is open, and fuel can therefore flow through the passage 31 past the valve 32 to effect movement of the displacement piston, and the displaced fuel from the other end of the cylinder containing the displacement piston flows by way of the passage 16, the axial drilling in the valve member 18 and the passage 21 to drain. The extent of movement of the displacement piston 30 is determined as in the previous example, by a signal derived from the sensing coil 27 which passes to the control circuit 26a, and partially energises the stack 24 of crystals. Such energisation produces pressurisation of the liquid between the pistons 26 and 27a and closure of the second valve. This arrests movement of the displacement piston which has now assumed a position removed from the pusher member 36 due to the effect of a relatively light spring disposed between the pusher member 36 and the displacement piston.

When the stack of crystals is fully energised, the first valve is opened and accumulator pressure is applied to the valve member of the valve 32 thereby closing the valve and also to the displacement piston 30. As a result of this fuel flows by way of the passage 33 to lift the valve member 34 from its seating, thereby to allow flow of fuel through the orifices 35 to a combustion space of the associated engine. During movement of the displacement piston, a point will be reached at which it engages with the pusher member 36, and further movement of the displacement piston results in movement of the valve member 34 onto its seating thereby to terminate injection of fuel to the engine.

As compared with the example of FIG. 1, the example of FIG. 2 has the advantage that flow of fuel through the orifices 35 can only occur when it is required, whereas in the example of FIG. 1, by virtue of the supply of fuel to the chamber 14 from a low pressuresource, a small amount of fuel could be displaced through the orifices 15, if the pressure conditions within the combustion chamber were suitable.

Referring now to FIG. 3, there is shown an alternative valve arrangement which can be used in the examples of FIG. 1 or FIG. 2. In the arrangement of FIG. 3, the stack 24 of crystals operates a piston 26 as in the example of FIG. 2, and the pressure of fuel delivered by the piston 26 is applied to a piston 37 which actuates the second valve, the latter being constituted by a valve member 38 having a head 39 which is movable onto a seating to prevent flow of fuel from the passage 16 to the passage 21. In addition, the pressure of fuel supplied by the piston 26 is applied to one end of a valve member 40 having a head 41 movable onto a seating to prevent the flow of fuel from the accumulator 10 to the passage 16. In addition, the head 41 is connected to a slidable closure plug 42 which provides for pressure balancing of the valve member 40. The valve member is additionally provided with a spring 43 acting to urge the head onto the seating. It will be appreciated that the valve member 40 together with the head 41 and the seating constitute the first valve, whilst the valve member 38, together with the head 39 constitute the second valve.

In operation, when the stack of crystals is fully energised, the head 41 of the first valve is lifted from its seating to allow flow of fuel from the accumulator 10 to the passage 16. At the same time the valve member 39 is held in contact with its seating to prevent flow of fuel from the passage 16 to the passage 21. In the de-energised state of the stack of crystals, the head 41 is in contact with its seating so that no fuel flows from the accumulator to the passage 16. However, by virtue of a spring 44, the head 39 is lifted from its seating and the passage 16 communicates with the passage 21. In the partially energised state of the stack of crystals the head 39 of the valve member 38 is in contact with the seating, but the pressure generated by piston 26 is insufficient to overcome spring 43 and therefore the passage 16 is effectively blocked so that no further movement of the displacement piston is possible.

The arrangement shown in FIG. 4 shows a modified form of the control valve which is shown in FIGS. 1 and 2. In the arrangement shown in FIGS. 1 and 2 the valve member 18 when in the closed position is acted upon by the spring 20 and also by the accumulator pressure. As a result considerable force is required to open the valve. In the arrangement shown in FIG. 4 the valve member 45 which corresponds to the valve member 18, is coupled to a piston member 46 by means of a flexible link. The piston member is subjected to the accumulator pressure and therefore balances the accumulator pressure acting on the valve member. A further difference lies in the fact that the valve member is fluted so that the fuel passing to the displacement piston flows via the fluted portion. The ribs of the fluted portion also serve to guide the movement of the valve member. A further difference lies in the construction of the second valve member 47. This is now provided with a central passage 48 communicating with the drain and the two valve members are movable into engagement to prevent flow of fuel through the passage. Moreover, the valve member is fluid pressure actuated, the valve member replacing the piston member 27a of FIG. 2 for this purpose.

Claims

We claim:

1. A fuel injection pumping apparatus for supplying fuel to internal combustion engines and comprising an accumulator in which fuel is stored at high pressure, a cylinder, a displacement piston contained within said cylinder, an outlet communicating with one end of said cylinder, valve means for controlling flow of fuel from a low pressure source to said one end of the cylinder, a first valve positioned intermediate the accumulator and the other end of said cylinder and operable to allow fuel under pressure from the accumulator to act on one end of said displacement piston thereby to cause movement of said piston to displace fuel through said outlet, a second valve through which said other end of the cylinder can be connected to a drain, actuating means for actuating said first and second valves whereby said displacement piston is moved to said one end of the cylinder to displace fuel through the outlet by opening the first valve and closing the second valve, said piston being moved away from said one end of the cylinder by closing the first valve and opening the second valve, sensing means for sensing the extent of movement of the displacement piston away from said one end of the cylinder, and control means responsive to the signal produced by said sensing means for operating said actuating means to reclose said second valve to halt the movement of the displacement piston away from said one end of the cylinder.

2. An apparatus as claimed in claim 1 in which said outlet defines a spray orifice through which fuel flows into a combustion space of the associated engine.

3. An apparatus as claimed in claim 1 including an injection valve for controlling the flow of fuel through a spray orifice, said injection valve being mounted within a cylinder and having a narrower end shaped for co-operation with a seating, the narrower end of the injection valve defining with the cylinder in which it is mounted a chamber communicating with said outlet, the wider end of the injection valve communicating with a source of fluid at a pressure lower than the accumulator pressure whereby when said first and second valves are operated the fuel under pressure delivered through said outlet will lift the valve member from its seating to allow flow of fuel through said spray orifice.

4. An apparatus as claimed in claim 3 including a push member disposed between the displacement piston and said injection valve whereby the injection valve is urged into contact with the seating to terminate the flow of fuel through the spray orifice at a predetermined position of the displacement piston.

5. An apparatus as claimed in claim 4 in which said valve means is responsive to the accumulator pressure applied to said displacement piston, said valve means being closed when accumulator pressure is applied to the displacement piston.

6. An apparatus according to claim 5 in which said actuating means comprises a piezo-electric stack of crystals.

7. An apparatus as claimed in claim 6 in which said first and second valves are operated mechanically by the stack of crystals.

8. An apparatus as claimed in claim 6 in which said first and second valves are operated by fluid pressure, said fluid pressure being generated by a piston operated by the stack of crystals.

9. An apparatus according to claim 8 in which said control means comprises an electronic control circuit.

10. An apparatus according to claim 9 in which said sensing means comprises a sensing coil, said sensing coil being positioned about the path of movement of the displacement piston.

11. An apparatus as claimed in claim 10 in which said valve members forming said first and second valves are disposed in end to end relationship.

12. An apparatus as claimed in claim 11 in which the valve member constituting said first valve is pressure balanced.

13. An apparatus according to claim 2 in which said actuating means comprises a piezo-electric stack of crystals.

14. A fuel injection pumping apparatus for supplying fuel to internal combustion engines and comprising an accumulator in which fuel is stored at high pressure, a cylinder, a displacement piston contained within said cylinder, an outlet communicating with one end of said cylinder, valve means for controlling the flow of fuel from a low pressure source to said one end of the cylinder, a first valve positioned intermediate the accumulator and the other end of said cylinder and operable to allow fuel under pressure from the accumulator to act on one end of said displacement piston thereby to cause movement of said piston to displace fuel through said outlet, a second valve through which said other end of the cylinder can be connected to a drain, actuating means for actuating said first and second valves whereby said displacement piston is moved to said one end of the cylinder to displace fuel through the outlet by opening the first valve and closing the second valve, said piston being moved away from said one end of the cylinder by closing the first valve and opening the second valve, a sensing coil positioned about the path of movement of the displacement piston, said sensing coil providing a signal indicative of the extent of movement of the displacement piston away from said one end of the cylinder and a control circuit responsive to the signal produced by said sensing coil for operating said actuating means to reclose said second valve thereby to halt the movement of the displacement piston away from said one end of the cylinder.

15. A fuel injection pumping apparatus for supplying fuel to internal combustion engines and comprising an accumulator in which fuel is stored at high pressure, a cylinder, a displacement piston contained within said cylinder, an outlet communicating with one end of said cylinder, valve means for controlling flow of fuel from a low pressure source to said one end of the cylinder, a first valve including a first slidable valve member, said first valve being positioned intermediate the accumulator and the other end of said cylinder and operable to allow fuel under pressure from the accumulator to act on one end of said displacement piston thereby to cause movement of said piston to displace fuel through said outlet, a second valve including a second valve member through which said other end of the cyliner can be connected to a drain, actuating means for actuating said first and second valve members whereby said displacement piston is moved to said one end of the cylinder to displace fuel through the outlet by opening the first valve and closing the second valve, said piston being moved away from said one end of the cylinder by closing the first valve and opening the second valve, sensing means for sensing the extent of movement of the displacement piston away from said one end of the cylinder, and control means responsive to the signal produced by said sensing means for operating said actuating means to reclose said second valve to halt the movement of the displacement piston away from said one end of the cylinder, said first and second valve members being disposed in end to end relationship, said second valve member being operated directly by said actuating means.

16. An apparatus as claimed in claim 15 in which said first valve member is pressure balanced.